MEDICAL 


Gift  of 


Panajna-Pacific  Intern1 
Exposition  Company. 


TEXT-BOOK 


or 


HUMAN    PHYSIOLOGY 


TEXT-BOOK 


OF 


HUMAN  PHYSIOLOGY 


INCLUDING 


HISTOLOGY   AND   MICROSCOPICAL  ANATOMY 


WITH    ESPECIAL  REFERENCE 


PRACTICE   OF  MEDICINE 


DR.  bf  LANDOIS 


FKOFESSOR    OF    PHYSIOLOGY    AND    DIRECTOR    OF   THE     PHYSIOLOGICAL     INSTITUTE     IN    THK 
UNIVERSITY    OF    GKEIFSVVALD 


TENTH    REVISED   AND    ENLARGED   EDITION 


EDITED  BY 


,  ALBERT  P.  . 

GY    M4<  ^GUtT-lk    IN\Tl4*E 
ANIA   COLLEGE   OF    DENTAL 
IN    THE    r'tBXn.*:.     inSTITUTE    OF1  ARTr"S?MrWcE'AM>     IMHSIK-v,    IHILA 

:'  :.  '  --.-     r    •:      v     ,r:-  :•  - 


I-KOFKSSOK    OF    PHYSIOLOGY    M4<  ^GUtT-lk    IN\Tl4*E       OTMSfelp^c^kKf;*:  ;     PROFESSOR    OF    PHYSIOLOGY 
IN    THE    PENNSYLVANIA   COLLEGE   OF    DENTAL    SURGERY  ;     LECTURER    ON    PHYSIOLOGY    AND   HYGIENE 

DELPHIA 


TRANSLATED   BY 

AUGUSTUS   A.  ESHiNER,  M.D. 

FRDFESSOR    OF    CLINICAL     MHUICINE     IN     T^       KiLADE|miArFC«,Y(   I  IM'     :      I'1I\^I     IAN    TO    THE     PHILADELPHIA 

HOSPITAL;    Assi 


ICINE     IN     T^  iyLADE|miArFC«,Y(   I  IM'     :      I'1I\^I     IAN    TO    THE     P 

iSir4»T  PH.gA(ULm.  to  imM.  PHM  ADI  1.1  m.\  </in  iiorKim    HOSPITAL 

9v  ^B  vH       flE     v^.  ••  w  i^ 

AND    TN'FlWMjfRY    ¥(Hf  NHRVOnS    DISKASK.S 


Mitb  394  irilustrrfticms 
PHILADELPHIA 

P.    BLAKISTON'S    SON    &    CO. 
1012  WALNUT  STREET 


COPYRIGHT,  1904,  BY  P.  BLAKISTON'S  Sox  &  Co 


PRESS    OF 

.   F.    FELL   COMPANY 
PHILADELPHIA 


905 

PUBLISHERS'  PREFACE. 


The  fourth  English  edition  of  Professor  Stirling's  translation  of 
Landois'  "Physiology,"  published  in  1891,  has  been  out  of  print  for 
some  years.  Since  the  date  of  publication  of  this  English  edition, 
the  work  has  passed  through  three  more  large  editions  in  Germany. 
On  each  occasion  Professor  Landois  still  further  enhanced  its  merits 
by  incorporating  all  those  results  of  physiological  investigation  which 
in  his  judgment  would  have  a  permanent  value  not  only  for  advanced 
students  but  for  practitioners  of  medicine  as  well;  and  hence  there  is 
probably  no  work  which  so  thoroughly  and  satisfactorily  represents 
the  existing  state  of  physiological  science  and  its  relations  to  pathology 
and  clinical  medicine,  as  that  of  Professor  Landois. 

For  the  reason  that  pathological  processes  are  but  variations  of 
physiological  processes  in  one  direction  or  another,  there  is  appended 
to  almost  every  section  those  variations  which  are  regarded  by  the 
clinician  as  pathological.  In  this  way  the  student  is  made  to  realize 
not  only  the  close  interdependence  of  physiology  and  pathology,  but 
the  necessity  for  a  thorough  and  accurate  knowledge  of  the  former  for 
an  intelligent  comprehension  of  the  latter.  The  work  of  Landois  thus 
becomes  a  guide  which  conducts  the  student  from  the  physiological 
laboratory  to  the  work  of  the  clinician.  That  it  has  been  successful 
in  this  respect,  and  that  it  meets  the  needs  of  students  and  practitioners 
of  medicine,  is  the  only  explanation  that  can  be  offered  for  the  ex- 
traordinary fact  that  it  has  passed  through  ten  large  editions  in  Ger- 
many in  twenty  years,  and,  in  additi'on,  has  been  translated  into  French, 
Russian,  English,  Italian,  and  Spanish. 

The  continued  success  of  each  successive  edition  in  Germany  and 
the  frequent  requests  for  an  English  edition  have  convinced  the  pub- 
lishers that  a  new  translation  would  be  acceptable  to  students  and 
practitioners  of  the  present  day  and  decided  them  to  issue  the  work 
in  its  present  form.  The  translation  was  intrusted  to  Dr.  A.  A.  Eshner, 
Professor  of  Clinical  Medicine  in  the  Philadelphia  Polyclinic.  In  this 
he  was  ably  assisted  by  Drs.  Bernard  Kphn,  E.  A.  Shumway,  Maurice 
Ostheimer,  R.  Max  Goepp,  Brooke  M.  Anspach,  C.  A.  Fife,  D.  J. 
McCarthy,  and  W.  B.  Stanton.  The  text  has  been  revised  and  edited 
by  Dr.  Albert  P.  Brubaker,  Professor  of  Physiology  in  the  Jefferson 
Medical  College. 

The  publishers  wish  to  express  their  appreciation  of  the  conscientious 
care  which  has  been  given  by  each  and  all  to  the  preparation  of  this 
edition. 


j 


PREFACE  TO  THE  TENTH  EDITION. 


In  spite  of  the  short  interval  that  has  elapsed  between  the  appear- 
ance of  the  ninth  and  that  of  this  new  edition  all  sections  of  the  book 
have  been  subjected  to  extensive  revision,  with  the  inclusion  of  the 
results  of  the  most  recent  investigations.  The  number  of  illustrations 
has  been  increased  and  some  have  been  replaced  by  better  ones. 

Since  the  book  has  been  placed  in  the  hands  of  students  and  phy- 
sicians in  ten  large  editions,  as  well  as  in  several  English  editions,  a 
Russian  translation  in  a  second  edition,  an  Italian,  a  French,  and  a 
Spanish  translation,  I  have  become  more  firmly  established  in  the 
conviction  that  the  plan  according  to  which  I  have  labored,  both  as 
author  of  this  book  and  as  teacher,  is  the  correct  one.  Physiology  is 
the  foundation  of  internal  medicine,  and  it  should,  therefore,  be  so 
taught  that  the  physician  can  continue  to  build  upon  it  and  find  sup- 
port in  it.  This  has  been  my  endeavor ;  in  this  sense  the  book  has  been 
revised  uniformly  throughout  in  this  edition. 

L.  LANDOIS. 

GREIFSWALD. 


VI 


FOREWORD. 


TENDENCY  AND  PURPOSE   OF  THE  WORK. 

In  the  preparation  of  the  forelying  concise  Textbook  of  Physiology 
the  author  has  been  governed  by  an  endeavor  to  provide  for  physicians 
and  students  a  book  that  should  supply  the  needs  of  the  practising 
physician  in  larger  measure  than  is  done  by  the  majority  of  similar 
works.  With  this  end  in  view  a  brief  outline  of  pathological  variations 
is  appended  in  every  section  to  the  description  of  the  normal  processes. 
This  is  done  for  the  purpose  of  directing  the  attention  of  the  student 
from  the  outset  to  the  field  of  his  future  professional  activity  and  of 
pointing  out  the  extent  to  which  the  morbid  process  represents  a  de- 
rangement of  the  normal.  On  the  other  hand,  opportunity  is  by  this 
means  afforded  the  practising  physician  to  renew  acquaintance  readily 
with  the  theoretical  doctrines  that  as  a  rule  slip  away  from  him  all  too 
soon  in  the  pursuit  of  his  vocation.  Here  he  can  without  effort  look 
back  from  the  morbid  phenomena  under  treatment  to  the  normal  pro- 
cesses and  in  the  recognition  of  these  obtain  new  suggestions  for  correct 
interpretation  and  treatment.  From  this  standpoint  the  author  has 
described  fully  all  those  methods  of  investigation  that  may  be  employed 
by  the  practitioner  with  great  advantage  and  that  as  a  rule  are  but 
briefly  treated  in  books  on  physiology.  Reference  may  be  made  here 
to  the  following  sections:  Blood-examination;  graphic  study  of  the 
normal  and  abnormal  heart -beat;  heart-sounds  and  heart-murmurs; 
the  pulse ;  the  venous  pulse ;  transfusion ;  normal  and  abnormal  re- 
spiratory murmurs;  ventilation;  examination  of  the  air  in  dwellings; 
the  sputum ;  deviations  from  the  normal  digestive  processes ;  diabetes ; 
cholemia;  the  digestion  in  febrile  patients;  thermometry  and  calor- 
imetry  in  the  febrile  state;  examination  of  drinking-water;  meat  and 
meat-preparations;  excessive  deposition  of  fat  and  muscle,  and  the 
means  for  its  relief ;  examination  of  the  normal  urine  and  the  determina- 
tion of  all  pathological  constituents,  as  well  as  of  urinary  concretions; 
uremia,  ammoniemia,  uric-acid  diathesis;  morbid  disturbances  in 
retention  and  evacuation  of  urine ;  pathological  alterations  in  the  sudorif- 
erous and  sebaceous  secretions;  galvanic  conductivity  through  the 
skin ;  gymnastics  and  therapeutic  gymnastics ;  pathological  alterations 
in  the  motor  functions;  laryngoscopy  and  rhinoscopy;  pathology  of 
phonation  and  articulation;  physiological  principles  underlying  the 
therapeutic  application  of  electricity;  constant  currents  and  electrical 
apparatus. 

In  the  consideration  of  every  individual  nerve  and  the  differ- 
ent nerve-centers  a  sketch  of  the  pathological  manifestations  is 
added.  With  relation  to  the  nerve-centers  the  derangements  of  the 
reflexes,  those  of  conduction  to  the  central  organs,  those  of  the  respira- 


Vlll  FOREWORD. 

tory  center,  together  with  the  means  for  resuscitating  asphyxiated 
persons,  and  the  group  of  angioneuroses,  have  received  especial  con- 
sideration. Particular  importance  has  been  attached  to  the  physio- 
logical topography  of  the  surface  of  the  cerebrum  in  man  with  reference 
to  modern  investigation  into  the  localization  of  the  functions  of  the 
brain.  The  same  principle  has  been  followed  also  with  relation  to 
the  physiology  of  the  organs  of  special  sense.  Evidence  of  this  will 
be  found  in  the  discussions  of  abnormalities  of  ocular  refraction,  the  use 
of  spectacles,  ophthalmoscopy,  the  orthoscope,  color-blindness  and  its 
practical  significance,  further  investigations  into  the  functions  of  the 
other  special  senses  and  their  principal  disorders.  The  embryological 
section  has  given  especial  consideration  to  the  subject  of  developmental 
defects,  and  to  malformations  as  the  most  important  of  these;  and  also 
to  the  means  for  determining  the  period  of  development  reached  by 
human  embryos. 

In  description  it  was  the  aim  of  the  author  to  be  as  concise  and 
comprehensive  as  possible.  Elaborate  discussions  have  been  scrupu- 
lously avoided.  At  the  same  time  the  typography  has  been  so  arranged 
that  the  more  important  and  purely  physiological  matters  are  presented 
in  conspicuous  type.  Also,  the  beginner  can  without  disadvantage  pass 
over  the  pathologic-physiological  sections;  the  student  during  the 
period  of  clinical  instruction  will,  however,  with  advantage  review  the 
field  of  normal  physiology  from  the  latter. 

The  author  has,  further,  considered  it  advisable  to  add  to  each 
physiological  section  a  brief  outline  of  the  historical  development  of 
the  subject  in  hand,  and  likewise  a  summary  of  the  comparative  physi- 
ology of  the  animal  kingdom.  Finally,  the  histology  and  microscopic 
anatomy  have  been  more  fully  considered  in  each  section  than  is  the 
case  with  most  textbooks  of  physiology. 

On  the  basis  of  the  plan  thus  outlined  the  appearance  of  the  fore- 
lying  work  is  I  believe  justified.  That  this  plan  has  not  been  fallacious 
is  indicated  by  the  numerous  discussions  in  the  medical  journals  of 
North  and  South  Germany,  Austria,  Switzerland,  Hungary,  Russia, 
France,  England,  Italy,  Scandinavia,  America,  which  have  received 
the  book  with  favor,  and  recognition.  The  author,  however,  is  par- 
ticularly gratified  that  the  book  has  been  received  with  approval  by 
physiologists.  In  order  to  dispel  any  anxiety  on  the  part  of  those  who 
perhaps  may  fear  that  the  scientific  eminence  of  our  science,  of  funda- 
mental importance  in  the  entire  domain  of  medicine,  may  suffer  from 
the  attempted  association  of  physiology  with  the  practical  department 
of  medicine,  I  shall  quote  a  few  words  from  a  letter  written  by  one  of 
our  most  illustrious  and  most  versatile  physiologists: 

"Should  anyone  publish  a  handbook  like  that  of  yours,  of  which 
the  first  half  is  before  me,  he  will  be  entitled  to  the  thanks  not  only  of 
the  students,  but  also  of  the  teacher  and  investigator.  And  as  it  is 
my  ambition  to  combine  in  myself  the  three  qualities  indicated,  my 
thanks  are  tendered  you  with  all  my  heart.  Your  pathological  descrip- 
tions are  in  their  condensed  brevity  so  masterfully  clear  that  I  promise 
myself  from  your  book  a  most  beneficial  action  and  reaction  upon  the 
field  of  clinical  medicine."  .... 

If  these  words  have  been  realized  I  should  find  in  this  fact  a  perfect 
reward  for  my  endeavors.  It  has  always  appeared  to  me  in  my  academic 
activity  as  a  teacher  that  my  principal  aim  must  lie  in  the  thorough 


FOREWORD.  IX 


preparation  of  physicians  for  physiological  thought.  And  if  to  this, 
my  aim,  there  be  apposed  the  statement  of  prouder  sound,  "we  make 
physiologists,"  this  would  not  deflect  me  from  my  course  as  a  teacher, 
of  which  I  believe,  in  the  words  of  the  master  Herophilus:  lam  ra>)-w  £?>«< 


L.  LANDOIS. 


TABLE    OF   CONTENTS. 


INTRODUCTION. 

The  Scope  and  Aim    of  Physiology  and  its  Relation  to  Allied  Branches  of 

Physical  Science, 17 

Matter,    18 

Forces, 19 

Law  of  the  Constancy  of  Energy, 23 

Animals  and  Plants, 25 

Kinetic  Energy  and  Life, 28 

PHYSIOLOGY  OF  THE  BLOOD. 

Physical  Properties  of  the  Blood, 29 

Microscopic  Examination  of  the  Blood, 31 

The  Red  Blood-corpuscles  (Erythrocytes) , 34 

Preservation  of  Red  Blood-corpuscles, 36 

Permeability  of  Erythrocytes. — Isotonia  (Hyperisotonia  and  Hypisotonia)  . 

— Demonstration  of  the  Stroma. — Lake  coloration  of  the  Blood, 37 

Form,  Size,  and  Number  of  Erythrocytes  in  Different  Animals, 40 

Development  of  Red  Blood-corpuscles, 41 

Destruction  of  Red  Blood-corpuscles, 43 

The  White  Blood-corpuscles  (Leukocytes) ,  the  Blood-plates  and  Elementary 

Granules, 45 

Abnormal  Changes  in  the  Red  and  White  Blood-corpuscles, 50 

Chemical  Constituents  of  the  Red  Blood-corpuscles, 51 

Preparation  of  Hemoglobin-crystals, 52 

Quantitative  Estimation  of  the  Hemoglobin _ 52 

Employment  of    the  Spectroscope  for  Hemoglobin  Examination;    Oxygen- 
combinations  of  Hemoglobin:   Oxyhemoglobin  and  Methemoglobin,  ...  55 

Carbon-monoxid  Hemoglobin  and  Carbon-monoxid  Poisoning, 58 

Other  Hemoglobin-combinations, 59 

Decomposition  of  Hemoglobin, 60 

Hemin  (Hematin  Chlorid) ;   Identification  of  Blood  by  Means  of  the  Hemin- 

test, 61 

Hematoidin, 63 

The  Colorless  Proteid  of  Hemoglobin, 63 

Proteid  Bodies  in  the  Stroma 63 

Remaining  Constituents  of  the  Red  Blood-corpuscles, 64 

Chemical  Constituents  of  the  Leukocytes, 64 

The  Blood-plasma  and  Its  Relation  to  the  Serum, 65 

Fibrin:  Its  General  Properties;  Coagulation, 65 

General  Phenomena  Attending  Coagulation, 67 

Nature  of  Coagulation, 68 

Source  of  the  Fibrinogenous  Substances, 70 

Relations  of  the  Red  Blood-corpuscles  to  Fibrin-formation, 71 

Chemical  Constitution  of  the  Blood-plasma  and  the  Serum, 72 

THE  GASES  OF  THE  BLOOD. 

Absorption  of  Gases  by  Solid  Bodies  and  by  Fluids, 74 

Diffusion  of  Gases:  Absorption  of  Gaseous  Mixtures, 75 

Separation  of  the  Gases  of  the  Blood, 76 

Quantitative  Estimation  of  the  Gases  of  the  Blood, 77 

Special  Facts  Concerning  the  Gases  of  the  Blood 78 

xi 


Xll  TABLE    OF    CONTENTS.      . 

PAGE 

As  to  the  Presence  of  Ozone  in  the  Blood, 79 

Carbon  Dioxid  and  Nitrogen  in  the  Blood, 80 

Estimation  of  the  Individual  Constituents  of  the  Blood, 81 

Arterial  and  Venous  Blood, 82 

The  Amount  of  Blood : 83 

Abnormal  Increase  in  the  Amount  of  Blood  or  of  Its  Individual  Parts,  ....  84 
Abnormal  Diminution  in  the  Amount  of  Blood  or  of    Its  Individual  Con- 
stituents,    86 

PHYSIOLOGY  OF  THE  CIRCULATION. 

Cause,  Purpose,  Division, 88 

The  Heart, .  89 

Arrangement  of  the  Muscle-fibers  of  the  Heart  and  Their  Physiological  Sig- 
nificance,    89 

Arrangement  of  the  Musculature  of  the  Ventricles, 90 

Pericardium;  Endocardium;  Valves, 91 

The  Coronary  Vessels;    Automatic  Regulation,  Nutrition,  and  Isolation  of 

the  Heart 93 

The  Movements  of  the  Heart.     Variations  in  Tone, 96 

Pathological  Disturbance  of  the  Function  of  the  Heart, 99 

The  Apex-beat.     The  Cardiogram, 100 

The  Time-relations  of  the  Movements  of  the  Heart, 104 

Pathological  Variations  in  the  Heart-beat, 107 

The  Heart-sounds, no 

Abnormalities  in  the  Heart-beat, 112 

Duration  of  the  Movement  of  the  Heart, 113 

The  Cardiac  Nerves, 114 

Irritability  of  the  Automatic  Motor  Centers  in  the  Heart  and  of  the  Heart- 
Muscle 115 

The  Cardiopneumatic  Movement, 121 

Influence  of   the  Respiratory  Pressure  on  the  Dilatation  and  Contraction 

of  the  Heart, 122 

THE  MOVEMENT  OF  THE  BLOOD  IN  THE  CIRCULATION. 

Toricelli's  Theorem  on  the  Velocity  of  Escape  of  Fluids, 125 

Propelling  Force,  Velocity  and  Lateral  Pressure, 126 

Movement  through  Capillary  Tubes, 128 

Continuous  and  Undulatory  Movement  in  Elastic  Tubes, 128 

Structure  and  Properties  of  the  Blood-vessels, .  .  . 129 

Pulse-movement. — Technic  of  Pulse-examination, 133 

The  Pulse-tracing,  the  Recoil-elevation  and  the  Elasticity-elevations, 138 

The  Dicrotic  Pulse 142 

Differences  in  the  Time-relations  of  the  Pulse, 143 

Variations  in  the  Strength,  the  Tension,  and  the  Volume  of  the  Pulse, 145 

Sphygmographic  Tracings  from  Different  Arteries, 146 

Phenomena  of  Anacrotism, 147 

Influence  of  the  Respiratory  Movements  on  Sphygmographic  Tracings, ....  149 

The  Influences  of  Pressure  on  the  Shape  of  Sphygmographic  Tracings, 152 

Velocity  of  Propagation  of  Pulse-waves, 153 

Propagation  of  Pulse-waves  in  Rubber  Tubes, 153 

Propagation- velocity  of  the  Pulse-waves  in  Man, 154 

Other  Pulsatory  Phenomena, 156 

Vibration  of  the  Body  Due  to  the  Action  of  the  Heart  and  the  Course  of  the 

Blood-waves, 157 

The  Movement  of  the  Blood, 158 

Schematic  Reproduction  of  the  Circulation, 160 

Capacity  of  the  Ventricles, 161 

Methods  for  Measuring  the  Blood-pressure, 162 

The  Blood-pressure  in  the  Arteries, 165 

The  Blood-pressure  in  the  Capillaries, 168 

The  Blood-pressure  in  the  Veins, 169 

The  Blood-pressure  in  the  Pulmonary  Artery, 169 

Measurement  of  the  Velocity  of  the  Blood-current , 171 


TABLE    OF    CONTENTS.  xiii 

The  Velocity  of  the  Current  in  the  Arteries,  Capillaries,  and  Veins,  ......  1*7*5 

Estimation  of  the  Capacity  of  the  Ventricles  from  the  Current-velocity  by 

the  Method  of  Carl  Vierordt,  .................................    ...  I76 

The  Duration  of  the  Circulation,.  ...  I77 

The  Work  of  the  Heart,  .........................  '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.}'.'.'.-.  178 

The  Movement  of  the  Blood  in  the  Smallest  Vessels,  .....................  178 

The  Migration  of  the  Blood-corpuscles  from  the  Vessels;   Stasis;    Diapedesis,  180 

The  Movement  of  the  Blood  in  the  Veins,  .......................  182 

Sounds  and  Murmurs  in  the  Arteries,  ..................................  183 

Acoustic  Phenomena  within  the  Veins,  .................................  184 

The  Venous  Pulse.     The  Phlebogram,  .................................  185 

The  Distribution  of  the  Blood,  .......................  !88 

Plethysmography,   ..................................................  X89 

Transfusion  of  Blood,  ................................................  XQO 

The  Ductless  Glands.      Internal  Secretions,  .............................  193 

Comparative  ............  ............................................  jgS 

Historical  ..........................................................  X 


PHYSIOLOGY  OF  RESPIRATION. 

Objects  and  Subdivisions,  ............................................  201 

Structure  of  the  Air-passages  and  the  Lungs,  ...........................  201 

Mechanism  of  the  Respiratory  Movements.     Abdominal  Pressure,  .........  204 

Respiratory  Volumes,  ...............................................  205 

The  Rate  of  Respiration,  ............................................  207 

The  Time  Relations  of  Respiratory  Movements.     Pneumatography  ........  207 

Types  of  Respiratory  Movements,  .....................................  210 

Pathological  Variations  in  the  Respiratory  Movements,  ..................  210 

Summary  of  the  Muscular  Mechanism  Concerned  in  Inspiration  and  Ex- 

piration,   ......................................................  2  12 

Action  of  the  Individual  Respiratory  Muscles,  ..........................  213 

Dimensions  and  Expansibility  of  the  Thorax,  ...........................  217 

Respiratory  Excursion  of  the  Lungs,  ...................................  218 

Variations  from  the  Normal  Percutory  Conditions  in  the  Thorax,   .........  220 

The  Normal  Respiratory  Sounds,  .....................................  221 

Pathological  Respiratory  Sounds,  .....................................  222 

Pressure  in  the  Air-Passages  during  Respiration,  ........................  223 

Mouth-breathing  and  Nasal-breathing,  .................................  224 

Modified  Respiratory  Acts,  ...........................................  225 

Chemistry  of  Respiration,  ..................................  226 

Quantitative  Estimation  of  the  Carbon  Dioxid,  the  Oxygen,  and  the  Aqueous 

Vapor  in  Gaseous  Mixtures,  ......................................  226 

Methods  of  Investigation,  ............................................  227 

Composition  and  Properties  of  Atmospheric  Air,  ........................  229 

Composition  of  Expired  Air,  ..........................................  231 

Extent  of  the  Daily  Interchange  of  Gases,  ..................  ...  232 

Factors  Influencing  the  Extent  of  the  Respiratory  Exchange  of  Gases,  .  .  232 

Diffusion  of  Gases  within  the  Respiratory  Organs  .......................  237 

Interchange  of  Gases  between  the  Blood  in  the  Pulmonary  Capillaries  and 

the  Air  in  the  Alveoli,  .............................  ...  238 

The  Respiratory  Gaseous  Exchange  as  a  Dissociation  Process..  .  240 

Cutaneous  Respiration,  ..............................  241 

Internal  Respiration  or  Tissue-respiration,  .............................  241 

Respiration  in  a  Closed  Space,  or  with  Artificial  Changes  in  the  Amounts 

of  Oxygen  and  Carbon  Dioxid  in  the  Respired  Air,  ......  244 

Respiration  of  Foreign  Gases,  ..............  245 

Other  Injurious  Substances  in  the  Inspired  Air  .................  245 

Renewal  of  the  Air  in  Living-rooms  (Ventilation).  Examination  of  tin-  Air,  246 
Normal  Secretion  of  Mucus  in  the  Air-passages.  The  Expectoration 

(Sputum)  ,  ............................................  249 

Effects  of  Atmospheric  Pressure,  ......................................  251 

Comparative.  Historical,  .........................................  254 


XIV  TABLE    OF    CONTENTS. 

PHYSIOLOGY  OF  DIGESTION. 

PAGE 

The  Mouth  and  Its  Glands, 256 

The  Salivary  Glands, , 257 

The  Secretory  Activity  of  the  Salivary  Glands, 259 

The  Nerves  of  the  Salivary  Glands, 259 

The  Influence  of  the  Nervous  System  on  the  Secretion  of  Saliva, 260 

The  Saliva  from  the  Individual  Glands, 262 

The  Mixed  Saliva,  the  Secretion  of  the  Mouth, 263 

Physiological  Actions  of  the  Saliva, 264 

Tests  for  Sugar, 267 

Quantitative  Estimation  of  Sugar, 268 

The  Mechanics  of  the  Digestive  Apparatus, 270 

The  Prehension  of  Food, 270 

The  Movements  of  Mastication,   270 

Structure  and  Development  of  the  Teeth, 272 

Movements  of  the  Tongue, 276 

The  Act  of  Swallowing  (Deglutition) , '.  277 

The  Movements  of  the  Stomach. — Vomiting, 280 

The  Movements  of  the  Intestines, 282 

The  Evacuation  of  Feces  (Defecation), 283 

Nervous  Influences  Affecting  the  Intestinal  Movements, 286 

The  Structure  of  the  Gastric  Mucous  Membrane, 289 

The  Gastric  Juice, 292 

The  Secretion  of  the  Gastric  Juice, 293 

Methods  of  Obtaining  the   Gastric  Juice.      The   Preparation   of  Artificial 

Digestive  Fluids;  Demonstration  and  Properties  of  Pepsin, 295 

The  Process  and  the  Products  of  Gastric  Digestion, 297 

The  Gases  of  the  Stomach, 301 

Structure  of  the  Pancreas, 302 

T.he  Pancreatic  Juice, 303 

The  Digestive  Activity  of  the  Pancreatic  Juice, 304 

The  Secretion  of  the  Pancreatic  Juice, 307 

The  Structure  of  the  Liver, 308 

Chemical  Constituents  of  the  Liver-cells,  \ 311 

Diabetes  Mellitus, 313 

The  Constituents  of  the  Bile, 315 

Secretion  of  Bile, 319 

Excretion  of  Bile, 321 

Resprption  of  Bile, 322 

Action  of  the  Bile, 324 

Final  Fate  of  the  Bile  in  the  Intestinal  Canal, 325 

The  Intestinal  Juice, 326 

Fermentative  Processes  in  the  Intestines  Due  to  Microbes;  Intestinal  Gases,  329 

Processes  in  the  Large  Intestine.     Formation  of  the  Feces, 335 

Morbid  Alterations  in  Digestive  Activity, 339 

Comparative  Physiology  of  Digestion, 343 

Historical, 346 

PHYSIOLOGY  OF  ABSORPTION. 

Structure  of  the  Organs  of  Absorption, 348 

Absorption  of  the  Digested  Food, 351 

Absorptive  Activity  of  the  Wall  of  the  Alimentary  Canal, 354 

Influence  of  the  Nervous  System, 359 

Nourishment  by  Means  of  "Nutritive  Enemata," 359 

System  of  Lacteal  and  Lymphatic  Vessels, 360 

Origin  of  the  Lymph-channels.     Lymphatics 361 

The  Lymph-glands, 363 

Properties  of  the  Chyle  and  the  Lymph, 366 

Quantitative  Relations  of  Lymph  and  Chyle, 368 

Origin  of  Lymph, 369 

Circulation  of  Chyle  and  Lymph, 371 

Absorption  of  Parenchymatous  Effusions, 373 

Lymph-stasis  and  Serous  Effusions, 374 


TABLE    OF    CONTENTS.  XV 

PAGE 

Comparative 375 

Historical, 375 

PHYSIOLOGY  OF  ANIMAL  HEAT. 

Sources  of  Heat 377 

Animals  with  Constant  and  with  Variable  Temperature, 381 

Methods  of  Estimating  the  Temperature:  Thermometry, 382 

Temperature-topography,    385 

Influences  Affecting  the  Temperature  of  Individual  Organs, 387 

Measurement  of  the  Volume  of  Heat:  Calorimetry, 389 

Heat-conduction  of  Animal  Tissues.      Expansibility  of  Animal  Tissues  by 

Heat, 390 

Variations  in  the  Mean  Bodily  Temperature, 391 

Regulation  of  the  Temperature, 394 

Heat-balance, 399 

Variations  in  Heat-production, : 400 

Relation  of  Heat-production  to  the  Work  Performed  by  the  Body, 400 

Accommodation  to  Variations  in  Temperature, 402 

Accumulation  of  Heat  in  the  Body, 403 

Fever,    404 

Artificial  Elevation  of  the  Bodily  Temperature, 406 

Employment  of  Heat, 407 

Post-mortem  Elevation  of  Temperature, 407 

The  Influence  of  Cold  upon  the  Body, 408 

Artificial  Reduction  of  the  Bodily  Temperature  in  Animals, 409 

Employment  of  Cold, 411 

The  Temperature  of  Inflamed  Parts 411 

Historical.     Comparative 41  * 

PHYSIOLOGY  OF  METABOLISM. 

Scope  of  Metabolism, 413 

SYNOPSIS  OF  THE  MOST  IMPORTANT  SUBSTANCES  USED  AS  FOOD. 

Water.     Examination  of  Drinking-water 413 

Structure  and  Secretory  Activity  of  the  Mammary  Glands, 417 

Milk  and  Milk-preparations, 4*9 

Eggs,    ; 423 

Meat  and  Meat-preparations, 423 

Vegetable  Foods, 426 

Condiments:  Coffee,  Tea,  Chocolate,  Alcoholic  Drinks  and  Spices, 428 

PHENOMENA  AND  LAWS  OF  METABOLISM. 

Metabolic   Equilibrium, 43° 

Metabolism  in  the  State  of  Starvation, 439 

Metabolism  with  an  Exclusive  Diet  of  Meat,  Albumin  or  Gelatin 442 

An  Exclusive  Diet  of  Fats  or  Carbohydrates, 443 

Laws  Governing  Metabolism  on  a  Mixed  Diet  of  Meat  and  Fat  or  Carbohy- 
drates,     443 

Origin  of  the  Fat  in  the  Body, 444 

Deposition  of  Fat  and  Flesh  in   the    Body  (Hypernutrition) .     Corpulence 

and  the  Means  for  its  Correction, 445 

The  Metabolism  of  the  Tissues, 44$ 

Regeneration, 45 I 

Transplantation  and  Adhesion, 454 

Increase  in  Size  and  in  Weight  in  the  Process  of  Growth, 455 

SUMMARY  OF  THE  CHEMICAL  CONSTITUENTS  OF  THE  ORGANISM. 

Inorganic  Constituents, 456 

Organic   Constituents.      The   Proteid   Bodies   or   Protein-Substances.     The 

True  Albuminous  Bodies, 457 

The  Albuminoid  Bodies, 

Nitrogenous  Glucosids, 462 


XVI  TABLE    OF    CONTENTS. 

PAGE 

Nitrogenous  Pigments, 462 

Organic  Non-nitrogenous  Acids, 462 

The  Fats, 462 

The  Alcohols, 464 

The  Carbodyhrates, 464 

Ammonia-derivatives  and  Their  Combinations, 467 

Aromatic  Bodies, 468 

Historical 468 

THE  SECRETION  OF  URINE. 

Structure  of  the  Kidney, 469 

The  Urine.     The  Physical  Characters  of  the  Urine, 472 

THE  ORGANIC  CONSTITUENTS  OF  THE  URINE. 

Urea, 475 

Qualitative  and  Quantitative  Estimation  of  Urea, 478 

Uric  Acid, -.•••-. 479 

Qualitative  and  Quantitative  Estimation  of  Uric  Acid, 482 

Kreatinin,  Xanthin-bases,  Oxaluric,  Oxalic,  and  Hippuric  Acids, 482 

Coloring-matters  of  the  Urine, 485 

Substances     Forming   Indigo,    Phenol,    Kresol,    Pyrocatechin ,  and   Skatol. 

Other  Substances, 487 

THE  INORGANIC  CONSTITUENTS  OF  THE  URINE. 

Spontaneous  Alterations  in  the  Urine  on  Standing;    Acid  and  Ammoniacal 

Urinary  Fermentation, 493 

Albumin  in  the  Urine:   Protein uria,  Albuminuria, 494 

Blood  and  Hemoglobin  in  the  Urine:  Hematuria,  Hemoglobinuria 497 

Biliary  Constituents  in  the  Urine:  Choluria, 500 

Sugar  in  the  Urine:  Glycosuria, 501 

Cystin, 503 

Leucin  and  Tyrosin, 503 

Sediments  in  the  Urine, 503 

Schematic  Resume  for  the  Recognition  of  all  of  the  Sediments  in  the  Urine,  506 

Urinary  Concretions, 507 

The  Physiological  Process  of  Urinary  Secretion, 509 

The  Preparation  of  the  Urine, 513 

The  Passage  of  Various  Substances  into  the  Urine, 514 

Influence  of  the  Nerves  upon  the  Secretion  of  the  Kidneys, 514 

Uremia;  Ammoniemia;  Uric-acid  Dyscrasia, 516 

Structure  and  Functions  of  the  Ureters, 517 

Structure  of  the  Urinary  Bladder  and  the  Urethra, 519 

Collection  and  Retention  of  the  Urine  in  the  Bladder.     Evacuation  of  the 

Urine 520 

Morbid  Derangement  of  Urinary  Retention  and  of  Micturition, 523 

Comparative.     Historical,    524 

FUNCTIONS  OF  THE  EXTERNAL  INTEGUMENT. 

Structure  of  the  Skin, 525 

The  Nails  and  the  Hair, 527 

The  Glands  of  the  Skin, 531 

The  Skin  as  an  External  Covering, 532 

Cutaneous  Respiration.      Cutaneous  Secretion.     Sebum.     Sweat.     Pigment- 
formation,  533 

Influences  Affecting  the  Secretion  of  Sweat  ;  Nervous  Control  Affecting  the 

Secretion  of  Sweat,   536 

Nervous  Control  Affecting  the  Secretion  of  Sweat, 536 

Physiological  Care  of  the  Skin.      Pathological  Abnormalities  in  the  Secre- 
tion of  Sweat  and  Sebum, 538 

Absorption  through  the  Skin.      Galvanic  Conductivity, 539 

Comparative.     Historical, * 540 


TABLE    OF    CONTENTS.  Xvii 


PHYSIOLOGY  OF  THE  MOTOR  APPARATUS. 


PAGE 


Structure  and  Arrangement  of  the  Muscles, 542 

Physical  and  Chemical  Properties  of  Muscular  Tissue,   547 

Metabolism  in  Muscle.     The  Source  of  Muscular  Energy, 549 

Muscular  Rigidity  (Cadaveric  Rigidity,  Rigor  Mortis) 552 

Irritability,  Stimulation,  and  Death  of  the  Muscle, 555 

Change  of  Shape  in  Active  Muscle 558 

The  Time-relations  of  Muscular  Contraction.  Myography.  Simple  Con- 
traction. Tetanus.  Isotony.  Isometry, 560 

Rapidity  of  Propagation  of  Muscular  Contraction 568 

Muscular  Work, _ 569 

The  Elasticity  of  Passive  and  Active  Muscle.     Myotonometry, 572 

Heat-production  in  Active  Muscle, 576 

The  Muscle-murmur, 578 

Fatigue  of  Muscle, 579 

Mechanism  of  the  Bones  and  Their  Attachments, 581 

Arrangement  and  Function  of  the  Muscles  in  the  Body, 583 

Gymnastic  Exercises  and  Therapeutic  Gymnastics.  Pathological  Varia- 
tions in  the  Motor  Functions 587 

SPECIAL  MOVEMENTS. 

Standing, 589 

Sitting, _ 592 

Walking,  Running,  Jumping, 592 

Comparative  Study  of  Motion, 596 

VOICE  AND  SPEECH. 

Scope  of  the  Voice.     Preliminary  Physical  Considerations  Concerning  the 

Production  of  Sound  in  Reed-apparatus 599 

Arrangement  of  the  Larynx 600 

Examination  of  the  Larynx 606 

Conditions  Influencing  the  Sounds  of  the  Vocal  Apparatus, 609 

Range  of  the  Voice, 6 10 

Speech.     The  Vowels, 6 1 1 

The  Consonants, 615 

Pathological  Variation  in  Voice  and  Speech,.  .  .  617 

Comparative.     Historical, 618 

GENERAL  PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM  AND 
ELECTRO-PHYSIOLOGY. 

General  Conception  of  the  Nervous  System.     Structure  and  Arrangement 

of  the  Elements  of  the  Nervous  System, , 621 

Cheniistry  of  Nervous  Tissue.     Mechanical  Properties  of  Nerves, 626 

Metabolism  in  Nerves, 628 

Irritability  of  Nerves.     Stimuli 629 

Diminished    Irritability;     Death   of   the    Nerve.      Nerve-degeneration   and 

Nerve-regeneration, 633 

ELECTRO-PHYSIOLOGY. 

Preliminary  Physical  Considerations.  The  Galvanic  Current.  Electro- 
motors. Conduction-resistance.  Ohm's  Law.  Conduction  through 

Animal  Tissues.     The  Rheocord, :  •  638 

The  Action  of  the  Galvanic  Current  upon  the  Magnetic  Needle.     The  Multi- 

plicator, •  •. • 64J 

Electrolysis.      Transition-resistance.      Galvanic      Polarization. 

Batteries  and  Unpolarizable  Electrodes.  Internal  Polarization  of 
Moist  Conductors.  Cataphoric  Action  of  the  Galvanic  Current.  Sec- 
ondary Resistance, •  •  •  •  •  • ;  •  643 

Induction.  The  Extra  Current.  Magnetization  of  Iron  by  the  Galvanic 
Current.  Voltaic  Induction.  Unipolar  Induction-effects.  Magneto- 
induction,  645 


XV111  TABLE    OF    CONTENTS. 

PAGE 

Du  Bois-Reymond's  Sliding  Induction-apparatus.      Pixii-Saxton's  Magneto- 
induction  Machine, 646 

Electrical   Currents  in   Resting  Muscle   and   Nerve.     Cutaneous   Currents. 

Glandular  Currents, 648 

Currents  of  Stimulated  Muscles  and  Nerves  and  of  Secretory  Organs, 652 

Currents  in  Nerves  and  in  Muscles  in  the  Electrotonic  State, 656 

Theories  and  Currents  in  Muscles  and  Nerves, 657 

Altered  Irritability  of  Nerve  and  Muscle  in  Electrotonus 660 

The  Development  and  the  Disappearance  of  Electrotonus.      The  Law  of 

Contraction.     The  Law  of  Polar  Stimulation, 663 

Rapidity  of  Conduction  of  the  Stimulus  in  Nerves, 667 

Double  Conduction  in  Nerves, 669 

Employment  of  Electricity  for  Therapeutic  Purposes.     Degenerative  Reac- 
tions of  Muscle  and  Nerve, 669 

Comparative.     Historical,    675 

PHYSIOLOGY  OF  THE  PERIPHERAL  NERVES. 

Classification  of  Nerve-fibers  According  to  Function, 677 

THE  CEREBRAL  NERVES. 

Olfactory  Tract  and  Bulb, 678 

Optic  Nerve  and  Tract, 679 

Oculomotor  Nerve, 680 

Trpchlear  Nerve, 682 

Trigeminal  Nerve, 683 

Abducens  Nerve, 693 

Facial  Nerve, 694 

Auditor}^  Nerve, 699 

Glossopharyngeal  Nerve, 703 

Vagus  Nerve 704 

Accessory  Nerve  of  Willis, 712 

Hypoglossal  Nerve, 713 

The  Spinal  Nerves, 713 

Sympathetic  Nervous  ^  System, 718 

Comparative.     Historical 721 

PHYSIOLOGY  OF  THE  NERVOUS  CENTERS. 

General  Considerations, 723 

THE  SPINAL  CORD. 

The  Structure  of  the  Spinal  Cord, 723 

The  Spinal  Reflexes, 728 

Inhibition  of  Reflexes, 731 

Centers  in  the  Spinal  Cord,    734 

Irritability  of  the  Spinal  Cord, 736 

Conducting  Paths  in  the  Spinal  Cord, 738 

THE  BRAIN. 

General  Outline  of  the  Structure  of  the  Brain, 741 

The  Medulla  Oblongata, 748 

Reflex  Centers  in  the  Medulla  Oblongata, 748 

The  Respiratory  Center  and  the  Innervation  ;of  the  Respiratory  Apparatus,  750 
The  Center  for  the  Inhibitory  Nerves  (Diminishing  the  Frequency  and  the 

Strength)  of  the  Heart  and  the  Fibers  Passing  to  the  Vagus, 758 

The  Center  for  the  Accelerator  and  Augmenting  Cardiac  Nerves  and  the 

Fibers  to  which  it  Gives  Rise, 760 

The  Vasomotor  Center  and  Nerves, 762 

The  Vasodilator  Center  and  Nerves, 771 

The  Spasm-center.  The  Sweating  Center, 773 

Psychic  Functions  of  the  Cerebrum, 774 

The  Motor  Cortical  Centers  of  the  Cerebrum 780 

The  Sensorial  Cortical  Centers, 785 


TABLE    OF    CONTENTS.  xix 

The  Cortical  Thermic  Center, 788 

Physiological  Topography  of  the  Surface  of  the  Cerebrum  in  Man 791 

The  Basal  Ganglia  of  the  Cerebrum,     The  Midbrain.      Forced  Movements. 

Other  Cerebral  Functions, 802 

Functions  of  the  Cerebellum, 807 

Protective  and  Nutritive  Apparatus  of  the  Brain 809 

Comparative.     Historical,    811 

PHYSIOLOGY  OF  THE  ORGANS  OF  SPECIAL  SENSE. 

Introductory  Remarks 813 

THE  VISUAL  APPARATUS. 

Preliminary  Anatomical  and  Histological  Observations.     The  Intraocular 

Pressure,   •  •  •  •  • 815 

Preliminary  Dioptric  Considerations, 823 

Application    of    Dioptric  Laws  to  the  Eye.     Construction  of   the    Retinal 

Image.     The  Ophthalmometer.     Erect  Images, 829 

Accommodation  of  the  Eye, 83 1 

Refractive  Power  of  the  Normal  Eye.     Anomalies  of  Refraction, 835 

Measure  of  the  Power  of  Accommodation, 837 

Spectacles,    839 

Chromatic  and  Spherical  Aberration.     Defective  Centering  of  the  Refracting 

Surfaces.     Astigmatism 840 

The  Iris, 841 

Entoptic  Phenomena.     Subjective  Optical  Manifestations 844 

Illumination  of  the  Eye,  and  the  Ophthalmoscope, 847 

The  Function  of  the  Retina  in  Vision, 850 

Perception  of  Colors, 856 

Color-blindness:  Its  Practical  Importance, 860 

Time-relations    of    Retinal    Stimulation.      Positive    and    Negative    After- 
images.    Irradiation.     Contrast,    862 

Ocular  Movements  and  Ocular  Muscles, 866 

Binocular  Vision, 870 

Single     Vision.     Identical     Retinal     Points.     Horopter.      Suppression     of 

Double  Images, 871 

Stereoscopic  Vision.     Judgment  of  Solidity, 873 

Estimation  of  Size  and  of  Distance.     False  Estimates  of  Size  and  Direction,  877 

Organs  for  the  Protection  of  the  Eye 879 

Comparative.     Historical,    881 

THE  AUDITORY  APPARATUS. 

Plan  of  the  Structure  of  the  Ear, 885 

Preliminary  Physical  Considerations, ...  886 

Auricle.     External  Auditory  Canal, 887 

The  Tympanic  Membrane, 888 

The  Auditory  Ossicles  and  Their  Muscles 890 

Eustachian  Tube.     Tympanic  Cavity 894 

Sound-conduction  in  the  Labyrinth, 896 

Structure  of  the  Labyrinth  and  the  Terminations  of  the  Auditory  Nerve, .  .  897 
Quality  of  Auditory  Perceptions.     Perception  of  the  Pitch  and  Intensity 

of  Tones, 899 

Perception  of  Timbre.     Analysis  of  Vowels, . 903 

Function  of  the  Labyrinth  in  the  Act  of  Hearing, 907 

Simultaneous  Action  of  Two  Tones.      Harmony.     Beat.      Discord.      Differ- 
ential Tones  and  Summation -tones, 908 

Auditory    Perception.     Fatigue    of    the    Ear.     Objective    and    Subjective 

Hearing.     Associated  Sensations.     Auditory  After-sensations. ..  910 

Comparative.     Historical,    912 

THE  OLFACTORY  APPARATUS. 

Structure  of  the  Olfactory  Apparatus 913 

Sensation  of  Smell, .  9i4 


XX  TABLE    OF    CONTENTS. 


THE  GUSTATORY  APPARATUS. 

Situation  and  Structure  of  the  Organs  of  Taste 916 

Gustatory  Sensations, 917 

THE  TACTILE  APPARATUS. 

Terminations  of  the  Sensory  Nerves, 920 

Sensory  and  Tactile  Sensations, 922 

Sense  of  Space, 924 

The  Pressure-sense, 927 

The  Temperature-sense, .  .  930 

Common  Sensation.     Pain, 934 

The  Muscular  Sense.     Power-sense, 936 

PHYSIOLOGY  OF  REPRODUCTION  AND  DEVELOPMENT. 

Varieties  of  Generation, 938 

The  Seminal  Fluid, 942 

The  Ovum, 946 

Puberty, . 951 

Menstruation, 951 

Erection, 955 

Ejaculation.     Reception  of  the  Seminal  Fluid, .  . 957 

Impregnation  of  the  Ovum, 958 

Cleavage,  Morula,  Blastula,  Gastrula,  Formation  of  the  Germinal  Layers. 

First  Rudiments  of  the  Embryo, 961 

Formations  from  the  Epiblast, 966 

Formations  from  the  Hypoblast  and  the  Mesoblast, 969 

Folding  Off  of  the  Embryo.     Formation  of  the  Heart  and  the  First  Circu- 
lation,      970 

Further  Development  of  the  Body, 972 

Formation  of  the  Amnion  and  the  Allantois, 974 

Human  Fetal  Membranes.     Placenta.     Fetal  Circulation, 975 

Chronology  of  Human  Development.     Fetal  Movements, 980 

Development  of  the  Osseous  System, 983 

Development  of  the  Vascular  System, 990 

Development  of  the  Alimentary  Canal, 993 

Development  of  the  Urinary  and  Sexual  Organs, .  . 995 

Development  of  the  Central  Nervous  System, 1000 

Development  of  the  Organs  of  Special  Sense, 1001 

Parturition,    1002 

Comparative.     Historical,    1004 


LIST  OF   ILLUSTRATIONS. 


FIG.  pAGE 

1.  Human  and  Amphibian  Colored  Blood-corpuscles 32 

2.  Apparatus  of  Abbe  and  Zeiss  for  Counting  the  Corpuscles 33 

3.  The  Melangeur  Pipet  or  Mixer, 33 

4.  Red  Blood-corpuscles, 34 

5.  Formation   of   Red   Blood-corpuscles    within   " Vaso-formative   Cells," 

from  the  Omentum  of  a  Rabbit  Seven  Days  Old, 42 

6.  White  Blood-corpuscles  of  Man  and  Frog, 45 

7.  Human  Leukocytes,  showing  Ameboid  Movements,    47 

8.  Various  Forms  of  Leukocytes  and  Erythrocytes, 48 

9.  " Blood-plates"  and  their  Derivatives, 49 

10.  Hemoglobin-crystals, 52 

1 1 .  V.  Fleischl's  Hemometer, 53 

1 2 .  Diagrammatic  Representation  of  the  Spectroscope  for  Study  of  the  Ab- 

sorption-spectra of  the  Blood, 55 

13.  14.  The  Absorption-spectra  of  Oxyhemoglobin,  and  of  Gas- free  Hemo- 

globin with  Increasing  Concentration, 56 

15.  The  Various  Absorption-spectra  of  Hemoglobin, 57 

1 6.  The  Absorption-spectra  of  Hematoporphyrin, 60 

1 7 .  Hemin-crystals 62 

1 8.  Hemin-crystals  Prepared  from  Blood-stains, 62 

19.  Hematoidin-crystals 63 

20.  Diagrammatic  Representation  of  Pfluger's  Pump  for  the  Extraction  of 

the  Gases  of  the  Blood, 77 

21.  Diagrammatic  Representation  of  the  Circulation, 88 

22.  Course  of  the  Muscle-fibers  in  the  Left  Auricle  (Joh.  Reid).     Distribu- 

tion of  Transversely  Striated  Muscle-fibers  on  the  Superior  Vena  Cava 

(Flischer),   90 

23.  Course  of  the  Muscle-fibers  in  the  Ventricles  (C.  Ludwig)  , 91 

24.  Semilunar  Valves  Closed  and  Opened, 93 

2  5 .   Diagrammatic  Representation  of  the  Auricular  Systole  with  Ventricular 

Diastole,  and  of  Auricular  Diastole  with  Ventricular  Systole, 96 

26.  Plaster  Cast  of  the  Ventricles  of  the  Human  Heart,  Viewed  from  Behind 

and  Above, 98 

27.  The  Closed  Pulmonary  Semilunar  Valves  of  Man,  Viewed  From  Below, .  99 

28.  Curves  of  the  Apex-beat, 101 

29.  Changes  of  the  Heart  during  Systole,  and  Sections  of  the  Thorax, 102 

30.  Contraction-curves  from  the  Ventricle  of  a  Rabbit  Registered  on  a  Plate 

Attached  to  a  Vibrating  Tuning-fork, 105 

3 1 .  Curves  Showing  the  Movements  of  the  Separate  Portions  of  the  Heart 

(Chauveau  and  Marey) , 1 06 

32.  Simultaneous  Record  Showing  Cardiogram,  the  Curve  of  the  Ventric- 

ular   Pressure  and  that  of  the  Aortic    Pressure  from  the    Dog  (K. 

Hurihle) , 107 

33.  Various  Forms  of  Pathological  Apex-beat  Curves, 109 

34.  Topography  of  the  Thorax  and  of  the  Thoracic  Viscera  (v.  Luschka 

and  v.  Dusch) , in 

35.  Landois'  Cardiopneumograph,  and  Cardiopneumatic  Curves  Obtained 

with  its  Aid, 122 

36.  Apparatus  for  the  Demonstration  of  the  Influence  of  Respiratory  Ex- 

pansion and  Contraction  of  the  Thorax  on  the  Heart  and  the  Cir- 
culation,                     124 

37.  Pressure-vessel  Filk'<l  with  Water 125 

38.  A   Pressure- vessel, 126 

xxi 


XX11  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE 

39.  Small  Arterial  Twig  Showing  the  Individual  Layers  of  the  Arterial  Wall,  130 

40.  Capillary  Vessels, 131 

41.  Poiseuille's  Box-cabinet  Sphygmometer, 134 

42.  The  Tubular  Sphygmometer  of  Herisson  and  Chelius, 134 

43.  Marey's  Sphygmograph  (Diagrammatic), 135 

44.  Brondgeest's  Pansphygmograph  Constructed  on  Upham's  and  Marey's 

Principle  of  the  Propagation  of  Movement  through  Air-containing 

Drums  Covered  with  Elastic  Membranes, 135 

45.  Landois'  Angiograph  Represented  Diagrammatic  ally 136 

46.  Dudgeon's  Sphygmograph, 137 

47.  Sphygmographic  Tracing  from  the  Radial  Artery  made  with  Landois' 

Angiograph  Attached  to  a  Vibrating  Tuning-fork, 138 

48.  Landois'  Gas-sphygmoscope, 138 

49.  Hemautographic  Tracing  from  the  Posterior  Tibial  Artery  of  a  Large 

Dog, 139 

50.  Sphygmographic  Tracings  from  Arteries, 140 

51.  Normal  Pulse-production  of  the  Dicrotic  Pulse, 143 

52.  Alternating  Pulse, 145 

53.  Tracing  from  the  Posterior  Tibial  Artery,  Recorded  on  the  Tablet  At- 

tached to  a  Vibrating  Tuning-fork  by  means  of  Landois'  Angiograph, .  147 

54.  Anacrotic  Tracings  from  the  Radial  Artery 148 

55.  Anacrotic  Pulse  Curves, 149 

56.  Influence  of  Respiration  on  the  Sphygmographic  Tracing  (RiegeF) , 150 

57.  The  Effect  of  Marked  Expiratory  and  Inspiratory  Pressure  on  Sphyg- 

mographic Curves, 151 

58.  Paradoxical  Pulse  (Kussmaul) , 152 

59.  Variations  in  the  Shape  of  Sphygmographic  Curves  Produced  by  In- 

creasing the  Pressure, : 152 

60.  Method  of  Recording  the  Pulse-curves  Obtained  from  an  Elastic  Tube 

on  a  Tablet  Attached  to  a  Vibrating  Tuning-fork, 154 

61.  Tracings  from  the  Carotid  and  Posterior  Tibial  Arteries 155 

62.  Tracing  from  the  Ulnar  Artery  on  a  Recording  Surface  Attached  to  a 

Vibrating  Tuning-fork, 156 

63.  Vibration  Curves  and  Apparatus  for  Registering  Same 158 

64.  Model  of  the  Circulation  by  Ernst  Heinrich  Weber, 161 

65.  Ludwig's  and  Pick's  Kymographs  (C.  Ludwig  and  Einbrodt) 163 

66.  Adolph  Pick's  Flat-spring  Kymograph, 164 

67.  Hurthle's  Kymograph, 164 

68.  A.  W.  Volkmann's  Hemodromometer  and  C.  Ludwig's  Rheometer, .  ...  172 

69.  Vierordt's  Hemotachometer;    Chauveau's  and  Lortet's  Dromograph; 

Dromographic  Curve, 173 

70.  Diagrammatic  Representation  of  Cybulski's  Photohemotachometer, .  .  .  174 

7 1 .  Small  Mesenteric  Vessel  from  a  Frog  showing  the  Migration  of  Leuko- 

cytes,    181 

72.  Various  Forms  of  Venous  Pulse,  chiefly  after  Friedreich 186 

73.  Mosso's  Plethysmograph, 189 

74.  Diagrammatic  Representation  of  the  Circulation 198 

75.  Cross-section  of  Several  Pulmonary  Alveoli, 202 

76.  Hutchinson's  Spirometer, 206 

77.  Brondgeest's  Tambour  and  Curve, 208 

78.  Air- volume  Recorder  (Pneumoplethysmograph)   (Gad), 209 

79.  Pneumatograms  Recorded  by  Means  of  Riegel's  Stethograph, 209 

80.  Frontal  Section  of  the  Thorax  at  the  Extremity  of  the  Twelfth  Rib 

on  Each  Side  to  Demonstrate  the  Form  of  the  Diaphragm  During 

Expiration  and  Inspiration, 213 

81.  Diagrammatic   Representation  of  the  Mechanism  of  the   Intercostal 

Muscles, .  . 216 

82.  Cyrtometer-curve  from  a  Case  of  Left-sided  Retraction  of  the  Thorax 

in  a  Twelve-year-old  Girl  (Eichhorsf) , 217 

83.  Sibson's  Thoracometer, 218 

84.  Topography  of  the  Boundaries  of  the  Lungs  and  the  Heart  during  In- 

spiration and  Expiration  (v.  Dusch} , 219 

85.  Apparatus  for  the  Collection  of  Expired  Air  (Andral  and  Gavarrei}; 

Carl  Vierordt's  Anthracometer, 226 

86.  Respiration  Apparatus  of  Scharling 227 


LIST    OF    ILLUSTRATIONS.  Xxiii 

FIG-  PAGE 

87.  Diagrammatic    Representation    of    Regnault    and    Reiset's    Respira- 

tion Apparatus, 228 

88.  Diagram  of  v.  Pettenkofer's  Respiration  Apparatus 229 

89.  Apparatus  for  Measuring  the  Temperature  of  the  Expired  Air, 231 

90.  Pulmonary  Catheter 239 

91.  Stratified    Ciliated    Cylindrical    Epithelium    of    the    Larynx    (Horse) 

(Toldf), 246 

92.  Objects  Found  in  the  Sputum, 250 

93.  Section  through  Lymph-follicles  of  the  Root  of  the  Tongue  ($chenk) ....  256 

94.  Histology  of  the  Salivary  Glands, 257 

95.  Diagrammatic  Representation  of  a  Salivary  Gland, 258 

96.  Potato  Starch, 265 

97.  Apparatus  for  the  Quantitative  Estimation  of  Sugar 268 

98.  The  Soleil-Ventzke  Saccharimeter, 269 

99.  Longitudinal  Section  through  an  Incisor  Tooth 272 

100.  Transverse  Section  through  Dentine, 273 

10 1.  Interglobular  Spaces  in  the  Dentine 273 

102.  Dentine  and  Enamel, 274 

103.  Transverse  Section  of  the  Root, 274 

104.  ] 

105.  y  Development  of  a  Tooth, 274,  275 

106.  J 

107.  Transverse  Section  through  the  Esophagus, 279 

108.  The  Perineum  and  its  Muscles, 284 

109.  The  Levator  Ani  and  External  Sphincter  Ani  Muscles, 285 

no.  Sectional  View  of  the  Gastric  Mucous  Membrane,  showing  the  Crater- 
like  Depressions  of  the  Gastric  Crypts, 289 

in.  Fundus-gland  of  the  Stomach, 290 

112.  Goblet-cells  of  the  Stomach.     Pyloric  Gland  of  the  Stomach, 290 

113.  Portion  of  a  Gastric  Gland, 290 

114.  Vertical  Section  through  the  Gastric  Mucous  Membrane, 291 

115.  Changes  in  the  Cells  of  the  Pancreas  in  the  Different  Stages  of  Ac- 

tivity,   . 302 

116.  Diagrammatic  Representation  of  an  Hepatic  Lobule, 309 

117.  Various  Appearances  of  the  Liver-cell 310 

118.  Blood-capillaries,  Finest  Biliary  Ducts,  and  Liver-cells,  in  Their  Mu- 

tual Relations  in  the  Rabbit's  Liver  (E.  Hering) 310 

119.  Interlobular  Bile-duct  from  the  Human  Liver  (Schenk),.  ...  310 

1 20.  Longitudinal  Section  through  the  Small  Intestine  of  a  Dog 327 

121.  Transverse  Section  through  Lieberkuhn's  Glands, 328 

122.  Bacterium  Aceti  and  Bacillus  butyricus, 330 

123.  Hay-bacillus  (Bacillus  subtilis) , 332 

124.  Longitudinal  Section  through  the  Large  Intestine, 336 

125.  Feces, 337 

126.  Bacteria  of  Feces, . 339 

127.  Structure  of  the  Absorption-apparatus  of  a  Villus, .  .  349 

128.  Blood-vessels  of  an  Intestinal  Villus, 350 

129.  Apparatus  for  Diosmosis, 352 

130.  Origin  of  the  Lymph-channels, 361 

131.  Blood-vessels,  Recticulum,  and  Sheath  of  a  Lymph-follicle, 364 

132.  Part  of  a  Lymph-gland, 365 

133.  Water  Calorimeter  (Favre  and  Silbermann) , 379 

134.  Walferdin's  Metastatic  Thermometer, 383 

135.  Diagrammatic   Representation  of  Thermo-electric  Apparatus  for  the 

Measurement  of  Temperature, 384 

136.  Variations  in  the  Bodily  Temperature  during  Health  within  Twenty- 

four  Hours, •  •  •  •                                               •  •  •  393 

137.  Milk-glands  during  Inaction  and  Secretion, .  .  417 

138.  Section  through  a  Grain  of  Wheat, 427 

139.  Section  through  a  Potato, 428 

140.  Yeast-cells  Growing, 429 

141.  Composition  of  Animal  and  Vegetable  Foods, .  .  436 

142.  Structure  of  the  Kidneys 47° 

143.  Graduated  Cylinder  and  Flask  for  Measuring  the  Amount  of  Urine,  ....  473 

144.  Urinometer, 473 


XXIV  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE 

145.  Graduated  Buret, 475 

146.  Urea  and  Urea  Nitrate, 476 

147.  Graduated  Pipet, 479 

148.  Different  Forms  of  Uric  Acid, 481 

149.  Kreatinin-zinc  Chlorid, 484 

150.  Hippuric  Acid, 485 

151.  Spectrum  of  Urobilin  in  Acid  Urine, 486 

152.  Spectrum  of  Urobilin  in  Alkaline  Urine, 486 

153.  Sediment  due  to  Acid  Urinary  Fermentation, 493 

154.  Sediment  due  to  Ammoniacal  Urinary  Fermentation 494 

155.  Micrococcus  ureas, 494 

156.  Esbach's  Albuminimeter 496 

157.  Thorn-apple  shaped  Blood-corpuscles  in  the  Urine, 497 

158.  Peculiar  Changes  in  the  Shape  of  the  Red  Blood-corpuscles  in  Case  of 

Renal  Hematuria  (Friedreich} , 497 

159.  Red  and  White  Blood-corpuscles  of  Varying  Size, 498 

1 60.  Greatly  Shrunken  Red  Blood-corpuscles  in  the  Urine  from  a  Case  of 

Catarrh  of  the  Bladder,  in  the  midst  of  numerous  Leukocytes  and 

Small  Crystals  of  Triple  Phosphates, 498 

161.  Spectroscope  for  Examination  of  the  Urine  as  to  the  Presence  of  Hemo- 

globin,      499 

162.  Cystin  and  Oxalate  of  Lime, 502 

163.  Leucin,  Tyrosin  and  Ammonium  Urate, 503 

164.  Fungi  in  Urine, 504 

165.  Epithelial  Tube-casts, 504 

166.  Blood-casts, 505 

167.  Casts  of  Leukocytes  (v.  Jaksch) , 505 

168.  Acid  Sodium  Urate  in  the  Form  of  Tube-casts 505 

169.  Finely  Granular  Tube-casts, 505 

170.  Coarsely  Granular  Tube-casts  (v.  Jaksch) , 505 

171.  Hyaline  Casts, 505 

172.  Calcic  Carbonate  and  Phosphate, 506 

173.  Ammonio-magnesium  Phosphate, 507 

174.  Imperfectly  Developed  Crystals  of  Ammonio-magnesium  Phosphate,.  .  507 

175.  Acid  Ammonium  Urate  (v.  Jaksch} , 507 

176.  Basic  Magnesium  Phosphate, 507 

177.  Lower  Portion  of  the  Male  Bladder,  with  the  Commencement  of  the 

Ureter,  Opened  through  a  Median  Incision  in  the  Anterior  Wall,  and 

spread  out  (Henle) , 518 

178.  Histology  of  the  Skin  and  the  Epidermoidal  Structures, 526 

179.  Cutaneous  Papillae  Deprived  of  their  Epidermis  and  the  Vessels  In- 

jected,   527 

1 80.  Transverse  Section  of  One-half  of  a  Nail,  through  the  True  Nail-bed 

(Biesiadecki} , 528 

181 .  Transverse  Section  of  a  Hair  below  the  Neck  of  the  Hair- follicle, 530 

182.  Longitudinal  Section  through  a  Hair- follicle,  with  the  Hair  in  Pro- 

cess of  Change  (v.  Ebner) , 530 

183.  Sebaceous  Gland  with  a  Lanugohair, 532 

184.  Histology  of  Muscular  Tissue, 543 

185.  Muscle-fibers  with  Nerve-ending,  from  the  Lizard  (W.  Kuhne), 544 

186.  Cross-section  through  the  Gastrocnemius  Muscle  of  the  Frog  (Grutzner),  545 

187.  Unstriated  Muscle-fibers,  isolated  by  means  of  Diluted  Alcohol, 546 

1 88.  Special  Forms  of  Unstriated  Muscle-fibers  from  the  Muscular  Coat  of 

the  Aorta  (v.  Ebner) , 546 

189.  Muscle-cells  from  the   Frog's   Stomach  with   Distinct   Fibrils    (Engel- 

mann) , 546 

190.  Sensory  Nerve  in  a  Tendon, 547 

191.  The  Microscopic  Phenomena  of  Muscular  Contraction  in  the  Individual 

Elements  of  the  Fibrils  (Engelmann), 559 

192.  Diagrammatic  Representation  of  v.  Helmholtz's  Myograph 561 

193.  Myogram  of  an  Isotonic  Contraction, 562 

194.  Muscle  Curves, 564 

195.  Muscle  Curves,  Tetanus, 566 

196.  Curves  of  Voluntary  Impulses, 567 

197.  Isometric  Muscular  Act 568 


LIST    OF    ILLUSTRATIONS.  XXV 

FIG-  PAGE 

198.  Blix's  Elasticity  Recorder, 574 

199.  Diagrammatic  Representation  of  the  Action  of  Muscles  on  the  Bones, .  .  585 

200.  Phases  of  the  Movement  of  Walking, 593 

201.  Slow  Walking,  Photographed  in  Instantaneous  Pictures  (Marey),.  .  594 

202.  Instantaneous  Photographs  of  a  Runner  (Marey), 594 

203.  Instantaneous  Photographs  of  a  High  Jump  (Marey), 595 

204.  Anterior  View  of  the  Larynx,  with  its  Ligaments  and  Muscular  In- 

sertions   60 1 

205.  Posterior  View  of  the  Larynx,  after  Removal  of  the  Muscles 60 1 

206.  Posterior  View  of  the  Larynx,  with  the  Muscles 602 

207.  Nerves  of  the  Larynx, 602 

208.  Diagrammatic  Horizontal  Section  through  the  Larynx, 603 

209.  Diagrammatic  Horizontal  Section  through  the  Larynx,  to  Illustrate 

the  Action  of  the  Arytenoid  Muscles, 603 

210.  Diagrammatic  Horizontal  Section  through  the  Larynx,  to  Illustrate 

the  Action  of  the   Internal  Thyroarytenoid  Muscles  in   Narrowing 

the  Glottis, 604 

211.  Vertical  Section  of  the  Head  and  Neck 605 

212.  Method  of  Making  a  Laryngoscopic  Examination, 606 

213.  The  Laryngoscopic  Image  During  Respiration, 606 

214.  Image  of  the  Larynx  when  a  Sound  is  Begun, 607 

215.  View  of  the  Trachea  as  far  as  the  Bifurcation 607 

216.  Position  of  the  Laryngeal  Mirror  in  the  Practice  of  Rhinoscopy 607 

217.  The  Rhinoscopic  Image, 608 

218.  Parts  Concerned  in  Phonation, 613 

219.  Tumors  of  the  Vocal  Cords,  Causing  Diphthongia, 617 

220.  Histology  of  Nervous  Tissues, 623 

221.  Medullated  Nerve-fiber  Stained  Black  by  Osmic  Acid 624 

222.  Transverse  Section  through  a  Portion  of  the  Median  Nerve 624 

223.  Degeneration  and  Regeneration  of  Nerves, 634 

224.  Diagrammatic  Representation  of  the  Rheocord  of  du  Bois-Reymond, .  .  641 

225.  Scheme  of  a  Galvanometer, 642 

226.  Scheme  of  an  Induction  Machine, 647 

227.  Magneto-induction  Apparatus  with  Stohrer's  Commutator, 647 

228.  Scheme  of  the  Muscle  Current, 649 

229.  Diagrammatic  Representation  of  the  Capillary  Electrometer, 649 

230.  Diagrammatic  Representation  of  Bernstein's  Differential  Rheotome,.  .  .  655 

231.  Nerve  Current  in  Electrotonus, 656 

232.  Diagrammatic  Representation  of  the  Electrotonic    Relations  of   Irri- 

tability, .'.  . 661 

233.  Testing  the  Irritability  in  Electrotonus, '.  .  .  662 

234.  Diagrammatic    Representation    of   the    Distribution    of   the    Electric 

Current  in  the  Arm  on  Galvanization  of  the  Ulnar  Nerve, 662 

235.  v.  Helmholtz's  Method  for  Determining  the  Propagation- velocity  of 

the  Nerve-stimulus, 668 

236.  Motor  Points  of  the  Radial  Nerve  and  of  the  Muscles  supplied  by 

it.     Dorsal  Aspect  of  the  Upper  Extremity  (Eichhorst) , 670 

237.  Motor  Points  of  the  Median  and  Ulnar  Nerves,  as  well  as  of  the  Muscles 

supplied  by  them.    Palmar  Aspect  of  the  Upper  Extremity  (Eichhorst) ,  670 

238.  Motor  Points  of  the  Sciatic  Nerve  and  its  Branches,  the  Peroneal  and 

Tibial  Nerves  (Eichhorst) , 671 

239.  Motor  Points  of  the  Peroneal  and  Tibial  Nerves  on  the  Anterior  As- 

pect of  the  Leg  and  Thigh.     Peroneal  Nerve  on  the  left,  Tibial  Nerve 

on  the  Right  (Eichhorst) , ;  .  672 

240.  Diagrammatic   Representation   of  the   Semidecussation  of  the  Optic 

Nerves, 679 

241.  Medulla  Oblongata  and  Quadrigeminate  Bodies,  Magnified,.  .  .  681 

242.  Medulla  Oblongata  and  Quadrigeminate  Bodies,  Magnified,.  .  .  683 

243.  Semidiagrammatic    Representation   of  the   Ocular   Nerves,   the   Con- 

nections of  the  Trigeminus  and  Its  Ganglia  and  Those  of  the  Facial 

and  Glossopharyngeal  Nerves, 690 

244.  Distribution  of  the  Sensory  Nerves  of  the  Head,  together  with  the  Situ- 

ation of  the  Motor  Points  on  the  Neck 691 

245.  Motor  Points  of  the  Facial  Nerve  and  of  the  Muscles  Supplied  by  It 

(Eichhorst) , 696 


XXVI  LIST    OF    ILLUSTRATIONS. 

FIG-  PAGE 

246.  Scheme  of  the  Branches  of  Vagus  and  Accessorius, 702 

247 .  Distribution  of  the  Cutaneous  Nerves  of  the  Upper  Extremity  (Henle} , .  714 

248.  Distribution  of  the  Cutaneous  Nerves  of  the  Lower  Extremity  (Henle} , .  715 

249.  Diagrammatic  Representation  of  the  Course  of  a  Thoracic  Branch  of 

the  Sympathetic 718 

250.  Transverse  Section  of  the  Spinal  Cord  at  the  Level  of  the  Eighth  Dor- 

sal Nerve  (Schwalbe) , 724 

251.  Scheme  of  the  Nerve  Distribution  of  the  Spinal  Cord, 725 

252.  System  of  Conducting  Tracts  in  the  Spinal  Cord,  at  the  Level  of  the 

Third  Dorsal  Vertebra  (Flechsig) , 726 

253.  Diagrammatic  Representation  of  the   Principal  Tracts  of  the  Spinal 

Cord, 727 

^254.   Diagrammatic  Representation  of  the  Structure  of  the  Brain, 743 

"255.  Course  of  the  Paths  for  Voluntary  Movement, 745 

256.  Course  of  the  Motor  and  Sensory  Paths  through  a  Transverse  Section 

of  the  Spinal  Cord, 746 

257.  Course  of  the  Sensory  Fibers  from  the  Posterior  Roots  through  the 

Spinal  Cord  upward  to  the  Cerebrum, 747 

258.  Cerebrum  of  Dog,  Rabbit,  Pigeon,  Frog,  and  Carp, 782 

259.  The    Psycho-optic    and    Psycho-auditory    Centers    and    the    Sensory 

Sphere  of  the  Dog's  Brain  (H.  Munk},. 786 

260.  The  Cerebrum  with  the  Principal  Convolutions  and  Sulci  (A.  Ecker) 

in  its  Longitudinal  Relation  to  the  Skull, 793 

261.  Secondary  Degeneration  of  the  Motor  Tracts  in  the  Cerebral  Peduncle, 

the  Pons  and  the  Pyramid  (Charcot) , 795 

262.  View  of  the  Median  Surface  of  the  Human  Brain, 796 

263.  Cerebrum  of  Man, 803 

264.  Frontal  Section  through  the  Cerebrum, 805 

265.  Lymphatic  Structure  of  the  Cornea, 815 

266.  Meridional  Section  through  the  Corneoscleral  Junction, 816 

267.  Diagrammatic  Representation  of  the  Blood-vessels  of  the  Eye   (Th. 

Leber) , 8 1 8 

268.  Layers  of  the  R.etina, 820 

269.  Transverse  Section  of  a  Mammalian  Retina  (Ramon  y  Cajal), 820 

270.  Fibers  of  the  Lens, 82 1 

271.  Horizontal  Section  through  the  Optic  Nerve,  at  its  Entrance  into  the 

Eyeball  through  the  Coats  of  the  Eye, 822 

272.  Action  of  Lenses  on  Light, 824 

273.  Refraction  of  Light, 825 

274.  Construction  of  the  Refracted  Ray, 825 

275.  Optical  Cardinal  Points, 826 

276.  Construction  of  the  Direction  of  the  Refracted  Ray 827 

277.  Construction  of  the  Image, 827 

278.  Refracted  Ray  in  Several  Media, 828 

279.  Visual  Angle  and  Retinal  Image, 829 

280.  Ophthalmometer  (v.  Helmholtz), 830 

281.  Anterior  Quadrant  of  a  Horizontal  Section  of  the  Eyeball, 832 

282.  Diagrammatic  Representation  of  Accommodation  for  Near  and  Far 

Objects, 833 

283.  The  Images  of  Purkinje-Sanson, 834 

284.  Schemer's  Experiment, 835 

285  and  286.   Refractive  Condition  of  the  Normal  Eye,  at  Rest  and  in  Ac- 
commodation,    836 

287  and  288.   Refractive  Condition  of  the  Short-sighted  and  the  Far-sighted 

Eye, 836 

289.  Power  of  Accommodation, 838 

290.  Cylindrical  Glasses  for  Astigmatism, 841 

291.  The  Entoptic  Shadows, 845 

292.  Apparatus  for  Illuminating  the  Back  of  the  Eye 847 

293.  Scheme  of  the  Indirect  Method, .  .  . 848 

294.  Action  of  a  Divergent  Lens, 848 

295.  Action  of  a  Divergent  Lens, 848 

296.  The    Optic-nerve    Entrance,   with   the    Surrounding   Structures,    of   a 

Normal  Eyeground  (Ed.  Jaeger) , ' 849 

297.  Mechanism  of  the  Orthoscope, 850 


LIST    OF    ILLUSTRATIONS.  XXvii 


FIG. 


298.  Horizontal  Section  of  the  Right  Eye, gr2 

299.  Perimetric  Chart  of  a  Healthy  and  of  a  Diseased  Eye, 854 

300.  Geometric  Color-chart, 858 

301.  Diagrammatic  Representation  of  the  Young- Helmholtz  Color  Theory  .  .  859 

302.  Lines  of  Traction  and  Axes  of  Rotation  of  the  Ocular  Muscles, .' .  .  869 

303.  Diagrammatic  Representation  of  Identical  and  Nonidentical  Retinal 

Points, 872 

304.  Horopter  for  the  Secondary  Position,  with  Convergence  of  the  Visual 

Axes, 872 

305.  I,  Diagrammatic   Representation  of  Brewster's  stereoscope;    II,  that 

of  Wheatstone;   III,  two  stereoscopic  drawings;    IV,  v.  Helmholtz's 

telestereoscope, 874 

306.  Wheatstone's  Prism-pseudoscope, 875 

307.  Ewald's  Mirror  Pseudoscope, 875 

308.  Rollett's  Glass  Plate  Apparatus, 878 

309.  Vertical  Section  through  the  Upper  Lid  (Waldeyer), 880 

310.  Eye  of  the  Cross-spider, 882 

311.  Individual  Eye  of  a  Libellula  Larva  (Dragon-fly), 882 

312.  Eye  of  a  Sea-snail  (Patella  coerulea), .  .  . 883 

313.  Eye  of  a  Sea-snail  (Haliotis  tuberculata) , 883 

314.  Diagrammatic  Representation  of  the  Auditory  Apparatus, 886 

315.  The  External  Auditory  Canal,  and  the  Tympanum, 888 

316.  Tympanic  Membrane  and  Auditory  Ossicles  (left)  viewed  from  Within 

(from  the  tympanic  cavity) , 889 

317.  Tympanic  Membrane  of  a  Newborn  Infant,  viewed  from  the  Outside, 

with  the  Handle  of  the  Malleus  shining  through, 889 

318.  Tympanic  Membrane  and  Ossicles  (left)  viewed  from  Within, 889 

319.  The  Auditory  Ossicles  (right), 891 

320.  Tympanic  Membrane  and  Auditory  Ossicles  (left),  enlarged, 892 

321.  Tensor  Tympani  Muscle;    the  Eustachian  Tube  (left),   893 

322.  Stapedius  Muscle  (right) , 894 

323.  Section  through  Eustachian  Tube  (diagrammatic), 895 

324.  External  Conformation  of  the  Labyrinth, 896 

325.  Scheme  of  the  Cochlea, 897 

326.  Organ  of  Corti, 898 

327.  Curve  of  a  Muscle  Note  and  Its  Overtones, 904 

328.  Flame  Pictures  and  Phonautographic  Tracings  of  the  Vowels, 906 

329.  Olfactory  Cells, 914 

330.  Nasal  Cavity  and  Nasopharynx, 914 

331.  Circumvallate  Papilla  and  Taste-buds, 917 

332 .  Vertical  Section  of  Skin, 920 

333.  Vater-Pacinian   Corpuscle, 921 

334.  Spherical  End-bulb  in  the  Human  Conjunctiva  (Longworth) , 921 

335.  Longitudinal   End-bulb, . 921 

336.  Grandry-Merkel  Corpuscles, 922 

337.  Tactile  Discs  with  Nerves  from  the  Epidermis  (snout  of  the  pig) 922 

338.  Nerve-endings  in  the  Corneal  Epithelium, 923 

339.  Compasses  for  Testing  Sensation, 926 

340.  Sieveking's  Esthesiometer, 926 

341.  Pressure  Points, 927 

342.  Landois'  Mercurial  Pressure-balance, 929 

343.  Cold-points  and  Heat-points, 931 

344.  Topography  of  the  Cold-sense  and  the  Heat-sense  on  the  Same  Part 

of  the  Anterior  Surface  of  the  Thigh, 933 

345.  Ovum  from  the  Uterus  of  a  Sexually  Mature  Proglottis  of  the  Taenia 

solium, 938 

346.  Encapsulated  Cysticerci  (from  Taenia  solium)  in  the  Flesh  of  the  Sar- 

torius  Muscle  in  Man, 938 

347.  Cysticerci  from  Taenia  solium,  with  their  Connective-tissue  Capsule 

Removed,    938 

348.  Cysticercus  from  Taenia  solium  with  Everted  Hollow  Bud  (Cephalic 

Segment) ,    939 

349.  Portion  of  an  Echinococcus-cyst  with  Brood-capsule,.  .  939 

350.  Taenia  mediocanellata •  •  •  939 

351.  Sexually  Active  (Middle)  the  Proglottis  of  Taenia  mediocanellata  (5<>m- 

tner) , 94° 


XXV111  LIST    OF    ILLUSTRATIONS. 

FIG.  PAGE 

352.  Heads   of  Taenia  solium  and  Tcenia  mediocanellata  and  Mature  Pro- 

glottids  of  Each 941 

353.  Seminal  Crystals, 942 

354.  Spermatozoa, 943 

355.  Spermatogenesis  (semidiagrammatic) , 945 

356.  A  Fresh  Ovum  from  the  Ovary  of  a  Woman  Thirty  Years  Old, 947 

357.  Mature  Rabbit  Ovum  (Waldeyer) , 948 

358.  Ovary  and  Polar  Globules, 949 

359.  Diagrammatic  Representation  of  a  Mesoblastic  Ovum  (Waldeyer), 950 

360.  White  and  Yellow  Yolk-globules 950 

361.  Diagrammatic  Longitudinal  Section  of  a  Hen's  Egg, 950 

362.  The  Ovary  and  the  Fallopian  Tube  (Henle) , 952 

363.  Sagittal  Section  through  the  Normal  Endometrium,  Together  with  a 

Portion  of  the  Contiguous  Muscular  Layer, 953 

364.  Horizontal  Section  of  the  Normal  Endometrium  (Orthmanri), 953 

365.  Fresh  Corpus  luteum  (Balbiani) , 953 

366.  Lutein-cells  from  the  Corpus  luteum  of  the  Cow  (His) , 954 

367.  Corpus  luteum  of  the  Cow,  enlarged  one  and  one-half  times  (His) , 954 

368.  Anterior  Pelvic  Wall  with  the  Urogenital  Diaphragm  (Henle), 956 

369.  Ovum  of  Scorpaena  scrofa, ; 959 

370.  Ovum  of  a  Starfish  (asteracanthion) , 959 

371.  Four  Stages  of  Division  of  an  Impregnated  Ovum  of  Echinus  saxatilis,  960 

372.  Development  of  the  Hypoblast  (Kupffer) , 962 

373.  Ovum  of  the  Rabbit  (van  Beneden) ...... 963 

374.  Germinal  Plate  of  Bird's  Egg, 964 

375.  Stages  of  Nuclear  Division  (Rabl) , 965 

376.  Schemata  of  Development, ._ 967 

377.  Lateral  View  of  the  Brain  of  a  Human  Embryo  (His) , 968 

378.  Scheme  of  the  Formation  of  the  Chorda  and  the  Coelom  through  Eva- 

gination  of  the  Hypoblast, 970 

379.  Isolated  Portion  of  Villi  from  a  Human  Placenta, 977 

380.  Section  through  the  Uterus  and  the  Attached  Placenta  at  the  Thirtieth 

Week  (Ecker), 978 

381.  Left-sided  Hare-lip, 985 

382.  Formation  of  the  Face  and  Developmental  Defects  of  the  Face, 986 

383.  Ossification  of  the  Innominate, 988 

384.  Development  of  the  Heart  (in  part  diagrammatic), 990 

385.  Development  from  the  Aortic  Arches, 991 

386.  Veins  of  the  Embryo, 992 

387.  Development  of  the  Veins  of  the  First  and  the  Second  Circulation,  and 

of  the  Portal  System, 993 

388.  Development  of  the  Intestine, 994 

389.  Development  of  the  Lungs, 994 

390.  Development  of  the  Great  Omentum, 994 

391.  Transverse  Section  through  the  Primitive  Kidney,  the  Rudimentary 

Duct  of  Muller,  and  the  Sexual  Gland  in  a  Chick  at  the  Fourth  Day 

(Waldeyer) , 996 

392.  Development  of  the  Internal  Organs  of  Generation, 997 

393.  Development  of  the  External  Genitalia, 998 

394.  Development  of  the  Eye, 1001 


INTRODUCTION. 


THE  SCOPE  AND  AIM  OF  PHYSIOLOGY  AND  ITS  RELATION  TO 
ALLIED  BRANCHES  OF  PHYSICAL  SCIENCE. 

Physiology  is  the  science  of  the  vital  phenomena  of  organs,  or,  briefly, 
the  study  of  life.  In  accordance  with  the  classification  of  organisms 
the  following  divisions  are  made,  namely,  Animal  Physiology,  Vegetable 
Physiology,  and  the  Physiology  of  the  Lowest  Forms  of  Life,  which 
occupy  the  boundary  between  animals  and  plants,  the  protists,  micro- 
organisms or  microbes,  and  the  elementary  organisms  or  cells  occupying 
the  same  plane.  It  is  the  aim  of  physiology  to  establish  these  phe- 
nomena, to  determine  their  regularity  and  their  causes,  and  to  correlate 
these  with  the  general  fundamental  laws  of  natural  science,  especially 
those  of  physics  and  chemistry.  The  relation  of  physiology  to  allied 
branches  of  natural  science  is  shown  in  the  following  scheme : 

BIOLOGY, 

The  science  of  organized  beings  or  organisms  (animals,  plants,  protists,  and  ele- 
mentary organisms). 

MORPHOLOGY. 

The  study  of  the  form  of  organisms. 

General  Morphology.  Special  Morphology. 

The  study  of  the  formed  elementary  The  study  of  the  parts  and  organs 

constituents  of  organisms  (Histology) :          of  organisms  (Organ ology,  Anatomy) : 

(a)  Histology  of  plants.  (a)  Phytotomy. 

(b)  Histology  of  animals.  (b)  Zootomy. 

PHYSIOLOGY. 

The  study  of  the  vital  phenomena  of  organisms. 
General  Physiology.  Special  Physiology. 

The  study  of  vital  phenomena  in  The  study  of  the  functions  of  indi- 

general:  vidual  organs: 

(a)  Of  plants.  (a)   Of  plants. 

(b)  Of  animals.  (b)   Of  animals. 

EMBRYOLOGY. 

The  study  of  the  generation  and  development  of  organisms. 
Morphologic   division  i .  Developmental  his-  Physiologic     division 

of  the  study  of  develop-      tory    of    the    individual      of  the  study  of  develop- 

being  (for  instance,  man) 
from  its  germ,  germinal 
history  (Ontogeny): 
(a)   In  plants. 
(6)   In  animals. 
2.  Developmental  his- 
tory of  entire  species  of 
organisms,  from  the  low- 
est forms  of  creation  up- 
ward,      family       history 
(Phytogeny) : 

(a)  In  plants. 

(b)  In  animals. 

17 


ment,  that  is,  the  study  of 
the  conformation  at  dif- 
ferent stages  of  develop- 
ment: 

(a)   General. 

(6)   Special. 


ment,  that  is,  the  study 
of  functional  activity 
during  development: 

(a)  General. 

(b)  Special. 


1 8  MATTER. 

If  it  be  desired  to  give  a  special  position  in  the  system  of  organisms  to  those 
beings  that  occupy  the  lowest  plane  of  development  and  that,  representing  to  a  cer- 
tain degree  the  prototype  in  the  family  history,  have  as  yet  not  been  differentiated 
into  animal  and  vegetable,  the  so-called  protists  (Haeckel),  these  likewise  would 
occupy  a  distinct  place  in  the  foregoing  arrangement  by  the  side  of  animals  and 
plants. 

Morphology  and  physiology  are  coordinate  branches  of  biology.  A 
knowledge  of  morphology  is  a  prerequisite  for  the  comprehension  of 
physiology,  inasmuch  as  the  functions  of  an  organ  can  be  correctly 
understood  only  if  its  external  form  and  its  internal  structure  are  pre- 
viously known.  The  developmental  history  occupies  an  intermediate 
position  between  morphology  and  physiology.  It  is  a  department  of 
morphology  in  so  far  as  it  has  to  do  with  a  description  of  the  parts  of 
the  developing  organism ;  it  is  a  physiologic  study  in  so  far  as  it  investi- 
gates the  functions  and  vital  phenomena  during  the  period  of  develop- 
ment of  the  organism.  In  all  the  branches  of  biologic  science  it  is  neces- 
sary to  enter  upon  a  consideration  of  physical  and  cbemical  principles. 


MATTER. 

The  entire  visible  world,  including  all  organisms,  consists  of  matter, 
that  is,  of  the  material  or  substance  that  occupies  space.  A  distinction 
is  made  between  ponderable  matter  (in  ordinary  language  often  desig- 
nated simply  matter),  which  can  be  weighed  upon  the  scales;  and  im- 
ponderable matter,  which  cannot  be  weighed  upon  the  scales.  The  latter 
is  designated  ether  (also  luminiferous  ether  or  light-ether).  Ponderable 
matter  or  bodies  possess  form  (or  shape),  that  is,  the  outline  of  their  limit- 
ing surfaces;  also  volume,  that  is,  the  amount  of  space  they  occupy;  and 
finally  an  aggregate  condition,  which  takes  a  solid,  liquid,  or  gaseous  form. 

The  ether  fills  the  space  of  the  universe,  at  any  rate,  with  certainty 
to  the  most  remote  visible  stars.  This  light-ether,  notwithstanding  its 
imponderability,  possesses  quite  definite  mechanical  properties.  It  is 
infinitely  more  attenuated  than  any  other  known  form  of  gas,  and  never- 
theless its  behavior  corresponds  rather  with  that  of  a  solid  body  than  with 
that  of  a  gas.  It  more  nearly  resembles  a  gelatinous  mass  than  air. 
It  takes  part  in  the  vibrations  of  the  atoms  of  the  most  distant  stars 
associated  with  the  luminous  phenomena  of  the  latter,  and  it  is  thus  the 
carrier  of  light,  which  through  its  vibrations  it  conducts  to  the  visual 
apparatus  with  inconceivable  rapidity  (300,000  kilometers  in  the 
second). 

Imponderable  matter  (ether)  and  ponderable  matter  (substance)  are 
not  sharply  delimited  from  each  other;  on  the  contrary,  the  ether  pene- 
trates the  interstices  present  in  the  smallest  particles  of  ponderable 
matter. 

If  ponderable  matter  be  conceived  to  be  divided  into  gradually 
smaller  and  smaller  parts,  in  the  process  of  progressive  subdivision  parts 
would  eventually  be  reached  whose  aggregate  condition  would  still  be 
recognizable.  These  are  designated  particles.  Particles  of  iron  would 
still  be  recognized  as  solid,  those  of  water  as  fluid,  and  those  of  oxygen 
as  gaseous.  If  it  be  conceived  that  the  process  of  division  of  the  parti- 
cles be  carried  to  a  further  degree,  a  point  will  finally  be  reached  beyond 
which  further  division  cannot  be  effected  either  by  mechanical  or  by 
physical  means.  In  this  way  the  molecule  is  obtained.  A  molecule, 


MATTER.  19 

accordingly,  is  the  smallest  portion  of  a  body  that  is  capable  of  existence 
in  a  free  state,  and  that,  further,  as  a  unit  no  longer  exhibits  the  aggre- 
gate condition.  The  molecule  is,  however,  not  the  ultimate  unit  of  the 
body.  On  the  contrary,  every  molecule  consists  of  a  collection  of  the 
smallest  units,  which  are  known  as  atoms.  An  atom  is  incapable  of 
occurring  alone  in  a  free  state,  but  atoms  unite  with  other  atoms  of 
the  same  or  of  different  character  to  form  atom-complexes,  desig- 
nated molecules.  Atoms  are  unconditionally  insusceptible  of  division; 
whence  the  name.  Atoms,  further,  are  conceived  to  be  of  constant  size 
and  solid  in  themselves.  From  the  chemical  standpoint  the  atom  of  an 
elementary  body  (element)  is  the  smallest  amount  of  an  element  that 
is  capable  of  entering  into  chemical  combination.  Just  as  ponderable 
matter  consists  in  its  ultimate  parts  of  ponderable  atoms,  so  also  does 
the  ether,  imponderable  matter,  consist  of  analogous  particles  of  smallest 
size,  namely,  ether-atoms. 

Within  ponderable  matter  the  ponderable  atoms  are  arranged  in 
quite  a  definite  order  with  relation  to  the  ether-atoms.  The  ponderable 
atoms  are  drawn  mutually  toward  one  another  (attraction) ;  the  pon- 
derable atoms  likewise  attract  the  imponderable  atoms;  but  the  ether- 
atoms  mutually  repel  one  another.  It  thus  comes  about  that  in  the 
ponderable  mass  ether-atoms  are  collected  about  every  ponderable  atom. 
These  collections,  designated  "dynamids"  by  Redtenbacher,  tend,  in 
accordance  with  the  powers  of  attraction  of  the  ponderable  atoms,  to 
approach  one  another,  but  only  so  far  as  permitted  thus  to  do  by  the 
repellent  power  of  the  surrounding  ether-atoms.  Therefore  the  pon- 
derable atoms  can  never  cohere  without  interstices,  but  the  entire  mass 
of  matter  must  be  considered  as  loose  in  texture  in  consequence  of  the 
interposed  ether-atoms,  which  prevent  immediate  contact  between  pon- 
derable atoms. 

The  aggregate  condition  of  the  body  depends  therefore  upon  the 
mutual  arrangement  of  the  molecules  (namely,  those  small  particles  of 
matter  that  may  still  occur  isolated  in  a  free  state). 

Within  solid  bodies,  which  are  characterized  by  constancy  of  volume, 
as  well  as  independence  of  form,  the  molecules  are  arranged  in  a  fixed 
and  unchangeable  relation  with  one  another.  In  fluid  bodies,  which  are 
characterized  by  constancy  of  volume,  though  by  variability  of  form, 
the  molecules  are  in  constant  movement,  just  as  in  a  mass  of  moving 
worms  or  insects  the  individual  animals  are  incessantly  changing  their 
place  with  relation  to  one  another.  If  this  movement  of  the  molecules 
attains  such  proportions  that  the  individual  molecules  scatter  in  all 
directions  (just  as  the  moving  collection  of  insects  separates  into  its 
constituent  parts),  the  body  becomes  gaseous,  and  is  characterized  in  this 
form  both  by  its  inconstancy  of  form  and  its  variability  in  volume.  The 
study  of  molecules  and  their  motor  phenomena  is  the  part  of  physics. 

FORCES. 

Gravitation;  Work  of  a  Force. — All  phenomena  appertain  to 
matter.  They  are  the  appreciable  expression  of  the  forces  inherent  in 
matter.  The'forces  themselves  are  not  appreciable ;  they  are  the  causes 
of  the  phenomena.  The  first  of  the  forces  to  be  considered  is  gravita- 
tion. According  to  the  law  of  gravitation  every  particle  of  ponderable 
matter  in  the  universe  attracts  every  other  particle  with  a  certain  degree 


2O  FORCES. 

of  force.  This  force  diminishes  inversely  as  the  square  of  the  distance 
between  the  two  bodies.  The  power  of  attraction  is  further  directly 
proportional  to  the  quantity  of  the  attracting  matter,  though  without 
any  relation  to  the  quality  of  the  body.  The  intensity  of  the  force  of 
gravitation  can  be  measured  by  the  extent  of  the  movement  that  it 
communicates  to  a  freely  falling  body  previously  supported  in  a  vacuum 
but  deprived  of  its  support.  This  figure  is  9.809,  because  the  force  of 
gravity  operating  for  one  second  upon  the  freely  falling  body  imparts 
to  this  a  velocity  of  9.809  meters. 

The  final  velocity  of  the  freely  falling  body  at  the  end  of  the  first  second  (deter- 
mined experimentally)  is  designated  thus,  g  =  9.809  meters.  The  velocity,  v,  of 
the  freely  falling  body  is  in  general  proportional  to  the  time,  t,  occupied  in  falling. 

Therefore  v  =  gt (i) ,  that  is,  at  the  end  of  the  first  second  v  =  g,  i  = 

g  =  9.809  meters. 

The  distance  through  which  the  body  falls,  s  =    ^t2   (2) ;    that  is,  the 

distance  through  which  a  body  falls  is  as  the  square  of  the  time  occupied  in  falling. 
From  (i)  and  (2)  there  follows  (by  eliminating  t)  v  =  \I28S ($}- 

The  velocity  is  as  the  square  root  of  the  distance  traversed  in  falling. 

v^ 
thus  —  =  s   (4) 

A  freely  falling  body,  and  also  in  general  every  mass  in  movement, 
possesses  kinetic  energy  (actual  energy) ;  it  is  to  a  certain  degree  a  reposi- 
tory of  force.  The  kinetic  energy  of  a  body  in  movement  is  always 
equal  to  the  product  of  its  weight  (determinable  by  scales)  and  the 
height  to  which  it  would  rise  from  earth  if  it  were  raised  from  the  earth 
with  the  velocity  peculiar  to  it. 

If  the  kinetic  energy  of  the  moving  body  be  designated  W  and  its  weight  P, 
then  W  =  P,  s;  then,  from  (4),  W  =  P—  (5). 

The  kinetic  energy  of  a  body  is  therefore  proportional  to  the  square 
of  its  velocity. 

If  an  accelerating  force  operating  on  a  body  ^(pressure,  traction,  or 
tension)  drives  it  for  some  distance  in  the  direction  of  its  activity,  the 
force  thus  expends  work.  This  is  equal  to  the  product  that  is  obtained 
if  the  amount  of  pressure  or  traction  that  propels  the  body  is  multiplied 
by  the  length  of  the  path  traversed. 

If  K  represents  the  pressure  or  the  traction  with  which  the  force  operates  upon 
the  body  and  S  the  path,  then  the  work  A  =  KS.  In  the  same  way  the  attraction 
between  the  earth  and  a  body  raised  above  it  (as,  for  instance,  a  ram)  is  a  source 
of  work. 

It  is  customary  to  express  the  value  of  K  in  kilograms,  but,  on  the 
other  hand,  that  of  S  in  meters.  Accordingly  the  unit  of  work  is  the 
kilogrammeter  (according  to  some  the  grammeter),  that  is,  the  force  that 
is  capable  of  raising  i  kilo  (according  to  some  i  gram)  to  the  height  of 
i  meter. 

Potential  Energy. — Transformation  of  Potential  Energy  into  Kinetic 
Energy,  and  the  Reverse. — In  addition  to  the  kinetic  energy  referred 
to,  bodies  may  possess  also  mechanical  potential  energy.  By  this' 
designation  is  understood  an  aggregation  of  forces  that  are  still  inhibited 
in  their  free  evolution,  and  that,  further,  are  causes  of  movement,  without 


FORCES.  21 

themselves  being  movement.  The  wound  clock-spring  prevented  from 
unwinding  by  a  catch,  the  stone  resting  upon  the  cornice  of  a  tower,  are 
illustrations  of  bodies  possessing  potential  energy.  Only  an  impulse  is 
required  to  evolve  actual  from  potential  energy  or  to  convert  the  poten- 
tial into  kinetic  energy.  The  stone  resting  upon  the  cornice  of  the  tower 
was  raised  to  that  place  by  means  of  work  (A). 

A  =  p,  s,  p  representing  the  weight  and  s  the  height,  p  =  m,  g,  thus  the 
equivalent  of  the  product  of  the  mass  (m)  and  the  force  of  gravity  (g) ;  therefore 
A  =  m,  g,  s. 

This  is  at  the  same  time  the  expression  for  the  potential  energy 
residing  within  the  stone.  This  elastic  energy  may  readily  be  converted 
into  kinetic  energy  by  causing  the  stone  to  fall  from  the  edge  of  the 
tower  by  means  of  a  slight  push.  The  actual  energy  of  the  stone  is 
equal  to  the  terminal  velocity  with  which  it  reaches  the  ground. 

=  \/2~gs  (see  3). 

v*  =  2gs 

mv3  =  2ings 
m    , 

— va  =  mgs 

m,  g,  s  represents  the  potential  energy  residing  within  the  stone  at 
rest  in  its  elevated  position;  —  v2  is  thus  the  kinetic  energy  correspond- 
ing to  this  potential  energy. 

Actual  energy  and  mechanical  potential  energy  can  be  transformed 
into  each  other  under  most  varied  conditions;  they  can  also  be  con- 
veyed from  one  body  to  another. 

Of  the  first  statement  the  movement  of  a  pendulum  furnishes  a  striking 
illustration.  The  pendulum-bob,  located  at  the  highest  point  of  the  excursion, 
and  which  must  be  considered  to  be  in  a  state  of  absolute  rest  at  this  point  for 
a  moment,  is,  exactly  as  the  resting  stone  in  the  previous  illustration,  provided 
with  potential  energy.  In  the  free  movement  that  now  takes  place  this  potential 
energy  is,  converted  into  kinetic  energy,  which  is  greatest  when  the  bob  with 
greatest  movement  is  in  the  vertical  plane.  Rising  again  from  this  point,  the 
kinetic  energy,  with  diminution  in  the  free  movement,  is  transformed  into  poten- 
tial energy,  which  again  attains  its  maximum  at  the  resting-point  at  the  height 
of  the  excursion.  In  the  absence  of  constantly  operating  resistances  (resistance 
of  the  air,  friction)  this  play  of  the  alternate  transformation  of  kinetic  energy  into 
potential  energy  and  the  reverse  taking  place  in  the  pendulum  would  continue 
uninterruptedly  (as  in  a  mathematical  pendulum).  If  it  be  conceived  that  the 
swinging  pendulum-bob  encounters  exactly  in  the  vertical  plane  a  movable  body 
resting  at  this  point,  such  as  a  sphere,  then  (assuming  perfect  elasticity  on  the 
part  of  the  pendulum-bob  and  the  sphere)  the  kinetic  energy  of  the  pendulum-bob 
would  be  transmitted  directly  to  the  sphere:  The  pendulum  would  come  to  rest, 
while  the  sphere  would  continue  in  movement  with  equal  kinetic  energy  (again 
providing  there  is  no  resistance).  This  is  an  instance  of  the  transmission  of 
kinetic  energy  from  one  body  to  another.  Finally  it  may  be  conceived  that  a 
coiled  clock-spring  in  unwinding  causes  another  to  become  coiled.  This  would  be 
an  instance  of  the  transmission  of  potential  energy  from  one  body  to  another. 

From  the  illustrations  given  the  general  proposition  may  be  deduced : 
If  in  a  system  the  individual  moving  masses  approach  a  final  condition 
of  equilibrium,  the  sum  of  the  kinetic  energies  in  the  system  will  be 
increased;  and  if  the  particles  are  removed  from  the  final  condition  of 
equilibrium,  then  the  sum  of  the  potential  energies  is  increased  at  the 
expense  of  the  kinetic  energies;  that  is,  the  kinetic  energies  diminish. 


22  HEAT. 

The  pendulum  approaching  the  vertical  plane  (the  position  of  equilibrium  for 
a  resting  pendulum)  from  the  highest  point  of  its  excursion  possesses  in  this 
position  the  greatest  amount  of  kinetic  energy ;  and  ascending  to  the  highest  point 
of  its  excursion  on  the  other  side  it  attains,  at  the  expense  of  the  progressively 
diminishing  movement  and  thereby  also  the  kinetic  energy,  again  gradually  the 
maximum  of  potential  energy. 

Heat :  Its  Relation  to  Kinetic  Energy  and  to  Potential  Energy. — If 

a  leaden  weight  be  thrown  from  the  summit  of  a  tower  to  the  earth 
and  there  encounter  an  unyielding  surface,  its  movement  in  mass 
will  come  to  rest,  but  the  kinetic  energy,  which  to  the  eye  appears 
dissipated,  is  transformed  into  an  actively  vibratory  movement  of  the 
atoms.  On  striking  the  ground  heat  is  generated,  the  amount  of  which 
is  proportionate  to  the  kinetic  energy  that  is  transformed  by  the  impact. 
At  the  moment  of  contact  on  the  part  of  the  falling  weight  the  atoms 
are  set  into  vibration  by  the  concussion.  They  impinge  upon  one 
another  and  then  rebound  in  consequence  of  the  potential  energy  that 
tends  to  prevent  their  immediate  apposition;  they  separate  to  a  maxi- 
mum degree  in  so  far  as  the  power  of  attraction  of  the  ponderable 
atoms  permits  and  they  oscillate  to  and  fro  in  this  manner.  All  atoms 
oscillate  like  a  pendulum  until  their  movement  is  transmitted  to  all 
the  surrounding  ether- atoms,  that  is,  until  the  heat  of  the  heated  mass 
is  radiated.  Heat  is  a  vibratory  movement  of  the  atoms.  As  the 
amount  of  heat  generated  is  proportionate  to  the  kinetic  energy  that 
is  transformed  by  the  impact,  it  must  be  possible  to  find  an  adequate 
measure  for  both  forms  of  force. 

The  heat-unit  (calory),  that  is,  the  energy  that  raises  the  tempera- 
ture of  i  gram  of  water  i°  C.,  serves  as  the  measure  of  the  amount 
of  heat.  This  heat-unit  corresponds  to  425.5  grammeters;  that  is,  the 
same  amount  of  energy  that  raises  the  temperature  of  i  gram  of  water 
i°  C.  is  capable  of  raising  a  weight  of  425.5  grams  to  a  height  of  i  meter; 
or,  a  weight  of  425.5  grams  falling  from  the  height  of  i  meter  would 
in  its  impact  generate  so  much  heat  as  would  raise  the  temperature  of 
i  gram  of  water  i°  C.  The  mechanical  equivalent  of  the  heat-unit  is 
therefore  425.5  grammeters. 

It  is  evident  that  from  the  impact  of  masses  in  motion  an  amount  of  heat  of 
immeasurable  degree  may  be  generated.  If  this  statement  be  applied  to  the 
planets,  their  impact  would  result  in  the  production  of  an  amount  of  heat  greater 
than  could  be  generated  by  any  form  of  earthly  combustion.  If  the  earth  were 
suddenly  checked  in  its  course  and  if  through  the  force  of  gravitation  it  plunged 
into  the  sun  [in  the  course  of  which  it  would  eventually  have  acquired  a  terminal 
velocity  of  630.7  kilometers  in  a  second]  an  amount  of  heat  would  be  generated  in 
consequence  of  the  collision  equivalent  to  that  produced  by  the  combustion  of 
more  than  5000  equally  heavy  masses  of  pure  carbon.  In  this  manner  the  dem- 
onstration can  be  made  scientifically,  that  even  the  sun's  heat  may  have  been 
produced  by  the  impact  of  cold  matter.  If  the  cold  matter  of  the  universe  were 
thrown  into  space,  and  there  left  to  the  attraction  of  its  particles,  the  impact  of 
these  masses  would  eventually  extinguish  the  light  of  the  stars.  In  the  same  way 
numerous  cosmic  bodies  still  collide  in  space,  and  innumerable  meteors  constantly 
plunge  into  the  sun  (from  9400  to  188,000  billions  of  kilos  in  each  minute). 
Thus,  the  action  of  the  force  of  gravitation  is  in  fact  perhaps  the  exclusive 
origin  of  all  heat.  The  following  is  an  instance  of  the  transformation  of  kinetic 
energy  into  heat:  The  smith  makes  a  piece  of  iron  hot  by  hammering.  The  fol- 
lowing is  an  instance  of  the  transformation  of  heat  into  kinetic  energy:  The  hot 
steam  of  the  steam-engine  causes  the  piston  to  rise.  The  following  is  an  illustra- 
tion of  the  transformation  of  potential  energy  into  heat :  The  unwinding  of  a  coiled 
metallic  spring,  rubbing  upon  a  rough  surface,  produces  heat  by  friction.  Exam- 


CHEMICAL    AFFINITY    OF    ATOMS.  23 

pies  of  like  character,  as  well  as  of  other  transformations,  could  be  readily  given 
in  any  number. 

Chemical  Affinity  of  Atoms  :  Relation  to  Heat. — While  the  force  of 
gravitation  acts  upon  the  particles  of  matter  without  reference  to  the 
character  of  the  body,  still  another  form  of  force  is  found  in  the  realm 
of  atoms,  which  is  effective  between  the  atoms  of  chemically  different 
bodies,  namely,  chemical  affinity.  This  is  the  force  by  means  of  which 
the  atoms  of  chemically  different  bodies  unite  in  chemical  combination. 
The  energy  itself  is  extremely  variable  between  the  atoms  of  different 
chemical  bodies. 

A  distinction  is  made  between  strong  chemical  affinities  (or  rela- 
tions) and  weak  affinities.  Just  as  it  is  possible  to  determine  the  kinetic 
energy  of  a  body  in  motion  from  the  amount  of  heat  that  it  generates 
in  its  impact  upon  an  unyielding  surface,  so  the  degree  of  chemical 
affinity  can  be  determined  from  the  amount  of  heat  that  is  produced, 
as  the  atoms  of  chemically  different  bodies  unite  in  chemical  combina- 
tion; for  if  a  complex  body  is  formed  from  individual,  chemically 
different  atoms  heat  is,  as  a  rule,  generated.  If  as  a  result  of  the 
force  of  affinity  the  atoms  of  i  kilo  of  hydrogen  and  8  kilos  of  oxygen 
unite  to  form  the  chemical  combination  water,  an  amount  of  heat  is 
generated  that  is  equal  to  that  developed  by  the  impact  of  a  weight  of 
47,000  kilos  in  falling  from  a  height  of  300  meters  above  the  surface  of  the 
earth.  One  gram  of  hydrogen  converted  into  water  by  addition  of 
oxygen  yields  34,460  heat-units  (calories).  One  gram  of  carbon  con- 
verted into  carbon  dioxid  yields  8080  calories. 

Whenever  in  the  course  of  chemical  processes  considerable  affinities 
are  satisfied  heat  is  set  free,  that  is,  generated  from  the  force  of  affinity. 
The  force  of  affinity  is  a  form  of  potential  energy  acting  between  the 
various  atoms  that  in  the  course  of  the  chemical  process  is  transformed 
into  heat.  It  is  thus  likewise  explicable  that  in  the  course  of  those 
chemical  processes  through  which  strong  affinities  are  dissolved,  in 
which  the  chemically  united  atoms  are  again  separated,  cooling  takes 
place,  or,  as  is  commonly  stated,  heat  becomes  latent.  That  is,  the 
energy  of  the  heat  rendered  latent  is  transformed  into  chemical  poten- 
tial energy,  and  this  in  turn,  after  disintegration  of  the  complex  chemical 
body,  appears  between  its  isolated,  individual  atoms  as  chemical  affinity. 

LAW  OF  THE  CONSTANCY  OF  ENERGY. 

Julius  Robert  v.  Mayer  (1842)  and  Hermann  Helmholtz  (1847)  have 
'established  the  important  law  that  in  a  system  that  receives  no  influ- 
ence or  impression  from  without  the  sum  of  all  the  contained  kinetic 
energies  is  always  equal.  The  energies  may  be  transformed  one  into 
another,  so  that  the  potential  energy  may  be  converted  into  kinetic 
energy,  and  the  reverse,  but  never  is  even  the  slightest  amount  of  the 
energy  lost.  The  transformation  that  takes  place  in  the  energies 
occurs  in  a  definite  manner,  so  that  from  a  definite  measure  of  a  given 
force  an  equally  definite  measure  of  the  new-appearing  force  always 
results.  . 

The  forces  occurring  in  the  animal  organism  appear  in  the  following 
modifications : 

i.  As  movement  in  mass  (generally  designated  simply  movement), 


24  LAW  OF  THE  CONSTANCY  OF  ENERGY. 

such  as  the  movement  of  the  entire  body,  of  the  extremities  and  many 
of  the  viscera;  also  appreciable  even  microscopically  in  cells. 

2.  As  movement  of  the  atom:  in  the  form  of  heat.     As  is  well  known, 
the  vibration  of  atoms  results  in  the  production  of  heat  or  of  light  or 
in  chemically  active  waves  in  accordance  with  the  number  of  vibrations 
in  the  unit  of  time.     The  smallest  number  of  vibrations  are  those  of 
heat,  the  highest  those  that  are  chemically  active,  and  between  the. 
two  are  the  vibrations  of  light.     In  the  human  body  only  heat-waves 
have  of   these   three   been  observed,  but   some  lower  forms  of   life  are 
capable  of  causing  also  luminous  phenomena. 

In  the  human  organism  movements  in  mass  are  constantly  trans- 
formed in  certain  organs  into  heat,  as,  for  instance,  the  kinetic  energy 
in  the  circulatory  organs,  and  which  is  transformed  into  heat  by  the 
resistance  within  the  vascular  apparatus.  The  measure  of  these  trans- 
formations also  is  the  unit  of  energy  =  i  grammeter,  and  the  unit  of 
heat  =  425.5  grammeters. 

3.  In  the  form  of  potential  energy  (latent  energy)  the  organism  con- 
tains many  chemical   combinations   characterized  especially  by  great 
complexity  of  constitution  and  imperfect  saturation  of  the  contained 
affinities,  and,  therefore,  by  their  great  tendency  to  break  down  into 
simpler  bodies.     The   body   is   capable   of  generating   both   heat   and 
kinetic  energy  from  potential  energies;  kinetic  energy,  however,  is  always 
in  combination  with  heat,   while  heat  may  be  produced  alone.     The 
simplest  measure  of  the  potential  energies  is  the  amount  of  heat  that 
can  be  obtained  by  the  combustion  of  the  chemical  bodies  in  question 
representing  the  potential  energy.     As  a  secondary  matter  the  number 
of  equivalent  units  of  energy  can  be  determined  in  turn  from  the  amount 
of  heat  generated. 

4.  It  is  known  that  the  phenomena  of  electricity,  magnetism  and 
diamagnetism,  may  make  themselves  manifest  in  two  directions,  namely, 
in  the  form  of  movement  of  minutest  particles,  which  may  be  recog- 
nized in  the  incandescence  of  a  thin  wire  (the  seat  of  great  resistance) 
traversed  by  a  strong  current;  and  also  in  the  form  of  movement  in 
mass,  as  exhibited  in  the  attraction  or  repulsion  of  the  magnetic  needle. 
In  the  body  electric  phenomena  appear  in  the  muscles,  nerves,  and  glands ; 
but  as  compared  with  other  forms  of  energy  they  are  of  subordinate 
importance.     It  is  not  improbable  that  the  electric  energy  of  the  body 
is  transformed  almost  wholly  into  heat.     The  endeavor  to  obtain  a 
measure  for  electric  energy,  the  unit  of  electricity,  as  a  means  of  direct 
comparison  with  the  heat-unit  and  the  unit  of  energy,  has  likewise  been 
attended  with  definite  success. 

Luminous  phenomena  do  not  occur  in  the  bodies  of  the  most  highly 
developed  animals.  The  significant  investigations  of  Hertz  have  shown 
that  the  phenomena  of  light  exhibit  the  greatest  analogy  with  those  of 
electricity  in  the  most  important  connections,  so  that  the  relations  be- 
tween the  two  forms  of  energy  must  accordingly  be  admitted. 

It  is  certain  that  in  the  body  also  the  different  forms  of  energy  can 
be  transformed  one  into  another  in  a  definite  and  constantly  invariable 
degree,  and  that  new  energy  never  develops  spontaneously  in  the  body, 
while  that  present  is  never  destroyed ;  and  thus  also  the  organisms  are 
a  theater  in  which  the  law  of  the  constancy  of  'energy  is  in  unceasing 
operation. 


ANIMALS    AND    PLANTS.  25 

The  original  statement  of  Julius  Robert  v.  Mayer  may  be  appropriately  quoted 
at  this  point:  "There  is  but  one  energy,  which  operates  with  unceasing  change  in 
dead  and  in  living  things,  and  nowhere  in  either  does  any  change  take  place 
without  alteration  'in  the  form  of  energy.  Physics  has  but  to  investigate  the 
metamorphoses  of  energy,  as  chemistry  has  to  investigate  the  transformations  of 
matter.  The  generation  as  well  as  the  destruction  of  energy  is  beyond  the  range 
of  human  thought  and  action:  Nothing  comes  from  nothing,  nothing  can  give  rise 
to  nothing.  If  chemistry  teaches  the  immutability  of  matter,  then  it  is  the  obliga- 
tion of  physics  to  demonstrate  the  quantitative  immutability  of  energy  notwith- 
standing all  variability  in  form.  Gravitation,  motion,  heat,  magnetism,  electricity, 
chemical  difference,  are  all  but  varying  modes  of  manifestation  of  one  and  the 
same  natural  force  that  reigns  throughout  the  universe,  for  any  one  can  under 
special  conditions  be  converted  into  another."  (Lucretius  Carus,  born  95  B.  C., 
had  already  said:  "Nullam  rem  a  nihilo  gigni,  ....  neque  ad  nihilum 
interimat  res.") 

ANIMALS  AND  PLANTS. 

Locked  up  in  the  constituent  elements  of  the  animal  body  is  an 
aggregation  of  chemical  potential  energies  (Lavoisier,  1789).  The  total 
amount  of  these  in  the  human  body  could  be  measured  if  the  entire 
cadaver  were  completely  burned  in  a  calorimeter  and  the  number  of 
heat-units  generated  were  noted  as  a  result  of  its  combustion.  The 
chemical  combinations  in  which  are  bound  up  the  potential  energy  are 
characterized  by  complexity  in  the  arrangement  of  their  atoms,  by 
imperfect  saturation  of  the  affinities  of  the  atoms,  by  a  relatively  small 
oxygen-content,  and  by  a  great  tendency  to  and  readiness  of  disintegra- 
tion. 

It  may  be  conceived  that  food  is  withheld  from  an  individual.  The 
fasting  person  loses  hourly  50  grams  of  body- weight;  the  tissues  in  which 
his  potential  energy  is  bound  up  are  thus  consumed.  Through  the 
taking  up  of  oxygen  combustion  continually  takes  place,  and  as  a 
result  of  this  process  the  complex  elements  of  the  body  are  converted 
into  simpler  ones,  whereby  the  potential  energy  forming  the  connecting 
link  between  them  is  transformed  into  kinetic  energy.  It  is  a  matter 
of  indifference  whether  the  process  of  combustion  takes  place  rapidly 
or  slowly;  the  same  amount  of  chemical  matter  always  yields  the  same 
amount  of  kinetic  energy,  as,  for  instance,  heat.  After  the  lapse  of 
a  certain  time  the  fasting  person  becomes  conscious  of  the  state  of 
threatened  exhaustion  of  his  stored  potential  energy,  and  the  condi- 
tion of  hunger  sets  in.  The  hungry  person  takes  food;  all  food  for  the 
animal  kindgom  is  derived  either  directly  or  indirectly  from  the  vege- 
table world.  Even  carnivorous  animals,  which  eat  the  flesh  of  other 
animals,  consume  in  the  final  analysis  organized  material  formed  from 
vegetable  food.  Thus,  the  existence  of  the  animal  kingdom  necessarily 
implies  unconditionally  the  previous  existence  of  the  vegetable  king- 
dom. 

Vegetable  structures  thus  contain  all  of  the  nutritive  materials 
necessary  for  the  animal  body.  In  addition  to  water  and  inorganic 
matters,  vegetables  contain,  among  other  organic  combinations,  espe- 
cially also  the  three  principal  representatives  of  nutrient  bodies,  namely, 
fats,  carbohydrates,  and  proteids.  All  of  these  are  the  seat  of  abundant 
potential  energy  in  accordance  with  the  complexity  of  their  chemical 
constitution. 


26  ANIMALS    AND    PLANTS. 

Fats  contain-      {  Cn  H— >°  (OH)  ==  fatt^  adds  ^ 
1  +  C3H5  (OH),=  glycerin  J 

(   C76.5 
Animal  fats  contain :  H  12.0 

(.  O  11.5 
Carbohydrates  contain:     C6H10O5 

p 

^50-55 
He.e-7.3 

Proteids  contain  in  percentages :     N15  _19 

019-24 
0.3-2.4 

Man,  who  partakes  of  a  certain  amount  of  these  nutrient  materials, 
adds  to  them  through  the  respiratory  process  the  oxygen  of  the  air, 
whence  there  results  a  process  of  combustion,  in  the  course  of  which 
chemical  potential  energy  is  converted  into  heat.  It  is  evident  that 
the  products  of  this  combustion  must  be  bodies  of  simple  constitution, 
bodies  with  uniform  arrangement  of  their  atoms,  with  most  complete 
saturation  of  the  affinities  of  their  atoms,  of  great  constancy,  partly 
rich  in  oxygen  and  possessing  slight  or  no  chemical  potential  energy. 
These  bodies  are  carbon  dioxid  (CO2),  water  (H2O),  and,  as  the  most 
important  representative  of  the  nitrogen-containing  derivatives,  urea 
(CO(NH2)2),  which,  while  endowed  with  a  small  measure  of  potential 
energy  is,  outside  of  the  body,  readily  transformed  into  CO2  and  ammonia 
(NH8). 

Thus,  the  animal  body  is  an  organism  in  which,  through  the  inter- 
mediation of  oxidation-phenomena,  the  complex  nutritive  matters  of 
the  vegetable  world,  representing  high  potential  energy,  are  trans- 
formed into  simple  chemical  bodies,  in  the  course  of  which  the  potential 
energy  is  transformed  into  an  equivalent  amount  of  kinetic  energy 
(heat,  work,  electric  phenomena). 

The  question  naturally  arises,  How  do  plants,  which,  as  the  first 
products  of  creation,  found  for  their  nourishment  no  preexisting  mate- 
rials endowed  with  potential  energy,  and  still  suffer  from  no  lack  thereof 
—how  do  plants  form  the  complicated  nutrient  matters  mentioned, 
rich  in  stored-up  potential  energy?  This  potential  energy  of  vegetable 
life  must  obviously  have  been  derived  from  some  other  form  of  energy, 
for  it  cannot  be  created  out  of  nothing.  This  kinetic  energy  is  furnished 
plants  through  the  light  of  the  sun,  whose  chemical  rays  they  absorb. 
Without  sunlight  there  can  be  no  vegetable  life.  From  the  air  and  the 
earth  the  vegetable  organism  obtains  CO2,  H2O,  NH3,  and  N,  of  which 
carbon  dioxid,  water,  and  ammonia  (from  urea)  constitute  also  the 
excrementitious  matters  of  the  animal  body.  The  plant  obtains  from 
the  rays  of  the  sun  the  kinetic  energy  of  its  light  and  converts  it  into 
potential  energy,  which,  as  in  all  vegetable  matter,  so  also  in  the  nutrient 
material  produced,  accumulates  in  the  process  of  the  growth  of  the  plant. 
This  formation  of  complex  chemical  combinations  takes  place  in  asso- 
ciation with  elimination  of  oxygen. 

The  Papillonacese,  as,  for  instance,  peas,  beans,  lupines,  acacias,  are  capable 
of  assimilating  the  free  nitrogen  of  the  air  in  the  tissues  of  their  root-bulbs,  through 
the  agency  of  symbiotic  micro-organisms  lodged  upon  these,  Rhizobium  legumino- 
sarum.  Thus,  these  plants  are  capable  of  building  up  their  nitrogen-containing 
tissues  even  in  soil  entirely  free  from  nitrogen.  In  this  way  they  play  an  im- 
portant fertilizing  role  in  agriculture  (lupine)  and  forestry  (acacia).  Also  lower 


ANIMALS    AND    PLANTS.  27 

forms   of  vegetable   life,  as,  for  instance,  the   anaerobic   bacterium,   Clostridium 
pasteurianum,  is  capable  of  assimilating  free  nitrogen. 

At  times  plants  also  exhibit  free  kinetic  energy  such  as  it  is  customary  to 
encounter  in  the  case  of  animals.  Certain  plants,  as,  for  instance,  the  aroids  and 
others,  develop  considerable  amounts  of  heat  during  the  flowering-period.  It  is 
also  to  be  borne  in  mind  that,  in  the  development  of  the  solid  parts  of  plants, 
the  transformation  of  formative  fluids  into  solid  matter  causes  heat  to  be  set  free. 
Absorption  of  oxygen  and  elimination  of  carbon  dioxid  have  also  been  observed 
in  plants.  These  processes  are,  however,  so  insignificant  as  compared  with  those 
described  as  typical  in  the  vegetable  kingdom,  that  they  may  be  considered  as 
of  little  or  no  importance. 

Thus,  plants  are,  on  the  whole,  organisms  that  through  the  agency 
of  reduction-processes  convert  simple  stable  combinations  into  complex 
ones,  with  the  transformation  of  kinetic  solar  energy  into  the  chemical 
potential  energy  of  vegetable  matter.  Animals  are  living  organisms  in 
which  through  the  agency  of  processes  of  oxidation  the  atom-groups 
of  complex  construction  furnished  by  plants  are  split  up,  the  potential 
energy  being  transformed  into  kinetic  energy,  which  makes  itself  mani- 
fest in  the  animal.  Thus  a  circulation  of  materials  and  a  constant 
interchange  of  energy  take  place  between  animals  and  vegetables.  All 
of  the  energy  of  animals  is  derived  from  plants  and  all  of  the  energy 
of  plants  is  derived  from  the  sun.  Therefore,  the  latter  is  the  cause, 
the  ultimate  source  of  all  of  the  energy  of  organism,  that  is,  of  life  as  a 
whole.  As  the  generation  of  the  sun's  heat  and  light  can  be  explained 
by  the  gravitation  of  masses,  so  it  is  possible  that  the  force  of  gravita- 
tion is  the  sole  ultimate  form  of  energy  for  all  living  things. 

"The  sun  is  the  constantly  bent  spring  that  brings  about  the  activity  in  the 
atmosphere,  that  raises  the  waters  to  the  clouds,  that  causes  the  tides.  Light,  the 
most  mobile  of  all  forms  of  force,  intercepted  by  the  earth  in  flight,  is  transformed 
by  plants  into  a  rigid  state,  for  plants  produce  upon  it  a  continuous  sum  of  chem- 
ical difference,  constitute  a  reservoir  in  which  the  fugitive  rays  of  the  sun  are 
fixed  and,  adapted  for  useful  purposes,  are  deposited.  Plants  take  one  form  of 
energy,  light,  and  reproduce  another,  chemical  difference.  In  the  course  of  the 
processes  of  life,  but  one  transformation,  both  of  matter,  as  well  as  of  energy,  takes 
place,  but  never  is  the  one  or  the  other  produced  "  (Julius  Robert  v.  Mayer,  1845). 
("Omnia  mutantur,  nihil  interit." — Ovid.) 

The  generation  of  kinetic  energy  in  the  animal  body  from  the  poten- 
tial energy  of  the  plant  can  be  ma'de  readily  comprehensible  by  means 
of  a  comparison.  The  atoms  of  the  matter  generated  in  organisms  may 
be  conceived  to  be  simple  small  bodies,  spherules  or  blocks.  So  long  as 
these  lie  in  a  single  layer  or  at  least  arranged  in  a  few  layers  upon  the 
ground,  a  condition  of  rest  and  constancy  will  prevail  in  consequence  of 
this  simple  and  stable  arrangement.  If,  however,  an  artificially  arranged 
formation  of  unstable  construction  is  built  up  from  the  small  bodies, 
there  will  be  required  (i)  the  motor  force  of  the  constructing  agency, 
which  raises  and  combines  the  units.  As  soon,  however,  as  (2)  an 
impulse  from  without  acts  upon  the  completed  unstable  structure,  the 
atoms  collapse  and  the  impact  of  their  fall  generates  heat  (eventually 
also  kinetic  energy  in  the  course  of  other  complicated  transformations), 
that  is,  the  energy  applied  by  the  constructing  agency  is  transformed 
into  the  form  of  energy  last  named.  In  plants  the  complicated  unstable 
construction  of  the  atom-groups  takes  place,  the  sun  being  the  con- 
structing agency.  In  the  animal  body,  wherein  the  plant  is  consumed, 
the  atomic  structure  is  disintegrated  into  simpler  elements,  with  the 
generation  of  kinetic  energy. 


28  KINETIC    ENERGY    AND    LIFE. 


KINETIC  ENERGY  AND  LIFE. 

The  forms  of  kinetic  energy  that  are  active  in  organisms,  namely, 
plants  and  animals,  are  precisely  the  same  as  those  that  are  recognizable 
in  inanimate  matter.  A  so-called  ''vital  energy,"  which  is  supposed  to 
act  as  a  special  form  of  force  of  peculiar  character  and  cause  and  control 
the  vital  phenomena  of  living  organisms,  does  not  exist.  The  forces 
of  all  matter,  both  organic  and  inorganic,  are  bound  up  in  their  smallest 
particles,  the  atoms.  As,  however,  the  smallest  particles  of  organ- 
ized matter  are  generally  united  in  a  most  complex  manner,  in  con- 
trast to  the  ordinarily  much  simpler  constitution  of  inorganic  bodies, 
the  forces  inherent  to  the  smallest  particles  of  organism  will  appear  in 
much  more  complicated  phenomena  and  combinations,  and  as  a  result 
the  explanation  of  the  vital  phenomena  in  the  organism  by  the  simple 
principles  of  physics  and  chemistry  is  rendered  extremely  difficult 
and  in  many  respects  appears  impossible. 

Metabolism  as  an  Index  of  Life. — A  special  form  of  interchange  in 
matter  and  energy  appears  peculiar  to  the  living  organisms  of  the  earth. 
This  consists  in  the  ability  to  adapt  themselves  to  the  materials  of 
their  environment,  and  to  assimilate  them,  so  that  for  a  time  they 
represent  integral  parts  of  the  living  being,  later  again  to  be  given  off. 
The  complete  chain  of  these  phenomena  is  designated  "metabolism,'1 
which  consists  accordingly  in  ingestion,  assimilation,  reduction  and 
excretion. 

It  has  already  been  suggested  that  metabolism  differs  in  character 
in  animals  and  in  plants.  As  a  matter  of  fact,  this  is,  as  has  been  shown, 
actually  the  case  in  animals  and  plants  typically  and  characteristically 
developed.  There  is,  however,  a  large  group  of  organisms  that  in  their 
complete  organization  exhibit  such  atypical  development  that  they 
must  be  considered  as  undifferentiated  fundamental  forms  of  organisms. 
They  cannot  be  recognized  as  either  plants  or  animals,  but  represent 
the  simplest  form  of  animate  matter.  These  organisms,  as  the  earliest 
and  most  primitive  forms,  have  been  designated  protists.  It  must  be 
assumed  absolutely  that  these  also  have  a  simple  metabolism  as  a  condi- 
tion of  life,  but  with  respect  to  this  adequate  observations  are  wanting. 


PHYSIOLOGY  OF  THE  BLOOD. 


PHYSICAL  PROPERTIES  OF  THE  BLOOD. 

The  color  of  the  blood  varies  from  bright  scarlet-red  in  the  arteries 
to  the  deepest  dark  bluish-red  in  the  veins.  Oxygen,  therefore  also 
the  air,  makes  it  bright  red,  while  deficiency  in  oxygen  renders  it  dark. 
The  oxygen-free  venous  blood  is  dichroic,  that  is,  it  appears  dark  red 
in  reflected  light  and  green  in  transmitted  light.  In  thin  layers  the  blood 
is  opaque,  as  one  can  readily  convince  himself,  if  blood  be  poured 
upon  a  glass  plate  and  be  permitted  to  flow  off,  by  attempting  to  read 
printed  matter  through  it.  The  blood  thus  behaves  as  a  covering 
pigment,  as  its  coloring  matter  is  suspended  in  the  plasma  in  the  form 
of  small  granules,  namely,  the  red  blood-corpuscles. 

For  this  reason  the  granular  coloring  matter  of  the  blood  can  be  separated 
from  the  blood-plasma  by  nitration.  This,  however,  is  possible  only  after  admix- 
ture of  the  blood  with  fluids  that  render  the  blood-corpuscles  rough  or  viscid.  If 
mammalian  blood  is  mixed  with  one-seventh  of  its  volume  of  concentrated  sodium 
sulphate,  or  if  frog's  blood  is  mixed  with  two  per  cent,  solution  of  cane  sugar,  and 
then  filtered,  the  blood-corpuscles  will  remain  upon  the  filter. 

The  reaction  of  blood  is  alkaline  from  the  presence  of  disodium 
phosphate  (Na2HPO4).  The  alkalinity  rapidly  diminishes  in  intensity 
after  escape  from  the  vessel,  and  the  more  rapidly  the  greater  the  pre- 
vious alkalinity.  The  change  depends  upon  the  development  of  an 
acid,  in  which  the  red  blood-corpuscles  take  part  in  consequence  of  a 
decomposition  of  as  yet  undetermined  origin.  This  generation  of  acid 
is  increased  by  high  temperature  and  the  addition  of  alkali. 

The  alkalinity  of  the  blood  is  diminished  (A)  by  active  muscular  exercise,  in 
consequence  of  the  development  of  acid  in  the  muscular  tissue.  (B)  By  coagulation. 
Fresh  clot  has  a  more  intensely  alkaline  reaction  than  blood-serum.  (C)  After  the 
persistent  use  of  soda  the  alkalinity  of  the  blood  is  increased,  and  after  the  use  of 
acid  it  is  diminished.  (D)  Old  blood  or  blood  dissolved  with  water  from  dry- 
places  generally  has  an  acid  reaction.  The  blood  of  children  and  women  exhibits 
a  lesser  degree  of  alkalinity  than  that  of  men,  and  that  of  nursing  women  a  lesser 
degree  of  alkalinity  than  that  of  pregnant  women.  The  alkalinity  is  less  also  dur- 
ing digestion  than  during  fasting. 

Method  of  Examinat^on. — As  in  consequence  of  the  normal  color  of  the  blood 
red  litmus-paper  cannot  be  employed  directly  in  testing  the  reaction,  the  following 
plan  is  pursued:  Blood  is  mixed  with  an  equal  volume  of  concentrated  solution  of 
sodium  sulphate,  and  the  mixture  is  placed  upon  highly  porous  and  sensitive  lilac- 
tinted  litmus  blotting-paper.  The  blood-corpuscles  remain  upon  the  surface  while 
fluid  is  taken  up  by  the  paper  and  gives  rise  to  the  reaction. 

For  the  quantitative  estimation  of  the  alkalinity  dilute  tartaric  acid  is  added 
to  a  volume  of  blood  (7.5  grams  of  crystalline  tartaric  acid  to  i  liter  of  water,  i 
cu.  cm.  of  which  saturates  3.1  mg.  of  soda)  until  the  blue  paper  is  reddened. 
One  hundred  cu.  cm.  of  human  blood  contains  the  alkaline  equivalent  of  from  260 
to  300  mg.  of  soda  (in  guinea-pigs  150  mg.,  in  carnivora  180  mg.  of  soda). 

Landois'  method  for  the  quantitative  determination  of  the  alkalinity  of  the  blood 
with  only  a  few  drops  of  blood :  Tartaric  acid  in  the  concentration  already  stated 
is  employed  to  neutralize  the  alkalinity  of  the  blood.  Of  this  the  following  mix- 
tures are  made  by  addition  of  concentrated  solution  of  neutral  sodium  sulphate: 
(i)  10  parts  of  tartaric-acid  solution  and  100  parts  of  concentrated  sodium- 

29 


30  PATHOLOGICAL. 

sulphate  solution;  (2)  20  parts  of  tartaric-acid  solution  and  90  parts  of  sodium- 
sulphate  solution;  (3)  30  parts  of  tartaric-acid  solution  and  80  parts  of  sodium- 
sulphate  solution;  (4)  40  parts  of  tartaric-acid  solution  and  70  parts  of  sodium- 
sulphate  solution;  (5)  50  parts  of  tartaric-acid  solution  and  60  parts  of  sodium- 
sulphate  solution;  (6)  60  parts  of  tartaric-acid  solution  and  50  of  sodium-sulphate 
solution;  (7)  70  parts  of  tartaric-acid  solution  and  40  parts  of  sodium-sulphate 
solution;  (8)  80  parts  of  tartaric-acid  solution  and  30  parts  of  sodium-sulphate 
solution;  (9)  90  parts  of  tartaric-acid  solution  and  20  parts  of  sodium-sulphate 
solution;  (10)  100  parts  of  tartaric-acid  solution  and  10  parts  of  sodium-sulphate 
solution.  To  each  glass  an  excess  of  crystallized  sodium  sulphate  is  added  to  the 
point  of  insolubility. 

Of  the  blood  to  be  examined  i  drop  is  mixed  in  a  graduated  tube  prepared 
for  the  purpose  with  an  equal-sized  drop  of  the  acid-sulphate  mixture.  Into  a 
glass  tube  with  a  diameter  of  i  mm.  and  drawn  out  at  one  extremity  mercury 
is  sucked  to  a  height  of  about  8  mm.  so  that  the  tube  is  filled  to  the  tip.  The  upper 
extremity  of  the  thread  of  mercury  is  marked  by  the  scratch  of  a  file.  The  mer- 
cury is  now  drawn  into  the  tube  until  its  lower  border  reaches  the  file-mark.  The 
upper  border  of  the  mercury  is  now  marked  with  another  file-scratch.  In  this 
way  the  small  measuring  apparatus  is  improvised. 

In  order  now  to  test  the  blood,  one  drop  of  the  tartaric-acid  sodium-sulphate 
mixture  is  sucked  up  to  the  lower  mark,  and  then,  after  scrupulously  drying  the 
tip,  the  blood  is  drawn  up  until  the  fluid  reaches  the  upper  mark.  After  again 
cleansing  the  tip  of  the  tube  its  contents  are  blown  into  a  watch-glass,  are  well 
stirred  and  then  tested  with  reagent-paper.  Successively  the  mixtures  2,  3,  4, 
etc.,  are  treated  in  the  same  way.  The  reagent-paper  is  cut  into  strips  3  mm. 
wide,  and  these  are  partially  dipped  in  the  blood-specimens  in  the  respective 
watch-glasses.  The  blood-corpuscles  collect  about  the  immersed  extremity  of 
paper,  while  the  fluid  is  sucked  up  beyond  and  indicates  the  reaction.  If  the 
test  has  been  made  successively  in  this  manner  with  the  mixtures  from  i  to  10 
it  will  be  readily  seen  when  the  blue  tint  of  the  alkaline  reaction  ceases  and  the 
red  tint  of  the  acid  reaction  begins. 

In  human  beings  the  blood  can  always  be  obtained  directly  from  a  small 
needle-puncture.  Exact  suction  into  the  tube  can  be  effected  with  certainty  and 
convenience  if  the  upper  extremity  of  the  meastiring  glass  is  connected  by  means 
of  a  short  rubber  tube  with  a  hypodermic  syringe,  the  movement  of  whose  piston 
through  a  twisting  motion  facilitates  an  exact  degree  of  suction.  All  of  the  tests 
must  be  completed  with  equal  rapidity  and  at  the  same  temperature. 

The  degree  of  alkalinity  in  the  adult  will  in  general  be  satisfied  by  mixture 
5  or  6,  and  in  the  child  by  mixture  4.  If  all  parts  of  the  blood  are  uniformly  dis- 
solved previously  by  addition  of  water  this  solution,  which  obviously  can  no 
longer  be  designated  blood,  exhibits  a  somewhat  higher  degree  of  alkalinity. 
If  blood  is  tested  slowly  by  the  method  described  the  alkalinity  will  be  that  of 
such  a  solution. 

Pathological. — Persistent  vomiting  and  chlorosis  are  attended  with  increased 
alkalinity,  while  diabetes,  as  well  as  cachectic  states,  rheumatism,  uremia,  leuke- 
mia, profound  anemia,  high  fever,  cholera,  carbon-monoxid  poisoning,  and  degen- 
eration of  the  liver  are  attended  with  diminished  alkalinity.  Poisons  that  cause 
destruction  of  red  blood-corpuscles  likewise  bring  about  reduction  in  the  alkalinity. 

Blood  has  a  peculiar  odor. 

This  "halitus  sanguinis"  differs  in  human  beings  and  in  animals,  and  depends 
upon  the  presence  of  volatile  fatty  acids.  If  sulphuric  acid  be  added  to  blood, 
and  these  acids  are  in  consequence  set  free  from  their  combination  with  the  alkali 
of  the  blood,  the  characteristic  odor  appears  more  distinctly. 

The  blood  possesses  a  salty  taste,  derived  from  the  salts  dissolved  in 
the  blood-plasma. 

The  specific  gravity  of  the  blood  is  1058  (from  1046  to  1067)  in  men, 
and  from  1051  to  1055  in  women,  while  the  blood  of  children  has  a  lower 
specific  gravity.  The  specific  gravity  of  the  red  blood-corpuscles  is 
1105,  that  of  the  plasma  from  1027  to  1028.3.  This  fact  explains  the 
tendency  of  the  former  to  sink  to  the  bottom. 

Method  of  Determination. — For  clinical  investigation  the  following  method  (a 
modification  of  that  described  by  Roy)  can  be  recommended.  In  a  glass  tube, 


MICROSCOPIC    EXAMINATION    OF    THE    BLOOD.  31 

narrow  at  the  bottom  and  covered  with  a  rubber  cap,  a  fresh  drop  of  blood  ob- 
tained by  puncture  with  a  needle  is  permitted  to  enter  from  below.  The  tube  is 
at  once  immersed  in  a  glass  vessel  filled  with  a  solution  of  olive-oil  in  chloroform, 
and  by  pressure  upon  the  rubber  cap  the  drop  of  blood  is  expelled  into  the  fluid. 
Various  concentrations  of  the  latter  with  a  specific  gravity  between  1050  and  1070 
are  prepared,  and  that  solution  in  which  the  drop  remains  suspended  indicates 
the  specific  gravity  of  the  blood. 

The  specific  gravity  is  dependent  principally  upon  the  hemoglobin-content 
of  the  blood,  much  less  upon  the  number  of  erythrocytes.  It  is  high  in  the  newborn, 
namely,  1066.  The  drinking  of  water  and  hunger  will  reduce  the  specific  gravity 
temporarily,  and  it  falls  also  after  loss  of  blood  and  is  lower  in  the  presence  of 
anemia,  chlorosis,  marasmus,  and  nephritis  (down  to  1025).  It  is  increased  by 
thirst,  the  digestion  of  solid  food,  by  sweating,  acute  loss  of  water  through  the 
intestines  and  the  kidneys,  as  well  as  cyanotic  stasis  (down  to  1068).  The  entrance 
of  an  increased  amount  of  salts  into  the  blood  is  shortly  followed  by  dilution, 
while  the  salts  of  the  biliary  acids,  on  the  other  hand,  exert  a  concentrating  influence. 
The  specific  gravity  is  increased  by  vasomotor  contraction  of  the  vessels  and,  con- 
versely, it  is  diminished  by  vascular  dilatation.  The  blood-serum  of  women  is 
heavier  than  that  of  men.  If  blood  is  made  artificially  to  pass  repeatedly  through 
an  organ  its  specific  gravity  increases  in  consequence  of  the  taking  up  of  dis- 
solved substances  and  the  giving  off  of  water. 

For  the  determination  of  the  specific  gravity  of  the  red  blood-corpuscles,  these 
must  be  isolated  by  sedimentation.  This  takes  place  rapidly  in  the  case  of  horses' 
blood.  The  erythrocytes  are  said  to  be  somewhat  heavier  in  women  and  to  con- 
tain more  hemoglobin  than  those  of  men. 

The  freezing-point  of  the  blood  is  about  — 0.56°  C.  It  increases  as 
the  oxygen-content  diminishes. 

MICROSCOPIC  EXAMINATION  OF  THE  BLOOD. 

The  red  blood-corpuscles  or  erythrocytes  (Fig.  i)  were  discovered  in 
man  by  Leeuwenhoeck  in  1673  and  in  the  frog  by  Swammerdam  in  1658. 

Physical  Properties. — Human  erythrocytes  are  coin-shaped  discs 
with  biconcave  surfaces  and  rounded  margins.  The  diameter  is  7.5  //, 
the  thickness  of  the  edge  2.5  /;.,  and  the  central  thickness  from  1.8  to  2 ,« 
(Fig.  i). 

In  health  the  diameter  varies  from  6  to  9  // ;  the  average  being  from  7.2  to 
7.8  fi.  The  corpuscles  are  diminished  in  size  by  inanition,  elevation  of  the  bodily 
temperature,  carbon  dioxid  and  morphin,  and  increased  in  size  by  oxygen,  a 
watery  state  of  the  blood,  cold,  ingestion  of  alcohol,  quinin,  hydrocyanic  acid. 
[Pathological  conditions  are  discussed  on  p.  50.] 

The  volume  of  an  erythrocyte  equals  0.000000077217  cu.  mm.,  the  superficies 
0.000128  sq.  mm.  If  the  total  volume  of  the  blood  in  man  be  assumed  to  be 
4400  cu.cm.,  all  of  the  contained  blood-corpuscles  have  a  superficies  of  2816  square 
meters,  that  is,  the  equivalent  of  a  square  with,  sides  of  80  paces.  In  a  second 
176  cu.cm.  of  blood  are  driven  into  the  lungs  and  whose  blood-corpuscles  exhibit 
a  superficies  of  81  square  meters,  that  is,  a  square  with  sides  13  paces.  The 
volume  of  all  of  the  erythrocytes  can  be  approximately  determined  by  introduc- 
ing the  blood  into  a  narrow  graduated  glass  tube  ("hemokrit"  of  Hedin),  either 
unmixed  or  defibrinated  or  mixed  with  an  equal  amount  of  a  preservative  fluid 
capable  of  preventing  coagulation,  as,  for  instance,  2.5  percent,  potassium-bichrom- 
ate solution  or  0.86  percent,  sodium-chlorid  solution  with  some  ammonium  oxalate, 
and  subjecting 'it  to  centrifugation.  Treated  in  this  manner  healthy  human 
blood  is  found  to  contain  from  42  to  48  per  cent,  of  corpuscles  (anemic  blood 
30  per  cent,  and  less).  The  erythrocytes,  however,  undergo  changes  in  vol- 
ume, at  least  after  escape  of  the  blood,  by  the  taking  up  or  giving  off  of  fluid 
material,  as  exhibited  beyond  doubt  by  shrunken  and  distended  forms.  Venous 
blood  contains  a  greater  volume  of  erythrocytes  than  arterial  blood. 

The  iveight  of  an  erythrocyte  can  be  determined  by  multiplying  its 
volume  by  its  specific  gravity  (1105)  =  0.000000085325  mg. 


32  MICROSCOPIC    EXAMINATION    OF    THE    BLOOD. 

Alexander  Schmidt  determined  the  weight  of  the  red  blood-corpuscles  in  100 
parts  of  blood  in  the  following  manner:  He  ascertained  (i)  the  percentage  of  dry 
residue  of  the  blood  =  T;  (2)  the  percentage  of  dry  residue  of  the  corresponding 
blood-serum  =  t;  (3)  the  dry  residue  of  the  erythrocytes  contained  in  100  grams 
of  blood  =  r;  the  dry  residue  of  the  serum  obtained  from  100  grams  of  blood  is 
then  T  —  r,  the  corresponding  amount  of  serum  -  — ;  further,  the  weight 

of  the  erythrocytes  in  100  parts  of  blood  =  100—  -— ;  the  latter  equals 

48  grams  in  100  grams  of  blood  from  a  man  and  35  grams  in  the  same  amount 
of  blood  from  a  woman. 

Number. — In  men  the  number  of  red  blood-corpuscles  is  more  than 
5,000,000,  while  in  women  it  is  about  4,000,000  in  i  cubic  millimeter, 
making  25  billions  in  5  kilos  of  blood.  The  number  is  in  inverse  pro- 
portion to  the  amount  of  the  plasma,  and  from  this  fact  it  will  be  seen 


FIG.  i. — A,  human  colored  blood-corpuscles:  i,  on  the  flat;  2,  on  edge;  3,  rouleau  of  colored  corpuscles.  B, 
amphibian  colored  blood-corpuscles:  i,  on  the  flat;  2,  on,  edge.  C,  ideal  transverse  section  of  a  human 
colored  blood-corpuscle  magnified  5000  times  linear:  ab,  diameter;  cd,  thickness. 

that  the  number  must  vary  in  accordance  with  the  state  of  contrac- 
tion of  the  vessels,  conditions  of  pressure  and  diffusion  -  currents 
and  the  like. 

The  number  of  red  blood-corpuscles  is  increased  in  venous  blood  (at  times 
in  small  cutaneous  veins  and  in  the  presence  of  stasis) ,  after  the  ingestion  of  solid 
food,  after  rest  at  night,  after  marked  loss  of  water  through  the  skin,  the  intestine 
or  the  kidneys,  during  inanition  (in  consequence  of  the  consumption  of  blood- 
plasma),  in  the  blood  of  the  newborn,  at  times  after  late  ligation  of  the  umbilical 
cord  (from  the  fourth  day  the  number  again  becomes  reduced) ,  in  persons  of 
vigorous  constitution  and  in  residents  of  the  country.  The  number  is  dimin- 
ished during  pregnancy  and  after  copious  libations.  The  capillaries  contain 
relatively  few  blood-corpuscles.  Apparent  increase  or  diminution  must  also  ac- 
company variations  in  the  amount  of  plasma,  and  to  this  fact  special  attention 
should  be  given  in  investigating  the  effect  of  certain  influences  upon  the  number 
of  erythrocytes.  Thus,  for  instance,  the  increased  number  observed  in  those  re- 
siding at  a  high  altitude  may  depend,  wholly  or  in  part,  upon  a  greater  or  lesser 
reduction  in  the  plasma.  •  In  the  earlier  stages  of  fetal  life  the  number  is  from  J 
to  i  million  in  i  cu.  mm. 

Method  of  Counting  Blood-corpuscles. — An  exact  mixing  apparatus  for  the 
dilution  of  the  blood  is  the  first  requirement.  For  this  purpose  the  mixer  of 
Potain  will  answer  (Fig.  3).  This  is  a  carefully  calibrated,  pipet-like  glass  instru- 


METHOD    OF    COUNTING    BLOOD-CORPUSCLES. 


33 


merit,  whose  tip  is  dipped  into  the  blood,  which  by  suction  through  a  rubber  tube 
is  drawn  into  the  pipet  either  to  the  mark  \  or  to  the  mark  i.  The  tip  carefully 
dried  is  then  immersed  in  3  per  cent,  sodium-chlorid  solution,  which  is  sucked  up 
until  it  reaches  the  mark  101.  By  shaking  the  mixer  a  spherule  (a)  in  the  bulbous 
enlargement  of  the  apparatus  is  moved  about  so  as  to  effect  a  homogeneous  mix- 
ture. If  the  blood  be  sucked  up  to  the  mark  \  the  mixture  will  be  as  i  to  200, 
and  if  up  to  the  mark  i  as  i  to  100. 

For  the  enumeration  of  the  cells  a  small  amount  of  the  blood-mixture  is  intro- 
duced into  the  Abbe-Zeiss  counting-chamber  (Fig.  2) ,  the  first  few  drops  being 
thrown  away.  Upon  a  slide  is  cemented  a  glass  cell,  o.i  mm.  deep,  upon  whose 
floor  are  etched  a  series  of  squares  and  which  is  surrounded  by  a  groove  or  depres- 
sion and  is  provided  with  a  cover-glass  to  be  placed  over  it.  The  space  overlying 
each  square  has  a  capacity  of  ?7TVo  cu.  mm.  The  number  of  cells  in  each  square 
is  estimated  and  this  multiplied  by  4000  gives  the  number  of  corpuscles  in  each 


FIG.  2. — Apparatus  of  Abbe  and  Zeiss  for  Counting  the  Cor- 
puscles: A,  in  section;  C,  surface  view  without  cover- 
glass;  B,  microscopic  appearance  with  the  blood-cor- 
puscles. 


FIG.  3.— The  Melangtur, 
pipet  or  mixer. 


cu.  mm.     The  result  thus  obtained  must  be  multiplied  by  100  or  200,  according 
as  the  blood  has  been  diluted  100  or  200  times.     To  ensure  greater  accuracy  the 
contents  of  a  large  number  of  squares  should  be  counted  and  the  average  take 
Vierordt,  Malassez,  Gowers,  and  others  have  devised  similar  forms  of  apparatu 
for  the  same  purpose. 

To  count  the  white  blood-corpuscles  alone  in  the  chamber  the  blood  i 
with  10  parts  of  a  £  per  cent,  solution  of  acetic  acid,  which  dissolves  out  the  red 
corpuscles.      It  is  advisable  to  stain  the  leukocytes  in  the  blood-mixer,  and 
can  be  done  with  some  such  solution  as  the  following:  50  cu.  cm    of  a  I  per  c 
of  solution  of  sodium  chlorid  with  5  drops  of  a  5  per  cent,  alcoholic  s 
gentian-violet  or  hexamethyl-violet. 
3 


34  THE    RED    BLOOD-CORPUSCLES. 

The  red  blood-corpuscles  are  characterized  by  their  great  elasticity, 
flexibility,  and  softness. 

THE  RED  BLOOD-CORPUSCLES  (ERYTHROCYTES). 

Individually  the  red  corpuscles  are  of  a  yellowish  color  with  a  greenish 
tint.  They  are  unprovided  with  either  capsule  or  nucleus,  but  consist 
throughout  of  a  homogeneous  mass.  This  consists  (i)  of  a  framework 
of  exceedingly  pale,  soft  protoplasm,  the  stroma  or  cytoplasm,  and  (2) 
of  the  red  blood  coloring-matter,  the  hemoglobin,  which  impregnates 
the  stroma  (like  paraplasm),  in  the  same  way  as  a  sponge  takes  up  fluid. 


INFLUENCES  AFFECTING  THE  VITAL  PHENOMENA  OF  RED  BLOOD- 
CORPUSCLES. 

Blood-corpuscles  retain  in  unimpaired  degree  their  vital  and  func- 
tional activities  in  shed  blood  and  even  in  defibrinated  blood  subse- 
quently returned  to  the  circulation.  Heat  has  an  influence  upon 
their  vitality.  If  blood  be  heated  to  a  temperature  in  the  neighbor- 
hood of  52°  C.  the  vital  activity  of  the  erythrocytes  is  destroyed. 
This  fact  is  evident  from  the  circumstance  that  the  corpuscles  in  such 
blood  are  soon  dissolved  when  returned  to  the  circulation.  Kept  in 


FIG.  4. — Red  Blood-corpuscles:  a,  b,  normal  human  red  corpuscles,  the  central  depression  more  or  less  in  focus; 
c,  d,  e,  mulberry,  and  g,  h,  crenated  forms;  k,  pale  corpuscles  decolorized  by  water;  1,  stroma;  f,  frog's  blood- 
corpuscle  acted  on  by  a  strong  saline  solution. 

the  cold — in  a  flask  exposed  to  the  influence  of  ice-water — mammalian 
blood  may  retain  its  functional  activity  for  4  or  5  days.  Removed 
from  the  body  for  a  longer  period  of  time  and  then  returned  to  the  cir- 
culation the  red  corpuscles  rapidly  undergo  destruction — an  evidence 
that  they  have  lost  their  vital  activities  within  this  time. 

The  erythrocytes  in  blood  recently  removed  from  a  vessel  frequently 
exhibit  changes  in  form  that  result  in  their  assuming  a  mulberry-like 
appearance.  These  have  been  attributed  to  active  contraction  on  the 
part  of  the  stroma.  Nevertheless,  it  must  as  yet  be  considered  doubtful 
whether  this  is  to  be  looked  upon  as  an  obvious  vital  phenomenon. 
It  is  true,  however,  that  Max  Schultze  has  observed  active  contractility 
and  motility  in  the  red  blood-corpuscles  of  quite  young  embryo 
chickens.  In  support  of  the  vital  activity  of  the  red  corpuscles  the 
fact  may  be  cited  that  certain  substances  dissolved  in  the  plasma  are 


INFLUENCES    AFFECTING    PHYSICAL    RED    BLOOD-CORPUSCLES.  35 

not  capable  of  diffusing  into  the  red  blood-corpuscles,  as,  for  instance, 
solutions  of  potassium,  of  iron,  and  of  manganese,  although  other  sub- 
stances do  enter,  as,  for  instance,  sugar  and  chloroform. 

Nucleated  erythrocytes  are  undoubtedly  cells,  while  the  non-nucleated  ery- 
throcytes  cannot  properly  be  so  considered.  The  latter  have,  therefore,  been 
designated  blood-plastids. 

INFLUENCES  AFFECTING  THE  PHYSICAL  PHENOMENA  OF  RED    BLOOD- 
CORPUSCLES. 

The  color  of  the  red  corpuscles  is  changed  characteristically  by  a 
number  of  gases.  Thus,  oxygen,  therefore  also  the  air,  renders  the 
blood  scarlet  red,  deficiency  of  oxygen  renders  it  dark  bluish  red,  carbon 
monoxid  renders  it  cherry  red,  nitrogen  monoxid  renders  it  violet  red. 
All  agents  that  cause  marked  contraction  of  the  erythrocytes  induce  a 
bright  scarlet-red  color;  as,  for  instance,  concentrated  solution  of  sodium 
sulphate,  from  the  action  of  which  the  corpuscles  become  mulberry- 
shaped  or  distorted  into  the  shape  of  a  key,  and  in  a  measure  attenu- 
ated. The  color  thus  produced  is  brighter  than  is  ever  observed  in  the 
arteries.  Those  agents  that  make  the  corpuscles  globular,  as  particu- 
larly water,  cause  the  color  of  the  blood  to  become  darker. 

If  a  dry  preparation  of  blood  be  treated  with  concentrated  solution  of  methyl- 
ene-blue  diluted  half  with  water  some  of  the  erythrocytes,  particularly  degenerated 
ones,  become  stained.  It  is  the  larger  ones  that  are  especially  numerous  in  the 
presence  of  anemia  and  leukemia. 

Change  in  Position  and  Form. — A  phenomenon  frequently  observed 
in  recently  shed  blood  is  the  arrangement  of  the  corpuscles  like  rolls  of 
coin  (Fig.  i,  A,  3). 

The  conditions  that  increase  the  coagulability  of  the  blood  favor  this  phenome- 
non, which  is  to  be  attributed,  in  addition  to  the  attraction  of  the  discs,  to  the 
formation  of  a  viscid  substance.  The  condition  is  favored  by  warming  moderately 
the  slide  upon  which  the  fresh  drop  of  blood  is  received.  If  under  such  circum- 
stances agents  are  added  to  the  blood  capable  of  causing  the  corpuscles  to  swell, 
the  rolls  separate  as  the  individual  corpuscles  are  transformed  into  globules.  The 
adhesive  substance  uniting  the  erythrocytes,  and  which  not  rarely  is  drawn  out 
into  filamentous  threads,  is  derived  from  the  peripheral  layer  of  the  corpuscles. 
It  consists  of  the  stroma-fibrih,  formed  on  the  surface  of  the  corpuscles  in  conse- 
quence of  the  inception  of  an  injury  at  the  periphery,  and  which  has  become  viscid. 

The  changes  in  shape  that  the  erythrocytes  may  gradually  undergo 
after  leaving  the  body,  up  to  the  point  of  dissolution,  are  of  especial 
interest.  Some  agents  bring  this  series  of  changes  about  in  rapid  suc- 
cession. If,  for  instance,  blood  is  exposed  to  the  action  of  the  spark  of 
a  Leyden  jar,  all  of  the  corpuscles  become  at  first  mulberry-shaped, 
that  is,  the  surface  becomes  rough  and  soon  covered  with  at  times 
small,  at  other  times  large,  round  nodules  (Fig.  4,  c  d  e).  If  the  action 
be  more  pronounced  the  blood-corpuscles  become  almost  globular,  with 
many  projecting  points,  thorn-apple-like  (gh);  this  is  probably  an 
indication  of  the  death  of  the  corpuscle.  At  a  further  stage  the  action 
causes  the  corpuscles  to  assume  a  perfectly  globular  shape  (ii).  In 
this  form  they  appear  smaller  than  normal,  as  their  disc-shaped  mass  is 
contracted  into  a  sphere  with  a  lesser  diameter.  The  globules  thus 
formed  are  viscid,  and  adjacent  corpuscles  readily  adhere  to  one  another 
'and  like  fat-globules  they  may  unite  to  form  larger  spheres.  If  the 


36  PRESERVATION  OF  RED  BLOOD-CORPUSCLES. 

action  be  continued  for  a  still  longer  time,  the  blood  coloring  matter 
eventually  separates  from  the  stroma  (k),  and  the  blood-plasma  con- 
sequently becomes  reddened,  while  the  stroma  is  recognizable  only  as 
a  faint  shadow  (i).  The  changes  in  shape  described  represent  the 
effects  also  of  a  number  of  other  injurious  agents  causing  dissolution 
of  the  red  blood-corpuscles.  Thus,  for  instance,  all  of  the  changes  in 
shape  can  be  observed  also  in  putrid  fluid. 

Influence  of  Heat. — If  a  blood-preparation  be  heated  upon  a  warm 
stage  the  corpuscles  will  be  seen  to  undergo  remarkable  changes  in 
shape  when  the  temperature  reaches  52°  C.  They  become  in  part 
globular,  in  part  drawn  out  into  the  shape  of  a  biscuit,  at  times  per- 
forated, or  larger  or  smaller  drops  of  the  substance  of  the  body  are  com- 
pletely constricted  off.  and  float  about  in  the  surrounding  fluid.  This 
is  an  evidence  that  considerable  degrees  of  heat  destroy  the  histological 
individuality  of  the  corpuscles.  If  the  temperature  be  high  and  its 
influence  long  continued,  the  erythrocytes  are  finally  entirely  dissolved. 
In  the  case  of  burns  the  blood-corpuscles  may  undergo  the  same 
changes  within  the  vessels. 

The  addition  to  blood  of  a  concentrated  solution  of  urea  acts  in  the  same 
way  as  heat.  Blood-corpuscles  can  be  broken  into  fragments  in  microscopic 
preparations  by  strong  pressure.  The  disintegration  of  blood-corpuscles  into  frag- 
ments may  be  designated  erythrocytotrypsy,  in  contradistinction  from  their  dis- 
solution, which  is  known  as  erythrocytolysis. 

If  a  finger  moistened  with  blood  be  passed  over  a  hot  glass  plate  so 
that  the  thin  layer  of  fluid  is  rapidly  dried,  the  most  remarkable  forms 
of  long  drawn-out  distorted  blood-corpuscles  can  be  seen.  This  ex- 
periment demonstrates  in  a  striking  manner  their  marked  softness  and 
elasticity. 

If  blood  be  mixed  with  a  concentrated  solution  of  mucilage  and  if,  while  being 
examined  under  the  microscope,  concentrated  solution  of  sodium  chlorid  is  added, 
the  corpuscles  become  drawn  out  into  longitudinal  masses  (dragon-shaped) .  The 
same  change  is  observed  if  blood  be  admixed  with  an  equal  amount  of  liquid  gela- 
tin at  a  temperature  of  36°  C.,  and  sections  are  made  after  the  gelatinous  mass 
has  hardened. 

PRESERVATION  OF  RED  BLOOD-CORPUSCLES. 

The  following  are  admirable  preservative  fluids  for  red  blood-cor- 
puscles : 

Pacini's  Mixture.  Hayem's  Fluid. 

Mercuric  chlorid,   2.  Mercuric  chlorid,  0.5. 

Sodium  chlorid,  4.  Sodium  sulphate,  5. 

Glycerin,  26.  Sodium  chlorid,   i. 

Distilled  water,  226.  Distilled  water,  200. 
To  be  diluted  with  two  parts  of  dis- 
tilled water  before  being  used. 

In  order  to  avoid  all  influence  of  the  air  in  the  examination  of  fresh 
blood  the  following  procedure  is  recommended:  A  drop  of  Pacini's  fluid 
is  placed  upon  a  portion  of  the  skin,  which  is  then  punctured  with  a  fine 
needle  through  the  fluid.  In  this  way  the  blood  rises  into  the  preserva- 
tive fluid  without  having  at  any  time  come  in  contact  with  the  air  and 
the  form  of  the  corpuscles  is  at  once  fixed. 

In  examining  blood  for  medico-legal  purposes  the  microscope  is 
naturally  always  employed.  Dried  spots  are  carefully  softened  by 


PERMEABILITY    OF    ERYTHROCYTES.  37 

means  of  concentrated  or  30  per  cent,  solution  of  potassic  hydrate,  or 
with  some  preservative  fluid,  without  friction.  By  softening  them  with 
the  aid  of  concentrated  tartaric-acid  solution  the  leukocytes  appear 
with  especial  distinctness.  Often,  however,  search  for  the  presence  of 
blood-corpuscles  will  be  fruitless.  Red,  suspicious  fluids  are  examined 
directly.  If  the  blood-corpuscles  in  the  fluid  have  possibly  already 
become  pale,  or  if  they  are  present  only  as  stroma,  the  addition  of  a 
wine-yellow  aqueous  solution  of  iodin-potassium-iodid  to  the  micro- 
scopic preparation  will  at  times  render  them  much  more  distinct. 
Saturated  solution  of  picric  acid,  20  per  cent,  solution  of  pyrogallic 
acid  and  30  per  cent,  solution  of  silver  nitrate  have  also  been  recom- 
mended for  this  purpose. 

PERMEABILITY  OF  ERYTHROCYTES.— ISOTONIA  (HYPERISO- 
TONIA  AND  HYPISOTONIA).— DEMONSTRATION  OF  THE 
STROMA-LAKE  COLORATION  OF  THE  BLOOD. 

All  substances  soluble  in  water  attract  water  with  a  certain  intensity. 
The  energy  by  means  of  which  this  attraction  takes  place  is  known  as 
hygroscopic  energy  or  osmotic  tension.  The  manner  in  which  this  behaves 
with  regard  to  living  cells  was  discovered  by  de  Vries  (1884).  A 
vegetable  cell  consists  of  a  membrane,  which  is  permeable  to  salts  and 
to  water.  This  membrane  is  in  contact  by  its  inner  surface  with  the 
adjacent  cell-protoplasm,  which  likewise  is  permeable  to  water,  but  not 
to  salts.  If  fresh  vegetable  cells  are  placed  in  distilled  water,  this 
passes  through  the  cell-membrane  and  through  the  cell-protoplasm, 
and  causes  the  cells  to  swell.  If,  however,  the  cells  are  placed  in  a  strong 
saline  solution,  the  cell-contents  shrink,  because  water  is  abstracted 
from  them.  The  shrinking  of  the  cellular  protoplasm  is  shown  by  the 
fact  that  the  protoplasm  contracts  upon  all  sides  and  becomes  detached 
from  the  cell-membrane.  This  detachment  of  the  shrunken  cell-body 
from  the  cell-wall  in  consequence  of  loss  of  water  is  designated  plasmolysis 
by  de  Vries. 

Plasmolysis  is  the  more  pronounced  the  more  concentrated  the 
saline  solution  surrounding  the  vegetable  cell.  The  saline  concentra- 
tion that  brings  about  the  first  signs  of  plasmolysis  can  be  determined 
experimentally  for  every  variety  of  cell.  The  different  salts  must  be 
employed  in  various  concentrations,  in  order  to  bring  about  the  same 
degree  of  plasmolysis.  Solutions  of  different  salts  that  exert  the  same 
effects  in  the  process  of  plasmolysis  are  designated  isotonic  solutions. 
The  necessary  concentrations  are  to  each  other  as  the  molecular  weights 
of  the  different  salts.  For  instance,  a  0.58  per  cent,  solution  of  sodium 
chlorid  causes  the  beginning  of  plasmolysis  in  the  same  way  as  a  i.oi 
per  cent,  solution  of  potassium  nitrate,  or  as  a  1.5  per  cent,  solution 
of  sodium  iodid.  The  molecular  weights  of  the  three  substances  are 
58,  10 1 ,  and  150  respectively.  Isotonic  solutions  have  the  same  freezing- 
point,  which  always  becomes  lower  with  increasing  concentration;  and 
also  the  same  boiling-point,  which  becomes  higher  with  the  degree  of 
concentration. 

There  is  thus  for  the  red  blood-corpuscles  a  given  concentration  for 
certain  but  not  all  substances  in  which  they  neither  shrink  nor  swell. 
For  mammalian  erythrocytes  this  is  a  0.9  per  cent,  solution  of  sodium 
chlorid — for  the  frog  0.6  per  cent.  If  the  equally  effective  degree  of 


38  PERMEABILITY  OF  ERYTHROCYTES. 

centration  is  determined  for  other  salts,  the  isotonic  solutions  will 
be  established.  Obviously  the  blood-plasma  likewise  is  such  an  isotonic 
solution,  as  the  erythrocytes  retain  their  form  perfectly  within  it. 
Those  solutions  are  hyper  isotonic,  that  is,  of  greater  concentration, 
that  abstract  water  from  the  erythrocytes  and  therefore  cause  them  to 
shrink;  while  those  solutions  are  designated  hypisotonic,  that  is,  of 
feebler  concentration,  that  yield  up  water  to  the  erythrocytes  and  there- 
fore cause  them  to  swell. 

Although  the  erythrocytes  preserve  their  form  in  isotonic  solutions, 
nevertheless  an  interchange  may  take  place  between  the  soluble  sub- 
stances in  their  interior  and  those  of  the  surrounding  fluid.  Thus, 
chlorids,  phosphates,  and  proteids,  for  instance,  pass  from  one  to  the 
other.  Under  such  circumstances,  however,  the  isotonia  is  preserved. 
If,  therefore,  substances  pass  from  the  erythrocytes  into  the  surrounding 
blood-plasma,  other  substances  must,  conversely,  pass  into  them  in 
order  to  preserve  the  isotonia.  The  red  corpuscles  thus  possess  the 
property  of  maintaining  a  constant  degree  of  osmotic  tension  with  refer- 
ence to  certain  substances.  If,  for  instance,  small  amounts  of  an  acid, 
and  also  carbon  dioxid,  be  added  to  blood,  albumin  and  phosphates 
pass  from  the  corpuscles  into  the  plasma,  while,  conversely,  chlorids 
pass  from  the  latter  into  the  erythrocytes  to  maintain  the  isotonia.  In 
consequence,  the  corpuscles  become  somewhat  globular  and  their  diam- 
eter diminishes  in  size.  The  blood-corpuscles  exhibit  the  reverse  inter- 
change and  effect  in  shape  after  addition  of  small  amounts  of  alkali. 

Van  't  Hoff  discovered  in  1887  the  law  that  the  interchange  of  sub- 
stances in  solution  takes  place  according  to  the  same  laws  as  those 
applicable  to  gases,  namely,  the  osmotic  pressure  corresponds  entirely 
to  the  tension  of  a  gas.  The  laws  of  gases  laid  down  by  Boyle- 
Mariotte  are,  therefore,  applicable  also  to  substances  in  solution.  Ac- 
cordingly, and  by  reason  of  the  diversity  of  the  soluble  substances  con- 
tained within  the  cells  and  in  the  surrounding  fluids  currents  must  arise 
between  the  two  in  consequence  of  the  osmotic  pressure.  If,  therefore, 
erythrocytes,  which  behave  like  sacs  filled  with  saline  solutions,  are 
placed  in  another  saline  solution,  phenomena  appear  entirely  analogous 
to  those  that  occur  when  a  sac  filled  with  gas  is  introduced  into  another 
gas. 

The  erythrocytes  floating  in  a  solution  retain  their  volume  only  if  the 
fluid  is  isotonic;  that  is,  if  it  exerts  the  same  osmotic  pressure  and  if 
the  substances  dissolved  in  the  surrounding  solution  cannot  enter  the 
corpuscles.  If  the  osmotic  pressure  in  the  surrounding  fluid  is  dimin- 
ished the  corpuscle  swells  until  it  becomes  completely  dissolved  in 
water,  whose  osmotic  pressure  is  zero.  The  blood  then  becomes  lake- 
colored.  Exactly  the  same  effect  as  is  produced  by  distilled  water 
must  be  produced  also  by  the  solution  of  a  substance,  quite  independ- 
ently of  the  degree  of  its  osmotic  pressure,  if  the  substance  in  solution 
readily  penetrates  the  blood-corpuscles,  and  therefore  can  exert  no 
pressure  upon  its  wall.  Under  such  circumstances  also  the  corpuscle 
will  undergo  dissolution  and  the  blood  become  lake-colored. 

The  phenomenon  of  the  blood  becoming  lake-colored,  which  is  easily 
recognizable,  indicates,  therefore,  that  the  blood-corpuscles  are  either 
in  a  solution  of  low  osmotic  pressure  or  in  a  solution  whose  osmotic 
pressure  is  not  manifest  because  the  wall  of  the  corpuscles  is  impervious 


PERMEABILITY    OF    ERYTHROCYTES. 


39 


to  the  substance  in  solution.  Among  those  solutions  in  which  the  blood- 
corpuscles  are  dissolved,  independently  of  the  degree  of  osmotic  pres- 
sure of  the  solution,  urea  occupies  the  first  place.  The  ammonium 
salts,  with  the  exception  of  the  sulphate,  behave  in  the  same  manner. 
Certain  exceptions  to  which  the  laws  of  osmotic  pressure  for  the  blood- 
corpuscles  do  not  appear  to  apply  H.  Koeppe  has  been  able  to  explain 
according  to  the  theory  of  solutions  of  van  't  Hoff.  The  circumstance 
must  be  taken  into  consideration,  as  Ostwald  was  the  first  to  point  out, 
whether,  in  accordance  with  the  concentration  of  their  solution,  the 
dissolved  substance  has  or  has  not  completely  dissociated  itself  into  its 
ions. 

Many  agents  separate  the  coloring-matter  from  the  stroma.  In 
consequence  the  hemoglobin  is  dissolved  in  the  blood-plasma,  and  the 
blood  becomes  transparent,  as  it  contains  the  coloring-matter  in  the 
form  of  a  transparent  pigment.  It  is,  therefore,  designated  lake- 
colored.  Lake-colored  blood  is  dark  red.  In  the  dissolution  of  the 
erythrocytes  the  change  does  not  affect  the  aggregate  condition,  but  it 
consists  only  in  a  transposition  of  the  hemoglobin,  which  leaves  the 
stroma  and  passes  over  into  the  blood-plasma.  Therefore,  no  reduction 
in  temperature  takes  place. 

Method. — For  the  microscopic  demonstration  of  the  stroma  it  is  recommended 
that  a  one  per  cent,  solution  of  tartaric  acid  blood  mixed  with  an  equal  volume 
of  concentrated  sodium  sulphate  be  carefully  added.  In  order  to  obtain  an 
abundance  of  stroma  for  chemical  examination,  denbrinated  blood  is  mixed  with  10 
volumes  of  a  solution  of  sodium  chlorid  containing  i  volume  of  the  concentrated 
solution  and  from  1 5  to  20  volumes  of  water.  In  this  the  stromata  are  precipitated 
as  a  whitish  sediment. 

The  following  agents  effect  separation  of  stroma  and  hemoglobin: 

(a)  Physical  agents:   (i)     Heating  of  the  blood  to  a  temperature  of  60°  C. 
The  degree  of  heat  differs,  however,  in  different  animals.      (2)   Repeated    freez- 
ing and  thawing.    (3)  The  static  spark,  although  not  after  salts  have  been  added 
to  the  blood,  and  the  constant  and  induced  currents. 

(b)  Chemically  active  substances  generated  within  the  body:  (4)  Bile  or  bile-salts. 
(5)  Serum  from  other  species  of  animals.     Thus,  for  instance,  the  serum  of  dogs' 
blood  and  of  frogs'  blood  dissolves  the   blood-corpuscles  of  the  rabbit   in  a  few 
minutes.     According  to  Rummo,  Maragliano,  and  Castellino  the  blood-serum  in 
cases  of  acute  infectious  disease  and  chronic  dyscrasias  is  said  to  be  destructive 
to  the  erythrocytes  of  healthy  individuals.  •  (6)  Lake-colored  blood  from  a  number 
of  other  species  of  animals. 

(c)  Other  chemical   reagents:  (7)     Water.     (8)     Exposure   to  the   vapors   of 
chloroform,    ether,  amylene;     small    amounts    of    alcohol,    paraldehyd,    thymol, 
nitrobenzol,  ethylic  ether,  acetone,  petroleum  ether,  and  others.      (9)    Antimony 
hydrid,    hydrogen  arsenid,    carbon  disulphid.      (10)     Solutions    of    certain    salts 
may  be  mixed  with  blood  in  a  definite  concentration  without  causing  change  in 
the   red  blood-corpuscles.     If  the  saline   solution  is  made  either  more   dilute  or 
more  concentrated,  dissolution  of  the  corpuscles  takes  place.     This  is  the  case,  for 
instance,  with    sodium  chlorid.       Traces  of  alkali  render   the  erythrocytes  more 
resistant  to  such  solutions,  while  traces  of  acid  exert  an  injurious  effect.'    Accord- 
ing to  Bernstein  and  Becker  salts  cause  an  increase  in  the  resistance  to  physical 
solvents,  but  a  reduction  to  chemical  solvents.       (n)    Addition  of  boric  acid,  i 
per  cent.,  to  amphibian  blood  causes  the  red  mass,  which  at  the  same  time  sur- 
rounds the  nucleus  when    present   and   is  designated  zooid,  to  escape  from  the 
stroma,  which  is  designated  ecoid,  to  withdraw  from  the  periphery  to  the  inte- 
rior of  the  corpuscles,  and  often  entirely  to  pass  out.    Briicker,  therefore,  consid- 
ers the  stroma  to  a  certain  degree  a  repository  within  which  is  lodged  the  remain- 
ing substance  of  the  blood-corpuscles  especially  endowed  with  vital  phenomena. 
(12)   Strong  acid  solutions  dissolve  the  blood-corpuscles,  while  weaker  solutions 
cause  precipitates   in  the  hemoglobin.     This  can  be  distinctly  observed    in  the 
case  of  carbolic  acid.       (13)   Alkalies  in  moderate  concentration  cause  sudden  dis- 
solution.    Addition  of  potassic-hydrate  solution  of  about  10  percent,  to  the  blood 


40  FORM,    SIZE,    AND    NUMBER    OF    ERYTHROCYTES    IN    ANIMALS. 

from  the  margin  of  a  cover-glass  permits  the  process  of  dissolution  to  be  readily 
observed  microscopically.  At  first  the  corpuscles  abruptly  become  globular  in 
jerks  and  thus  apparently  smaller;  later  they  swell  up  like  soap-bubbles. 

The  influence  of  the  gaseous  content  of  the  red  blood-corpuscles  upon  their 
solubility  is  remarkable.  The  corpuscles  in  blood  containing  much  carbon  dioxid 
are  dissolved  most  readily;  those  in  blood  containing  much  oxygen  are  much  less 
readily  dissolved;  while  between  the  two  are  the  corpuscles  containing  much 
carbon  monoxid.  Total  removal  of  the  gases  of  the  blood  causes  of  itself  the  devel- 
opment of  a  lake-color. 

The  erythrocytes  possess  a  certain  degree  of  resistance  to  the  action 
of  solvents. 

The  following  method  may  be  employed  to  determine  this  degree  readily.  A 
drop  of  blood  is  mixed  with  an  equal  amount  of  a  3  per  cent,  solution  of  sodium 
chlorid,  and  then  as  much  distilled  water  is  added  as  is  required  to  dissolve  all  of 
the  red  blood-corpuscles.  The  method  is  carried  out  as  follows  with  human 
blood:  With  the  aid  of  the  blood-mixer  of  the  blood-corpuscle  counting-apparatus 
(Fig.  3)  blood  is  collected  from  a  puncture  of  the  skin  up  to  the  mark  i,  and  is 
expelled  for  microscopic  examination  into  a  concave  glass  cell,  in  which  previously 
an  equal  amount  of  a  3  per  cent,  solution  of  sodium  chlorid  had  been  placed. 
Well  admixed,  all  of  the  erythrocytes  will  be  preserved.  Now,  by  means  of  the 
same  apparatus,  distilled  water  is  added,  and  the  changes  observed  under  the 
microscope  until  all  of  the  red  corpuscles  are  dissolved.  The  glass  cell  is  covered 
after  each  addition  in  order  to  prevent  evaporation.  The  erythrocytes  of  some 
persons  are  more  readily  dissolved  than  is  normal,  being  soft  and  plastic  and  under- 
going striking  changes.  In  addition,  reference  may  be  made  to  the  following 
states:  All  blood-mixtures  that  jeopardize  the  normal  condition  of  the  erythro- 
cytes, such  as  cholemia,  intoxications  with  substances  that  cause  dissolution  of 
the  blood-corpuscles  and  high  grades  of  venosity.  Interesting  observations  may 
be  made  further  in  the  presence  of  blood-diatheses  and  infectious  processes,  hemo- 
globinuria,  and  burns.  The  resistance  appears  diminished  in  case  of  anemia  and 
of  fever. 

FORM,  SIZE,  AND  NUMBER  OF  ERYTHROCYTES  IN 
DIFFERENT  ANIMALS. 

All  mammals,  with  the  exception  of  the  camel,  the  llama,  the  alpaca, 
and  related  animals,  as  well  as  the  cyclostomata  among  fish,  for  instance 
the  lamprey,  have  coin-shaped  circular  erythrocytes.  The  mammalia 
excepted  have  oval  erythrocytes  without  nuclei,  while  birds,  reptiles, 
amphibia  (i,  B)  and  fish,  with  the  exception  of  the  cyclostomata,  have 
similarly  shaped  erythrocytes  with  nuclei. 

Size — M  =  o.ooi  Millimeter. 

Coin-shaped  Oval  Blood-corpuscles. 

Blood-corpuscles.  Short  Diameter.  Long  Diameter. 

Elephant,     9.4     //  Llama,        4.2  //  7.5    /u 


Man,  7.5 

Dog,  7.2 

Rabbit,  7.16 

Cat,  6.2 

Sheep ,  5.0 

Goat,  4-25 
Musk-deer,  2.5 


Pigeon,       6.5   "  14.7 

Frog,         16.3  "  23.0    ' 

Triton,      19.5   "  29.3    ' 

Proteus,  35.6   "  58.2    ' 

The  corpuscles  of  the  amphiuma  are  about  a 
third  larger  than  those  of  proteus. 


Among  vertebrates,  the  blood  of  the  amphioxus  is  colorless.  The  large  blood- 
corpuscles  of  many  amphibia  can  be  seen  with  the  naked  eye.  In  those  of  the 
frog  a  nucleolus  is  demonstrable.  It  is  readily  explicable  that  the  larger  the 
blood-corpuscles  the  smaller  must  be  their  number  and  their  total  superficies  in 
a  given  volume  of  blood.  Only  in  birds  is  the  number  relatively  larger  than  in 
other  classes  of  vertebrates,  notwithstanding  the  greater  size  of  the  corpuscles. 
This  probably  depends  upon  the  fact  that  in  them  metabolism  exhibits  the 
greatest  energy.  Among  mammals  carnivcra  have  a  larger  number  of  blood- 


DEVELOPMENT   OF    RED    BLOOD-CORPUSCLES.  41 

corpuscles  than  herbivora.  In  goats  the  blood  contains  19,000,000  blood-corpus- 
cles in  the  cubic  millimeter;  in  the  llama,  13,186,000;  in  the  bull  finch,  3,600,000; 
in  the  lizard,  1,292,000;  in  the  frog,  408,900;  in  the  proteus,  33,600.  During 
the  sleep  of  winter  Vierordt  observed  the  number  of  blood-corpuscles  in  the  mar- 
mot diminish  from  7,000,000  to  2,000,000  in  a  cu.  mm. 

In  invertebrates  the  blood  is  generally  colorless,  with  colorless  cells.  In  some 
invertebrates,  for  instance  the  earth-worm,  the  larva  of  the  large  gnat,  and  others, 
the  plasma  is  red  and  contains  hemoglobin,  but  the  blood-corpuscles  are  colorless. 
Red,  violet,  brownish,  greenish,  opalescent  blood,  with  colorless  corpuscles  (ame- 
boid cells),  is  found  in  some  mussels.  In  the  cephalopods  and  in  certain  snails 
and  crabs  a  bluish,  globulin-like  coloring-matter  is  present  in  the  blood,  containing 
copper  and  combining  with  oxygen,  hemocyanin,  which  is  decolorized  by  a  defi- 
ciency of  oxygen.  Certain  round-worms  have  a  green  respiratory  pigment,  chloro- 
cruorin,  while  other  animals  have  a  yellow,  red,  or  brown  pigment  of  similar 
function . 

DEVELOPMENT  OF  RED  BLOOD-CORPUSCLES. 

A.  The  embryonal  development  of  the  blood-corpuscles  begins  in  the 
chicken  as  early  as  the  first  day.  The  corpuscles  develop  in  groups 
within  large  globules  of  protoplasm  that  detach  themselves  from  the 
walls  of  the  vascular  spaces  resulting  from  the  apposition  of  the  forma- 
tive cells.  At  first  they  are  globular,  rough,  nucleated,  larger  than 
the  permanent  cells  and  unpigmented.  At  a  later  period  they 
take  up  the  coloring-matter  and  attain  their  definite  form,  with  reten- 
tion of  the  nucleus.  Only  when  the  vessels  enter  into  communication 
with  the  heart,  are  the  corpuscles  swept  away  or  isolated  in  groups, 
and  then  become  set  free  in  the  circulation.  Remak  demonstrated  all 
stages  of  their  multiplication  by  division.  Cells  dividing  by  mitosis 
are  observed  most  abundantly  between  the  third  and  the  fifth  day  of 
incubation,  but  no  longer  after  their  escape. 

Multiplication  takes  place  by  division  also  in  the  larvae  of  amphibia, 
as  well  as  during  fetal  life  in  mammals  in  the  spleen,  the  bone-marrow 
and  the  liver,  and  in  the  circulating  blood.  Neumann,  further,  found 
in  the  liver  of  the  embryo,  protoplasmic  cells— descendants  of  the  vas- 
cular endothelium  or  of  the  liver-cells — enclosing  red  blood-corpuscles. 
Besides,  there  were  found  in  the  liver  cells  with  large  nuclei,  in  part  con- 
taining hemoglobin,  in  part  free  from  hemoglobin,  which  divided  by 
mitosis  and  then,  with  shrinking  of  the  nucleus,  became  transformed 
into  definitive  blood-corpuscles.  Foa  and  Salvioli  observed  endogenous 
formation  in  the  lymphatic  glands,  in  addition  to  the  liver  and  spleen, 
also  within  large  protoplasmic  cells.  The  spleen  also  is  considered  a 
seat  for  the  formation  of  the  red  blood-corpuscles,  though  only  during 
embryonal  life.  Here  the  red  corpuscles  are  believed  to  be  formed  of 
yellow,  round,  nucleated  cells,  representing  transitional  forms. 

From  the  embryonal  bodies  (erythroblasts),  always  at  first  nucleated, 
there  result,  in  the  later  stages  of  embryonal  life,  the  characteristically 
shaped  and  at  the  same  time  non-nucleated  corpuscles;  the  nucleus, 
together  with  a  portion  of  the  protoplasm,  disappearing.  In  the  human 
embryo  only  nucleated  corpuscles  are  present  in  the  fourth  week.  In 
the  third  month  they  constitute  only  from  one-eighth  to  one-quarter  of 
all  the  erythrocytes,  while  at  the  end  of  fetal  life  nucleated  corpuscles 
are  found  only  with  great  rarity  (Fig.  8). 

According  to  some  observers,  mammalian  erythrocytes  contain  a  nucleus-like 
central  body,  which  Lavdowsky  considers  as  the  remains  of  nuclear  substance. 
According  to  J.  Arnold,  the  central  body  sometimes  observed  consists  of  a  gran- 


42  DEVELOPMENT    OF    RED    BLOOD-CORPUSCLES. 

ular-filamentous  transformation  of  the  previous  nucleus.  This  body,  designated 
nucleoid,  is  surrounded  by  a  zone  of  paraplasm,  enclosing  hemoglobin  and  gran- 
ular and  hyaline  matter  "in  a  filamentous  framework.  Nucleoid  and  paraplasm 
may  under  certain  conditions  be  extruded  from  the  erythrocytes.  Perhaps  these 
contribute  to  the  formation  of  blood-plates. 

B.  Development  of  Vessels  and  Blood-corpuscles  in  the  Earliest  Pest- 
embryonal  Period. — Following  J.  Arnold,  Golubew  believes  that  the 
blood  -  capillaries  present  in  the  tail  of  frog -larvae  form  in  various 
situations  at  first  solid  buds  that  grow  more  and  more  deeply  into  the 
tissues,  enter  into  anastomotic  union  with  adjacent  buds  and  finally 
become  hollow,  with  disappearance  of  their  protoplasmic  contents. 
The  capillaries  would  thus  like  an  intricate  branched  network  make 
their  way  into  the  tissues  and  spread  like  a  foreign  intruder.  Ranvier 
observed  the  same  process  of  growth  in  the  omen  turn  of  newborn  cats. 
The  development  of  the  capillaries  and  at  the  same  time  of  the  blood- 
corpuscles  in  their  interior  has  been  observed  in  an  especially  instruc- 
tive manner  in  the  large  omentum  of  the  young  rabbit.  .When  a 

week  old,  the  omentum  in 
these  animals  exhibits  dull- 
white  spots  in  whose  in- 
terior lie  so-called  vessel- 
forming  or  vaso-formative 
cells  (Fig.  5),  that  is, 
strongly  refracting  cellular 
elements  varying  widely  in 
shape,  and  provided  with 
protoplasmic  processes  (a). 
The  protoplasm  of  these 
cells  resembles  that  of  the 
lymph-cells,  particularly 
with  respect  to  its  mark- 

FlG.  5. — Formation  of  Red  Blood-corpuscles  within  "Vaso-forma-  ^^1 1  Tr     rp.ft-a  r>-rin  cr     r>li  a  t-a  r>t  Ar 

five  Cells,"  from  the  Omentum  of  a  Rabbit  Seven  Days  Old: 
r,  r,  the  formed  corpuscles;   K,  K,  nuclei  of  the  yaso-forma-  in      the      interior    OI      these 

capuiariis."'  a>  pr°cesses  which  ultimatdy  unite  to  form  cellular  structures  can  be 

seen  rod-shaped  nuclei  ar- 
ranged longitudinally  (K  K)  and  red  blood-corpuscles  (r  r),  both  sur- 
rounded by  protoplasm.  From  the  vessel-forming  cells  protoplasmic 
shoots  and  processes  arise,  which  in  part  terminate  free  and  in  part 
unite  to  form  a  delicate  network.  In  some  places  nucleated  connec- 
tive-tissue corpuscles  arranged  longitudinally  lie  upon  the  structures. 
These  constitute  the  beginning  of  the  connective-tissue  perivascular 
sheath. 

The  vessel  -  forming  cells  appear  in  various  shapes,  either  longi- 
tudinally cylindrical,  with  pointed  extremities,  or  round  or  oval,  rather 
resembling  large  lymph -cells  or  connective-tissue  cells.  These  cells 
are  always  the  seat  of  origin  of  non-nucleated  erythrocytes,  which  thus 
arise  in  the  protoplasm  of  the  vessel-forming  cells,  as  the  chlorophyl- 
grains  or  starch-granules  arise  in  the  protoplasm  of  vegetable  cells. 
Only  after  the  blood-corpuscles  have  thus  formed  within  their  interior 
do  these  cells  unite  through  their  processes  with  the  vascular  system. 
Their  tubular  arrangement  becomes  connected  with  adjacent  vessels 
and  the  blood-corpuscles  are  washed  away.  In  rabbits  from  four  to 
six  weeks  old  these  areas  contain  fewer  and  fewer  corpuscles.  If  it  be 


DESTRUCTION  OF  RED  BLOOD-CORPUSCLES.  43 

borne  in  mind  that  Schafer  observed  similar  formative  processes  in  the 
subcutaneous  connective  tissue  of  young  rats,  the  question  must  arise 
whether  such  blood-forming  stations  do  not  exist  in  many  parts  of  the 
body  and  constitute  seats  for  the  regeneration  of  the  blood. 

For  purposes  of  demonstration  it  is  only  necessary  to  observe  omentum  of 
suitable  age  in  a  fresh  state  in  peritoneal  fluid,  evaporation  being  prevented  by 
applying  paraffin  to  the  edges  of  the  cover-glass.  Landois  saw  preparations  of 
this  highly  interesting  developmental  process  in  the  laboratory  of  Ranvier  at 
Paris  with  such  a  degree  of  distinctness  as  to  leave  in  his  mind  no  doubt  as  to 
the  accuracy  of  the  observation.  Neumann  saw  analogous  formations  in  the 
embryonal  liver,  Wissotzky  in  the  amnion  of  the  rabbit,  Nicolaides  in  the  mesen- 
tery of  the  guinea-pig,  Klein  in  the  amniotic  sac  of  the  chicken's  egg,  Bayerl  in 
the  cartilaginous  capsules  of  ossifying  cartilage,  Leboucq  and  Hayem  in  other 
situations,  all  indicative  of  the  fact  that  the  blood-cells  develop  endogenously 
in  certain  cellular  structures  of  considerable  size  whose  protoplasm  serves  at  the 
same  time  for  the  formation  of  the  vessel-wall. 

C.  At  a  later  period  of  life  the  red  blood-corpuscles  develop  from 
special  nucleated  cells,  the  erythroblasts.  It  is  believed  that  the  latter 
gradually  assume  the  form  and  color  of  perfect  erythrocytes.  Accord- 
ing to  Neumann  they  possess  blood  coloring-matter  from  the  outset. 
In  caudate  amphibia  and  fish  the  spleen,  and  in  all  other  vertebrates, 
the  bone-marrow  constitutes  the  seat  for  the  formation  of  those  juve- 
nile forms  that  multiply  by  division.  Particularly  in  the  latter  all  stages 
of  the  transformation  may  be  seen,  especially  pale,  contractile  cells 
resembling  white  blood-corpuscles,  and  later  on  red  nucleated  corpuscles 
that  must  be  considered  as  the  progenitors  of  the  red  corpuscles  and 
that  are  capable  of  undergoing  multiplication  by  mitosis. 

After  copious  loss  of  blood  the  process  of  transformation  and  the 
entrance  into  the  blood-stream  is  said  to  be  observed  in  especially 
marked  degree.  J.  Arnold  found  in  the  protoplasm  of  the  nucleated 
erythrocytes  of  bone-marrow  granules  resembling  those  of  hemo- 
globin-free cells.  In  the  process  of  transformation  into  red  blood- 
corpuscles  these  granules  become  invisible  through  transformation. 
The  products  of  the  mitotic  division  of  the  pale  cells  especially  are  to 
be  considered  as  the  progenitors  of  the  nucleated  erythrocytes.  In  the 
red  bone-marrow,  perhaps  also  in  the  spleen,  the  small  veins  and  most 
of  the  capillaries  have  no  definite  wall.  The  formed  erythrocytes  accord- 
ingly can  at  any  time  be  swept  into  the  circulation  from  these  parts. 

The  bones  of  the  skull  and  most  of  those  of  the  trunk  contain  red  (blood- 
forming)  marrow,  while  the  extremities  contain  only  fatty  marrow,  or  only  the 
upper  portions  of  the  femur  and  the  humerus  contain  red  marrow.  When  active 
regenerative  processes  are  taking  place  in  the  blood  the  fatty  marrow  may  be 
transformed  into  red  marrow,  and  indeed  from  the  upper  portion  of  the  bones 
named  downward,  even  through  all  the  bones  of  the  extremities.  Red,  blood- 
corpuscle-forming  marrow  may  develop  even  in  the  ossitk-d  laryngeal  cartilages 
and  in  pathological  bony  tumors. 

DESTRUCTION  OF  RED  BLOOD-CORPUSCLES. 

As  erythrocytes  are  being  constantly  formed,  it  must  be  assumed 
that  they  are  being  constantly  destroyed.  Further,  the  situations  are 
known  in  which  this  occurs  especially.  Among  these  is  first  the  liver, 
as  the  elements  of  the  bile  are  formed  from  blood  coloring-matter 
and  the  blood  of  the  hepatic  veins  contains  a  smaller  number  of  red 
blood-corpuscles.  The  splenic  pulp  also  contains  cells  indicative  of 


44  DESTRUCTION    OF     RED    BLOOD-CORPUSCLES. 

disintegration  of  erythrocytes.  These  are  the  blood-corpuscle-con- 
taining cells  described  in  connection  with  the  spleen.  The  investigations 
of  Quincke  have  rendered  it  probable  that  the  red  blood-corpuscles 
— whose  span  of  life  may  cover  more  than  three  or  four  weeks — if  they 
are  to  be  eliminated  are  taken  up  by  the  white  blood-corpuscles  of  the 
liver-capillaries  and  by  perhaps  identical  cells  of  the  splenic  pulp  and 
of  the  bone-marrow,  and  preferably  deposited  in  the  liver-capillaries, 
the  spleen,  and  the  bone-marrow.  The  erythrocytes  taken  up  are, 
without  having  previously  been  dissolved,  converted  in  part  into  yellow 
and  in  part  into  colorless  iron-albuminates,  hematosiderin,  which  can 
be  demonstrated  microchemically  in  part  in  granular,  in  part  in  soluble 
form,  giving  rise  to  a  greenish  discoloration  on  addition  of  ammonium 
sulphid.  In  the  spleen  and  in  the  bone-marrow,  in  part  perhaps  also  in 
the  liver,  these  are  again  employed  for  the  regeneration  of  red  blood-cor- 
puscles, while  another  portion  of  the  iron  is  eliminated  through  the  liver. 

Latschenberger  has  found  pigmented  and  colorless  plates  in  the  blood,  the 
latter  at  times  in  flakes  of  fibrin,  and  these  he  considers  as  the  terminal  prod- 
ucts of  the  disintegration  of  all  morphological  blood-elements.  The  pigmented 
plates  are  derived  from  the  erythrocytes  and  exhibit  in  part  the  iron-reaction  of 
hematosiderin,  and  in  part  that  of  biliary  coloring-matter.  These  plates  are 
retained  and  further  transformed  in  the  spleen  and  in  the  bone-marrow. 

As  a  sign  of  the  degeneration  of  the  erythrocytes  that  may  precede  their 
death  Ehrlich  mentions  their  property  of  staining  violet  with  eosin-hematoxylin 
or  blue  with  methylene-blue.  The  rarity  with  which  cells  containing  blood-cor- 
puscles are  found  in  the  general  circulation  justifies  the  conclusion  that  corpuscles 
are  taken  up  within  the  spleen,  the  liver,  and  the  bone-marrow,  being  favored  by 
the  slowness  of  the  circulation  in  these  parts. 

Pathological. — Among  pathological  conditions  there  may  be  quantitative  dis- 
turbances in  the  processes  of  blood-destruction  and  blood-formation.  Accumula- 
tion of  iron-containing  materials  from  red  blood-corpuscles  may  take  place  in  the 
spleen,  the  bone-marrow,  and  the  liver-capillaries:  (i)  if  the  destruction  of  red 
blood-corpuscles  is  increased,  as,  for  instance,  in  cases  of  anemia;  (2)  if  the  for- 
mation of  new  red  elements  from  old  material  is  retarded.  If  elimination  through 
the  liver-cells  is  interfered  with,  the  iron  accumulates  in  them,  and  it  is  then 
present  in  the  blood-plasma  also  in  increased  amount,  and  it  may  be  eliminated 
by  other  glands,  although  a  deposit  of  iron  may  take  place  in  these  (cortex  of  the 
kidney,  pancreas)  within  the  glandular  cells  and  in  the  tissue-elements  of  other 
organs. 

After  abundant  regeneration  of  blood  in  dogs  the  leukocytes  of  the  liver- 
capillaries  are  in  the  course  of  four  weeks  enormously  rich  in  iron-containing 
granules;  likewise  the  cells  of  the  spleen,  of  the  bone-marrow,  of  the  lymphatic 

¥  lands,  further  the  liver-cells  and  the  epithelium  of  the  cortex  of  the  kidney. 
he  iron-reaction  in  the  two  situations  last  named  takes  place  also  after  intro- 
duction of  hemoglobin  or  of  iron-salts  into  the  blood. 

Within  thrombi  and  also  in  extravasations  of  blood  that  diffuse  into  the  sur- 
rounding living  tissue  hematosiderin  likewise  develops,  in  addition  to  hematoidin, 
which  forms  when  not  in  contact  with  the  tissues.  The  stage  of  iron-reaction  of 
the  products  of  the  disintegration  of  the  erythrocytes  is,  however,  not  of  con- 
sequence, as  in  the  progress  of  time  the  residuum  no  longer  exhibits  this  reaction. 

V.  Recklinghausen  designates  as  hemochromatosis  a  brownish  discoloration  of 
the  tissues  dependent  upon  abnormal  dissolution  of  erythrocytes  or  local  extrava- 
sations of  blood,  and  which  is  caused  by  the  iron-containing  hematosiderin  and 
the  iron-free  hemofuscin  derived  from  it.  Landois  observed  these  conditions  after 
extensive  transfusion. 

If  it  be  remembered  that  after  repeated  copious  loss  of  blood  and 
after  every  menstruation  the  blood  is  regenerated  within  a  relatively 
short  period  of  time,  it  is  evident  that  an  active  process  of  regeneration 
must  take  place.  As  to  the  amount  of  corpuscles  destroyed  daily  the 
amount  of  biliary  and  urinary  pigment  formed  from  the  blood  coloring- 
matter  affords  some  idea. 


THE     WHITE    BLOOD-CORPUSCLES.  45 

THE  WHITE  BLOOD-CORPUSCLES  (LEUKOCYTES),  THE  BLOOD- 
PLATES  AND  ELEMENTARY  GRANULES. 

Through  the  lymph-stream  colorless  cells,  designated  white  blood- 
corpuscles  or  leukocytes,  are  swept  into  the  blood.  In  addition  to  the 
blood  they  are  found  in  the  lymph,  in  adenoid  tissue,  in  bone-marrow 
and  as  wandering  cells  in  the  connective  tissues  of  various  parts,  as  well 
as  between  glandular  and  epithelial  cells.  They  consist  of  globular 
masses  of  viscid,  bright  or  granular,  highly  refracting,  soft,  motile, 
unencapsulated  protoplasm  (Fig.  6).  In  the  fresh  state  (A)  they 
exhibit  no  nucleus,  which  appears  only  after  addition  of  water  or  acetic 
acid  (B),  and  in  consequence  of  which  also  the  definition  becomes  more 
distinct.  Water,  besides,  renders  the  contents  more  granular  and  more 
turbid,  while  acetic  acid  causes  them  to  clear  up.  The  nucleus  contains 
one  or  more  nucleoli.  The  diameter  of  the  cells  varies  from  4  to  13  //. 
The  leukocytes  are  dissolved  by  peptone. 

In  accordance  with  their  form  and  size  leukocytes  are  differentiated 
as  follows:  (i)  Small  lymphocytes,  approximating  erythrocytes  in  size, 
with  a  large,  round,  deeply  staining  nucleus  and  a  thin  margin  of  proto- 
plasm.    (2)  Large  cells,  with 
an    extensive     oval,     feebly 
staining  nucleus  and  a  heavy 
cortical  layer  of  protoplasm.  "  ^. 

(3)     Cells    resembling    those       jg§^  HP 
last  described  except  that  the 
nucleus    is    constricted.     (4) 
Somewhat  smaller  cells,  con- 
stituting   about    three-quar-        FlG  6  _A)  human  white  ^00^0^,^,  without  any  re- 

terS      Of      the      total      number,  agent;  B,  after  the  action  of  water;  C,  after  acetic  acid; 

.    ,  ,  ,  111^-1  D.  frog's  corpuscles,  changes  of  shape  due  to  ameboid 

with  polymorphous,  lobulated  movement, 

or  variously   convoluted  nu- 
clei, or  nuclei  separated  into  from  one  to  four  parts.     The  last  three 
forms  of  cells  have  a  genetic  connection. 

The  leukocytes  increase  by  division,  in  part  by  mitosis,  in  part  by 
amitosis  especially  in  their  germ-centers,  that  is,  the  lymphatic  glands 
and  adenoid  tissues.  Division  has  not  as  yet  been  observed  in  the  small 
lymphocytes  found  in  the  lymphatic  glands  (Fig.  8,00).  Perhaps  these 
represent  juvenile  forms.  Also  sessile  cells  in  the^  connective  tissue 
may  undergo  multiplication  by  division  and  send  their  offspring  into  the 
blood  through  the  lymph-stream. 

The  number  of  leukocytes  in  a  given  division  of  the  vascular  system 
may  differ  widely.  At  times  they  may  be  found  increased  in  one  place 
or  another,  as,  for  instance,  as  a  result  of  chemotaxis,  while  at  other  times 
a  large  number  may  be  sent  into  the  blood-stream  from  the  lymphatic 
apparatus.  The  increase  is  designated  leukocytosis. 

The  number  of  leukocytes  is  considerably  less  in  shed  blood  than  in 
circulating  blood.  Immediately  after  removal  from  the  vessels  nine- 
tenths  of  all  of  the  leukocytes  are  destroyed  (fibrin-formation). 

Local  heat  diminishes,  and  cold  increases,  the  number  of  leuko- 
cytes in  the  vessels  of  the  part  of  the  body  treated,  as  they  are  re- 
strained in  the  blood-vessels  contracted  by  cold. 


46 


THE    WHITE    BLOOD-CORPUSCLES. 


NUMBER    OF    LEUKOCYTES    IN    PROPORTION  TO   THE  RED  BLOOD- 
CORPUSCLES  IN  SHED  BLOOD. 


UNDER  NORMAL  CONDITIONS. 

IN  VARIOUS  SITUATIONS. 

UNDER  VARIOUS  CONDITIONS. 

i     335,  Welcker, 
i     357,  Moleschott, 
i     500-800,  v.  Jaksch, 
(In  children  the  number 
is  said  to  be  somewhat 
greater  than  in  adults.) 

Splenic  vein,  i  :  60, 
Splenic  artery,  i  :  2260, 
Hepatic  vein,  i  :  170, 
Portal  vein,    i  :  740, 
The  number  is  in  general 
greater    in     the     veins 
than  in  the  arteries. 

The  number  is  increased 
by  digestion,  blood-let- 
ting,    long-continued 
suppuration,    menstru- 
ation, the  puerperium, 
the  death-agony,  tonic 
medicaments      (quinin, 
bitters)  ,     ingestion     of 
nuclein,  gout. 
The    number    is     dimin- 
ished   by    hunger    and 
impaired  nutrition. 

The  movement  of  the  leukocytes — observed  by  Wharton  Jones  in  1846 
in  the  ray,  and  by  Davaine  in  1850  in  man — which  has  been  desig- 
nated ameboid,  because  it  corresponds  entirely  with  that  of  the  ameba, 
is  due  to  alternate  contraction  and  relaxation  of  the  protoplasm 
surrounding  the  nucleus.  It  can  be  recognized  especially  from  the 
fact  that  processes  are  sent  out  from  the  surface  and  withdrawn  (Fig.  7) 
like  the  pseudopods  of  the  ameba.  At  the  same  time  the  protoplasm 
has  an  internal  current,  which  can  be  seen  particularly  in  the  polymor- 
phonuclear  cells.  Movement  has  been  seen  also  in  the  nucleus  itself. 
The  movement  is  attended  with  two  sets  of  phenomena:  (i)  The  migra- 
tion of  the  cells,  inasmuch  as  they  draw  themselves  along  by  means  of 
protrusion  and  retraction  of  their  viscid  processes.  In  this  way  they 
may  migrate  even  through  the  interstices  of  intact  vessels.  Arnold 
considers  the  capability  of  certain  wandering  cells  to  develop  into 
epithelioid  or  giant  cells  as  demonstrated.  (2)  The  taking  up  of 
small  granules,  such  as  fat,  pigment,  foreign  bodies,  which  at  first  adhere 
to  the  surface  and  through  the  internal  current  are  drawn  into  the 
interior  of  the  leukocytes  and  which  filially  may  be  again  extruded,  in 
the  same  way  as  amebae  take  up  food.  Thus  they  take  up  fat-globules, 
peptones  and  albuminous  bodies  that  have  gained  entrance  into  the 
blood-stream  and  which  they  may  later  deposit  elsewhere. 

Metschnikoff  dwells  upon  the  activity  of  the  leukocytes  in  retrogressive  pro- 
cesses, the  parts  to  be  broken  down  being  taken  up  in  the  forms  of  particles  and 
therefore  in  a  measure  devoured.  He  designates  the  cells  with  these  activities 
as  devouring  cells — phagocytes.  Thus  they  act  as  chondroclasts  and  osteoclasts 
in  the  absorption  of  cartilage  and  bone  respectively.  Cells  of  similar  activity 
are  found  in  the  tails  of  batrachia,  and  which  take  up  portions  of  the  tissue, 
as,  for  instance,  fragments  of  fibrils,  in  the  disappearance  of  the  tails  during 
the  process  of  metamorphosis.  (See  also  absorption  of  the  deciduous  teeth.) 
Thus,  schizomycetes  or  particles  of  other  substances  that  have  gained  entrance 
into  the  blood  have  been  found  taken  up  in  part  by  leukocytes.  Later,  the  leu- 
kocytes yield  up  these  substances  to  the  endothelial  cells  of  the  capillaries  of  the 
liver  and  the  lungs,  less  commonly  of  the  spleen.  The  motility  of  the  leuko- 
cytes is  destroyed  by  quinin. 

The  leukocytes  exhibit  still  another  interesting  peculiarity,  namely  that  of 
chemotaxis  (chemotropism) ,  which  consists  in  the  attraction  of  freely  motile 
cells— like  some  lower  organisms — by  certain  substances,  and  their  repulsion  by 
certain  others.  Especially  the  metabolic  products  of  pathogenic  and  non-path- 
ogenic microorganisms  exert  a  strong  attractive  influence  upon  the  leukocytes. 


HUMAN    LEUKOCYTES,    SHOWING    AMEBOID    MOVEMENTS. 


47 


If,  therefore,  colonies  of  staphylococcus  (bacteria  of  suppuration)  collect  at  a  given 
part  of  the  body  their  metabolic  products  attract  the  leukocytes  from  the  neighbor- 
ing vessels,  and  in  this  way  inflammatory  reaction  and  suppuration  result.  The 
poison  is  either  eliminated  with  the  pus  or  is  destroyed  by  the  phagocytic  activity 
of  the  leukocytes.  The  leukocytes  also  secrete  special  chemical  substances  that 
destroy  the  injurious  microorganisms.  These  substances  are  known  as  alexins. 

In  warm-blooded  animals  the  leukocytes  exhibit  movement  for  a 
long  time  upon  a  warm  stage — at  a  temperature  of  40°  C.  for  about  two 
or  three  hours;  a  temperature  of  47°  C.  induces  rigidity:  heat-rigidity 
and  death.  The  lowest  degree  of  temperature  at  which  ameboid  move- 
ment is  possible  is  14°  C.  In  cold-blooded  animals,  such  as  the  frog 
the  leukocytes  can  be  seen  to  make  their  way  out  of  a  small  coagulated 
blood-clot  in  a  moist 
chamber  and  move 
about  in  the  express- 
ed serum,  v.  Reck- 
linghausen  observed 
motile  phenomena  on 
the  part  of  leukocytes 
in  a  moist  chamber 
for  as  long  as  three 
wreeks.  Oxygen  is 
necessary  for  the 
moArement.  Induc- 
tion-currents cause 
the  leukocytes  sud- 
denly to  become 
round,  like  irritated 
amebae  through  re- 
traction of  all  of 
their  processes.  If  the  electric  current  be  not  too  strong,  the  leuko- 
cytes resume  their  movements  in  the  course  of  a  short  time.  Strong 
and  long-continued  currents  destroy  them,  causing  them  further  to  swell 
and  undergo  complete  disintegration.  The  dissolution  of  white  blood- 
corpuscles  is  known  as  leukocytolysis .  It  occurs  as  a  normal  phenom- 
enon in  the  circulating  lymph  and  in  the  blood  in  limited  degree. 

With  regard  to  the  -source  and  the  functional  significance'  of  the  different 
varieties  of  leukocytes  complete  knowledge  is  as  yet  wanting.  An  attempt  has 
been  made  to  obtain  a  sharper  differentiation  of  the  leukocytes  through  the 
property  of  the  smallest  granules  within  the  protoplasm  of  the  cells  to  stain  only 
with  acid  or  with  basic  or  with  neutral  pigments. 

Method. — Recently  shed  blood  is  spread  in  a  thin  layer  upon  a  cover-slip, 
dried  in  the  air,  then  placed  in  an  air-bath  at  a  temperature  of  i25°C.  for  two  hours. 
Next  it  is  stained,  washed  with  water,  dried  in  the  air  and  enclosed  in  Canada 
balsam. 

The  granules  of  the  oxyphile  or  eosinophile  cells  (Fig.  8,  a,b,  with  unstained 
nucleus;  "in  c  the  nucleus  is  stained  violet  with  hematoxylon)  are  stained  only 
by  acid  pigments,  such  as  a  saturated  solution  of  eosin  in  5  per  cent,  carbolglycerin. 
The  source  of  these  cells  is  the  bone-marrow.  In  normal  human  blood  they  con- 
stitute only  about  10  per  cent,  of  all  of  the  leukocytes,  but  in  cases  of  leukemia 
they  pass  in  large  number  from  the  bone-marrow  into  the  blood-stream— -myel- 
ogenous  leukemia. 

The  fine  granules  of  the  large  mononuclear  cells  of  normal  blood  are  stained 
only  by  basic  pigments,  such  as  a  concentrated  watery  solution  of  methylene-blue 
(f,  g),  as  well  as  those  of  the  majority  in  lymphemic  blood.  The  cells  known  as 
mast-cells  contain  basophile  granules  of  other  size  (d,  e).  These  cells  are  rare  in 
normal  blood,  but  they  often  occur  in  large  number  in  leukemic  blood.  Mast- 


FIG.  7. — Human  Leukocytes,  Showing  Ameboid  Movements. 


48 


VARIOUS  FORMS  OF  LEUKOCYTES  AND  ERYTHROCYTES. 


cells  may  be  found  also  in  the  connective  tissue  of  other  organs  in  the  vicinity 
of  the  epithelial  layer,  as,  for  instance,  in  cutaneous  areas  the  seat  of  chronic 
inflammation,  and  from  which  they  then  find  their  way  into  the  blood. 

Fine  neutrophile  granules  are  rendered  visible  by  neutral  stains,  as,  for  instance, 
acid  fuchsin  neutralized  with  methylene-blue.  These  cells  exhibit  peculiarly 
sharp,  polymorphous  nuclear  figures  (h)  or  apparently  several  small  nuclei.  They 
are  encountered  in  abundance  in  normal  blood  and  in  the  presence  of  leukocytosis 
(i  is  such  a  cell  in  the  fresh  state,  while  in  k  and  1  the  nucleus  alone  is  stained). 
The  smaller  number  of  neutrophile  cells  contain  a  large  nucleus,  surrounded  by 
a  thin  layer  of  protoplasm  (m  n) .  They  are  derived  from  the  spleen  and  the  bone- 
marrow.  Between  these  two  forms  (h  and  m  n)  there  are  transitional  varieties. 
The  leukocytes  h  i  migrate  in  the  presence  of  inflammation.  In  cachectic  states 
the  mononuclear  cells  (m  n)  preponderate,  while  both  forms  are  increased  in  num- 
ber in  association  with  acute  leukocytosis.  The  lymphocytes  o  o,  with  a  large 
reticulated  nucleus,  are  derived  from  the  lymphatic  glands. 

Neusser  found  numerous  granules  of  nucleoalbumin  in  the  leukocytes  in  cases 
of  gout  as  the  forerunners  of  uric-acid  formation.  The  leukocytes  exhibit  the  reac- 
tion for  glycogen  in  the  presence  of  progressive  suppuration. 


FIG.  8. — Various  Forms  of  Leukocytes  and  Erythrocytes.     X  1000.    [All  figures  are  drawn  after  the  same  scale: 
i,  a  normal  erythrocyte  drawn  into  the  scale;   i  =  i  /u-.] 

The  blood-plates  of  Bizzozero  (Fig.  9)  deserve  especial  consideration 
as  a  third  morphological  constituent  of  the  blood.  These  are  pale,  color- 
less, viscid,  biconcave  discs  of  varying  size,  averaging  3  P.  in  diameter. 
One  cu.  mm.  contains  245,000  plates.  Bizzozero  has  observed  them 
in  the  circulating  blood — in  the  mesentery  of  the  guinea-pig  and  the 
wing  of  the  bat.  They  collect  in  large  numbers  upon  a  thread  immersed 
in  fresh  blood.  They  can  be  obtained  from  escaping  blood  after  ad- 
mixture with  one  per  cent,  solution  of  osmic  acid  or  with  Hay  em's 
fluid  (Fig.  9,  3).  In  shed  blood  they  rapidly  undergo  transformation 
into  varied  shrunken  forms  (5),  disintegrating  into  small  particles  and 


THE    BLOOD-PLATES. 


49 


being  finally  dissolved.  Where  they  are  collected  together  they  readily 
cohere  into  masses  (7),  and  pass  over  into  aggregations  resembling 
stroma-fibrin,  which  in  coagulated  blood  may  be  united  with  shreds 
of  fibrin  (6,  8). 

Bizzozero  believes  that  they  furnish  the  material  for  the  fibrin  in  the  process 
of  coagulation,  and  he,  as  well  as  Eberth  and  Schimmelbusch,  attribute  the  initial 
formation  of  white  thrombi  to  them.  According  to  Lowit  they  are  formed  from 
disintegrated  leukocytes,  and  according  to  Lilienfeld  from  the  nuclein  and  albumin 
of  the  nuclei  of  these  cells.  According  to  Wooldridge  they  are  globulin-precipi- 
tates from  the  plasma.  J.  Arnold  followed  their  extrusion  and  detachment  from 
ery throcy tes ;  in  smaller  measure  they  are  derived  from  leukocytes.  Halla  found 
them  increased  in  pregnant  women,  Mosen  after  hemorrhage,  Afanassiew  in  the 
presence  of  regenerative  states  of  the  blood,  Cadet  in  association  with  hunger, 
Hayem  after  the  crisis  of  certain  infectious  diseases,  and  Fusari  in  cases  of  afebrile 
anemia.  They  are  diminished  in  the  presence  of  fever,  as  well  as  of  severe  infec- 
tions and  blood-stasis,  and  also  after  injection  of  leech-extract.  The  blood  of 
cold-blooded  animals  and  of  birds  contains  also  small  spindle-shaped,  nu- 
cleated cells. 


FIG.  9. — "Blood-plates"  and  Their  Derivatives:  i,  a  red  blood-corpuscle  on  the  flat;  2,  on  the  side;  3,  unchanged 
blood-plates;  4,  lymph  corpuscle,  surrounded  by  blood-plates;  5,  altered  blood-plates;  6,  lymph  corpuscle 
with  two  heads  of  fused  blood-plates  and  threads  of  fibrin;  7,  group  of  fused  blood-plates;  8,  small  group  ot 
partially  dissolved  blood-plates  with  fibrils  of  fibrin. 

Demonstration  in  Mass. — If  10  parts  of  blood  are  mixed  with  i  part  of  a  0.2 
per  cent,  solution  of  ammonium  oxalate  in  0.7  per  cent,  solution  of  sodium  chlorid, 
and  the  mixture  is  centrifugated,  a  grayish-red  layer  principally  of  leukocytes 
will  form  above  the  ery  throcy  tes,  and  over  this  a  white  layer  consisting  almost 
solely  of  blood-plates,  while  above  all  is  the  clear  plasma. 

In  addition,  a  few  small  granules,  so-called  elementary  granules, 
occur  in  the  blood.  These  are  irregular  masses  of  protoplasm  derived 
from  disintegrated  leukocytes  or  blood-plates. 

According  to  H.  F.  Miiller  there  are  constantly  present  also,  especially  after 
the  ingestion  of  food,  minute,  globular,  highly  refracting  granules,  which  are  not 
fat,  and  which  he  designates  blood-dust,  or  nemokonien. 

Coagulated  blood  contains  delicate  threads  of  fibrin  (Fig.  9,  6,  8), 
strung  like  a  spider's  web  between  the  corpuscles.  They  become  iso- 
lated after  dissolution  of  the  corpuscles.  Where  many  such  threads 
occur  together  a  nodular  accumulation  takes  place. 


50        ABNORMAL   CHANGES    IN    RED    AND    WHITE    BLOOD-CORPUSCLES. 

ABNORMAL  CHANGES  IN  THE  RED  AND   WHITE    BLOOD- 
CORPUSCLES. 

Loss  of  blood  is  always  followed  by  diminution  in  the  number  of  erythrocytes 
in  proportion  to  the  extent  of  the  hemorrhage,  and  the  number  may  fall  to  even 
less  than  400,000  in  the  cu.  mm.  The  loss  is  soon  made  good  by  the  absorp- 
tion of  lymph  from  the  tissues.  Menstruation  furnishes  an  indication  that 
moderate  loss  of  red  blood-corpuscles  may  be  replaced  in  twenty-eight  days. 
In  case  of  considerable  loss  of  blood,  causing  a  reduction  in  all  of  the  formative 
processes,  this  period  may  be  prolonged  to  five  weeks.  In  cases  of  acute  febrile 
disease  the  elevation  of  temperature  is  generally  attended  with  a  reduction  in  the 
number  of  red  blood-corpuscles,  though  with  an  increase  in  the  number  of  white 
corpuscles.  Chronic  diseases  diminish  the  number  and  often  the  hemoglobin-con- 
tent of  the  erythrocytes  in  still  greater  degree.  In  some  individuals,  in  whom 
the  red  blood-corpuscles  are  deficient  in  resistance,  these  undergo  dissolution 
in  consequence  of  the  action  of  profound  cold  upon  peripheral  portions  of  the 
body,  as,  for  instance,  from  the  application  of  ice-water,  while  the  blood-plasma 
becomes  reddened  and  hemoglobinuria  may  even  develop. 

Diminished  regenerative  activity  on  the  part  of  new  erythrocytes  will  also 
cause  reduction  in  their  number,  as  blood-corpuscles  are  constantly  undergoing 
destruction.  If  with  this  there  be  associated  direct  loss  of  blood,  as,  for  instance, 
menstruation,  the  reduction  may  become  considerable.  In  the  case  of  chlorosis 
a  congenital  deficiency  in  the  development  of  the  blood-forming  and  blood-pro- 
pelling apparatus,  that  is  the  vascular  system,  appears  to  constitute  the  cause. 
The  heart  and  the  vessels  are  small,  and  the  absolute  number  of  blood-corpuscles 
may  be  reduced  even  one-half.  In  the  blood-corpuscles  themselves,  whose  relative 
number  may  be  either  maintained  or  even  reduced  as  much  as  one-third,  the  hemo- 
globin is  reduced  about  one-third.  The  total  volume  of  erythrocytes  has  been 
found  diminished.  The  iron-content  of  the  blood  has  been  reduced,  even  to  one- 
half.  Courses  of  treatment  with  iron  again  increase  the  amount  of  hemoglobin 
and  iron  in  the  blood.  So-called  progressive  pernicious  anemia,  which  is  char- 
acterized by  the  fact  that  the  progressive  impoverishment  of  the  blood  may  even 
finally  terminate  fatally,  is  probably  dependent  upon  some  profound  derange- 
ment of  the  blood-forming  organs.  In  the  presence  of  this  disease  the  erythro- 
cytes are  reduced  in  number,  while  their  hemoglobin-content  is  increased.  Invo- 
lution-forms, disintegrat ing-products  (microcytes  and  poikilocytes)  and  earlier 
developmental  stages  of  erythrocytes  (nucleated  erythrocytes  of  normal  and  of 
excessive  size :  normoblasts  and  megaloblasts)  are  also  present .  Numerous  chronic 
intoxications,  as  with  lead,  swamp -miasm  or  syphilis,  are  likewise  attended 
with  reduction  in  the  number  of  blood-corpuscles. 

The  size  of  the  corpuscles  varies  in  disease  between  2.9  and  12.9  //,  with  an 
average  size  of  from  6  to  8  //.  Dwarf  blood-corpuscles  (6  i*  and  below,  microcytes) 
have  been  considered  as  juvenile  forms  and  are  found  in  abundance  in  almost 
all  forms  of  anemia  (Fig.  8,  6).  Giant  corpuscles  (megalocytes,  10  n  and  above) 
are  found  constantly  in  cases  of  pernicious  anemia,  occasionally  in  cases  of  leuke- 
mia, chlorosis,  and  cirrhosis  of  the  liver  (Fig.  8,  4,  5,  represents  a  nucleated 
megalocyte  as  the  forerunner  of  a  non-nucleated  megalocy  te) .  If  the  erythrocytes 
exhibit  marked  variation  in  form  and  size,  they  are  designated  poikilocytes  (Fig. 
8,  6). 

Abnormalities  in  the  form  of  the  red  blood-corpuscles  have  been  observed  after 
severe  burns.  The  corpuscles  appear  much  reduced  in  size  and  the  thought  sug- 
gests itself  that  under  the  influence  of  the  heat  accompanying  the  burn  droplets 
of  the  corpuscles  have  become  detached,  in  the  same  way  as  this  can  be  ob- 
served in  microscopic  preparations  on  application  of  heat.  Disintegration 
of  blood-corpuscles  in  many  such  droplets  (erythrocytotrypsy)  has  been 
observed  in  connection  with  various  disorders,  as,  for  instance,  severe 
malarial  fevers.  These  particles  represent  fragments  of  blood-corpuscles  and 
not  independent,  intact,  small,  individual  corpuscles.  From  these  fragments 
there  result  dark  pigment-particles  closely  related  to  hematin  and  which  at  first 
float  about  in  the  blood  (melanemia) .  This  condition  can  be  developed  artificially 
in  rabbits  by  introducing  carbon  disulphid  (7  parts  to  90  parts  of  oil)  subcutane- 
ously.  The  leukocytes  take  up  a  number  of  these  particles,  which  later  on  are 
found  deposited  in  various  tissues,  particularly  the  spleen,  the  liver,  the  brain, 
and  the  bone-marrow. 

In  some  cases  the  red  blood-corpuscles  exhibit  abnormal  softness,  so  that  they 


CHEMICAL    CONSTITUENTS    OF    THE    RED    BLOOD-CORPUSCLES.  51 

undergo  marked  changes  in  form  as  the  result  even  of  slight  extraneous  influences. 
With  regard  to  lessened,  resistance  on  the  part  of  the  erythrocytes,  reference  may 
be  made  to  p.  35.  The  nitrogen-content  of  the  erythrocytes  is  diminished  in 
cases  of  secondary  anemia,  and  it  is  increased  in  cases  of  pernicious  anemia.  In 
the  interior  of  the  erythrocytes  of  birds,  frogs,  turtles,  etc.,  low  forms  of  animals 
develop  at  times  in  the  form  of  round  pseudovacuoles,  and  out  of  which  free 
blood-worms  subsequently  develop.  Also  in  cases  of  malarial  infection  in  human 
beings  microbes  of  varying  form  (hemameba,  Lavcran)  have  been  observed  within 
the  erythrocytes,  and  which  probably  are  conveyed  by  stinging  insects  (mos- 
quitos) — in  the  same  way  as  Texas  fever  is  conveyed  by  ticks.  They  destroy 
the  red  blood-corpuscles  and  in  turn  are  destroyed  by  quinin. 

The  white  blood-corpuscles  are  generally  increased1  in  all  acute  diseases  in 
which  exudation  takes  place.  They  exhibit  excessive  increase  in  association 
with  so-called  leukemia.  In  this  disease  the  proportion  of  red  to  white  blood- 
corpuscles  may  be  as  2  to  i.  In  consequence,  the  blood  acquires  an  appear- 
ance as  if  it  were  mixed  with  milk.  At  the  same  time  the  number  of 
erythrocytes  is  diminished.  Leukemia  depends  upon  hyperplasia  of  the  lymphoid 
tissue  or  the  bone-marrow.  These  causes  are  responsible  for  lymphatic  and 
myelogenous  leukemia  respectively.  Lymphocytes  and  myelocytes  are  to  be 
carefully  differentiated.  The  enlargement  of  the  spleen  is  only  secondary;  there- 
fore a  pure  variety  of  lienal  leukemia  is  not  accepted.  Myelogenous  leukemia 
belongs  probably  among  the  active  forms  of  leukocytosis.  An  active  leukocytosis 
is  one  that  results  through  movement  or  migration  of  leukocytes  into  the  blood- 
current.  This  may  involve  the  polynuclear — neutrophile  or  eosinophile — or  the 
mixed  cells — the  latter  with  involvement  of  mononuclear  elements  containing 
granules:  myelemia.  The  passive  form  of  leukocytosis  comprises  the  various 
forms  of  lymphemia. 

CHEMICAL  CONSTITUENTS  OF  THE  RED  BLOOD-CORPUSCLES. 

The  blood  coloring-matter  hemoglobin — abbreviated  Hb — causes 
the  red  color  of  the  blood.  It  is  found  besides  in  muscular  tissue 
and  in  traces,  probably  only  as  a  contamination  through  dissolved 
cells,  in  the  blood-plasma.  In  the  spectroscope  it  exhibits  an  absorp- 
tion-band in  the  green  (Fig.  15,  4).  Its  percentage-composition  ac- 
cording to  Hiifner  is  for  the  blood  of  swine,  as  compared  with  that  for 
the  ox,  in  parentheses,  C,  54.71  (54-66);  H,  7.38  (7.25);  N  17.43 
(17.70);  S,  0.479  (o-447);  Fe,  0.399  (0.336);  O,  19.602  (19.543).  For 
one  atom  of  iron  there  are  two  atoms  of  sulphur  in  the  horse,  and  three 
in  the  dog.  According  to  Hufner,  the  formula  is  C636H1025N164FeS3O181) ; 
the  molecular  weight  is  14,129.  Hemoglobin  is  soluble  in  water;  when 
heated  it  coagulates  only  with  decomposition,  retaining  the  sulphur 
in  firm  union.  Although  it  is  a  colloidal  substance,  it  nevertheless 
undergoes  crystallization  in  all  classes  of  vertebrates  from  which  it  has 
thus  far  been  obtained,  in  figures  belonging  to  the  rhombic  system, 
principally  in  rhombic  plates  or  prisms,  and  from  the  guinea-pig  in 
rhombic  tetrahedra.  The  squirrel,  however,  forms  an  exception,  in- 
asmuch as  its  crystals  appear  as  hexagonal  plates.  The  crystals 
simply  separate  in  all  classes  of  vertebrate  after  slow  evaporation  of 
blood  rendered  lake-colored,  though  with  varying  degrees  of  readiness. 

It  is  to  be  inferred  that  the  variations  in  the  form  of  the  crystals  in  different 
animals  are  dependent  upon  slight  changes  in  chemical  constitution.  The  hemo- 
globin is  readily  crystallized  from  the  blood  of  man,  the  dog,  the  mouse,  the  guinea- 
pig,  the  rat,  the  marmot,  the  cat,  the  leech,  the  horse,  the  rabbit,  birds,  and  rish; 
and  with  difficulty  from  the  blood  of  sheep,  oxen,  and  swine;  and  not  at  all  from 
the  blood  of  the  frog.  Rarely  the  hemoglobin  of  a  single  blood-corpuscle  can  be 
seen  to  form  a  small  crystal  with  inclusion  of  the  stroma,  as  Landois  also  ob- 
served in  the  case  of  rabbits'  blood  that  had  stood  for  a  long  time.  Within  the 
large  blood-corpuscles  of  fish  the  small  crystal  lies  at  times  within  the  stroma 
by  the  side  of  the  nucleus.  In  this  class  of  vertebrates  colorless  crystals  also  have 
at  times  been  observed. 


52 


PREPARATION     OF    HEMOGLOBIN-CRYSTALS. 


The  crystals  of  hemoglobin  are  doubly  refracting  and  pleochromatic, 
that  is,  they  appear  bluish  red  in  transmitted  light  and  scarlet  red  in 
reflected  light.  The  crystals,  which  contain  from  3  per  cent,  to  9  per 

cent,  of  water  of  crystallization  and 
therefore  become  disintegrated  from  es- 
cape of  this  water  on  exposure  to  the 
air,  are  always  soluble  in  water,  though 
different  varieties  dissolve  with  varying 
degrees  of  facility.  They  are  more 
readily  soluble  in  dilute  alkali.  The 
solutions  are  dichroic,  that  is,  they  ap- 
pear red  in  reflected  light  and  greenish 
in  transmitted  light.  They  are  insolu- 
ble in  alcohol,  ether,  chloroform,  and 
fats. 


As  a  result  of  the  process  of  crystalliza- 
tion the  hemoglobin  itself  appears  to  under- 
go an  internal  change.  Previous  to  crystal- 
lization it  does  not  diffuse  as  a  true  colloidal 
body;,  but  it  actively  decomposes  hydrogen 
dioxid.  Dissolved  in  the  form  of  crystals, 
however,  it  is  slightly  diffusible,  and  does 
not  decompose  hydrogen  dioxid,  through  the 
action  of  which  it  is  decolorized.  The  crys- 
tals of  hemoglobin  collect  like  an  acid  at  the 
positive  pole  of  an  electric  current.  As  the 
hemoglobin  thus  exhibits  alterations  after  its 
separation  from  the  erythrocytes,  Hoppe- 
Seyler  believed  that  the  oxyhemoglobin  was  united  with  lecithin  within  the 
erythrocytes,  and  also  the  hemoglobin.  The  former 'combination  he  designated 
arterin  and  the  latter  phlebin. 


FIG.  10. — Hemoglobin-crystals:  a  b,  from  hu- 
man blood;  c,  from  the  cat;  d,  from  the 
guinea-pig;  e,  from  the  marmot;  and  f, 
from  the  squirrel. 


PREPARATION  OF  HEMOGLOBIN-CRYSTALS. 

Method  of  Rollett. — Defibrinated  blood,  made  lake-colored  by  freezing  and 
thawing,  is  poured  into  a  shallow  vessel,  whose  bottom  is  covered  therewith  to  a 
height  of  only  i£  mm.  Evaporation  is  permitted  to  take  place  slowly  in  a  cool 
place  and  as  a  result  the  crystals  separate. 

Method  of  Hoppe-Seyler. — Defibrinated  blood  is  mixed  with  10  volumes  of 
a  solution  of  sodium  chlorid  or  of  sodium  sulphate  (i  volume  of  a  concentrated 
solution  to  9  volumes  of  water)  and  permitted  to  stand.  After  the  lapse  of  two 
days  the  clear  supernatant  layer  is  removed  with  a  pipet,  while  the  thick  sediment 
of  blood-corpuscles  is  washed  with  water  into  a  glass  flask,  and  shaken  with  an 
equal  volume  of  ether  until  the  blood-corpuscles  are  dissolved.  After  standing  for 
a  short  time  the  supernatant  ether  is  removed,  and  the  lake-colored  fluid  filtered 
in  the  cold;  then  one-fourth  volume  of  cold  (o°)  alcohol  is  added.  This  mixture 
is  permitted  to  stand  for  several  days  at  a  temperature  of — 5°  C.  The  crystals 
that  will  thus  have  formed  in  abundance  can  be  collected  upon  a  filter  and  dried 
by  pressure  between  blotting-paper.  Through  the  gradual  action  of  the  alcohol 
upon  the  hemoglobin-solution,  by  introduction  into  a  dialyzer,  it  is  possible  to  obtain 
crystals  several  millimeters  long. 

Method  of  Gscheidlen. — Gscheidlen  obtained  the  largest  crystals,  several  centi- 
meters in  length,  by  melting  in  small  glass  tubes  defibrinated  blood  that  had 
been  exposed  to  the  air  for  24  hours,  and  preserving  for  several  days  at  a  tem- 
perature of  37°  C.  Spread  upon  a  glass  plate  the  crystals  readily  appear. 

QUANTITATIVE  ESTIMATION  OF  THE  HEMOGLOBIN. 

(a)  From  Its  Iron-content. — As  in  the  dry  state  (100°  C.)  hemoglobin  contains 
0.42  per  cent,  of  iron  by  weight,  the  amount  of  hemoglobin  can  be  estimated 
from  the  amount  of  iron  in  the  blood.  If  m  represents  in  percentage  the  weight 


QUANTITATIVE    ESTIMATION    OF    THE    HEMOGLOBIN.  53 

of  metallic  iron  found,  the  percentage  of  hemoglobin  in  the  blood  will  be  as  100 
m  :  0.42.  The  mode  of  procedure  is  as  follows:  A  measured  amount  of  blood  is 
reduced  to  ash  and  this  is  exhausted  with  hydrochloric  acid  for  the  preparation 
ot  tcrnc  chlond.  Next  the  ferric  chlorid  is  converted  into  ferrous  chlorid  and 
this  is  titrated  with  a  solution  of  potassium  permanganate. 

(6)  Colorimelric  Method.—  A  dilute  watery  solution  of  crystallized  hemoglobin 
is  prepared,  the  exact  strength  of  which  is  thus  known.  With  this  are  compared 
watery  dilutions  of  the  blood  to  be  examined,  water  being  added  to  the  latter 
until  the  color  is  the  same  as  that  of  the  hemoglobin-solution.  The  specimens  to 


FIG.  ii. — -V.  Fleischl's  Hemometer.     To  wash  out  the  graduated  pipet  the  larger  tube  held  over  it  is  employed. 

be  compared  are  contained  in  similar  vessels  of  exactly  the  same  thickness  (hema- 
tinometer).  Hoppe-Seyler  has  recently  devised  a  colorimetric  double  pipet  for 
this  purpose.  The  blood-specimens  are  saturated  with  carbon  monoxid. 

For  clinical  purposes  v.  Fleischl's  hemometer  is  recommended  (Fig.  n).  This 
consists  of  a  cylinder  mounted  upon  a  metallic  plate  and  divided  into  two  equal 
parts,  which  are  closed  at  one  extremity  by  a  disc  of  glass.  Each  half  is  filled 
with  water,  and  then  a  measured  amount  of  blood,  obtained  with  a  pipet  of  deter- 
mined capacity  from  a  punctured  wound,  is  introduced  into  the  one  half  and 
dissolved.  The  color  of  the  red  solution  thus  produced  is  compared  with  that  of 
a  ruby-red  glass  wedge  viewed  through  the  clear  water  in  the  other  half  of  the 
cylinder  and  capable  of  being  moved  forward  and  backward  by  a  screw,  until 


54  EMPLOYMENT    OF    THE    SPECTROSCOPE. 

the  color  appears  the  same  in  both.  The  illumination  of  the  blood-solution  and 
the  red  wedge  takes  place  from  below  by  means  of  the  light  of  a  lamp.  The 
glass  wedge  is  provided  with  a  scale,  and  when  the  colors  in  the  two  halves  of 
the  cylinder  are  alike  the  number  on  the  wedge  indicates  the  amount  of  hemo- 

flobin  in  terms  of  percentage  of  the  normal  blood;  thus,  for  instance,  the  figure 
o  indicates  that  the  examined  blood  contains  80  per  cent,  of  the  hemoglobin  in 
normal  blood. 

(c)  With  the  aid  of  the  spectroscope  Preyer  found  that  a  solution  of  0.8  per 
cent,  of  pxyhemoglobin  in  water — i  cm.  thick — yielded  in  addition  to  red  and 
yellow  the  first  band  of  green  in  the  spectroscope  (Fig.  15,  i).  Of  the  blood  to 
be  examined  about  0.5  cu.  cm.  is  taken  and  is  diluted  with  water  until  the  identical 
of  effect  in  the  spectroscope  is  obtained.  In  addition  to  having  the  layers  of  fluid 
equal  thickness — namely  i  cm. — the  width  of  the  slit  in  the  spectroscope  and  the  dis- 
tance between  this  and  the  vessel,  as  well  as  the  intensity  of  the  source  of  light 
(stearin  candle),  must  be  the  same.  If  k  represents  the  amount  of  hemoglobin  in 
percentage  that  permits  the  passage  of  the  green  color  (0.8  per  cent.),  and  b  the 
volume  of  blood  to  be  examined  (about  0.5  cu.  cm.),  and  w  the  amount  of  water 
necessary  for  dilution,  then  x  equals  the  amount  of  hemoglobin  in  the  blood  to 
be  examined  expressed  in  percentage,  that  is  x  =k  (w+b) :  b.  It  is  advantageous 
to  add  a  trace  of  potassic  hydrate  to  the  blood  and  to  saturate  it  with  carbon 
monoxid. 

The  amount  of  hemoglobin  is  in  men  13.77  per  cent,  of  the  total 
volume  of  blood,  in  women  12.59  per  cent.,  in  pregnant  women — with 
progressive  diminution — from  12  to  9  per  cent.  According  to  Lichten- 
stern  and  Winternitz  the  hemoglobin  is  most  abundant  in  the  blood 
of  the  newborn,  but  this  is  no  longer  the  case  after  the  age  of  ten  weeks. 
Between  six  months  and  five  years  of  age  it  is  smallest  in  amount  and 
reaches  its  second  maximum  between  twenty-one  and  forty-five  years, 
after  which  it  falls  again.  The  hemoglobin  in  female  blood  grows  less 
after  the  tenth  year.  The  ingestion  of  food  is  followed  by  transitory 
diminution  in  the  amount  of  hemoglobin  in  consequence  of  the  dilution 
of  the  blood. 

The  amount  of  hemoglobin  in  different  animals  is  as  follows:  9.7  per  cent,  in 
the  dog;  9.9  per  cent,  in  cattle;  10.3  per  cent,  in  sheep;  12.7  per  cent,  in  swine; 
13.1  per  cent,  in  the  horse,  and  from  1 6  to  17  per  cent,  in  birds. 

In  moist  erythrocytes  Hoppe-Seyler  found  the  hemoglobin  to  con- 
stitute 40.4  per  cent,  of  all  the  organic  elements,  while  in  the  dry  cor- 
puscles the  amount  was  95.5  per  cent.,  the  amount  being  smaller  in  the 
nucleated  corpuscles  of  animals. 

Pathological. — A  reduction  in  the  amount  of  hemoglobin  in  the  blood  takes 
place  during  convalescence  from  febrile  diseases,  as  well  as  in  the  presence  of 
pulmonary  tuberculosis,  carcinoma,  ulcer  of  the  stomach,  diseases  of  the  heart, 
chronic  disease,  chlorosis,  leukemia,  pernicious  anemia,  and  in  conjunction  with 
vigorous  mercurial  treatment  for  syphilis.  In  the  presence  of  hunger  the  hemo- 
globin is  more  resistant  than  the  remaining  solid  elements  of  the  blood. 

EMPLOYMENT  OF  THE  SPECTROSCOPE  FOR  HEMOGLOBIN 

EXAMINATION. 

The  spectroscope  (Fig.  12  and  Fig.  161)  consists  (i)  of  a  tube  A,  having  at 
its  peripheral  extremity  a  slit  S,  which  can  be  made  larger  and  smaller.  At  the 
other  extremity  is  a  double  convex  lens  C,  known  as  a  collimator,  so  adjusted 
that  the  slit  is  placed  exactly  at  the  focus  of  this  lens.  Light,  from  the  sun  or 
a  lamp,  illuminating  the  slit,  passes  therefore  in  parallel  lines  through  C.  (2)  The 
prism  P,  by  means  of  which  parallel  rays  are  refracted  and  broken  up  into  the 
spectral  colors,  r-v.  An  astronomic  telescope,  inverting  the  image,  is  directed 
toward  the  spectrum  r-v,  which  appears  magnified  from  6  to  8  times  to  the  view 
of  the  observer  B  with  the  aid  of  the  telescope.  (3)  The  tube  O  contains  a  delicate 
scale  M  etched  upon  glass,  and  the  image  of  which  when  illuminated  is  thrown 
upon  the  surface  of  the  prism,  whence  it  is  in  turn  reflected  to  the  eye  of  the 


OXYGEN-COMBINATIONS    OF    HEMOGLOBIN.  55 

observer.  In  this  way  the  observer  can  see  the  spectrum  and  in  or  over  it  the 
scale.  To  exclude  extraneous,  disturbing  light,  the  prism  and  the  inner  extremities 
of  these  tubes  are  enclosed  within  a  metallic  capsule  whose  interior  is  colored 
black. 

Absorption-spectra. — If  a  colored  medium,  as,  for  instance,  a  solution  of  blood, 
be  placed  between  the  slit  of  the  spectroscope  and  a  source  of  light,  the  interposed 
solution  does  not  permit  the  passage  of  all  of  the  rays  of  white  light,  but  some 
of  these  are  absorbed.  Therefore,  that  portion  of  the  spectrum  whose  rays  are 
not  permitted  to  pass  appears  dark  to  the  observer. 


FIG.  12. — Diagrammatic  Representation  of  the  Spectroscope  for  Study  of  the  Absorption-spectra  of  the  Blood. 

Flame-spectra. — If  combustible  substances  are  permitted  to  burn  before  the 
slit  in  a  non-luminous  (gas)  flame  at  the  extremity  of  a  platinum  wire  the  elements 
of  the  ash  yield  bands  of  a  special  color  occupying  a  definite  position.  Thus, 
sodium  gives  rise  to  a  yellow,  potassium  to  a  red  and  a  violet  line,  which  are  found 
on  combustion  of  the  ash  of  almost  all  organs.  If  sunlight  alone  is  permitted 
to  pass  through  the  slit  the  spectrum  exhibits  a  large  number  of  lines  (Fraun- 
hofer's  lines)  occupying  definite  positions  within  the  colors  and  according  to  which 
different  parts  of  the  spectrum  can  be  localized.  These  are  designated  A,  B,  C,|D, 
etc.,  a,  b,  c,  etc.  (Fig.  15). 

OXYGEN -COMBINATIONS   OF   HEMOGLOBIN:   OXYHEMOGLOBIN  AND 

METHEMOGLOBIN. 

Oxygen-hemoglobin  or  Oxyhemoglobin — abbreviated  to  O-Hb — is  read- 
ily developed  when  hemoglobin  comes  in  contact  with  oxygen  or  with  air 
(details  on  p.  78).  Oxyhemoglobin  is  somewhat  less  readily  soluble 
than  hemoglobin.  On  spectroscopic  analysis  it  exhibits  two  dark 
absorption-bands  in  the  yellow  and  the  green,  whose  position  and 
width  in  an  0.18  per  cent,  solution  are  shown  in  Fig.  15  (2). 

Oxyhemoglobin  is  contained  within  the  erythrocytes  in  the  circu- 
lating blood  of  the  arteries  and  capillaries,  as  may  be  demonstrated  by 
spectroscopic  examination  of  the  ear  of  the  rabbit  and  of  the  thin  layers 
of  skin  between  two  fingers  placed  in  apposition.  It  is  an  exceedingly 
unstable  chemical  combination,  yielding  its  oxygen  even  through  the 
influence  of  such  agents  as  release  absorbed  gases,  as,  for  instance,  setting 
free  of  gas  through  the  action  of  an  air-pump  or  the  passage  of  other 


56  OXYGEN-COMBINATIONS    OF    HEMOGLOBIN. 

gases,  particularly  carbon  monoxid,  and  heating  to  the  boiling-point. 
Also  in  the  circulating  blood  the  oxygen  is  readily  given  up  to  the 
tissues  of  the  body,  so  that  in  animals  dead  from  suffocation  only 
gas-free  —  reduced  —  hemoglobin  is  found  in  the  veins.  Also  con- 
stituents of  the  serum  and  sugar  remove  the  oxygen.  By  addition  of 
reducing  substances  to  a  solution  of  oxyhemoglobin,  as,  for  instance, 
ammonium  sulphid,  the  two  bands  of  oxyhemoglobin  disappear  and 
reduced  gas-free  hemoglobin  results  (Fig.  15,  4).  This  is  recognizable 
from  its  wide  ill-defined  absorption-band.  Agitation  with  air,  how- 
ever, at  once  restores  both  bands  through  the  formation  of  oxyhemo- 
globin. Solutions  of  oxyhemoglobin  are  readily  distinguished  by  their 
scarlet  color  from  the  wine- violet-red  tint  of  reduced  hemoglobin. 

The  yellowish-green  color  of  the  solar  spectrum  thrown  isolated  upon  the 
closed  upper  eyelid  causes  a  sensation  of  dark.  If  the  base  of  two  fingers  be 
ligated  to  the  point  of  interrupting  the  circulation  it  will  be  seen  on  spectro- 
scopic  examination  of  the  intervening  red  cutaneous  seam  that  the  oxyhemo- 


(X9 


aBC 


Eb      F 


FIGS.  13  and  14. — The  Absorption-spectra  of  Oxyhemoglobin  (Fig.  13)  and  of  Gas-free  Hemoglobin  (Fig.  14  ) 
with  Increasing  Concentration.     The  letters  of  the  lower  line  indicate  the  Fraunhofer  lines.     The  figures 
at  the  side  indicate  the  percentage-strength  of  the  solutions  (after  Rollett). 

globin  is  soon  transformed  into  reduced  hemoglobin.  This  reaction  is  delayed 
under  the  influence  of  cold;  it  is  accelerated  in  youth,  during  muscular  activity 
or  with  suppression  of  breathing  and  generally  also  in  the  presence  of  fever.  A 
beating  heart  also  exerts  a  reducing  influence  upon  oxyhemoglobin.  The  absorp- 
tion-spectra naturally  vary  with  the  concentration  of  the  solution ;  in  the  presence 
of  a  greater  amount  of  hemoglobin  the  bands  are  wider  and  may  become  confluent, 
and  finally  the  largest  part  of  the  spectrum  may  thus  become  dark.  Figs.  13  and 
14  show  how  the  absorption -bands  appear  in  solutions  of  varying  strengths:  from 
a  i  per  cent,  solution  (above)  the  concentration  progressively  diminishes  down- 
ward by  gradations  of  o.i  per  cent.,  until  at  O  O  the  fluid  is  without  hemo- 
globin. The  thickness  of  the  layers  of  fluid  is  placed  at  i  cm. 

Spectroscopic  examination  of  small  blood-spots,  possibly  for  medico-legal 
purposes,  may  be  of  the  greatest  importance.  Often  a  minute  spot  is  sufficient. 
Dissolved  with  one  or  two  drops  of  distilled  water  it  may  be  introduced  longitu- 
dinally in  a  thin  glass  tube  before  the  narrow  slit  of  the  spectroscope,  and  the 
two  bands  of  oxyhemoglobin  appear. 

Preserved  in  alcohol,  oxyhemoglobin  is  transformed  into  a  modification  in- 
soluble in  water  but  otherwise  identical,  namely  parahemoglobin. 


OXYGEN-COMBINATIONS    OF    HEMOGLOBIN. 


57 


A  second  oxygen-containing  isomeric,  but  chemically  more  stable 
crystallizable  combination  is  methemoglobin,  whose  molecule  contains 
the  same  amount  of  oxygen  as  oxy hemoglobin,  but  in  different  ar- 
rangement. Its  spectrum  closely  resembles  that  of  hematin  in  acid 
solution  (Fig.  15,  5).  The  band  toward  the  red  is  the  heaviest,  while 
the  others  are  narrow  and  are  in  part  designated  as  not  characteristic. 

Demonstration. — i.  By  oxidizing  substances,  such  as  ozone,  potassium  iodid, 
chlorates,  nitrates.  2.  By  reducing  substances,  such  as  nascent  hydrogen  and 
pyrogallol.  3.  By  indifferent  influences,  such  as  prolonged  heating  or  slow  desic- 
cation of  the  blood.  Potassium  permanganate,  potassium  ferrocyanid  and  ferri- 
cyanid  exert  an  intense  effect,  while  nitrites  transform  the  oxyhemoglobin  into 


Red.   Orange. 


Yellow. 


Green. 


Cyanid  Blue. 


110 


Oxyhemoglobin 
0.18  per  cent. 


Oxyhemoglobin 
0.18  per  cent. 


Carbon-monoxid 
hemoglobin. 


Gas-free  or  reduced 
hemoglobin. 


Methemoglobin ; 

also  hematin  in 

acid  solution. 


Hematin  in 
alkaline  solution. 


Hemochromogen  in 

alkaline  solution; 

also  reduced  hematin. 


A    a 


FIG.  15.— The  Various  Absorption-spectra  of  Hemoglobin.     In  all  of  the  spectra  the  various  Fraunhofer  lines 
and  a  scale  in  millimeters  are  drawn. 

a  mixture  of  methemoglobin  and  nitrogen-monoxid  hemoglobin.  Not  alone 
lake-colored  blood,  but  also  the  hemoglobin  of  intact  erythrocytes  may  be 
transformed  into  methemoglobin,  as,  for  instance,  by  potassium  chlorate, 
antifebrin  and  other  substances,  and  also  by  intoxication  with  these  sub- 
stances. Often  both  conditions  are  present  in  combination.  The  occurrence 
of  methemoglobin  in  solutions  in  the  blood-plasma  of  a  poisoned  individual  is 
designated  methemo plasm  ia,  and  the -occurrence  of  the  methemoglobin  in  the  pre- 


58  CARBON-MONOXID   'HEMOGLOBIN. 

served  blood-corpuscles  methemacytosis.  Lesser  degrees  of  the  latter  may  recede 
spontaneously  in  the  body  without  destruction  of  the  erythrocytes.  Profound 
influences  resulting  in  the  production  of  methemoglobin  destroy  the  blood- 
corpuscles  and  require  transfusion. 

Preparation  of  Crystals. — To  the  solution  of  isolated  erythrocytes  described  on 
p.  37  is  added  double  its  volume  of  a  concentrated  solution  of  ammonium  sul- 
phate, and  evaporation  is  permitted  to  take  place  in  the  cold.  There  form  brown- 
ish-red needles,  prisms  or  plates  with  marked  pleochroism.  Methemoglobin 
develops  in  part  spontaneously  in  the  body,  as,  for  instance,  in  bloody  urine, 
in  the  sanguinolent  contents  of  cysts,  in  old  extravasates  and  in  dried  blood- 
crusts.  The  addition  of  a  trace  of  ammonia  to  a  solution  of  methemoglobin  pro- 
duces an  alkaline  solution  of  methemoglobin,  which  exhibits  two  bands  similar  to 
those  of  oxyhemoglobin,  but  of  which  the  first  is  the  wider  and  extends  the  more 
toward  the  red.  If  a  reducing  solution  of  ammonium  sulphid  be  added  to  solu- 
tions of  methemoglobin,  reduced  hemoglobin  develops. 

CARBON-MONOXID  HEMOGLOBIN  AND  CARBON-MONOXID 

POISONING. 

Carbon-monoxid  hemoglobin  is  a  more  stable  combination  than  the 
preceding  and  is  produced  when  carbon  monoxid  is  brought  into  con- 
tact with  hemoglobin  or  oxyhemoglobin.  It  is  cherry-red  in  color, 
not  dichroic,  and  it  exhibits  in  the  spectrum  two  absorption-bands 
that  closely  resemble  those  of  oxyhemoglobin,  but  are  somewhat 
closer  together  and  more  toward  the  violet  (Fig.  15,  3).  It  can  be 
readily  recognized,  however,  from  the  fact  that  reducing  substances, 
which  influence  the  oxyhemoglobin,  do  not  dissolve  these  bands,  that 
is,  do  not  transform  the  carbon-monoxid  hemoglobin  into  reduced 
hemoglobin.  A  further  means  of  recognition  consists  in  the  sodium- 
test:  a  10  per  cent,  solution  of  sodium  hydroxid  added  to  carbon-mon- 
oxid hemoglobin  and  heated  gives  rise  to  a  cinnabar-red  color.  The 
same  solution  added  to  oxyhemoglobin  produces  a  black-brown- 
greenish  mass.  The  spectrum-analytical  examination  and  the  sodium- 
test  permit  the  recognition  of  three-tenths  carbon-monoxid  hemoglobin 
mixed  with  seven-tenths  oxyhemoglobin. 

Carbon-monoxid  hemoglobin  reactions :  Modified  sodium-test:  The  blood  is 
diluted  20  times  and  an  equal  amount  of  sodium  hydroxid  of  a  specific  gravity 
of  1.34  is  added  in  a  test  tube.  Carbon-monoxid  blood  assumes  a  beauti- 
ful red  color  after  addition  of  ammonium  sulphid — 2  grams  of  sulphur  being 
added  to  100  grams  of  yellow  ammonium  sulphid — and  30  per  cent,  acetic  acid, 
while  normal  blood  assumed  a  greenish-gray  coloration.  Both  kinds  of  blood 
exhibit  also  differences  in  color  when  treated  as  follows:  Dilute  potassic 
hydrate  is  added,  and  then  a  few  drops  of  a  watery  solution  of  pyrogallic  acid; 
the  mixture  is  shaken  at  once  and  permitted  to  stand  protected  from  the  air. 
For  the  purpose  of  the  test,  blood  made  lake-colored  with  water  may  be  used, 
as  well  as  blood  in  which  the  erythrocytes  are  preserved  by  addition  of 
concentrated  solution  of  sodium  sulphate.  Three  cu.  cm.  of  blood  are  diluted 
with  1 1 oo  cu.  cm.  of  water;  10  cu.  cm.  of  this  are  mixed  with  2  cu.  cm.  of 
2  per  cent,  solution  of  grape-sugar  and  2  cu.  cm.  of  saturated  solution  of  barium 
carbonate  or  lime-water,  and  the  whole  is  heated  almost  to  the  boiling-point. 
From  4  to  5  volumes  of  lead  acetate  added  to  the  blood  cause  a  distinct  differ- 
ence accordingly  as  oxygen  or  carbon-monoxid  blood  is  present. 

Oxidizing  substances,  as,  for  instance,  solutions  of  potassium  permanganate — 
0.025  per  cent.,  potassium  chlorate — 5  per  cent.,  and  dilute  chlorin-water,  render 
solutions  of  carbon-monoxid  hemoglobin  cherry-red,  while  they  render  solutions 
of  oxyhemoglobin  pale  yellow.  Both  varieties  of  hemoglobin  thus  treated  acquire 
the  bands  of  methemoglobin,  the  carbon-monoxid  hemoglobin  considerably  later. 
Subsequent  addition  of  ammonium  sulphid  transforms  the  forms  of  hemoglobin 
thus  altered  back  again  into  oxyhemoglobin  and  carbon-monoxid  hemoglobin. 

By  reason  of  its  greater  constancy  carbon-monoxid  hemoglobin  resists  putre- 
faction for  a  long  time,  as  well  as  the  action  o£ hydrogen  sulphid. 


POISONING    WITH    CARBON    MONOXID.  59 

If  carbon  monoxid  be  inspired  it  gradually  displaces,  volume  for 
volume,  the  oxygen  of  the  hemoglobin,  and  death  finally  results; 
1000  cu.  cm.  of  carbon  monoxid  will  kill  human  beings  if  breathed 
at  once.  Small  amounts  of  carbon  monoxid  in  the  air  (TTro~Trnnr)»  how- 
ever, suffice  to  generate  comparatively  large  amounts  of  carbon-monoxid 
hemoglobin  within  a  short  time.  As  by  means  of  long-continued 
treatment  of  carbon-monoxid  hemoglobin  with  other  gases,  particularly 
oxygen, — passing  them  through — the  carbon  monoxid  may  be  grad- 
ually again  separated  from  the  hemoglobin,  with  the  re-formation  of 
oxy hemoglobin,  so  in  the  body  also  the  carbon  monoxid  is  eliminated 
through  the  respiratory  process  in  the  course  of  a  few  hours,  a  por- 
tion of  the  carbon  monoxid  apparently  being  oxidized  into  carbon 
dioxid. 

Poisoning  with  Carbon  Monoxid. — Carbon  rnonoxid  results  from  incomplete 
combustion  of  carbon,  as,  for  instance,  through  premature  closure  of  stove-valves 
and  badly  smoking  lamps.  It  occurs  in  illuminating  gas  in  a  proportion  of  from 
12  to  28  per  cent.  As  carbon  monoxid  has  200  times  as  great  an  affinity  for 
hemoglobin  as  oxygen,  more  and  more  of  the  latter  is  displaced  from  the  blood 
by  the  breathing  of  air  containing  carbon  monoxid,  and  life  naturally  can  continue 
only  so  long  as  sufficient  oxygen  is  conveyed  by  the  blood  as  is  necessary  to  main- 
tain the  processes  of  oxidization  essential  to  life.  Death  occurs  amid  peculiar 
phenomena,  even  before  all  of  the  oxygen  is  expelled  from  the  blood;  under  the 
most  unfavorable  circumstances  one-fifth  of  the  oxygen  will  be  retained  in  the 
blood. 

Applied  directly  to  nerve  and  muscle  the  gas  has  no  influence  whatever. 
Acting  through  the  blood,  however,  phenomena  appear  that  are  indicative 
primarily  of  stimulation,  but  secondarily  of  paralysis  of  the  nervous  system. 
Thus,  there  occur  at  first  severe  headache,  great  restlessness,  excitement, 
increased  cardiac  and  respiratory  activity,  salivation,  tremor,  twitching,  and 
spasm.  Later,  mental  confusion,  exhaustion,  drowsiness,  and  paralysis  set  in,  and 
even  loss  of  consciousness,  labored  stertorous  breathing,  finally  complete  loss  of 
sensibility,  cessation  of  breathing  and  of  the  heart-beat  and  death.  The  tem- 
perature at  the  beginning  exhibits  an  elevation  of  perhaps  a  few  tenths  of  a  degree 
C.;  then  there  follows  a  decline  of  about  i°  C.  and  more.  The  pulse-beat  at 
first  exhibits  increased  energy,  while  later  the  pulse  becomes  small  and  frequent. 

Garland-like  constrictions  of  the  vessels,  followed  later  by  marked  dilatation, 
with  hyperemia  of  the  viscera,  accompanied  by  a  fall  in  the  blood-pressure, 
indicate  primary  stimulation  and  secondary  paralysis  of  the  vasomotor  center. 
The  change  in  temperature  mentioned  is  to  be  referred  to  the  same  cause.  This 
would  also  explain  the  appearance  of  sugar  in  the  urine  sometimes  observed — 
in  dogs  only  after  abundant  feeding  of  proteid.  After  the  intoxication  has  ter- 
minated the  excretion  of  urea  is  said  to  be  increased,  because  the  albuminates 
exhibit  a  greater  tendency  to  disintegration.  In  cases  of  poisoning  the  great 
hyperemia  of  the  viscera  with  fluid  cherry-red  blood  and  the  dilatation  of  the 
vessels  are  conspicuous.  Further,  there  are  friability  and  softening  of  the 
brain,  marked  catarrh  of  the  respiratory  organs  and  granular  degeneration  of  the 
muscles.  Liver,  kidneys,  and  spleen  appear  hyperemic,  large,  flabby,  in  a  state 
partly  of  granular  and  partly  of  fatty  degeneration.  All  of  the  muscles  and 
viscera  exhibit  an  exquisite  cherry-red  color.  The  spots  of  postmortem  lividity 
are  bright  red. 

Poisoned  persons  if  still  living  should  be  at  once  brought  into  the  fresh  air. 
High  degrees  of  intoxication  demand  transfusion.  After  recovery  from  the 
poisoning,  sometimes  paralysis,  rarely  anesthesia,  trophic  disorders  and  derange- 
ment of  cerebral  activity  persist.  If  mixed  with  pure  oxygen  carbon  nionoxid 
acts  less  rapidly. 

OTHER  HEMOGLOBIN-COMBINATIONS. 

Nitric-oxid  hemoglobin  is  formed  when  nitric  oxid  enters  into  com- 
bination with  hemoglobin. 

As  this  gas  in  contact  with  oxygen  is  at  once  transformed  into  nitrous  acid, 


6o 


DECOMPOSITION    OF    HEMOGLOBIN. 


all  of  the  oxygen  must  first  be  removed  from  the  blood  and  the  apparatus,  possibly 
through  the  passage  of  hydrogen,  in  the  preparation  of  nitric-oxid  hemoglobin. 
For  this  reason  it  cannot  be  formed  within  the  body.  Nitric-oxid  hemoglobin  is 
a  still  more  active  chemical  combination  than  carbon-monoxid  hemoglobin.  It 
is  of  a  bluish-violet  color  and  in  the  spectrum  it  exhibits  two  absorption-bands, 
pretty  much  like  those  of  the  two  other  gas-combinations,  but  less  intense,  and 
not  dissolved  by  reducing  substances. 

The  three  combinations  of  hemoglobin  with  oxygen,  carbon  monoxid 
and  nitric  oxid  just  considered  crystallize  like  gas-free  hemoglobin. 
They  are  isomorphous  and  their  solutions  are  not  dichroic.  All  three 
gases  unite  in  equal  amounts  with  hemoglobin  and  they  can  be  ex- 
pelled in  a  vacuum. 

Hydrocyanic  acid  also  forms  readily  decomposed  combinations  with  hemo- 
globin. These  develop  in  cases  of  hydrocyanic-acid  poisoning,  and  they  exhibit 
two  bands  that  are  situated  somewhat  nearer  the  violet  than  those  of  oxyhemo- 
globin  and  are  slowly  obliterated  by  reducing  substances.  This  hydrocyanic-acid 
hemoglobin  appears  to  consist  of  hydrocyanic  acid  plus  oxyhemoglobin.  There 
is,  besides,  a  further  combination  of  hydrocyanic  acid  with  oxygen-free  hemo- 
globin. 

DECOMPOSITION  OF  HEMOGLOBIN. 

Hemoglobin  can  be  decomposed  into:  (i)  iron-containing,  pig- 
mented  hematin  and  (2)  albuminoid,  colorless  globin,  containing  sul- 
phur: (a)  by  addition  of  all  acids,  even  feeble  carbon  dioxid  in  the 
presence  of  much  water;  (b)  by  strong  alkalies;  (c)  by  all  agents  that 
coagulate  albumin,  as  well  as  by  heat  at  a  temperature  of  from  70°  to 
80°  C. ;  (d)  by  ozone. 

Hematin. — C32H32N4FeO4  represents  about  4  per  cent,  of  the  hemo- 
globin in  the  dog.  It  is  of  blackish-blue  color  in  reflected  light,  brown 
in  transmitted  light,  insoluble  in  water,  alcohol  and  ether,  but  soluble 
in  dilute  alkalies  and  acids,  as  well  as  in  alcohol  containing  sulphuric 
acid  or  ammonia.  It  does  not  occur  within  the  body.  Hematin  thus 
developed  appears  in  an  amorphous  form,  although  it  has  also  been 
possible  to  produce  it  crystallized  in  needles  and  rhombic  plates. 


i. 


2. 


700  650     600 

BO        D 


550 


500 

Eb         F 


450 


FIG.  16. — The  Absorption-spectra  of  Hematoporphyrin,  with  the  Fraunhofer  Lines  and  a  Scale  Whose  Figures 
Indicate  the  Wave-lines  of  Light  in  Millionths  of  a  Millimeter. 

In  the  decomposition  of  hemoglobin  containing  oxygen  hematin  at  once 
results,  oxygen  being  bound.  On  the  other  hand,  oxygen-free  hemoglobin  yields 
in  a  similar  process  of  decomposition,  at  first  a  forerunner  of  hematin  deficient 
in  oxygen,  namely  purple-red  hemochromogen  (C34H36NFe4O5) .  This,  however, 
is  transformed  into  hematin  in  the  presence  of  oxygen  by  taking  up  the  latter. 
Hematin  therefore  represents  an  oxidization-stage  of  hemochromogen.  The  latter 


IDENTIFICATION    OF    BLOOD.  6l 

substance  is  soluble,  with  exclusion  of  oxygen,  in  dilute  alkalies,  with  the  formation 
of  a  cherry-red  color,  and  exhibits  two  absorption-bands,  namely,  one  between 
D  and  E,  and  another  and  narrower  between  E  and  b  (Fig.  15,  7). 

Hemochromogen  can  be  prepared  in  crystalline  form  by  mixing  upon  a  glass 
slide  one  drop  of  defibrinated  blood  with  one  drop  of  pyridin  and  covering  the 
whole.  The  preparation  exhibits  the  absorption-bands  and  at  times  also  small 
crystals  arranged  in  the  form  of  stars  or  sheaves.  In  the  bloody  extract  of 
spirit-preparations  no  longer  fresh  putrefaction  often  produces  the  beautiful  red 
hemochromogen  in  alkaline  solution. 

Dilute  acids  in  alcoholic  solution  withdraw  the  iron  from  the  hemochromogen 
and  there  thus  results  hematoporphyrin — C16H18N2O3,  which  is  isomeric  with 
bilirubin,  and  is  permanent  in  the  air.  This  can  also  be  prepared  from  hematin 
by  means  of  strong  sulphuric  acid.  It  exhibits  in  acid  solution  a  small  absorption- 
band  in  the  orange  and  a  wider  band  in  the  yellowish-green  (Fig.  16,  i).  The 
spectrum  of  the  same  substance  in  alkaline  solutions  is  shown  in  Fig.  16,  2. 

Hematin  occurs  in  solution  as — 

(A)  Hematin  in  acid  solution.     If  acetic  acid  be  added  to  a  solution  of  hemo- 
globin the  latter  becomes  mahogany-brown  in  color,  as  hematin  in  acid  solution 
develops  and  is  recognized  by  four  absorption-bands  in  the  yellow  and  the  green 
(Fig.  15,  5)- 

(B)  If  this   solution   be   over-saturated  with   ammonia  hematin  in  alkaline 
solution  develops,  exhibiting  an  absorption-band  at  the  junction  between  the  red 
and  the  yellow  (Fig.  15,  6). 

(C)  Addition  of  reducing  agents  causes  disappearance  of  this  band  and  pro- 
duces  twro  wide   bands   in  the  yellow,  due  to  the  reduced   hematin  thus   formed 
(Fig.  15,  7),  and  which,  according  to  Hoppe-Seyler,  is  identical  with  the  hemo- 
chromogen in  alkaline  solution. 

Hematin  is  prepared  in  substance  by  precipitation  from  a  solution  of  hemin 
in  a  weak  alkali  by  addition  of  a  dilute  acid. 

Hemoglobin  is  transformed  into  green  sulphur-methemoglobin  by  hydrogen 
sulphid.  This  substance  also  causes  the  green  coloration  of  putrid  portions  of 
the  cadaver. 

Hematin  when  reduced  in  alkaline  solution  with  tin  and  hydrochloric 
acid  yields  urobilin.  The  latter  results  likewise  through  the  action  of 
hydrogen  dioxid  on  acid  hematin. 

Urobilin  is  occasionally  found  in  cysts,  exudates,  and  transudates.  It  forms 
likewise  in  sterile  blood  kept  at  the  temperature  of  the  body. 

HEMIN   (HEMATIN   CHLORID);   IDENTIFICATION  OF  BLOOD   BY 
MEANS  OF  THE  HEMIN-TEST. 

Teichmann  prepared  in  1853  from  the  anhydrid  of  hematin  crystals 
that  Hoppe-Seyler  recognized  as  hematin  chlorid — C32H30N4O3FeHCl. 
As  these  may  be  obtained  in  characteristic  form  even  from  traces  of 
blood  they  play  an  important  role  in  forensic  medicine.  The  demonstra- 
tion of  their  presence  depends  upon  the  fact  that  the  hemoglobin  dried 
and  heated  with  an  excess  of  water-free  acetic  acid — so-called  glacial 
acetic  acid,  which  must  burn  on  a  glass  rod  held  in  the  flame — and 
addition  of  sodium  chlorid  yields  hemin-crystals  (Figs.  17  and  18). 
These  appear  in  the  form  of  small  rhombic  plates,  columns,  or  rods, 
although  they  probably  belong  to  the  monoclinic  system.  Not 
rarely  they  take  the  form  of  hemp-seeds  or  shuttles  or  paragraph- 
signs.  At  times  some  lie  crossed  or  in  tufts.  In  crystalline  form  the 
hemin-crystals  of  all  varieties  of  blood  examined  are  identical.  They 
are  doubly  refracting,  appearing  yellow  and  glistening  under  the 
polarization-microscope,  in  contrast  with  their  dark  surroundings, 
with  marked  absorption  of  the  light  parallel  with  the  longitudinal  axis 
of  the  crystal.  They  are  pleochromatic,  that  is,  bluish-black  and  glisten- 


62  IDENTIFICATION    OF    BLOOD. 

ing   like   polished   steel    in   reflected   light    and    mahogany-brown    in 
transmitted  light. 

(1)  Preparation  from  Dry  Blood-stains. — Several  particles  of  the  dry  mass  are 
placed  upon  a  glass  slide,  two  or  three  drops  of  glacial  acetic  acid  and  a  minute 
crystal  of  sodium  chlorid  are  added,  and  after  the  cover-slip  has  been  placed  in 
position  heat  is  carefully  applied  some  distance  above  a  spirit-lamp  until  a  number 
of  small  bubbles  form.     On  cooling  the  crystals  will  be  visible  in  the  preparation 
(Fig.  1 8). 

(2)  Preparation  from,  stains  upon  porous  bodies,  from  which  the  hemoglobin 
cannot  be  scraped.     The  stained  object — fabric,  wood — is  extracted  with  a  dilute 
solution  of  potassic  hydrate  and  then  with  water.     To  both  filtered  solutions  a 
solution  of  tannic  acid  is  added,  and  finally  acetic  acid  until  an  acid  reaction  is  pro- 
duced.   The  resulting  precipitate  is  washed  upon  a  filter,  then  to  a  portion  thereof 
upon  a  glass  slide  a  crystal  of  sodium  chlorid  is  added,  and  the  whole  is  dried. 
Finally,  the  dried  object  is  treated  according  to  the  method  just  described. 

(3)  Preparation  from  Liquid  Blood. — The  blood  should  always  have  been  pre- 
viously dried  slowly  and  carefully.     Then  the  process  is  continued  as  in  the  first 
method. 


4  -A  ^     ^ 


FIG.  i"j.  —  Hemin-crystals:  i,  from  a  human  being;  2,  from  a 
seal;  3,  from  a  calf;  4,  from  a  pig;  5,  from  a  lamb;  6, 
from  a  pike;  j,  from  a  rabbit. 


FIG.  18.  —  Hemin-crystals  Pre- 
pared  from  Blood-stains. 


(4)  Preparation  from  Dilute  Solutions  Containing  Hemoglobin.  —  To  the  fluid 
is  added  ammonia,  next  tannic  acid  and  then  acetic  acid  until  the  reaction  is 
acid.  A  blackish  precipitate  of  hematin  tannate  forms  rapidly.  This  is  washed 
upon  a  filter  with  distilled  water,  then  dried  and  heated  in  the  same  way  as  accord- 
ing to  the  first  method,  except  that  instead  of  sodium  chlorid  a  crystal  of  ammo- 
nium chlorid  is  added. 

Not  rarely  at  least  small  hemin-crystals  can  be  obtained  from  putrid  and  lake- 
colored  blood,  but  under  such  circumstances  the  test  often  fails.  Dried  with  iron- 
rust,  as  upon  weapons,  blood  usually  no  longer  yields  the  reaction.  Under  such  cir- 
cumstances the  matter  is,  according  to  Heinrich  Rose,  scraped  away  and  boiled 
with  dilute  potassium-hydrate  solution.  If  blood  be  present  the  dissolved  hematin 
forms  a  fluid  that  in  thin  layers  presents  a  bile-green  color,  but  in  thick  layers  a 
red  color. 

Hemin-crystals  have  been  demonstrated  in  all  classes  of  vertebrates,  as  well 
as  in  the  blood  of  the  earth-worm.  From  some  kinds  of  blood,  as,  for  instance, 
that  of  cattle  and  of  swine,  only  irregular  masses,  scarcely  recognizable  as  having 
crystalline  form,  at  times  develop.  Hemochromogen  ,  hematoporphyrin,  blood 
rubbed  with  sand  or  animal  charcoal,  addition  of  certain  salts  of  iron,  lead, 
mercury,  and  silver  and  lime  prevent  the  development  of  the  reaction.  The 
crystals  of  hemin  are  insoluble  in  water,  alcohol,  ether,  and  chloroform.  They 
are  dissolved  by  concentrated  sulphuric  acid,  with  expulsion  of  hydrochloric  acid 
and  the  development  of  a  violet-red  color.  They  are  dissolved  by  dilute  alkalies. 
If  a  solution  of  hemin-crystals  in  ammonia  is  evaporated,  then  heated  to  130°  C., 
next  treated  with  boiling  water,  which  removes  the  ammonium  chlorid  formed, 


HEMATOIDIN.  63 

hematoporphyrin  results.  This  is  a  bluish-black,  amorphous  powder,  becoming 
brown  when  rubbed.  Its  solutions  in  caustic  alkalies  are  dichroic:  that  is  brownish- 
red  in  reflected  light,  garnet-red  in  a  thick  layer  with  transmitted  light  and  olive- 
green  in  a  thin  layer.  The  acid  solutions  are  monochromatic — brown. 

For  the  preparation  of  hemin-crystals  in  large  amount,  it  is  advisable  to  heat 
dry  horses'  blood  with  10  parts  of  formic  acid  until  bubbles  form.  If  the  hemin- 
crystals  are  suspended  in  methyl-alcohol,  they  dissolve  after  addition  of  iodin 
and  application  of  heat,  with  the  development  of  a  purple  color,  which  becomes 
brown  after  addition  of  bromin  and  green  after  the  passage  of  chlorin-gas.  All 
of  these  exhibit  a  characteristic  appearance  in  the  spectroscope.  The  glacial  acetic 
acid  may  be  replaced  by  an  alcoholic  solution  of  oxalic  or  tartaric  acid,  and  the 
sodium  chlorid  by  salts  of  iodin  or  bromin.  In  the  latter  event  bromin-hematin 
or  iodin-hematin  is  formed. 

HEMATOIDIN. 

An  important  derivative  of  hemoglobin  is  sorrel-colored  hematoidin- — 
C32H36N4O6  (Fig.  19),  which  forms  in  the  body  from  hematin  through 
loss  of  iron  and  taking  up   of   water  when- 
ever blood  stagnates  [outside  of  the  circula- 
tion and  undergoes    decomposition,    as,    for 
instance,    in    apoplectic    extravasations     of 
blood,    in    coagulated  plugs  in  blood-vessels 
(thrombi).     It   develops    regularly  in   every 
Graafian    follicle   from    the    drop    of   blood 
poured  out  at  the  menstrual  rupture  of  the 
follicle.     It  is  free  from  iron,  crystallizes  in 
clinorhombic     prisms,     and     is     soluble    in         FIG.  19.— Hematoidin-crystais. 
chloroform  and  in  warm  alkalies.     Probably 
it  is  identical  with  the  biliary  coloring-matter,  bilirubin. 

Pathological. — After  extensive  dissolution  of  blood  in  the  vessels,  as,  for 
instance,  after  transfusion  with  foreign  blood,  hematoidin-crystals  have  been  ob- 
served in  the  urine. 

THE  COLORLESS  PROTEID  OF  HEMOGLOBIN. 

This  is  designated  globin  and  is  closely  related  to  histon. 

Demonstration. — A  solution  of  hemoglobin  is  made  feebly  acid  with  hydro- 
chloric acid,  then  one-fifth  volume  of  alcohol  is  added  and  the  mixture  is  shaken  with 
ether.  The  coloring-matter  is  taken  up  by  the  ether  and  the  globin  is  precipitated 
by  the  ammonia.  Hydrochloric  or  nitric  acid  likewise  precipitates  the  globin, 
which,  however,  is  redissolved  on  boiling.  Hematin  and  globin  are  probably  not 
the  sole  products  of  the  decomposition  of  hemoglobin.  As  hemoglobin-crystals 
can  be  decolorized  under  special  conditions,  it  is  most  probable  that  they  owe  their 
form  to  the  proteid  body.  On  introducing  hemoglobin-crystals  with  alcohol  in  a 
dialyzer  surrounded  by  ether  acidulated  with  sulphuric  acid  Landois  succeeded 
in  decolorizing  the  crystals. 

PROTEID  BODIES  IN  THE  STROMA. 

These  constitute  from  5.10  to  12.24  per  cent,  of  the  dry  red 
blood-corpuscles  of  man,  including  a  globulin  participating  in  fibrin- 
formation  and  possible  traces  of  a  sugar-forming  ferment.  Under 
special  conditions  it  has  been  observed  that  the  stromata,  coherent 
in  masses,  form  a  substance — stroma-fibrin — resembling  fibrin. 

L.  Brunton  has  found  in  the  nuclei  of  nucleated  red  blood-corpuscles  a  mucin- 
containing  body,  Miescher  nuclein  and  Kossel  histon  united  with  the  latter. 


64          REMAINING    CONSTITUENTS    OF    THE    RED    BLOOD-CORPUSCLES. 

THE  REMAINING  CONSTITUENTS  OF  THE  RED  BLOOD- 
CORPUSCLES. 

The  red  corpuscles  contain  further:  Lecithin,  1.867  Per  cent,  in  dry 
erythrocytes;  urea,  equally  divided  between  erythrocytes  and  serum; 
cholesterin,  0.151  per  cent.;  no  fats;  lactic  acid,  in  the  dog. 

Lecithin  and  cholesterin  can  be  obtained  by  agitating  considerable  amounts 
of  stroma  or  isolated  blood-corpuscles  with  ether.  If  the  ether  is  permitted  to 
evaporate  the  characteristic  globular  myelin-forms  of  lecithin  and  the  crystals 
of  cholesterin  will  be  recognized. 

Water,  631.63  in  the  thousand. 

After  abstraction  of  considerable  quantities  of  blood  the  amount  of  water 
diminishes  and  the  amount  of  dry  substance,  as  well  as  the  nitrogen  of  the  ery- 
throcytes, increases.  The  opposite  effect  is  brought  about  by  infusion  of  physio- 
logic salt-solution. 

Inorganic  matters,  7.28  in  the  thousand,  particularly  combinations 
of  potassium  and  phosphoric  acid.  The  phosphoric  acid  is  derived 
only  from  consumed  lecithin,  the  sulphuric  acid  in  large  part  from  the 
hemoglobin  consumed  in  the  analysis.  Some  manganese  also  is 
present. 

Blood-analysis. — One  thousand  parts  by  weight  of  horses'  blood  are  made  up 
as  follows : 

344.18  parts  blood-corpuscles,  with  128  of  solids — 383  in  the  dog, 
655.82  parts  plasma,  with  10  per  cent,  of  solids — 617  in  the  dog. 
One  thousand  parts  by  weight  of  moist  blood-corpuscles  are  made  up  as 
follows : 

Solids,    367.9  (swine),  400.1  (cattle),  435  (horse), 

Water, 632.1  (swine),  599.9  (cattle),  565  (horse). 

The  solids  include : 

Hemoglobin, 261          (swine)  280.5       (cattle) 

Albumin,    86.1                      107 

Lecithin,  cholesterin  and  other  organic  matters, .  .  12.0 

Inorganic  matters, 8.9 

Including  potassium, 5-543 

magnesium,    0.158 

chlorin, 1.504 

phosphoric   acid, 2.067 

sodium,  o 


7-5 
4.8 
0.747 
0.017 


0.703 
2.093 


CHEMICAL  CONSTITUENTS  OF  THE  LEUKOCYTES. 

Leukocytes  from  the  plasma  of  lymphatic  glands,  as  well  as  pus- 
corpuscles  contain  proteids  as  follows:  little  albumin,  alkali- albuminate 
and  an  albuminate  resembling  myosin  and  coagulating  at  48°,  two 
globulins  coagulable  at  48.5°  and  75°  C.  respectively,  together  with 
serum-globulin,  peptone  and  a  coagulating  ferment,  further  consider- 
able nucleins  from  the  nuclei,  nucleo-histon,  little  glycogen,  lecithin, 
cerebrin,  cholesterin,  fats,  protagon,  inosite,  amidovalerianic  acid. 

Lymphocytes  contain  11.5  per  cent,  of  dry  matter.  In  100  parts  by  weight 
of  dry  pus  there  are  0.416  earthy  phosphates,  0.143  sodium  chlorid,  0.606  sodium 
phosphate,  0.202  potassitmi,  in  part  in  the  form  of  monopotassium  phosphate. 


THE    BLOOD-PLASMA    AND    ITS    RELATION    TO    THE     SERUM.  65 

THE  BLOOD-PLASMA  AND  ITS  RELATION  TO  THE  SERUM. 

The  unmodified  fluid  of  the  blood  is  known  as  plasma.  In  this,  how- 
ever, there  separates,  generally  soon  after  escape  of  the  blood  from  the 
vessels,  a  nbrillated  substance,  namely  fibrin.  After  this  separation, 
the  remaining  clear  fluid,  which  no  longer  undergoes  coagulation  spon- 
taneously, is  known  as  serum.  The  plasma  is  a  clear,  transparent, 
somewhat  consistent  fluid,  which  in  most  animals  is  almost  colorless, 
but  in  human  beings  is  yellowish  and  in  the  horse  of  citron-yellow 
color. 

DEMONSTRATION  OF  PLASMA. 

(A)  Without  admixture.     As  plasma  cooled  to  a  temperature  of  o°  C.  does 
not  undergo  coagulation,  the  blood  flowing  from  a  vein — particularly  of  the  horse, 
which    is  peculiarly  suitable   on  account  of  the  slowness  of  coagulation  and  the 
rapidity  with  which  sedimentation  of  the  blood-corpuscles  takes  place-; — is  received 
into  a  narrow,  graduated  cylinder   standing  in  a   cold  mixture.     In  the  blood, 
which  remains  fluid,  the  erythrocytes  sink  to  the  bottom  within  a  few  hours,  and 
the  plasma  forms  above  a  clear  fluid,  which  can  be  removed  with  a  cooled  pipet. 
If  this  is  further  passed  through  a  filter  upon  an  ice-cold  funnel  the  plasma  will 
also  be  freed  from  leukocytes. 

The  amount  can  be  read  from  the  graduated  cylinder,  but  only  approximately, 
because  of  the  presence  of  plasma  between  the  sedimented  corpuscles.  If  heated, 
the  plasma,  in  so  far  as  it  contains  leukocytes,  is  transformed,  through  the  forma- 
tion of  fibrin,  into  a  tremulous  jelly.  If,  however,  it  be  whipped  with  a  rod  the 
fibrin  will  be  obtained  as  a  stringy  mass.  Plasma  free  from  leukocytes  is  not 
capable  of  coagulation. 

If  the  amount  of  fibrin  in  a  volume  of  plasma  isolated  by  whipping  (varying 
between  0.7  and  i.o  per  cent.)  and  in  the  same  manner  the  amount  in  a  volume 
of  blood  be  determined  the  two  results  afford  a  basis  for  estimating  the  amount 
of  plasma  in  the  blood. 

(B)  With  saline  admixture.     If  the  blood  flowing  from  a  vein  into  a  graduated 
cylinder  be    mixed  with    agitation  with  }  volume   of   concentrated   solution    of 
sodium    sulphate    or    with    a    25    per    cent,    solution    of    magnesium    sulphate 
(i  volume    to  4  volumes  of  blood),  the  cells  sink  to  the  bottom  in  a  cool  place, 
while  the  clear  supernatant  saline  plasma,  which  can  be  measured,  is  pipetted  off. 
If  the  salt  be  removed  from  the  plasma  by  means  of    the  dialyzer  coagulation 
takes  place.     The  same  result  is  brought  about  by  dilution  with  water. 

FIBRIN:  ITS  GENERAL  PROPERTIES;  COAGULATION. 

Fibrin  is  the  substance  that  brings  about  coagulation  in  shed  blood 
as  well  as  in  plasma  and  likewise  in  lymph,  and  in  the  chyle,  by 
solidification.  If  the  fluids  mentioned  are  placed  at  rest  and  left  to 
themselves  the  fibrin  forms  innumerable  microscopically  delicate  (Fig.  9) 
doubly  refracting  filaments,  which  hold  the  blood-cells  together  like 
a  spider's  web,  and  with  the  cells  form  a  mass  of  gelatinous  consistency 
that  is  known  as  blood-clot  (placenta  sanguinis}.  At  first  this  is  quite 
diffluent  and  it  is  only  in  the  course  of  from  two  to  fifteen  minutes  that 
a  number  of  filaments  appear  upon  the  surface  that  can  be  removed  with 
a  needle,  while  the  interior  of  the  blood-mass  is  still  liquid.  In  a  short 
time  the  filaments  extend  throughout  the  entire  mass.  The  blood  in 
this  stage  of  coagulation  has  been  designated  cruor.  Later,  in  the 
course  of  from  twelve  to  fifteen  hours,  the  threads  of  fibrin  contract 
more  and  more  firmly  about  the  corpuscles,  and  there  then  results  the 
more  solid,  gelatinous,  tremulous  substance,  which  can  be  cut  with  a 
knife,  and  which  has  expressed  a  clear  fluid,  known  as  blood-serum 
(serum  sanguinis}.  The  blood-clot  takes  the  shape  of  the  vessel  in  which 
5 


66  FIBRIN. 

the  blood  has  been  received.     By  solution  with  water  of  the  blood- 
corpuscles  in  the  broken-up  blood-clot  the  fibrin  can  be  isolated. 

If  the  blood-corpuscles  sink  rapidly  in  the  blood,  and  if  the  advent 
of  coagulation  be  delayed,  the  upper  layer  of  the  blood-clot  is  only 
stained  yellow  on  account  of  the  absence  of  enclosed  erythrocytes. 
This  is  the  rule  with  horses'  blood,  but  it  has  been  observed  in  the  case 
of  human  blood,  particularly  when  inflammation  was  present  in  some 
part  of  the  body.  Therefore,  this  layer  has  also  been  designated  crusta 
phlogistica.  Such  blood  is  richer  in  fibrin  and  therefore  coagulates  more 
slowly. 

The  crusta  forms  also  under  other  conditions,  but  the  cause  of  its  formation 
is  not  always  clear.  Thus  it  occurs  when  the  specific  gravity  of  the  blood-cor- 
puscles is  increased  or  that  of  the  plasma  is  diminished,  as  in  cases  of  hydremia 
and  chlorosis,  in  consequence  of  which  the  corpuscles  sink  more  rapidly,  and 
during  pregnancy.  The  taller  and  narrower  the  vessel,  the  higher  is  the  crusta. 

It  can  be  readily  understood  why  the  blood-clot  undergoes  greater  contraction 
and  appears  more  contracted  in  the  neighborhood  of  the  unpigmented  layer  free 
from  corpuscles. 

If  freshly  shed  blood  is  whipped  with  a  rod  the  filaments  of  fibrin 
that  form  collect  about  the  rod,  and  in  this  way  the  fibrin  is  obtained 
as  a  fibrous,  grayish-yellow  mass  from  the  blood  now  become  defi- 
brinated. 

The  plasma  exhibits  analogous  phenomena,  but  it  forms  only  a  soft, 
tremulous  jelly,  by  reason  of  absence  of  the  resistant  blood-corpuscles. 
The  plasma  undergoes  coagulation  only  when  it  contains  leukocytes. 
If  these  be  removed  by  filtration  the  plasma  is  no  longer  coagulable. 

Although  the  fibrin  appears  voluminous,  it  constitutes  only  from 
o.i  to  0.3  per  cent,  of  the  mass  of  the  blood.  In  this  connection,  it  is 
noteworthy  that  in  two  different  specimens  of  the  same  blood  the 
amount  of  fibrin  may  vary  considerably. 

Fibrin  is  insoluble  in  water  or  ether.  Alcohol  causes  it  to  shrink  by 
dehydration,  while  hydrochloric  acid  causes  it  to  swell  and  assume  a 
vitreous  appearance,  with  transformation  into  syntonin.  In  the  fresh 
state  fibrin  is  tough  and  elastic.  If  dried,  it  becomes  horn-like,  trans- 
lucent, brittle,  and  pulverizable. 

Fresh  fibrin  is  capable  of  actively  decomposing  hydrogen  dioxid  into  water 
and  oxygen,  just  as  other  fresh  animal  or  vegetable  tissue  is  likewise  capable  of 
doing.  Boiled  or  preserved  in  alcohol  it  loses  this  power.  In  the  fresh  state 
it  is  soluble  in  from  6  to  8  per  cent,  solutions  of  sodium  nitrate  or  sodium 
sulphate,  with  the  formation  of  globulin;  and  in  dilute  alkalies  and  ammonia, 
with  the  formation  of  alkali-albuminate.  These  solutions  are  not  coagu- 
lated by  heat.  Also  weak  solutions  of  haloid  salts  (sodium  chlorid,  ammonium 
chlorid,  potassium  iodid,  sodium  iodid,  sodium  fluorid,  ammonium  fluorid)  dis- 
solve fibrin  at  a  temperature  of  40°,  as,  for  instance,  sodium-chlorid  solution,  from 
7  to  20  parts  in  the  thousand,  with  the  production  of  globulin-bodies  and  pro- 
peptone.  Fibrin  from  swine  is  dissolved  by  0.5  per  cent,  hydrochloric  acid 
and  also  by  malic,  oxalic,  butyric,  acetic,  citric,  and  lactic  acids;  fibrin  from 
cattle,  with  greater  difficulty.  Fibrin  exposed  to  air  for  a  considerable  time  is  not 
soluble  in  nitric  acid,  although  it  is  soluble  in  neurin.  As  a  result  of  putrefaction 
it  likewise  undergoes  solution,  with  the  formation  of  albumin.  Fibrin  contains 
lime,  iron,  and  magnesium. 

According  to  Schmiedeberg  the  fibrin  obtained  from  plasma  has  the 
elementary  formula  C108H162N30SO34,  while  blood-fibrin  has  the  following 
composition:  C112H16gN30SO35  -f-  ^H2O. 


GENERAL    PHENOMENA    ATTENDING    COAGULATION.  67 

GENERAL  PHENOMENA  ATTENDING  COAGULATION. 

Blood  does  not  undergo  coagulation  in  immediate  contact  with  the  living 
and  unaltered  vessel-wall.  Therefore,  Bnicke  was  able  to  preserve  unco- 
agulated  for  eight  days  blood  cooled  to  o°  in  the  still  beating  heart  of  dead 
turtles.  The  blood  coagulates  rapidly  within  the  dead  heart  or  vessels 
(but  not  in  the  capillaries)  or  within  other  channels,  as,  for  instance,  the 
urethra.  If  blood  stagnates  in  a  living  vessel,  coagulation  takes  place  in 
the  central  axis,  because  it  is  here  not  in  contact  with  the  living  vessel- 
wall.  Coagulation  is  of  the  greatest  importance  in  the  control  of  hem- 
orrhage from  injured  vessels,  which  otherwise  might  terminate  fatally. 
The  injured  and  necrotic  tissues  of  the  wound  and  the  vessel-wall  lead 
to  the  formation  of  the  occluding  thrombus  by  coagulation. 

If  the  vessel-wall  is  altered  by  pathological  processes,  as,  for  instance,  rough 
or  inflamed  in  consequence  of  a  lesion  of  the  intima,  coagulation  may  take  place 
in  such  a  situation  even  though  the  circulation  be  maintained". 

Coagulation  of  the  blood  is  prevented  or  retarded: 

(a)  By  addition  of  alkalies  or  of  ammonia,  even  in  small  amounts; 
further,  of  concentrated  solutions  of  neutral  salts  of  alkalies  and  earths 
— alkaline  chlorids,  also  sulphates,    phosphates,  nitrates,    carbonates  ; 
disodium  phosphate  in  3  per  cent,  solution,  soluble  salts  of  calcium, 
strontium  and  barium  dissolved  in  the  blood  to  the  extent  of   0.5   per 
cent.     Simultaneous  addition  of  sodium  chlorid  inhibits  coagulation  in 
still  further  degree.     Magnesium  sulphate — i  volume  of  a  28  per  cent, 
solution  to  3^  volumes  of  horses'  blood — acts  most  effectively  in  inhibit- 
ing coagulation. 

(b)  By  precipitation  of  the  calcium  by  means  of  oxalic  acid. 

Feeble  acids  also  exert  an  inhibiting  effect.  Thus,  coagulation  ceases  after 
addition  of  acetic  acid  to  the  point  of  producing  an  acid  reaction.  The  presence 
of  a  large  amount  of  carbon  dioxid  likewise  retards  coagulation;  therefore,  venous 
blood — and  also  the  blood  after  asphyxiation — coagulates  more  slowly  than  arte- 
rial blood. 

(c)  By  addition  of  egg-albumin,  sugar-solution,  glycerin,  soaps  or 
much  water.     If  uncoagulated  blood  be  brought  in  contact  with  a  layer 
of  already  separated  fibrin  coagulation  is  retarded. 

(d)  Cold  (o°  C.)  retards  coagulation  for  as  long  as  an  hour.    If  blood 
be  permitted  to  freeze  at  once,  it  will  still  be  liquid  on  thawing,  when  it 
undergoes  coagulation.      Coagulation  is  retarded  also  when  the   shed 
blood  is  exposed  to  high  pressure;  likewise  when  it  is  brought  in  con- 
tact with  foreign  substances  to  which  it  does  not  adhere,  as,  for  instance, 
anointed  substances. 

(e)  The  blood  of  embryo  birds  does  not  coagulate  at  all  before  the 
twelfth  or  fourteenth  day  on  account  of  the  absence  of  fibrin-forming 
cells,  and   that  of  the  hepatic  veins  but  slightly.     Blood   from  the  dog 
passed  only  through  the  heart  and  the  lungs  does  not  coagulate  for  a  long 
time.     Blood  from  the  renal  vein,  also  blood  cut  off  from  circulation 
through  the  liver  and  intestines,  does  not  coagulate  at  all.     Fetal  blood 
at  the  moment  of  birth  coagulates  early,  but  slowly,  as  the  amount  of 
fibrin  it  contains  is  small.    Menstrual  blood  exhibits  a  slighter  tendency 
to  undergo  coagulation  if  admixed  with  a  considerable  amount  of  alkaline 
mucus  from  the  genital  canal. 


68  COAGULATION    IS    ACCELERATED. 

(/)  In  cases  of  bleeders'  disease — hemophilia — coagulation  appears  to  be  want- 
ing on  account  of  deficiency  in  the  fibrin-generators,  in  consequence  of  which 
wounds  of  the  vessels  are  not  occluded  by  fibrinous  thrombi.  The  peptic  ferment 
of  the  pancreas  dissolved  in  glycerin  and  injected  into  the  blood  inhibits  its  coagu- 
lation, as  does  also  the  diastatic  ferment.  Schmidt-Mulheim  noted  the  same  result 
after  injection  of  pure  peptone  into  the  blood  of  dogs — 0.5  gram  to  i  kilo  of  dog, 
and  1.5  of  rabbit.  This  is  effective,  however,  only  in  the  presence  of  the  liver. 
The  buccal  secretion  of  the  leech,  the  poison  of  vipers  and  the  highly  toxic  substance 
in  the  serum  of  eels'  blood  likewise  inhibit  coagulation. 

Coagulation  is  accelerated: 

(a)  By  contact  with  foreign  substances  to  which  the  blood  adheres, 
as,  for  instance,  threads  and  needles  introduced  into  the  veins.  Also 
the  entrance  of  air-bubbles  into  the  vessels  or  the  passage  of  other 
indifferent  gases,  as,  for  instance,  nitrogen  and  hydrogen,  exerts  an 
accelerating  effect.  Removed  from  the  vein,  the  blood  coagulates 
quickly  on  the  walls  of  the  container,  on  its  surface  exposed  to  the  air, 
on  the  rod  with  jvhich  it  is  whipped,  etc. 

(6)  Many  products  of  the  retrogressive  metamorphosis  of  albuminates, 
including  uric  acid,  glycin,  taurin,  leucin,  tyrosin,  guanin,  xanthin, 
hypoxanthin  (not  urea),  as  well  as  the  biliary  acids,  further  lecithin, 
cholin  hydrochlorate,  protagon,  accelerate  coagulation  through  in- 
creased ferment-formation.  Added  in  excess,  however,  they  exert  an 
inhibiting  effect.  Solutions  of  gelatin  injected  into  the  veins  cause  the 
blood  to  coagulate  almost  instantly  after  escape  from  the  vessels. 

(c)  If  hemorrhage  takes  place  rapidly  the  last  amounts  of  blood 
coagulate  earliest.     Fresh  fibrin,  if  permitted  to  remain  for  a  consider- 
able time  in  blood,  is  again  dissolved  in  part. 

(d)  Heating  to   a  temperature  of  from   39°  to   55°  C.   accelerates 
coagulation. 

In  the  shed  blood  of  man  coagulation  begins  in  the  course  of  three 
minutes  and  forty-five  seconds;  in  that  of  woman  after  two  minutes 
and  thirty  seconds.  Hunger  exerts  an  accelerating  effect. 

Among  vertebrates  the  blood  of  birds  coagulates  almost  instantly,  that  of 
cold-blooded  animals  distinctly  more  slowly,  while  the  blood  of  mammals  occupies 
an  intermediate  position.  The  blood  of  invertebrates,  which  mostly  is  colorless, 
forms  a  soft,  white  fibrinous  coagulum. 

As  the  process  of  coagulation  involves  a  change  in  the  aggregate 
state,  heat  demonstrable  with  the  thermometer  must  be  set  free. 

In  blood  removed  from  a  vein  the  degree  of  alkalinity  diminishes 
up  to  the  point  of  completed  coagulation,  probably  from  the  formation 
of  acid  in  the  blood  as  a  result  of  decomposition-processes. 

In  the  process  of  coagulation  a  diminution  in  the  amount  of  oxygen  in  the 
blood  has  been  observed,  although  this  takes  place  also  in  blood  that  has  not  yet 
undergone  coagulation.  There  is,  likewise,  elimination  of  traces  of  ammonia. 
Both  processes,  however,  appear  not  to  stand  in  causal  relation  with  the  formation 
of  fibrin. 

NATURE  OF  COAGULATION. 

Alexander  Schmidt  discovered  in  1861  that  coagulation  is  a  fermen- 
tative process  that  consists  in  the  transformation  of  the  soluble  albumin 
of  the  plasma  into  the  solid  substances  of  the  fibrin  through  the  activity 
of  an  enzyme  that  is  designated  fibrin-ferment  or  thrombin.  This  pro- 
teid  is  nothing  but  fibrinogen. 


NATURE    OF    COAGULATION.  69 

The  enzymes  or  hydrolytic  ferments  behave  in  common  in  the  organism 
in  such  a  manner  that  they  break  up  the  bodies  upon  which  they  act  into 
two  other  substances  by  taking  up  water.  It,  therefore,  appears  probable  that 
as  a  result  of  the  action  of  thrombin  decomposition  of  the  fibrinogen  into  fibrin 
and  a  lesser  amount  of  a  globulin-body  that  remains  liquid  and  that  Hammarsten 
has  designated  fibrin- globulin,  takes  place,  with  the  taking  up  of  water. 

Demonstration  of  Fibrinogen — C112H168N30SO35. — Pulverized  sodium 
chlorid  is  added  to  lymphatic  transudate  to  the  point  of  saturation. 
The  fluid  poured  out  into  the  serous  sac  surrounding  the  testicle 
(hydrocele)  is  especially  useful  for  this  purpose.  The  precipitated 
fibrinogen  is  collected  upon  a  filter.  This  substance  is  found  also  in 
the  lymph  and  in  the  chyle. 

Saline  plasma  also  is  capable  of  precipitating  fibrinogen  by  admixture  of  equal 
volumes  of  plasma  and  a  concentrated  solution  of  sodium  chlorid.  For  purposes 
of  purification  it  may  then  be  dissolved  rapidly  and  repeatedly  in  a  dilute — 
8  per  cent. — solution  of  sodium  chlorid  and  again  precipitated  by  a  concentrated 
solution  of  sodium  chlorid.  The  fibrinogen  contained  in  the  sodium-chlorid  solu- 
tion is  precipitated  by  addition  of  water  and  is  rapidly  changed  so  that  it 
resembles  fibrin.  Fibrinogen  in  saline  solution  coagulates  at  a  temperature  of 
from  52°  to  55°  C.  Solutions  free  from  salt  do  not  coagulate  if  quickly  brought 
to  the  boiling-point. 

Fibrinogen  behaves  like  globulin.  It  is  soluble  in  dilute  alkalies  and  it  is 
precipitated  from  such  solutions  by  the  passage  of  carbon  dioxid.  It  is  further 
soluble  in  dilute  solution  of  sodium  chlorid,  while  addition  of  large  amounts  of 
sodium  chlorid  causes  its  precipitation  as  a  soft,  viscous,  tough  mass.  It  is 
dissolved  also  by  dilute  hydrochloric  acid,  although  it  is  soon  transformed  into  a 
body  resembling  syntonin  (acid  albuminate) .  In  the  fresh  state  it  actively 
decomposes  hydrogen  dioxid.  Its  specific  rotatory  power  is  52.2°. 

Demonstration  of  Fibrin-ferment — Thrombin. — Blood-serum  from  cat- 
tle, which  contains  a  larger  amount  of  ferment  than  the  serum  of  carnivora, 
is  admixed  with  twenty  times  its  volume  of  strong  alcohol.  The  result- 
ing precipitate  is  collected  upon  a  filter  after  the  lapse  of  from  two  to 
four  weeks.  It  contains  the  coagulated  albumin  and  the  ferment.  It 
is  dried  over  sulphuric  acid  and  reduced  to  powder.  One  dram  of  this 
powder  is  stirred  for  ten  minutes  in  65  cu.  cm.  of  water.  If  the  mixture 
is  not  filtered, (the  ferment,  dissolved  in  water,  alone  passes  through 
the  filter.  X 

Thrombin  is  formed  from  a  forerunner,  a  zymogen,  which  is  present  within 
the  leukocytes  and  is  designated  prothrombin.  Both  are  soluble  with  greater 
difficulty  in  an  excess  of  acetic  acid  than  globulins.  Even  small  amounts  of  the 
ferment  may  cause  coagulation  of  fluids  containing  fibrinogen  and  most  readily 
at  a  temperature  of  40°  C.  Prothrombin  is  destroyed  at  a  temperature  of  65  , 
thrombin  at  a  temperature  between  70°  and  75°.  The  amount  of  ferment  formed 
in  the  blood  is  the  'greater  the  longer  the  time  that  has  elapsed  between  the 
escape  and  the  coagulation  of  the  blood.  Blood  flowing  directly  from  the  vein  in 
alcohol  yields  no  ferment. 

Coagulation. — If  the  separate  solutions  (i)  of  the  fibrinogenous  sub- 
stance and  (2)  of  the  ferment  are  admixed  fibrin-formation  takes  place 
at  once.  The  most  favorable  temperature  for  this  is  that  of  the  body. 
A  temperature  of  o°  C.  prevents  coagulation,  while  the  boiling  tem- 
perature destroys  the  ferment.  The  amount  of  ferment  is  a  matter  of 
indifference.  Larger  amounts  cause  more  rapid,  but  not  increased, 
separation  of  fibrin.  For  the  formation  of  fibrin  the  presence  of  a 
certain  amount  of  salt  in  the  fluid  is  requisite — one  per  cent,  sodium 
chlorid.  Otherwise  the  process  takes  place  but  slowly  and  is  only 
partial.  The  presence  of  a  calcium-salt  favors  coagulation.  If  the 


70  SOURCE    OF    THE    FIBRINOGENOUS    SUBSTANCES. 

calcium  is  precipitated  by  alkali-oxalate  this  prevents  coagulation, 
although  it  is  true  that  the  presence  of  a  large  amount  of  ferment  in  the 
blood  is  capable  of  neutralizing  the  influence  of  the  calcium.  Fibrin- 
ogen  and  fibrin  contain  equal  amounts  of  calcium.  Probably  the 
action  of  the  calcium  bears  some  relation  to  -the  formation  of  the  fibrin- 
ferment,  for  the  plasma  contains  a  substance  that  exerts  a  marked 
coagulative  effect  after  addition  of  calcium-salts. 

According  to  Kossel  and  Lilienfeld  the  leukonuclein  contained  in  the  nuclei 
of  the  leukocytes,  and  the  nucleinic  acid  resulting  from  its  decomposition,  accelerate 
coagulation. 

If  coagulation  has  taken  place  in  the  plasma  of  the  blood,  all  of  the 
fibrinogenous  material  in  the  serum  is  utilized  for  the  formation  of 
fibrin.  On  the  other  hand,  fibrin-ferment  will  still  be  present  in  the 
serum  in  sufficient  amount.  Therefore,  if  blood-serum  be  added  to  a 
fluid  containing  fibrinogen,  as,  for  instance,  hydrocele-fluid,  coagulation 
will  at  once  take  place  anew. 

SOURCE  OF  THE  FIBRINOGENOUS  SUBSTANCES. 

Alexander  Schmidt  has  found  that  both  fibrin-factors  are  formed 
from  the  destruction  of  leukocytes.  In  the  circulating  blood  of  man 
and  of  mammals,  the  fibrinogenous  substance  is  already  dissolved  in 
the  plasma  as  a  soluble  product  of  the  physiologic  involution-processes 
of  the  white  cells.  The  circulating  blood,  however,  contains  a  much 
larger  number  of  leukocytes  than  was  previously  believed.  As  soon  as 
the  blood  is  shed,  large  numbers  of  white  blood-corpuscles  are  dissolved 
— according  to  Alex.  Schmidt  71.7  per  cent,  in  the  horse.  The  decom- 
position-products dissolve  in  the  blood-plasma,  and  as  a  result  the  fibrin- 
ferment  develops,  to  a  certain  extent  as  a  cadaveric  product,  causing 
the  separation  of  fibrin.  Accordingly  the  fibrin-ferment  does  not  preexist 
within  the  uninjured  corpuscles.  Also  the  so-called  transitional  forms 
between  colorless  cells  and  erythrocytes  in  mammalian  blood  furnish 
the  fibrin-factors  as  a  result  of  their  destruction,  which  takes  place 
immediately  after  escape  of  the  blood ;  likewise  perhaps  also  the  blood- 
plates.  The  ferment  develops  with  the  escape  of  the  blood,  and  its 
formation  reaches  the  maximum  during  the  process  of  coagulation 
itself. 

The  influence  of  adhesion  in  favoring  coagulation  depends  upon  the  fact 
that  as  a  result  the  blood-corpuscles  are  caused  to  give  up  a  portion  of  their 
contents — phosphoric  acid  and  alkaline  phosphates — to  the  plasma,  to  combine 
with  salts  of  calcium  and  magnesium  present  principally  in  the  plasma.  If  the 
calcium  be  precipitated  from  the  blood  by  means  of  oxalic  acid — i  gram  of 
potassium  oxalate  to  i  liter  of  blood — coagulation  no  longer  takes  place.  If,  how- 
ever, calcium  chlorid  be  again  added  to  this  mixture  coagulation  will  result. 

In  the  blood  of  amphibia  and  birds  it  is  the  red  blood-corpuscles  that  after 
escape  undergo  destruction  in  large  numbers  and  furnish  the  fibrin-forming  mate- 
rials. In  the  blood  of  these  animals  Alex.  Schmidt  convinced^  himself  at  the  same 
time  that  also  the  fibrinogenous  substance  was  originally  a  constituent  of  the  blood- 
corpuscles. 

It  is  thus  clear  that  as  soon  as  the  fibrin-factors  pass  into  solution  in 
consequence  of  dissolution  of  the  blood-corpuscles  the  separation  of 
fibrin  must  take  place  through  the  combination  of  the  two  substances. 

If  considerable  amounts  of  leukocytes  are  introduced  into  the  circulation  of 
an  animal  they  are  quickly  dissolved  in  large  numbers  in  the  blood,  so  that  even 


RELATIONS  OF  THE  RED  BLOOD-CORPUSCLES.  71 

death  may  take  place  in  consequence  of  widespread  coagulation.  If  the  animal 
survive  immediate  death  by  reason  of  the  moderate  extent  of  coagulation,  the 
blood  subsequently  will  be  wholly  incoagulable  in  consequence  of  the  absence  of 
leukocytes. 

All  protoplasmic  structures  may  in  combination  with  plasma  set  the 
fibrin-ferment  free.  The  nitrogenous  metabolic  products  of  proteids 
are  likewise  capable  of  producing  fibrin-ferment  in  plasma  free 
from  cells.  These  latter  active  substances  can  be  extracted  from  the 
tissues — cells  of  the  liver,  the  spleen,  the  lymph-glands,  red  and  white 
blood-corpuscles,  frog-muscle — by  means  of  alcohol.  If  after  alcoholic 
extraction  the  residue  of  such  tissues  is  extracted  with  water,  this 
watery  extract  absolutely  inhibits  coagulation.  The  substance  thus 
extracted  by  water  is  designated  by  Alex.  Schmidt  cytoglobin,  which  is 
the  forerunner  of  fibrinogen  and  also  of  serum-globulin. 

In  accordance  with  the  preponderance  in  the  plasma  of  either  of 
the  substances  capable  of  extraction  with  alcohol  or  cytoglobin,  coagu- 
lation is  induced  or  inhibited  respectively.  Within  the  living  body  the 
inhibitory  action  of  the  cells  preponderates,  while  outside  the  body 
the  coagulating  effect  is  operative.  Those  substances,  such  as  the 
cytoglobin,  that  inhibit  coagulation  within  the  circulation  furnish  out- 
side of  the  body  the  material  for  the  formation  of  fibrin.  As  Alex. 
Schmidt,  after  addition  of  cytoglobin  to  filtered  plasma,  induced  coagu- 
lation by  addition  of  extractives  in  large  amount,  the  amount  of  fibrin 
was  more  than  doubled.  The  blood  retains  its  fluidity  in  the  circulation 
as  long  as  the  amount  of  cytoglobin  exceeds  that  of  the  proteid  metabolic 
products  of  the  tissues.  The  blood  may,  however,  remain  fluid  also 
because  both  of  these  do  not  pass  over  into  the  plasma. 

Pathological. — From  the  investigations  of  Alex.  Schmidt  in  collaboration  with 
his  pupils  Jakowicki  and  Birk,  it  has  been  shown  that  even  healthy  functionating 
blood  contains  some  fibrin-ferment  from  the  destruction  of  white  blood-corpuscles 
normally  undergoing  dissolution,  and  in  greater  amount  in  venous  than  in  arterial 
blood.  Nevertheless,  it  is  always  more  abundant  in  shed  blood.  The  fact,  how- 
ever, is  particularly  noteworthy  that  the  amount  of  fibrin-ferment  in  the  blood 
in  cases  of  septic  fever  may  increase  to  such  a  degree  that  spontaneous  coagulation- 
thrombosis  takes  place  and  even  terminates  fatally.  After  injection  of  putrid 
matters  leukocytes  are  dissolved  in  large  number,  but  the  ferment  is  present  rather 
abundantly  also  in  the  blood  of  febrile  patients  generally.  Also  injection  of  pep- 
tone, of  hemoglobin  and  in  lesser  degree  of  distilled  water  is  followed  by  dissolution 
of  numerous  leukocytes.  There  are  thus  true  blood-diseases  in  which  the  products 
of  the  dissolution  of  the  leukocytes  accumulate  in  the  blood-plasma.  In  conse- 
quence, spontaneous  coagulation  naturally  occurs  within  the  circulatory  organs,  and 
as  a  result  death  may  even  be  brought  about.  At  least  febrile  elevation  of  tempera- 
ture usually  takes  place.  At  the  termination  of  such  conditions  the  coagulability 
of  the  blood  is  naturally  diminished. 

Wooldridge  showed  that  a  fibrinogen — tissue- fibrinogen — occurs  in  the  chyle  and 
in  the  lymph  as  a  product  of  the  lymphatic  glands.  In  human  beings  in  whom 
blood-stasis  exists  in  any  part  of  the  body,  coagulation  may  take  place,  with 
the  formation  of  thrombi,  through  admixture  of  lymph,  as  a  certain  amount  of 
ferment  is  already  present  in  the  blood.  The  intestinal  mucosa,  the  skin,  and  the 
lungs  also  appear  to  produce  small  amounts  of  fibrinogen  constantly,  while  the 
liver  and  the  kidneys  constantly  destroy  it. 

RELATIONS    OF    THE    RED     BLOOD-CORPUSCLES     TO     FIBRIN- 
FORMATION. 

After  it  had  been  determined  by  a  number  of  investigators  that  also 
the  erythrocytes  of  birds,  of  the  horse,  of  the  frog,  may  contribute  to  the 


72  CHEMICAL    CONSTITUTION    OF    BLOOD-PLASMA    AND    SERUM. 

production  of  fibrin,  Landois  was  able  in  1874  to  follow  directly  under 
the  microscope  the  transformation  of  the  stromata  of  the  red  blood-cor- 
puscles of  mammals  into  fibrin-fibers.  If  a  drop  of  defibrinated  rabbit's 
blood  be  introduced  into  frog's  serum,  without  agitation,  it  will  be 
observed  that  the  erythrocytes  attach  themselves  to  one  another.  They 
become  viscous  upon  the  surface,  and  on  pressure  on  the  cover-slip  it 
will  be  seen  the  adhesion  can  be  broken  up  only  with  a  certain  amount 
of  force,  the  adjoining  surfaces  of  the  swollen,  globular  corpuscles  often 
being  drawn  out  into  threads.  Even  after  the  process  has  been  in 
operation  for  a  short  time,  all  of  the  corpuscles  are  transformed  into 
globules  of  lesser  diameter  and  those  lying  nearest  the  periphery  permit 
their  hemoglobin  to  escape.  The  decolorization  progresses  from  the 
periphery  of  the  drop  to  the  center,  and  finally  only  a  coherent  mass  of 
stroma  remains.  The  substance  of  the  stroma  exhibits  great  tenacity. 
At  first  the  round  contours  of  the  individual  blood-corpuscles  can  still 
be  recognized,  but  as  soon  as  a  current  is  set  up  in  the  surrounding  fluid 
by  pressure  upon  or  movement  of  the  cover-glass,  the  stroma-mass 
becomes  agitated  to  and  fro  and  the  stromata  lying  close  together  and 
adherent  to  one  another  become  drawn  out  into  delicate  filaments  and 
bands,  with  simultaneous  disappearance  of  the  previous  contour  of 
the  cells.  In  this  way  the  formation  of  fibrin-filaments  from  the  stro- 
mata of  the  red  blood-corpuscles  can  be  followed  step  by  step.  Erythro- 
cytes from  human  beings  and  from  animals  undergoing  dissolution  in 
the  serum  of  different  animals  often  exhibit  the  same  phenomena. 

Stroma-fibrin  can  be  prepared  also  in  the  following  simple  manner:  A  one 
per  cent,  solution  of  sodium  chlorid  is  shaken  in  a  reagent-glass  with  ether  and 
a  few  drops  of  defibrinated  blood.  The  mixture  soon  becomes  lake-colored. 
Put  aside,  the  ether,  which  rises  to  the  tpp,  carries  with  it  the  filamentous  stroma- 
fibrin  to  the  surface  of  the  fluid. 

Stroma-fibrin  and  Plasma-fibrin. — Landois  has  designated  stroma- 
fibrin  that  which  arises  directly  from  the  stroma  of  the  erythrocytes. 
On  the  other  hand,  the  fibrin  that  is  produced  through  the  combination 
of  the  fibrin-factors  dissolved  in  the  coagulating  fluid — plasma — is 
plasma- fibrin,  or  ordinary  fibrin.  Both  designations  are  fully  justified, 
if  only  to  indicate  the  mode  of  origin  of  the  fibrinous  mass. 

Substances  that  cause  rapid  dissolution  of  the  erythrocytes  bring 
about  extensive  coagulation,  as,  for  instance,  injection  of  bile  or  salts 
of  the  biliary  acids,  or  of  lake-colored  blood  into  the  veins.  The 
effective  agent  under  these  circumstances  is  the  stroma,  through  the 
development  of  the  ferment,  and  in  lesser  degree  the  hemoglobin.  As 
foreign  blood  after  injection  often  undergoes  rapid  disintegration  in  the 
blood-stream  of  the  recipient,  extensive  coagulation  is  often  observed 
under  such  circumstances,  while  at  the  same  time  the  individual 
smaller  vessels  are  often  occluded  by  plugs  of  stroma-fibrin . 

CHEMICAL   CONSTITUTION    OF   THE    BLOOD-PLASMA   AND    THE 

SERUM. 

The  proteids  constitute  about  8  or  10  per  cent,  of  the  plasma.  Of 
these  only  about  0.2  per  cent,  are  bodies  producing  fibrin.  If  these  be 
eliminated  through  the  process  of  coagulation,  the  plasma  is  trans- 
formed into  serum.  The  specific  gravity  of  human  serum  is  between  1027 
and  1029.  The  blood-plasma  contains,  besides,  the  following  proteids: 


SERUM-ALBUMIN,    SERUM-GLOBULIN.  73 

(a)  Serum-albumin — C78H120N20SO24 — from  3  to  4  Per  Cent. — Its  per- 
centage-composition is  C  53.1,  H  7.1,  N  15.9,  S  1.9,  O  22,  Ash  0.22.     Its 
coagulation-temperature  is  from  51°  to  53° C.;  its  specific  rotatory  power 
— 61°.     In  the  horse  and  the  rabbit  it  crystallizes  in  hexagonal  prisms, 
with  a    pyramid    upon  one  side.     The  crystals  are  doubly  refracting, 
up  to  i  cm.  in  length,  and  are  coagulable  by  heat. 

It  is  a  remarkable  fact  that  serum-albumin  is  absent  from  the  blood  of 
starving  snakes  and  it  makes  its  appearance  only  after  feeding. 

(b)  Serum-globulin — also  known  as  fibrino plastic  substance  or  para- 
globulin  and  also  as  serum-casein — from  2  to  4  per  cent.       If   magne- 
sium sulphate  in  substance  is  added  to  serum  to  the  point  of  saturation, 
serum-globulin  is  precipitated  at  a  temperature  of  35°  C.     It  is  washed 
upon  a  filter  with  concentrated  solution  of  magnesium  sulphate.     It  is 
soluble  in  a  10  per  cent,  solution  of  sodium  chlorid,  and  coagulates  at  a 
temperature  of  from  69°  to  75°  C.     Its  specific  rotatory  power  is — 47.8°, 
and  its  formula  is  C117H174N3oSO38. 

After  precipitation  of  the  serum-globulin  from  the  serum  by  means  of  mag- 
nesium sulphate  the  serum-albumin  is  precipitated  by  further  saturation  with  so- 
dium sulphate.  Neutral  ammonium  sulphate,  added  to  the  point  of  saturation, 
precipitates  all  of  the  proteids  of  the  blood-serum,  arid  also  those  of  egg- albumin 
and  of  milk  ;  further,  propeptone,  but  not  peptones.  Globulin  can  be  precipitated 
also  by  dialysis  of  the  serum,  as  it  is  insoluble  in  solutions  free  from  salt. 

During  hunger  the  amount  of  globulin  increases,  while  that  of  albumin  dimin- 
ishes. After  abstraction  of  blood  the  amount  of  globulin  in  the  blood  increases. 
Paraglobulin  occurs  also  in  erythrocytes,  as  well  as  in  the  fluids  of  the  connective 
tissue  and  the  cornea.  According  to  von  Jaksch,  100  cu.  cm.  of  blood  contain 
22.62  grams  of  albumin,  while  an  equal  amount  of  serum  contains  more  than  8 
grams.  The  latter  figure  varies  under  pathological  conditions. 

Fats — from  o.i  to  0.2  Per  Cent. — Neutral  fats — stearin,  palmitin, 
olein — occur  in  the  form  of  minute  microscopic  droplets,  whose  presence 
often  renders  the  serum  of  a  milky  turbidity  after  abundant  ingestion 
of  fat  and  also  of  milk.  They  are  more  abundant  during  hunger  and 
in  drunkards.  There  occur,  besides,  soaps,  lecithin,  and  its  decompo- 
sition-product, glycerin-phosphoric  acid,  and  cholesterin.  Hiirthle 
found  cholesterin  oleate  and  palmitate — 0.17  per  cent.  According  to 
Hanriot  a  ferment,  known  as  lipase,  occurs  in  blood  and  which  breaks 
up  neutral  fat  into  glycerin  and  fatty  acids.  Lipase  is  found  also  in  the 
pancreas  and  in  the  liver,  and  traces  also  in  some  other  parts  of  the 
body. 

A  certain  amount  of  grape-sugar — from  o.i  to  0.15  per  cent.,  some- 
what more  in  the  blood  of  the  hepatic  veins,  derived  from  the  liver  and 
the  muscles  and  increased  after  loss  of  blood ;  some  glycogen — increased 
in  cases  of  diabetes;  a  trace  of  animal  gum,  a  reducing  substance, 
insusceptible  of  fermentation  and  soluble  in  ether,  jecorin,  which  is  a 
combination  of  dextrose  and  lecithin  ;  a  dextrose-forming  diastatic  fer- 
ment, inactive  at  a  temperature  of  65°  C.  For  a  discussion  of  the  sugar- 
destroying  power  of  the  blood  reference  may  be  made  to  the  section  on 
the  liver. 

The  amount  of  sugar  in  the  blood  is  increased  by  absorption  of  sugar  from 
the  intestinal  tract,  and  in  greatest  degree  in  the  blood  of  the  portal  and  hepatic 
veins.  It  is  increased  also  in  arterial  blood,  although  here  it  is  rapidly  changed. 

For  purposes  of  demonstration  blood  is  coagulated  by  boiling  after  addition  of 
sodium  sulphate,  and  the  amount  of  sugar  in  the  expressed  fluid  is  determined 
with  the  aid  of  Fehling's  solution.  Pavy  digested  the  blood  thrice  successively 


74  ABSORPTION    OF    GASES    BY    SOLID    BODIES    AND    FLUIDS. 

with  six  times  its  volume  of  alcohol,  then  boiled  and  expressed  the  product.     The 
extract,  which  is  evaporated,  contains  all  of  the  sugar. 

Kreatin,  urea — during  hunger  0.035  per  cent.,  in  the  stage  of  maxi- 
mum formation  0.153  per  cent. ;  at  times  succinic  acid,  hippuric  acid,  and 
uric  acid  (i  :  6000  in  gouty  individuals);  guanin  (?  carbamic  acid);  in 
the  blood  after  death  also  sarcolactic  acid.  All  of  these  are  present  in 
exceedingly  small  amount. 

Inorganic  matters  —  0.85  per  cent.;  principally  sodium-combina- 
tions. The  amount  of  salts  is  increased  by  a  meat-diet,  while  it  is  dimin- 
ished by  a  vegetable  diet.  Ammonium  is  present  in  the  proportion  of 
i  mg.  to  100  cu.  cm.,  and  three  or  four  times  as  abundantly  in  the  blood 
of  the  portal  vein. 

Human  blood-serum  contains  the  following  salts  : 

Sodium  chlorid, 4.92  in  1000. 

Sodium  sulphate, 0.44 

Sodium  carbonate, 0.21        " 

Sodium  phosphate, o^S       " 

Calcium  phosphate,          1  ,( 

Magnesium  phosphate,   / °-73 

The  alkaline  reaction  of.  the  serum  depends  principally  upon  the  sodium  car- 
bonate present.  It  is  only  half  that  of  the  blood. 

The  serum  of  blood  containing  carbon  dioxid  in  large  amount  exhibits  a  more 
pronounced  alkaline  reaction  and  the  amount  of  chlorin  contained  is  diminished. 
This  is  dependent  upon  the  fact  that  hydrochloric  acid  and  water  enter  the  blood- 
corpuscles,  while  the  alkali  remains  behind. 

If  salts  in  considerable  amount  are  introduced  into  the  blood,  the  larger  amount 
disappears  in  the  course  of  a  few  minutes,  diffusing  principally  into  the  tissues. 
Gradually  they  are  eliminated  from  the  body  through  the  kidneys.  The  same 
statement  is  applicable  to  sugar  and  peptone. 

Water — about  90  per  cent. 
Yellowish  pigments. 

One  pigment  can  be  separated  by  agitation  with  methyl-alcohol.  It  exhibits 
two  absorption-bands  of  lipochrome,  like  lutein.  Hydrobilirubin  was  found  by 
Maly,  and  choletelin  by  MacMunn. 

Blood,  and  also  blood-serum  free  from  cells,  as  well  as  lymph,  possess  bacter- 
icidal properties,  which  are  augmented  by  increase  in  the  alkalinity,  but,  on  the 
other  hand,  disappear  on  addition  of  water,  on  heating  to  a  temperature  of  55°  C., 
on  exposure  to  diffuse  daylight,  and  likewise  if  mineral  matters  are  removed  by 
dialysis.  Egg-albumin  and  fresh  milk  exhibit  the  same  properties.  The  corpuscle- 
destroying— globulicidal — action  of  fresh  serum  is  peculiar  to  the  latter,  in  con- 
junction with  its  bactericidal  effect  after  bacterial  invasion.  Both  properties 
are  due  to  certain  proteid  bodies  known  as  alexins.  The  serum  of  an  individual 
rendered  immure  by  inoculation  to  any  infectious  disease  exerts  an  antitoxic 
effect  against  the  poison  of  the  corresponding  infectious  agent,  and  it  can  there- 
fore be  employed  against  the  latter  for  curative  purposes. 

Large  numbers  of  microbes  may  gain  entrance  into  the  blood-stream  during 
the  death-agony. 

The  serum  of  individuals  suffering  from  typhoid  fever  contains  a  substance 
of  diagnostic  importance,  designated  agglutinin,  which  causes  agglutination  of 
typhoid  bacilli  in  cultures. 

THE  GASES  OF  THE  BLOOD. 

ABSORPTION    OF    GASES    BY    SOLID    BODIES    AND    BY    FLUIDS. 

Between  the  particles  of  solid,  porous  bodies  and  gaseous  substances  there 
exists  a  marked  attraction  of  such  a  character  that  the  gases  are  attracted  by  the 
solid  bodies  and  condensed  within  their  pores;  that  is,  the  gases  are  absorbed  by 
the  solid  bodies.  Thus,  for  instance,  one  volume  of  boxwood  charcoal,  at  a  tern- 


DIFFUSION    OF    GASES.  75 

perature  of  12°  C.  and  a  pressure  of  760  mm.  of  mercury,  absorbs  35  volumes  of 
carbon  dioxid,  9.4  volumes  of  oxygen,  7.5  volumes  of  nitrogen,  1.5  volumes  of 
hydrogen.  The  absorption  of  the  gases  is  invariably  attended  with  the  generation 
of  heat,  which  is  in  proportion  to  the  energy  with  which  absorption  takes  place. 
Non-porous  bodies  are  in  an  analogous  manner  surrounded  intimately  upon  their 
surface  by  a  layer  of  condensed  gas. 

Fluids  are  in  like  manner  capable  of  taking  up  or  absorbing  gases.  In  this 
connection  it  has  been  learned  that  a  given  amount  of  fluid  at  different  pressures 
nevertheless  always  absorbs  an  equal  volume  of  gas.  Whether  the  pressure  be 
great  or  small,  the  volume  of  gas  absorbed  is  always  the  same.  It  is,  however, 
known,  according  to  the  law  of  Boyle-Mariotte,  governing  the  compression  of  gases, 
that  with  twice,  thrice  or  greater  amounts  of  pressure,  twice,  thrice  or  greater 
amounts  of  gas  by  weight  are  contained  within  an  equal  volume  of  gas.  From 
this  there  is  formulated  the  law  that  while  at  varying  pressures  the  volume  of 
gas  absorbed  remains  the  same,  the  amount  of  gas  by  weight  contained  within 
the  same  volume  is  directly  proportional  to  the  amount' of  pressure.  If,  therefore, 
the  pressure  is  zero  the  amount  of  the  absorbed  gas  must  likewise  be  zero; 
whence  it  follows  that  fluids  under  the  air-pump  in  a  vacuum  may  be  deprived  of 
their  absorbed  gases. 

The  coefficient  o£  absorption  represents  that  volume  of  gas  that  is  absorbed 
by  i  volume-unit  of  a  fluid  at  a  given  pressure  and  temperature.  From  what 
has  been  said  with  regard  to  the  volume  of  absorbed  gases  the  coefficient  of  ab- 
sorption must  be  wholly  independent  of  the  pressure. 

The  temperature  has  an  important  influence  upon  the  coefficient  of  absorption. 
When  the  temperature  is  low  the  coefficient  is  highest,  declining  at  a  higher  tem- 
perature and  becoming  zero  when  the  fluid  boils.  From  this  it  follows  that  ab- 
sorbed gases  can  also  be  expelled  from  fluids  by  heating  the  latter  to  the  boiling- 
point.  The  coefficient  of  absorption  increases,  however,  for  various  fluids  and 
gases  with  increasing  temperature  in  a  peculiar,  and  by  no  means  uniform,  manner, 
which  must  be  determined  empirically  for  each.  At  the  temperature  of  the  body 
the  coefficient  of  absorption  of  carbon  dioxid  is  0.5283,  of  nitrogen  0.0119,  of  oxy- 
gen, at  a  pressure  of  699  mm.,  0.0231. 

DIFFUSION  OF  GASES;  ABSORPTION  OF  GASEOUS  MIXTURES. 

Gases  that  do  not  enter  into  chemical  combination  with  one  another  are 
capable  of  forming  a  uniform  mixture.  If,  for  instance,  the  necks  of  two  flasks 
are  connected  of  which  the  lower  contains  carbon  dioxid  and  the  upper,  placed 
vertically  and  inverted  above  the  other,  contains  hydrogen,  both  gases  combine, 
independently  of  differences  in  specific  gravity,  within  each  flask  so  as  to  form 
identical  mixtures.  This  phenomenon  is  known  as  the  diffusion  of  gases.  If  a 
porous  membrane  be  previously  interposed  between  the  two  gases  the  interchange 
of  gases  takes  place  just  the  same.  Nevertheless  different  gases  pass  through  the 
interstices  of  the  membrane  with  unequal  rapidity  in  the  same  way  as  in  the 
case  of  fluids  in  the  process  of  endosmosis,  so  that  at  first  a  larger  amount  of  gas 
will  be  present  upon  the  one  side  than  upon  the  other.  According  to  Graham 
the  rapidity  with  which  gases  pass  through  the  interstices  is  inversely  as  the 
square  root  of  their  specific  gravity,  but  according  to  Bunsen,  not  exactly  so. 

Gases  mutually  exert  no  pressure  upon  one  another.  Therefore  a  gas  escapes 
from  a  space  containing  another  gas  as  from  a  vacuum.  If,  accordingly,  the  sur- 
face of  a  fluid  in  which  a  gas  is  absorbed  be  placed  in  communication  with  a  large 
amount  of  another  gas,  the  absorbed  gas  passes  over  into  the  other  gas.  Therefore, 
absorbed  gases  can  be  removed  if  the  fluids  containing  them  are  treated  with 
other  gases  by  agitation  or  by  passing  them  through. 

If  two  or  more  gases  in  mixture  lie  over  a  fluid  within  a  closed  space  the  separate 
gases  will  be  absorbed,  and  according  to  weight  in  proportion  to  the  pressure  to 
which  each  gas  would  be  exposed  if  it  were  alone  present  in  the  space.  This 
pressure  is  known  as  partial  pressure.  The  amount  of  gas  absorbed  from  mixtures 
is  therefore  proportionate  to  the  partial  pressure.  The  partial  pressure  of  a  gas 
in  a  space  partially  filled  by  a  fluid  is  at  the  same  time  an  expression  of  the  ten- 
sion of  the  absorbed  gas  in  this  fluid. 

The  air  contains  0.2096  volume  of  oxygen  and  0.7904  volume  of  nitrogen. 
If,  therefore,  one  volume  of  air  is  present  at  a  pressure  P  over  water,  the  partial 
pressure  under  which  oxygen  is  absorbed  is  0.2096  x  P,  and  that  for  nitrogen 
equals  0.7904  x  P.  At  a  temperature  of  o°  C.  and  at  760  mm.  pressure  i  volume 


76  SEPARATION  OF  THE  GASES  OF  THE  BLOOD. 

of  water  absorbs  0.02477  volume  of  air,  consisting  of  0.00862  volume  of  oxygen 
and  0.01615  volume  of  the  nitrogen.  It  accordingly  contains  34  per  cent,  of 
oxygen  and  66  per  cent,  of  nitrogen.  Water,  therefore,  absorbs  from  the  atmos- 
pheric air  an  amount  of  gas  that  is  by  percentage  richer  in  oxygen  than  the  air 
itself. 

SEPARATION  OF  THE  GASES  OF  THE  BLOOD. 

The  expulsion  of  the  gases  of  the  blood  and  their  collection  for  chemical 
.analysis  are  effected  by  means  of  the  mercurial  air-pump.  The  Pfluger 
pump  for  the  extraction  of  gases  is  illustrated  diagrammatically  in  Fig.  20. 
It  consists  of  a  blood-receptacle  (A),  a  glass  flask  with  a  capacity  of  from  250 
to  300  cu.  cm.,  drawn  out  above  and  below  into  tubes,  each  of  which  can  be 
closed  by  means  of  a  stop-cock  (a  b).  The  cock  b  is  an  ordinary  stop-cock,  while 
the  cock  a  has  a  channel  passing  through  its  longitudinal  axis  and  opening  at  x 
in  such  a  manner  that  in  accordance  with  its  adjustment  it  leads  either  into  the 
receptacle  (position  x  a)  or  downward  through  the  lower  tube  (position  x'  a') . 
This  receptacle  is  first  completely  deprived  of  air  by  application  to  a  mercurial 
air-pump  and  is  then  weighed.  Next,  the  extremity  x'  is  tied  in  an  artery  or  a 
vein  of  an  animal  and  by  placing  the  lower  cock  in  the  position  x  a  the  blood  is 
permitted  to  flow  into  the  receptacle.  When  the  desired  amount  has  been  col- 
lected the  lower  cock  is  again  placed  in  the  position  x'  a',  the  exterior  is  carefully 
cleaned  and  the  receptacle  is  weighed  in  order  to  determine  the  weight  of  the 
blood  collected. 

The  second  portion  of  the  apparatus  is  the  froth-vessel  chamber  (B) ,  likewise 
drawn  out  above  and  below  into  tubes,  which  can  be  closed  by  means  of  the 
cocks  c  and  d.  The  purpose  of  the  froth-chamber  is  to  take  up  the  froth  formed 
in  consequence  of  the  active  escape  of  the  gases  from  the  blood.  Below,  the  froth- 
chamber  is  connected  with  the  receptacle  by  means  of  a  ground-glass  tube  and 
above  likewise  through  a  well-fitting  tube  with  the  drying  apparatus  (G).  This 
consists  of  a  U-shaped  tube  expanded  below  into  a  glass  bulb.  The  latter  is  half 
filled  with  sulphuric  acid,  while  each  arm  contains  bits  of  pumice-stone  saturated 
with  sulphuric  acid.  In  passing  through  this  apparatus,  which  likewise  may  be 
closed  by  means  of  the  two  stop-cocks  e  and  f,  the  gases  of  the  blood  yield  up 
their  watery  vapor  to  the  sulphuric  acid,  so  that  they  may  be  conveyed  through 
the  cock  f  in  a  perfectly  dry  state. 

The  short  tube  D  is  similarly  connected  with  the  prolongation  from  f  by 
means  of  a  properly  ground  surface,  and  it  is  provided  with  a  small  manometer 
from  which  the  degree  of  vacuum  can  be  read.  The  tube  D  communicates  with 
the  pump -apparatus  proper.  This  consists  of  two  large  glass  flasks,  E  and  F, 
terminating  above  and  below  in  open  tubes,  the  lower  of  which,  Z  and  w,  are 
connected  by  means  of  a  rubber  tube  G.  Both  flasks  and  the  tube  are  filled  with 
mercury  to  about  half  the  height  of  the  flasks.  The  flask  E  is  secured,  while  the 
flask  F  can  be  raised  and  lowered  by  means  of  a  pulley-apparatus  attached  to  a 
stand.  When  F  is  raised  E  becomes  filled,  and  when  F  is  lowered  E  is  emptied. 
The  upper  extremity  of  E  divides  into  two  tubes,  g  and  H,  of  which  g  is  connected 
with  D.  The  tube  h,  passing  upward,  becomes  greatly  narrowed  and  further  on 
is  so  curved  that  its  free  extremity,  i,  dips  into  a  basin  containing  mercury,  v, 
with  its  opening  below  the  tube  for  the  reception  of  the  gases,  J  (eudiometer- 
tube)  completely  filled  with  mercury.  At  the  junction  of  g  and  H  there  is  a  cock 
with  a  double  channel,  which  in  the  position  H  connects  the  flask  E  with  A  B  G  D, 
and  in  the  position  K  closes  A  B  G  D  and  connects  the  flask  E  with  the  tube  J. 

In  the  first  place,  B  G  D  is  completely  exhausted  of  air  by  the  following  steps: 
The  stop-cock  is  placed  in  the  position  K;  and  F  is  raised  until  globules  of  mercury 
pass  from  the  free  tube  i,  which  is  as  yet  not  placed  below  J,  into  the  basin.  Then 
the  stop-cock  is  placed  in  the  position  H,  when  F  is  depressed.  Next,  the  cock 
is  placed  again  in  the  position  K,  and  so  on,  until  the  manometer  y  indicates 
that  evacuation  has  taken  place.  Now,  J  is  placed  over  i.  If  the  cocks  c  and  b 
are  opened,  so  that  the  receptacle  A  communicates  with  the  remainder  of  the 
apparatus,  the  gases  of  the  blood  pass  actively  into  B,  with  the  generation  of  foam, 
and  through  G,  dried,  to  E.  The  depression  of  F  brings  them  principally  into  E. 
Finally,  the  cock  is  placed  in  the  position  K,  while  F  is  raised,  and  the  gases  are 
conveyed  to  J  above  the  mercury.  Repeated  depression  and  elevation  of  G  with 
appropriate  adjustment  of  the  cock  will  finally  bring  all  of  the  gases  into  J. 

The  removal  of  the  gases  from  the  blood  is  materially  facilitated  by  placing 
the  recipient  A  in  a  vessel  containing  water  at  a  temperature  of  60°  C.  It  is 


QUANTITATIVE    ESTIMATION    OF    GASES    OF    THE    BLOOD. 


77 


advisable  in  the  analysis  of  the  gases  of  the  blood  to  evacuate  at  once  the  blood 
discharged  from  the  vein  into  the  receptacle,  because  on  standing  outside  of  the 
body  the  amount  of  oxygen  undergoes  a  diminution. 

Mayow,  in  1670,  was  the  first  to  observe  gases  arise  from  the  blood  in  a  vacuum, 
and  Priestley  demonstrated  the  presence  of  oxygen  and  Davy  that    of  carbon 


FIG.  20. — Diagrammatic  Representation  of  Pfliiger's  Pump  for  the  Extraction  of  the  Gases  of  the  Blood. 


dioxid.  Magnus,  in  1857,  investigated  the  percentage-composition  of  the  gases 
of  the  blood.  The  important  recent  investigations  have  been  made  principally 
by  Loth.  Meyer,  in  1837,  and  by  C.  Ludwig  and  Pfliiger  and  their  pupils. 

QUANTITATIVE  ESTIMATION   OF  THE   GASES  OF  THE  BLOOD. 

The  evacuated  gases  consist  of  oxygen,  carbon  dioxid,  and  nitrogen. 

The  gases  of  the  blood  obtained  with  the  aid  of  the  pump  will  be  found  in 
the   eudiometer-tube    (Fig.  20,  J),  an  accurately  graduated  glass   tube   in  wrhose 


78  THE  GASES  OF  THE  BLOOD. 

closed  upper  portion  two  platinum  wires,  p  n,  are  soldered.  The  eudiometer  is 
closed  below  by  mercury. 

Estimation  of  the  Carbon  Dioxid. — A  globule  of  potassic  hydrate  fused  to  a 
platinum  wire  and  moistened  on  its  surface  is  brought  from  below  through  the 
mercury  into  the  gaseous  mixture.  The  carbon  dioxid  unites  with  the  potassium 
hydrate  to  form  potassium  carbonate.  After  remaining  in  place  for  a  considerable 
period  of  time,  the  globule  is  removed  in  the  same  way.  The  diminution  in  the 
volume  of  the  gases  indicates  the  volume  of  the  carbon  dioxid  removed. 

Estimation  of  the  Oxygen. — In  the  same  way  as  in  estimating  the  carbon  dioxid 
a  globule  of  phosphorus  is  introduced  into  the  eudiometer-tube  by  means  of 
a  platinum  wire  and  which  takes  up  the  oxygen  for  the  formation  of  phosphoric 
acid;  or  a  dry  globule  of  coke  or  papier  mache  saturated  with  a  solution  of  pyro- 
gallic  acid  in  potassic  hydrate,  which  eagerly  takes  up  oxygen.  After  removal  of 
the  globule  the  diminution  in  volume  of  the  gases  indicates  the  amount  of  oxygen. 

The  oxygen  can  be  determined  most  accurately  and  most  rapidly,  according 
to  Volta  and  Bunsen,  by  explosion  in  the  eudiometer.  An  abundance  of  hydro- 
gen, whose  volume  is  carefully  determined,  is  introduced  into  the  eudiometer- tube. 
Then  an  electric  spark  is  made  to  pass  through  the  tube  between  the  wires  p  and 
n.  The  oxygen  and  the  hydrogen  combine  to  form  water.  In  consequence  a 
reduction  in  the  volume  takes  place  in  the  eudiometer,  of  which  a  third  represents 
the  oxygen  required  for  the  formation  of  the  water. 

Estimation  of  the  Nitrogen. — If  the  carbon  dioxid  and  the  oxygen  are  removed 
from  the  gas-container  according  to  the  methods  described  the  remainder  consists 
of  nitrogen. 

SPECIAL  FACTS  CONCERNING  THE  GASES  OF  THE  BLOOD. 

Oxygen  is  present  in  arterial  blood  from  the  dog  on  an  average  to  the 
amount  of  18.3  volumes  per  cent.,  at  a  temperature  of  o°  C.  and  i  meter  of 
mercurial  pressure.  Arterial  blood  is  saturated,  according  to  Pfltiger, 
to  T9Q-,  according  to  Hiifner  that  of  the  dog  to  |i>  with  oxygen. 
By  means  of  thorough  artificial  respiration  in  animals  in  the  state 
of  apnea  or  by  active  agitation  of  the  blood  with  air  the  amount  of 
oxygen  can  be  brought  up  to  23  volumes  per  cent.  Venous  blood  con- 
tains on  the  average  8.15  volumes  per  cent,  less  of  oxygen  than  arterial 
blood,  although  the  amount  of  oxygen  varies  widely  in  accordance 
with  the  tissues  and  the  circulatory  conditions.  Sczelkow  found 
6  volumes  per  cent,  in  the  blood  of  resting  muscles.  Only  traces  are 
present  in  the  blood  after  asphyxiation.  In  the  more  highly  colored 
blood  of  active  glands,  such  as  the  salivary  glands  and  the  kidneys, 
oxygen  is  undoubtedly  present  in  larger  amount  than  in  ordinary, 
darker  venous  blood. 

The  oxygen  occurs  in  the  blood  as  follows: 

(a)  From  o.i  to  0.2  volume  per  cent,  are  in  a  state  of  simple  absorp- 
tion in  the  plasma — thus  only  a  minimal  portion,  not  exceeding  that 
which  distilled  water  at  the  temperature  of  the  blood  and  at  the  partial 
pressure  of  oxygen  in  the  air  of  the  lungs  would  take  up. 

(b)  Almost  all  of  the  oxygen  of  the  blood  is  combined  chemically, 
and  with  the  hemoglobin  of  the  erythrocytes,  with  which  it  forms  oxy- 
hemoglobin  ;    it    is  therefore  not  subject    to  the    laws  of    absorption. 
The  total  amount  of  blood  acts  with  regard  to  the  chemical  absorption 
of  oxygen  like  a  gas-free  solution  of  hemoglobin,  except  that  the  absorp- 
tion of  oxygen  by  the  blood  takes  place  more  rapidly  than  by  a  solution 
of   hemoglobin.     At  a  temperature  of  o°  and  at  moderate  atmospheric 
pressure — 760  mm.  of  mercury — i   gram  of  hemoglobin  takes  up  from 
1.6  to  1.8  cu.  cm.  of  oxygen — according  to  Hiifner  1.592  cu.  cm. 


OZONE    IX    THE    BLOOD.  79 

The  absorption  of  oxygen  on  the  part  of  the  blood  is  thus  independent  of 
the  pressure.  This  is  seen  also  in  shed  blood,  which,  on  the  one  hand,  permits 
more  abundant  escape  of  the  chemically  combined  oxygen  only  when  the  pressure 
becomes  reduced  to  about  30  mm.  of  mercury  (at  a  temperature  of  12°  C.  with 
increasing  temperature  at  a  lower  pressure),  while,  on  the  other  hand,  it  takes  up 
only  little  more  oxygen  even  if  the  air-pressure  be  enormously  high,  up  to  six 
atmospheres.  The  same  phenomenon  is  exhibited  by  the  blood  in  the  living 
body,  for  both  on  the  highest  mountains  as  well  "as  in  the  deepest  valleys 
it  takes  up  oxygen  in  accordance  with  its  requirements.  Also,  animals  breathing 
in  a  closed  space  are  capable  of  abstracting  the  oxygen  from  the  surrounding  air 
down  to  the  minutest  trace. 

In  spite  of  the  chemical  combination  existing  between  the  hemo- 
globin and  the  oxygen,  the  total  amount  of  oxygen  in  the  blood  can 
be  driven  out  by  those  agents  that  set  free  absorbed  gases:  (a)  by 
evacuation  ;  (b)  by  boiling  ;  (c)  by  the  passage  of  the  gases  ;  because 
the  chemical  union  of  oxyhemoglobin  is  so  feeble  that  it  is  broken 
up  by  the  physical  procedures  named. 

Among  chemical  agents,  reducing  substances,  such  as  ammonium 
sulphid,  hydrogen  sulphid,  solutions  of  alkaline  subsalts,  iron  filings, 
etc.,  extract  oxygen  from  the  blood. 

The  amount  of  iron  present  in  the  blood — 0.55  in  1000  parts — is  in  direct 
proportion  to  the  amount  of  hemoglobin,  this  to  the  number  of  erythrocytes  and 
the  latter  in  turn  approximately  to  the  specific  gravity  of  the  blood.  The  amount 
of  oxygen  taken  up  by  the  blood  has  been  shown  to  be  almost  proportional  to 
the  specific  gravity  of  the  blood.  It  is,  therefore,  also  proportional  to  the  amount  of 
iron  in  the  blood.  According  to  Hoppe-Seyler  i  atom  of  iron  may  combine  with 
2  atoms  of  oxygen  in  the  blood.  According  to  Bohr  the  combination  is  said  to  be  an 
unstable  one.  The  latter  investigator  even  differentiates,  several  varieties  of  com- 
bination between  oxygen  and  hemoglobin,  in  accordance  with  the  amount  of 
bound  oxygen — namely,  0.4  or  0:75  or  3  cu.  cm.  of  oxygen,  at  a  temperature 
of  15°  C.  and  an  oxygen-pressure  of  150  mm. — to  i  gram  of  hemoglobin.  Also 
carbon  monoxid  is  believed  by  Bohr  to  be  taken  up  in  varying  amounts  in  an 
analogous  manner. 

Immediately  after  escape  of  the  blood  a  slight  loss  of  oxygen  takes  place  as 
a  physiological  manifestation  of  tissue-respiration  within  the  living  blood. 
After  having  been  outside  the  circulation  for  some  time  the  amount  of  oxygen  is 
found  to  undergo  progressive  diminution,  and  after  a  long  time  and  at  a  high 
temperature  the  oxygen  may  have  wholly  disappeared  from  the  blood.  This  latter 
loss  of  oxygen  is  due  to  decomposition  within  the  shed  blood,  in  consequence  of 
which  reducing  substances  form  and  these  take  up  the  oxygen.  Not  all  varieties 
of  blood  act  .in  this  connection  with  equal  energy  in  the  destruction  of  oxygen. 
The  venous  blood  of  active  muscles  acts  most  energetically,  while  the  blood  of 
the  hepatic  veins  is  scarcely  at  all  active.  In  place  of  the  oxygen  that  has  dis- 
appeared carbon  dioxid  makes  its  appearance  in  the  blood,  whose  color  becomes 
dark.  At  times  the  amount  of  carbon  dioxid  is  even  larger  than  that  of  the 
oxygen  destroyed. 

AS  TO  THE  PRESENCE  OF  OZONE  IN  THE  BLOOD. 

On  account  of  the  varied  and  in  part  active  oxidation-processes  that 
take  place  through  the  intermediation  of  the  blood,  the  question  has 
been  raised  whether  the  oxygen  in  the  blood  may  not  be  present 
in  the  form  of  ozone  (O3).  However,  neither  in  the  blood  itself 
nor  yet  in  the  gases  evacuated  from  the  blood  can  ozone  be  found. 
Nevertheless,  the  red  blood-corpuscles,  as  well  as  the  hemoglobin,  have 
a  definite  relation  to  ozone. 

The  hemoglobin  acts  as  a  conveyer  of  ozone,  that  is,  it  is  capable  of 
taking  away  the  ozone  from  other  bodies,  and  conveying  it  to  other 
oxi  Hzable  substances. 


80  CARBON    DIOXID    AND    NITROGEN    IN    THE    BLOOD. 

Oil  of  turpentine  that  has  been  exposed  to  the  air  for  a  considerable  time 
always  contains  ozone.  Among  reagents  for  ozone  are  potassium-iodid  paste, 
which  becomes  blue,  as  the  ozone  releases  the  combination  of  iodin  and  potassium, 
and  the  iodin  causes  the  starch-paste  to  become  blue;  further,  freshly  prepared 
solution  of  guaiac-resin  in  alcohol,  which  also  is  made  blue  by  ozone.  A  solution 
of  guaiac  is  dropped  in  water,  the  resin  forming  a  milky  precipitate,  and  oil  of 
turpentine  is  added.  At  first  no  reaction  occurs,  but  if  blood  or  hemoglobin  be 
added,  with  agitation,  a  bluish  discoloration  appears,  that  is,  the  blood  takes  the 
ozone  from  the  oil  of  turpentine  and  conveys  it  to  the  guaiac-resin. 

It  has  been  stated  that  hemoglobin  acts  as  an  ozone-producer;  that  is,  it  is 
capable  of  generating  ozone  from  the  inactive  oxygen  of  the  air  with  which  it 
comes  in  contact.  For  this  reason,  red  blood-corpuscles  alone  also  cause  guaiac 
to  become  blue.  The  reaction  is  most  successful  if  the  solution  of  guaiac  is  per- 
mitted to  dry  upon  blotting-paper  and  then  several  drops  of  blood  diluted  from 
5  to  10  times  are  added.  That  under  these  circumstances  the  condition  is  one 
of  stimulation  of  the  surrounding  oxygen  through  the  hemoglobin,  is  shown  by 
the  observation  that  even  red  blood-corpuscles  containing  carbon  monoxid  bring 
about  the  blue  coloration,  naturally  not  when  the  extraneous  oxygen  of  the  air  is 
excluded.  According  to  Pfluger  these  reactions  take  place  only  with  decompo- 
sition of  the  hemoglobin,  and  for  this  reason  it  is  believed  that  the  blood-corpus- 
cles as  such  do  not  act  as  producers  of  ozone." 

Also  hydrogen  sulphid  is  decomposed  by  the  blood,  as  by  ozone  itself,  into 
sulphur  and  water.  Hydrogen  dioxid  likewise  is  decomposed  by  the  blood  into 
oxygen  and  water.  This  can  be  prevented  by  the  addition  of  a  small  amount  of 
hydrocyanic  acid.  Crystallized  hemoglobin  does  not  bring  this  result  about,  and 
hydrogen  dioxid  can  be  cautiously  injected  into  the  veins  of  animals.  From  this 
it  would  appear  that  unaltered  hemoglobin  has  no  ozone-producing  effect. 

There  are  three  varieties  of  oxygen:  (i)  Ordinary  or  inactive  oxygen  (O2) , 
as,  for  instance,  that  of  atmospheric  air.  (2)  Active  or  nascent  oxygen  (O),  which 
can  never  occur  in  the  free  state,  but  which  on  its  development  at  once  enters 
into  chemical  combination  as  a  most  powerful  oxidizing  agent.  This  is  capable 
of  oxidizing  water  into  hydrogen  dioxid,  the  nitrogen  of  the  air  into  nitrous  and 
nitric  acids,  and  also  carbon  monoxid  into  carbon  dioxid — which  ozone  is  not 
capable  of  doing.  This  gas  certainly  plays  an  important  role  in  the  organism. 
(3)  Ozone  (O3)  forms  through  the  breaking  up  of  certain  molecules  of  ordinary 
oxygen  (O2)  into  two  atoms  each  (O),  and  union  of  each  of  these  atoms  with  an 
undecomposed  molecule  of  oxygen.  Ozone  is  a  form  of  oxygen  compressed  to 
two-thirds  of  its  volume. 

CARBON  DIOXID  AND  NITROGEN  IN  THE  BLOOD. 

Carbon  dioxid  is  present  in  arterial  blood  in  from  34  to  38  volumes 
per  cent.,  at  a  temperature  of  o°  C.  and  a  pressure  of  i  meter;  in 
venous  blood  on  the  average  in  9.2  volumes  per  cent,  more  than  in 
arterial  blood,  varying  greatly  in  accordance  with  the  situation  and 
the  circulatory  conditions.  The  total  amount  of  carbon  dioxid  in 
the  blood  does  not  equal  even  one-half  of  that  which  the  blood 
would  actually  be  capable  of  taking  up.  Thus,  the  blood  after  asphyxi- 
ation may  contain  as  much  as  52.6  volumes  per  cent.  The  amount  of 
carbon  dioxid  in  the  lymph  after  asphyxiation  is  less  than  that  in  the 
blood.  The  carbon  dioxid  can  be  completely  pumped  out  of  the  total 
volume  of  blood  without  the  formation  of  acids  in  the  process  of  evac- 
uation— in  consequence  of  decomposition  of  the  constituents  of  the 
blood — which  might  take  part  in  driving  out  the  carbon  dioxid. 

The  Carbon  Dioxid  of  the  Plasma  or  the  Serum. 

(a)  This  is  absorbed  in  smallest  part  simply  by  the  blood-plasma. 

(b)  The  largest  part  of  the  carbon  dioxid  is  combined  chemically 
with  the  blood-plasma,  independently  of   the   pressure.     This  combi- 
nation may  take  place  in  the  following  manner: 

i.  A  portion  of  the  carbon  dioxid  is  loosely  combined  with  sodium  carbonate, 
forming  sodium  bicarbonate,  one  equivalent  of  carbon  dioxid  being  taken  up  by 


INDIVIDUAL    CONSTITUENTS    OF    THE    BLOOD.  8l 

the  simple  carbonate:  CO3Na2  -f  CO2  4-  H2O  =2CO3NaH.  In  this  way  considerable 
amounts  of  carbon  dioxid  may  be  bound.  As  the  sodium  bicarbonate  releases  the 
carbon  dioxid  but  slowly  in  a  vacuum,  while  blood  releases  it  with  violence,  it 
must  be  borne  in  mind  that  perhaps  sodium  combined  with  a  proteid  (serum- 
globulin  alkali)  contains  the  carbon  dioxid  in  a  complex  combination,  from 
which  it  readily  separates  in  a  vacuum. 

2.  A  minimal  portion  of  the  carbon  dioxid  of  the  plasma  might  be  combined 
chemically  with  neutral  sodium  phosphate:  One  equivalent  of  this  salt  may 
combine  with  one  equivalent  of  carbon  dioxid,  so  that  acid  sodium  phosphate 
and  acid  sodium  carbonate  result:  PO4Na2H  +  CO2  +  H2O  =  PO4NaH2  +  CO3XaH. 
In  the  process  of  evacuation  the  carbon  dioxid  escapes,  with  the  formation  of 
neutral  sodium  phosphate.  As,  however,  the  sodium  phosphate  formed  in  blood- 
ash  has  resulted  almost  wholly  from  the  combustion  of  lecithin  and  nuclein,  only 
the  small  amount  of  this  salt  already  present  in  the  plasma  can  be  taken  into 
consideration. 

The  Carbon  Dioxid  in  the  Blood-corpuscles. 

The  erythrocytes  also  contain  carbon  dioxid  in  loose  chemical  com- 
bination. In  denbrinated  human  blood  31.12  volumes  per  cent,  of 
carbon  dioxid  have  been  found  in  the  serum,  and  only  4.5  in  the  blood- 
corpuscles.  The  combination  of  the  carbon  dioxid  is  effected  in  part, 
through  the  hemoglobin,  therefore  through  the  formation  of  carbohem- 
oglobin,  in  part  from  the  globulin-alkali  combinations  of  the  erythro- 
cytes. The  leukocytes  also  combine  with  carbon  dioxid  in  accordance 
with  the  character  of  the  constituents  of  the  serum,  and  in  about  the 
proportion  of  from  T^  to  \  of  the  absorptive  power  of  the  serum. 

According  to  Bohr  there  are  three  varieties  of  carbon-dioxid  combination 
with  hemoglobin,  which,  while  closely  resembling  one  another,  take  up  different 
amounts  of  carbon  dioxid — namely  1.5,  3  and  6  cu.  cm.  of  carbon  dioxid  respec- 
tively to  i  gram  of  hemoglobin,  at  the  same  partial  pressure  for  the  carbon  dioxid 
and  at  the  same  temperature.  Spectroscopically,  carbon-dioxid  hemoglobin  re- 
sembles reduced  hemoglobin,  except  that  its  absorption-band  lies  somewhat  nearer 
the  violet,  and  it  absorbs  more  light  in  the  green.  Hemoglobin  can  take  up  oxy- 
gen and  carbon  dioxid  at  the  same  time,  and  each  independently  of  the  other. 
Therefore  it  is  probable  that  oxygen  and  carbon  dioxid  unite  with  different  con- 
stituents of  the  hemoglobin. 

The  amount  of  carbon  dioxid  in  the  blood  is  diminished  by  alcoholic  intoxica- 
tion, while  it  is  increased  by  inhalation  of  ether,  wrhich  reduces  the  amount  of 
oxygen.  Subcutaneous  injection  of  morphin  or  chloral  diminishes  the  amount 
of  oxygen.  After  administration  of  iodin,  mercury,  sodium  oxalate  and  nitrate 
there  is  a  reduction  in  the  amount  of  carbon  dioxid  in  arterial  blood.  The  same 
result  is  brought  about  in  the  blood  of  animals  by  injection  of  peptone  into  the 
veins,  and  also  in  the  febrile  state  on  account  of  the  lessened  alkalinity  of  the 
blood. 

Nitrogen  is  present  in  the  blood  in  the  proportion  of  from  1.4  to  1.6 
volumes  per  cent,  in  a  state  of  simple  absorption. 

For  every  100  parts  of  nitrogen  there  are  2.1  parts  of  argon,  which,  however, 
is  present  only  in  the  plasma.  The  blood  contains  more  nitrogen  when  the 
number  of  erythrocytes  is  larger  than  when  the  number  is  smaller  and  when  the 
blood  is  lake-colored.  Jolyet  and  Sigalas  believe,  therefore,  that  the  erythrocytes, 
like  solid  bodies,  absorb  nitrogen  at  their  surface.  On  standing  outside  the  body,, 
the  blood  yields  small  amounts  of  ammonia,  particularly  with  access  of  oxygen 
and  application  of  heat,  perhaps  in  consequence  of  decomposition  of  an  as  yet 
unknown  ammonium-salt. 

ESTIMATION  OF  THE  INDIVIDUAL  CONSTITUENTS  OF  THE 

BLOOD. 

Estimation  of  the  Water  and  of  All  of  the  Solid  Constituents  of  the  Total  Blood 
or  of  the  Serum. — About  5  grams  of  serum  or  defibrinated  blood  are  evaporated 
in  a  crucible  of  known  weight  over  a  water-bath  and  dried  in  a  drying  chamber 
6 


82  ARTERIAL  AND  VENOUS  BLOOD. 

at  a  temperature  of  no0  C.  The  loss  of  weight  represents  the  amount  of  water 
that  was  present.  The  dry  residue  is  determined  by  subtracting  the  weight  of 
the  crucible.  For  clinical  purposes  Stintzing  weighs  a  few  drops  of  blood  in  a 
Hight,  covered  glass  dish.  This  he  dries  for  six  hours  at  a  temperature  of  65°  C. 
-raaid  weighs  the  residue.  The  amount  of  water  was  found  to  be  in  men  78.3, 
Tin  women  79.8.  The  dry  residue  corresponds  approximately  with  the  amount  of 
rproteids  contained  in  the  blood  and  it  declines  in  the  presence  of  anemia. 

Estimation  of  the  Fibrin. — A  measured  volume  of  blood  is  whipped  with  a  rod. 
After  complete  separation,  all  of  the  fibrin  is  collected  upon  a  satin  filter  and 
washed  with  water;  then  placed  in  a  dish  and  again  washed  with  water,  alcohol 
and  ether;  next  dried  in  a  drying  chamber  at  a  temperature  of  110°  C.,  and 
finally  weighed.  Kossler  and  Pfeiffer  estimate  the  amount  of  nitrogen  in  the 
serum  and  in  the  plasma  according  to  the  method  of  Kjeldahl;  the  difference 
represents  the  amount  of  nitrogen  in  the  fibrin.  The  fibrin  in  100  cu.  cm.  of  plasma 
contains  39  mg.  of  nitrogen  (from  30.8  to  45).  The  fibrin  is  increased  in  cases  of 
pneumonia,  acute  articular  rheumatism,  erysipelas,  scarlet  fever,  peritonitis  (to 
between  80  and  152  mg.). 

Estimation  of  the  Fats  (Ethereal  Extract}  in  the  Serum  or  the  Total  Blood. — • 
About  15  grams  of  defibrinated  blood  or  serum  are  dried  in  a  dish  at  first  over 
a  water-bath,  then  in  a  drying  chamber  at  a  temperature  of  120°  O.,  rubbed  up, 
and  placed  in  a  flask  with  ether,  which  is  repeatedly  renewed. 

The  method  just  described  is  followed  in  preparing  an  alcoholic  extract  from 
the  total  blood  or  the  serum. 

Estimation  of  the  Inorganic  Salts  in  the  Total  Blood  or  Serum. — About  25  grams 
are  dried  in  a  weighed  platinum  crucible  and  then  reduced  to  ash  over  a  free 
flame  at  red  heat.  The  amount  of  ash  is  determined  by  weighing.  If  this  ash 
be  repeatedly  extracted  with  hot  water,  and  the  latter  be  entirely  evaporated  in 
a  weighed  dish,  the  weight  of  the  salts  soluble  in  water  will  be  obtained. 

Estimation  of  the  Total  Proteids  in  Blood  or  Serum. — E.  Salkowski  precipitates 
all  albuminates  by  means  of  sodium  chlorid  and  acetic  acid.  For  this  purpose 
he  places  20  grams  of  pulverized  sodium  chlorid  and  50  cu.  cm.  of  blood  in  a  dry 
flask  and  adds  100  cu.  cm.  of  a  mixture  of  7  volumes  of  concentrated  solution 
of  sodium  chlorid  and  i  volume  of  acetic  acid,  agitating  for  20  minutes  and 
filtering-  The  filter  is  dried  and  weighed.  V.  Jaksch  takes  i  gram  of  blood  from 
a  cupping  glass,  estimates  the  amount  of  nitrogen  contained  by  the  method  of 
Kjeldahl,  and  multiplies  the  result  obtained  by  6.25. 

Estimation  of  the  Proteids  of  the  Blood-corpuscles. — If  the  proteids  contained 
in  one  part  by  weight  of  the  total  blood  and  also  of  the  serum  have  been  deter- 
mined, and  if  the  amount  obtained  for  the  serum  be  deducted  from  that  obtained 
for  the  total  blood  in  the  proportion  in  which  red  blood-corpuscles  and  serum  are 
present  in  the  total  blood,  the  result  will  represent  the  proteids  of  the  blood-corpus- 
cles, although  only  approximately. 

Estimation  of  the  Red  Blood-corpuscles  by  Weight. — Defibrinated  blood  is  mixed 
with  thrice  its  volume  of  a  concentrated  solution  of  sodium  sulphate  and  filtered. 
The  blood-corpuscles  remaining  upon  the  filter  are  coagulated  by  immersing  the 
filter  in  boiling  concentrated  solution  of  sodium  sulphate.  Then  the  filter  can  be 
washed  out  with  distilled  water,  after  which  it  is  dried  and  weighed.  The  increase 
in  the  weight  of  the  previously  weighed  filter  is  due  to  the  presence  of  the  blood- 
corpuscles. 

ARTERIAL  AND  VENOUS  BLOOD. 

Arterial  blood  contains  in  solution  all  those  materials  that  are  neces- 
sary for  the  nutrition  of  the  tissues,  many  that  are  to  be  employed  in 
secretion  and  in  addition  the  larger  amount  of  oxygen.  Venous  blood 
need  contain  less  of  these  matters,  while  the  waste  materials  of  the 
tissues,  the  products  of  retrogressive  metamorphosis,  will  be  present  in 
greater  amount,  including  a  larger  quantity  of  carbon  dioxid.  As, 
however,  the  interchange  through  the  blood  takes  place  rapidly,  no 
great  difference  in  many  of  these  substances  can  be  looked  for  at  a 
given  moment.  In  many  respects  analysis  fails  to  furnish  conclusive 
evidence.  A  little  consideration,  further,  will  show  that  the  blood  from 


THE    AMOUNT    OF    BLOOD.  83 

some  veins  must  be  characterized  by  special  peculiarities,  such  as  the 
blood  from  the  portal  vein  and  the  hepatic  veins.  The  essential  differ- 
ences between  the  two  kinds  of  blood  may  be  summarized  as  follows : 

ARTERIAL  BLOOD  CONTAINS 
More  Less 

Oxygen,     water,      fibrin,      extractives,       Carbon    dioxid,    blood-corpuscles,    pro- 
salts,    at   times   chlorids,   sugar,   fat;  teids,  alkali,  urea, 
and  the  temperature  is  on  an  average 
i°  C.  higher. 

The  bright  red  color  of  arterial  blood  is  due  to  oxy hemoglobin,  to 
which  it  is  peculiar;  while  the  dark  color  of  venous  blood  is  due  to  a 
deficiency  in  oxyhemoglobin  and  an  abundance  of  reduced  hemoglobin. 
The  larger  amount  of  carbon  dioxid  in  venous  blood  is  not  responsible 
for  the  dark  color,  for  if  equal  amounts  of  oxygen  be  added  to  two 
portions  of  blood  and  to  the  one  also  carbon  dioxid,  the  latter  effects 
no  change  in  color. 

THE  AMOUNT  OF  BLOOD. 

The  amount  of  blood  in  the  adult  equals  y1^  of  the  body- weight, 
in  the  newborn  -£-$. 

According  to  A.  Schiicking  the  amount  of  blood  in  the  infant  when  the 
umbilical  vein  is  ligated  immediately  after  birth  is  j^,  while  that  in  the  infant 
when  ligation  is  practised  later  is  as  much  as  ^  of  the  body- weight.  Immediate 
ligation,  therefore,  causes  a  reduction  of  the  amount  of  blood  in  the  newborn 
child  of  about  100  grams.  Further,  the  number  of  red  corpuscles  is  less  in  the 
blood  of  the  newborn  child  after  immediate  ligation  than  in  that  of  infants  in 
which  ligation  is  practised  later. 

For  the  estimation  of  the  amount  of  blood,  first  practised  by  Valen- 
tine in  1838  and  by  Ed.  Weber  in  1850  by  unreliable  methods,  the  fol- 
lowing may  be  employed : 

Welckefs  Method. — Blood  from  the  incised  carotid  of  a  previously  weighed 
animal,  with  a  cannula  tied  in  the  vessel,  is  received  into  a  weighed  flask, 
in  which  it  is  defibrinated  by  agitation  with  pebbles.  It  is  then  measured. 
A  portion  of  the  defibrinated  blood  is  made  cherry-red  by  the  passage  of  carbon 
monoxid,  because  ordinary  blood  possesses  varying  coloring  power  in  accordance 
with  the  amount  of  oxygen  present.  Now  a  \—- shaped  cannula  is  tied  in  both 
extremities  of  the  divided  carotid  and  a  0.9  per  cent,  solution  of  sodium 
chlorid  is  permitted  to  flow  steadily  from  a  pressure- vessel,  while  the  resulting 
wash- water  that  escapes  from  the  divided  jugular  veins  and  the  inferior 
vena  cava  is  collected  until  it  becomes  as  clear  as  water.  Then  the  entire 
body  is  minced,  and  with  the  exception  of  the  weighed  contents  of  the 
stomach  and  intestines,  whose  weight  is  deducted  from  that  of  the  body,  the 
mass  is  extracted  with  water  and  expressed  after  the  lapse  of  24  hours.  This 
water  and  the  sodium-chlorid  wash- water  are  mixed  and  weighed.  A  portion  of 
this  mixture  is  likewise  saturated  with  carbon  monoxid.  Of  this  a  specimen  is 
placed  in  a  glass  chamber  with  parallel  walls,  i  cm.  apart — a  so-called  hema- 
tinometer,  while  in  a  second  chamber  water  is  added  to  the  undiluted  blood 
from  a  buret  until  both  fluids  exhibit  the  same  shade  of  color.  From  the  amount 
of  water  that  is  necessary  to  make  the  dilution  of  the  blood  of  the  same  tint  as 
the  wash-water  the  amount  of  blood  present  in  the  latter  can  be  estimated.  In 
mincing  the  muscles  alone  the  coloring-matter  yielded  by  them  can  be  considered 
as  muscle-pigment  and  need  not  be  taken  into  account.  By  multiplying  the 
volume  of  blood  by  its  specific  gravity  the  absolute  weight  of  the  blood  can 
be  determined.  As  the  differences  in  the  color  of  the  specimens  can  be  esti- 
mated most  accuratelv  this  method  is  to  be  commended. 


84  ABNORMAL    INCREASE    IN    THE    AMOUNT    OF    BLOOD. 

The  weight  of  the  blood  of  mice  has  been  found  to  be  from  y^  to  -^ 
of  the  body-weight,  exclusive  of  gastric  and  intestinal  contents;  of 
guinea-pigs  -1—  (from  -^  to  -1 ) ;  of  rabbits  ^  (from  ~  to  -^-) ;  of  dogs 
13  (from  4  to  ^);  of  cats  ~;  of  birds  from  ^  to  ^-  of  frogs  ^  to  ~; 
of  fish  from  ^  to  ^. 

Vierordt's  method,  which  is  based  upon  the  determination  of  the  amount  of 
blood  by  indirect  means,  is  discussed  under  circulation  time. 

The  specific  gravity  also  should  be  determined  in  a  study  of  the 
blood.  In  states  of  inanition  the  amount  of  blood  has  been  observed 
to  be  reduced.  Obese  individuals  have  relatively  less  blood.  After 
hemorrhage  the  blood  lost  is  readily  replaced  by  water,  while  the  blood- 
corpuscles  are  only  gradually  regenerated.  After  extensive,  deple- 
thoric  transfusion  with  defibrinated  blood  Landois,  as  well  as  Panum, 
observed  the  amount  of  blood  and  its  specific  gravity  to  be  maintained. 

In  the  living  animal  Grehant  and  Quinquaud  permitted  a  measured  amount 
of  carbon  dioxid  to  be  inspired,  then  withdrew  a  quantity  of  blood  and  estimated 
the  amount  of  carbon  monoxid  present.  From  this  the  amount  of  blood  can  be 
readily  determined.  A  quantity  of  carbon-monoxid  blood  could  also  be  transfused 
and  shortly  thereafter  the  proportion  of  shed  blood  containing  carbon  monoxid, 
and  that  free  from  carbon  monoxid,  be  estimated. 

The  estimation  of  the  amount  of  blood  in  individual  organs  is  made  after 
sudden  ligation  of  their  veins  during  life.  The  organs  are  cut  up  into  small  pieces 
and  the  amount  of  blood  contained  in  the  wash-water  is  determined  by  comparison 
with  a  specimen  of  blood  to  be  diluted.  The  estimation  after  death  in  a  state 
of  freezing  is  to  be  rejected. 

ABNORMAL    INCREASE    IN    THE    AMOUNT    OF    BLOOD    OR    ITS 

INDIVIDUAL   PARTS. 

An  increase  in  the  total  mass  of  blood  uniformly  in  all  its  parts  is  known  as 
polyemia  or  plethora.  It  may  occur  as  a  morbid  manifestation  in  individuals  with 
excessive  nutritive  and  assimilative  activity.  A  marked  bluish-red  color  of  the 
external  integument,  with  swollen  veins  and  large  arteries  and  a  hard  and  full 
pulse,  injection  particularly  of  the  capillaries  and  smaller  vessels  of  the  visible 
mucous  membranes  are  the  readily  explicable  signs,  accompanied  by  cerebral 
hyperemia,  which  may  give  rise  to  attacks  of  vertigo,  and  hyperemia  of  the  lungs, 
which  may  give  rise  to  dyspnea.  Also  after  amputation  of  large  portions  of  the 
extremities,  with  avoidance  of  loss  of  blood,  a  relative  increase  in  the  amount  of 
blood  has  been  described  (plethora  apocoptica) . 

Polyemia  can  be  induced  artificially  by  injection  of  blood  from  the  same 
species.  If  the  normal  amount  of  blood  be  increased  up  to  83  per  cent,  no  ab- 
normal condition  develops;  in  particular,  the  blood-pressure  does  not  become 
permanently  raised.  The  blood  finds  its  way  especially  into  the  greatly  distended 
capillaries,  which  as  a  result  become  stretched  beyond  their  normal  elasticity. 
An  increase  in  the  amount  of  blood,  however,  up  to  150  per  cent,  jeopardizes  life 
directly,  with  considerable  variations  in  blood-pressure,  and  which  Landois  has 
observed  to  terminate  fatally  in  consequence  of  direct  rupture  of  vessels. 

Following  upon  the  injection  of  blood  the  formation  of  lymph  rapidly  in- 
creases. Then  the  serum  is  disposed  of  in  the  course  of  one  or  two  days,  the 
water  being  eliminated  principally  through  the  urine,  and  the  proteids  in  part 
converted  into  urea.  Therefore,  the  blood  at  this  time  appears  to  be  richer  in 
red  blood-corpuscles.  The  red  blood-corpuscles  undergo  destruction  much  more 
slowly  and  the  materials  furnished  by  them  are  converted  in  part  into  urea  and 
in  part  into  the  biliary  pigment,  though  not  constantly.  Nevertheless  an  excess 
of  red  blood-corpuscles  may  be  observed  for  as  long  as  a  month. 

That  as  a  matter  of  fact  the  blood-corpuscles  are  slowly  destroyed  in  the 
process  of  metabolism  is  shown  from  the  circumstance  that  the  formation  of  urea 
is  greater  when  the  animal  ingests  the  same  amount  of  blood  than  if  it  receives 
an  equal  amount  by  transfusion.  In  the  latter  event  a  moderate  increase  in 


ABNORMAL    INCREASE    IN    THE    AMOUNT    OF    BLOOD.  85 

the  amount  of  urea  persists  often  for  a  number  of  days  as  a  sign  of  slow  destruc- 
tion of  the  red  corpuscles.  Marked  plethora  is  attended,  further,  with  loss  of 
appetite  as  well  as  a  tendency  to  hemorrhages  from  the  mucous  membranes. 

Serous  polyemia  is  the  name  given  to  that  condition  of  the  blood  in  which 
the  amount  of  serum  or  plasma  is  increased.  The  condition  can  be  produced 
artificially  by  injecting  into  the  veins  of  animals  serum  from  the  same  species. 
Under  such  circumstances  the  water  is  soon  excreted  with  the  urine,  while  the 
albumin  is  decomposed  into  urea,  without  passing  over  into  the  urine.  An  animal 
forms  more  urea  from  a  given  amount  of  injected  serum  than  from  an  equal 
amount  of  blood — an  indication  that  the  blood-corpuscles  are  capable  of  being 
preserved  for  a  longer  time  than  the  serum.  If,  however,  an  animal  be  injected 
with  the  serum  from  another  species,  in  which  the  blood-corpuscles  of  the  recip- 
ient undergo  solution,  as,  for  instance,  if  dogs'  serum  be  injected  into  a  rabbit, 
the  blood-cells  of  the  recipient  are  dissolved  and  hemoglobinuria  develops,  and 
even  death  may  take  place  if  the  dissolution  be  extensive. 

Simple  increase  in  the  amount  of  water  in  the  blood,  aqueous  polyemia,  occurs 
as  a  transitory  phenomenon  after  copious  ingestion  of  fluid,  but  increased  diuresis 
soon  restores  the  normal  conditions.  Disease  of  the  kidneys  attended  with  de- 
struction of  the  secreting  parenchyma  of  the  glands  induces,  together  with  aqueous 
polyemia,  often  general  anasarca  through  the  leakage  of  water  into  all  of  the 
tissues.  Ligation  of  the  ureter  likewise  gives  rise  to  an  increase  in  the  watery 
elements  of  the  blood.  Stint  zing  and  Gumprecht  found  the  dry  residue  of  small 
amounts  of  blood  after  evaporation  of  the  water  to  be  from  19.8  per  cent,  in 
women  to  21.6  per  cent,  in  men,  while  in  cases  of  anemia  it  falls  to  8.5  per  cent. 

An  increase  of  the  red  blood-corpuscles  beyond  the  normal  mean — polycy- 
ihemic  plethora  or  hyperglobulia — has  been  thought  to  be  present  in  robust  individ- 
uals when  hemorrhages  that  have  regularly  taken  place  cease  and  in  general  all  of 
the  symptoms  of  polyemia  are  present.  The  cessation  of  menstrual,  hemorrhoidal, 
and  nasal  hemorrhages  is  considered  as  a  cause,  as  well  as  the  omission 
of  venesection  previously  employed  systematically.  Nevertheless,  the  poly- 
cythemia  under  such  circumstances  is  only  inferred  and  not  established  by  enu- 
meration. On  the  other  hand,  a  condition  of  polycythemia  has  been  positively 
observed.  Thus,  after  transfusion  of  blood  from  the  same  species  a  portion  of  the 
blood-plasma  is  soon  consumed,  while  the  blood-corpuscles  are  preserved  for  a 
longer  time.  An  increase  in  the  number  of  red  blood-corpuscles  up  to  8,820,000 
in  a  i  cu.  cm.  in  case  of  severe  heart-disease,  with  marked  stasis,  in  which  more 
water  escapes  from  the  vessels  by  transudation,  is  a  remarkable  fact.  The  num- 
ber is  for  the  same  reason  greater  also  in  cases  of  hemiparesis  upon  the  paralyzed 
side  presenting  phenomena  of  stasis. 

After  attacks  of  diarrhea  that  cause  a  reduction  in  the  amount  of  water  in 
the  blood  there  is  likewise  an  increase  in  the  number  of  red  corpuscles,  and  it  is 
probable  that  the  same  result  is  brought  about  by  profuse  sweating  and  by 
polyuria.  Agents  that  influence  the  caliber  of  the  vessels,  such  as  alcohol,  chloral 
hydrate,  amyl  nitrite,  give  rise  to  an  increase  in  number  when  they  cause  con- 
traction of  the  vessels  and  to  a  diminution  when  they  cause  relaxation.  A 
transitory  increase  in  the  ancestors  of  the  red  blood-corpuscles  is  encountered 
as  a  reparative  process  after  profuse  hemorrhage  or  after  acute  disease.  In 
cachectic  states  the  increase  is  permanent  on  account  of  interference  with  the 
transformation  into  red  corpuscles.  In  the  last  stages  of  cachectic  states  the 
number  progressively  diminishes,  as  at  this  time  the  production  of  the  ancestral 
forms  also  ceases. 

The  designation  hyper  albuminous  plethora  has  been  applied  to  an  increase 
of  the  albuminates  in  the  plasma  such  as  it  may  be  inferred  occurs  after  abundant 
absorption  from  the  digestive  tract.  The  same  condition  may  be  induced  experi- 
mentally by  injection  of  serum  from  the  same  species  of  animal,  the  elimination  of 
urea  increasing  at  the  same  time.  Injection  of  egg-albumin  induces  albu- 
minuria. 

Melitemia  or  an  excess  of  sugar  in  the  blood.  The  sugar  of  the  blood 
is  eliminated  in  part  with  the  urine,  in  marked  degree  up  to  i  kilo  daily,  and 
the  amount  of  urine  may  be  increased  to  25  kilos.  To  replace  this  loss  an 
abundance  of  nourishment  and  much  fluid  are  necessary,  and  in  this  way  the 
amount  of  urea  may  at  the  same  time  be  increased  threefold.  The  marked  pro- 
duction of  sugar  also  induces  destruction  of  proteid  tissue,  so  that  the  amount  of 
urea  is  increased,  even  if  the  supply  of  albumin  be  insufficient.  The  patients 
emaciate,  all  of  the  glands,  particularly  the  testicles,  undergo  atrophy  or  degenera- 


86  ABNORMAL    DIMINUTION    IN    THE    AMOUNT    OF    BLOOD. 

tion,  the  skin  and  the  bones  become  thin,  while  the  nervous  system  resists  the 
longest.  The  crystalline  lens  becomes  turbid  in  consequence  of  the  presence  of 
sugar  in  the  fluids  of  the  eye,  which  abstract  water  from  the  lens.  Wounds 
heal  badly  on  account  of  the  abnormal  constitution  of  the  blood.  If  a  drop 
of  blood  be  spread  upon  a  glass  slide,  then  treated  with  a  solution  of  Bieberich's 
scarlet  or  alkaline  methylene-blue  and  heated  for  ten  minutes  at  a  temperature 
of  35°,  it  will  not  take  the  stain  if  derived  from  a  case  of  diabetes,  while  normal 
blood  is  stained.  Instead  of  grape-sugar  excessive  accumulation  of  inosite  or  of 
milk-sugar  has  also  been  found  in  the  blood  and  in  the  urine. 

Lipemia. — Increase  in  the  amount  of  fat  in  the  blood  occurs  normally 
after  the  ingestion  of  food  rich  in  fat,  as,  for  instance,  in  nursing  kittens,  so 
that  the  serum  itself  may  acquire  a  milky  turbidity.  Pathologically,  this  is 
observed  in  still  more  marked  degree  in  drunkards  and  in  obese  individuals.  In 
conjunction  with  marked  destruction  of  proteids  in  the  body,  therefore,  in  a  large 
number  of  wasting  diseases,  the  amount  of  fat  in  the  blood  is  increased;  likewise 
after  abundant  administration  of  easily  digestible  carbohydrates,  together  with 
much  fat,  in  the  food.  V.  Jaksch  found  traces  of  fatty  acids  in  the  blood 
of  febrile  and  leukemic  patients.  After  injuries  to  bones  involving  the  marrow 
large  numbers  of  fat-globules  often  pass  from  the  vessels  of  the  marrow,  in  part 
unprovided  with  walls,  into  the  blood-stream,  so  that  fat  may  even  find  its  way 
into  the  urine,  and  may  give  rise  to  dangerous  fat-emboli  in  the  lungs. 

The  salts  are  usually  preserved  with  great  tenacity.  If  sodium  chlorid 
be  withheld,  albuminuria  results;  and  if  salts  in  general,  paralytic  phenomena. 
Excessive  administration  of  salty  food,  as  in  the  form  of  pickled  meat,  has  not 
rarely  been  followed  by  death  through  fatty  degeneration  of  the  tissues,  par- 
ticularly of  the  glands.  Withdrawal  of  calcium  and  phosphoric  acid  brings  about 
softening  or  atrophy  of  the  bones.  In  the  presence  of  infectious  diseases  and 
of  anasarca  the  amount  of  salts  in  the  blood  has  often  been  found  increased, 
while  in  the  presence  of  inflammation  (sodium  chlorid  is  wanting  in  the  urine 
in  cases  of  pneumonia)  and  of  cholera  the  amount  is  diminished. 

The  amount  of  fibrin  in  the  blood  is  increased  in  the  presence  of  inflamma- 
tion, particularly  of  the  lungs  or  the  pleura.  Therefore  venesection  under  such 
circumstances  is  followed  by  the  formation  of  the  so-called  buffy  coat.  The 
fibrin  may  be  increased  also  in  other  diseases  attended  with  blood-destruction. 
Sigm.  Mayer  observed  an  increase  likewise  after  repeated  venesection.  Blood 
rich  in  fibrin  usually  coagulates  more  slowly  than  blood  deficient  in  fibrin,  although 
exceptions  to  this  statement  are  not  wanting. 

ABNORMAL  DIMINUTION  IN  THE  AMOUNT  OF  BLOOD  OR  OF  ITS 
INDIVIDUAL  CONSTITUENTS. 

Reduction  in  the  mass  of  the  blood  as  a  whole — true  oligemia — occurs  after 
every  direct  loss  of  blood.  In  the  newborn  a  hemorrhage  of  even  a  few  cu.  cm., 
in  children  a  year  old  a  hemorrhage  of  250  cu.  cm.,  and  in  adults  a  loss  of  one- 
half  of  their  blood  may  prove  dangerous.  Women  withstand  better  than  men 
even  considerable  loss  of  the  blood.  In  them  the  regeneration  of  the  blood 
appears  to  take  place  more  readily  and  more  quickly  in  consequence  of  the  periodic 
restoration  of  the  blood  lost  at  each  menstrual  period.  Obese  persons,  as  well  as 
the  aged  and  the  debilitated,  are  less  tolerant  to  loss  of  blood.  The  hemorrhage 
is  the  more  dangerous  the  more  rapidly  it  takes  place.  General  pallor  and  coldness 
of  the  skin,  a  sense  of  fear  and  oppression,  relaxation,  the  appearance  of  spots 
before  the  eyes,  roaring  in  the  ears  and  vertigo,  loss  of  voice  and  syncopal  attacks 
usually  accompany  profuse  hemorrhage.  Dyspnea  ("and  breathing  rapidly  he 
exhales  life  in  a  purple  stream:"  Sophocles'  Antigone),  cessation  of  glandular 
secretion,  profound  loss  of  consciousness,  then  dilatation  of  the  pupils,  involuntary 
discharge  of  urine  and  feces,  and  finally  general  convulsions  are  the  positive 
premonitions  of  rapid  death  from  hemorrhage.  In  the  state  of  greatest  danger 
life  can  be  saved  only  by  transfusion. 

As  much  as  one-quarter  of  the  normal  amount  of  blood  can  be  withdrawn 
from  animals  without  permanently  lowering  the  blood-pressure  in  the  arteries, 
because  the  latter  by  contraction  adapt  themselves  to  the  smaller  volume  of  blood 
in  consequence  of  the  anemic  irritation  of  the  vasomotor  center  in  the  medulla 
oblongata.  Loss  of  blood  up  to  one-third  of  the  volume  of  blood  causes  marked 
reduction  in  the  blood-pressure.  Dogs  recover  after  loss  of  one-half  of  the  volume 


ABNORMAL    DIMINUTION    IN    THE    AMOUNT    OF    BLOOD.  87 

of  blood.  If  two-thirds  be  removed  one-half  of  the  animals  die,  while  the  remaining 
half  recover  spontaneously. 

If  the  hemorrhage  does  not  terminate  fatally,  the  water  of  the  blood,  with 
the  dissolved  salts,  is  first  replaced  through  absorption  from  the  tissues,  with 
gradual  increase  in  the  blood-pressure;  and  later  the  proteids.  Considerable 
time  is  required  for  the  regeneration  of  the  blood-corpuscles.  The  blood,  there- 
fore, contains  for  a  time  an  abnormal  amount  of  water — hydremia;  and  finally  it 
exhibits  an  abnormal  deficiency  in  cells — oligocythemia,  hypoglobulia.  With  the 
increased  lymph-stream  toward  the  blood  the  leukocytes  are  soon  considerably 
increased  above  their  normal  number.  Also  fewer  red  blood-corpuscles  appear  to 
be  consumed  during  the  period  of  restitution,  as,  for  instance,  in  the  formation 
of  bile. 

After  moderate  venesection  in  animals  Buntzen  observed  the  volume  of  blood 
restored  in  a  few  hours,  and  after  severe  hemorrhage  in  the  course  from  24  to  48 
hours.  The  red  blood-corpuscles,  however,  were,  after  venesection  of  from  i.i 
to  4.4  per  cent,  of  the  body-weight,  fully  restored  to  the  normal  only  after  the 
lapse  of  from  7  to  34  days.  The  commencement  of  the  regenerative  process  could 
be  recognized  in  the  course  of  48  hours.  During  this  period  of  reorganization  the 
number  of  the  embryonal  forms  of  the  blood-corpuscles  was  increased.  The 
newly  formed  blood-corpuscles  appear  at  first  to  contain  less  hemoglobin  than 
normal.  Also  in  human  beings  the  duration  of  the  period  of  regeneration  ap- 
pears to  be  dependent  upon  the  amount  of  hemorrhage.  The  reduction  in  the 
amount  of  the  hemoglobin  of  the  blood  after  venesection  is  approximately  pro- 
portional to  the  amount  of  the  blood  removed. 

Of  especial  significance  is  the  state  of  metabolism  in  the  body  of  an  anemic 
patient.  The  decomposition  of  proteids  is  increased,  and  as  a  result  the  elimina- 
tion of  urea  is  increased.  The  combustion  of  fats  in  the  body  is,  however, 
correspondingly  diminished,  and  the  amount  of  carbon  dioxid  given  off  is  cor- 
respondingly reduced.  Anemic  as  well  as  chlorotic  patients  therefore  readily 
put  on  fat.  The  same  significance  is  to  be  attached  to  the  lipomatosis  of 
anemic  convalescents  after  acute  diseases  interfering  with  blood-formation.  The 
fattening  of  animals  is,  accordingly,  favored  by  occasional  venesection.  The  same 
statement  is  applicable  to  intercurrent  hunger.  Aristotle  had  already  pointed 
out  that  swine  and  birds  readily  take  on  considerable  fat  after  days  of  intercurrent 
hunger. 

Anemia  results  also  from  failure  on  the  part  of  the  blood-forming  organs. 
The  alarming  anemia  from  the  presence  of  the  bothriocephalus,  which  may  pursue 
a  course  similar  to  pernicious  anemia  is  remarkable.  It  is  probably  dependent 
upon  a  toxic  effect  induced  by  the  parasite,  which  impairs  the  vitality  of  the 
blood-corpuscles. 

Excessive  concentration  of  the  blood  through  loss  of  water  is  designated  dry 
oligemia.  This  condition  has  been  observed  in  human  beings  after  copious, 
watery  diarrhea,  particularly  in  cases  of  cholera,  and  the  thick,  tarry  blood  stag- 
nates in  the  veins.  Probably  copious  loss  of  water  through  the  skin  as  a  result 
of  diaphoretic  treatment,  particularly  in  association  with  restriction  of  fluids,  may 
give  rise  to  dry  oligemia,  even  though  only  in  moderate  degree. 

If  the  proteids  of  the  blood  are  diminished  in  abnormal  degree  a  condition  of 
hy palbuminous  oligemia  is  present.  The  proteids  may  be  diminished  more  than 
half.  In  their  place  an  excessive  amount  of  water  usually  finds  its  way  into  the 
blood,  so  that  the  salts  of  the  plasma  are  likewise  diminished.  Loss  of  proteids 
from  the  blood  is  due  directly  to  albuminuria,  which  may  furnish  even  25  grams 
of  proteid  daily;  to  long-continued  suppuration,  extensive  weeping  cutaneous  sur- 
faces, excessive  loss  of  milk,  albuminous  diarrhea  (dysentery).  Frequent  and 
copious  hemorrhage,  also,  induces  at  first  hypalbuminous  oligemia,  as  the  loss 
primarily  is  principally  made  good  by  the  taking  up  of  water  into  the  vessels. 
V.  Jaksch  found  that  the  amount  of  proteids  failed  to  decline  in  correspondence 
with  the  reduction  in  the  number  of  blood-corpuscles. 


PHYSIOLOGY  OF  THE  CIRCULATION. 


CAUSE,  PURPOSE,  DIVISION. 

The  blood  maintains  itself  within  the  vascular  system  in  an  unin- 
terrupted circulating  movement  that,  proceeding  from  the  cardiac  ven- 
tricles through  the  largest  arterial  trunks 
k  arising  therefrom  (the  aorta  and  the  pul- 

monary artery)  to  the  furthermost  branches 
of  these  vessels,  then  through  a  system  of 
capillary  vessels,  from  which  it  is  collected 
into  the  venous  channels,  which  progressively 
increase  in  size  by  coalescence,  terminates 
finally  in  the  auricles. 

The  cause  of  this  circulatory  movement 
resides  in  the  difference  in  pressure  to  which 
the  blood  is  exposed  in  the  aorta  and  the 
pulmonary  artery,  on  the  one  hand,  and  the 
two  venae  cavae  and  the  four  pulmonary 
veins  on  the  other.  The  blood  naturally 
flows  continuously  toward  that  portion  of 
the  closed  system  of  tubes  where  the  pres- 
sure is  lowest.  The  greater  this  difference  in 
pressure  the  more  active  will  be  the  move- 
ment of  the  stream.  Abolition  of  this  differ- 
ence in  pressure,  as  after  death,  will  natur- 
ally cause  a  cessation  of  the  flow. 

The  purpose  of  the  circulation  is,  on  the 
one  hand,  to  carry  nourishment  through  the 
blood  to  all  the  tissues  of  the  body,  while  on 
the  other,  the  blood  carries  away  from  the 
tissues  to  the  organs  of  excretion  the  waste 
products  of  their  metabolism. 

The  circulation  of  the  blood  is  divided 
into: 

1.  The  greater  circulation,  comprising  the 
pathway  from  the  left   auricle  and  the  left 
ventricle  through  the  aorta  and  its  branches, 
the  capillaries  and  the   veins    of   the    body, 
to  the  termination  of  the  two  venae  cavse  in 
the  right  auricle. 

2.  The  lesser   circulation,  comprising  the 
pathway  of  the  right  auricle  and  the  right  ventricle,   the  pulmonary 
artery,  the  pulmonary  capillaries  and  the  four  pulmonary  veins  arising 
therefrom  up  to  their  point  of  entrance  into  the  left  auricle. 

3.  The    portal  circulation  is  occasionally  considered   as  a   separate 
circulatory  system,  although  it  is  only  a  second  capillary  ramification 

88 


FIG.  21. — Diagrammatic  Representa- 
tion of  the  Circulation:  a,  right 
auricle;  A,  right  ventricle;  b, 
left  auricle;  B,  left  ventricle;  i, 
pulmonary  artery;  2,  aorta,  with 
semilunar  valves;  1,  lesser  cir- 
culation; k,  greater  circulation, 
including  superior  vena  cava,  o; 
G,  greater  circulation,  including 
inferior  vena  cava,  u;  d  d,  intesti- 
nal tract;  m,  mesenteric  arteries; 
q,  portal  vein;  L,  liver;  h,  hepa- 
tic veins. 


THE     HEART.  89 

inserted  into  a  venous  pathway.  It  is  composed  of  the  portal  vein, 
which  represents  the  union  of  the  veins  of  the  abdominal  viscera — the 
superior  gastric,  the  superior  and  inferior  mesenteric,  and  the  splenic 
veins— and  which  breaks  up  in  the  liver  into  capillaries  that  again  unite 
to  form  the  hepatic  veins,  which  empty  into  the  inferior  vena  cava. 

Strictly  speaking,  this  differentiation  of  the  portal  system  into  a  separate 
circulation  is  not  justifiable.  In  many  animals  similar  conditions  are  found  in 
still  other  organs,  as,  for  example,  the  suprarenal  of  the  snake  and  the  kidney 
of  the  frog.  When  an  artery  breaks  up  into  numerous  small  branches  that  shortly 
reunite,  without  the  intervention  of  capillaries,  to  again  form  an  artery,  the  cluster 
of  branches  thus  formed  is  called  a  "wonderful  network,"  rete  mirabile,  such  as 
is  seen  in  apes  and  edentates.  Microscopical  networks  of  this  character  are  found 
in  the  mesentery  of  man.  The  glomerulus  of  Bowman's  capsule  in  the  kidney  also 
is  an  example  of  this  peculiar  arterial  division.  Analogous  formations  in  the  veins 
are  called  venous  "wonderful  networks." 

THE  HEART. 

The  mammalian  heart-muscle  (Fig.  184,  8)  is  composed  of  short,  closely  and 
finely  striated,  unicellular  elements  which  are  devoid  of  sarcolemma  and,  in  man, 
from  50  to  70  //  long  and  from  15  to  23  /u  wide.  The  ends  are  rather  blunt  and 
generally  split,  and  by  these  split  ends  the  fibers  are  joined  together  anastomotically 
to  form  a  network.  The  individual  muscle-cells  are  united  by  a  cement-substance, 
which  is  soluble  in  33  per  cent,  potassium-hydrate  solution  and  is  stained  black 
by  silver  nitrate.  Each  cell  at  its  center  contains  a  nucleus,  rarely  two  smaller 
nuclei,  14  u-  long  by  7  //  wide,  in  its  central  axis.  The  transversely  striated  sub- 
stance frequently  contains  molecular  granules  arranged  in  rows.  The  fibrils  are 
placed  side  by  side  and  are  divided  by  the  perimysium  into  bun  dies,  which,  after 
solution  of  the  connective  tissue  by  boiling,  may  be  isolated.  The  shape  of  the 
bundles  on  transverse  section  is  rather  circular  in  the  auricles,  while  in  the  ventricles 
it  is  rather  flat  and  laminated;  here  also  several  of  the  smaller  bundles  may  unite 
to  form  a  thicker  band.  The  interstices  between  the  bundles  serve  to  carry  the 
lymph-vessels. 

ARRANGEMENT  OF  THE  MUSCLE-FIBERS  OF  THE  HEART  AND 
THEIR  PHYSIOLOGICAL  SIGNIFICANCE. 

Musculature  of  the  Auricle. — The  study  of  the  embryonal  heart  furnishes  the 
key  to  the  understanding  of  the  complicated  arrangement  of  the  muscle-fibers. 
The  simple  heart-tube  of  the  embryo  exhibits  an  outer  circular  and  an  inner 
longitudinal  layer  of  muscle-fibers.  The  septum  is  formed  later,  so  that  it  is 
obvious  that  both  in  the  ventricles  as  well  as  in  the  auricles  the  fibers  belong, 
in  part  at  least,  to  both  halves,  as  they  originally  enclose  only  a  single  cavity. 
On  the  other  hand,  the  fibers  of  the  auricles  are  generally  separated  from  those 
of  the  ventricles  by  the  fibrous  ring;  nevertheless  certain  of  the  muscle-bundles 
pass  from  the  auricles  to  the  ventricles.  In  the  auricles  the  embryonal  arrange- 
ment of  the  fibers  remains  fundamentally  unchanged.  In  the  ventricles  the 
arrangement  is  obliterated  because  during  the  process  of  development  the  fibers 
here  undergo  a  peculiar  bending  and  looping,  as  in  the  stomach,  together  with 
a  spiral  rotation. 

The  musculature  of  the  auricles  is  in  general  arranged  in  two  layers:  an  outer 
transverse,  which  is  continuous  over  the  two  auricles,  and  an  inner  longitudinal. 
The  outer  fibers  can  be  traced  from  the  entering  veins  upon  the  anterior  and 
posterior  walls.  The  inner  fibers  are  especially  prominent  where  they  are  attached 
vertically  to  the  fibrous  rings,  but  in  certain  parts  of  the  anterior  wall  in  particular 
they  are  not  arranged  continuously.  On  the  septum  of  the  auricles  the  ring-like 
muscular  layer  surrounding  the  oval  fossa,  the  opening  of  the  oval  foramen  in 
the  embryo,  is  especially  prominent.  Around  the  openings  of  the  veins  emptying 
into  the  auricles  are  found  circular  muscle-bundles;  these  are  least  well  marked 
around  the  inferior  cava,  while-  around  the  superior  cava  they  are  well  developed 
and  extend  upward  around  the  vessels  for  2.5  cm.  (Fig.  22,  II).  At  the  entrance 
of  the  four  pulmonary  veins  in  man  and  in  some  mammals,  transversely  striated 
muscle-fibers,  arranged  in  an  inner  circular  and  an  outer  longitudinal  layer,  ex- 


90  MUSCULATURE    OF    THE    VENTRICLES. 

tend  upon  the  pulmonary  veins  as  far  as  the  hilus  of  the  lung;  in  other  animals 
(apes,  rats)  they  extend  even  into  the  lung  itself;  indeed,  in  some  mammals 
(mouse,  bat)  this  muscular  layer  penetrates  the  lung  so  far  that  in  the  small 
veins  the  entire  wall  is  composed  almost  wholly  of  striated  muscle-fibers.  Muscle- 
fibers,  chiefly  circular,  are  also  found  at  the  termination  of  the  great  cardiac 
vein  and  in  the  coronary  valve  of  Thebesius.  Many  elastic  fibers  are  present 
in  the  perimysium  of  the  auricles. 

From  the  physiological  standpoint  the  foregoing  anatomical  data 
explain  the  following  facts  with  relation  to  the  contractions  of  the 
auricles. 

The  auricles  are  able  to  contract  independently  of  the  ventricle's; 
this  is  particularly  manifest  in  the  cessation  of  the  heart's  activity,  as 
under  such  circumstances  two  or  more  contractions  of  the  auricle  alone 
are  often  seen  to  take  place,  followed  now  and  then  by  a  single  con- 
traction of  the  ventricle.  However,  when  the  action  of  the  heart  is 


n 

FIG.  22. — I,  Course  of  the  Muscle-fibers  in  the  Left  Auricle:  the  outer  transverse  and  the  inner  longitudinal  fibrous 
layer  are  visible  and  in  addition  the  circular  fibers  of  the  pulmonary  veins,  v.p.  V,  left  ventricle  (Joh.  Reid). 
II,  Distribution  of  Transversely  Striated  Muscle-fibers  on  the  Superior  Vena  Cava  (Elischer):  a,  entrance 
of  the  azygos  vein;  v,  auricle. 

unimpaired  the  auricles  in  their  contraction  transmit  the  motor  impulse 
to  the  ventricles.  Whether  this  stimulation  is  brought  about  through 
nerve-fibers  or,  as  is  more  probable,  through  connecting  muscle-bundles, 
has  not  yet  been  decided  with  certainty. 

The  two  chief  layers  of  fibers  (transverse  and  longitudinal),  which 
cross  each  other,  serve  to  effect  uniform  contraction  of  the  auricular 
cavity  from  all  sides,  as  is  the  case  likewise  with  most  hollow  muscular 
organs. 

The  circular  fibers  surrounding  the  entering  venous  trunks,  through 
their  contraction,  which  occurs  in  unison  with  that  of  the  auricles, 
cause  in  part  an  emptying  of  blood  into  the  auricle  and  in  part  a  hin- 
drance to  a  return  of  the  blood  in  any  considerable  measure. 

ARRANGEMENT  OF  THE  MUSCULATURE  OF  THE  VENTRICLES. 

The  Muscle-fibers  of  the  Ventricles. — Beneath  the  pericardium  there  is  first 
met  an  outer  longitudinal  layer  (Fig.  23,  A),  consisting  of  only  occasional 
bundles  on  the  right  ventricle,  while  on  the  left  it  comprises  a  compact  layer  of 
about  one-eighth  of  the  entire  thickness  of  the  wall.  A  second  layer  of  longitu- 
dinal fibers  lies  on  the  inner  surface  of  the  ventricles,  being  especially  well  marked 
at  the  orifices,  as  well  as  inside  the  perpendicularly  placed  papillary  muscles, 


PERICARDIUM;  ENDOCARDIUM;  VALVES.  91 

while  in  other  situations  it  is  replaced  by  the  irregularly  running  fibers  of  the 
muscular  trabeculae.  Between  the  two  longitudinal  layers  lies  the  most  powerful 
transverse  layer,  the  fibers  of  which  are  separable  into  individual,  leaf -like, 
ring-shaped  bundles.  The  three  layers,  however,  are  not  wholly  independent  and 
separated  from  each  other,  but  rather  there  is  a  gradual  transition  between  the 
transverse  and  the  outer  and  inner  longitudinal  layers  by  means  of  oblique  fibers. 
The  common  assumption  is  that  the  entire  outer  longitudinal  layer  passes 
gradually  into  the  transverse  and  this  in  turn  wholly  into  the  inner  longitudinal, 
as  is  shown  diagrammatically  in  Fig.  23,0.  This  is  not  justifiable,  and  is  negatived 
by  the  great  preponderance  in  the  thickness  of  the  middle  layer.  In  general  the 
outer  longitudinal  fibers  pursue  such  a  course  as  to  intersect  the  course  of  the 
fibers  of  the  inner  longitudinal  layer  at  an  acute  angle.  The  intervening  trans- 
verse layer  constitutes  the  medium  for  a  gradual  transition  between  these  courses. 


FIG.  23.— Course  of  the  Muscle-fibers  in  the  Ventricles:  A,  course  upon  the  anterior  surface;  B,  view  of  the  apex 
with  the  "whirl"  (Henle);  C,  diagrammatic  representation  of  the  course  of  a  muscle-fiber  within  the  wall 
of  the  ventricle:  D,  course  of  such  a  fiber  into  the  papillary  muscle  (C.  Ludwig). 

At  the  apex  of  the  left  ventricle  external  longitudinal  fibers,  uniting  in  the 
so-called  "whirl"  (B),  pass  in  a  curved  direction  inward  and  upward  within  the 
muscle-substance  and  extend  into  the  papillary  muscles  (D).  Nevertheless  it  is 
an  error  to  consider  that  all  of  the  ascending  fibers  in  the  papillary  muscles  are 
derived  from  these  vertical  muscle-bundles  of  the  outer  surface,  as  many  arise 
independently  from  the  wall  of  the  ventricle.  Neither  can  the  origin  of  these 
longitudinal  fibers  on  the  outer  surface  of  the  heart  be  traced  solely  to  the  fibrous 
rings  or  to  the  roots  of  the  arteries.  Finally,  mention  should  be  made  of  the  special 
circular  layer  of  fibers  that  surrounds  the  left  orifice  like  a  sphincter.  Numerous 
lymph-vessels  are  present  in  all  the  interstices  between  the  muscle-fibers  and  the 
blood-vessels.  These  eventually  empty  into  the  lymph- vessels  and  nodes  of 
the  mediastinum. 

PERICARDIUM  ;  ENDOCARDIUM  ;  VALVES. 

The  pericardium,  which  includes  between  its  two  layers  a  lymph-space— the 
pericardial  cavity — containing  a  small  amount  of  lymph,  exhibits  the  structure  of 
a  serous  membrane;  that  is,  it  is  composed  of  connective  tissue  containing  delicate 


92  PERICARDIUM;  ENDOCARDIUM;  VALVES. 

elastic  fibers,  and  is  covered  on  its  free  surface  with  a  single  layer  of  irregular 
polygonal,  flat,  endothelial  cells.  A  rich  network  of  lymph-vessels  lies  within  the 
pericardium  itself,  as  well  as  more  deeply  toward  the  muscle-mass  of  the  heart. 
Stomata  are  wanting  in  both  layers  of  the  pericardium.  In  the  subserous  tissue 
of  the  pericardium,  especially  in  the  sulci  for  the  coronary  vessels,  are  deposits 
of  fat,  and  lymphatics. 

The  endocardium  presents  all  of  the  characteristics  of  a  vessel-wall.  Facing 
the  cavity  of  the  heart,  there  is  first  a  single  layer  of  flat,  polygonal,  nucleated 
endothelial  cells.  Then  there  comes,  as  the  true  groundwork  of  the  whole  mem- 
brane, a  layer  of  delicate  elastic  fibers  (more  marked  in  the  auricles,  and  even 
forming  a  f enestrated  membrane) ,  in  the  midst  of  which  but  little  connective 
tissue  occurs.  The  latter,  much  more  loosely  arranged  and  intermixed  with  elas- 
tic fibers,  is  present  in  larger  amount  toward  the  heart-muscle.  Scattered 
bundles  of  unstriated  muscular  fibers,  usually  arranged  longitudinally,  are  found 
between  the  elastic  elements  (in  smaller  amount  in  the  auricles) .  These  obviously 
have  the  task  of  combating  the  pressure  and  the  tension  exerted  on  the  endocar- 
dium during  the  cardiac  contraction;  for  wherever  throughout  the  body  a  wall 
composed  of  soft  parts  is  exposed  to  repeated  high  pressure  muscular  elements 
are  found,  and  never  elastic  tissue  alone.  The  endocardium  is  non- vascular. 

The  valves — both  the  arterial  (semilunar)  and  the  venous  (mitral  and  tricuspid) 
— also  are  a  part  of  the  endocardium.  The  venous  and  arterial  orifices  on  the 
right  side  are  separated  from  each  other  in  the  wall  of  the  ventricle,  while  the 
two  orifices  on  the  left  are  united  into  a  single  large  opening.  The  valves  are 
attached  to  their  basal  margins  by  means  of  resistant  fibrous  rings  composed  of 
connective-tissue  and  elastic  fibers.  They  consist  of  two  layers:  (i)  The  fibrous, 
which  is  a  direct  continuation  of  the  fibrous  ring,  and  (2)  a  layer  of  elastic  elements. 
The  elastic  layer  of  the  auriculo-ventricular  valves  is  a  direct  prolongation  of  the 
endocardium  of  the  auricle,  and  is  therefore  directed  toward  that  cavity.  At 
their  bases  the  valves  are  united  by  their  adjacent  margins.  The  tendinous  cords 
are  inserted  on  the  free  margin  and  on  the  under  surface  of  the  valves.  The 
semilunar  valves  possess  a  thin,  elastic  layer,  thickened  at  their  base  and  turned 
toward  the  arteries. 

The  auriculo-ventricular  valves  contain  also  striated  muscle-fibers.  Radiating 
fibers,  arising  from  the  auricles,  extend  into  the  valves,  and  it  is  their  function 
in  part  to  retract  the  valves  toward  their  bases  during  the  time  of  auricular  systole, 
and  thus  to  enlarge  the  passage-way  for  the  flow  of  blood  into  the  ventricles. 
Paladino  describes  still  other  longitudinal  fibers  derived  from  the  ventricles. 
Besides  these,  there  is  directed  rather  [toward  the  ventricular  aspect,  a  con- 
centric muscular  layer,  following  the  basal  attachment  of  the  valves,  which 
appears  to  have  a  sphincter-like  action — drawing  the  bases  of  the  valves  together 
during  the  period  of  ventricular  contraction  when  the  valves  are  under  tension, 
and  thus  preventing  excessive  distention.  The  larger  of  the  tendinous  cords  also 
contain  striated  muscle-fibers;  and  the  Thebesian  and  Eustachian  valves  like- 
wise contain  a  delicate  muscular  network. 

The  name  "Purkinje's  fibers"  has  been  applied  to  a  grayish  network  of 
muscular  elements  found  in  mammals  and  in  birds  chiefly  beneath  the  endocar- 
dium of  the  ventricle,  but  occurring  also  in  the  muscular  mass  itself.  These 
appear  to  represent  a  stage  of  embryonal  development  (on  account  of  the  partial 
striation) .  They  are  absent  in  man  and  in  the  lower  vertebrates. 

Blood-vessels  occur  in  the  auriculo-ventricular  valves  in  considerable  number 
only  where  there  are  muscle-fibers.  In  children  delicate  vessels  extend  to  the 
free  margin  of  the  valve.  The  semilunar  valves  are  devoid  of  blood-vessels  except 
under  pathological  conditions.  A  network  of  lymphatics  extends  from  the  endo- 
cardium to  the  middle  of  the  valves. 

Weight  and  Size  of  the  Heart. — According  to  W.  Muller,  the  weight  of  the 
heart  in  children  and  in  older  persons  having  a  body- weight  up  to  40  kilos,  is  5 
grams  for  every  kilo  of  body-weight ;  in  individuals  having  a  body-weight  of  from 
50  to  90  kilos,  the  proportion  is  4  grams  of  heart  for  each  kilo;  in  individuals 
having  a  body-weight  of  100  kilos,  3.5  grams  of  heart  for  each  kilo  of  body-weight. 
The  auricles  become  stronger  with  increasing  age.  The  right  ventricle  weighs 
half  as  much  as  the  left.  In  man  the  heart  weighs  309  grams;  in  woman,  274 
grams.  Blosfeld  and  Dieberg  found  the  heart  in  man  to  weigh  346  grams;  in 
woman,  from  310  to  340  grams.  The  thickness  of  the  left  ventricle  in  man  aver- 
ages 11.4  mm.;  in  woman,  10.15  mm.;  the  thickness  of  the  right  ventricle,  4.1 
and  3.6  mm.  respectively. 


THE    CORONARY    VESSELS.  93 

THE    CORONARY    VESSELS;    AUTOMATIC    REGULATION,  NUTRI- 
TION, AND  ISOLATION  OF  THE  HEART. 

With  reference  to  the  origin  of  the  coronary  arteries  the  question  at 
once  arises  whether  the  orifices  of  these  vessels  are  closed  by  the  eleva- 
tion of  the  semilunar  valves  during  systole  as  a  result  of  the  application 
of  the  valve-leaflets  to  the  walls  of  the  vessels  or  whether  such  occlusion 
does  not  take  place. 

Anatomical. — The  two  coronary  arteries  arise  from  the  region  of  the  sinus 
of  Valsalva.  The  point  of  origin  varies:  (i)  It  is  either  within  the  concavity  of 
the  sinus;  or  (2)  the  mouths  of  the  vessels  are  not  completely  within  the  range 
of  the  margin  of  the  valve,  and  this  is  frequently  the  case  with  the  left  coronary 
of  man  and  the  ox;  or  (3)  the  orifices  project  beyond  the  margins  of  the  valve 
(this  is  rare).  These  findings  alone  make  it  improbable  that  closure  of  the 
mouths  of  the  coronary  arteries  by  the  semilunar  valves  during  ventricular  systole 
is  a  constant  physiological  phenomenon. 

AUTOMATIC  REGULATION  OF  THE  HEART. 

According  to  Briicke  the  openings  of  the  coronary  arteries  are 
covered  by  the  semilunar  valves  during  systole,  so  that  they  can  be 
filled  only  during  diastole.  The  advantage  of  this  arrangement  resides 
in  the  fact  that  (a)  the  diastolic  distention  of  the  ventricular  vessels 
stretches  the  muscular  fibers  of  the  ventricular  wall  and  thus  corre- 
spondingly dilates  the  ventricle  for  the  reception  of  the  blood  that 
pours  in  from  the  auricle  during  diastole.  (6)  On  the  other  hand, 
the  systolic  distention  of  the  coronary  arteries  would  be  useless  because 
the  dilatation  of  the  ventricular  wall  (due  to  the  distention  of  the 
arteries  already  mentioned)  would  resist  the  systolic  contraction, 
and  because  the  systolic  distention  of  the  coronary  arteries  and  the 
expulsion  of  the  blood  from  them  would  unnecessarily  diminish  the 
power  of  the  ventricle.  Accordingly,  the  diastolic  distention  of  the 
coronary  arteries*  would  be  most  consistent  with  the  mechanical 
conditions  present.  This  mechanism  Briicke  has  designated  the  "auto- 
matic regulation  of  the  heart." 


FIG.  24. — Semilunar  Valves,  Closed.  Semilunar  Valves,  Opened. 

This  theory  and  its  underlying  principles  are  untenable,  for — 

1.  The  filling  under  high  pressure  of  the  coronary  arteries  of  a  dead  heart 
not  only  is  followed  by  no  dilatation,   but   actually  causes  a  contraction    of  the 
cavity  of  the  ventricle. 

2.  The  chief  branches  of  the  coronary  arteries  lie  in  the  sulci  of  the  heart 
embedded  in  the  loose  subpericardial  fatty  tissue,  where  their  dilatation  and  con- 
traction could  scarcely  have  any  effect  upon  the  size  of  the  cavities  of  the  heart. 

3.  Brown-S6quard  found  in  animals  and  v.  Ziemssen  in  a  woman  with  a  large 
deficiency  in  the  wall  of  the  left  thorax  that  the  coronary  pulse  was  synchronous 
with  that  in  the  pulmonary  artery.     Newell-Martin  and  S'edgwick,  by  introducing 
manometers  into  the  coronary  and  carotid  arteries  of  a  large  dog,  obtained  simul- 


94  AUTOMATIC  REGULATION  OF  THE  HEART. 

taneous  pulsatory  elevations.  In  accordance  with  these  observations  is  the  fact 
that  an  incised  coronary  artery  spurts  continuously,  with  systolic  exacerbations, 
as  do  all  other  arteries/ 

4.  If  a  strong  stream  of  water  is  passed  intermittently  through  a  sufficiently 
large  tube  introduced  into  the  left  auricle  of  a  fresh  pig's-heart,  and  it  is  forced, 
through  the  auriculo-ventricular  orifice  on  into  the  aorta;   and  if  the  aorta  beyond 
its  arch  is  connected  with  a  large  tube  directed  upward   (in  order  to  establish 
pressure  in  the  aorta) ,  the  water  will  be  seen  to  spurt  continuously  from  the 
divided  coronary  artery,  with  systolic  exacerbations. 

5.  There  is  constantly  present  in  the  sinuses  of  Valsalva  an  amount  of  blood 
sufficient  to  fill  the  arteries  in  question  during  systole. 

6;  The  valves  when  elevated  are  not  applied  closely  against  the  wall  of  the 
aorta,  even  with  the  greatest  amount  of  pressure  that  can  be  exerted  by  the 
ventricle.  On  the  contrary,  there  remains  between  each  valve-leaflet  and  the 
aortic  wall  a  semilunar  space  filled  with  blood,  as  is  shown  in  Fig.  24. 

7.  Undoubted  cases  of  extensive  destruction  of  the  semilunar  valves  that 
with  certainty  render  closure  of  the  mouths  of  the  coronary  arteries  impossible 
are  directly  opposed  to  this  theory. 

8.  Observations    on   muscle   have    shown   that  during  contraction  its  small 
vessels  undergo  dilatation  and  the  blood-stream  through  it  is  accelerated.     It  is, 
therefore,  difficult  to  believe  that  in  the  contracted  heart-muscle  the  movement 
of  the  blood  should  cease. 

As,  during  the  systole,  the  small  arterial  branches  lying  close  to  the 
ventricular  cavity  are  exposed  to  a  pressure  greater  than  that  of  the 
aorta  a  systolic  compression  of  their  lumen  occurs,  with  a  forcing  out 
of  their  contents  in  the  direction  of  the  veins.  The  ventricular  con- 
traction thus  aids  the  flow  of  the  blood  in  the  coronary  vessels ;  marked 
dilatation  of  the  heart  diminishes  it. 

The  capillary  vessels  of  the  myocardium  are  numerous  in  correspond- 
ence with  the  energetic  activity  of  the  heart;  they,  like  the  small  vessels 
generally,  lie  within  the  muscle-bundles  in  contact  with  the  muscle- 
cells.  With  their  transition  into  veins  several  of  them  coalesce  almost 
at  once  to  form  a  large  vein,  from  which  the  extremely  easy  passage  of 
the  blood  into  the  veins  is  readily  understood.  The  veins  are  provided 
with  valves.  As  a  result  it  happens  that  (i)  with 'the  systole  of  the 
right  auricle  (therefore  during  the  ventricular  diastole)  the  venous 
stream  is  interrupted;  (2)  with  contraction  of  the  ventricle  the  flow  of 
blood  in  the  cardiac  veins  is  accelerated  in  the  same  way  as  it  is  in  the 
veins  of  the  muscles.  This  systolic  acceleration  of  the  venous  flow 
permits  of  the  conclusion  that  the  arterial  circulation  is  not  interrupted 
at  this  time. 

The  coronary  arteries,  between  which  no  anastomoses  occur,  are  characterized 
by  the  great  thickness  of  their  elastic  and  connective-tissue  intima,  and  this  per- 
haps explains  the  frequency  of  calcification  in  these  vessels.  Many  of  the  lower 
vertebrates  have  no  vessels  in  the  heart-substance  (anangiotic  hearts) — for  example, 
the  frog;  but  this  statement  is  disputed. 

The  motor  disturbances  and  even  the  complete  cessation  of  action 
that  have  been  observed  in  the  heart  after  partial  or  complete  occlu- 
sion of  the  coronary  vessels  are  of  importance,  particularly  as  analogous 
conditions  are  observed  in  man  in  consequence  of  occlusion  or  narrowing 
of  the  coronary  arteries  (for  example,  as  a  result  of  calcification). 

Method. — In  rabbits,  under  the  influence  of  curare  and  with  artificial  respira- 
tion, or  after  previous  section  of  the  vagi  (in  order  to  exclude  the  inhibitory 
influence  of  this  nerve),  it  is  possible  to  clamp  off  the  coronary  arteries  close  to 
their  origin  from  the  aorta  with  a  spring  clamp.  Ligation  is  less  satisfactory,  as 
it  cannot  be  accomplished  without  wounding  the  heart.  In  dogs  it  is  possible 
to  push  a  glass  rod  provided  with  a  button-like  extremity  from  the  subclavian 


AUTOMATIC    REGULATION    OF    THE    HEART.  95 

artery  into  the  mouth  of  a  coronary  artery.     Injections  of  various  substances 
capable  of  causing  occlusion  have  also  been  tried. 

In  1867,  v.  Bezold  noted  in  rabbits  after  clamping  off  the  coronary 
artery  that  the  heart-beat  grew  rapidly  smaller  and  smaller;  then 
the  contractions  occurred  in  groups,  periodically;  later  on  the  regular 
movement  of  the  ventricle  ceased  entirely,  and  in  its  place  the  muscle- 
wall  exhibited  a  peculiar  fibrillary  contraction;  finally  the  heart  stood 
still.  As  the  circulation  was  reestablished  after  removal  of  the  clamp, 
the  phenomena  appeared  in  reverse  order  until  the  heart  regained  its 
normal  beat. 

If  in  a  dog  the  right  descending  coronary  artery  and  the  circumflex 
artery,  together  with  the  artery  of  the  septum,  are  occluded,  the  heart 
soon  ceases  to  beat.  The  closure  of  only  two  of  the  three  arteries  caused 
a  cessation  of  contraction  in  9  out  of  14  animals;  while  closure  of  the 
septal  artery  or  of  the  right  coronary  artery  alone  had  no  effect.  In 
almost  all  instances  the  auricles  likewise  cease  beating.  The  heart  of 
a  dog  that  has  once  ceased  to  beat  recovers  only  with  great  difficulty. 
It  appears  that  the  fibrillary  contractions  are  due  to  irritative  injury  in- 
flicted during  the  operation,  and  not  alone  to  the  stasis  of  the  blood. 

If  in  rabbits  only  the  left  coronary  artery  is  occluded  the  beat  of  the 
left  heart  is  slowed  and  weakened,  while  the  right  heart  pulsates  without 
change.  As  a  result  it  occurs  that  the  left  half  of  the  heart  can  no  longer 
empty  itself  completely,  so  that  particularly  the  left  auricle  becomes 
filled  to  distention  with  blood,  while  at  the  same  time  the  unaffected 
right  heart  continues  to  drive  blood  into  the  lungs.  In  consequence 
edema  of  the  lungs  develops  as  a  result  of  the  high  pressure  in  the 
lesser  circulation  which  is  transmitted  from  the  right  heart  through  the 
pulmonary  vessels  into  the  left  auricle.  According  to  Sig.  Mayer 
persistent  dyspnea  has  a  similar  effect,  with  earlier  weakening  of  the  left 
than  of  the  right  ventricle;  the  pulmonary  edema  preceding  death  can 
be  explained  in  this  manner. 

The  heart  in  the  higher  animals  can  maintain  its  activity  only  when 
the  circulation  of  blood  through  its  walls  is  maintained.  The  heart 
from  which  the  blood  is  completely  removed  rapidly  ceases  to  con- 
tract. The  coronary  circulation  must  convey  the  necessary  oxygen 
and  nutritive  materials  to  the  myocardium,  as  well  as  remove  the 
metabolic  products  from  it.  The  excised  "isolated"  mammalian  heart, 
which  is  fed  at  body-heat  through  the  coronary  vessels  with  bright-red 
blood,  remains  active. 

Langendorff  maintains  the  circulation  in  the  isolated  heart  by  allowing  the 
coronary  arteries  to  be  filled  from  the  aorta.  Other  fluids,  for  example,  lake- 
colored  blood  or  serum,  are  incapable  of  maintaining  the  heart's  activity.  At 
most,  such  solutions  (as,  for  example,  alkaline  salt-solution  mixed  with  egg-albu- 
min— 1000  albumin  diluted  with  water,  o.i  sodium  chlorid,  o.i  calcium  chlorid, 
0.075  potassium  chlorid),  in  so  far  as  they  exert  a  slightly  irritating  effect,  are 
capable  of  stimulating  the  heart  for  a  time.  If  the  heart  is  placed  in  pure 
oxygen  the  pulsation  may  be  maintained  for  a  considerable  time  by  passing 
serum  through  the  cardiac  vessels. 

Also  the  isolated  frog's  heart  can  be  included  in  a  circulation  by 
means  of  suitable  tubes.  To  maintain  its  contractions  oxygen  and 
nutritive  fluid  are  necessary  to  distend  its  cavities.  This  object  is 
best  fulfilled  by  arterial  blood;  indifferent  fluids  (0.6  percent,  sodium 
chlorid)  quickly  bring  about  a  condition  of  "apparent  death,"  from 
which,  however,  the  organ  can  be  revived  by  nutritive  fluids. 


96 


THE  MOVEMENTS  OF  THE  HEART. 


The  frog's  heart  is  less  readily  exhausted  than  that  of  the  higher  vertebrates.- 
Serum-albumin,  alkaline  salt-solutions  of  blood,  or  of  milk,  made  slightly  viscid 
with  albumin  or  gum  arabic  and  sattirated  with  oxygen,  are  capable  of  main- 
taining the  activity  of  the  heart  for  a  long  time. 

Pathological.— In  the  presence  of  so-called  sclerosis  of  the  coronary  arteries 
in  old  age  there  occur  acute  or  chronic  attacks  of  cardiac  disability.  Weakness 
of  the  heart,  alterations  in  rhythm  and  frequency  (to  8  in  a  minute),  constitute, 
together  with  dyspnea,  syncope,  stasis,  attacks  of  pulmonary  edema,  the  most 
characteristic  phenomena ;  and  they  may  terminate  in  death  from  so-called  heart- 
failure.  In  a  case  of  occlusion  of  the  left  coronary  artery  in  a  man  Hammer 
saw  the  pulse  fall  from  So  to  8,  the  beats  being  interrupted  by  spasmodic  vibra- 
tion. 

THE  MOVEMENTS  OF  THE  HEART.     VARIATIONS  IN  TONE. 

Method. — In  addition  to  direct  observation,  the  kinematograph  may  be  used 
to  great  advantage  for  recording  and  projecting  the  movements  of  the  heart,  par- 
ticularly at  a  slow  rate. 


S.a.-D.v. 


D.a.-S.v. 


FIG.  25. — Diagrammatic  Representation  of  the  Auricular  Systole  with  Ventricular  Diastole,  and  of  Auricular 

Diastole  with  Ventricular  Systole. 


The  movement  of  the  heart  is  appreciable  as  alternate  contraction 
and  relaxation  of  the  heart- walls.  The  entire  motor  phenomenon 
designated  the  cardiac  cycle  consists  of  three  parts:  contraction 
of  the  auricles  (auricular  systole);  contraction  of  the  ventricles  (ven- 
tricular systole),  and  the  pause,  during  which  the  auricles  and  the  ven- 
tricles are  relaxed  (diastole).  During  the  contraction  of  the  auricles  the 
ventricles  are  at  rest,  during  the  contraction  of  the  ventricles  the  auricles 
are  relaxed.  The  following  phenomena  can  be  noted  successively  during 
a  cycle  of  the  heart : 

(A)   The  blood  streams  into  the  auricles,  which  in  consequence  are- 
distended.     The  cause  for  this  resides  in: 


THE  MOVEMENTS  OF  THE  HEART.  97 

1.  The  pressure  of  the  blood  in  the  venae  cavae  (on  the  right)  and 
the  pulmonary  veins  (on  the  left),  which  is  greater  than  the  pressure 
within  the  auricles. 

2.  The  elastic  traction  of  the  lungs,  which  after  the  completed  con- 
traction tends  to  separate  the  relaxed  yielding  walls  of  the  auricles  lying 
in  contact  with  each  other.     The  auricular  appendages  are  distended 
coincidently  with  the  auricles.     The  appendages  serve  in   a  measure 
as   reservoirs   for  the   auricles,  to   accommodate   the  large  amount  of 
blood  flowing  in  from  the  veins. 

(B)  The  Auricles  Contract. — There  occur  in  rapid  sequence: 

1.  The  contraction  and  evacuation  of  the  auricular  appendages  in  the 
direction  of  the  auricle.     Simultaneously,  the  entering  veins  are  con- 
stricted by  the  contraction  of  their  circular  muscular  layers,  especially 
the  superior  vena  cava  and  the  site  of  entrance  for  the  pulmonary 
veins. 

2.  The  walls  of  the  auricles  contract  rapidly  in  a  wave-like  manner 
from   above   downward,    particularly   toward   the   auriculo-ventricular 
orifices,  in  consequence  of  which — 

3.  The  blood  is  forced  downward  into  the  relaxed  ventricles,  which 
now  become  considerably  dilated.     As  a  result  of  the  auricular  con- 
traction there  occur: 

(a)  A  slight  stasis  of  the  blood  in  the  large  venous  trunks,  such  as 
can  be  readily  observed  particularly  in  rabbits  on  exposure  of  the  point 
of  junction  of  the  jugular  and  subclavian  veins  after  division  of  the 
muscles  of  the  chest.  There  is  no  actual  reflux  of  the  blood,  but  only 
a  slight  stasis  due  to  partial  interruption  of  the  flow  into  the  auricle, 
because,  as  has  been  stated,  the  sites  of  entrance  for  the  veins  are  nar- 
rowed; because,  further,  the  pressure  in  the  superior  vena  cava  and  in 
the  pulmonary  veins  soon  counteracts  the  tendency  to  regurgitation ; 
and,  finally,  because  in  the  further  ramifications  of  the  inferior  and 
to  some  extent  also  of  the  superior  cava  and  of  the  cardiac  veins, 
valves  prevent  the  reflux.  In  the  blood  thus  stagnated  in  the  venae 
cavae  the  movement  of  the  heart  causes  a  regular  pulsating  phenome- 
non that,  when  abnormally  increased,  may  give  rise  to  the  appearance 
of  a  venous  pulse. 

(6)  The  principal  motor  effect  of  the  auricular  contraction  is  the 
distention  of  the  relaxed  ventricles,  which  in  small  measure  are  dilated 
by  the  elastic  traction  of  the  lungs. 

Earlier  and  later  investigators  have  attributed  the  distention  of  the  ven- 
tricles in  part  to  the  elasticity  of  the  muscular  walls.  It  has  been  thought  that 
the  strongly  contracted  ventricular  walls,  like  a  compressed  rubber  bulb,  in  re- 
turning to  their  resting  normal  shape,  through  their  own  elasticity,  aspirate  the 
blood  with  negative  pressure.  Such  suction-power  on  the  part  of  the  ventricle  is, 
however,  effective  only  in  slight  degree,  if  at  all. 

(c)  With  the  distention  of  the  ventricles  the  auriculo-ventricular 
valves  at  once  float  upward  (Fig.  26),  being  in  part  forced  up  by  the 
counter-stroke  of  the  blood  from  the  wall  of  the  ventricle;  in  part  they 
are  capable,  by  reason  of  their  lower  specific  gravity,  to  spread  out  and 
float  horizontally;  in  part,  finally,  they  are  drawn  upward  by  the  longi- 
tudinal muscular  fibers  passing  from  the  auricles  upon  the  valves. 

(C)  The  ventricles  now  contract  and  the  auricles  relax.     In  this  phase— 
i.  The  muscular  walls  contract  on  all  sides  and  reduce  the  size  of 

the  ventricular  cavity. 
7 


98 


THE  MOVEMENTS  OF  THE  HEART. 


2.  At  the  same  time  the  blood  presses  against  the  under  surface 
of  the  auriculo- ventricular  valves,  the  inverted  margins  of  which 
interdigitate  and  become  hermetically  applied  to  one  another  (Fig.  26). 
The  valve-leaflets  are  prevented  from  being  forced  back  into  the 
auricular  cavity,  because  the  tendinous  cords  hold  their  under  surface 
and  margins  firmly  like  an  inflated  sail.  The  approximation  of  the 
edges  of  adjacent  valves  is  favored  further  by  the  circumstance 
that  the  tendinous  fibers  always  pass  from  one  papillary  muscle  to 
the  edges  of  two  opposed  valves.  To  the  extent  that  the  lower  ven- 


FIG.  26. — Plaster  Cast  of  the  Ventricles  of  the  Human  Heart,  Viewed  from  Behind  and  Above.  The  walls  are 
removed,  only  the  fibrous  rings  and  the  auriculo-ventricular  valves  being  retained:  L,  left;  R,  right  ventricle; 
S,  situation  of  the  septum;  F,  left  fibrous  ring,  with  closed  mitral  valve;  D,  right  fibrous  ring,  with  closed  tri- 
cuspid  valve;  A,  aorta,  with  the  left  (ci)  and  the  right  (c)  coronary  artery;  5,  sinus  of  Valsalva;  P,  pul- 
monary artery. 

tricular  wall  approaches  the  valves  during  contraction  and  thus  might 
render  possible  a  bulging  backward  of  the  valves  into  the  auricle,  com- 
pensation is  provided  by  the  shortening  of  the  papillary  muscles  and 
of  the  large  muscle-containing  tendinous  cords  themselves.  The  valves 
when  closed  present  an  approximately  horizontal  surface.  There  re- 
mains, therefore,  in  the  ventricles,  even  at  the  height  of  contraction, 
always  a  remnant  of  blood,  the  so-called  residual  blood. 

3.  When  the  pressure  in  the  ventricle  exceeds  that  in  the  arterial 


PATHOLOGICAL    DISTURBANCE    OF    FUNCTION    OF    HEART.  99 

vessels,  the  semilunar  valves  are  opened,  become  stretched  like  tendon 
above  their  concave  sinuses  (Fig.  24),  without  becoming  applied  to  the 
arterial  wall,  and  allow  the  blood  to  enter. 

Goltz  and  Gaule  found,  by  means  of  maximal  and  minimal  manometers,  a 
negative  pressure  in  the  ventricles  during  a  certain  phase  of  the  heart's  con- 
traction amounting  in  the  dog  to  — 23.5  mm.  of  mercury  in  the  left  ventricle. 
They  suspected  that  this  phase  coincided  with  the  diastolic  dilatation  and  for 
which  they  thus  assumed  a  considerable  power  of  aspiration.  Moens  is  of  the 
opinion  that  this  negative  pressure  prevails  in  the  ventricle  shortly  before  the 
systole  has  reached  its  maximum.  He  explains  the  aspiration  as  being  produced 
by  the  formation  of  a  vacuum  in  the  ventricle,  which  must  develop  as  a  result  of 
the  active  movement  of  the  blood,  through  the  aorta  and  the  pulmonary  artery, 
behind  the  circulating  mass  of  blood,  therefore  in  the  ventricle.  Gaule  and  Mink 
believe  that  the  systolic  enlargement  of  the  aorta  must  at  the  same  time  cause  a 
dilatation  of  the  conus  arteriosus  of  the  left  ventricle. 

(D)  After  the  ventricular  contraction  has  attained  its  height  and 
relaxation  has  commenced,  the  semilunar  valves  close  with  an  audible 
sound  (Fig.  27).  The  diastole  of  the  ventricle  is  followed  by  the  pause. 
Under  normal  conditions  the  two  halves  of  the  heart  contract  and  relax 
simultaneously  and  uniformly. 

The  heart-muscle  exhibits  in  its  activity  certain  variations  in  tone,  that  is, 
it  does  not  with  every  systole  contract  from  the  same  degree  of  relaxation  to 
the  same  degree  of  contraction,  but,  rather,  there  follow  in  rhythmical  periods 
series  of  contractions  that  arise  from  a  considerable 
degree  of  relaxation  of  the  heart-muscle,  alternating 
with  series  of  contractions  that  begin  in  a  less  com- 
plete degree  of  relaxation.  With  the  latter  the  degree 
of  contraction  is  greater  than  with  the  former.  These 
variations  in  tone  have  been  found  especially  in  the 
auricle  of  the  tortoise-heart.  When  the  arterial  blood- 
pressure  is  moderately  increased,  the  heart  expels  a 
larger  amount  of  blood;  if,  however,  the  arterial 
pressure  is  greatly  increased,  the  amount  of  blood 
expelled  at  each  systole  becomes  less.  Extracts  of 
testicle,  suprarenal  gland,  pituitary  gland  and  spleen 
in  0.7  per  cent,  sodium-chlorid  solution  added  to  blood 
exert  a  tonic  effect  upon  the  heart;  the  extent  of  the 
contractions  increases  and  the  beats  become  more 
regular.  Under  the  influence  of  alcohol  the  heart  FIG.  27. — The  Closed  Pulmonary 
exhibits  a  marked  degree  of  relaxation  and  a  low  v^'i11^  Valvfs  °*  Man» 

degree  of  contraction.     The  influence  of  various  poi- 
sons is  variable.     Heat  increases  the  variations  in  tone. 

Whether  the  relaxation  of  the  heart-muscle  is  an  active  dilatation  or  not  has 
been  decided  in  the  affirmative  by  some  investigators.  Stimulation  of  the  vagus 
(likewise  digitalis  and  strychnin)  is  said  to  increase  the  active  dilatation; 
while  section  of  the  vagus  (likewise  atropin)  is  said  to  diminish  it. 

PATHOLOGICAL     DISTURBANCE    OF    THE     FUNCTION    OF    THE 

HEART. 

All  obstructions  to  the  blood-flow  through  the  different  portions  of  the  heart 
or  of  the  vessels  connecting  them  give  rise  to  a  permanent  increase  in  the  work 
of  that  portion  of  the  heart  especially  concerned  with  relation  to  the  affected 
section  of  the  circulation,  and  in  consequence  to  an  increase  in  the  thickness  of 
the  muscular  walls,  with  dilatation  of  the  cavity.  Should  the  resistance  affect  not 
alone  one  section  of  the  heart,  but  consecutively  other  parts  further  on  in  the 
course  of  the  blood-stream,  these  also  will  undergo  secondary  hypertrophy.  If, 
in  addition  to  increasing  the  muscle-substance  of  the  affected  portion  of  the  heart, 
its  cavity  is  at  the  same  time  dilated,  as  is  often  the  case,  the  condition  is  designated 
excentric  hypertrophy,  or  hypertrophy  with  dilatation. 

The  obstructions  under  consideration  in  the  domain  of  the  vascular  channels 
are:  constriction  (stenosis)  of  the  arterial1  or  venous  orifipes  arid  likewise  defective 


IOO  THE    APEX-BEAT.       THE    CARDIOGRAM. 

closure  (insufficiency)  of  the  valves.  The  latter  causes  resistance  to  the  blood- 
flow  by  permitting  regurgitation  of  a  portion  of  the  blood  already  propelled 
onward.  In  this  way  there  results: 

1.  Hypertrophy  of  the  left  ventricle  from  hindrances  to  the    blood-flow  in 
the  territory   of   the    greater   circulation,    chiefly   in  the  arteries  and  capillaries, 
not  in  the  veins.     In  this  category  belongs  stenosis  of  the  aortic  orifice  and  of  the 
aorta  further  on;  also  calcification  and  loss  of  elasticity  in  the  large  arteries, 
irregular  dilatations  of  the  arterial  walls  (aneurysm) ;  insufficiency  of  the  aortic 
valves,  as  a  result  of  which  the  left  ventricle  is  continually  subject  to  the  aortic 
pressure;    finally,  affections  of  the  kidney,   in  consequence  of  which   a  greater 
arterial  pressure  is  required  in  order  that  the  urine  may  be  excreted.     In  the 
presence  of  mitral  regurgitation  also,  hypertrophy  of  the  left  ventricle  is  necessary 
for  compensation,  and  a  similar  enlargement  occurs  in  the  left  auricle  in  conse- 
quence of  the  heightened  pressure  in  the  lesser  circulation. 

2.  Hypertrophy   of  the  left   auricle  results   from  mitral   stenosis   and  from 
mitral  regurgitation,  and  also  consecutively  to  aortic  regurgitation  because  the 
auricle  must  overcome  the  uninterrupted  aortic  pressure  that  is  present  in  the 
left  ventricle. 

3.  Hypertrophy   of  the   right   ventricle   results    from  (a)  hindrances   to  the 
blood-flow  in  the  territory  of  the  lesser  circulation.     These  are :  (a)  atrophy  of  vascu- 
lar areas  of  considerable  size  in  the  lungs  in  consequence  of  destruction,  contrac- 
tion   or  compression    of    the    lungs   and    from   loss    of   numerous  capillaries    in 
emphysematous  lungs.      (/?)   Overdistention  of  the  lesser  circulation  with  blood  in 
consequence  of  stenosis  of  the  mitral  orifice  or  of  insufficiency  of  the  mitral  valve ; 
also  consecutively  to  hypertrophy  of  the  left  auricle  resulting  from  aortic  regur- 
gitation.    (b)   Hypertrophy  of  the  right  ventricle  must  occur  also  in  conjunction 
with  insufficiency  of  the  pulmonary  valves,  which  permits  the  blood  to  regurgi- 
tate into  the  ventricle,  so  that  the  pressure  of    the  pulmonary  artery  prevails 
continually  in  the  cavity.     This  condition  is  exceedingly  rare. 

4.  Hypertrophy  of  the  right  auricle  develops  consecutively  to  the  condition 
last  mentioned,  likewise  in  association  with  stenosis  of  the  right  auriculo-ventricu- 
lar  orifice,  or  from  insufficiency  of  the  tricuspid  valve.     This  condition  is  un- 
common.    When  several  obstructions  in  the  circulation  occur  together  there  is 
a  combination  of  the  resulting  phenomena.     O.  Rosenbach  has  investigated  the 
manner  and  method  by  which  the  heart  maintains  its  activity  after  the  occur- 
rence of  valvular  lesions.     If  the  aortic  valves  were  perforated,  with  or  without 
simultaneous  injury  to  the  mitral  and  tricuspid  valves,  the  heart  performed  first 
an  increase  of  work,  which  counteracted  the  physical  defects,  so  that  the  blood- 
pressure  did  not  fall.     The  heart,  therefore,  possesses  reserve  powers,  which  are 
brought  into  play  only  when  they  are  required.     In  consequence  of  the  valvular 
insufficiency  dilatation  first  develops  as  a  result  of  the  regurgitation  of  blood  into 
the  affected  chamber  of  the  heart.     Then  follows  hypertrophy,  but  until  this  is 
completed  the  compensation  must  be  effected  by  the  reserve  power. 

Under  the  conditions  that  especially  render  diastole  difficult  there  should  yet 
be  mentioned :  large  effusions  into  the  pericardial  sac  or  pressure  on  the  heart  from 
tumors.  The  systole  is  greatly  interfered  with  by  adhesions  between  the  heart 
and  the  connective  tissue  of  the  mediastinum.  Under  such  circumstances  the 
surrounding  tissues,  even  the  thoracic  wall,  must  be  drawn  upon  with  each  con- 
traction of  the  heart,  so  that  systolic  retraction  and  diastolic  projection  occur 
in  the  situation  of  the  apex-beat. 

THE  APEX-BEAT.     THE  CARDIOGRAM. 

By  the  term  apex-beat  (ictus  s.  impulsus  cordis)  is  understood  the 
visible  and  palpable  elevation  of  a  circumscribed  area  of  the  fifth  (less 
commonly  the  fourth)  left  intercostal  space,  caused  by  the  action  of  the 
heart.  At  times  the  apex-beat  is  less  distinct,  especially  when  the 
heart  strikes  against  the  fifth  rib  itself.  Changes  in  the  position  of 
the  body  alter  somewhat  the  situation  and  the  force  of  the  apex-beat. 
A  graphic  representation  of  this  movement  can  be  obtained  by  means  of 
a  registering  apparatus — the  apex-beat  tracing  or  the  cardiogram. 

Method. — To  obtain  a  tracing  of  the  apex-beat  the  cardiograph  of  Marey  may 
be.employed.  ,The  •iitstrume,nt  has  beentmodified  by  various  investigators.  The 


THE    APEX-BEAT.       THE    CARDIOGRAM. 


101 


pansphygmograph  of  Brondgeest  is  essentially  the  same  as  Marey's  apparatus, 
with  unimportant  changes.  Marey's  sphygmograph  can  also  be  used.  In  animals 
the  cardiogram  can  be  registered  by  ligating  the  tube  of  the  pansphygmograph  in 
the  pericardium. 

In  the  normal  tracing  of  the  apex-beat  of  man  (A)  or  of  the  dog  (B) 
the  following  details  are  distinguishable :  a  b  corresponds  to  the  period  of 
the  pause  and  of  the  contraction  of  the  auricles.  As  the  auricles  con- 
tract in  the  direction  of  the  heart's  axis  from  the  right  and  above  to  the  left 
and  downward  it  is  not  surprising  that  the  apex  of  the  heart  advances 
toward  the  intercostal  space.  In  this  portion  of  the  tracing  there  can 
be  seen  generally  two  or  even  three  slight  elevations  which  may  be  due 
to  the  rapidly  successive  contractions  of  the  venous  endings,  the  auricular 
appendages,  and  the  auricles  themselves. 


Kill 


FIG.  28. — A,  Normal  apex-beat  tracing  from  man.  B,  from  a  dog;  C,  tracing  of  an  accelerated  apex-beat  from 
a  dog;  D  and  E,  normal  apex-beat  tracings  from  man  recorded  upon  a  vibrating  tuning-fork  plate.  Each 
serration  represents  0.01613  second  of  time.  In  all  of  the  tracings  a  b  indicates  the  auricular  contraction, 
b  c,  the  ventricular  contraction;  d,  the  closure  of  the  aortic  valves;  e,  the  closure  of  the  pulmonary  valves; 
e  f,  relaxation  of  the  ventricles. 

Naturally  the  last,  occasionally  distinct,  elevation,  occurring  shortly  before  b 
(corresponding  to  B  v  and  C  v  in  Fig.  31),  will  be  looked  upon  as  the  true  auricular 
contraction;  v.  Ziemssen  and  Ter  Gregorianz  were  able  to  register  the  elevation 
of  the  auricular  appendix  preceding  the  auricular  contraction  in  a  woman  with 
an  exposed  heart. 

The  line  b  c  is  caused  by  the  ventricular  contraction.  It  is  this  alone 
that  is  appreciable  to  the  palpating  finger  as  the  apex-beat.  The  first 
sound  of  the  heart  commences  with  the  beginning  of  the  ventricular 
contraction. 


102 


THE    APEX-BEAT.       THE    CARDIOGRAM. 


The  cause  of  the  ventricular  impulse  resides  in  the  following  factors  : 

1.  The  base  of  the  heart  (the  junction  of  auricles  and  ventricles), 
which  in  diastole  presents  the  form  of  a  transverse  ellipse  (Fig.  29,  I,  F 
G),  is  contracted  to  a  rather  circular  figure  (a  b).     In  this  way,  the  large 
diameter  of  the  ellipse  (F  G)  is  naturally  diminished  and  the  small 
diameter  (d  c)  is  increased,  and  in  consequence  the  base  is  brought  nearer 
to  the  chest-wall  (e).     This  alone,  however,  does  not  produce  the  apex- 
beat,  but  the  base  of  the  heart,  thus  brought  somewhat  nearer  the  chest- 
wall,  and  hardened  during  systole,  affords  the  apex  the  possibility  of 
making  the  movement  that  constitutes  the  apex-beat. 

2.  The  ventricles,  which  during  the  period  of  relaxation  have  their 
apex  (Fig.  29,  II,  i)  directed  obliquely  downward  in  the  line  of  their  long 


FIG.  29. — I.  Horizontal  Section  through  the  Heart  and  the  Lungs,  Together  with  the  Chest-walls,  for  the  Demon- 
stration of  the  Change  in  the  Shape  of  the  Base  of  the  Heart  during  the  Contraction  of  the  Ventricles:  F  G, 
transverse  diameter  of  the  ventricles  during  diastole;  c,  position  of  the  anterior  ventricular  wall;  a  b,  transverse 
diameter  of  the  ventricles  during  systole  with  e,  the  position  of  the  anterior  ventricular  wall  during  systole. 
II.  Lateral  View  of  the  Position  of  the  Heart:  i,  the  apex-beat  during  diastole;  p,  during  systole  (in  part 
after  C.  Ludwig  and  Henke). 

diameter,  so  that  the  angles  (b  c  i  and  a  c  i)  formed  by  the  junction 
of  the  ventricular  axis  with  the  diameter  of  the  base  are  unequal, 
represent  a  symmetrical  cone,  with  its  axis  perpendicular  to  its  base. 
Accordingly,  the  apex  (7)  must  be  elevated  from  below  and  behind  for- 
ward and  upward  (p)  (W.  Harvey:  "Cor  sese  erigere"),  and  it  thus 
thrusts  itself,  hardened  during  systole,  into  the  intercostal  space 
(Fig.  29,  II). 

3 .  During  the  systolic  contraction  the  ventricles  of  the  heart  undergo 
a  slight  spiral  rotation  about  their  long  axes  ("lateraleminclinationem," 
W.  Harvey),  so  that  the  apex  is  carried  from  behind  slightly  forward, 


THE    APEX-BEAT.       THE    CARDIOGRAM.  103 

while  at  the  same  time  a  considerable  area  of  the  left  ventricle  is  turned 
forward.  This  rotation  is  due  to  the  fact  that  many  of  the  fibers  of 
the  ventricular  muscles  that  arise  from  the  portion  of  the  fibrous  ring 
that  is  turned  toward  the  chest-wall  at  the  junction  of  the  right  auricle 
and  ventricle  pass  obliquely  from  above  and  to  the  right  downward  and 
to  the  left,  in  part  to  the  posterior  aspect  of  the  left  ventricle.  Thus, 
they  draw  the  apex  of  the  heart  upward  in  the  direction  of  their  course, 
and  its  posterior  aspect  slightly  toward  the  anterior  wall  of  the  thorax. 
This  rotatory  movement  is  favored  by  the  circumstance  that  the  aorta 
and  the  pulmonary  artery,  which  are  applied  to  each  other  in  a  slightly 
spiral  manner,  effect  a  rotation  of  the  heart  in  the  same  direction  at  the 
time  of  systolic  tension. 

According  to  an  earlier  opinion  the  cardiac  impulse  was  held  to  be  produced 
or  at  least  increased  by : 

4.  The  recoil  that  the  ventricles  are  supposed  to  experience  (like  a  dis- 
charged firearm)  at  the  instant  when  the  column  of  blood  empties  itself  into  the 
aorta  and  the  pulmonary  artery.  The  apex  would,  of  course,  be  driven  in  the 
opposite  direction  by  this  recoil,  that  is,  downward  and  a  little  outward.  Landois, 
however,  has  pointed  out  that  the  blood-column  is  discharged  into  the  vessels 
0.08  second  after  the  beginning  of  the  ventricular  contraction,  while,  on  the  other 
hand,  the  apex-beat  begins  simultaneously  with  the  first  sound. 

As,  however,  the  apex-beat  is  observed  in  bloodless  hearts  taken 
from  animals  after  death,  and  as  the  apex  of  the  heart  is  not,  as  it 
would  be  on  the  theory  of  the  recoil,  displaced  downward  and  to  the 
left  during  systole,  but  upward  and  to  the  right  (as  has  been  confirmed 
by  v.  Ziemssen  in  a  woman  whose  heart  was  exposed),  the  recoil  cannot 
be  regarded  as  a  factor  in  the  problem. 

After  the  ventricles  by  their  systolic  movement  have  traced  the 
greatest  part  of  the  apex-beat  curve,  as  far  as  its  apex  (c),  the  curve 
rapidly  descends  and  the  ventricles  pass  from  a  state  of  extreme  con- 
traction to  one  of  relaxation.  Soon,  however,  two  small  elevations 
appear  in  the  descending  limb  of  the  curve  at  d  and  e.  These  are  due 
to  the  abrupt  closure  of  the  semilunar  valves,  which,  being  effected  with 
a  certain  degree  of  force,  is  transmitted  along  the  axis  of  the  ventricles 
as  far  as  the  apex,  and  through  the  latter  even  causes  concussion  of  the 
intercostal  space;  d  corresponds  to  the  closure  of  the  aortic  valves,  e  to 
that  of  the  pulmonary  valves.  The  valves,  therefore,  do  not  close  at 
the  same  time,  there  being  an  interval  of  about  from  0.05  to  0.09  second 
on  the  average.  Owing  to  the  greater  pressure  of  the  blood  in  the 
aorta  the  aortic  valves  close  earlier  than  those  of  the  pulmonary  artery. 

While  investigators  are  agreed  that  the  first  sound  of  the  heart  begins  at 
the  point  b  of  the  cardiogram,  various  statements  have  been  made  with  regard 
to  the  point  at  which  the  registration  of  the  second  sound  of  the  heart  takes  place. 
Martius  designates  the  depression  between  c  and  d  (Fig.  28,  E)  as  the  point  that 
corresponds  to  the  second  heart-sound;  Landois  the  apices  d  and  e,  when  the 
tension  of  the  semilunar  valves  is  increased;  Hiirthle,  Einthoven  and  Geluk  0.02 
second  after  e;  Marey  and  Fredericq  about  midway  between  e  and  f ;  and,  finally, 
Edgren  at  a  point  immediately  in  front  of  f . 

Method. — In  order  to  determine  the  time  when  the  heart-sounds  are  heard, 
their  vibrations  are  transmitted  to  a  microphone  attached  to  the  thorax.  The 
instrument,  which  is  thrown  into  vibration  by  each  sound  of  the  heart,  opens 
and  closes  an  electric  circuit  with  each  vibration  and  thus  attracts  an  electromagnet, 
or  sets  a  capillary  electrometer  (Fig.  229)  in  motion.  If  by  means  of  another 
contrivance  the  cardiogram  is  made  to  register  at  the  same  time,  the  points  on 
the  latter  at  which  the  heart-sounds  are  heard  can  be  seen. 

From  the  point  e  to  the  foot  of  the  curve  (at  f)  comprises  the  time 
during  which  complete  diastolic  relaxation  of  the  ventricles  takes  place. 


104  TIME-RELATIONS    OF    THE    MOVEMENTS    OF    THE    HEART. 


THE  TIME-RELATIONS  OF  THE  MOVEMENTS  OF  THE  HEART. 

Method. — The  time-relations  of  the  individual  phases  of  the  movements  of 
the  heart  can  be  most  reliably  discerned  in  the  curves  of  the  apex-beat : 

When  the  distance  traversed  at  a  uniform  rate  in  a  unit  of  time  is  known 
for  the  registering  surface,  the  time  corresponding  to  each  portion  of  the  curve 
can  be  ascertained  by  direct  measurement  (as  in  the  case  of  pulse-curves) . 

Landois  determined  the  time  by  having  the  curves  traced  on  a  tablet 
vibrating  on  the  arm  of  a  large  tuning-fork  (Fig.  60) .  The  curve  then  contains  in 
all  of  its  segments  small  undulations  due  to  the  vibrations  of  the  tuning-fork. 
In  Fig.  28,  D  and  E  represent  apex-beat  curves  of  healthy  students  registered 
in  this  way  (in  D  the  elevation  d  is  not  distinct).  A  complete  vibration  of  the 
tuning-fork  (from  the  apex  of  one  undulation  to  that  of  the  next)  corresponds 
to  0.01613  second;  by  counting  the  number  of  undulations  and  multiplying  by  the 
factor  the  time  is  obtained.  Although  there  is  a  certain  regularity  in  the  time 
of  the  individual  phases  of  the  movement,  the  readings  nevertheless  vary  between 
wide  limits  even  in  healthy  individuals. 

The  value  of  a  b,  which  is  equivalent  to  the  pause  plus  the  auricular 
contraction,  is  subject  to  the  widest  variations  and  depends  chiefly  on 
the  frequency  of  the  pulse ;  for,  the  more  rapidly  the  heart-beats  follow 
one  another,  the  shorter,  naturally,  will  be  the  pause,  until  it  finally 
disappears  altogether.  Even  when  the  rate  of  the  heart  is  slow,  it  is 
often  impossible  to  distinguish  in  the  curve  the  portion  corresponding 
to  the  pause,  which,  owing  to  the  gradual  filling  of  the  heart  and  the 
resulting  slight  bulging  of  the  intercostal  space,  has  a  gently  ascending 
form,  from  that  due  to  the  auricular  contraction  and  appearing  as  a 
hillock.  In  one  case  in  which  the  heart-beats  were  55  in  a  minute, 
Landois  found  the  pause  to  be  0.4  second  and  the  auricular  contrac- 
tion 0.177  second.  In  Fig.  28,  A,  the  pause  plus  the  auricular  con- 
traction, when  the  heart  beats  74  times  in  a  minute,  is  found  on 
measurement  to  be  0.5  second.  In  D  the  corresponding  period  a  b  is 
equivalent  to  from  19  to  20  vibrations,  or  0.32  second;  in  E  the  period 
is  equivalent  to  26  vibrations,  corresponding  to  0.42  second. 

The  ventricular  systole  is  estimated  from  b,  the  beginning  of  the 
contraction,  to  e,  the  completed  closure  of  the  semilunar  valves  of  the 
pulmonary  artery.  It,  therefore,  extends  from  the  first  to  the  second 
heart-sound.  This  period  is  also  variable,  though  considerably  more 
constant.  When  the  action  of  the  heart  is  accelerated,  the  period 
becomes  less,  when  the  action  is  slower  the  period  increases;  in  E  it  is 
0.32  second,  in  D  0.29  second;  when  the  heart-beats  were  only  55  Lan- 
dois found  it  to  be  0.34  second;  but  when  the  frequency  is  exceedingly 
great  it  declines  to  0.199  second. 

Landois  was  able  to  ascertain  the  interesting  fact  that  when  the  left  ventricle 
is  enormously  hypertrophied  and  dilated,  the  duration  of  the  ventricular  contrac- 
tion does  not  materially  exceed  the  normal. 

That  the  ventricle  contracts  more  slowly  when  the  action  of  the  heart  is 
weakened  is  shown  when  the  registering  instrument  is  placed  on  the  ventricle  of 
an  animal  that  has  been  killed,  and  the  heart-beat  is  recorded.  In  Fig.  30,  from 
the  ventricle  of  a  rabbit  the  slow  heart-beats  (B)  are  at  the  same  time  of  longer 
duration. 

This  affords  an  opportunity  to  determine  accurately  the  length  of  the  period 
to  be  allowed  for  the  ventricular  systole.  Landois  thought  it  wise,  in  order  to 
avoid  misunderstanding,  to  distinguish  the  following  three  separate  factors: 

1.  The  interval  between  the  two  heart-sounds,  that  is,  from  the  beginning  of 
the  first  to  the  end  of  the  second  sound  (Fig.  2  8 ,  b — e) . 

2.  The  time  occupied  by  the  blood  in  entering  the  aorta:  This  evidently  ter- 
minates at  the  depression  between  c  and  d  (Fig.  28,  E) ;  its  beginning,  however, 


TIME-RELATIONS    OF    THE    MOVEMENTS    OF    THE    HEART.  105 

does  not  coincide  with  b,  as  from  0.085  to  °-°73  to  0.06  second  elapses  between  the 
beginning  of  the  ventricular  contraction  and  the  opening  of  the  semilunar  valves 
of  the  aorta.  According  to  this  calculation  the  entrance  of  the  blood  into  the 
aorta  (aortic  inflow)  would  occupy  from  0.08  to  0.09  second.  Landois  arrived  at 
this  result  by  the  following  calculation:  The  interval  between  the  first  sound  of 
the  heart  and  the  pulse  at  the  axillary  artery  is  0.137  second.  The  propagation 
of  the  pulse-wave  along  the  distance  from  the  root  of  the  aorta  to  the  axillary 
artery,  which  is  equivalent  to  30  centimeters,  cannot  occupy  more  than  0.052 
second  of  this  time  (corresponding  to  the  analogous  velocity  in  the  distance — -50 
cm. — from  the  axillary  to  the  radial  artery  =  0.087).  Hence,  the  pulse-wave  in 
the  aorta  cannot  take  place  earlier  than  0.137  minus  0-052  =0.085  second  after 
the  beginning  of  the  first  sound  of  the  heart.  Landois  found  in  agreement  with 
Hurthle  that  in  some  cardiograms  the  point  that  marks  the  beginning  of  the  flow 
of  blood  into  the  arteries,  or,  what  is  the  same  thing,  the  time  of  the  opening  of 
the  semilunar  valves,  is  indicated  in  the  ascending  limb  by  a  small  interval  between 
b  and  c.  The  current  in  the  pulmonary  artery  is  not  interrupted  until  the  point 
e  is  reached. 

3.  Finally,  the  time  occupied  by  the  muscular  contraction  of  the  ventricle 
may  be  considered.  The  contraction  begins  at  b,  reaches  its  greatest  degree  at  c, 
and  is  not  followed  by  complete  relaxation  until  f  is  reached.  The  apex  of  the 
curve  c  may,  however,  be  higher  or  lower,  according  as  the  intercostal  space 
yields  more  or  less;  the  position  of  c  is,  therefore,  variable. 

The  time  that  elapses  between  d  and  e,  that  is,  between  complete 
closure  of  the  semilunar  valves  and  of  the  pulmonary  artery,  is  greater 
in  proportion  as  the  pressure  within  the  aorta  exceeds  that  within  the 


FIG.  30. — Contraction-curves  from  the  Ventricle  of  a  Rabbit  Registered  on  a  Plate  Attached  to  a  Vibrating  Tuning- 
fork  (one  vibration  m  0.01613  second):  A,  soon  after  death;  B,  taken  while  the  ventricle  was  in  process  of 
dying. 

pulmonary  artery,  as  the  closure  of  the  valves  is  effected  by  the  pres- 
sure from  above.  This  interval  may  vary  from  0.05  second  to  more 
than  twice  that  length  of  time;  in  the  latter  event  the  second  sound  of 
the  heart  is  also  duplicated.  If,  however,  the  tension  in  the  aortic 
system  diminishes  and  the  pressure  in  the  pulmonary  artery  rises,  the 
interval  between  d  and  e  may  be  diminished  to  such  a  degree  that  the 
two  coincide  at  one  point  in  the  curve. 

The  time  occupied  by  the  ventricles  in  relaxing  (e  f )  after  closure 
of  the  pulmonary  valves  is  also  subject  to  a  certain  degree  of  variation; 
in  healthy  adults  the  average  may  be  given  as  o.i  second. 

When  the  action  of  the  heart  is  greatly  accelerated,  the  time  occupied  by  the 
pause  is  the  first  to  become  shortened,  as  Bonders  and  Landois  have  found;  then 
the  time  occupied  by  the  auricular  and  ventricular  systole  also  is  shortened,  in 
lesser  degree,  though  quite  distinctly.  With  the  highest  degree  of  pulse-frequency 
the  beginning  of  the  auricular  systole  coincides  with  the  closure  of  the  arterial 
valves  of  the  preceding  heart-beat,  a  phenomenon  that  is  strikingly  illustrated 
in  the  tracing  from  a  dog  (Fig.  28,  C). 

As  during  the  registration  of  apex-beat  curves  the  heart  is  separated  from  the 
registering  instrument  by  the  soft  parts  of  the  intercostal  space,  which  vary  in 
thickness  and  in  resistance  and  cannot  in  every  case  follow  the  movements  of  the 
heart  with  entire  ease,  it  cannot  be  expected  that  the  various  portions  of  the  curve 
shall  coincide  with  mathematical  accuracy  with  the  corresponding  phases  of  the 
heart's  movements. 


io6 


TIME-RELATIONS    OF    THE    MOVEMENTS    OF    THE    HEART. 


Gibson  had  the  opportunity  of  taking  cardiograms  from  a  case  of  fissure  of 
the  sternum  in  a  man,  and  obta'ined  the  following:  time-values:  Auricular  contrac- 
tion (a  b)  =0.115,  ventricular  contraction  (b  d)  =0.28,  interval  between  the 
closure  of  the  valves  (d  e)  =  0.09,  ventricular  diastole  (e  f)  =  o.u,  pause  =  0.45 
second. 

In  large  mammals  (horses)  Marey  and  Chauveau,  in  1861,  by  a  most 
thorough  method  obtained  records  of  the  phases  of  the  movements  of  the  heart 
in  the  following  manner:  Long  catheter-like  tubes,  provided  at  their  lower  ex- 
tremity with  a  closed  and  compressible  rubber  bulb,  were  connected  by  means  of 
a  flexible  piece  of  tubing  attached  to  the  other  end  with  the  registering  drum  of 
the  cardiograph  (Fig.  44,  KS).  It  is  evident  that  with  every  compression  of  the 


Aorta. 


Apex 
of  the 
Heart. 


FIG.  31. — Curves  Showing  the  Movements  of  the  Separate  Portions  of  the  Heart  (Chauveau  and  Marey). 


rubber  bulb  the  stylus  connected  with  the  registering  drum  of  the  instrument  will 
be  elevated. 

Fig.  31  shows  a  number  of  curves:  In  making  A  the  rubber  bulb  was  in  the 
right  auricle,  having  been  introduced  through  the  jugular  vein  and  the  superior 
vena  cava;  in  making  B  the  bulb  was  introduced  into  the  right  ventricle  through 
the  tricuspid  orifice;  in  making  D  it  was  introduced  through  the  carotid  as  far 
as  the  root  of  the  aorta;  in  making  C,  through  the  semilunar  valves  of  the  aorta 
into  the  left  ventricle;  and,  finally,  in  making  E  the  bulb  was  applied  externally 
to  the  apex  of  the  heart  between  this  and  the  inner  aspect  of  the  chest-wall.  In 
all  of  the  curves  v  indicates  the  auricular  contraction,  V  the  ventricular  contrac- 
tion, s  the  closure  of  the  semilunar  valves  (which  occurred  earlier  in  B  than  in  C), 
and  P  the  pause.  As  the  recording  surface  moves  at  a  uniform  rate  and  the 


PATHOLOGICAL    VARIATIONS    IN    THE    HEART-BEAT.  107 

scale  for  the  distance  covered  in  each  second  is  given,  the  individual  periods  of 
time  can  be  measured. 

It  seems  probable,  however,  that  the  introduction  of  the  tubes  into  the  heart 
is  not  without  influence  on  the  regular,  undisturbed  course  of  its  activity. 

In  order  to  determine  the  conditions  present  coincidently  with  the  pressure 
in  the  ventricle  and  in  the  aorta  in  the  dog,  Hiirthle  employed  his  blood-pressure 
recorders  (Fig.  67),  which  were  connected  by  means  of  tubes  with  the  interior 
of  the  ventricle  and  of  the  aorta.  A  cardiogram  was  taken  at  the  same  time. 
The  vertical  lines  o,  i,  2,  3  indicate  conditions  identical  in  time  in  the  three  curves. 
The  point  o  corresponds  with  the  beginning  of  the  ventricular  contraction  and 
the  first  sound  of  the  heart ;  while  the  entrance  of  the  blood  into  the  aorta  occurs 
after  an  interval,  namely  at  the  point  i.  The  points  2  and  3,  according  to  Hiirthle, 
indicate  the  closure  of  the  semilunar  valves  (second  sound  of  the  heart).  Fred- 
ericq  obtained  similar  results  by  means  of  other  experiments. 

One  point  remains  to  be  cleared  up,  namely,  whether  the  auricle  and  the 
ventricle  work  in  exact  alternation,  in  such  a  way  that  the  auricle  relaxes  at  the 
instant  when  the  ventricle  begins  to  contract,  or  whether  the  ventricle  begins  to 


Cardiogram. 

Aorta> 
Time-Recorder. 


Ventricle 

FIG.  32. — Simultaneous  Record  Showing  Cardiogram,  the  Curve  of  the  Ventricular  Pressure  and  that  of  the  Aortic 
Pressure,  from  the  Dog.     Each  division  of  the  time-curve  =  o.oi  second  (K.  Hiirthle). 

contract  while  the  auricle  still  remains  contracted  for  a  short  time,  so  that  for 
a  short  period  of  time  at  least  the  entire  heart  is  contracted.  Heart-beat  curves 
taken  from  human  subjects  appear  to  show  that  the  ventricular  contraction  begins 
as  the  auricular  contraction  ends;  v.  Ziemssen  and  Ter  Gregorianz,  who  made 
curves  directly  from  the  auricle  of  the  exposed  heart  of  a  woman,  are  likewise 
in  accord  with  the  view  that  the  auricular  contraction  continues  for  a  time  while 
the  ventricles  are  beginning  to  contract;  and  also  Heigl,  on  the  strength  of  a 
similar  observation. 

A.  Fick,  who  believes  that  the  contractions  alternate,  considers  this  alternation 
as  a  means  for  maintaining  the  pressure  in  the  large  venous  trunks  approximately 
constant.  As  the  auricle  relaxes  at  the  instant  when  the  ventricular  systole  begins, 
there  is  no  impediment  to  the  flow  of  venous  blood  into  the  auricle;  whereas  if 
the  auricular  contraction  were  to  persist,  the  blood  would  be  dammed  back.  As, 
further,  the  auricle  contracts  at  the  instant  of  ventricular  relaxation,  there  will 
be  no  abnormal  pressure  in  the  veins.  In  this  way  the  pressure  within  the  auricle 
may  remain  more  uniform  and  the  blood-stream  in  the  ends  of  the  veins  more 
constant. 

PATHOLOGICAL  VARIATIONS  IN  THE  HEART-BEAT. 

The  position  of  the  heart-beat  is  altered:  (i)  By  the  accumulation  of  fluid 
^serum,  pus  or  blood)  or  of  gases  in  one  pleural  cavity.  Copious  effusions  into 
the  pleural  cavity,  which  at  the  same  time  compress  the  lung  and  force  it  upward, 
may  displace  the  heart  as  far  as  the  right  nipple.  Effusions  into  the  right  pleura 
cause  displacement  of  the  heart  to  the  left.  As  the  right  heart  is  forced 


IO8  PATHOLOGICAL    VARIATIONS    IN    THE    HEART-BEAT. 

to  greater  exertion  in  order  to  propel  the  blood  through  the  compressed  lung, 
the  apex-beat  under  such  circumstances  is  usually  accentuated.  Marked  disten- 
tion  of  the  lungs  (emphysema),  which  depresses  the  diaphragm,  also  causes  down- 
ward and  inward  displacement  of  the  apex-beat.  Conversely,  elevation  of  the 
diaphragm,  as  a  result  of  contraction  of  the  lungs  or  of  pressure  by  the  abdominal 
organs,  has  the  effect  of  displacing  the  apex-beat  upward — sometimes  as  far  as 
the  third  intercostal  space — and  a  little  to  the  left.  Thickening  of  the  muscular 
wall  of  the  heart  with  dilatation  of  the  cavities  (hypertrophy  and  dilatation) ,  when 
it  affects  the  left  ventricle,  causes  an  increase  in  the  length  and  breadth  of  the 
chamber,  and  the  accentuated  apex-beat  becomes  palpable  to  the  left  of  the 
nipple-line,  sometimes  in  the  axillary  line  in  the  sixth,  seventh,  or  even  eighth 
intercostal  space.  Hypertrophy  and  dilatation  of  the  right  ventricle  cause  an 
increase  in  the  width  of  the  heart:  the  apex-beat  is  felt  further  to  the  right, 
sometimes  even  to  the  right  of  the  sternum,  but  at  the  same  time  also  a  certain 
distance  beyond  the  left  nipple-line.  In  the  rare  cases  of  transposition  of  the 
viscera,  in  which  the  heart  is  situated  in  the  right  half  of  the  thorax ,  the  apex-beat 
is  of  course  found  in  exactly  the  corresponding  situation  on  the  right  side  of  the 
thorax.  Landois  was  the  first  to  take  an  apex-beat  curve  from  a  heart  of  this 
kind  and  found  that  it  presented  all  of  the  normal  features.  When  the  heart-beat 
extends  to  the  left  beyond  the  nipple-line  or  to  the  right  beyond  the  parasternal 
line,  the  area  of  cardiac  impulse  is  enlarged  transversely,  a  condition  that  always 
indicates  hypertrophy  of  the  heart.  When  this  transverse  enlargement  is  unusu- 
ally great,  the  apex-beat  may  extend  over  several  intercostal  spaces  or  over  both 
sides  of  the  thorax. 

The  apex-beat  appears  abnormally  weak  in  association  with  atrophy  and 
degeneration  of  the  heart-muscle,  or  when  the  innervation  of  the  controlling  nerves 
is  impaired.  The  cardiac  impulse  may  be  weakened  or  even  completely  obliterated 
also  when  the  heart  is  forced  away  from  the  chest-wall  by  an  accumulation  of  fluid 
or  of  gas  in  the  pericardium,  by  a  greatly  distended  left  lung,  or  by  an  effusion  into 
the  left  pleural  cavity.  The  same  condition  results  either  when  the  left  ventricle 
is  imperfectly  filled  during  contraction  (in  consequence  of  marked  stenosis  of  the 
mitral  orifice)  or  when,  owing  to  extreme  narrowing  of  the  aortic  orifice,  it  can 
empty  itself  but  gradually  and  slowly. 

An  increase  of  the  apex-beat  is  observed  in  the  presence  of  hypertrophy  of 
the  walls  of  the  heart,  as  well  as  in  association  with  the  most  diverse  irritative 
conditions  (psychic,  inflammatory,  febrile,  toxic)  affecting  the  heart  and  its  con- 
trolling nerves.'  Extreme  hypertrophy  of  the  left  ventricle  causes  a  heaving  apex- 
beat,  so  that  a  portion  of  the  chest-wall  is  elevated,  with  systolic  concussion. 

In  some  cases  the  apex-beat  is  quite  distinct  or  even  abnormally  distinct, 
while  the  pulse  is  quite  small.  This  phenomenon  is  due  to  insufficient  emptying 
of  the  ventricles  (spurious  contraction  of  the  heart) . 

Systolic  retraction  is  not  infrequently  observed  on  the  anterior  chest -wall 
in  the  third  and  fourth  intercostal  spaces  on  the  left  side  under  normal  conditions, 
especially  when  the  action  of  the  heart  is  accentuated  and  when  there  is  excentric 
hypertrophy  of  the  ventricles.  As  the  apex  is  somewhat  displaced  with  each 
ventricular  contraction  and  the  ventricles  at  the  same  time  diminish  in  size,  the 
yielding  soft  parts  of  the  intercostal  space  are  drawn  in  to  fill  the  vacuum  thus 
formed.  When  the  heart  is  adherent  to  the  pericardium  and  the  surrounding 
connective  tissue,  movement  of  the  heart  during  systole  becomes  impossible  and 
the  apex-beat  is  replaced  by  systolic  retraction  of  the  apical  area.  Under  such 
circumstances  the  chest-wall  bulges  during  diastole,  in  a  measure  representing  a 
kind  of  diastolic  apex-beat. 

The  changes  in  the  apex-beat  that  occur  in  association  with  functional  dis- 
orders of  the  heart  are  best  studied  by  tracing  apex-beat  curves,  as  has  been  done 
by  a  number  of  clinicians  since  Landois  first  published  his  method  in  1876. 

In  the  curve  shown  in  Fig.  33,  P,  in  reduced  size  and  obtained  from  a  case  of 
marked  hypertrophy  and  dilatation  of  the  left  ventricle,  the  ventricular  contrac- 
tion as  a  rule  is  exceedingly  large  (b  c) ,  although  the  time  occupied  in  contraction 
by  the  greatly  increased  muscular  mass  of  the  ventricular  wall  is  not  materially 
longer  than  under  normal  conditions.  The  curves  P  and  Q  were  obtained  from 
a  man  with  a  high  grade  of  excentric  hypertrophy  of  the  left  ventricle,  resulting 
from  insufficiency  of  the  semilunar  valves  of  the  aorta.  The  curve  Q  was  taken 
purposely  at  a  point  near  the  epigastrium  where  systolic  retraction  was  present. 
Although  the  position  of  the  individual  portions  of  the  curve  is  changed,  the 
individual  phases  of  the  heart's  action  are  nevertheless  well  shown. 


PATHOLOGICAL    VARIATIONS    IN    THE    HEART-BEAT. 


109 


Fig.  E  represents  the  apex-beat  in  a  case  of  stenosis  of  the  aortic  orifice. 
The  auricular  contraction  (a  b)  is  quite  brief,  the  ventricular  contraction  is  visibly 
prolonged  and  after  a  short  rise  (b  c)  exhibits  a  series  of  indentations  (c  e)  caused 
by  the  mass  of  blood  forcing  its  way  through  the  stenotic  and  roughened  entrance 
to  the  aorta. 

Fig.  F  represents  the  apex-beat  in  a  case  of  insufficiency  of  the  mitral  valve; 
a  b  is  well  marked  in  consequence  of  the  increased  activity  of  the  left  ventricle; 
the  shock  (d)  caused  by  the  closure  of  the  aortic  valves  is  slight  on  account  of 
the  diminished  tension  in  the  arterial  system.  On  the  other  hand,  the  shock  of 
the  accentuated  pulmonic  second  sound  (e)  stands  like  a  huge  accent  high  upon 
the  summit  of  the  curve.  In  consequence  of  the  tension  in  the  pulmonary  artery 


FIG.  33.  —Various  Forms  of  Pathological  Apex-beat  Curves.  In  all  of  these  curves  a  b  indicates  the  auricular 
contraction;  b  c,  the  ventricular  contraction;  d,  the  close  of  the  aortic  semilunar  valves;  e,  that  of  the  pul- 
monary valves;  e  f,  the  time  occupied  by  the  relaxation  of  the  ventricles. 

the  pulmonary  second  sound  may  be  so  accentuated  and  it  may  follow  so  quickly 
after  the  second  aortic  sound  (d)  that  the  two  almost  or  quite  coincide  (H  and  K) . 

The  curve  in  a  case  of  stenosis  of  the  left  auriculo-ventricular  orifice  (G) 
presents  first  of  all  a  long,  irregular,  indented  auricular  contraction  (a  b) ,  due  to 
the  fact  that  the  blood  is  forced  through  the  narrow  orifice  with  considerable 
agitation  and  friction.  The  ventricular  contraction  (b  c)  is  feeble  on  account  of 
the  imperfect  filling  of  the  left  chamber.  The  closures  of  the  two  valves  d  and  e 
are  separated  by  a  comparatively  long  interval  and  the  ear  distinctly  hears  a 
duplicated  second  heart-sound.  The  aortic  valves  close  rapidly  because  the  aorta 
receives  only  a  small  amount  of  blood,  while  the  more  abundant  flow  of  blood 
into  the  pulmonary  artery  causes  retarded  closure  of  the  pulmonary  valves. 

When  the  heart-beats  are  rapid  and  weak  and  the  tension  in  the  aorta  and 
the  pulmonary  artery  is  low,  the  signs  of  closure  of  the  valves  in  the  latter 


110  THE    HEART-SOUNDS. 

may  be  entirely  obliterated,  as  in  curve  L  taken  from  a  girl  with  exophthalmic 
goiter  who  suffered  from  nervous  palpitation  of  the  heart. 

In  rare  cases  of  mitral  insufficiency — a  condition  in  which  the  right  ventricle 
is  greatly  overfilled  with  blood,  while  the  left  contains  but  little,  so  that  the  right 
has  to  work  harder  to  empty  itself  than  does  the  left — a  peculiar  action  of  the 
heart  has  been  observed,  both  ventricles  appearing  at  times  to  contract  together 
and  then  again  the  right  ventricle  alone  (Fig.  M  after  Malbranc) .  Curve  I ,  which 
appears  in  every  respect  like  a  normal  apex-beat  curve,  was  taken  when  the  entire 
heart  was  active;  there  was  present  an  arterial  pulse  corresponding  to  this  apex- 
beat.  Curve  II,  on  the  other  hand,  appears  to  have  been  recorded  by  the  right 
heart  alone,  and  it  accordingly  lacks  the  closure  of  the  aortic  valves  (d) ;  nor 
was  there  an  arterial  pulse  corresponding  to  this  contraction. 

With  respect  to  the  cases  just  considered  Landois  expressed  the  opinion  as 
early  as  1879  that  the  phenomenon  could  not  be  explained  on  the  mere  supposition 
that  the  right  ventricle  alone  is  active  during  the  phases  in  question,  without  any 
parallel  action  on  the  part  of  the  left.  He  regarded  such  a  condition  as  impossible, 
if  for  no  other  reason  because  of  the  common  arrangement  of  the  muscles  in  the 
two  ventricles  and  their  equally  common  innervation.  The  period  of  apparent 
rest  of  the  left  ventricle  is  probably  no  more  than  a  period  of  exceedingly  feeble 
action,  not  strong  enough  to  record  itself  in  the  apex-beat  curve  by  the  closure 
of  the  aortic  valves  and  by  a  pulse  in  the  arteries.  This  supposition  has  in  fact 
been  confirmed  by  Riegel  and  Lachmann,  Eger,  Eichhorst,  Stern,  H.  E.  Hering, 
and  others. 

THE  HEART-SOUNDS. 

On  listening  over  the  region  of  the  heart,  either  directly  with  the 
ear  applied  to  the  thorax,  or  with  the  aid  of  the  stethoscope,  or  in  ani- 
mals to  the  exposed  heart,  two  sounds  are  audible  that  really  do  not 
deserve  the  name  of  tones,  but  which  in  contradistinction  from  pathologi- 
cal heart-murmurs  are  designated  heart-sounds.  As  they  possess  a  cer- 
tain tonal  color,  it  has  been  possible  to  determine  their  musical  pitch. 

The  first  sound  of  the  heart  is  somewhat  duller,  longer,  and  lower 
in  pitch  by  a  third  or  fourth,  fluctuating  between  d  sharp  and  g,  not 
clearly  denned,  especially  at  the  beginning,  and  synchronous  with  the 
ventricular  systole.  The  second  sound  of  the  heart  is  clearer,  more 
valvular,  shorter,  and  therefore  more  distinctly  marked,  varying  between 
f  sharp  and  b  flat,  clearly  defined,  and  synchronous  with  the  closure  of 
the  semilunar  valves.  The  first  sound  is  separated  from  the  second 
by  a  short  interval,  and  the  second  sound  from  the  succeeding  first 
sound  by  a  longer  interval.  In  musical  parlance  the  first  sound  appears 
as  a  rising  beat  to  the  second,  which  is  then  followed  by  the  pause. 
The  vibration-values  and  the  rhythm  may  accordingly  be  expressed 
as  follows : 

Y 


Bu  -  tup  (lub-dup)  Bu'-  tup  (lub-dup) 

The  first  sound  is  caused  by  two  factors.  As  it  is  heard,  though 
faintly,  in  excised  hearts  in  which  the  auriculo- ventricular  valves  are 
prevented  from  being  stretched  and  relaxed,  and  as  it  is  heard  also 
when  the  movement  and  closure  of  the  valves  are  prevented  by  means 
of  a  finger  introduced  into  the  auriculo- ventricular  orifice,  the  principal 
cause  of  the  sound  is  to  be  sought  in  the  muscular  murmur,  produced  by 
the  contracting  muscular  fibers  of  the  ventricles. 


THE    HEART-SOUNDS. 


Ill 


The  sound  is  augmented  and  reinforced  by  the  tension  and  vibra- 
tions of  the  auriculo-ventricular  valves  and  their  tendinous  bands  at 
the  instant  of  ventricular  contraction. 

Wintrich,  in  1873,  succeeded  by  the  use  of  suitable  resonators  in  dis- 
tinguishing one  sound  from  the  other;  the  clearer  and  shorter  valvular 
sound  from  the  deeper  and  more  protracted  muscular  tone. 


FIG.  34. — Topography  of  the  Thorax  and  of  the  Thoracic  Viscera:  a.  d.,  right  auricle;  o.  s.,  left  auricle;  v.  d., 
right  ventricle;  I,  left  ventricle  with  It  apex  of  the  heart;  A,  aorta;  II,  pulmonary  artery;  C,  superior  vena 
cava;  L  L,  boundaries  of  the  lungs;  P  P,  boundaries  of  the  parietal  pleura  (v.  Luschka  and  v.  Dusch). 

Under  pathological  conditions,  such  as  typhoid  fever  and  fatty  heart,  in  which 
the  heart-muscle  is  greatly  enfeebled,  the  first  sound  of  the  heart  may  be  inaudible. 
In  the  presence  of  insufficiency  of  the  aortic  valves,  when,  owing  to  the  regurgita- 
tion  of  the  blood  from  the  aorta  into  the  ventricle,  the  mitral  valve  is  made  tense 
gradually  and  before  the  ventricular  systole  begins,  the  first  sound  of  the  heart 
is  also  not  infrequently  absent.  Both  of  these  pathological  instances  prove  that 
the  cooperation  of  muscle-tone  and  valve-tone  is  required  for  the  production  of 
the  first  sound  of  the  heart  and  that  when  one  of  these  elements  is  lost  the  heart- 
sound  may  become  inaudible.  It  should  further  be  mentioned  that  the  vibra- 
tions of  the  semilunar  valves  before  or  during  their  closure  and  the  vibrations 
of  the  fluid  elements  of  the  blood  itself  have  been  adduced  as  contributory  factors 
in  the  explanation  of  the  first  sound  of  the  heart. 


112  ABNORMALITIES    OF    THE    HEART-BEAT. 

The  cause  of  the  second  sound  of  the  heart,  according  to  the  gener- 
ally accepted  view,  is  the  abrupt  closure  of  the  semilunar  valves.  It 
is,  therefore,  said  to  be  chiefly  a  valvular  sound.  It  is,  however,  in  part 
due  also  to  a  sudden  concussion  of  the  fluid  particles  in  the  large  arterial 
vessels. 

Landois  has  shown  from  apex-beat  curves  taken  from  healthy  in- 
dividuals that  the  semilunar  valves  of  the  aorta  and  those  of  the  pul- 
monary artery  do  not  close  at  the  same  time.  As  a  rule,  however,  the 
difference  in  time  is  so  slight  that  the  two  sets  of  valves  generate  only 
one  sound.  On  the  other  hand,  if,  owing  to  increase  of  the  difference 
in  pressure  in  the  aorta  and  in  the  pulmonary  artery,  this  interval  be- 
comes greater,  a  duplication  or  splitting  of  the  second  sound  may  become 
quite  perceptible.  This  may  occur  in  perfectly  healthy  individuals, 
especially  at  the  end  of  inspiration  or  at  the  beginning  of  expiration. 
It  is  important  to  remember,  however,  that  although  the  second  sound 
corresponds  with  the  closure  of  the  semilunar  valves,  it  appears  proved 
that  the  closure  itself  gives  rise  to  no  sound ;  it  is  only  an  instant  later, 
when  the  tension  of  the  valves  becomes  greater,  that  the  second  sound 
becomes  audible. 

It  is  generally  believed  that  the  points  on  the  chest-wall  at  which  the  heart- 
sounds  are  heard  most  distinctly  on  auscultation  correspond  to  the  points  in  the 
neighborhood  of  which  they  are  produced. 

The  first  valvular  sound  produced  at  the  right  auriculo-ventricular  orifice  is 
heard  most  distinctly  at  the  junction  of  the  fifth  rib  with  the  sternum  on  the 
right  side,  and  is  transmitted  from  that  point  somewhat  inward  and  obliquely 
upward  along  the  sternum  (Fig.  34,  i).  As  the  left  auriculo-ventricular  orifice  is 
directed  more  posteriorly,  toward  the  interior  of  the  thorax,  and  is  covered  in 
front  by  the  arterial  orifices,  the  first  mitral  valvular  sound  is  heard  best  at  the 
apex  or  immediately  above  it,  where  a  strip  of  the  left  auricle  is  in  immediate 
contact  with  the  chest-wall  (1^  I) .  As  the  orifices  of  the  aorta  and  pulmonary 
artery  are  so  close  together,  it  is  advisable  to  listen  for  the  aortic  second  heart- 
sound  in  the  prolongation  of  the  axis  of  the  aorta,  that  is,  at  the  right  border 
of  the  sternum,  at  the  inner  extremity  of  the  right  costal  cartilage  (at  2).  The 
pulmonic  second  heart-sound  is  heard  most  distinctly  in  the  second  left  intercostal 
space  a  little  to  the  left  and  beyond  the  edge  of  the  sternum  (at  II).  The  aortic 
second  sound  is  clearer,  sharper,  and  shorter,  and  is  heard  over  a  larger  area  than 
the  pulmonic  second  sound. 

To  determine  the  intensity  of  the  heart-sounds  quantitatively  H.  Vierordt 
inserts  between  the  chest-wall  and  the  ear  a  series  of  solid  rubber  plugs,  which 
are  poor  conductors  of  sound,  placed  one  upon  the  other  in  the  form  of  a  column. 

ABNORMALITIES  IN  THE  HEART-BEAT. 

Accentuation  of  the  first  sound  of  the  heart  in  both  ventricles  indicates  a 
more  powerful  contraction  of  the  ventricular  muscle  and  a  consequent,  sudden,  and 
increased  tension  of  the  auriculo-ventricular  valves. 

Accentuation  of  the  second  sound  is  a  sign  of  increased  tension  in  the  interior 
of  the  corresponding  large  vessels.  Hence  accentuation  of  the  pulmonic  second 
sound,  which  is  such  an  important  diagnostic  sign,  always  indicates  hyperemia 
and  excessive  tension  in  the  lesser  circulation. 

Feeble  heart-sounds  are  caused  by  sluggish,  weakened  heart-action  or  abnormal 
ischemia;  they  are  observed  particularly  in  cases  of  morbid  degeneration  of  the 
heart-muscle.  The  cause  of  weakness  of  individual  heart-sounds  can  be  deduced 
from  the  foregoing  explanation. 

The  term  embryocardia  is  used  when  the  two  sounds  of  the  heart  are  exactly 
alike  with  respect  to  strength  and  the  intervals  between  heart-beats,  resembling 
the  ticking  of  a  clock;  the  phenomenon  indicates  weakening  of  the  heart-muscle. 

Irregularities  in  the  structure  of  individual  valves  may  render  the  heart- 
sounds  impure  by  causing  irregular  vibrations.  When  pathological  cavities  filled 
with  air  are  present  in  the  immediate  neighborhood  of  the  heart,  they  may  act  as 


DURATION    OF    THE    MOVEMENT    OF    THE    HEART.  113 

resonators  and  reinforce  the  heart-sounds,  so  that  the  latter  often  assume  a 
metallic,  ringing  character.  Both  the  first  and  the  second  heart-sound  may  be 
duplicated  or  split.  Duplication  of  the  first  sound  of  the  heart  is  explained  by 
failure  of  the  tricuspid  and  mitral  valves  to  contract  at  the  same  time.  Some- 
times a  sound  may  be  heard  that  is  caused  by  the  contraction  of  a  well-developed 
auricle  and  precedes  the  first  sound  like  a  presystolic  murmur.  As  the  closure  of 
the  aortic  valves  does  not  coincide  exactly  with  that  of  the  pulmonary  valves, 
duplication  or  splitting  of  the  second  sound  merely  represents  an  exaggeration  of 
physiological  conditions.  All  factors  that  cause  acceleration  in  the  closure  of  the 
aortic  valves — such  as  ischemia  of  the  left  ventricle — and  retardation  in  the  closure 
of  the  pulmonary  valves — such  as  the  presence  of  an  excessive  quantity  of  blood 
in  the  right  ventricle,  and  both'  factors  together  when  there  is  stenosis  of  the 
left  auriculo- ventricular  orifice — favor  duplication  of  the  second  sound. 

When  the  valves  of  the  heart  are  the  seat  of  irregularities  in  association  with 
either  stenosis  or  insufficiency,  throwing  the  blood-stream  into  eddies  or  oscilla- 
tions or  producing  friction,  the  heart-sounds  are  replaced  by  murmurs,  that  is, 
sounds  produced  by  the  fluids  and  always  associated  with  "circulatory  disturb- 
ances and  the  valvular  changes  referred  to.  It  is  rare  for  deposits  and  new-growths 
projecting  into  the  ventricle  to  give  rise  to  murmurs  in  the  absence  of  valvular 
lesions  or  circulatory  disturbances.  Heart-murmurs  are  always  associated  with 
the  systole  or  diastole.  As  a  rule,  systolic  murmurs  are  louder  and  more  accentu- 
ated than  diastolic.  Sometimes  they  are  so  loud  that  even  the  thorax  is  thrown 
into  vibration — purring  tremor. 

Diastolic  murmurs  always  depend  on  structural  changes  in  the  mechanism  of 
the  heart,  such  as  insufficiency  of  the  arterial  valves  or  stenosis  of  the  venous 
orifices  (usually  on  the  left  side  only).  Systolic  murmurs  are  not  always  due  to 
disturbances  of  the  cardiac  mechanism.  In  the  left  heart  systolic  murmurs  may 
be  caused  by  insufficiency  of  the  mitral  valve,  stenosis  at  the  aortic  orifice  and 
by  calcification  or  abnormal  dilatation  affecting  the  ascending  aorta.  Systolic 
murmurs  in  the  right  heart,  which  are  much  more  rare,  are  due  to  insufficiency 
of  the  tricuspid  valve  or  stenosis  at  the  pulmonary  orifice. 

Systolic  murmurs  are  often  present,  although  never  so  loud,  in  cases  without 
any  valvular  lesion,  being  caused  by  abnormal  vibration  of  the  valves  or  of  the 
walls  of  the  arteries.  They  are  heard  most  frequently  at  the  pulmonary  orifice, 
next  at  the  mitral,  and  more  rarely  at  the  aortic  and  tricuspid  orifices.  Anemia 
and  acute  febrile  affections  are  the  causes  of  these  murmurs. 

Heart-murmurs  are  sometimes  produced  by  the  friction  of  opposed  roughened 
surfaces  of  the  inflamed  pericardium  (friction-murmurs) .  The  friction-sound  may 
be  both  audible  and  palpable. 

DURATION  OF  THE  MOVEMENT  OF  THE  HEART. 

The  excised  heart  continues  to  beat  independently  for  a  time:  in 
cold-blooded  animals  for  a  long  period,  even  for  days,  in  warm- 
blooded animals  for  a  much  shorter  time.  The  last  vestige  of  cardiac 
action  has,  however,  been  observed  in  the  rabbit  after  15^  hours,  in  the 
mouse  after  46^  hours,  in  the  dog  after  96^  hours,  and  in  a  three-months- 
old  human  embryo  after  4  hours.  The  contraction  of  the  excised  heart 
may  be  reinforced  and  accelerated  by  irritation.  The  contraction  of  the 
ventricle  first  becomes  enfeebled,  and  it  is  further  observed  that  the 
contraction  of  the  auricle  is  not  always  followed  by  a  ventricular  systole, 
two  or  more  auricular  contractions  being  succeeded  by  only  one  feebler 
ventricular  movement.  The  contractions  of  the  ventricles,  in  addition 
to  being  more  infrequent,  require  a  longer  time  for  their  completion, 
and  give  the  impression  of  being  labored  and  sluggish  (Fig.  30).  Later, 
the  ventricles  cease  to  contract  altogether  and  only  the  auricles  continue 
to  beat  feebly.  Direct  irritation  of  the  ventricles,  however,  as  by  a 
prick,  is  followed  by  a  single  contraction.  Still  later  the  left  auricle 
ceases  while  the  right  auricle  continues  to  beat,  and  it  is  the  right 
auricular  appendage  that  continues  to  beat  the  longest,  being  accord- 
ingly known  to  the  ancients  as  "ultimum  moriens."  The  same  obser- 
8 


114  THE    CARDIAC    NERVES. 

vation  has  been  made  in  executed  criminals.  In  the  opened  heart  the 
papillary  muscles  fail  to  contract  synchronously  with  the  auricular  wall 
after  from  two  to  three  minutes.  Engelmann  made  the  interesting 
observation  that  the  muscles  of  the  auricle  may  lose  their  power  of 
contracting,  in  response  to  irritation  of  the  vagus  or  as  a  result  of  immer- 
sion and  swelling  in  water,  without  losing  the  power  of  conducting 
stimuli.  An  analogous  phenomenon  has  been  observed-  with  respect 
to  the  nerves. 

After  the  heart  has  ceased  beating  altogether,  it  can  be  temporarily 
roused  by  direct  stimulation,  especially  by  heat;  and  again  the  auricles 
and  auricular  appendages  are  the  last  to  react.  As  a  rule,  when  the  heart 
has  been  temporarily  stimulated  to  greater  activity  it  ceases  to  beat  the 
earlier;  before  the  orderly  succession  of  beats  ceases  altogether  tremu- 
lous, "undulating"  movement  of  the  muscle-bundles  usually  takes 
place.  In  mammals,  when  the  irritability  of  the  heart  has  ceased,  it 
can  be  temporarily  restored  by  injecting  arterial  blood  into  the  coronary 
vessels.  In  the  frog  the  heart,  which  at  first  becomes  rigid,  may  be 
revived  by  filling  its  cavities  with  fresh  blood.  As  the  heart  uses  up 
oxygen  and  eliminates  carbon  dioxid,  it  is  quite  conceivable  that  it 
should  beat  longer  in  oxygen  than  in  nitrogen,  hydrogen,  carbon  dioxid, 
hydrogen  sulphid  or  in  a  vacuum,  even  when,  to  avoid  desiccation, 
aqueous  vapor  is  generated  in  the  vacuum.  When  the  heart,  after  it 
has  ceased  to  beat,  is  returned  to  a  medium  containing  oxygen,  it 
begins  to  beat  again. 

THE  CARDIAC  NERVES. 

The  cardiac  plexus  is  formed  by :  i .  The  cardiac  branches  of  the  trunk  of  the 
vagus  nerve ;  these  include  cardiac  branches  from  the  external  branch  of  the  supe- 
rior laryngeal  nerve,  the  inferior  laryngeal  nerve,  and  sometimes  the  pulmonary 
branches  of  the  vagus,  in  larger  number  on  the  right  than  on  the  left  side.  2.  The 
superior,  middle,  inferior,  and  lowest  cardiac  branches  from  the  three  cervical 
ganglia  and  the  first  thoracic  ganglion  of  the  sympathetic  nerve,  which  frequently 
vary  in  number  and  in  size  (sometimes  one  of  the  branches  accompanies  the 
descending  branch  of  the  hypoglossus  for  a  part  of  its  course) .  The  branches  of 
the  plexus  are  the  deep  and  the  superficial  nerves;  the  latter  usually  contain  a 
ganglion  at  the  bifurcation  of  the  pulmonary  artery  beneath  the  arch  of  the  aorta. 
The  following  structures  are  regarded  as  belonging  to  the  cardiac  plexus: 

(a)  The  right  and  left  coronary  plexuses,  which  convey  the  vasomotor  nerves 
of  the  coronary  vessels  through  the  vagus  portion  and  the  dilators  through  the 
sympathetic;  and  in  addition  contain  sensory  fibers  derived  from  the  vagus  and 
passing  principally  to  the  pericardium.  In  patients  suffering  from  disease  of  the 
heart  the  presence  of  sensory  nerves  is  indicated  by  the  occurrence  of  constant 
or  paroxysmal  pain.  In  the  frog,  reflex  phenomena  may  be  induced  from  the 
ventricle  in  the  various  portions  of  the  heart,  and  they  probably  have  their  reflex 
center  in  the  medulla  oblongata. 

(6)  The  nerves  embedded  in  the  heart-muscle  and  in  the  furrows,  which  are 
richly  supplied  with  ganglia  and  which  have  been  designated  the  automatic 
motor  centers  of  the  heart.  The  heart  contains  a  circle  of  nerves  richly  supplied 
with  ganglia  at  the  edge  of  the  interauricular  septum  and  another  at  the  junction 
of  the  auricles  and  the  ventricles.  Wherever  the  two  meet  they  exchange  fibers. 
The  ganglia  are  for  the  most  part  found  near  the  pericardium.  In  mammals  the 
two  larger  ganglia  are  situated  close  to  the  orifice  of  the  superior  vena  cava;  in 
birds  the  largest  node  of  nerve-tissue,  containing  thousands  of  ganglia,  occupies 
the  posterior  point  of  decussation  of  the  longitudinal  and  transverse  sulci.  These 
nodes  of  nerve-tissue  send  smaller  branches  into  the  muscular  walls  of  the  auricles 
and  ventricles,  and  these  branches  in  turn  are  the  seat  of  smaller  ganglia. 

In  the  frog  a  large  collection  of  ganglia,  Remak's  ganglion,  is  situated,  together 
with  the  vagus  fibers,  within  the  wall  of  the  sinus  of  the  vena  cava  (the  dilated 
orifice  of  the  venag  cavas  in  the  right  auricle  whose  independent  movement  pre- 


IRRITABILITY    OF    THE    AUTOMATIC    MOTOR    CENTERS.  115 

cedes  that  of  the  auricles).  From  this  ganglion  the  vagus  fibers  pass  as  the 
anterior  and  posterior  septal  nerves,  each  of  which  is  provided  with  a  ganglion  at 
the  auriculo-ventricular  junction,  the  ventricular  ganglion,  or  Bidder's  ganglion. 
The  nerve-fibers,  which  are  for  the  most  part  non-medullated,  can  be  traced 
further  in  connection  with  the  ganglia. 

The  motor  fibers  terminate  with  slightly  clubbed  extremities  in  each  muscle- 
cell;  the  sensory,  which  are  derived  from  medullated  fibers,  in  flat,  expanded 
terminal  plexuses,  which  are  quite  abundant  in  the  endocardium  and  the  peri- 
cardium. 

All  ganglion-cells  are  bipolar  or  multipolar.  In  the  frog  most  of  them  are 
surrounded  by  a  network  of  fibers;  in  Bidder's  ganglion  spindle-shaped  cells  with 
two  processes,  one  at  each  extremity,  predominate.  In  the  rabbit  and  in  the  frog 
the  ganglion-cells  belonging  to  the  sympathetic  system  have  two  nuclei,  while  the 
vagus  ganglia  have  only  one.  After  division  of  the  vagus  branches  (in  the  frog) 
the  spiral  process  and  the  pericellular  network  from  which  it  originates  undergo 
degeneration.  The  straight  process  gives  off  the  muscle-nerves.  The  bulb  of  the 
aorta  contains  numerous  nerves  for  its  muscle-fibers;  but  whether  it  contains 
ganglia  also  is  doubtful. 

IRRITABILITY   OF   THE   AUTOMATIC   MOTOR   CENTERS   IN   THE 
HEART  AND  IN  THE  HEART-MUSCLE. 

There  are  at  the  present  time  only  two  theories  with  regard  to  the 
irritability  of  the  heart  and  its  spontaneous  rhythmic  action. 

1.  The  older   theory  teaches    that    the  "automatic    centers"  that 
excite  the  movements  and  maintain  an  orderly  rhythm   are   situated 
within  the  heart  and  that  this  function  resides  in  the  ganglia. 

2.  It  is  assumed  that  not  one  but  several  such  centers  are  present 
in  the  heart  and  are  connected  with  one  another  by  conducting  paths. 
So   long   as   the   heart   is   intact   the  various    centers    are    stimulated 
to  rhythmic  activity  in  a  definite  order  from  the  principal  center,  the 
impulse  being  conveyed  through  the  conducting  paths  from  that  center. 
The  forces  that  excite  these  regular  continuous  movements  are  not  known. 
If,  however,  diffuse  stimuli,  of  which  the  simplest  is  a  strong  electrical 
current,  are  applied  to  the  heart,  all  of  the  centers  are  thrown  into  action 
and   a  spasmodic   contraction   of  the  heart  takes  place  without   any 
rhythm  of  movement.     The  dominating  center  is  situated  in  the  auri- 
cles (in  the  frog),  whence,  therefore,  the  regular  progressive  movements 
usually   proceed.     When   its   irritability   is   reduced,    as   by    applying 
opium  to  the  septum  with  a  cotton  pledget,  a  different  set  of  centers 
appears  to  gain  control,  and  the  movement  may  then  be  propagated 
from  the  ventricles  to  the  auricles. 

3.  The  nerve-centers  of  the  auricles  are  more  irritable  than  those  of 
the  ventricles;  hence  they  continue  to  beat  independently  for  a  longer 
time  when  the  heart  is  left  to  itself. 

4.  All  stimuli  of  moderate  strength  acting  directly  on  the  heart  cause 
primarily  an  increase  in  the  rhythmic   heart-beats;    stronger   stimuli 
cause,  in  a  short  while,  diminution  progressing  to  paralysis,  often  pre- 
ceded by  spasmodic  tremulous  "undulation  or  flickering."     Increased 
activity  on  the  part  of  the  heart  exhausts  its  strength  the  more  rapidly. 

5.  Individual  weak  stimuli,  such  as  are  insufficient  to  exert  any  effect 
on  the  heart,  may  be  rendered  efficient  by  repetition,  as  the  heart  is 
capable  of  summation  of  the  individual  stimuli. 

6.  Even  the  feeblest  stimuli  that  are  at  all  capable  of  exciting  a 
contraction  always  excite  an  active  contraction,  that  is,  "the  minimal 
stimulus  has  a  maximal  effect." 


Il6  IRRITABILITY    OF    THE    AUTOMATIC    MOTOR    CENTERS. 

7.  Each  contraction  of  the  heart  is  followed  by  a  short  period  during 
which  the  heart  is  less  susceptible  to  subsequent  stimuli  (Marey's  re- 
fractory period)  and  the  conducting-power  of  the  muscle-substance  is 
reduced. 

8.  Stimulation  of  the  heart-centers,  apparently  reflex,  takes  place 
on  the  inner  surface  of  the  heart.     Feeble  stimuli  from  this  surface  are 
more  effective  in  accelerating  and  exciting  the  action  of  the  heart  than 
stimuli  from  the  external  surface  of  the  heart.     Stronger  stimuli,  which 
cause  arrest  of  the  heart,  also  act  more  readily  from  the  internal  than 
from  the  external  surface  of  the  heart;  under  such  conditions  also  the 
ventricular  portion  is  always  first  to  be  paralyzed. 

9.  Portions  of  the  heart  that  are  devoid  of  ganglia  are  incapable  of 
independent  movement  unless  a  stimulus  be  applied ;  they  contract  only 
once  to  a  single  direct  stimulus,  or  they  may  beat  rhythmically  if  the 
stimuli  are  applied  continuously.     Such  a  stimulus  may  be  provided  by 
the  continuous  pressure  of  fluid  within  the  cavities  of  the  heart  or  by 
means  of  chemical  agents  brought  in  contact  with  the  heart. 

10.  The  pulsations  of  stimulated  portions  of  the  heart  devoid  of 
ganglia  indicate  that  the  ganglia  are  not  absolutely  necessary  for  the 
production  of  rhythmic  contractions ;  but  the  ganglia  are  more  irritable 
than  the  muscle  itself.     They  control  also  the  regular  alternating  action 
of  the  various  portions  of  the  heart,  so  that  normal  cardiac  action  must 
be  regarded  as  under  the  control  of  the  ganglia. 

11.  If  the  heart  be  cut  in  such   a  way  that   the   individual   pieces 
remain  in   communication,  the  regular   contractions   beginning  in  the 
auricles   and   propagated   in   peristaltic   or  undulating  movements   to 
the  ventricles  persist  for  some  time.     When,   however,  the  heart  is 
completely  divided  into  two  pieces,  auricle  and  ventricle,  the  movements 
of  both  continue  separately — naturally,  no  longer  in  orderly  succession, 
but  quite  independently. 

The  principal  experiments  on  which  the  foregoing  propositions  are  based  are 
as  follows: 

Experimental  Division  and  Ligation  of  the  Heart. — These  experiments  have 
been  performed  chiefly  on  frogs'  hearts.  Ligation  differs  from  division  in  the  fact 
that  the  physiological  connection  is  destroyed  by  drawing  a  ligature  tightly  around 
the  parts  and  loosening  it  again,  while  the  anatomical  continuity  of  the  heart -wall 
and  the  integrity  of  the  cavities  of  the  heart  are  maintained. 

i.  Stannius'  Experiment. — After  separation  in  a  frog's  heart  of  the  sinus  of 
the  venae  cavae  from  the  auricle,  either  by  incision  or  by  constriction,  the  heart 
is  arrested  in  diastole,  while  the  sinus  continues  to  beat  independently.  If  the 
heart  be  again  divided  at  the  auriculo- ventricular  junction,  the  ventricle,  as  a 
rule,  begins  at  once  to  beat  again,  while  the  auricles  continue  in  diastolic  arrest. 
In  accordance  with  the  position  of  the  second  line  of  division  the  auricles  may 
continue  to  beat  in  association  with  the  ventricles,  or  the  auricles  alone  may 
contract,  while  the  ventricles  remain  at  rest. 

The  experiment  has  been  interpreted  in  the  following  manner:  The  sinus  of 
the  venae  cavae  contains  Remak's  ganglion,  which  is  remarkable  for  its  extreme 
irritability,  while  Bidder's  ganglion,  which  is  situated  at  the  auriculo-ventricular 
junction,  possesses  a  lesser  degree  of  irritability.  In  the  normal  heart  the  latter 
receives  its  motor  impulses  from  the  former.  Wnen  the  sinus  of  the  venae  cavse 
is  severed,  the  stimulating  Remak's  ganglion  is  without  any  influence  on  the  heart. 
The  latter  becomes  arrested  for  two  reasons:  because  Bidder's  ganglion  by  itself 
does  not  possess  .sufficient  power  to  set  the  heart  in  motion,  and  because  the 
division  stimulates  the  inhibitory  nerves  of  the  heart  (vagus),  which  are  situated 
at  this  point.  Pulsation  can,  however,  be  induced  in  a  heart  that  has  been  ar- 
rested in  this  way  by  irritation  of  Bidder's  ganglion,  as  by  gently  pricking  the 
auriculo-ventricular  junction,  or  by  the  passage  of  a  moderately  strong  constant 


IRRITABILITY    OF' THE    AUTOMATIC    MOTOR    CENTERS.  117 

current.  In  the  latter  event  the  ventricular  beat  sometimes  precedes  that  of  the 
auricles.  If,  now,  the  auriculo-ventricular  junction  be  divided,  the  ventricle 
begins  to  pulsate,  partly  because  the  procedure  stimulates  Bidder's  ganglion,  and 
partly  because  the  heart  is  no  longer  under  the  influence  of  the  vagus,  which  had 
been  stimulated  by  the  first  division.  If  the  division  at  the  auriculo-ventricular 
junction  is  made  in  such  a  way  as  to  leave  Bidder's  ganglion  in  the  auricle,  the 
latter  would  pulsate  and  the  ventricle  remain  at  rest;  if  the  ganglion  is  divided 
into  two  halves,  both  the  auricles  and  the  ventricles  pulsate,  because  each  is 
stimulated  by  its  own  half  of  the  ganglion. 

2.  When  the  ventricle  alone  is  divided  in  the  frog's  heart  by  ligature  or  in- 
cision at  the  auriculo-ventricular  furrow,  the  sinus  and  the  auricles  continue  to 
beat  undisturbed,  while  the  ventricle  is  arrested  in  diastole;  the  ventricle  responds 
to  a  local  irritant  with  a  single  contraction.     If  the  incision  is  made  in  such  a  way 
as  to  leave  the  lower  edge  of  the  interauricular  septum  attached  to  the  ventricle, 
the  latter  also  continues  to  pulsate.     In  the  case  of  the  rabbit's  heart,  also,  the 
ventricles  continue  to  pulsate  if  a  small  strip  of  the  auricles  is  preserved,  separated 
from  the  auricular  nerves. 

3.  Experiments  performed  by  A.  Fick  in  1874  first  showed  that  the  irritative 
process  in  the  contractile  tissue  of  the  frog's  heart  is  propagated  in  all  directions 
and  that  the  entire  frog's  heart  acts  in  a  measure  like  a  single  continuous  muscle- 
fiber.     Thus,  for  example,  a  transverse  incision,  involving  the  ventricle  of  the 
frog's  heart,  does  not  prevent  the  appended  flap  from  taking  part  in  the  systolic 
contraction.     This  is  shown  also  by  the  following  experiments  of  Engelmann.     If 
the  heart  is  cut  into  strips,  as  by  zigzag  incisions,  in  such  a  manner  that  the 
individual  pieces  remain  in  connection  with  one  another  by  means  of    muscle- 
substance,  the  strips  pulsate  in  regular  succession,  in  whatever  way  they  may  be 
connected  with  one  another,  as  a  result  of  the  direction  of  the  incisions.     The 
velocity  of  propagation,  under  such  circumstances,  is  from  ten  to  thirty  millimeters 
in  the  second.     These  experiments  also  confirm  the  observation  that  the  continuous 
stimulus  that  propagates  the  contraction  is  not  conducted  by  nerve-paths  but 
by  the  substance  of  the  contractile  mass. 

4.  When  the  apex  of  the  heart  has  been  separated  from  the  rest  of  the  organ 
by  a  ligature  it  ceases  to  take  part  in  the  contraction  of  the  heart,  which  continues 
to  pulsate;    a  direct  stimulus,  such  as  a  stab  of  the  apex,  is  followed' by  only  a 
single  contraction.     If  the  heart  is  filled  with  saline  solution  under  pressure  (both 
of  which  act  as  stimuli) ,  the  apex  will  continue  to  pulsate.     The  same  thing  is 
observed  after  poisoning  with  delphinin  or  quinin.     If  a  cannula  is  tied  in  the 
ventricle  from  a  point  above  the  auriculo-ventricular  junction  to  the  apex,  the 
latter  is  likewise  arrested;  if,  however,  the  apical  portion  is  filled  through  this 
cannula  with  oxygenated  blood  under  steady  pressure,  the  apex  will  pulsate. 

The  excised  apex  of  the  heart  resting  spontaneously,  when  stimulated  by 
induction-currents,  responds  to  the  weakest  efficient  stimulation  by  a  maximal 
contraction;  but  the  application  of  tetanizing  currents  is  not  followed  by  true 
tetanus.  Closing  and  opening  the  constant  current  applied  to  the  severed  apex 
give  rise  only  to  the  ordinary  closing  and  opening  contractions. 

5.  When  the  point  of  ligation  is  within  the  auricles,  the  pulsations  of  the 
heart  occur  in  successive  periods  (group -f ormation) ,  and  the  contractions  often 
increase  in  strength  by  regular  gradations  (stair-case  ascent) . 

6.  When  the  bulb  of  the  aorta,  which  is  devoid  of  ganglia,  is  isolated  by  con- 
striction (frog),  it  continues  to  pulsate  when  the  internal  pressure  is  moderate; 
after  it  has  ceased  beating,  a  single  stimulus  will  give  rise  to  a  series  of  renewed 
contractions.     The  number  of  contractions  is  increased  by  raising  the  temperature 
to  35°  C.  and  by  increasing  the  internal  pressure. 

7.  The  isolated  venae  cavae  and  their  sinuses  exhibit  normal  contractions.     If 
they  are  still  connected  with  the  heart  they  will   control  the  movements  of  the 
heart,  that  is,  contraction  of  the  entire  heart  may  be  induced  from  the  position 
of  each  of  the  large  veins  and  the  rhythm  of  the  heart  may  be  thus  influenced. 
Conduction  takes  place  only  through  the  muscle-substance  and  not  through  the 
nerves.     Porter  maintains  with  regard  to  the  hearts  of  the  dog  and  the  cat  that 
any  part  of  the  heart  that  is  excised  may  continue  to  pulsate  if  only  it  be  suffi- 
ciently nourished. 

In  opposition  to  the  doctrine  that  has  just  been  expounded,  namely 
that  the  stimulating  influence  is  sent  out  by  the  cardiac  ganglia,  it  may 
be  observed  that  this  theory  has  recently  begun  to  waver.  In  view  of  the 


Il8  DIRECT    STIMULATION    OF    THE    HEART. 

fact  that  the  embryonal  heart,  in  which  it  has  been  impossible  to  dem- 
onstrate the  presence  of  ganglia,  pulsates  like  the  heart  of  certain  inverte- 
brates, some  recent  investigators  assert  that  the  automatism  of  the  cardiac 
action  resides  in  the  muscle  itself.  Similarly,  His,  Jr.,  and  Romberg, 
on  developmental  grounds,  teach  that  the  ganglia  belong  really  to  the 
sensory  nerves  of  the  heart,  and  that,  therefore,  there  are  no  automatic 
nerve-centers  at  all.  When  Krehl  and  Romberg  isolated  portions  of 
the  rabbit's  heart  devoid  of  ganglia  by  crushing,  but  in  such  a  way  that, 
so  long  as  the  circulation  was  maintained,  they  represented  anatomical 
portions  of  the  heart,  they  found  that  these  pieces  continued  to  pulsate 
for  hours.  It  is  said  that  even  excision  of  the  entire  septum  of  the 
frog's  heart,  including  Remak's  ganglion,  has  no  disturbing  effect  on 
the  heart-beat. 

The  propagation  of  the  contraction  from  the  auricles  to  the  ventricles 
is  said  to  take  place  through  the  muscle-fibers  that  pass  from  the  former 
to  the  latter.  That  the  conduction  of  the  stimuli  from  auricle  to  ven- 
tricle, which  does  not  take  place  continuously,  but  periodically  in  the 
same  rhythm  as  the  heart-beats,  is  not  transmitted  through  the  nerve- 
paths  is  proved  by  the  slow  rate  at  which  it  is  effected,  the  conduction 
being  300  times  slower  than  in  motor  nerves. 

Engelmann  expresses  his  views  upon  these  questions  as  follows : 

The  muscle-cells  of  the  heart  itself  and  not  a  system  of  nerve-ganglia  constitute 
the  excito-motor  central  organ ;  as  such  they  generate  the  motor  stimuli  that  cause 
the  heart  to  beat.  As  those  muscle-cells  that  surround  the  large  veins  emptying 
into  the  heart  are  most  susceptible  to  the  irritating  influence  of  automatic  move- 
ment, the  systolic  contraction  occurs  first  at  this  point,  to  spread  then  in  a  peris- 
taltic manner  successively  to  the  auricles,  the  ventricles,  and  the  bulb  of  the 
aorta.  The  motor  stimulus  is  propagated  directly  from  muscle-cell  to  muscle-cell. 
All  of  the  muscle-cells  of  the  entire  heart  form  together  a  single  physiologically 
conducting  contractile  mass.  Within  each  individual  portion  of  the  heart-^- venous 
trunks,  venous  sinuses,  auricles,  ventricles,  bulb  of  the  aorta — the  motor  stimulus 
is  propagated  rapidly,  in  a  manner  comparable  to  the  contraction  of  a  striated 
muscle.  Those  muscle-cells,  on  the  other  hand,  that  form  the  connecting  bridges 
between  the  individual  portions  of  the  heart  conduct  slowly,  in  a  manner 
comparable  to  unstriated  or  embryonal  muscles.  Consequently  every  individual 
portion  of  the  heart  contracts  practically  at  the  same  time  as  a  whole;  while,  on 
the  other  hand,  the  systole  of  each  portion  of  the  heart  situated  farther  on  in 
the  course  of  the  blood-stream  can  take  place  only  after  an  actual  interval,  long 
enough  for  the  blood  to  be  carried  from  one  part  of  the  heart  into  the  next.  As 
the  fibers  of  the  heart-muscle,  in  the  act  of  contraction,  temporarily  lose  their 
contractility  and  conducting  power,  as  a  sort  of  fatigue-phenomenon,  they  contain 
within  themselves  the  periodicity  of  contraction  and  relaxation — systole  and  dias- 
tole. A  cycle  of  the  entire  heart  may  be  induced  from  any  point  in  the  large 
veins.  When  the  cardiac  stimuli  succeed  one  another  slowly,  each  individual  car- 
diac cycle  becomes  shorter,  but  more  powerful.  The  blood  is  then  propelled  in 
larger  quantities  and  with  greater  force;  while  if  the  succession  is  more  rapid, 
less  blood  is  propelled  with  a  lesser  degree  of  force. 

Direct  Stimulation  of  the  Heart. — All  direct  cardiac  stimuli  act  much  more 
vigorously  from  the  internal  than  from  the  external  surface  of  the  heart.  When 
the  stimulation  is  severe  or  protracted,  the  ventricular  portion  is  always  paralyzed 
first. 

(a)  Thermic  Stimuli. — Descartes  had  already  observed  in  1644  that  the  eel's 
heart  could  be  made  to  pulsate  more  rapidly  by  the  application  of  heat.  Alex.  v. 
Humboldt  explained  the  acceleration  of  the  pulse  that  takes  place  in  man  in  a 
hot  medium  in  the  same  way.  As  the  temperature  continues  to  rise,  the  heart- 
beats at  first  often  reach  a  considerable  frequency.  They  then  become  more 
infrequent  again,  and  finally  cease  altogether,  and  the  muscle  is  found  to  be  con- 
tracted. As  a  rule,  the  ventricular  portion  is  arrested  before  the  auricles,  some- 
times after  a  period  of  tetanic  undulatory  spasm.  At  a  temperature  of  25°  C. 
and  above,  the  ligated  frog's  heart  immersed  in  a  0.6  per  cent,  saline  solution, 


MECHANICAL    STIMULI.       ELECTRICAL    STIMULI.  119 

soon  becomes  arrested,  and  continues  at  rest  if  kept  at  this  temperature.  Up  to 
38°  C.  Landois  has  seen  it  recover  if  removed  quickly.  The  inner  surface  of  the 
heart  reacts  much  more  readily  to  all  degrees  of  temperature  than  the  external 
surface.  If  the  heart,  after  having  been  arrested,  is  removed  from  the  warm 
bath,  it  begins  to  beat  rapidly  after  a  pause,  which  may  be  interrupted  by  one  or 
two  beats,  the  frequency  gradually  diminishing  until  the  normal  rate  is  attained. 
If  the  ventricle  alone  is  heated,  the  frequency  of  pulsation  is  not  increased. 
The  volume  and  the  extent  of  the  cardiac  contractions  increase  up  to  a  tem- 
perature of  about  20°  C.,  and  beyond  that  point  they  begin  to  diminish  again. 
The  functional  power  increases  between  8°  and  33°  C.;  but  the  frequency  increases 
more  than  the  efficiency  of  the  pulsations.  The  duration  of  the  contraction  at 
20°  C.  is  only  about  one -tenth  of  what  it  is  at  5°  C.  The  heated  heart  reacts  to 
rapidly  intermittent  stimuli,  the  cold  heart  only  when  the  intervals  are  of  consid- 
erable length.  The  mammalian  heart  ceases  to  beat  at  from  44.5°  to  45°  C. 

As  the  heat  of  the  blood  diminishes,  the  heart  pulsates  more  slowly. 
When  a  frog's  heart  is  placed  on  ice  between  two  watch-glasses,  its  rate  diminishes 
considerably;  between  4°  C.  and  o°  C.  the  pulsations  of  the  frog's  heart  cease. 
When  a  frog's  heart  is  suddenly  removed  from  warm  water  and  placed  on  ice,  the 
beat  is  accelerated;  conversely,  when  it  is  transferred  from  ice  to  warm  water, 
the  beat  is  at  first  slowed  and  only  after  a  time  accelerated. 

(b)  Mechanical  Stimuli. — Pressure  applied  to  the  outside  of  the  heart   causes 
an  acceleration  of  the  cardiac  action.     In  man  also  light  pressure  applied  to  the 
auriculo-ventricular  junction  of  an  exposed  heart  gave  rise  to  a  secondary  shorter 
contraction  of  both  ventricles  following  each  heart-beat.     Heavy  pressure  causes 
an  irregular,  undulatory  contraction  of  the  muscle,  such  as  may  be  produced  by 
compressing  the  excised  heart  of  a  warm-blooded  animal  between    the    fingers. 
Increase  of  the  blood-pressure  in  the  interior  of  the  heart  effects  a  similar  accelera- 
tion, and  decrease  of  the  pressure  a  corresponding  diminution  in  the  number  of 
heart-beats.     When  the  intracardiac  pressure  is  excessive,  the  overstimulation 
results  in  irregularity  or  even  slowing  of  the  heart-beat.     A  resting  heart  that  is 
still  irritable  will  react  by  a  single  contraction  to  a  mechanical  impulse  (prick). 

(c)  Electrical  Stimuli. — A  moderately  strong  constant  current  passing  continu- 
ously through  the  heart  produces  an  increase  in  its  rate.     Ziemssen  succeeded  in 
accelerating  the  beat  of  an  exposed  heart  two-fold  or  three-fold  by  passing  a 
strong   galvanic   current   uninterruptedly   through   the   ventricles.     Exceedingly 
strong  constant  currents,  as  well  as  tetanizing  faradic  currents,  produce  tetanic 
undulatory  contractions  of  the  heart-muscle,  with  lowering  of  the  blood-pressure. 

If  the  ventricle  of  the  frog's  heart  has  been  permanently  relaxed  by  being 
clamped  at  the  auriculo-ventricular  junction,  and  one  electrode  of  a  constant 
current  is  applied  to  the  ventricular  wall,  and  the  other  to  any  portion  of  the 
trunk,  systolic  contraction  of  the  ventricle  takes  place  when  the  'current  is  closed 
only  if  the  kathode  is  placed  in  contact  with  the  ventricle;  conversely  when  the 
current  is  opened  only  if  the  anode  is  in  contact  with  the  heart-wall.  The  feeblest 
faradic  currents  accelerate  the  heart-beat;  stronger  currents  produce  irregularities, 
which  may  go  on  to  fibrillation. 

A  single  induction-impulse  applied  to  the  ventricle  in  systolic  contraction  has 
no  effect  either  in  the  frog  or  in  the  mammal.  When,  however,  it  is  applied  to 
the  ventricle  in  diastolic  relaxation,  the  succeeding  systole  takes  place  earlier.  The 
auricles  and  the  apex  of  the  heart,  which  is  devoid  of  ganglia,  but  may  be  excited 
to  activity  by  suitable  stimulation,  react  in  the  same  way.  During  their  systole 
an  induction-impulse  is  ineffective,  but  in  diastolic  rest  the  impulse  gives  rise  to  a 
contraction,  which  is  followed  by  a  ventricular  contraction.  Even  strong  tetan- 
izing induction-currents  applied  to  the  heart  are  unable  to  produce  tetanus  of  the 
entire  musculature.  There  develop  between  the  electrodes  localized,  white,  cylin- 
drical elevations,  as  in  the  muscles  of  the  intestines,  which  may  persist  for  several 
minutes.  After  severe  and  continued  tetanization  the  undulatory  contractions 
outlast  the  stimulus.  Also  the  isolated  apex  of  warm-blooded  animals  may  exhibit 
this  undulatory  contraction  only  so  long  as  the  stimulus  lasts.  The  heart  of  a 
previously  warmed  frog,  as  well  as  the  isolated  apex,  reacts  to  electric  stimuli  by 
flickering.  The  fibrillating  or  flickering  rabbit's  heart  often  returns  spontaneously 
to  its  normal  contractions,  the  dog's  heart  with  greater  difficulty.  After  the 
contractions  of  the  frog's  heart  have  become  weak  and  irregular,  they  can  be 
made  regular  and  isochronous  with  the  rhythm  of  the  stimulus  by  means  of  elec- 
tric stimuli  applied  in  rhythmical  succession.  The  feeblest  stimuli  that  are  at  all 
efficient  act  as  well  in  this  connection  as  the  strongest;  even  with  the  weakest 


120  CHEMICAL    STIMULI. 

stimulus  the  contraction  of  the  heart  is  the  most  vigorous  possible.  Hence,  this 
minimal  electrical  heart-stimulus  is  as  effective  as  a  maximal  stimulus. 

V.  Ziemssen  was  unable  even  with  strong  induction-currents  to  cause 
a  variation  in  the  rate  of  the  beat  of  the  exposed  human  heart.  The  ventricular 
diastole  alone  appeared  to  be  no  longer  complete,  and  in  addition  certain  minor 
irregularities  were  observed  in  the  contractions.  By  opening  and  closing  or  by 
reversing  a  strong  constant  current  applied  to  the  heart  of  a  woman,  it  was  possible 
to  increase  the  number  of  heart-beats,  and  the  increased  number  of  pulsations  cor- 
responded with  the  number  of  the  electrical  impulses.  For  example,  from  a 
normal  of  80  the  number  of  heart-beats  was  raised  to  from  120  to  140  to  180 
by  the  application  of  from  120  to  140  to  180  electrical  impulses.  Conversely,  it 
was  possible  also  to  reduce  the  normal  number  of  pulsations  from  80  to  60  or  50 
by  applying  an  equal  number  of  powerful  stimuli.  In  the  healthy  subject  also 
v.  Ziemssen  found  that  he  could  influence  the  rhythm  and  the  strength  of  the 
heart  by  applying  an  electrical  current  through  the  chest-wall. 

(d)  Chemical  Stimuli. — Many  chemical  agents,  particularly  when  applied  in  a 
state  of  dilution  to  the  inner  surface  of  the  heart,  increase  the  number  of  pulsa- 
tions, but  when  applied  in  concentrated  form  or  when  allowed  to  act  for  some 
time  diminish  the  number  or  paralyze  the  heart.  Bile  and  biliary  salts  diminish 
the  number  of  heart-beats,  as  does  also  absorption  of  the  bile  into  the  blood. 
In  dilute  solution,  however,  both  accelerate  the  action  of  the  heart.  The  same 
effect  is  produced  by  acetic,  tartaric,  citric  and  phosphoric  acids.  Chloroform  and 
ether  when  applied  to  the  inner  surface  of  the  heart  have  a  distinctly  retarding 
or  even  paralyzing  effect;  in  small  amounts  ether  accelerates  the  heart-beats. 
Opium,  strychnin,  alcohol,  and  chloral  hydrate  have  an  analogous  action.  Klug 
caused  blood  impregnated  with  various  gases  to  pass  through  the  frog's  heart  and 
found  that  sulphurous  acid,  chlorin-gas,  nitrous-oxid  gas,  hydrogen  sulphid  and 
carbon  monoxid  acted  as  heart-poisons.  In  the  same  way,  blood  saturated  with 
carbon  dioxid  exhausts  the  heart,  which,  however,  may  recover  if  the  carbon 
dioxid  escapes.  A  deficiency  of  oxygen  produces  a  grouped  rhythm,  in  the  same 
way  as  the  phenomena  of  asphyxiation  manifest  themselves  in  the  respiratory 
apparatus  in  grouped  movements. 

Rossbach  found  that  local  irritation  of  a  circumscribed  area  of  the  frog's 
ventricle  by  means  of  mechanical,  chemical,  or  electrical  stimuli  during  contraction 
causes  immediate  relaxation  in  partial  diastole  of  the  part  to  which  the  stimulus 
is  applied.  The  immediate  after-effect  of  this  form  of  irritation  is  a  permanent 
shrinking  of  the  irritated  portion  of  the  heart-fibers,  and  this  is  likewise  strictly 
confined  to  the  area  of  irritation.  The  shrunken  portion  ceases  to  functionate 
and  remains  permanently  robbed  of  its  vital  properties.  If  the  same  stimuli  are 
applied  during  diastole,  the  irritated  portion  relaxes  earlier  than  the  portion  that 
has  not  been  irritated,  and  the  diastole  of  the  irritated  portion  lasts  longer  than 
that  of  the  non-irritated  portion.  If  the  weakest  stimuli  are  allowed  to  act  for 
a  considerable  length  of  time  on  any  part  of  the  frog's  ventricle,  the  irritated 
portion  always  relaxes  earlier  than  the  non-irritated,  and  the  diastole  of  the 
irritated  portion  lasts  longer  than  that  of  the  non-irritated. 

Heart- poisons  comprise  such  substances  as  have  a  special  effect  in  diminishing 
or  abolishing  the  movements  of  the  heart.  In  this  respect  the  neutral  salts  of 
potassium  are  most  remarkable.  In  small  doses  they  accelerate  the  heart-beat. 
Yellow  potassium  ferrocyanid,  when  injected  into  a  frog's  heart,  will  cause  systolic 
arrest  of  the  ventricles,  even  when  greatly  diluted.  If  blood  subsequently  enters 
the  ventricle  as  the  result  of  the  contraction  of  the  auricle,  the  ventricle  may 
again  take  part  in  the  contraction.  Under  such  conditions,  the  ventricular  muscles 
sometimes  relax  in  areas  after  first  undergoing  reddening.  The  contraction  of  the 
ventricle,  which  is  exceedingly  sluggish,  later  travels  from  the  auriculo- ventricular 
junction  in  a  peristaltic  wave  to  the  apex.  The  Javanese  arrow-poison,  antiar, 
causes  systolic  arrest  of  the  ventricles,  with  diastolic  arrest  of  the  auricles;  mus- 
carin  causes  diastolic  arrest  of  the  heart,  which  can  be  overcome  by  means  of 
atropin.  Some  of  the  heart-poisons  in  small  doses  cause  slowing  and  in  larger 
doses  not  infrequently  acceleration  of  the  heart -beat:  digitalis  (and  the  toxic 
substances  of  oleander  and  the  mayflower,  which  are  similar  to  it),  morphin,  and 
nicotin.  Others  in  small  doses  cause  acceleration  and  in  large  doses  slowing: 
veratrin,  aconitin,  camphor. 


THE    CARDIOPNEUMATIC    MOVEMENT.  121 

THE  CARDIOPNEUMATIC  MOVEMENT. 

As  the  heart  during  systole  occupies  a  smaller  space  in  the  interior 
of  the  thorax  than  during  diastole,  air  must  enter  the  thorax  as  the  heart 
contracts  if  the  glottis  is  open.  When,  however,  the  heart  relaxes  in 
diastole,  air  must  escape  through  the  open  glottis  as  the  heart  enlarges. 
A  similar  influence  must  be  due  to  differences  in  the  degree  of  fulness 
of  the  intrathoracic  vascular  trunks.  This  cardio pneumatic  movement  is, 
in  animals  in  which  during  hibernation  the  respiratory  movements  are 
suspended,  of  the  greatest  importance  for  the  maintenance  of  metabolism, 
which  continues  in  moderate  degree.  The  interchange  of  carbon  and 
oxygen  in  the  lungs  is  greatly  facilitated  by  agitation  of  the  pulmonary 
gases,  and  this  interchange  suffices  to  aerate  the  blood  passing  slowly 
through  the  lungs. 

Method. — The  movement  may  be  demonstrated  by  means  of: 

1.  The  manometric  flame,  the  trachea  of  a  curarized  animal  being  opened 
and  connected  with  a  bifurcated  tube,  one  branch  of  which  leads  to  the  gas-tubing 
and  the  other  to  a  small  gas-flame.     As  in  this  manner  a  free  communication  is 
established  between  the  organ  of  respiration  and  the  gas-supply,  the  movements 
of  the  heart  will  be  transmitted  to  the  gas-flame.     In  man  it  is  possible,  after  a 
little  practice,  to  transmit  the  movement  in  an  analogous  manner  to  the  gas- 
flame  through  one  nostril  after  closure  of  the  other  nostril  and  the  mouth,  or 
through  the  mouth  after  closure  of  the  two  nostrils. 

2.  By  acoustic  means,  namely  by  introducing  an  exceedingly  sensitive  whistle 
constructed  from  a  hollow  sphere,  in  animals  into  the  trachea  divided  transversely, 
in  man — especially  when  the  heart's  action  is  stimulated — into  the  mouth,  after 
closure  of  the  nose,  it  is  possible  to  demonstrate  the  cardiopneumatic  movement, 
particularly  if  the  whistle  is  blown  continuously  and  with  extreme  softness. 

3.  By  means  of  the  cardiopneumograph  (Fig.  35).     This  consists  of  a  tube, 
which  is  held  between  the  lips  (D),  while  respiration  is  suspended,  the  glottis  is 
opened  and  the  nostrils  are  closed.     The  extremity  of  the  tube,  which  is  bent 
upward,  perforates  a  small  plate  (T) ,  over  which  a  delicate  membrane  consisting 
of  a  mixture  of  collodion  and  castor-oil  is  stretched  with  moderate  force.     From 
the  center  of  the  membrane  a  glass  thread  (H)  passes  over  the  free  edge  of  the 
plate  and  is  provided  at  its  extremity  with  a  delicate  hair,  which  registers  the 
movements  of   the  membrane  on  a  tablet  (S)  moved   by  clockwork.     Every  ex- 
piratory movement   of  air  causes   depression   and  every  inspiratory  movement 
elevation  of  the  recording  point.     Attached  to  the  side  of  the  tube  is  a  valve 
with  a  sufficiently  large  opening  (K)  and  which  may  be  opened  to  allow  the  indi- 
vidual to  breathe  freely  during  a  pause.     The  periodic  movements  of  the  respiratory 
gases  propelled  by  the  heart-beat  cause  associated  movements  in  the   delicate 
collodion  membrane,  and  these  are  in  turn  transmitted  to  the  recording  lever. 

The  graphic  curve  (Fig.  35,  A  and  B)  exhibits  the  following  details: 

1 .  The  respiratory  gases  undergo  a  sudden  expiratory  movement  coincidently 
with  the  first   sound    of   the    heart    because    at    the   instant    of   the   ventricular 
systole  the  blood  from  the  ventricles  has  not  yet  left  the  thorax,  while  venous 
blood  is  pouring  into  the  right  auricle  through  the  venae  cavae,  and  because  in  the 
same  instant  of  systole  the  dilating  branches  of  the  pulmonary  artery  must  cause 
approximately  the  same  quantity  of  air  to  escape  from  the  nearest  air-passages 
in  the  lungs.     In  fact,  the  blood  contained  in  the  right  auricle  does  not  leave  the 
thorax  at  all;  it  is  only  transferred  to  the  lesser  circulation.     This  expiratory 
movement  would  often  be  greater  if  it  were  not  limited  by  two  factors,  namely: 
(a)  because  the  muscular  mass  of  the  ventricle  occupies  a  somewhat  smaller  vol- 
ume during  contraction,  and  (6)  because  the  thoracic  cavity  in  the  region  of  the 
fifth  intercostal  space  is  somewhat  enlarged  outwardly  by  the  apex-beat. 

2.  There  follows  immediately  a  marked  inspiratory  movement  of  the  respira- 
tory gases,  in  consequence  of  which  the  large  ascending  limb  of  the  curve  is  re- 
corded.    As  soon  as  the  blood- wave  has  advanced  from  the  root  of  the  aorta  to 
those  portions  of  the   large  arteries   that  lie  at  the  boundaries  of  the  thoracic 
cavity,  a  much  larger  quantity  of  arterial  blood  begins  to  leave  this  cavity,  because 
venous  blood  is  at  the  same  time  being  poured  into  it  through  the  venae  cavae. 


122 


INFLUENCE    OF    RESPIRATORY    PRESSURE    ON    THE    HEART. 


This  inspiratory  movement  would  also  be  larger  were  it  not  for  a  slight  diminution 
in  the  volume  of  the  oral  and  nasal  cavities,  attended  with  an  expiratory  move- 
ment that  takes  place  at  the  same  time  on  account  of  the  filling  of  its  arteries — 
oral  pulse,  nasal  pulse. 

3.  After  the  second  sound  of  the  heart  (at  2),  which  at  times  causes  a  slight 
depression  at  the  apex  of  the  curve,  the  blood  is  dammed  back  in  the  thorax, 
in  correspondence  with  the  retrograde  wave.     As  a  result  a  second  expiratory 
movement  manifests  itself  in  the  descending  portion  of  the  curve. 

4.  The  subsequent  secondary  wave-movement  of   the  blood  from  the  heart 
immediately  again  causes  an  inspiratory  movement  of  gases,  which  produces  the 
recoil  elevation  in  the  arteries  of  the  body. 

5.  More  blood  now  begins  to  flow  into  the  thorax  through  the  veins  with 
slight  fluctuations,  and  the  next  heart -beat  takes  place. 


FIG.  35. — Landois'  Cardiopneumograph,  and  Cardiopneumatic  Curves  Obtained  with  its  Aid.  A  and  B,  from 
man;  i  and  2  correspond  to  the  period  of  the  first  and  second  heart-sounds;  C,  curves  from  the  dog;  D, 
showing  the  instrument  in  use- 

Pathological. — In  the  healthy  human  subject  a  crepitating  sound  is  not  rarely 
heard  close  to  the  heart,  resulting  from  the  movement  of  the  air  in  the  lungs, 
brought  about  by  the  movement  of  the  heart.  If  there  are  near  the  heart  abnor- 
mally narrow  places  in  the  bronchi,  through  which  the  respiratory  gases  are  forced, 
so  that  they  generate  a  sound  or  murmur,  a  fairly  loud,  sibilant  or  whistling 
murmur,  known  as  the  pathological  Cardiopneumatic  murmur,  is  heard  in  rare 
cases.  In  the  presence  of  cardiac  lesions  characterized  by  considerable  fluctuations 
in  the  quantity  of  blood  in  the  vessels  of  the  lesser  circulation,  the  cardiopneumatic 
movement  must  be  quite  marked,  as,  for  example,  in  cases  of  insufficiency  of  the 
pulmonary  and  mitral  valves. 


INFLUENCE  OF  THE   RESPIRATORY    PRESSURE  ON  THE    DILA- 
TATION AND  CONTRACTION  OF  THE  HEART. 

The  variations  in  pressure  to  which  all  the  parts  within  the  thorax 
are  subjected  by  its  inspiratory  expansion  and  expiratory  contraction 
exert  a  visible  influence  on  the  diastole  and  systole  of  the  heart. 

The  conditions  in  various  positions  of  the  resting  thorax  with  the 
glottis  open  will  be  considered  first.  The  diastolic  dilatation  of  the 
cavity  of  the  heart  is  brought  about  by  the  elastic  traction  of  the  lungs, 
as  well  as  by  the  inflow  of  venous  blood  and  the  elastic  stretching  of  the 
relaxing  muscular  walls.  This  traction  is  greater  in  proportion  as  the 


INFLUENCE    OF    RESPIRATORY    PRESSURE    ON    THE    HEART.  123 

lungs  are  more  fully  expanded  (inspiration),  and  become  less  effective 
in  proportion  as  the  lungs  have  already  been  contracted  (expiration). 
From  this  it  follows : 

1.  That  in  the  most  extreme  expiratory  position  of  the  thorax,  with 
the  greatest  possible  contraction  of  the  pulmonary  tissue,  when,  there- 
fore, what  is  left  of  the  effective  elastic  traction  of  the  lungs  is  exceedingly 
slight,  but  little  blood  enters  the  cavities  of  the  heart;  the  heart  during 
diastole  is  small  and  contains  but  little  blood.     Accordingly,  the  systolic 
contractions  will  be  small,  that  is,  a  small  pulse  results. 

2.  In  the  most  extreme  inspiratory  position,  when  the  elastic  lungs 
are  distended  to  their  utmost,  the  force  of  the  elastic  traction  of  the 
lungs  is,  naturally,  greatest,  being  in  fact  equivalent  to  30  millimeters 
of  mercury.     The  effect  of  this  traction  may  be  great  enough  to  counter- 
act the  contractions  of  the  thin-walled  auricles  and  auricular  appendages 
and  prevent  these  structures  from  emptying  their  contents  completely 
into  the  ventricles.     In  cases  of  cardiac  weakness  it  would  even  appear 
as  if  the  ventricular  activity  were  impaired  by  the  strong  elastic  pulmo- 
nary traction,  as  the  diminution  in  the  strength  of  the  heart-sounds  that  is 
sometimes  observed  attests.     The  heart,  therefore,  is  greatly  distended 
in  diastole  and  filled  with  blood ;  nevertheless  the  resulting  pulse-waves 
may  be  small  in  consequence  of  the  limitation  of  auricular  activity. 
Thus,  Bonders  often  found  the  pulse  smaller  and  slower. 

3.  When  the  thorax  is  in  the  position  of  moderate  rest,  a  condition 
in  which  the  elastic  traction  of  the  lungs  is  of  moderate  strength  only, 
namely,  7.5  millimeters  of  mercury,  the  conditions  for  the  action  of  the 
heart  are  most  favorable.     On  the  one  hand,  diastolic  distention  of  the 
cavities  of  the  heart  is  adequate,  and,  on  the  other  hand,  their  complete 
evacuation  during  systole  is  not  impeded. 

A  much  greater  influence  on  the  action  of  the  heart  is  exerted 
by  the  increase  or  diminution  in  the  intrathoracic  pressure  produced 
voluntarily  by  muscular  action. 

1.  If  the  thorax  is  first  brought  into  the  position  of  deepest  inspira- 
tion, then  the  glottis  is  closed,  and  now  the  space  within  the  chest  is 
greatly  reduced  with  the  aid  of  the  expiratory  muscles;  the  cavities  of 
the  heart  may  be  so  greatly  compressed  as  to  cause  momentary  sus- 
pension of  the  movement  of  the  blood  within  them.     In  this  position 
the  elastic  traction  is  greatly  diminished,  and  in  addition  the  pulmonary 
air,  which  is  under  high  tension,  exerts  pressure  on  the  heart  and  the 
intrathoracic   vessels.     As   no    venous   blood    can   enter   the   thoracic 
cavity  from  without,  the  visible  veins  become  enlarged,  the  blood  is 
driven  more  rapidly  into  the  left  heart,  and  the  latter  empties  itself 
into  the  circulation  as  quickly  as  possible.     The  lungs  are,  as  a  result, 
anemic  and  the  cavities  of  the  heart  empty.     Therefore,  there  is  plethora 
in  the  greater  circulation,  associated  with  anemia  in  the  lesser  and  in  the 
heart.     The  heart-sounds  cease,  the  pulse  disappears. 

2.  If,  conversely,  the  glottis  is  closed,  while  the  thorax  is  in  the 
position  of  most  extreme  expiration,  and  the  thoracic  cavity  is  now  for- 
cibly dilated  in  inspiration,  the  heart  is  strongly  dilated;  for  the  cavities 
of  the  heart  are  distended  not  only  by  the  elastic  traction  of  the  lungs, 
but  also  on  account  of  the  extreme  rarefaction  of   the  pulmonary  air. 
The  contents  of  the  veins  are  poured  copiously  into  the  right  heart, 
and  in  proportion  as  the  right  auricle  and  the  ventricle  are  capable  of 


124 


INFLUENCE    OF    RESPIRATORY    PRESSURE    ON    THE    HEART. 


overcoming  the  outward  traction,  the  blood-vessels  of  the  lungs  will 
be  distended  with  blood.  Much  less  blood  will  be  driven  out  of  the 
left  heart,  so  that  the  pulse  may  even  be  temporarily  arrested.  The 
result  is  an  overdistended,  enlarged  heart  and  '  the  presence  of  an 
increased  amount  of  blood  in  the  lesser  circulation,  as  compared  with 
the  greater. 

As,  when  the  breathing  is  normal,  the  tension  of  the  pulmonary  air 
is  diminished  during  inspiration  and  increased  during  expiration,  this 
normal  alternation  of  pressure  tends  to  assist  the  circulation:  inspira- 
tion hastens  the  venous  and  lymphatic  flow  through  the  venae  cavae 
(if  the  axillary  or  the  jugular  vein  is  opened  during  an  operation,  air 
may  be  sucked  in  and  cause  death)  and  thus  favors  complete  diastole ; 


FIG.  36.— Apparatus  for  the  Demonstration  of  the  Influence  of  Respiratory  Expansion  (II)  and  Contraction  (I) 
of  the  Thorax  on  the  Heart  and  the  Circulation. 


expiration  hastens  the  movement  of  blood  into  the  arterial  system  and 
favors  systolic  emptying  of  the  heart.  At  the  same  time  the  val- 
vular arrangement  of  the  heart  secures  a  constant  direction  to  the 
accelerated  blood-current. 

The  elastic  traction  of  the  lungs  also  exerts  a  favorable  influence  on 
the  lesser  circulation,  which  is  contained  entirely  within  the  thorax; 
for  the  blood  within  the  pulmonary  capillaries  is  under  the  same  pres- 
sure as  the  pulmonary  air,  while  that  of  the  pulmonary  veins  is  under 
lower  pressure,  as  the  elastic  traction  of  the  lungs  by  distending  the 
left  auricle  necessarily  hastens  the  flow  of  blood  from  the  pulmonary 
veins  into  the  left  auricle.  On  the  other  hand,  the  elastic  traction  of 


MOVEMENT    OF    THE    BLOOD    IN    THE    CIRCULATION.  125 

the  lungs  is  prevented  from  interfering  to  any  marked  degree  with  the 
action  of  the  right  ventricle  and,  therefore,  with  the  movement  of 
blood  through  the  pulmonary  artery,  because  of  the  sufficient  resistance 
of  the  blood,  right  ventricle  and  the  pulmonary  artery  against  the  elastic 
pulmonary  traction. 

The  apparatus  illustrated  in  Fig.  36  shows  clearly  the  influence  of  inspiratory 
and  expiratory  movements  on  the  expansion  of  the  heart  and  on  the  current  of 
blood  in  the  large  vascular  channels  leading  to  and  from  the  heart.  The  large 
glass  bottle  represents  the  thorax,  and  its  bottom  has  been  replaced  at  D  by  an 
elastic  rubber  membrane,  which  represents  the  diaphragm.  '  P  P  are  the  lungs;  L 
the  trachea,  the  entrance  to  which  (glottis)  may  be  closed  by  means  of  a  stop- 
cock; H  is  the  heart;  E  represents  the  course  of  the  venae  cavae;  and  A  the  aorta. 
When  the  tracheal  stop-cock  is  closed  and  the  expiratory  position,  as  shown  at  I, 
is  established  by  elevating  the  membrane  D,  with  diminution  in  the  size  of  the 
thoracic  cavity,  the  air  in  P  P  is  condensed,  while  at  the  same  time  the  heart  H 
is  compressed;  the  venous  valve  closes,  while  the  arterial  valve  is  opened  and  the 
fluid  is  driven  out  through  A.  The  manometer  M,  inserted  into  the  flask,  shows 
the  increased  intrathoracic  pressure.  Again,  when  the  stop-cock  1  is  closed  (in 
II),  and  the  membrane  is  strongly  depressed,  the  lungs  pp  expand,  and  with 
them  the  heart  h.  The  venous  valve  opens,  while  the  arterial  valve  closes,  and 
the  venous  blood  enters  the  heart  through  e.  Thus,  inspiration  always  hastens 
the  venous  and  inhibits  the  arterial  flow,  while  expiration  inhibits  the  venous 
and  hastens  the  arterial  flow.  If  the  glottis  (L  and  1)  remains  open,  the  air  in  P  P 
and  p  p  naturally  is  changed  as  the  thorax  passes  from  the  inspiratory  to  the 
expiratory  position  (D  and  d).  Accordingly,  the  effect  on  the  heart  (H  and  h) 
and  on  the  blood-vessels  is  smaller,  but  even  under  such  conditions  it  must  persist 
in  small  measure. 


THE  MOVEMENT  OF  THE  BLOOD  IN  THE 
CIRCULATION. 

TORICELLPS  THEOREM  ON  THE  VELOCITY  OF  ESCAPE  OF 

FLUIDS. 

According  to  Toricelli's  law,  the  velocity  (v)  with  which  a  fluid  escapes,  for 
example,  through  an  opening  in  the  floor  of  a  hollow  cylindrical  vessel,  is  equal 
to  the  velocity  that  a  freely  falling  body  would  attain  in 
falling  from  the  level  of  the  fluid  to  the  level  of  the  open- 
ing (the  height  of  the  propelling  force  h) . 

Hence  v  =  1/2  g  h;  in  which  g  =  9.8  meters. 

The  velocity  of  outflow  increases,  as  has  been  shown 
experimentally,  as  the  height  of  the  propelling  force 
(h)  increases,  and  it  preserves  the  ratio  of  i,  2,  3 
as  the  propelling  force  increases  in  the  ratio  of  i,  4,  9; 
that  is,  the  velocity  of  outflow  is  proportionate  to  the 
square  root  of  the  height  of  the  propelling  force.  It  thus 
followrs  that  the  velocity  of  outflow  depends  solely  on  the 
distance  between  the  level  of  the  fluid  and  the  opening, 
and  not  on  the  nature  of  the  escaping  fluid.  Whenever  a 
fluid  is  found  escaping  with  a  definite  velocity,  the  force 
that  causes  the  flow  may  be  expressed  by  the  height  of 
a  column  of  fluid  (h)  in  a  vessel  the  height  of  the  pro- 
pelling force. 

Toricelli's  law,  however,  is  applicable  only  when  all  FIG. 
possible  resistance  that  may  be  offered  to  the  escape  of 
the  fluid  is  left  out  of  account.  As  a  matter  of  fact, 
certain  resisting  forces  are  present  in  any  physical  ex- 
periment of  this  kind.  Hence,  the  force  that  is  ex- 
pressed by  the  height  of  the  propelling  force  (h)  not 

only  causes  the  escape  of  the  fluid,  but  also  overcomes  the  sum  of  all  the  resist- 
ances. These  two  forces  may  be  expressed  by  the  heights  of  two  columns  of 
water  superposed  the  one  upon  the  other ;  namely,  by  the  height  of  the  velocity 


37. — Pressure- v  e  s  s  e  1 
Filled  with  Water:  h, 
height  of  the  column  of 
fluid;  F,  height  of  the 
velocity;  D,  height  of  the 
resistance. 


126 


PROPELLING    FORCE,    VELOCITY    AND    LATERAL    PRESSURE. 


F   (which    effects    the  velocity  of  escape)   and  the    height    of   the    resistance   D 
(which  overcomes  any  resistance  that  may  be  present) :  hence  h  =  F  -f-  D. 

PROPELLING  FORCE,  VELOCITY  AND  LATERAL  PRESSURE. 

If  a  fluid  passes  through  a  tube  (which  it  completely  fills) ,  the  first  thing  to 
determine  is  the  propelling  force  h  with  which  the  current  flows  at  different  points 
in  the  tube.  The  degree  of  the  propelling  force  depends  on  two  factors: 

1.  The  velocity  of  the  current,  v; 

2.  The  pressure  (resistance-height)  to  which  the  fluid  is  subjected  at  different 
points  in  the  tube,  D. 

1.  The  velocity  of  the  current  v  is  determined:   (a)   from  the  lumen  of  the 
tube  1,  and  (6)   from  the   quantity  of  fluid  q,  that  passes  through  the  tube  in  a 
given  unit  of  time.     Then  v  =  q  :  1.     Both  values,  q  as  well  as  1,  can  be  deter- 
mined directly  by  measurement.     The  circumference  of  a  circular  tube,  the  diameter 

of  which  is  d,  is  3.14  X  d.     The  cross-section  (the  lumen  of  the  tube)  is  1  =  -  -  X  d2. 
After  the  value  of  v  has  been  determined  in  this  way,  the  so-called  velocity- 
height  F   (of  hydraulic  engineers)   can  be  estimated  from  v;  that  is,  the  height 
from  which  a  body  would  have  to  fall  in  a  vacuum  in  order  to  acquire  the  velocity 

of  v.     This  is  F  =  —   (in  which  g  indicates  the  distance  through  which  the  body 

falls  in  one  second,  or  4.9  meters). 

2.  The  pressure  D  (resistance-height)  is  measured  directly  at  various  points 
in  the  tube  by  inserting  manometer- tubes  (Fig.  38). 

The  propelling  force  at  any  selected  point  in  the  tube  will  thus  be: 


For  experimental  investigation  the  large  cylindrical  pressure- vessel  (Fig.  38,  A) 
may  be  used,  within  which  by  a  suitable  arrangement  water  can  be  maintained 
at  a  constant  level  h.  The  rigid  tube  a  b,  passing  off  from  the  bottom  of  the 

vessel,  and  of  uniform  size,  is 
provided  with  a  number  of 
vertical  tubes  (i,  2,  3)  consti- 
tuting a  piezometer,  for  the 
measurement  of  the  pressure; 
at  the  extremity  b  the  tube  is 
provided  with  an  opening  di- 
rected upward.  From  the  lat- 
ter the  water,  providing  the 
level  at  h  remains  the  same, 
will  be  thrown  to  a  constant 
height,  and  this  distance  is 
equivalent  to  F,  the  velocity- 
height.  As  the  pressure  Dlt 
D2<  D3  in  the  manometric  tubes 

1,2,3  can  be  read  off  directly, 

III  *  "  '          ' 


FIG.  38. — A  Pressure-vessel,  A,  with  Outflow  Tube,  a  b,  and  Manom- 
eters, Di,D2  D3,  Inserted  at  Different  Points. 


it  follows  that  the  propelling 
force  of  the  water  at  the  posi- 
tion of  the  tubes  I,  II,  III  is 
respectively  h  =  F  -f  Dt;  F  + 
D2;  F  +  D3. 

At  the  extremity  of  the  tube  (at  b)  where  Dt  =o,h  =  F  +  o,  hence  h  = 
F.  Within  the  pressure- vessel  itself,  it  is  the  constant  force  h  .that  influences 
the  movement  of  the  fluid. 

It  is,  therefore,  at  once  apparent  that  the  propelling  force  of  the  water 
has  become  progressively  smaller  from  the  point  where  the  fluid  enters  the 
tube  from  the  pressure- vessel  to  the  end  of  the  tube  b.  The  water  in  the 
pressure-vessel  falling  from  h  rises  at  b  only  to  the  height  F.  This  diminution 
in  the  propelling  force  is  due  to  the  resistances  encountered  by  the  current  in  the 
tube,  which  neutralize  a  part  of  the  kinetic  energy  (that  is,  convert  it  into  heat). 
As,  when  the  water  has  reached  b,  the  motor  power  h  in  the  vessel  has  been  re- 
duced to  F,  the  difference  having  been  neutralized  by  the  resistances,  the  sum  of 
these  resistances  must  be  D  =  h  -  F,  from  which  it  follows  that  h  =  F  -}-  D, 


METHOD    OF    ESTIMATING    THE    RESISTANCES.  127 

METHOD  OF  ESTIMATING  THE  RESISTANCES. 

When  a  fluid  passes  through  a  tiibe  of  uniform  caliber  throughout  its  entire 
length,  the  propelling  force  h  diminishes  progressively  in  consequence  of  the 
resistances  that  operate  uniformly  at  every  point.  The  sum  of  all  the  resistances 
in  the  tube  is,  therefore,  directly  proportional  to  its  length.  In  a  tube  of  uniform 
caliber  the  fluid  passes  through  each  transverse  section  at  a  constant  velocity; 
hence  v  (and,  therefore,  F)  is  the  same  at  any  point  in  the  tube.  The  diminution 
that  takes  place  in  the  propelling  force  h  can,  therefore,  be  due  only  to  a  diminution 
of  the  pressure  D,  as  F  remains  the  same  everywhere  (and  h  "=  F  -f  D).  The 
experiment  with  the  pressure- vessel  shows,  in  fact,  that  the  pressure  progressively 
diminishes  toward  the  discharging  extremity  of  the  tube.  In  a  tube  of  uniform 
width  the  pressure-height  found  to  prevail  in  the  manometer-tube  is  the  expression 
of  the  sum  of  the  resistances  that  must  be  overcome  by  the  current  in  its  course 
from  the  point  examined  to  the  free  discharge-opening  of  the  tube. 

Forms  of  Resistance. — The  resistances  encountered  by  a  stream  of  fluid 
reside  first  of  all  in  the  cohesion  of  the  fluid-particles.  The  outermost  parietal 
layer  of  the  fluid,  which  is  in  contact  with  the  tube,  remains  absolutely  quiescent 
during  the  passage  of  the  current.  All  the  other  layers  of  the  fluid,  which  may 
be  concerned  as  a  series  of  concentric  cylinders  one  within  the  other,  move  with 
a  progressively  increasing  velocity  from  the  periphery  to  the  axis  of  the  tube, 
while  the  axial  thread  itself  finally  represents  the  most  rapidly  moving  portion  of 
the  fluid.  In  the  displacement  of  these  cylindrical  layers  of  fluid  at  their  surfaces 
of  contact,  the  particles  of  fluid  in  juxtaposition  must  naturally  be  pulled  apart 
and  a  portion  of  the  active  propelling  force  will  be  lost.  The  degree  of  resistance 
depends  essentially  on  the  degree  of  cohesion  between  the  particles  of  fluid;  the 
more  intimate  the  cohesion  between  the  fluid-particles,  the  greater  will  be  the 
resistance;  and  conversely.  It  is  thus  evident  that  the  resistances  encountered 
by  the  viscous  blood  in  its  passage  must  be  greater  than  those  that  would  be 
encountered,  for  example,  by  water  or  ether.  Four  and  one-half  times  as  much 
pressure  would  be  required  to  drive  the  same  quantity  of  blood  as  of  water  through 
a  tube. 

Heat  diminishes  the  cohesion  of  the  particles  and  it  is,  therefore,  a  means 
for  diminishing  the  resistance  encountered  by  the  current.  It  is  also  evident  that 
the  resistances  are  only  the  result  of  movement,  as  the  forcible  separation  of  the 
fluid-particles  does  not  begin  until  the  column  is  set  in  motion.  It  is,  further, 
obvious  that  the  greater  the  velocity  of  the  current — the  greater  the  number 
of  fluid-particles  that  are  torn  apart  in  a  unit  of  time — the  greater  will  be  the 
sum  of  the  resistances.  The  parietal  layer  of  fluid  in  contact  with  the  surface  of 
the  tube  remains,  as  has  been  said,  in  absolute  quiescence;  it  follows,  therefore, 
that  the  material  composing  the  walls  of  the  tube  has  no  influence  on  the  resistances. 

INFLUENCE  OF  INEQUALITIES  IN  THE  SIZE  OF  THE  TUBE. 

When  the  velocity  of  the  current  remains  the  same,  the  intensity  of  the 
resistances  depends  on  the  diameter  of  the  tube;  the  smaller  the  diameter  the 
greater  the  resistance,  and  the  larger  the  diameter  the  less  the  resistance.  The 
resistances,  however,  increase  more  rapidly  in  narrower  tubes  than  the  diameter 
of  the  tubes  increases.  This  has  been  proved  by  experimental  investigation. 

In  tubes  that  exhibit  inequality  in  size  in  their  course,  the  velocity  of  the 
current  varies,  being  naturally  slower  in  the  wide  portions  and  more  rapid  in  the 
narrower  portions.  In  general  the  velocity  of  the  current  in  tubes  of  unequal 
caliber  is  inversely  proportional  to  the  transverse  section  of  the  different  portions 
of  the  tube,  that  is,  if  the  tubes  are  cylindrical  inversely  proportional  to  the  square 
of  the  diameter  of  the  circular  transverse  section. 

While  in  tubes  of  uniform  size  the  propelling  force  of  the  moving  fluid  dimin- 
ishes uniformly  section  by  section,  the  diminution  is  not  uniform  in  tubes  of 
unequal  width;  for  since,  as  has  just  been  shown,  the  resistance  is  greater  in  a 
narrow  than  in  a  wide  tube,  the  diminution  in  the  propelling  force  must  naturally 
be  greater  in  the  narrow  places  than  in  the  wide  places.  At  the  same  time,  i't 
has  been  shown  that  the  pressure  in  the  wider  places  is  greater  than  the  sum  of 
the  resistances  still  to  be  overcome;  while,  on  the  other  hand,  at  the  narrower 
places  it  is  smaller  than  the  sum  of  these  resistances. 

Curvature  and  tortuosity  of  the  vessels  give  rise  to  new  resistances.  In  con- 
sequence of  centrifugal  force  the  fluid-particles  cling  more  closely  to  the  convex 


128  MOVEMENT    THROUGH    CAPILLARY    TUBES. 

side  of  the  arch  and  thus  encounter  a  greater  resistance  to  their  progress  than  on 
the  concave  side. 

When  the  tube  divides  into  two  or  more  branches,  the  propelling  force  is 
also  diminished  on  account  of  the  creation  of  additional  resisting  forces.  When 
a  current  is  divided  into  two  smaller  currents,  some  fluid-particles  will  be  retarded, 
while  others  will  be  accelerated  on  account  of  the  unequal  velocity  of  the  various 
layers  of  the  fluid.  Many  particles  that  in  the  main  current,  as  a  part  of  the 
axial  stream,  had  the  greatest  velocity  will  in  the  secondary  currents  when  situated 
in  the  parietal  layers  move  more  slowly;  while,  conversely,  many  parietal  layers 
in  the  main  current  become  more  centrally  situated  in  the  secondary  current 
with  increased  velocity.  As  a  result  of  the  resistance  thus  produced  a  part  of 
the  propelling  force  is  naturally  lost.  The  separation  of  the  fluid-particles  as  the 
current  divides  has  a  similar  effect.  If,  on  the  other  hand,  two  tubes  join  to  form 
a  single  tube,  additional  resistance  acting  in  a  manner  opposite  to  that  described 
must  lessen  the  propelling  force.  The  sum  total  of  the  mean  velocity  in  both 
branches  of  the  current  is  independent  of  the  angle  formed  at  the  point  of  division. 
The  opening  of  a  lateral  branch  that  forms  part  of  a  tube  accelerates  the  main 
current  to  the  same  degree,  irrespective  of  the  size  of  the  angle  formed  by  the 
lateral  branch  with  the  main  tube. 

MOVEMENT  THROUGH  CAPILLARY  TUBES. 

The  movement  of  fluids  through  capillary  tubes  is,  in  accordance  with  the 
capillary  attraction  prevailing  in  capillary  vessels,  and  in  contravention  of  the 
laws  that  have  just  been  developed,  governed  by  certain  rules,  for  the  formulation 
of  which  credit  is  due  Poiseuille.  These  rules  are  as  follows: 

1.  The  quantity  of  fluid  that  escapes  from  a  capillary  tube  is  proportional  to 
the  pressure. 

2.  The  time  necessary  for  the  escape  of  a  like  quantity  of  fluid  (the  pressure, 
the  diameter  of  the  tube,  and  the  temperature  remaining  the  same)  is  propor- 
tional to  the  length  of  the  tube. 

3 .  The  products  of  the  outflow  (all  other  conditions  remaining  the  same)  vary 
with  the  fourth  power  of  the  transverse  diameter. 

4.  The  velocity  of  the  current  is  proportional  to  the  pressure-height  and  to 
the  square  of  the  diameter,  and  inversely  proportional  to  the  length  of  the  tube. 

5.  The  resistances  in  the  capillary  tubes   are  proportional   to   the  velocities 
of  the  current. 

CONTINUOUS  AND  UNDULATORY  MOVEMENT  IN  ELASTIC  TUBES. 

If  an  uninterrupted,  uniform  stream  of  fluid  is  permitted  to  flow  through  an 
elastic  tube,  the  movement  of  this  current  is  subject  to  the  same  laws  that  govern 
its  passage  through  rigid  tubes.  If  the  propelling  force  increases  or  diminishes, 
the  elastic  tubes  are  either  dilated  or  constricted,  and  their  relation  to  the  column 
of  fluid  is,  therefore,  simply  like  that  of  wider  or  narrower  rigid  tubes. 

If,  however,  successive  amounts  of  fluid  are  introduced  at  intervals  into  an 
elastic  tube  entirely  filled  with  fluid,  the  initial  portion  of  the  tube  will  be  suddenly 
distended  in  accordance  with  the  amount  of  fluid  introduced.  The  impact  imparts 
to  the  fluid-particles  an  oscillatory  movement,  which  rapidly  communicates  itself 
to  all  the  fluid-particles  from  the  beginning  to  the  end  of  the  tube ;  there  results 
a  positive  wave,  which  rapidly  propagates  itself  through  the  entire  tube.  If  the 
elastic  tube  be  closed  at  its  peripheral  extremity,  the  positive  wave  will  rebound 
at  the  point  of  closure;  it  becomes  a  positive  recurrent  wave  and  it  may  even 
pass  backward  and  forward  repeatedly,  becoming  gradually  smaller  and  smaller, 
until  it  finally  subsides.  Hence,  in  a  closed  tube  of  such  character,  the  sudden 
periodic  impulsion  of  a  mass  of  fluid  produces  only  a  wave-like  movement,  that 
is,  merely  an  oscillatory  movement  or  the  movement  of  a  form. 

3.  If,  however,  additional  amounts  of  fluid  are  at  intervals  pumped  into  the 
initial  portion  of  an  elastic  tube  entirely  filled  with  fluid  already  in  continu- 
ous movement,  the  continuous  movement  is  combined  with  the  undulatory 
movement.  In  such  a  case  the  continuous  movement  of  the  fluid,  that  is,  the 
displacement  or  movement  of  the  fluid  in  mass  through  the  tube,  must  be  rigidly 
distinguished  from  the  undulatory  or  oscillating  movement,  the  movement  of 
the  change  in  form  of  the  column  of  fluid.  The  former  is  a  translatory,  the  latter 
an  oscillatory  movement.  The  continuous  movement  is  slower  in  elastic  tubes v 
while  the  undulatory  movement  is  more  rapid. 


STRUCTURE    AND    PROPERTIES    OF    THE    BLOOD-VESSELS.  I2Q 

The  conditions  in  the  arterial  system  are  the  same  as  those  just  described. 
The  blood  in  the  arteries  is  already  engaged  in  continuous  motion  from  the  root 
of  the  aorta  to  the  capillaries  (continuous  movement) ;  and  the  injection  at  inter- 
vals of  a  mass  of  blood  into  the  root  of  the  aorta  with  each  systole  of  the  left 
ventricle  produces  a  positive  wave  (pulse) ,  which  propagates  itself  with  great 
rapidity  to  the  end  of  the  arterial  system,  while  the  constant  movement  progresses 
much  more  slowly. 

It  is  of  great  importance  to  compare  the  movements  of  fluids  in  rigid  tubes 
with  the  movements  of  fluids  in  elastic  tubes.  When  a  certain  quantity  of  fluid 
is  forced  into  a  rigid  tube  under  a  certain  pressure,  an  equal  quantity  of  fluid 
will  at  once  escape  from  the  end  of  the  tube,  unless  such  a  result  is  prevented  by 
the  development  of  special  resistances.  The  conditions  are,  however,  different  in 
the  case  of  an  elastic  tube.  Immediately  after  the  injection  of  a  definite  quantity 
only  a  relatively  small  quantity  of  fluid  escapes  at  first,  the  escape  of  the  re- 
mainder taking  place  only  after  the  injecting  force  has  subsided. 

If  equal  quantities  of  fluid  are  injected  at  intervals  into  a  rigid  tube,  a  corre- 
sponding amount  escapes  with  each  impulse  and  the  discharge  continues  as  long 
as  the  impulse,  and  the  pause  between  each  two  periods  of  escape  is  always  equal 
to  the  period  between  two  impulses.  In  the  case  of  elastic  tubes  the  conditions 
are  different.  As  the  escape  of  the  fluid  continues  for  some  time  after  the  cessation 
of  the  impulse,  it  will  always  be  possible  to  establish  a  continuous  outflow  through 
elastic  tubes  by  making  the  interval  between  two  injections  shorter  than  the 
duration  of  the  outflow  that  takes  place  after  the  impulse  has  been  completed. 
Thus,  the  periodic  injection  of  fluid  into  a  rigid  tube  produces  an  isochronous, 
sharply  limited  outflow  of  fluid,  which  can  become  permanent  only  when  fluid 
enters  the  tube  in  a  continuous  stream.  In  the  case  of  elastic  tubes,  on  the  other 
hand,  intermittent  introduction  of  fluid  produces  under  the  same  conditions  a 
continuous  outflow  with  systolic  reinforcement. 

Hamel's  investigations  have  shown  that  elastic  tubes  permit  the  passage  of 
more  fluid  when  they  are  supplied  in  a  rhythmical  pulsatory  manner  than  when 
the  fluid  enters  in  an  uninterrupted  stream  under  constant  pressure.  The  advan- 
tage of  the  rhythmical  impulse  for  the  propulsion  of  the  circulating  fluid,  as  com- 
pared with  a  uniform  pressure,  appears  to  reside  in  the  fact  that  the  alternating 
movement  preserves  the  elasticity  of  the  arterial  walls. 

STRUCTURE  AND  PROPERTIES  OF  THE  BLOOD-VESSELS. 

The  large  blood-vessels  in  the  body  are  designed  solely  for  the  purpose  of 
acting  as  conducting  canals  for  the  mass  of  blood,  while  the  thin-walled  capillary 
vessels  effect  the  interchange  of  substances  between  the  blood  and  the  tissues  and 
in  the  opposite  direction. 

The  Arteries  differ  from  the  veins  in  the  possession  of  thicker  walls  in  con- 
sequence of  the  considerable  development  of  muscular  and  elastic  elements,  as 
well  of  a  greatly  developed  middle  tunic,  with  a  relatively  thin  adventitial 
coat.  The  walls  of  the  arteries  consist  of  three  coats  (Fig.  39) : 

The  intima  is  lined  on  its  inner  surface  by  a  nucleated  endothelium  (a) 
consisting  of  flat,  irregular,  oblong  cells.  External  to  the  endothelium  is  a  thin, 
finely  granular  layer  containing  more  or  less  distinct  fibers  and  numerous 
spindle-shaped  or  stellate  protoplasmic  cells  embedded  in  a  corresponding  system 
of  plasma-canals.  To  the  outer  side  of  this  is  the  inner  elastic  layer  (b),  which 
in  the  smallest  arteries  is  represented  by  a  structureless  or  fibrous,  elastic  mem- 
brane and  in  the  medium-sized  arteries  by  a  fenestrated  membrane;  while  in  the 
largest  it  assumes  the  appearance  of  a  stratified,  fibrous  or  fenestrated,  elastic 
membrane  consisting  of  two  or  three  layers  and  united  by  connective  tissue.  All  of 
the  larger  and  medium-sized  arteries  contain  longitudinal  fibers  situated  between 
two  elastic  plates.  Acting  together  with  the  circular  fibers  they  are  capable 
of  narrowing  the  caliber  of  the  vessel ;  but  they  possess  also  the  faculty  of  widening 
the  lumen  and  maintaining  it  at  a  uniform  width.  On  the  other  hand,  it  is  im- 
probable that  they  are  capable  of  independent  action  or  that  such  independent 
action  is  capable  of  dilating  the  vessel. 

The  middle  coat  has  for  its  most  characteristic  constituent  unstriated  muscle- 
fibers  (c).  In  the  smallest  arteries  this  appears  to  be  composed  of  scattered, 
transverse,  smooth  muscle-fibers  occupying  an  intermediate  position  between  the 
intima  and  the  adventitia.  The  connecting  material  consists  of  a  finely  granular 
tissue  traversed  by  a  few  delicate  elastic  fibers.  Passing  from  the  smallest  to  the 
9 


130 


STRUCTURE    AND    PROPERTIES    OF    THE    BLOOD-VESSELS. 


smaller  arteries,  the  number  of  unstriated  muscle-fibers  increases  progressively 
until  they  form  a  strong  layer  of  circular  muscle-fibers  with  almost  complete  dis- 
appearance of  the  connecting  substance.  The  outer  elastic  layer  forms  the  bound- 
ary between  the  media  and  the  adventitia.  In  the  large  arteries  the  connecting 
substance  greatly  predominates  over  all  other  tissues:  Separated  by  layers  of 
delicate  fibrous  tissue  there  are  numerous  (as  many  as  50)  thick,  elastic,  fibrillated 
or  fenestrated  membranes  arranged  in  concentric  layers  and  chiefly  in  the  trans- 
verse direction.  Scattered  here  and  there  between  these  membranes  are  occa- 
sional smooth  muscle-cells  arranged  transversely,  less  commonly  obliquely,  or 
longitudinally. 

The  initial  portions  of  the  aorta  and  pulmonary  artery,  the  arteries  in  bones 
and  the  retinal  arteries  are  devoid  of  muscle-tissue.     The  descending  aorta  and 
the  common  iliac  and  popliteal  arteries  possess  oblique  and  longitudinal  muscle- 
fibers  lying  among  the  transverse  fibers.     The  renal,  splenic  and  internal  sper- 
matic arteries  contain  longitudinal  bundles  at 
the  inner  surface  of  the  media;  the  umbilical 
arteries,  which  are  exceedingly  rich  in  muscle- 
tissue,  contain  longitudinal  bundles  both  on 
the  inner  and  on  the  outer  surface. 

The  external  or  adventitious  coat  in  the 
smaller  arteries  is  a  delicate,  structureless 
membrane  containing  a  few  protoplasmic 
cells.  In  somewhat  larger  vessels  there  is  an 
additional  layer  of  elastic  tissue  of  delicate 
fibers  containing  strands  of  fibrillated  con- 
nective tissue  (d) .  In  the  medium-sized  and 
largest  arteries  the  greater  part  of  the  ad- 
ventitia consists  of  bundles  of  fibrillated 
connective  tissue  containing  connective-tissue 
cells,  and  not  infrequently  an  admixture  of 
fat-cells,  running  obliquely  and  crossing  each 
other  at  numerous  points.  Among  them  and 
chiefly  toward  the  media  are  found  fibrous  or 
fenestrated  elastic  layers.  At  the  boundary 
between  the  adventitia  and  the  media  the 
elastic  elements  in  the  smaller  and  medium- 
sized  arteries  fuse  to  form  a  more  indepen- 
dent elastic  membrane  (Henle's  outer  elastic 
membrane).  Longitudinal  unstriated  mus- 
cle-fibers in  scattered  bundles  are  found  in 
the  adventitia  of  the  arteries  of  the  penis,  of 
the  descending  aorta,  the  renal,  splenic,  in- 
ternal spermatic,  iliac,  hypogastric,  and 
superior  mesenteric  arteries. 

Bonnett  suggests  the  following  natural 
division  of  the  layers  of  the  arterial  wall: 
i .  The  intima  embraces  the  endothelial  tube 
and  the  tissues  as  far  as  the  inner  elastic 
layer.  2 .  The  media  contains  all  those  parts 
that  are  situated  between  the  inner  and  the 
outer  elastic  layer.  3.  The  adventitia  includes  the  layers  found  to  the  outer  side  of 
the  elastic  membrane. 

The  Capillaries,  which  undergo  frequent  division  without  suffering  diminu- 
tion in  caliber,  and  in  their  subsequent  course  unite  again,  have  diameters 
varying  from  5  to  6  fj,  (retina,  muscles)  to  from  10  to  20  //  (bone-marrow,  liver, 
choroid)  The  tubes  are  formed  of  a  single  layer  of  nucleated  endothelial  cells, 
with  protoplasmic  cell-bodies,  which  in  the  smaller  tubes  are  spindle-shaped 
and  in  the  larger  vessels  are  more  polygonal  (as  is  the  case  with  the  cells  ot 
serous  cavities);  they  are  connected  by  numerous  intercellular  bridges  in  the 
depths  of  the  cell-substance  (like  epithelial  cells).  The  boundaries  of  the  cells 
are  demonstrable  as  black  lines  by  injection  of  a  solution  of  silver  nitrate 
stained  cement-substance  exhibits  in  some  places  intercalated  areas  of  larger 
size.  Whether  these  are  to  be  regarded  as  true  openings  or  stomata,  through 
which  it  is  possible  for  red  and  white  cells  to  escape,  or  merely  as  denser  aggre- 
gations of  the  stained  cement-substance  is  still  an  undecided  question.  Delicate 


FIG.  39. — Small  Arterial  Twig  Showing  the  In- 
dividual Layers  of  the  Arterial  Wall:  a, 
endothelium;  b,  elastic  inner  coat;  c, 
layer  of  circular  muscle-fibers;  d,  con- 
nective-tissue adventitia. 


STRUCTURE    AND    PROPERTIES    OF    THE    BLOOD-VESSELS. 


anastomosing  fibrils  derived  from  non-medullated  nerves  terminate  by  small 
end-plates  in  the  capillary  walls.  Ganglia  in  communication  with  the  nerves  of 
capillary  vessels  are  found  only  in  the  distribution  of  the  sympathetic  nerves. 
The  minute  blood-vessels  that  communicate  directly  with  the  capillaries  possess, 
in  addition  to  endothelium,  an  entirely  structureless  investing  membrane. 

The  Veins  differ  from  the  arteries  in  the  main  in  the  fact  that  they  have  a 
larger  caliber  than  the  corresponding  arteries  and  thinner  walls  on  account  of 
the  much  feebler  development  of  the  elastic  and  muscular  elements.  Among  the 
latter  longitudinal  fibers  are  much  more  commonly  found  than  transverse.  Veins 
are  also  distinctly  more  distensible  with  the  same  degree  of  traction.  The  adven- 
titia  is  as  a  rule  relatively  the  thickest  coat.  The  presence  of  valves  is  limited 
to  certain  areas  of  the  body. 

The  intinia  or  internal  coat  is  provided  with  short  endothelial  cells,  beneath 
which,  in  the  smallest  veins,  is  a  structureless  layer,  which  in  the  somewhat  larger 
vessels  is  composed  principally  of  longitudinal  elastic  fibers  (always  thinner  than 
in  the  arteries).  In  the  large  veins  this  layer  may  assume  the  character  of  a 
fenestrated  membrane,  which  here  and  there  in  the  femoral  and  iliac  veins  is  even 
duplicated.  It  is  held  together  by  a  delicate  connective  tissue  containing 
spindle-cells.  The  intima  in 
the  femoral  and  popliteal  veins 
contains  a  few  scattered  muscle- 
fibers. 

The  media  or  middle  coat  in 
the  larger  veins  is  constituted 
of  alternate  layers  of  elastic  and 
muscular  elements,  with  a  fairly 
abundant  fibrillar  connective 
tissue.  The  media  is  always 
thinner,  however,  than  in  the 
corresponding  arteries.  The 
number  of  these  alternating 
layers  becomes  progressively 
smaller  in  the  following  veins, 
in  the  order  of  their  enumera- 
tion: popliteal  vein,  veins  of 
the  lower  extremity,  veins  of 
the  upper  extremity,  superior 
mesenteric,  the  remaining  veins 
of  the  abdominal  cavity,  the 
hepatic,  pulmonary,  and  coro- 
nary veins.  The  following  veins 
are  altogether  devoid  of  mus- 
cle-tissue: the  veins  of  bones, 
muscles,  the  central  nervous 
system  and  its  membranes,  the 
retinal  veins,  the  superior  cava 
with  the  large  trunks  that  empty  into  it,  and  the  upper  portion  of  the  inferior 
cava.  In  these  vessels  the  media  is  much  more  feebly  developed.  In  the  smallest 
veins  the  media  consists  merely  of  a  delicate  fibrillar  connective  tissue  in  which  a 
few  scattered  longitudinal  and  transverse  unstriated  muscle-cells  make  their  ap- 
pearance as  the  center  of  the  circulation  is  approached. 

The  adventitia  or  external  coat  of  the  veins  is,  generally  speaking,  thicker  than 
that  of  the  corresponding  arteries.  It  always  contains  more  abundant  connective 
tissue,  usually  consisting  of  longitudinal  fibers,  and  on  the  other  hand  fewer  large- 
meshed  networks  of  elastic  elements.  Some  veins,  however,  contain  also  longi- 
tudinal muscle  fibers:  the  renal  vein,  the  portal  vein,  the  inferior  cava  in  the 
hepatic  region,  the  veins  of  the  lower  extremity.  The  valves  consist  of  finely 
fibrillated  connective  tissue  in  which  stellate  cells  are  embedded;  the  convex 
surface  of  the  valves  is  covered  with  a  network  of  elastic  fibers,  and  both  surfaces 
are  invested  with  endothelium.  The  valves  contain  many  muscle-fibers. 

The  sinuses  of  the  dura  mater  are  spaces  lined  with  endothelium  between 
duplicatures,  or  cleft-like  invaginations  of  this  membrane. 

Cavernous  spaces  may  be  regarded  as  having  been  produced  by  numerous 
divisions  and  anastomose's  of  fairly  large  veins  of  unequal  size,  closely  following 
one  another.  The  vessel-wall  frequently  appears  cribriform  or  like  a  sponge — the 


FIG.  40. — Capillary  Vessels,— the  Boundaries  of  the  Cells  (Cement- 
substance  between  the  Endothelial  Cells)  have  been  Stained 
Black  with  Silver  Nitrate  and  the  Nuclei  of  the  Endothelial 
Cells  Made  Prominent  by  Staining. 


132  STRUCTURE    AND    PROPERTIES    OF    THE    BLOOD-VESSELS. 

interior  traversed  by  trabeculae  or  threads.  The  surface  directed  toward  the 
blood  is  covered  with  endothelium.  The  investing  wall  consists  of  connective 
tissue,  which  is  often  quite  firm  and  tendinous,  as  in  erectile  tissue.  It  not  infre- 
quently contains  unstriated  muscle-fibers. 

An  example  of  an  analogous  cavernous  formation  in  arteries  is  found  in  the 
coccygeal  gland  of  man.  This  mysterious  structure,  which  is  richly  supplied  with 
sympathetic  nerve-fibers,  consists  of  nucleated  connective  tissue  and  represents  a 
convolution  of  ampulliform  or  spindle-shaped  dilatations  of  the  median  sacral 
artery,  traversed  and  surrounded  by  unstriated  muscle-fibers. 

The  vasa  vasorum  do  not  differ  in  structure  from  other  vessels  of  similar  caliber. 

Intercellular  blood-channels  devoid  of  walls  are  present  in  the  granulation-tissue 
of  wounds.  At  first  nothing  but  blood-plasma  is  found  between  the  constituent 
cells,  and  it  is  not  until  later  that  blood-cells  are  driven  through  the  channels  by 
the  blood-current.  In  the  incubated  egg  the  primary  basis  of  the  blood-vessels 
is  formed  in  a  manner  similar  to  that  of  the  formative  cells  of  the  germinal  layer. 
The  blood-vessels  without  walls  in  the  bone-marrow  and  in  the  spleen  are  con- 
sidered on  p.  43. 

Among  the  properties  of  blood-vessels  their  contractility  should  be 
mentioned  first,  that  is,  the  ability  to  contract  by  virtue  of  the  unstriated 
muscle-fibers  contained  in  their  walls.  The  intensity '  and  force  with 
which  this  contraction  takes  place  are  proportional  to  the  degree  pof 
development  of  the  muscle-tissue. 

Heat  causes  contraction  of  the  blood-vessels  (in  the  mesentery  of  the  frog) . 
Excised  arteries  contract  when  filled  with  dilute  alkaline  solutions,  digitalin, 
atropin,  and  antiarin.  The  isolated  apex  of  the  heart  also  beats  more  freely  in 
alkaline  solutions.  When  the  vessels  are  filled  with  a  dilute  solution  of  lactic  acid 
they  dilate,  and  the  apex  of  the  heart  when  immersed  in  such  a  solution  also 
beats  more  rapidly.  According  to  Roy,  blood-vessels  undergo  shortening  under 
the  influence  of  heat,  if  precautions  are  taken  to  prevent  evaporation  and  the 
load  remains  the  same. 

If  blood  containing  an  admixture  of  certain  substances — such  as  amyl 
nitrite,  chloral  hydrate,  morphin,  quinin,  and  atropin — is  allowed  to  flow  through 
the  vessels  of  a  recently  excised,  living  organ,  dilatation  takes  place;  urea 
and  sodium  chlorid  have  the  same  effect  on  the  renal  vessels;  while  digitalin 
and  veratrin  cause  contraction. 

The  capillaries  also  possess  the  power  of  dilating  and  contracting, 
derived  from  the  protoplasmic  granules  of  the  cells  of  which  they  are 
composed. 

The  capillaries  have  been  designated  "protoplasm  in  tubular  form,"  and 
motor  phenomena  have  been  observed  in  them,  especially  after  irritation  in  the 
living  animal.  Strieker  observed  this  chiefly  in  the  capillaries  of  young  frog- 
spawn.  At  a  later  period  of  the  animal's  life  the  reaction  of  the  capillaries  to 
stimuli  is  much  less  distinct.  Rouget  observed  the  same  phenomena  also  in  new- 
born mammals.  Similar  observations  have  been  made  by  Golubew  and  Tarchanoff. 
Accordingly,  the  shape  of  individual  cells  varies  with  the  quantity  of  blood  con- 
tained in  the  vessels.  In  greatly  distended  vessels  the  cells  are  flat;  but  when 
the  vessel  is  collapsed,  the  cells  are  more  cylindrical  and  project  into  the  lumen. 

Among  the  physical  properties  of  blood-vessels  their  elasticity 
should  next  be  mentioned.  The  elasticity  is  slight,  that  is,  the  vessels 
offer  little  resistance  to  the  distending  forces,  such  as  pressure  or  trac- 
tion; but  it  is,  at  the  same  time,  complete,  that  is,  after  the  distending 
force  has  ceased  to  act,  the  vessels  regain  their  previous  form. 

According  to  Ed.  Weber,  Wertheim  and  A.  W.  Volkmann,  the  length  of  blood- 
vessels (like  that  of  moist  portions  of  the  animal  body  generally)  does  not  increase 
in  proportion  to  the  weight  employed  to  extend  it,  but  the  elongation  is  considera- 
bly less  with  progressive  increase  in  the  weight.  Hence  the  extensibility  of  the 
dead  artery  is  greatest  when  it  has  been  slightly  distended  by  intravascular  pres- 


PULSE-MOVEMENT. 

sure.  After  repeated  experiments,  however,  Wundt  was  led,  as  a  result  of  ex- 
perimental observations,  to  the  conclusion  that  blood-vessels  also  are  subject  to 
the  general  law  of  elasticity  mentioned.  He  maintains  that  it  is  necessary  to  take 
into  consideration  not  only  the  first  distention  that  occurs  after  the  application 
of  the  load,  but  also  the  "elastic  after-effect"  that  follows  gradually. 

This  terminal  distention,  which  often  proceeds  slowly,  is  so  gradual  during  the 
last  moments  that  observation  with  a  magnifying  lens  is  necessary  to  determine 
when  the  condition  of  definitive  distention  is  completed.  Deviations  from  the 
general  law  occur;  for  when  a  certain  load  is  exceeded,  lesser  degrees  of  distention 
and  at  the  same  time  permanent  changes  not  infrequently  result.  A  normal  vein 
may  be  stretched  at  least  50  per  cent,  without  exceeding  the  limit  of  elasticity. 

Pathological. — Nutritive  disturbances  modify  the  elasticity  of  the  arteries. 
When  death  has  been  preceded  by  marasmus,  the  arteries  are  found  relatively 
more  dilated  than  under  normal  conditions.  Beginning  connective-tissue  forma- 
tion in  the  intima,  combined  with  fatty  degeneration,  at  first  increases  the  dis- 
tensibility  and  diminishes  the  strength  of  the  wall.  As  the  development  of  the 
connective  tissue  progresses  in  cases  of  arteriosclerosis,  the  elasticity  and  firmness 
of  the  arteries  are  again  augmented.  Diminished  distensibility  is  found  also  in 
connection  with  atheroma,  in  cases  of  nephritis  and  in  the  arteries  of  drunkards. 

A  property  peculiar  to  the  walls  of  the  blood-vessels  is  their  power 
of  cohesion,  which  enables  them  to  resist  rupture,  even  when  the  in- 
ternal tension  is  considerable.  It  has  been  found  that  the  carotid 
artery  does  not  rupture  until  the  internal  pressure  has  been  raised 
artificially  to  fourteen  times  the  normal.  The  resistance  of  veins  to 
rupture  is  relatively  greater  than  that  of  arteries  with  the  same  thick- 
ness of  wall.  According  to  Grehant  and  Quinquaud  the  carotid  and 
iliac  arteries  in  man  resist  a  pressure  up  to  eight  atmospheres  and  the 
veins  more  than  half  of  this  amount. 

Pathological. — Diminished  power  of  cohesion  of  the  blood-vessels,  especially 
the  arteries,  is  not  uncommon  in  old  age. 

PULSE-MOVEMENT.— TECHNIC  OF  PULSE-EXAMINATION. 

The  physicians  of  antiquity  devoted  more  attention  to  abnormal  excitation 
of  the  pulse  than  to  the  normal  pulse.  Thus,  Hippocrates  (460-377  B.  C.)  speaks 
only  of  the  former  condition  and  applies  to  it  the  term  ojvyptf.  Later, 
Herophilus  (300  B.  C.)  in  particular  compared  the  normal  pulse  (Trafy6fi 
with  the  abnormally  excited  pulse.  He  laid  especial  stress  on  the  time-relations 
existing  between  dilatation  and  contraction  of  the  arterial  tube  and  defined  more 
accurately  the  properties,  volume,  fulness  (a^vy^  raxvg)  and  frequency 
(a<j)vyfj.6g  TTVKVO^) .  His  Alexandrian  colleague  Erasistratus  (who  died  280  B.  C.) 
was  the  first  to  make  correct  statements  in  regard  to  the  propagation  of 
the  pulse-waves;  for  he  stated  distinctly  that  the  pulse  appears  earlier  in  the 
arteries  nearer  the  heart  than  in  the  more  distant  vessels.  Erasistratus  also  felt 
the  pulse  below  a  cannula  introduced  in  the  continuity  of  an  artery.  Archigenes 
claims  especial  interest,  particularly  with  respect  to  the  pathology  of  the  pulse, 
because  he  was  the  first  to  designate  the  dicrotic  pulse,  which  he  had  the  oppor- 
tunity of  observing  in  febrile  diseases.  Galen  (131-202  A.  D.)  determined  more 
accurately  than  his  predecessors  the  principles  governing  expansion  and  contraction 
of  the  arteries  during  the  movement  of  the  pulse.  His  explanation  of  the  slow 
pulse  was  that  the  time  of  expansion  was  prolonged.  Galen  made  also  note- 
worthy observations  with  regard  to  the  rhythm  of  the  pulse  and  the  effect  of 
temperament,  sex,  age,  season  of  the  year,  climate,  sleep  and  waking,  emotional 
influences,  and  cold  and  warm  baths.  Cusanus  (1565)  was  the  first  to  count  the 
pulse-beats  with  a  time-piece. 

INSTRUMENTS  EMPLOYED  IN  THE  EXAMINATION  OF  THE  PULSE. 

It  is  possible  by  means  of  instrumental  examination  to  obtain  trustworthy 
information  with  regard  to  the  nature  of  the  movement  of  the  pulse.  Apart  from 
those  instruments  by  means  of  which  the  undulatory  movement  in  the  arterial 
tube  can  be  demonstrated  only  after  this  has  been  opened,  the  following  are 
worthy  of  mention: 


134 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE. 


Poiseuille's  Box-sphygmometer. — The  exposed  artery  (Fig.  41,  a  a)  is  en- 
closed for  a  distance  in  its  continuity  in  an  oblong  box  (K  K) ,  filled  with  some 
indifferent  fluid.  There  communicates  with  the  interior  of  the  box  a  graduated 
vertical  tube  (b),  filled  to  a  certain  point,  in  which  the  fluid  rises  and  falls, 
in  accordance  with  the  quantity  of  blood  contained  in  the  artery.  The  box  is 
constructed  like  an  ordinary  box,  one  half  representing  the  body  and  the  other 
half  the  lid.  A  circular  opening  is  made  in  each  end  of  the  box,  one  half  being 
contributed  by  the  body  and  the  other  half  by  the  lid,  in  which  the  artery 
is  hermetically  sealed  by  means  of  soft  fat.  Poiseuille  found  the  distention  of 
the  carotid  during  diastole  in  the  horse  to  be  equal  to  ^,  and  in  the  dog  to 
^  of  the  entire  volume  of  the  arterial  segment.  The  instrument  does  not  record 
any  more  minute  details  in  regard  to  the  movement  of  the  artery  during  the 
phases  of  the  pulse. 

Herisson's  Tubular  Sphygmometer  (Fig.  42)  consists  of  a  glass  tube  closed  at 
its  lower  extremity  by  an  elastic  membrane  and  filled  to  a  certain  level  with 
mercury.  The  apparatus  is  placed  vertically  on  the  skin  over  a  pulsating  artery, 
the  beats  of  which  set  the  column  of  mercury  in  motion.  A  similar  instrument 


FIG.  41. — Poiseuille's  Box-cabinet  Sphygmometer:  a  a,  the  exposed  artery; 
K  K,  the  surrounding  box  with  the  vertical  tube  and  scale  b. 


FIG.  42. — The  Tubular 
Sphygmometer  of 
Herisson  and  Chelius. 


was  used  in  1850  by  Chelius,  who  succeeded  with  its  aid  in  discovering  the  double 
beat  of  the  normal  pulse.  "After  it  (the  mercury)  has  been  raised  by  the  impact 
of  the  blood-wave,  it  falls  again  as  suddenly  to  its  lowest  level,  after  first  making 
another  short  pause  at  some  intermediate  point." 

Marey's  Sphygmo graph  is  based  on  a  combination  of  the  lever  (which  was  first 
employed  by  Vierordt  in  1855  m  the  construction  of  his  "sphygmograph")  with 
an  elastic  spring  (Fig.  43,  A).  The  latter,  which  is  screwed  fast  at  one  extremity 
(z) ,  while  the  other  extremity  is  free  and  provided  with  a  round  pad  (y) ,  presses 
against  the  radial  artery  with  a  force  equal  to  that  of  the  spring.  To  the  upper 
part  of  the  pad  is  fixed  a  short  vertical  ratchet  (k) ,  which,  when  acted  upon  by 
a  weak  spring  (e) ,  turns  a  small  cogwheel  (t) ,  from  the  axis  of  which  a  light 
wooden  lever  (v)  extends  almost  horizontally.  This  writing  lever  is  provided  at 
its  outer  extremity  with  a  delicate  point  (s) ,  which  records  the  movements  of 
the  pulse  on  the  smoked  surface  of  a  plate  (P)  made  by  clockwork  (u)  to  pass  in 
front  of  the  point  of  the  writing  lever  at  a  uniform  rate.  Marey's  instrument  is 
trustworthy  and  is  quite  extensively  used. 

Marey's  sphygmograph  is  adapted  solely  for  the  radial  pulse.      It  is  placed 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE.  135 

lengthwise  on  the  forearm,  where  it  is  steadied  by  means  of  two  short  metallic 
supports  (S)  and  fastened  with  a  tape,  which  must  not  be  drawn  too  tight.  The 
apparatus  is  also  provided  with  a  secondary  screw  (H),  which  can  be  made  to 
act  on  the  spring  (A).  If  the  screw  is  tightened  the  spring  is  compressed  and 
rendered  shorter,  less  yielding  and  movable  with  greater  difficulty;  when  the  pres- 
sure is  entirely  released,  the  spring  (A)  has  free  play,  is  more  yielding  and  the 
position  of  the  pad  (y)  is  higher. 


FIG.  43. — Marey's  Sphygmograph  (Diagrammatic). 

Marey's  Sphygmograph  with  Transmission  of  Air — of  which  many  modifications 
have  been  made,  for  example  by  Knoll;  Fig.  44  illustrates  the  modification  de- 
signed by  Brondgeest  and  designated  "pansphygmograph" — is  constructed  on  the 
principle  of  the  pneumatic  telegraph.  Two  pairs  of  shallow  metallic  cups — (S  S 
and  S'  S')  so-called  Upham's  capsules — are  each  pierced  from  below  at  their  center 
by  a  small  tube.  The  ends  of  these  tubes  are  connected  with  rubber  tubes  (K 
and  K') .  Over  the  mouth  of  each  of  the  four  cups  a  delicate  rubber  membrane  is 


7' 


FIG.  44. — Brondgeest's  Pansphygmograph  Constructed  on  Upham's  and  Marey's  Principle  of  the  Propagation  of 
Movement  through  Air-containing  Drums  Covered  with  Elastic  Membranes.  The  figure  represents  also 
diagrammatically  Marey's  cardiograph. 

stretched  and  from  the  middle  of  each  of  the  two  rubber  membranes  S  and  S' 
there  projects  a  button-shaped  process  (p  and  p'),  which  is  applied  to  the  pulsating 
artery  and  held  in  place  by  metallic  arches  B  B',  the  extremities  of  which  rest 
on  the  surrounding  skin.  From  the  center  of  each  of  the  other  two  rubber  mem- 
branes, which  are  directed  horizontally  upward,  there  projects  a  knife-edge,  which 
is  applied  close  to  the  balancing  center  (h  and  h')  of  the  delicate  writing  levers 
Z  and  Z'.  It  is  evident  that  any  pressure  applied  to  the  buttons  will  cause  a 


136 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE. 


bulging  upward  of  the  membrane  of  each  of  the  upper  cups,  the  movements  of 
which  are  propagated  to  the  writing  levers. 

The  instrument  sketched  in  Fig.  44  shows  the  entire  registering  apparatus 
in  duplicate.  An  instrument  of  this  kind  may,  therefore,  be  placed  with  the  two 
pads  on  two  different  arteries;  for  example,  when  it  is  desired  to  demonstrate  that 
the  pulse  occurs  earlier  in  the  arteries  near  the  heart  than  in  more  distant  vessels. 

Although  the  instruments  described  are  convenient  to  handle,  it  has  been 
found  by  experience  that  sudden  variations  in  pressure  are  not  accurately  recorded 
in  consequence  of  vibration  of  the  instrument  itself;  while  when  the  variations 
in  pressure  are  less  sudden,  the  records  may  under  certain  circumstances  be  fairly 
accurate.  Another  disadvantage  is  that  the  movement  of  the  writing  lever  Z  is 
not  entirely  synchronous  with  that  of  the  button  p.  For  this  reason  instruments 
constructed  on  this  principle  are  not  well  adapted  for  accurate  time  work.  The 
entire  apparatus  may  also  be  filled  with  water,  in  which  event  leaden  pipes  are 
used  instead  of  the  connecting  rubber  tubes.  Thus  adapted,  the  apparatus  is 
more  accurate  for  slower  movements,  while  a  pneumatic  instrument  is  better 
adapted  for  rapidly  varying  phases,  such  as  are  presented  by  the  movements  of 
the  pulse. 

Landois1  Angiograph. — From  one  extremity  of  a  plate  (Fig.  45,  G  G)  serving 
as  a  base,  arises  a  pair  of  arms,  between  the  upper  parts  of  which  the  lever  (d  r) 
moves  freely  between  two  points.  The  long  arm  of  this  lever  is  provided  with  a 
pad  (e),  directed  downward,  which  is  to  be  applied  to  the  pulse.  The  short  arm  of 
the  lever  on  the  other  side  carries  a  counter-weight  (d) ,  heavy  enough  to  maintain 


FIG.  45. — Landois'  Angiograph  Represented  Diagrammatically.     In  order  to  shorten  the  figure 
a  piece  has  been  cut  out  of  the  writing  lever. 


the  entire  lever  in  equilibrium.  The  extremity  (r)  carries  a  spring-ratchet,  which 
presses  against  a  cogwheel.  The  latter  is  immovably  fixed  to  the  axis  of  the 
light  writing  lever  c  f,  which  is  also  suspended  between  points  and  is  supported 
by  the  two  uprights  q  and  attached  to  the  opposite  end  of  the  base  G  G.  The 
writing  lever  also  is  maintained  in  perfect  equilibrium  by  means  of  a  small  counter- 
weight. The  needle  k  is  suspended  from  the  extremity  of  the  writing  lever  1, 
where  it  is  secured  by  a  hinge  and  is  readily  movable;  it  is  carried  by  its  own 
weight  toward  the  tablet  (shown  in  the  figure  in  profile) ,  and  as  it  moves  up  and 
down  it  records  the  curve  with  a  slight  scratching  movement  on  the  delicately 
smoked  surface  of  the  tablet. 

The  lever  d  r  at  a  point  approximately  opposite  the  juncture  with  the  pad  e 
supports  on  the  end  of  a  vertical  rod  the  flat  plate  q  for  the  reception  of  weights 
to  increase  the  load  on  the  pulse.  The  advantages  of  the  instrument  are :  (i)  The 
load  can  be  varied  at  will  and  can  be  accurately  determined  (while  in  Marey's 
sphygmograph  the  pressure  of  the  spring  increases  as  the  lever  is  raised) ;  (2) 
although  the  needle  is  constantly  in  contact  with  the  smoked  surface,  it  never- 
theless records  with  a  minimum  degree  of  friction;  (3)  the  movement  of  the 
writing  lever  is  a  vertical  up-and-down  movement  and  not  a  curved  movement 
as  in  Marey's  apparatus,  thus  considerably  facilitating  an  accurate  study  and 
measurement  of  the  curves.  In  the  construction  of  his  sphygmograph  Sommer- 
brodt  adopted  the  improvements  embodied  in  Landois'  angiograph. 

In  the  choice  of   a    sphygmograph   the  guiding  principle  should  be  that  the 


INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE.  137 

most  complete  instrument  and  the  one  whose  curves  most  closely  correspond  with 
the  pressure-variations  actually  taking  place  in  the  artery  is  that  in  which  the 
resistance  within  the  apparatus  itself  is  reduced  to  a  minimum,  in  which  those 
parts  that  execute  the  largest  movements  are  as  light  as  possible,  but  in  which 
the  bulk  of  that  portion  of  the  instrument  that  is  directly  set  in  motion  by  the 
movement  of  the  blood  in  the  artery,  is  strong  enough  and  heavy"  enough  for  its 
equilibrium  to  be  but  slightly  disturbed  by  even  considerable  force. 

Useful  sphygmographs  have  been  described  by  other  investigators,  as  Nau- 
mann,  Frey,  and  others.  For  practical  purposes  Dudgeon's  instrument,  which  is 
easily  manipulated,  may  be  recommended; 

the  load  is  applied  by  the  pressure  of  a  spring,  . 

or,  better,  by  a  weight  and  beam,  and  the 
tablet  moves  horizontally.  A  system  of  lines 
is  recorded  together  with  the  curve,  making  it 
possible  to  determine  by  measurement  the  size 
and  chronological  development  of  the  pulse- 
beats. 

Nomenclature  of  Pulse-tracings. — In  every 
pulse-tracing  (sphygmogram  or  arterio- 
gram)  there  are  distinguishable  the  as- 
cending limb,  the  apex,  and  the  descend- 
ing limb.  Irregular  elevations  in  the  course 
of  the  descending  limb  are  called  catacrotic 
elevations,  while  those  in  the  ascending  limb 
are  known  as  anacrotic  elevations.  The  de- 
scending limb  almost  always  contains  sec- 
ondary elevations,  while  the"  ascending  limb 
almost  always  appears  as  a  simple  rising 
line.  When  a  recoil-elevation,  which  will  be 
described  more  fully  later  on,  occurs  once  or  FlG>  46.— Dudgeon's  Sphygmograph. 

twice  in  the  descending  limb,  the  sphygmo- 

graphic  curve  is  called  dicrotic  or  tricrotic.  When,  as  happens  if  the  pulse- 
beats  follow  one  another  in  rapid  succession,  the  succeeding  beat  cuts  off  the 
recoil-elevation  of  the  preceding  curve,  the  curve  is  called  monocrotic. 

Method  of  Making  Sphygmographic  Tracings. — The  tracings  are  recorded  on 
smooth  glazed  paper  like  that  used  for  visiting  cards,  which  has  been  covered  with 
a  delicate  translucent  layer  of  soot  by  exposure  over  burning  camphor  or  a 
smoking  lamp.  The  tracing  is  fixed  by  immersing  the  paper  in  a  solution  of 
shellac  and  alcohol,  after  which  it  is  allowed  to  dry. 

Mensuration  of  Sphygmographic  Tracings. — When  a  tablet  is  made  to  move 
at  a  uniform  rate  by  means  of  clockwork,  the  vertical  height  and  horizontal 
length  of  individual  portions  of  the  tracing  can  be  measured  with  a  fine  rule. 
The  distance  traversed  by  the  tablet  in  a  second  being  known,  it  is  possible  by 
actual  measurement  to  compute  the  duration  of  the  individual  portions  of  the 
pulse-movement.  Accurate  measurements  of  this  kind  must  be  made  under  the 
microscope  with  the  aid  of  an  ocular  micrometer,  a  low  magnification  and  direct 
illumination  being  employed.  The  sections  to  be  measured  are  placed  be- 
tween two  lines  that,  in  the  case  of  sphygmographs  like  Marey's,  which  make 
a  curved  tracing,  must  be  arcs  of  a  circle  (of  which  the  writing  lever  is  the 
radius) ,  and  in  the  case  of  the  angiograph  must  be  vertical. 

An  especially  convenient  method  consists  in  recording  the  curve  on  a 
tablet  attached  to  one  end  of  a  vibrating  tuning-fork  (Fig.  60).  Another  less 
accurate  method  consists  in  recording  the  vibrations  of  a  tuning-fork  on  the  tablet 
of  the  sphygmograph  at  the  same  time  that  a  Sphygmographic  tracing  is  being 
recorded,  the  latter  being  above  the  tuning-fork  record. 

The  Gas-sphygmoscope. — To  meet  the  objection  that  has  frequently  been  urged 
against  instruments  for  registering  the  pulse,  namely  that  the  secondary  elevations 
observed  in  the  sphygmogram  are  due  to  the  after- vibrations  of  the  apparatus 
from  inertia,  Landois  constructed  a  gas-sphygmoscope,  in  which  the  movement  of 
solid  bodies  is  excluded  and  any  after-vibration  of  inert  masses  that  have  been 
set  in  motion  is,  therefore,  impossible. 

The  superficial  arteries,  whose  movement  is  communicated  to  the  overlying 
skin,  will,  naturally,  through  the  movement  imparted  to  this  layer  of  the  skin, 
cause  also  a  movement  in  the  contiguous  layers  of  air.  The  thin  layer  of  air 
above  the  pulsating  cutaneous  area  (Fig.  48)  a  is  excluded  by  means  of  a  shallow 


138  INSTRUMENTS    FOR    INVESTIGATING    THE    PULSE. 

metallic  gutter  b,  which  is  placed  on  the  skin  so  that  its  concavity  covers  the 
artery  like  a  small  tunnel.  The  narrow  space  between  the  wall  of  the  tunnel 
and  the  skin  is  filled  with  illuminating  gas.  To  this  end  one  extremity  of  the 
metallic  tunnel  is  connected  with  the  gas-tube  g,  while  the  other  extremity  com- 
municates by  means  of  a  short  rubber  connecting  piece  x  q  with  a  small  tube  t, 
bent  upward  at  an  angle  and  the  point  of  which  is  drawn  out  to  a  minute  opening 
for  the  escape  of  the  gas.  The  gas  is  allowed  to  pass  through  the  metallic  tunnel, 
under  low  pressure,  the  inflow  being  regulated  so  that  the  flame  v  is  not  more 
than  a  few  millimeters  long.  It  is  readily  seen  that  the  flame  increases  in  height 
synchronously  with  each  pulse-beat  and  that  the  descent  is  interrupted  by  a 
distinct  after-beat,  von  Kries  photographed  the  image  of  the  flame. 


The  measurements  of  the  accompany- 
ing curve  are  as  follows : 

1-2  =     7.5  =  0.121  sec. 
1—3  =  16       =  0.258 
1-4  =  22.5  =  0.363 
i-5  =  39-5   =  °-638 


FIG.    47. — Sphygmographic     Tracing     from 

Radial  Artery  Made  with  Landois'  Angiograph 


the 


Attached  5  to  a  Vibrating   Tuning-fork, 
indentation  corresponds  to  0.01613  sec. 


Each 


Hem-autography. — If  a  freely  exposed  artery  be  divided  in  an  animal  so  that 
the  blood-stream  spurts  forth  and  is  allowed  to  impinge  on  a  glass  plate  or  a  sheet 
of  paper  moved  vertically  at  some  distance,  the  resulting  tracing  will  coincide 
almost  perfectly  with  the  normal  curve  of  the  artery  as  recorded  by  the  sphygmo- 
graph.  In  addition  to  the  primary  elevation  (Fig.  49,  P),  the  recoil-elevation  (R) 
and  the  elasticity-elevations  (e  e)  are  appreciable.  This  self-registration  of  the 


FIG.   48. — Landois'    Gas-sphygmoscope. 

blood-wave  furnishes  a  convincing  proof  that  the  movement  is  produced  in  the 
blood  itself  and  is  communicated  as  an  undulatory  movement  to  the  arterial  wall. 
By  determining  the  quantity  of  blood  contained  in  the  several  portions  of  the 
hemautographic  tracing  it  is  found  that  the  quantity  of  blood  that  escapes  from 
the  divided  artery  during  systole  is  to  the  quantity  that  escapes  during  diastole 
(that  is  during  contraction  and  dilatation  of  the  vessel)  approximately  as  7  :  10. 
The  quantity  of  blood  that  escapes  during  a  unit  of  time  while  the  artery  is  di- 
lating is  equal  to  a  little  more  than  twice  the  quantity  that  escapes  during  a  unit 
of  time  while  the  vessel  is  contracting. 

THE   PULSE-TRACING,    THE    RECOIL-ELEVATION   AND    THE 
ELASTICITY-ELEVATIONS. 

The  sphygmogram  presents  an  ascending  limb,  recorded  during  the 
distention  (diastole)  of  the  artery;  the  apex  (Fig.  50,  P);  and  the  de- 
scending limb,  which  corresponds  to  the  contraction  (systole)  of  the 


ORIGIN    AND    PROPERTIES    OF    THE    DICROTIC    ELEVATION. 


artery.  The  most  conspicuous  features  of  the  sphygmographic  tracing 
are  the  two  entirely  distinct  elevations  in  the  descending  limb  of  the 
curve.  The  more  prominent  of  the  two  occupies  approximately  the 
center  of  the  descending  limb,  where  it  appears  as  a  distinct  elevation 
(R);  it  is  known  as  the  dicrotic  after-beat  or,  with  reference  to  its  origin, 
as  the  recoil-elevation. 

The  sphygmographic  tracing  reproduces  the  chronological  course  of  the 
pressure  exerted  by  the  undulatory  movement  of  the  blood  on  the  arterial  wall, 
the  pad  of  the  sphy gmograph ,  which  is  supported  on  a  spring,  rising  and  falling 
with  the  variations  in  pressure;  the  instrument  therefore  records  "pressure- 
pulse." 

ORIGIN  AND   PROPERTIES  OF  THE  DICROTIC  ELEVATION. 

The  recoil-elevation  (also  designated  secondary  or  dicrotic)  is  pro- 
duced in  the  following  manner:  After  the  column  of  blood  propelled 
into  the  arterial  system  by  the  ventricular 
systole  has  generated  a  positive  wave, 
which,  beginning  at  the  aorta,  extends 
rapidly  to  all  of  the  arteries,  even  to  the 
minutest  arterial  branches,  in  which  it 
disappears,  the  arteries  contract  as  soon  as 
closure  of  the  semilunar  valves  prevents 
the  further  entrance  of  blood.  The  elasti- 
city and  the  active  contraction  of  the 
blood-vessels  thus  exerts  a  counter  pressure 
on  the  blood-column.  The  blood  is  forced 
to  seek  an  outlet.  In  its  progress  toward 
the  periphery  it  finds  no  obstacle  in  its 
path,  but  the  portion  that  escapes  toward 
the  center  of  the  circulation  recoils  from 
the  already  closed  semilunar  valves.  The 
impact  of  the  blood  sets  up  another  posi- 
tive wave,  which  is  again  propagated  into 
the  arteries  and  disappears  as  before  in 
the  remotest  minute  branches.  If,  how- 
ever, there  is  sufficient  time  for  the  com- 
plete development  of  the  sphygmographic 
tracing,  a  second  reflected  wave  is  pro- 
duced in  the  proximal  arteries  (especially 
in  the  short  course  of  the  carotids,  but 
also  in  the  arteries  of  the  upper  ex- 
tremities, but  not  in  those  of  the  lower  extremities  because  of  their 
great  length)  in  the  same  way  as  the  first.  Just  as  the  pulse  appears 
somewhat  later  in  the  more  peripheral  arteries  than  in  those  nearer  the 
heart,  so  the  secondary  wave,  produced  by  the  recoil  of  the  blood  from 
the  aortic  valves,  also  appears  later  in  the  more  distant  arteries.  Both 
kinds  of  waves,  the  primary  and  the  secondary  pulse-wave,  and  possibly 
also  the  tertiary  recoil -wave,  originate  at  the  same  point  and  are  propa- 
gated in  the  same  way.  The  longer  the  distance  to  be  traveled  before 
they  reach  a  given  point  in  the  artery,  the  later  will  be  their  arrival 
at  that  point. 

The  following  laws  with  regard  to  the  recoil-elevation  have  been 
determined  experimentally : 


FIG.  49. — Hemautographic  Tracing  from 
the  Posterior  Tibial  Artery  of  a  Large 
Dog:  P,  primary  pulse-wave;  R,  re- 
coil-elevation; e  e,  elasticity-eleva- 
tions. 


140 


ORIGIN    AND    PROPERTIES    OF    THE    DICROTIC    ELEVATION. 


i.  The  dicrotic  elevation  appears  later  in  the  descending  limb 
of  the  curve  the  longer  the  artery,  measured  from  the  heart  to  the 
peripheral  termination  of  the  artery.  (The  curves  in  Figs.  47,  53  and 
57  may  be  measured  to  confirm  this  point.) 


XIV 


xv 


FIG.  50. — I,  II,  III,  Sphygmographic  tracings  from  the  carotid  artery;  IV,  from  the  axillary;  V .  IX,  from  the  radial; 
X,  bigeminate  pulse  from  the  radial;  XI,  XII,  sphygmographic  tracings  from  the  femoral;  XIII,  from 
the  posterior  tibial;  XIV,  XV,  from  the  dorsalis  pedis.  In  all  of  the  tracings  P  indicates  the  apex  of  the 
curve;  R,  the  dicrotic  elevation;  e  e,  the  elasticity-elevations;  k,  the  elevation  caused  by  the  closure  of  the 
aortic  semilunar  valves. 


The  shortest  accessible  arterial  course  is  that  of  the  carotids,  where  the  dicrotic 
elevation  attains  its  greatest  height  about  0.35  or  0.37  second  after  the 
beginning  of  the  pulse.  The  next  shortest  accessible  arterial  course  is  that 
of  the  upper  extremity,  where  the  apex  of  the  dicrotic  elevation  is  traced  about 
0.36  or  [0.38  or  0.40  second  after  the  beginning  of  the  pulse.  The  longest 


ORIGIN    AND    PROPERTIES    OF    THE    ELASTICITY-ELEVATION.  141 

course  is  that  of  the  arteries  of  the  lower  extremity,  in  which  the  apex  of 
the  recoil-elevation  is  formed  about  0.45  or  0.52  or  0.59  second  after  the 
beginning  of  the  curve,  in  accordance  with  the  size  of  the  individual.  In  children 
and  in  small  individuals  the  recoil-elevation  occurs  accordingly  earlier  in  all  of 
the  arteries.  If  a  rubber  tube  be  connected  with  the  carotid  or  the  femoral  artery 
of  a  dog,  the  sphygmographic  tracing  may  be  recorded  also  from  this  tube. 
Under  such  circumstances  the  interval  between  the  beginning  of  the  curve  and 
the  dicrotic  elevation  will  naturally  be  directly  proportional  to  the  length  of  the 
tube. 

2.  The  dicrotic  elevation  in  the  descending  limb  of  the  curve  will  be 
the  lower   and    the   more  indistinct   the   greater  the   distance   of   the 
artery  from  the  heart.      It  is  not  surprising  that  the  secondary  wave 
becomes  smaller  and  more  indistinct  the  further  it  must  travel  in  the 
arterial  tube. 

3.  The   dicrotic   elevation   in  the   pulse   will   be   more   distinct  the 
shorter  and  the  more  vigorous  the  primary  pulse- wave.     It  is,  there- 
fore, relatively  largest  with  a  short,  powerful  systole  of  the  heart. 

4.  The  dicrotic  elevation  is  greater  the  greater  the  tension  in  the 
arterial  tube. 

In  Fig.  50  IX  and  X  are  recorded  with  low,  V  and  VI  with  moderate, 
and  VII  with  high  tension  of  the  arterial  wall. 

Influences  Affecting  Vascular  Tens-ion. — A  number  of  influences  are  known 
that  affect  the  tension  in  the  arterial  tube.  The  tension  is  diminished  by  beginning 
inspiration,  vasomotor  paralysis,  venesection,  intermission  of  the  heart's  action, 
heat,  and  elevation  of  a  part  of  the  body.  The  tension  is  increased  by  beginning 
expiration,  accelerated  heart-action,  stimulation  of  the  vasomotor  nerves,  inter- 
ference with  the  flow  of  blood  to  the  periphery  (as  by  conditions  of  inflammatory 
stasis),  certain  poisons  (such  as  lead),  compression  of  other  large  arterial  trunks, 
the  effect  of  cold  and  of  electricity  on  the  small  vessels  of  the  skin,  and  inter- 
ference with  the  venous  flow.  Likewise,  exposure  of  the  arterial  trunks  is  followed 
by  increased  vascular  tension  on  account  of  the  stimulation  caused  by  the  atmos- 
pheric air  coming  in  contact  with  the  arterial  wall.  Increased  arterial  tension  is 
observed  also  in  association  with  a  variety  of  morbid  conditions.  When  the  ten- 
sion is  high,  the  entire  sphygmographic  tracing  is,  as  a  rule,  lower. 

In  conformity  with  the  conditions  named,  increased  tension  will  be  indicated 
by  a  lower,  more  indistinct  dicrotic  elevation;  and  diminished  tension  in  the 
arterial  tube,  on  the  other  hand,  by  an  enlarged  and  more  distinct  dicrotic  eleva- 
tion. A  consideration  of  the  laws  governing  the  dicrotic  elevation  is  of  great 
practical  significance  in  the  study  of  the  pulse.  Moens  asserts  that  the  interval 
elapsing  between  the  primary  elevation  and  the  dicrotic  wave  increases  directly 
as  the  diameter  of  the  vessel,  and  that  the  thickness  of  the  wall  diminishes  as  the 
coefficient  of  elasticity  becomes  smaller. 

ORIGIN  AND  PROPERTIES  OF  THE  ELASTICITY-ELEVATION. 

In  addition  to  the  dicrotic  elevation  a  series  of  more  numerous, 
though  much  less  distinct,  often  almost  imperceptible,  movements  are 
appreciable  in  the  sphygmographic  tracing.  These  (marked  e  e  in  Fig. 
50)  are  produced  by  the  vibrations  of  the  elastic  vessel,  which  behaves 
like  a  tense  elastic  membrane  when  it  is  rapidly  and  vigorously  stretched 
by  the  pulse-wave,  just  as  a  relaxed  elastic  sheet  of  rubber  undergoes 
a  series  of  oscillations  when  it  is  suddenly  and  vigorously  stretched 
and  made  tense.  Similarly,  the  elastic  tube  will  exhibit  oscillatory 
movements  when  it  passes  suddenly  from  a  condition  of  tension  to  one 
of  relaxation.  These  minor  elevations  produced  in  the  sphygmographic 
tracing  by  the  elastic  vibrations  of  the  arterial  wall  are  known  as  elas- 
ticity-elevations. 

As  the  elasticity-elevations  are  due  to  the  vibrations  of  the  stretched 
coat  of  the  blood-vessel,  the  following  facts  will  be  readily  understood: 


142  THE    DICROTIC    PULSE. 

1.  In  the  same  artery  the  variations  in  elasticity  increase  in  num- 
ber as  the    tension    of   the    arterial    wall    increases.     Especially    high 
tension  has  been  encountered  chiefly  during  the  cold  stage  of  malarial 
fever  (intermittent  fever),  and  precisely  in  this  connection  has  the  most 
obvious  increase  in  the  elevations  also  been  observed. 

2.  If  the  tension  of  the  arterial  wall  is  greatly  diminished,  the  elas- 
ticity-elevations may  disappear.     As  diminution  in  the  tension  favors 
the  development  of  a  dicrotic  elevation,  the  two  kinds  of  elevations  have, 
with  respect  to  their  magnitude,  an  inverse  relation  to  each  other. 

3.  In  the  presence  of  diseases  of  the  vessel-wall  that  diminish  or 
even  destroy  its  elasticity,  the  elasticity-elevations  are  either  greatly 
diminished  'in  size  or  altogether  abolished. 

4.  The  greater  the  distance  of  the  artery  from  the  heart,  the  greater 
will  be  the  elasticity-elevations  in  the  descending  limb  of  the  curve. 

5.  When  the  mean  pressure  in  an  artery  is  heightened  on  account  of 
interference  with  the  flow  of  blood  in  the  arteries,  the  elasticity-eleva- 
tions are  nearer  the  apex  of  the  curve. 

6.  The   elasticity-elevations   vary   in   number   and   position   in   the 
sphygmographic  tracings  from  the  different  arteries  in  the  human  body. 

When  the  arm  is  held  in  the  vertical  position,  relaxation  and  diminution  in 
the  elastic  tension  appear  in  the  course  of  five  minutes  in  the  arteries  of  the  upper 
extremity,  which  at  the  same  time  contain  less  blood. 

The  elevations  that  are  designated  elasticity-elevations  are  believed  by  Moens 
to  owe  their  origin  to  numerous  small  waves  that  appear  to  be  superadded  to 
the  dicrotic  elevation.  Grashey  thinks  them  only  in  part  due  to  elastic  vibrations. 

The  laws  governing  the  movement  of  the  pulse  may  be  most  readily  demon- 
strated by  means  of  investigations  in  regard  to  the  undulatory  movements  in 
elastic  rubber  tubes,  as  has  been  done  by  Marey,  Landois,  Moens,  Grashey,  G.  v. 
Liebig,  and  others, 

THE  DICROTIC  PULSE. 

Under  the  influence  of  excessive  elevation  of  temperature  the  pulse  in  man 
is  sometimes  observed  to  be  composed  of  two  beats  (Fig.  50),  the  first  being  large 
and  the  second  small  and  apparently  secondary  to  the  first.  A  couple  of  these 
beats  always  correspond  to  a  single  systole  of  the  heart.  By  the  sense  of  touch 
it  is  quite  possible  to  feel  the  two  unequal  beats  separately.  The  study  of  the 
pulse  with  the  sphygmograph  has  taught  that  the  dicrotic  pulse  is  only  an 
exaggeration  of  the  normal  pulse.  The  palpable  secondary  beat  is  only  a  greatly 
magnified  dicrotic  elevation,  which  under  normal  conditions  cannot  be  recognized 
by  the  palpating  finger,  but  which,  when  increased  by  some  morbid  condition, 
becomes  recognizable  by  the  sense  of  touch.  As  regards  the  causes  that  are 
responsible  for  this  increase  in  the  size  of  the  dicrotic  elevation,  Landois'  investiga- 
tions have  yielded  the  following  results : 

1.  The  production  of  a  dicrotic  pulse  is  favored  by  a  short  primary  pulse- 
wave,  such  as  occurs  usually  in  the  presence  of  fever,  a  condition  in   which  the 
contractions  of  the  heart  are  comparatively  rapid  and  unproductive. 

2.  The  dicrotic  pulse  is  favored  by  reduction  of  the   tension  in  the  arterial 
system.     A  short  systole  combined  with  diminished  arterial    tension  offers  the 
most  favorable  condition  for  the  production  of    the  dicrotic  pulse.      Sometimes 
the  dicrotic  pulse  is  felt  only  in  a  certain  arterial  distribution,   while  in  all  the 
others  the  pulse-beat  is  single.     This  happens  especially  in  the  brachial  artery  on 
one  or  other  side  of  the  body.      Under  such  circumstances  the   conditions    for 
the  production  of  dicrotism  in  the  corresponding  arterial  area  must  be  especially 
favorable.     These  conditions  will  be  found  in  the    local  diminution  of   vascular 
tension  in  this  area  in  consequence  of  paralysis  of  the  vasomotor   nerves  con- 
trolling it.      If  the  tension  be  increased,  as  can  readily  be  done  by  compressing 
adjacent  or  other  arterial  trunks  of  considerable  size  or  the  corresponding  veins, 
the  dicrotic  pulse  is  converted  into  a  single  pulse.      In  the  presence  of  fever,  dicro- 
tism appears  to  be  due  to  the  elevation  of  temperature  (from  39°  to  40°  C.),  which 
causes  greater  distention  of  the  artery  and  shorter  and  quicker  heart-beats. 


DIFFEREXCES    IN    THE    TIME-RELATIONS    OF    THE    PULSE.  143 

3.  It  is  absolutely  indispensable  for  the  production  of  the  dicrotic  pulse  that 
the  arterial  wall  possess  its  normal  elasticity.  In  old  persons  with  calcined  arterial 
walls  dicrotism  does  not  appear. 

In  Fig.  51,  A,  B,  C  illustrate  the  gradual  transition  from  the  normal  radial 
curve  (A)  to  the  dicrotic  pulse  (B,  C),  in  which  the  recoil-elevation  (r)  appears 
as  an  independent  elevation. 


FIG.  51. — Normal  Pulse-production  of  the  Dicrotic  Pulse.     P.  caprizans— P.  monocrotus. 

If  in  the  presence  of  dicrotism  of  febrile  origin  the  pulse  becomes  more  and 
more  frequent,  the  next  succeeding  pulse-beat  may  begin  before  the  descending 
portion  of  the  recoil-elevation  is  completed  (Fig.  51,  D,  E,  F),  or  it  may  even 
begin  at  the  apex  (G) — P.  caprizans.  Finally,  if  the  next  succeeding  beat  begins 
in  the  depression  (z)  between  the  primary  elevation  (p)  and  the  recoil-elevation 
(r) ,  the  latter  disappears  altogether,  and  the  curve  (H)  assumes  the  monocrotic 
form. 

DIFFERENCES  IN  THE  TIME-RELATIONS  OF  THE  PULSE. 

FREQUENT  AND  INFREQUENT  PULSE. 

In  accordance  with  the  number  of  pulse-beats  in  one  minute,  the  pulse  is 
designated  either  frequent  or  infrequent.  Under  the  influence  of  fever  or  other 
agencies  the  number  of  pulse-beats  may  be  considerably  increased  until  they 
reach  120  or  more.  Reduction  of  the  pulse-beats  to  about  40  is  observed  under 
certain  normal  conditions  (during  the  puerperium,  in  states  of  hunger,  and  as  an 
idiosyncrasy  in  some  individuals) .  In  rare  cases  these  limits  may  be  exceeded  in 
either  direction.  In  periodic  attacks  as  many  as  250  pulse-beats  have  been 
counted.  Such  attacks  must  be  designated  pyknocardia  (the  term  tachycardia  is 
incorrect  because  rn^i^  is  equivalent  to  quick).  Abnormal  infrequency  or 
spanicardia  (the  term  bradycardia  is  incorrect  because  fipafivf  is  equivalent  to 
slow)  also  occurs;  15,  10,  and  even  8  beats  in  the  minute  have  been  counted. 
Under  such  conditions,  disease  of  the  cardiac  nerves  or  of  the  muscle  from  over- 
exertion  or  disorders  in  the  coronary  circulation  should  be  thought  of. 

Deepening  of  the  respiration  without  acceleration  usually  causes  some  increase 
in  the  frequency  of  the  pulse.  Accelerated  but  superficial'  breathing  is  without 
effect,  while  deep,  rapid  respirations  increase  the  number  of  pulse-beats. 

QUICK  AND  SLOW  PULSE. 

When  the  development  of  the  pulse-wave  is  such  that  the  distention  of  the 
arterial  tube  goes  on  slowly  to  its  maximum  and  collapse  of  the  distended  artery 
likewise  occurs  gradually,  the  slow  pulse  is  produced;  while  under  opposite 
conditions  the  quick  pulse  results.  Among  the  factors  that  increase  the  quickness 
of  the  pulse  are:  slowness  of  cardiac  action;  greatly  diminished  resistance  of  the 
arterial  coats;  dilatation  of  the  smallest  arteries,  diminishing  the  resistance  to 
the  flow  of  blood;  greater  proximity  to  the  heart.  The  curve  in  a  sphygmo- 
graphic  tracing  from  a  quick  pulse  is  high  and  the  apex  pointed;  a  slow  pulse 
yields  a  low  sphygmographic  curve,  the  ascending  portion  being  particularly  short, 
while  the  apex  is  broad. 


144         CONDITIONS    INFLUENCING    THE    FREQUENCY    OF    THE    PULSE. 

CONDITIONS  ^INFLUENCING  THE  FREQUENCY  OF  THE  PULSE. 

In  the  normal  adult  male  the  number  of  pulse-beats  is  71  or  72  in  the  minute, 
in  the  female  about  80.  Other  factors  that  influence  the  frequency  are : 

(a)  Age: 

Beats  in  the  Beats  in  the 

Minute.  Minute. 

New-born 130—140  ioth-1 5th  year 78 

1  year 120—130  i5th-2oth .  70 

2  years 105  2oth-25th  70 

3  100  25th~5oth  70 

4 97  6oth  year 74 

5  94—  90       8oth  year 70 

10  years about    90  8oth~9oth  year over  80 

(b)  The    length    of   the  body  stands  in  a  definite  relation  to  the  frequency  of 
the  pulse.     Volkmann  gives  the  formula  pl==j^~1  in  which  P  and   P!    represent 
the    pulse-frequency   and    L   and    L1  the    body-length.      Rameaux   suggests   the 
following   formula:     Nx  =  Nj/j^'f  in  which  N  and    N\    represent  the    ptilse-fre- 
quency  and  D  and  Dx  the  body-length.     By  means  of  this  formula  the    pulse- 
frequency  has  been   calculated  from  the  body-length  in   a  number  of  healthy 
individuals  with  the  following  results: 

Length  of  the  Body  Pulse: 

in  Units  of  10  Cm.                                                                     Estimated  Observed. 

80-90 90  103 

90—100 86  91 

IOO— HO 8l  87 

no— 120 78  84 

120-130 75  78 

130-140 72  76 

140-150 69  74 

150—160 67  68 

160—170 65  65 

170—180 63  64 

Over  180 60  60 

As  it  is  possible  to  determine  the  pulse-frequency  from  the  body-length,  it 
must  also  be  possible  to  calculate  the  body-length  from  the  pulse-frequency.  For 
this  purpose  the  following  is  deduced  from  the  foregoing  formula: 

D    -DN2 
D'-NT 

These  calculations,  naturally,  have  only  a  theoretical  interest,  and  it  is  obvious 
that  for  purposes  of  comparison  none  but  perfectly  healthy  individuals  of  the 
same  age  and  sex  and  living  under  absolutely  identical  conditions  must  be  selected. 

(c)  Of  other  factors  that  influence  the  frequency  of  the  pulse,  it  has  been 
observed  that  muscular  activity,  heightening  of  the  arterial  blood-pressure,  in- 
gestion   of  food,   elevation   of  temperature,   pain,   unpleasant   sensations  in  the 
alimentary  tract,  nausea,  and  psychic  or  sexual  excitement  accelerate  the  pulse. 

Further,  the  pulse  is  somewhat  more  frequent  in  the  standing  position  (also 
when  the  body  is  raised  passively)  than  in  the  recumbent  posture.  Music  accel- 
erates the  heart-beat  in  man  and  in  animals  and  at  the  same  time  raises  the 
blood-pressure.  Exposure  to  increased  atmospheric  pressure  diminishes  the 
pulse-frequency.  In  the  latter  condition  the  first  elasticity-elevation  more 
nearly  approaches  the  summit. 

^  (d)  The  diurnal  periodicity  of  the  pulse-frequency  is  of  especial  interest.  The 
variations  rarely  exceed  a  few  beats  and  in  a  general  way  they  correspond  with 
the  course  of  the  temperature-curve.  According  to  Haun  the  pulse  is  most  fre- 
quent with  the  advent  of  winter  and  is  least  frequent  with  that  of  summer. 

(e)  Frequency  of  the  pulse  in  various  animals:  Elephant  28,  high-bred  stallion 
about  30  (in  mares  and  work-horses  it  is  a  little  higher),  neat  cattle  about  50, 
sheep  and  swine  75,  dog  95,  cat  130,  rabbit  from  120  to  150  in  one  minute. 


VARIATIONS    IN    THE    RHYTHM    OF    THE    PULSE.  145 

VARIATIONS  IN  THE   RHYTHM  OF  THE  PULSE   (ALLORRHYTHMIA) . 

When  the  finger  is  applied  to  the  normal  artery  no  special  rhythm  is  observed, 
the  beats  apparently  succeeding  one  another  at  regular  intervals,  although  small 
differences  may  be  observed  in  the  intervals  between  the 'pulse-beats;  any  more 
complicated  rhythm  must  be  considered  an  abnormal  pulse-movement.  Some- 
times a  beat  is  suddenly  dropped  from  the  normal  succession — omission  of  the 
pulse.  When  this  is  due  simply  to  weakness  of  the  systole,  the  pulse  is  designated 
intermittent;  when  due  to  the  absence  of  systole,  the  pulse  is  designated  deficient. 
The  latter  occasionally  occurs  in  the  obese  and  has  no  pathological  significance. 
More  rarely  a  series  of  pulse-beats  is  characterized  by  the  successive  diminution 
of  individual  beats,  followed  after  an  interval  by  a  return  to  the  original  strength — 
P.  myurus.  Sometimes  a  supernumerary  pulse-beat  appears  to  be  interpolated 
in  the  normal  series — intercurrent  pulse.  These  forms  of  pulse  are  not  infre- 
quently produced  reflexly  through  the  gastro-intestinal  tract,  or  they  are 
observed  in  cases  of  neurasthenia  after  psychical  disturbances,  often  after  intoxi- 


FIG.   52. — Alternating   Pulse. 

cation  with  alcohol  or  tobacco,  in  the  absence  of  any  changes  in  the  heart. 
Occasionally  an  intereurrent  systole  of  the  auricles  takes  place  in  conjunction  with 
the  deficient  or  the  intermittent  pulse.  The  regular  alternation  from  a  high  to  a 
low  pulse  is  known  as  alternating  pulse.  The  peculiarity  of  the  bigeminate  pulse 
consists,  according  to  Traube,  in  the  circumstance  that  the  pulse-beats  always 
occur  in  pairs,  so  that  the  second  beat  always  begins  close  to  the  descending 
limb  of  the  curve  of  the  first.  In  the  same  way  a  tr {geminate  or  a  quadri- 
gciuinate  pulse  may  be  produced.  Knoll  found  in  experiments  on  animals  that 
these  varieties  of  the  pulse  occur  whenever  greater  resistances  develop  in  the 
circulation,  increasing  the  demands  on  the  heart.  In  man  also  their  occur- 
rence points  to  a  disproportion  between  the  strength  of  the  heart-muscle  and  the 
work  to  be  performed.  Absolute  irregularity  of  the  heart  is  designated  arrhythmia 
or  delirium  cordis. 

VARIATIONS  IN  THE   STRENGTH,   THE   TENSION,   AND   THE 
VOLUME  OF  THE  PULSE. 

The  relative  strength  of  the  pulse-beat  (strong  and  feeble  pulse)  may  be  deter- 
mined by  observing  the  weight  the  pulse  is  capable  of  raising.  For  this  purpose 
a  weighted  sphygmograph  may  be  used,  the  pad  of  which  is  applied  to  a  section 
of  the  artery  that  must  be  constant  in  extent.  The  writing  lever  naturally  ceases 
to  act  as  soon  as  the  pressure  on  the  artery  exceeds  the  strength  of  the  pulse- 
beat.  The  load  directly  indicates  the  strength  of  the  pulse.  According  to  G.  v. 
Liebig  the  pulse  in  a  man  with  a  tendency  to  pulmonary  tuberculosis  is  readily 
compressed  (feeble)  and  it  has  at  the  same  time  a  tendency  to  dicrotism. 

The  pulse  appears  hard  or  soft  when  the  artery,  in  conformity  with  the 
mean  blood-pressure  but  independently  of  the  strength  of  the  individual  beat, 
offers  a  greater  or  lesser  resistance  to  the  palpating  finger — hard  and  soft  pulse. 
The  pulse  is  said  to  be  full  when  the  artery  is  greatly  distended  and  over- 
filled, irrespective  of  the  size  of  the  pulse  itself,  and  empty  when  the  artery  is 
thin  and  poorly  filled. 

In  determining  the  tension  of  an  artery  and  of  the  pulse,  that  is,  whether  the 
latter  is  hard  or  soft,  it  should  always  be  noted  whether  the  artery  exhibits  that 
quality  only  during  the  pulse-wave  or  also  while  the  vessel  is  at  rest.  All  arteries 
are  harder  during  the  pulse-beat  than  in  their  resting  state,  but  an  artery  that 
during  the  pulse-beat  is  quite  hard  may  during  the  pause  between  the  beats  appear 
hard,  or  under  other  circumstances  soft,  as,  for  example,  in  cases  of  aortic  in- 
io 


146  SPHYGMOGRAPHIC    TRACINGS    FROM    DIFFERENT    ARTERIES. 

sufficiency,  in  which,  after  the  contraction  of  the  left  ventricle,  a  large  quantity 
of  blood  flows  back  into  the  ventricle  through  the  leaky  semilunar  valves  of  the 
aorta,  and  the  arteries  consequently  become  relatively  bloodless.  The  pulse-ten- 
sion is  lowest  in  the  standing,  higher  in  the  sitting,  and  highest  in  the  recumbent 
position. 

Other  things  being  equal,  the  volume  of  the  pulse-waves  may  be  directly 
determined  from  the  size  of  the  sphygmographic  tracings.  Thus,  the  following 
types  of  pulse  are  distinguished:  the  large  and  the  small  pulse;  the  unequal  pulse; 
the  extremely  weak  pulse,  which  is  felt  only  as  a  succession  of  faint  tremors 
(tremulous  pulse);  and  the  indistinct,  scarcely  appreciable  pulse  (filiform  and 
insensible  pulse).  A  large  soft  pulse  is  designated  a  dilated  pulse;  a  small  hard 
pulse  a  contracted  pulse ;  a  small  pulse  of  great  frequency  a  vermicular  pulse ;  a 
large,  hard,  frequent  pulse  a  serrate  pulse;  a  large,  extremely  hard  pulse  a  vibrant- 
pulse  ;  and  a  pulse  that  is  different  in  two  corresponding  arteries  on  opposite  sides 
of  the  body  (due  to  stenosis,  compression  or  kinking  on  one  side)  a  different  pulse. 

SPHYGMOGRAPHIC  TRACINGS  FROM  DIFFERENT  ARTERIES. 
SPHYGMOGRAPHIC  CURVE  FROM  THE  CAROTID  ARTERY. 

(Fig.  50,  I,  II,  III;  Fig.  57,  C  and  Ct.) 

The  ascending  limb  is  exceedingly  steep,  the  apex  of  the  curve  (Fig.  50, 1,  P), 
traced  with  a  minimum  degree  of  friction,  being  pointed  and  prominent.  The 
first  elevation  below  the  apex  is  a  small  one,  the  valve-closure  elevation  (Fig. 
I,  K) ;  this  is  due  to  the  positive  wave,  which  is  produced  during  the  abrupt 
closure  of  the  semilunar  valves  at  the  root  of  the  aorta  and  is  propagated  with 
but  little  loss  of  force  into  the  carotid  artery.  Close  to  this  elevation  and  visible 
only  in  curves  traced  with  a  minimum  of  friction  is  the  highest  elasticity- 
elevation,  which  is  small  (Fig.  50,  II,  e).  Further  down,  but  still  above  the 
middle  of  the  descending  limb,  is  the  dicrotic  elevation  (R),  which  is  usually 
larger  and  is  produced  by  the  recoil  of  the  positive  wave  from  the  already  closed 
semilunar  valves.  Relatively,  that  is,  in  comparison  with  the  remaining  portions 
of  the  curve,  the  dicrotic  elevation  is  slight,  in  consequence  of  the  high  tension 
prevailing  in  the  carotid  artery.  After  the  dicrotic  elevation  has  been  formed, 
the  descending  limb  falls  at  first  abruptly  to  about  the  upper  third  and  from 
this  point,  in  well-traced  curves,  the  writing  lever  in  its  downward  movement 
usually  traces  two  more  small  elevations,  the  upper  of  which  is  an  elasticity- 
elevation,  while  the  lower,  which  under  favorable  conditions  appears  much  larger 
(Fig.  50,  III,  Rj) ,  represents  the  second  dicrotic  elevation.  We  have  here  a  true 
tricrotism,  which  is  the  more  readily  recorded  in  the  carotid,  because  that 
artery  is  shorter  than  the  arteries  of  the  extremities. 

SPHYGMOGRAPHIC  TRACING  FROM  THE  AXILLARY  ARTERY. 

(Fig.  50,  IV.) 

The  ascending  limb  of  the  curve  is  exceedingly  steep.  Not  far  from  the  apex 
there  is  a  small  valve-closure  elevation  (K) ,  not  unlike  that  seen  in  the  carotid 
tracing.  Below  the  middle  is  found  the  dicrotic  elevation  (R),  which  is  fairly 
high,  higher  than  in  the  carotid  tracing,  because  in  the  axillary  artery  the  reduc- 
tion in  arterial  tension  permits  of  a  greater  development  of  the  dicrotic  wave. 
Further  down,  between  the  apex  of  the  recoil-elevation  and  the  foot  of  the  curve, 
two  or  three  smaller  elasticity-elevations  (e  e)  are  seen. 

SPHYGMOGRAPHIC  TRACING  FROM  THE  RADIAL  ARTERY. 

(Fig.  47;  Fig.  50.  V-X;  Fig.  57,  R  and  R'.) 

The  ascending  limb  (Fig.  50,  V)  is  of  medium  height;  the  ascent  is  moderately 
abrupt  and  suggests  the  shape  of  the  letter  f.  The  apex  (P)  is  usually  well  marked. 
Below  the  apex  there  appear,  when  the  tension  is  considerable,  two  (V,  e  e) ,  when 
the  tension  is  slight,  only  one  elasticity-elevation  (VI,  IX,  e).  There  then  follows 
at  about  the  middle  of  the  descending  limb  the  recoil-elevation  (R),  which  is 
usually  well  marked.  This  is  the  more  distinct  and  the  better  pronounced  the 
larger  the  number  of  factors  present  that  favor  the  development  of  the  secondary 
wave.  It  is  smallest  when  the  pulse  is  small  and  hard,  and  the  artery  is  greatly 
distended  (Fig.  50,  VII,  R) ;  larger  when  the  tension  is  moderate;  greatest  in  the 


SPHYGMOGRAPHIC    TRACINGS    FROM    DIFFERENT    ARTERIES.  147 

dicrotic  pulse.  In  the  remaining  portion  of  the  descending  limb,  down  to  the 
base  of  the  curve,  two  or  three  lesser  elevations  are  encountered,  the  first  two 
being  elasticity-elevations  (e  e)  and  the  lowest  appreciable  only  in  rare  cases 
and  probably  indicating  a  second  recoil-wave.  The  sphygmographic  curve  of  the 
brachial  artery  at  the  bend  of  the  elbow  is  somewhat  larger,  but  does  not  differ 
materially  from  the  radial  curve. 

SPHYGMOGRAPHIC  TRACING  FROM  THE  FEMORAL  ARTERY. 

(Fig.  50,  XI,  XII.) 

The  ascending  limb  is  steep  and  high;  on  the  apex  of  the  curve,  which  is  quite 
frequently  somewhat  flat  and  broad,  there  is  recorded  the  closure  of  the  semilunar 
valves  (K) .  From  that  point  the  curve  falls  in  an  abrupt  manner  to  about  the 
lower  third.  The  recoil-elevation  (R)  appears  late  after  the  beginning  of  the 
curve,  and  beyond  that  point  the  curve  is  interrupted  in  both  its  ascending 
and  its  descending  portion  by  small  elasticity-elevations  (e  e) . 


and  Fig.  53.) 

pedis  artery  the  signs  indi- 
apparatus   (the  heart)    are 


SPHYGMOGRAPHIC  TRACINGS  FROM  THE  DORSALIS  PEDIS  ARTERY  AND 
FROM   THE  POSTERIOR  TIBIAL  ARTERY. 

(Fig.  50,  XIV,  XV.)      (Fig.  50,  XIII, 

In  the  sphygmographic  tracing  from  the  dorsalis 
eating  the  great  distance  from  the  wave-producing 
obvious.  Thus,  the  ascending  limb  of  the  curve 
exhibits  a  gradual  ascent  and  is  low,  while  the  re- 
coil-elevation takes  place  late.  In  the  descending 
limb  two  elasticity-elevations  are  found  so  near 
the  apex  (Fig.  50,  e  ex)  that  the  upper  one  usually 
occupies  a  point  close  to  the  latter.  The  elasticity- 
elevations  in  the  lower  portion  of  the  descending 
limb  are,  as  a  rule,  poorly  developed.  The  tracing 
from  the  posterior  tibial  artery  in  many  respects 
resembles  the  preceding,  especially  with  regard  to 
the  time-relations. 

The  tracing  shown  in  Fig.  53  was  taken  from  a 
medical  student,  whose  height  was  180  cm.,  with  the 
aid  of  the  angiograph,  a  moderate  weight  being 
used  and  the  tracing  being  recorded  on  a  tablet 
attached  to  a  vibrating  tuning-fork. 


FIG.  53. — Tracing  from  the  Pos- 
terior Tibial  Artery,  Recorded 
on  the  Tablet  Attached  to  a  Vi- 
brating Tuning-fork  by  means 
of  Landois'  Angiograph. 


By      measurement 
it  is  found  that 


1-4 
1-6 


9-5 

.  20 

3°  -5 
,61 


One  vibration  is 
equivalent  to 
0.01613  second 


=  0.153  second 

=  o-323 
=  0.492 
=  0.984 


PHENOMENA  OF  ANACROTISM. 

As  a  rule,  the  ascending  limb  in  the  sphygmographic  tracing  presents  the 
shape  of  the  letter  f,  with  a  rather  abrupt  rise.  The  pulse-beat  throws  the  arterial 
wall  into  elastic  vibration,  as  has  been  explained,  the  number  of  vibrations  de- 
pending largely  upon  the  degree  of  arterial  tension. 

In  general  the  distention  of  the  artery,  or  the  tracing  of  the  ascending  limb 
of  the  curve,  which  is  the  same  thing,  is  completed  so  rapidly  that  the  time  is 
equivalent  to  a  single  elastic  vibration.  The  long-drawn-out  f-shaped  figure  is 
practically  nothing  but  a  long-drawn-out  elastic  vibration.  When,  however,  the 
number  of  elastic  vibrations  is  small,  and  the  evolution  of  the  ascending  limb  of 
the  curve  is  relatively  prolonged,  two  long-drawn-out  hump-like  curves  are  some- 
times seen  in  the  ascending  limb  of  the  tracing.  A  condition  of  this  kind,  however, 
is  still  to  be  regarded  as  normal.  (See  the  elevations  in  Fig.  50,  VIII,  at  i  and  2 ; 
and  at  X  i  and  2.)  If,  however,  a  number  of  closely  set  elastic  vibrations  are 
produced  toward  the  upper  portion  of  the  ascending  limb  of  the  sphygmographic 
tracing,  so  that  the  apex  appears  cut  off  obliquely  from  the  ascending  limb  and 
indented,  there  results  the  phenomena  of  anacrotism  (Fig.  54,  a  a),  which,  like 
the  dicrotic  pulse,  belong  in  the  domain  of  pathology. 

Anacrotism  is  observed:   i.  When  the  time  occupied  by  the  inflow  of  blood 


148  PHENOMENA    OF    ANACROTISM. 

is  longer  than  the  duration  of  the  elastic  vibration,  for  example  in  cases  of  dilatation 
and  hypertrophy  of  the  left  ventricle.  This  is  illustrated  in  Fig.  54,  A,  which 
represents  the  radial  curve  from  a  patient  with  contracted  kidney.  Under  such 
conditions  the  great  mass  of  blood  propelled  with  each  systole  requires  an  ab- 
normally long  time  to  effect  distention  of  the  already  greatly  distended  artery. 

2.  When  the  distensibility  of  the  arterial  tube  is  diminished,  a  quantity  of 
blood,  which  in  itself  is  not  increased,  will  require  a  longer  time  to  effect  distention 
of  the  walls.     Such  a  condition  is  observed  in  old  persons  whose  arterial  walls 
have  acquired  great  rigidity.     As  cold  tends  to  contract  the  arteries,  so  that  they 
are  reduced  to  a  condition  of  diminished  distensibility,  it  is  not  difficult  to  under- 
stand that  the  pulse  is  likely  to  assume  the  characters  of  anacrotism  within  an 
hour  after  a  cool  bath   (Fig.   54,  D).     The  carotid  pulse  in  the  rabbit  becomes 
anacrotic  after  irritation  of  the  vasomotor  nerves. 

3.  When,  owing  to  blood-stasis  as  a  result  of  extreme  retardation  of  the  blood- 
current,  such  as  occurs  in  paralyzed  limbs,  the  quantity  of  blood  injected  into 
the  arterial  system  with  each  systole  is  incapable  of  effecting  normal  distention 
of  the  arterial  wall,  anacrotic  elevations  are  seen  in  the  sphygmographic  tracing 
(Fig.  54,  B). 

4.  When,  after  ligation  of  an  artery,  the  blood  can  enter  the  peripheral  segment 
through  the  relatively  small  collateral  circulation  only  within  a  comparatively 
long  time,  the  distention  of  the  arterial  coat  will  be  marked  by  several  elastic 
vibrations.     Wolff  succeeded  in  producing  these  in  tracings  from  the  radial  artery 
not  yet  possessing  distinct  anacrotic  characters  by  applying  compression  above 
the  brachial  artery  and  thus  retarding  the  flow  of  blood  into  the  radial  artery. 
Also  in  cases  of  aortic  stenosis,  a  condition  in  which  the  blood  can   enter  the 
arteries  but  slowly  through  the  aorta,  anacrotism  has  frequently  been  observed 
(Fig.  54,  C). 


FIG.  54. — Anacrotic  Tracings  from  the  Radial  Artery:  a  a,  anacrotic  notches. 

In  the  same  category  belongs  also  the  phenomenon  of  the  so-called  recurrent 
pulse.  When  the  radial  artery  is  compressed  at  the  wrist,  the  pulse  at  once 
reappears  at  a  point  situated  peripherally  from  the  site  of  compression,  being 
transmitted  by  the  arterial  palmar  arches.  The  tracing  from  such  a  pulse  ex- 
hibits anacrotism  and  in  addition  (as  is  readily  understood)  a  diminished 
recoil-elevation,  as  well  as  more  numerous  and  more  distinct  elasticity- 
elevations. 

5.  A  peculiar  form  of  anacrotism  is  observed  in  connection  with  high  grades 
of  aortic  insufficiency.  The  most  characteristic  sign  of  this  lesion  is  the  permanent 
patency  of  the  aorta.  Hence,  not  only  will  waves  be  propagated  in  the  root  of 
the  aorta  by  the  movements  of  the  ventricle,  but  also  the  contraction  of  the 
hypertrophied  left  auricle  will  cause  a  wave-movement  in  the  ventricular  blood 
that  is  at  once  propagated  through  the  patulous  orifice  of  the  relatively  flaccid 
aorta  and  its  branches.  This  is  followed  by  the  true  pulse- wave,  which  is  pro- 
duced by  the  contraction  of  the  ventricle.  It  is  obvious  that  not  only  is  the 
wave  produced  by  the  contraction  of  the  auricle  smaller,  but  it  also  precedes 
the  principal  wave.  The  peculiarity  of  the  anacrotism  in  sphygmographic  tracings 
from  large  vascular  trunks,  taken  from  cases  of  insufficiency  of  the  aortic  valves, 
is  that  the  auricular  wave  occurs  before  the  ventricular  wave  in  the  ascending 
limb.  This  anacrotism  manifests  itself  in  curves  taken  from  the  larger  vascular 
trunks  because  the  wave,  in  itself  but  small,  gradually  disappears  as  it  advances 
peripherally  toward  the  smaller  vessels. 

Fig.  55,  I,  represents  a  sphygmographic  tracing  from  the  carotid  of  a  man. 
It  exhibits  an  abrupt  ascending  limb,  caused  by  the  force  of  the  hypertrophied 
heart.  At  the  apex  of  the  curve  there  appear  quite  constantly  two  sharp  inden- 
tations, the  more  anterior  of  which,  having  a  narrower  base,  requires  less  time  for 


INFLUENCE    OF    THE    RESPIRATORY    MOVEMENTS.  149 

its  development  than  the  second.  The  anterior  (A)  is  the  anacrotic  auricular 
wave,  the  second  (V)  the  ventricular  wave. 

Fig.  55,  II,  represents  a  sphygmographic  tracing  from  the  subclavian  artery 
of  the  same  individual.  It  is  recognized  at  once  by  the  peculiarity  that  the 
anacrotic  notch  (a)  occupies  approximately  the  junction  of  the  lower  and  middle 
thirds  of  the  ascending  limb.  The  recoil-elevation  (R)  in  this  curve  also  is  rela- 
tively small,  for  the  same  reason  as  in  the  carotid  curve.  Below  the  recoil-eleva- 
tion are  seen  feebly  developed  elasticity-elevations. 

Tracings  from  the  femoral  artery  made  with  a  minimum  of  friction  on  the 
part  of  the  writing  stylus  exhibit  an  indentation  (Fig.  55,  III,  a)  immediately 
preceding  the  ascending  limb  of  the  curve,  which  is  blurred  in  coarse  curves.  A 
comparison  of  this  indentation  with  the  anacrotic  notch  at  the  lower  portion  of 
the  ascending  limb  of  the  curve  from  the  subclavian  artery  (Fig.  II)  will  convince 
the  observer  that  the  anacrotic  auricular  notch  must  be  sought  in  this  well-marked 
elevation. 

It  should  be  mentioned  at  this  point  that  sphygmographic  tracings  from  cases 
of  aortic  insufficiency  are  characterized  further  by  the  following  peculiarities: 


FIG.  55.— I,  II,  III,  Curves  Exhibiting  Anacrotic  Elevation,  a,  in  Association  withflnsufficiency  of  the 

Aortic  Valves. 

i ,  the  great  height  of  the  curve ;  2 ,  the  rapid  fall  of  the  writing  lever  from  the  apex. 
Both  of  these  peculiarities  are  due  to  the  fact  that  a  large  quantity  of  blood  is 
thrown  into  the  arteries  by  the  enlarged  and  hypertrophied  ventricle,  a  considerable 
portion  of  which  flows  back  into  the  ventricle  after  the  completion  of  the  systole. 
In  accordance  with  observations  i  and  2  the  pulse  is  therefore  a  quick  one.  3,  A 
distinct  notch  is  not  rarely  found  at  the  apex  representing  an  elastic  vibration  of 
the  greatly  distended  arterial  wall.  4,  In  tracings  taken  from  cases  of  aortic 
insufficiency,  as,  for  example,  in  that  shown  in  Fig.  55,  I,  the  recoil-elevation  (R) 
is  moderate  as  compared  with  the  size  of  the  curve,  because,  owing  to  the  lesion 
of  the  aortic  valves,  the  pulse-wave  in  its  recoil  does  not  impinge  upon  a  suffi- 
ciently large  surface.  When  the  destruction  of  the  semilunar  valves  is  considerable, 
the  recoil-elevation  must  be  produced  by  the  impact  of  the  recurrent  wave  against 
the  opposite  ventricular  wall.  Below  the  recoil-elevation  the  curve  presents  two 
or  three  faintly  marked  elasticity-oscillations  (i,  2,  3).  The  enormous  height  of 
the  entire  curve  is  sufficiently  explained  by  the  massive  column  of  blood  injected 
into  the  arterial  system  by  the  greatly  hypertrophied  and  dilated  ventricle. 

INFLUENCE  OF  THE  RESPIRATORY  MOVEMENTS  ON  SPHYG- 
MOGRAPHIC TRACINGS. 

The  respiratory  movements  exert  a  distinct  influence  on  the  move- 
ments of  the  pulse  by  virtue  of  two  different  factors:  (i)  the  purely 
physical  diminution  of  arterial  pressure  that  accompanies  each  inspira- 
tion, and  the  increase  attendant  upon  each  expiration;  (2)  the  variations 
in  blood-pressure,  due  to  excitation  of  the  vasomotor  nerve  centers, 
which  attend  the  respiratory  movements. 


150  INFLUENCE    OF    THE    RESPIRATORY    MOVEMENTS. 

When  it  is  remembered  that  during  inspiration,  owing  to  the  dila- 
tation of  the  thorax,  the  arterial  blood  is  retained  in  larger  quantities 
within  the  chest-cavity,  while  the  venous  blood  is  more  actively  drawn 
into  the  right  auricle  by  aspiration,  it  is  evident  that  the  tension  within 
the  arteries  must  at  first  dimmish  during  inspiration.  The  expiratory 
diminution  in  the  size  of  the  thorax,  on  the  other  hand,  favors  the 
flow  of  arterial  blood  into  the  vascular  trunks  and  dams  the  venous 
blood  back  toward  the  venae  cavae, — two  factors  that  tend  to  heighten 
the  tension  in  the  arterial  system.  Furthermore,  the  expiration  that 
immediately  precedes  an  inspiration  allows  less  blood  to  enter  the  heart, 
so  that  systolic  contractions  at  the  beginning  of  inspiration  throw  a 
somewhat  smaller  quantity  of  blood  into  the  aorta;  the  opposite  result 
attends  the  inspiration  that  immediately  precedes  an  expiration. 

These  variations  in  tension  explain  the  differences  in  the  size  of 
sphygmographic  tracings  taken  during  inspiration  and  during  expira- 
tion, as  seen  in  Fig.  56,  and  in  Fig.  50,  I,  III,  IV,  in  which  /  indicates 
the  inspiratory,  and  E  the  expiratory  curve.  The  differences  are  as 
follows:  (i)  the  greater  tension  in  the  arteries  during  expiration  causes 
a  general  heightening  of  the  level  of  all  curves  coinciding  with  expira- 
tion; (2)  during  expiration  the  ascending  limb  is  prolonged  because  the 
expiratory  movement  of  the  thorax  tends  to  increase  the  force  of  the 
wave  produced  during  expiration;  (3)  the  magnitude  of  the  recoil-ele- 
vation must  be  less  on  account  of  the  increase  in  pressure  during  ex- 


FIG.  56. — Influence  of  Respiration  on  the  Sphygmographic  Tracing  (after  Riegel). 

piration;  (4)  for  the  same  reason  the  elasticity-elevations  are  more 
distinct  and  approach  more  nearly  the  level  of  the  apex  of  the  curve. 
During  the  stage  of  expiration  the  pulse  is  somewhat  more  frequent 
than  during  the  stage  of  inspiration. 

This  purely  mechanical  effect  of  the  respiratory  movements  is  modi- 
fied by  the  stimulation  of  the  vasomotor  center  that  takes  place  at  the 
same  time.  Owing  to  this  nervous  influence  the  arterial  pressure — 
which,  it  is  true,  is  lowest  during  inspiration — begins  to  rise  during 
inspiration  and  continues  to  increase  until  the  end  of  that  phase,  reaching 
its  maximum  at  the  beginning  of  expiration.  During  the  remainder 
of  expiration  the  blood-pressure  falls,  and  again  reaches  its  lowest  level 
at  the  beginning  of  inspiration.  These  influences  leave  their  imprint 
upon  the  sphygmographic  curves,  which,  accordingly,  present  the  signs 
of  increasing  or  diminishing  arterial  tension,  in  accordance  with  the 
phases  of  respiration.  There  is  thus  to  a  certain  extent  a  displace- 
ment of  the  pressure- curve  to  correspond  with  the  respiratory  curve. 

The  statements  of  different  observers  vary  with  regard  to  the  effect 
of  strong  expiratory  pressure  and  of  forced  inspiration  on  the  shape  of 
the  pulse- waves.  The  simplest  way  of  producing  strong  expiratory 
pressure  is  by  means  of  Valsalva's  experiment.  During  this  procedure 
there  is  at  first  an  increase  in  the  blood-pressure,  with  the  formation  of 
pulse-waves  resembling  those  produced  during  ordinary  expiration — 


INFLUENCE    OF    THE    RESPIRATORY    MOVEMENTS.  151 

the  recoil-elevation  particularly  being  distinctly  less  pronounced.  If, 
however,  the  forced  pressure  is  maintained,  the  sphygmographic  curves 
begin  to  exhibit  signs  of  diminished  tension.  This  is  due  to  the  influ- 
ence of  the  vasomotor  center,  acting  reflexly  through  the  pulmonary 
nerves.  It  must  be  assumed  that  forced  pressure — such  as  is  produced 
in  Valsalva's  experiment — when  continued,  exerts  a  depressing  effect 
on  the  vasomotor  center.  Coughing,  singing,  and  reciting  act  in  a 
manner  similar  to  Valsalva's  experiment;  the  pulse-frequency  being 
at  the  same  time  increased.  On  the  conclusion  of  Valsalva's  experi- 
ment the  blood-pressure  rises  until  it  exceeds  the  normal  by  almost  as 
much  as  it  had  before  been  diminished,  to  return  again  to  the  normal 
after  a  few  minutes. 

Conversely,  when  the  circulation  is  more  completely  emptied  by 
means  of  J.  Miilier's  experiment,  the  sphygmographic  curve  at  first 
exhibits  the  characteristic  signs  of  diminished  pulse-tension,  particularly 
a  higher  and  more  distinct  recoil-elevation.  After  a  time,  however, 


FIG.  57.—  The  Effect  of  Marked  Expiratory  and  Insoiratory  Pressure  on  Sphygmographic  Curves:  C  and  R, 
tracings  made  from  the  carotid  (C)  and  the  radial  (R)  during  Miilier's  experiment;  Q  and  Rj,  similar  tracings 
made  during  Valsalva's  experiment.  The  curves  were  recorded  on  a  tablet  attached  to  a  vibrating  tuning- 


fork. 


likewise  owing  to  nervous  influences,  increased  tension  may  manifest 
itself.  In  Fig.  57,  C  and  R  represent  carotid  and  radial  curves  recorded 
during  Miilier's  experiment,  in  which  the  great  recoil-elevation  clearly 
shows  the  diminished  tension  in  the  vessels;  Cl  and  Rj  represent  curves 
taken  from  the  same  individual  during  Valsalva's  experiment  and  clearly 
show  the  opposite  condition. 

Expiration  into  a  vessel  like  a  spirometer  (Waldenburg's  respiratory  apparatus, 
for  example)  filled  with  compressed  air  has  the  same  effect  as  Valsalva  s  experi- 
ment, causing  after  a  time  a  slight  lowering  of  the  blood-pressure  and  a  simulta- 
neous increase  in  the  frequency  of  the  pulse.  Conversely,  inspiration  of  rarefied 
air  from  the  same  apparatus  acts  like  Muller's  experiment,  heightening  the  effect 
of  inspiration,  and  it  may  after  a  time  increase  the  blood-pressure,  which,  as  the 
experiment  is  continued,  may  remain  high  or  fall  again. 

Inspiration  of  compressed  air  lowers  the  mean  blood-pressure,  and  the  after- 
effect is  maintained.  The  pulse  during  and  after  the  experiment  is  increased  in 
frequency.  Expiration  into  rarefied  air  increases  the  blood-pressure. 

These  last-mentioned  alterations  emanate  from  the  nervous  system;  they  are 
not  produced  as  readily  and  are  not  equally  marked  in  all  individuals. 

Exposure  to  compressed  air  (in  the  pneumatic  chamber)  lowers  the  pulse- 
curve:  the  elasticity-oscillations  become  correspondingly  more  distinct,  as  the 
recoil-elevation  diminishes  and  finally  disappears.  At  the  same  time  the  heart's 


152        INFLUENCES    OF    PRESSURE    ON    SPHYGMOGRAPHIC    TRACINGS. 

action  becomes  slower  and  the  blood-pressure  is  raised.  Exposure  to  rarefied  air 
has  the  opposite  effect  as  the  sign  of  diminished  tension  in  the  arterial  system; 
but  only  when  as  a  result  the  breathing  is  enfeebled  and  the  pulse  is  accelerated. 
Pathological. — In  the  presence  of  adhesions  between  the  heart  and  the  large 
blood-vessels,  on  the  one  hand,  and  the  surrounding  structures  on  the  other,  the 


FIG.  58. — Paradoxical  Pulse  (after  Kussmaul). 

pulse  may  be  much  diminished  in  size  and  otherwise  altered  during  inspiration  r 
or  it  may  even  disappear  altogether.  This  phenomenon  has  been  called  the 
paradoxical  pulse.  It  is  due  to  flattening  of  the  subclavian  artery  in  consequence 
of  elevation  of  the  first  rib.  Varieties  of  this  pulse  can  be  produced  also  in  healthy 
individuals  by  voluntary  alteration  of  the  breathing  during  inspiration. 

THE   INFLUENCES   OF   PRESSURE   ON   THE   SHAPE   OF   SPHYG- 
MOGRAPHIC TRACINGS. 

The  changes  induced  in  the  movement  of  the  pulse  by  increasing  the  pressure 
upon  it  affect  both  the  shape  of  the  sphygmographic  curves  and  their  time-rela- 
tions. Fig.  59  shows  at  a,  b,  c,  d  and  e  a  series  of  radial  curves;  a  was  taken 
with  a  minimal  pressure  and  the  remainder  with  a  pressure  of  100,  200,  250 
and  450  grams  respectively.  The  curves  A  and  B,  on  the  other  hand,  show  the 
time-relations  of  curves  taken  when  the  pressure  was  progressively  increased.  A 
study  of  these  curves  yields  the  following  results : 


FIG.  59. — Variations  in  the  Shape  of  Sphygmographic  Curves  Produced  by  Increasing  the  Pressure. 


1.  With  a  small  load  the  recoil-elevation  is  relatively  indistinct;  the  entire 
curve  appears  high. 

2.  With  a  moderate  load,  about  from  100  to  200  grams,  the  recoil-elevation 
is  most  distinct;  the  entire  curve  appears  somewhat  smaller. 

3.  As  the  load  is  increased,  the  height  of  the  recoil-elevation  diminishes. 

4.  The  smaller  elasticity-oscillation  immediately  preceding  the  recoil-elevation 
manifests  itself  only  when  the  load  becomes  considerable  (from  200  to  300  grams). 

5.  The  quickness  of  the  pulse  varies  as  the  load  is  increased,  the  time  required 
for  the  development  of  the  ascending  limb  being  shortened,  and  that  required  for 
the  descending  limb  prolonged. 

6.  The  height  of  the  entire  curve  diminishes  as  the  load  increases. 

These  points  sufficiently  emphasize  the  importance  of  taking  the  load  of  the 
registering  instrument  into  consideration  and  the  necessity  of  indicating  the  actual 


VELOCITY    OF    PROPAGATION    OF    PULSE-WAVES.  153 

weight  employed,  in  order  to  form  a  correct  interpretation  of  the  shape  of  the 
pulse-waves. 

It  appears  from  an  examination  of  the  radial  curves  A  and  B,  the  former  of 
which  was  taken  with  a  weight  of  100  grams,  and  the  latter  with  a  weight  of  220 
grams,  from  the  same  individual  and  at  the  same  time (i  vibration  =  0.01613  second) , 
that  changes  in  the  load  may  produce  differences  also  in  the  chronological  develop- 
ment of  the  sphygmogram. 

When  the  pressure  on  an  artery  is  continued  for  a  considerable  period  of  time, 
the  force  of  the  pulse  gradually  increases.  If  the  greater  load  is  then  removed 
and  a  smaller  one  substituted,  the  sphygmographic  curve  not  infrequently  assumes 
the  form  of  a  dicrotic  pulse-wave  and  the  recoil-elevation  becomes  distinctly 
marked.  During  the  high  pressure  the  blood  is  forced  to  make  a  passage  for  itself 
by  dilating  the  collateral  vessels.  If,  then,  the  main  channel  is  again  thrown 
open,  the  entire  bed  of  the  stream,  of  course,  suddenly  becomes  much  wider.  In 
consequence,  there  results  a  greater  development  of  the  recoil-elevation.  Tracing 
X  in  Fig.  50  represents  such  a  dicrotic  series,  taken  after  the  application  of  a 
heavy  weight. 

VELOCITY  OF  PROPAGATION  OF  PULSE-WAVES. 

As  the  pulse-wave  passes  from  the  root  of  the  aorta  into  all  the  arteries  toward 
the  periphery,  the  pulse  is  felt  earlier  in  the  arteries  nearer  the  heart  than  in  those 
at  a  greater  distance.  This  phenomenon  was  variously  confirmed  and  variously 
disputed  until  E.  H.  Weber  determined  the  movement  of  rapidity  of  the  pulse- 
wave  from  the  difference  in  time  of  the  pulse  in  the  external  maxillary  artery 
and  in  the  dorsalis  pedis  artery  and  found  it  to  be  9.240  meters  in  a  second.  With 
such  great  velocity  of  the  pulse-wave,  says  this  investigator,  it  cannot  be  regarded 
as  a  short  wave  traveling  along  the  arteries,  but  so  long  that  a  single  pulse-wave 
cannot  find  room  in  the  entire  distance  from  the  beginning  of  the  aorta  to  the 
artery  of  the  big  toe. 

PROPAGATION  OF  PULSE-WAVES  IN  RUBBER  TUBES. 

As  it  is  possible  by  the  intermittent  injection  6f  water  into  rubber  tubes  to 
produce  waves  similar  to  those  produced  by  the  pulse,  it  is  important  to  learn 
the  results  that  have  been  obtained  from  a  study  of  this  undulatory  movement. 

According  to  E.  H.  Weber,  the  propagation-velocity  of  these  waves  is  11.259 
meters  in  one  second.  Positive  and  negative  waves  are  propagated  with  equal 
velocity  and  the  velocity  of  the  waves  is  the  same  whether  they  have  been  pro- 
duced slowly  or  rapidly. 

2.  According  to  Bonders,  the  velocity  of  the  waves  is  directly  proportional 
to  the  coefficient  of  elasticity  of  the  walls  of  the  tubes.     It  is  proportional  to  the 
square  root  of  the  coefficient  of  elasticity  of  the  walls  of  the  tubes,  with  the  same 
lateral  pressure. 

3.  The  velocity  of  the  waves  increases  with  the  thickness  of  the  walls;  it  is 
proportional  to  the  square  root  of  the  thickness  of  the  walls,  with  the  same  lateral 
pressure. 

4.  The  velocity  is  inversely  proportional  to  the  square  root  of  the  diameter 
of  the  tubes,  the  pressure  remaining  constant. 

5.  According  to  Marey,  the  velocity  diminishes  as  the  specific  gravity  of  the 
fluid  increases.     It  is  inversely  proportional  to  the  square  root  of  the  specific 
gravity. 

Experiments  with  Rubber  Tubes. — In  determining  the  time-relations  Landois 
employed  the  following  method.  He  recorded  the  waves  by  means  of  the  angio- 
graph  on  a  recording  surface  attached  to  a  vibrating  tuning-fork  (Fig.  60).  After 
measuring  a  certain  distance  on  a  long  rubber  tube,  the  extremities  a  and  b  are 
placed  under  the  pad  of  the  sphygmograph .  B  is  a  compressible  bulb,  by  com- 
pression of  which  a  positive  wave  is  thrown  into  the  tube,  Q  is  a  portable  mercu- 
rial manometer,  which  indicates  the  pressure  in  the  apparatus.  As  the  pulse- 
wave  first  passes  through  at  a  and  then  at  b,  two  elevations,  i  and  2,  are  recorded. 
Each  small  indentation  is  equivalent  to  0.01613  second.  The  time-relations  can 
be  determined  by  simply  counting  these  indentations. 

Propagation-velocity  of  Water-waves  and  Mercury-waves  within  Elastic  Tubes. — 
Landois'  experiments,  published  in  1879,  yielded  a  propagation-velocity  of  11.809 
meters  in  i  second,  with  an  internal  pressure  of  75  millimeters  of  mercury. 


154  PROPAGATION-VELOCITY    OF    THE    PULSE-WAVES    IN    MAN. 

Landois  was  unable  to  find  any  difference  in  the  propagation-velocity  whether 
the  waves  were  produced  rapidly  or  slowly,  or  whether  they  were  large  or  small. 

In  order  to  determine  whether  the  material  of  which  the  elastic  tube  is  made 
has  any  influence  on  the  propagation- velocity  of  pulse- waves,  Landois  employed 
a  rather  rigid,  slightly  distensible  tube  made  of  gray  vulcanized  rubber.  It  was 
found  that  the  propagation-velocity  of  the  waves  in  this  tube  is  greater  than 
in  a  softer  and  more  distensible  elastic  tube. 

This  observation  is  in  accord  with  the  fact  that  the  intravascular  pressure 


FIG.  60. — Method  of  Recording  the  Pulse-curves  Obtained  from  an  Elastic  Tube  on  a  Tablet  Attached  to  a  Vibrat- 
ing Tuning-fork.     Each  indentation  is  equivalent  to  0.01613  second. 

exerts  a  demonstrable  influence  on  the  propagation- velocity  of  the  pulse- waves; 
for  when  the  pressure  was  raised,  the  waves  were  propagated  with  a  somewhat 
diminished  velocity.  This  phenomenon  is  due  to  the  fact  that  the  distensibility 
of  rubber  tubes  increases  with  the  pressure,  whereas  in  the  arteries  the  distensibility 
of  the  walls  diminishes  under  the  same  conditions. 

The  influence  exerted  by  the  specific  gravity  of  the  fluid  was  determined  by 
Landois  for  mercury,  the  waves  of  which  move  with  about  one-fourth  the  velocity 
of  waves  produced  in  water. 

PROPAGATION- VELOCITY  OF  THE  PULSE-WAVES  IN  MAN. 

Method  of  Examination. — Landois  attached  to  two  different  arteries  long 
levers  consisting  of  reeds  and  so  arranged  that  they  both  recorded  their  pulse- 
curves  simultaneously  on  the  same  recording  surface  attached  to  a  vibrating  tuning- 
fork.  A  quick  tap  on  the  fork  noted  the  identical  moment  on  both  curves,  and 
by  counting  the  indentations  from  this  point  to  the  beginning  of  each  curve  the 
difference  in  time  was  obtained. 

In  this  way  Landois  developed  the  following  values  from  a  student  174  cm. 


PROPAGATION-VELOCITY    OF    THE    PULSE-WAVES    IN    MAN.  155 

in  height:  The  difference  between  the  carotid  and  the  radial  was  0.074  second 
(the  distance  being  estimated  as  62  cm.) ;  between  the  carotid  and  the  femoral, 
0.068  second;  between  the  femoral  (at  the  fold  of  the  groin)  and  the  posterior 
tibial,  0.097  second  (the  estimated  distance  being  91  cm.). 

Results.' — The  foregoing  observations  yield  a  propagation-velocity  for  the 
pulse- waves  in  the  distribution  of  the  arteries  of  the  upper  extremities  of  8.43 
meters  in  i  second,  and  for  the  arteries  of  the  lower  extremities  9.40  meters  in  i 
second. 

It  appears  that  in  the  less  distensible  arteries  of  the  lower  extremities  the 
propagation-velocity  is  greater  for  the  same  distance  than  in  the  arteries  of  the 
upper  extremities.  For  the  same  reason  it  is  less  in  the  peripheral  arteries  and 
in  the  more  yielding  arteries  of  the  child. 

Modifying  Influences. — Increase  in  blood-pressure  accelerates,  reduction  in 
blood-pressure  diminishes,  the  propagation-velocity  of  the  pulse-wave.  Hence,  in 
animals,  hemorrhage,  slowing  of  the  heart-beat  through  stimulation  of  the  vagus, 
division  of  the  spinal  cord,  dilatation  of  the  vessels  (by  heat,  profound  morphin- 
narcosis  or  amyl  nitrite)  cause  retardation;  while,  on  the  other  hand,  irritation  of 
the  spinal  cord  causes  an  acceleration  in  the  movement  of  the  pulse-wave. 

The  length  of  the  pulse-waves  is  found  by  multiplying  the  time  occupied  by 
the  entrance  of  the  blood  into  the  aorta,  which  is  from  0.08  to  0.09  second,  by 
the  propagation- velocity  of  the  pulse-waves. 

A  more  convenient  method  is  to  apply  the  two  tambours  of  Brondgeest's  pan- 
sphygmograph  (Fig.  44)  to  the  two  points  on  the  artery  to  be  examined  and 
have  one  writing-lever  record  its  tracing  above  that  of  the  other  on  a  plate  at- 
tached to  a  tuning-fork.  The  method  may  be  made  quite  trustworthy  by  con- 
structing both  apparatus  with  leaden  pipes  and  filling  these  with  water,  in  which 
the  propagation  of  the  pulse-wave  is  quite  uniform.  A  short  tap  on  the  tuning- 
fork  (at  points  indicated  by  the  arrows  in  Fig.  61)  marks  the  identical  instant 


FIG.  61. — Tracings  from  the  Carotid  and  Posterior  Tibial  Arteries,  Made  Simultaneously  with  Brondgeest's  Pan- 
sphygmograph  on  a  Tablet  Attached  to  a  Vibrating  Tuning-fork.     The  arrows  indicate  identical  moments. 

in  the  two  curves.  The  difference  in  time  is  determined  by  simply  counting  the 
vibrations.  Fig.  61  shows  the  curves  from  the  carotid  and  the  posterior  tibial 
taken  at  the  same  time  from  a  tall  healthy  student.  The  time-difference  is  0.137 
second. 

If  the  arteries  are  widely  separated  or  if  the  observation  is  made  on  the  heart 
and  on  an  artery,  it  is  possible  to  connect  the  two  pads  by  means  of  a  forked 
tube  with  a  single  writing-lever,  and  the  two  pulse-curves,  when  traced  one  into 
the  other,  can  be  recognized  in  the  sphygmogram. 

In  Fig.  62,  A  is  the  curve  of  the  ulnar  artery,  B  the  same,  together  with  the 
curve  produced  by  the  contraction  of  the  ventricle  v  H  p  running  through  it,  and 
obtained  by  means  of  a  forked  tube.  In  the  curve  B,  H  indicates  the  apex  of  the 
ventricular  contraction,  P  the  primary  pulse-apex  of  the  ulnar  curve;  v  indicates 
the  beginning  of  the  ventricular  contraction,  p  that  of  the  ulnar  pulse.  t  appears 
from  these  curves  that  the  interval  between  the  beginning  of  the  ventricular  con- 
traction and  the  beginning  of  the  pulse  in  the  ulnar  artery,  in  the  individual 
examined,  was  equivalent  to  9  vibrations  =0.15  second. 


Grashey  applied  two  sphygmographs  to  two  different  arteries  and  caused  the 
writing-levers  to  strike  sparks  into  their  respective  curves  from  a  spark-inductor, 
so  that  the  sparks  marked  the  identical  instant  of  time  in  each  curve. 
way  he  determined  the  propagation-velocity   (from  the  difference  between  the 
radial  pulse  and  that  of  the  dorsalis  pedis)  to  be  8.5  meters  in  i  second. 

Pathological. — In  cases  presenting  diminished  elasticity  of  the  arteries,  as,  for 


156  OTHER    PULSATORY    PHENOMENA. 

instance,  due  to  calcification,  the  propagation  of  the  pulse-wave  must  be  more 
rapid.  Local  dilatation  of  the  arteries,  such,  for  example,  as  has  long  been 
known  in  the  form  of  aneurysms,  cause  a  retardation  of  the  pulse-wave ;  local  steno- 
sis has  a  similar  effect.  Relaxation  of  the  vessel-walls  during  high  fever  retards 
the  movement  of  the  pulse- wave. 

In  Accordance  with  what  has  been  said  concerning  the  course  of  the  recoil- 
wave,  its  time  of  appearance  must  also  be  affected  by  the  differences  mentioned. 


FIG.  62. — Tracing  from  the  Ulnar  Artery  on  a  recording  surface  Attached  to  a  Vibrating  Tuning-fork  (i  =  0.01613 
sec.):  P,  the  apex  of  the  curve;  e  e,  elasticity- vibrations;  R,  recoil-elevation;  B,  curves  from  the  same  ulnar 
artery,  taken  at  the  same  time  with  v  H  P  =  the  ventricular  contraction  of  the  same  individual. 

It  must  appear  earlier  when  the  blood-pressure  is  raised,  and  also  in  atheromatous 
than  in  healthy  arteries;  but  relatively  late  in  the  elastic  arteries  of  the  child. 
The  latter  point  was  determined  by  Landois  by  mensuration.  While  in  a  man, 
30  years  of  age  and  172  cm.  in  height,  the  apex  of  the  recoil-elevation  was  reached 
0.387  second  after  the  beginning  of  the  radial  curve,  Landois  found  that  the  apex 
in  a  girl,  8  years  old  and  103  cm.  in  height,  occurred  at  the  end  of  0.387  second, 
evidently  indicating  a  relative  delay. 

OTHER  PULSATORY  PHENOMENA. 

Oral  and  Nasal  Pulse;  Tympanic  Pulse. — In  consequence  of  the  pulsatory 
movement  in  the  arteries  of  the  soft  tissues,  the  air  contained  within  the  oral 
and  nasal  cavities  is  also  set  into  pulsating  movement  when  the  glottis  is  closed, 
and  which  can  be  registered  with  the  aid  of  the  cardiopneumograph.  The  tracings 
obtained  in  this  way,  and  which  must  closely  resemble  the  sphygmographic 
tracings  from  the  carotid  artery,  are  of  course  relatively  small,  but  they  can  be 
made  larger  by  increasing  the  force  of  the  heart.  This  pulse  may  be  considerably 
intensified  in  the  presence  of  pathological  enlargement  of  the  heart,  dilatation 
of  the  left  ventricle  and  thickening  of  its  walls.  If  a  ring  containing  a  soap- 
bubble  be  inserted  hermetically  between  the  lips,  the  light-reflex  in  the  bubble 
(seen  in  a  mirror)  reproduces  almost  perfectly  the  oscillations  of  the  oral  pulse. 
As  a  result  of  the  systolic  swelling  of  the  vascular  soft  parts  in  the  tympanic  cavity 
analogous  pulsation  may  be  observed  in  the  intact  drumhead,  or  possibly  in  small 
bubbles  of  froth  accidentally  adherent  to  openings  in  a  perforated  membrane. 

If  the  visual  field  be  darkened,  each  pulse-beat  during  violent  exertion  is  often 
accompanied  by  a  pulsatory  illumination.  Conversely,  if  the  visual  field  be  brightly 
illuminated,  a  corresponding  obscuration  of  the  field  may  take  place.  Pulsation 
is  sometimes  observed  in  the  retinal  arteries  with  the  ophthalmoscope,  especially 
in  cases  of  aortic  insufficiency. 

The  orbicularis  palpebrarum  muscle  under  similar  conditions  contracts  syn- 
chronously with  the  pulse.  This  contraction  appears  to  be  due  to  the  fact  that 
the  beat  of  the  pulse  excites  the  sensory  nerves  and  reflexly  causes  a  contraction. 
In  this  connection  attention  should  be  called  to  an  observation  made  by  the 
brothers  Edward  and  William  Weber,  which  seems  to  be  in  accord  with  this  point. 
They  found  that,  in  walking,  the  pulse  and  the  step  not  infrequently  coincide. 
Landois  believed  that  this  phenomenon  may  be  explained  by  assuming  that  the 
pulse-beat  stimulates  the  muscular  mass  of  the  thigh  into  contraction,  to  which 
gradually  all  the  muscles  of  the  thigh  accommodate  themselves  at  each  step.  As 
the  blood-vessels  dilate  while  the  muscles  are  contracting  and  the  movement  of 
the  venous  blood  is  accelerated,  the  coincidence  of  pulse  and  step  has  the  addi- 
tional advantage  that  the  mass  of  blood  to  be  moved,  which  is  greater  during  the 
pulse-beat,  is  thereby  better  enabled  to  pass  through  the  masses  of  muscle-tissue. 


VIBRATION  OF  THE  BODY  DUE  TO  ACTION  OF  THE  HEART.    157 

When  the  legs  are  crossed,  the  pulse-beat  and  the  recoil-elevation  are  dis- 
tinctly recognized  in  the  supported  limb. 

If  with  the  body  at  rest  in  the  recumbent  position  the  lower  and  upper  incisors 
are  brought  gently  in  contact  and  kept  so,  a  double  beat  of  the  teeth  against  each 
other  will  become  audible,  as  the  pulse-wave  in  the  facial  arteries  elevates  the 
lower  jaw.  The  rapidly  succeeding  second  impact  is  not  due  to  the  recoil- 
elevation,  however,  but  to  the  concussion  produced  by  the  closure  of  the  semilunar 
valves. 

A  pulsatory  movement  is  communicated  to  the  brain  by  the  large  arteries 
at  its  base  and  in  which  all  the  individual  features  of  sphygmographic  tracings 
made  from  the  cerebral  arteries  are  recognized. 

Among  the  pathological  phenomena  of  the  arterial  pulse  must  be  mentioned 
the  systolic  pulsations  in  the  epigastrium,  which  are  produced  in  part  by  the 
heart  in  cases  of  hypertrophy  of  the  right  or  left  ventricle  when  the  diaphragm 
is  depressed,  and  in  part  by  the  forcible  pulsation  of  the  abdominal  aorta  or  of 
the  celiac  axis,  which  is  usually  dilated  under  such  conditions.  Abnormal  dilata- 
tions (aneurysms)  of  the  arteries  also  occasion  abnormally  strong  pulsations  in 
other  situations,  as,  for  example,  in  the  trachea  in  cases  of  aneurysm  of  the  ascend- 
ing or  transverse  position  of  the  aorta. 

Hypertrophy  and  dilatation  of  the  left  ventricle  may  cause  marked  pulsation 
in  the  arteries  lying  nearest  the  heart.  In  the  presence  of  similar  conditions  in- 
volving the  right  ventricle  the  pulsation  of  the  pulmonary  artery  in  the  second 
left  intercostal  space  is  intensified  and  becomes  both  visible  and  palpable  (Fig.  34). 
In  cases  of  aortic  insufficiency  with  good  compensation  in  vigorous  individuals 
when  the  spleen  is  swollen  and  palpable  (acute  infection),  this  organ  also  pulsates. 
Pulsation  is  visible  also  in  the  penis.  In  cases  of  exophthalmic  goiter  the  spleen 
may  pulsate  for  months. 


VIBRATION    OF    THE    BODY    DUE    TO    THE    ACTION    OF    THE 
HEART  AND  THE  COURSE  OF  THE  BLOOD-WAVES. 

The  movement  of  the  heart  and  of  the  pulse  communicates  a  vibration  to 
the  body  as  a  whole.  When  a  person  stands  erect  on  the  platform  of  a  spring- 
scales,  the  pointer  instead  of  assuming  a  position  of  rest  plays  up  and  down  in 
accordance  with  the  phases  of  the  heart's  action. 

In  his  observations  (Fig.  63,  I)  Landois  employed  a  low  box  open  at  the 
top  (K),  with  a  number  of  rubber  bands,  close  together,  stretched  across,  not  far 
from  one  of  the  narrow  sides  at  a  b.  A  quadrangular  board  (B)  was  then  placed 
with  one  extremity  resting  on  the  rubber  bands  and  the  other  on  the  narrow  edge 
of  the  box.  The  subject  to  be  experimented  with  (A)  takes  his  position  on  this 
board  and  stands  erect  and  steady. 

In  order  to  determine  the  cause  of  the  individual  indentations  in  the  curve, 
the  vibration-curve  and  the  curve  of  the  apex-beat  were  recorded  at  the  same 
time  for  the  same  individual.  For  this  purpose  one  box  (p)  of  Brondgeest's  pan- 
sphygmograph  (Fig.  44)  is  applied  to  the  vibrating  board,  and  the  pad  of  the 
other  box  to  the  situation  of  the  apex-beat  in  the  person  to  be  examined.  Both 
writing-levers  record  their  curves  on  the  plate  attached  to  the  vibrating  tuning- 
fork:  the  upper  is  the  vibration-curve,  the  lower  the  curve  of  the  apex-beat. 

As  it  is  impossible  to  exclude  the  marked  vibrations  in  the  apparatus  itself, 
the  information  obtained  with  regard  to  the  mode  of  production  of  the  vibrations 
is  only  approximately  accurate.  At  the  instant  of  ventricular  systole  there  occurs 
a  short  depression,  corresponding  to  the  greater  pressure  of  the  body  on  the 
elastic  support ;  then  the  body  rises  suddenly  in  response  to  the  upward  impulse 
of  the  blood- wave  in  the  carotid  and  subclavian  arteries.  After  the  closure  of 
the  semilunar  valves,  which  is  registered  by  a  slight  elevation,  the  blood-wave, 
as  it  courses  down  the  body  again,  causes  increased  pressure  on  the  platform. 
The  upward  movement  that  now  follows  may  be  due  to  the  centripetal  wave  that 
precedes  the  dicrotic  wave.  The  number  of  inertia-oscillations  of  the  vibrating 
base  that  take  place  until  the  next  heart-beat  will  depend  on  the  duration  of 
the  individual  heart-beats. 

Pathological.— In  cases  of  insufficiency  of  the  aortic  valves  the  vibration  com- 
municated to  the  body  by  the  action  of  the  heart  is  marked  (Fig.  63,  III).  The 
highest  apex  of  the  curvet  as  well  as  the  characteristic  drop  immediately  preceding 
the  ascending  limb,  corresponds  to  the  ventricular  systole.  Below  the  apex  of  the 


158  THE  MOVEMENT  OF  THE  BLOOD. 

highest  elevation  is  a  small  notch,  which  is  produced  by  a  slight  vibration  com- 
municated to  the  blood  by  the  partly  destroyed  semilunar  valves  in  their  ineffective 
effort  at  closure.  The  enormous  wave  of  blood  that  passes  through  the  descending 
aorta  to  the  iliac  artery  after  the  closure  of  the  semilunar  valves  is  the  cause  of 


FIG.  63. — I.  Elastic  Platform  for  Registering  Vibration-curves.  II.  Vibration-curves  Taken  from  the  Body 
of  a  Healthy  Individual.  III.  Vibration-curves  Taken  from  a  Man  Suffering  from  Aortic  Insufficiency  and 
a  High  Degree  of  Cardiac  Hypertrophy. 


the  lowest  drop  of  the  elastic  platform.  This  is  followed  by  a  rise  caused  by 
the  centripetal  movement  of  the  wave.  The  third  rise,  which  then  follows  and 
which  is  relatively  low,  appears  to  correspond  with  the  development  of  the  dicrotic 
wave  in  the  portion  of  the  arterial  system  that  is  directed  downward. 

THE  MOVEMENT  OF  THE  BLOOD. 

The  closed  system  of  blood- vessels  with  its  many  branches,  endowed  as 
its  walls  are  with  elasticity  and  contractility,  is  not  only  completely 
filled  with  blood,  but  it  is  in  fact  overfilled.  The  volume  of  the  entire  mass 
of  blood  slightly  exceeds  the  available  space  within  the  entire  vascular 
system.  It  follows,  therefore,  that  the  mass  of  blood  everywhere  exerts 
a  pressure  on  the  vessel-walls  that  causes  a  corresponding  distention  of 
the  elastic  coats.  This  is  true,  however,  only  during  life.  After  death 
the  muscles  of  the  blood-vessels  relax  and  blood-plasma  escapes  into 
the  tissues,  so  that  the  vessels  after  death  are  found  partially  empty. 

If  the  volume  of  blood  be  conceived  as  equally  distributed  in  the 
entire  vascular  system,  and  as  everywhere  subject  to  the  same  pressure, 
it  would  be  in  a  condition  of  passive  equilibrium,  as  is  the  case  shortly 
before  death.  If,  however,  the  pressure  to  which  the  blood  is  subjected 
be  heightened  at  one  point  of  the  system  of  tubes,  the  blood  will  escape 
from  this  point  of  increased  pressure  to  some  point  where  the  pressure 
is  less;  the  movement  (displacement  of  the  blood-column)  is,  therefore, 
the  result  of  the  existing  difference  in  pressure.  If  the  venae  cavae  or 
the  aorta  in  a  living  animal  be  suddenly  occluded,  the  blood  will  continue 
to  flow  at  a  gradually  diminishing  rate  until  the  differences  in  pressure 
in  the  entire  circulation  have  been  equalized. 

The  velocity  of  the  blood-stream  is  directly  proportional  to  the 


THE    MOVEMENT    OF    THE    BLOOD.  159 

difference  in  pressure  and  inversely  proportional  to  the  resistance  en- 
countered by  the  blood-current. 

The  difference  in  pressure  that  produces  the  movement  of  the  blood 
is  created  by  the  heart.  In  the  greater  as  well  as  in  the  lesser  circulation 
the  point  of  highest  pressure  is  at  the  root  of  the  arterial  system,  and  the 
point  of  lowest  pressure  at  the  terminal  portions  of  the  veins.  Hence, 
the  blood,  constantly  flows  from  the  arteries  through  the  capillaries 
and  into  the  large  venous  trunks. 

The  heart  maintains  the  difference  in  pressure  necessary  for  the 
circulation  of  the  blood  by  throwing  a  certain  quantity  of  blood  into 
the  root  of  the  aorta  at  each  systole,  after  first  withdrawing  a  like  quan- 
tity of  blood  from  the  terminations  of  the  venous  trunks  by  means  of 
the  diastole  of  the  auricles. 

To  these  laws  relating  to  the  causes  of  the  movement  of  the  blood- 
mass,  and  which  were  formulated  chiefly  by  E.  H.  Weber,  must  be 
added  an  important  one  by  Bonders.  That  investigator  demonstrated 
that  the  heart,  by  the  work  it  performs,  not  only  produces  the  difference 
in  pressure  necessary  for  the  movement  of  the  blood,  but  it  also  increases 
the  mean  pressure  existing  in  the  circulatory  system.  The  terminal 
portions  of  the  large  veins  that  empty  into  the  heart  are  larger  and 
more  elastic  than  the  initial  portions  of  the  arteries;  and  if  the  heart 
transfers  the  same  mass  of  fluid  from  the  veins  into  the  beginnings  of  the 
arteries,  the  arterial  pressure  must  be  increased  in  greater  degree  than 
the  venous  pressure  is  diminished,  and  the  pressure  as  a  whole  must  be 
raised. 

The  movement  of  the  blood-mass  would  be  jerky  or  intermittent 
( i )  if  the  walls  of  the  tube  were  rigid ;  for  pressure  exerted  on  the  fluid 
contained  in  rigid  tubes  is  propagated  at  once  throughout  the  entire 
length  of  the  tubes,  and  the  movement  of  the  fluid  ceases  simultaneously 
with  the  impact  that  causes  the  increase  in  the  pressure.  (2)  The  move- 
ment would  be  intermittent  also  within  elastic  tubes  if  the  interval 
between  two  successive  systoles  were  longer  than  the  duration  of  the 
movement  of  the  column  necessary  to  equalize  the  difference  in  pressure 
produced  by  the  systole.  If,  however,  this  interval  is  shorter  than  is 
necessary  for  equalizing  the  pressure,  the  current  becomes  continuous. 
The  more  rapidly  systole  follows  upon  systole,  the  greater  will  be  the 
difference  in  pressure,  the  elastic  walls  of  the  arterial  tubes  at  the  same 
time  undergoing  greater  distention.  In  the  continuous  current  thus 
produced  the  sudden  increase  in  pressure  caused  by  the  systolic  injec- 
tion of  a  mass  of  blood  corresponding  to  the  size  of  the  ventricular  cavity 
can  always  be  recognized  as  an  intermittent,  jerky  acceleration  of  the 
current  (pulse). 

This  intermittent  acceleration  of  the  current  is  propagated  along  the 
arterial  pathway  with  the  velocity  of  the  pulse- wave,  as  both  are  due 
to  the  same  cause.  Each  pulse-beat  is  therefore  attended  with  a  tem- 
porary, rapidly  advancing  acceleration  of  the  fluid-particles.  Just  as 
the  form  of  the  pulse-movement,  however,  is  not  simple,  so  also  is  this 
pulsatory  acceleration  of  the  current  not  simple.  The  latter  appears  in 
the  complicated  form  of  the  current  pulse-curve,  which  likewise  exhibits 
the  primary  elevation  and  the  recoil-elevation  like  a  (pressure-)sphygmo- 
graphic  curve.  Every  up-stroke  in  the  limb  of  the  curve  corresponds 
to  an  acceleration  and  every  down-stroke  to  a  retardation  of  the  moving 
particles  of  fluid. 


l6o  SCHEMATIC    REPRODUCTION    OF    THE    CIRCULATION. 

Physical  Explanation. — The  conditions  detailed  may  be  illustrated  by  means 
of  simple  physical  experiments.  If  a  rigid  tube  be  connected  with  the  nozzle  of 
a  syringe,  every  movement  of  the  piston  will  be  followed  by  an  intermittent 
expulsion  of  water,  which  will  correspond  in  time  exactly  to  the  movement  of 
the  piston.  The  effect  of  the  intermittent  injection  of  fluid  into  an  elastic  system 
of  tubes  is  best  exemplified  in  a  fire-hose.  Here  the  air  contained  in  the  air- 
chamber — which  is  under  elastic  tension — takes  the  place  of  the  elasticity  of  the 
tubes  themselves  in  the  circulatory  apparatus.  With  slow  intermittent  strokes 
of  the  pump,  the  stream  of  water  is  interrupted;  but  if  the  movements  of  the 
pump  are  more  frequent,  the  compressed  air  in  the  air-chamber  effects  a  continuous 
outflow,  although  a  distinct  acceleration  of  the  stream  is  seen  in  correspondence 
with  each  stroke  of  the  pump. 

Landois  was  able  without  difficulty  to  demonstrate  that  the  particles  of  water 
in  an  elastic  tube  are  set  in  motion  during  the  passage  of  the  current  by  every 
pulsatile  wave,  in  correspondence  with  the  picture  presented  by  the  sphygmo- 
graphic  tracing,  by  introducing  in  the  course  of  a  long  elastic  tube,  in  which  both 
a  continuous  and  an  undulatory  movement  could  be  produced  by  intermittent 
pumping,  a  short  glass  tube  containing  a  thread  passing  through  an  opening  in 
the  side  and  floating  to  and  fro  in  the  stream.  Immediately  in  front  of  the 
thread  a  sphygmograph  was  connected  with  the  tube.  Each  pulse-beat  caused  a 
synchronous  movement  of  the  sphygmograph  and  of  the  thread,  each  upward 
stroke  of  the  writing  lever  corresponding  to  a  more  marked  oscillation  of  the 
thread  toward  the  periphery  (acceleration) ,  while  each  downward  stroke  was 
marked  by  a  slight  diminution  in  the  oscillatory  movement  (retardation) . 

In  the  capillary  vessels  the  pulsatory  acceleration  of  the  current 
ceases  with  the  disappearance  of  the  pulse-wave.  The  two  movements 
are  gradually  extinguished  by  the  marked  resistance  encountered  by  the 
blood  in  the  capillary  system.  It  is  only  when  the  capillary  vessels 
are  greatly  dilated  and  the  pressure  in  the  arterial  system  increases  that 
both  pulse  and  pulsatory  acceleration  of  the  current  are  sometimes 
communicated  to  the  initial  portions  of  the  veins  through  the  capillaries. 
Such  conditions  are  observed  in  the  vessels  of  the  salivary  glands  after 
stimulation  of  the  facial  nerve,  which  dilates  the  vascular  channels. 
After  constriction  of  the  finger  with  an  elastic  band,  which  impedes  the 
return  flow  of  venous  blood,  and  causes  an  increase  in  the  arterial  pres- 
sure, with  dilatation  of  the  capillaries  of  the  finger,  the  swollen  skin  is 
seen  to  become  intermittently  more  deeply  red  isochronously  with  the 
well-known  throbbing  sensation.  This  is  the  capillary  pulse. 

Pathological. — The  capillary  pulse  is  found  sometimes  when  the  action  of  the 
left  ventricle  is  greatly  increased,  for  example  in  cases  of  aortic  insufficiency  and 
of  exophthalmic  goiter,  and  often  in  cases  of  jaundice. 

SCHEMATIC  REPRODUCTION  OF  THE  CIRCULATION. 

The  arrangement  of  the  circulation  as  described  permits  a  reproduction  by 
physical  means,  of  the  most  essential  conditions,  in  the  so-called  model  of  the  circu- 
lation. Weber's  model  will  be  briefly  described  here.  The  arterial  system  and 
the  somewhat  larger  venous  system  are  represented  by  portions  of  animal  intestine 
(Fig.  64). 

The  system  of  capillaries  between  the  two  is  formed  by  a  glass  tube  of  sufficient 
size,  the  lumen  of  which,  however,  is  occupied  by  a  piece  of  sponge.  A  short 
section  of  intestine  into  each  extremity  of  which  a  piece  of  glass  tube  is  tied 
represents  the  heart.  The  glass  tube  directed  toward  the  arterial  trunk  is 
provided  with  the  necessary  valves,  which  are  reproduced  by  having  a  piece 
of  small  intestine  project  beyond  the  edges  of  the  glass  tube  and  securing  its  free 
margins  with  three  threads.  Through  this  piece  of  intestine  water  can  enter 
only  in  the  direction  from  the  glass  tube  toward  the  free  intestine,  but  not 
in  the  opposite  direction,  as  the  free  edges  would  then  come  together  and  close 
the  lumen.  From  the  venous  side  a  similar  valve,  mounted  on  the  extremity 
of  a  separate  piece  of  tube,  is  inserted  into  the  glass  tube  directed  toward 


CAPACITY  OF  THE  VENTRICLES.  l6l 

the  heart.  The  two  valves  open  in  the  same  direction.  The  entire  apparatus 
is  moderately  distended  with  water  by  means  of  a  funnel.  By  compressing  the 
heart-piece  the  contents  are  made  to  flow  through  the  arterial  valve  into  the 
arterial  portion.  When  the  compression  ceases,  the  contents  return  from  the 
venous  portion  through  the  venous  valve  into  the  heart.  By  means  of  this 
apparatus  the  blood-current  becomes  continuous  when  the  heart  is  com- 
pressed in  rapid  succession,  and  the  movement  of  the  pulse  can  be  demon  - 


Arterial  Valve. 


Capillaries. 
FIG.  64. — Model  of  the  Circulation  by  Ernst  Heinrich  Weber. 

strated.  The  latter  does  not  extend  beyond  the  capillary  region  because  the 
great  resistance  offered  by  the  many  pores  of  the  sponge  destroys  the  force 
of  the  pulse-waves. 

More  complicated  models  of  the  circulation,  which,  however,  do  not  essentially 
illustrate  more  than  this  primitive  model  by  E.  H.  Weber,  have  been  designed  by 
numerous  investigators. 

CAPACITY  OF  THE  VENTRICLES. 

As  the  heart  creates  the  difference  in  pressure  necessary  for  the 
circulation  of  the  blood  by  throwing  a  definite  quantity  of  blood  into 
the  roots  of  the  two  large  arteries  every  time  the  ventricles  are  emptied 
by  systolic  contraction,  it  is  desirable  to  determine  this  quantity  of 
blood. 

As  the  right  and  left  ventricles  must  contract  simultaneously,  and 
as,  in  addition,  the  same  quantity  of  blood  must  pass  through  the 
lesser  circulation  as  through  the  greater,  it  follows  that  the  capacity 
of  the  right  ventricle  must  be  equal  to  that  of  the  left.  It  must  be 
remembered,  however,  that  a  moderate  quantity  of  blood  always  remains 
in  the  ventricle,  as  this  does  not  empty  itself  completely,  even  at  the  height 
of  its  contraction. 

Methods. — i.  The  capacity  of  the  ventricles  is  determined  directly  by  filling  the 
chambers  of  the  flaccid  heart  after  death  with  a  coagulable  material  and  measuring 
the  coagulated  mass.  This  is  an  uncertain  method,  because  the  pressure  in  the 
living  ventricles  during  their  diastole,  following  the  contraction  of  the  auricles,* 
is  not  known. 

2.  Indirect  Estimation. — A.  W.  Volkmann,  in  1850,  estimated  the  capacity  of 
the  left  ventricle  in  the  following  manner.  The  cross-section  of  the  aorta  and 
the  velocity  of  the  blood-current  in  the  vessel  are  determined.  From  these 
data  the  quantity  of  blood  that  passes  through  the  aorta  in  a  unit  of  time  is  cal- 
culated. As  the  total  quantity  of  blood  in  the  body  (jV  °f  the  body-weight)  is 
known,  the  time  required  for  the  passage  of  this  quantity  through  the  aorta  can 
easily  be  calculated.  Finally,  if  the  number  of  systoles  that  occur  during  the 
time  of  circulation  be  known,  the  quantity  of  blood  for  each  systole  will  correspond 
to  the  capacity  of  the  ventricle.  On  the  basis  of  numerous  animal  experiments 
Volkmann  estimated  the  ventricular  capacity  to  be  equal  to  ^  of  the  body- 
weight;  or  187.5  grams  f°r  a  rnan  weighing  75  kilograms.  The  accuracy  of  this 
method  also  leaves  much  to  be  desired,  because  the  velocity  of  the  current  in 
the  aorta,  which  according  to  C.  Ludwig  and  Dogiel  is  subject  to  considerable 
ii 


l62  METHODS    FOR    MEASURING    THE    BLOOD-PRESSURE. 

fluctuations,  can  only  be  determined  approximately.  Tigerstedt  considers  Volk- 
mann's  figure  much  too  high.  He  determined  the  quantity  of  blood  expelled  by 
the  left  ventricle  with  each  systolic  contraction  in  the  rabbit  by  introducing  in 
the  continuity  of  the  aorta  an  instrument  resembling  a  current-meter.  From 
animal  experiments  he  estimates  that  in  man  only  69  cubic  centimeters  are  ex- 
pelled at  each  ventricular  contraction. 

Place  calculated  as  follows:  A  man  uses  about  500  liters  of  oxygen  in  24 
hours.  In  order  that  the  venous  blood,  which  contains  on  the  average  7  volumes 
per  cent,  less  of  oxygen  than  arterial  blood,  may  take  up  this  quantity  of  oxygen, 
about  7000  liters  of  blood  must  be  driven  through  the  lungs  in  24  hours.  Allowing 
100,000  heart -beats  for  the  24  hours,  only  70  cubic  centimeters  are  propelled  with 
each  systole. 

Other  more  recent  investigators  also  have  calculated  that  the  quantity  of 
blood  expelled  with  each  systole  is  equal  only  to  $  of  the  capacity  of  the  dead 
ventricle,  or  60  cubic  centimeters. 

METHODS  FOR  MEASURING  THE  BLOOD-PRESSURE. 

A.  In  Animals. — i.  Hales'  Tube. — Stephen  Hales,  in  1727,  first  fastened  a  long 
glass  tube  in  the  lateral  wall  of  a  vessel  and  determined  the  blood-pressure  by 
measuring  the  height  of  the  vertical  column  of  blood  in  the  tube. 

Hales'  tube  was  fitted  at  its  lower  extremity  with  a  short  copper  tube,  bent 
at  a  right  angle  and  directed  toward  the  heart ;  it  therefore  really  represented  a 
so-called  Pitot's  tube.  Pitot,  in  1731,  used  a  similar  tube  to  determine  the 
velocity  of  the  current  in  rivers.  The  water  entering  the  horizontal  portion  of 
the  tube,  which  is  directed  up-stream,  rises  in  the  vertical  portion,  which  projects 
above  the  water,  to  a  level  proportional  to  the  velocity  of  the  current.  This 
level  represents  the  "velocity-altitude"  and  it  indicates  that  the  water  flows  with 
a  velocity  equivalent  to  that  attained  by  a  body  falling  freely  from  a  height  equal 
to  the  velocity-altitude.  If  a  Pitot  tube  (Fig.  70,  II,  o  p  x)  be  introduced  into  a 
closed  tube  through  which  flows  a  fluid  under  pressure,  and  an  ordinary  manom- 
eter (x  y)  be  introduced  at  the  same  time,  the  latter  will  register  only  the  tension 
of  the  wall;  but  in  a  Pitot  tube  the  fluid  will  rise  to  a  higher  level,  for  this  column 
of  fluid  indicates  not  only  the  tension  of  the  blood,  but  also  its  velocity-altitude. 
In  arteries,  however,  the  latter  is  extremely  small  as  compared  with  the  former. 

2.  Poiseuille's  Hematodynamometer. — Poiseuille,  in  1828,  used  a  U-shaped  man- 
ometer-tube filled  with  mercury,  which  he  inserted  laterally  by  means  of  a  rigid 
connecting  piece  into  the  wall  of  the  vessel.     A  I — shaped  tube  may  also  be  used 
to  connect  the  blood-vessel  with  the  manometer,  the  short  continuous  extremities 
being  inserted  into  the  open  vessel  (Fig.  65,  I,  a  a)  and  the  vertical  limb  being 
connected  with  the  manometer  (M)  by  means  of  a  leaden  tube. 

3.  Ludwig's  Kymograph. — Carl  Ludwig,  in  1847,  placed  a  float  (Fig.  65,  I,  d  s) 
on  a  column  of  mercury  (as  James  Watt  had  already  done  for  the  manometer  of 
the  steam-engine) .     To  the  float  was  attached  a  vertical  wire  carrying  a  writing- 
contrivance,  which  records  not  only  the  height  of  the  blood-pressure,  but  also  the 
variations  in  the  pulse-waves  on  the  drum  (C) ,  which  is  made  to  rotate  by  clock- 
work.    A.   W.   Volkmann   gave  the  name   of  kymograph    (wave-tracer)    to  this 
instrument.     The  difference  between  the  levels  of  the  mercurial  columns   (c  d) 
in  the  two  parts  of  the  tube  indicates  the  pressure  within  the  vessel  (the  height 
of  the  column  of  mercury  multiplied  by  13.5  gives  the  pressure-altitude  of  the 
corresponding  blood-column) .     Setschenow  added  a  stopcock  at  the  center  of  the 
lower  bend  of  the  tube  (at  b) .     When  this  stopcock  is  turned  so  as  to  leave  only 
a  narrow  orifice  of  communication,  the  pulse-waves  cease  to  manifest  themselves 
and  the  instrument  records  only  the  mean  pressure.     In  this  form  the  instrument 
is  the  most  reliable  for  this  purpose. 

The  pulsatory  variations  in  pressure  are  recorded  by  the  kymograph  as  simple 
elevations  (Fig.  65,  III)  and,  therefore,  they  do  not  in  the  least  correspond  to 
the  curves  obtained  with  the  sphygmograph.  After  the  mercury  has  once  been 
set  in  motion  by  the  pulse-beats,  it  simply  undergoes  movements  up  and  down 
by  virtue  of  its  own  oscillations  and  all  the  finer  shades  of  the  pulse  are  completely 
obliterated.  For  this  reason  the  kymograph  can  be  used  only  for  recording  the 
blood-pressure,  and  never  for  pulse-tracings. 

In  order  to  determine  the  mean  pressure  from  a  long  blood-pressure  tracing 
presenting  numerous  elevations  and  depressions,  the  planimeter  is  employed.  This 
instrument  is  carried  over  the  entire  outline  of  the  surface  occupied  by  the  curve — 


METHODS    FOR    MEASURING    THE    BLOOD-PRESSURE.  ^3 

namely  the  curved  line,  the  abscissa  {base)  and  the  initial  and  terminal  ordin 

obtained  by  counting  the  squares.     A.  W.  Volkmann  cut  out  the  cuTe-ar^a  and 
weighed  it,  and  then  compared  with  it  the  rectangle  made  from  the 
and  havinp-  the  samp  Kac^-lin^   m  +v,~4-  ,>«  ~-n.:±..  j_  &  , 

1     1  to 


which  is  frequently  attached  to  steam-engines 

A  hollow  spring  bent  in  the  shape  of  the 'letter  C  (F)  and  filled  with  alcohol 


FIG.  65. — I,  Carl  Ludwig's  Kymograph;  II,  Adolph  Pick's  hollow-spring  kymograph;  III,  blood- pressure  curves 
(above)  and  respiratory  curves  (below),  traced  at  the  same  time  (after  C.  Ludwig  and  Einbrodt). 

is  brought  into  connection  at  its  lower  extremity  (a)  with  the  lateral  wall  of  the 
artery  (x  x)  by  means  of  a  suitable  cannula,  while  the  other  extremity  of  the 
spring  is  closed.  As  soon  as  the  internal  pressure  is  increased,  the  bent  spring 
is  straightened  out.  The  closed  extremity  (b)  is  connected  with  an  upright 
rod  (g),  which  acts  on  a  system  of  writing-levers  (hike)  composed  of  delicate 
pieces  of  reed,  which  records  the  variations  in  pressure  on  a  moving  recording 
surface.  Both  the  blood-pressure  and  the  variations  in  the  pulse  are  recorded; 
the  latter,  however,  without  their  characteristic  peculiarities.  Hiirthle  reduced 
the  apparatus  to  one-fourth  of  its  original  size,  in  which  form  the  results 
recorded  are  quite  accurate  because  of  the  slight  displacement  of  fluid. 

5.  A.  Pick's  Flat-spring  Kymograph  (Fig.  66)  has  been  used  in  preference  to 
any  other  by  its  inventor  since  1885.  A  tube,  i  mm.  thick  and  filled  with  air  (Fig. 
66,  a  a),  communicates  with  the  blood-vessel  by  means  of  a  cannula  (c),  and 
ends  in  an  excavated  expansion  covered  with  a  rubber  membrane,  from  which  a 
point  (s)  projects  downward.  The  latter  presses  upon  a  tightly  stretched  hori- 


1 64 


METHODS    FOR    MEASURING    THE    BLOOD-PRESSURE. 


zontal  steel  spring  (F),  which  articulates  by  means  of  a  connecting  piece  (b) 
through  two  joints  (d  i}  with  a  writing-lever  (H} .  The  parts  of  the  instrument  are 
held  in  a  metallic  frame  (R  K).  In  order  to  determine  the  absolute  values  of 
variations  in  pressure  the  apparatus  must  first  be  graduated  empirically  by  com- 
paring it  with  a  mercurial  manometer. 

6.  Hurthle's  Manometer  (Fig.  67)  is  a  similar  instrument.  A  small  metallic 
drum  (Fig.  67,  d)  is  intercalated  in  the  course  of  an  artery  (c  c)  by  means  of 
tubes.  The  drum  is  covered  with  a  thin  rubber  membrane,  from  the  center  of 
which  a  process  (e)  projects.  The  latter  is  supported  by  a  spring  (F),  to  which,. 


Fio.  66. — Adolph  Pick's  Flat-spring  Kymograph. 

at  some  convenient  point  that  can  be  varied  at  will  (v),  the  writing-lever  is  at- 
tached. The  whole  contrivance  is  attached  to  a  stationary  rod  (i  i)  by  means 
of  a  carrier  (T).  This  apparatus  also,  like  the  preceding  one,  must  first  be  gradu- 
ated empirically  in  order  to  determine  in  advance  the  height  to  which  the  point 
(s)  of  the  writing-lever  gradually  rises  with  increasing  pressure  (from  o  to 
100  mm.  of  mercury). 

Hiirthle  also  constructed  a  torsion-manometer  according  to  the  plan  of  Rov, 
the  pressure  being  measured  by  the  torsion  of  a  steel  spring. 

B.  In  man  the  blood-pressure  within  an  artery  can  be  measured  in  the  sim- 
plest manner  by  means  of  a  graduated  sphygmograph.  The  weight  that  just 


FIG.  67. — Hurthle's  Kymograph. 

suffices  to  arrest  the  movement  of  the  writing-lever  corresponds  to  the  tension 
of  the  vessel.  The  radial  artery  of  healthy  students  examined  in  this  way  under 
Landois'  direction  and  loaded  for  a  distance  of  i  cm.  exhibited  an  average  blood- 
pressure  of  550  grams. 

Manometric  Method. — v.  Basch  determined  the  blood-pressure  by  a  mano- 
metric  method,  applying  his  sphygmomanometer  to  the  pulsating  vessel.  The 
hollow,  air-containing  cushion  applied  to  the  artery  communicates  with  an  aneroid 
barometer,  the  pointer  of  which  indicates  the  pressure.  As  soon  as  the  pressure 
indicated  by  the  latter  slightly  exceeds  the  pressure  in  the  artery,  the  latter  is 


THE    BLOOD-PRESSURE    IN    THE    ARTERIES.  165 

compressed  and  pulsation  beyond  the  point  of  compression  is  abolished.  In  the 
temporal  artery  the  pressure  is  from  80  to  1  10  mm.  of  mercury. 

Both  of  the  foregoing  methods  not  only  demonstrate  the  blood-pressure  within 
the  arteries,  but  the  pressure  exerted  by  the  cushion  must  exceed  the  arterial 
pressure  to  a  degree  sufficient  to  compress  the  empty  artery  (which  in  itself  repre- 
sents a  gaping  tube).  As  compared  with  the  blood-pressure,  however,  the  resist- 
ance of  the  artery  is  extremely  slight,  being  only  4  mm.  of  mercury,  although 
naturally  greater  in  cases  of  arteriosclerosis.  In  the  same  way  the  resistance 
offered  by  the  soft  parts  superposed  upon  the  artery  must  also  be  overcome  and 
in  individuals  of  firm  fiber  with  an  abundance  of  fat  this  resistance  is  not  incon- 
siderable. In  this  way  v.  Basch  found  in  adults  a  pressure  of  from  135  to  165 
mm.  of  mercury  in  the  radial  artery;  from  80  to  no  mm.  in  the  superficial  tem- 
poral. Federn  thinks  it  is  lower,  namely  from  80  to  100  mm.  of  mercury. 

In  children  the  blood-pressure  increases  with  age,  size,  and  weight.  In  the 
superficial  temporal  it  was  found  to  be  97  mm.  between  2  and  3  years  of  age, 
and  113  mm.  of  mercury  between  12  and  13  years  of  age.  The  blood-pressure 
rises  immediately  after  exercise;  it  is  higher  in  the  recumbent  than  in  the  sitting 
posture,  and  in  the  latter  than  in  the  erect  posture.  After  a  cold,  as  well  as  after 
a  hot,  bath  the  blood-pressure  is  at  first  raised  and  the  flow  of  urine  is  increased. 

Hurthle  employs  the  plethysmograph  (Fig.  73)  in  the  following  manner  for 
measuring  blood-pressure.  The  glass  cylinder  communicates  with  a  mercurial 
manometer.  The  forearm,  first  rendered  bloodless  by  firmly  bandaging  it,  is 
introduced  into  a  cylinder  containing  water  and  closed  in  hermetically.  When 
the  blood  is  allowed  to  flow  freely  into  the  arm,  the  fluid  in  the  cylinder  is  dis- 
placed and  enters  the  manometer.  The  blood  continues  to  flow  into  the  arm  until 
the  manometric  pressure  is  equivalent  to  the  blood-pressure.  The  mean  pressure 
in  the  arm  is  said  to  be  about  100  mm.  of  mercury.  Sphygmomanometers  have 
been  constructed  by  Marey  and  Mosso  on  similar  principles. 

THE  BLOOD-PRESSURE  IN  THE  ARTERIES. 

The  blood-pressure  in  the  arteries  is  quite  considerable,  varying 
within  fairly  wide  limits.  In  the  larger  arteries  of  large  mammals  and 
probably  also  of  man  it  is  between  140  and  160  mm.  of  mercury. 

Examples  : 

Carotid  of  the  horse,  i6imm.(Poiseuille).  Aorta  of  the  frog,  22-29mm.(Volkmann). 
212-214  mm.  (Volk-  Brachial  artery  of  the  pike,  35-84  mm. 
mann)  .  (Volkmann)  . 

dog,  151  mm.  (Poiseuille)  .      Brachial  artery  in  man  (after  operation) 
"     130-190  mm.   (Lud-  110-120    mm.    (Faivre)  ;    perhaps    a 

wig).  little    too    low    on     account  of    the 

goat,  118-135  mm.  (Volk-          traumatism  and  the  disease. 

mann)  . 

'  '  rabbit  ,   9  o  mm  .  (Volkmann)  . 
>  "  chicken,  88-171   mm.  (Volk- 

mann) . 

In  patients  about  to  be  subjected  to  amputation  of  the  thigh  E.  Albert,  with 
the  aid  of  a  manometer,  found  the  blood-pressure  in  the  anterior  tibial  artery  above 
the  ankle  to  be  between  100  and  160  mm.  of  mercury.  The  pulsatory  elevation 
of  the  column  of  mercury  was  from  17  to  20  mm.  Coughing  caused  an  increase  of 
between  20  and  30  mm.;  firm  bandaging  of  the  healthy  leg  an  increase  of  15 
mm.;  passive  elevation  of  the  body,  in  consequence  of  which  the  length  of  the 
hydrostatic  column  of  blood  was  augmented,  an  increase  of  40  mm.  of  mercury. 

The  pressure  in  the  aorta  of  large  mammals  is  estimated  to  be  between  200 
and  250  mm.  of  mercury.  In  general,  the  blood-pressure  is  lower  in  large  than 
in  small  animals  because,  on  account  of  the  greater  length  of  the  blood-channels, 
a  greater  resistance  is  to  be  overcome.  In  exceedingly  young  and  exceedingly  pic 
animals  the  pressure  is  lower  than  in  individuals  at  the  height  ^of  their  vital 


In  embryos  the  arterial  pressure  is  scarcely  one-half  as  great  as  in  the  new- 
born, but  the  venous  pressure  is  greater.  The  difference  between  the  arterial 
and  the  venous  pressure  in  embryos  was  found  to  be  scarcely  one-half  as  great 
as  in  full-grown  animals. 


l66  THE    BLOOD-PRESSURE    IN    THE    ARTERIES. 

Within  the  large  arteries  the  blood-pressure  undergoes  relatively 
slight  diminution  toward  the  periphery,  because  the  differences  in  the 
resistance  in  various  sections  of  the  large  tubes  are  inconsiderable. 
As  soon,  however,  as  the  arteries  undergo  frequent  division  and  their 
caliber  accordingly  becomes  greatly  diminished,  the  blood-pressure 
rapidly  diminishes,  because  the  propulsive  power  of  the  blood  is 
weakened  by  the  effort  to  overcome  the  increased  resistances  produced 
in  this  way. 

The  arterial  pressure  increases  directly  with  the  quantity  of 
blood  present  in  the  arteries,  and  conversely.  The  pressure,  therefore, 
Increases  Diminishes 

1.  As  the  heart's  action  becomes  stronger     i.  As  the  heart's  action  becomes  feebler 

and  more  rapid.  and  slower. 

2.  In  plethoric  individuals.  2.  In  anemic  individuals. 

3.  After    considerable    increase    in    the     3.  After  profuse  hemorrhage  or  loss  from 

quantity  of  blood  by  the  direct  in-  the  blood  in  some   other  way,  as 

jection  of  blood,  and  also  after  cop-  for  example,  by   profuse  sweating 

ious  ingestion  of  food.  or  copious  diarrhea. 

The  increase  and  decrease  in  blood-pressure  is  not  directly  proportional  to 
the  increase  and  decrease  in  the  quantity  of  blood.  By  virtue  of  their  muscular 
libers  the  blood-vessels  possess  the  faculty  of  adapting  themselves  within  fairly 
wide  limits  to  the  variable  volume  of  blood.  The  blood-pressure,  therefore,  does 
not  rise  at  once  when  the  quantity  of  blood  is  moderately  increased.  The  cir- 
cumstance that  fluid  rapidly  transudes  from  the  blood  into  the  tissues  also  assists 
in  maintaining  a  constant  blood-pressure.  Moderate  venesection,  in  the  dog  up 
to  28  per  cent,  of  the  body-weight,  is  not  followed  by  any  noteworthy  diminution 
in  the  blood-pressure.  After  slight  hemorrhages  the  pressure  may  even  rise,  but 
the  removal  of  a  large  quantity  of  blood  is  followed  by  a  considerable  fall  in  the 
blood-pressure,  and  the  loss  of  from  4  to  6  per  cent,  of  the  body-weight  reduces 
it  to  zero.  Increased  pressure  within  the  vessels  produced  by  engorgement  tends 
to  dilate  the  cutaneous  and  muscular  vessels,  especially  those  of  the  extremities, 
and  affects  the  arteries  in  the  viscera  but  little.  After  the  pressure  has  fallen,  the 
visceral  blood-vessels  return  to  their  original  caliber  much  more  promptly  than 
do  the  cutaneous  and  muscular  blood-vessels. 

The  arterial  pressure  rises  as  the  capacity  of  the  arteries  is 
diminished,  and  conversely.  This  is  accomplished  by  contraction  or 
relaxation  of  the  unstriated  muscle-fibers  of  the  arterial  wall. 

The  pressure  within  a  certain  area  of  the  arterial  system  rises 
or  falls  accordingly  as  the  blood-vessels  in  neighboring  areas  undergo 
contraction — or  even  become  impermeable  from  compression  or  ligation 
— or  dilatation.  The  application  of  heat  or  cold  to  a  circumscribed  portion 
of  the  body,  also  of  pressure  or  diminution  of  pressure  (the  latter  by 
introducing  an  extremity  into  a  closed  space  containing  rarefied  air,  as, 
for  example,  Junod's  cupping  boot),  and  the  effect  of  stimulation  or 
paralysis  of  certain  vasomotor  areas,  furnish  striking  proofs  of  the  cor- 
rectness of  this  statement. 

The  respiratory  movements  produce  regular  variations  in  the 
arterial  pressure,  known  as  respiratory  pressure- variations — the 
pressure  falling  with  each  deep  inspiration  and  rising  with  each  expira- 
tion. These  variations  are  readily  explained  by  the  fact  that  at  each 
expiration  the  blood  in  the  aorta  is  subjected  to  the  increased  pressure 
of  the  compressed  air  in  the  thorax,  while  with  each  inspiration  the  blood 
undergoes  a  diminution  in  pressure,  in  consequence  of  the  influence  of 
the  rarefaction  of  the  air  in  the  lungs,  on  the  aorta.  In  addition,  the  in- 
spiratory  expansion  of  the  thorax  tends  to  draw  the  blood  from  the  venae 
cavae  into  the  heart,  while  during  expiration  the  blood  stagnates,  and 


THE    BLOOD-PRESSURE    IN    THE    ARTERIES.  167 

in  this  way  influences  the  blood-pressure.     The  changes  are  greatest 
in  the  arteries  nearest  the  thorax. 

The  respiratory  variations  in  blood-pressure  are  in  part  dependent 
upon  changes  in  the  nervous  impulses  sent  out  by  the  vasomotor  center, 
which  coincide  with  the  respiratory  movements,  and  by  virtue  of  which 
the  arteries  contract  and  thus  increase  the  arterial  pressure  (Traube- 
Hering's  pressure-variations).  Fig.  65  III  shows  a  respiratory  curve 
(heavy  line)  and  a  blood-pressure  curve  traced  at  the  same  time.  This 
figure  shows  that  at  the  instant  when  expiration  begins  (at  ex),  the 
blood-pressure  curve  rises  along  with  the  expiratory  pressure,  and,  con- 
versely, that  both  curves  fall  from  the  instant  that  inspiration  begins 
(at  in) ;  yet  the  blood-pressure  curve  begins  to  rise  a  little  earlier  (at  c) 
than  expiration  itself  has  begun,  that  is,  during  the  last  part  of  inspira- 
tion. This  is  due  to  the  contraction  of  the  arteries,  which  begins  a  little 
earlier  in  obedience  to  impulses  sent  out  by  the  vasomotor  center.  The 
effect  of  the  arterial  contraction  is  reinforced  by  the  circumstance  that 
during  the  inspiratory  stage  the  heart  is  more  completely  emptied  on 
account  of  the  increased  venous  flow.  The  respiratory  variations  in 
blood-pressure  are  observed  also  during  artificial  respiration ;  if  this  be 
suddenly  interrupted  (in  curarized  animals),  the  resulting  irritation  of 
the  medulla  oblongata  due  to  the  dyspnea  causes  a  considerable  rise  in 
the  blood-pressure. 

In  accordance  with  the  depth  of  the  respirations  and  the  corresponding  pres- 
sure-variations of  the  air  within  the  thorax,  great  inequalities  are  observed" in  the 
respiratory  fluctuations.  This  is  evident. from  the  fact  that  in  man  during  quiet 
inspiration  the  diminution  of  pressure  in  the  trachea  is  equivalent  to  only  i  mm. 
of  mercury,  while  during  the  deepest  possible  inspiration  (with  the  respiratory 
canal  tightly  closed)  the  diminution  is  57  mm.  Conversely,  quiet  expiration  in 
man  is  attended  with  an  increase  in  the  pressure  in  the  trachea  of  only  2  or  3 
mm.,  while  vigorous  contraction  of  the  abdominal  muscles  causes  an  increase  of 
87  mm.  of  mercury. 

Kronecker  and  Heinricius  attribute  the  variations  to  mechanical  causes, 
namely  to  the  compression  of  the  heart  that  accompanies  respiration  (because, 
according  to  them,  rhythmical  injections  of  air  into  the  pericardium,  which  com- 
press the  heart,  also  give  rise  to  analogous  variations  in  blood-pressure).  Any 
interference  with  the  diastole  of  the  heart  lowers  the  blood-pressure;  as  soon, 
therefore,  as  the  lung  has  been  distended  during  inspiration  sufficiently  to  displace 
the  heart,  diastole  is  interfered  with  and  the  tension  in  the  aortic  system  is  in 
consequence  lowered.  As  soon  as  the  air  can  escape  from  the  lungs  and  these 
organs  contract,  a  greater  quantity  of  blood  enters  the  heart,  and  the  arterial 
pressure  rises. 

The  movements  of  the  pulse  cause  intermittent  variations  in  the 
mean  arterial  pressure,  the  so-called  pulsatory  pressure-variations.  The 
column  of  blood  injected  into  the  aortic  system  by  the  ventricle  at  each 
systole,  acting  in  conjunction  with  the  positive  wave,  produces  an  in- 
crease of  pressure  in  the  arterial  system  corresponding  to  this  positive 
wave.  The  increase  in  pressure  finds  corresponding  expression  in  the 
various  elevations  of  the  sphygmogram ;  it  also  travels  along  the  arteries 
with  the  same  velocity  as  the  pulse-waves. 

In  the  larger  arteries  of  the  horse  Volkmann  found  the  pulsatory  increase  of 
pressure  to  be  T^,  and  in  the  dog  TV  of  the  total  pressure.  Hurthle/with  the  aid 
of  his  hemodynamometer,  found  that  the  pulsatory  increase  of  pressure  in  the 
rabbit  was  equal  to  almost  one-third  of  the  pressure  during  the  interval  between 
pulse-beats. 

None  of  the  pressure-recording  instruments  described  shows  the  form  of  these 
pressure-variations  with  sufficient  accuracy;  most  of  them  merely  record  elevations 


l68  THE    BLOOD-PRESSURE    IN    THE    CAPILLARIES. 

and  depressions.  Hiirthle's  kymograph,  however,  furnishes  sufficiently  accurate 
pictures  of  the  pressure-variations  in  the  arteries :  these  resemble  sphygmographic 
tracings.  Hence,  the  sphygmographic  pulse-tracing  is  at  the  same  time  a  faithful 
expression  of  the  pulsatory  variations  in  blood-pressure. 

Muscular  exertion  increases  the  blood-pressure.  At  the  beginning 
of  a  muscular  contraction  the  pressure  sometimes  undergoes  a  tempo- 
rary fall. 

When  the  heart's  action  is  interrupted  by  continuous  stimulation 
of  the  vagus  or  a  high  positive  respiratory  pressure,  the  blood-pressure 
diminishes  enormously  in  the  arteries;  while,  on  the  other  hand,  it 
increases  in  the  venous  trunks  because  the  blood  flows  from  the  arteries 
into  the  veins  in  order  to  equalize  the  difference  in  pressure.  This  experi- 
ment shows  that  when  the  difference  in  pressure  is  (almost)  abolished, 
the  resting  blood  continues  to  exert  some  pressure  on  the  blood-vessel 
walls ;  that  is,  in  consequence  of  distention  with  blood,  even  in  the  resting 
state,  a  lower  pressure  is  exerted  on  the  walls. 

Pathological. — In  man  it  has  been  found  that  the  blood-pressure,  as  determined 
by  v.  Basch's  method,  is  increased  in  association  with  chronic  inflammation  of 
the  kidneys,  arteriosclerosis,  lead-colic,  after  injections  of  ergotin,  and  in  cases 
of  cardiac  hypertrophy  with  dilatation.  It  is  diminished  in  the  presence  of  cardiac 
insufficiency.  Digitalis  often  raises  the  blood-pressure  in  cases  of  cardiac  disease ; 
after  the  injection  of  morphin  the  pressure  falls.  During  fever  the  blood-pressure 
usually  falls,  as  the  shape  of  the  pulse-curves  also  indicates;  in  cases  of  cardiac 
insufficiency,  chlorosis  and  pulmonary  tuberculosis  the  blood-pressure  is  also  low. 
If  the  pressure  falls  to  about  75  mm.  in  cases  of  diphtheria  (children) ,  the  prognosis 
is  grave. 


THE  BLOOD-PRESSURE  IN  THE  CAPILLARIES. 

Method. — Owing  to  the  minute  diameter  of  the  capillaries  the  pressure  within 
these  vessels  cannot  be  determined  directly.  By  applying  a  small  glass  disc  of 
known  dimensions  to  the  vascular  substratum  and  weighting  it  in  a  suitable 
manner  until  the  capillaries  become  pale,  the  degree  of  pressure  that  just  over- 
comes the  pressure  within  the  capillary  region  is  determined  approximately.  The 
calculation  is  made  as  follows :  The  pressure  (expressed  in  centimeters  of  a  column 
of  water)  is  obtained  by  dividing  the  number  that  represents  the  compressing 
weight  (weight  +  the  weight  of  the  glass  disc)  by  the  number  of  square  centi- 
meters contained  in  the  surface  pressed  upon.  In  the  capillaries  of  the  finger, 
when  the  hand  is  held  up,  this  pressure  is  24  mm.  of  mercury,  and  with  the  hand 
dependent,  62  mm. ;  in  the  ear  it  is  20  mm. ;  in  the  gums  of  the  rabbit  32  mm. 

Roy  and  Graham  Brown  press  the  vascular  area  to  be  examined  from  below 
against  a  rigid  glass  disc  by  means  of  an  elastic  bladder  provided  with  a  manom- 
eter; the  microscope  can  then  be  focused  on  the  glass  disc. 

The  tension  of  the  blood  in  the  capillaries  of  a  circumscribed  area 
is  increased  by:  (i)  Dilatation  of  the  small  arteries  supplying  the  area. 
If  the  latter  are  dilated,  the  blood-pressure  can  be  propagated  from  the 
large  trunks  with  less  loss.  (2)  Increase  of  pressure  in  the  small  arteries 
supplying  the  area.  (3)  Constriction  of  the  veins  draining  the  capil- 
lary area.  Occlusion  of  the  veins  causes  a  fourfold  increase  in  the 
pressure.  (4)  Increased  pressure  in  the  veins,  as,  for  example,  by 
change  of  position  (hydrostatic  pressure).  Diminution  of  the  blood- 
pressure  in  the  capillaries  is  brought  about  by  the  opposite  conditions. 

Also,  changes  in  the  diameter  of  the  capillaries  must  have  some  influence  on 
the  internal  pressure.  The  inherent  power  of  movement  (movement  of  the  proto- 
plasm) of  the  capillary  cells,  as  well  as  the  pressure,  swelling,  and  consistency  of 
the  surrounding  body-tissues  must  be  considered  in  this  connection.  As  the 


THE    BLOOD-PRESSURE    IN    THE    VEINS.  169 

resistance  to  the  blood-current  is  greatest  in  the  small  arteries  and  in  the  capillary 
system,  the  blood — especially  in  long  capillaries — must  be  subject  to  different 
degrees  of  pressure  at  the  beginning  and  at  the  end  of  such  capillaries.  In  the 
middle  of  the  capillary  system  the  pressure  may  not  be  much  less  than  one-half 
the  pressure  prevailing  in  the  main  arterial  trunks.  The  capillary  pressure  exhibits 
many  variations  in  different  parts  of  the  body.  Thus,  in  the  erect  position,  the 
pressure  in  the  capillaries  both  of  the  intestine  and  of  the  glomeruli  of  the  kidneys, 
as  well  as  in  those  of  the  lower  extremities,  will  be  greater  than  in  those  of  other 
regions  of  the  body;  in  the  former  case  on  account  of  the  two-fold  resistance 
offered  by  the  duplicate  arrangement  of  the  capillaries;  in  the  latter  case,  from 
purely  hydrostatic  influences. 

THE  BLOOD-PRESSURE  IN  THE  VEINS. 

In  the  large  venous  trunks  near  the  heart  (innominate,  subclavian, 
and  common  jugular  veins)  the  blood  is  under  a  negative  pressure, 
which  is  on  the  average  equivalent  approximately  to  o.i  mm.  of  mercury. 
This  enables  the  lymph-stream  to  empty  itself  freely  into  the  large  venous 
trunks. 

As  the  distance  from  the  heart  increases,  the  lateral  pressure  in  the 
venous  trunks  gradually  increases.  In  the  external  facial  vein  of  the 
sheep  it  is  +0.3  mm.,  in  the  brachial  4.1  mm.,  in  branches  of  the  brachial 
9  mm.;  in  the  femoral  11.4  mm.  The  following  conditions  influence  the 
pressure  in  the  veins : 

1.  All  factors  that  tend  to  diminish  the  difference  in  pressure  exist- 
ing between  the  arterial  and  the  venous  system,  which  maintains  the 
circulation  of  the  blood,  necessarily  increases  the  pressure  in  the  veins, 
and  conversely. 

2.  General  plethora  increases  the  pressure  in  the  veins,  while  anemia 
diminishes  it. 

3.  A  special  influence  on  the  tension  in  the  large  trunks  situated  near 
the  heart  is  exerted  by  the  respiration;  for  during  each  inspiration  the 
pressure  diminishes  and  the  blood  rushes  toward  the  thoracic  cavity; 
while  with  each  expiration  the  pressure  increases  and  the  blood  stag- 
nates.    This  effect  is  intensified  in  proportion  to  the  depth  of  the  res- 
pirations, and  when  the  respiratory  passages  are  closed  it  must  be  par- 
ticularly great. 

4.  The  slight  stagnation  of  the  blood  in  the  venae  cavae  that  accom- 
panies every  contraction  of  the  right  auricle  has  already  been  discussed 
in  the  section  devoted  to  the  movements  of  the  heart     The  respiratory, 
as  well  also  as  the  cardiac,  fluctuations  can  sometimes  be  detected  in 
the  common  jugular  vein  of  healthy  individuals. 

5.  Changes  in  the  position  of  the  limbs  or  of  the  body  through 
hydrostatic  influences  modify  the  pressure  in  the  veins  in  various  ways. 
The  highest  pressure  is  found  in  the  veins  of  the  lower  extremities,  and 
they   are   accordingly  most   abundantly   supplied   with   muscle-tissue. 
When  the  muscles  and  valves  in  these  veins  become  insufficient,  dila- 
tation is  likely  to  develop  (varices). 

THE   BLOOD-PRESSURE   IN  THE    PULMONARY  ARTERY. 

Method. — Direct  estimation  of  the  pressure  in  the  pulmonary  artery  was  made 
in  1850  by  C.  Ludwig  and  Beutner,  who  opened  the  left  pleural  cavity  and  con- 
nected the  tube  of  a  manometer  directly  with  the  left  pulmonary  artery,  artificial 
respiration  being  resorted  to.  In  this  way  the  lesser  circulation  of  the  left  lung 
was  interrupted  completely  in  cats  and  rabbits  and  almost  completely  in  dogs.  In 
addition  to  this  disturbance,  the  normal  flow  of  the  venous  blood  into  the  right 


170  THE    BLOOD-PRESSURE    IN    THE    PULMONARY    ARTERY. 

heart  ceases  as  soon  as  the  thoracic  cavity  is  opened,  because  the  elastic  traction 
of  the  lungs  is  abolished  and  the  right  heart  itself  is  exposed  to  the  full  pressure  of 
the  air. 

The  pressure  was  found  to  be  in  the  dog  29.6,  in  the  cat  17.6,  and  in  the 
rabbit  12  mm.  of  mercury  (in  the  dog  3  times,  rabbit  4  times,  and  in  the  cat  5 
times  less  than  the  pressure  in  the  carotid) . 

Faivre  and  Chauveau,  in  1856,  introduced  a  catheter  into  the  right  ventricle 
through  the  jugular  vein  and  connected  it  with  a  manometer. 

Knoll  reached  the  pulmonary  artery  through  the  anterior  mediastinum,  with- 
out opening  the  pleural  cavities,  and  introduced  a  cannula  laterally  into  the  trunk 
of  the  vessel.  By  this  method  he  was  able  to  observe  the  pressure  in  the  artery 
during  spontaneous  breathing  without  restricting  the  lesser  circulation  and  with- 
out displacing  the  heart.  He  thus  found  a  mean  pressure  of  12.2  mm.  of  mercury 
in  the  rabbit. 

Indirect  estimation  can  be  made  by  comparing  either  the  muscular  walls  of 
the  right  with  those  of  the  left  ventricle,  or  the  thickness  of  the  walls  of  the  pul- 
monary artery  and  of  the  aorta,  for  it  must  be  assumed  that  there  is  a  definite 
relation  between  the  thickness  of  the  walls  and  the  pressure  within  the  vessels. 

Beutner  and  Marey  estimate  the  relation  of  the  pulmonary  pressure 
to  the  aortic  pressure  as  i :  3 ;  Goltz  and  Gaule,  as  2  :  5.  Pick  and  Badoud, 
in  the  dog,  found  the  pressure  in  the  pulmonary  artery  to  be  60  mm., 
and  in  the  carotid  in  mm.  of  mercury.  According  to  Knoll  the  pul- 
monary pressure  in  the  rabbit  is  6.8  times  less  than  the  pressure  in  the 
carotid.  In  a  child  the  pressure  in  the  pulmonary  artery  is  relatively 
greater  than  in  the  adult. 

The  pulmonary  pressure  exhibits  certain  rhythmical  variations  due  to  varia- 
tions in  the  tone  of  the  heart's  action.  When  the  air-pressure  in  the  lung  falls, 
the  pressure  in  the  lesser  circulation  also  falls,  and  conversely. 

The  expansion  of  the  lungs  in  the  thoracic  cavity  is  maintained  by  the  nega- 
tive pressure  on  their  outer  pleural  surface.  When  the  glottis  is  open,  the  inner 
surface  of  the  lungs  and  the  walls  of  the  alveolar  capillaries  traversing  the  lungs 
are  exposed  to  the  full  pressure  of  the  air.  The  heart  and  the  large  vascular 
trunks  of  the  thorax,  however,  are  subject  not  to  the  full  pressure  of  the  air,  but 
to  the  pressure  of  the  air  minus  the  pressure  corresponding  to  the  elastic  traction 
of  the  lungs.  The  trunks  of  the  pulmonary  artery  and  veins  are  accordingly 
subject  to  the  same  pressure-conditions.  The  elastic  traction  of  the  lungs  is 
proportional  to  the  degree  of  expansion  of  the  lungs.  The  blood  in  the  pul- 
monary capillaries  will  thus  have  a  tendency  to  flow  from  these  capillaries  into 
the  large  vascular  trunks.  As  the  elastic  traction  of  the  lungs  affects  chiefly  the 
more  delicate  pulmonary  veins,  and  as  re  gurgitation  of  the  blood  is  prevented  by 
the  semilunar  valves  of  the  pulmonary  artery,  as  well  as  by  the  contraction  of 
the  right  ventricle,  it  follows  from  these  pressure-conditions  that  the  capillary 
blood  in  the  lesser  circulation  is  drained  into  the  pulmonary  veins. 

Thin-walle'd  tubes  embedded  within  the  substance  of  the  walls  of  an  elastic, 
distensible  sac  suffer  a  modification  of  their  lumen,  in  accordance  with  the  manner 
in  which  the  sac  is  distended;  for,  if  the  sac  is  directly  inflated  so  that  the  air- 
pressure  in  its  interior  increases,  the  lumen  of  the  tubes  is  diminished;  if,  however, 
the  sac  is  distended  by  rarefying  the  air  in  the  closed  space  surrounding  it,  the 
tubes  embedded  in  the  wall  dilate.  When  the  distention  is  brought  about  in  the 
latter  way,  namely  by  the  negative  pressure  of  aspiration,  the  two  pulmonary 
sacs  within  the  thoracic  cavity  are  maintained  in  a  state  of  distention;  therefore 
the  vessels  of  air-containing  lung  are  more  dilated  than  the  vessels  of  collapsed 
lung.  Consequently,  more  blood  flows  through  the  lungs  when  they  are  distended 
within  the  thorax  than  when  they  are  collapsed.  Inspiratory  distention  has  a 
similar  effect  and  increases  the  flow  of  blood.  The  negative  pressure  prevailing 
in  the  lungs  during  inspiration  causes  a  considerable  dilatation  particularly  of 
the  pulmonary  veins,  into  which  vessels,  therefore,  the  pulmonary  blood  readily 
flows;  whereas  the  blood  of  the  pulmonary  artery,  flowing  through  thick-walled 
trunks  under  high  pressure,  undergoes  scarcely  any  alteration.  The  velocity  of 
the  blood  in  the  pulmonary  vessels  is,  therefore,  increased  during  inspiration. 

The  blood-pressure  in  the  lesser  circulation  is  higher  also  when  the  lungs  are 
in  a  state  of  distention.  Contraction  of  the  vessels,  which  causes  an  increase  of 


MEASUREMENT    OF    THE    VELOCITY    OF    THE    BLOOD-CURRENT.        171 

pressure  in  the  greater  circulation,  has  the  same  effect  in  the  lesser  circulation 
because  more  blood  flows  into  the  right  heart.  The  vessels  of  the  lesser  circulation 
are  exceedingly  elastic  and  their  tonicity  is  slight;  hence  impermeability  even  of 
large  pulmonary  branches  is  readily  compensated  for. 

Forcible  contraction  of  the  abdominal  muscles  (straining)  causes  at  first  a 
marked  increase  in  the  flow  of  blood  from  the  pulmonary  veins,  which,  however, 
gradually  ceases,  because  the  blood  finds  difficulty  in  entering  the  pulmonary 
vessels.  When  the  abdomen  is  relaxed,  the  blood  again  enters  the  pulmonary 
vessels  in  large  quantities. 

Noteworthy  in  this  connection  are  the  experiments  of  Severini,  who  found 
that  the  flow  of  blood  through  the  pulmonary  vessels  is  freer  and  more  rapid  when 
the  lungs  are  filled  with  air  rich  in  carbon  dioxid,  than  with  air  containing  a  larger 
percentage  of  oxygen.  He  believes  that  these  gases  affect  the  vascular  ganglia 
in  the  lesser  circulation  that  control  the  size  of  the  vessels. 

According  to  Morel,  electrical  and  mechanical  stimulation  of  the  abdominal 
organs  causes  a  considerable  increase  of  the  blood-pressure  in  the  pulmonary 
artery  (dog).  According  to  v.  Basch,  increase  of  blood-pressure  in  the  capillaries 
of  the  lungs  produces  greater  rigidity  and,  therefore,  diminished  elasticity  of  the 
alveolar  walls. 

Pathological. — The  pressure  in  the  pulmonary  area  is  increased  in  man  in 
connection  with  many  morbid  disturbances  of  the  circulation  and  always  produces 
accentuation  of  the  second  pulmonic  sound,  which  is  such  an  important  pathogno- 
monic  sign.  It  also  causes  an  increase  in  size  and  an  earlier  appearance  of  the 
corresponding  elevation  in  the  apex-beat  curve.  But  little  has  been  determined 
with  regard  to  the  effect  of  physiological  conditions;  temporary  suspension  of 
breathing  is  said  always  to  be  followed  by  an  increase  in  pressure.  The  influ- 
ence of  the  vasomotor  nerves  on  the  vessels  of  the  lesser  circulation  is  not  so 
great  as  that  upon  those  of  the  greater  circulation.  Influences  that  cause  a 
rise  or  a  fall  in  the  blood-pressure  in  the  greater  circulation  through  the  agency 
of  the  vasomotor  or  vasodilator  nerves  have  no  effect  whatever  on  the  pressure 
in  the  lesser  circulation.  Plethora  of  the  pulmonary  capillaries  is  followed  by 
enlargement  of  the  lungs,  with  more  complete  distention  of  the  alveoli.  The 
causes  may  be  a  diminished  flow  from  the  pulmonary  veins  or  disturbances  in  the 
left  heart.  The  development  of  pulmonary  edema  is  discussed  on  p.  224. 

MEASUREMENT  OF   THE  VELOCITY  OF  THE  BLOOD-CURRENT. 

The  following  instruments  are  used  for  determining  the  velocity  of  the  blood- 
current  in  the  vessels : 

i.  Alfred  Wilhelm  Volkmann's  hemodromometer  measures  directly  the  progress 
of  the  blood-column  through  a  glass  tube  in  a  blood-vessel. 

A  glass  tube  shaped  like  a  hairpin,  130  cm.  long  and  2  or  3  mm.  wide  and 
mounted  on  a  scale  (Fig.  68,  A),  is  fastened  to  a  metallic  basal  piece  (B)  in  such 
a  manner  that  each  limb  passes  to  a  stopcock  perforated  all  the  way  through 
in  one  direction  and  halfway  through  in  the  other.  The  basal  piece  is  perforated 
lengthwise  and  the  two  extremities  are  provided  with  short  cannulae  (c  c), 
which  are  tied  into  the  two  ends  of  the  divided  blood-vessel.  The  entire 
apparatus  is  next  filled  with  a  0.6  per  cent,  sodium-chlorid  solution.  The  stop- 
cocks, which  are  provided  with  an  arrangement  of  cogs  so  that  they  always  turn 
together,  are  first  placed  as  shown  in  Fig.  I :  the  blood  then  simply  flows  length- 
wise through  the  basal  piece;  that  is,  in  the  same  straight  direction  as  the  artery. 
If  at  a  given  moment  the  stopcocks  are  turned  as  shown  in  Fig.  68,  II,  the  blood 
is  forced  to  flow  through  the  longer  channel  represented  by  the  glass  tube.  The 
blood  will  be  seen  pushing  the  paler  column  of  water  before  it  and  the  instant 
should  be  noted  at  which  it  reaches  the  extremity  of  the  limb  of  the  tube.  The 
length  of  the  tube  being  known  and  the  time  occupied  by  the  blood  in  passing 
through  it  being  determined,  the  velocity  for  the  unit  of  time  and  the  unit  of  length 
of  the  course  is  readily  obtained. 

Volkmann  found  the  velocity  of  the  current  in  the  carotid  of  the  dog 
to  be  between  205  and  357  mm. ;  in  the  carotid  of  the  horse,  306;  in  the 
facial  of  the  horse,  232 ;  and  in  the  metatarsal  artery,  56  mm. 

The  observation  occupies  only  a  few  seconds.     The  tube  is  narrower  than  the 


172        MEASUREMENT    OF    THE    VELOCITY    OF    THE    BLOOD-CURRENT. 

blood-vessel;  nevertheless  the  blood  is  said  not  to  flow  more  rapidly  through  it 
than  through  the  larger,  uninjured  blood-vessel.  The  intercalation  of  the  tube 
offers  additional  resistance  to  the  blood-current,  in  consequence  of  which  increased 
retardation  must  be  produced.  The  apparatus  is  evidently  imperfect;  for  the 
larger  respiratory  and  pulsatory  variations  of  pressure  in  the  arterial  system  do  not 
produce  any  perceptible  changes  in  pressure. 


•i 


FIG.  68. — A.  A.  W.  Volkmann's  Hemodromometer.     B.  C.  Ludwig's  Rheometer. 

2.  Carl  Ludwig's  rkeometer  measures  the  velocity  of  the  blood-stream  from 
the  amount  of  blood  that  passes  from  the  artery  into  a  communicating  graduated 
glass  bulb. 

Two  communicating  glass  bulbs  (Fig.  68,  B,  A  and  B),  of  the  same  capacity 
and  accurately  graduated,  are  attached  by  their  lower  extremities  to  metallic  discs 
e  6j  by  means  of  tubes  c  and  d.  Each  disc  can  be  turned  about  the  axis  x  y  in  such 
a  way  that  after  it  has  been  turned  the  tube  c  communicates  with  f  and  the  tube 
d  with  g;  f  and  g  are,  in  addition,  provided  with  horizontal  cannulae  h  and  k, 
which  are  tied  into  the  extremities  of  the  divided  artery.  When  the  instrument 


MEASUREMENT    OF    THE    VELOCITY    OF    THE    BLOOD-CURRENT. 

is  in  the  position  shown  in  the  figure,  h  is  tied  in  the  central,  and  k  in  the  peripheral 
extremity  of  the  vessel  (for  example,  the  carotid).  The  bulb  A  is  filled  with  oil 
and  the  bulb  B  with  defibrinated  blood.  At  a  given  moment  the  blood-current 
is  permitted  to  enter  through  h ;  the  oil  is  displaced  by  the  blood  and  passes  over 
into  B,  while  the  defibrinated  blood  flows  out  from  B  through  k  into  the  peripheral 
portion  of  the  vessel.  As  soon  as  the  oil  reaches  m,  the  time  is  again  noted,  and 
the  entire  apparatus  A  B  is  turned  about  the  axis  x  y,  so  that  B  occupies  the  place 
of  A.  The  phenomenon  is  thus  repeated,  and  the  observation  may  often  be  con- 
tinued for  some  time.  By  observing  the  time  required  by  the  inpouring  blood 
to  fill  one  of  the  bulbs  the  quantity  for  each  unit  of  time  (second)  can  be  cal- 
culated. 

3.  Carl  Vierordt's  hemotachometer  measures  the  velocity  of  the  blood-cur- 
rent by  means  of  a  device  modeled  after  Eitelwein's  velocity- quadrant,  which 
is  constructed  on  the  principle  that  a  pendulum  suspended  in  a  moving  fluid  is 
deflected  by  the  current  in  proportion  to  the  velocity. 

The  apparatus  consists  of  a  small  metallic  box  (Fig.  69,  I.  A)  with  parallel 
glass  sides  and  provided  at  the  narrow  extremities  with  two  cannulae  (e,  a)  for  the 


.  iG.  69. — Vierordt's  Hemotachometer:   II,  Chauveau's  and  Lortet's  dromograph;   III,  the  dromographic  curve 

according  to  Chauveau. 

entrance  and  exit  of  the  blood.  Within  the  box,  opposite  the  entering  blood- 
current,  hangs  a  small  pendulum  (p) ,  the  oscillations  of  which  are  read  off  on  a 
curvilinear  scale  and  which  increase  with  the  velocity  of  the  current.  Before 
making  an  observation,  water  is  allowed  to  flow  through  the  instrument  for  the 
purpose  of  determining  the  velocity  of  the  fluid  that  corresponds  to  each  degree 
of  deviation  of  the  pendulum. 

4.  Chauveau's  and  Lortet's  dromograph  is  constructed  on  the  same  principle, 
and  is  in  addition  provided  with  a  recording  contrivance. 

A  sufficiently  wide  tube  (Fig.  69,  II,  A  B),  provided  with  a  lateral  tube  C, 
which  can  be  connected  with  a  manometer,  is  introduced  into  the  divided  artery 
(carotid  of  the  horse) .  At  a  there  is  a  small  linear  opening  closed  with  a  rubber 
plate  through  which  a  light  pendulum  a  b  projects  into  the  tube.  The  pendulum 
is  prolonged  upward  as  a  thin  indicator  (b),  which  makes  excursions  proportional 
to  the  velocity  of  the  current,  and  which  can  be  read  off  on  the  scale  S  S.  G  repre- 
sents a  handle  for  fixing  the  instrument.  The  apparatus  is  first  tested  with  water 
to  determine  the  excursions  corresponding  to  the  various  velocities.  As  the 
indicating  pendulum  is  exceedingly  light  it  records  the  slightest  changes  in  velocity. 


174 


MEASUREMENT    OF    THE    VELOCITY    OF    THE    BLOOD-CURRENT. 


i. 


The  velocity-curve  (Fig.  69,  III)  is  recorded  by  permitting  smoked  paper  to 
pass  slowly  before  the  tip  of  the  indicator  in  the  direction  of  its  long  axis.  The 
apparatus  is  of  value  because  it  registers  the  characteristic  variations  in  the  veloc- 
ity of  the  blood-current  that  accompany  each  beat  of  the  pulse.  The  dromographic 
curve  resembles  a  pulse-curve,  and,  like  the  latter,  it  possesses  a  primary  (P),  as 
well  as  a  secondary,  recoil-elevation  (R)  . 

5.  Cybulski  s  photoheniotachometer  is  constructed  on  the  principle  of  Pitot's 
tube. 

When  fluid  flows  through  a  tube  d  e  (Fig.  70,  //)  in  the  direction  indicated  by 
the  arrows,  the  column  of  fluid  stands  at  a  higher  level  in  the  manometer  p  than  in 

the  manometer  m.  While  m  y 
indicates  only  the  lateral  pressure, 
p  x  indicates  the  lateral  pressure 
and  in  addition  the  velocity-height 
of  the  fluid.  The  velocity  of  the 
current  in  the  tube  may  then  be  de- 
termined from  the  difference  in  the 
two  levels.  Fluid  may  be  per- 
mitted empirically  to  pass  through 
the  tube  II  d  e  with  varying  ve- 
locity and  the  difference  in  level 
between  the  two  tubes  p  m  that 
corresponds  to  the  different  de- 
grees of  velocity  at  the  current  be 
determined. 

The  form  of  Pitot's  tube  em- 
ployed by  Cybulski  is  somewhat 
different,  being  bent  at  a  right 
angle  (/,  c  p}.  The  extremity  c  is 
tied  into  the  central,  and  the  ex- 
tremity p  into  the  peripheral,  por- 
tion of  the  divided  artery.  When 
the  blood  is  allowed  to  flow  freely, 
the  fluid  rises  to  a  higher  level  in 
the  manometer  a,  which  lies  in  the 
direction  of  the  current,  than  in  b. 
In  order  to  avoid  excessive 
length  in  the  manometers  a  and  b 
and  thus  to  render  the  apparatus 
practically  useful,  Cybulski  con- 
nects the  manometers  a  and  b  by  a 
tube  shaped  like  a  hairpin,  which  is 
filled  with  air  and  can  be  closed  by 
means  of  a  stopcock  (i)  applied 
above  the  bend.  The  fluid  is  allowed 
to  rise  to  the  points  i  and  2.  If 
the  stopcock  (i)  is  then  closed,  the 
tubes  represent  an  air-manometer 
,°ufbaCybU'Ski  S  j"  ^ich  the  difference  between  the 
levels  i  and  2  is  sharply  defined. 

As  the  surfaces  of  the  columns 

of  fluid  i  and  2  continually  alter  their  position  with  respiration  and  pulse-beat, 
that  is,  as  the  manometers  record  the  respiratory  and  pulsatory  variations  in  the 
velocity  of  the  fluid  passing  through  the  tube  c  p,  the  fluctuations  of  the  two 
levels  may  be  advantageously  photographed  with  a  camera  provided  with  a 
rapidly  moving  background,  K. 

Fig.  C  is  a  reproduction  of  the  curves  obtained  from  the  carotid  artery  of  the 
dog.  During  the  time  represented  by  the  interval  between  il  and  i  the  velocity 
was  238  mm.;  in  the  phase  between  2jand  2,  225  mm.;  and,  finally,  between  3t  and 
3,177  mm.  The  velocity  is  greatest  at  the  end  of  inspiration  and  at  the  beginning 
of  expiration.  Asphyxia  at  first  increases  the  velocity.  It  is  increased  by  paraly- 
sis of  the  sympathetic  and  becomes  smaller  when  the  nerve  is  stimulated.  Divi- 
sion of  the  vagus  increases  the  velocity,  while  stimulation  of  the  nerve  naturally 
diminishes  it. 


FI°-  7° 


VELOCITY    OF    THE    CURRENT.  175 

THE  VELOCITY  OF  THE  CURRENT  IN  THE  ARTERIES, 
CAPILLARIES,  AND  VEINS. 

In  analyzing  the  results  of  observation  on  the  velocity  of  the  blood 
it  must  be  constantly  borne  in  mind  that  the  sectional  area  of  the 
arterial  system  beginning  with  the  trunk  of  the  aorta  increases  pro- 
gressively by  subdivision  of  the  branches,  so  that  in  the  capillary 
system  the  sectional  area  of  the  blood-channel  is  increased  yoo-fold 
and  more.  From  this  point,  owing  to  the  reunion  of  the  venous  trunks, 
the  sectional  area  again  diminishes,  but  it  is  still  greater  than  at  the 
beginning  of  the  arterial  system. 

Exceptions  are  found  in  the  common  iliac  arteries,  which,  taken  together, 
are  narrower  than  the  trunk  of  the  aorta.  The  cross-section  of  the  four  pulmo- 
nary veins,  taken  together,  is  also  somewhat  smaller  than  that  of  the  pulmonary 
artery. 

An  equal  quantity  of  blood  must  pass  through  each  successive  trans- 
verse section  of  both  the  greater  and  the  lesser  circulation.  Therefore, 
the  same  quantity  of  blood  must  flow  through  the  aorta  and  the  pul- 
monary artery  in  spite  of  the  great  difference  between  the  pressure  in 
the  two  vessels. 

The  velocity  of  the  blood-current  in  the  individual  transverse  sections 
of  the  blood-channel  must,  thus,  be  inversely  proportional  to  the 
lumen  or  their  sectional  area. 

Hence,  there  is  a  marked  progressive  diminution  in  the  velocity 
from  the  root  of  the  aorta  and  pulmonary  artery  to  the  capillaries; 
so  that  in  mammals  it  is  only  0.8  mm.  a  second  (in  the  frog  0.53  mm.), 
and  in  man  from  0.6  to  0.9  mm.  According  to  A.  W.  Volkmann  the 
velocity  of  the  blood  in  mammals  is  500  times  less  in  the  capillaries 
than  in  the  aorta.  Therefore,  the  total  cross-section  of  all  the  capil- 
laries must  be  500  times  greater  than  that  of  the  aorta.  In  the  small 
afferent  arteries  Bonders  found  that  the  velocity  was  still  10  times 
greater  than  in  the  capillary  vessels. 

In  the  venous  trunks  the  velocity  again  becomes  accelerated,  being, 
in  the  large  trunks,  from  0.5  to  0.75  times  less  than  in  the  correspond- 
ing arteries. 

The  velocity  of  the  blood-current  does  not  depend  on  the  height  of 
the  mean  blood-pressure,  and  it  may  accordingly  remain  the  same  both 
in  anemic  and  in  plethoric  vessels. 

On  the  other  hand,  the  velocity  in  a  given  section  of  the  circulation 
is  determined  by  the  difference  between  the  pressure  in  the  cross-section 
at  the  beginning  and  that  at  the  end  of  the  section.  It  will,  therefore, 
depend  on,  i,  the  vis  a  tergo  (heart's  action)  and,  2,  the  amount  of 
resistance  at  the  periphery  (dilatation  or  narrowing  of  the  smaller 
vessels)  to  the  arterial  current. 

In  accordance  with  the  slight  difference  in  pressure  in  the  arterial  and 
venous  systems  in  the  fetus  the  velocity  here  is  low. 

In  the  arteries  every  pulse-beat  causes  an  acceleration  in  the  move- 
ment of  the  current  (as  well  as  an  increase  in  the  blood-pressure)  corre- 
sponding to  the  form  of  the  pulse-curve.  In  large  vascular  trunks 
C.  Vierordt  found  the  pulsatory  increase  of  velocity  to  be  from  i  to  ^  of  the 
velocity  during  the  diastole.  These  pulsatory  variations  in  the  veloc- 
ity of  the  current  have  been  recorded  by  Chauveau  by  means  of  his 


176  ESTIMATION    OF    THE    CAPACITY    OF    THE    VENTRICLES. 

dromograph.  Fig.  69  III  shows  the  velocity-curve  taken  from  the 
carotid  of  a  horse  and  which  corresponds  with  the  pulse-curve  in 
indicating  the  primary  elevation  (P),  as  well  as  the  dicrotic  elevation 
(R).  Examination  of  an  extremity  with  the  plethysmograph  also 
discloses  this  velocity-pulsation  or  volume-pulsation.  In  the  small 
arteries  an  additional  pulsatory  acceleration  is  observed,  which  occurs 
more  rapidly  in  the  first  phase  than  in  the  later  ones.  The  small  trunks 
themselves  are  not  visibly  distended  under  such  circumstances.  As 
the  capillary  region  is  approached  this  phenomenon,  ..like  the  pulse- 
movement  in  general,  disappears. 

In  the  arteries  the  velocity  must  be  retarded  by  each  inspiration 
and  increased  by  each  expiration;  but  the  differences  here  are  exceed- 
ingly small. 

If  what  has  been  said  in  the  foregoing  concerning  the  influence  of  the  respira- 
tory pressure  on  the  dilatation  and  contraction  of  the  heart,  and,  therefore,  on  the 
movement  of  the  blood,  be  compared,  it  will  be  evident  that  the  respiration  must 
also  have  an  accelerating  influence  on  the  blood-current.  Likewise,  artificial 
respiration  has  the  same  effect:  When  artificial  respiration  is  suspended  in  a 
curarized  animal,  the  blood-current  at  once  becomes  slower.  If,  however,  the 
suspension  is  continued  for  some  time,  the  current  becomes  again  accelerated 
in  consequence  of  the  resulting  dyspneic  irritation  of  the  vasomotor  center. 

In  the  veins  many  derangements  in  the  uniform  flow  of  the  blood 
occur :  i .  Regular  fluctuations  caused  by  respiration  and  the  movements 
of  the  heart  at  the  points  where  the  large  trunks  empty  into  the  heart. 
2.  Irregular  effects  due  to  pressure,  friction  in  the  direction  of  the 
current  or  in  the  opposite  direction,  changes  in  the  position  either  of 
the  body  or  of  the  limbs,  a  pump-like  action  in  the  iliac  vein  due  to 
walking,  etc.  During  extension  and  outward  rotation  of  the  thigh  the 
crural  vein  relaxes  and  collapses  in  the  iliac  fossa  and  the  internal 
pressure  becomes  negative;  while  when  the  thigh  is  flexed  and  elevated, 
the  vein  becomes  filled  to  distention  and  the  pressure  rises.  By  means 
of  this  pump-like  action  the  blood  (with  the  aid  of  the  valves)  is  forced 
upward.  A  somewhat  similar  phenomenon  takes  place  during  walking. 

ESTIMATION    OF    THE    CAPACITY    OF  THE  VENTRICLES    FROM 

THE  CURRENT- VELOCITY  BY  THE  METHOD  OF 

CARL  VIERORDT. 

There  may  be  considered  at  this  point  Vierordt's  attempt  to  estimate  the 
capacity  of  the  ventricles,  which  is  based  on  the  velocity  of  the  blood-current 
in  the  innominate  artery,  in  the  aorta  immediately  before  the  origin  of  this  trunk ^ 
as  well  as  in  the  coronary  arteries;  although  his  ^premises  are  exceedingly 
uncertain. 

(a)  The  velocity  of  the  current  in  the  right  carotid  is  26.1  cm.  in  a  second; 
the  cross-section  of  the  vessel  is  0.63  square  cm.;  hence,  the  quantity  of  blood 
that  flows  through  it  is  26.1  X  0.63  =  16.4  cu.  cm.  (i). 

(&)  The  velocity  of  the  current  in  the  right  subclavian  artery  is  26.1  cm.  a 
second;  the  cross-section  of  the  vessel  is  0.99  square  cm.;  hence,  the  quantity  of 
blood  that  flows  through  it  is  26.1  cm.  X  °-99  =  25-8  cu-  cm-  (2)  By  adding  i 
and  2  the  quantity  of  blood  that  flows  through  the  innominate  artery  is  obtained: 
16.4  +  25.8  =  42.2  cu.  cm.  The  cross-section  of  this  artery  is  1.44  square  cm. 

(c)  The  cross-section  of  the  aorta  immediately  before  the  origin  of   the  in- 
nominate artery  is  4.39  square  cm.;  the  velocity  of  the  current  in  the  aorta  is 
estimated  to  be  about  one-fourth  greater  than  in  the  innominate,  that  is,  36.6 
cm.;  hence,  the  quantity  of  blood  that  flows  through  it  is  161  cu.  cm.  (3). 

(d)  The  quantity  of  blood  that  flows  through  the  two  coronary  arteries  may 
be  assumed  to  be  4  cu.  cm.  (4).     Hence,  the  entire  quantity  of  blood  that  flows 


THE    DURATION    OF    THE    CIRCULATION.  177 

through  the  cross-section  of  these  vessels  is  (1  +  2  +  3  +  4)  207  2  cu  cm  As 
the  left  ventricle  must  furnish  this  quantity  of  blood  in  a  second,  and  as,  in  addition 
one  and  one-fifth  of  the  systole  corresponds  to  i  second,  the  quantity  of  blood 

thrown  into  the  aorta  at  each  systole  must  be  172  cu.  cm.,  or  180  grams  of  blood 

which  is  the  capacity  of  the  left  ventricle. 

THE  DURATION  OF  THE  CIRCULATION. 

The  question  as  to  the  time  required  by  the  blood  to  make  the  entire  circuit 
of  the  circulation  was  first  investigated  by  Edward  Hering,  in  1829,  in  horses  by 
injecting  a  solution  of  potassium  ferrocyanid  into  the  external  jugular  vein  and 
noting  the  time  when  this  substance  first  appeared  in  blood  withdrawn  from  the 
corresponding  vein  on  the  opposite  side  of  the  neck.  Carl  Vierordt,  in  1858,  per- 
fected the  technic  of  these  experiments  by  having  a  number  of  cups  on  a  rotating 
disc  pass  at  uniform  intervals  beneath  the  opened  vein  on  the  opposite  side  of 
the  body.  The  first  appearance  of  the  2  per  cent,  solution  of  potassium  ferro- 
cyanid is  recognized  by  adding  ferric  chlorid  to  the  serum  separated  from  the 
specimen  of  blood  and  the  development  of  a  Prussian-blue  reaction.  The  duration 
of  the  circulation  was  found  to  be  as  follows: 

In  the  horse 31.5  sec.     In  the  goose 10.89  sec. 

dog    16.7    '  duck    10.64    " 

rabbit 7.79  "  buzzard 6.73    " 

hedge-hog 7.61"  "        cock e  17     " 

cat  6.69  " 

A  comparison  of  these  values  with  the  normal  pulse-frequency  of 
the  same  animals  yields  the  following  laws: 

1.  The  average  duration  of  the  circulation  corresponds  with  27  con- 
tractions of  the  heart.     Applying  this  figure  to  man,  the  duration  of 
the  circulation  is  22.5  seconds,  with  72  pulse-beats  in  the  minute. 

If,  therefore,  the  entire  quantity  of  blood  passes  through  the  heart  in  22.5 
seconds,  ^  of  the  entire  quantity  must  pass  through  in  i  second.  This  quantity 
is  designated  the  second-volume  of  the  circulation.  The  latter  multiplied  by  60 
gives  the  minute-volume,  and  as  there  are  72  heart-beats  in  the  minute,  the  minute- 
volume  divided  by  72  represents  the  amount  of  blood  propelled  at  each  beat  of 
the  heart,  that  is,  the  pulse-volume  of  the  ventricles.  The  last  calculations,  how- 
ever, are  exposed  to  serious  sources  of  error. 

2.  In  general  the  mean  duration  of  the  circulation  in  two  species 
of  warm-blooded   animals   is  inversely   proportional  to  the  pulse-fre- 
quency. 

Of  the  influences  that  affect  the  duration  of  the  circulation  there  may  be 
mentioned: 

1.  A  greater  length  of  the  vascular  channel  (for  example,  from  the  metatarsal 
vein  of  one  foot  to  that  of  the  other)  requires  a  longer  time  than  a  shorter  channel. 
This  excess  in  time  may  be  equivalent  to  about  10  per  cent,  of  the  diameter  of 
the  circulation. 

2.  Young  animals,  with  shorter  vascular  channels  and  greater  pulse-frequency, 
have  a  shorter  circulation-time  than  old  animals. 

3.  Rapid  and  effective  contractions  of  the  heart,  as  during  muscular  exertion, 
shorten  the  time.     On  the  other  hand,  rapid  but  ineffective  contractions  (as  after 
division  of  both  vagi) ,  and  slow  but  correspondingly  larger  contractions  (as  with 
slight  irritation  of  the  vagus) ,  appear  to  have  scarcely  any  effect. 

Carl  Vierordt  has,  further,  attempted  to  determine  the  quantity  of  blood  in 
man  from  his  investigations  in  the  following  manner:  In  all  warm-blooded  animals 
the  circulation  is  completed  by  27  contractions  of  the  heart;  hence,  the  entire 
quantity  of  blood  must  be  equal  to  27  times  the  ventricular  capacity;  therefore,  in 
man,  27  times  187.5  grams,  or  5062.5  grams.  This  quantity  of  blood,  estimated 
as  TV  of  the  body-weight,  would  correspond  to  a  body-weight  of  65.8  kilos. 

In  1879  Landois  called  attention  to  the  fact  that  potassium  ferrocyanid,  being 
a  neutral  potassium-salt,  is  a  heart-poison,  which,  in  small  doses,  accelerates,  and 
in  large  doses  paralyzes,  the  heart.  These  experiments,  in  the  course  of  which 


178  THE  WORK  OF  THE  HEART. 

numerous  animals  die,  thus,  of  themselves,  cause  disturbances  in  the  circulation. 
It  was  therefore  suggested  that  the  experiments  be  repeated  with  a  substance 
that  truly  is  chemically  indifferent,  or  perhaps  with  the  microscopic  demonstra- 
tion of  particles  introduced  into  the  circulation  (such  as  heterogeneous  blood- 
corpuscles,  milk-globules  or  pigment-granules) .  Accordingly,  L.  Hermann,  in  1884, 
selected  the  innocuous  sodium  ferrocyanid.  Wolff,  thus  found  the  duration  of  the 
circulation  in  the  rabbit  to  be  5^5  seconds,  and  it  is  therefore  probable  that  in  other 
animals  also  the  time  is  shorter  than  that  given  by  Vierordt.  Landois  injected 
mammalian  blood-corpuscles  into  the  lateral  abdominal  vein  of  frogs  and  searched 
for  them  microscopically  on  the  opposite  side.  In  this  way  he  found  the  time  from 
7  to  1 1  seconds,  v.  Kries  has  recently  expressed  some  doubt  as  to  the  general 
applicability  of  the  method  even  from  a  physical  standpoint.  The  substances  first 
encountered  .are  carried  along  only  in  the  axial  stream  of  the  blood-vessels,  and 
no  conclusion,  therefore,  can  be  drawn  from  their  appearance  as  to  the  circulation 
of  the  entire  mass  of  the  blood. 

Stewart  employed  a  different  method.  If  the  electrical  resistance  offered  by 
an  unopened  artery  is  first  determined  with  a  galvanometer,  and  at  a  given  moment 
some  saline  solution  is  injected  into  the  circulation,  the  galvanic  resistance  will  be 
diminished  when  the  saline  blood  passes  through  the  section  in  communication 
with  the  galvanometer.  The  instant  when  this  takes  place  is  also  noted.  In  this 
way  Stewart  found  for  the  lesser  circulation  about  one-fifth  of  the  entire  duration 
of  the  circulation  ( =  10.4  seconds,  in  the  rabbit  and  in  the  dog).  The  duration  of 
the  circulation  in  the  kidney  was  8  seconds,  in  the  liver  3.8  seconds. 

A  venous  state  of  the  blood  increases  the  duration  of  the  circulation. 

Pathological. — In  the  presence  of  fever  the  duration  of  the  circulation  appears 
to  be  increased. 

THE  WORK  OF  THE  HEART. 

Following  the  method  of  Johann  Alfons  Borelli  and  Daniel  Passavant,  Julius 
Robert  v.  Mayer  estimated  the  work  of  the  heart  according  to  physical  principles. 
The  work  performed  by  a  motor  is  expressed  in  kilogrammeters,  that  is,  the  num- 
ber of  kilos  that  the  motor  is  capable  of  raising  to  the  height  of  i  meter  in  the 
unit  of  time. 

Robert  v.  Mayer  calculated  that  the  left  ventricle  propels  with  each  systole 
0.188  kilo  of  blood,  and,  in  order  to  raise  it  into  the  aorta,  has  to  overcome  the 
pressure  existing  in  that  vessel,  corresponding  to  a  column  of  blood  3.21  meters 
in  length.  The  work  of  the  ventricle  at  each  systole  is,  therefore,  equivalent  to 
0.188  X  3-21  =  0.604  kilogrammeter.  Allowing  75  systoles  for  each  minute,  the 
work  of  the  left  ventricle  in  24  hours  is  equal  to  0.604  X  75  X  60  X  24  =  65,230 
kilogrammeters.  The  work  of  the  right  ventricle  is  only  about  £  of  that  of 
the  left,  or,  in  other  words,  about  21,740  kilogrammeters.  The  work  of  the  two 
ventricles  taken  together  is,  therefore,  86,970  kilogrammeters.  The  work  per- 
formed by  a  laborer  during  8  working-hours  equals  300,000  kilogrammeters, 
thus  not  quite  four  times  as  much  as  that  of  the  heart.  As  all  of  the  kinetic 
energy  of  the  heart  is  converted  by  the  resistance  encountered  within  the  circula- 
tion into  heat,  the  work  of  the  heart  must  result  in  supplying  the  body  with 
heat:  425.5  grammeters  correspond  to  i  unit  of  heat,  that  is,  the  same  force 
that  is  capable  of  raising  425.5  grams  to  a  height  of  i  meter  is  also  capable 
of  raising  the  temperature  of  i  cu.  cm.  of  water  i°  C.  The  body,  therefore, 
acquires  by  the  conversion  of  the  kinetic  energy  of  the  heart  about  204,000 
units  of  heat. 

As  i  gram  of  coal  yields  8080  units  of  heat  when  consumed,  the  working  heart 
accomplishes  as  much  for  the  body  as  if  more  than  25  grams  of  coal  were  burned 
in  it  for  the  production  of  heat.  The  values  given  would  be  much  smaller  if  the 
capacity  of  the  ventricles  were  assumed  to  be  smaller;  for  example,  60  cubic  centi- 
meters; on  that  basis  the  work  of  the  heart  would  be  equivalent  only  to  20,000 
kilogrammeters,  or  -^  of  the  entire  muscular  work  of  the  body. 

THE  MOVEMENT  OF  THE   BLOOD   IN  THE  SMALLEST 

VESSELS. 

In  the  study  of  the  movement  of  the  blood  in  the  smallest  vessels 
microscopic  observation  of  transparent  portions  of  living  animals  is  the 


THE    MOVEMENT    OF    THE    BLOOD    IN    THE    SMALLEST    VESSELS.       179 

most  important  method,  and  it  has  been  repeatedly  employed  by  various 
investigators  since  the  time  of  Malpighi,  who  was  the  first  to  observe  the 
circulation  of  the  blood  in  the  pulmonary  vessels  of  the  frog. 

Method. — Suitable  objects  for  study  with  transmitted  light  are  the  tails  of 
tadpoles  and  young  fishes;  the  web,  the  tongue,  as  well  as  the  mesentery  stretched 
and  secured  by  means  of  pins  on  a  strip  of  wax  pasted  to  the  object- 
carrier,  or  the  lung  of  a  curarized  frog;  in  mammals  the  wing  of  the  bat  and  the 
nictitating  membrane,  drawn  out  from  the  orbit  and  spread  out  by  means  of 
threads  over  a  vertical  glass  slide ;  and  much  less  advantageously  the  mesentery. 

The  following  objects  can  be  examined  with  a  low  power  by  reflected  light: 
the  blood-vessels  of  the  frog's  liver,  of  the  pia  mater  in  the  rabbit,  of  the  frog's 
skin,  and  of  the  mucous  membrane  on  the  inner  aspect  of  the  lip  in  human  beings, 
as  well  as  of  the  palpebral  and  bulbar  conjunctivas. 

With  respect  to  the  form  and  arrangement  of  the  capillaries  in  the  various 
tissues,  the  following  points  are  worthy  of  note: 

1.  The  diameter  of  the  smallest  vessels,  which    permits   the  passage  of  the 
blood-corpuscles   only   in   single   file,   may,    however,  vary  from   2  to  5  //,    and 
in   the    larger    vessels    naturally    permits    the     passage    of    several    corpuscles 
abreast. 

2.  The  Length  is,  on  the  average,  about  0.5  millimeter;  beyond  this  limit  the 
vessels  either  originate  by  the  division  of  small  arteries,  or  unite  to  form  veins. 

3.  The  number  of  capillaries  is  extremely  variable,  being  largest  in  tissues  in 
which  metabolism  is  most  active,  as  the  lungs,  the  liver,  and  the  muscles;  and 
smaller  in  others,  like  the  sclera  and  the  nerve-trunks. 

4.  The  presence  of  numerous  anastomoses  is  particularly  striking,  with  the 
formation  of  plexuses,  the  shape  of  which  depends  principally  on  the  form  and 
structure  of  the  basal  tissue.     Thus,  the  capillaries  are  arranged  simply  in  loops 
in  the  papillae  of  the  skin;  as  polygonal,  retiform  meshworks  in  the  serous  mem- 
branes and  on  the  surface  of  many  glandular  acini;  as  longitudinal  tubes  running 
close  together  between  the  muscles  and  the  nerve-fibers  and  between  the  straight 
uriniferous  tubules;  in  a  radiating  manner,  converging  to  a  central  point  in  the 
liver;  and  in  the  form  of  arcade-like  loops  at  the  free  border  of  the  iris  and  at 
the  corneo-scleral  junction. 

With  regard  to  the  transition  of  the  smallest  arteries  into  the  capillaries,  a 
distinction  should  be  made  as  to  whether  the  minute  arterial  twigs  are  end- 
arteries — that  is,  such  as  do  not  anastomose  with  other  arterial  twigs  of  the  same 
order,  but  break  up  directly  into  capillaries,  and  communicate  with  neighboring 
arterial  twigs  only  by  means  of  capillaries;  or  whether  before  breaking  up  into 
capillaries  the  neighboring  arteries  communicate  by  liberal  anastomoses,  large 
enough  to  be  called  arterial.  The  presence  or  absence  of  arterial  anastomoses 
is  important  with  respect  to  the  nutrition  of  the  region  supplied  by  the  vessels. 

In  observing  the  blood-current  itself  it  will  be  seen  at  once  that  the 
red  blood-cells  progress  only  along  the  center  of  the  vessel  in  the  axial 
stream,  while  the  parietal,  transparent  layer  of  plasma  remains  entirely 
free  from  them.  The  latter,  designated  Poiseuille's  space,  is  recognizable 
especially  in  the  smallest  arteries  and  veins,  in  which  the  axial  stream 
occupies  three-fifths,  and  the  light  layer  of  plasma  one-fifth,  of  the 
entire  width  of  the  vessel.  It  is  less  distinct  in  the  capillaries.  Accord- 
ing to  Rud.  Wagner,  Poiseuille's  space  is  wholly  absent  in  the  smallest 
vessels  of  the  lungs  and  the  gills.  The  red  blood-cells  pass  through  the 
smallest  capillaries  in  single  file.  In  larger  vessels  they  move  close  to- 
gether, frequently  turning  and  twisting  in  their  course.  On  the  whole, 
the  rate  of 'progress  in  the  larger  vessels  is  uniform;  occasionally,  how- 
ever, as  when  there  is  a  sharp  bend  in  a  vessel,  the  movement  is  at  times 
somewhat  retarded,  at  times  again  accelerated.  Wherever  the  stream 
divides,  a  blood-cell  occasionally  remains  attached  to  the  projecting 
ridge  at  the  point  of  division,  bending  at  its  edges  on  each  side  into  the 
bifurcation  of  the  capillary,  and  appearing  somewhat  thinned  at  the 
center.  Often  it  may  adhere  in  this  way  for  a  long  while,  until,  the  cur- 


l8o       MIGRATION    OF    THE    BLOOD-CORPUSCLES    FROM    THE    VESSELS. 

rent  becoming  accidentally  stronger  on  one  side,  it  is  set  free,  whereupon 
it  rapidly  regains  its  former  shape  by  virtue  of  its  inherent  elasticity. 
When  two  vessels  join  to  form  one,  the  elasticity  of  the  red  blood-cells 
is  again  put  to  proof.  Cells  at  such  points  are  not  infrequently  heaped 
up  and  pushed  together  in  one  direction  or  another.  Occasionally,  an 
accumulation  of  this  kind  causes  a  temporary  stagnation  first  in  one  of 
the  branches  and  then  in  the  other;  the  obstruction  is  then  removed, 
and  for  some  time  both  capillaries  continue  to  pour  their  contents  into 
the  collecting  tube,  during  which  process  the  corpuscles  are  shaken  up, 
like  dice  in  a  box. 

The  movement  of  the  white  blood-cells  is  entirely  different.  They 
roll  along  the  walls  of  the  blood-vessels,  their  peripheral  zone  bathed  by 
the  plasma  of  Poiseuille's  space  and  their  inner  spherical  surface  pro- 
jecting into  the  procession  of  red  blood- cells.  The  explanation  of  this 
peculiar  property  on  the  part  of  the  leukocytes  of  keeping  close 
to  the  vessel-wall  has  been  furnished  by  Schklarewski,  who  dem- 
onstrated by  certain  physical  experiments  that  in  capillary  tubes 
in  general  (as,  for  example,  glass  tubes),  containing  artificial  mixtures 
of  different  kinds  of  granular  bodies,  those  possessing  the  lowest  specific 
gravity  are  forced  to  the  wall  when  a  current  is  set  up  in  the  tube,  while 
those  having  a  higher  specific  gravity  move  along  in  the  middle  of  the 
stream.  Thus,  when  once  forced  against  the  wall,  the  leukocytes  must 
keep  on  rolling,  partly  on  account  of  the  viscosity  of  their  surface,  which 
causes  them  to  adhere  readily  to  the  vessel- wall,  and  partly  because  the 
surface  directed  toward  the  axis  of  the  vessel,  where  the  current  is 
swiftest,  receives  the  most  effective  impulse,  often  by  the  direct  impact 
of  red  corpuscles  driven  against  it.  The  rolling  movement  is  not  rarely 
intermittent,  probably  because  different  parts  of  the  leukocytes  adhere 
with  equal  tenacity  to  the  vessel- wall.  The  viscosity  of  the  leukocytes 
is  also  in  part  responsible  for  their  slower  movement,  which  is  from  ten 
to  twelve  times  slower  than  that  of  the  red  blood-cells;  this  is,  however, 
in  part  also  due  to  the  fact  that,  owing  to  their  parietal  position,  the  larger 
portion  of  the  body  of  the  leukocyte  projects  into  the  peripheral  layers 
of  the  cylindrical  stream,  where  the  current  is  least  rapid. 

It  is  an  interesting  observation  that  in  the  vessels  first  formed  in  the  incu- 
bated egg,  as  well  as  in  young  tadpoles,  the  movement  of  the  blood  from  the 
heart  is  intermittent. 

The  velocity  of  the  stream  is  influenced  also  by  the  diameter  of  the  vessels 
at  a  given  point.  The  latter  is  subject  to  periodical  variations,  not  only  in  vessels 
provided  with  muscular  tissue,  but  also  in  the  capillaries— in  the  latter  in  conse- 
quence of  spontaneous  contraction  of  the  protoplasmic  cells  that  form  their 
walls. 

In  the  pulmonary  capillaries  the  blood-stream  is  more  rapid  than  in  those 
of  the  greater  circulation,  whence  it  may  be  concluded  that  the  total  sectional 
area  of  the  pulmonary  capillaries  must  be  smaller  than  that  of  all  of  the 
capillaries  of  the  body  (of  the  greater  circulation) . 

THE  MIGRATION  OF  THE  BLOOD-CORPUSCLES  FROM  THE 
VESSELS  ;  STASIS  ;  DIAPEDESIS. 

If  the  circulation  be  observed  in  the  mesenteric  vessels  it  is  not  rarely  possible, 
especially  if,  after  the  application  of  a  mild  irritant  to  this  vascular  tissue  (the 
contact  of  the  air  alone  is  sufficient),  an  inflammatory  process  begins  to  develop, 
to  see  the  migration  of  leukocytes  in  varying  numbers  through  the  vessel-wall. 
Instead  of  rolling  along  in  a  jerky  manner  in  the  plasmatic  zone,  the  cells  gradually 
move  more  and  more  slowly,  accumulate  in  increasing  numbers  and  adhere  firmly 


MIGRATION    OF    THE    BLOOD-CORPUSCLES    FROM    THE    VESSELS.       l8l 


to  the  wall;  soon  they  begin  to  penetrate  into  the  wall  and  ultimately  they  make 
their  way  completely  through  it  and  wander  for  some  distance  further  into  the  peri- 
vascular  tissue.  It  is  still  a  matter  of  doubt  whether  the  corpuscles  force  their 
way  through  interendothelial  stomata,  supposed  to  be  present,  and  then  enter 
the  lymphatic  vascular  system,  or  whether  they  simply  pass  through  the  cement- 
substance  between  the  endothelial  cells.  Several  successive  steps  can  be  distin- 
guished in  this  process  of  migration,  which  is  known  as  diapedesis ; — (a)  adhesion  of 
the  leukocytes  to  the  inner  surface  of  the  vessel  (after  gradual  retardation  in  their 
progress  along  the  wall  up  to  that  point) ;  (b)  extension  of  processes  into  and 
through  the  vessel-wall;  (c)  withdrawal  of  the  cell-body,  which  appears  con- 
stricted at  the  instant  of  its  passage  through  the  wall  of  the  compression;  (d)  com- 
plete passage  through  the  vessel-wall  and  the  further  progress  of  the  leukocyte  by 
virtue  of  its  ameboid  movement. 

Hering  observed  that,  even  under  normal  conditions,  the  leukocytes  in  larger 
vessels,  which  are  surrounded  by  lymph-spaces,  pass  into  the  lymph-spaces.  This 
observation  explains  why  cells  may  be  found  even  in  such  lymph  as  has  not  yet 
passed  through  any  gland.  The  cause  of  the  migration  from  the  vessels  resides, 
in  part,  in  the  independent  power  of  movement  on  the  part  of  the  leukocytes;  in 
part  it  is  a  physical  phenomenon,  namely  filtration  of  the  colloid  mass  of  the  cell- 
bodies  through  the  force  of  the  blood-pressure,  and  in  the  latter  connection,  there- 
fore, essentially  dependent  upon  the  intravascular  pressure  and  the  velocity  of  the 
blood-current.  Hering  regards  the  migration  of  leukocytes  and  even  of  a  few 
red  blood-cells  from  the  small  vessels  into  the  lymphatics  as  a  normal  process, 
which  he  was  able  to  observe  in  the  mesentery  of  the  frog.  The  red  blood-cells 
escape  from  the  vessel  in  the  presence  of  obstruction  to  the  venous  flow,  which 
causes,  first,  escape  of  blood-plasma  through  the  vessel-wall,  and  with  the 
plasma  the  erythrocytes  are  also  forced  through,  undergoing  a  marked  change  of 
shape  on  account  of  the  torsion  to  which  they  are  subjected  at  the  moment  when 
they  pass  through  the  vessel-wall,  but  regaining  their  shape  again  after  the  passage 
is  completed. 

The  migration  of  blood-cells  had  already  been  described  in  1824  by  Dutrochet 
and  in  1846  by  Waller;    the  phenomenon  was  next   more    carefully  studied  by 
Cohnheim.     According  to  the  latter,  the  migration  is  a  sign  of  inflammation,  and 
the  leukocytes,  which  accumulate  in 
considerable  numbers  in  the  tissue, 
are  to  be  regarded  as  true  pus-cor- 
puscles, which  may  later  multiply  by 
division.       It    should,    however,    be 
distinctly   stated  that,   in   addition, 
the   connective-tissue   cells   are  also 
capable,  by  multiplication,  of  produc- 
ing pus-corpuscles,  which  differ  by 
their  greater  size  from  the  migrated 
leukocytes  found  in  pus. 

When  a  vascular  part  is  sub- 
jected to  severe  irritation,  hyper- 
emic  reddening  and  swelling  of  the 
part  are  at  once  observed.  It  has 
been  shown  by  microscopic  examina- 
tion of  transparent  parts  that  both 
the  capillaries  and  the  smaller  ves- 
sels become  dilated  and  engorged 
with  blood-cells;  sometimes  dilata- 
tion is  preceded  by  a  temporary 
contraction  of  brief  duration.  At 
the  same  time,  a  change  in  the  ve- 
locity of  the  blood-stream  is  observed  in  the  vessels.  Rarely,  and,  as  a  rule, 
only  for  a  short  time,  the  blood-stream  is  accelerated;  but  generally  it  is  retarded. 
If  the  irritation  be  continued,  the  retardation  soon  becomes  so  great  that  the 
current  only  advances  intermittently,  and  a  to-and-fro  movement  of  the  blood- 
column  is  observed,— a  sign  that  obstruction  has  already  taken  place  in  peripherally 
situated  vascular  areas.  Finally,  the  current  in  the  distended  vessels  comes  to  a 
complete  standstill  (stasis) .  Bonders  points  out  the  greater  number  of  leukocytes 
in  stagnating  blood,  and  believes  correctly  that  this  accumulation  of  leukocytes 
is  a  greater  obstacle  to  their  progress,  as  compared  with  the  erythrocytes. 


FIG.  71. — Small  Mesenteric  Vessel  from  a  Frog  Show- 
ing the  Migration  of  Leukocytes:  w  w,  vessel-wall; 
a  a,  Poiseuille's  space;  r  r,  red  blood-corpuscles;  1 1, 
leukocytes  moving  along  the  wall,  at  c  c  in  various 
stages  of  migration;  f  f,  migrated  cells. 


While 


182  THE    MOVEMENT    OF    THE    BLOOD    IN    THE    VEINS. 

these  processes  are  going  on,  the  migration  of  the  leukocytes  and  rarely  also  of 
the  red  cells  takes  place.  Under  favorable  conditions  the  stasis  may  be  relieved, 
generally  with  a  reversal  in  the  order  of  the  phenomena  that  have  attended  its 
development.  The  escape  of  blood-corpuscles  through  the  intact  wall  of  the  vessel 
is  designated  diapedesis.  The  swelling  of  inflamed  parts  is  due  in  part  to  the 
dilatation  of  the  vessels,  but  chiefly  to  the  escape  of  plasma  into  the  tissues. 

THE  MOVEMENT  OF  THE  BLOOD  IN  THE  VEINS. 

In  the  smallest  veins,  which  are  formed  by  the  union  of  capillaries, 
the  velocity  of  the  blood-current  is  greater  than  in  the  capillaries,  but 
slower  than  in  the  smallest  arteries.  At  the  same  time,  the  current 
is  everywhere  uniform,  and  according  to  hydrodynamic  laws  the  venous 
current  would  continue  with  absolute  regularity  to  the  heart,  if  it  were 
not  subject  to  other  disturbances.  Such  disturbances,  however,  are 
operative  in  various  directions.  Among  special  peculiarities  of  the 
veins  to  which  interference  with  the  uniformity  of  the  current  is  attrib- 
utable the  following  may  be  mentioned: 

i.  The  relative  relaxation,  the  great  distensibility  and  compress- 
ibility of  even  the  larger  trunks;  2,  the  incomplete  distention,  which 
does  not  increase  to  any  considerable  degree  the  elastic  tension  of  the 
walls;  3,  the  numerous  and  at  the  same  time  free  anastomoses  among 
neighboring  trunks,  both  in  the  same  tissue-plane  and  from  above  down- 
ward. By  this  means  it  is  possible  for  the  blood,  when  the  venous 
area  is  partly  compressed,  to  escape  through  numerous  readily  distensible 
channels,  and  thus  the  occurrence  of  actual  stasis  is  prevented;  4,  the 
presence  of  numerous  valves,  which  permit  the  blood-current  to  move 
only  in  a  centripetal  direction.  These  are  wanting  in  the  smallest 
veins,  and  they  are  most  numerous  in  the  medium-sized  veins.  The 
valves  are  of  great  hydrostatic  significance,  inasmuch  as  they  divide 
long  columns  of  blood,  as,  for  example,  in  the  crural  vein  when  the  body 
is  in  the  erect  position,  into  sections,  thus  preventing  the  entire  column 
from  exerting  its  hydrostatic  pressure  down  to  the  lowest  portions  of 
the  vein. 

As  soon  as  pressure  is  exerted  on  a  vein,  the  nearest  valves  below  the 
point  of  pressure  close  and  those  next  above  open,  thus  leaving  a  free 
passage  for  the  blood  to  the  heart.  The  pressure  on  the  veins  may  be 
of  varied  character:  in  the  first  place  from  without,  by  contact  with 
various  objects.  Further,  thickened  and  contracted  muscles  may  com- 
press the  veins,  especially  in  the  movements  of  the  extremities.  That 
the  blood  escapes  in  a  stronger  stream  from  an  opened  vein  when  the 
muscles  are  moved  at  the  same  time  can  be  seen  whenever  venesection  is 
practised.  If  the  muscles  are  permanently  contracted,  the  venous 
blood,  escaping  from  the  muscles,  collects  in  the  parts  that  are  not 
moved,  especially  in  the  cutaneous  veins.  The  pulsatory  pressure  in 
the  arteries  accompanying  the  veins  also  tends  to  accelerate  the  venous 
current. 

Direct  observations  have  been  made  as  to  the  velocity  of  the  venous  blood- 
current  with  the  hemodromometer  and  the  rheometer.  Thus,  Volkmann  found 
a  velocity  of  225  mm.  in  a  second  for  the  jugular  vein;  but  in  view  of  the  low 
pressure  that  prevails  in  the  venous  system,  the  employment  of  instruments  for 
measuring  the  velocity  is  necessarily  attended  with  marked  deviations  from  the 
normal.  Reil  observed  that  the  quantity  of  blood  escaping  from  an  opening  in  an 
artery  was  two  and  a  half  times  as  great  as  the  quantity  of  blood  escaping  from 
a  similar  opening  in  a  vein. 


SOUNDS    AND    MURMURS    IN    THE    ARTERIES.  183 

As  the  smaller  venous  branches  unite  to  form  larger  ones,  the  lumen 
gradually  diminishes  toward  the  venae  cavae :  hence  the  velocity  of  the 
current  must  increase  in  the  same  proportion.  The  velocity  in  the 
venae  cavae  may  be  half  as  great  as  that  in  the  aorta. 

Borelli  estimated  the  capacity  of  the  venous  system  as  four  times  as  large  as 
that  of  the  arteries.  According  to  A.  v.  Haller  the  proportion  is  as  9  14. 

As  the  pulmonary  veins  are  narrower  than  the  pulmonary  arteries, 
the  blood  moves  more  rapidly  through  the  former  than  through  the  latter. 

SOUNDS  AND  MURMURS  IN  THE  ARTERIES. 

The  acoustic  phenomena  observed  in  the  arteries  must,  from  a  strictly  physical 
standpoint,  be  designated  as  murmurs.  Nevertheless  it  is  customary  in  medical 
nomenclature,  following  the  example  of  Skoda,  to  apply  the  term  sound  to  those 
acoustic  phenomena  that  are  of  short  duration  and  sharp  definition,  like  the  heart- 
sounds;  while  those  that  are  of  longer  duration  and  are  not  distinctly  delimited 
are  designated  murmurs  in  the  narrower  sense.  In  many  cases  a  sharp  distinction 
between  the  two  is,  therefore,  impossible. 

In  the  carotid,  and  more  rarely  in  the  subclavian,  two  distinct  sounds  are 
heard  in  approximately  four-fifths  of  all  healthy  individuals.  These  sounds  cor- 
respond in  duration  and  pitch  to  the  two  sounds  of  the  heart  and  must  be  inter- 
preted as  due  to  propagation  of  the  sound  from  the  heart  by  means  of  the  blood 
as  far  as  the  carotid,  and  they  are,  accordingly,  designated  transmitted  heart- 
sounds.  Sometimes  the  second  sound  of  the  heart  alone  is  heard,  as  the  site  of 
its  production  is  nearer  the  carotid.  The  second  sound  of  the  pulmonary  artery, 
which  is  in  close  contact  with  the  aorta,  may  also  be  transmitted  to  the  point 
mentioned. 

Sounds  and  murmurs  occur  either  spontaneously  or  only  after  the  application 
of  external  pressure,  by  means  of  which  the  lumen  of  the  vessel  is  narrowed. 
Accordingly  a  distinction  is  made  between  (i)  spontaneous  sounds  and  murmurs 
and  (2)  pressure-sounds  and  pressure-murmurs. 

Arterial  murmurs  are  developed  most  easily  by  exerting  pressure  on  a  circum- 
scribed portion  of  a  large  artery,  for  example,  the  femoral.  The  pressure  must  be 
so  regulated  that  only  a  small  portion  of  the  lumen  remains  open  for  the  passage 
of  the  blood  (stenotic  murmurs}.  As  a  result,  a  small  stream  of  blood  will  pass 
through  the  stenotic  point  with  great  rapidity  and  force,  and  enter  the  wider  por- 
tion of  the  artery  beyond  the  site  of  compression.  This  so-called  pressure-stream 
throws  the  fluid-particles  into  active  oscillatory  and  rotatory  movement  and 
thus  produces  the  murmur  in  the  wider,  peripheral  portion  of  the  vessel.  Analo- 
gous conditions  prevail  wherever  there  is  a  kink,  a  sharp  bend  or  a  tortuosity 
in  the  course  of  the  artery.  The  phenomenon  is,  therefore,  as  a  rule  a  pressure- 
murmur  generated  within  the  fluid.  With  regard  to  the  question  as  to  the  origin 
of  these  murmurs,  Geigel  takes  the  stand  that  they  are  due  to  static  transverse 
vibrations  of  the  vessel-walls.  Below  the  point  of  compression  a  thrill  is  felt 
in  the  walls  of  the  large  arteries  synchronously  with  the  pressure-murmur.  In 
cases  of  aortic  insufficiency,  exophthalmic  goiter,  and  circumscribed  arteriosclerosis 
this  thrill  is  much  more  marked  than  in  normal  cases,  and  it  is  also  appreciable 
over  smaller  arteries. 

A  murmur  of  like  character  is  that  at  times  heard  over  the  subclavian  artery 
synchronously  with  the  pulse  and  designated  subclavian  murmur.  This  is  pro- 
duced by  adhesions  of  the  two  layers  of  the  pleura  at  the  apices  of  the  lungs, 
especially  in  association  with  tuberculosis  and  other  diseases  of  the  lungs,  and  in 
consequence  of  which  the  subclavian  artery,  as  a  result  of  torsion  and  kinking, 
undergoes  local  stenosis,  which  sometimes  manifests  itself  by  diminution  or  absence 
of  the  pulse-wave  in  the  radial  artery  (paradoxical  pulse) . 

Pathological. — It  is  evident  that  murmurs  will  develop  in  the  human  body 
likewise:  (a)  When,  owing  to  morbid  conditions,  the  arterial  tube  is  dilated  at 
some  point  where  the  blood-current  is  forcibly  introduced  from  a  normal  portion 
of  the  artery.  Such  dilatations  (aneurysms)  quite  generally  give  rise  to  murmurs 
(bruits) .  (6)  Pressure-murmurs  will  be  generated  whenever  an  organ  exerts  pres- 
sure on  an  artery,  as,  for  example,  by  the  greatly  enlarged  uterus  during  preg- 
nancy, and  by  a  pathological  tumor  pressing  upon  a  large  artery. 


184  ACOUSTIC    PHENOMENA    WITHIN    THE    VEINS. 

In  all  cases  in  which  there  is  no  external  pressure,  it  is  found  that  the  pro- 
duction of  spontaneous  acoustic  phenomena  is  greatly  facilitated  if,  during  the 
period  of  arterial  diastole,  the  arterial  wall  is  as  relaxed  as  possible  and,  therefore, 
becomes  suddenly  and  greatly  distended  at  the  time  of  the  pulse-wave,  that  is, 
when  the  systolic  minimum  of  tension  of  the  arterial  wall  is  rapidly  displaced  by 
the  diastolic  maxirmim  of  tension.  This  is  particularly  the  case  with  aortic  in- 
sufficiency, a  condition  in  which  the  arteries  are  often  the  seat  of  widespread 
murmurs.  If  even  during  arterial  rest  the  minimum  of  tension  of  the  arterial 
wall  is  relatively  high,  the  acoustic  phenomena  are  faint  and  may  even  disappear 
altogether. 

The  following  factors  favor  the  development  of  arterial  murmurs:  (i)  A  suffi- 
cient degree  of  delicacy  and  elasticity  of  the  vessel-walls;  (2)  a  low  peripheral 
resistance,  that  is,  accelerated  and  unobstructed  escape  of  the  blood  from  the  end 
of  the  vascular  channel;  (3)  a  material  difference  between  the  pressure  ot  the  fluid 
in  the  stenotic  portion  and  that  of  the  fluid  in  the  peripheral  dilatation;  (4)  large 
size  of  the  artery. 

Murmurs  may  be  heard  also  in  normal  pulsating  arteries,  especially  when 
the  vessel  is  the  seat  of  sharp  bends  or  tortuosities.  In  almost  all  cases  in  which 
arterial  murmurs  are  heard,  one  or  several  of  the  foregoing  factors  can  be  demon- 
strated. It  is  evident  that  murmurs  of  this  kind  will  be  most  marked  when  two 
or  three  large  arteries  are  found  in  close  apposition.  Hence  the  rather  loud 
murmur  generated  in  the  many  tortuous  and  dilated  arterial  trunks  of  the  gravid 
uterus  (uterine  or  placental  souffle)  and  the  much  less  distinct  funic  souffle  in  the 
two  umbilical  arteries.  In  this  category  belongs  also  the  so-called  cerebral  murmur 
heard  in  almost  one-half  of  all  infants  with  thin  skulls,  as  well  as  the  murmur 
heard  over  the  morbidly  enlarged  spleen,  and  the  thrill  in  the  thyroid  gland  in 
cases  of  exophthalmic  goiter. 

When  auscultation  is  practised  over  the  ulnar  artery  under  the  favorable 
conditions  mentioned,  especially  in  lean  individuals,  every  pulse-beat  is  found  to 
be  accompanied  by  two  acoustic  phenomena,  which  coincide  with  the  primary 
and  the  dicrotic  elevation.  In  old  persons  especially,  and  in  individuals  with  a 
bigeminate  pulse,  the  two  sounds  are  quite  distinct.  Friedreich  believes  the  first 
sound  to  be  produced  by  the  vessel-wall,  that  is,  the  sudden  tension  of  the  artery 
distended  during  diastole.  The  second  murmur  naturally  is  feebler,  in  correspond- 
ence with  the  lesser  degree  of  distention  of  the  artery  by  the  dicrotic  elevation. 
Occasionally  a  third  sound  is  heard  between  the  other  two,  which  corresponds  to 
the  elasticity-oscillations  between  the  apex  of  the  curve  and  the  dicrotic  elevation. 
In  the  radial  artery  and  in  the  dorsalis  pedis  only  a  single  murmur  is,  as  a  rule, 
heard  synchronously  with  the  pulse-beat. 

In  cases  of  aortic  insufficiency  characteristic  acoustic  phenomena  are  present 
in  the  femoral  artery.  When  the  vessel  is  compressed,  there  is  heard  a  double 
blowing  (murmur) ,  the  first  element  of  which  is  due  to  the  fact  that  a  large  mass 
of  blood  is  driven  to  the  periphery  synchronously  with  the  pulse,  and  the  second 
to  the  fact  that  during  the  contraction  of  the  artery  a  large  quantity  of  blood 
flows  back  into  the  ventricle.  On  the  other  hand,  if  the  artery  is  not  compressed, 
two  feebler  sounds  are  heard,  which  are  due  to  the  fact  that  the  auricle  and  the  ven- 
tricle send  a  wave  of  blood  into  the  arterial  system  in  rapid  succession  (Fig.  55,  III) . 
Gerhardt  similarly  heard,  in  cases  of  insufficiency  of  the  pulmonary  valves,  two 
dull  sounds  over  every  portion  of  the  pulmonary  surface.  In  other  cases  (when 
there  is  also  tricuspid  insufficiency)  the  second  sound  is  produced  by  the  sudden 
snapping  closure  of  the  valves  in  the  femoral  veins,  caused  by  the  rebound  of 
the  venous  blood.  Also,  when  the  arteries  are  rigid  (atheroma)  a  double  sound 
is  sometimes  heard  synchronously  with  the  pulse- wave.  This  sound  is  attributed 
to  the  anacrotism  of  the  pulse  observed  under  such  conditions. 

ACOUSTIC   PHENOMENA  WITHIN   THE  VEINS. 

The  Venous  Hum. — Above  the  clavicle,  in  the  fossa  between  the  origin  of  the 
two  heads  of  the  sternocleidomastoid  muscle,  most  commonly  on  the  right  side, 
there  is  heard  in  many  individuals  (40  per  cent.)  a  sound  that  may  be  continuous, 
or  synchronous  with  the  diastole  of  the  heart,  or  even  with  inspiration,  and  of  a 
roaring  or  buzzing,  sometimes  hissing  or  singing,  character.  This  sound  is  generated 
within  the  bulb  of  the  common  jugular  vein  and  is  called  a  venous  hum.  If 
present  even  when  no  pressure  is  exerted  with  the  stethoscope,  it  is  a  pathological 
symptom.  The  phenomenon  may  be  heard  in  almost  any  subject  if  pressure  be 


THE    VENOUS    PULSE.       THE    PHLEBOGRAM.  185 

exerted  and  the  head  is  at  the  same  time  turned  to  the  opposite  side  and  slightly 
upward.  The  pathological  venous  hum  occurs  chiefly  in  young  anemic  individuals 
in  whom  also  a  thrill  is  felt  over  the  vessel;  it  is  present  also  in  cases  of  goiter, 
at  times  in  youthful  individuals,  but  it  becomes  less  common  with  advancing  age 

The  cause  of  the  venous  hum  resides  in  the  whirling  entrance  of  the  blood 
from  the  relatively  narrow  portion  of  the  common  jugular  vein  into  the  dilated 
bulb  situated  below.  It  appears  to  be  generated  chiefly  when  the  walls  of  the 
thinner  portion  of  the  vein  are  in  fairlv  close  apposition,  so  that  the  blood-stream 
is  obliged  to  force  its  way  through.  This  explains  the  fact  that  the  occurrence  of 
the  phenomenon  is  favored  by  pressure  and  by  turning  the  head  to  the  side 
and  slightly  upward.  The  intensity  of  the  sound  depends  upon  the  velocity  of 
the  blood  as  it  passes  through  the  narrow  portion  of  the  vein,  and  for  this  reason 
the  act  of  inspiration  and  the  diastole  of  the  heart,  both  factors  accelerating  the 
venous  flow,  intensify  the  venous  hum.  The  same  is  true  with  regard  to  the 
favorable  influence  of  the  erect  posture.  In  rare  cases  a  sound  similar  to  the 
venous  hum  is  heard  in  the  subclavian,  axillary,  thyroid  (in  cases  of  goiter),  facial 
and  innominate  veins,  the  superior  vena  cava,  the  crural  vein,  and  the  inferior 
vena  cava  at  the  blunt  margin  of  the  liver. 

Regurgitant  Murmurs. — The  expiratory  murmur  heard  at  times  in  the 
crural  vein  after  sudden  efforts  at  bearing-down  is  produced  by  a  centrifugal 
current  of  blood  passing  through  the  vein  at  the  bend  of  the  knee,  the  valves 
being  incompetent  or  entirely  absent.  When  the  valves  in  the  bulb  of  the  jugular 
vein  are  incompetent,  a  regurgitant  murmur  may  be  produced  either  during 
expiration  (expiratory  jugular- valve  murmur)  or  during  the  systole  of  the  heart 
(systolic  jugular- valve  murmur) .  In  the  presence  of  insufficiency  of  the  tricuspid 
valve  a  systolic  murmur  has  been  heard  in  the  crural  vein  when  its  valves  were 
incompetent. 

Valvular  Sounds  in  the  Veins. — Forced  expiration  may  give  rise  to  valvular 
sounds  in  the  crural  vein,  as  the  valves  close  with  a  snap  under  the  pressure  of 
the  blood  forced  back.  In  the  presence  of  insufficiency  of  the  tricuspid  valve  a 
large  quantity  of  blood  is  thrown  back  into  the  venae  cavae  at  each  ventricular 
systole.  Under  such  circumstances  also  the  venous  valves  may  close  suddenly 
with  the  production  of  a  sound.  The  phenomenon  occurs  both  in  the  bulb  of  the 
jugular  vein  and  in  the  crural  vein  at  the  bend  of  the  knee,  but  only  when  the 
respective  valves  are  competent. 

THE  VENOUS  PULSE.  THE  PHLEBOGRAM. 

Method. — If  the  movements  of  a  vein  are  recorded  by  means  of  a  lightly 
weighted  sphygmograph — a  heavy  load  would  compress  the  vein  or  at  least 
obliterate  the  delicate  details  of  the  curve — a  characteristic  form  will  be  observed 
in  a  successful  venous  pulse-curve  or  phlebogram  (Fig.  72). 

In  the  proper  interpretation  of  the  details  of  the  phlebogram  it  is  especially 
important  to  determine  its  chronological  relations  to  the  phases  of  the  heart's 
action;  hence,  it  is  advisable  to  record  a  cardiogram  and  a  phlebogram  simulta- 
neously (on  a  recording  surface  attached  to  a  vibrating  tuning-fork) .  The  begin- 
ning of  the  carotid  pulse  coincides  approximately  with  the  apex  of  the  cardiogram, 
that  is  to  say,  with  the  descending  limb  of  the  phlebogram. 

The  venous  pulse  within  the  common  jugular  vein  is  a  normal  phenomenon. 
A  pulsating  movement  synchronous  with  the  movements  of  the  heart  is  frequently 
observed  in  the  course  of  this  vein.  (Compare  Fig.  34.)  The  movement  may 
extend  only  to  the  lower  portion  of  the  vein,  the  so-called  bulb,  or  higher  up  to 
the  trunk  of  the  vein  itself.  When  the  valves  of  the  common  jugular  vein  above 
the  bulb  are  incompetent,  a  condition  that  is  not  at  all  rare,  even  in  healthy  per- 
sons, the  phenomenon  is  particularly  marked.  The  undulating  movement  ad- 
vances from  below  upward;  as  a  rule,  it  is  observed  only  when  the  subject  lies 
quietly  in  the  horizontal  position;  it  is  more  common  on  the  right  than  on  the 
left  side,  because  the  course  of  the  right  vein  is  straight  and  the  vessel  is  nearer 
the  heart  than  the  left  vein.  The  movement  is  propagated  more  slowly  than  the 
arterial  pulse-wave. 

The  venous  pulse  possesses  the  peculiarities  of  the  movement  of  the  heart.  The 
tracing  exhibits  in  a  marked  degree  all  of  the  details  of  tin-  a]  u-x-bcat  curve, especially 
in  connection  with  the  pathological  conditions  to  be  discussed  presently,  and  it  there- 
fore closely  resembles  such  a  curve,  as  is  shown  beyond  a  doubt  by  a  comparison 
of  the  venous  pulse-curve  (Fig.  72,  i)  with  the  apex-beat  curve  (Fig.  28,  A). 


i86 


THE  VENOUS  PULSE.   THE  PHLEBOGRAM. 


If  it  be  considered  that  the  distended  jugular  vein,  in  which  the  blood  is 
subject  only  to  slight  pressure,  communicates  directly  with  the  auricle,  it  will  be 
readily  understood  that  a  contraction  of  the  auricle  will  be  propagated  peripherally 
into  the  jugular  vein  as  a  positive  wave.  In  Fig.  72,  9  and  10  represent  the 
venous  pulse  from  healthy  individuals :  the  section  a  b  corresponds  to  the  auricular 
contraction.  Landois  has  occasionally  seen  this  composed  of  two  slight  elevations, 
corresponding  to  the  contraction  of  the  auricular  appendage  and  the  auricle.  As 
the  blood  of  the  right  auricle  is  subsequently  thrown  into  agitation  by  the  sudden 
tension  of  the  tricuspid  valve,  the  closure  of  the  latter,  which  is  synchronous  with 
the  systole  of  the  right  ventricle,  sends  a  positive  wave  into  the  jugular  vein, 
and  this  appears  in  9  and  10  as  the  section  b  c.  Finally,  the  sudden  closure  of 
the  pulmonary  valves  may  even  be  propagated  through  the  blood  in  the  ventricle 
as  far  as  the  auricle  and  still  further  up  in  the  jugular  vein,  and  be  registered  by 
the  production  of  a  small  positive  wave  (e) .  As  the  aorta  is  in  immediate  contact 
with  the  pulmonary  artery,  a  delicate  wave  may,  on  sudden  closure  of  the  aortic 
valves  (in  9  at  d),  be  generated  at  this  point  in  a  similar  manner.  During  the 


FIG.  72. — Various  Forms  of  Venous  Pulse,  Chiefly  after  Friedreich:  1-8,  with  tricuspid  insufficiency;  9  and  10, 
venous  pulse  from  the  jugular  vein  of  a  healthy  individual.  In  all  of  the  curves  a  b  indicate  contraction  of 
the  right  auricle;  b  c,  that  of  the  right  ventricle;  d,  closure  of  the  aortic  valves;  e,  closure  of  the  pulmonary 
valves;  e  f,  diastole  of  the  right  auricle. 

diastole  of  the  auricle  and  of  the  ventricle  blood  flows  freely  toward  the  heart, 
and  in  consequence  the  vein  collapses  and  the  writing-lever  makes  a  down-stroke. 

According  to  Knoll  the  normal  jugular  pulse  is  due  partly  to  the  positive  wave 
caused  by  the  contraction  of  the  right  auricle  and  partly  to  the  negative  wave 
caused  by  the  dilatation  of  the  ventricle ;  while,  the  increase  in  the  venous  pressure 
that  takes  place  between  these  two  phases  is  brought  about  by  interference  with 
the  flow  of  venous  blood  to  the  heart  during  the  auricular  pause. 

In  the  sinuses  of  the  skull  the  blood  likewise  exhibits  pulsatory  movement, 
because  blood  flows  freely  into  the  heart  during  diastolic  relaxation.  Under 
favorable  conditions  this  pulsatory  movement  may  be  propagated  as  far  as  the 
veins  of  the  retina  and  thus  give  rise  to  the  retinal  venous  pulse,  which  was  familiar 
to  the  earlier  investigators. 

Pathological.— The  venous  pulse  may  be  much  larger  and  much  more  pro- 
nounced in  all  its  characteristic  parts  in  cases  of  tricuspid  insufficiency.  A  mo- 
ment's reflection  will  show  that  under  such  circumstances  every  contraction  of 
the  right  ventricle  must  cause  regurgitation  of  a  certain  quantity  of  blood  into 


THE    VENOUS    PULSE.       THE    PHLEBOGRAM.  187 

the  veins,  by  which  a  marked  wave  may  be  produced.  As  a  rule,  the  common 
jugular  vein  pulsates  quite  strongly  in  cases  of  tricuspid  insufficiency;  but  when 
the  valves  at  the  bulb  of  the  jugular  vein  are  still  competent,  the  pulse  is  not 
propagated  into  the  vein  itself.  The  jugular  pulse  is,  therefore,  not  a  necessary 
sign  .of  tricuspid  insufficiency,  but  only  a  sign  of  insufficiency  of  the  valves  of 
the  jugular  vein.  The  ventricular  systole,  however,  is  always  propagated  into 
the  inferior  vena  cava,  which  is  without  valves,  and  there  it  produces  especially 
the  so-called  liver-pulse.  Each  ventricular  contraction  throws  a  large  quantity  of 
blood  as  far  as  the  hepatic  veins  and  thus  the  liver  undergoes  systolic  swelling 
and  distention  due  to  injection. 

The  figures  from  2  to  8  represent  tracings  from  the  common  jugular  vein. 
In  all  the  curves,  a  b  indicates  the  auricular  contraction;  the  contracting  auricle 
throws  a  positive  wave  into  the  veins.  This  portion  of  the  curve  appears  at  times 
as  a  simple  anacrotic  basal  elevation  (3).  Not  infrequently  (as  particularly  in  i, 
representing  a  curve  from  one  of  the  thyroid  veins)  two  or  three  small  notches 
make  their  appearance  at  this  point,  and  these  may  be  compared  with  the  analo- 
gous elevations  in  the  cardiogram. 

In  accordance  with  the  tension  of  the  vein,  as  well  as  with  the  freedom  of 
the  flow  of  blood  from  the  vein  to  the  heart,  and  also  with  the  respiratory  position 
of  the  thorax,  the  auricular  notch  may  appear  in  the  descending  portion  of  the 
foregoing  curve,  as  in  5  and  8;  at  times  alternately  as  in  3  and  8  (see  7) ;  at  other 
times,  a  portion  of  the  auricular  wave  may  be  in  the  descending  portion  of  the 
foregoing  curve,  while  the  remainder  is  found  in  the  ascending  portion  of  the 
same  curve,  as  in  6,  2  and  4.  When  the  action  of  the  auricle  is  exceedingly  feeble, 
the  auricular  wave  may  even  be  entirely  abortive  as  in  7  at  f . 

The  ventricular  elevation  is  caused  by  the  large  blood-wave  thrown  back  into 
the  vein  by  the  evacuation  of  the  ventricle.  The  apex  of  this  wave  (c)  is  at  times 
higher,  at  other  times  lower,  in  accordance  with  the  tension  in  the  vein  and  the 
pressure  of  the  sphygmograph.  It  is  usually  followed  by  at  least  one  notch  (4, 
5,  6  e),  produced  by  the  sudden  closure  of  the  semilunar  valves  of  the  pulmonary 
artery.  It  is  not  surprising  that  the  closure  of  these  valves  produces  an  undulatory 
movement  in  the  ventricle  that  is  propagated  through  the  constantly  open  tricuspid 
valve  into  the  auricle  and  the  veins.  The  adjacent  aorta  may  even  produce  a 
small  wave  next  to  e  by  the  closure  of  its  valves  (as  in  i  and  2  d) .  When  the 
valve-closure  becomes  feebler  in  consequence  of  diminished  tension  in  the  large 
arteries,  the  aortic-valve  wave  d  is  the  first  to  disappear  (as  in  4  and  5) ;  later 
also  the  elevation  due  to  closure  of  the  pulmonary  valves  e  disappears  (as  in  3 
and  7).  After  the  closure  of  the  valves  the  curve  falls,  in  correspondence  with 
the  diastole  of  the  heart,  as  far  as  f. 

An  especially  distinct  venous  pulse  may  be  produced  also  when  the  right 
auricle  is  greatly  overdistended,  as  in  cases  of  mitral  insufficiency  or  stenosis. 
In  rare  instances  other  veins  pulsate  in  addition  to  the  common  jugular,  such  as 
the  external  jugular,  some  of  the  facial  veins,  the  anterior  jugular  vein,  the  thyroid, 
the  external  thoracic,  and  the  veins  of  the  upper  and  lower  extremities.  Landois 
on  one  occasion  saw  extensive  venous  pulsation  in  a  moribund  woman  without 
any  cardiac  lesion,  in  whom  the  autopsy  revealed  an  enormous,  white,  fibrinous 
clot  extending  from  the  right  ventricle  into  the  auricle  and  making  closure  of 
the  tricuspid  valves  impossible;  even  the  cutaneous  veins  on  the  anterior  surface 
of  the  thorax  could  be  seen  pulsating  strongly. 

It  is  evident  that  pulsations  similar  to  those  produced  in  the  veins  of  the 
greater  circulation  in  cases  of  tricuspid  insufficiency  must  also  be  produced  in 
the  pulmonary  veins  in  cases  of  mitral  insufficiency.  Such  pulsations  are,  however, 
not  directly  visible;  although  it  may  be  possible  to  demonstrate  their  presence  by 
observing  the  cardiopulmonary  movement. 

In  rare  cases  the  veins  on  the  backs  of  the  hands  and  the  feet  are  seen  to 
pulsate,  because  the  arterial  pulse  is  propagated  to  the  veins  through  the  capillaries, 
or  possibly  through  some  direct  communication  between  the  arterial  branches 
and  the  veins.  This  phenomenon  may  occur  even  under  normal  conditions,  espe- 
ciallv  when  the  peripheral  extremities  of  the  arteries  are  dilated  and  relaxed,  or 
when  the  pressure  within  them  becomes  high  and  falls  rapidly  again,  as  in  cases 
of  aortic  insufficiency. 

Diastolic  collapse  of  the  veins  of  the  neck  is  observed  in  association  with  heart- 
disease  at  the  instant  when  the  tricuspid  valve  opens.     It  is  due  to  deficiem 
traction  of  the  right  auricle.     In  cases  in  which  the  interior  of  an  artery  c 
municates  directly  with  the  interior  of  a  vein  as  a  result  of  traumatism  or  rupture, 
the  arterial  pulse  is  propagated  into  the  venous  channels. 


l88  THE     DISTRIBUTION    OF    THE    BLOOD. 

THE  DISTRIBUTION  OF  THE  BLOOD. 

The  metkods  employed  for  determining  the  quantity  of  blood  contained  in 
individual  organs  and  members  must  unfortunately  as  yet  be  regarded  as  inade- 
quate, (i)  The  quantity  of  blood  contained  in  the  part  may  be  determined  after 
death  in  frozen  cadavers.  This  method  is  inaccurate,  because  after  death,  par- 
ticularly through  the  stimulation  of  the  vasomotor  center,  the  quantity  of  blood 
contained  in  any  given  part  undergoes  profound  changes  in  consequence  of  the 
fact  that  different  parts  of  the  body  die  and  freeze  at  different  times.  (2)  A  part 
may  be  forcibly  ligated  off  from  an  animal  during  life,  then  be  at  once  severed,  and 
the  quantity  of  blood  in  the  tissues  be  determined  while  they  are  still  warm.  This 
method  is,  unfortunately,  inapplicable  to  many  internal  organs. 

J.  Ranke  determined  in  this  way  the  distribution  of  the  blood  in  the 
living  rabbit  at  rest.  He  found  one-fourth  of  the  entire  quantity  of 
blood  in  (a)  the  resting  muscles,  (b)  the  liver,  (c)  the  circulatory  organs 
(heart  and  large  arterial  trunks),  (d}  the  remaining  organs  taken  to- 
gether; of  the  last  the  lungs  contained  between  7  and  9  per  cent. 

The  amount  of  blood  is  influenced  by:  (i)  The  anatomical  distribution  of  the 
vessels  in  general,  that  is,  the  number  o'f  vessels  in  individual  parts  of  the  body; 
(2)  especially  the  size  of  the  vessels,  which  is  dependent  upon  physiological  causes: 
(a)  the  blood-pressure  within  them;  (b)  the  state  of  irritability  of  the  vasocon- 
strictor or  vasodilator  nerves;  (c)  the  condition  of  the  tissues  in  which  the  vessels 
are  situated,  for  example,  the  intestinal  vessels  during  the  absorption  of  alimentary 
juices;  the  muscular  vessels  during  the  contraction  of  the  muscles  (vessels  in  in- 
flamed parts). 

The  most  important  factor  influencing  the  quantity  of  blood  in 
an  organ  is  the  activity  of  the  latter.  In  this  connection  the  ancient 
dictum  "ubi  irritatio,  ibi  affluxus"  is  applicable.  Examples  are 
afforded  by  the  salivary  glands,  the  stomach,  and  the  muscles  during 
activity.  As,  however,  under  normal  conditions  of  the  body,  the 
individual  organs  in  many  ways  relieve  one  another,  one  organ  may 
in  the  course  of  a  day  be  found  in  a  condition  of  greater  plethora  at 
one  time  and  another  organ  at  another  time.  The  variations  in  the  dis- 
tribution of  the  blood  coincide  with  the  alternations  in  the  functional 
activity  of  the  organs.  Thus,  while  one  organ  is  in  a  state  of  increased 
activity,  the  remainder  often  are  resting:  the  process  of  digestion  is 
attended  with  muscular  lassitude  and  mental  relaxation;  severe  mus- 
cular exertion  delays  digestion;  when  the  skin  is  reddened  and  secreting 
freely,  the  action  of  the  kidneys  is  temporarily  in  abeyance.  Some 
organs  (the  heart,  the  respiratory  organs,  and  certain  nerve-centers) 
appear  to  maintain  a  constant  level  of  activity  and  contain  the  same 
quantity  of  blood  at  all  times. 

While  an  organ  is  active,  the  amount  of  blood  present  may  increase 
up  to  30  per  cent,  or  even  to  47  per  cent.  The  organs  of  locomotion  in 
young  and  vigorous  individuals  are  likewise  relatively  more  plethoric 
than  those  of  older  individuals  with  a  feebler  muscular  system. 

During  mental  activity  the  carotid  is  dilated,  and  the  dicrotic  elevation  of 
the  carotid  curve  is  increased,  while  the  radial  exhibits  reverse  conditions,  and 
the  pulse  is  accelerated. 

In  this  condition  of  greater  activity  the  increased  amount  of  blood 
usually  undergoes  more  rapid  renewal  at  the  same  time;  for  example, 
after  muscular  exertion  the  duration  of  the  circulation  is  diminished. 
This  circumstance  may  be  affected  by  a  great  variety  of  influences  that 
govern  the  movement  of  the  blood. 


PLETHYSMOGRAPHY. 


189 


The  development  of  the  heart  and  the  large  blood-vessels  is  responsible  for 
certain  differences  in  the  distribution  of  the  blood  in  children  and  in  adults.  From 
childhood  to  puberty  the  heart  is  relatively  small  and  the  vessels  are  relatively 
large.  After  puberty,  on  the  contrary,  the  heart  is  large  and  the  arteries  are 
comparatively  small.  Accordingly,  the  arterial  blood-pressure  in  the  greater  cir- 
culation must  be  lower  in  a  child  than  in  an  adult.  The  pulmonary  artery  is 
relatively  large  in  childhood,  the  aorta  relatively  small;  after  the  onset  of  puberty 
both  arteries  are  approximately  of  the  same 'size.  Hence,  it  follows  that  the 
blood-pressure  in  the  pulmonary  vessels  of  the  child  must  be  relatively  higher 
than  in  the  adult. 

PLETHYSMOGRAPHY. 

The  plethysmograph  is  an  instrument  employed  to  determine  and  register  the 
amount  of  blo'od  in  an  extremity  and  its  variations.  It  is  a  perfected  apparatus, 
modeled  after  the  "  box-sphygmometer"  described  by  Chelius  in  1850  (Fig.  41).  It 
consists  of  a  long  container  (G),  designed  for  the  reception  of  an  entire  extremity. 
The  opening  around  the  introduced  part  is  made  air-tight  by  means  of  rubber,  and 
the  interior  of  the  vessel  is  tilled  with  water.  In  the  lateral  wall  of  the  receptacle 
is  a  communicating  tube,  which  also  is  filled  with  water  to  a  certain  level.  As 
each  pulse-beat  causes  an  enlargement  of  the  extremity  as  a  result  of  the  increased 
flow  of  arterial  blood,  the  water  in  the  tube  will  indicate  the  magnitude  of  this 
positive  variation  in  the  quantity  of  blood,  which  will  be  transmitted  to  the  drum 
(T),  covered  with  an  elastic  membrane,  and  with  which  is  connected  a  writing 
lever  moving  in  a  horizontal  direction. 

The  cylinder  G  may  also  be  filled  with  air.  v.  Kries  connects  the  tube  with 
a  gas-burner  instead  of  with  the  registering  drum  (T) ,  so  that  the  variations  in 
the  size  of  the  arm  are  reproduced  in  the  flame,  the  flickerings  of  which  may  be 
photographed. 


FIG.  73. — Mosso's  Plethysmograph:   F,  communicating  flask,  by  elevation  of  the  level  of  which  the  hydrostatic 
"  pressure  may  be  increased;   T,  the  inscribing  apparatus. 

Individual  organs  (spleen,  kidney)  may  be  enclosed  in  a  box-like  apparatus 
in  a  similar  manner  for  the  purpose  of  observing  fluctuations  in  their  size:  onco- 
graph. 

The  fluctuations  of  the  plethysmograph  permit  recognition  of  the  following 
phenomena: 

i.  Pulsatory  fluctuations  in  volume. — As  the  venous  current  in  the  resting 
extremity  may  be  regarded  as  uniform,  any  rise  in  the  volume-curve  must  indicate 
a  greater  velocity  in  the  movement  of  the  arterial  blood-current  toward  the  periph- 
ery, and  the  reverse.  The  curves  registered  by  this  apparatus  represent  volume- 
pulsations  and  resemble  a  dromographic  curve"  (Fig.  69,  III).  A  rise  in  the  limb 
of  the  curve  indicates  a  greater  flow  of  arterial  blood,  while  a  fall  indicates  a 
diminution  in  the  flow.  If  the  level  of  the  curve  remains  the  same,  it  is  to  be 
inferred  that  the  arterial  inflow  of  blood  is  equal  to  the  venous  outflow. 

At  first  sight  the  plethysmographic  tracing  (volume-curve,  current-pulse) 
presents  a  great  similarity  to"  the  sphygmographic  tracing  (pressure-pulse),  espe- 
cially from  the  fact  that"  both  exhibit  the  dicrotic  elevation.  More  careful  ex- 
amination, however,  reveals  several  differences:  In  the  plethysmographic  tracing 
(current-pulse)  the  curve  descends  to  a  much  lower  level  after  the  primary  apex. 


TRANSFUSION    OF    BLOOD. 

This  marked  fall,  which  is  not  accompanied  by  a  corresponding  fall  in  the  pressure, 
is  attributed  by  v.  Kries  to  a  peripheral  reflection,  that  is,  one  in  which  a  positive 
wave  is  reflected  as  such.  The  dicrotic  elevation  (secondary  wave)  appears,  further, 
somewhat  earlier  in  the  plethysmographic  curve  (current-pulse)  than  in  the 
sphygmographic  curve;  although  it  also  has  a  centrifugal  course,  as  in  the  sphyg- 
mo graphic  curve. 

2.  The  respiratory  fluctuations,  which  correspond  to  the  respiratory  fluctua- 
tions in  blood-pressure.  Active  breathing  and  cessation  of  breathing  produce  a 
diminution  in  volume.  Further,  the  part  has  been  observed  to  undergo  enlarge- 
ment in  consequence  of  effects  at  bearing  down  and  coughing,  and  reduction  in 
size  during  sobbing.  3.  Certain  periodic  fluctuations,  dependent  upon  periodic- 
regulatory  movements  of  the  vessels,  particularly  of  the  smaller  arteries.  4.  Vari- 
ous fluctuations  due  to  accidental  causes  that  bring  about  alterations  in  the 
blood-pressure,  such  as  change  of  position  producing  hydrostatic  effects;  dilatation 
or  contraction  of  other  large  vascular  areas.  5.  Muscular  movements  in  the  ex- 
tremity introduced  into  the  plethysmograph  cause  a  reduction  in  volume,  because 
the  venous  pulse  is  accelerated,  and  in  addition  the  musculature  itself  is  somewhat 
reduced  in  size,  in  spite  of  the  fact  that  the  intramuscular  vessels  are  dilated. 

6.  High  (from  33°  to  36°  C.)    and  low   (from  4°  to  8°  C.)    temperature,  when 
applied  to  the  skin  of  the  arm,  increase  the  volume  of  the  member  in  consequence 
of  paresis  of  the  muscular  coat  of  the  blood-vessels  caused  by  the  thermic  stimuli. 

7.  Mental  exertion  diminishes  the  volume  of  the  extremity;  sleep  has  the  same 
effect.     8.  Compression  of  the  afferent  artery  causes  diminution,  while  constriction 
of  the  veins  naturally  causes  an  increase  in  the  volume.     9.  Irritation  of  the  vaso- 
motor  nerves  is  followed  by  a  decrease,  that  of  the  vasodilators  by  an  increase, 
in  volume. 


TRANSFUSION  OF  BLOOD. 

Transfusion  is  the  physiological  introduction  of  blood  into  the  vascu- 
lar system  of  a  living  being. 

The  first  mention  of  direct  exchange  of  blood  between  two  individuals  from 
vessel  to  vessel  takes  us  back  to  the  time  of  Cardanus.  After  the  discovery  of 
the  circulation  of  the  blood,  Potter  in  England  again  called  attention  to  the  prac- 
ticability of  transfusion.  Numerous  experiments  were  made  on  animals.  Attempts 
were  made  by  the  introduction  of  fresh  blood  particularly  to  resuscitate  animals 
that  had  bled  to  death.  The  physicist,  Boyle,  as  well  as  the  anatomist,  Lower, 
took  an  especially  active  part  in  these  experiments.  The  blood  of  the  same  or 
of  another  species  was  used.  The  first  transfusion  in  man  was  practised  by  Jean 
Denis  in  Paris  in  1667  with  lamb's  blood. 

(a)  The  erythrocytes  are  the  most  important  constituents  to  which  the  re- 
suscitating power  of  the  blood  is  due.  They  retain  their  functions  even  after  the 
blood  has  been  defibrinated.  The  changes  in  the  red  blood-cells  produced  by 
time  and  by  prolonged  exposure  to  high  temperatures  have  been  described  on 
p.  36. 

(6)  With  respect  to  the  gases  contained  in  the  blood,  it  is  to  be  remembered 
that  oxygenated  blood  under  no  circumstance  is  injurious.  Venous  blood  can, 
however,  be  infused  into  the  blood-vessels  of  a  living  being  without  injury,  provided 
the  respiration  is  sufficient  to  arterialize  the  infused  blood  in  its  passage  through 
the  pulmonary  capillaries.  Under  such  circumstances  the  carbon  dioxid  contained 
in  the  blood  is  replaced  by  oxygen  in  the  process  of  respiration.  If  the  respiration, 
however,  is  arrested  or  if  it  is  not  carried  on  with  sufficient  activity,  the  blood, 
still  rich  in  carbon  dioxid,  will  be  conveyed  to  the  left  heart  and  on  through  the 
arteries  of  the  medulla  oblongata.  In  consequence  there  results  violent  irritation 
of  the  centers  in  that  region,  followed  later  by  paralysis  and  even  by  death. 

(c)  The  fibrin  or  the  substances  forming  it  take  no  part  in  the  resuscitating 
activity  of  the  blood.     Therefore,  defibrinated  blood  is  capable  within  the  body 
of  assuming  with  equal  success  all  of  the  functions  that  belong  to  non-defibrinated 
blood, 

(d)  Investigations,  especially  by  Worm-Muller,  have  shown  that  the  vascular 
system  (dog)  is  capable  of  taking  up  an  excess  of  foreign  blood  up  to  83  per  cent., 


TRANSFUSION    OF    BLOOD.  19! 

without  injurious  consequences.  It  follows  that  the  vascular  system  possesses 
to  a  certain  degree  the  power  of  accommodating  itself  to  large  quantities  of  blood, 
just  as  it  is  known  to  possess  the  power  of  adapting  itself  to  a  diminished  volume 
of  blood,  as,  for  example,  after  hemorrhage. 

Transfusion  is  practised:  i.  In  cases  of  acute  anemia,  especially  after  a 
hemorrhage  when  it  is  sufficiently  great  to  threaten  the  life  of  the  patient. 
The  object  under  such  circumstances  is  to  replace  directly  with  new  blood 
(from  150  to  500  cu.  cm.)  that  which  has  been  lost  and  is  necessary  to  main- 
tain life. 

2 .  In  cases  of  poisoning  in  which  the  blood  has  been  vitiated  by  the  admix- 
ture of    a  toxic  substance   and   has  thus  become  unfit   to   maintain   the    vital 
functions,  a  large  quantity  of  this  vitiated  blood  may  be  removed  by   copious 
venesection   under  suitable   conditions   and  normal   blood   be   introduced  into 
the  vessels  in  place  ,of  the  blood  withdrawn  (depietory  transfusion).     The   chief 
form  of  intoxication  amenable  to  this  treatment  is  that  with  carbon   monoxid. 
Also  the  admixture  of  other  poisons  with  the  blood,  especially  those  that    dis- 
solve the  erythrocytes  or  that  cause   marked  methemoglobinemia,    as,   for  ex- 
ample,   potassium  chlorate,  as  well  as  other  toxic  substances  (ether,  chloroform, 
chloral  hydrate,  opium,  morphin,  strychnin,  snake-venom),  may  likewise  furnish 
an  indication  to  replace  the  poisoned  mass  of  blood  with  normal  blood. 

3.  Under  certain   morbid  conditions,   abnormal   states   of  the  blood    may 
develop  in  the  body  and  threaten  its  integrity;    these  may  affect  both  the  mor- 
phological elements,  and  the  composition  of  the  blood.     The  morbid  alterations 
in  the  constitution  of   the  blood  include  poisoning  with   urinary   constituents 
(uremia) ,  with  biliary  constituents  (cholemia)  and  with  carbon  dioxid.     If  severe 
they  may  cause  death.     Therefore,  in  desperate  cases  of  this  kind,  especially 
when  the  cause  is  a  temporary  one,  the  vitiated  blood  may  be  in  part  replaced 
by  normal  blood.     Whether  hydremia,  oligocythemia  and  pernicious  anemia  are 
indications  for  transfusion  will  depend  on  the  correct  interpretation  of  the  under- 
lying disease. 

Between  a  quarter-hour  and  a  half-hour  after  transfusion,  in  accordance  with 
the  amount  of  blood  introduced,  a  more  or  less  violent  febrile  reaction  takes 
place. 

The  operative  procedure  varies  accordingly  as  defibrinated  or  non-defibrinated 
blood  is  employed.  When  a  defibrination  is  to  be  practised,  the  blood  obtained 
by  venesection  from  a  healthy  human  being  is  collected  in  a  vessel  and  beaten 
with  a  small  rod  until  the  fibrin  has  been  completely  removed.  The  blood  is 
then  filtered  through  an  atlas-filter,  without  pressure,  is  heated  to  .the  tem- 
perature of  the  body  by  placing  the  vessel  in  warm  water,  and  it  is  conveyed 
into  the  opened  vessel  with  the  aid  of  the  buret-infuser  of  Landois  or  a  syringe. 
The  vessel  selected  may  be  a  vein,  as,  for  example,  the  basilic  at  the  bend 
of  the  elbow,  or  the  long  saphenous  vein  at  the  internal  malleolus.  Under  such 
circumstances  the  blood  is  injected  in  the  direction  toward  the  heart.  The 
blood  may  be  injected  also  into  an  artery  (the  radial  or  the  posterior  tibial), 
either  in  the  centrifugal  or  in  the  centripetal  direction.  In  any  event,  care  must 
be  exercised,  especially  when  the  blood  is  injected  into  the  veins,  to  guard  against 
the  entrance  of  air,  as  such  an  accident  might  even  cause  death.  Death  occurs 
when  the  air  that  has  entered  the  right  heart  is  churned  up  into  froth  by  the 
movements  of  the  heart  and  in  this  form  is  pumped  into  the  smaller  branches 
of  the  lesser  circulation,  thus  arresting  the  flow  of  blood  through  the  lungs.  After 
the  injection  of  air  into  the  arterial  system  a  few  small  bubbles  of  air  may  possibly 
pass  through  the  capillaries  of  the  greater  circulation  and  thus  be  found  every- 
where in  the  vessels.  They  disappear  at  once,  however,  because  the  oxygen 
enters  into  chemical  combination  and  the  nitrogen  is  absorbed. 

If  defibrinated  blood  is  not  to  be  infused  the  divided  vein  of  the  donor  is 
connected  by  means  of  a  tube  with  the  vessel  of  the  recipient,  so  that  direct  trans- 
fusion takes  place.  The  blood  may  also  be  taken  up  with  an  oiled  syringe,  to 
which  the  blood  does  not  adhere,  and  transfused  at  once  without  defibrination. 
The  latter  procedure,  however,  is  attended  with  the  great  danger  that  coagula- 
tion may  take  place  during  the  operation,  in  consequence  of  which  blood-clots  may 
readily  be  introduced  into  the  circulation  of  the  recipient.  The  resulting  obstruc- 
tion and  even  more  so  the  possible  conveyance  of  coagula  to  the  heart  and  into 
the  lesser  circulation,  may  even  threaten  life. 

Landois  has  transfused  without  injury  into  animals  the  non-coagulable  blood 
that  has  been  sucked  by  leeches  after  removal  from  them  by  stripping.  From 


IQ2  TRANSFUSION    OF    BLOOD. 

the  cephalic  extremity  of  the  leech  hardened  in  alcohol,  dried  and  pulverized,  a 
decoction  can  be  prepared  by  admixture  with  0.9  per  cent,  saline  solution  (one 
head  is  boiled  for  ten  minutes  with  6  cu.  cm.  of  a  saline  solution,  and  then  filtration 
is  practised).  This  decoction,  when  mixed  in  the  proportion  of  6  cu.  cm.  to  15 
cu.  cm.  of  blood  obtained  by  venesection,  suffices  to  maintain  the  latter  in  a  fluid 
state.  The  mixture  will  not  coagulate  for  some  time  and  can  be  used  without  fear 
of  injury.  By  this  means  the  dreaded  effect  of  the  fibrin-ferment  may  be  avoided. 

In  Man  the  Infection  of  Animal  Blood  is  Unjustifiable  under  Any  Circumstances. 
— Direct  transfusion  of  blood  from  the  carotid  of  a  lamb  into  the  brachial  vein 
of  a  man  was  formerly  employed  not  infrequently  for  therapeutic  purposes.  It 
is  to  be  remembered,  however,  that  the  erythrocytes  of  the  sheep  are  rapidly 
dissolved  in  human  blood,  and  in  consequence  the  most  efficient  constituents  of 
the  transfused  blood  are  destroyed.  In  a  general  way,  it  is  found  that  the  blood- 
serum  of  many  mammals  has  a  rapid  hemolytic  effect  upon  the  blood-cells  of 
other  species  of  mammals.  Thus,  the  serum  of  dog's  blood  has  a  rapid  and  intense 
hemolytic  action,  while  that  of  the  horse  and  of  the  rabbit  is  relatively  slow  in 
action.  The  erythrocytes  of  mammals  possess  a  variable  power  of  resistance  to 
the  sera  of  other  species  of  mammals.  Thus,  the  erythrocytes  of  the  rabbit,  when 
mixed  with  the  blood  of  another  species,  are  readily  dissolved;  while  the  cells  of 
the  cat  and  the  dog  exhibit  much  greater  resistance.  The  rapidity  with  which 
erythrocytes  are  destroyed  in  the  blood  of  another  species  is  proportional  to  the 
rapidity  with  which  the  blood-cells  of  the  blood  of  the  other  species  are  dissolved 
in  the  blood-serum  of  the  recipient.  Thus,  for  instance,  rabbit's  blood  and  lamb's 
blood  disintegrate  within  a  few  minutes  in  the  circulation  of  a  dog.  When  there 
is  a  difference  in  the  size  of  the  blood-corpuscles  of  the  two  species,  the  hemolysis 
can  readily  be  observed  in  small  specimens  of  blood  obtained  by  puncture.  As 
the  erythrocytes  dissolve,  the  blood-plasma  is  stained  red  by  the  liberated  hemo- 
globin. A  portion  of  this  liberated  material  may  supply  the  demands  of  metabo- 
lism in  the  body  of  the  recipient  and  be  utilized  for  katabolism  and  anabolism, 
while  part  of  it  is  used  up  in  the  formation  of  bile.  When,  however,  the  quantity 
of  hemoglobin  liberated  by  the  erythrocytes  is  considerable,  hemoglobin  is  excreted 
in  the  urine,  and  to  a  less  extent  in  the  intestine,  in  the  ramifications  of  the  bron- 
chial tree  and  into  the  serous  cavities.  In  the  last  the  hemoglobin  may  subse- 
quently undergo  absorption.  Thus,  in  man  hemoglobinuria  has  been  observed 
after  the  injection  of  more  than  100  grams  of  lamb's  blood. 

When  blood  from  another  species  is  transfused  into  an  animal,  the  blood-cor- 
puscles of  the  latter  may  undergo  partial  disintegration.  This  is  the  case  when 
the  erythrocytes  of  the  recipient  are  readily  soluble  in  the  serum  of  the  trans- 
fused blood.  Upon  this  fact  depends  the  great  danger  of  transfusing  a  consider- 
able quantity  of  heterogeneous  blood  into  the  rabbit,  whose  erythrocytes  so 
readily  undergo  solution.  The  same  thing  would  happen  if  a  dog's  blood  were 
transfused  into  the  veins  of  a  man.  In  animals  whose  erythrocytes  readily  un- 
dergo solution,  as,  for  example,  the  rabbit,  the  injection  of  many  kinds  of  sera, 
as,  for  example,  that  of  the  dog,  of  man,  of  the  pig,  of  sheep,  and  of  the  cat,  is 
followed  by  alarming  symptoms,  in  accordance  with  the  quantity  of  blood  in- 
troduced, namely:  acceleration  of  respiratory  frequency  to  the  point  of  dyspnea, 
convulsions,  and  even  death  from  asphyxia.  Under  such  circumstances  all  the 
stages  of  hemolysis  can  be  seen  in  a  specimen  of  blood  obtained  by  puncture. 
Animals  possessing  more  resistent  erythrocytes,  such  as  dogs,  tolerate  the  injec- 
tion of  heterogeneous  sera,  as,  for  example,  from  sheep,  neat  cattle,  horses  and 
pigs,  without  exhibiting  such  marked  symptoms.  The  injected  foreign  serum, 
being  of  feeble  potency,  is  disposed  of  in  the  circulation  of  the  recipient,  before 
it  has  time  to  attack,  not  to  say  dissolve,  the  blood-cells  to  any  great  extent. 

The  process  of  hemolysis  is  accompanied  by  two  other  phenomena,  which 
render  the  transfusion  of  heterogeneous  blood  especially  dangerous:  i.  Before  the 
erythrocytes  are  dissolved,  they  usually  adhere  together  tenaciously  and  form 
small  masses,  consisting  of  from  10  to  20  or  more  blood-cells,  which  are  obviously 
capable  of  obstructing  large  capillary  areas.  When  these  masses  have  been  present 
in  the  blood  for  some  time  they  yield  up  their  hemoglobin,  leaving  only  the  fused 
remains  of  stroma.  This  forms  a  viscid,  tenacious,  stringy  mass  (stroma-fibrin) , 
which  likewise  may  occlude  the  smaller  vessels.  2.  The  sudden  appearance  of 
large  quantities  of  dissolved  hemoglobin  in  the  blood  of  an  animal  may  cause 
extensive  coagulation,  principally  in  the  venous  system,  but  also  in  the  larger 
vessels  throughout  a  considerable  extent.  The  processes  described  may  produce 
death  either  suddenly  or  after  a  protracted  course.  Dissolved  hemoglobin  causes 


THE    DUCTLESS    GLANDS.       INTERNAL    SECRETIONS.  193 

in  the  circulation  the  dissolution  of  numerous  leukocytes,  from  whose  disintegration 
the  fibrin-factors  result.  It  is  curious  that  hemoglobin  exposed  to  the  air  gradually 
loses  this  property;  also  fibrin-ferment  in  contact  with  hemoglobin  is  gradually 
destroyed  or  rendered  inactive. 

As  numerous  small  vessels  are  occluded  as  a  result  of  the  processes  described,  the 
signs  of  impeded  circulation  and  of  stasis  will  be  encountered  in  the  different  organs 
of  the  body.  In  man,  the  injection  of  lamb's  blood  is  followed  by  a  bluish-red  dis- 
coloration of  the  skin.  The  obstacles  encountered  by  the  blood-current  in  the  lungs 
cause  dyspnea  or  even  laceration  of  the  small  vessels  in  the  air-passages  and  bloody 
expectoration.  The  dyspnea  may  increase  if  interference  with  the  free  circulation 
of  the  blood  develops  at  the  respiratory  center.  The  digestive  organs,  for  the  same 
reason,  exhibit  increased  intestinal  peristalsis,  diarrhea,  evacuation  of  the  bowels, 
tenesmus,  vomiting  and  abdominal  pain.  These  phenomena  are  explained  by  the 
fact  that  any  disturbance  of  the  circulation  in  the  abdominal  vessels  is  followed  by 
increased  peristaltic  movements.  In  the  kidneys  secondary  degeneration  of  the 
glandular  substance  takes  place  in  consequence  of  occlusion  of  the  vessels.  The 
uriniferous  tubules  are  occluded  by  casts  consisting  of  coagulated  albuminous 
material.  In  the  muscles  the  occlusion  of  numerous  vessels  may 'cause  stiffness, 
or  even  rigidity  from  coagulation  of  myosin,  just  as  in  Stenson's  experiment, 
together  with  increased  heat-production.  Also  the  nervous  system,  the  organs 
of  special  sense  and  the  heart  may  exhibit  various  disturbances,  all  of  which  can 
be  attributed  to  the  occlusion  of  vessels  and  the  resulting  interference  with  the 
circulation.  It  is  interesting  to  note  that  the  transfusion  of  foreign  blood  is 
followed  as  a  rule  within  half  an  hour  by  the  development  of  active  fever.  Finally, 
it  should  be  mentioned  that  lacerations  of  the  vessel-walls  have  also  been  observed. 
These  explain  the  obstinate  hemorrhages  that  may  occur  not  only  on  the  free 
surfaces  of  mucous  and  serous  membranes,  but  also  in  the  parenchyma  of  organs, 
as  well  as  in  surgical  wounds.  The  blood  itself  coagulates  slowly  and  imperfectly. 
By  far  most  of  the  facts  bearing  on  the  transfusion  of  heterogeneous  blood  that 
have  been  mentioned  were  discovered  through  Landois'  investigations. 

Attempts  to  inject  other  substances  instead  of  blood  are  not  to  be  commended: 
from  0.75  per  cent,  to  0.9  per  cent,  saline  solution,  while  capable  of  improving 
the  circulatory  conditions  in  a  purely  mechanical  way,  and  thus  exerting  a  favora- 
ble influence,  is  obviously  incapable  of  supporting  life  in  cases  of  severe  anemia, 
in  which  the  quantity  of  blood  remaining  in  the  body  is  insufficient  to  maintain 
the  vital  processes. 


THE  DUCTLESS  GLANDS.  INTERNAL  SECRETIONS. 

Within  comparatively  recent  times  there  has  been  attributed  to  the 
ductless  glands,  whose  activity  is  still,  for  the  most  part,  shrouded  in 
obscurity,  a  special  and  important  function,  namely,  the  production  of 
substances  that  enter  the  circulation  and  there  in  some  peculiar  way 
excite  certain  activities,  or  render  innocuous  certain  poisonous  sub- 
stances generated  in  the  process  of  metabolism,  either  by  destroying 
these  or  by  manufacturing  an  antidote.  In  a  similar  manner  it  has  been 
asserted  of  a  number  of  other  organs  in  the  body  that,  in  addition  to 
their  special  function,  they  exert  an  important  influence  on  the  economy- 
by  means  of  such  internal  secretion.  Thus,  Brown-Se"quard  and  d'Ar- 
sonval  asserted  that  the  kidneys  are  in  part  concerned  in  rendering 
innocuous  the  toxic  substances  that  accumulate  in  the  body  after 
nephrectomy;  Tigerstedt  and  Bergman,  that  the  kidneys  produce  a 
substance — renin — that  increases  the  blood-pressure  and  has  a  powerful 
influence  on  the  peripheral  nerve-centers.  The  substances  under 
consideration  can  be  obtained  from  the  corresponding  organs  in  the 
form  of  extracts  and  their  action  can  then  be  tested  upon  the  animal 
body. 

The  spleen  is  contained  in  a  firm  fibrous  capsule,  which  at  the  hilus  gives  off 
an  investment  for  the  entering  blood-vessels.     From  the  inner  surface  of  the  cap- 
13 


194  THE    DUCTLESS    GLANDS.       INTERNAL    SECRETIONS. 

sule  and  the  surface  of  the  vascular  sheaths  there  pass  off  numerous  intersecting 
and  branching  trabeculae  (the  trabeculae  of  the  spleen) ,  which  form  a  rich  mesh- 
work  in  the  interior  of  the  viscus,  comparable  to  the  cavities  of  a  sponge.  Fibril- 
lated  connective  tissue,  mixed  with  elastic  and  unstriped  muscle-fibers,  forms  the 
foundation  of  this  portion  of  the  viscus.  The  interior  of  the  meshes  contains  a 
delicate  reticulum  of  adenoid  tissue  (Fig.  131),  which,  together  with  the  cellular 
elements  contained  in  the  meshes,  is  designated  the  splenic  pulp. 

The  smaller  arterial  branches,  which  gradually  lose  their  fibrous  sheath,  ulti- 
mately break  up  into  brush-shaped  terminal  twigs  without  anastomoses  (peni- 
cils) .  The  points  of  division  of  the  small  arterial  branches  serve  for  the  lodgment 
of  the  whitish  Malpighian  vesicles,  which  may  attain  the  size  of  a  pinhead  and 
the  structure  of  which  in  every  respect  resembles  that  of  solitary  lymph-follicles. 
The  Malpighian  bodies  are  found  on  examination  to  be  spherical,  lymphatic  masses 
that  have  partially  separated  from  the  vascular  sheath.  In  some  animals,  instead 
of  exhibiting  a  spherical  form,  they  appear  as  loose  arterial  sheaths,  in  a  measure 
as  perivascular  lymphatic  sheaths,  so  to  speak,  which  may  extend  to  the  smallest 
arterial  twigs.  According  to  Tomsa,  lymphatic  vessels  coming  from  the  Malpigh- 
ian vesicles  are  found  in  the  subsequent  course  of  the  arterial  sheath  as  far  as 
the  hilus  of  the  spleen.  Other  lymphatics  form  a  network  in  the  capsule. 

With  regard  to  the  connection  between  the  ends  of  the  arteries  and  the  veins, 
it  is  supposed  that  there  is  no  continuous  channel  between  the  smallest  capillary  ar- 
terial twigs  and  the  smallest  venous  branches  and  that  the  meshwork  of  the  pulp- 
reticulum  represents  an  intermediate  vascular  area  devoid  of  walls.  The  blood, 
accordingly,  passes  through  the  meshwork  of  the  spleen  traversed  by  the  reticu- 
lum, just  as  the  lymph-stream  passes  through  the  spaces  of  the  lymphatic  glands. 
According  to  another  view,  there  is  really  a  closed  vascular  channel  connecting  the 
ultimate  arterial  and  the  corresponding  venous  capillaries,  which,  however,  con- 
sists of  dilated  spaces  (like  the  cavernous  spaces  in  erectile  tissues) .  These  inter- 
mediary spaces  are,  however,  completely  surrounded  by  spindle-shaped  endothe- 
lium. 

Within  the  meshes  of  the  reticulum  are  found  cellular  elements  of  various 
kinds:  (i)  White  blood-corpuscles  of  various  sizes,  some  swollen  and  filled  with  a 
granular  material;  (2)  leukoblasts  or  embryonal  forms  of  leukocytes,  which  multi- 
ply by  division;  (3)  erythrocytes ;  (4)  embryonal  forms  of  the  latter,  also  desig- 
nated erythroblasts,  which  multiply  by  mitosis;  (5)  so-called  blood-corpuscle-con- 
taining cells. 

The  numerous  nerves  of  the  spleen  consist  of  so-called  Remak's  fibers;  they 
are  sensory,  motor,  and  vasomotor. 

Of  the  chemical  constituents  there  should  be  mentioned  globulin  and  nucleo- 
albumin,  nucleinic  acid,  leucin,  tyrosin,  xanthin,  hypoxanthin,  taurin;  further 
lactic,  butyric,  acetic,  formic,  succinic,  uric,  and  glycero-phosphoric  (?)  acids; 
as  well  as  fats,  cholesterin,  a  gluten-like  body,  glycogen,  inosite,  iron-containing 
pigments,  and  even  free  iron  oxid.  The  pulp  becomes  black  on  addition  of  ammo- 
nium sulphid.  The  ash  is  rich  in  phosphoric  acid  and  iron,  but  poor  in  chlorin- 
combinations. 

With  respect  to  the  function  of  the  spleen,  the  following  points  are  note- 
worthy : 

1.  The  spleen  may  be  removed  without  injury  to  the  individual,  as  has  been 
proved  both  in  animals  and  in  man  (more  than  QO  cases,  with  about  40  recoveries). 
After  removal  of  the  spleen  the  hematopoietic  activity  of  the  bone-marrow  appears 
to  be  increased.     In  frogs,  extirpation  of  the  spleen  has  been  observed  to  be  fol- 
lowed by  the  appearance  of  brownish-red  nodules  in  the  intestine,  which  have 
been  regarded  as  vicarious  spleens.     Tizzoni  speaks  of  splenic  neoplasms  in  the 
omentum  (horse,  dog)  after  obliteration  of  the  parenchyma  and  blood-vessels  of 
the  spleen.     In  extremely  rare  cases  total  absence  of  the  spleen  has  been  observed 
in  man. 

2.  By  virtue  of  its  unstriped  muscle-fibers  the  spleen  is  capable  of  undergoing 
change  in  volume.      Irritation  of  the  spleen  or  of  its  nerves  (by  heat  or  electricity, 
by  quinin,  eucalyptus,  ergot,  and  other  agents)  causes  diminution  in  the  size  of 
the  viscus,  with  anemia  and  granular  change.     As  the  spleen  is  found  to  be  en- 
larged a  few  hours  after  digestion,  at  a  time  when  the  digestive  organs  have  per- 
formed their  work  and  contain  less  blood,  the  spleen  has  been  regarded  as  an 
apparatus  for  the  regulation  of  the  vascularity  of  the  digestive  organs. 

According  to  Roy  the  circulation  in  the  spleen  is  dependent  not  alone  upon 
the  blood-pressure  in  the  splenic  artery,  but  in  marked  degree  on  the  contraction 


THE    DUCTLESS    GLANDS.       INTERNAL    SECRETIONS.  195 

of  the  unstriped  muscle-fibers  of  the  capsule  and  the  trabeculae,  and  which  manifests 
itself  in  rhythmical  movements  lasting  one  minute. 

Paralysis  of  the  splenic  nerves,  as  in  connection  with  certain  febrile  intoxica- 
tions (malarial  fever,  typhoid  fever),  causes  enlargement  of  the  organ.  Division 
of  the  nerves  has  the  same  effect.  After  extirpation  of  the  small  nerve-trunks 
scattered  in  the  hilus  Landois  has  observed  circumscribed  enlargement  of  the 
organ,  with  bluish-red  discoloration. 

3.  The  spleen  has  been  regarded  as  a  hematopoietic  organ.     In  favor  of  this 
view  is  the  fact  that  after  extirpation  the  erythrocytes  are  diminished;  further,  the 
fact  that  a  splenic  infusion  (or  decoction,  also  an  infusion  of  bone-marrow),  when 
injected  under  the  skin  or  into  the  peritoneal  cavity,  causes  an  increase  of  the 
erythrocytes.     The  spleen  is  also  a  breeding-place  for  leukocytes.     The  blood  from 
the  splenic  vein  always  contains  numerous  leukocytes,  many  of  which  are  subse- 
quently destroyed  in  the  circulation.     Bizzozero  and  Salvioli  discovered  that  a 
few  days  after  great  loss  of  blood  the  spleen  became  swollen,  and  the  parenchyma 
was  found  to  be  rich  in  nucleated  embryonal  erythrocytes. 

4.  Other  investigators  regard  the  spleen  as  an  organ  for  the  destruction  of 
blood-corpuscles,  the  presence  of  so-called  "blood-corpuscle-containing  cells"  par- 
ticularly supporting  such  a  view.     These  cells  are  large  leukocytes  that  have  taken 
up  red  blood-corpuscles  after  the  manner  of  phagocytes  (similar  cells  are  found 
also  in  extravasations  of  blood) .     The  red  blood-cells  gradually  undergo  degenera- 
tion within  the  leukocytes  and  yield  as  derivatives  of  hemoglobin  iron-containing 
pigments  resembling  hematin.     The  spleen,  therefore,  contains  more  iron  than 
can  be  accounted  for  by  the  amount  of  unaltered  blood  it  contains.     If  with  this 
fact  there  be  yet  compared  the  occurrence  in  the  spleen  of  disintegration-products 
and  of  higher  oxidation-products  of  the  albuminous  bodies,  the  spleen  may  prop- 
erly be  regarded  as  an  organ  for  the  destruction  of  erythrocytes.     Additional  sup- 
port for  this  view  is  found  in  the  appearance  of  the  salts  of  the  red  blood-corpuscles 
in  the  splenic  juice.     According  to  Schiff,  extirpation  of  the  spleen  has  no  effect 
on  either  the  absolute  or  the  relative  quantity  of  the  red  and  white  blood-cor- 
puscles. 

Even  in  the  normal  state  the  spleen  exhibits  frequent  changes  in  size  in  the 
course  of  the  day,  particularly  in  conformity  with  varying  activity  of  the  digestive 
organs.  In  this  respect  the  spleen  resembles  the  arteries.  Its  vasomotor  nerves 
have  their  center  in  the  medulla  oblongata.  Stimulation  of  that  center,  especially 
by  asphyxia,  causes  contraction  of  the  spleen.  From  the  center  fibers  pass  through 
the  spinal  cord  (which  is  said  to  contain  between  the  first  and  fourth  cervical  verte- 
brae ganglionic  cells  that  likewise  influence  the  contraction  of  the  spleen) ,  further 
through  the  left  splenic  nerve  and  the  semilunar  ganglion  into  the  splenic  plexus. 
Irritation  of  the  nerves,  as  well  as  the  direct  application  of  cold  to  the  spleen 
or  even  to  the  splenic  region,  causes  contraction  of  the  viscus.  Paralysis  of  the 
nerves,  by  curare  or  by  protracted  narcosis,  causes  enlargement  of  the  spleen. 
Apparently  only  the  peritoneal  investment  contains  sensory  nerves. 

Pressure  on  the  splenic  vein  causes  slight  enlargement  of  the  spleen.  In  har- 
mony with  this  fact  is  the  observation  that  increased  blood-pressure  within  the 
splenic  vein  (in  the  presence  of  portal  congestion  or  after  the  cessation  of  hemor- 
rhoidal  or  menstrual  bleeding)  is  frequently  attended  with  splenic  enlargement. 
The  injection  of  splenic  extract  has  an  effect  opposite  to  that  of  injection  of 
suprarenal  extract. 

The  thymus  gland  is  relatively  well  developed  during  fetal  life  and  continues 
to  grow  during  the  first  two  years  of  life;  but  about  the  tenth  year  it  becomes 
stationary  in  size  and  later  degenerates  to  form  the  so-called  thymic  fat-body,  the 
tissues  of  which  still  contain  the  remains  of  the  lymphoid  thymus-parenchyma. 
As  long  as  it  persists,  the  thymus  appears  to  have  the  function  of  a  lymph-gland; 
for  in  the  embryo,  which  possesses  no  lymph-glands,  it  is  functionally  active,  and 
in  reptiles  and  amphibia,  which  also  possess  no  lymph-glands,  it  is  a  permanently 
functionating  organ. 

The  thymus  consists  of  acini  varying  in  size  from  0.5  to  1.5  mm.  and  possessing 
the  structure  of  simple  lymph-follicles.  The  lymph-cells  lying  within  the  reticulum 
may  exhibit  various  stages  of  disintegration.  In  addition,  there  are  found  scattered 
through  the  organ  peculiar  and  mysterious  concentric  bodies,  especially  during  the 
time  of  involution.  Numerous  small  lymph- vessels  in  part  traverse  the  interior 
of  the  organ  and  in  part  spread  out  upon  its  surface.  Blood-vessels  are  relatively 
numerous. 

Among  the  chemical  constituents  there  should  be  mentioned — in  addition  to 


196  THE    DUCTLESS    GLANDS.       INTERNAL    SECRETIONS. 

gelatin,  albumin,  sodium  albuminate,  sugar  and  fat — leucin,  thymus-nucleinic  acidr 
xanthin,  hypoxanthin;  formic,  acetic,  butyric,  lactic,  and  succinic  acids.  In  the 
ash,  potassium  and  phosphoric  acid  preponderate  over  sodium,  calcium,  magnesium 
(ammonium  ?) ,  chlorin,  and  sulphuric  acid. 

Extirpation  of  the  thymus  gland  in  the  frog  is  fatal.  According  to  Svehla  the 
infusion  of  thymus  juice  causes  a  fall  of  blood-pressure  and  acceleration  of  pulse, 
while  large  doses  are  fatal. 

The  thyroid  gland  is  an  organ  provided  with  vasomotor  and  secretomotor 
nerves,  and  composed  of  a  richly  cellular  connective-tissue  framework,  containing 
closed  circular  or  oval  acini  (from  0.04  to  o.i  mm.  in  diameter),  which  in  the 
embryo  and  the  new-born  are  lined  with  a  single  layer  of  nucleated,  granular, 
cuboidal  cells.  In  50  per  cent,  of  all  subjects  accessory  thyroid  glands,  up  to 
four,  are  associated  with  the  main  gland;  a  small  detached  gland  is  occasionally 
found  in  front  of  the  descending  aorta.  In  addition,  accumulations  of  epithelial 
cells  are  found  in  the  acini  and,  in  embryos,  also  beneath  the  common  capsule. 
From  birth  the  cells  secrete  a  colloid  substance  by  a  transformation  of  their  proto- 
plasm, at  the  same  time  undergoing  morphological  changes.  Some  of  the  cells 
are  destroyed  in  this  process  of  colloid  degeneration. 

The  acini  of  the  thyroid  gland  evacuate  their  contents  in  part  by  rupture, 
with  destruction  of  the  epithelium,  in  part,  in  the  process  of  pure  colloid-produc- 
tion, by  secretion  into  the  intercellular  interstices;  and  in  this  way  the  secretion 
reaches  the  interfollicular  lymph-spaces  and  then  the  blood. 

Blood-vessels  of  considerable  size  and  importance  enter  the  organ.  Lymph- 
vessels  partly  begin  in  the  interior  among  the  acini,  and  partly  form  a  network  in 
the  capsule  that  surrounds  the  entire  organ. 

The  constituents  of  the  thyroid  gland  are  colloid,  nucleoalbumin,  iodothyrin, 
leucin,  xanthin;  lactic,  succinic,  and  volatile  fatty  acids. 

According  to  Schiff,  Zesas,  J.  Wagner  and  others,  extirpation  of  the  thyroid 
gland  is  followed  by  death,  with  the  symptoms  of  chronic  intoxication.  Dysphagia, 
vomiting  and  digestive  disturbances,  acceleration  of  the  breathing;  later  dyspnea, 
alteration  of  the  action  of  the  heart,  somnolence,  slow  and  hesitating  movements 
with  fibrillar  twitchings,  which  may  go  on  to  intermittent  tonic  convulsions  (tetany) , 
palsies,  alterations  in  cutaneous  sensibility,  desquamation  of  the  skin,  lowering  of 
the  body-temperature  and  of  the  blood-pressure,  are  the  symptoms  that  precede 
death.  Albuminuria,  reduction  of  the  amount  of  oxygen  in  the  arterial  blood 
and  degenerations  in  the  central  and  peripheral  nervous  system  were  observed  by 
Albertoni  and  Tizzoni,  Langhans,  Kopp  and  Capobianco.  In  man,  also,  total 
extirpation  of  the  thyroid  gland  (cachexia  strumipriva)  is  a  serious  matter  and 
often  terminates  fatally  from  tetany. 

The  morbid  phenomena  may  be  counteracted,  at  least  temporarily,  by  the 
internal  administration  of  fresh  or  dry  thyroid-gland  substance,  or  by  the  sub- 
cutaneous injection  of  thyroid-gland  extract  or  iodothyrin.  The  symptoms  may 
be  prevented  by  grafting  a  thyroid  gland  successfully  in  some  other  portion  of 
the  body,  and  permitting  the  organ  to  form  adhesions.  These  facts  prove  that 
the  thyroid  gland  produces  a  substance  that  is  indispensable  for  normal  metabo- 
lism. Stated  more  accurately,  the  function  of  the  thyroid  gland  is  to  neutralize 
a  substance  produced  in  the  body,  the  accumulation  of  which  has  a  toxic  influence 
on  the  nervous  system. 

The  accessory  thyroid  glands  and  the  hypophysis  appear  to  possess  similar 
functions:  they  undergo  compensatory  hypertrophy  after  extirpation  of  the  thy- 
roid gland.  Other  investigators  attribute  the  condition  known  as  myxedema, 
that  is,  mucoid  infiltration  of  the  subcutaneous  tissues  of  the  head  and  neck,  with 
profound  disturbances  of  the  nervous  system,  to  the  point  of  idiocy,  to  loss  of  the 
function  of  the  thyroid. 

Especially  noteworthy  is  the  enlargement  of  the  thyroid  gland,  together  with 
the  palpitation  of  the  heart  and  protrusion  of  the  eyeballs,  in  the  condition  known 
as  exophthalmic  goiter,  which  appears  to  be  due  to  simultaneous  (toxic  ?)  irritation 
of  the  accelerator  nerve  of  the  heart,  the  sympathetic  fibers  of  the  unstriated 
muscles  in  the  orbit  and  in  the  eyelids,  as  well  as  of  the  dilator  nerves  of  the 
vessels  of  the  thyroid  gland.  Myxedema  and  exophthalmic  goiter  seem  to  stand 
in  a  certain  antagonistic  relation  to  each  other,  the  former  depending  on  diminished, 
the  latter  on  augmented,  activity  of  the  thyroid  gland  (hence  extirpation  has  been 
recommended  in  cases  of  exophthalmic  goiter).  Landois  observed  in  dogs  that 
had  been  fed  on  thyroid  glands  a  marked  increase  in  the  number  and  force  of  the 
cardiac  contractions.  The  ingestion  of  thyroid  gland  causes  an  increased  con- 


THE    DUCTLESS    GLANDS.       INTERNAL    SECRETIONS.  197 

sumption  of  oxygen  and  therefore  a  more  rapid  breaking  down  of  the  tissues  (for 
which  reason  it  is  a  familiar  therapeutic  procedure  for  reducing  weight) .  According 
to  Schondorff  the  body-fat  is  first  transformed,  the  albumin  not  being  attacked  until 
the  fat  has  been  reduced  to  a  certain  minimum.  The  substance  (solely?)  active 
in  this  connection  is  iodothyrin,  a  body  prepared  in  1896  by  Baumann,  and  con- 
taining nitrogen,  phqsphorus,  and  iodin.  In  some  localities  marked  enlargement 
of  the  thyroid  gland  (goiter)  is  quite  common,  and  is  not  infrequently  associated 
with  idiocy  and  cretinism.  In  those  cases  in  which  the  goiter  is  designated  a 
follicular  hyperplasia  of  the  thyroid  gland,  the  condition  can  be  made  to  disappear 
by  the  administration  of  preparations  of  the  thyroid  gland.  Fr.  Hofmeister  found, 
after  extirpation  of  the  thyroid  gland  in  rabbits,  degeneration  in  the  cartilages  and 
disturbances  in  the  growth  of  the  bones. 

According  to  Gegenbaur  the  thyroid  gland  is  an  actively  functionating  organ 
in  some  of  the  remote  orders  of  animals  (for  example,  among  the  tunicates,  in 
which  it  appears  as  a  groove  and  secretes  a  digestive  juice) ,  which  in  vertebrates 
has  undergone  involution. 

The  suprarenal  bodies  consist  of  a  medullary  and  a  cortical  layer,  and  contain 
compartments  formed  by  connective  tissue  and  bounded  by  blood-vessels.  In 
the  cortical  layer  the  compartments  are  oblong  and  radiate,  while  in  the  medullary 
layer  they  are  rather  circular.  The  former  contain  (embedded  in  a  reticulum) 
polyhedral,  nucleated,  protoplasmic  cells  without  walls,  the  substance  of  which 
contains  pigment  and  fat-granules,  and  is  darker  and  more  resistent  than  that 
of  the  medullary  cells.  The  medullary  layer  contains  also  small  and  multipolar, 
large  sympathetic  nerve-cells.  Both  cortex  and  medulla  are  richly  supplied  with 
nerve-fibers.  The  blood-vessels  are  relatively  abundant. 

The  suprarenal  bodies  contain  the  constituents  of  connective  and  of  nervous 
tissue,  besides  leucin,  hypoxanthin,  benzoic  and  taurocholic  acids,  taurin,  inosite, 
fat  and  pigment-forming  bodies.  Of  inorganic  substances  potassium  and  phos- 
phoric acid  preponderate. 

The  function  of  the  suprarenal  bodies  is  practically  unknown.  After  extirpa- 
tion of  one  suprarenal  body,  the  other  undergoes  hypertrophy  to  double  its  original 
size.  Bilateral  extirpation  is  followed  by  death,  with  the  symptoms  'of  poisoning 
and  paralysis.  These  symptoms,  however,  do  not  develop  if  a  small  piece  is 
allowed  to  remain.  It  appears,  therefore,  that  the  suprarenal  bodies  also  are 
designed  to  destroy  a  poisonous  substance  in  the  body,  which  exhibits  its  injurious 
effects  after  extirpation  of  the  glands.  The  injection  of  a  watery  extract  of  supra- 
renal body  is  said  to  arrest  temporarily  the  toxic  symptoms  that  make  their 
appearance  after  extirpation. 

Injection  of  the  extract  obtained  from  the  medullary  substance  of  healthy 
animals  (and  which  does  not  contain  albumin  and  is  soluble  in  alcohol)  gives  rise 
to  marked  contraction  of  the  arteries  and  increase  in  blood-pressure,  slowing  of 
the  pulse  by  central  stimulation  of  the  vagus,  or  even  arrest  of  the  auricles.  After 
section  of  the  vagi  the  heart  again  becomes  more  rapid  and  stronger,  owing  to  the 
action  of  the  drug  on  the  substance  of  the  heart  itself.  The  extract  has  the  same 
constricting  effect  on  small  blood-vessels  and  hence  raises  the  blood-pressure.  The 
splanchnic  nerve  contains  vasodilator  and  secretory  fibers  for  the  organ.  The 
breathing  is  superficial  and  accelerated.  Large  doses  injected  intravenously  cause 
death  through  enfeeblement  of  the  central  nervous  system,  dyspnea,  and  cardiac 
paralysis.  In  frogs  muscular  paralysis  results. 

Brown-Se"quard  believed  that  one  of  the  functions  of  the  suprarenal  bodies 
is  to  inhibit  excessive  pigment-formation.  In  agreement  with  this  view,  Tizzoni 
found,  after  extirpation  of  the  organs  (in  rabbits),  abnormal  pigmentations,  espe- 
cially on  the  lips,  and  Boinet  in  the  blood  and  subcutaneous  cellular  tissues  (of 
rats) .  In  conditions  in  which  erythrocytes  are  dissolved  and  converted  into  pig- 
ment the  suprarenal  bodies  are  found  to  be  especially  rich  in  pigment.  In  the 
medullary  layer  a  substance  is  formed  that  becomes  brown  when  exposed  to  the 
air  or  brought  in  contact  with  alkaline  tissues.  In  man  the  skin  often  presents  a 
bronzed  pigmentation  (bronzed  skin,  Addison's  disease)  when  the  suprarenal 
bodies  and  their  capsules  have  undergone  (tuberculous)  degeneration.  _  In  hemi- 
cephalous  monsters  the  organs  are  atrophic,  even  when  only  the  anterior  halves 
of  the  hemispheres  are  absent. 

Hypophysis  Cerebri.  CoccygeaL  Gland.  Carotid  Gland. — But  little  is  known 
concerning  the  function  of  the  pituitary  body.  The  posterior  portion  belongs  to 
the  infundibulum,  and  here  the  nervous  elements  are,  to  a  large  extent,  displaced 
by  connective  tissue  and  blood-vessels;  while  the  anterior  portion  represents  a 


198 


COMPARATIVE. 


constricted  off  and  modified  part  of  the  invaginated  mucous  membrane  of  the 
pharynx  and  contains  glandular  ducts  with  clear  or  dark  cells.  The  extract  ob- 
tained from  the  pituitary  body  contains  iodin  and  causes  an  increase  in  the  blood- 
pressure,  which,  however,  is  less  than  that  caused  by  an  extract  of  suprarenal 
gland;  the  heart-beat  becomes  slower  and  more  forcible. 

The  function  of  the  coccygeal  gland,  which  is  situated  at  the  extremity  of  the 
coccyx,  is  unknown. 

The  carotid  gland,  which  occurs  in  man  and  mammals,  and  contains  a  con- 
voluted plexus  consisting  of  intricately  anastomosing  capillaries  within  an  epithe- 
lioid  cellular  mass,  supported  by  a  reticulum,  has  been  compared  by  Stilling  to 
the  suprarenal  bodies.  Its  function  is  unknown. 

COMPARATIVE. 

The  heart  in  fishes  (Fig.  74,  /)  and  in  the  gill-bearing  larvae  of  amphibia  is 
a  simple  venous  organ,  consisting  of  auricle  and  ventricle.  The  latter  sends  the 
blood  to  the  gills,  where  it  is  arterialized,  and  passing  to  the  aorta  it  is  dis- 


I. 


FIG.  74. — Diagrammatic  Representation  of  the  Circulation.  7.  In  Fish:  A,  auricle  with  the  sinus  venosus  (5); 
V,  ventricle;  B,  bulb  of  the  aorta-,  c,  branchial  arteries;  i  i,  branchial  vessels;  D,  branchiales  veins;  E,  circulus 
cephalicus  aortae;  F,  common  aorta;  G,  caudal  artery;  H,  ductus  of  Cuvier;  /,  anterior  cardinal  vein;  K, 
posterior  cardinal  vein;  7_,  caudal  vein;  M  M,  kidneys.  II.  In  the  Frog:  7,  sinus  venosus;  77,  right  auricle; 
777,  left  auricle;  IV,  ventricle;  V,  common  trunk  of  the  aorta  and  bulb,  giving  off  the  following:  i,  pulmonary 
arteries;  2,  arch  of  the  aorta;  3,  carotid  arteries;  4,  lingual  arteries  (5  carotid  gland);  6,  axillary  arteries; 
7,  common  aorta;  8,  celiac  artery;  9,  cutaneous  arteries;  y,  pulmonary  veins;  p  p,  lungs.  777.  In  Saurians: 
7,  right  auricle  with  venae  cavar,  77,  right  ventricle;  777,  left  auricle;  IV,  left  ventricle;  V,  anterior  common 
aorta;  i,  pulmonary  artery;  2,  arch  of  the  aorta;  3,  carotid  arteries;  4,  posterior  common  aorta;  5,  celiac 
artery;  6,  subclavian  arteries;  7,  pulmonary  arteries;  8,  lungs.  IV.  In  Turtles:  7,  right  auricle  with  venae 
cavae;  77,  right  ventricle;  777,  left  auricle;  7 F,  left  ventricle,  i,  right  aorta;  2,  left  aorta;  3,  posterior  common 
aorta;  4,  celiac  artery;  5,  subclavian  arteries;  6,  carotid  arteries;  7,  pulmonary  arteries;  8,  pulmonary  veins. 


tributed  to  all  parts  of  the  body,  returning  finally  through  the  capillaries  and 
the  veins  to  the  auricle.  The  amphibia  (frog,  II)  have  two  auricles  and  one  ven- 
tricle. From  the  latter  there  arises  a  single  vessel,  which,  after  giving  off  the 


HISTORICAL.  199 

pulmonary  arteries,  becomes  the  aorta  and  supplies  all  the  organs  of  the  body. 
The  veins  of  the  greater  circulation  empty  into  the  right,  those  of  the  lesser  circu- 
lation into  the  left,  auricle.  Fishes  and  amphibia  possess  a  dilated  bulbus  arterio- 
sus  at  the  beginning  of  the  aorta;  and  this  is  partly  covered  with  strong  muscular 
tissue.  Among  reptiles  the  saurians  (///)  possess' two  separate  auricles,  but  the 
two  ventricles  are  only  imperfectly  divided.  The  aorta  and  pulmonary  artery 
arise  separately  from  the  latter.  The  venous  blood  of  the  greater  and  the  lesser 
circulation,  which  flows  separately  into  the  right  and  the  left  auricle,  becomes 
mixed  in  the  cavity  of  the  ventricle.  In  some  reptiles,  however,  the  opening  in 
the  ventricular  septum  appears  to  be  capable  of  (voluntary  or  reflex?)  closure. 
The  complete  separation  of  the  two  halves  of  the  heart  in  turtles  is  shown  in 
Fig.  IV.  The  lower  vertebrates  possess  valves  at  the  orifice  of  the  vena  cava, 
which  are  rudimentary  in  birds  and  in  some  of  the  mammals.  All  birds  and 
mammals,  like  man,  possess  two  separate  auricles  and  two  separate  ventricles.  In 
the  halicore,  a  graminivorous  marine  animal  resembling  the  whale,  the  ventricular 
portion  of  the  heart  is  divided  by  a  deep  cleft  into  two  halves.  In  bats  the  veins 
of  the  wings  pulsate.  The  lowest  of  all  vertebrates,  the  amphioxus,  has  no  heart 
at  all,  but  rhythmically  contracting  vessels. 

Of  the  ductless  glands,  the  thymus  and  the  spleen  are  found  constantly  in 
vertebrates.  The  latter  is  wanting  only  in  the  amphioxus  and  in  a  few  fishes. 

Among  invertebrates  closed  blood-channels  with  pulsating  movements  are 
only  found  occasionally,  as,  for  example,  in  the  echinoderms  (sea-urchin,  star-fish, 
holothurians)  and  in  the  higher  worms.  Insects  possess  in  the  dorsal  region  a 
central  circulatory  organ  (the  "dorsal  vessel"),  a  contractile,  longitudinal  duct, 
capable,  by  virtue  of  its  muscle-fibers,  of  dilating,  and  provided  with  valves — 
which  propels  the  blood  rhythmically  into  the  interstices  of  all  the  organs.  Insects 
have  no  closed  circulation.  Shell-fish  and  snails  have  a  heart  and  lacunar  blood- 
channels.  Cephalopods  (sepia,  cuttle-fish)  have  three  hearts:  an  arterial,  simple 
body-heart,  and  two  venous,  simple  branchial  hearts,  one  at  the  base  of  each  gill. 
The  circulation  in  most  of  these  animals  is  closed.  The  lowest  animals  have 
either  (multiple)  pulsating  vacuoles,  which  propel  the  colorless  (blood-)  juice  into 
the  soft  body-parenchyma,  like  the  infusoria;  or  they  are  totally  devoid  of  any 
kind  of  vascular  apparatus,  the  circulation  of  the  juices  being  effected  by  the 
movements  of  the  body  (gregarines) .  In  the  group  of  celenterates  (polyps,  jelly- 
fish) there  is  a  "water-vascular  system,"  which  conveys  the  nutritive  juice  directly 
from  the  digestive  cavity,  and,  at  the  same  time,  acts  as  a  respiratory  organ,  as 
the  water  (which  contains  oxygen)  passes  through  the  system  of  tubes. 


HISTORICAL. 

The  ancients  (Empedocles,  born  473  B.  C.)  were  familiar  with  the  movement 
of  the  blood,  but  were  ignorant  of  the  "circulation."  According  to  Aristotle 
(384  B.  C.)  the  heart,  the  acropolis  of  the  body  (which  is  present  in  every  blood- 
animal),  prepares  the  blood  within  its  cavities  and  sends  it  through  the  arteries 
as  a  nutrient  fluid  to  all  the  different  parts  of  the  body,  like  a  system  of  constantly 
dividing  brooks,  irrigating  the  land  and  moistening  and  fertilizing  it.  The  blood 
however,  never  flows  back  to  the  heart. 

Praxagoras  (341  B.  C.)  named  the  "arteries"  (as  well  as  the  trachea);  he  was 
the  first  to  distinguish  arteries  from  veins.  Together  with  Herophi-lus  and  Erasis- 
tratus  (300  B.  C.) ,  trje  famous  physicians  of  the  Alexandrian  school,  he  is  responsible 
for  the  erroneous  view,  based  on  the  fact  that  arteries  are  empty  after  death, 
that  the  arteries  contain  air  conveyed  to  them  through  the  respiration  (hence  the 
name  "artery").  Galen  (131-203  A.  D.)  refuted  this  error  by  vivisection.  "When- 
ever,", he  says,  "I  injured  an  artery  I  saw  blood  escape.  And  when  I  tied  a 
portion  of  an  artery  by  means  of  two"  ligatures  at  either  extremity,  I  showed  that 
the  included  portion  was  full  of  blood." 

Even  then  the  theory  of  the  exclusively  centrifugal  movement  of  the  blood 
was  maintained;  it  was  erroneously  supposed  that  communicating  orifices  existed 
in  the  septum  between  the  right  and  the  left  heart. 

Miguel  Serveto  (a  Spanish  monk,  who  was  burned  as  a  heretic  in  Irene va  i: 
1553  at  Calvin's  instigation)  was  the  first  to  show  that  the  septum  of  the  heart 
has  no  openings.     He,  therefore,  searched  for  a  communication  between  the  right 
and  the  left  heart  and  thus  succeeded,  in  1546.  in  discovering  the  lesser  circulation: 
"fit  autem  communicatio  haec  non  per  parietem  cordis  medium  (septum),  ut  vulgo 


200  HISTORICAL. 

creditur,  sed  magno  artificio  a  cordis  dextro  ventriculo,  longo  per  pulmones  ductu, 
agitatur  sanguis  subtilis;  a  pulmonibus  praeparatur,  flavus  efficitur  et  a  vena 
arteriosa  (Arteria  pulmonalis)  in  arteriam  venosam  (Venae  puimonales)  trans- 
funditur."  Almost  a  quarter  of  a  century  later,  in  1589,  Caesalpinus  traced  the 
course  of  the  greater  circulation.  He  was  the  first  to  use  the  word  "circulation." 
Later,  Fabricius  ab  Aquapendente  (Padua,  1574)  also  recognized  and  confirmed 
the  centripetal  movement  of  the  blood  in  the  veins  (which  until  that  time  was 
almost  universally  believed  to  be  centrifugal,  although  Vesalius  was  familiar 
with  the  centripetal  current  in  the  main  trunks)  from  the  position  of  the  valves 
in  the  veins,  of  which  he  made  an  accurate  study,  although  they  had  been  men- 
tioned in  the  middle  of  the  fifth  century  after  Christ  by  Theodoretus,  Bishop  of 
Syria,  also  by  Sylvius,  by  Vesalius  (1534)  and  by  Canani  (1546) .  William  Harvey, 
a  pupil  of  Fabricius  (until  1604),  finally  constructed,  between  the  years  1616  and 
1619,  partly  from  his  own  investigations  and  partly  from  the  results  of  former 
observers,  the  picture  of  the  circulation  of  the  blood,  the  greatest  physiological 
achievement,  which  was  published  in  1628  and  marks  a  new  epoch  in  physiology. 

With  respect  to  individual  features  of  the  vascular  system,  the  following  is 
yet  worthy  of  mention:  According  to  Hippocrates  the  heart  is  a  fleshy  organ  and 
the  root  of  all  the  vessels ;  he  was  familiar  with  the  large  vessels  originating  from 
the  heart,  the  valves,  the  chordae  tendineag,  the  auricles,  and  the  closure  of  the 
semilunar  valves.  Aristotle  first  named  the  aorta  and  the  venae  cavae,  the  school 
of  Erasistratus  the  carotid;  the  latter  also  explained  the  function  of  the  venous 
valves.  In  Cicero  mention  is  made  of  the  distinction  between  arteries  and  veins. 
Celsus,  in  the  fifth  century  after  Christ,  pointed  out  that  the  veins,  when  opened 
below  a  compressing  bandage,  bleed.  Aretaeus  (50  A.  D.)  knew  that  arterial 
blood  is  bright  red  and  venous  blood  dark.  Pliny  (died  79  A.  D.)  described  the 
pulsating  fontanel  in  man.  The  presence  of  a  bone  in  the  septum  of  large  mam- 
mals (ox,  stag,  elephant)  was  known  to  Galen  (131—203  A.  D.).  In  his  opinion 
the  veins  ultimately  communicate  with  the  arteries  by  means  of  the  finest  tubes, 
and  this  view  was  later  confirmed  by  de  Marchettis  (1652)  and  Blancard  (1676) 
with  the  aid  of  injections,  and  by  Malpighi,  who  made  microscopic  observations 
of  the  circulation  of  the  blood  in  cold-blooded  animals,  as  well  as  by  William 
Cowper  (1697) ,  who  made  similar  observations  on  warm-blooded  animals.  Stenson, 
who  was  born  in  1638,  first  demonstrated  the  muscular  nature  of  the  heart,  al- 
though a  statement  to  like  effect  had  already  been  made  by  the  Hippocratic  and 
Alexandrian  schools.  Cole  demonstrated  the  progressive  increase  in  the  width  of 
the  arterial  area  as  the  capillary  region  is  approached.  Joh.  Alfons  Borelli  (1608— 
1679)  was  the  first  to  estimate  the  power  of  the  heart  according  to  the  laws  of 
hydraulics.  Craanen,  in  1685,  described  systolic  contractions  in  the  pulmonary 
veins;.  Leeuwenhoeck  (1694)  the  anatomical  arrangement  of  the  heart-muscle 
fibers  among  themselves.  Chirac,  in  1698,  ligated  a  coronary  artery  of  the  heart 
in  a  dog,  without,  it  is  true,  producing  any  result. 

According  to  Aristotle,  turtles  can  live  for  a  short  time  after  the  heart  has 
been  removed. 

Many  of  the  ancients  (the  Israelites,  Empedocles,  Kritias,  Lucretius)  believed 
that  the  vital  principle  of  the  body,  and  even  the  soul  (Aristotle  and  Galen) ,  had 
its  seat  in  the  blood.  Aristotle  was  familiar  with  the  poisonous  effects  of  the 
vapor  of  burning  charcoal;  Porcia  voluntarily  chose  to  die  by  inhaling  it.  Vene- 
section was  practised  by  Greek  physicians  soon  after  the  Trojan  war. 

The  iron  in  the  red  blood-corpuscles  was  discovered  by  Menghini  in  1746. 


PHYSIOLOGY  OF  RESPIRATION. 


OBJECTS  AND   SUBDIVISIONS. 

The  purpose  of  respiration  is  to  convey  to  the  body  the  oxygen 
necessary  for  its  oxidation-processes,  as  well  as  to  remove  the  carbon 
dioxid  resulting  from  the  combustion  processes.  The  activity  required 
for  this  purpose  is  most  effectively  rendered  by  the  lungs.  A  distinction 
is  made  between  external  and  internal  respiration.  The  first  embraces 
the  exchange  of  gases  between  the  outer  air  and  the  gases  of  the  blood 
contained  in  the  respiratory  organs  (lungs  and  skin) ;  the  second  in- 
cludes the  exchange  of  gases  between  the  capillary  blood  of  the  systemic 
circulation  and  the  body  tissues. 

STRUCTURE  OF  THE  AIR-PASSAGES  AND  THE  LUNGS. 

The  lungs  are  compound  tubular  (grape-like?)  glands  that  secrete  carbon 
dioxid,  and  each  of  which  sends  its  excretory  duct  (bronchus)  to  the  common  air- 
passage,  the  trachea. 

The  trachea  has  for  its  foundation  a  number  of  C-shaped,  superposed,  hya- 
line, cartilaginous  arches,  held  together  by  a  rigid  fibrous  membrane  of  closely 
woven  elastic  network,  intermixed  with  connective  tissue,  arranged  principally 
in  a  longitudinal  direction.  The  cartilages  serve  the  function  of  keeping  the 
lumen  of  the  tube  patulous  under  the  varying  pressure-relations.  They  subserve 
a  similar  purpose  in  the  bronchi  and  their  branches.  They  do  not  occur  in  air- 
passages  having  a  diameter  of  i  mm.  or  less;  and  even  in  bronchioles  of  greater 
size  they  are  less  numerous  and  more  irregular,  occurring  especially  at  the  bifurca- 
tions in  the  form  of  irregular  platelets. 

An  outer  layer  of  connective  and  elastic  tissue  covers  the  air-passages  and 
branches  of  the  bronchial  tree.  On  the  side  toward  the  esophagus  this  layer  is 
reinforced  by  additional  elastic  elements  and  a  few  bundles  of  longitudinal  un- 
striated  muscle-fibers.  The  trachea  contains  unstriated  muscle-fibers,  especially 
arranged  transversely,  connecting  the  ends  of  the  cartilaginous  arches  posteriorly 
and  being  inserted  into  the  cartilages  by  means  of  elastic  tendons.  This  transverse 
layer  is  again  covered  by  longitudinal  bundles.  The  mucous  membrane,  besides 
containing  connective  tissue  and  leukocytes,  is  especially  rich  in  longitudinal 
elastic  fibers,  which  attain  their  greatest  size  immediately  beneath  the  epithelial 
basement  membrane.  The  outer,  narrow,  scarcely  separable  submucosa  is  com- 
posed principally  of  connective  tissue,  and  attaches  the  mucous  membrane  to  the 
cartilages  with  their  connecting  fibrous  membrane.  The  epithelium  of  the  trachea 
is  a  stratified,  ciliated  epithelium,  with  the  cilia  waving  toward  the  glottis,  and 
with  many  interspersed  goblet-cells.  Numerous  branched,  tubular,  mucous 
glands,  with  larger,  brighter  cells  and  smaller,  darker  ones  (Gianuzzi's  crescents) 
are  founxl  beneath  the  muscular  layer  of  the  trachea  and  bronchi.  These  glands 
are  of  a  mixed  type  and  have  secretory  ducts  connected  with  their  serous  alveoli, 
but  not  with  the  mucous  tubules.  They  secrete  the  viscid  mucus  that  catches  the 
dust -particles  of  the  inspired  air  and  is  then  removed  from  the  bronchial  tree  and 
larynx  by  means  of  the  ciliated  epithelium.  The  air-passages  are  richly  supplied 
with  lymph-vessels  and  lymph-follicles,  but  are  rather  poor  in  nerves  and  blood- 
vessels. Ganglia  are  found  on  the  nerve-trunks. 

The  direction  in  which  the  branches  of  the  bronchi  penetrate  into  their  respec- 
tive lobes  corresponds  with  the  inspiratory  movement  of  the  chest-wall  covering 
each  lobe;  for  example,  the  direction  of  the  bronchi  in  the  upper  lobe  is  upward, 
forward,  and  outward. 

The  small  bronchi  are  distinguished  from  the  larger  ones  by  a  diminution  in 

201 


2O2 


STRUCTURE    OF    THE    AIR-PASSAGES    AND    THE    LUNGS. 


the  amount  of  cartilage,  and  by  the  presence  of  a  complete  layer  of  circular  muscle- 
fibers;  mucous  glands  are  wanting,  and  the  epithelium  is  less  developed.  Goblet- 
cells  secreting  mucus  are  found  as  far  as  the  smaller  air-passages. 

After  the  small  bronchi  have  by  repeated  branching  become  diminished  in 
diameter  to  from  0.5  to  0.4  mm.,  they  are  succeeded  by  the  smallest  bronchi, 
which  already  bear  a  few  alveoli  on  their  walls.  The  smallest  bronchi  still  possess 
ciliated  epithelium  and  unstriated  muscle-fibers. 

The  respiratory  bronchioles  are  the  direct  continuation  of  the  smallest  bronchi. 
In  the  bronchioles  the  cylindrical  epithelium  is  gradually  replaced,  at  first  on  one 
side  only,  by  small,  squamous  cells,  and  later  by  a  mixed  epithelium  of  large 
plates  and  small,  squamous  cells.  At  the  same  time  the  mural  alveoli  become 
more  numerous. 


FIG.  75. — Cross-section  of  Several  Pulmonary  Alveoli:  A,  alveolus  with  the  blood-capillaries  (c)  that  arise  from 
larger  vessels  (g  g)  bounding  the  alveoli.  B,  the  epithelium  of  an  alveolus:  i,  nucleated  cells;  2,  non-nu- 
cleated platelets;  3,  large,  fused,  non-nucleated  plates.  C,  section  of  an  alveolus  with  its  epithelium  and 
subjacent  capillaries.  D,  alveolus,  with  its  border  covered  by  pulmonary  epithelium  and  plates.  E,  alveolus 
whose  boundary  is  indicated  only  by  elastic  fibers  (f  f). 


From  these  respiratory  bronchioles  there  arise,  finally,  the  blind,  alveolar 
ducts,  which  are  completely  lined  with  mixed  epithelium,  containing  the  small, 
squamous  cells  only  in  small  nests.  The  alveolar  ducts  subdivide  further,  and  still 
contain  a  few  isolated  muscle-fibers  in  their  walls.  These  subdivisions  are  entirely 
surrounded  by  numerous  closely  packed,  hemispherical  or  spheroidal  air-sacs 
(alveoli) . 

Concerning  the  structure  of  the  alveoli,  the  following  is  to  be  noted  (Fig.  75): 
(i)  The  supporting  membrane  of  the  sac  is  structureless,  elastic,  with  enclosed 
nuclei.  Fine  pores  in  the  walls  of  the  septa  connect  neighboring  alveoli.  (2) 
Networks  of  numerous,  fine,  elastic  fibers  surround  the  air-sacs,  and  give  to  the 
pulmonary  tissue  its  great  elasticity.  As  the  elastic  fibers  are  characterized  by 


STRUCTURE    OF    THE    AIR-PASSAGES    AND    THE    LUNGS.  203 

considerable  power  of  resistance,  they  are  often  found  retaining  their  characteristic 
arrangement  in  the  expectoration  of  patients  suffering  from  pulmonary  diseases. 
This  is  an  infallible  sign  that  the  pulmonary  tissue  is  undergoing  destruction.  (3) 
The  branches  of  the  rich  capillary  network  pass  rather  toward  the  lumen  of  the 
alveoli.  The  respiratory  epithelium  of  the  alveoli  is  a  single  layer  of  squamous 
epithelium.  In  it  may  be  found  scattered  nucleated,  protoplasmic  cells  (i) ,  which 
are  transformed  later  into  small  (from  7  to  15  //),  non-nucleated,  bright  (2)  or 
dark  platelets.  Finally,  several  of  the  latter  unite  to  form  larger  (from  22  to  45  //) , 
non-nucleated  plates.  (3)  Here  and  there  incomplete  fissures  may  be  seen  in 
these  plates,  which  indicate  previous  interspaces  between  the  platelets.  The  plates 
have  been  transformed  from  original  cuboidal  cells  by  the  stretching  of  the  lungs 
during  respiration. 

See  estimates  the  number  of  alveoli  at  809^  millions,  and  their  respiratory 
area  at  81  square  meters  (54  times  as  great  as  the  surface  of  the  body).  The 
alveoli  are  grouped  together  by  connective  tissue  into  distinct  pulmonary  lobules. 

The  blood-vessels  of  the  lungs  belong  to  two  distinct  systems : 

A.  The  system  of  the  pulmonary  vessels  (the  lesser  circulation) .     The  branches 
of  the  pulmonary  artery  follow  those  of  the  air-passages,  and  are  so  closely  applied 
to  the  latter  that  their  pulsations  may  be  communicated  to  the  contained  air. 
The  capillaries  arising  from  these  branches  form  a  rich  network  of  moderately 
fine  tubules.     The  pulmonary  veins,  whose  branches  likewise  accompany  the  air- 
passages,  are  collectively  narrower  than  the  pulmonary  artery,  as  a  result  of  the 
loss  of  water  that  the  blood  undergoes  in  the  lungs. 

B.  The  system  of  the  bronchial  vessels  conveys  the  nutrient  material  for  the 
respiratory  organs.     The  bronchial  arteries,  following  the  bronchi,  give  to  them 
branches,  as  well  as  to  the  lymphatic  glands  at  the  hilus  of  the  lungs,  the  large 
trunks   of  the   pulmonary   vessels    (vasa  vasorum),  and  the  pulmonary  pleura. 
Numerous  anastomoses  occur  between  the  branches  of  the  bronchial  and  pul- 
monary arteries.     Part  of  the  vessels  arising  from  the  capillaries  communicate 
with  the  beginnings  of  the  pulmonary  veins ;  and  for  this  reason  any  considerable 
stagnation  of  blood  in  the  lesser  circulation  causes  a  like  stagnation  in  the  circula- 
tion in  the  bronchial  mucous  membrane,  with  resulting  bronchial  catarrh.     An- 
other part  of  the  bronchial  capillaries  forms  special  veins,  which,  as  bronchial  veins, 
traverse  the  posterior  mediastinum,   and  empty  into  the  trunks  of  the  azygos 
veins,  the  intercostal  veins,  or  the  superior  vena  cava.     The  veins  from  the  smaller 
bronchi,  and  even  from  the  bronchi  of    the  fourth  class,  empty  collectively  into 
the  pulmonary  veins ;  and  the  anterior  bronchial  veins  also  communicate  with  the 
pulmonary  vessels. 

The  interstitial  tissue  of  the  lungs  is  rich  in  lymphadenoid  tissue  and  is 
traversed  by  a  network  of  fine  lymph-channels.  A  coarser,  irregular  system  of 
lymph- vessels  surrounds  the  pulmonary  lobules,  larger  bronchi,  and  blood-vessels. 
These  lymph-channels  and  vessels  become  injected  when  animals  are  made  to 
inhale  powdered,  soluble  dyes.  The  coloring-matter  penetrates  the  viscid  inter- 
stitial substance  between  the  epithelium,  though  according  to  Klein  through  small 
pores  that  are  present. 

In  the  walls  of  the  pulmonary  alveoli  the  finest  lymph-tubules  form  a  delicate 
system  of  canals  lying  in  the  spaces  between  the  blood-capillaries.  These  canals 
exhibit  enlargements  at  the  points  of  intersection.  Lymph- vessels  extend  along 
the  bronchi,  forming  a  dense,  longitudinally  meshed  network  in  the  mucosa  and 
submucosa,  and  finally  reaching  the  lymphatic  glands  at  the  roots  of  the  lungs. 

The  rapidity  with  which  fluids  are  absorbed  in  the  lungs,  even  when  introduced 
in  considerable  quantities,  is  remarkable.  Landois  has  often  seen  this  after  in- 
jecting water  into  the  trachea  of  living  animals,  and  Peiper  has  demonstrated  it 
for  many  other  substances.  Even  blood  is  taken  up  in  like  manner,  Nothnagel 
having  found  blood-corpuscles  in  the  interstitial  pulmonary  tissue  from  three  to 
five  minutes  after  injection  into  the  trachea. 

In  the  pulmonary  pleura,  which  is  exceedingly  rich  in  elastic  fibers,  the  net- 
works of  superficial  pulmonary  lymph-vessels  begin  as  free  stomata.  In  like 
manner  the  lymph-vessels  of  the  parietal  pleura  communicate  by  means  of  sto- 
mata in  many  places  (on  the  diaphragm  only  in  certain  localities)  with  the  pleural 
cavity;  according  to  Klein  even  with  the  free  surface  of  the  bronchial  mucous 
membrane.  The  lymph, vessels  of  the  veins  of  the  lesser  circulation  lie  between 
the  media  and  the  adventitia. 

The  nerves  of  the  lungs,  bronchi,  trachea,  and  larynx  have  ganglia. 

It  appears  that  the  function  of  the  unstriated  muscle-fibers  in  the  trachea  and 


204  MECHANISM    OF    THE    RESPIRATORY    MOVEMENTS. 

in  the  entire  bronchial  tree  is  to  offer  resistance  within  the  air-passages  to  the 
increased  pressure  that  occurs  in  all  forced  expirations,  as  in  speaking,  singing, 
blowing,  straining.  According  to  the  testimony  of  many  investigators  the  vagus 
is  the  motor  nerve ;  upon  it  depends  the  so-called  pulmonary  tone  when  the  tension 
within  the  air-passages  is  increased.  Irritation  of  the  vagus,  or  of  the  lung  directly, 
does  not  induce  sudden,  expiratory  movements  (as  can  be  seen  by  fastening  a 
manometer  in  the  trachea) .  The  only  result  of  irritation  of  the  vagus  is  an  increase 
in  the  resistance  of  the  air  passing  through  the  small  bronchi  that  have  been  nar- 
rowed by  the  irritation.  Section  of  the  vagus  also  is  said  to  increase  the  volume 
of  the  lungs.  Atropin  paralyzes,  pilocarpin  stimulates,  the  bronchial  muscles  of 
the  dog,  while  reflex  stimulation  takes  place  through  sensory  branches  of  the 
vagus.  During  deepest  inspiration  the  unstriated  muscles  of  the  air-passages  con- 
tract, and  during  forced  expiration  they  are  relaxed. 

Pathological. — Irritation  of  the  unstriated  muscles,  causing  spasmodic  narrow- 
ing of  the  smaller  bronchi,  may  give  rise  to  asthmatic  attacks.  If  the  escape  of 
air  from  the  alveoli  is  thus  made  difficult  or  obstructed,  an  acute  inflation  of  the 
lungs — acute  emphysema — may  result. 

According  to  Sandmann  a  reflex  effect  may  be  produced  upon  the  bronchial 
muscles  from  the  mucous  membrane  of  the  nose  and  the  larynx.  This  would  explain 
the  occurrence  of  asthma  attending  nasal  affections,  such  as  polypoid  growths  of 
the  mucous  membrane.  In  addition  to  the  elements  of  the  connective,  elastic, 
and  muscular  tissues,  and  of  the  mucous  membrane,  the  lungs  contain  lecithin, 
inosite,  uric  acid  (taurin  and  leucin  in  the  ox;  guanin  (?),  xanthin,  hypoxanthin  in 
the  dog),  also  sodium,  potassium,  calcium,  magnesium,  iron  oxid,  considerable 
phosphoric  acid,  also  chlorin,  sulphuric  acid,  silicic  acid,  and  carbon.  In  cases  of 
diabetes  sugar  has  been  found;  in  the  presence  of  purulent  infiltration  glycogen 
and  sugar;  in  that  of  renal  degeneration  urea,  oxalic  acid,  and  ammonium-salts; 
in  that  of  autointoxications  leucin  and  tyrosin. 

MECHANISM   OF    THE    RESPIRATORY    MOVEMENTS. 
ABDOMINAL   PRESSURE. 

The  mechanism  of  breathing  consists  in  an  alternating  dilatation  and 
contraction  of  the  thoracic  cavity.  The  dilatation  of  the  cavity  is  termed 
inspiration,  and  the  narrowing  expiration.  The  whole  outer  surface  of 
both  elastic  lungs  is,  by  means  of  its  smooth,  moist  covering  of  pleura, 
intimately  and  hermetically  applied  to  the  inner  surface  of  the  chest- 
wall,  which  in  its  turn  is  covered  by  the  parietal  pleura.  Hence,  it  is 
evident  that  every  expansion  of  the  thorax  is  accompanied  by  a  corre- 
sponding expansion  of  the  lungs,  and  every  contraction  compresses 
those  organs.  These  movements  of  the  lungs  are,  therefore,  wholly 
passive,  being  dependent  on  the  thoracic  movements. 

By  reason  of  their  complete  elasticity  the  lungs  are  able  to  follow 
every  change  in  the  capacity  of  the  thorax,  without  causing  the  two 
layers  of  the  pleura  ever  to  separate.  The  cavity  of  the  unexpanded 
thorax  is  greater  than  the  volume  of  the  collapsed  lungs  when  removed 
from  the  body;  therefore,  the  lungs  in  their  natural  position  within  the 
chest  must  be  stretched,  and  they  are,  to  a  certain  degree,  in  a  state  of 
elastic  tension.  This  tension  varies  directly  with  the  size  of  the  thoracic 
cavity.  If  the  pleural  cavity  be  opened  by  a  perforation  from  without 
or  by  a  wound  of  the  lungs  from  within,  the  elasticity  of  the  lungs  causes 
them  to  collapse,  and  there  arises  an  air-space  between  the  outer  surface 
of  the  lungs  and  the  inner  surface  of  the  thorax  (pneumothorax).  The 
affected  lung  is  incapacitated  for  respiration.  Double  pneumothorax 
is  accordingly  fatal. 

The  degree  of  the  elastic  traction  of  the  stretched  lung  may  be  measured  by 
introducing  a  manometer  through  an  intercostal  space  into  the  pleural  cavity  of 
a  dead  body.  The  elastic  tension  here  is  the  same  as  that  in  the  living  body  dur- 
ing a  state  of  quiet  expiration,  and  is  equal  to  6  mm.  of  mercury.  In  a  patient 


RESPIRATORY    VOLUMES. 


205 


with  perforation  of  an  intercostal  space  Aron  found  the  elastic  tension  to  be  from 
4.5  to  6.8  mm.  If,  however,  the  thorax  is,  by  force  applied  from  the  outside, 
brought  into  the  expanded  position  assumed  during  inspiration,  the  elastic  trac- 
tion will  be  increased  to  30  mm. 

If  the  glottis  be  closed  during  inspiratory  dilatation  of  the  thorax, 
the  elastic  lungs  also  will  expand,  and  there  will  be  produced  a  rarefac- 
tion of  the  air  within  the  lungs,  as  this  air  must  expand  to  a  greater 
volume.  If  the  glottis  is  now  suddenly  opened,  the  atmospheric  air 
will  enter  the  lungs,  until  the  density  of  the  air  within  equals  that  of 
the  atmosphere.  On  the  other  hand,  if  the  chest  and  the  lungs  be  com- 
pressed by  expiratory  efforts,  with  a  closed  glottis,  the  air  in  the  lungs 
will  become  denser,  that  is,  compressed  into  a  smaller  volume.  If  the 
glottis  now  be  opened,  air  will  escape  from  the  lungs,  until  the  internal 
and  external  pressures  are  equalized.  As  the  glottis  is  open  during 
ordinary  respiration,  the  adjustment  of  the  diminished  or  increased 
air-pressure  during  inspiration  and  expiration  will  occur  gradually.  It 
is  certain,  however,  that  there  exists  in  the  air  within  the  lungs  a  slight 
negative  pressure  during  inspiration  and  a  slight  positive  pressure 
during  expiration.  This  may  be  measured  in  the  trachea  of  persons 
having  wounds  of  this  tube,  and  equals  i  mm.  during  inspiration  and 
from  2  to  3  mm.  during  expiration.  According  to  J.  R.  Ewald  the 
total  figures  are  only  o.i  mm.  and  0.13  mm.  respectively. 

The  so-called  abdominal  pressure  within  the  abdomen  is  generally 
increased  during  expiration,  and  declines  during  inspiration  in  man  and 
in  dogs,  while  in  rabbits  it  is  increased  during  inspiration.  Moderate 
increase  of  the  abdominal  pressure  increases  somewhat  the  arterial 
blood-pressure,  as  well  as  the  action  of  the  heart;  more  pronounced 
increase  of  abdominal  pressure  diminishes  both. 

RESPIRATORY   VOLUMES. 

The  lungs  never  completely  empty  themselves  of  air.  Therefore,  in 
filling  and  emptying  the  lungs  during  inspiration  and  expiration,  only 
a  part  of  the  contained  air  is  subjected  to  change,  the  amount  depending 
on  the  depth  of  the  respirations. 

Hutchinson  in  this  connection  established  the  following  distinctions : 

i.  Residual  air  is  the  volume  of  air  that  remains  in  the  lungs  after 

complete  expiration.     This  can  be  estimated  approximately  after  death 

by  collecting  over  water  the  air  from  the  lungs  after  ligating  the  trachea. 

H.  Davy  and  Grehant  estimated  the  amount  during  life  in  the  following  man- 
ner: The  subject  makes  a  forcible  expiration,  and  then  breathes  for  a  while  from 
and  into  a  spirometer,  filled  with  a  measured  quantity  of  hydrogen.  If  it  can  be 
assumed  that  the  residual  air  has  been  completely  admixed  with  the  hydrogen, 
the  percentage  of  air  in  the  spirometer  after  forced  expiration  will  indicate  the 
quantity  of  residual  air.  The  observers  named  found  the  amount  to  be  from  1200 
to  1700  cu.  cm.  Berenstein,  by  a  similar  method,  estimated  the  residual  air  to 
be  equal  to  from  one-fifth  to  one-fourth  of  the  vital  capacity. 

The  following  wholly  different  method  has  also  been  employed  to  determine 
the  residual  air:  The  amount  of  an  unknown  volume  of  air  x  can  be  calculated 
from  the  increase  in  volume  that  it  undergoes  when  the  pressure  upon  it  is  lessened, 
for  this  increase  in  volume  is  directly  proportional  to  the  quantity  of  gas,  and 
to  the  diminution  in  the  pressure  upon  it.  If  Pj  is  the  original  pressure  to  which 
the  gas  is  exposed,  P2  the  other,  lessened  pressure,  and  d  the  measurable  increase 
in  volume  of  x,  then 

x  =  (P2Xd)  :   (P!  —  P2). 

For  carrying  out  this  experiment  Pfltiger  constructed  his  pneumometer.     The  sub- 


206 


RESPIRATORY    VOLUMES. 


ject  is  placed  in  a  large,  hermetically  sealed  chamber  (human  cabinet) ,  in  which 
at  first  the  pressure  equals  that  of  the  atmosphere  (P^.  The  contained  air  is 
then  rarefied  by  means  of  a  pump,  until  the  pressure  P2  is  obtained,  as  indicated 
by  a  manometer  inserted  in  the  chamber.  In  this  process  a  part  of  the  residual 
air  (x)  will  naturally  escape  during  quiet  expiration.  This  is  collected  and  meas- 
ured (d)  by  means  of  a  spirometer  connected  in  an  air-tight  manner  with  the 
air-passages.  In  this  way  Pfliiger  found  x  to  be  from  400  to  800  cu.  cm.  Gad, 
working  with  different  apparatus  based  on  the  same  principle,  estimates  the  residual 
air  to  be  half  the  vital  capacity;  Schenck  gives  the  proportion  of  the  former  to 
the  latter  as  i  to  3.7. 

2.  Reserve  air  is  the  additional  volume  of  air  that  can  be  forced  out 
after  a  quiet  expiration.     It  measures  from  1248  to  1804  cu.  cm. 

The  procedure  of  H.  Davy  and  Grehant  may  also  be  applied  to  the  estimation 
of  reserve  air. 

3 .  Respiratory  or  .tidal  air  is  the  volume  of  air  that  is  taken  in  and 
given  off  during  quiet  respiration.     In  adults  under  normal  conditions  it 

amounts  to  about  507  cu.  cm. — between 
367  and  699  cu.  cm.,  according  to  Vier- 
ordt;  in  the  new-born  about  one-quar- 
ter of  this  amount. 

4.  C omplemental  air  is  the  term  ap- 
plied by  Hutchinson  to  the  additional 
volume   of   air   that   may   be   taken  in 
during  a  forced  inspiration  immediately 
succeeding  a  quiet  one. 

5.  Vital  capacity  indicates  the  vol- 
ume of  air  that  escapes  from  the  lungs 
between  the  highest  phase  of  inspiration 
and    the    lowest    phase  of    expiration. 
For   Germans   it   amounts   to  3222  cu. 
cm.  on  an  average,  and  for  Englishmen 
to  3772  cu.  cm. 

From  the  foregoing  it  follows  that 
after  a  quiet  inspiration  both  lungs 
contain  about  from  3000  to  3900  cu.  cm. 
of  air  ( i  -f  2  -f-  3 ) ;  after  a  quiet  expi- 
ration from  2500  to  3400  cu.  cm.  (i  -f- 
2).  From  this,  as  from  3,  it  follows 
that  during  quiet  respiration  only  about 
one-sixth  or  one-seventh  of  the  air  in  the  lungs  is  changed. 

If,  during  a  series  of  quiet  respirations,  a  solitary  inhalation  of  hydrogen  be 
made,  and  if  the  expired  air  be  examined  to  determine  how  long  the  hydrogen 
may  be  detected  in  it,  it  will  likewise  be  found  that  the  air  in  the  lungs  com- 
pletely renews  itself  (becomes  free  of  hydrogen)  in  from  6  to  10  respirations. 

Donders  estimates  that  the  combined  bronchial  tree  and  trachea  contain  about 
500  cu.  cm.  of  air. 

The  vital  capacity  is  determined  by  means  of  Hutchinson 's  spirometer  (Fig. 
76).  The  determination  is  of  importance  in  persons  suffering  from  disease  of  the 
thoracic  organs.  The  vital  capacity  may  be  influenced  by  consolidation,  destruc- 
tion, or  emphysema  of  the  pulmonary  tissue;  by  the  presence  of  fluids,  blood,  air, 
or  new-growths  in  the  thoracic  cavity;  by  diminished  mobility  of  the  chest;  by 
weakness  of  the  respiratory  muscles ;  by  enlargement  of  the  heart  or  pericardium ; 
or  by  distention  of  the  abdomen. 

By  means  of  a  large  tube  provided  with  a  mouth-piece,  the  subject  (holding  his 
nostrils  closed)  blows  his  expiratory  air  into  a  graduated  gasometer  bell- jar  that 
is  suspended  over  water  and  evenly  balanced  by  a  system  of  weights  rand  pulleys. 


FIG.  76. — Hutchinson's  Spirometer. 


THE    RATE    OF    RESPIRATION.  207 

After  complete  expiration  the  tube  is  closed,  and  the  increase  of  air  within  the 
jar  indicates  the  vital  capacity,  provided  the  water  outside  and  that  inside  the 
jar  are  at  the  same  level.  It  is  also  advisable  to  allow  the  expired  air  to  cool, 
until  it  is  of  the  temperature  of  the  surrounding  air. 

Of  the  factors  that  influence  vital  capacity  the  following  are  known: 

1.  Stature. — Every  inch  of  additional  height  between  5  and  6  feet  is  accom- 
panied by  about  130  cu.  cm.  increase  in  the  vital  capacity. 

2.  The  volume  of  ike  trunk  is,  on  the  average,  seven  times  that  of  the  vital 
capacity. 

3.  The  Body-weight. — An  increase  in  weight  of  7  per  cent,  above  the  normal 
is  accompanied  by  a  diminution  in  the  vital  capacity  of  37   cu.  cm.  for  every 
additional  kilogram. 

4.  Age. — The  vital  capacity  reaches  its  maximum  at  thirty-five  years;  from 
this  up  to  the  sixty-fifth  year,  and  backward  to  the  fifteenth  year,  23.4  cu.  cm. 
must  be  deducted  for  each  year. 

5.  Sex. — Arnold  found  the  average  to  be  3660  cu.   cm.  for  men,  and  2550 
cu.  cm.  for  women.     For  the  same  stature  and  chest-measurement,  the  relation  of 
the  vital  capacity  of  men  to  that  of  women  is  as  10  to  7. 

6.  Social  position  and  occupation  have  a  decided  influence  on  the  physical 
condition  and  nutrition,  and  hence  also  on  the  vital  capacity.     Arnold  established 
three  classes,  of  which  each  preceding  class  exceeds  the  one  following  by  200  cu.  cm. 
greater  vital  capacity:   (a)  soldiers  and  sailors;    (b)  artisans,  compositors,  police; 
(c)  paupers,  the  nobility,  and  students. 

7.  Miscellaneous. — The  vital  capacity  is  greatest  in  the  standing  position,  and 
when  the  stomach  is  empty.     It  is  diminished  after  great  effort,  and  also  in  de- 
bilitated conditions  of  the  body.     It  is  greater  in  advanced  pregnancy  than  in  the 
puerperium.     To  a  certain  extent  practice  with  a  spirometer  can  increase  the 
vital  capacity. 

THE    RATE    OF    RESPIRATION. 

The  rate  of  respiration  varies  in  adults  between  12,  16,  and  24  in  a 
minute.  Four  pulse-beats  on  an  average  thus  occur  with  every  respira- 
tion. Many  factors  influence  the  rate: 

1.  The  Position  of  the  Body. — In  adults  Guy  noted  13  respirations 
to  the  minute  in  the  recumbent  posture,  19  in  the  sitting  posture,  and 
23  in  the  standing  posture. 

2.  Age. — In  300  individuals  Quetelet  found  the  rate  of  respiration 
to  be  as  follows: 

Age.  Respirations.  Age.  Respirations. 

Up  to  i  year 44     Between  20  and  25  years 18.7 

At  5  years 26  25  and  30  years 16 

Between  15  and  20  years 20  3°  and  5°  years 18.1 

In  the  new-born  the  rate  is  between  62  and  68. 

3.  Activity. — In  children  between  two  and  four  years  old,  Gorham 
counted  32  respirations  to  the  minute  in  the  standing  posture,  and  24 
during  sleep.     As  a  result  of  bodily  exertion    the   rate  of  respiration 
increases  before  that  of  the  heart-beat.     The  increase  in  respiratory 
movements  is  incited  by  metabolic  products  furnished  by  the  muscles 
engaged  in  activity.     In  connection  with  violent  muscular  activity  the 
pulse-rate  is  increased  principally  by  excitation  of  the  center  for  the 
cardio-accelerator  nerves. 

4.  Increase  in  the  surrounding  temperature,  also  febnle  elevation  c 
the  bodily  temperature,  will  increase  the  rate  of  respiration,  which  may 
even  assume  a  dyspneic  character. 

THE  TIME  RELATIONS  OF   RESPIRATORY  MOVEMENTS. 
PNEUMATOGRAPHY. 

In  order  to  obtain  information  with  regard  to  the  periodic  relations 
of  the  various  phases  of  the  respiratory  movements,  it  is  necessary  1 


20  8 


THE    TIME     RELATIONS    OF    RESPIRATORY    MOVEMENTS. 


trace  respiratory  curves  (pneumatograms)  by  means  of  recording  in- 
struments. 

Method. — The  graphic  method  can  be  applied  in  three  different  ways :  i .  The 
representation  of  the  range  of  motion  in  the  individual  parts  of  the  thorax  may 
be  obtained  in  the  following  manner: 

(a)  K.  Vierordt  and  Ludwig  arranged  an  instrument  in  which  the  movement 
of  a  definite  part  of  the  thorax  was  communicated  to  a  lever,  whose  longer  arm 
traced  the  curve  on  a  rotating  drum.  In  like  manner  Riegel  constructed  his 
double  stethograph  on  the  principle  of  the  lever.  It  consisted  of  two  levers  on 
the  same  support,  arranged  for  use  on  a  patient  in  such  way  that  one  lever  was 
applied  to  a  certain  spot  on  the  healthy  side  of  the  chest,  and  the  other  lever 
to  the  corresponding  spot  on  the  affected  side.  A  sphygmograph  may  be  em- 
ployed for  recording  the  respiratory  curve,  the  instrument  being  placed  free  outside 
of  the  chest  upon  a  stand  and  applied  in  such  manner  that  only  the  pad  of  the 
elastic  stylus  touches  the  chest-wall  at  one  point.  J.  Rosenthal  constructed  a 
lever  to  register  the  movements  of  the  diaphragm  in  animals  (phrenograph) ;  it 


FIG.  77. — A,  Brondgeest's  Air-cushion  for  Recording  the  Respiratory  Curves.  B,  A  Respiratory  Curve  of  a  Healthy 
Individual,  Recorded  on  a  Plate  Attached  to  a  Vibrating  Tuning-fork  (i  vibration  =  0.01613  sec.),  to  Deter- 
mine the  Time-relations. 


was  inserted  through  an  opening  in  the  abdomen,  and  rested  against  the  dia- 
phragm. 

(b)  The  air-cushion  of  Brondgeest's  pan  sphygmograph  (Fig.  77,  A)  is  con- 
structed on  the  principle  of  air-transference.  This  instrument  consists  of  a  saucer- 
shaped  brass  vessel  (a),  over  which  is  stretched  a  double-layered  rubber  mem- 
brane (b  c) .  Between  the  layers  of  this  covering  there  is  enough  air  to  make  the 
outer  membrane  bulge.  This  cushion  is  placed  on  a  certain  part  of  the  thorax, 
and  fastened  with  bands  (d  d)  that  pass  around  the  chest.  Every  enlargement 
of  the  thorax  presses  against  the  membrane  c,  producing  a  diminution  of  the  air- 
space within  the  capsule.  The  latter  is  connected  by  means  of  the  tube  S  with 
the  recording  chamber  that  is  pictured  in  Fig.  44 . 

Instead  of  this  capsular  arrangement,  Marey,  in  the  construction  of  his  pneu- 
mograph,  uses  a  piece  of  thick,  cylindrical,  elastic  rubber  tubing.  This  is  fastened 
by  bands  like  a  girdle  around  the  chest,  and  is  connected  by  a  tube  with  the 
recording  drum. 

2.  The  variations  in  the  volume  of  the  chest  or  in  the  exchanged  respiratory 
gases  may  be  graphically  recorded  as  follows: 

For  this  purpose  E.  Hering  places  an  animal  in  an  air-tight,  closed  chamber, 


THE    TIME    RELATIONS    OF    RESPIRATORY    MOVEMENTS. 


209 


with  two  openings  in  its  walls.  The  trachea  of  the  animal  having  been  previously 
cut  across,  a  cannula  is  fastened  in  the  pulmonary  end,  and  is  attached  to  a  tube 
passing  through  one  of  the  openings  in  the  chamber  (respiration  being  conducted 
undisturbed  through  this  tube) .  Through  the  other  opening  passes  a  manometer- 
tube,  filled  with  water,  and  pro- 
vided with  a  recording  float.  The 
same  experiment  may  be  conducted 
with  a  human  subject,  provided  the 
breathing  tube  be  placed  in  the 
mouth  and  the  nose  be  held  closed. 
Gad  (Fig.  78)  has  succeeded  in  re- 
cording graphically  the  variations  in 
the  volume  of  the  respired  air  by 
means  of  an  apparatus:  the  expired 
air  lifts  a  light,  balanced  box,  which 
is  closed  off  by  water.  In  rising, 
this  box  moves  a  recording  lever. 
During  inspiration  the  box  sinks. 

3.  The  variations  in  the  rapidity  FIG.  78.— Air-volume  Recorder  (Pneumoplethysmograph) 
with  which  the  respiratory  gases  are  (after  Gad), 

changed  may  be  recorded  as  follows  : 

A  tube  is  fastened  in  the  trachea  of  an  animal,  or  in  the  mouth  of  a  human 
subject  (holding  the  nostrils  closed),  in  the  same  way  as  with  the  dromograph 
(Fig.  69) .  The  pendulum  (made  broader  for  this  purpose)  will  swing  to  and  fro 
during  inspiration  and  expiration,  and  will  record  the  velocity  of  the  currents  of 
air  entering  and  leaving  the  lungs. 


FIG.  79.-Pneumatograms  Recorded  by  Means  of  Riegel's  Stethograph:   /,  normal  curve;    {.]nsflrr, 
with  emphysema;  a,  inspiratory  limb,  bt  summit,  c,  expiratory  limb  of  the  curve.  The  small  elevations  are  due 
to  the  pulsations  of  the  heart. 

The  curve  in  Fig.  77  B  was  drawn  upon  a  vibrating  tuning-fork  plate,  by 
means  of  the  air-cushion  of  Brondgeest's  pansphygmograph,  applied  to  t 
form  process  of  a  health v  man.     The  inspiration   (ascending  limb)  beg 
moderate  rapidity,  is  accelerated  in  the  middle,  and  again  becomes  slower  towar 

14 


210  TYPES    OF    RESPIRATORY    MOVEMENTS. 

the  end.     The  expiration  begins  with  moderate  rapidity,  is  then  accelerated,  and 
finally  becomes  much  slower  in  the  last  part. 

Inspiration  is  somewhat  shorter  than  expiration ;  in  adult  males  the 
proportion  is  6  :  7,  according  to  Sibson;  in  women,  children,  and  old 
persons  it  is  6  :  8  or  6  :  9.  Vierordt  found  the  relation  10  :  14.1  (up  to 
24.1);  J.  R.  Ewald  found  it  n  :  12.  Cases  in  which  inspiration  and 
expiration  are  of  equal  length,  or  in  which  the  latter  is  even  the  shorter, 
are  observed  only  exceptionally. 

Small  irregularities  may  be  observed  occasionally  on  various  parts  of  the 
curve.  These  are  due  to  the  fact  that  the  thoracic  movements  are  at  times  the 
result  of  successive  contractions  of  the  respiratory  muscles.  Now  and  then  power- 
ful heart-beats  also  cause  vibrations  of  the  thoracic  wall  (Fig.  79). 

If  respiration  proceeds  uninterruptedly  and  quietly,  there  is  usually 
no  real  pause,  i.  <?.,  complete  rest  of  the  thorax.  Sometimes  the  lowest 
flattened  part  of  the  expiratory  limb  is  incorrectly  taken  for  the  pause. 
Of  course,  a  pause  may  voluntarily  be  made  at  any  phase  of  the 
movement. 

If  the  respirations  be  deep,  but  slow,  an  expiratory  pause  is  almost  invariably 
noted;  on  the  other  hand,  it  is  always  lacking  in  rapid  respiration.  An  inspiratory 
pause  is  never  noted  under  normal  conditions,  but  it-  may  occur  under  patho- 
logical conditions. 

TYPES    OF   RESPIRATORY   MOVEMENTS. 

Curves  recorded  from  various  parts  of  the  thorax  throw  light  upon 
the  so-called  type  of  respiration.  Hutchinson  was  the  first  to  show 
that  women  expand  the  thorax  by  producing  an  elevation  of  the  sternum 
and  ribs — costal  or  thoracic  respiration  ;  while  men  produce  the  same 
effect  by  depression  of  the  diaphragm — abdominal  or  diaphragmatic 
respiration. 

If  the  height  of  the  curves  taken  in  men  and  women  from  the  manubrium, 
gladiolus,  ensiform  process,  and  epigastrium  be  compared,  it  will  be  seen  that  the 
excursion  of  the  sternum  is  most  pronounced  in  women,  while  that  of  the  epigas- 
trium (through  the  diaphragm)  predominates  in  men. 

This  difference  between  the  sexes,  in  the  type  of  costal  and  diaphragmatic 
breathing,  holds  good  only  in  quiet  respiration.  In  deep  and  forced  respiration 
the  enlargement  of  the  thoracic  cavity  is  brought  about  in  both  sexes  principally 
by  a  pronounced  elevation  of  the  chest  and  ribs.  In  this  case  the  epigastrium, 
even  in  men,  is  drawn  in  rather  than  forced  out.  During  sleep  the  type  of  respira- 
tion is  thoracic  in  both  sexes,  and  the  inspiratory  expansion  of  the  thorax  precedes 
the  elevation  of  the  abdominal  wall. 

It  has  recently  been  again  pointed  out  that  the  costal  type  arises  principally 
from  compression  of  the  lower  ribs  by  corsets  or  tight  belts,  especially  as  a  decided 
abdominal  type  is  encountered  in  savage  women.  It  is  only  a  conjecture  that  the 
costal  type  may  be  a  natural  tendency,  the  result  of  pregnancy,  during  which 
abdominal  respiration  may  become  obstructive  and  harmful  by  exerting  pressure 
on  the  uterus.  Some  affirm,  while  others  deny,  that  the  difference  in  type  is 
evident  during  sleep  with  the  clothing  completely  removed,  and  also  in  young 
children.  Some  investigators  maintain  that  the  costal  type  is  found  in  children 
of  both  sexes;  they  attribute  this  to  a  greater  flexibility  of  the  ribs  in  children 
and  women,  which  thus  allows  the  thoracic  muscles  to  exert  a  more  extensive 
influence  on  the  ribs. 

PATHOLOGICAL   VARIATIONS   IN   THE   RESPIRATORY   MOVE- 
MENTS. 

Changes  in  the  Character  of  the  Movements. — In  the  presence  of  affections  of 
the  respiratory  apparatus  the  expansion  of  the  thorax  may  be  diminished  to  the 


PATHOLOGICAL    VARIATIONS    IN    THE    RESPIRATORY    MOVEMENTS.    211 

extent  of  5  or  6  cu.  cm.  on  one  or  both  sides.  When  the  apices  are  affected,  as 
occurs  so  frequently  in  cases  of  tuberculosis  of  the  lungs,  the  subnormal  expansion 
in  the  upper  parts  of  the  thorax  is  a  characteristic  feature.  Retraction  of  the 
intercostal  spaces,  the  ensiform  process,  and  the  lower  insertions  of  the  ribs  occurs 
during  marked  inspiratory  rarefaction  of  air  in  the  thorax,  such  as  may  take 
place  in  the  presence  of  laryngeal  stenosis.  If  this  phenomenon  be  confined  princi- 
pally to  the  upper  parts  of  the  thorax,  it  shows  that  the  subjacent  part  of  the 
lung  is  diseased  and  capable  of  little  expansion. 

In  persons  suffering  from  chronic,  advanced  disease  of  the  respiratory  organs, 
without  impairment  in  the  activity  of  the  diaphragm,  the  insertion  of  the  latter 
manifests  itself  on  the  outer  surface  of  the  body  by  a  shallow  groove  (Harrison's 
groove) ,  passing  horizontally  outward  from  the  ensiform  cartilage,  and  due  to  the 
marked  retraction. 

The  period  of  inspiration  is  lengthened  in  persons  suffering  from  constriction 
of  the  trachea  or  larnyx;  that  of  expiration  in  those  who  must  call  into  play  all 
the  expiratory  muscles,  by  reason  of  an  emphysematous  condition  of  the  lungs 
(Fig.  72,  II).  Occasionally,  in  emphysematous  subjects,  a  short  expiratory  effort 
precedes  the  inspiration. 

Changes  in  the  Rhythm  of  the  Movements. — All  disturbances  of  the  respiratory 
apparatus  of  any  degree  of  magnitude  will  produce  an  increase  in  the  frequency 
or  depth  of  the  respirations,  or  both  together.  This  phenomenon  is  termed  dysp- 
nea. The  possible  causes  of  dyspnea  are  various:  i.  Restriction  of  the  respira- 
tory exchange  of  gases  in  the  blood,  as  a  result  of  (a)  diminution  of  the  respiratory 
surface  (pulmonary  diseases) ,  (6)  contraction  of  the  air-passages,  (c)  diminution  in 
the  number  of  red  blood-corpuscles,  (d)  disturbances  in  the  mechanism  of  respira- 
tion (affections  of  the  respiratory  muscles  and  their  nerves,  painful  affections  of 
the  thoracic  walls),  (e)  weakness  in  the  circulation,  especially  the  lesser  circulation, 
principally  as  a  result  of  various  cardiac  affections. 

2 .  Febrile  conditions  are  a  further  cause  of  increase  in  the  frequency  of  respira- 
tion. The  febrile  blood  heats  the  respiratory  center  in  the  medulla  oblongata, 
and  thus  incites  dyspneic  respiratory  movements  up  to  from  30  to  60  in  the  minute 
(heat-dyspnea).  If  the  carotids  of  animals  be  placed  in  hot  tubes,  the  same  result 
is  produced.  Under  the  influence  of  hysterical  irritability,  a  nervous  pathological 
increase  in  the  respiratory  rate  may  be  produced  in  rare  cases.  Respiratory  pauses 
of  considerable  duration  are  uncommon,  but  they  may  occur  (in  one  patient  with 
cardiac  and  renal  disease  a  pause  of  thirty-seven  seconds  was  observed  during  sleep). 

A  remarkable  change  in  the  rhythm  of  respiration  is  known  as  Cheyne-Stokes' 
breathing.  This  manifests  itself  as  a  suffocation-phenomenon  in  affections  that 
alter  the  normal  supply  of  blood  to  the  brain,  or  that  change  the  composition 
of  the  blood,  for  example,  cerebral  affections,  cardiac  diseases,  or  uremic  intoxica- 
tion. Under  such  circumstances  pauses  of  from  one-half  to  three-fourths  of  a 
minute  alternate  with  series  of  from  20  to  30  respirations,  likewise  extending  over 
from  one-half  to  three-fourths  of  a  minute.  The  respirations  of  a  single  series  are 
first  superficial ;  they  then  become  deeper  and  dyspneic,  and  then  again  more  super- 
ficial. After  this  a  pause  occurs,  and  at  this  time  the  eyeballs  roll,  the  pupils  are 
contracted  and  do  not  react,  and  the  blood-pressure  falls.  In  severe  cases  complete 
loss  of  consciousness,  analgesia,  abolition  of  the  reflexes,  and  even  inability  to 
swallow,  rarely,  toward  the  end  of  the  pause,  also  muscular  twitchings  have  been 
observed  during  the  pauses.  When  the  respiratory  movements  commence  again, 
the  pupils  become  larger  and  reactive.  It  has  often  been  observed  that  conscious- 
ness, lost  during  the  pause,  has  been  partially  regained  whenever  the  respirations 

In  agreement  with  Rosenbach  and  Luciani  the  cause  of  Cheyne-Stokes' 
breathing  is  referred  to  variations  in  the  irritability  of  the  respiratory  center, 
which  reaches  its  lowest  point  during  the  pause.  Luciani  compares  the  phe- 
nomenon with  that  of  the  periodically  grouped  heart-beats.  He  observed  i 
set  in  after  injury  to  the  medulla  above  the  respiratory  center,  after  the  apnea 
in  animals  profoundly  poisoned  with  opium,  and  finally  in  the  last  stage  of  as- 
phyxia attending  respiration  in  a  closed  space. 

Cheyne-Stokes'  respiration  is  most  readily  explained  by  assuming  the  pau 
to  be  a  period  of  asphyxia,  and  the  series  of  respirations  to  be  agonal.     Under 
the  reviving  influence  of  the  latter,  the  respiratory  center  recovers  from  the  pre- 
vious state  of  exhaustion. 

During  hibernation  this  form  of  breathing  is  normal  in  the  dormouse, 
hedge-hog,  and  the  alligator.     If  frogs  are  kept  immersed  in  water,  or  if  the 


212  MUSCULAR    MECHANISM    IN    INSPIRATION    AND    EXPIRATION. 

aorta  be  clamped,  they  lose  the  power  of  reaction  in  a  few  hours.  When  taken 
out  of  the  water,  or  when  the  clamp  is  removed,  they  recover  immediately,  and 
they  invariably  exhibit  the  phenomenon  of  Cheyne-Stokes'  respiration.  In  such 
frogs  the  circulation  may  be  interrupted  for  a  time,  during  which  this  form  of 
breathing  still  continues. 

Curtailment  of  the  blood-supply  in  frogs  by  blood-letting  results  in  periodically 
grouped  respirations.  These  are  followed  by  a  stage  of  single,  infrequent  respira- 
tions, and  finally  the  breathing  stops  completely.  During  the  pauses  between  the 
periods,  each  mechanical  irritation  of  the  skin  will  give  rise  to  a  series  of  respirations. 
Periodic  respiration,  without  variations  in  the  depth  of  the  separate  respirations 
(so-called  Biot's  respiration),  also  occurs  normally  in  sleep.  While  the  nervous 
centers  are  endeavoring  to  obtain  rest,  they  forget,  to  a  certain  extent,  to  send 
out  respiratory  impulses,  and  the  organism  takes  no  notice  of  these  short  pauses. 
Periodic  irregularities  in  respiration  also  are  frequently  of  reflex  origin.  Muscarin, 
digitalin,  curare,  chloral,  hydrogen  sulphid,  and  the  toxins  of  some  infectious  dis- 
eases (typhoid  fever,  diphtheria,  scarlet  fever)  are  likewise  capable  of  exciting 
periodic  respirations. 

SUMMARY    OF  THE  MUSCULAR   MECHANISM  CONCERNED    IN 
INSPIRATION    AND    EXPIRATION. 

A.  INSPIRATION. 

I.  During  quiet  inspiration  the  following  muscles  are  active: 

1.  The  diaphragm  (phrenic  nerve,  from  the  third  and  fourth  cervical  nerves). 

2 .  The  external  intercostal  and  intercartilaginous  muscles  (intercostal  nerves) . 

3 .  Long  and  short  elevators  of  the  ribs  (posterior  branches  of  the  dorsal  nerves) . 
In  a  state  of  rest  the  elastic  traction  of  the  lungs  appears  to  draw  the  chest 

together  somewhat  with  tension  on  all  sides.  Accordingly  the  elastic  force  thus 
exerted  would  act  as  an  aid  to  the  beginning  of  inspiration.  Also  Landerer  con- 
siders the  thorax  at  rest  to  be  an  apparatus  tending  toward  the  attitude  of  inspira- 
tion, by  means  of  the  elasticity  in  an  upward  direction  of  the  six  upper  ribs. 

II.  During  forced  inspiration  the  following  muscles  are  active: 

(a)  Trunk-muscles. 

1.  The  three  scalene  muscles  (muscular  branches  of  the  cervical  and  brachial 
plexuses) . 

2.  Sterno-cleido-mastoid  (external  branch  of  the  spinal  accessory  nerve). 

3.  Trapezius  (external  branch  of  the  spinal  accessory,  and  muscular  branches 
of  the  cervical  plexus) . 

4.  Lesser  pectoral  (anterior  thoracic  nerves). 

5 .  Posterior  superior  serratus  (dorsal  nerve  of  the  scapulas) . 

6.  Rhomboids  (dorsal  nerve  of  the  scapulae) . 

7.  Extensor  muscles  of  the  vertebral  column  (posterior  branches  of  the  dorsal 
nerves). 

The  assumption  that  the  greater  anterior  serratus  (long  thoracic  nerve)  and  the 
subclavius  (brachial  plexus)  are  accessory  muscles  of  inspiration  is  unwarranted. 

(b)  Laryngeai  muscles. 

1 .  Sterno-hyoid  (descending  branch  of  the  hypoglossus) . 

2 .  Sterno-thyroid  (descending  branch  of  the  hypoglossus) . 

3.  Posterior  crico-arytenoid  (inferior  laryngeal  branch  of  the  vagus). 

4.  Thyro-arytenoid   (inferior  laryngeal  nerve). 

(c)  Facial  muscles. 

1.  Anterior  and  posterior  dilators  of  the  nares  (facial  nerve). 

2 .  Levator  of  the  ala  nasi  (facial  nerve) . 

3.  The  muscles  that  separate  the  lips  and  open  the  mouth  during  extreme 
forced  respiration — gasping — (facial  nerve). 

(d)  Muscles  of  the  palate  and  pharynx. 

1 .  Elevator  of  the  veil  of  the  palate  (facial  nerve) . 

2.  Azygos  of  the  uvula  (facial  nerve). 

3.  According  to  Garland,  the  pharynx  is  always  narrowed. 

B.  EXPIRATION. 

I.  During  quiet  expiration  the  size  of  the  thoracic  cavity  is  reduced  essentially 
by  the  weight  of  the  chest-walls,  together  with  the  elasticity  of  the  lungs,  costal 
cartilages,  and  abdominal  muscles. 


ACTION    OF    THE    INDIVIDUAL    RESPIRATORY    MUSCLES. 


213 


II.  During  forced  expiration  the  following  muscles  are  employed : 

1.  The  abdominal  muscles  (internal  or  anterior  abdominal  nerves,  branches  of 
the  intercostal  nerves  from  the  8th  to  the  i2th). 

2.  Internal  intercostal  muscles   (the  parts  lying  between  the  ribs),  and  the 
infracostal  muscles  (intercostal  nerves). 

3 .  The  triangular  muscle  of  the  sternum  (intercostal  nerves) . 

4.  (?)  Posterior  inferior  serratus  (external  branches  of  the  dorsal  nerves). 

5.  (?)  Quadratus  lumborum  (muscular  branches  of  the  lumbar  plexus). 


ACTION  OF  THE  INDIVIDUAL  RESPIRATORY  MUSCLES. 

A.  Inspiration. — i.  The  diaphragm  arises  by  six  processes  from  the  six  lower 
costal  cartilages  and  contiguous  osseous  parts  of  the  ribs  (costal  portion) ,  by  three 
processes  from  the  upper  four  lumbar  vertebrae  (lumbar  portion) ,  and  from  the  ensi- 
form  process  (sternal  portion).  It  presents  a  double  dome,  with  the  convexity 
toward  the  thoracic  cavity,  and  contains  the  liver  in  its  larger,  right-sided  con- 
cavity, and  the  stomach  and  the  spleen  in  its  smaller,  left-sided  cavity.  In  a  state 
of  rest  the  intra-abdominal  pressure  and  the  elasticity  of  the  abdominal  wall  press 
these  organs  against  the  under  surface  of  the  diaphragm,  in  such  a  manner 
that  it  bulges  into  the  thoracic  cavity.  This  position  is  aided  by  the  elastic 
traction  of  the  lungs.  The  central  part  of  the  diaphragm  (central  tendon)  is,  to 
a  great  extent,  fused  on  its  upper  surface  with  the  pericardial  sac.  This  part, 
which  supports  the 
heart  and  is  pierced 
by  the  inferior  vena 
cava  (foramen  quad- 
rilaterum) ,  projects 
downward  into  the 
abdominal  cavity  in 
a  state  of  rest ;  and  in 
casts  made  of  the 


FIG  80. — Frontal  Section  of  the  Thorax  at  the  Extremity  of  the  Twelfth  Rib  on 
Each  Side  (12.  C),  to  Demonstrate  the  Form  of  the  Diaphragm  during  Ex- 
piration (Z  e-Z  e)  and  during  Inspiration  (Z  i-Z  i) :  T  e-T  e,  thoracic  wall  in 
a  state  of  expiration;  i  i,  during  inspiration;  C  t,  central  tendon.  The  ar- 
rows indicate  the  direction  of  the  movements  during  inspiration. 


diaphragm  it  can  be 
recognized  as  the 
lowest  part  of  the 
middle  portion  (Fig. 

80). 

During  c  o  n- 
traction  of  the  dia- 
phragm the  two 
dome-like  projec- 
tions are  flattened, 
and  the  thoracic 
cavity  is  enlarged 
downward.  At  the 
same  time  the  dis- 
tal, arched,  muscular  parts  become  flatter,  and  are  drawn  away  from 
the  chest-wall,  to  which  they  are  closely  applied  during  expiration.  The 
middle  part  of  the  central  tendon,  upon  which  the  heart  rests,  takes 
no  considerable  part  in  the  movement  during  quiet  inspiration;  but 
during  forced  inspiration  it  also  is  depressed  to  a  certain  extent. 

In  the  recumbent  posture  (especially  in  men),  with  full  light  on  the  thorax, 
the  contraction  of  the  diaphragm  can  often  be  seen  directly  in  the  form  of 
like  movement  beginning  in  the  sixth  intercostal  space  and  running  downward 
through  from  one  to  three  intercostal  spaces  in  accordance  with  the 
inspiration. 

The  diaphragm  undoubtedly  plays  the  most  important  part  in  e 
thorax.     Briicke   further  maintains   that   the   diaphragm,   besides  enlarg 
thorax  in  a  vertical  direction,  also  expands  the  lower  part  in  a  transvers 
tion  :   namely  when  it  compresses  the  abdominal  organs  from  above,  the 


214  ACTION    OF    THE    INDIVIDUAL    RESPIRATORY    MUSCLES. 

endeavor  to  escape  laterally,  and  thus  spread  out  themselves,  as  well  as  the  adja- 
cent thoracic  wall.  If  the  abdominal  contents  be  removed  from  an  animal,  the 
lower  ribs  are  seen  to  be  drawn  inward  with  every  contraction  of  the  diaphragm ; 
therefore,  the  presence  of  the  viscera  is  necessary  for  the  normal  action  of  the 
diaphragm. 

In  order  to  obtain  some  idea  as  to  the  extent  of  thoracic  enlargement  due  to 
the  action  of  the  diaphragm,  Landois  carried  out  the  following  experiment:  A 
tracheal  cannula  was  fastened  in  the  body  of  a  well-built,  female,  newly  born 
child  that  had  died  of  hemorrhage.  The  body  was  completely  immersed  in  water, 
and  the  lungs  were  inflated.  The  vital  capacity  was  estimated  from  the  amount 
of  water  displaced.  The  abdomen  was  then  opened,  the  viscera  removed,  and  a 
wax  cast  was  taken  of  the  under  surface  of  the  diaphragm,  with  uninflated  lungs 
(that  is,  in  the  position  of  expiration).  Hereupon,  a  quantity  of  air  equal  to  the 
determined  vital  capacity  was  introduced  into  the  lungs,  and  after  the  air-passages 
were  closed,  a  second  wax  cast  was  taken  of  the  diaphragm  in  this  last  position. 
The  difference  in  volume  between  these  casts  was  determined,  and  it  was  found 
that  the  proportion  between  the  expansion  due  to  the  diaphragm  and  that  due 
to  all  other  causes  was  1:2^.  These  figures  are,  of  course,  only  approximately 
correct;  for,  in  the  first  place,  the  removal  of  the  abdominal  viscera  permits  of 
unimpeded  descent  of  the  diaphragm  (which  is,  to  a  certain  extent,  compensated 
for  by  the  taking  of  the  wax  cast);  and,  secondly,  the  arch  of  the  actively  con- 
tracting diaphragm  presents  a  form  differing  from  that  produced  passively  by 
inflation  of  the  lungs.  However,  there  is  no  other  means  at  hand  for  determining 
the  thoracic  expansion  produced  by  the  diaphragm. 

By  increasing  the  intra-abdominal  pressure,  each  diaphragmatic  contraction 
increases  the  flow  of  venous  blood  from  the  abdominal  organs  to  the  inferior 
vena  cava. 

The  great  importance  of  the  diaphragm  in  the  respiratory  process  can  be 
realized  from  the  fact  that  bilateral  section  of  the  phrenic  nerves  in  young  rabbits 
is  followed  by  death.  These  nerves  contain,  as  has  been  shown  experimentally, 
a  few  sensory  fibers  for  the  pleura,  the  pericardium,  and  a  portion  of  the  peri- 
toneum. In  animals,  irritation  of  the  lowest  five  intercostal  nerves  causes  local, 
inconsiderable  contraction  of  the  marginal  part  of  the  diaphragm. 

The  contraction  of  the  diaphragm,  is  not  to  be  regarded  as  a  simple  muscular 
contraction,  for  its  duration  is  from  four  to  eight  times  that  of  the  latter.  It  is, 
therefore,  to  be  designated  as  a  tetanic  movement  of  short  duration. 

2.  The  Elevators  of  the  Ribs. — At  their  vertebral  extremity  (which  lies  at  a 
much  higher  level  than  the  sternal  extremity)  the  ribs  are  articulated  at  their 
heads  and  tubercles  with  the  bodies  and  transverse  processes  of  the  vertebrae. 
A  horizontal  axis  passes  through  both  joints,  and  upon  this  axis  the  rib  is  capable 
of  rotating  upward  and  downward.  If  the  axes  of  a  pair  of  ribs  be  prolonged 
from  both  sides  until  they  meet  in  the  middle  line,  an  angle  is  formed  that  is 
large  (125°)  for  the  upper  ribs  and  smaller  (88°)  for  the  lower  ones.  An  imaginary 
plane  may  be  passed  through  the  arch  of  each  rib,  which  inclines,  in  a  state  of 
rest,  from  behind  and  inward,  forward  and  outward.  If  the  rib  turns  on  its  axis, 
this  inclined  plane  is  raised  more  toward  the  horizontal.  As  the  axes  of  the  upper 
ribs  pass  rather  in  a  frontal  direction  and  those  of  the  lower  ribs  rather  in  a  sagittal 
direction,  elevation  of  the  upper  ribs  causes  an  expansion  of  the  cavity  from 
behind  forward,  and  elevation  of  the  lower  ones  an  enlargement  from  within 
outward  (as  the  movements  of  the  ribs  inclined  downward  are  perpendicular  to 
their  axes).  At  the  same  time  the  costal  cartilages  undergo  slight  torsion,  which 
brings  their  elasticity  into  play. 

All  of  the  inspiratory  muscles  that  act  directly  on  the  walls  of  the 
thorax  produce  the  desired  result  by  elevating  the  ribs.  In  this  con- 
nection the  following  points  are  to  be  observed :  (a)  Elevation  of  the  ribs 
causes  a  widening  of  the  intercostal  spaces,  (b)  When  the  upper  ribs 
are  elevated,  all  of  the  lower  ribs  and  also  the  sternum  are  raised  at  the 
same  time,  as  all  of  the  ribs  are  bound  together  by  the  soft  structures  in 
the  intercostal  spaces,  (c)  During  inspiration  there  occurs  an  eleva- 
tion of  the  ribs  and  a  widening  of  the  intercostal  spaces.  An  exception 
is  made  of  the  lowest  rib,  which  does  not  actually  form  a  part  of  the 
thorax.  It  moves  downward,  not  upward,  at  least  during  deep  in- 


ACTION    OF    THE    INDIVIDUAL    RESPIRATORY    MUSCLES.  215 

spiration.  (d)  If,  on  a  preparation  of  the  chest,  the  ribs  be  elevated, 
with  widening  of  the  intercostal  spaces,  as  occurs  during  an  inspiratory 
movement,  then  all  those  muscles  may  be  regarded  as  elevators  of  the 
ribs  whose  origin  and  insertion  approach  each  other.  Hence,  only 
these  muscles  can  be  designated  as  muscles  of  inspiration.  From  this 
point  of  view  the  scalene  muscles,  the  long  and  short  elevators  of  the 
ribs,  and  the  posterior  superior  serratus  are  to  be  recognized  as  un- 
doubted inspiratory  muscles.  They  are  also  to  be  considered  as  the 
muscles  having  the  greatest  influence  on  the  ribs  during  inspiration. 

Of  the  intercostal  muscles,  according  to  this  experiment,  only  the 
external  and  the  intercartilaginous  portions  of  the  internal  can  be  desig- 
nated as  inspiratory  muscles.  The  remainder  of  the  internal  (the  parts 
covered  by  the  external)  are  lengthened  during  elevation  of  the  ribs, 
and  shortened  when  the  ribs  are  lowered.  As  a  muscle  always  exhibits 
its  activity  by  shortening,  the  internal  intercostal  muscles  have  been 
regarded  as  depressors  of  the  ribs  (that  is,  as  expiratory  muscles). 

Fig.  8 1,  I,  shows  that  when  the  rods  a  and  b,  representing  the  depressed  ribs, 
are  elevated,  the  interspace  (intercostal  space)  must  become  wider:  ef  >cd.  On 
the  left  side  of  the  figure  it  may  be  seen  that  when  the  rods  are  elevated,  the  line 
g  h,  representing  the  external  intercostal  muscles,  is  shortened  (i  k  <  gh) ,  while  1  m, 
representing  the  internal  intercostals,  is  lengthened  (1  m  <  o  n).  Fig.  81,  II, 
shows  that  the  intercartilaginous  muscles,  designated  by  g  h,  and  the  external 
intercostal  muscles,  designated  by  1  k,  are  shortened  by  elevation  of  the  ribs. 
The  latter  position  of  these  muscular  fibers  may  be  represented  by  the  shortened 
diagonals  of  the  dotted  rhomboids. 

The  controversy  over  the  mechanism  of  the  intercostal  muscles  dates  back 
to  ancient  times:  Galen  (131-203  A.  D.)  regarded  the  external  intercostal  muscles 
as  inspiratory  and  the  internal  as  expiratory  muscles.  Hamburger  (1727),  fol- 
lowing Willis'  investigations,  agreed  with  this  view,  and  also  recognized  the  inter- 
cartilaginous muscles  as  inspiratory  muscles.  A.  v.  Haller,  who  was  Hamburger's 
direct  opponent,  considered  both  internal  and  external  intercostals  as  muscles  of 
inspiration;  while  Vesalius  (1540)  regarded  them  both  as  expiratory  muscles. 
Masoin  and  R.  du  Bois-Reymond  admitted  the  latter  view,  but  only  for  forced 
respiration.  Finally,  Landerer,  who  observed  that  the  upper  two  or  three  inter- 
costal spaces  became  narrower  during  inspiration,  believed  that  both  sets  were 
active  during  both  inspiration  and  expiration.  As  they  hold  the  ribs  together, 
they  have  the  sole  function  of  transmitting  the  traction  imparted  to  them  simply 
through  the  chest-walls.  They  would,  therefore,  remain  active  even  when  the 
distance  between  their  points  of  insertion  becomes  greater. 

After  mature  consideration  of  all  the  conditions,  Landois  was  unable  to  accept 
any  of  these  views  unconditionally.  It  is  obvious  that  the  external  intercostal 
and  intercartilaginous  muscles  can" act  together  only  during  inspiration,  while  the 
internal  can  be  active  only  during  expiration  (the  latter  statement  having  been 
confirmed  by  Martin  and  Hartwell  in  dogs  by  means  of  vivisection) ;  but  elevation 
and  depression  of  the  ribs  are  not  the  chief  results  attained  by  the  action  of  these 
muscles.  It  was  rather  Landois'  opinion  that  the  chief  purpose  of  the  external 
and  intercartilaginous  muscles  is  to  counteract  the  inspiratory  widening  of  the 
intercostal  spaces  and  the  synchronous  increase  in  the  elastic  traction  of  the  lungs. 
The  function  of  the  internal  intercostal  muscles  is  to  offer  resistance  to  the  ex- 
piratory distention  that  occurs  during,  forced  expiratory  efforts,  as  in  coughing. 
Without  muscular  resistance  the  intercostal  tissues  would  be  so  stretched  through 
the  uninterrupted  traction  and  pressure  that  regular  respiratory  movements  would 
become  impossible. 

The  lesser  pectoral  (and  the  greater  anterior  serratus  ?)  is  capable  of 
assisting  in  the  elevation  of  the  ribs  only  when  the  shoulders  are  held 
in  a  fixed  position,  partly  through  a  firm  propping  up  of  the  arms,  and 
partly  by  the  rhomboid  muscles,  as  is  instinctively  done  by  dyspneic 
patients. 


216 


ACTION    OF    THE    INDIVIDUAL    RESPIRATORY    MUSCLES. 


3.  Muscles  Acting  upon  the  Sternum,  the  Clavicle,  and  the  Spinal  Col- 
umn.— If  the  head  be  held  in  a  fixed  position  by  the  muscles  of  the  back  of 
the  neck,  the  sterno-cleido-mastoid  can  enlarge  the  thorax  in  an  upward 
direction  by  raising  the  manubrium,  together  with  the  sternal  extremity 
of  the  clavicle,  thus  assisting  the  scalene  muscles.     In  like  manner,  but 
to  a  lesser  extent,  the  clavicular  insertion  of  the  trapezius  .may  become 
efficient.    A  stretching  of  the  dorsal  portion  of  the  vertebral  column  must 
result  in  an  elevation  of  the  upper  ribs  and  a  widening  of  the  intercostal 
spaces,  by  means  of  which  the  inspiratory  capacity  is  substantially  in- 
creased.    During  deep  inspiration  this  stretching  is  effected  involuntarily. 

4.  In  forced    respiration    every    inspiration    is   accompanied  by   a 
descent  of  the  larynx  and  a  widening  of  the  glottis.     At  the  same  time 

the  palate  is  raised,  in  order 
to  allow  the  air  to  enter 
with  the  least  possible  resist- 
ance. 

5.  Forced  respiration  is 
first  made  evident  in  the 
face  by  an  inspiratory  dila- 
tation of  the  nostrils  (horse, 
rabbit).  During  marked 
dyspnea  the  cavity  of  the 
mouth  is  enlarged  with  each 
inspiration  by  a  dropping  of 
the  jaw  (gasping). 

B.  Expiration.  —  Quiet 
expiration  is  accomplished 
without  muscular  effort.  It 
is,  first  of  all,  dependent 
principally  upon  the  weight 
of  the  thorax,  which  has  a 
tendency  to  fall  back  from 
its  elevated  position  to  the 
lower  expiratory  position. 
This  is  assisted  by  the  elas- 
ticity of  the  various  parts. 
When  the  costal  cartilages 
are  elevated,  their  lower 
borders  are  slightly  rotated 
from  below  forward  and  up- 
ward, and  their  elasticity  is  thus  brought  into  play.  Hence,  as  soon  as 
the  inspiratory  forces  are  relaxed,  the  cartilages  return  to  their  lower 
and  no  longer  distorted  expiratory  position.  At  the  same  time,  the 
elasticity  of  the  distended  lungs  draws  the  thoracic  walls,  as  well  as 
the  diaphragm,  together  on  all  sides.  Finally,  the  tense,  elastic  ab- 
dominal walls,  which  become  stretched  and  pushed  forward,  especially 
in  men,  return  to  their  non-distended  state  of  rest  when  the  pressure 
of  the  diaphragm  from  above  is  released.  It  is  self-evident  that  when 
the  body  is  in  an  inverted  position,  the  effect  of  the  weight  of  the  thorax 
is  removed,  and  is  replaced  by  the  weight  of  the  abdominal  viscera 
pressing  upon  the  diaphragm. 

Among  the  muscles  that  are  brought  into  action  only  during  forced 


ii 


FIG.  81. — I,  II.  Diagrammatic  Representation  of  the  Mechanism 
of  the  Intercostal  Muscles. 


DIMENSIONS    AND    EXPANSIBILITY    OF    THE    THORAX. 


217 


respiration,  the  abdominal  muscles  stand  foremost.  They  dimmish  the 
size  of  the  abdominal  cavity,  and  thus  press  the  viscera  upward  against 
the  diaphragm.  The  triangular  muscle  of  the  sternum  draws  downward 
the  sternal  extremities  of  the  united  cartilages  and  bones  of  the  ribs 
from  the  third  to  the  sixth,  which  have  been  elevated  during  inspira- 
tion. The  posterior  inferior  serratus  depresses  the  four  lowest  ribs,  the 
others  necessarily  following,  being  assisted  by  the  quadratus  lumborum, 
which  is  capable  of  depressing  the  last  rib.  According  to  Henle,  how- 
ever, the  posterior  inferior  serratus  fixes  the  lower  ribs  so  as  to  with- 
stand the  pull  of  the  diaphragm,  thus  aiding  inspiration.  Landerer 
even  asserts  that  in  the  lower  parts  of  the  chest  the  movements  of  the 
ribs  enlarge  the  thoracic  cavity  downward. 

In  the  erect  posture  and  with  a  fixed  spinal  column,  deep  inspiration  and 
expiration  are  accompanied  by  a  displacement  of  the  bodily  equilibrium.  During 
inspiration  the  center  of  gravity  is  moved  slightly  forward  by  the  protrusion  of  the 
chest  and  the  abdominal  walls.  In  deep  inspiration  the  straightening  of  the 
spinal  column  and  the  consequent  throwing  back  of  the  head  act  as  a  compensation 
for  the  projection  of  the  anterior  trunk- wall. 

DIMENSIONS  AND   EXPANSIBILITY   OF   THE    THORAX. 

It  is  of  considerable  importance  for  the  physician  to  know  the  dimensions  of 
the  thorax,  as  well  as  the  extent  of  its  expansion  in  various  directions.  With 
inspiration  the  thorax  is  enlarged  in  all  its  diameters.  The  diameters  of  the  thorax 
are  determined  by  means  of  calipers;  the  circumference  is  measured  by  means  of 
the  centimeter  tape-measure. 

In  well-built  men  the  upper  circumference  of  the  chest,  close  under 
the  arms,  measures  88  cm.;  in  women  it  is  82  cm.  The  lower  circum- 
ference, at  the  level  of  the  en- 
siform  cartilage,  is  82  cm.  in 
men  and  78  cm.  in  women. 
When  the  arms  are  held  hori- 
zontally the  measurement  taken 
during  expiration  just  below 
the  nipples  and  the  angles  of 
the  scapulae  equals  half  the 
body-length,  that  is,  82  cm.  in 
men;  during  deepest  inspira- 
tion it  is  89  cm.  At  the  level 
of  the  ensiform  cartilage  the 
circumference  is  about  6  cm. 
less.  In  old  persons  the  upper 
circumference  is  diminished, 
being  smaller  than  the  lower 
measurement.  Usually  the  right 
half  of  the  thorax  is  some- 
what larger  than  the  left,  on  account  of  the  greater  muscular 
velopment.  The  longitudinal  diameter  of  the  thorax,  from  the  clavicle 
to  the  lowest  edge  of  the  ribs,  varies  considerably. 

The  transverse  diameter  (distance  between  the  lateral  surfaces, 
in  men,  from  25  to  26  cm.,  above  and  below;   in  women,  from  23  to  24 
cm.     Above  the  nipples  it  is  about  i  cm.  greater.     The  antero-posteno 
diameter  (measured  from  the  anterior  surface  of  the  sternum  t 
of  a  spinous  process)  is  17  cm.  in  the  upper  part  of  the  thorax,  and  19  cm. 


FIG.  82. — Cyrtometer-curve  from  a  Case  of  Left-sided 
Retraction  of  the  Thorax  in  a  Twelve-year-old  Girl 
(after  Eichhorst). 


2l8 


RESPIRATORY    EXCURSION    OF    THE    LUNGS. 


FIG.  83. — Sibson's  Thoracometer. 


in  the  lower  part.  Valentin  found  that  during  deepest  inspiration  in 
men,  the  circumference  of  the  thorax  at  the  level  of  the  ensiform  carti- 
lage increased  between  yV  and  y;  Sibson  found  this  increase  to  be  yV 
at  the  level  of  the  nipples. 

Various  instruments  have  been  devised  to  determine  the  degree  of  movement 

(elevation  or  depression)  made  by  a  definite  part  of  the  thorax  during  respiration. 

The  cyrtometer  of  Woillez  is  quite  useful :  A  measuring  chain  with  stiffly  movable 

links  is  applied  to  the  outer  sur- 
face of  the  thorax  in  a  definite 
direction,  for  example,  trans- 
versely at  the  level  of  the  epi- 
gastrium or  the  nipples,  or  per- 
pendicularly through  the  mam- 
millary  or  the  axillary  line.  In 
two  places  the  links  are  loosely 
movable,  permitting  a  removal 
of  the  chain  without  changing  its 
form  as  a  whole.  The  inner  out- 
line of  the  chain  is  traced  on  a 
sheet  of  paper,  and  the  form  of 
the  thorax  is  thus  obtained  (Fig. 
82).  If  the  instrument  is  first 
applied  in  the  state  of  expiration, 
and  then  during  inspiration,  there 
is  obtained  a  diagrammatic  repre- 
sentation of  the  extent  of  move- 
ment in  the  various  parts  of  the 
thorax.  The  same  purpose  is 
served  by  shadow-diagrams  or 
photograms  taken  at  the  various 
periods  of  respiration.  A  compli- 
cated apparatus  has  also  been 

constructed  of  numerous  little  rods,  which  rest  on  the  thorax  and  rise  and 
fall  with  the  respiratory  movement  and  can  be  fixed  in  a  given  position. 

The  tkoracometer  of  Sibson  (Fig.  83)  measures  the  elevation  of  selected  parts 
of  the  sternum.  It  consists  of  two  metal  rods,  joined  at  right  angles,  of  which  one 
(A)  is  applied  to  the  spinal  column.  On  B  is  the  movable  arm  C,  which  carries 
at  its  end  the  toothed  bar  (Z)  directed  perpendicularly  downward.  The  latter  is 
supplied  with  a  spring,  and  ends  below  in  a  ball,  which  rests  upon  that  part  of 
the  sternum  to  be  investigated.  The  toothed  bar,  by  means  of  a  small  cogwheel, 
moves  the  indicator  (o) ,  which  shows  the  excursions  of  the  sternum  on  an  enlarged 
scale. 

RESPIRATORY  EXCURSION   OF  THE   LUNGS. 

The  boundaries  and  the  size  of  the  lungs  in  a  state  of  rest  on  the  ante- 
rior surface  of  the  thorax  are  shown  in  Fig.  34.  The  shaded  bounda- 
ries L  L  indicate  the  borders  of  the  lungs,  while  the  dotted  lines 
P  P  show  the  extent  of  the  parietal  pleura  (boundaries  of  the  pleural 
cavity).  In  the  living  subject  the  extent  of  the  lungs  can  be  determined 
by  percussion,  that  is,  by  striking  the  chest- wall  (through  an  interposed 
thin  plate  of  horn:  Piorry's  plessimeter)  by  means  of  a  small  cushioned 
hamrner  (Wintrich's  percussion-hammer).  Wherever  pulmonary  tissue 
containing  air  lies  in  contact  with  the  chest- wall,  a  sound  is  obtained 
like  that  produced  by  striking  a  vessel  containing  air  (resonant  per- 
cussion-note). Where  the  underlying  parts  contain  no  air,  the  sound 
is  like  that  produced  by  striking  the  thigh  (flat  percussion-note).  If 
the  parts  containing  air  are  thin,  or  are  partly  deprived  of  their  air,  the 
note  is  dull. 

Fig.  84  in  connection  with  Fig.  34  shows  the  boundaries  of  the  lungs 


RESPIRATORY    EXCURSION    OF    THE    LUNGS. 


2I9 


on  the  anterior  chest-wall.  The  apices  of  the  lungs  extend  above  the 
clavicles  anteriorly  to  a  distance  of  from  3  to  7  cm. ;  on  the  posterior 
surface  they  extend  above  the  spines  of  the  scapulae  to  the  level  of  the 
seventh  spinous  process.  On  the  right  side  the  lower  border  of  the 
lung,  in  a  position  of  rest,  begins  at  the  right  edge  of  the  sternum  at  the 
insertion  of  the  sixth  rib,  and  extends  horizontally  outward  to  about  the 
upper  edge  of  the  sixth  rib  in  the  mammillary  line,  and  the  upper  edge 
of  the  seventh  rib  in  the  axillary  line.  On  the  left  side  (apart  from  the 
position  of  the  heart)  the  lower  border  of  the  lung  extends  downward 
for  the  same  distance.  In  Fig.  84  the  line  at  b  indicates  the  lower 
boundary  of  the  lungs  in  a  state  of  rest.  Posteriorly,  both  lungs  extend 
to  the  tenth  rib. 


[Fio.  84. — Topography  of  the  Boundaries  of  the  Lungs  and  the  Heart  during  Inspiration  and  Expiration 

(after  v.    Dusch). 

During  the  deepest  possible  inspiration  the  lungs  descend  anteriorly 
below  the  sixth  rib  as  far  as  the  seventh ;  posteriorly  as  far  as  the  eleventh 
rib.  At  the  same  time  the  diaphragm  withdraws  from  the  wall  of  the 
thorax.  During  forced  expiration  the  lower  borders  of  the  lungs  rise 
almost  for  the  same  distance  as  they  sink  during  inspiration.  In  Fig. 
84  the  line  m  n  shows  the  limit  of  the  border  of  the  right  lung  during 
deep  inspiration,  and  h  1  indicates  the  same  border  during  complete 
expiration. 

The  relation  between  the  border  of  the  left  lung  and  the  heart  de- 
serves especial  attention.  In  Fig.  34  may  be  seen  an  almost  triangular 
space,  extending  to  the  left  of  the  sternum  from  the  middle  of  the  inser- 
tion of  the  fourth  rib  to  the  sixth  rib.  This  space  represents  that  part 
of  the  heart  which  lies  in  direct  contact  with  the  chest-wall  when  the 


220        NORMAL  PERCUTORY  CONDITIONS  IN  THE  THORAX. 

thorax  is  at  rest.  Within  these  limits,  represented  by  the  triangle  t  t'  t" 
in  Fig.  84,  percussion  yields  the  cardiac  dulness ;  that  is,  a  flat  per- 
cussion-note is  obtained  here. 

In  the  larger  triangle  d  d'  d"  a  relatively  thin  layer  of  pulmonary 
tissue  separates  the  heart  from  the  chest-wall,  and  a  dull  note  is  obtained 
on  percussion.  Only  outside  this  triangle  is  the  so-called  pulmonary 
resonance  obtained.  On  deeper  inspiration  the  inner  border  of  the  left 
lung  passes  completely  over  the  heart,  as  far  as  the  mediastinal  insertion 
(Fig.  34),  and  thus  the  flat  percussion-note  is  confined  to  the  small  tri- 
angle t  i  i'.  On  the  other  hand,  during  forced  expiration  the  edge  of  the 
lung  recedes  so  far  that  the  cardiac  dulness  embraces  the  space  t  e  e'. 

VARIATIONS    FROM    THE    NORMAL    PERCUTORY    CONDITIONS 

IN  THE  THORAX. 

The  investigation  of  the  normal  percutory  conditions  and  their  pathological 
variations  is  of  the  greatest  importance  for  the  physician.  Suggestions  of  percus- 
sion (also  of  the  abdomen)  are  found  as  far  back  as  Aretaeus  (81  A.  D.).  The 
real  discoverer,  however,  is  Auenbrugger  (d.  1809),  whose  fundamental  work  was 
elaborated  especially  by  Piorry  and  Skoda;  the  latter  developed  the  physical 
theory  of  percussion  (1839). 

Over  the  area  of  the  lungs  the  otherwise  clear,  resonant  percussion-note  is 
impaired  when  the  lungs  have  to  a  greater  or  lesser  extent  lost  their  normal  air- 
content;  an  airless  space  of  4  sq.  cm.  on  the  outer  surface  of  the  lungs  will  yield 
a  dull  note.  The  note  is  impaired  also  when  the  lung  is  compressed  from  without. 
The  percussion-note  is  louder  or  hyperresonant  in  lean  individuals  with  thin  chest- 
walls,  or  after  deep  inspiration,  or  in  the  condition  of  permanent  expansion  that 
occurs  in  emphysematous  persons. 

It  should  also  be  noted  whether  the  percussion-note  is  of  high  or  of  low  pitch ; 
this  quality  being  dependent  to  a  certain  extent  on  the  degree  of  tension  in  the 
elastic  pulmonary  tissue,  but  especially  on  the  tension  of  the  thoracic  wall.  As 
this  tension  is  increased  during  inspiration,  and  diminished  during  expiration, 
there  should  be  recognized  a  corresponding  difference  in  the  pitch  of  the  note. 
Deepest  inspiration  produces  a  higher  pitch,  on  account  of  the  increased  tension 
of  the  chest-wall  and  the  lungs ;  but  at  the  same  time  the  note  diminishes  in  dura- 
tion and  intensity,  as  the  more  highly  stretched  parts  possess  a  diminished  ampli- 
tude of  vibration.  Sometimes  in  the  terminal  phase  of  the  deepest  possible  in- 
spiration there  occurs  still  another  change  in  the  percussion-note,  in  that  there  is 
produced,  a  certain  restoration  of  the  depth  and  intensity,  falling  short,  however, 
of  the  original  volume.  During  complete  expiration  the  intensity  is  lessened  and 
the  pitch  lowered. 

Percussion  of  the  larynx  and  the  trachea  yields  a  clear  tympanitic  note,  whose 
pitch  depends  upon  the  size  of  the  cavity.  The  note  is  highest  when  the  mouth 
and  the  nose  are  open,  or  when  the  tongue  is  protruded,  or  when  straining  efforts 
are  made  with  closed  glottis;  it  becomes  lower  when  the  head  is  extended  back- 
ward, or  during  the  act  of  swallowing,  as  well  as  during  intonation.  It  is  higher 
at  the  end  of  deep  inspiration  than  during  expiration.  Affections  of  the  lungs 
that  lessen  the  normal  tension  lower  the  pitch  of  the  note. 

When  the  percussion-note  partakes  of  a  drum-like  character,  approaching  a 
musical  sound,  with  distinguishable  high  and  low  pitch,  it  is  termed  tympanitic. 
If  a  hollow  rubber  ball  applied  to  the  ear  be  tapped  with  the  finger,  a  typical 
tympanitic  sound  will  result,  the  pitch  of  which  is  higher  the  smaller  the  diameter 
of  the  ball.  Tapping  the  trachea  in  the  neck  will  also  yield  a  tympanitic  note. 
The  tympanitic  note  consists  of  a  primary  tone,  together  with  several  harmonic 
overtones,  arising  from  an  air-space  surrounded  by  relaxed  and  movable  walls  (the 
non-tympanitic  tone  consists  of  the  membrane-tone  of  a  tightly  stretched  wall). 
The  tympanitic  note  in  the  chest  is  always  of  pathological  origin.  It  is  found 
in  the  presence  of  a  cavity  within  the  lung-substance  (when  the  mouth  is  closed, 
and  especially  when  the  nose  is  closed  at  the  same  time,  the  note  becomes  deeper), 
also  in  the  presence  of  air  in  a  pleural  cavity,  as  well  as  in  association  with  dimin- 
ished tension  of  the  pulmonary  tissue.  The  tympanitic  note  is  closely  allied  to 
metallic  tinkling,  which  arises  in  large,  pathological,  pulmonary  cavities,  as  well 


THE    NORMAL    RESPIRATORY    SOUNDS.  221 

as  when  the  pleural  cavity  contains  air,  when  the  conditions  are  suitable  for  a  more 
uniform  reflection  of  the  sound-waves  within  the  cavity.  When  a  percussion- 
stroke  is  made  over  cavities,  especially  in  the  upper  anterior  part  of  the  lung, 
the  air  at  times  escapes  with  a  peculiar  ringing  and  hissing  sound — the  cracked- 
pot  sound  (or  coin-sound). 

In  practising  percussion  it  should  be  observed  by  the  sense  of  touch  whether 
the  underlying  parts  offer  a  feeling  of  greater  or  lesser  resistance  to  the  stroke ;  and 
at  the  same  time  the  vibratory  power  may  be  noted.  Under  normal  conditions 
small  vibratory  power  is  associated  with  a  well-developed  bony  framework,  thick 
soft  parts,  and  tense  muscles.  Pathologically,  lessened  vibration  always  occurs  in 
connection  with  an  airless  condition  of  the  lungs,  and  is  associated  with  a  dull 
percussion-note.  Diminution  of  the  resistance  to  the  percussion-stroke  is  found 
normally  in  slender  chests.  Pathologically,  it  occurs  when  there  is  a  considerable 
amount  of  air  under  the  chest-wall,  hence  in  the  presence  of  pneumothorax  and 
of  abnormal  expansion  of  the  lungs  by  means  of  air. 

If  the  handle  of  a  tuning-fork  be  placed  upon  the  chest-wall,  the  fork  will 
sound  loud  over  spaces  rilled  with  air,  and  will  yield  a  weak  note  over  spaces 
containing  little  or  no  air  (Baas'  phonometry). 

THE  NORMAL  RESPIRATORY  SOUNDS. 

By  listening  over  the  chest- wall,  either  directly  or  by  means  of  a 
stethoscope,  the  vesicular  murmur  can  be  heard  during  inspiration, 
wherever  the  lungs  are  in  contact  with  the  walls  of  the  thorax.  The 
character  of  this  sound  can  be  imitated  if  the  mouth  be  placed  in  the 
position  necessary  for  the  act  of  sipping,  and  a  sound  between  f  and  v 
be  softly  emitted.  The  sound  is  a  sipping,  rustling,  hissing  one.  It 
is  due  to  the  sudden  expansion  of  the  pulmonary  vesicles  by  the  entrance 
of  inspired  air  (hence  the  term  vesicular)  and  also  to  the  friction  of  the 
air  passing  through  the  alveoli.  The  sound  is  at  times  softer,  at  times 
louder.  It  is  constantly  louder  in  children  under  the  age  of  twelve 
years,  as  the  air- vesicles  are  one-third  narrower  than  in  adults,  and 
cause  greater  friction  with  the  entering  air. 

During  expiration  the  air,  when  leaving  the  vesicles,  gives  rise  to  a 
weak  puffing  sound  of  an  uncertain  soft  character. 

The  cardiopulmonary  murmur  heard  in  the  vicinity  of  the  heart  when  the 
latter  contracts  during  systole  likewise  has  a  vesicular  character. 

Bronchial  breathing  may  be  heard  in  the  larger  air-passages  during 
inspiration  and  expiration,  and  resembles  the  sound  of  a  loud,  sharp  h 
or  sh.  Outside  of  the  neck  (larynx  and  trachea)  it  may  be  heard  be- 
tween the  shoulder-blades  at  the  level  of  the  fourth  dorsal  vertebra 
(point  of  bifurcation),  especially  during  expiration.  It  is  somewhat 
louder  to  the  right,  on  account  of  the  larger  caliber  of  the  right  bronchus. 
In  all  other  parts  of  the  thorax  it  is  obscured  by  the  vesicular  murmur. 
The  bronchial  breathing  arises  entirely  in  the  larynx,  from  the  forma- 
tion of  air- vortices,  by  reason  of  the  marked  constriction  of  the  air- 
passage  at  the  glottis.  This  laryngeal  stenosis-sound  causes  a  resonance 
of  the  tracheo-bronchial  air-column,  and  thus  produces  the  specific 
character  of  bronchial  breathing,  which  the  listener  hears  transmitted 
along  the  large  tubes  of  the  bronchial  tree. 

It  has  been  maintained  that,  if  the  air-filled  lungs  of  an  animal  be  applied 
to  the  neck  over  the  larynx  or  trachea,  the  bronchial  breathing  produced  there 
will  become  vesicular.     In  that  case  it  must  be  supposed  that  vesicular  respiration 
arises  from  a  weakening  and  acoustic  transformation  of  tubular  respiration  by  r 
transference  through  the  air- vesicles.     Added  to  this  is  the  fact  that  it  is  impos 
to  produce  any  sound  by  forcibly  driving  air  through  narrow  straws. 


222  PATHOLOGICAL    RESPIRATORY    SOUNDS. 

During  forced  respiration  rustling  sounds  often  arise  at  the  mouth 
and  nostrils;  with  these  sounds  the  primary  tone  of  the  oral  cavity 
(usually  the  vowel-sound  ah)  is  often  mingled  in  mouth-breathing. 

PATHOLOGICAL  RESPIRATORY  SOUNDS. 

The  recognition  of  the  succussion-sound,  the  friction-sound,  and  many  catar- 
rhal  sounds  dates  back  to  Hippocrates  (460-377  B.  C.).  The  actual  foundation  of 
auscultation  on  a  physical  basis  was  laid  by  Laennec  (1816),  and  its  classical 
development  is  due  to  Skoda  (1839). 

Bronchial  breathing  arises  over  the  entire  area  of  the  lungs,  either  when  the 
air-vesicles  have  become  airless  (through  exudation)  or  when  the  lungs  are  com- 
pressed from  without.  In  both  cases  the  condensed  pulmonary  tissue  conducts 
the  bronchial  respiration  to  the  walls  of  the  thorax.  Bronchial  breathing  will 
also  be  heard  over  pathological  cavities  of  considerable  size  that  communicate  with 
a  large  bronchus,  provided  the  cavities  lie  sufficiently  near  the  thoracic  wall  and 
have  walls  of  considerable  resistance.  If  there  is  no  movement  of  air  in  the  cavity, 
the  sounds  may  be  wholly  conducted  out  through  the  trachea ;  or  during  expiration 
a  stenosis-sound  (like  that  at  the  glottis)  may  arise  in  the  communicating  bronchus, 
and  may  be  rendered  amphoric  by  the  resonant  cavity. 

Amphoric  breathing  resembles  the  sound  produced  by  blowing  across  the 
mouth  of  a  bottle.  It  may  arise  when  there  occurs  in  the  lungs  a  cavity  at  least 
the  size  of  a  fist,  through  which  the  air  passes  in  such  a  manner  that  there  is  pro- 
duced the  characteristic  sound  with  a  peculiar  metallic  echo.  If  the  lung  is 
partly  expansible  and  contains  air,  and  the  pleural  cavity  also  contains  air,  the 
resonance  of  the  latter,  together  with  the  exchange  of  air  in  the  lung,  will  also 
produce  the  amphoric  sound. 

If  the  respiratory  sounds  have  no  definite  character,  so  that  they  oscillate 
between  vesicular  and  bronchial  breathing,  they  are  termed  indefinite  respiratory 
sounds.  Frequently  a  deep  respiration  or  expectoration  of  mucus  will  make  the 
character  of  the  sound  more  evident. 

If  the  air  meets  with  resistance  in  its  passage  through  the  lungs,  various 
phenomena  may  result:  (a)  At  times  the  air- vesicles  are  not  all  filled  simultane- 
ously, but  intermittently.  This  occurs  (especially  at  the  apices)  when  partial 
swelling  of  the  walls  of  the  air-passages  obstructs  the  steady  interchange  of  air; 
cogwheel  respiration  is  the  result.  Occasionally  this  is  heard  in  perfectly  normal 
lungs,  when  the  muscles  of  the  chest  contract  in  an  intermittent  fashion,  (b)  If  a 
bronchus  leading  to  a  pulmonary  cavity  is  narrowed  in  such  manner  that  the  air 
meets  with  a  temporary  resistance,  the  inspiratory  sound  is  at  first  like  that  of 
a  loud  G,  and  then  goes  over  during  the  latter  two-thirds  of  inspiration  into  a 
bronchial  or  amphoric  sound.  This  is  termed  a  metamorphosing  sound,  (c)  Rales 
are  produced  in  the  larger  air-passages  when  the  air  causes  bubbling  of  the  con- 
tained mucus.  In  the  smaller  air-spaces  rales  arise  either  when  the  walls  of  the 
latter  are  separated  from  the  fluid  contents  during  inspiration,  or  when  their  walls 
are  in  contact  and  are  suddenly  separated  from  each  other.  Rales  are  distinguished 
as  moist  (arising  in  watery  contents)  or  as  dry  (in  tough,  tenacious  contents) ; 
further,  as  inspiratory  or  expiratory,  or  continuous;  also  coarse,  fine,  or  irregular 
rales,  the  high-pitched  crepitant  rales,  and  finally  the  metallic  tinkling  rales  produced 
by  the  resonance  of  large  cavities,  (d)  If  the  mucous  membrane  of  the  bronchi  is 
so  swollen  or  so  covered  with  mucus  that  the  air  must  force  its  way  through, 
there  arises  frequently  in  the  larger  passages  a  deep  humming  purr — sonorous 
rhonchus;  and  in  the  smaller  tubes  a  clear  whistling  sound — sibilant  rhonchus. 
In  cases  of  widespread  bronchial  catarrh  a  thrill  may  often  be  felt  in  the  chest- 
wall — bronchial  fremitus — caused  by  the  numerous  rales. 

When  the  lung  is  collapsed  and  the  pleural  cavity  contains  fluid  and  air, 
a  sound  may  be  heard  on  shaking  the  chest,  similar  to  that  produced  by  shaking 
a  large  bottle  containing  water  and  air — the  succussion-splash  of  Hippocrates. 
Rarely  a  higher-pitched  similar  sound  may  be  heard  in  pulmonary  cavities  the 
size  of  a  fist. 

When  the  opposed  layers  of  the  pleura  are  roughened  by  inflammatory 
processes,  and  rub  against  each  other  in  the  act  of  respiration,  a  friction- phenomenon 
is  produced.  This  may  be  partly  felt  (often  by  the  patient  himself)  and  partly 
heard.  The  sound  is  usually  creaking,  and  may  be  compared  to  that  produced 
by  bending  new  leather.  Friction-sounds  are  produced  also  by  the  heart's  action 
between  the  two  layers  of  the  diseased  roughened  pericardium. 


PRESSURE    IN    THE    AIR-PASSAGES    DURING    RESPIRATION.  223 

During  loud  speaking  or  singing  the  chest-wall  vibrates— vocal  fremitus— as 
a  consequence  of  the  propagation  throughout  the  bronchial  tree  of  the  vibrations 
of  the  vocal  bands.  This  vibration  naturally  is  most  pronounced  in  the  region  of 
the  trachea  and  the  large  bronchi.  If  the  ear  be  applied  to  the  chest-wall  the 
voice  can  be  heard  only  as  an  unintelligible  hum.  If  the  pleural  cavity  contains 
air  or  a  large  effusion,  or  if  the  bronchi  are  occluded  by  large  quantities  of  mucus 
the  vocal  fremitus  is  weakened  or  entirely  absent.  On  the  other  hand  all  factors 
that  cause  bronchial  breathing  will  increase  the  vocal  fremitus.  Hence  the  latter 
will  be  more  marked  also  in  those  localities  where  bronchial  breathing  is  heard 
even  under  normal  conditions.  The  ear  under  such  circumstances  will  hear  the 
sounds  conducted  to  the  chest-wall  with  increased  intensity.  This  is  termed 
bronckopkony. 

If  a  pleural  effusion  or  a  pulmonary  inflammation  causes  a  flattening  of  the 
bronchi,  the  sound  of  the  voice  in  the  chest  sometimes  assumes  a  peculiar  bleating 
quality — egopkony. 

Doubtless  the  gradations  of  increased  or  diminished  fremitus  could  be  readily 
demonstrated  by  means  of  the  sensitive  flame  (observed  in  a  rotating  mirror)  or 
by  the  use  of  the  microphone.  For  the  former  there  should  be  employed  an  appa- 
ratus similar  to  the  gas-sphygmoscope,  with  the  lower  part  widened  in  the  shape 
of  a  funnel. 

PRESSURE  IN  THE  AIR-PASSAGES  DURING  RESPIRATION. 

If  a  manometer  be  fastened  in  the  trachea  of  an  animal  in  such  a  manner 
that  respiration  is  not  interfered  with,  the  instrument  will  show  a  negative  pressure 
—3  mm.  of  mercury)  during  inspiration,  and  a  positive  pressure  during  expira- 
tion. Donders  has  modified  this  experiment  for  man  by  introducing  a  U-shaped 
manometer-tube  through  one  nostril,  and  instructing  the  subject  to  breathe  quietly 
through  the  other  nostril  with  the  mouth  closed.  He  found  that  during  each 
quiet  inspiration  the  mercury  showed  a  negative  pressure  of  i  mm.,  and  during 
each  expiration  a  positive  pressure  of  2  or  3  mm.  Aron  experimented  with  patients 
having  a  tracheal  fistula  as  the  result  of  operation,  and  found  during  inspiration 
a  pressure  of  from — 2  to — 6.6  mm.  of  mercury,  during  expiration  from  +0.7  to 
+  6.3  mm.  of  mercury.  In  speaking,  the  corresponding  fluctuation  was  from 
— 6  to  +  7 ,  and  when  coughing  from  — 6  to  +46.1. 

As  soon  as  the  air  is  drawn  in  and  expelled  with  greater  force,  the  fluctuations 
of  pressure  become  more  marked,  especially  in  the  acts  of  speech,  singing,  and 
coughing.  If  forced  respiration  be  practised  with  the  mouth  and  one  nostril 
closed,  so  that  the  respiratory  canal  communicates  only  with  the  manometer, 
the  greatest  inspiratory  pressure  is  — 57  mm.  (between  36  and  74),  and  the  greatest 
expiratory  pressure  is  +87  (between  82  and  100)  mm. 

Notwithstanding  the  higher  expiratory  pressure,  it  must  not  be  inferred  that 
the  expiratory  muscles  are  stronger  than  those  of  inspiration ;  for  during  the  latter 
act  a  series  of  resisting  forces  must  be  overcome,  leaving  a  much  diminished 
supply  of  force  for  the  aspiration  of  the  mercury.  These  resisting  forces  are:  (i) 
The  elastic  tension  of  the  lungs,  which  amounts  to  6  mm.  during  complete  ex- 
piration, but  reaches  30  mm.  during  deepest  inspiration.  (2)  The  lifting  of  the 
weight  of  the  thorax.  (3)  The  elastic  torsion  of  the  costal  cartilages.  (4)  The 
depression  of  the  abdominal  viscera  and  the  elastic  distention  of  the  abdominal 
walls.  All  these  resisting  forces  aid  the  expiratory  muscles  during  expiration. 
With  these  facts  in  view,  there  is  no  doubt  that  the  combined  strength  of  the 
inspiratory  muscles  is  greater  than  that  of  the  expiratory  muscles. 

As  the  lungs,  by  reason  of  their  elasticity,  have  a  tendency  to  collapse,  they 
naturally  exert  a  negative  pressure  within  the  thoracic  cavity.  In  dogs  this 
amounts  to  from  7.1  to  7.5  mm.  of  mercury  during  inspiration,  while  in  expiration 
it  is  naturally  less,  namely  only  4  mm.  The  analogous  values  obtained  by  different 
investigators  on  the  dead  body  vary;  Hutchinson  fixes  them  at  4.5  mm.  and  3  mm. 

The  greatest  pressure  during  inspiration  and  expiration  seems  small  when 
compared  to  the  blood-pressure  in  the  large  arteries.  If,  however,  the  pressure- 
values  obtained  for  the  respired  air  be  estimated  for  the  entire  superfices  of  the 
thorax,  considerable  results  are  obtained. 

To  measure  the  muscular  respiratory  power  in  case  of  illness,  a  U-shaped 
mercurial  manometer  may  be  employed,  provided  with  an  attachment  suitable  for 
introduction  into  a  nostril  or  the  mouth  (Waldenburg's  pnciimatomctcr} .  The  in- 
spiratory pressure  alone  may  be  reduced  (in  the  presence  of  almost  all  diseases 


224  MOUTH-BREATHING    AND    NASAL    BREATHING. 

impairing  the  expansion  of  the  lungs),  or  only  the  expiratory  pressure  may  fall 
(in  cases  of  emphysema  and  of  asthma) ,  or  both  may  be  weakened  (as  occurs  in 
feeble  persons) . 

If  a  forced  inspiration  rarefies  the  air  in  the  air-passages,  the  trachea  and 
bronchi  become  narrowed  and  shortened;  the  reverse  occurs  during  expiration. 

If  a  lung  be  inflated,  air  will  steadily  escape  through  the  walls  of  the  alveoli 
and  trachea.  The  same  thing  takes  pla'ce  during  violent  expiratory  efforts  (cuta- 
neous emphysema  attending  whooping-cough) ,  so  that  pneumothorax,  entrance  of 
air  into  the  blood-vessels,  and  even  death  may  result. 

If  a  dog  be  made  to  breathe  through  Muller's  valve,  by  means  of  which  the 
resistance  to  respiration  may  be  increased  at  will,  it  is  found  that  a  pressure  of 
40  cm.  of  water  is  still  readily  overcome,  that  a  higher  pressure  can  be  overcome 
for  a  short  time,  and  one  of  70  cm.  not  at  all. 

Until  birth  the  airless  lungs  lie  collapsed  (atelectatic)  in  the  chest-cavity,  and 
fill  it,  so  that  pneumothorax  is  not  produced  if  the  thorax  be  opened  in  a  dead 
fetus.  Even  in  children  that  have  lived  for  eight  days  and  have  breathed  normally, 
the  lungs  do  not  collapse  when  the  pleural  cavity  is  opened,  but  remain  in  contact 
with  the  chest-wall.  It  is  only  after  further  growth  that  the  thorax  becomes  so 
large  that  the  lungs  must  expand  under  elastic  tension;  only  then  will  opening 
of  the  thorax  cause  the  lungs  to  contract  into  a  smaller  volume.  Hermann  calls 
attention  to  the  fact  that  a  lung  containing  air  cannot  be  emptied  by  pressure 
from  without.  The  reason  for  this  is  that  the  small  bronchi  will  be  closed  by 
the  pressure  before  the  air  can  leave  the  alveoli.  The  muscles  of  expiration, 
therefore,  have  not  the  power  to  compress  the  lungs  until  they  are  airless;  but, 
on  the  other  hand,  the  inspiratory  muscular  power  is  sufficient  to  expand  the 
lungs  beyond  the  state  of  elastic  equilibrium.  Hence,  the  physical  attributes  of 
the  lungs  limit,  to  a  certain  extent,  the  mechanism  of  respiration:  the  muscles  of 
inspiration  expand  the  lungs  and  at  the  same  time  increase  their  elastic  tension, 
while  the  expiratory  muscles  can  only  diminish  the  tension,  without  being  able 
to  abolish  it  altogether. 

MOUTH-BREATHING  AND  NASAL  BREATHING. 

Quiet  respiration  is  usually  performed  with  the  mouth  closed,  pro- 
vided the  nose  be  unobstructed.  The  current  of  air  passes  through  the 
naso-pharyngeal  cavity,  and  there  undergoes  certain  changes:  (i)  Its 
temperature  is  increased  to  the  extent  of  -f  of  the  difference  between 
its  original  temperature  and  that  of  the  body.  (2)  At  this  increased 
temperature  it  is  saturated  with  aqueous  vapor.  These  changes  are 
made  so  that  the  cold,  dry  air  does  not  irritate  the  lining  of  the  lungs. 
(3)  Dust-particles  may  cling  to  the  mucus  covering  the  irregular  walls 
of  the  air-passages,  and  are  again  conveyed  outward  by  the  ciliated 
epithelium.  The  nasal  secretion  possesses  qualities  harmful  to  many 
bacteria  (for  example,  anthrax-bacilli),  thus  demonstrating  the  salutary 
effect  of  nasal  breathing  when  there  is  danger  of  contagion.  (4)  Finally, 
by  means  of  the  sense  of  smell  bad  air  and  air  impregnated  with  injurious 
admixtures  can  be  recognized.  When  the  mouth  is  open  no  current  of 
air  passes  through  the  nose  during  respiration. 

Pathological. — Permanent  obstruction  of  the  nose,  leading  to  exclusive  mouth- 
breathing,  may  result  in  a  long  series  of  harmful  effects;  namely,  catarrhal  condi- 
tions of  the  pharynx,  the  air-passages,  and  the  middle  ear,  abnormal  formations 
in  the  bones  of  the  mouth  and  the  nose,  pains  in  the  facial  muscles,  changes  in 
speech,  disturbances  of  intellect  (difficulty  in  fixing  the  attention). 

Another  important  phenomenon  is  the  appearance  of  edema  of  the  lungs; 
that  is,  an  exudation  of  serum  from  the  blood  into  the  pulmonary  alveoli.  The 
causes  of  this  condition  are:  (i)  marked  obstruction  to  circulation  in  the  aortic 
system;  for  example,  after  ligation  of  all  of  the  carotid  arteries,  or  of  the  arch 
of  the  aorta  in  such  a  position  that  only  one  carotid  remains  pervious;  (2)  occlusion 
of  the  pulmonary  veins;  (3)  cessation  of  action  in  the  left  ventricle  (following 
mechanical  injury),  while  the  right  ventricle  still  continues  to  beat.  All  of  these 
causes  will  produce  at  the  same  time  anemia  of  the  brain,  resulting  in  anemic 


MODIFIED    RESPIRATORY    ACTS. 


225 


irritation  of  the  vasomotor  center,  and  consequent  contraction  of  the  small  arteries 
This  will  cause  an  increased  amount  of  blood  to  enter  the  veins  and  the  right 
heart,  whose  driving  power  increases  the  pulmonary  edema. 

v.  Basch  believes  that  an  overfilling  of  the  pulmonary  capillaries  diminishes 
the  elasticity  of  the  alveoli,  thus  making  the  latter  to  a  certain  extent  more  rigid 
The  expansibility,  therefore,  of  the  lungs  is  diminished. 

MODIFIED  RESPIRATORY  ACTS. 

There  are  a  number  of  characteristic,  partly  involuntary,  partly  voluntary, 
variations  of  the  respiratory  movements,  to  which  the  not  altogether  suitable 
term  abnormal  respiratory  acts  has  been  applied. 

Coughing  consists  in  a  sudden  violent  expiratory  effort,  usually  succeeding 
a  deep  inspiration  and  closure  of  the  glottis,  during  which  effort  the  glottis  is 
sprung  open,  and  any  solid,  fluid  or  gaseous  substance  that  may  be  irritating  the 
respiratory  mucous  membrane  is  expelled.  The  lips  are  parted  during  this  act. 
It  may  be  a  voluntary  or  a  reflex  act,  in  the  latter  case  being  subject  to  the  will 
only  to  a  certain  degree. 

Hawking  consists  in  a  rather  long  expiratory  effort  through  the  narrow 
space  between  the  root  of  the  tongue  and  the  depressed  soft  palate  for  the  purpose 
of  removing  foreign  bodies.  If  the  hawking  be  accomplished  in  an  intermittent 
fashion,  it  is  accompanied  by  a  springing  open  of  the  glottis  (mild,  voluntary 
coughing) .  This  act  is  performed  only  voluntarily. 

Sneezing  consists  in  a  sudden  expiratory  effort  through  the  nose,  accom- 
panied by  a  sudden  opening  of  the  naso-pharynx,  previously  closed  by  the  soft 
palate.  The  purpose  is  to  expel  mucus  or  foreign  bodies.  It  is  very  seldom  per- 
formed with  the  mouth  open,  and  is  preceded  by  a  single  or  by  repeated  spas- 
modic inspiration.  The  glottis  is  always  wide  open.  This  act  occurs  only  as  a 
reflex  through  irritation  of  the  sensory  nerves  of  the  nose,  or  as  a  result  of  a 
bright  light  suddenly  falling  upon  the  retina.  The  reflex  may  be  to  a  certain 
extent  inhibited  by  marked  excitation  of  sensory  nerves,  such  as  rubbing  the 
nose,  or  pressing  the  hyoid  bone  forcibly  upward.  Habitual  use  of  nasal  irritants, 
such  as  snuff,  blunts  the  sensory  nerves  against  reflex  excitation.  Coughing  and 
sneezing  rarely  occur  simultaneously. 

Snorting  and  Blowing  the  Nose ;  Snuffing ;  Sniffing. — Noisy,  forced  breathing 
through  the  nose  is  designated  snorting.  Blowing  the  nose  consists  in  a  strong, 
noisy,  expiratory  effort  made  through  nostrils  that  have  been  narrowed,  either  by 
the  fingers  or  by  the  muscles  of  the  nose  and  the  upper  lip,  the  object  being  to 
remove  either  foreign  bodies  or  mucus.  Snuffing  consists  of  drawing  substances 
up  into  the  nose  by  a  noisy  inspiration,  the  mouth  being  closed,  and  the  nostrils 
often  being  narrowed  by  the  action  of  the  muscles  of  the  nose  and  the  upper  lip. 
Sniffing  consists  in  drawing  air  up  into  the  nose  by  a  succession  of  short 
inspiratory  efforts,  for  the  purpose  of  smelling.  The  act  is  frequently  accompanied 
by  rustling  noises  and  movements  of  the  nostrils,  while  the  mouth  is  held  closed. 
All  these  actions  are  voluntary. 

Snoring  results  from  breathing  with  the  mouth  open,  the  current  of  air 
during  both  inspiration  and  expiration  causing  noisy,  vibrating  movements  of  the 
relaxed  soft  palate.  It  usually  occurs  involuntarily  during  sleep,  but  it  may  also 
be  produced  voluntarily. 

Gargling  consists  in  the  noisy  slow  escape  of  the  expired  air  in  the  form 
of  bubbles  through  a  mass  of  fluid  held  between  the  root  of  the  tongue  and  the 
soft  palate,  while  the  head  is  thrown  back.  The  act  is  voluntary. 

Crying  is  called  forth  by  the  emotions,  and  consists  in  short,  deep  inspira- 
tions, with  prolonged  expirations,  the  glottis  being  narrowed,  and  the  muscles  of 
the  face  and  jaw  being  relaxed  (with  contraction  of  the  zygomaticus  minor) ;  tears 
are  secreted,  and  lamenting,  inarticulate  sounds  are  often  emitted.  In  conjunction 
with  intense,  prolonged  crying  there  often  arise  sudden,  spasmodic,  involuntary 
contractions  of  the  diaphragm,  which,  when  attended  with  valve-like  approxima- 
tion of  the  vocal  bands,  give  rise  to  the  inspiratory  sound  known  as  sobbing.  This 
act  is  purely  involuntary.  The  sobbing  that  occurs  so  frequently  during  the 
agonal  period  may  be  explained  by  the  electrical  influence  of  the  contraction  of 
the  heart  on  the  phrenic  nerves,  which  become  highly  irritable  in  the  act  of  dying. 

Sighing  is  a  prolonged  respiratory  movement,  usually  accompanied  by  a 
mournful  sound,  often  aroused  involuntarily  by  painful  emotions. 

Laughing  consists  in  a  quick  succession  of  short  expirations  through  vocal 
15 


226 


CHEMISTRY    OF    RESPIRATION. 


bands  that  are  stretched  for  high  notes,  and  are  alternately  approximated  and 
separated,  while  characteristic,  inarticulate  sounds  are  emitted  from  the  larynx, 
with  vibrations  of  the  soft  palate.  The  mouth  is  usually  open,  and  the  face  is 
drawn  into  a  characteristic  position  by  the  zygomaticus  major  (not  the  risorius 
muscle).  Laughing  is  usually  aroused  involuntarily  by  agreeable  conceptions,  or 
by  feeble,  sensory  irritation,  such  as  tickling.  It  may  to  a  certain  extent  be 
repressed  by  the  will,  as  by  forcibly  closing  the  mouth  and  holding  the  breath; 
also  by  painful  irritation  of  sensory  nerves,  as  by  biting  the  tongue  or  the  lips. 

Yawning  consists  in  a  prolonged,  deep  inspiration,  with  the  mouth,  the 
palatal  arch  and  the  glottis  widely  open,  successively  calling  into  play  numerous 
inspiratory  muscles.  Expiration  is  shorter,  and  both  are  often  accompanied  by  a 
prolonged,  characteristic  sound.  There  also  occurs  frequently  a  general  stretching 
of  the  bodily  muscles.  The  act  is  always  involuntary,  being  usually  incited  by 
sleepiness  or  monotony. 

CHEMISTRY  OF  RESPIRATION. 

The  problem  here  is  to  estimate  qualitatively  and  quantitatively 
the  gases  expelled  during  respiration.  If  the  results  be  compared  with 
the  gaseous  composition  of  inspired,  atmospheric  air,  a  picture  may  be 
obtained  of  the  interchange  of  gases  occurring  during  respiration. 

QUANTITATIVE   ESTIMATION    OF    THE    CARBON   DIOXID,    THE 

OXYGEN,  AND  THE   AQUEOUS  VAPOR  IN   GASEOUS 

MIXTURES. 

Estimation  of  the  Carbon  Dioxid. 

The  volume  of  carbon  dioxid  may  be  estimated  by  means  of  Vierordt's 
antkracometer  (Fig.  85,  II).  The  gaseous  mixture  is  received  and  enclosed  in  a 
graduated  tube  r  r,  previously  filled  with  water,  and  provided  at  one  end  with 


T[ 


FIG.  85.— I.  Apparatus  for  the  Collection  of  Expired  Air  (after  Andral  and  Gavarret). 
II.  Carl  Vierordt's  Anthracometer. 


a  bulb  of  known  capacity.  The  bottle  n,  filled  with  a  solution  of  potassium 
hydrate,  is  then  screwed  on  the  end-piece  h.  The  stop-cock  is  opened,  and  the 
potassium-solution  is  allowed  to  run  up  into  the  tube,  the  latter  being  agitated 


METHODS    OF    INVESTIGATION. 


227 


until  all  the  carbon  dioxid  is  absorbed  by  the  potassium,  with  the  forma- 
tion of  potassium  carbonate.  Then  the  solution  is  allowed  to  run  back  into  the 
bottle,  the  stop-cock  is  closed,  and  the  potassium-bottle  is  removed.  The  end  of 
the  tube  is  dipped  into  water,  and  the  latter  is  allowed  to  rise  in  the  tube.  The 
volume  of  water  thus  admitted  is  equal  to  the  volume  of  carbon  dioxid  removed 
by  the  potassium-solution. 

Determination  by  Weight. — A  considerable  volume  of  the  gaseous  mixture 
is  passed  through  Liebig's  bulbs,  filled  with  a  solution  of  potassium  hydrate  and 
arranged  in  a  combination  such  as  that  of  Scharling's  apparatus  (Fig.  86,  e,  f,  g). 

Determination  by  Titration. — A  considerable  volume  of  the  air  to  be  exam- 
ined is  conducted  through  a  definite  quantity  of  a  known  solution  of  barium 
hydrate.  The  carbon  dioxid  combines  to  form  barium  carbonate.  The  solution 
is  then  neutralized  with  a  titrated  solution  of  oxalic  acid.  The  quantity  of  oxalic 
acid  necessary  to  neutralize  the  remaining  barium  hydrate  varies  inversely  with 
the  amount  of  barium  already  combined  with  the  carbon  dioxid. 

Estimation  of  the  Oxygen. 

The  volume  of  oxygen  may  be  determined  in  two  ways:  (a)  By  combining  the 
gas  with  potassium  pyrogallate.  Vierordt's  anthracometer  may  be  employed  for 
this  purpose,  substituting  a  solution  of  potassium  pyrogallate  for  that  of  potassium 
hydrate.  (6)  By  explosion  in  an  eudiometer. 

Estimation  of  the  Aqueous  Vapor. 

The  volume  of  air  to  be  examined  is  allowed  to  pass  either  through  a  bulb- 
apparatus  containing  concentrated  sulphuric  acid,  or  through  a  tube  filled  with 
pieces  of  calcium  chlorid.  In  both  cases  the  water  is  energetically  abstracted, 
and  the  increase  in  weight  will  give  the  amount  of  water  in  the  air  examined. 

METHODS  OF  INVESTIGATION. 

Collecting  the  Expired  Air. 

If  only  the  gases  exhaled  from  the  lungs  are  to  be  collected,  the  bell-jar 
of  the  spirometer  (Fig.  76)  may  be  used,  suspended  in  a  concentrated  solution 
of  sodium  chlorid  to  limit  the  gas-absorption.  Andral  and  Gavarret  permitted 
several  successive  expirations  to  be  made  into  a  large  bell- jar  (Fig.  85,  I,  C). 
For  this  purpose  a  mouth-piece  M  was  applied  in  an  air-tight  manner  over  the 
mouth,  the  nostrils  being  closed;  the  direction  of  the  air-current  was  regulated  by 


FIG.  86. — Respiration  Apparatus  of  Scharling. 

means  of  two  so-called  Muller's  mercurial  valves  (a,  b),  which  allowed  the  air  to 
pass  only  in  the  direction  of  the  arrows. 

If  the  gases  given  off  from  the  skin  during  perspiration  are  to  be  investigated, 
as  well  as  those  from  the  lungs,  then  the  subject  must  be  placed  in  a  closed  cham- 
ber, from  which  the  gases  may  be  withdrawn  for  experimental  purposes. 

The  Most  Important  of  the  Respiration  Apparatus.— (a)  The  apparatus  of  Schar- 
ling (Fig    86)   consists  primarily  of  a  closed  chamber  A,  capable  ot  contain: 
a  human  being.     The  chamber  has  an  afferent  opening  z,  and  an  efferent  opening 
b.     The  latter  is  connected  with  an  aspirating  contrivance  C,  consisting  of  a  g< 
sized  barrel  filled  with  water.     It  is  evident  that  when  the  water  flows  out  ot  the 


228 


METHODS    OF    INVESTIGATION. 


barrel,  an  uninterrupted  stream  of  fresh  air  enters  the  chamber  A,  and  the  air 
in  the  chamber,  mixed  with  the  respired  gases,  escapes  toward  the  barrel.  Con- 
nected with  the  afferent  opening  z  is  a  set  of  Liebig's  bulbs  d,  filled  with  a  solution 
of  potassium  hydrate  through  which  the  entering  air  passes  and  is  deprived 
of  its  carbon  dioxid,  so  that  the  subject  breathes  air  completely  free  of  carbon 
dioxid.  Upon  leaving  the  efferent  opening  b  the  air  is  first  conducted  through 
the  tube  e,  in  which  the  aqueous  vapor  is  absorbed  by  sulphuric  acid,  and  its 
amount  may  be  determined  by  the  increase  in  the  weight  of  the  tube.  Then  the  air 
passes  through  the  potassium-bulbs  f,  where  all  the  carbon  dioxid  is  absorbed. 
The  tube  g,  filled  with  sulphuric  acid,  is  intended  for  the  purpose  of  absorbing 
the  aqueous  vapor  conveyed  by  the  air  from  f .  The  increase  in  weight  of  f  -f-  g 
represents  the  weight  of  the  absorbed  carbon  dioxid.  The  volume  of  air  inter- 
changed may  be  estimated  from  the  contents  of  the  barrel. 

(6)   Regnault  and  Reiset's  apparatus   (Fig.   87)   consists  of  a  bell- jar  R,  in 
which  is  placed  the  animal  (dog)  to  be  experimented  upon.      Surrounding  this 


CaCh 


FIG.  87. — Diagrammatic  Representation  of  Regnault  and  Reiset's  Respiration  Apparatus. 


jar  is  a  cylinder  g  g,  which  may  be  used  for  calorimetric  observations,  a 
thermometer  t  being  introduced  for  this  purpose.  The  bell-jar  has  leading  into 
it  the  tube  c,  through  which  is  introduced  a  measured  quantity  of  oxygen  (Fig. 
87,  O),  which  (Fig.  87,  CO3)  has  given  off  to  the  potassium  hydrate  any  remaining 
admixture  of  carbon  dioxid.  The  oxygen  in  the  measuring  vessel  O  is  forced 
toward  the  bell-jar  R  by  a  solution  of  calcium  chlorid,  coming  from  a  basin  pro- 
vided with  large  bottles  (Ca  C12).  From  R  pass  the  tubes  d  and  e,  connected  by 
rubber  tubes  with  the  communicating  potash-bottles  (K  OH,  k  o  h),  which 
may  be  alternately  raised  and  lowered  by  means  of  the  scale-beam  w.  By  these 
means  the  air  is  aspirated  from  R,  and  the  carbon  dioxid  is  absorbed  by  the  solution 
of  potassium  hydrate.  At  the  end  of  the  experiment  the  increase  in  weight  of 
the  bottles  represents  the  quantity  of  carbon  dioxid  expired.  The  amount  of 
oxygen  inspired  is  measured  directly  in  the  measuring  vessel  O.  Finally,  the 
manometer  f  shows  whether  there  is  a  difference  between  the  air-pressure  within 
the  jar  and  that  on  the  outside. 

(c)  The  most  complete  apparatus  is  that  of  v.  Pettenkofer  (Fig.  88) .  A  cham- 
ber Z,  made  of  metal  and  provided  with  a  door  and  a  window,  has  an  opening  for 
the  entrance  of  air  at  a.  A  double  suction-pump  P  P1(  driven  by  steam,  renews 


COMPOSITION    AND    PROPERTIES    OF    ATMOSPHERIC    AIR.  229 

continuously  the  air  in  the  chamber.  This  air  is  first  conducted  into  the  vessel  b 
which  is  tilled  W1th  pumice-stone  saturated  with  water.  Here  the  air  becomes 
saturated  with  aqueous  vapor,  and  then  passes  through  the  gasometer  c,  which 
indicates  the  total  volume  of  the  interchanged  air;  tht  latter  is  then  discharged 
into  the  outer  atmosphere. 

The  main  tube  x,  leading  from  the  chamber,  carries  a  mercurial  manometer  q 
±9r  the  detection  of  possible  variations  in  pressure  within  the  room      This  tube 
gives  off  a  branch  tube  n, through  which  the  air  passes  for  chemical  examination 
I  he  air  in  this  tube  is  driven  by  a  suction-apparatus  M  M1?  constructed  on  the 
principle  of  Muller  s  mercurial  valve,  and  worked  by  the  same  steam-engineias 


.FiG.  88. — Diagram  of  v.  Pettenkofer's  Respiration  Apparatus. 

the  pump  P  Pj.  Before  entering  the  pump  the  air  passes  through  the  sulphuric- 
acid  bulbs,  from  whose  increase  in  weight  the  amount  of  aqueous  vapor  can  be 
estimated.  After  leaving  the  pump  the  air  passes  through  the  tube  R,  filled  with 
baryta-water,  which  absorbs  the  carbon  dioxid.  The  quantity  of  air  passing 
through  the  branch  tube  n  is  then  measured  by  the  gasometer  u,  after  which  it 
finally  passes  into  the  atmosphere.  The  second  branch  tube  N  provides  for^an 
examination  of  the  air  before  entering  the  chamber,  by  an  apparatus  identical 
with  that  placed  on  the  tube  n.  The  excess  of  carbon  dioxid  and  water  found 
in  n  over  that  in  N  is  due  to  the  respiratory  activity  of  the  subject  placed  in  the 
chamber. 

COMPOSITION  AND  PROPERTIES  OF  ATMOSPHERIC  AIR. 

The  dry  atmosphere  contains: 

Percentage  in  Percentage  in 

Gas.  Weight.  Volume. 

0 23.015  20.922  Including  i  per  cent,  in 

N 76.985  79-02  volume  of  argon,  together 

CO2 0.029-0.034  with  helion,  and  i  part  of 

krypton  in  20,000  parts  of 
air. 

The  air  contains  likewise  xenon,  neon,  coronium   (lighter  than  hydrogen), 
and  less  than  one-millionth  part  of  aetherium   (which  latter  possesses  a  specific 


230  COMPOSITION    AND    PROPERTIES    OF    ATMOSPHERIC    AIR. 

gravity  only  To<jo7  that  of  hydrogen,  but  a  power  of  heat-conduction  100  times 
as  great  as  that  element,  and  a  density  of  only  T^THF  "that  of  the  air).  These 
elements  have  not  been  investigated  physiologically.  ^therium  is  probably 
a  composite  substance,  and  perhaps  plays  the  role  that  has  been  previously 
ascribed  to  luminiferous  ether. 

Aqueous  vapor  is  always  present;  its  amount  usually  increases 
with  the  height  of  the  temperature.  With  reference  to  the  humidity 
of  the  air  there  must  be  distinguished :  (a)  the  absolute  humidity,  that 
is,  the  quantity  of  aqueous  vapor  contained  in  a  volume  of  air;  (b)  the 
relative  humidity,  that  is,  the  quantity  of  aqueous  vapor  contained  in 
a  volume  of  air  in  relation  to  its  temperature.  The  latter  increases  with 
rising  temperature. 

The  relative  humidity  is  determined  either  by  means  of  the  hygrometer  of 
Klinkerfues  or  by  the  psychrometer  of  August.  The  latter  consists  of  two  accu- 
rately graduated  thermometers,  the  bulb  of  one  being  kept  constantly  moistened 
by  means  of  a  wet  cloth.  As  a  result  of  evaporation  of  the  water  on  the  bulb, 
cooling  will  take  place,  and  the  fall  of  the  thermometer  will  vary  directly  with 
the  rapidity  of  evaporation,  that  is,  with  the  dryness  of  the  atmosphere.  From  the 
difference  in  the  readings  of  the  two  thermometers  the  tension  of  the  aqueous  vapor 
in  the  air  may  be  calculated  according  to  the  formula :  e  =  e1  -k  X  (t  -t1)  X  b ; 
in  which  e  represents  the  desired  tension  of  the  aqueous  vapor  in  the  air  at  the  pre- 
vailing temperature,  as  indicated  by  the  dry  thermometer;  e1  the  tension  of  the 
aqueous  vapor  that  prevails  when  the  air  is  completely  saturated  with  watery 
vapor  at  the  temperature  of  the  moist  thermometer  (to  be  ascertained  from  works 
on  physics);  b  the  state  of  the  barometer  in  millimeters  of  mercury;  t  the  tem- 
perature of  the  dry  thermometer,  and  t1  that  of  the  moist  thermometer  (expressed 
in  degrees  Centigrade)  ;  and  k  an  empirically  obtained  constant  =  o.ooi. 

Experience  has  taught  that  man  breathes  best  in  an  air  that  is  not  completely 
saturated  with  watery  vapor  in  accordance  with  its  temperature,  but  only  to 
70  per  cent,  of  that  amount.  Air  that  is  too  dry  irritates  the  mucous  membranes 
of  the  respiratory  organs;  while  air  that  is  too  moist  arouses  a  feeling  of  uncom- 
fortable oppression,  and  in  warmer  air  a  sensation  of  oppressive  sultriness.  At  a 
lower  temperature  (15°  C.)  dry  air  is  more  comfortable  than  moist  air;  at  from 
24°  to  29°  C.  dry  air  feels  cooler  than  moist  air.  With  marked  dryness  of  the 
atmosphere  a  temperature  of  29°  C.  is  well  borne;  but  exceedingly  damp  air  becomes 
unendurable  for  any  length  of  time  at  24°  C.  In  the  living  room  and  in  the  sick- 
room attention  should,  therefore,  be  paid  to  the  correct  degree  of  atmospheric 
humidity.  (Sprinkling  with  water,  or  in  winter  placing  a  basin  of  water  on  the  stove 
may  be  resorted  to.)  Rooms  that  are  too  damp,  on  account  of  dampness  of  the 
walls  or  the  floor,  are  prejudicial  to  health. 

The  following  factors  are  known  to  influence  the  absolute  quantity  of  aqueous 
vapor  in  the  air:  (i)  At  the  sea-shore  during  the  day  the  amount  is  increased 
with  a  rising  temperature,  and  diminished  with  a  falling  temperature.  (2)  In  the 
flat,  inland  country  the  humidity  rises  from  sunrise  to  noon,  then  diminishes  until 
evening;  rises  again  during  the  first  part  of  the  night,  and  finally  falls  again. 
(3)  On  high  mountains  the  mid-day  decrease  in  humidity  does  not  occur.  (4)  _ South- 
western winds  in  summer  are  accompanied  by  the  greatest  humidity,  while  east 
winds  in  winter  bring  the  lowest  degree  of  humidity. 

With  reference  to  the  relative  amount  of  moisture  it  is  to  be  noted:  (i)  that 
it  is  usually  greatest  at  sunrise,  and  least  toward  noon;  (2)  that  it  is  diminished  on 
high  mountains;  (3)  that  it  is  greater  in  winter  than  in  summer;  (4)  that  it  is 
usually  greater  with  south  and  west  winds  than  with  north  and  east  winds. 

In  the  course  of  the  year's  changes,  that  air  which  is  found  to  be  the  richest 
in  water  absolutely  is  the  poorest  relatively.  For  example,  the  air  in  summer 
contains  absolutely  about  three  times  as  much  watery  vapor  as  in  midwinter,  and 
still  the  summer  air  is  relatively  dryer  than  that  of  winter.  In  the  course  of  the 
seasons  the  absolute  humidity  rises  and  falls  with  the  mean  temperature.  The 
average  relative  humidity  amounts  to  about  70  per  cent,  in  temperate  climates. 

With  increasing  elevation  above  sea-level  the  density  of  the  air 
diminishes. 

It  likewise  diminishes  with  increase  of  temperature. 


COMPOSITION    OF    EXPIRED    AIR. 


231 


With  every  increase  of  about  186  meters  in  elevation  above  the 
surface  of  the  earth,  the  temperature  (irregularly,  it  is  true)  falls  i°  C. 

Above  a  level  of  4000  meters  the  cold  increases  in  greater  proportion;  at  a 
level  of  7000  meters  the  most  severe  degree  of  cold  prevails  without  variation, 
being  the  same  at  all  seasons. 

COMPOSITION  OF  EXPIRED  AIR. 

The  expired  air  is  rich  in  carbon  dioxid,  of  which  it  contains  on  an 
average  4.38  per  cent,  by  volume  (from  3.3  to  5.5  per  cent.)  during 
quiet  respiration.  The  amount  of  carbon  dioxid  is,  therefore,  more  than 
100  times  greater  than  in  the  atmosphere. 

The  expired  air  contains  less  oxygen  (on  an  average  4.782  per  cent, 
less     by    volume)    than     inspired,     atmospheric     air, 
namely,  only  16.033  per  cent,  by  volume.  A 

Hence,  during  respiration  there  is  more  oxygen 
taken  into  the  body  from  the  air  than  there  is  carbon 
dioxid  expelled;  so  that  the  volume  of  the  expired 
air  is  from  one-fiftieth  to  one-fortieth  less  than  the 
volume  of  inspired  air  (under  the  same  conditions  of 
temperature,  humidity,  and  pressure).  This  relation 
of  the  expired  carbon  dioxid  to  the  inspired  oxygen 
(4.38  :  4.782)  is  termed  the  respiratory  quotient: 

=  4.?&)  =  0-916- 

A  small  excess  of  nitrogen  is  admixed  with  the 
expired  air.  It  has  been  found  that  not  all  of  the 
nitrogen  taken  up  with  the  food  appears  again  in  the 
excretions  (urine  and  feces). 

The  expired  air  during  quiet  respiration  is  satur- 
ated with  aqueous  vapor.  It  is,  therefore,  evident 
that,  by  reason  of  the  changes  in  the  amount  of  water 
contained  in  the  air,  a  varying  quantity  of  water  must 
be  excreted  by  the  body  through  the  lungs.  With 
rapid  respirations  Moleschott  observed  the  percentage 
of  aqueous  vapor  to  fall.  The  surrounding  tempera- 
ture also  has  an  influence  on  the  amount  of  water  given 
off:  the  minimum  occurs  at  15°  C.,  while  below  this 
point  the  amount  increases  moderately,  and  above  the 
quantity  rises  rapidly. 

The  expired  air  possesses  a  considerable  degree  of 
heat  (on  an  average  36.3°  C.),  which  at  moderate  ex- 
ternal temperatures  approaches  quite  closely  that  of 
the  body;  but  even  with  extreme  variations  of  the 
surrounding  temperature  the  degree  of  heat  main- 
tains itself  within  the  same  limits. 

Valentin    and    Brunner    employed    the    instrument  repre- 
sented in  Fig.   89  to  determine  the  temperature  of  the  expired 
air.     It    consists    of    a  glass  tube  A  A,  with  a  mouth-piece  £ 
and    an    inserted,    delicate    thermometer    C.     Inspiration    is    made  through  the 
nose,  and  the  air  is  slowly  expelled  through  the  mouth-piece  into  the  tube. 
Temperature  of  the  Air.  Temperature  of  the  Expired  Air. 

-6.3°  C.  +29-8°  C. 

+  i7°-i9°C  +  36.2-37°  C. 

+  44°  C. 


FIG.  89. — Apparatus 
for  Measuring 
the  Temperature 
of  the  Expired 
Air. 


232  EXTENT    OF    THE    DAILY    INTERCHANGE    OF    GASES. 

It  would  certainly  be  highly  interesting  to  determine  whether  the  temperature 
of  the  expired  air  undergoes  change  by  reason  of  inflammations,  disturbances  of 
the  circulation,  or  degenerations  in  the  lungs. 

Mosso  and  Rondelli  allowed  dogs  to  breathe  air  at  a  temperature  of  from 
150°  to  160°  C.,  and  found  that  the  air  in  the  bronchi  was  of  a  higher  temperature 
(39.3°  or  37.8°  C.)  than  the  rectum. 

The  diminution  in  volume  of  the  expired  air  mentioned  already 
is  compensated  for  by  the  warming  of  the  inspired  air  in  the  air- 
passages,  and  by  the  tension  of  the  contained  aqueous  vapor,  so  that 
the  volume  of  the  air  expired  is  even  one-ninth  greater  than  that  of  the 
air  inspired. 

Exceedingly  small  quantities  of  ammonia  are  admixed  with  the 
expired  air,  amounting  to  about  0.0204  gram  in  twenty-four  hours;  they 
are  probably  evolved  from  the  blood. 

Small  quantities  of  hydrogen  and  marsh-gas  (CH4),  both  absorbed 
from  the  intestines,  are  likewise  exhaled.  Reiset  observed  that  in  herbiv- 
orous animals  the  marsh-gas  exhaled  in  twenty-four  hours  amounted  to 
as  much  as  30  liters. 

The  aqueous  vapor  condensed  by  low  temperature  from  the  expired  air  of 
some  persons  acts  as  a  poison  when  injected  subcutaneously,  in  consequence  of 
the  presence  of  a  volatile  base.  These  are  exceptions,  however. 

EXTENT  OF  THE  DAILY  INTERCHANGE  OF  GASES. 

As  more  oxygen  is  normally  taken  in  than  is  excreted  in  the  carbon 
dioxid  (equal  volumes  of  oxygen  and  carbon  dioxid  containing  equal 
quantities  of  oxygen),  a  part  of  the  oxygen  taken  in  must  be  used  for 
other  oxidation-purposes.  According  to  the  extent  of  the  latter,  there 
must  be  considerable  variation  in  the  relation  of  the  inspired  oxygen  to 
the  expired  carbon  dioxid  (the  quotient  —*,  which  is  given  as  being 
on  an  average  0.916  during  normal,  quiet  respiration).  Within  the 
limits  of  the  normal  vital  processes,  not  only  may  the  excretion  of 
carbon  dioxid  be  less  than  the  stated  average,  but  it  may  even  be  con- 
siderably in  excess  of  the  absorption  of  oxygen.  With  such  varia- 
tions it  is  evident  that  the  estimation  of  the  amount  of  carbon 
dioxid  alone  cannot  be  a  reliable  measure  of  the  total  interchange  of 
gases.  A  complete  insight  into  the  gaseous  balance  can  be  obtained 
only  by  a  simultaneous  estimation  of  the  oxygen  taken  in  and  of  the 
carbon  dioxid  given  off. 

SUMMARY  OF  THE  GASEOUS  INTERCHANGE. 

Absorption  in  twenty-four  hours :  Excretion  in  twenty-four  hours : 

Oxygen,    744    gm.  =516,500    cu.  cm.          Carbon  dioxid,   900  gm.  =455,500  cu. 
(Carl  Vierordt) .  cm.    (Carl  Vierordt) ,  hourly  31.5- 

5 1 1-658 gm. (Speck).  33     gm.    (J.     Ranke) ;       32.8-33.4 

(The  volumes  are  determined  for  o°  gm.     (v.    Liebermeister) ;     34   gm. 

and  the  mean  barometer.)  (Panum) ;  36  gm.  (Scharling). 

Water,  640   gm.  (Valentin);     330  gm. 
(Carl  Vierordt). 

FACTORS   INFLUENCING   THE    EXTENT    OF   THE    RESPIRATORY 
EXCHANGE  OF  GASES. 

The  process  of  carbon-dioxid  formation  consists  probably  of  two 
separate  stages.  In  the  first  place,  through  the  presence  of  oxygen 


EXTENT    OF    THE    RESPIRATORY    EXCHANGE    OF    GASES.  233 

in  the  tissues,  there  are  formed  combinations  containing  carbon  dioxid 
which  are  oxidation-products  of  substances  containing  carbon  The 
second  step  consists  in  the  separation  of  this  carbon  dioxid, 'which 
can  take  place  even  without  the  absorption  of  oxygen.  Both  processes 
do  not  always  take  place  uniformly;  at  times  there  is  a  preponderance 
in  the  formation  of  substances  destined  for  decomposition  and  carbon- 
dioxid  formation,  while  at  other  times  the  liberation  of  carbon  dioxid 
predominates,  with  a  diminution  in  the  substances  mentioned. 

The  respiratory  interchange  of  gases  (also  the  respiratory  quotient)  is,  within 
wide  limits,  independent  of  the  amount  of  oxygen  in  the  air  and  the  pressure  of 
the  atmosphere.  According  to  Schmiedeberg  the  oxidation  in  the  tissues  depends 
upon  a  synthesis  accompanied  by  a  separation  of  water,  for  which  purpose  the 
blood  supplies  the  necessary  oxygen. 

The  processes  under  consideration  are  affected  by: 
i.  Age. — Until  the  body  is  fully  developed,  the  output  of  carbon 
dioxid^ increases,  while  from  that  point  it  diminishes  with  the  decline 
in  bodily  strength.  Hence,  in  young  persons  the  absorption  of  oxygen 
is  relatively  greater  in  comparison  with  the  carbon  dioxid  given  off.  At 
all  other  periods  of  life  both  values  correspond  rather  closely.  For 
example : 


Age. 
Years. 

In  Twenty-four 
CO*  Excreted  in  Grams  —  Carbon. 

Hours. 
O  Absorbed  in  ( 

375  gra 

652 
809 

854 
914 

757 
689 

jrams. 

ms. 

8,  

443    £Tc 

ims  =  121  ca 
=  209 
=  259 
=  274 

=  293 

=  242 

=    211 

rbon 

15,  
16,  

T-T-O    5ic 
.  .  .     766 

o  ^o 

18-20  
20-24, 
40-60  
60-80,  .... 

.  .  .  1003 
.  .  .1074 
.  .  .    889 
.  .  .    810 

In  children  the  excretion  of  carbon  dioxid  is  absolutely  less,  but  rela- 
tively greater,  than  in  adults;  weight  for  weight,  children  excrete  almost 
twice  as  much  carbon  dioxid  as  adults.  The  new-born  also  consumes 
relatively  more  oxygen  than  adults.  In  the  fetus  of  the  sheep  the  con- 
sumption of  oxygen  was  found  to  be  only  one-sixteenth  that  in  the  full- 
grown  animal. 

2.  Sex. — Males  from  the  eighth  year  to  advanced  age  give  off  about 
one-third  more  carbon  dioxid  than  do  females.     This  difference  is  still 
more  marked  at  the  time  of  puberty,  when  it  amounts  to  about  one-half. 
After  the  cessation  of  menstruation  there  is  an  increase,  and  in  old  age 
again  a  decrease  in  the  amount  of  carbon  dioxid  given  off.     Pregnancy 
progressively  increases  the  output,  for  evident  reasons. 

Young  girls,  under  otherwise  similar  conditions,  exhale  less  carbon  dioxid  than 
boys;  the  proportion  being  100  :  140.  Boys  of  from  nine  to  twelve  years  of  age 
exhale  from  33  to  34  grams  in  an  hour.  In  the  thirteenth  year  the  excretion  of 
carbon  dioxid  rises  rapidly,  and  maintains  itself  at  a  high  level  until  the  nine- 
teenth year  (from  42  to  45  grams  in  an  hour).  Then  it  falls  between  twenty 
and  thirty  years  to  38  grams;  and,  finally,  between  thirty-five  and  sixty  years  ft 
is  from  34  to  37  grams.  Girls  between  eight  and  ten  years  old  excrete  from  23 
to  25  grams;  between  eleven  and  thirty  years  old  they  exhale  from  26  to  32  grams, 
and  at  sixty-five  years  of  age  26  grams.  Younger  and  lighter  individuals  of  both 
sexes,  with  their  greater  body  surface,  give  off  more  carbon  dioxid  (in  propor- 
tion to  their  weight)  than  older,  heavier,  and  more  compact  persons. 

3.  Constitution. — As   a   rule,    muscular,    active    individuals    require 
more   oxygen   and   excrete    more    carbon    dioxid    than    less   muscular 


234  EXTENT    OF    THE    RESPIRATORY    EXCHANGE    OF    GASES. 

and  energetic  persons  of  the  same  size  and  weight.  The  consumption 
of  oxygen  and  the  excretion  of  carbon  dioxid  are  in  inverse  proportion 
to  the  extent  of  body  surface.  In  this  connection  the  respiratory 
gaseous  interchange  pursues  a  course  parallel  with  that  of  heat-pro- 
duction. 

4.  Diurnal  and  Nocturnal  Variations. — In  general  there  is  during 
sleep  a  diminution  in  the  excretion  of  carbon  dioxid  as  compared  with 
the  waking  state  (the  proportion  being  100  :  145,  in  the  most  extreme 
case  100  :  169).     This  is  proportional  to  the  diminution  of  the  general 
metabolism  resulting  from  the  constant  heat  of  the  surroundings  (the 
bed),  the  darkness,  the  absence  of  muscular  activity,  and  the  abstinence 
from  food  (see  5,  9,  6,  7).     According  to  v.  Pettenkofer  and  C.  v.  Voit 
and  others  a  slight  accumulation  of  oxygen  seems  to  take  place  during 
sleep.     After  awaking  in  the  morning  the  respirations  become  deeper 
and  more  rapid,  with  at  first  an  increase  in  the  excretion  of  carbon 
dioxid.     In  the  course  of  the  morning,  however,  the  excretion  diminishes 
again,  until  the  midday  meal  causes  a  fresh  increase  to  the  maximum. 
A  falling  off  takes  place  again  in  the  afternoon,  and  finally  an  incon- 
siderable increase  is  produced  by  the  evening  meal. 

During  hibernation,  in  which,  together  with  the  taking  of  food,  respiration  is 
entirely  discontinued,  and  the  interchange  of  gases  is  carried  on  only  by  diffusion 
in  the  lungs  and  the  cardio-pneumatic  movements,  the  excretion  of  carbon  dioxid 
falls  to  yV>  and  the  absorption  of  oxygen  to  ¥V  of  the  respective  amounts  during 
the  waking  state.  Therefore,  much  less  carbon  dioxid  is  given  off  than  there  is 
oxygen  absorbed,  so  that  the  body  weight  may  even  increase  in  consequence  of 
the  excess  of  oxygen  taken  up. 

5.  Influence  of  the  Surrounding  Temperature. — The  bodily  tempera- 
ture of  cold-blooded  animals  is  easily  raised  by  an  increase  in  the  sur- 
rounding temperature.     Under  such  circumstances  the  animals  give  off 
more  carbon  dioxid  than  in  a  cooler  state.     For  example,  a  frog  exposed 
to  a  surrounding  temperature  of  39°  C.  excreted  almost  three  times  as 
much  carbon  dioxid  as  when  the  temperature  was  6°  C.     Warm-blooded 
animals  behave  in  a  varying  manner  with  changes  in  the  surrounding 
temperature,  accordingly  as  the  bodily  temperature  remains  constant, 
or  is  correspondingly  raised  or  lowered.     In  the  latter  case,  as  in  cold- 
blooded  animals,   a  considerable  decrease  occurs  in  the  excretion  of 
carbon  dioxid,  when  the  body  is  cooled  under  the  influence  of  cold 
surroundings.     Conversely,  elevation  of  the  bodily  temperature  (also  in 
the  presence  of  fever)  gives  rise  to  increase  in  the  excretion  of  carbon 
dioxid.     The  behavior  is  exactly  the  reverse  when  the  bodily  tempera- 
ture remains  constant  on  exposure  to  varying  surrounding  temperature. 
With  increasing  cold  of  the  surrounding  medium,  the  consequent  reflex 
stimulation  causes  an  increase  in  the  oxidation-processes  of  the  body, 
as  well  as  in  the  number  and  depth  of  the  respirations.     As  a  result, 
more  oxygen  is  taken  up  and  more  carbon  dioxid  is  given  off.     The 
involuntary  muscular  movement  that  occurs  when  the  body  is  cooled 
has  the  most  obvious  influence  on  the  increase  in  the  gaseous  inter- 
change.    The  season  of  the  year  also  has  an  influence  on  the  interchange 
of  gases;   in  January  a  man  consumed  32.2  grams  of  oxygen  hourly,  in 
July  only   31.8   grams.     In  animals  the  carbon-dioxid  excretion  was 
found  to  be  about  one-third  higher  with  a  surrounding  temperature 
below  8°  C.  than  with  a  temperature  above  38°  C.     When  the  tempera- 
ture of  the  air  increases  (without  change  in  the  bodily  temperature), 


EXTENT    OF    THE    RESPIRATORY    EXCHANGE    OF    GASES.  235 

the  respiratory  activity  and  the  excretion  of  carbon  dioxid  diminish, 
while  the  pulse  remains  nearly  constant.  It  has  been  shown  that  when 
there  is  a  sudden  change  from  cold  to  warm  surroundings,  the  carbon- 
dioxid  output  diminishes  considerably;  and,  conversely,  when  the 
change  is  from  warm  to  cold,  the  excretion  increases  considerably. 

6.  Muscular  Exertion  produces  a  considerable  increase  in  oxygen- 
consumption  and  carbon-dioxid  elimination,  which,  for  instance,  may 
be  three  times  as  great  in  walking  as  in  a  quiet,  recumbent  position. 
Every  kilogrammeter  supplies  3^  milligrams  of  carbon  dioxid;  therefore, 
each  additional  gram  of  carbon  dioxid  formed  is  the  equivalent  of  300 
kilogrammeters.     The  establishment  of  a  certain  degree  of  tension  in 
the  muscles  requires  more  metabolic  change  than  the  maintenance  of 
this  tension. 

The  increase  in  the  interchange  of  oxygen  and  carbon  dioxid  begins  almost 
immediately  after  the  work  commences.  In  a  few  minutes  it  attains  a  constant 
height  of  at  most  from  seven  to  nine  times  the  amount  during  rest.  After  the 
work  is  finished,  the  consumption  of  oxygen  falls  in  from  3  to  15  minutes  to 
the  rate  during  rest.  The  respiratory  quotient  remains  essentially  unchanged 
during  work.  During  light  work  there  is  relatively  a  little  more  oxygen  consumed 
than  during  heavy  labor.  The  production  of  carbon  dioxid  is  diminished  with 
practice,  that  is,  with  a  more  economically  applied  exertion  of  the  muscles. 

The  gaseous  exchange  is  to  a  certain  extent  under  the  influence  of  the  vagus 
nerve,  which  in  part  inhibits  and  in  part  accelerates  the  heart's  activity.  Irrita- 
tion of  this  nerve  may  produce  a  diminution  in  metabolism,  characterized  by  a 
more  pronounced  fall  in  the  absorption  of  oxygen  than  in  the  excretion  of  carbon 
dioxid;  or  it  may  call  forth  an  increase  in  metabolism,  distinguished  by  a  greater 
rise  in  the  output  of  carbon  dioxid  than  in  the  oxygen  taken  in. 

7.  Ingestion   of  Food   causes  a  not  inconsiderable  increase   in   the 
carbon-dioxid  excretion,  which  is  in  general  governed  by  the  quan- 
tity of  food.     Hence,  the  increase  is  generally  most  pronounced  (about 
25  per  cent.)  from  one-half  to  one  hour  after  the  chief  meal  (dinner). 
The  increase   in  the   consumption   of  oxygen   that  follows  the  intro- 
duction of  food  into  the  stomach  depends  in  part  upon  the  increased 
muscular  activity  of  the  alimentary  canal;   nevertheless,  the  increased 
exhalation  of  carbon  dioxid  cannot  be  attributed  to  this  alone.     It  is  also, 
and  to  a  greater  extent,  dependent  on  the  heat-producing  activity  of  the 
digestive  glands — as  in  the  case  of  the  salivary  glands.     In  addition, 
some  of  the  carbon  dioxid  is  derived  from  oxidation,  in  the  course  of 
urea-formation,  of  a  part  of  the  carbon  contained  in  the  proteids. 

The  quality  of  the  food  also  has  some  influence.  According  to 
Magnus-Levy  a  proteid  diet  causes  a  much  greater  increase  in  the  con- 
sumption of  oxygen  (about  from  70  to  90  per  cent.)  than  does  carbo- 
hydrate food  (which  increases  the  consumption  about  39  per  cent.),  or 
a  fat-diet  (which  causes  an  increase  of  only  15  per  cent.),  as  experiments 
on  dogs  show. 

A  fasting  adult  weighing  50  kilos  inspires  in  one  hour  eight  liters  of  air  for 
each  kilo;  he  consumes  0.45  gram  of  oxygen,  and  forms  0.5  gram  of  carbon  dioxid. 
The  ingestion  of  food  raises  these  figures  to  nine  liters  of  air,  0.5  gram  of  oxygen 
and  0.6  gram  of  carbon  dioxid.     The  deposition  of  fat  following  a  carbohydrate 
diet,  is  attended  with  an  increase  in  the  amount  of  carbon  dioxid  given  off. 
results  partly  from  combustion  of  the  carbohydrates,  and  partly  from  their  trans- 
formation into  fat,  during  which  process  carbon  dioxid  is  separated, 
tory  quotient  is  also  increased  as  a  result  of  fat-formation  following  an  abundant 
carbohydrate  diet;   the  quotient  under  such  conditions  may  even  rise  above  1.2. 

The  absorption  of  oxygen  is  uninfluenced  by  direct  injection  into  the 


236 


EXTENT  OF  THE  RESPIRATORY  EXCHANGE  OF  GASES. 


blood  either  of  non-nitrogenous  or  of  nitrogenous  substances.  The 
output  of  carbon  dioxid  changes  to  a  certain  extent  in  correspondence 
with  the  combustion  of  these  substances  by  means  of  a  constant  quantity 
of  oxygen. 

Hunger  greatly  reduces  the  combustive  processes  in  dogs;  but  in 
guinea-pigs  it  produces  at  most  a  small  reduction  in  the  consumption  of 
oxygen. 

8.  The  Number  and  the  Depth  of  the  Respirations  have  practically  no 
influence  on  the  formation  of  carbon  dioxid,  or  on  the  oxidation- 
processes  in  the  body,  the  latter  being  regulated  rather  by  the  tissues 
themselves  through  a  mechanism  as  yet  unknown.  These  factors, 
however,  have  been  observed  to  exert  an  evident  influence  on  the  removal 
of  the  carbon  dioxid  already  formed  in  the  body.  An  increase  in  the 
number  of  respirations,  the  depth  remaining  the  same,  as  well  as  an 
increase  in  their  depth,  the  number  remaining  the  same,  results  in  an 
absolute  increase  in  the  output  of  carbon  dioxid.  The  quantity  seems 
relatively  diminished,  however,  when  viewed  with  reference  to  the 
amount  of  gases  interchanged.  Example: 


NUMBER  OF 
RESPIRATIONS 
IN  EACH  MINUTE 

EXCHANGED 
VOLUME 
OF  AIR. 

CONTAINED 
C02 

PER  CENT. 
CO2. 

DEPTH 

OF 

RESPIRATION. 

CONTAINED 
C02 

PER  CENT. 
C02. 

12 

6,000 

258  cu.cm. 

=  4-3  P-C. 

500 

21  cu.cm 

=  4-3  P.C. 

24 

12,000 

420 

=  3-5     ' 

1000 

36 

=  3-6     " 

48 

24,000 

744 

=  3-1 

1500 

5i 

=  3-4 

96 

48,000 

1392 

=  2.9    ' 

20OO 

64 

=  3-2 

3000 

72 

=  2-4 

Deep  respirations,  and  also  artificial  respiratory  movements,  increase  the 
absorption  of  oxygen  into  the  blood  to  the  point  of  saturation.  Limitation  of 
the  supply  of  oxygen  diminishes  its  consumption  in  the  body  in  considerably 
greater  measure  than  does  hunger.  Naturally,  increased  activity  of  the  respiratory 
muscles  causes  in  itself  a  greater  interchange  of  gases. 

9.  Exposure  to  Light  causes  an  increase  in  the  excretion  of  carbon 
dioxid  in  frogs,  mammals,  and  birds,  even  in  frogs  deprived  of  their 
lungs  or  of  their  cerebral  hemispheres,  or  in  those  in  which  the  spinal  cord 
has  been  divided  high  up.     At  the  same  time  the  consumption  of  oxygen 
is  increased.     The  same  processes  occur  in  individuals  without  eyes, 
though  to  a  more  limited  extent.     Rodents  and  birds  show  the  maxi- 
mum in  red  light,  toads  in  violet  light.     According  to  Aducco  starving 
pigeons  lose  weight  more  quickly  in  the  light  than  in  the  dark.     Quincke 
demonstrated  that  certain  tissues,  such  as  leukocytes  and  parts  of  fresh 
tissues,  attract  more  oxygen  to  themselves  under  the  influence  of  light 
than  in  the  dark. 

The  nitrogenous  metabolism  of  animals  remains  unchanged  during  exposure 
to  light.  The  increased  output  of  carbon  dioxid  is,  therefore,  to  be  attributed  to 
an  increased  transformation  of  fat;  hence,  animals  accumulate  more  fat  when 
kept  in  the  dark. 

10.  Blood-letting  produces  no  diminution  in  the  respiratory  exchange 
of  gases,  but  does  cause  an  increase  in  the  nitrogenous  excretion.     Pro- 
found anemic  conditions  diminish  the  interchange  of  gases. 

11.  Changes  in  the  Atmospheric  Pressure  produce  a  slight  diminu- 
tion in  the  interchange  of  gases  if  breathing  is  made  easier;    but  if 


DIFFUSION    OF    GASES    WITHIN    THE    RESPIRATORY    ORGANS.          237 

breathing  is  made  more  difficult,  there  is  a  slight  increase.  By  inspira- 
tion of  compressed  air  the  absorption  of  oxygen  is  increased  to  an  ex- 
ceedingly small  extent.  In  order  to  give  off  one  gram  of  carbon  dioxid,  a 
smaller  amount  of  air  is  needed  at  a  low  atmospheric  pressure  than  with 
a  high  barometer.  There  is  no  diminution  in  the  excretion  of  carbon 
dioxid  on  high  mountains.  The  effects  of  artificially  rarefied  air  and 
of  the  rarefied  atmosphere  of  high  altitudes  are  not  the  same.  A  rare- 
faction of  air  to  450  mm.  of  mercury  still  has  no  effect,  the  metabolic 
changes  proceeding  unaltered.  In  the  air  of  high  altitudes  metabolism 
is  increased,  and  respiration  becomes  more  frequent  and  deeper.  Ac- 
cording to  A.  and  J.  Loewy  and  Zuntz  the  greater  amount  of  light  at 
high  altitudes  is  the  exciting  factor. 

12.  In  the  presence  of  artificially  induced  dyspnea,  as  by  tightly 
compressing  the  thorax,  the  proteid  metabolism  is  increased — the  amount 
of  urea  being  increased — and  there  is  an  increase  in  the  excretion  of 
oxalic  acid,  acetone,  ammonia,  and  sulphur  in  the  urine. 

Pathological. — According  to  the  experiments  of  Grehant  on  {logs,  it  -appears 
that  intense  inflammation  of  the  bronchial  mucous  membrane  will  diminish 
the  output  of  carbon  dioxid,  even  if  there  be  fever. 

In  cases  of  diabetes  the  body  is  able  to  take  up  the  necessary  amount  of 
oxygen,  but  the  quantity  of  carbon  dioxid  given  off  is  diminished,  and  the  respira- 
tory quotient  is  low. 

Among  the  poisons,  thebain  increases  the  output  of  carbon  dioxid,  while  mor- 
phin,  codein,  narcein,  narcotin,  and  papaverin  diminish  it.  Curare  lowers  the 
metabolism  enormously,  the  absorption  of  oxygen  falling  about  35.2  per  cent., 
and  the  excretion  of  carbon  dioxid  about  37.4  per  cent.  Section  of  the  spinal 
cord  has  a  similar  effect. 

DIFFUSION  OF  GASES  WITHIN  THE  RESPIRATORY  ORGANS. 

In  the  pulmonary  alveoli  the  air  is  richest  in  carbon  dioxid  and 
poorest  in  oxygen.  Further  on,  from  the  smallest  bronchioles  to  the 
larger  ones  and  then  onward  to  the  bronchi  and  the  trachea,  the  respired 
air  becomes,  step  by  step,  gradually  more  like  the  atmospheric  air. 
Hence  it  is  that  if  the  expired  air  of  a  respiration  be  collected  in  two 
halves,  the  first  half  (coming  from  the  larger  air-passages)  contains  less 
carbon  dioxid  (3.7  volumes  per  cent.)  than  the  second  half  (5.4  volumes 
per  cent.).  This  inequality  in  the  proportion  of  the  gases  at  various 
levels  of  the  respiratory  organs  necessarily  causes  a  continuous  diffusion  of 
gases  between  the  various  levels,  and  also,  finally,  between  the  gases  in 
the  larynx  and  nasal  cavities  and  the  outside  atmosphere.  The  carbon 
dioxid  constantly  diffuses  from  the  depths  of  the  air- vesicles  toward  the 
outer  air,  while  the  oxygen  of  the  latter  diffuses  toward  the  gaseous 
mixture  in  the  pulmonary  alveoli.  This  diffusion  is  doubtless  assisted 
materially  by  the  constant  shaking  of  the  respiratory  gases  by  the 
cardio-pneumatic  movements.  During  hibernation,  and  also  in  cases 
of  apparent  death  of  long  duration,  this  must  be  the  only  means 
for  the  exchange  of  gases  within  the  lungs.  Ordinarily,  however,  this 
mechanism  is  insufficient  for  the  respiratory  process;  so  that  the  ex- 
change of  air  produced  by  inspiration  and  expiration  must  be  added  to 
it.  By  this  latter  means  atmospheric  air  is  introduced  into  those  parts 
of  the  lungs  lying  nearest  to  the  large  air-passages,  from  which  and  into 
which  the  diffusion-currents  of  oxygen  and  carbon  dioxid  pass  more 
readily,  on  account  of  the  greater  differences  in  the  tension  of  the  gases. 


238  INTERCHANGE    OF    GASES. 

If  the  inspired  air  contains  a  diminished  quantity  of  oxygen,  the  necessary 
amount  of  oxygen  can  still  be  supplied  to  a  certain  extent  by  more  rapid  and 
deeper  respirations. 

INTERCHANGE  OF  GASES  BETWEEN  THE  BLOOD   IN  THE  PUL- 
MONARY CAPILLARIES  AND  THE  AIR  IN  THE  ALVEOLI. 

This  interchange  of  gases  is  accomplished  almost  exclusively  by 
chemical  processes,  independently  of  the  diffusion  of  gases. 

For  the  determination  of  the  gaseous  interchange  it  is  first  necessary  to  ascer- 
tain the  tension  of  the  oxygen  and  the  carbon  dioxid  in  the  venous  blood  of  the 
pulmonary  capillaries.  Pfluger  and  Wolffberg  have  accomplished  this  by  cathe- 
terization  of  the  lungs.  An  opening  is  made  in  the  trachea  of  a  dog,  and  an 
elastic  catheter  (Fig.  90,  a)  is  introduced  into  the  bronchus  leading  to  the  lower 
lobe  of  the  left  lung.  In  order  to  have  the  bronchus  fit  closely  around  the  catheter, 
the  latter  is  made  to  pierce  a  rubber  sac  inflated  by  means  of  a  communicating 
rubber-ball  pump  c.  In  this  way  no  air  from  that  part  of  the  lung  can  escape  at 
the  side  of  the  catheter.  The  tube  is  at  first  closed  at  its  outlet,  and  the  dog  is 
allowed  to  breathe  independently  and  as  quietly  as  possible.  After  four  minutes 
the  alveolar  air  in  the  closed-off  part  of  the  lungs  is  in  complete  equilibrium  with  the 
blood- gases.  By  means  of  a  mercurial  air-pump  the  air  in  the  lungs  is  sucked 
out  of  the  catheter  (at  6)  and  analyzed.  The  tension  of  the  carbon  dioxid  and 
the  oxygen  in  this  air  will  indicate  in  an  indirect  way  the  tension  of  these  two 
gases  in  the  venous  blood  of  the  pulmonary  capillaries. 

For  the  direct  estimation  of  the  gases  in  various  specimens  of  blood,  these 
gases  are  removed  by  shaking  the  blood  with  another  kind  of  gas.  The  composi- 
tion of  the  mixture  will  indicate  the  proportions  in  which  the  blood-gases  have 
been  mixed,  and  will  thus  serve  to  determine  their  tension.  It  is  desirable  to  use 
as  much  blood  as  possible  with  a  small  quantity  of  gas;  the  amount  of  the  latter 
should  be  about  the  same  as  that  supposed  to  be  present  in  the  blood. 

In  the  following  table  are  shown  the  tension  and  the  percentage  of 
oxygen  and  carbon  dioxid  in  arterial  and  venous  blood,  as  well  as  in  the 
atmosphere  and  the  air  of  the  closed-off  alveoli : 

I.  V. 

Tension   of  O   in   arterial  blood  =  Tension  of  O  in  the  alveolar  air  of 

29.6   mm.    of   mercury;     increased   by  the  catheterized  lung  =  27.44  mm.  of 

warming;    corresponding  to  a  gaseous  mercury;    corresponding  to  3.6  vol.  per 

mixture  containing  3.9  per  cent,  of  O.  cent. 

II.  VI. 

Tension  of  CO2  in  arterial  blood  =  Tension  of  CO2  in  the  alveolar  air 

21  mm.  of  mercury;    corresponding  to      of  the  catheterized  lung  =  27  mm.  of 
2.8  vol.  per  cent.  mercury;     corresponding   to    3.56    vol. 

per  cent. 
III. 

Tension  of  O  in  venous  blood  =  22  VII. 

mm.  of  mercury;    corresponding  to  2.9  Tension  of  O  in  the  atmosphere  = 

vol.  per  cent.  158  mm.  of  mercury;   corresponding  to 

20. 8  vol.  per  cent. 
IV. 

Tension  of  CO2  in  venous  blood  =  VIII. 

41  mm.  of  mercury;    corresponding  to  Tension  of  CO2  in  the  atmosphere  = 

5.4  vol.  per  cent.  0.38  mm.  of  mercury;   corresponding  to 

from  0.03  to  0.05  vol.  per  cent. 

If  the  tension  of  the  oxygen  in  the  atmosphere  (VII)  be  compared 
with  that  in  venous  blood  (III)  or  in  the  alveoli  (V)  it  will  be  seen  that  the 
absorption  of  oxygen  into  the  blood  during  respiration  can  occur  in  the 
form  of  an  equalization  of  tension.  Likewise  a  comparison  of  the 
tension  of  the  carbon  dioxid  in  the  atmosphere  (VIII)  with  that  in 
venous  blood  (IV)  or  with  that  in  alveolar  air  (VI)  might  explain  the 


INTERCHANGE    OF    GASES.  239 

excretion  of  that  gas  in  a  similar  manner.     Nevertheless,  the  respiratory 
interchange  of  gases  is  a  chemical  process. 

According  to  v.  Fleischl  the  concussion  to  which  the  venous  blood  is  subjected 
on  being  pumped  into  the  pulmonary  arteries  provides  for  a  more  ready  escape  of 
the  carbon  dioxid,  a  point  that  is  of  the  greatest  importance  with  respect  to  the 
respiratory  process. 

The  absorption  of  oxygen  from  the  alveolar  air  for  the  purpose  of 
oxidation  of  the  venous  blood  in  the  pulmonary  capillaries  is  a  chemical 
process,  as  the  gas-free  hemoglobin  in  the  lungs  takes  up  oxygen  to 
form  oxy hemoglobin.  That  this  absorption  depends,  not  on  diffusion 
of  the  gases,  but  on  the  atomic  combination  pertaining  to  the  chemical 
process,  is  shown  by  the  fact  that  the  blood  does  not  take  up  more 
oxygen  when  the  pure  gas  is  respired  than  when  atmospheric  air  is 
respired;  further,  that  animals  that  are  made  to  breathe  in  a  small, 
closed  space  will  absorb  into  their  blood  all  of  the  oxygen  but  traces,  to 
the  point  of  suffocation.  If  the  respiratory  absorption  of  oxygen  were 
a  diffusion-process,  much  more  oxygen  would  have  to  be  taken  up  in  the 
first  case  in  accordance  with  the  partial  pressure  of  the  gas;  while  in 
the  latter  case  such  an  extensive  absorption  could  not  take  place. 


FIG.  90. — Pulmonary  Catheter. 

Even  in  highly  rarefied  air  (high  balloon-voyages)  the  absorption  of 
oxygen  remains  independent  of  the  partial  pressure.  However,  in  a 
space  containing  rarefied  air  a  longer  time  and  a  more  vigorous  shaking 
are  required  for  the  absorption  of  oxygen  by  the  blood  at  the  tempera- 
ture of  the  body;  that  is,  the  absorption  of  oxygen  is  not  diminished, 
but  is  retarded.  In  this  way  is  explained  the  death,  for  example,  of  the 
aeronauts  Sivel  and  Croce*-Spinelli,  during  an  ascension  to  a  height 
where  the  atmospheric  pressure  is  only  one-third  the  normal. 

The  laws  of  diffusion  come  into  play  in  connection  with  the    absorption  of 
oxygen  only  to  the  extent  that  the  oxygen,  in  order  to  reach  the  red 
puscles,  must,  first  of  all,  diffuse  into  the  plasma,  where  it  immediately  ente: 
chemical  combination  with  the  erythrocytes. 

The  excretion  of  carbon  dioxid  from  the  blood  into  the   alveolar 
air  could  also  be  well  represented  in  the  form  of  an  equalization  of 
sion  (diffusion) ;  but  here  again  chemical  processes  are  operative  al 
they  have  not  yet  been  investigated  in  many  details, 
of  oxygen  by  the  erythrocytes  produces  at  the  same  time  an  expulsioi 


240      RESPIRATORY  GASEOUS  EXCHANGE  AS  A  DISSOCIATION  PROCESS. 

of  the  carbon  dioxid.  This  is  proved  by  the  fact  that  the  whole  of  the 
carbon  dioxid  is  more  easily  expelled  from  the  blood  if  oxygen  be  at  the 
same  time  introduced  than  if  all  gases  are  withdrawn.  The  result  is 
different  in  the  case  of  the  serum,  which  when  subjected  to  a  vacuum  will 
give  up  only  a  part  of  the  carbon  dioxid,  while  from  5  to  9  volumes  per 
cent,  are  still  retained ;  the  latter  can  be  released  only  by  the  addition  of 
acids.  As  this  carbon  dioxid,  which  exists  in  firm  chemical  combina- 
tion, also  escapes  on  addition  of  erythrocytes,  the  corpuscles  must  contain 
a  substance  that  acts  like  an  acid  in  expelling  the  carbon  dioxid. 

THE   RESPIRATORY   GASEOUS   EXCHANGE   AS   A   DISSOCIATION 

PROCESS. 

Some  forms  of  gas  enter  into  true  chemical  combination  with  other 
substances]  when  associated  at  a  certain  high  degree  of  partial  pressure 
of  the  gas  in  question.  This  chemical  combination,  however,  is  again 
dissolved  as  soon  as  the  partial  pressure  diminishes  and  reaches  a  certain 
low  level.  Hence,  by  alternately  raising  and  lowering  the  partial  pres- 
sure, a  chemical  combination  of  the  gas  can  be  formed  and  again  broken 
up.  This  process  is  called  dissociation  of  gases.  The  minimal  partial 
pressure  is  constant  for  the  various  substances  and  gases  in  question; 
but  still  the  temperature,  as  in  the  case  of  the  absorption  of  gases,  has 
a  marked  influence ;  namely,  increase  in  temperature  diminishes  the 
partial  pressure  at  which  dissociation  occurs. 

Calcium  carbonate  may  be  taken  as  an  example  to  illustrate  the  dissociation  of 
gases.  When  this  substance  is  heated  in  the  air  to  440°  C.,  carbon  dioxid  escapes 
from  the  chemical  combination;  but  it  is  gradually  taken  up  again  by  the  calcium, 
after  cooling  has  taken  place. 

The  chemical  combinations  containing  carbon  dioxid,  and  also  those 
containing  oxygen,  namely,  the  oxy hemoglobin  and  the  carbon-dioxid 
compounds,  behave  in  a  similar  manner  within  the  blood-stream;  these 
also  exhibit  the  process  of  dissociation.  If  these  gaseous  combinations 
are  placed  under  conditions  in  which  the  partial  pressure  of  these  gases  is 
exceedingly  low  (that  is,  when  they  are  present  in  small  amounts),  the 
compounds  are  dissociated;  that  is,  they  give  off  carbon  dioxid  or  oxygen, 
as  the  case  may  be,  to  the  surrounding  medium.  If,  however,  they  are 
now  again  brought  into  a  medium  in  which,  on  account  of  an  abundance 
of  these  gases,  the  partial  pressure  of  the  oxygen  or  the  carbon  dioxid 
is  high,  they  are  again  taken  up  in  chemical  combination  by  these  gases. 

The  hemoglobin  of  the  blood  in  the  pulmonary  capillaries  finds  a 
plentiful  supply  of  oxygen  in  the  alveoli;  therefore,  it  combines  with 
the  oxygen,  under  the  high  partial  pressure  of  that  gas,  forming  the 
chemical  compound  oxy  hemoglobin.  On  its  way  through  the  capil- 
laries of  the  greater  circulation,  the  hemoglobin  comes  in  contact  with 
tissues  poor  in  oxygen;  the  oxy  hemoglobin  is  dissociated,  its  oxygen 
passes  to  the  tissues,  and  the  blood,  with  gas-free  or  reduced  hemoglobin, 
returns  to  the  right  heart  and  thence  to  the  lungs,  in  order  to  take  up 
oxygen  anew. 

The  carbon  dioxid  meets  the  circulating  blood  in  largest  amount  in 
the  tissues.  The  high  partial  pressure  of  the  gas  in  this  situation  causes 
the  constituents  of  the  blood  to  enter  into  chemical  combination  with 
the  carbon  dioxid.  In  the  lungs,  however,  the  partial  pressure  for 
carbon  dioxid  is  low,  the  gas  is  dissociated,  and  it  is  excreted.  It  is 


CUTANEOUS    RESPIRATION.  241 

thus  evident  that,  as  concerns  the  blood,  the  giving  up  of  oxygen  and 
the  absorption  of  carbon  dioxid  in  the  tissues,  and,  conversely,  the 
absorption  of  oxygen  and  the  giving  up  of  carbon  dioxid  in  the  lungs, 
are  processes  that  take  place  simultaneously. 

CUTANEOUS  RESPIRATION. 

Method. — If  a  human  being  or  an  animal  is  placed  in  the  chamber  of  a  respira- 
tion-apparatus (such  as  Scharling's  or  v.  Pettenkofer's) ,  and  the  gases  passing  to 
and  from  the  lungs  are  conducted  through  a  respiratory  tube,  so  that  none  of 
the  gaseous  interchange  of  the  lungs  enters  the  chamber,  but  only  the  transpiration 
of  the  skin,  information  can  thus  be  obtained  concerning  the  cutaneous  respira- 
tion. The  procedure  of  leaving  the  whole  head  of  the  subject  outside  the  chamber, 
the  neck  being  fixed  air-tight  in  its  wall,  is  less  correct.  The  cutaneous  respiration 
of  a  circumscribed  part  of  the  body — for  instance,  of  an  extremity — -may  be  studied 
by  enclosing  the  part  in  an  air-tight  cylinder  similar  to  that  used  for  the  arm  in 
employing  the  plethysmograph. 

In  twenty-four  hours  a  healthy  man  loses  through  his  skin — which 
contains  the  respiratory  organ  in  the  moist  sweat-glands,  richly  supplied 
with  blood-vessels — QT  of  his  entire  body- weight,  which  is  greater 
than  the  loss  through  the  lungs,  since  it  bears  a  ratio  to  the  latter  of 
3:2.  Of  this  large  loss  of  weight  only  from  8  to  10  grams  are  referable 
to  the  carbon  dioxid  given  off.  The  remainder  is  comprised  in  the 
evaporation  of  water.  Elevation  of  the  surrounding  temperature  is 
attended  with  an  increase  in  the  amount  of  carbon  dioxid  given  off. 
The  excretion  at  between  29°  and  33°  C.  amounts  to  8  grams  in  twenty- 
four  hours;  above  33°  C.  it  is  20  grams  (sweating  begins  at  this 
point);  and  at  38.4°  C.  the  amount  is  27.5  grams.  Active  muscular 
exercise  likewise  produces  an  increased  excretion. 

Absorption  of  oxygen  by  the  skin  has  also  been  demonstrated,  the 
amount  absorbed  being  either  equal  to  the  volume  of  carbon  dioxid 
given  off,  or  a  little  less. 

As  the  excretion  of  carbon  dioxid  by  the  skin  is  only  about  -^ 
of  that  by  the  lungs,  and  as  the  absorption  of  oxygen  is  only  about  Tfo  of 
that  by  the  lungs,  it  is  evident  that  the  respiratory  activity  of  the  skin 
is  in  any  event  but  slight.  It  is  uncertain  whether  or  not  the  skin  gives 
off  gaseous  nitrogen  or  ammonia.  According  to  Funke  the  skin  secretes 
hourly  0.0824  gram  of  soluble  nitrogen,  this  quantity  being  increased 
in  the  presence  of  renal  disease. 

According  to  Rohrig,  the  excretion  of  carbon  dioxid  and  of  water  exhibits 
certain  daily  variations.  It  is  increased  during  digestion,  after  the  application  of 
cutaneous  irritants,  in  the  presence  of  obstruction  to  pulmonary  respiration,  of 
hyperemia  of  the  skin,  and  when  the  blood  contains  an  increased  number  of 
erythrocytes. 

In  warm-blooded  animals,  with  thick,  dry  epidermoid  structures,  the  cuta- 
neous interchange  of  gases  is  still  less  than  it  is  in  man.  In  frogs  and  other  am- 
phibia, with  a  constantly  moist  skin,  cutaneous  respiration  becomes  highly  impor- 
tant. The  skin  here  supplies  from  two-thirds  to  three-fourths  of  the  total  quantity 
of  carbon  dioxid  excreted,  and  in  hibernating  frogs  the  proportion  is  still  greater. 
The  skin  is,  therefore,,  a  more  important  respiratory  organ  than  the  lungs.  Im- 
mersion in  oil  will,  consequently,  kill  these  animals  more  readily  than  will  hgatic 
the  lungs. 

INTERNAL  RESPIRATION  OR  TISSUE-RESPIRATION. 

The  terms  internal  respiration  and  tissue-respiration  are  used  to  desig- 
nate the  interchange  of  gases  between  the  capillaries  of  the  greater  cir- 
16 


242  INTERNAL    RESPIRATION    OR    TISSUE-RESPIRATION. 

dilation  and  the  tissues.  Those  organic  constituents  of  the  tissues  that 
contain  carbon  are  subjected  during  their  vital  activity  to  a  process  of 
gradual  oxidation,  with  the  formation  of  carbon  dioxid.  Hence,  the 
following  inferences  may  be  drawn : 

r.  The  chief  seat  for  the  absorption  of  oxygen  and  the  formation  of 
carbon  dioxid  is  to  be  found  within  the  tissues  themselves.  That  the 
oxygen  rapidly  penetrates  from  the  capillary  blood  into  the  tissues  is 
shown  by  the  fact  that  this  blood  rapidly  becomes  richer  in  carbon 
dioxid  and  poorer  in  oxygen,  while  oxygenated  blood,  kept  warm  out- 
side the  body,  changes  much  more  slowly  and  incompletely.  Further, 
if  fresh  pieces  of  tissue  be  placed  in  defibrinated  blood  rich  in  oxygen, 
the  oxygen  rapidly  diminishes.  Also,  the  circumstance  that  frogs  de- 
prived of  their  blood  exhibit  almost  as  great  an  interchange  of  gases  as 
do  normal  animals  indicates  that  the  gaseous  interchange  takes  place 
in  the  tissues  themselves.  Moreover,  if  the  chief  seat  of  oxidation  lay, 
not  in  the  tissues  themselves,  but  in  the  blood,  then,  if  oxygen  were 
withheld  from  the  blood  (during  suffocation),  those  reducing  substances 
that  consume  the  oxygen  in  the  process  of  oxidation  should  accumulate 
in  the  blood.  This  is  not  the  case,  for  even  the  blood  of  suffocated 
animals  contains  only  a  trace  of  reducing  substances.  The  absorption 
of  oxygen  into  the  tissues  may  occur  in  the  form  of  a  temporary  storing 
of  the  gas,  perhaps  with  the  formation  of  intermediate  lower  oxida- 
tion-products. This  is  followed  by  a  period  of  more  rapid  separation 
of  carbon  dioxid.  Thus,  the  absorption  of  oxygen  and  the  excretion  of 
carbon  dioxid  in  the  tissues  do  not  necessarily  proceed  on  parallel  lines 
and  to  the  same  extent. 

A  clear  picture  of  the  development  of  carbon  dioxid  in  the  tissues  is  furnished 
by  the  fact  that  a  larger  amount  of  this  gas  is  found  in  the  cavities  of  the  body 
and  in  their  gases  and  fluids  than  in  the  blood  of  the  capillaries.  Pfliiger  and 
Strassburg  found  the  tension  of  the  carbon  dioxid  (in  millimeters  of  mercury) 
as  follows : 

In  arterial  blood, 21.28  mm.      In  bile, 50.0  mm. 

"  the  peritoneal  cavity,  ....  58.8  '   hydrocele-fluid, 46.5 

"  acid  urine, 68.0 

The  abundance  of  carbon  dioxid  in  these  fluids,  as  compared  with  that  in  the 
blood,  can  arise  only  from  the  addition  to  them  of  the  carbon  dioxid  generated  in 
the  tissues. 

In  the  lymph  of  the  thoracic  duct  the  tension  of  the  carbon  dioxid  (from  33.4 
to  37.2  mm.  of  mercury)  is,  indeed,  greater  than  in  the  arterial  blood,  but  it  is 
still  considerably  less  than  in  the  venous  blood.  This  fact  does  not,  however,  justify 
the  conclusion  that  only  a  small  quantity  of  carbon  dioxid  is  formed  in  the  tissues 
from  which  the  lymph  is  collected.  It  rather  permits  the  inference,  either  that 
the  lymph  possesses  less  attraction  for  the  carbon  dioxid  formed  in  the  tissues 
than  does  the  capillary  blood,  where  chemical  forces  are  active  in  the  production 
at  least  of  a  partial  combination  of  the  gas;  or  that  in  the  course  of  the  slow 
lymph-current  the  carbon  dioxid  is  partially  given  back  to  the  tissues  by  equaliza- 
tion of  tension;  or,  finally,  that  carbon  dioxid  is  formed  independently  in  the 
blood.  Furthermore,  it  is  to  be  pointed  out  that  those  muscles  that  are  known 
to  be  the  principal  producers  of  carbon  dioxid  furnish  this  gas  abundantly  to  the 
blood,  their  tissues  being  relatively  poor  in  lymph- vessels. 

The  amount  of  uncombined,  free  carbon  dioxid,  capable  of  being  pumped  out, 
in  the  fluids  and  gases  mentioned  indicates  that  the  carbon  dioxid  passes  over 
from  the  tissues  into  the  blood  in  an  uncombined  free  state.  However,  Preyer 
believes  that  the  gas  is  carried  over  into  the  blood  of  the  veins  also  in  chemical 
combination. 

The  interchange  of  oxygen  and  carbon  dioxid  varies  considerably  in  the  differ- 
ent tissues.  In  the  first  rank  belong  the  muscles,  which  in  a  state  of  activity 


INTERNAL    RESPIRATION    OR    TISSUE-RESPIRATION'.  243 

excrete  a  large  amount  of  carbon  dioxid  and  consume  much  oxygen.  The  inter- 
change of  gases  in  tissues  is  increased  during  their  activity.  The  secreting  salivary 
glands,  kidneys,  and  pancreas  are  no  exception  to  this  rule;  for  although,  in  the 
secreting  state,  bright  red  blood  flows  away  from  them  through  the  dilated  vessels, 
still  this  apparently  relative  diminution  in  the  carbon  dioxid  of  the  venous  blood 
is  more  than  compensated  for  by  its  absolute  increase  through  the  marked  increase 
in  volume  of  the  blood  passing  through  these  organs. 

Active  reduction-processes  take  place  in  most  tissues.  If  coloring-matters, 
such  as  alizarin-blue,  indophenol-blue,  or  methylene-blue,  be  introduced  into  the 
blood  of  animals,  the  tissues  will  soon  be  stained.  Those  organs  that  have  an 
especially  strong  affinity  for  oxygen  (such  as  the  liver,  the  cortex  of  the  kidneys, 
and  the  lungs),  abstract  oxygen  from  these  coloring-matters,  and  change  them  into 
colorless  reduction-products.  The  pancreas  and  the  submaxillary  gland  have 
almost  no  reducing  power. 

2.  The  blood  itself,  like  all  of  the  tissues,  is  a  seat  for  the  consumption 
of  oxygen  and  the  formation  of  carbon  dioxid.     This  is  proved  by  the  fact 
that  blood  removed  from  the  body  quickly  becomes  poorer  in  oxygen 
and  richer  in  carbon  dioxid;    further,  by  the  circumstance  that  in  the 
oxygen-free  blood  of  asphyxiated  persons  and  in  the  blood-corpuscles 
there  are  always  found  small  quantities  of  reducing  agents,  which  become 
oxidized  on  the  addition  of  oxygen.     At  all  events,  this  gaseous  inter- 
change is  but  slight  as  compared  with  that  occurring  in  all  the  other 
tissues.     It   is   incontestable  that   the  walls   of  the   blood-vessels,   by 
means  of  their  contained  muscular  fibers,   also  consume  oxygen  and 
produce  carbon  dioxid,  although  this  process  is  so  insignificant  that  the 
blood  undergoes  no  visible  change  in  color  throughout  its  arterial  course. 

C.  Ludwig  and  his  pupils  have  proved  by  specially  adapted  experiments  that 
transformation  into  carbon  dioxid  can  actually  occur  within  the  blood.  If  sodium 
lactate,  which  is  easily  oxidized,  be  mixed  with  blood,  and  this  mixture  be  sent 
through  the  blood-vessels  of  a  recently  excised  organ  that  is  still  alive  (such  as 
the  kidney  or  the  lung) ,  a  more  abundant  consumption  of  oxygen  and  formation 
of  carbon  dioxid  will  occur  in  this  mixed  blood  than  would  occur  in  pure  blood 
similarly  transfused. 

3.  It  may  in   advance  be   concluded   as  probable  that  the  living 
pulmonary  tissue  also  consumes  oxygen  and  generates  carbon  dioxid. 
By  passing  arterial  blood  through  lungs  that  have  been  deprived  of  air, 
C.  Ludwig  and  Miiller  succeeded  in  demonstrating  a  diminution  in  the 
oxygen  and  an  increase  in  the  carbon  dioxid.     Bohr  and  Henriques  con- 
cluded further  from  their  experiments,  in  which  they  restricted  to  a 
considerable  degree  the  circulation  of  blood  through  the  bodily  tissues, 
and  found  no  significant  diminution  in  the  excretion  of  carbon  dioxid 
from  the  lungs,  that  the  pulmonary  tissue  is  not  limited  to  a  mere 
excretion  and  absorption  of  gases,  but  that  it  besides  possesses  the  prop- 
erty of  forming  carbon  dioxid  from  substances  that  are  derived  from 
the  other  tissues.     In  like  manner  they  assumed  that  oxygen  is  actively 
taken  up  by  the  lungs;    that  is,  the  lungs  secrete  carbon  dioxid  and 
absorb  oxygen  like  a  secreting  gland. 

As  the  total  amount  of  carbon  dioxid  and  oxygen  in  the  whole 
volume  of  blood  at  any  one  time  is  only  about  4  grams,  while  the  amount 
of  carbon  dioxid  excreted  daily  is  900  grams,  and  the  amount  of  oxygen 
absorbed  is  774  grams,  it  is  evident  that  the  interchange  of  gases  pro- 
ceeds with  great  rapidity,  that  the  absorbed  oxygen  must  be  consumed 
and  the  carbon  dioxid  formed  must  be  excreted  quickly. 

As  a  result  of  an  increased  introduction  of  acids  into  the  body  there  is  a 
diminution  in  the  consumption  of  oxygen  (and  in  the  production  of  heat),  which 
in  a  high  degree  may  give  rise  to  an  internal  asphyxia  of  the  tissues. 


244  RESPIRATION    IN    A    CLOSED    SPACE. 

RESPIRATION    IN    A    CLOSED    SPACE,    OR    WITH    ARTIFICIAL 

CHANGES  IN  THE  AMOUNTS  OF  OXYGEN  AND  CARBON 

DIOXID  IN  THE  RESPIRED  AIR. 

Respiration  in  a  closed  space  results  in  (i)  a  gradual  diminution  of  the  oxygen, 
(2)  a  simultaneous  increase  of  the  carbon  dioxid,  and  (3)  a  diminution  in  the 
volume  of  gas.  If  the  space  is  only  of  moderate  size,  the  animal  consumes  the 
oxygen  almost  completely,  the  blood  becomes  almost  free  of  oxygen,  and  death 
finally  results,  accompanied  by  asphyxial  convulsions.  The  absorption  of  oxygen 
occurs,  therefore,  through  chemical  combination,  independently  of  the  laws  of 
absorption. 

In  larger  closed  spaces  considerable  accumulation  of  carbon  dioxid  takes 
place  before  the  oxygen  is  diminished  to  such  an  extent  that  life  is  threatened. 
As  the  carbon  dioxid  can  be  excreted  from  the  body  only  when  its  tension  is  greater 
in  the  blood  than  in  the  surrounding  air,  there  will  be  retention  of  the  gas  as  the 
amount  expired  into  the  enclosed  space  increases;  and,  finally,  a  return  of  the 
carbon  dioxid  into  the  body  may  take  place.  This  occurs  while  the  oxygen  is 
still  sufficient  to  support  life.  Death  results,  therefore,  directly  from  poisoning  by 
carbon  dioxid,  with  the  symptoms  of  dyspnea  of  short  duration,  to  which  are 
added  stupor  and  subnormal  temperature.  This  manner  of  death  has  been  ob- 
served in  rabbits,  after  they  had  reabsorbed  some  of  the  carbon  dioxid  that  had 
been  excreted  previously  by  them. 

In  pure  oxygen,  or  in  an  atmosphere  rich  in  oxygen,  animals  breathe  in  a  per- 
fectly normal  manner.  A  little  more  oxygen  is  absorbed,  but  still  the  amount  of 
carbon  dioxid  excreted  is  not  increased.  In  closed  spaces  filled  with  oxygen, 
animals  finally  die  through  the  reabsorption  of  their  excreted  carbon  dioxid. 
Rabbits  have  thus  been  observed  to  die  after  they  had  absorbed  an  amount  of 
carbon  dioxid  equal  to  half  the  volume  of  their  body,  although  the  enclosed  air 
still  contained  over  50  per  cent,  of  oxygen. 

Human  beings  and  animals  can  still  breathe  an  air-mixture  containing  only 
9  per  cent,  of  oxygen;  deepened  respirations  set  in  at  10  per  cent.,  and  discomfort 
at  8  per  cent.  Animals  breathe  with  difficulty  and  lose  consciousness  at  7  per 
cent.;  pronounced  dyspnea  makes  its  appearance  at  4.5  per  cent.,  and  quite 
rapid  suffocation  at  3  per  cent.  The  air  expired  by  man  under  normal  conditions 
still  contains  between  14  and  18  per  cent,  of  oxygen.  Mammals  placed  in  a  gaseous 
mixture  poor  in  oxygen  consume  slightly  less  oxygen. 

The  metabolism  of  animals  is  unchanged  by  variations  in  the  amount  of 
oxygen  in  the  respired  air  between  the  limits  of  10.5  and  87  per  cent.  If  the 
oxygen  falls  below  10.5  per  cent.,  there  is  an  increase  in  the  excretion  of  nitrogen, 
carbon  dioxid,  lactic  acid,  and  oxalic  acid  through  the  urine. 

If  the  amount  of  carbon  dioxid  in  the  inspired  air  be  increased,  the  respiratory 
movements  are  increased,  but  the  excretion  of  carbon  dioxid  and  the  absorption  of 
oxygen  are  diminished. 

Inspiration  is  actively  stimulated  by  a  deficiency  of  oxygen,  as  well  as  by  an 
excess  of  carbon  dioxid.  The  dyspnea  that  is  induced  under  the  condition  first 
stated  is  prolonged  and  severe,  while  under  the  second  condition  the  respiratory 
activity  soon  diminishes.  A  deficiency  of  oxygen  further  causes  a  greater  and 
more  prolonged  rise  in  the  blood-pressure  than  does  an  excess  of  carbon  dioxid. 
Finally,  the  consumption  of  oxygen  by  the  body  is  less  restricted  by  a  diminution 
of  the  oxygen  in  the  air  than  by  an  excess  of  carbon  dioxid.  Death  from  limitation 
in  the  supply  of  oxygen  is  preceded  by  violent  irritative  phenomena  and  convul- 
sions, which  are  absent  in  case  of  death  from  excess  of  carbon  dioxid.  Finally,  in 
conjunction  with  poisoning  by  carbon  dioxid,  the  excretion  of  this  gas  is  greatly 
diminished. 

If  animals  be  supplied  with  a  gaseous  mixture  similar  to  the  atmosphere,  but 
in  which  the  nitrogen  is  replaced  by  hydrogen,  they  breathe  quite  normally;  the 
hydrogen  of  the  mixture  does  not  undergo  any  noteworthy  change  in  volume. 
Increase  or  diminution  in  the  amount  of  nitrogen  in  the  air  simply  causes  a  greater 
or  lesser  absorption  of  the  gas  by  the  fluids  of  the  body. 

Cl.  Bernard  found  that  if  an  animal  be  made  to  respire  in  a  closed  space, 
it  became,  up  to  a  certain  point,  accustomed  to  the  successive  deterioration  of 
the  air.  If  he  placed  a  bird  under  a  glass  bell-jar,  it  lived  for  several  hours;  but 
if,  before  its  death,  another  bird  were  added  from  the  fresh  air,  the  latter  imme- 
diately died  in  convulsions. 


RESPIRATION    OF    FOREIGN    GASES.  245 

It  is  remarkable  that  frogs,  when  placed  in  air  free  from  oxygen,  will  for 
several  hours  give  off  just  as  much  carbon  dioxid  as  in  air  containing  oxygen, 
and  this  without  any  obvious  disturbances.  Hence,  the  formation  of  carbon  dioxid 
must  be  independent  of  the  absorption  of  oxygen,  and  the  carbon  dioxid  must  be 
set  free  in  the  decomposition  of  other  compounds.  Finally,  however,  complete 
motor  paralysis  sets  in,  while  the  circulation  for  a  time  remains  undisturbed. 

RESPIRATION  OF  FOREIGN  GASES. 

No  gas  is  able  to  support  life  without  a  sufficient  admixture  of  oxygen.  Hence, 
without  oxygen,  all  other  gases  will  quickly  cause  suffocation  (in  two  or  three 
minutes) ,  even  though  they  be  in  themselves  harmless  and  indifferent. 

Completely  indifferent  gases  are  represented  by  nitrogen,  hydrogen,  and 
marsh-gas  (CH4).  The  blood  of  an  animal  breathing  any  of  these  gases  yields 
no  oxygen  to  it. 

Poisonous  Gases. 

(a)  Those  displacing  oxygen:  (i)  Carbon  mpnoxid  (CO).     (2)  Hydrocyanic  acid 
(CNH)  displaces  (?)  oxygen  from  the  hemoglobin,  with  which  it  forms  a  more  stable 
compound,  and  it  thus  kills  with  great  rapidity.     Further,  it  prevents  the  forma- 
tion of  ozone  from  the  oxygen  in  the  blood.     Blood-corpuscles  charged  with  hydro- 
cyanic acid  lose  the  property  of  decomposing  hydrogen  dioxid  into  water  and 
oxygen. 

(b)  Narcotic  gases:   (i)   Air  containing  o.i  per  cent,  of  carbon  dioxid  has  been 
designated  as  "bad  air";  still,  the  discomfort  experienced  in  such  an  atmosphere 
(for  example,  in  overcrowded  rooms)  arises  rather  from  offensive  exhalations  of 
unknown  character  than  from  the  carbon  dioxid  itself.     Air  containing  i  per  cent, 
of  carbon  dioxid  produces  marked  discomfort;  with  10  per  cent,  life  is  endangered, 
and  with  a  higher  percentage  death  ensues,  accompanied  by  symptoms  of  coma. 
(2)   When  nitrous  oxid  (N2O)  is  respired,  mixed  with  one-fifth  its  volume  of  oxy- 
gen, it  causes  in  from  one  and  one-half  to  two  minutes  a  short,  evanescent,  especially 
pleasurable  state  of  intoxication  (laughing-gas) ,  which  is  followed  by  an  increased 
excretion  of  carbon  dioxid.      (3)   Pure  ozonized  air  produces  similar  effects;  it  also 
causes  short,  agreeable  excitement,  then  drowsiness  and  rapidly  transient  sleep. 

(c}  Reducing  gases,  (i)  Hydrogen  sulphid  (H2S)  rapidly  deprives  the  erythro- 
cytes  of  all  oxygen,  forming  sulphur  and  water  by  oxidation;  death  occurs  quickly, 
even  before  the  gas  can  effect  any  change  in  the  hemoglobin,  with  the  formation 
of  sulphur-methemoglobin.  In  addition,  hydrogen  sulphid  forms  in  the  blood 
sodium  sulphid  from  sodium  carbonate,  the  new  compound  rapidly  causing  death. 

(2)  Hydrogen  phosphid,  phosphin  (PH3),  is  oxidized    in  the  blood  to    form 
phosphoric  acid  and  water,  with  decomposition  of  the  hemoglobin. 

(3)  Hydrogen  arsenid,   arsin  (AsHs),  and   hydrogen  antimonid,  stibin  (SbH8), 
act  like  hydrogen  phosphid,  but  in  addition  they  allow  the  hemoglobin  to  pass 
out  of  the  stroma,  so  that  the  excreta,  as  the  urine,  contain  hemoglobin. 

(4)  Cyanogen  (C2N2)  withdraws  oxygen  and  further  decomposes  the  blood. 
Irrespirable  gases   cannot  be  inspired  at  all,  as  they  cause  reflex  spasm  of 

the  glottis  on  entering  the  larynx.  If  introduced  forcibly  into  the  air-passages, 
they  give  rise  to  violent  inflammatory  processes,  followed  by  other  disturbances 
and  death.  Included  in  this  class  are  hydrochloric  acid  (HC1) ,  hydrofluoric  acid 
(HF1),  sulphurous  acid  (SO2),  nitrous  acid  (N2O4),  nitric  acid  (N,O5).  ammonia 
(NH3),  chlorin,  fluorin,  iodin,  bromin,  undiluted  ozone,  and  pure  carbon  dioxid. 

OTHER  INJURIOUS  SUBSTANCES  IN  THE  INSPIRED  AIR. 

Particles  of  dust  are  among  the  impurities  of  the  atmosphere  that  are  harmful 
in  large  quantities  and  after  long-continued  action.     Most  of  these  particles  are 
expelled  externally  by  means  of  the  ciliated  epithelium  of  the  respiratory  organs, 
whose  cilia  wave  toward  the  larynx.     Some  of  the  dust-particles,  however,  pene- 
trate the  epithelium  of  the  air- vesicles,  and  thus  reach  the  interstitial  pulmonary 
tissue,  from  which  they  frequently  pass  through  the  lymph- vessels  to  the  lymphatic 
glands  of  the  lungs.     For  this  reason  coal-dust  is  found  deposited  in  the  lun, 
of  all  elderly  persons,  blackening  the  alveoli.     In  moderate  amounts 
stances  are  harmless  in  the  tissues;    but  if  the  deposits  become  large,  they  may 
cause  pulmonary  diseases  that  may  finally  lead  to  disintegration  of  the  lungs. 
The  particles  penetrate  between  the  alveolar  epithelium  into  the  i 
monary  tissue,  and  then  into  the  lymphatic  vessels  and  glands.     In  many  trades 


246  RENEWAL    OF    THE    AIR    IN    LIVING-ROOMS. 

the  work  must  be  done  in  a  dusty  atmosphere,  and  they  are  thus  rendered  detri- 
mental to  health.  Charcoal-burners,  grinders,  stone-cutters,  file-cutters,  weavers, 
spinners,  tobacco-workers,  sawyers,  millers,  bakers,  and  others  suffer  from  various 
affections  of  the  lungs,  induced  by  the  dust  of  their  trades.  During  a  year's  work 
a  workman  in  a  horse-hair  mill  inhales  15  grams  of  dust,  in  a  saw-mill  27  grams, 
in  a  woolen  mill  30  grams,  in  a  grinding  mill  37.5  grams,  in  an  iron-foundry  42 
grams,  in  a  snuff-factory  108  grams,  in  a  cement-factory  336  grams. 

The  ciliated  epithelium  is  exceedingly  sensitive  to  mechanical  excitation.  The 
coordinated,  continuous  movement  of  the  cilia  on  a  larger  surface  does  not  depend 
wholly  upon  an  external  (mechanical)  conduction  of  the  stimulus,  but  also  upon 
an  internal  conduction  (as  in  the  nervous  system). 

There  is  no  doubt  that  with  the  inspired  air  the  germs  of  infectious  diseases 
are  often  taken  into  the  respiratory  organs,  whence  they  gain  entrance  into  the 
body.  Thus,  the  diphtheria-bacillus  becomes  localized  in  the  pharynx  and  the 
larynx,  the  glanders-bacillus  in  the  nose,  the  germ  of  whooping-cough  in  the  bronchi, 
the  microbes  of  hay-fever  and  ozena  in  the  nose,  the  influenza-bacillus  in  the  air- 


Outer  layer 

Intermediary  forms 

Inner  layer 
Squamous  cells 

FIG.  91. — Stratified  Ciliated  Cylindrical  Epithelium  of  the  Larynx  (Horse)  (after  Toldt). 

passages,  the  pneumonia-bacilhis  in  the  air- vesicles.  The  cause  of  tuberculosis, 
the  bacillus  tuberculosis,  enters  the  air-filled  pulmonary  tissue  with  the  dust  of 
tuberculous  sputa,  and  may  spread  from  that  focus  through  all  of  the  tissues.  In 
a  similar  manner  leprosy  arises  from  the  bacillus  lepras.  The  cause  of  malaria, 
the  plasmodium  malariae  possessed  of  ameboid  movement,  reaches  the  blood 
partly  through  the  respiratory  organs,  changes  the  hemoglobin  within  the  red 
corpuscles  into  melanin,  and  causes  their  destruction.  In  the  same  way  the 
blood  is  invaded  by  the  exciting  agents  of  smallpox  (micrococcus  vaccinas), 
the  spirillum  of  relapsing  fever,  the  still  little  known  microbe  of  measles,  and  the 
as  yet  undiscovered  germ  of  scarlet  fever,  etc. 

Many  disease-germs  enter  the  mouth  with  the  air,  others  with  the  food,  and 
are  swallowed,  so  that  they  undergo  development  in  the  intestinal  tract.  This  is 
true  of  cholera  (comma-bacillus),  dysentery,  typhoid  fever  (bacillus  typhosus), 
and  amebic  enteritis  (amceba  coli;  the  amceba  coli  mitis  is  less  virulent,  and  the 
amceba  intestina  vulgaris  is  harmless).  In  cattle,  anthrax  arises  in  the  same  way 
from  bacterium  anthracis. 

RENEWAL    OF    THE    AIR    IN    LIVING-ROOMS     (VENTILATION). 
EXAMINATION  OF  THE  AIR. 

Fresh  air  is  one  of  the  most  necessary  conditions  for  salutary  existence  on  the 
part  both  of  the  healthy  and  of  the  sick.  It  may  be  assumed  that  a  sufficient 
renewal  of  the  air  in  living-rooms  will  be  assured,  if  800  cu.  ft.  of  space  be  allowed 
for  every  inmate  of  a  room,  and  about  1000  cu.  ft.  for  every  sick  person.  The  neces- 
sary space  for  the  inmates  of  dwellings,  schools,  barracks,  penal  institutions,  and 
hospital-wards  should  be  measured  accordingly,  and  the  allotment  of  space  to  the 
individuals  should  be  made  only  in  this  proportion.  However,  this  standard  has 
been  materially  departed  from  in  various  countries. 

In  overcrowded  spaces  the  amount  of  carbon  dioxid  at  first  increases.  The 
normal  amount  in  the  air  (0.5  in  1000)  has  been  found  increased  in  comfortable 
living-rooms  to  from  0.54  to  0.7  in  1000;  in  badly  ventilated  sick-rooms  to  2.4 
in  1000;  in  overcrowded  auditoriums  to  3.2  in  1000;  in  pits  to  4.9  in  1000;  in 
school-rooms  to  7.2  in  1000.  Although  it  is  not  the  amount  of  carbon  dioxid 


RENEWAL    OF    THE    AIR    IN    LIVING-ROOMS.  247 

that  makes  the  air  of  crowded  spaces  injurious,  but  rather  the  exhalations  from 
the  outer  and  inner  surfaces  of  the  body,  which  at  the  same  time  render  the  air 
offensive  to  the  sense  of  smell,  still  the  amount  of  carbon  dioxid  is  an  indication 
of  the  degree  of  vitiation  of  the  atmosphere.  To  determine  whether  or  not  the 
ventilation  is  sufficient  in  spaces  crowded  with  individuals,  the  carbon  dioxid  of 
the  air  should  be  estimated  quantitatively  at  the  time  of  occupation;  hence,  in 
school-rooms,  if  possible,  shortly  before  the  close  of  the  school-session ,  or  in  sick- 
wards  or  dormitories  (barracks)  shortly  before  daybreak.  As  a  good,  comfortable 
room-atmosphere  contains  less  than  0.7  of  carbon  dioxid  in  1000,  the  ventilation 
of  a  space  must  be  considered  insufficient  if  more  than  i.o  in  1000  is  found. 

The  atmosphere  contains  only  0.0005  cubic  meter  of  carbon  dioxid  in  i  cubic 
meter  of  air,  and  an  adult  produces  hourly  0.0226  cubic  meter  of  carbon  dioxid. 
Therefore,  it  will  be  found  on  calculation  that  ventilation  must  supply  113  cubic 
meters  (for  a  child  60  cubic  meters)  of  fresh  air  hourly  for  each  person  if  the  carbon 
dioxid  in  the  living-room  is  to  be  kept  below  0.7  in  1000 — 0.7  :  1000  =  (0.0226  -f 
x  X  0.0005) :  x'  hence,  x  =  113.  If  the  amount  of  carbon  dioxid  in  the  air  of  a 
room  be  allowed  to  reach  i.o  in  1000,  then  an  hourly  ventilation  of  45  cubic 
meters  is  sufficient  for  an  adult,  and  24  cubic  meters  for  a  child. 

The  following  method  is  employed  to  determine  whether  a  living-room  has 
sufficient  ventilation.  A  large  quantity  of  carbon  dioxid  is  generated  in  the 
room,  as  much  as  i  or  2  liters  hourly  for  every  cubic  meter  of  space.  The  burning 
of  stearin-candles  may  be  employed  as  the  source  of  carbon  dioxid,  each  candle 
producing  12  liters  of  gas  in  one  hour;  a  gas-burner  supplies  100  liters  an  hour; 
an  adult  man  produces  22.6  liters  by  respiration,  and  a  school-child  12  liters 
hourly.  If  sufficient  carbon  dioxid  has  been  produced  at  the  end  of  an  hour,  the 
generator  is  removed,  and  the  first  estimation  of  carbon  dioxid  in  the  air  is  made, 
according  to  the  method  described  later  on.  At  the  end  of  another  hour,  during 
which  the  windows  and  doors  are  kept  closed,  the  second  estimation  of  carbon 
dioxid  is  made.  The  amount  of  fresh  air  that  has  entered  by  ventilation  during 

this  hour  is  calculated  by  the  following  formula:    C  =  2.3  X  m  X  log.   -  --*,    in 

which  C  represents  the  volume  in  cubic  meters  of  fresh  air  that  has  entered  by 
ventilation  in  one  hour,  m  the  volume  of  room-space  in  cubic  meters,  p  the  amount 
of  carbon  dioxid  contained  in  i  cubic  meter  of  the  air  in  the  room  at  the  first 
estimation,  expressed  in  cubic  meters,  q  the  amount  of  carbon  dioxid  in  each 
cubic  meter,  found  at  the  second  estimation  and  expressed  in  cubic  meters,  a  the 
carbon  dioxid  in  atmospheric  air  =  0.0005  cubic  meter  in  i  cubic  meter  of  air. 
Example:  In  a  school-room,  containing  40  children,  the  first  estimation  of  car- 
bon dioxid  is  made  shortly  before  the  close  of  school.  If  the  result  be  2  in  1000,  it 
will  indicate  the  presence  of  0.002  carbon  dioxid  in  i  cubic  meter  of  air.  After 
the  children  have  gone,  the  windows  and  doors  are  again  closed,  and  the  second 
analogous  estimation  is  made  at  the  end  of  an  hour.  If  the  result  be  i  in  1000, 
there  will  be  o.ooi  carbon  dioxid  in  i  cubic  meter  of  air.  The  size  of  the  school- 
room is  600  cubic  meters.  The  quantity  of  fresh  air  that  has  entered  the  space 
during  the  hour  can  be  estimated  according  to  the  foregoing  formula:  C  =  2-3X 

600     X    log.          0.002-0.0005    =    I38oX    log.        ^^    =    1380    X      log.   3      -     1380      X 
o.ooi — 0.0005  0.0005 

0.4771213  =  658.3  cubic  meters.  Hence,  658.4  cubic  meters  of  fresh  air  have 
entered  the  school-room  by  ventilation.  As  one  child  requires  60  cubic  meters  of 
fresh  air  hourly,  the  40  pupils  require  40  X  60  =  2400  cubic  meters  of  fresh  air 
in  one  hour;  but,  as  a  matter  of  fact,  the  ventilation  of  this  space  amounts  to 
only  658.4  cubic  meters;  therefore,  1741.6  cubic  meters  are  still  wanting.  Hence, 
either  a  better  ventilation  must  be  provided,  or  fewer  children  should  be  allowed 
to  attend  the  school.  A  ventilation  that  amounts  to  more  than  three  times  the 
room-space  hourly  will  be  found  to  give  rise  to  an  unpleasant  draft,  and  is,  there- 
fore, often  directly  harmful  in  winter.  For  the  school-room  in  question  containing 
600  cubic  meters  of  space,  only  1800  cubic  meters  of  ventilation  hourly  would  be 
permissible;  hence,  there  is  only  space  in  that  room  for  at  most  30  pupils  (30  >< 
60  =  1800).  As  the  space  receives  only  658  cubic  meters  of  ventilation  hourly, 
provision  must  be  made  by  better  ventilation  for  the  addition  of  1 142  cubic  meters 
more  of  fresh  air;  but  without  further  ventilation  place  could  be  found  in  the 
school  for  only  u  children  (658  -r-  60). 

In  ordinary  living-rooms,'  in  which  the  necessary  space  (800  cu.  f 
for  every  inmate,  the  air  is  sufficiently  renewed  by  the  numerous  pores  pos^ 
by  the  walls  of  the  rooms,  as  well  as  by  the  going  in  and  out,  and  further,  in  win- 


248  RENEWAL    OF    THE    AIR    IN    LIVING-ROOMS. 

ter,  by  stoves  (a  well-heated  stove  providing  a  ventilation  of  from  40  to  90  cubic 
meters  of  air  hourly).  That  this  ventilation  is  sufficient  is  proved  by  the  fact 
that  the  amount  of  carbon  dioxid  in  the  room  remains  constant.  When  there  is 
a  more  considerable  difference  between  the  temperature  in  the  room  and  that 
outside  (as  in  winter) ,  the  ventilation  is  more  than  sufficient. 

If,  however,  the  cubic  space  allotted  to  each  inmate  is  too  small,  as  in  over- 
crowded hospitals,  narrow  ship-quarters,  etc.,  then  the  necessary  change  of  air 
must  be  provided  for  by  means  of  contrivances  for  artificial  ventilation.  The 
same  must  be  done  if  noxious  exhalations  are  given  off  by  the  sick.  Above  all, 
however,  it  is  to  be  noted  that  the  natural  ventilation  through  the  pores  of  walls 
is  greatly  limited  if  they  be  damp.  At  the  same  time,  damp  walls  are  prejudicial 
to  health  by  reason  of  their  greater  conduction  of  heat,  and  also  because  the  germs 
of  infectious  diseases  can  develop  in  them,  as  in  moist  ground  generally. 

Ventilation  may  be  accomplished  either  by  aspiration,  the  exchange  of  air 
being  brought  about  by  suction-power;  or  by  pulsion,  the  fresh  air  being  pumped 
into  the  room. 

The  carbon  dioxid  contained  in  the  air  of  a  living-room  may  be  estimated 
as  follows:  A  baryta-solution  is  prepared,  containing  10  grams  of  crystallized 
barium  hydrate  and  0.5  gram  of  barium  chlorid  in  i  liter  of  water.  A  large, 
dry,  accurately  graduated,  6-liter  flask  is  filled  with  air  from  the  room  to  be  in- 
vestigated, by  blowing  the  air  for  some  time  down  to  the  bottom  of  the  flask  by 
means  of  a  bellows.  Then,  by  means  of  a  pipet  100  cu.  cm.  of  the  baryta-solution  are 
allowed  to  run  into  the  flask,  naturally  displacing  100  cu.  cm.  of  the  air.  The 
flask  is  then  closed  with  a  rubber  cap,  and  is  allowed  to  stand  for  two  hours, 
being  shaken  occasionally.  In  this  way  all  the  carbon  dioxid  is  absorbed  by  the 
baryta-solution.  Then,  25  cu.  cm.  of  the  clear,  supernatant  fluid  are  withdrawn 
into  a  medicine-bottle,  and  are  titrated  with  a  normal  oxalic-acid  solution  from 
a  graduated  buret,  until  a  drop  of  the  mixture,  when  placed  upon  turmeric  paper, 
does  not  form  a  brown  stain,  that  is  until  the  reaction  is  neutral.  A  few  drops  of 
a' solution  of  0.2  gram  of  rosolic  acid  in  100  cu.  cm.  of  dilute  alcohol  may  also  be 
added  to  the  baryta-solution  in  the  medicine-bottle,  producing  a  red  coloration. 
When  oxalic  acid  is  added,  the  mixture  is  decolorized  by  the  slightest  excess  of 
this  acid.  To  prepare  the  normal  oxalic-acid  solution,  2.8636  grams  of  pure, 
crystallized,  undecomposed  oxalic  acid,  dried  by  having  stood  over  concentrated 
sulphuric  acid  under  a  glass  bell- jar  for  four  hours,  are  dissolved  in  i  liter  of  water; 
i  cu.  cm.  of  this  solution  is  equivalent  to  i  mgm.  of  carbon  dioxid.  The  number  of 
cubic  centimeters  of  acid-solution  added  to  the  baryta-solution  is  noted.  Now, 
25  cu.  cm.  of  the  original  baryta-solution,  with  which  nothing  has  been  done,  are 
titrated  in  like  manner  with  the  normal  acid-solution  to  the  point  of  neutralization; 
here  also  the  amount  of  the  acid-solution  added  is  noted.  By  subtraction  the 
difference  is  found  between  the  amounts  of  normal  acid-solution  added  in  both 
titrations.  Each  cubic  centimeter  of  this  difference  is  equivalent  to  i  mgm.  of 
carbon  dioxid,  and  the  resulting  value  must  be  multiplied  by  4,  in  view  of  the 
fact  that  only  25  cu.  cm.  of  the  100  cu.  cm.  of  baryta-solution  were  titrated.  The 
result  gives  the  milligrams  of  carbon  dioxid  in  six  liters  minus  100  cu.  cm.  of  air. 

The  milligrams  of  carbon  dioxid  thus  determined  are  converted  into  cubic 
centimeters  by  multiplying  them  by  0.508  (as  0.508  cu.  cm.  of  carbon  dioxid,  at 
o°  C.  and  760  mm.  of  barometric  pressure,  weighs  i  mgm.).  The  volume  of  the 
air  is  further  reduced  to  o°  C.  and  760  mm.  of  barometric  pressure.  This  is  done 

according  to  the  formula  V,  =     —  — v-  B —         ,  in  which  V,  represents   the   re- 

760.  (i  +  0.003665.0  ' 

duced  volume  desired,  V  the  volume  of  air  taken  in  the  flask  for  the  experi- 
ment, B  the  barometer-reading  taken  at  the  time  of  the  experiment,  and  t  the 
temperature  in  the  investigated  room.  By  this  reduction-procedure  the  results 
can  be  obtained  in  percentages  for  possible  comparisons. 

Example:  Twenty-five  cu.  cm.  of  the  baryta-solution  are  neutralized  by  means 
of  24.6  cu.  cm.  of  the  oxalic-acid  solution;  25  cu.  cm.  of  the  baryta-solution  after 
the  absorption  of  carbon  dioxid  (taken  from  the  experiment-flask)  are  neutralized 
by  means  of  only  21.5  cu.  cm.  of  the  oxalic-acid  solution.  The  difference  between 
them,  24.6  —  21.5  =3.1,  represents  3.1  mgm.  of  carbon  dioxid,  which  have  been 
absorbed  in  the  25  cu.  cm.  of  baryta-solution.  Accordingly,  there  are  contained 
in  the  100  cu.  cm.  of  baryta-solution  employed  12.4  mgm.  of  carbon  dioxid 
(4  X  3-i).  If  it  be  assumed  that  the  large  flask  of  air  contains  4100  cu.  cm.,  of 
which  100  cu.  cm.  have  been  displaced  by  an  equal  volume  of  baryta-solution 
that  has  been  run  in,  so  that  there  remains  a  volume  of  air  equal  to  4000  cu.  cm.; 


NORMAL    FORMATION    OF    MUCUS    IN    THE    AIR-PASSAGES.  249 

and  if,  at  the  time  of  the  experiment,  the  temperature  of  the  living-room  was  20° 
C.,  and  the  barometer-reading  750  mm.,  then  the  reduced  volume  of  air  corre- 
sponding to  the  4000  cu.  cm.  is  Vl  =  __^^J^_>^  =  3678  cu.  cm.,  in  which 

are  contained  12.4  mgm.  carbon  dioxid.  One  mgm.  of  carbon  dioxid,  how- 
ever, equals  0.508  cu.  cm.;  hence,  there  were  in  3678  cu.  cm.  of  air  6.299  cu.  cm. 
of  carbon  dioxid  (12.4  X  0.508).  In  1000  cu.  cm.  air  this  amounts  to  1.7  cu.  cm. 
(according  to  the  formula  x :  1000  =  6.299  :  3678),  or  1.7  of  carbon  dioxid  in  1000. 

NORMAL  SECRETION  OF  MUCUS  IN  THE  AIR-PASSAGES. 
THE  EXPECTORATION  (SPUTUM). 

The  mucous  membrane  of  the  respiratory  tract  is  covered  by  a  thin 
layer  of  mucus.  This  mechanically  hinders  further  formation  of  mucus 
by  preventing  the  usual  irritation  of  the  air  and  dust.  Additional 
mucus  is  secreted  only  in  so  far  as  it  is  rendered  necessary  to  replace 
that  lost  by  evaporation.  As  a  rule,  increased  circulation  of  blood  in 
the  tracheal  mucous  membrane  is  attended  with  increased  secretion. 
Division  of  the  nerves  on  one  side  (in  the  cat)  gives  rise  to  redness  on 
the  same  side,  with  increased  secretion. 

On  "catching  cold"  (for  instance,  as  a  result  of  covering  the  abdomen  with 
ice)  the  mucous  membrane  first  becomes  completely  pale,  and  then  deep  red, 
with  marked  increase  in  the  secretion.  Injection  of  sodium  carbonate  and  ammo- 
nium chlorid  restricts  the  secretion.  The  local  application  of  alum,  silver  nitrate, 
or  tannic  acid  dries  the  mucous  membrane,  so  that  the  epithelium  is  cast  off. 
Apomorphin,  emetin,  and  pilocarpin  actively  stimulate  the  secretion;  atropin  and 
morphin  limit  it. 

Even  under  normal  conditions  hawking  and  coughing  will  cause  the 
expectoration  of  slimy,  viscid  material,  which  may  be  derived  from 
the  entire  respiratory  tract,  and  is  always  mixed  with  a  little  saliva. 
In  the  presence  of  catarrhal  conditions  or  of  more  serious  disease  the 
expectoration  becomes  more  profuse,  and  is  often  mixed  with  charac- 
teristic products.  It  contains: 

1.  Epithelial  cells,  especially  squamous  cells  from  the  mouth  and 
the  throat  (Fig.  92,  8),  more  rarely  alveolar  epithelium  (2),  still  more 
rarely  ciliated  epithelium  (7)  from  the  larger  air-passages.     Not  rarely 
changes  are  found  in  the  epithelium  as  a  result  of  maceration,  including 
the  cylindrical  cells  that  have  already  lost  their  cilia  (6)  and  contain 
swollen  nuclei. 

Alveolar  epithelium  (2),  with  a  diameter  from  two  to  four  times  that  of  a 
leukocyte,  is  found  especially  in  the  morning-sputum,  but  only  in  that  from  per- 
sons over  30  years  of  age.  In  younger  persons  its  presence  indicates  diseased 
conditions  of  the  pulmonary  parenchyma.  Alveolar  epithelium  is  found  also  in 
a  state  of  fatty  degeneration  and  filled  with  pigment-granules  (3);  also  in  the 
form  of  myelin-degenerated  cells  (4),  that  is,  cells  filled  with  clear  refractive 
droplets  of  varying  size,  some  being  colorless,  and  some  having  absorbed  pigment- 
granules  (dust-particles).  Also  mucin  in  myelin-forms,  that  is,  in  the  form  of 
coagulated  nerve-substance,  is  found  constantly  in  the  sputum  (5).  Mucus  is 
stained  yellow  by  safranin,  while  albumin  is  stained  red. 

2.  Leukocytes   (9)  are  present  in  large  number  in  yellow  sputum, 
and  in  smaller  number  in  clear  sputum.     They  are  to  be  looked  upon 
as  white  blood-corpuscles  that  have  wandered  from  the  blood-vessels. 
They  also  are  often  found  in  changed  forms  and  in  a  state  of  dissolution ; 
they  may  be  shrivelled  up,  filled  with  fat-granules,  or  they  may  appear 
as  conglomerations  of  granules;    and,  finally,  isolated  nuclei  indicate 
the  destruction  of  their  cell-body. 


25° 


NORMAL    FORMATION    OF    MUCUS    IN    THE    AIR-PASSAGES. 


Eosinophile  cells  are  found  in  the  sputum  from  cases  of  asthma,  and  also  in 
the  nasal  secretion  from  cases  of  acute  coryza  and  of  nasal  polyps.  Leukocytes 
containing  hemosiderin  are  found  after  capillary  hemorrhages  in  the  air-passages. 

The  fluid  substance  of  the  sputum  contains  much  mucus,  derived 
from  the  mucous  glands  and  the  goblet-cells,  also  some  nuclein  and 
lecithin,  and  the  constituents  of  the  saliva,  according  to  the  amount 
mixed  with  the  sputum.  Albumin  is  found  in  the  sputum  only  in  cases 
of  inflammation  of  the  air-passages;  its  amount  increases  with  the 
degree  of  inflammation.  Urea  has  been  found  in  the  sputum  in  cases 
of  advanced  nephritis. 

Pathological. — In  the  presence  of  catarrhal  conditions  the  sputum  is  usually 
at  first  glairy  and  slimy  (sputa  cruda) ;  later,  it  becomes  more  consistent  and 
yellow  (sputa  cocta) . 


FIG.  92. — Objects  Found  in  the  Sputum:  i,  detritus  and  dust-particles;  2,  pigmented  alveolar  epithelium;  3, 
fatty  degenerated  and  partially  pigmented  alveolar  epithelium;  4,  alveolar  epithelium  showing  myelin-de- 
generation;  5,  free  myelin-forms;  6,  7,  desquamated  ciliated  epithelium,  partly  changed  and  deprived  of  its 
cilia;  8,  squamous  epithelium  from  the  mouth;  9,  leukocytes;  10,  elastic  fibers;  n,  fibrinous  cast  of  a  small 
bronchus;  i  2  leptothrix  buccalis,  together  with  cocci  bacilli,  and  spirochetae;  a,  fatty-acid  crystals  and  free 
fatty  granules;  b,  hematoidin;  c,  Charcot's  crystals;  d,  cholesterin. 

Under  pathological  conditions  there  may  be  found  in  the  sputa : 

(a)   Erythrocytes,  always  from  rupture  of  a  blood-vessel. 

(6)  Elastic  fibers  (10)  from  destroyed  pulmonary  alveoli.  Usually  they  occur 
in  small  bundles  of  delicate  fibers,  which  at  times  suggest  the  rounded  walls  of 
the  alveoli  by  their  curved  arrangement.  Naturally,  they  always  indicate 
destruction  of  pulmonary  tissue. 

(c)  Much  more  rarely,  in  the  presence  of  rapid  and  extensive  disintegration 
of  the  lungs,  there  occur  larger  fragments  of  pulmonary  debris,  embracing  several 
alveoli ;  likewise  small  pieces  of  fibro-cartilage  or  unstriated  muscle-fibers  from  the 
small  air-passages. 

(d)  Colorless  coagula  of  fibrin  (n)  may  be  found,  and  are  usually  to  be  recog- 
nized as  casts  of  the  smaller  or  larger  air-passages.     They  are  formed  in  connection 
with  inflammatory  processes  in  the  lungs  or  bronchi  that  are  attended  with   a 
fibrinous  exudation  into  the  tubules.     They  are  thus  found  frequently  in  cases  of 
pneumonia  in  adults,  in  cases  of  bronchial  croup,  and  also,  rarely,  in   cases  of 
severe  influenza. 


EFFECTS    OF    ATMOSPHERIC    PRESSURE.  251 

(e)  Crystals  of  various  kinds :  Fatty-acid  crystals  (a) ,  arranged  in  bundles  of 
fine  needles,  usually  lying  in  whitish,  cheesy,  fetid  lumps  of  sputum.  They  indi- 
cate a  more  profound  process  of  decomposition  affecting  the  stagnating  secretion 
and  the  underlying  tissue.  Crystals  of  leucin  and  tyrosin  are  rarely  found  as 
decomposition-products  of  the  albuminates.  Tyrosin  is  found  more  abundantly 
after  rupture  of  an  old  abscess  into  the  lungs.  Colorless,  octahedral  or  rhombic 
platelets  with  elongated  points — Charcot's  crystals  (c) — have  been  found  in  the 
expectoration  in  cases  of  asthma,  hang  in  and  on  peculiar,  spirally  wound  plugs 
of  exudate  from  the  narrow  air-passages;  they  have  also  been  found  in  connection 
with  other  exudative  affections  of  the  bronchi.  These  structures,  also  called 
Curschmann's  spirals,  are  produced  when  the  respiratory  air,  in  passing  by,  draws 
out  parts  of  the  secretion  into  threads,  and  rolls  them  spirally  to  and  fro.  Hema- 
toidin-crystals  (6),  from  old  effusions  of  blood  in  the  lungs,  occur  rarely;  likewise 
cholesterin-crystals  (d) ,  arising  from  broken-up  collections  of  pus. 

(/)  Fungi  and  other  low  organisms  are  found  in  the  sputum,  being  taken  in 
during  inspiration.  The  threads  of  leptothrix  buccalis  (12)  occur  frequently, 
having  been  detached  from  deposits  on  the  teeth.  Mycelial  threads  and  spores  are 
found  in  the  sputum  in  cases  of  thrush,  which  occurs  frequently  in  the  mouths 
of  nursing  infants  as  white,  spreading  deposits  (oidium  albicans).  Among  the 
bacteria,  the  mucous-membrane  streptococci  (mostly  diplococci)  are  constantly 
found,  and  frequently  the  micrococcus  albus  liquefaciens  and  harmless  saprophytes; 
pyogenic  cocci  usually  occur  only  in  cases  of  pulmonary  tuberculosis.  In  the 
presence  of  gangrene  of  the  lungs  monads  and  cercomonads  have  been  found,  in 
cases  of  pneumonia  at  times  the  bacillus  pneumonias  of  Friedlander,  in  cases  of 
influenza  the  influenza-bacillus  of  Pfeiffer  and  Canon,  in  cases  of  whooping-cough  a 
minute  diplococcus  (according  to  Czaplewski  and  Hensel  a  non-motile  bacillus), 
in  cases  of  mumps  a  bacterium  similar  to  the  gonococcus,  in  cases  of  measles  the 
bacillus  causing  that  disease,  in  cases  of  pulmonary  tuberculosis  without  exception 
the  tubercle-bacillus.  Rarely  the  sarcina  is  found;  this  is  encountered  more  fre- 
quently in  the  stomach  in  the  presence  of  gastric  catarrh,  and  also  in  the  urine. 

With  regard  to  its  external  appearance  sputum  may  be  described  as  mucous, 
muco-purulent,  or  purulent.  When  heated  at  60°  C.  all  sputa  are  reduced  to  a 
uniform  degree  of  fluidity. 

The  sputum  may  have  an  abnormal  coloration.  Thus,  it  may  be  red  from 
blood-pigment;  if  it  remains  long  in  the  lungs,  the  blood-pigment  may  run  through 
a  whole  scale  of  colors  (as  in  external,  visible  blood-tumors),  and  it  may  thus  give 
the  sputa  a  dark-red,  bluish-brown,  brownish-yellow,  deep-yellow,  yellowish-green, 
or  grass-green  color.  The  sputum  is  sometimes  yellow  in  cases  of  jaundice. 
Colored  dust,  if  accidentally  inspired,  may  also  color  the  expectoration. 

The  odor  of  the  sputa  is  usually  stale,  and  more  or  less  unpleasant.  It  be- 
comes ill-smelling  when  it  has  remained  for  some  time  in  pathological  cavities  in 
the  lungs;  it  is  stinking  in  the  presence  of  gangrene  of  the  lungs. 

EFFECTS  OF  ATMOSPHERIC  PRESSURE. 

At  the  normal  pressure  of  the  atmosphere,  with  the  barometer  regis- 
tering 760  mm.  of  mercury,  a  pressure  is  exerted  on  the  entire  surface 
of  the  body  amounting  to  from  15,000  to  20,000  kilos,  corresponding 
to  the  extent  of  surface — 103  kilos  to  each  square  decimeter.  This 
pressure  acts  on  the  body  equally  from  all  sides,  and  in  those  internal 
air-spaces  as  well  which  are  in  direct  communication  with  the  outer 
air  either  constantly — as  the  respiratory  tract,  the  sinuses  of  the 
frontal,  superior  maxillary,  and  ethmoid  bones — or  only  temporarily 
—as  the  digestive  tract  and  the  tympanic  cavity.  If  an  air-filled  space, 
for  example  the  tympanic  cavity,  be  closed  off  from  the  outer  air  for 
some  time,  a  rarefaction  of  the  gases  in  the  space  occurs,  as  a  result  of 
the  consumption  of  oxygen  and  its  replacement  by  a  smaller  volume  of 
carbon  dioxid.  As  the  fluids  of  the  body  (blood,  lymph,  secretions, 
parenchymatous  juices)  are  practically  incompressible,  their  volume 
may  be  regarded  as  unchanged  by  the  prevailing  pressure, 
however,  absorb  gases  from  the  atmosphere  in  accordance  with  the  pre- 


252  EFFECTS    OF    ATMOSPHERIC    PRESSURE. 

vailing  pressure — that  is,  the  partial  pressure  of  the  several  gases — and 
also  with  their  temperature.  The  solid  constituents  of  the  body  are 
composed  of  innumerable  and  minute  elementary  parts,  such  as  cells 
and  fibers,  of  which  each  presents  only  a  microscopic  extent  of  surface 
to  the  influence  of  the  pressure.  Hence,  the  prevailing  atmospheric 
pressure  for  every  cell  can  be  estimated  only  at  a  few  milligrams,  a 
pressure  under  which  even  the  most  delicate  histological  structures 
develop  with  ease.  As  an  example  of  the  action  of  atmospheric  pressure 
on  larger  masses,  attention  may  be  called  to  the  fact  that,  as  a  result 
of  the  adhesion  of  the  smooth,  sticky,  articular  surfaces  of  the  shoulder- 
joints  and  the  hip-joints,  the  arm  and  the  thigh  are  supported  without 
the  aid  of  muscular  activity;  so  that,  for  example,  the  thigh  is  still  held 
in^  the  acetabulum  after  all  of  the  soft  parts  around  the  neck  of  the  femur, 
including  the  articular  capsule,  are  divided. 

An  ordinary  increase  in  barometric  pressure  has  an  influence  on 
the  respiratory  activity  in  that  it  stimulates  slightly  the  respiratory 
movements,  while  a  fall  in  barometric-pressure  has  the  opposite 
effect.  The  absolute  amount  of  carbon  dioxid  remains  the  same;  but 
in  connection  with  the  lessened  frequency  of  respiration  attending  a 
low  barometer,  the  percentage  is  naturally  somewhat  increased. 

Marked  diminution  in  the  atmospheric  pressure,  such  as  occurs  in  ascending 
mountains  or  in  balloon-voyages  (the  highest  known  ascension,  without  loss  of  con- 
sciousness having  been  made  by  Berson  of  Berlin,  to  a  height  of  9145  meters  at 
a  temperature  of  — 47.7°  C.),  causes  a  series  of  characteristic  phenomena:  (i)  As 
a  result  of  great  diminution  in  the  pressure  on  surfaces  in  direct  contact  with  the 
air,  they  undergo  marked  congestion.  Hence,  there  occur  redness  and  swelling 
of  the  skin  and  exposed  mucous  membranes,  even  to  the  extent  of  causing  hemor- 
rhages from  the  more  delicate  parts,  as  the  nose,  the  lungs,  the  gums;  turgidity  of 
the  cutaneous  veins,  profuse  sweating,  marked  secretion  from  the  mucous  mem- 
branes. The  arteries  become  more  empty;  at  one-half  the  atmospheric  pressure 
the  blood-pressure  in  the  radial  artery  begins  to  fall.  (2)  Other  direct  effects 
of  diminished  pressure  are  a  feeling  of  weight  in  the  legs,  as  the  atmospheric  pres- 
sure alone  is  not  sufficient  to  keep  the  head  of  the  femur  in  the  acetabulum ;  bulg- 
ing of  the  tympanic  membrane  by  the  air  in  the  tympanic  cavity,  until  the  differ- 
ence in  tension  is  equalized  through  the  Eustachian  tube,  and  as  a 'consequence 
pain  in  the  ears  and  even  impairment  of  hearing.  (3)  The  diminution  in  the 
tension  of  oxygen  in  the  surrounding  air  causes  difficulty  in  breathing  and  oppres- 
sion of  the  chest,  as  a  result  of  which  the  respirations  become  more  rapid  (also 
the  pulse),  deeper,  and  irregular.  At  an  elevation  of  from  3000  to  4000  meters 
the  respiration  and  pulse  are  increased  one-fourth ;  when  the  atmospheric  pressure 
is  reduced  from  one-third  to  one-half,  the  blood  loses  oxygen,  and  in  consequence 
there  is  incomplete  removal  of  the  carbon  dioxid  from  the  blood  and  a  considerable 
diminution  in  the  oxidation-processes  in  the  body.  When  the  atmospheric  pres- 
sure is  one-half  or  less,  the  amount  of  carbon  dioxid  in  the  arterial  blood  is  dimin- 
ished, and  the  amount  of  nitrogen  decreases  in  proportion  to  the  diminution  in 
atmospheric  pressure.  Rabbits  kept  under  a  pressure  of  from  300  to  400  mm.  of 
mercury  die  on  the  third  day,  and  present  widespread  fatty  degeneration,  espe- 
cially of  the  heart. 

In  men  and  in  animals,  residence  in  high,  mountainous  regions  appears  to 
increase  in  the  course  of  a  few  days  the  amount  of  hemoglobin  in  the  blood  and 
the  number  of  red  corpuscles.  This  effect  should  be  favorable  for  the  absorption 
of  oxygen.  A  noteworthy  phenomenon  is  the  appearance  of  numerous  microcytes 
in  the  first  few  days.  Dyspnea  from  various  causes  also  has  a  similar  effect  in 
man.  (4)  In  consequence  of  the  diminution  in  the  density  of  the  air,  the  latter 
is  not  able  to  produce  loud  tones  in  the  larynx  through  the  vibrations  of  the  vocal 
bands;  hence,  the  voice  appears  faint  and  altered.  (5)  In  consequence  of  the 
determination  of  blood  to  the  external  parts  in  contact  with  the  air,  the  internal 
parts  become  relatively  poor  in  blood ;  hence  result  diminution  in  the  secretion  of 
urine,  muscular  weakness,  digestive  disturbances,  dulness  of  the  senses,  fainting 
spells,  all  of  which  phenomena  are  intensified  by  the  conditions  mentioned  in 


EFFECTS    OF    ATMOSPHERIC    PRESSURE.  253 

paragraph  (3) .  According  to  the  observations  made  by  Whimper  on  himself  during 
the  ascent  ot  the  highest  peak  in  the  Andes,  the  body  can,  to  a  certain  extent 
accustom  itself  with  respect  to  these  latter  phenomena.  At  an  elevation  of  from 
7000  to  8000  meters  loss  of  consciousness  occurs  at  times;  the  aeronauts  Croce- 
bpmelli  and  Sivel  lost  their  lives  at  a  height  of  8600  meters,  where  the  rarefied 
air  contains  only  72  per  cent,  of  oxygen  (the  air-pressure  being  241  mm  of  mer- 
cury). In  dogs  a  marked  fall  in  the  blood-pressure  occurred  first  at  200  mm  of 
mercury,  accompanied  by  a  small,  slow  pulse. 

The  inhabitants  of  high,  mountainous  regions  are  sometimes  attacked  by  an 
illness  (mountain-sickness),  which  consists  essentially  of  symptoms  similar  to  those 
described,  especially  anemia  of  the  internal  organs,  and  which  is  accompanied  bv 
a  diminution  in  the  amount  of  hemoglobin  in  the  blood.  Alexander  von  Hum- 
boldt  found  remarkable  roominess  of  the  thorax  in  the  inhabitants  of  the  high 
Andes.  This  phenomenon  has  been  attributed  to  a  diminution  in  the  carbon 
dioxid  of  the  blood,  which  serves  as  a  stimulant  to  the  respiratory  center  At  an 
elevation  of  from  6000  to  8000  feet  above  the  sea,  water  contains  only  about  one- 
third  the  amount  of  air  absorbed;  therefore  fish  cannot  longer  live  in  it. 

Animals  can  be  subjected  to  a  still  greater  rarefaction  of  the  atmosphere  under 
the  receiver  of  an  air-pump.  Under  such  conditions  birds  die  when  the  air-pressure 
is  reduced  to  120  mm.  of  mercury;  mammals  at  40  mm.  of  mercury.  Frogs 
endure  repeated  evacuation,  and  as  a  result  they  become  much  distended  by 
escaping  gases  and  aqueous  vapor;  after  the  entrance  of  air,  however,  they  col- 
lapse completely.  Hoppe-Seyler  ascribes  the  cause  of  death  in  warm-blooded 
animals  to  the  development  of  gas  in  the  blood,  the  bubbles  obstructing  the  capil- 
laries. Landois  has  often  been  able  to  confirm  this  phenomenon,  and  as  far  back 
as  1879  he  suggested  that  the  development  of  gas-bubbles  in  the  parenchymatous 
juices,  especially  of  the  nervous  system,  might  act  injuriously  through  mechanical 
laceration  of  the  tissues.  Sudden  reduction  of  a  previously  high  air-pressure  may 
act  in  a  similar  manner.  The  free  gas  that  forms  in  the  blood  is  almost  pure 
nitrogen.  The  presence  of  air  in  the  arteries  of  the  spinal  cord  produces  anemic 
paralysis,  and  later  local  destruction  of  the  nerve-elements.  Redi  and  Wepfer,  in 
1685,  were  the  first  to  observe  death  from  blowing  air  into  the  veins,  as  a  result 
of  mechanical  obstruction  to  the  circulation. 

Local  diminution  of  the  air-pressure  results  in  marked  congestion  and  swelling 
of  the  tissues  in  the  affected  part ;  this  is  shown  in  the  simplest  manner  by  cupping. 
Under  the  name  of  the  ' '  cupping-boot ' '  Junod  described  an  apparatus  for  the  rare- 
faction of  air,  made  to  include  a  whole  extremity;  this  apparatus  rendered  possible 
a  reduction  to  one-third  in  the  air-pressure  surrounding  the  leg.  By  this  means 
from  2  to  3  kilos  of  blood  may  be  aspirated  into  the  leg,  thus  producing  a  temporary 
withdrawal  of  blood  from  other  parts  of  the  body,  without  causing  a  permanent 
loss  of  blood  to  the  body.  The  energetic  application  is  exceedingly  painful,  and 
the  after-effects  persist  for  48  hours. 

Marked  increase  of  the  atmospheric  pressure  is  accompanied  by  phenomena  that 
may  for  the  most  part  be  explained  as  the  reverse  of  those  described  in  the  dis- 
cussion of  diminution  of  the  air-pressure.  They  have  been  observed  many  times, 
partly  in  so-called  pneumatic  cabinets,  in  which,  for  therapeutic  purposes,  the 
pressure  is  gradually  increased  to  one  and  one-fifth,  two  and  two-fifths  atmos- 
pheres and  more;  partly  in  closed  reservoirs  used  in  construction  under  water, 
and  out  of  which  the  water  is  forced  by  pumping  air  in.  Under  such  conditions  men 
work  at  times  even  under  a  pressure  of  four  and  one-half  atmospheres.  The  fol- 
lowing phenomena  are  worthy  of  attention:  (i)  Pallor  and  dryness  of  the  external 
surfaces,  collapse  of  the  cutaneous  veins,  reduction  in  perspiration  and  the  secretions 
from  mucous  membranes,  greater  supply  of  blood  to  the  abdominal  organs.  (2) 
Pressing  inward  of  the  tympanic  membrane  (until  the  Eustachian  tube  allows  the 
compressed  air  in  the  tympanic  cavity  to  escape,  often  with  a  noise) ;  considerable 
pain  in  the  ears  and  even  impairment  of  hearing.  (3)  A  feeling  of  lightness  and 
freshness  during  respiration.  The  respirations  become  slower  (from  2  to  4  in  a 
minute),  inspiration  is  made  easier  and  shortened,  expiration  is  lengthened,  and 
the  pause  is  distinct.  The  capacity  of  the  lungs  is  increased,  owing  to  freer  move- 
ment of  the  diaphragm,  in  consequence  of  diminution  in  the  gases  contained  in 
the  intestine.  G.  v.  Liebig  has  noted  an  increase  in  the  absorption  of  oxygen; 
Panum  found  that  with  the  same  volumes  of  air  interchanged,  the  excretion  of 
carbon  dioxid  is  increased;  the  venous  blood  appears  to  be  reddened.  (4)  Diffi- 
culty in  speaking,  a  nasal  metallic  tone  to  the  voice,  inability  to  whistle.  (5)  In- 
creased secretion  of  urine;  on  account  of  the  more  rapid  oxidation  in  the  body, 


254  COMPARATIVE.       HISTORICAL. 

there  is  increased  activity  of  metabolism,  increase  in  muscular  energy,  increased 
appetite,  subjective  feeling  of  warmth.  The  pulse  is  slower,  and  the  pulse-curve 
lower. 

On  account  of  the  invigorating  and  stimulating  effect  of  a  sojourn  in  moder- 
ately compressed  air,  the  employment  of  the  latter  has  been  practised  for  thera- 
peutic purposes ;  and  it  has  been  found  that  repeated  applications  have  produced 
favorable  after-effects  of  considerable  duration.  Unduly  rapid  increase  of  pressure 
is  to  be  avoided  and  likewise  unduly  rapid  removal  of  the  pressure. 

Waldenburg  and  others  have  constructed  apparatus  in  the  form  of  a  spirom- 
eter;  either  compressed  air  maybe  inspired  from  its  bell-jar,  or  the  bell- jar  may 
be  filled  with  rarefied  air,  into  which  the  expirations  are  made.  Both  methods 
are  used  in  suitable  cases  for  therapeutic  purposes. 

Paul  Bert  has  found  at  an  excessively  high,  artificial  atmospheric  pressure, 
over  30  vol.  per  cent,  oxygen  in  the  arterial  blood  of  animals  (investigated  at 
700  mm.  of  mercury).  If  the  amount  of  oxygen  reaches  35  vol.  per  cent.,  death 
occurs,  accompanied  by  convulsions.  At  a  somewhat  lower  point  the  bodily  tem- 
perature falls,  the  oxidation-processes  in  the  body  are  reduced,  strange  to  say, 
and  as  a  result  of  this  the  formation  of  carbon  dioxid  and  urea  is  diminished. 
Greatly  compressed  oxygen  also  produces  the  effect  of  a  relative  deficiency  of 
oxygen;  animals  die  in  it,  exhibiting  signs  of  suffocation  with  greatly  reduced 
metabolic  processes. 

Frogs  exhibit  in  compressed  oxygen  (up  to  14  atmospheres)  the  same  phe- 
nomena as  they  would  in  a  vacuum  or  in  pure  nitrogen.  There  occurs  paralysis 
of  the  central  nervous  system,  at  times  preceded  by  convulsions.  Then  the  heart 
stops  beating  (but  not  the  lymph-hearts) ,  and  at  the  same  time  the  motor  nerves 
lose  their  irritability;  finally,  the  direct  muscular  irritability  disappears. 

Under  exceedingly  high  pressure  of  oxygen  (thirteen  atmospheres)  an  excised 
frog's  heart  beats  scarcely  one-fourth  the  time  that  it  remains  active  in  the  air. 
If  the  quiet  heart  be  brought  into  the  air,  the  pulsations  may  return.  Under  a 
pressure  of  100  atmospheres  the  frog's  muscles  still  contract  normally,  and  only 
at  400  atmospheres  do  they  become  paralyzed. 

Phosphorus  ceases  to  be  luminiferous  under  high  pressure  of  oxygen,  but  not, 
however,  the  phosphorescent  organisms, — for  example,  the  lamprey, — or  the  phos- 
phorescent bacteria,  such  as  those  of  meat  (micrococcus  Pflugeri).  Exceedingly 
high  atmospheric  pressure  is  injurious  to  plants  also. 

COMPARATIVE.     HISTORICAL. 

Mammals  have  lungs  similar  to  those  of  man.  Those  of  birds  exhibit  a  spongy 
structure;  they  are  fused  with  the  inner  surface  of  the  chest-wall,  and  have,  on 
their  outer  surface,  openings  that  lead  into  large,  thin- walled  air-sacs,  lying  among 
the  viscera.  These  air-sacs  further  communicate  with  the  cavities  in  the  bones, 
which  contain  air  instead  of  marrow,  in  order  to  provide  greater  lightness  (pneu- 
maticity  of  the  bones).  There  is  no  diaphragm.  In  reptiles  the  lungs  are  divided 
into  larger  and  smaller  divisions  of  vesicles;  in  snakes  one  lung  atrophies,  while 
the  other  becomes  greatly  drawn  out  and  elongated,  in  accordance  with  the  form 
of  the  body.  Frogs  pump  air  into  their  lungs  by  contraction  of  the  pharyngeal 
sac,  the  nostrils  being  closed  and  the  larynx  opened.  Turtles  fill  their  lungs  with 
air  by  a  sucking  movement.  Amphibia  (frog)  possess  two  simple  lungs,  each  of 
which  in  its  structure  to  a  certain  extent  represents  an  enormous  infundibulum 
with  its  alveoli.  When  young  (until  their  metamorphosis)  they  live  as  aquatic 
animals,  and  breathe  by  means  of  gills;  the  perennibranchiates  (proteus)  indeed, 
like  the  fishes,  breathe  in  this  manner  throughout  life.  Among  fishes  the  dipnoi, 
besides  their  gills,  possess  a  swimming-bladder,  abundantly  supplied  with  afferent 
and  efferent  vessels,  constituting  an  internal  respiratory  organ  remotely  comparable 
to  the  lungs.  By  the  term  "gills"  is  meant  an  organ  for  respiration  in  water, 
constructed  in  the  form  of  numerous,  vascular,  plate-like  diverticula.  Among  the 
fishes,  the  mud-fish  (cobitis)  exhibits  an  intestinal  respiration,  when  there  is  lack 
of  water  and  it  buries  itself  in  mud;  in  this  process  air  is  swallowed  on  the  upper 
surface  of  the  water,  the  oxygen  is  abstracted  in  the  intestines,  and  carbon  dioxid 
is  discharged  through  the  anus.  Insects  and  centipedes  respire  through  tracheas, 
which  consist  of  numerous  air-canals  distributed  throughout  the  body  and  com- 
municating with  the  atmosphere  on  the  outer  surface  of  the  body  by  means  of 
openings  (stigmata)  that  can  be  closed.  As  insects  possess  no  true  circulatory 
movement  of  the  blood,  the  air  conducted  through  tubes  penetrates  from  all  sides 


COMPARATIVE.       HISTORICAL. 


255 


into  the  blood-filled  body-cavities;  while  in  the  lung-breathing  vertebrates  the 
blood  conducted  through  tubes  is  brought  from  the  whole  body  to  the  respiratory 
organ.  The  stigmata  on  the  outer  surface  of  the  body,  constituting  the  entrances 
to  the  tracheas,  are  provided  with  peculiar  contrivances  for  closing,  and  can  be 
employed  for  the  emission  of  sounds.  Arachnids  respire  by  means  of  tracheas  and 
lung-like  air-sacs  (tracheal  pouches) ;  crabs,  by  means  of  gills.  Mussels  and  cephalo- 
pods  possess  fully  developed  gills;  snails  have  partly  gills,  partly  lungs.  Among 
the  lower  animals,  gill-like  formations  are  still  found  among  the  round  worms  and 
in  the  echinoderms ;  intestinal  respiration  occurs  in  the  tunicates  and  many  of  the 
mites.  Respiration  by  means  of  a  water- vascular  system,  a  system  of  canals  through 
which  water  flows,  is  peculiar  to  the  medusas  and  the  flat  worms.  The  lowest  animal 
forms — protozoa,  sponges,  polyps — do  not  possess  a  special  respiratory  organ;  in 
them  the  surfaces  in  contact  with  water  carry  on  the  respiratory  interchange  of 
gases. 

Historical. — Aristotle  (384  B.  C.)  regarded  the  object  of  respiration  to  be  the 
cooling  of  the  body,  in  order  to  moderate  the  internal  heat.  He  observed  cor- 
rectly that  the  warmest  animals  also  respire  most  actively,  but  in  the  interpretation 
he  reversed  cause  and  effect;  for  the  warm-blooded  animals  do  not  respire  on 
account  of  their  heat  (for  cooling  purposes) ,  but  they  are  warm  as  a  result  of  their 
more  active  respiration  (combustion). 

Galen  (203-131  B.  C.)  already  observed  the  purifying  action  of  the  respiratory 
organ,  assuming  that  the  "soot"  was  removed  from  the  body  with  the  expired 
air,  together  with  the  expired  water.  The  most  important  experiments  concerning 
the  mechanics  of  respiration  date  from  Galen.  He  maintained  that  the  lungs 
passively  follow  the  movements  of  the  thorax,  that  the  diaphragm  is  the  most 
important  respiratory  muscle,  that  the  external  intercostals  are  inspiratory  mus- 
cles, and  the  internal  intercostals  expiratory.  He  divided  the  intercostal  nerves 
and  muscles,  and  observed  that  loss  of  voice  followed.  After  dividing  the  spinal 
cord  at  progressively  higher  levels,  he  found  that  successively  higher  thoracic 
muscles  became  paralyzed.  Theophilus  Philaretus  taught  that  the  circulation 
could  be  improved  by  loud  crying,  singing,  or  speaking.  Oribasius  (360  A.  D.) 
observed  that  both  lungs  collapsed  in  the  presence  of  double  pneumothorax. 
Vesalius  (1540)  first  described  artificial  respiration  as  a  means  of  reanimating  and 
stimulating  the  heart's  action.  Malpighi  (1661)  described  the  peculiar  structures 
of  the  lungs.  Lower  (1669).  saw  the  blood  become  bright  red  in  the  lungs. 
Borelli  (died  1679)  first  explained  most  thoroughly  the  mechanism  of  the  respira- 
tory movements. 

The  chemical  processes  attending  respiration  were  already  suspected  by 
Mayow  (1679):  "Ignis  et  vita  iisdem  particulis  aereis  sustinetur."  However, 
more  accurate  knowledge  could  be  obtained  only  after  the  discovery  of  the  several 
gases  coming  under  observation.  J.  B.  van  Helmont  (died  1644)  discovered  car- 
bon dioxid,  and  found  that  the  air  was  vitiated  by  respiration;  but  Black  (1757) 
first  discovered  the  excretion  of  carbon  dioxid  during  respiration.  In  1774  Pristley 
and  Scheele  discovered  oxygen.  Lavoisier,  in  1775,  found  the  nitrogen,  and  at 
the  same  time  ascertained  the  composition  of  the  atmosphere.  The  same  investi- 
gator also  represented  the  formation  of  carbon  dioxid  and  water  during  respiration 
as  being  the  result  of  combustion  within  the  lungs.  J.  Ingenhousz  (1779)  dis- 
covered the  respiration  of  plants — the  absorption  of  carbon  dioxid  and  the  giving 
off  of  oxygen  during  that  process.  Senebier  (1785)  found  that  this  exhaled  oxygen 
arose  from  decomposition  of  the  carbon  dioxid.  Vogel  and  others  definitely  proved 
the  existence  of  carbon  dioxid  in  venous  blood.  Hoffmann  and  others  demon- 
strated the  presence  of  oxygen  in  arterial  blood.  Lavoisier  with  Seguin,  in  1789, 
made  the  first  communication  concerning  the  quantitative  absorption  of  oxygen 
and  excretion  of  carbon  dioxid  during  respiration.  More  complete  insight  into  the 
interchange  of  gases  during  respiration  could  be  obtained  only  after  Magnus  ex- 
tracted and  analyzed  the  gases  from  arterial  and  venous  blood. 


PHYSIOLOGY  OF  DIGESTION. 


THE  MOUTH  AND  ITS  GLANDS. 

The  mucous  membrane  of  the  mouth  contains  sebaceous  glands  at  the  red 
edge  of  the  lips.  It  consists  of  fibrillar  connective  tissue  intermixed  with  fine 
elastic  fibers.  Toward  the  free  surface  it  forms  papillae,  of  which  the  largest 
(0.5  mm.)  are  found  on  the  lips  and  the  gums,  including  some  with  double 
points — twin  papillae.  The  smallest  are  on  the  palate  and  in  the  fold-like  duplica- 
tures  of  the  mucosa.  The  submucous  tissue,  which  passes  directly  over  into  the 
mucosa,  is  thickest  and  most  dense  where  the  mucous  membrane  is  immovably 
attached  to  the  periosteum  of  the  maxilla  and  the  palate,  and  also  in  the  vicinity 
of  glandular  involutions;  while  it  is  most  delicate  over  movable  and  folded  parts. 

The  surface  is  lined  by  stratified  nucleated 
squamous  epithelium  (Fig.  92,  8),  and  it  is,  as  a 
rule,  strongest  and  consists  of  the  largest 
number  of  layers  in  regions  where  the  papillae 
are  longest.  A  diplosoma  is  found  in  the 
deeper  cells  of  the  surface  of  the  tongue. 

All  of  the  glands  of  the  mouth,  in- 
cluding the  salivary  glands,  are  divided, 
with  reference  to  their  secretion,  into 
three  groups:  (i)  albuminous  or  serous 
glands,  whose  secretion  contains  albumin; 
(2)  mucous  glands,  whose  ropy  secretion 
contains  mucin,  together  with  some  albu- 
min; (3)  mixed  glands,  whose  acini  secrete 
partly  albumin  and  partly  mucin,  as,  for 
example,  the  submaxillary  gland  in  man. 
For  a  description  of  their  structure  refer- 
ence may  be  made  to  page  258. 

Numerous  mucous  glands — termed  buccal, 
palatine,  lingual  or  molar  muciparous  glands,  in 
accordance  with  the  region  in  which  they  occur 
— are  present  in  the  tissue  of  the  mucosa,  their 
bodies  appearing  macroscopically  as  tiny  white 
nodules.  They  represent  the  type  of  simple  branched  tubular  glands.  The  con- 
tents of  their  secreting  cells  are  partly  mucus,  which  is  expelled  at  the  time  of 
secretion.  The  excretory  duct,  formed  of  connective  and  elastic  tissues,  with 
a  narrow  outlet,  is  lined  by  a  single  layer  of  cylindrical  epithelium.  One  duct 
often  receives  that  of  a  neighboring  gland.  The  labial  glands  are  mixed  glands. 

The  small  glands  of  the  tongue  deserve  special  consideration.  Two  morpho- 
logically and  physiologically  distinct  glands  can  be  distinguished,  namely  (i) 
mucous  glands  (E.  H.  Weber's  glands),  situated  especially  near  the  root  of  the 
tongue;  compound  alveolar  glands,  with  bright,  transparent,  secreting  cells  and 
mural  nuclei,  and  a  rather  thick  membrana  prbpria;  and  (2)  serous  glands  (von 
Ebner's  glands) ,  situated  about  the  circumvallate  papillae  (and  the  foliate  papillae 
in  animals),  and  consisting  of  convoluted  and  branched  tubules,  characterized  by 
small,  narrow  cells,  filled  with  droplets  of  secretion,  containing  a  centrosome  and 
yielding  an  albuminous  secretion.  Halfwav  up  between  the  cells  the  intercellular 
secretory  ducts  are  found.  (3)  The  Blandin-Nuhn  glands,  within  the  tip  of  the 
tongue,  consist  of  glandular  lobules  secreting  mucus  and  saliva,  and  are,  therefore, 
mixed  glands.  Delicate  varicose  nerve-fibers  pass  up  to  the  cells. 

256 


FIG.  93. — Section  through  Lymph-folli- 
cles of  the  Root  of  the  Tongue 
(after  Schenk):  B,  lymph-follicles; 
V,  depression;  A,  adenoid  connec- 
tive tissue;  S,  mucous  glands;  E, 
epithelium. 


THE    SALIVARY    GLANDS. 


257 


Of  the  blood-vessels,  which  are  abundant,  the  larger  lie  in  the  submucosa, 
while  the  smaller  penetrate  into  the  papillae,  in  which  they  form  either  capillary 
networks  or  simple  loops. 

Of  the  lymph-vessels  the  larger  trunks,  which  form  a  coarse  meshwork,  lie  in 
the  submucosa,  while  the  smaller,  forming  a  finer  network,  pass  through  the  mucous 
membrane  itself.  The  cutaneous  follicles  or  lymph-follicles  constitute  a  part  of 
the  lymphatic  apparatus.  They  form  an  almost  coherent  layer  on  the  back  of  the 
tongue  at  its  root.  Several  of  these  lymph-follicles  always  collect  into  a  round 
mass,  surrounded  by  connective  tissue,  and  raising  .  the  mucous  membrane 
somewhat.  In  the  center  of  every  such  collection  is  a  depression  (Fig.  93)  into  the 
bottom  of  which  mucous  glands  empty  and  fill  thesmall  crater  with  mucous  secretion. 

The  tonsils  exhibit  on  the  whole  the  same  formation, — crypt-like  depressions, 
into  the  sinuses  of  which  small  mucous  glands  empty,  and  surrounded  by  masses  of 
from  10  to  20  lymph-follicles.  Layers  of  firm  connective  tissue  form  a  sheath  about 
the  tonsils.  The  pharyngeal  and  tubal  tonsils  exhibit  a  similar  structure. 

Many  medullated  nerve-fibers,  coming  from  the  submucous  tissue,  ramify  in 
the  mucous  membrane  and  terminate  in  part  in  separate  papillas  in  the  form  of 
Krause's  end-bulbs,  in  larger  number  on  the  lips  and  the  soft  palate,  in  smaller 
number  on  the  cheeks  and  the  floor  of  the  mouth.  Probably  the  nerves  also 
spread  out  in  the  form  of  fine  terminal  nodules  between  the  epithelial  cells,  accord- 
ing to  the  Cohnheim-Langerhans  mode  of  distribution.  Functionally  these  are 
sensory  nerves  and  nerves  of  touch. 


THE  SALIVARY  GLANDS. 

The  salivary  glands  and  also  the  pancreas  are  compound  tubular 
glands.  The  excretory  ducts,  formed  of  connective  and  elastic  tissues 
(Wharton's  duct  contains  also  unstriated  muscle-fibers)  are  lined  with 


Fio.  94.-Histology  of  the  Salivary  GUu£:  J^J  j 

ti^S^^^^ 


Into  the  structureless  membrane  of  the  acinus 
incorporated  a  layer  °V^ 

cells  (Fig.  94,  D).     Next  to  the  outer  wall  of  the  acinus 
17 


258 


THE    SALIVARY    GLANDS. 


lymph-cavities,  and  beyond  these  the  blood-capillaries  run  in  a  net-like 
meshwork.     The  lymph- vessels  leave  the  gland  at  the  hilum. 

The  secreting  cells  are  of  varying  structure,  accordingly  as  the  sali- 
vary gland  secretes  mucus  (sublingual  gland  in  man,  submaxillary  gland 
in  the  dog)  or  albumin  (parotid  gland  in  man),  or  is  a  mixed  gland 
(submaxillary  gland  in  human  beings). 

Two  kinds  of  cellular  elements  are  found  in  the  acini  of  the  sub- 
maxillary gland  of  the  dog  and  the  sublingual  gland  of  human  beings: 
(i)  The  so-called  mucous  cells  (Fig.  94,  B,  c),  which  bound  the  secretory 
cavity.  They  possess  a  membrane  and  are  filled  with  a  flattened 
nucleus  turned  toward  the  acinus- wall.  Centrosomes  are  difficult  to 
recognize.  The  cell-body  is  abundantly  impregnated  with  mucin,  which 

gives  it  a  bright,  highly  refractive  ap- 
pearance. On  account  of  their  mucous 
contents  the  cell-bodies  hardly  stain 
with  carmine  at  all,  while  the  nucleus 
takes  up  the  stain.  A  process  given  off 
by  the  cell  applies  itself  in  a  curved 
manner  to  the  inner  wall  of  the  acinus. 
The  true  protoplasm  of  the  cell  is 
drawn  out  in  a  thread-like  network 
from  the  nucleus  through  the  mucin- 
mass.  (2)  The  other  variety  of  cellular 
elements  form  crescent-shaped  complex 
bodies  (Fig.  94,  B,  d) — Gianuzzi's  cres- 
cents, Heidenhain's  composite  marginal 
cells — that  lie  in  direct  contact  with  the 
wall  of  the  acinus.  Each  crescent  con- 
sists of  a  number  of  small,  closely 
packed,  angular  cells,  with  albuminous 
contents  and  nuclei  and  separated  with 
difficulty.  They  are  granular,  darker, 
without  mucous  contents,  easily  impreg- 
nated by  stains,  and  exhibit  secreting 
spaces  between  the  cells. 

The  parotid  gland  (Fig.  95),  secret- 
ing albumin  in  man  and  in  mammals, 
contains  but  one  kind  of  secretory  cells, 
namely,  cubical  cells,  with  a  coarse-meshed  protoplasm,  staining  little 
with  pigments,  without  a  membrane,  with  serrated,  readily  stained, 
centrally  situated,  highly  refractive  nuclei,  without  nucleoli,  with  secre- 
tory ducts  between  them.  The  smaller  cells  of  the  salivary  tubules 
bear  a  diplosoma  near  their  free  surface.  The  salivary  glands  of 
animals  that  secrete  saliva  free  from  mucus  present  similar  features. 

By  means  of  fine  ducts,  the  so-called  intercalary  pieces,  the  terminal  portions 
of  the  glands  communicate  with  the  thicker  salivary  tubules.  The  cells  of  these 
tubules,  which,  in  their  outer  portions,  appear  fibrillated,  and  at  times  contain 
yellow  granules  (Fig.  94,  E),  bear  a  diplosoma  near  the  surface.  These  salivary 
tubules  empty  into  the  excretory  ducts.  It  is  not  improbable  that  these  different 
portions  of  the  gland  also  secrete  different  constituents  of  the  saliva. 


FIG.  95. — Diagrammatic  Representation  of  a 
Salivary  Gland:  a,  excretory  duct;  r,  r, 
salivary  tubules;  s,  intercalary  portion; 
e,  e,  terminal  portions.  P,  terminal  por- 
tions of  the  parotid  gland,  with  intercel- 
lular secretory  ducts  (stained  black), 
passing  over  into  the  excretory  duct  (a) 
of  the  intercalary  portion  (s);  r,  parotid 
cell  at  rest;  t,  the  same  cell  after  secre- 
tion. 


THE    SECRETORY    ACTIVITY    OF    THE    SALIVARY    GLANDS.  259 

THE  SECRETORY  ACTIVITY  OF  THE  SALIVARY  GLANDS. 

If  the  submaxillary  gland  of  a  dog  is  excited  to  active  secretion  by 
stimulation  of  its  nerves,  the  mucous  cells  are  after  a  while  no  longer  seen 
but  in  their  stead  only  smaller  protoplasmic  cells,  devoid  of  mucus,  within 
the  acini.  The  mucous  cells  have  discharged  their  mucus  into  the  secre- 
tion of  the  gland,  while  their  shrunken,  dark-granular  protoplasmic  cell- 
bodies  remain  (Fig.  94,  C).  These  are  capable,  after  a  certain  period 
of  rest,  of  producing  new  mucus. 

In  regard  to  the  crescents  Stohr  believes  that  they  are  produced  mechanically 
by  inequality  in  the  secretory  phases  in  adjacent  acinus-cells.  The  cells  reduced 
in  size  after  having  discharged  their  mucus  are  pressed  to  the  wall  by  other  cells 
filled  with  mucus  and  therefore  much  swollen,  and  thus  the  flattened  composite 
marginal  cells  are  formed.  Recently  R.  Krause  and  others,  differing  from  this 
state  that  the  composite  marginal  cells  secrete  only  serum  and  have  no  relation 
with  the  mucous  cells. 

In  the  parotid  gland  of  the  rabbit,  after  secretion  induced  by  stimula- 
tion of  the  sympathetic  nerve,  the  gland-cells  assume  a  more  shrunken 
appearance,  and  their  contents  become  more  granular  and  more  readily 
stained.  The  nuclei  appear  rounder  and  exhibit  a  nucleolus  (Fig.  95). 

Ranvier  observed  in  the  secretion  of  the  albuminous  glands  (submaxillary 
gland  in  the  rat)  that,  after  stimulation,  many  motile  vacuoles  were  formed  in  the 
gland-cells.  The  water  of  the  secretion  is  formed  in  the  vacuoles,  and  in  its 
excretion,  carries  with  it  the  soluble  ferment  of  the  cells.  A  similar  phenomenon 
occurs  within  mucous  cells  and  also  in  goblet-cells.  Morphological  changes  occur 
also  in  the  cells  of  the  salivary  tubules. 

THE  NERVES  OF  THE  SALIVARY  GLANDS. 

All  the  salivary  glands  derive  their  nerve-supply  from  two  sources,  namely 
from  the  sympathetic  nerve  and  from  a  cranial  nerve.  The  nerve-fibers,  chiefly 
medullated,  in  part  also  non-medullated,  pass  in  at  the  hilum  and  form  a  plexus 
rich  in  ganglion-cells  between  the  lobules  of  the  gland. 

The  sympathetic  nerve  sends  branches  (a)  to  the  submaxillary  and  sublingual 
glands,  derived  from  the  plexus  surrounding  the  external  maxillary  artery  (Fig. 
243) ;  (b)  filaments  pass  to  the  parotid  gland  from  the  sympathetic  plexus,  which, 
piercing  the  parotid,  surrounds  the  external  carotid  artery. 

Of  the  cranial  nerves,  (a)  the  submaxillary  and  sublingual  glands  are  supplied 
by  filaments  from  the  chorda  tympani  branch  of  the  facial  nerve,  (b)  To  the 
parotid  gland  fibers  pass  from  the  glosso-pharyngeal  nerve  in  the  dog,  especially 
from  its  tympanic  branch,  which  sends  fibers  through  the  tympanic  plexus  to  the 
lesser  superficial  petrosal  nerve.  Together  with  the  latter  the  former  pass  down- 
ward over  the  anterior  surface  of  the  petrous  portion  of  the  temporal  bone,  then 
through  the  sphenoidal  fissure  to  the  otic  ganglion.  With  the  latter  they  con- 
tinue through  communicating  branches  to  the  auriculo-temporal  nerve  (from  the 
third  division  of  the  trigeminal  nerve) ,  which,  covered  by  the  parotid  gland,  on 
its  way  to  the  temple,  sends  the  fibers  to  the  gland. 

The  submaxillary  ganglion,  which  gives  off  fibers  to  the  submaxillary  and 
sublingual  glands,  derives  its  roots  from  the  tympanico-lingual  plexus,  as  well  as 
from  the  sympathetic  plexus  about  the  external  maxillary  artery. 

With  regard  to  the  terminal  distribution  of  the  nerves  to  the  salivary  glands, 
two  varieties  are  to  be  distinguished:  (i)  the  vasomotor  nerves,  which  give  branches 
to  the  muscular  walls  of  the  blood-vessels,  and  (2)  the  true  glandular  nerves. 

According  to  Arnstein  the  latter  form  a  surrounding  network  outside  of  the 
gland-tubules.  From  this  plexus  fine  filaments  pierce  the  membrana  propria  and 
terminate  on  the  surface  of  the  secreting  cells  with  a  peculiar  end-apparatus: 
namely,  branched  twigs  possessing  tiny  bulbs  or  mulberry-shaped  masses.  The 
same  condition  exists  in  the  sebaceous,  sudoriferous,  and  mammary  glands  and 
in  the  pancreas. 


260  INFLUENCE    OF    NERVES    ON    THE    SECRETION    OF    SALIVA. 

THE  INFLUENCE   OF  THE  NERVOUS  SYSTEM   ON  THE 
SECRETION  OF  SALIVA. 

The  Submaxillary  Gland. — Stimulation  of  the  facial  nerve  at  its 
root  causes  profuse  secretion  of  limpid  saliva  deficient  in  the  specific 
constituents.  At  the  same  time  the  blood-vessels  of  the  gland  undergo 
, dilatation.  The  capillaries,  in  the  presence  of  increased  blood-pressure 
in  them,  undergo  such  a  degree  of  dilatation  that  the  pulsating  move- 
ment of  the  arteries  is  transmitted  into  the  veins.  More  than  four 
times  as  much  blood  flows  back  from  the  vein,  which,  besides,  appears 
almost  bright  red  in  color  and  contains  more  than  one-third  as  much 
oxygen  as  the  venous  blood  of  the  unstimulated  gland.  In  spite  of  the 
relatively  large  amount  of  oxygen  in  venous  blood,  the  secreting  gland 
consumes  absolutely  more  oxygen  than  the  inactive  gland. 

The  facial  nerve  contains  two  sets  of  functionally  different  fibers: 
(i)  true  secretory  nerves  and  (2)  vasodilatator  nerves.  It  is  not  per- 
missible to  regard  the  phenomenon  of  secretion  as  a  simple  result  of 
increased  circulatory  activity. 

Stimulation  of  the  sympathetic  nerve  causes  the  scanty  secretion  of 
a  viscid,  gelatinous,  ropy  saliva,  containing  the  specific  constituents, 
particularly  mucus  and  the  salivary  corpuscles,  in  abundance,  and  having 
a  specific  gravity  of  from  1007  to  1010.  At  the  same  time,  with  de- 
crease in  the  blood-pressure,  the  blood-vessels  of  the  gland  undergo 
contraction,  so  that  the  small  amount  of  blood  escapes  from  the  veins 
with  a  dark-blue  color. 

The  sympathetic  nerve  likewise  contains  two  sets  of  functionally  different 
nerve-fibers,  (i)  true  secretory  fibers  and  (2)  vasoconstrictor  nerves.  Continued 
stimulation  of  the  chorda  tympani  and  the  sympathetic  nerve  alters  the  secretions, 
making  them  more  nearly  alike,  and  thus  teaches  that,  essentially,  the  saliva  pro- 
duced by  stimulation  of  the  chorda  tympani  and  that  produced  by  stimulation  of 
the  sympathetic  nerve  differ  not  specifically,  but  only  in  degree.  With  increasing 
nerve-stimulation  the  secretion  increases,  and  with  it  the  amount  of  contained  salts. 
The  organic  constituents  depend,  in  addition  to  the  intensity  of  the  stimula- 
tion, upon  the  condition  of  the  gland,  whether  at  rest  or  exhausted.  The 
constitution  of  the  blood  and  the  circulatory  conditions  in  the  gland  likewise 
influence  the  composition  of  the  saliva. 

That  the  secretion  of  the  glands  cannot  be  considered  as  a  simple  filtration 
as  the  result  of  changes  in  blood-pressure,  but  that  it  occurs  as  an  independent 
function  in  conjunction  with  changes  in  the  blood-vessels,  will  appear  from  the 
following  considerations : 

1.  The  secretory  activity  of  the  gland,  on  stimulation  of  the  nerves,  continues 
for  some  time  even  after  all  blood-vessels  have  been  ligated. 

2 .  Atropin  and  daturin  destroy  the  activity  of  the  secreting  fibers  in  the  chorda 
tympani,  but  not  that  of  the  vasodilator  fibers. 

3.  The  pressure  in  the  excretory  ducts  of  the  salivary  glands,  which  can  be 
measured  by  means  of  a  manometer  tied  in  the  duct,  may  be  almost  twice  as 
great  as  that  in  the  arteries  of  the  gland,  having  reached  about  290  mm.  of  mercury 
in  the  excretory  duct  of  the  submaxillary  gland.     With  increase  in  the  pressure 
the  amount  of  saliva  diminishes,  as  does  likewise  the  amount  of  work  performed 
by  the  gland. 

4.  The  salivary  glands,  in  the  same  way  as  nerves  and  muscles,  also  fatigue, 
especially  after  injection  of  acids  or  alkalies  into  the  excretory  duct.     This  indi- 
cates that  the  secretory  structure  is  independent  of  the  circulation  and  under  the 
influence  of  the  nerves. 

5.  That  in  the  secretion  of  saliva  the  cellular  activity  of  the  glands  also  is 
evident  is  shown  by  the  researches  of  Zerner,  who,  after  intravenous  injection  of 
indigo-carmine,  found  this  substance  within  the  mucous  cells  and  the  rod-cells. 

It  must,  therefore,  be  inferred  that  the  nerves  exert  a  direct  influence  on  the 


INFLUENCE    OF    NERVES    ON    THE    SECRETION    OF    SALIVA.  261 

secreting  cells  of  the  glands,  independent  of  any  mediation  on  the  part  of  the 
blood-vessels.  As  the  direct  anatomical  connection  between  the  nerve-fibers  and 
the  secreting  cells  appears  proved,  so,  also,  is  the  physiological  connection  to  be 
accepted. 

During  the  process  of  secretion  the  temperature  of  the  submaxillary  gland 
rises  about  1.5°  C.  The  gland,  as  well  as  the  venous  blood  leaving  it,  is  not  rarely 
warmer  than  the  arterial  blood.  Between  the  irritation  of  the  nerve  and  the 
beginning  of  secretion,  from  1.2  to  24  seconds  elapse. 

Paralytic  Secretion  of  Saliva. — By  this  term  is  understood  the  persistent  secre- 
tion of  limpid  saliva  from  the  submaxillary  gland,  which  sets  in  twenty-four  hours 
after  division  of  the  cerebral  nerves,  whether  the  sympathetic  nerve  is  also  injured 
or  is  preserved.  It  increases  for  perhaps  eight  days;  then,  with  degeneration  of 
the  gland,  it  decreases.  The  injection  of  small  amounts  of  curare  into  the  artery 
of  the  gland  also  produces  the  condition,  which  is  prevented  by  apnea,  while 
dyspnea  favors  it.  After  a  unilateral  lesion  both  glands  are  said  to  take  part 
in  the  secretion.  According  to  Langley,  after  division  of  the  chorda  tympani,  its 
central  end  acquires  increased  irritability.  This  exerts  a  centripetal  effect  upon 
the  salivary  center  on  both  sides.  At  the  same  time,  soon  after  the  division,  a 
ganglionic  local  secreting  center,  situated  in  the  gland  of  the  same  side,  also  is 
stimulated,  so  that,  if  all  of  the  nerve-fibers  passing  to  the  gland  are!later'separated, 
the  salivary  secretion  from  the  gland  still  continues. 

The  Sublingual  Gland. — Probably  the  conditions  existing  here  en- 
tirely resemble  those  found  in  the  submaxillary  gland. 

The  Parotid  Gland. — Stimulation  of  the  sympathetic  nerve  alone 
does  not  cause  the  secretion  of  saliva  in  the  parotid  in  the  dog.  This 
occurs  only  when  the  branch  from  the  glosso-pharyngeal  nerve  to  the 
parotid,  which  is  accessible  in  the  tympanic  plexus  within  the  tympanic 
cavity,  is  also  stimulated  at  the  same  time.  Then  a  viscid  saliva,  rich 
in  organic  elements,  is  poured  out.  Stimulation  of  the  cerebral  branch 
alone  produces  a  clear,  watery  saliva,  with  few  organic  constituents, 
but  containing  salivary  salts. 

According  to  Langley,  the  sympathetic  nerve  also  contains  independent  secre- 
tory fibers,  which  can  be  demonstrated  only  by  stimulation  soon  after  the  termi- 
nation of  the  irritation  of  the  tympanic  nerve.  After  destruction  of  the  tym- 
panic plexus,  the  parotid  gland  atrophies.  Stimulation  of  the  glosso-pharyngeal 
nerve  in  the  rabbit  causes  secretion  also  in  the  glands  of  the  tongue,  with  redness 
of  the  foliate  papillae. 

In  the  intact  body  excitation  of  the  nerves  causing  secretion  of  saliva 
occurs  through  reflex  influences,  a  watery  (cerebral)  saliva  being  secreted 
under  normal  conditions.  The  nerve-fibers  conveying  the  impulse  cen- 
tripetally  are:  (i)  the  gustatory  nerves;  (2)  the  sensory  fibers  of  the 
trigeminal  and  glosso-pharyngeal  nerves  of  the  entire  buccal  cavity. 
These  seem  also  to  cause  the  secretion  of  saliva  by  mechanical  irritation 
through  the  movements  of  mastication.  Pfliiger  found  that,  on  the 
side  upon  which  mastication  took  place,  one-third  more  saliva  was 
secreted.  Cl.  Bernard  observed  the  secretion  to  cease  in  horses  while 
drinking.  (3)  The  olfactory  nerves,  excited  by  certain  exhalations. 
(4)  The  gastric  branches  of  the  pneumogastric  nerve,  especially  in  asso- 
ciation with  strangling  movements.  (5)  Even  the  irritation  of  distant 
sensory  nerves,  such  as  those  of  the  conjunctiva,  by  the  application  of 
irritating  fluids  in  carnivora. 

Further,  stimulation  of  the  central  extremity  of  the  divided  sciatic  nerve  causes 
the  secretion  of  saliva.     In  this  category  is  probably  to  be  included  also  the  saliv 
tion  sometimes  observed  in  pregnant  women.     By  irritation  of  distant 
nerves  both  centers  are  excited  reflexly;    when  nearby  nerves  are  irritated,  the 
center  on  the  same  side  is  especially  excited. 


262  THE    SALIVA    FROM    THE    INDIVIDUAL    GLANDS. 

The  reflex  center  for  the  secretion  of  saliva  is  situated  in  the  medulla 
oblongata,  at  the  origin  of  the  seventh  and  ninth  cranial  nerves.  The 
center  for  the  sympathetic  fibers  also  is  situated  here.  If  the  center 
is  directly  irritated  mechanically,  as  by  pricking,  salivation  occurs; 
suffocation  has  the  same  effect.  This  reflex  may  be  inhibited  by  irrita- 
tion of  certain  sensory  nerves,  as  by  drawing  forward  loops  of  intestines. 

The  reflex  center  is  in  direct  communication  with  the  cerebral  hemi- 
spheres, as  is  evident  from  the  fact  that,  with  the  thought  of  savory 
substances,  especially  during  the  state  of  hunger,  watery  salivation  takes 
place.  Irritation  of  the  cerebral  cortex,  in  the  region  of  the  cruciate 
sulcus  (Fig.  258)  also  causes  a  flow  of  saliva  in  the  dog.  Also  central 
disease  in  human  beings  may  induce  abnormalities  in  the  secretion  of 
saliva  through  their  influence  upon  the  intracranial  center. 

As  long  as  all  nerve-irritation  is  suppressed,  no  secretion  of  saliva 
takes  place,  as,  for  instance,  during  sleep.  Secretion  likewise  ceases 
immediately  after  division  of  all  of  the  glandular  nerves. 

Inflammations  of  the  buccal  cavity,  neuralgia  involving  the  nerves  of  the 
mouth,  irruption  of  the  teeth,  ulcers  of  the  mucous  membrane,  spongy  conditions 
of  the  gums  (as  from  the  long-continued  use  of  mercury)  often  induce  active 
secretion  of  saliva  (salivation,  ptyalism),  which  rarely  is  unilateral. 

The  parotid  gland  in  the  sheep  (ruminant)  secretes  continually.  Division  of 
all  of  the  afferent  nerves  does  not  affect  this  secretion.  Perhaps  this  gland  con- 
tains a  center  through  which  secretion  is  excited. 

Certain  poisons  also  cause  salivation  by  direct  nerve-irritation,  especially  pilo- 
carpin.  Some,  particularly  atropin,  paralyze  the  cerebral  salivary  nerves,  and 
thus  cause  a  cessation  of  secretion.  Administration  of  muscarin  under  these  con- 
ditions causes  resumption  of  the  secretion.  Pilocarpin  acts  by  irritation  of  the 
chorda  tympani.  Administration  of  atropin  during  the  resulting  salivation 
causes  this  to  cease.  Conversely,  in  the  condition  of  abolished  secretion  of  saliva 
following  the  administration  of  atropin,  pilocarpin  or  physostigmin  causes  a  re- 
sumption of  the  secretion.  Curare  acts  as  a  sialogog  by  irritation  of  the  center. 

THE  SALIVA  FROM  THE  INDIVIDUAL  GLANDS. 

Method. — For  obtaining  the  isolated  saliva  from  the  individual  glands  a  thin 
metal  tube  is  introduced  into  the  excretory  duct.  If  masticatory  movements  are 
then  performed,  or  if  a  pungent  substance  be  placed  upon  the  tongue,  the  saliva 
will  flow  from  the  tube,  drop  by  drop. 

Parotid  saliva  is  not  ropy,  dropping  readily,  of  alkaline  reaction,  with 
a  specific  gravity  of  from  1003  to  1006.  It  contains  6.84  per  cent,  of 
total  solids,  of  which  3.40  per  cent,  are  inorganic.  On  standing  it  be- 
comes cloudy  and  precipitates,  together  with  some  globulin,  calcium 
carbonate,  which  is  dissolved  in  fresh  saliva  as  bicarbonate. 

Through  the  precipitation  of  calcium,  salivary  calculi  may  be  formed  in  the 
excretory  ducts;  dental  calculi  likewise  may  form,  enclosing  leptothrix- threads 
and  bacteria. 

Of  the  organic  constituents  of  parotid  saliva  the  most  important  is 
ptyalin;  mucin  is  absent.  Saliva  contains,  further,  small  amounts  of  a 
globulin-like  body,  alkali- albuminate  and  albumin,  together  with  some 
urea,  traces  of  volatile  acid,  and  it  appears  never  to  be  free  from  potas- 
sium or  sodium  sulphocyanid,  which  is  wanting  in  some  animals. 

This  substance  is  recognized,  after  acidulating  the  saliva  slightly  with  hydro- 
chloric acid,  by  adding  a  solution  of  ferric  chlorid,  when,  with  the  formation  of 
ferric  sulphocyanid  a  dark  red  color  results.  Potassium  sulphocyanid  reduces 


THE    MIXED    SALIVA,    THE    SECRETION    OF    THE    MOUTH.  263 

hydriodic  acid  when  added  to  saliva,  with  the  development  of  a  yellow  color,  and 
the  formation  of  iodin,  which  can  be  recognized  by  the  addition  of  starch. 
It  is  absent  when  the  flow  of  bile  into  the  intestine  is  prevented.  It  is  formed 
through  proteid  metabolism,  perhaps  from  the  contained  cyanogen.  As  potassium 
sulphocyanid  is  toxic  for  plants  and  microorganisms,  it  may  be  concluded  that 
it  acts,  within  certain  limits,  as  a  disinfectant  for  the  buccal  cavity. 

The  inorganic  elements  in  the  saliva  are  mainly  potassium  and  sodium  chlorids, 
with  calcium  bicarbonate,  and  calcium  and  sodium  sulphates,  phosphates,  and 
chlorates. 

The  submaxillary  saliva  is  alkaline,  sometimes  strongly  alkaline. 
On  standing  for  some  time  it  precipitates  fine  crystals  of  calcium  car- 
bonate, together  with  an  amorphous,  albuminoid  substance.  It  always 
contains  mucin,  and  it  is,  therefore,  as  a  rule  somewhat  ropy;  also 
ptyalin — less  than  in  the  parotid  secretion;  and  only  0.0037  Per  cent, 
potassium  sulphocyanid. 

In  the  submaxillary  saliva  of  the  dog  there  were  found  1.755  of  organic  matter, 
of  which  0.662  was  mucin;  from  2.604  to  3.662  of  inorganic  salts;  and  from  0.263 
to  1.123  °f  soluble  salts. 

Pfliiger  investigated  the  gases  of  the  submaxillary  saliva  and  found,  in  100 
cu.  cm.  of  saliva,  0.6  of  oxygen,  64.7  of  carbon  dioxid,  partly  removable  by  exposure 
to  a  vacuum  and  in  part  capable  of  being  expelled  by  phosphoric  acid;  and  0.8  of 
nitrogen;  or  of  gases  in  100  volumes  0.91  of  oxygen,  97.88  of  carbon  dioxid,  and 
i. 2 1  of  nitrogen.  Kiilz  found  in  human  parotid  saliva  as  much  as  1.46  volumes 
per  cent,  of  oxygen  and  3.2  of  nitrogen,  4.7  of  carbon  dioxid  removable  by 
suction,  and  62  of  combined  carbon  dioxid. 

The  sublingual  saliva,  more  viscous  and  more  coherent  than  the 
submaxillary  saliva,  is  strongly  alkaline  in  reaction.  It  contains  much 
mucin,  numerous  salivary  corpuscles  and  some  potassium  sulphocyanid; 
but  its  composition  has,  on  the  whole,  not  been  determined  accurately. 

THE  MIXED  SALIVA,  THE  SECRETION  OF  THE  MOUTH. 

The  buccal  fluid  is  a  mixture  of  the  secretions  of  the  salivary  glands 
and  the  small  glands  of  the  mouth. 

Physical  Properties. — It  is  an  opalescent,  tasteless  and  odorless, 
somewhat  ropy  fluid,  with  a  specific  gravity  of  from  1002  to  1006,  and 
an  alkaline  reaction,  due  to  alkaline  phosphates. 

Between  midnight  and  morning  the  reaction  may  be  faintly  acid.  The  decom- 
position of  epithelium,  of  salivary  corpuscles  or  of  remains  of  food  by  microbes  may 
also  cause  the  reaction  to  be  acid  temporarily,  particularly  after  long  fasting  and 
after  much  talking.  In  the  presence  of  digestive  disturbances  and  of  fever  the 
reaction  is  not  rarely  acid,  in  consequence  of  stagnation  and  insufficient  secretion; 
therefore,  also,  the  mouth  is  dry. 

The  amount  in  twenty-four  hours  is  between  200  and  1500  grams, 
according  to  Bidder  and  Schmidt  between  1000  and  2000  grams.  The 
total  solids  in  the  secretion  amount  to  5.8  per  cent. 

The  solids  are :  2.2  of  epithelium  and  mucus,  1.4  of  ptyalin  and  albumin,  2.2 
of  salts  and  0.04  per  cent,  of  potassium  sulphocyanid  in  1000. 
especially  potassium,  phosphoric  acid  and  chlorin. 

Microscopical  Constituents.— (a)  The  salivary  corpuscles,  from  8  to  n  //  m  size, 
are  nucleated,  protoplasmic,  spherical  cells,  without  a  limiting  membrane 
exhibit  as  a  vital  phenomenon  so-called  molecular  movements  on  the  part  of  then 
numerous  dark  granules,  which  are  embedded  in  the  protoplasm,  through  whose 
internal  flowing  movement  they  are  set  into  a  tremulous,  dancing  locomotion, 
which  ceases  with  the  death  of  the  cells.  Salivary  corpuscles  can  be  easily  brought 
into  view  by  slight  pressure  upon  the  excretory  ducts  beneath  the  tongue. 


264  PHYSIOLOGICAL    ACTIONS    OF    THE    SALIVA. 

(6)  Desquamated  squamous  epithelium  is  never  absent,  and  is  present  in 
abundance  in  association  with  catarrh  of  the  buccal  cavity  (Fig.  92,  8). 

(c)  Living  organisms,  which  grow  as  saprophytes  upon  the  buccal  fluid  and 
remains  of  food,  at  times  in  carious  teeth,  consist  of  the  threads  of  the  leptothrix 
buccalis  (Fig.  92,  12),  which  turn  blue,  as  a  rule,  on  addition  of  iodin,  and  multiply 
with  enormous  rapidity.  Leptothrix  vegetations  enter  the  dental  tubules  and 
cause  caries  of  the  teeth.  The  zooglea-form  of  the  leptothrix  appears  as  a  cream- 
like,  yellowish,  smeary  deposit  on  the  teeth.  Miller  found  in  all  healthy  human 
beings,  in  addition  to  the  ordinary  leptothrix  buccalis,  another  variety,  the  lepto- 
thrix buccalis  maxima,  also  the  iodococcus  vaginatus,  the  bacillus  buccalis  maximus, 
the  spirillum  sputigenum  and  the  spirochaeta  dentium.  Further,  pathogenic 
bacteria  may  be  present,  as,  for  instance,  those  of  pneumonia,  of  diphtheria,  etc. 

Chemical  Properties. — (a)  Organic  constituents :  a  globulin-like  albu- 
minous substance,  mucin,  ptyalin;  fats  and  urea  are  present  only  in 
traces;  about  130  mg.  of  potassium  or  sodium  sulphocyanid  in  twenty- 
four  hours. 

(b)  Inorganic  constituents:  sodium  chlorid,  potassium  chlorid,  potas- 
sium sulphate,  alkaline  and  earthy  phosphates  and  ferric  phosphate. 

According  to  Schonbein,  saliva  contains  traces  of  nitrous  salts,  which  are  recog- 
nizable from  the  yellow  color  produced  by  metadiamidobenzol  in  saliva  diluted  five 
times  with  water  after  addition  of  a  few  drops  of  dilute  sulphuric  acid ;  also  traces 
of  ammonia.  Fresh  saliva  is  said  to  contain  hydrogen  dioxid,  which  oxidizes 
the  ammonia  to  nitrous  acid;  though  when  the  reaction  of  the  saliva  is  acid 
nitric  acid  is  formed. 

Abnormal  Constituents  of  the  Saliva.. — In  cases  of  diabetes  lactic  acid  has  been 
found  as  a  result  of  decomposition  of  the  sugar.  It  dissolves  the  calcium  of  the 
teeth  and  may  thus  give  rise  to  caries,  as  in  cases  of  diabetes,  v.  Frerichs  found 
leucin,  and  an  increased  amount  of  urea  and  albumin  were  observed  in  cases  of 
nephritis,  and  uric  acid  in  cases  of  uremia.  Of  foreign  substances  that  are  admin- 
istered there  appear  in  the  saliva  mercury,  potassium,  metallic  and  free  iodin  and 
bromin,  the  last  displacing  an  equivalent  amount  of  chlorin  from  the  salivary 
chlorids,  lead,  morphin,  lithium,  and  sodium  chlorid. 

Of  the  salivary  glands  in  the  new-born  infant  only  the  parotid  contains  ptyalin. 
In  the  submaxillary  gland  and  in  the  pancreas  the  diastatic  ferment  appears  to 
be  formed  not  earlier  than  the  end  of  the  second  month.  Therefore  the  nourish- 
ment of  infants  with  starches  is  not  advisable.  It  is  a  remarkable  fact  that  in 
new-born  infants  suffering  from  thrush  (due  to  oidium  albicans)  no  ptyalin  is 
demonstrable  in  the  saliva.  For  the  infant  that  takes  milk  alone,  the  diastatic 
action  of  the  saliva  is  not  indispensably  necessary.  Therefore,  the  mucous  mem- 
brane of  the  mouth  appears  to  be  but  slightly  moistened  during  the  first  two 
months,  though  an  abundance  of  saliva  is  secreted  later  .  Also,  the  glands  usually 
attain  a  considerable  size  only  after  the  first  half-year  of  life.  The  irruption  of 
the  first  teeth  causes  the  secretion  of  much  saliva  in  consequence  of  the  irritation 
of  the  buccal  mucous  membrane. 


PHYSIOLOGICAL  ACTIONS  OF  THE  SALIVA. 

The  most  important  action  of  the  saliva  is  amylolytic  or  diastatic, 
that  is,  the  conversion  of  starch  into  sugar  and  dextrin.  This  is  due 
to  the  ptyalin,  an  unformed,  hydrolytic  ferment  or  enzyme  which,  even 
when  present  in  small  amounts,  causes  the  starch  to  take  up  water  and 
become  soluble,  with  absorption  of  heat,  although  the  ferment  itself 
undergoes  no  material  change.  Ptyalin  is  not  present  in  the  saliva  of 
true  carnivora. 

According  to  Dubrunfaut,  O' Sullivan,  Musculus  and  v.  Mering,  maltose  and 
dextrin,  both  soluble  in  water,  are  formed  from  starch  (or  glycogen)  by  the  dias- 
tatic ferment  of  the  saliva  (and  of  the  pancreas) : 


PHYSIOLOGICAL    ACTIONS    OF    THE    SALIVA.  265 

io(C12H20010)  +  8(H20)  =  8(C12H220U)  +  2(C12H20O10) 

Starch         +       Water      =  Maltose        +  Dextrin. 

The  exact  course  of  events  is  as  follows:  At  first  with  liquefaction  of  the 
starch-paste  amylodextrin  is  formed.  This  does  not  reduce  Fehling's  solution;  it  is 
colored  blue  by  iodin  and  is  the  principal  constituent  of  the  preparation  formerly 
called  soluble  starch  or  amydulin.  It  is  transformed  into  three  molecules  of 
erythrodextrin,  which  reduces  Fehling's  solution  feebly,  and  is  colored  red  by 
iodin.  The  erythrodextrin  is  transformed  into  three  molecules  of  achroodextrin, 
which  reduces  Fehling's  solution,  but  is  not  stained  by  iodin.  From  this  iso- 
maltose and  maltose  are  formed,  the  latter  being  formed  from  the  former  by  the 
action  of  ptyalin.  Isomaltose  undergoes  fermentation  with  greater  difficulty 
than  maltose.  Finally  all  the  starch  is  changed  into  maltose  and  dextrose. 

When  little  ferment  is  present  and  the  action  is  of  short  duration,  the  saliva  or 
the  pancreatic  juice  produces  isomaltose  principally;  when  much  ferment  is  pres- 
ent and  the  action  is  of  longer  duration,  the  formation  of  maltose  and  of  some 
dextrose  is  favored.  The  maltose  subsequently  may  be  changed  in  the  intestine 
into  dextrose,  but  the  greater  part  is  absorbed  unchanged. 

Kirchof,  in  1811,  showed  that  dextrose  is  formed  from  starch,  by  boiling 
with  dilute  sulphuric  or  hydrochloric  acid. 

Demonstration  of  Ptyalin. — This  depends,  as  in  the  case  of  all  hydrolytic  fer- 
ments, upon  the  fact  that  a  voluminous  precipitate  formed  in  the  saliva  carries  the 


FIG.  96. — Potato  Starch. 


ferment  down  with  it  mechanically,  and  from  it  the  latter  is  then  isolated  by  simple 
means.     For  this  purpose  the  saliva  is  strongly  acidulated  with  phosphoric  acic 
lime-water  is  added  until  the  reaction  is  rendered  alkaline.     As  a  res 
precipitate  of  basic  calcium  phosphate  forms,  carrying  the  ptyalin  down  w 
This  precipitate  is  collected  upon  a  filter  and  the  ptyalin  is  dissolved  out 
the  aid  of  a  little  water.     Alcohol  precipitates  the  ptyalm  in  this  watery  e 
as  a  white  powder.     By  repeated  solution  in  water,  and  subsequent  precipitatic 
with  alcohol,  the  ptyalin  is  obtained  in  an  absolutely  pure 

The  cells  of  the  glands  first  contain  ptyalin  in  a  preliminary  stage 
a  ptyalinogenic  substance,  from  which  ptyalin  is  formed  only  during .  * 
Ptyalin  contains  nitrogen,  is  free  from  ash,  but  yields  no  xanthoproteic  react 
It  is  precipitated  from  solution  by  neutral  or  basic  lead  acetate. 

deCTPWi?tSichy  taS  "ptval-  could  be  extracted  with  glycerin  containing 
water  from   the   salivary    glands   of  human  beings  or  swine,   cleansed,    minced, 


266  PHYSIOLOGICAL    ACTIONS    OF    THE    SALIVA. 

placed  in  strong  alcohol  and  then  dried.  After  standing  for  several  days,  the 
glycerin  is  poured  off  and  to  it  alcohol  is  added,  precipitating  the  ptyalin.  This 
is  collected  on  a  filter  and  then  dissolved  in  water.  In  order  to  free  it  from  any 
albumin  that  may  be  adherent  to  it,  the  aqueous  solution  is  rapidly  heated  to 
60°  C.,  with  the  result  that  the  albumin  is  precipitated,  while  the  ptyalin  remains 
unimpaired  in  solution  in  the  filtrate. 

The  following  details  are  worthy  of  consideration  with  respect  to  the  action 
of  the  saliva  in  the  process  of  saccharification: 

(a)  The  process  of  saccharification  is  recognized:  (i)  from  the  disappearance  of 
the  starch.  The  addition  of  a  little  iodin  to  a  thin  solution  of  starch  produces 
a  blue  color.  If,  now,  saliva  is  added  and  the  liquid  is  shaken,  the  blue  color 
quickly  disappears.  (2)  Directly  by  demonstration  of  the  presence  of  sugar 
by  appropriate  tests. 

(6)  The  process  pursues  a  most  favorable  course  at  a  temperature  between 
35°  C.  and  46°  C.;  it  is  slower  in  the  cold;  at  55°  C.  the  action  of  the  ferment  be- 
comes weaker,  and  at  75°  C.  it  is  destroyed.  Ptyalin  is  distinguished  from 
diastase,  that  is  the  diastatic  ferment  formed  in  germinating  grain,  by  the 
fact  that  the  latter  exhibits  its  saccharifying  action  only  at  a  temperature  between 
60°  and  69°  C.  Ptyalin  also  breaks  up  salicin  into  "saligenin  and  grape-sugar. 

(c~)  The  ptyalin,  as  a  ferment,  remains  unchanged  in  the  process  of  sac- 
charification. Nevertheless,  when  once  employed,  it  will  not  possess  the  same 
activity  in  a  second  experiment. 

(d)  The  diastatic  activity  is  greatest  in  the  morning.     It  then  declines,  rising 
again  toward  noon  and  falling  once  more  toward  evening.     It  declines  also  after 
every  ingestion  of  food. 

(e)  The  action  of  the  saliva  is  most  intense  when  its  reaction  is  feebly  acid, 
though  it  takes  place  also  when  the  reaction  is  alkaline   or  neutral.     Ptyalin 
causes  the  production  of  sugar  in  the  acid  gastric  juice  of  human  beings  only 
when  the  acidity  is    due    to    organic  acids,  such  as    lactic  or  butyric  acid,  but 
not  when  it  is  due  to  free  hydrochloric  acid.     The  production  of  dextrin  occurs 
in  either  event.     In  the  former    case,  therefore,  saccharification    may  be    con- 
tinued in  the  stomach,   although  the  ptyalin   is    destroyed    by  the    hydrochloric 
acid  or  digested  by  the  pepsin.     The  presence  of  peptone  is  said  to  be  necessary 
for  the  production  of  sugar.     The  production  of  butyric  and  lactic  acids  in  consid- 
erable amount  may  exert  an  inhibitory  effect  on  the  formation  of  sugar.     Neutral- 
ization of  these  acids,  however,  permits  the  process  to  begin  anew. 

(f)  The  addition  of  sodium  chlorid,  ammonium  chlorid,  or  sodium  sulphate 
(in   about  4  per  cent,   solution)   increases  the  fermentative  activity  of  ptyalin, 
as  do  also  the  acetates  of  quinin,  strychnin,  and  morphin  ;  further,  curare  and 
0.625  per  cent,  sulphuric  acid. 

(g)  Much   alcohol   and  potassium  hydroxid   destroy  the  ptyalin;     exposure 
to  the  air  for  a  considerable  time  weakens  it;    sodium  carbonate  and  magnesium 
sulphate  delay  its  action;   while  salicylic  acid  inhibits  saccharification,  as  does  also 
much  atropin. 

(Ji)  Ptyalin  acts  but  feebly  and  gradually  on  unboiled  starch  only  after 
the  lapse  of  2  or  3  hours;  while  it  acts  rapidly  upon  starch  swollen  by  boiling 
(starch-paste) . 

(i)  The  different  kinds  of  starch  are  transformed  with  varying  rapidity  in 
accordance  with  the  quantity  of  cellulose  contained  in  each:  unboiled  potato- 
starch  (Fig.  96)  in  not  less  than  2  or  3  hours;  unboiled  corn-starch  within  2  or 
3  minutes;  wheat-starch  more  quickly  than  rice-starch.  When  rubbed  up  into 
powder  or  boiled,  all  starches  act  in  the  same  way. 

(fe)  The  mixture  of  saliva  from  all  of  the  -glands  is  more  effective  than  that 
from  any  one  gland  alone;  the  mucus  is  inactive. 

Ptyalin  produces  free  hydrogen  sulphid  from  radishes,  onions,  garlic,  and 
the  like,  which  contain  sulphur.  This  fact  explains  the  presence  of  the  gas  named 
in  the  intestines  after  the  ingestion  of  the  foregoing  substances. 

The  saliva  takes  part  in  dissolving  in  the  mouth  articles  of  food 
soluble  in  water. 

The  saliva  moistens  articles  of  food  ingested  in  a  dry  state,  renders 
possible,  by  its  viscosity,  the  formation  of  the  bolus  and  facilitates 
deglutition  through  the  slipperiness  afforded  by  the  mucus  it  contains. 
The  mucus  is  later  evacuated  with  the  feces. 


TESTS    FOR    SUGAR.  267 

Recently  the  presence  of  peptone-producing  ferments  in  the  saliva  has  been 
discovered,  but  they  are  perhaps  merely  absorbed  from  the  intestine  and  again 
excreted  in  the  saliva  (as  occurs  in  the  urine). 

TESTS  FOR  SUGAR. 

Trammer's  test,  like  several  others,  depends  upon  the  fact  that  sugar  in  hot 
alkaline  solution  acts  as  a  reducing  agent;  here  a  metallic  oxid  is  transformed 
into  a  suboxid.  To  one-half  as  much  potassium-hydrate  or  sodium-hydrate 
solution,  of  a  specific  gravity  of  1.25,  is  added  the  fluid  to  be  tested.  Then  a 
weak  solution  of  cupric  sulphate  is  added  drop  by  drop  until  the  bluish  precipitate 
that  appears  at  first  and  consists  of  cupric  oxid,  is  again  dissolved  by  agitation. 
If  sugar  is  present,  the  precipitate  again  forms  a  deep-blue  solution  after 
agitation.  If  heat  is  applied  gradually  almost  up  to  the  boiling-point  a  yellowish 
or  reddish  cloud  is  formed  from  above,  which  is  finally  precipitated  as  brownish- 
red  cuprous  oxid  or  as  yellowish-red  cupric  oxid:  2CuO  —  O  =»  Cu2O. 

Cuprous  oxyhydrate  is  dissolved  also  by  other  organic  substances,  though  only 
certain  sugars — maltose,  grape-sugar,  fruit-sugar  and  milk-sugar,  but  not  cane- 
sugar — cause  final  reduction.  Fluids  previously  turbid  must  be  filtered  and  possibly 
treated  with  basic  lead  acetate.  In  the  latter  event  the  excess  of  lead  is  precipi- 
tated by  sodium  phosphate;  then  filtration  is  practised.  When  the  amount  of 
sugar  is  exceedingly  small,  concentration  of  the  fluid  over  the  water-bath  may  be 
necessary.  If  small  amounts  of  sugar,  less  than  0:5  per  cent.,  are  present,  to- 
gether with  ammonia,  uric  acid,  and  kreatinin,  instead  of  a  yellow  precipitate, 
merely  a  yellow  solution  of  cuprous  oxid  may  result.  The  addition  of  an  excess 
of  cupric  sulphate,  which  should  always  be  avoided,  causes  confusion  by  the 
precipitation  of  black  cupric  oxid. 

Bottger's  test  is  made  with  an  alkaline  solution  of  bismuth  oxid,  best  prepared 
according  to  Nylander  as  follows:  Bismuth  subnitrate  2  grams,  sodio-potassium 
tartrate  4  grams,  and  sodium  hydrate  (8  per  cent.)  100  grams.  One  cu.  cm.  of 
this  mixture  is  added  to  10  cu.  cm.  of  the  fluid  to  be  tested.  Upon  boiling  for 
several  minutes  the  sugar  present  causes  reduction  to  metallic  bismuth,  with  the 
formation  of  a  black  precipitate. 

Moore's  and  Heller's  test:  Sufficient  sodium  or  potassium  hydrate  is  added 
to  the  fluid  to  give  it  a  strongly  alkaline  reaction.  On  boiling,  a  yellowish,  brownish 
or  brownish-black  color  results  from  the  formation  of  humus-substances.  If, 
after  cooling,  one  drop  of  concentrated  sulphuric  acid  is  added,  the  odor  of  burnt 
sugar  (caramel)  and  formic  acid  develops. 

Mulder's  and  Neubauer's  test:  If  a  solution  of  indigo-carmin,  made  alkaline 
by  sodium  carbonate,  is  added  to  a  fluid  containing  sugar  until  a  pale-blue  color 
is  produced,  and  heat  is  applied,  the  color  becomes  successively  green,  purple, 
reel  and  yellow.  Agitated  with  atmospheric  air  the  fluid  again  acquires  the 
blue  color. 

Molisch's  tests:  To  £  cu.  cm.  of  the  fluid  to  be  tested,  2  drops  of  a  17  per  cent, 
alcoholic  solution  of  a-naphthol  or  of  a  solution  of  thymol  are  added ;  with  dilute 
solutions  of  sugar  a  small  quantity  of  solid  a-naphthol  may  be  used  instead  of 
the  solution.  Then  i  or  2  cu.  cm.  of  concentrated  sulphuric  acid  are  added 
and  the  fluid  is  rapidly  shaken.  In  the  presence  of  sugar  the  a-naphthol  mix- 
ture becomes  deep  violet  in  color,  the  thymol-solution  deep  red.  Subsequent 
dilution  with  water  causes  a  precipitate  of  the  same  color,  which  is  insoluble 
in  concentrated  hydrochloric  acid.  Albumin,  casein  and  peptone  also  yield 
this  reaction,  but  the  precipitate  appearing  upon  the  addition  of  water  is  solubl< 
in  concentrated  hydrochloric  acid. 

Phenylhydrazin  test:   To  7  cu.  cm.  of  the  fluid  in  a  test-tube  a  small  amoun 
of  phenylhydrazin  chlorid  (0.2)  and  also  of  sodium  acetate  (0.3)  are  added.    Heat 
is  applied  until  solution  takes  place,  water  being  added  if  necessary, 
kept  in  boiling  water  for  an  hour.     The  contents  are  then  poured  into  a  conical 
glass,  at  the  bottom  of  which  characteristic  yellow,  microscopical  tufts  of  fine, 
long  needles  of  phenylglucosazone  are  found,  which  are  almost  insoluble  in  water; 
while  maltose  produces  an  analogous  substance,  phenylmaltosazone,  which  is 
soluble  in  hot  water. 

From  all  fluids  to  be  tested  for  sugar,  any  albumin  present  should  first 
removed;  from  the  urine   by  boiling,  after  slight  acidulation  with  acetic  acid 
from  the  blood,  by  the  method  described  on  page  73;  the  alcohol  is  driven 
heat. 


268 


QUANTITATIVE    ESTIMATION    OF    SUGAR. 


QUANTITATIVE  ESTIMATION  OF  SUGAR. 

By  Fermentation.  (An  illustration  of  yeast  is  given  in  Fig.  140.)  For  this 
purpose  the  apparatus  illustrated  in  Fig.  97  is  employed.  In  the  glass  flask 
a  is  measured  a  quantity  (as,  for  example,  20  cu.  cm.)  of  fluid  containing  sugar, 
to  which  yeast  is  added.  The  flask  b  contains  concentrated  sulphuric  acid.  The 
entire  apparatus  is  weighed  immediately  after  being  filled.  At  ordinary  tem- 
perature (between  10°  and  40°  C.),  most  energetically  at  25°  C.,  the  sugar  breaks 
up  into  2  molecules  of  alcohol  and  2  molecules  of  carbon  dioxid  : 


C6H1206  =  2(C2H60) 

Sugar       =   2  Al 


2(C02) 

2  Carbon  dioxid. 


FIG.  97. — A 


In  addition  some  glycerin  and  succinic  acid  are  formed.  The  carbon  dioxid 
escapes  through  the  flask  b,  and  returns  to  the  sulphuric  acid  any  water  that  it  may 
have  taken  with  it.  If  the  decomposition  is  concluded  in  the  course  of  about  two 
days,  the  apparatus  is  again  weighed.  From  the  loss  in  weight  the  amount  of  sugar 
that  was  contained  in  the  20  cu.  cm.  of  fluid  is  estimated,  in  accordance  with  the 
fact  that  100  parts  by  weight  of  sugar  free  from  water  are  equal  to  48.89  parts  of 
carbon  dioxid,  or  that  100  parts  of  carbon  dioxid  by  weight  correspond  to  204.54 
parts  of  sugar. 

By  Titration,  with  Fehling's  alkaline  cupric-oxid  solution  based  on  Trommer's 
test.  The  deep-blue  titration-fluid,  composed  of  cupric  sulphate,  potassium  ace- 
tate, sodium  hydrate  and  water,  is  so  prepared  that  all  of  the  cupric  oxid  in  10 
cu.  cm.  of  the  solution  will  be  reduced  to  yellowish-red  cuprous  oxid  by  just  0.05 
gram  of  grape-sugar.  For  example,  as  in  determining  the  amount  of  sugar  in 
urine,  10  cu.  cm.  of  Fehling's  solution  are  placed  in  a  porcelain  dish,  and  gradually 
IPil  diluted  with  40  cu.  cm.  of  water  and  heat 

>  ^  ^.       applied    almost  up   to   the  boiling-point.       The 

urine,  previously  diluted  to  from  10  to  20 
times  its  volume,  is  dropped  from  a  burette  into 
the  hot  titration-solution,  and  stirred  until 
every  trace  of  blue  color  has  disappeared  or  until 
one  drop  of  the  fluid  no  longer  produces  a  red 
color  on  blotting-paper  saturated  with  acetic 
acid  and  potassium  ferrocyanid.  The  amount 
of  urine  needed  is  now  read  from  the  scale  of  the 
burette,  making  allowance  for  the  dilution,  and 
it  will  then  be  known  that  the  amount  of  urine 
used  for  reduction  contained  0.05  gram  of 

grape-sugar.     From  this  the  amount  of    sugar  in  the   entire    quantity   of   urine 
excreted  can  be  readily  estimated. 

By  Polarization. — Sugar  possesses  the  peculiarity  of  turning  the  plane  of  polar- 
ized light  to  the  right,  just  as  albumin  turns  it  to  the  left.  Specific  polarizing 
power  is  the  term  applied  to  the  degree  of  rotation  that  i  gram  of  the  substance 
in  question,  dissolved  in  i  cu.  cm.  of  water,  forming  a  layer  10  cm.  thick,  the 
length  of  the  tube  of  the  apparatus,  effects  with  yellow  "light.  For  dextrose 
this  is  +56.  As  the  rotatory  power  is  directly  proportional  to  the  quantity 
of  the  substance  dissolved  in  the  fluid,  the  degree  of  deflection  affords  informa- 
tion as  to  the  amount  of  the  optically  active  substance  contained  in  the  fluid. 
In  making  the  observation,  the  Soleil-Ventzke  polarization-apparatus  (Fig.  98) 
shows  on  its  scale  to  the  right  directly  the  percentage  of  sugar;  to  the  left,  that 
of  albumin. 

The  light  derived  from  the  lamp  encounters  a  crystal  of  calcspar  at  a.  Two 
Nicol's  prisms  are  placed  at  v  and  s;  that  at  v  can  be  rotated  about  the  visual 
axis,  while  the  other  is  fixed.  The  Soleil  double  plate  of  quartz  is  attached  at  m; 
one-half  of  this  deflects  the  plane  of  polarized  light  as  far  to  the  right  as  the  other 
deflects  it  to  the  left.  At  c  the  field  of  vision  is  covered  by  a  plate  of  levorotatory 
quartz.  At  b  c  is  placed  a  compensator  formed  of  two  dextrorotatory  prisms  of 
quartz,  which  can  be  moved  laterally  by  means  of  the  screw  g  in  such  a  way 
that  the  polarized  light  sent  through  the  apparatus  must  pass  through  a  thinner 
or  thicker  layer  of  the  dextrorotatory  quartz  in  accordance  with  the  degree  of 
rotation.  With  these  dextrorotatory  prisms  in  a  certain  position,  the  deflection 
of  the  levorotatory  quartz  at  n  is  exactly  neutralized.  In  this  position  the 
scale  and  vernier  placed  upon  the  compensator  will  be  exactly  at  O,  and  both 


atus  for  the  Quantitative 
imation  of  Sugar. 


QUANTITATIVE    ESTIMATION    OP    SUGAR. 


269 


halves  of  the  double  plate  at  m  appear  of  the  same  color  to  the  observer,  who 
looks  from  v  through  the  telescope  introduced  at  e.  By  appropriate  rotation 
of  the  Nicol  s  prism  at  v,  a  bright  rose  color  is  preferably  selected  fn  this  position 
the  telescope  must  be  so  adjusted  that  the  vertical  dividing  line  of  the  double 
plate  is  plainly  visible.  Thus  adjusted  the  instrument  is  ready  for  use  The 
tube,  10  cm  long,  is  filled  with  the  fluid  to  be  examined,  which  must  be  perfectly 
clear—should  it  contain  albumin,  this  must  be  removed  by  boiling  and  filtering— - 
and  the  tube  is  introduced  into  the  apparatus  between  m  and  n.  By  rotating  the 
Nicol  s  prism  at  v,  the  rose-red  color  is  again  brought  into  view.  Then  the  com- 


FIG.  98.— The  Soleil-Ventzke  Saccharimeter. 


pensator  at  g  is  turned  until  both  halves  of  the  field  of  vision  are  exactly  of  the 
same  color.  When  this  has  been  done,  the  number  of  divisions  the  zero-mark  of 
the  vernier  has  been  moved  to  the  right — in  the  case  of  albumin  to  the  left — 
can  be  read  directly  from  the  scale.  The  number  of  divisions  read  off  shows 
directly  the  number  of  grams  of  the  rotatory  substance  in  100  cu.  cm.  of  the 
fluid.  Turbidity  that  persists  in  spite  of  filtering  often  disappears  after  addition 
of  a  drop  of  acetic  acid  or  a  few  drops  of  a  solution  of  sodium  carbonate  or  lime- 
water,  with  subsequent  filtration.  For  a  description  of  other  apparatus  employed 
for  the  same  purpose — the  polaristrobometer  of  Wild,  the  polarimeter  of  Zeiss, 


270  THE    MECHANICS    OF    THE    DIGESTIVE    APPARATUS. 

and  the  half-shadow  apparatus  of  Laurent,  Lippich,  and  others — the  text-books 
on  physics  and  chemistry  should  be  consulted. 

THE  MECHANICS  OF  THE  DIGESTIVE  APPARATUS. 

The  mechanism  of  the  digestive  apparatus  comprises : 

1.  The  prehension  of  the  food,  the  movements  of  mastication  and 
of  the  tongue,  insalivation,  and  the  formation  of  the  bolus. 

2.  The  movements  of  deglutition. 

3.  The  movements  of  the  stomach  and  the  small  and  large  intestines. 

4.  The  expulsion  of  fecal  matter. 


THE  PREHENSION  OF  FOOD. 

Liquid  food  is  taken  into  the  mouth  (i)  by  suction.  While  the  lips 
are  applied  hermetically  about  the  utensil  containing  the  fluid,  the 
tongue,  moving  downward  and  at  the  same  time  flattened,  often  in 
conjunction  with  depression  of  the  lower  jaw,  causes  the  fluid  to  enter 
the  buccal  cavity.  Herz  found  that  the  negative  pressure  produced 
by  the  suction  of  infants  equals  from  3  to  10  mm.  of  mercury. 
(2)  The  liquid  is  sipped  when  it  is  brought  directly  in  contact  with 
the  lips,  and  then  is  drawn  by  aspiration  into  the  buccal  cavity, 
together  with  air,  with  a  characteristic  sound.  (3)  Liquid  can  also  gain 
entrance  into  the  buccal  cavity  by  being  poured,  the  lower  lip,  as  a  rule, 
being  applied  to  the  containing  vessel. 

Among  the  solid  articles  of  food,  the  smaller  particles,  supported 
by  the  lips,  are  picked  up  by  the  tongue;  of  the  larger  particles  a  piece 
is  bitten  off  by  the  chisel-shaped  incisor  and  sharp  canine  teeth,  and 
then,  for  further  comminution,  it  is  brought  between  the  rough  surfaces 
of  the  bicuspid  and  molar  teeth. 


THE  MOVEMENTS  OF  MASTICATION, 

The  articulation  of  the  lower  jaw  is  divided  into  two  cavities,  one  above  the 
other,  by  an  interarticular  cartilage,  which  also  fulfils  the  duty  of  preventing 
mutual  direct  pressure  of  the  articular  surfaces  during  the  energetic  action  of  the 
muscles  of  mastication,  in  the  act  of  chewing.  The  articular  capsule,  considerably 
strengthened  by  the  external  ligament  particularly,  is  so  capacious  as  to  permit, 
in  addition  to  elevation  and  depression  of  the  lower  jaw,  also  of  displacement  of 
the  head  of  the  inferior  maxilla  forward  upon  the  articular  tubercle,  although  the 
meniscus  does  not  leave  the  head  of  the  bone,  which  it  covers  like  a  cap. 

The  movements  of  mastication  include:  (a)  Elevation  of  the  jaw, 
which  is  effected  by  the  united  action  of  the  temporal,  masseter  and 
internal  pterygoid  muscles.  If  the  inferior  maxillary  bone  had  pre- 
viously been  greatly  depressed,  so  that  the  condyles  of  the  bone  were 
moved  forward  upon  the  articular  eminences,  they  now  drop  back 
into  the  articular  cavity. 

If,  in  raising  the  lower  jaw,  the  bone  is  maintained  in  a  particular  position, 
the  action  of  the  muscle  that  would  move  the  maxilla  from  this  position  is  lost, 
as  is  shown  by  the  following:  (i)  In  elevating  the  lower  jaw  when  it  is  pushed  as 
far  forward  as  possible,  the  action  of  the  temporal  muscles  is  lost,  because  these, 
in  raising  the  jaw,  draw  it  backward  at  the  same  time.  (2)  When  the  lower  jaw 
is  pushed  as  far  backward  as  possible,  the  temporal  muscles  alone  exert  an  ele- 


THE    MOVEMENTS    OF    MASTICATION.  271 

vating  action,  because  the  other  muscles  would  tend  also  to  draw  it 'forward  at 
the  same  time.  (3)  When  the  lower  jaw  is  displaced  laterally,  the  elevating  action 
of  the  temporal  muscles  is  lost. 

(b)  The  downward  movement  of  the  lower  jaw  is  partly  due  to  its 
weight  and  partly  to  moderate  contraction  of  the  anterior  bellies  of  the 
digastric  and  by  the  mylohyoid  and  geniohyoid  muscles.     These  mus- 
cles act  more  powerfully  when  the  mouth  is  opened  widely  and  forcibly. 
The  fixation  of  the  hyoid  bone  necessary  for  this  purpose  is  effected  by 
the  omohyoid   and    sternohyoid,  as  well   as   the   combined    action   of 
the  sterno thyroid  and  thyrohyoid  muscles. 

As  the  articular  heads  of  the  bones  move  forward  upon  the  articular  tubercles 
when  the  inferior  maxilla  is  greatly  depressed,  it  has  been  assumed  that,  in  this 
case,  the  external  pterygoid  muscles  actively  favor  this  displacement.  When  the 
mouth  is  opened  to  an  especially  marked  degree,  the  head  is  bent  backward, 
and,  with  the  hyoid  bone  fixed,  the  posterior  bellies  of  the  digastric  muscles,  as 
well  as  the  stylohyoid  muscles,  enter  into  action.  Some  animals  possess  upper 
jaws  capable  of  movement  upward  and  downward,  as,  for  instance,  parrots,  croco- 
diles, snakes,  and  fish. 

(c)  Displacement  of  one  or  of  both  articular  heads  of  the  inferior 
maxillary  bone  forward  or  backward,     (i)  Projection  forward  of  the 
lower  jaw  is  caused  by  the  action  of  the  external  pterygoid  muscles. 
As  under  such  circumstances  the  articular  head  of  the  bone  slips  upon 
the  articular  tubercle,  and  therefore  also  moves  downward,  the  surfaces 
of  the  lateral  teeth  must  separate  from  each  other  in  this  position. 
(2)  Backward  displacement  is  caused  by  the  action  of  the  internal 
pterygoid  muscles.     (3)  The  articular  head  on  one  side  is  drawn  for- 
ward and  then  backward  again  by  the  external  and  internal  pterygoid 
muscles  of  the  same  side,  a  transverse  movement  of  the  inferior  maxilla 
taking  place  at  the  same  time.     The  more  the  lower  jaw  is  depressed, 
the  more  ineffective  are  these  movements. 

In  the  movements  of  mastication,  with  which  both  elevation  and  de- 
pression of  the  lower  jaw,  as  well  as  with  a  transverse  grinding  movement 
are  often  combined,  the  food  to  be  masticated  is  kept  between  the 
opposing  surfaces  of  the  teeth  by  the  muscles  of  the  lips  (orbicularis 
oris)  and  the  buccinators  from  without  and  by  the  action  of  the  tongue 
from  within.  The  sensibility  of  the  masticatory  muscles,  together  with 
the  sensibility  of  the  teeth  and  the  mucous  membrane  of  the  mouth  and 
lips,  determines  the  amount  of  force  to  be  expended  by  the  muscles  of 
the  lower  jaw  for  the  purpose  of  mastication.  By  reason  of  simultane- 
ous insalivation,  the  divided  particles  cohere,  so  that  they  can  be  readily 
formed  into  an  oval  bolus  on  the  dorsum  of  the  tongue. 

The  muscles  of  mastication,  together  with  the  mylohyoid  and  the  anterior 
belly  of  the  digastric,  receive  their  motor  nerves  from  the  motor  portion  of  the 
third  division  of  the  trigeminal  nerve.  The  hypoglossal  nerve  innervates  the 
geniohyoid,  thyrohyoid,  omohyoid,  and  sternohyoid  muscles,  as  well  as  the  sterno- 
thyroid.  The  buccinator,  the  posterior  belly  of  the  digastric,  the  stylohyoid  and 
the  muscles  of  the  face  that  take  part  in  opening  and  closing  the  mouth  are  sup- 
plied by  the  facial  nerve.  The  common  nervous  center  for  the  movements  o 
mastication  lies  in  the  medulla  oblongata. 

When  the  mouth  is  shut,  the  permanent  position  of  the  jaws  in  contact  with 
each  other  is  due  to  atmospheric  pressure,  as  the  buccal  cavity  is  made  completely 
free  of  air,  while  the  entrance  of  air  is  prevented  anteriorly  by  the  lips  and  pos- 
teriorly by  the  veil  of  the  palate.  The  pressure  of  the  atmospheric  air  corresponds 
to  a  column  of  mercury  of  from  2  to  4  mm.  high. 


272 


STRUCTURE  AND  DEVELOPMENT  OF  THE  TEETH. 


STRUCTURE  AND  DEVELOPMENT  OF  THE  TEETH. 

The  tooth  is  to  be  regarded  as  a  modified  papilla  of  the  mucous  membrane 
of  the  jaw,  of  exceptional  size  and  peculiar  structure.  In  its  simplest  form  it 
appears  as  a  horny  tooth,  as,  for  instance,  in  the  lamprey  and  the  duck-bill,  in 
which  the  connective-tissue  framework  of  the  papilla  is  covered  externally  with 
layers  of  hard,  horny  epithelium,  comparable  with  the  formation  of  hair  and  of 
bristles.  In  the  formation  of  human  teeth  a  thick  layer  covering  the  papillary 
cone  is  transformed  into  the  firm  layer  of  calcified  dentine.  The  epithelium  of  the 
papilla  produces  the  enamel,  while  an  accessory  deposit  takes  place  around  the 
base  of  the  cone  in  the  form  of  a  thin  covering  of  bone  (cement) . 

The  dentine,  ivory,  or  tooth-bone,  which  surrounds  the  cavity  of  the  tooth 
(Fig.  99)  and  the  root-canal,  is  firm,  elastic  and  brittle.  It  appears,  when 
subjected  to  special  treatment,  to  be  composed  of  fibrils,  which  unite  to  form 
lamellae,  and  these  in  turn  make  up  the  dentine  and  are  traversed  perpendicularly 

by  the  dentinal  tubules.  These  numerous,  long, 
corkscrew-like,  spiral  dentinal  tubules  begin 
with  free  openings  from  1.3  //  to  2.2  u  in  diam- 
eter in  the  interior  of  the  tooth,  and  traverse 
the  dentine  to  its  outermost  layer.  The  tubtiles 
are  bounded  by  an  extremely  resistent,  thin 
cuticle-like  layer,  the  dentinal  sheath  (Fig. 
100),  which  is  most  unyielding  to  chemical 
agents.  Within  the  cavities  of  the  dentinal 
tubules  and  completely  filling  them  lie  soft 
fibers,  the  dentinal  fibrils,  which  are  to  be  con- 
sidered as  enormously  elongated  processes  from 
the  superficial  pulp-cells,  the  odontoblasts. 

The  dentinal  tubules,  and  also  their  con- 
tents, the  dentinal  fibrils,  anastomose  throughout 
their  entire  course  by  means  of  processes.  Most 
of  them  terminate  near  the  enamel,  or  they 
penetrate  by  means  of  delicate  processes  into  the 
cement  substance  between  the  enamel  prisms. 
Only  a  few  bend  over,  forming  an  arch  and 
joining  one  another  (Fig.  102,  A,  c},  while 
others  pass  over  into  the  interglobular  spaces 
(Fig.  101).  The  latter  are  small,  uncalcified 
areas  of  the  ground-substance,  or  dilated  tubules 
located  in  greater  number  particularly  near  the 
periphery  of  the  dentine,  and  bound  by  spherical 
surfaces.  With  the  naked  eye  peculiar  lines 
can  be  seen  in  the  dentine,  particularly  that  of 
the  elephant's  tooth,  running  parallel  with  the 
contour  of  the  tooth  (Schreger's  lines) ,  which 
depend  upon  the  fact  that,  at  these  points,  all 
of  the  dentinal  tubules  pursue  a  similar  course 
as  respects  their  main  curves.  A  special  canal- 
system,  rising  from  the  root,  lies  between  the 
dentine  on  one  side  and  the  enamel  and  cement 
on  the  other,  and  communicates  with  the  other  cavities  of  the  tooth. 

The  enamel  (vitreous  substance),  the  hardest  substance  in  the  body,  as 
hard  as  apatite  or  quartz,  covers  the  free  projecting  crown  of  the  tooth.  It 
consists  of  perpendicular,  hexagonal  prisms  (Fig.  102,  B,  C),  arranged  side  by  side 
like  palisades,  and  united  by  cement-substance.  These  prisms  are  from  3  fi  to  5  p 
wide,  varying  in  thickness  throughout  their  course,  at  the  same  time  arching 
in  different  directions,  and  they  exhibit,  after  the  action  of  acids,  a  coarse,  trans- 
verse striation,  which,  however,  is  absent  in  entirely  fresh  prisms.  As  regards 
their  nature,  the  enamel-prisms  are  elongated  and  calcified  cylindrical  epithelium 
of  the  dentinal  papilla.  Retzius  described,  in  enamel,  the  presence  of  dark, 
brownish  bands,  running  parallel  to  the  outer  border  of  the  enamel^  and  due  to 
the  deposition  of  air  in  the  enamel  (Fig.  99).  Fully  formed  enamel  is  in  marked 
degree  negatively  doubly  refracting  and  uniaxial,  while  developing  enamel  is  posi- 
tively doubly  refractive. 

The  cuticula,  the  membranous  capsule  of  the  enamel,  covers  the  free  surface 


FIG.  99. — Longitudinal  Section  through 
an  Incisor  Tooth:  s,  enamel;  d, 
dentine;  cd,  tooth-cavity;  c,  cement. 


STRUCTURE  AND  DEVELOPMENT  OF  THE  TEETH. 


273 


FIG.  100. — Transverse  Sec- 
tion through  Dentine. 
The  light  rings  are  the 
dentinal  sheaths,  the 
dark  centers  with  the 
bright  points  are  the 
dentinal  fibrils  lying  in 
the  dentinal  tubules. 


of  the  enamel  as  a  structureless  membrane,  i  /n  or  2  fi  thick,  which,  in  the  case  of 
young  teeth,  exhibits  an  epithelium-like  arrangement,  and  is  derived  from  the  outer 
epithelial  layer  of  the  enamel  organ. 

The  cement  (osseous  substance)  consists  of  a  thin  bony   layer  covering  the 
root  of  the  tooth,  with    a   nbrillated   ground-substance  and  provided  with  Shar- 
pey's  fibers    (Fig.     103,    a).     Haversian    canals    and 
lamellae  are  found  only  in  the  thick  layers  of  cement 
at  the  apex  of  the  root,  the  former  at  times  leading 
into  the  tooth-cavity.     Thin   layers    of   cement    may 
even    be    unprovided   with  bone-corpuscles. 

Chemistry  of  the  Solid  Constituents  of  the  Tooth. — 
The  teeth  consist  of  a  framework  of  calcareous  sub- 
stance, infiltrated  with  calcium  phosphate  and  car- 
bonate, like  the  bones,  (i)  The  dentine  contains  of 
organic  matter  27.7,  of  calcium  phosphate  and  car- 
bonate 72.06,  of  magnesium  phosphate  0.75,  with 
traces  of  iron,  fluorin  and  sulphuric  acid,  potassium, 
sodium,  and  carbon  dioxid.  (2)  The  enamel  pos- 
sesses as  its  organic  basis  a  substance  resembling 
the  proteid  of  epithelial  cells.  It  contains  of  inor- 
ganic matter — in  addition  to  3.60  of  organic  matter 
— calcium  phosphate  and  carbonate  96.00,  magnesium 
phosphate  1.05,  with  traces  of  calcium  fluorid,  an  in- 
soluble chlorin-combination,  potassium,  sodium,  and 
carbon  dioxid.  (3)  The  composition  of  the  cement  is 
identical  with  that  of  true  bone. 

The  Soft  Parts  of  the  Tooth. — The  tooth-pulp  in  the 

adult  tooth  represents  the  remains  of  the  dental  papilla,  about  which  the  hard- 
ening layer  of  dentine  has  been  deposited.  It  consists  of  connective  tissue,  at 
times  not  distinctly  fibrous,  and  rich  in  capillaries,  with  connective-tissue  cells 
and  leukocytes.  The  most  superficial  layer  of  cells,  which,  not  unlike  epithelium, 
lie  close  together  next  to  the  dentine,  is  formed  of  unencapsulated  odontoblasts, 

25  //  long  by  2  fi  wide,  from  which  the 
production  of  the  dentine  proceeds. 
They  send  long  processes  into  the  den- 
tinal tubules,  while  the  nucleated  cell- 
body,  resting  on  the  surface  of  the 
pulp,  forms  a  connection  with  the  pulp 
and  with  neighboring  odontoblasts  by 
means  of  other  processes.  Numerous 
medullated  nerve-fibers,  becoming  non- 
medullated  after  repeated  division, 
penetrate  between  the  odontoblasts  and 
end  beneath  the  dentine  in  free  ex- 
tremities presenting  nodular  thickening 
in  places.  Other  nerve-fibers  lie  partly 
in  the  dentinal  tubules,  in  part  in  the 
substance  of  the  dentine.  Most  of  them 
appear  to  end  free,  in  a  brush-like 
radiation.  A  plexus  of  fine  nerve-fibers 
lies  beneath  the  enamel.  The  epidenti- 
nal  canal-system  is  provided  with  a 
special  nerve-apparatus,  which  in  part 
penetrates  into  the  enamel.  The  ar- 
teries of  the  tooth  often  lie  in  grooves 
in  the  nerve-branches.  The  capillaries 
even  penetrate  to  the  odontoblast-layer. 
The  periosteum  of  the  root  of  the  tooth 
and,  at  the  same  time,  of  the  alveolar  cavity,  is  of  a  delicate  structure,  without 
elastic  fibers,  but  rich  in  nerves  and  blood-vessels.  The  gums  have  no  mucous 
glands  and  are  characterized  by  their  long,  vascular  papillae. 

The    development   of   the   teeth   begins   as   early   as  the  fortieth    day    (Rose). 
Throughout  the  entire  length  of  the  alveolar  margin  there  is  a  projecting  ridge, 
formed  of  a  thick  epithelial  layer,  the  denial  ridge  (Ing.  104,  a).     From  this  epitne- 
18 


FIG.   101. — Interglobular  Spaces  in  the  Dentine. 


274 


STRUCTURE  AND  DEVELOPMENT  OF  THE  TEETH. 


lial  layer  a  furrow,  also  filled  with  epithelium,  forms  in  the  jaw,  the  dental  groove, 
which  thus  runs  beneath  the  base  of  the  dental  ridge.  The  dental  groove  grows 
deeper  throughout  its  entire  length,  acquiring  a  form  resembling  the  transverse  sec- 
tion of  elongated  formative  epithelial  cells;  this  is  the  enamel  organ.  From  the 
depth  of  the  jaw  there  grows  toward  the  enamel  organ  a  conical  papilla,  formed  of 
mucous  tissue,  the  dentinal  papilla  (Fig.  104,  c),  in  such  a  way  that  its  apex  sup- 


FIG.    102.— ,4,  Section  of  a  Tooth  at  the  Junction  (6)  between  Dentine  and  Enamel:  a,  enamel;  c,  dentinal 
tubules;  B,  enamel  prisms  greatly  magnified  ;  C,  the  same  prisms  in  transverse  section. 

ports  the  enamel  organ  like  a  double  cap.  The  connecting  parts  of  the  enamel 
organ,  lying  between  the  dentinal  papillae  of  the  separate  teeth,  now  disappear, 
through  hyperplasia  of  the  connective  tissue,  which  next  gradually  surrounds  the 
dentinal  papilla  and  its  enamel  organ  as  the  dental  sac  (Fig.  104,  d,  Fig.  105). 
Of  the  epithelial  cells  of  the  enamel-organ  those  (Fig.  105,  3)  that  cover  the 
head  of  the  papilla  as  a  continuous  layer  form  cylindrical  epithelium,  which  later, 


FlG.  103.— Transverse  Section  of  the  Root:  a, 
cement,  with  bone-corpuscles;  &,  dentine  with 
dentinal  tubules;  c,  junction  between  the  two. 


a 


FIG.  104. — a,  Dental  ridge;  b, 
enamel  orga.n;  c,  site  of  the 
beginning  dentinal  papilla; 
d,  first  trace  of  the  dental  sac. 


bv  calcification,  hardens  into  the  enamel  prisms.  The  layer  of  cells  of  the  double 
cap  however,  which  is  turned  upward  toward  the  dental  sac  (Fig.  105,  i),  flatten! 
out  softens  down  and  through  a  process  of  horny  metamorphosis  becomes  the 
cuticula  while  the  epithelial  cells  lying  between  the  two  layers  gradually  under- 
go complete  atrophy  through  a  peculiar  intermediary  metamorphosis  in  which 
they  resemble  the  star-shaped  cells  of  mucous  tissue  (Fig.  105,  2).  Accordi 


STRUCTURE  AND  DEVELOPMENT  OF  THE  TEETH. 


275 


v.  Brunn  the  enamel  extends  along  down  the  entire  root  of  the  tooth  during  the 
process  of  development,  but  is  subsequently  lost  in  this  situation. 

The  dentine  is  formed  on  the  uppermost  surface  of  the  protruding  connective- 
tissue  dentinal  papilla,  the  odontoblasts  (Fig.  105;  Fig.  106,  k)  arranged  here  in 
a  continuous  layer  becoming  calcified,  but  in  such  a  manner  that  uncalcified  fibers, 
the  dentinal  fibrils,  remain.  "By  means  of  the  process  of  the  pulp  each  odonto- 
blast is  connected  with  the  deeper  lying,  grad- 
ually growing  cells  of  the  young  pulp,  so  that 
when  an  odontoblast  is  ossified  down  to  the 
rudiment  of  its  fibril  another  takes  its  place, 
without  the  continuity  of  the  fibril  being  inter- 
rupted. Accordingly,  each  dentinal  fibril  with 
its  anastomoses,  must  be  considered  as  a  rudi- 
ment of  several  communicating  odontoblasts." 
In  the  hardening  of  dentine  the  same  process 
occurs  as  in  that  of  ossification  by  osteoblasts. 

The  cement  is  derived  from  the  soft  connec- 
tive tissue  of  the  alveolar  process  by  ossification. 
This  connective  tissue  arises  from  the  entire 
base  of  the  dental  sac. 

The  Shedding  of  the  Teeth. — Even  during  the 
development  of  the  milk-teeth,  a  special  enamel 
organ  (Fig.  105,  c)  for  the  permanent  teeth 
forms  by  the  side  of  that  for  the  temporary 

teeth ;     but  its   growth  is   held   in   check  until   the    FlG-   105.— a,  Dental  ridge;  6,  enamel  or- 


time  for  the  shidding  of  the  teeth.     The  papilla         ^^^S^^S  £ 

of   the   permanent    tOOth   IS    absent    at    the    begin-  amel  cell    layer;    c,  dentinal  papilla, 

ning.     As  the  permanent  tooth  grows,  its  dental          with  blood-vessels  and  layer  of  elon- 
sae  first  breaks  through  the  alveolar  wall  of  the         ffi±tS±d£tSfcS^ 
temporary  tooth  from  below.     The  tissue  of  this 
dental    sac,    acting    as    an    eroding    granulation- 
tissue,  causes  absorption  of  the  root  of  the  temporary  tooth  and  later  also  of 
its  body,  up  to  the  crown,  without  its  blood-vessels  undergoing  atrophy.     The 
ameboid  cells  of  the  granulation-tissue  engage  in  a  process  of  undermining  in 
the  absorption  of  the  temporary  teeth  by  means  of  processes  they  send  out,  taking 
up,  like  phagocytes,  calcareous  fragments  of  the  disintegrating  tooth. 

From  the  ninth  month  to  the  second  year  the  twenty  temporary  teeth  appear 

in  the  following  order:  lower  internal  incisors, 
a  upper  internal  incisors,   upper  external  inci- 

sors,   lower    external    incisors,    first    molar, 
canine  and  second  molar  teeth. 

The  shedding  of  the  teeth  begins  in  the 
seventh  year,  in  the  same  order  (the  decidu- 
ous molars  being  replaced  by  the  bicuspids) . 
Then  three  new  molars  appear  behind  the 
bicuspid  teeth,  the  most  posterior  at  about 
the  age  of  twenty  years,  therefore  called 
"wisdom-teeth."  They  may,  however,  ap- 
pear as  late  as  the  eightieth  year.  Thus, 
the  adult  has  thirty-two  teeth. 

According  to  Zuckerkandl,  epithelial  re- 
mains are  found  in  the  gums  behind  the  last 
molar  teeth,  which  must  be  regarded  as  the 
rudiment  of  a  fourth  undeveloped  molar  tooth. 
An  analogous  condition  has  been  noted  in 
animals. 

The  uninterrupted  growth  of  the  incisor 
teeth    may    be    readily  observed   in  rodents, 
replacing  the  free  ends  worn  off  by  chewing. 
If  the  opposing  incisor  teeth  of  a  rodent  are  extracted,  the  remaining  teeth,  no 
longer  worn  off  by  mutual  attrition,  grow  from  the  jaw  in  the  form  of  a  long  arch. 
That  in  human  beings  also  a  continual  replacement  of  the  teeth  must  occur  canno 
be  doubted.     Landois  has  observed  the  advance  toward  the  masticating  si 
and  the  final  disappearance  in  from  8  to  9  years  of  rachitic,   atrophic,  circul 
zones    that    must    have    formed   on   the  permanent   teeth   of  a  boy  even  before 


FIG.  106. — a,  Dental  ridge;  b,  enamel  organ; 
c,  dentinal  papilla;  /,  enamel;  g,  dentine; 
h,  gap  between  enamel  organ  and  den- 
tinal papilla;  k,  odontoblast  layer. 


276  MOVEMENTS  OF  THE  TONGUE. 

eruption.  This  proves  the  forward  growth  and  the  wear  of  the  teeth  at  their  free 
ends.  Only  when,  in  old  age,  the  power  of  regeneration  becomes  diminished, 
do  the  teeth  have  worn-off  surfaces.  During  the  embryonal  life  of  the  baleen 
whale,  dental  sacs  are  noted  in  the  jaws,  which,  however,  undergo  atrophy;  in 
their  place  whalebone  develops  later.  Tooth-bearing  edentates,  whose  teeth  are 
unprovided  with  enamel,  nevertheless  possess  an  enamel-organ,  whose  function 
it  is,  like  a  matrix,  to  insure  for  the  developing  tooth  sufficient  room  for  its  forma- 
tion. The  edentulous  armadillo  possesses  an  embryonal  dental  ledge,  which 
has  also  been  found  in  birds  and  turtles  as  the  last  rudiment  of  a  former  den- 
tition. 

MOVEMENTS  OF  THE  TONGUE. 

The  tongue  keeps  the  food  between  the  opposing  surfaces  of  the  teeth 
during  mastication;  it  collects  the  finely  divided  particles  of  food,  held 
together  by  the  saliva  and  forms  them  into  a  bolus,  and  finally  it  trans- 
fers the  bolus  along  its  dorsal  surface  into  the  pharynx  at  the  time  of 
deglutition. 

The  course  of  the  muscle-fibers  in  the  tongue  is  three-fold:  longitudinal,  from 
the  tip  to  the  root  of  the  tongue;  transverse,  originating  mainly  from  the  septum 
of  the  tongue  stretched  longitudinally;  and  vertical,  traversing  the  thickness  of 
the  organ.  The  muscles  of  the  tongue  are  in  part  confined  to  this  organ  alone; 
in  part  they  pass  to  the  tongue  from  other  fixed  points,  namely,  the  hyoid  bone, 
the  lower  jaw,  the  styloid  process  and  the  palate. 

Microscopically  the  muscle-fibers  are  striated  transversely,  surrounded  by  deli- 
cate sarcolemma,  and  frequently  divided  like  a  fork  at  their  extremities.  The 
bundles  interlace  with  one  another  to  a  considerable  extent,  and  small  deposits  of 
fat  are  found  in  the  spaces  between  them. 

The  movements  of  the  tongue  give  rise  in  part  to  changes  in  form,  in  part  to 
changes  in  position. 

1.  Shortening  and  widening,  through  the  longitudinal  lingual  muscle,  aided 
by  the  hyoglossus. 

2.  Elongation  and  narrowing,  through  the  transverse  lingual  muscle. 

3.  Excavation  of  the  dorsum  of  the  tongue  in  the  form  of  a  longitudinal 
furrow,  through  contraction  of  the  transverse  lingual  muscle,  with  simultaneous 
action  of  the  median  vertical  fibers. 

4.  Arching  the  dorsum  of  the  tongue:   (a)  transversely,  through  contraction  of 
the  lowermost    transverse  fibers;     (6)   longitudinally,  through  the  action  of  the 
lowermost  longitudinal  muscles. 

5.  Protrusion  of  the  tongue,  through  the  genioglossus,  aided  somewhat  by 
the  geniohyoid,  passing  from  the  hyoid  bone  toward  the  chin;    at  the  same  time 
the  tongue  usually  becomes  elongated  and  narrowed. 

6.  Retraction  of  the  tongue  through  the  hyoglossus,  chondroglossus  and  stylo- 
glossus;  also  as  a  rule  with  shortening  and  widening  of  the  tongue. 

7.  Depression  of  the  tongue  upon  the  floor  of  the  mouth  is  effected  in  the 
median  line  by  the  genioglossus;   at  the  sides  by  the  hyoglossus.     By  depression  of 
the  hyoid  bone  the  floor  of  the  mouth  can  be  made  even  much  deeper. 

8.  Elevation  of  the  tongue  to  the  palate:   (a)  at  the  tip,  through  the  anterior 
portions  of  the  upper  longitudinal  fibers;   (6)  in  the  center,  through  elevation  of 
the  entire  hyoid  bone  by  the  mylohyoid  muscle  (trigeminal  nerve) ;   and  (c)  at  the 
root,  through  the  styloglossus  and  palatoglossus  muscles,  as  well  as  indirectly  by 
the  stylohyoid  muscle  (facial  nerve) . 

9.  Lateral  deflection  of  the  protruded  tongue  is  effected  by  the  genioglossus 
(toward  the  opposite  side) ;  while   similar  deflection  of  the  tongue,  lying  in  the 
mouth,  is  effected   by  the    styloglossus,  hyoglossus,  chondroglossus    and   palato- 
glossus muscles.     Further  lateral  deflection  of  the  tongue,  so  that  the  tip  comes  to 
lie  behind  the  last  bicuspid  tooth,  is  effected  through  the  combined  action  of  the 
styloglossus  and  Hyoglossus  muscles  on  one  side  and  the  genioglossus  on  the  other 
side. 

The  motor  nerve  of  the  tongue  is  the  hypoglossal.  In  case  of  unilateral 
paralysis  the  tip  of  the  tongue  lying  at  rest  in  the  mouth  is  directed  toward  the 
unaffected  side,  because  the  tone  of  the  unparalyzed  longitudinal  fibers  shortens 
the  unaffected  side  to  some  extent.  If,  however,  the  tongue  is  protruded,  the  tip 
deviates  toward  the  paralyzed  side.  This  is  dependent  on  the  direction  pursued  by 


THE    ACT    OF    SWALLOWING.  277 

the  genioglossus  muscle  from  the  middle  line  (internal  mental  spine)  backward 
and  outward,  the  direction  of  whose  traction  the  tongue  must  naturally  follow. 
The  tongue  in  killed  animals  sometimes  exhibits  fibrillary  twitchings  for  an  entire 
day. 

THE  ACT  OF  SWALLOWING  (DEGLUTITION). 

The  propulsion  of  the  contents  of  the  alimentary  canal  is  effected 
by  a  motor  process  whereby  the  canal  contracts  upon  the  contained 
mass;  and  as  this  contraction  progresses  throughout  the  entire  length  of 
the  tube,  the  contents  are  pushed  on  before  it.  This  movement  is 
called  peristalsis. 

The  first  and  most  complicated  act  of  this  movement  is  deglutition, 
in  which  the  following  stages  can  be  distinguished : 

1.  The  mouth  is  closed  by  the  orbicularis  oris  muscle  (facial  nerve). 

2.  The   jaws   are  pressed   together  by  the  muscles   of  mastication 
(trigeminal  nerve);    in  this  way  the  lower  jaw  becomes  a  fixed  point, 
permitting  the  action  of  the  muscles  passing  from  the  lower  jaw  to  the 
hyoid  bone. 

3.  The  tip  of  the  tongue,  the  back  of  the  tongue,  and  the  root  of  the 
tongue  are  successively  pressed  against  the  hard  palate,  and  in  this 
way  the  contents  of  the  mouth  Hjolus  or  fluid)  are  forced  toward  the 
pharynx.  •• 

4.  When  the  bolus  has  passe^j^e  anterior  palatine  arches,  having 
been  made  slippery  by  the  mucus  of  the  tonsillar  glands,  its  return  % 
the  mouth  is  prevented  by  the  contraction  of  the  palatoglossus  muscles 
lying  in  the   anterior  palatine  arches,  which  bring  these  arches  firmly 
in  contact  with  each  other,  like  the  scenes  in   a  theater,  and  by  the 
back  of  the  tongue,  which  is  elevated  by  the  styloglossus  muscle. 

5.  The  bolus  now  lies  behind  the  anterior  palatine  arches  and  the 
root  of   the  tongue,  within  the  pharynx  and  exposed  to  the  succes- 
sive  action  of   the  three   constrictor  muscles  of    the   pharynx,  which 
push  it  onward.     The  action  of  the  superior  constrictor  muscle,  which 
contracts  first,  is  always  combined  with  horizontal  elevation,  through 
the   elevator  of   the  veil  of   the  palate   (facial   nerve),  and  tension  of 
the  soft  palate,  through  the  tensor  of  the  veil  of  the  palate  (trigeminal 
nerve;    otic  ganglion).     The  superior  constrictor,  through  the  pterygo- 
pharyngeal  muscle,  presses  the  posterior  and  lateral  pharyngeal  wall 
firmly  against  the  posterior  edge  of  the  veil  of  the  palate  horizontally 
elevated  and  made  tense  like  a  cushion  (Passavant's  cushion),  while  the 
edges  of  the  posterior  palatine  arches  are  at  the  same  time  approximated 
through  the  palatopharyngeal  muscles.     In  this  way  the  nasopharyngeal 
cavity  is  closed,  so  that  food  is  prevented  from  passing  readily  upward 
into  the  nasal  cavity. 

In  persons  with  congenital  or  acquired  defects  of  the  soft  palate,  food  can 
enter  the  nose  during  the  act  of  deglutition. 

The  elevation  of  the  veil  of  the  palate  can  be  readily  demonstrated  by  intro- 
ducing a  fine  probe  through  one  nostril,  along  the  floor  of  the  nasal  cavity,  until 
its  posterior  extremity  rests  upon  the  veil  of  the  palate.  With  every  movement  of 

~  from  the  nostril,  is 


nected  with  a  gas-pipe,   the  other  with  a  burner.     Every  movement  of  deglutition 
is  attended  by  movement  of  the  flame. 


278  THE    ACT    OF    SWALLOWING. 

6.  Responding  to  the  successive  contractions  of  the  superior,  middle, 
and  inferior  constrictors  of  the  pharynx  and  the  esophageal  muscles, 
the  bolus  is  forced  downward.     During  this  time  the  entrance  to  the 
larynx  must  be  kept   closed,  to  prevent  food  from  passing  into  the 
trachea. 

7.  According  to  Kronecker  and  Falk,  semisolid  foods  and  fluids  in  the 
mouth  are  forced  through  the  pharynx  and  the  esophagus  by  vigorous 
contraction  of  the  muscles  closing  the  mouth,  particularly  the  mylo- 
hyoid  muscles.     If  the  act  of  swallowing  is  repeated  several  times  in 
rapid  succession,  as  in  drinking,  only  the  last  is  followed  by  movements 
of  contraction  in  the  pharynx  and  the  esophagus,   for  every  act  of 
swallowing  in  the  mouth  exerts  an  inhibitory  effect  upon  the  lower 
portions  of  the  esophagus,  through  stimulation  of  the  glossopharyngeal 
nerve.     That  solid  and  semisolid  articles  of  food  are,  however,  pushed 
slowly  through  the  esophagus,  by  peristalsis  alone,  has  been  demonstrated 
by  the  Rontgen  rays  on  admixture  of  bismuth  subnitrate  with  the  bolus. 

According  to  Meltzer  and  Kronecker,  the  duration  of  the  act  of  deglutition  in 
the  mouth  is  0.3  second.  Then  the  constrictors  of  the  pharynx  contract;  0.9 
second  later  the  superior,  1.8  seconds  later  the  middle,  and  3  seconds  later  the 
inferior  constrictor  of  the  pharynx.  The  constriction  of  the  cardiac  orifice,  after 
the  food  has  passed  into  the  stomach,  is  th^Jinal  movement  of  the  series. 

On  auscultation  of  the  stomach  two^^fcads  are  heard  during  deglutition:  (i) 
the  squirting  sound,  which  is  due  to  the^^^Pthat  the  material  swallowed  is  forced 
irjgp  the  stomach,  and  (2)  the  squeezing  !^md,  due  to  peristalsis  occurring  at  the 
end  of  deglutition  forcing  the  contents  of  the  esophagus  through  the  cardia.  The 
latter  is  a  rale  and,  as  such,  is  dependent  on  the  presence  of  air  in  the  mass  swal- 
lowed. 

Closure  of  the  larynx  is  brought  about  as  follows:  (a)  The  lower  jaw 
being  fixed,  the  larynx  is  drawn  upward  and  forward  beneath  the  root  of 
the  tongue,  which  is  arched  over  it.  This  is  effected  by  a  movement  of 
the  hyoid  bone  forward  and  upward  through  the  action  of  the  geniohyoid, 
the  anterior  belly  of  the  digastric,  and  the  mylohyoid  muscles  together 
with  an  approximation  of  the  larynx  to  the  hyoid  bone,  through  the  thyro- 
hyoid  muscle,  (b)  While  the  tongue,  besides,  is  drawn  somewhat  backward 
by  the  styloglossus  muscles,  it  presses  the  epiglottis  over  the  entrance  to 
the  larynx,  so  that  food  can  now  slide  over  it.  (c)  The  epiglottis, 
further,  is  pulled  down  over  the  entrance  to  the  larynx  by  the  action 
of  the  reflector  epiglottidis  and  the  aryepiglottic  muscle. 

Intentional  injuries  of  the  epiglottis  in  animals,  or  destruction  of  the  epiglottis 
in  human  beings,  cause  choking  readily  from  the  entrance  of  liquids  into  the 
larynx,  while  solid  foods  can  be  swallowed  with  scarcely  any  trouble.  In  dogs, 
however,  colored  liquids  pass  directly  from  the  back  of  the  root  of  the  tongue 
downward  into  the  pharynx,  without  necessarily  staining  the  upper  surface  of 
the  epiglottis,  hidden  under  the  overhanging  root  of  the  tongue. 

(d)  Finally,  closure  of  the  glottis  by  the  constrictors  of  the  larynx 
prevents  the  entrance  of  swallowed  substances  into  the  larynx.  This 
closure  is  brought  about  through  reflex  influences. 

In  order  that  the  pharynx  itself  shall  not  be  drawn  down  with  the  de- 
scending bolus  it  is  drawn  upward  by  the  stylopharyngeal,  salpingo- 
pharyngeal  and  basopharyngeal  muscles  during  the  activity  of  the 
pharyngeal  constrictors. 

Nervous  Supply. — The  nerves  of  the  pharynx  are  comprised  in  the  pharyngeal 
plexus,  formed  by  branches  from  the  pneumogastric,  the  glossopharyngeal  and 
the  sympathetic.  The  act  of  deglutition' is  voluntary- only  in  so  far  as  it  takes 


THE    ACT    OF    SWALLOWING.  279 

place  in  the  mouth.     The  passage  of  the  bolus  through  the  palatine  arches  on 

^p^^-^e^^c^-£^^ 

nerves  an  question  for  the  striated  muscles  lies  in  the  medulla  oblongata      Degluti- 
rftSn'^LSS^™  mrt        Stat?  °f  unconsei°usn^s,  as  well  as  after  destruction 
-,™,ti   «.rPhPH,,m  and  pons.    Irritation  of  the  ninth  cranial  nerve  prevents  the 


—  S. 


Me. 


Within  the  esophagus  (Fig.  107),  the  stratified  squamous  epithelium 
of  which  is  kept  slippery  by  the  mucus  from  small  mucous  glands  opening 
at  the  edges  of  the  folds  of  mucous  membrane,  the  downward  movement 
takes  place  also  involuntarily  through  a  coordinated  muscular  act  a 
peristaltic  movement  of 
the  external  (longitu- 
dinal) and  the  internal 
(circular)  unstriated 
muscle-fibers. 

In  the  upper  part  of 
the  esophagus,  in  which  lie 
striated  muscle-fibers,  peris- 
talsis is  much  more  rapid 
than  in  the  lower  portion. 
The  movements  of  the 
esophagus  never  originate 
spontaneously,  but  they  al- 
ways follow  on  a  previous 
act  of  deglutition.  Thus, 
if  a  bolus  be  introduced 
into  the  esophagus  through 
an  external  wound,  it  re- 
mains where  it  was  placed; 
it  is  carried  downward  only 
when  movements  of  deglu- 
tition are  initiated  above. 
The  peristalsis  extends 
throughout  the  e  h  t  i  r  e 

length  of  the  esophagus,  even  if  this  be  ligated  or  a  portion  has  been  excised. 
The  peristalsis,  likewise,  continues  downward  in  a  dog,  even  after  meat  is  with- 
drawn from  the  esophagus,  though  it  has  been  halfway  down. 

Exceedingly  large  and  exceedingly  small  masses  of  food  are  swallowed  with 
greater  effort  than  those  of  medium  size.  Dogs  are  able  to  swallow  a  bolus 
weighing  450  grams.  Deglutition  becomes  difficult  in  consequence  of  great  dilata- 
tion of  the  thorax,  as  in  Miiller's  experiments  ;  likewise  in  consequence .  of  con- 
traction of  the  thorax,  as  in  Valsalva's  investigations. 

The  motor  nerve  of  the  esophagus  is  the  pneumogastric — after  division  of  which 
on  both  sides  food  remains  in  the  esophagus,  particularly  its  lower  part. 

Goltz  discovered  the  remarkable  fact  that  the  ganglionic  plexuses  situated  in 
the  esophagus  and  the  stomach  of  the  frog  acquire  greatly  increased  irritability 
when  the  brain  and  spinal  cord  or  both  pneumogastric  nerves  are  destroyed. 
Esophagus  and  stomach  contract  vigorously  like  a  string  of  pearls,  even  after 
slight  irritation,  while  animals  with  an  uninjured  central  nervous  system  swallow 
fluid  introduced  simply  by  peristalsis.  It  should  be  borne  in  mind  that  human 
beings  with  an  enfeebled  nervous  system  (hysteria)  not  rarely  exhibit  similar  spas- 
modic contraction  of  the  esophagus  (globus  hystericus).  Schiff  observed  spas- 
modic contraction  of  the  esophagus  in  dogs  also  after  section  of  both  pneumo- 
gastric nerves. 

The  heart -beats  are  accelerated  with  each  act  of  swallowing,  while  the  blood- 
pressure  falls,  the  need  of  respiration  diminishes  and  some  movements,  such  as 
labor-pains  and  erection,  are  inhibited.  All  of  these  movements  are  brought  about 
through  reflex  influences. 


FIG.  107. — Transverse  Section  through  the  Esophagus.  E,  epithe- 
lium ;  St,  mucous  membrane ;  Se,  mucous  gland  ;  Me,  circular 
muscle-fibers ;  Ml,  longitudinal  muscle-fibers ;  G,  capillaries  ; 
B,  connective  tissue;  S,  submucosa. 


280  THE    MOVEMENTS    OF    THE    STOMACH. 

THE  MOVEMENTS  OF  THE  STOMACH.— VOMITING. 

Three  methods  are  employed  for  determining  the  position  of  the  stomach: 
(a)  the  introduction  of  a  rubber  bougie  through  the  esophagus,  whose  passage  along 
the  greater  curvature  of  the  stomach  can  be  palpated;  (6)  electric  transillumina- 
tion  of  the  stomach  by  means  of  a  small  round  incandescent  light  attached  to 
the  extremity  of  a  stomach-tube.  The  stomach  is  previously  suitably  dilated 
by  the  development  of  carbon  dioxid  from  sodium  bicarbonate  administered; 
the  interpretation  requires  great  care ;  (c)  the  Rontgen  rays  have  also  been  em- 
ployed after  filling  the  stomach  with  meat  mixed  with  bismuth  subnitrate,  the 
latter  being  impervious  to  the  x-rays. 

For  registering  the  gastric  ^  movements,  a  _  rubber  bulb,  introduced  through 
an  external  gastric  fistula  in  animals,  and  applied  in  various  situations  in  the  in- 
terior of  the  stomach,  is  employed.  The  bulb  is  connected  with  a  writing-ap- 
paratus by  means  of  a  column  of  air.  Einhorn  has  used  the  gastrograph  in 
human  beings.  This  consists  of  a  metallic  capsule  attached  to  the  extremity  of 
a  rubber  tube,  which  is  swallowed.  With  every  movement  of  the  stomach 
the  metallic  parts  in  the  interior  of  the  capsule  are  brought  into  contact,  and  thus 
employed  to  effect  an  electrical  registration.  A  series  of  photographs  taken  with 
Rontgen  rays  also  affords  information  as  to  the  course  of  the  movements  and 
the  evacuation  of  the  gastric  contents. 

The  anterior  surface  of  the  empty  stomach  lies  in  a  frontal  position,  with  a 
slight  tendency  to  the  right  and  upward,  while  the  posterior  surface  accordingly 
occupies  the  opposite  position.  When  the  stomach  is  moderately  distended,  the 
anterior  surf  ace .  rises  about  the  lesser  curvature  as  an  axis,  so  that  it  forms  an 
angle  of  from  45°  to  48°  with  the  horizon.  When  the  distention  is  more  marked, 
the  stomach  comes  progressively  to  occupy  more  nearly  the  horizontal  position, 
so  that  its  anterior  surface  gradually  becomes  the  superior  surface. 

The  muscular  coat  of  the  stomach  consists  of  an  external  or  longitudinal  layer 
of  fibers,  a  middle  or  circular  layer,  and  an  internal  or  oblique  layer,  one  layer 
passing,  over  into  another  in  many  places.  At  the  pylorus  the  musculature  forms 
a  circular  sphincter-rmiscle  (sphincter  of  the  pylorus) ,  whose  fibers  continue  into  the 
pyloric  valve.  At  the  cardiac  orifice  also  the  muscle-fibers  are  grouped  into  a 
sphincter  muscle. 

The  movements  of  the  stomach  are  of  two  kinds :  i .  The  rotatory- 
rubbing  movement,  by  means  of  which  the  walls  of  the  stomach  lying 
in  immediate  contact  with  the  ingesta  move  to  and  fro  with  a  slow 
displacing  action.  These  movements  succeed  one  another  periodically, 
each  cycle  occupying  several  minutes. 

These  movements  can  be  imitated  by  slowly  rolling  or  mdlding  a  ball  between 
the  palms  of  the  hands  by  means  of  rotatory  movements  of  the  hands  in  opposite 
directions.  Indeed,  hair  swallowed  by  cattle  and  dogs  is  formed  into  a  regular 
ball  in  the  stomach.  The  object  of  this  rotatory  movement  is  thoroughly  to 
moisten  the  surface  of  the  stomach-contents  with  the  secretion  of  the  gastric 
glands,  and  at  the  same  time  to  favor  its  escape  by  the  pressure  and  the  continu- 
ous passage  of  ingesta,  as  well  as  to  detach  the  already  loosened  and  softened 
superficial  layers  of  the  food.  Further,  the  admixture  of  the  ingesta  with  the 
gastric  juice  is  effected  in  this  way.  This  movement  may  be  either  diminished,  in 
the  presence  of  gastric  disease,  such  as  gastric  ulcer,  or  increased,  as  when  there 
is  stenosis  or  dilatation. 

2.  The  other  kind  of  movement  is  a  peristalsis  of  periodic  recur- 
rence, in  conjunction  with  rhythmic  opening  and  closure  of  the  pylorus, 
as  a  result  of  which  the  partly  dissolved  gastric  contents  are  little  by 
little  propelled  into  the  duodenum,  commencing  after  an  interval  of  fif- 
teen minutes  and  ending  at  about  the  fifth  hour.  Each  wave  lasts 
twenty  seconds,  with  an  interval  of  from  fifteen  to  twenty  seconds 
between  waves.  This  peristalsis  is  most  active  from  the  pyloric  antrum 
toward  the  pylorus.  According  to  Rudinger,  the  longitudinal  fibers 
passing  toward  the  pylorus,  in  contracting,  especially  when  the  pyloric 
antrum  is  full,  cause  dilatation  of  the  pylorus. 


THE    MOVEMENTS    OF    THE    STOMACH.  281 

Evacuation  of  the  stomach  occurs  only  when  the  intestine  is  free  from  con- 
tents. The  following  experiment  will  serve  to  determine  when  the  ingesta  enter 
the  intestine.  In  the  presence  of  an  alkaline  reaction  in  the  intestine,  salol  is 
decomposed  into  carbolic  acid  and  salicylic  acid;  the  latter  can  be  recognized  in 
the  urine  from  the  violet  color  produced  upon  adding  ferric  chlorid.  In  healthy 
persons  this  reaction  begins  in  from  half  an  hour  to  an  hour  and  disappears  after 
twenty-four  hours;  while  in  the  presence  of  motor  insufficiency  of  the  stomach 
it  is  delayed  from  three  to  twenty-four  hours.  Liquids  are  rapidly  propelled  from 
the  stomach  into  the  intestine. 

The  thick,  muscular  walls  of  the  stomach  in  many  grain-eating  birds  aid  in 
triturating  the  ingesta.  The  energy  of  muscular  action  necessary  for  this  purpose 
has  often  been  measured  by  earlier  investigators,  who  found  that  glass  balls  were 
broken,  and  lead  pipes  that  could  be  flattened  only  by  a  pressure  of  40  kilograms 
were  compressed,  in  the  stomach  of  the  turkey.  The  masticating  stomach  of  many 
insects  also  is  capable  of  similar  activity. 

Mechanical  stimulation  causes  contraction  of  the  muscular  layers  directly 
affected ;  as  does  also  application  of  potassium-salts,  segmentary  contraction  of  the 
circular  muscles  often  taking  place  at  the  same  time.  Sodium-salts,  on  the  con- 
trary, usually  cause  semicircular  contractions  or  contractions  progressing  toward 
the  cardiac  orifice.  At  the  pyloric  antrum  the  stimulations  as  a  rule  spread  more 
rapidly.  Electrical  stimulation  of  the  internal  surface  of  the  stomach  causes  no 
movement.  The  contraction  induced  by  stimulation  of  the  intestinal  mucous  mem- 
brane is  always  less  than  that  due  to  stimulation  of  the  external  surface  of  the  in- 
testine. In  human  beings  both  endogastric  and  percutaneous  electrical  stimulation 
are  without  demonstrable  effect  on  the  evacuation  and  the  secretion.of  the  stomach. 

Nervous  Activity. — Openchowski  and  his  pupils  make  the  following  statements 
with  respect  to  the  influence  of  the  nerves  upon  the  movements  of  the  stomach: 
The  cardia  contains  automatic  ganglion-cells,  which  are  connected  with  the  pneu- 
mogastric and  the  sympathetic  nerves.  A  center  for  the  contraction  of  the  cardiac 
orifice  is  situated  in  the  posterior  quadrigeminal  bodies,  whence  the  paths  pass 
downward,  mainly  through  the  pneumogastric,  and  in  lesser  degree  through  the 
splanchnic  nerves.  The  center  for  opening  the  cardia  lies  in  the  corpus  striatum, 
and  in  connection  therewith  one  in  the  cruciate  sulcus  of  the  central  cortex,  in 
the  dog;  the  pneumogastric  nerves  constitute  the  conducting  paths.  Dilatation 
centers  are  situated  also  in  the  upper  portion  of  the  spinal  cord,  whence  the  path 
passes  through  the  sympathetic  nerve  (aortic  plexus,  lesser  splanchnic  nerve). 
Reflex  opening  of  the  cardiac  orifice  can  be  induced  by  irritation  of  the  sensory 
splanchnic  nerves,  and  of  the  sciatic  also. 

The  body  of  the  stomach  contains  also  automatic  ganglia,  connected  with  the 
pneumogastric  and  the  sympathetic  nerves.  A  center  for  contraction  is  situated 
in  the  corpora  quadrigemina,  whence  paths  pass  through  the  pneumogastric  nerves 
and  the  spinal  cord,  and  from  the  latter  into  the  sympathetic.  The  upper  cord 
contains  inhibitory  centers;  the  paths  pass  through  the  sympathetic  and  the 
splanchnic  nerves. 

The  pylorus  contains  automatic  ganglia.  It  exhibits  a  certain,  varying  degree 
of  tone  during  closure:  the  splanchnic  nerve  may  more  fully  open  the  pylorus, 
while  the  pneumogastric  tends  to  close  it.  The  center  for  opening  the  cardiac 
orifice  inhibits  the  movement  of  the  pylorus ;  the  path  passes  through  the  spinal 
cord  and  the  splanchnic  nerves.  Inhibitory  pyloric  centers  are  situated  in  the 
corpora  quadrigemina  and  the  olivary  bodies;  the  path  passes  through  the  spinal 
cord.  The  cortical  center  for  opening  the  cardia  causes  simultaneous  contraction 
of  the  pylorus;  the  path  passes  through  the  pneumogastric  nerves.  Centers  for 
the  contraction  of  the  pylorus  are  situated  in  the  corpora  quadrigemina;  the  path 
passes  through  the  pneumogastric  nerves,  a  few  fibers  through  the  spinal  cord  and 
the  sympathetic  nerve. 

Stimulation  of  the  peritoneum  and  also  of  the  skin  causes  reflex 
of   the  pylorus  and  of  the  small  intestine.      Stimulation   of  the  central 
of  one  pneumogastric,  the  other  being  intact,  gives  rise  to  immobility  of  the  pylorus, 
contraction  of  the  stomach  and  dilatation  of  the  cardiac  orifice, 
temperature  to  25°  C.  causes  movements  in  the  excised  empty  stomach. 

Vomiting  takes  place  in  consequence  of  contraction  of  the  walls  of  the  s 
the  pyloric   sphincter  being  at  the  same  time  closed.     It   occurs  most  readily 
when  the  stomach  is  distended.     Dogs  usually  distend  the  stomach  greatly  b 
vomiting,  bv  swallowing  air.      There   is  no    doubt    that    in   infants  vomitl 
due    principally  to  contractions  of   the  walls  of   the   stomach,   though   will 


282  THE    MOVEMENTS    OF    THE    INTESTINES. 

the  slightest  spasmodic  cooperation  of  abdominal  pressure.  When  the  act  of 
vomiting  is  attended  with  straining,  abdominal  pressure  comes  energetically  into 
play. 

The  contractions  of  the  walls  of  the  stomach  that  cause  a  general  diminution  in 
the  size  of  the  viscus  can  be  recognized  when  the  stomach  is  exposed.  The  pylorus 
contracts ;  then  wave-like  contractions  appear  from  the  pyloric  extremity  upward 
to  the  body  of  the  stomach.  The  uppermost  portion  of  the  stomach,  including 
the  cardia,  does  not  contract,  but  the  cardiac  orifice  is  opened  by  the  con- 
traction of  the  longitudinal  muscle-fibers,  which  pass  toward  the  esophageal 
opening,  and  therefore  must  act  as  dilators  when  the  stomach  is  full. 

The  actual  ejection  of  the  contents  of  the  stomach  is  immediately  preceded 
by  an  eructation-like  movement,  dilating  the  intrathoracic  portion  of  the  esopha- 
gus. This  takes  place  in  such  a  manner  that,  with  the  glottis  closed,  violent, 
jerky  inspiration  suddenly  occurs,  causing  the  esophagus  to  be  distended  by  gas 
rising  from  the  stomach.  At  the  same  time  the  larynx  and  the  hyoid  bone  are 
drawn  forcibly  forward  by  the  combined  action  of  the  geniohyoid  and  sternohyoid, 
together  with  the  stern othyroid  and  thyrohyoid  muscles,  with  obliteration  of  the 
laryngeal  angle.  As  a  means  of  support  the  lower  jaw  is  even  moved  horizontally 
forward;  as  a  result  air  passes  from  the  pharynx  downward  to  the  upper  portion 
of  the  esophagus.  At  the  same  time  the  projection  and  the  inclination  of  the  head 
favor  dilatation  of  the  esophagus.  If,  now,  sudden  abdominal  pressure  is  exerted, 
supported  by  the  intrinsic  movements  of  the  stomach,  the  contents  of  the  viscus 
will  be  ejected.  If  the  vomiting  be  long  continued,  there  may  even  be  antiperis- 
talsis  of  the  duodenum,  as  a  result  of  which  bile  enters  the  stomach  and  becomes 
admixed  with  the  vomited  matters. 

Children,  in  whom  the  fundus  of  the  stomach  is  not  sacculated,  vomit  more 
readily  than  adults,  in  whom  the  fundus  must  contract  forcibly. 

The  center  for  the  act  of  vomiting  is  situated  in  the  medulla  oblongata.  It 
is  connected  with  the  respiratory  center,  as  experience  teaches  that  attacks  of 
nausea  can  be  overcome  by  rapid,  deep  respiration.  The  act  of  vomiting  can  be 
inhibited  likewise  in  animals  by  means  of  artificial  respiration.  On  the  other  hand, 
the  administration  of  emetics  does  not  permit  the  development  of  apnea. 

The  act  of  vomiting  may  be  excited  by  chemical  or  mechanical  irritation  of 
the  centripetal  nerves  of  the  mucous  membrane  of  the  palate,  the  pharynx,  the 
root  of  the  tongue  and  the  stomach;  also,  under  certain  conditions  (pregnancy)  by 
irritation  of  the  uterus,  of  the  intestines  (peritonitis) ,  and  also  of  the  genito-urinary 
apparatus ;  finally  by  direct  stimulation  of  the  vomiting  center. 

The  act  of  vomiting  excited  by  repulsive  conceptions  appears  to  result  from 
the  transmission  of  stimuli  from  the  cerebrum  through  conducting  fibers  to  the 
vomiting  center.  The  act  of  vomiting  is  also  common  in  connection  with  cerebral 
disease.  Irritation  of  the  central  stump  of  the  pneumogastric  nerve  is  capable 
of  inducing  vomiting. 

The  ruminating  process  in  ruminants  resembles  the  act  of  vomiting.  Also  in 
human  beings  eructation  of  food  resembling  morbid  rumination  has  been  observed 
as  the  expression  of  a  gastric  neurosis.  There  exists  under  such  circumstances 
relative  insufficiency  of  the  cardiac  orifice  of  the  stomach  :  with  the  glottis  closed, 
the  contents  of  the  stomach  on  attenuation  of  the  air  in  the  thorax  rise  into 
the  mouth.  Forced  expiratory  pressure  is  capable  of  preventing  this  phenomenon. 

Emetics  act  (i)  directly  upon  the  vomiting  center  (as,  for  instance,  apomorphin) . 
Central  vomiting  ceases  after  destruction  of  the  corpora  quadrigemina,  or  division 
of  the  anterior  columns  of  the  spinal  cord  or  destruction  of  all  the  spinal  sympa- 
thetic fibers  that  pass  to  the  stomach.  (2)  Other  emetics  act  upon  the  vomiting 
center  through  reflex  influences  from  the  stomach  or  the  intestine  (copper  sulphate, 
tartar  emetic).  The  irritation  reaches  the  gastric  musculature  through  the  pneu- 
mogastric nerves.  (3)  Both  of  these  modes  of  action  may  be  combined.  Emetics 
may  also  remove  mucus  from  the  respiratory  organs.  It  would  appear  that  emetics 
exert  a  favorable  influence  upon  the  respiratory  movements,  through  irritation 
of  the  respiratory  center,  as,  for  instance,  in  small  children. 

THE  MOVEMENTS  OF  THE  INTESTINES. 

For  observing  the  peristaltic  movements  in  animals,  the  abdominal  cavity  is 
opened  under  a  0.9  per  cent,  sodium-chlorid  solution  at  blood-temperature  in 
order  to  avoid  the  entrance  of  air  ;  or  the  observations  may  be  made  through  the 
shaved  and  uninjured  abdominal  walls. 


THE    EVACUATION    OF    FECES.  283 

The  small  intestine  exhibits  peristaltic  movements  in  a  classical 
manner.  The  progressive  constriction  of  the  canal,  which  forces  the 
contents  before  it,  always  passes  from  above  downward.  After  death 
and  on  exposure  of  the  coils  of  intestine  to  the  air,  peristalsis  is  often 
seen  to  develop  in  several  parts  of  the  intestine  at  the  same  time,  and  as  a 
result  the  intestinal  loops  acquire  the  appearance  of  a  mass  of  crawling 
worms.  In  addition  to  these  movements,  pendulum-like  movements  of 
the  intestine  also  occur,  by  which  the  contents  are  moved  some  distance 
first  in  one  direction  and  then  in  the  other.  The  advance  of  new  intestinal 
contents  and  the  resulting  increased  distention  of  the  tube  due  to  solid 
contents  or  gas  causes  renewed  movement. 

The  large  intestine  exhibits  less  active  and  less  extensive  move- 
ments. When  the  abdominal  walls  are  thin,  or  in  the  sac  of  a  hernia, 
peristalsis  may  be  felt  and  even  seen.  Herbivora  exhibit  more  active 
peristalsis  than  carnivora.  Perhaps  the  transmission  of  peristalsis  takes 
place  directly  through  the  musculature,  as  in  the  heart  and  the  ureter. 
The  ileo-cecal  valve,  as  a  rule,  does  not  permit  the  usually  more  con- 
sistent contents  of  the  large  intestine  to  pass  back  into  the  small  intes- 
tine. During  sleep,  at  night,  the  movements  of  the  stomach  and  the 
intestines  cease. 

If  fluid  material  is  gradually  introduced  into  the  rectum  from  a  height  of 
one  meter  of  water-pressure  through  an  intestinal  tube,  it  may  pass  upward  through 
the  ileo-cecal  valve  into  the  small  intestine,  and,  with  great  care,  it  may  reach 
the  stomach  and  esophagus,  and  even  escape  from  the  mouth  and  nose.  In  this 
way  the  entire  intestinal  tract  in  the  living  subject  can  be  irrigated,  and  with  cura- 
tive results  ;  as,  for  instance,  in  cases  of  cholera  (i  or  2  per  cent,  solution  of 
tannic  acid  in  7.5  per  cent,  solution  of  sodium  chlorid).  Eight  or  nine  liters  are 
sufficient  to  fill  the  entire  alimentary  canal. 

A  crystal  of  sodium  chlorid  applied  externally  to  the  intestine  causes  con- 
traction at  that  point,  with  upward  peristalsis,  while  potassium  chlorid  induces 
only  local  contraction.  Particles  saturated  with  sodium-chlorid  solution  and  in- 
troduced into  the  rectum  are  carried  upward,  in  part  even  to  the  stomach,  through 
the  mediation 'of  nervous  irritation,  perhaps  of  the  muscularis  mucosae. 

Pathological. — -If  an  inflammatory  or  catarrhal  condition  of  the  intestinal 
mucous  membrane  develops  rapidly  in  consequence  of  an  acute  inflammatory 
irritation,  contractions  of  the  inflamed  portion,  at  first  marked,  occur  in  the  full 
intestine.  When  the  affected  portion  has  been  emptied  the  movements  are  no 
longer  more  marked  than  normal.  If  further  contents  reach  the  inflamed  portion, 
the  peristaltic  downward  movement  takes  place  more  rapidly  than  normal  and 
diarrhea  results.  At  times  a  greatly  contracted  piece  of  the  intestine  is  pushed 
into  a  neighboring  portion  (invagination,  intussusception).  Reduction  in  the 
bodily  temperature  is  followed  by  a  decrease  in  the  peristalsis. 

That  antiperistalsis,  that  is  a  movement  upward  toward  the  stomach,  occurs 
was  formerly  considered  proved  by  the  appearance  of  fecal  vomiting  in  connection 
with  intestinal  obstruction  due  to  stenosis  in  human  beings  with  occlusion  of  the 
bowel.  The  investigations  of  Nothnagel,  however,  throw  doubt  upon  this  con- 
clusion, as  he  failed  to  observe  effective  antiperistalsis  after  artificial  occlusion  of 
the  bowel.  The  fecal  odor  of  the  vomited  matter  may  also  depend  upon  its  pro- 
longed sojourn  in  the  duodenum,  whence,  as  the  well-known  bilious  vomiting 
shows,  ingesta  may  be  returned  into  the  stomach. 

THE  EVACUATION  OF  FECES  (DEFECATION). 

The  contents  of  the  intestine  remain  in  the  small  intestine  about 
three  hours,  and  for  a  further  twelve  hours  in  the  large  intestine,  where 
they  become  inspissated,  and  in  the  lower  portion  formed  into  the 
fecal  mass.  Through  the  peristaltic  movement,  the  feces  are  forced 
onward  to  a  point  somewhat  above  that  portion  of  the  rectum  which 


284 


THE    EVACUATION    OF    FECES. 


is  surrounded  by  both  sphincter-muscles,  of  which  the  upper  or  internal 
is  formed  of  unstriated  and  the  external  of  striated  muscle-fibers. 

Immediately  after  the  act  of  defecation  the  external  sphincter  (Fig. 
1 08,  S;  Fig.  109)  usually  contracts,  and  remains  contracted  for  some  time. 
When  the  muscle  relaxes,  the  elasticity  of  the  parts  surrounding  the 
anal  opening,  particularly  of  both  the  sphincter-muscles,  is  sufficient  to 
insure  closure  of  the  anus.  In  the  interval  of  rest  or  until  the  pressure 
of  the  feces  again  occurs,  there  is  no  evidence  of  a  permanent  contrac- 
tion (tonic  innervation)  of  the  anal  sphincters.  As  long  as  the  fecal 
matters  lie  above  the  rectum,  they  give  rise  to  no  conscious  sensation. 


FIG.  108. — The  Perineum  and  its  Muscles:  i,  anus;  2,  coccyx;  3,  ischial  tuberosity;  4,  tuberososacral  ligament; 
5,  acetabulum;  B,  bulbocavernosus  muscle;  Ts,  superficial  transverse  perineal  muscle;  F,  fascia  of  the  deep 
transverse  perineal  muscle;  J,  ischiocavernosus  muscle;  O,  internal  obturator  muscle;  S,  external  sphincter 
ani  muscle;  L,  levator  ani  muscle;  P,  pyriformis  muscle. 

It  is  only  their  descent  into  the  rectum  that  causes  the  feeling  of 
tenesmus.  At  the  same  time  the  stimulation  of  the  sensory  nerves  of 
the  rectum  causes  reflex  stimulation  of  the  sphincters.  The  center  for 
this  reflex  (Budge's  anospinal  center)  is  situated  in  the  lumbar  cord. 

In  animals,  after  division  of  the  spinal  cord  above  this  center,  the  anal  opening 
closes  actively  when  touched ;  but  soon  after  this  reflex  contraction  the  sphincters 
relax,  and  the  anus  may  thus  remain  open  for  a  time.  This  is  due  to  the  fact 
that  the  active  voluntary  contraction  of  the  external  sphincter-muscle,  already 
mentioned,  under  the  control  of  the  will  (cerebrum),  which  keeps  the  anus 
closed  for  some  time  after  each  evacuation  of  the  bowel,  is  absent.  In  dogs,  in 


THE    EVACUATION    OF    FECES.  285 

which  the  posterior  roots  of  the  lower  lumbar  and  the  sacral  nerves  were  divided, 
Landois  observed  that,  while  recovery  was  otherwise  normal,  the  anus  remained 
open.  Not  rarely  a  portion  of  the  fecal  mass  protruded  for  a  considerable  time, 
as  the  sensibility  in  the  rectum  and  anus  was  lost  in  such  animals.  Neither  was 
reflex  contraction  of  the  sphincters  possible,  nor  could  voluntary  closure  of  the 
anus,  induced  by  the  sense  of  feeling  alone,  take  place,  although  this  would  other- 
wise have  doubtless  been  possible. 

An  excitomotor  as  well  as  an  inhibitomotor  influence  may  be  exerted 
upon  the  external  anal  sphincter,  as  upon  any  voluntary  muscle,  from 
the  cerebrum.  Nevertheless,  closure  can  be  maintained  only  for  a 
certain  time  if  the  pressure  from  above  is  considerable.  Finally  ener- 
getic peristalsis  overcomes  even  the  strongest  voluntary  stimulation. 


FIG.    109.— The  Levator   Ani   and   External   Sphincter   Ani   Muscles. 


The  evacuation  of  feces,  which  takes  place  habitually  in  human  be- 
ings at  a  definite  interval,  once  or  twice  daily,  rarely  oftener,  begins  with 
active  peristalsis  in  the  large  intestine  which  passes  downward  to  the 
rectum.     In  order  that  the  sphincter  muscles  may  not  be  excited  to 
reflex  activity  by  the  advancing  column  of  feces,  it  appears  that  an 
inhibitory  center  for  the  sphincter-reflex,  capable  of  voluntary  stimula- 
tion, must  become  active.     This  is  situated  in  the  brain  (Masius 
poses  in  the  optic  thalamus),  whence  its  fibers  pass  through  the  cere- 
bral peduncles  to  the  anospinal  center.      During  stimulation  of 
inhibitory    apparatus,  the   column  of    feces   passes  through  t 
without  causing  its  reflex  closure. 


286        NERVOUS    INFLUENCES    AFFECTING    INTESTINAL    MOVEMENTS. 

The  active  peristalsis  necessary  to  cause  defecation  may  be  favored 
and  to  a  certain  extent  excited,  partly  by  pressure,  partly  by  short 
voluntary  movements  of  the  external  sphincter  and  the  levator  ani 
muscles,  whereby  the  my  enteric  plexus  of  the  lower  portion  of  the  large 
intestine  is  stimulated  mechanically,  with  the  result  that  active  peris- 
taltic movements  of  the  large  intestine  are  soon  set  up.  The  expulsion 
of  feces  is  favored  by  active,  voluntary  abdominal  pressure,  principally 
with  inspiratory  depression  of  the  diaphragm.  The  soft  parts  of  the 
pelvic  floor  are  forced  downward  conically  with  a  strong  effort  at  stool, 
whereby  the  anal  mucous  membrane,  which  coincidently  becomes  filled 
with  venous  blood,  is  at  times  everted.  It  is  the  function  of  the  levator 
ani  muscle  (Figs.  108  and  109)  voluntarily  to  elevate  the  soft  parts 
forming  the  pelvic  floor  and  thus,  in  elevating  the  anus,  in  a  measure 
to  slide  it  over  the  descending  column  of  feces.  At  the  same  time  it 
prevents  relaxation  of  the  soft  parts  of  the  pelvic  floor,  particularly  the 
pelvic  fascia.  As  the  fibers  of  both  levator  ani  muscles  converge  down- 
ward, and  mix  with  those  of  the  external  anal  sphincter,  they  coinci- 
dently aid  the  sphincter  when  energetic  contraction  takes  place,  as  they 
bear  approximately  the  same  relation  to  the  anus  that  the  strings  of  a 
tobacco-pouch  bear  to  its  opening.  When  the  desire  for  stool  is 
marked  the  closure  of  the  anus  can  be  made  more  secure  by  pressure 
from  without  through  forcible  rotation  of  the  thighs  outward  and  the 
action  of  the  gluteal  muscles. 

During  the  normal  interval  between  evacuations  of  the  bowel,  the 
feces  appear  to  descend  only  to  the  lower  extremity  of  the  sigmoid 
flexure.  From  this  point  to  the  anus  the  rectum  normally  is  usually 
free  from  feces.  The  strong  circular  fibers  of  the  muscularis,  which 
Nelaton  termed  the  third  anal  sphincter,  appear,  by  their  contraction, 
to  arrest  the  further  advance  of  the  fecal  matter. 

NERVOUS  INFLUENCES  AFFECTING  THE  INTESTINAL  MOVE- 
MENTS. 

The  automatic  center  for  the  movements  of  the  intestinal  canal  is 
the  greatly  developed  myenteric  plexus,  which  is  embedded  between 
the  longitudinal  and  circular  layers  of  the  muscular  coat.  It  is  this 
that  is  responsible  for  the  movements  that  continue  for  some  time  in 
an  excised  portion  of  intestine,  just  as  they  occur  in  the  heart. 

This  plexus,  constituted  mainly  of  non-medullated  nerves,  distributes  fibers 
that,  after  again  forming  a  network,  pass  to  the  unstriated  muscle-fibers.  The 
cells  of  the  plexus  possess  an  axis-cylinder  process  and  several  protoplasmic  pro- 
cesses. Nerve-fibers  pass  through  the  mass  of  ganglia,  while  others  surround 
the  ganglion-cells  with  their  extremities.  Special  nerve  -  plexuses,  containing 
ganglia,  are  found  upon  the  blood-vessels  and  lymph- vessels  of  the  intestinal 
wall. 

When  this  center  is  free  from  all  stimulation,  the  intestine  remains  in 
a  state  of  rest,  resembling  the  apnea  that  occurs  with  absence  of  stimu- 
lation of  the  medulla  oblongata.  This  occurs  during  intra-uterine  life, 
as  it  does  also  with  respect  to  respiration,  in  consequence  of  the  large 
amount  of  oxygen  in  the  fetal  blood.  This  condition  may  be  termed 
intestinal  rest — aperistalsis.  It  is  observed  also  during  sleep,  perhaps 
in  consequence  of  the  greater  amount  of  oxygen  in  the  blood. 

The  circulation  through  the  intestinal  vessels  of  blood  containing 


NERVOUS    INFLUENCES    AFFECTING    INTESTINAL    MOVEMENTS.        287 

the  usual  amount  of  gases  gives  rise  to  the  quiet  peristaltic  movement 
of  the  healthy  individual — euperistalsis. 

All  stimuli  transmitted  to  the  my  enteric  plexus  increase  peristalsis, 
which  finally  may  progress  to  violent  movement,  with  rumbling  in  the 
intestines  (borborygmus),  and  may  even  cause  involuntary  discharge 
of  feces  and  spasmodic  contraction  of  the  intestinal  musculature.  This 
condition,  which  corresponds  to  dyspnea,  may  be  designated  dysper- 
istalsis. 

This  condition  may  be  caused  (a)  by  interruption  of  the  circulation  in  the 
intestines,  ft  matters  not  whether  anemia,  as  after  compression  of  the  aorta,  or 
venous  hyperemia  is  thereby  induced.  The  exciting  agent  here  is  the  deficiency 
of  oxygen,  or  the  excess  of  carbon  dioxid.  Even  slighter  circulatory  disturbances 
in  the  intestinal  blood-vessels,  as,  for  instance,  venous  stasis  in  connection  with 
abundant  transfusion  into  the  veins,  whereby  transitory  overdistention  of  the 
venous  system,  and  therefore  stasis  in  the  portal  system  occurs,  give  rise  to  in- 
creased peristalsis.  This  takes  the  form  of  noises  and  rumbling  in  the  intestines, 
together  with  involuntary  defecation,  if,  in  consequence  of  transfusion  of  hetero- 
geneous blood,  stasis  becomes  marked,  as  a  result  of  thrombosis  of  the  intestinal 
blood-vessels.  Landois  explains  in  this  way  the  irresistible  inclination  to  stool 
and  the  increased  peristalsis  that  attend  certain  forms  of  cardiac  weakness  of  acute 
onset  and  sclerosis  of  the  coronary  arteries,  in  consequence  of  which  the  circulation 
in  the  intestines  suddenly  ceases.  A  similar  state  of  affairs  is  observed  even  under 
normal  conditions.  Landois  believed  that  the  persistent  pressure  in  constipated 
individuals  induces  the  evacuation  that  eventually  takes  place,  as  much  by  exciting 
peristalsis  through  the  venous  stasis  in  the  intestines  as  by  mechanical  pressure 
upon  the  intestinal  canal.  Also  the  increased  peristalsis  that  constantly  attends 
approaching  death  depends,  undoubtedly,  upon  circulatory  disturbances  and  thus 
upon  an  alteration  in  the  amount  of  gases  in  the  blood  in  the  intestines.  The 
same  statement  is  applicable  to  the  increased  intestinal  movement  that  attends 
certain  emotional  disturbances,  as,  for  instance,  fear.  Here  the  stimulation  of 
the  brain  passes  through  the  medulla  oblongata  (containing  the  center  for  the 
vasomotor  nerves)  to  the  intestinal  nerves  and  causes  circulatory  disturbances  in 
the  intestines  (coincidently  with  pallor).  Restoration  of  the  normal  circulatory 
condition  restores  the  intestines  to  quiet  peristalsis.  Salvioli  caused  blood  to 
flow  artificially  through  excised  pieces  of  intestine  by  means  of  cannulas  intro- 
duced into  the  blood-vessels,  and  found  that  blood  rich  in  oxygen  caused  intestinal 
rest,  while  interruption  of  the  circulation  caused  contractions  of  the  intestines. 
B6kai  was  able  to  overcome  the  dysperistalsis  induced  by  the  introduction  of 
carbon  dioxid  into  the  intestines  by  introducing  oxygen  into  the  intestinal  cavity. 

(6)  Direct  irritation  of  the  intestine  causes  movement  not  only  of  the  part 
directly  affected,  but  also  of  the  neighboring  part  of  the  intestines,  especially  that 
lying  toward  the  pylorus.  The  cumulative  effect  of  stimuli  is  shown  here ;  that  is 
feeble  stimuli,  which  are  too  weak  to  excite  movement  when  applied  but  once, 
do  so  on  persistent  repetition,  as  exposure  of  the  intestines  to  the  air,  in  more 
marked  degree  in  the  presence  of  carbon  dioxid  and  chlorin,  the  introduction  of 
certain  irritating  substances  into  the  intestine,  marked  distention  of  the  intestinal 
canal,  especially  with  coincident  difficulty  in  or  obstruction  to  defecation  (which 
occurs  frequently  in  human  beings),  or  direct  irritation  of  different  kinds,  also 
inflammatory  processes  involving  the  intestine  either  from  within  or  from  without. 
In  this  connection,  the  observation  is  of  interest  that  induced  currents  applied 
to  a  hernial  sac  containing  intestine  excite  active  peristalsis  in  the  hernia.  Local 
irritation  of  a  portion  of  the  intestine  with  a  tetanizing  induced  current  causes 
a  circular  constriction,  which  advances  especially  toward  the  stomach  when  the 
current  is  of  considerable  strength.  The  shortening  of  the  longitudinal  fibers  that 
are  stimulated  at  the  same  time  extends  in  both  directions. 

With  increasing  temperature  intestinal  rest  first  results — from  irritation  of  the 
splanchnic  nerves;  when  the  temperature  reaches  43°  C.  intestinal  movement  is 
resumed. 

All  persistent  stimuli  of  moderate  strength  cause  cessation  of  dys- 
peristaltic  intestinal  movement  from  overstimulation.  This  condition 
may  be  designated  intestinal  exhaustion  or  intestinal  paresis. 


288        NERVOUS    INFLUENCES    AFFECTING    INTESTINAL    MOVEMENTS. 

This  state  of  rest  of  the  intestine  is  thus  widely  different  from  that  attending 
the  condition  of  aperistalsis.  Persistent  stasis  of  blood  in  the  intestinal  vessels 
leads  finally  to  intestinal  exhaustion,  as,  for  instance,  when  thrombosis  occurs  in 
the  intestinal  vessels  after  transfusion  of  blood  from  a  different  species.  Distention 
of  the  vessels  with  indifferent  fluids,  after  compression  of  the  aorta  had  previously 
excited  active  peristalsis,  likewise  causes  cessation  of  peristaltic  movement.  In 
the  same  category  belongs  also  the  condition  of  rest  noted  after  the  temperature 
of  the  intestine  has  been  reduced  to  19°  C.  Severe  intestinal  inflammation  also 
has  a  similar  effect.  Under  favorable  conditions  the  intestine  may  recover  from 
this  stage  of  exhaustion  after  the  irritation  has  ceased.  This  takes  place,  as  a 
rule,  through  a  transitional  stage  attended  with  active  peristalsis.  Thus  the  intro- 
duction of  arterial  blood  into  the  vessels  of  the  exhausted  intestine  causes  at  first 
active  peristaltic  movements,  followed  by  normal  peristalsis. 

The  continuous  application  of  strong  stimuli  finally  causes  complete 
paralysis  of  the  intestine  in  human  beings  as  seen  after  inflammations, 
traumatisms,  incarcerations,  and  the  like.  The  intestine  becomes 
greatly  distended,  as  the  paralyzed  muscularis  is  no  longer  able  to  offer 
any  resistance  to  the  gases  expanded  by  the  heat  (meteorism). 

The  Peripheral  Intestinal  Nerves. — Of  the  nerves  passing  to  the  intestine  the 
pneumogastric  nerve  increases  the  movements  of  the  small  intestine  and  the  upper 
portion  of  the  large  intestine,  either  by  conveying  the  stimuli  applied  to  it  to 
the  myenteric  plexus,  or  by  causing  contractions  of  the  stomach,  which,  in  turn, 
as  true  mechanical  impulses,  excite  the  intestine  to  movement.  The  pneumogastric 
nerves  also  contain  several  inhibitomotor  fibers. 

The  splanchnic  nerve — -the  greater  derived  from  the  sixth  to  the  ninth,  and 
the  lesser  from  the  tenth  and  eleventh  dorsal  ganglia— is  (i)  the  inhibitory  nerve 
for  the  intestinal  movements,  but  only  so  long  as  the  blood  in  the  capillaries  has  not 
become  venous  while  the  circulation  in  the  intestine  remains  undisturbed.  If  the 
latter  condition  has  arisen,  irritation  of  the  splanchnic  causes  increased  peristalsis. 
If  arterial  blood  be  introduced,  the  inhibitory  action  is  prolonged.  Irritation  of 
the  origin  of  the  splanchnic  nerve  in  the  dorsal  cord  also  produces  the  inhibitory 
effect  under  analogous  circumstances,  even  in  the  presence  of  irritation  of  the 
spinal  cord  as  a  result  of  strychnin-poisoning,  with  the  occurrence  of  general 
tetanic  convulsions.  O.  Nasse  believes  that  it  may  be  concluded  from  the  experi- 
ments that,  in  addition  to  these  readily  exhausted  inhibitory  fibers,  paralyzed  by 
venosity  of  the  blood,  there  are  present  (2)  motor  fibers  that  are  excitable  for 
a  longer  time,  inasmuch  as  stimulation  of  the  splanchnic  nerve  after  death  always 
causes  peristalsis  of  the  stomach  and  intestines,  as  does  stimulation  of  the  pneu- 
mogastric nerve.  (3)  The  splanchnic  nerve  is  also  the  vasomotor  nerve  of  all  of 
the  arteries  and  veins  of  the  intestines,  including  the  portal  vein,  thus  controlling 
the  largest  vascular  area  of  the  body.  Stimulation  of  the  splanchnic  nerve  causes 
contraction,  its  division  dilatation,  of  all  of  the  intestinal  blood-vessels  possessing 
muscle-fibers.  In  the  latter  event  an  enormous  accumulation  of  blood  takes  place 
in  the  intestinal  vessels,  so  that  anemia  of  other  parts  of  the  body  results,  and 
in  consequence  even  death  may  take  place  from  anemia  of  the  medulla  oblon- 
gata.  (4)  The  splanchnic  nerve  is,  finally,  the  sensory  nerve  of  the  intestines, 
and,  as  such,  it  is  extremely  sensitive. 

Almost  all  the  cells  of  the  solar  plexus  are  included  in  the  course  of  the  fibers 
of  the  splanchnic  nerve.  Nicotin  paralyzes  these  cells,  while  the  peripheral  fiber 
retains  its  irritability. 

Stimulation  of  the  nervi  erigentes  causes  contraction  of  the  longitudinal  mus- 
cular fibers  and  relaxation  of  the  circular  fibers  of  the  rectum;  while  irritation  of 
the  hypogastric  nerves  has  the  opposite  effect  according  to  Fellner. 

Stimulation  of  the  sigmoid  gyrus  on  the  cerebral  cortex  of  the  dog,  as  well 
as  of  parts  lateral  to  and  behind  it,  excites  intestinal  movements  through  the 
pneumogastric  nerves,  as  does  likewise  stimulation  of  the  optic  thalamus.  Inhibi- 
tory fibers  pass  from  both  of  these  situations  through  the  spinal  cord,  from  which 
they  make  their  exit  near  the  middle  of  the  dorsal  cord. 

The  drugs  that  affect  the  intestine  are  (i)  those  that  diminish  the  irritability 
of  the  myenteric  plexus,  and  thus  decrease  peristalsis,  even  to  the  point  of  intes- 
tinal rest,  like  belladonna;  (2)  those  that  stimulate  the  nerves  inhibiting  peris- 
talsis, and  paralyze  in  large  doses,  like  opium  or  morphin.  The  drugs  of  these 
two  classes  cause  constipation.  Elevation  of  temperature  (also  during  fever) 


THE    STRUCTURE    OF    THE    GASTRIC    MUCOUS    MEMBRANE. 


289 


diminishes  intestinal  peristalsis  through  irritation  of  the  splanchnic  nerve.  (3) 
Other  drugs  stimulate  the  motor  apparatus;  such  as  nicotin,  to  the  point  of 
intestinal  cramps,  muscarin,  caffein  and  some  laxatives,  which  thus  act  as  evacu- 
ants.  The  movement  excited  by  muscarin  can  be  neutralized  by  atropin.  As, 
in  consequence  of  the  rapid  movement  of  the  intestinal  contents,  the  contained 
fluid  can  be  absorbed  in  but  small  measure,  the  frequent  evacuations  that  follow 
are  at  the  same  time  liquid.  (4)  Among  purgatives,  mention  should  be  made 
of  those  that  irritate  the  intestines  directly,  such  as  colocynth  and  croton-oil.  It 
is  supposed  that  agents  of  this  kind  cause  a  watery  transudation  from  the  blood- 
vessels into  the  intestine,  just  as  croton-oil  also  causes  vesicles  on  the  external 
skin.  (5)  Certain  laxative  salts,  sodium  sulphate,  magnesium  sulphate  and  others, 
liquefy  the  intestinal  contents  by  retaining  for  their  solution  in  the  intestine  the 
water  of  the  intestinal  contents;  if,  therefore,  they  are  injected  into  the  blood- 
vessels of  an  animal,  constipation  may  even  result.  (6)  Calomel  (mercurous 
chlorid)  restricts  the  absorptive  power  of  the  walls  of  the  intestine,  and  also 
putrefactive  decomposition  in  the  bowels.  Therefore  the  fecal  evacuations  are 
thin,  with  little  odor,  and  of  a  greenish  color  from  admixture  of  unchanged  bili- 
verdin. 

THE  STRUCTURE  OF  THE  GASTRIC  MUCOUS  MEMBRANE. 

The  surface  of  the  mucous  membrane  of  the  stomach  exhibits  numerous  small 
depressions,  the  gastric  crypts  (foveolae  gastricae,  Fig.  no),  lined  by  a  single 
layer  of  mucous  goblet  cells  (Fig.  112,  d).  These  cells  are  sharply  delimited 
at  the  cardiac  orifice  from  the  stratified  squamous  epithelium  of  the  esophagus; 
and  at  the  pyloric  extremity  from  the  true  cylindrical  epithelium  of  the 
duodenum.  The  cells  with  almost  homogeneous  contents  are  provided  with 
elliptical  nuclei  containing  nucleoli.  Between  their  narrowed,  lower  ends  are 
scattered  oblong  or  spindle-shaped,  unencapsulated,  nucleated  elements,  exhibiting 
mitosis,  which  are  intended  to  replace  desquamated  cells.  All  cells  are  completely 
open  upon  their  free  surface,  so  that 
nothing  prevents  the  escape  of  the  mucus 
elaborated  by  mucous  metamorposis  from 
the  cell-protoplasm.  The  simple  tubular 
gastric  glands,  generally  several  in  num- 
ber, empty  into  the  bottom  of  the  gastric 
crypts.  They  occur  in  two  different 
forms : 

1 .  As  true  gastric  glands,  peptic  glands 
of  the  fundus  (Fig.    114),   which  number 
about    five    millions,     the    largest    being 
present  in  the  fundus.     The  structureless 
membrana  propria  of  simple  tubular  form, 
has,  on  its  internal  surface,  two  different 
kinds  of  cells :   (a)  the  chief  cells  (Fig.  in, 
II,  a),  the  adelomorphous  ceils  of  Rollett; 
small,    unencapsulated,     nucleated,  ^pale 
cells  lying  close  together,  lining  the  inner 
lumen    of    the     glands,     and    (b)    larger, 
mainly  scattered,  plainly  projecting  parie- 
tal cells  (Fig.  in,  II,  h),  the  delomorphous 
cells  of  Rollett,  ovoid  or  crescentic,  without 
a    membrane,    darkly     granular,    readily 
stained  with  osmic  acid  and  aniline-blue, 
containing,  at  times,  several  nuclei.     They 
cause   bulbous   projections   of   the   mem- 
brana   propria.      In    human    beings    the 
parietal  cells  are  thought  to  reach  to  the 

lumen  of  the  spaces  within  the  gland.     They  are  even  found  scattered  under  the 
epithelium  of  the  crypts  and  the  surface  of  the  mucous  membrane,  as  well  as  i 
isolated  pyloric  glands.     Between  the  chief  cells  secretory  spaces  are  present,  and 
likewise  between  neighboring  parietal  cells,  while,  at  the  same  time,  with  the  latter 
delicate  branching  and  anastomosing  passages  in  part  lead  from  the  excrete 
duct  of  the  gland  into  the  interior  of  the  parietal  cells  and  in  part  form  a  network 
surrounding  them. 

2.  Only  in  the  vicinity  of  the  pylorus,  where  the  mucous  membrane  has  a 


FIG.  no. — Sectional  View  of  the  Gastric  Mucous 
Membrane,  Showing  the  Crater-like  Depres- 
sions of  the  Gastric  Crypts:  a,  a,  the  most 
prominent  projections  of  the  mucous  mem- 
brane (from  a  dog). 


2QO 


THE    STRUCTURE    OF    THE    GASTRIC    MUCOUS    MEMBRANE. 


rather  yellowish- white  appearance,  are  the  pyloric  glands  (Fig.  112,  A)  found,  in 
general  in  smaller  number.  At  their  lower  extremity  their  ducts  are  not  rarely 
divided  into  two  or  more  blind  sacs.  Their  cellular  contents  consist,  as  a  rule, 


FIG.  in. — I.  Transverse  Section  through  the  Duct  of  a  Fundus-gland :  a.  membrana  propria;  b,  goblet-cells; 
c,  reticular  connective  tissue.  II.  Sect-ion  through  the  Glands  of  the  Fundus:  a,  chief  cells;  h,  parietal 
cells;  r,  reticular  tissue  of  the  mucous  membrane  between  the  glandular  tubules;  c,  divided  blood-vessels. 


FIG.  112.- 


Isolated  goblet-cells;  A,   pyloric  gland 
of  the  stomach. 


FIG.  113. — M,  Portion  of  a  gastric  gland  with 
chief  cells  (h  h)  and  parietal  cells  (b  b);  the 
latter  exhibit  intracellular  secretory  canals. 
Between  the  chief  cells  intercellular  secretory 
ducts  (z  z)  penetrate  for  some  distance;  a, 
excretory  duct  of  the  gland. 


THE    STRUCTURE    OF    THE    GASTRIC    MUCOUS    MEMBRANE. 

Ce"8' 


291 


The  scanty  supporting  structure  of  the  gastric  mucous  membrane  consists  of 
reticular  -connective  tissue  with  leukocytes,  mixed  with  fibrillary  connective  tissue 
and  elastic  fibers.  The  mucous  membrane  possesses  a  special  muscular  layer  the 
musculans  nrncosae  This  passes  as  a  rather  thick  stratum  under  the  base  of  the 
gland,  often  exhibiting  an  inner  circular  and  an  outer  longitudinal  layer  From 


FIG.  114. — Vertical  Section  through  the  Gastric  Mucous  Membrane:  g  g,  the  crypts  of  the  surface;  p,  the  mouths 
of  the  peptic  tubules  (fundus  glands)  with  parietal  cells  (x)  and  chief  cells  (y);  a  v  c  c  ,  artery,  vein  and  capil- 
laries of  the  mucous  membrane;  i,  capillary  network  for  the  passage  of  the  mouth  of  the  gland-duct;  d  d, 
the  lymphatic  vessels  of  the  mucous  membrane,  passing  over,  at  e,  into  a  large  trunk  (semidiagrammatic 
representation). 


this  stratum  a  number  of  bundles  of  fibers  pass  upward  between  the  glands  and 
around  them.  They  appear  to  be  intended  for  active  evacuation  of  the  glandular 
tubules. 

Numerous  blood-vessels  (Fig.  114)  enter  from  the  fibrillary  connective  tissue 
of  the  submucosa  (a) ,  spread  out  into  a  longitudinal  capillary  network  (c  c)  between 
the  glands,  and  reach  the  free  surface,  where  they  again  form  a  fine  meshwork  (i  i) 
just  under  the  epithelium,  and  through  the  meshes  of  which  the  mouths  of  the 
ducts  (g)  make  their  appearance.  Collecting  at  this  point  the  veins  unite  in  the 
submucosa  to  form  trunks  of  considerable  size  (v). 


292  THE    GASTRIC    JUICE. 

The  lymphatic  vessels  of  the  gastric  mucous  membrane  begin  rather  close 
beneath  the  epithelium  as  bulbous  or  loop-like  formations  (d  d) ,  then  pass  per- 
pendicularly to  the  submucosa,  where  they  attain  a  considerable  size  (e)  through 
the  union  of  adjacent  branches.  The  nerves  are  the  same  as  those  of  the  intestine. 
The  submucosa  consists  of  bundles  of  connective  tissue  with  elastic  fibers  and 
embedded  fat-cells. 

THE  GASTRIC  JUICE. 

The  gastric  juice  is  a  fairly  clear,  colorless,  levorotatory,  readily 
filtered  fluid,  with  a  strongly  acid  reaction,  an  acid  taste  and  a  character- 
istic odor.  From  the  presence  of  free  hydrochloric  acid,  it  counteracts 
putrefaction  and,  in  part,  fermentation.  Its  specific  gravity,  when  the 
stomach  is  empty  (fasting),  ranges  between  1004  and  1006.5;  after  the 
ingestion  of  food,  from  1010  to  1020,  and  more  than  1020  when  the 
production  of  acid  is  diminished.  Its  amount  was  said  by  Beaumont, 
in  1843,  from  observations  upon  a  human  being  with  a  gastric  fistula, 
to  be  only  180  grams  daily.  According  to  Griinewald,  in  1853,  it 
was  estimated  in  a  similar  case  to  be  26.4  per  cent,  of  the  body- weight 
in  twenty-four  hours.  Finally  it  was  placed  by  Bidder  and  Carl 
Schmidt,  after  comparative  observations  upon  dogs,  as  6|  kilograms  in 
the  day,  corresponding  to  y-Q  of  the  body-weight.  The  gastric  juice 
contains : 

1.  Pepsin,   the   characteristic,   nitrogenous,    hydrolytic   ferment   or 
enzyme  that  dissolves  proteids:  from  0.41  to  1.17  per  cent. 

2.  Hydrochloric  acid  occurs  free  in  the  gastric  juice:  from  0.2  to  0.3 
per  cent. 

3.  Lactic  acid  may  also  be  found,  either  from  fermentation  of  carbo- 
hydrates (fermentation  lactic  acid)  or  from  being  dissolved  out  of  the 
meat  of  the  food  (sarcolactic  acid). 

Reactions. — Hydrochloric  acid  alone,  and  in  the  free  state,  is  identified  by 
Gunzburg's  reagent:  To  a  few  drops  of  filtered  gastric  juice  an  equal  number  of 
drops  of  a  solution  of  2  grams  of  phloroglucin  and  i  gram  of  vanillin  in  30  grams 
of  alcohol  are  added,  and  the  mixture  is  evaporated  in  a  porcelain  dish  over  the 
water-bath,  with  the  development  of  a  rose-red  color.  Resorcin,  2.5  grams,  dis- 
solved in  50  grams  of  dilute  alcohol,  with  addition  of  1.5  grams  of  cane-sugar, 
may  be  employed  in  a  manner  analogous  to  the  foregoing  reagent,  likewise  giving 
rise  to  a  red  color. 

Reaction  for  Lactic  Acid. — A  freshly  prepared  blue  mixture  of  10  cu.  cm.  of 
a  4  per  cent,  solution  of  carbolic  acid,  with  20  cu.  cm.  of  distilled  water  and  one 
drop  of  ferric  chlorid,  is  colored  yellow  by  lactic  acid.  To  5  cu.  cm.  of  the  gastric 
juice  to  be  tested  i  or  2  drops  of  hydrochloric  acid  are  added,  and  the  mixture  is 
evaporated  over  a  free  flame  to  the  thickness  of  sirup.  The  residue  is  extracted 
with  a  little  ether,  is  then  poured  into  a  reagent  glass  containing  5  cu.  cm.  of 
water,  one  drop  of  a  5  per  cent,  solution  of  ferric  chlorid  is  added,  and  the  mixture 
is  shaken.  A  greenish-yellow  color  appears  even  when  i  part  of  lactic  acid  in 
1000  is  present.  The  gastric  contents,  evaporated  to  the  consistency  of  sirup,  to 
expel  the  alcohol,  are  extracted  by  shaking  with  ether.  The  filtrate,  on  addition 
of  an  alcoholic  solution  of  iodin  and  being  heated,  yields  iodoform,  in  consequence 
of  the  formation  of  acetaldehyd  from  the  lactic  acid. 

Hydrochloric  acid  and  organic  acids  together  yield  the  following  reactions. 
To  demonstrate  the  total  free  acids  (those  not  combined  with  albumin),  Congo- 
red  is  used,  also  in  the  form  of  reagent-paper.  It  indicates  the  presence  of  free 
hydrochloric  acid  or  a  considerable  amount  of  free  organic  acids  by  becoming  blue 
in  color.  The  same  information  is  afforded  by  dark-red  benzopurpurin,  which  is 
changed  to  a  violet  color,  and  also  by  tropaeolin  OO.  A  little  of  a  concentrated 
alcoholic  solution  of  the  latter,  heated  with  4  drops  of  gastric  juice  in  a  dish,  yields 
a  bluish-violet  stain. 


THE    SECRETION    OF    THE    GASTRIC    JUICE.  293 

4.  For  a  consideration  of  the  milk-ferment,  reference  may  be  made 
to  page  300. 

5.  The  large  amount  of  mucus  adherent  to  the  surface  of  the  mucosa 
is  a  secretion  of  the  mucous  goblet-cells. 

6.  Inorganic  matters  are  present  in  percentages  for  human  beings 
(and  for  dogs,  in  parenthesis)  as  follows:  Water,  994.40  (973.06);  hydro- 
chloric acid,  0.20  (2.84);   calcium  chlorid,  0.06  (0.96);   sodium  chlorid, 
1.46^(2.82);    potassium  chlorid,  0.55  (1.09);    ammonium  chlorid  (0.5); 
calcium,  magnesium,  and  iron  phosphates,  0.125  (2.7).     Organic  matters, 
principally  pepsin,  are  present  to  the  amount  of  0.32  per  cent.  (1.71). 

Of  foreign  substances,  the  following  appear  in  the  gastric  juice  after 
introduction  into  the  body:  potassium  sulphocyanid,  iron  lactate, 
potassium  ferrocyanid,  sugar,  etc.  Ammonium  carbonate  is  found  in 
the  presence  of  uremia. 

THE  SECRETION  OF  THE  GASTRIC  JUICE. 

During  the  course  of  digestion  characteristic  changes  take  place  in 
the  chief  cells,  and  in  the  parietal  cells  of  the  fundus  glands  and  in  the 
cells  of  the  pyloric  glands. 

The  chief  cells  contain  granules  that  are  consumed  during  the  process 
of  secretion.  The  granules  contain  the  pepsin-forming  substance,  which 
is  transformed  into  pepsin.  The  size  of  the  chief  cells  diminishes  also 
during  secretion.  At  rest  these  cells  take  from  the  lymph,  material  for 
the  production  of  the  granules.  The  parietal  cells,  during  the  period 
of  secretion,  appear  first  to  be  swollen,  then  to  become  smaller.  All 
of  the  cells,  further,  are  darker,  and  the  nucleus  of  the  cells  of  the 
pyloric  glands  moves  toward  the  center.  The  secretory  ducts  become 
more  distended. 

In  some  animals  the  chief  cells,  during  secretion,  bear  a  fringe  of 
short,  hair-like  processes  (Tornier's  "brush-fringe"!),  directed  toward 
the  lumen  of  the  gland. 

The  pepsin  is  formed  in  the  chief  cells.  If  these  are  swollen,  they 
produce  much  pepsin;  if  shrunken,  they  produce  but  little.  The  pyloric 
glands  also  secrete  pepsin,  though  in  much  less  amount.  During  the 
first  stage  of  hunger  the  pepsin  accumulates;  while  during  the  period 
of  digestive  activity  it  is  eliminated,  as  it  is  also  when  hunger  is  pro- 
tracted. 

Klemensiewicz  removed  the  pyloric  portion  of  the  stomach  of  a  dog  with  two 
incisions;  sutured  the  duodenum  to  the  stomach,  and  allowed  the  pyloric  portion, 
still  in  communication  with  its  blood-vessels,  to  heal  in  the  abdominal  wound, 
after  closure  of  its  lower  extremity  by  sutures.  The  secretion  of  this  portion  of 
the  stomach  was  viscid  and  alkaline,  containing  2  per  cent,  of  solid  matters, 
including  pepsin. 

The  glands  themselves  contain  no  pepsin,  but  only  a  zymogen, 
namely,  the  pepsinogenic  substance  or  propepsin,  which  occurs  in 
the  granules  of  the  chief  cells.  The  zymogen,  of  itself,  exerts  no  influ- 
ence upon  proteids.  If,  however,  it  be  treated  with  hydrochloric 
acid  or  sodium  chlorid,  it  is  transformed  into  pepsin.  In  addition  to 
pepsin,  the  pepsinogenic  substance  may  be  extracted  from  the  mucous 
membrane  of  the  stomach  by  means  of  water  free  from  acid.  The 
milk-ferment  also  originates  in  the  chief  cells. 

The  hydrochloric  acid  is  formed  by  the  parietal  cells.     It  is  found 


294  THE    SECRETION    OF    THE    GASTRIC    JUICE. 

on  the  free  surface  of  the  mucous  membrane,  as  well  as  in  the  excretory 
ducts  of  the  gastric  glands.  In  the  depth  of  the  glandular  tubules, 
however,  the  reaction  is  generally  alkaline.  The  acid  must,  therefore, 
be  advanced  rapidly  from  the  depth  to  the  surface. 

Sarcolactic  acid  can  be  rapidly  extracted  as  such  from  the  chyme. 
For  the  production  of  lactic  acid  through  fermentation  in  the  stomach  it 
is  necessary  that  the  carbohydrates  have  been  present  for  a  consider- 
able time.  This  does  not  occur  in  the  healthy  individual,  but  in  asso- 
ciation with  great  diminution  in  the  production  of  hydrochloric  acid, 
stagnation  of  the  ingesta  in  the  stomach,  and  interference  with  gastric 
absorption,  particularly  in  the  presence  of  gastric  carcinoma. 

Lactic-acid  bacteria  are  always  present  in  the  stomach,  though  they  exhibit 
no  activity  in  the  presence  of  healthy  gastric  juice  on  account  of  the  anti-fermenta- 
tive influence  of  the  hydrochloric  acid.  Lactic  acid  develops,  however,  only  in 
the  absence  of  free  hydrochloric  acid,  which  is  particularly  often  the  case  in  the 
presence  of  gastric  carcinoma. 

The  hydrochloric  acid  first  secreted  at  once  combines  in  the  stomach 
with  the  proteids  to  form  acid  albumin ates.  These  do  not  yield  the 
color-reactions  of  free  acid.  As  the  secretion  progresses  free  hydro- 
chloric acid  makes  its  appearance.  If  the  secretion  of  gastric  juice  be 
enfeebled  it  may,  therefore,  happen  that  the  production  of  hydrochloric 
acid  is  not  sufficient  to  permit  of  the  appearance  of  free  hydrochloric 
acid. 

When  the  tests  for  hydrochloric  acid  in  the  stomach-contents  are  distinctly, 
even  though  feebly,  positive,  sufficient  hydrochloric  acid  is  present;  an  unusually 
strong  reaction  is  indicative  of  abnormally  increased  production.  If  the  reaction 
is  wanting,  a  decinormal  hydrochloric-acid  solution  is  added  to  a  measured  amount 
of  gastric  contents  until  a  distinct  reaction  is  obtained  by  Giinzburg's  test.  The 
amount  of  hydrochloric  acid  consumed  is  then  proportional  to  the  degree  of  the 
hydrochloric-acid  insufficiency  present. 

In  regard  to  the  production  of  free  acid,  the  following  appears  to  be 
established.  The  parietal  cells  secrete  hydrochloric  acid  from  the 
chlorids  that  the  mucous  membrane  takes  up  from  the  blood.  There- 
fore, the  production  of  hydrochloric  acid  ceases  when  the  chlorids  are 
withdrawn  from  the  food,  as  well  as  in  the  state  of  hunger.  The  active 
agent  in  this  connection  has  not  been  discovered;  yet  it  is  established 
that,  if  carbon  dioxid  acts  continuously  on  the  chlorids,  nevertheless, 
hydrochloric  acid  is  expelled  by  the  much  weaker  carbon  dioxid.  Maly 
and  others  assume  that  the  production  of  hydrochloric  acid  takes  place 
within  the  parietal  cells  as  follows : 

2Na2HPO4+3CaCl2=Ca3(PO4)2+4NaCl-f2HCl. 

The  bases  set  free  by  the  separation  of  the  hydrochloric  acid  are 
excreted  in  the  urine,  with  the  development  of  a  slightly  acid  reaction. 

When  the  stomach  is  empty  the  gastric  juice  contains  some  hydro- 
chloric acid,  but  a  more  abundant  secretion  is,  according  to  Pawlow, 
brought  about  in  a  most  striking  manner  by  the  appetite,  and  also  by 
the  stimulation  of  the  food  under  natural  conditions,  as  well  as  by 
water,  meat-extractives,  and  even  by  indigestible  matters  when  intro- 
duced into  the  stomach.  Under  these  circumstances  the  mucous  mem- 
brane is  reddened  from  increased  activity  of  the  circulation,  so  that  the 
outflowing  venous  blood  is  lighter  in  color.  The  excitation  of  the  secre- 
tion is  a  reflex  process.  The  sensory  nerves  of  the  pharynx  and  the 


METHODS    OF    OBTAINING    THE    GASTRIC    JUICE.  295 

stomach  excite,  in  a  centripetal  direction,  the  medulla  oblongata  which 
contains  the  center  for  this  reflex.  The  centrifugal  path  to  the  mucous 
membrane  traverses  the  pneumogastric  nerves,  after  the  division  of 
which  the  reflex  is  abolished.  The  mucous  membrane  subsequently 
furnishes  a  moderate  amount  of  a  feebly  active,  paralytic  secretion. 
During  sleep  in  the  stage  of  digestion,  the  amount  of  acid  increases. 

Heidenhain  found  in  experiments  upon  dogs— in  which,  in  the  same  way  as 
the  pylorus,  he  isolated  the  fundus  for  the  formation  of  a  blind  sac— that  mechan- 
ical irritation  induced  only  local  secretion.  If,  however,  absorption  of  digested 
substances  took  place  at  the  point  of  irritation,  the  secretion  spread  out  over  a 
larger  surface. 

Small  quantities  of  alcohol,  introduced  into  the  stomach,  increase  the  secretion 
Of  the  gastric  juice,  while  large  amounts  abolish  it  and  enfeeble  the  movements 
ot  the  stomach.  Fat  inhibits  the  secretion  of  the  gastric  juice.  Artificial  digestion 
is  somewhat  disturbed  by  alcohol  up  to  2  per  cent.,  and  in  greater  degree  by  10 
per  cent,  alcohol;  20  per  cent,  alcohol  retards,  while  still  larger  amounts  abolish 
it.  Beer  and  wine  retard  digestion,  and  undiluted  they  prevent  artificial  diges- 
tion. The  administration  of  large  amounts  of  sodium  chlorid  diminishes  the  secre- 
tion of  hydrochloric  acid,  while  the  ingestion  of  much  sugar  only  delays  it  After 
two  days  of  fasting  the  secretion  of  hydrochloric  acid  ceases  (in  the  dog).  Gastric 
ulcers  cause  reflex  increase  in  the  production  of  hydrochloric  acid;  jaundice, 
nervous  gastric  affections  and  anemias,  a  reflex  diminution. 

The  gastric  juice,  which  passes  into  the  duodenum  after  digestion 
is  completed,  is  neutralized  by  the  alkalis  of  the  intestinal  and  of  the 
pancreatic  juices.  The  pepsin  is  absorbed  as  such,  and  can  be  found  in 
small  amounts  in  the  urine  and  in  the  muscle-juice. 

If  the  gastric  juice  is  removed  completely  through  a  gastric  fistula, 
the  alkalies  in  the  intestines  become  so  abundant  that  the  urine  is  ren- 
dered alkaline. 

The  acid  gastric  juice  in  the  new-born  is  quite  intensely  active.  It  most 
readily  digests  casein,  and  next  in  order  fibrin  and  other  proteids.  In  consequence 
of  excessive  acidity  of  the  gastric  juice,  large  masses  of  casein,  difficult  of  digestion, 
form  in  the  stomach  of  infants,  and  are  especially  tough  after  the  ingestion  of 
cow's  milk. 

The  following  drugs  are  excreted  by  the  gastric  juice  after  introduction  into 
the  body-juices:  Morphin,  veratrin,  caffein,  quinin,  antipyrin,  chloroform,  chloral 
hydrate,  methyl-alcohol,  ethyl-alcohol  and  acetone. 

Comparative. — According  to  Klug,  the  parietal  cells  of  grain-eating  birds  pre- 
pare also  pepsin,  in  addition  to  hydrochloric  acid.  The  gastric  glands  of  the  frog, 
which  possess  only  parietal  cells,  likewise  secrete  pepsin;  the  pyloric  glands  of  the 
dog,  which  contain  only  chief  cells,  nevertheless  secrete  acid.  Accordingly  both 
kinds  of  cells  secrete  hydrochloric  acid. 

METHODS  OF  OBTAINING  THE  GASTRIC  JUICE. 

THE  PREPARATION  OF  ARTIFICIAL  DIGESTIVE  FLUIDS;    DEMONSTRA- 
TION  AND   PROPERTIES   OF   PEPSIN. 

To  obtain  the  gastric  juice  Spallanzani  had  fasting  dogs  swallow  bits  of  sponge 
enclosed  in  perforated  leaden  capsules,  and  withdrew  them  after  they  had  become 
saturated  with  the  gastric  juice.  In  order  to  prevent  admixture  with  the  secre- 
tions of  the  mouth,  the  sponge  is  best  introduced  through  an  opening  made  in 
the  esophagus  ligated  above. 

Beaumont  (1825-1833),  an  American  physician,  was  the  first  to  obtain  gastric 
juice  from  a  human  being,  in  the  case  of  the  Canadian  hunter,  Alexis  St.  Martin, 
whose  stomach  had  been  opened  by  a  bullet-wound,  with  the  formation  of  a  per- 
manent gastric  fistula.  Various  substances  were  introduced  directly  into  the 
stomach  through  the  opening,  and  examined  from  time  to  time  as  to  their  digestion. 

Guided  by  this,  Bassow,  in  1842,  was  the  first  to  establish  an  artificial  gastric 
fistula  in  a  dog.  The  wall  of  the  stomach  is  opened  below  the  xiphoid  process, 
and  the  margins  of  the  gastric  opening  are  united  by  suture  to  the  margins  of 


296  METHODS    OF    OBTAINING    THE    GASTRIC    JUICE. 

the  wound  in  the  abdominal  walls.  A  short  tube  with  a  terminal  plate  is  placed 
in  the  fistula  in  such  a  manner  that  the  plate  lies  in  contact  with  the  margin  of 
the  mucous  membrane.  The  tube  possesses  a  screw-thread,  upon  which  an  appro- 
priate cannula  can  be  so  screwed  that  the  terminal  plate  lies  upon  the  abdominal 
wall  outside  of  the  margins  of  the  wound.  The  parts  are  joined  in  the  following 
manner  H  -H.  As  a  rule  the  opening  of  the  cannula  is  corked.  If  in  such 
dogs  the  excretory  ducts  of  the  salivary  glands  are  additionally  ligated,  unmixed 
gastric  juice  is  secured. 

According  to  C.  A.  Ewald  and  Leube,  dilute  gastric  juice  can  be  obtained  from 
human  beings  by  introducing  water  into  the  empty  stomach  through  a  tube  that 
acts  like  a  siphon,  and  withdrawing  the  fluid  by  siphonage  after  a  short  time. 

An  important  advance  was  made  by  Eberle,  in  1834,  who  taught  that  artificial 
gastric  juice  could  be  prepared  by  extracting  pepsin  from  the  gastric  mucous 
membrane  by  means  of  dilute  hydrochloric  acid.  Dilute  hydrochloric  acid  serves 
for  the  extraction  of  the  triturated  gastric  mucous  membrane — 0.088  per  cent,  for 
the  digestion  of  fibrin,  0.16  per  cent,  for  the  digestion  of  coagulated  albumin — 
being  added  anew,  in  quantities  of  a  half  liter  every  six  or  eight  hours.  The  later 
extracts  are  even  more  active  than  the  first.  The  fluid  collected  is  filtered  and 
in  it  are  placed,  at  the  temperature  of  the  body,  the  substances  to  be  digested. 
It  is,  however,  necessary  to  add  more  hydrochloric  acid  from  time  to  time.  That 
degree  of  acidity  affects  digestion  most  ^  favorably  that  most  causes  the  proteids 
to  swell.  According  to  Klug,  gastric  juice  containing  0.6  per  cent,  of  hydro- 
chloric acid  and  o.i  per  cent,  of  pepsin  is  most  effective.  Pepsin  from  dogs  is 
especially  active.  Digestion  pursues  a  favorable  course  between  37°  and  40°  C.; 
while  it  ceases  in  the  cold,  as  well  as  at  higher  temperatures. 

The  hydrochloric  acid  employed  may  be  replaced,  to  a  certain  extent,  by 
other  halogen-acids,  whose  activity  is  inversely  proportional  to  their  molecular 
weight ;  further  by  from  six  to  ten  times  as  much  lactic  acid;  by  nitric  acid;  in 
a  much  less  effective  manner,  finally,  by  oxalic,  sulphuric,  phosphoric,  acetic, 
formic,  succinic,  tartaric,  and  citric  acids.  In  general,  the  acids  with  greater 
acidity  act  more  powerfully,  with  the  exception  of  sulphuric  acid.  The  action  of 
the  different  acids  varies,  however,  accordingly  as  fibrin,  casein,  solid  or  liquid 
albumin  is  employed. 

v.  Wittich  showed  that  pure  pepsin  can  be  extracted  from  the  gastric  mucous 
membrane  by  means  of  glycerin  also.  After  cleaning  the  mucous  membrane,  it  is 
left  in  alcohol  for  twenty-four  hours,  then  dried,  pulverized  and  sifted,  and  then 
extracted  for  a  week  in  glycerin.  On  addition  of  alcohol  to  the  filtered  extract 
pepsin  is  precipitated,  and  this,  dissolved  in  dilute  hydrochloric  acid,  yields  active 
gastric  juice. 

The  preparation  of  perfectly  pure  pepsin  has  been  effected  by  W.  Kiihne  by 
exposing  comminuted  pigs'  stomachs  to  autodigestion  with  dilute  hydrochloric 
acid  at  the  temperature  of  the  body.  The  mass,  which  is  for  the  most  part  liquefied, 
is  saturated  with  ammonium  sulphate,  by  which  pepsin  and  albumoses  still  present 
are  precipitated.  The  residue  collected  on  the  filter  is  again — and  if  necessary 
repeatedly — digested  in  the  incubator,  after  addition  of  dilute  hydrochloric  acid. 
If,  finally,  all  of  the  albumin  has  been  converted  into  peptone,  the  pepsin  alone  is 
precipitated  by  repeated  saturation  with  ammonium  sulphate,  and  is  collected  on 
the  filter.  It  is  dissolved  in  water,  its  salts  are  removed  by  dialysis  and  it  is  finally 
precipitated  in  a  pure  state  by  alcohol.  Briicke  had  previously  prepared  pure 
pepsin  by  causing  a  voluminous  precipitate  in  the  digestive  mixture  including  the 
pepsin,  and  separating  the  latter.  Pekelharing  found  that  a  strongly  active  arti- 
ficial gastric  juice,  on  dialysis  with  water,  caused  the  separation  of  a  precipitate 
of  pepsin. 

In  all  the  processes  of  extraction,  the  yield  of  pepsin  is  greatest  when  the 
mucous  membrane,  protected  from  putrefaction,  is  exposed  to  the  air  for  some 
time,  as  subsequently  propepsin  and  pepsin  are  formed  in  the  gland-cells. 

Pure  pepsin  is  a  colloid  substance.  It  does  not  yield  the  reactions 
of  albumin  to  the  following  tests:  It  does  not  respond  to  the  xantho- 
proteic  test,  is  not  precipitated  by  acetic  acid  and  potassium  ferrocyanid, 
by  tannic  acid,  mercuric  chlorid,  argentic  nitrate  or  iodin.  In  other 
respects  it  is  to  be  included  among  the  albuminoid  substances.  Pepsin, 
when  heated  to  a  temperature  of  from  55°  to  60°  C.  or  above,  in  acid 
solution,  is  rendered  inactive. 


THE    PROCESS    AND    THE    PRODUCTS    OF    GASTRIC    DIGESTION.          297 

THE    PROCESS    AND    THE    PRODUCTS    OF  GASTRIC    DIGESTION. 

The  mixture  of  finely  divided  food  and  gastric  juice  is  designated 
chyme.  Upon  this  the  gastric  juice  exerts  its  action. 

ACTION  UPON  PROTEIDS. 

The  pepsin  and  the  free  hydrochloric  acid  are  capable  of  transforming 
the  proteids,  at  the  temperature  of  the  body,  into  a  readily  soluble 
modification  that  has  been  designated  peptone.  In  this  process  the 
proteids  are  changed  first  into  bodies  possessing  the  character  of  synto- 
nins,  and  in  this  condition  the  solid  proteids  are  swollen.  Syntonin  is 
an  acid-albuminate.  By  neutralization,  with  cautious  addition  of  an 
alkali,  the  albumin  is  precipitated.  Then,  by  combination  with  water 
and  division  into  numerous  small  molecules,  a  product  results,  which 
is,  to  a  certain  extent,  an  intermediary  body  between  albumin  and 
peptone — the  albumose  of  W.  Kuhne  and  Chittenden  (propeptone  of 
Schmidt-Mulheim).  This  is  soluble  in  water,  readily  soluble  in  dilute 
acids,  alkalies  and  salts.  These  solutions  are  not  precipitated  by  boiling, 
but  by  acetic  acid  and  potassium  ferrocyanid,  as  well  as  by  acetic  acid 
and  saturation  with  sodium  chlorid  or  magnesium  sulphate.  Albumose 
is  precipitated  by  nitric  acid,  but  it  is  redissolved,  with  the  production 
of  an  intense  yellow  color  when  heated,  and  it  is  again  precipitated  on 
cooling.  Some  albumoses  possess  diffusibility. 

With  the  continued  action  of  the  gastric  juice,  the  albumose  passes 
over  into  soluble  and  readily  diffusible  peptone.  The  unchanged  pro- 
teids behave  toward  the  peptones  as  anhydrids  with  a  large  albumin- 
molecule.  The  production  of  peptone  and  its  solution  result,  therefore, 
from  decomposition  with  the  taking  up  of  water,  brought  about  by  the 
hydrolytic  ferment,  pepsin.  This  action  takes  place  best  at  the  tem- 
perature of  the  body. 

According  to  W.  Kuhne,  the  proteid  molecule  contains  two  different  substances, 
namely  hemi-albumin  and  anti-albumin.  By  the  action  on  these  of  hydrochloric 
acid  syntonin  is  produced.  This  is  next  broken  up  into  the  two  primary  albu- 
moses: protalbumose,  soluble  in  water,  and  hetero-albumose,  soluble  in  salt- 
solutions.  Both  are  then  transformed  into  deutero-albumoses,  which,  in  contra- 
distinction to  the  primary  albumoses,  are  not  precipitated  in  neutral  solution  by 
saturation  with  sodium  chlorid.  Deutero-albumose  in  contradistinction  to  pro- 
talbumose is  not  precipitated  by  copper  sulphate.  ^  The  deutero-albumoses  are 
then  decomposed  into  peptones :  hemipeptone  and  antipeptone. 

The  pepsin  enters  into  intimate  relations  with  the  proteid  molecule. 
The  greater  the  amount  of  pepsin  present,  the  more  rapidly,  to  a  certain 
degree,  does  digestion  take  place.  The  pepsin  itself  undergoes  almost  no 
change,  and  if  care  is  taken  to  keep  the  amount  of  hydrochloric  acid 
always  the  same,  it  is  able  to  digest  new  amounts  of  albumin  (one 
part 'to  about  500,000  parts).  Nevertheless  some  pepsin  is  consumed 
in  the  process  of  digestion. 

The  proteids  are  introduced  into  the  stomach  either  in  a  liquid  or 
in  a  solid  form.  Of  the  liquid  proteids  only  casein  is  at  once  coagulated 
in  solid  form  and  precipitated  and  then  redissolved.  The  other  liquid 
proteids  remain  liquid,  are  converted  into  the  condition  of  syntonms, 
and  then  immediately  into  albumoses  and  finally  into  peptones,  that  is, 
actually  digested. 

Uncoagulated  and  coagulated  proteids,  globulins,  fibrin,  som 


298          THE    PROCESS    AND    THE    PRODUCTS    OF    GASTRIC    DIGESTION. 

of  vitellin,  chondrigen,  collagen,  and  elastin,  though  with  difficulty,  are 
in  the  same  way  converted  into  albumoses  and  peptones;  while  neuro- 
keratin,  keratin,  and  nuclein  remain  undigested. 

During  the  digestion  of  albumin,  absorption  of  heat  takes  place, 
demonstrable  by  the  thermometer.  Accordingly  the  temperature  of  the 
chyme  in  the  stomach  falls,  in  the  course  of  two  or  three  hours,  from 
0.2°  to  0.6°  C. 

The  coagulated  proteids  may  be  designated  the  anhydrids  of  the 
liquid  proteids  and  the  latter  in  turn  the  anhydrids  of  the  peptones. 
Thus  the  peptones  represent  the  highest  possible  stage  of  hydration  of 
the  proteid  bodies. 

Peptones  may  also  be  obtained  from  proteids  with  the  aid  of  such  agents  as 
usually  cause  hydration,  particularly  by  treatment  with  superheated  steam  vapor, 
through  the  action  of  strong  acids,  caustic  alkalies,  ferments  of  putrefaction  and 
some  other  ferments,  as  well  as  by  ozone. 

The  proteid  anhydrids  may  be  reconverted  from  this  stage  of  hydra- 
tion by  the  abstraction  of  water. 

By  heating  with  acetic-acid  anhydrid  at  a  temperature  of  80°  C.  peptone  is 
transformed  into  syntonin.  Also  by  heating  to  a  temperature  of  170°  C.,  through 
the  action  of  the  galvanic  current  in  the  presence  of  sodium  chlorid,  and  through 
the  action  of  alcohol  together  with  salts,  peptone  is  retransformed  into  albumin. 
Albumose  was  thus  first  seen  to  result  from  fibrin-peptone. 

Properties  of  Peptones. — (i)  They  are  readily  and  completely  soluble 
in  water.  ( 2 )  They  diffuse  readily  through  membranes ,  more  readily  than 
propeptones.  (3)  They  also  filter  much  more  readily  than  albumin 
through  the  pores  of  animal  membranes.  (4)  From  a  mixture  of  pep- 
tone, propeptone,  albumin  and  pepsin,  first  neutralized  and  then  feebly 
acidulated  with  acetic  acid,  neutral  ammonium  sulphate  added  in  excess 
precipitates  everything  except  peptone.  (5)  Peptones  are  not  precipi- 
tated by  boiling,  or  by  nitric  acid,  or  acetic  acid  and  potassium  ferro- 
cyanid,  or  by  acetic  acid  or  by  saturation  with  sodium  chlorid.  (6)  They 
are  precipitated  by  phosphotungstic,  by  phosphomolybdic  acid,  and  by 
biliary  acids;  precipitated  by  tannic  acid,  they  are  redissolved  in  an 
excess.  Other  precipitating  agents  are  mercuric  chlorid  and  nitrate, 
mercuric  iodid ,  potassium  iodid .  ( 7 )  They  yield  all  of  the  color-reactions 
of  albumin.  (8)  With  sodium  hydrate  and  copper  sulphate  in  the  cold, 
they  give  a  purple-red  color  (biuret-reaction). 

The  biuret-reaction  is  yielded  also  by  propeptone,  as  well  as  by  a  proteid  body, 
the  so-called  alkophyr,  formed  coincidently  in  the  process  of  artificial  digestion  and 
soluble  in  strong  alcohol.  Gelatin-peptone  and  gelatin  are  precipitable  by  tri- 
chloracetic  acid,  while  albumin-peptone  is  redissolved  in  an  excess  of  this  acid. 
This  is  a  useful  means  of  differentiating  these  peptones.  The  peptones  of  the 
various  proteid  bodies  are  distinguished  by  the  amount  of  sulphur  they  contain, 
with  some  of  which  this  substance  is  but* loosely  combined,  while  with  others 
it  is  firmly  united.  All  have  a  disagreeable  and  bitter  taste. 

In  order  to  demonstrate  the  rapidity  with  which  fibrin  is  digested  by  the 
gastric  juice,  Grunhagen  places  in  a  funnel  the  fibrin  that  has  been  saturated  with 
0.2  per  cent,  hydrochloric  acid,  moistens  it  with  digestive  fluid  and  notes  the 
rapidity  with  which  the  fibrin  gradually  melts  away,  drop  by  drop,  and  finally  is 
entirely  dissolved.  Grutzner  stains  the  fibrin  with  carmine,  saturates  it  with  o.i 
per  cent,  hydrochloric  acid,  and  places  it  in  the  digestive  fluid.  The  more  rapidly 
the  latter  becomes  stained  uniformly  red,  in  consequence  of  digestion  of  the  fibrin, 
the  more  energetic,  naturally,  is  the  digestive  action. 

Quantitative  Estimation  of  the  Activity  of  Pepsin. — Of  a  solution  of  egg-albumin 
(3  grams  in  160  cu.  cm.  of  0.4  per  cent,  hydrochloric  acid)  two  specimens  of  10 


THE    PROCESS    AND    THE    PRODUCTS    OF    GASTRIC    DIGESTION.          299 

cu.  cm.  are  taken,  5  cu.  cm.  of  gastric  juice  being  added  to  the  one  and  5  cu.  cm. 
of  water  to  the  other.  The  mixtures  are  poured  into  Esbach's  tubes  up  to  the 
mark  U.  Both  tubes  are  then  kept  for  one  hour  at  a  temperature  of  37°  C  after 
which  Esbach's  reagent  is  added  up  to  the  level  of  the  mark  R,  and  the  amount 
of  the  precipitate  in  both  tubes  is  noted  after  the  lapse  of  twenty-four  hours.  Pep- 
tone is  not  precipitated.  Chronic  gastric  catarrh  and  carcinoma  yield  low  digestive 
values,  while  hypersecretion  of  the  gastric  juice  may  increase  the  digestive  in- 
tensity. 

Preparation  of  Pure  Peptone. — The  diluted  digestive  solution,  freed  from  albu- 
minates  by  boiling,  and  with  an  almost  neutral  reaction,  is  first  saturated,  while 
boiling,  with  ammonium  sulphate,  filtered  when  cool,  again  heated,  after  beginning 
to  boil  made  strongly  alkaline  by  adding  ammonia  and  ammonium  carbonate* 
again  saturated  in  the  heat  with  ammonium  sulphate, -filtered  after  cooling,  again 
heated  until  the  odor  of  ammonia  has  disappeared,  again  saturated  with  the  salt, 
hot,  and  acidulated  with  acetic  acid.  The  fluid,  filtered  in  the  cold,  contains  pure 
peptone. 

The  peptones  are  undoubtedly  those  modifications  of  proteids  that 
are  intended,  after  absorption  from  the  digestive  tract,  and  later  through 
the  blood,  to  be  employed  to  replace  the  proteids  consumed  by  the  pro- 
cess of  metabolism  in  the  living  organism. 

If  much  albumin  has  already  been  digested  by  the  gastric  juice,  the  pepsin  is 
precipitated  and  becomes  inactive  if  some  hydrochloric  acid  is  not  again  added 
from  time  to  time.  Admixture  with  bile  in  the  test-tube  impairs  the  activity  of 
pepsin;  nevertheless  the  entrance  of  bile  into  the  stomach  causes  no  permanent 
derangement,  as  renewed  amounts  of  pepsin  are  at  once  secreted  by  the  gastric 
mucous  membrane.  The  stomach  digests  less  well  food  that  has  not  been  thor- 
oughly masticated  or  properly  insalivated.  The  presence  of  blood  or  of  serum 
prevents  the  action  of  pepsin,  as  well  as  of  trypsin  and  of  the  lab-ferment.  Heated 
to  a  temperature  of  65°  C.  the  pepsin  in  the  gastric  juice  becomes  inactive,  pure 
pepsin  even  at  a  temperature  of  55°  C.  Concentrated  acids,  alum  and  tannic  acid 
abolish  the  process  of  peptic  digestion.  Alkalinity  of  the  gastric  juice,  as,  for 
instance,  from  the  presence  of  large  amounts  of  saliva,  also  concentrated  solution 
of  alkaline  salts,  such  as  sodium  chlorid,  magnesium  sulphate  and  sodium  sulphate, 
have  the  same  effect,  as  do  also  sulphurous  and  arsenous  acids,  and  potassium 
iodid;  while  small  amounts  of  sodium  chlorid  increase  the  secretion  and  favorably 
influence  the  action  of  the  pepsin.  The  salts  of  the  heavy  metals,  which  form 
precipitates  with  pepsin,  peptones  and  mucin,  disturb  gastric  digestion.  According 
to  Langley  and  Eakins,  alkalies  rapidly  destroy  pepsin,  and  propepsin  less  rapidly. 
Acids  (as  lactic,  acetic  and  hydrochloric)  precipitate  the  gastric  mucus  and  stimu- 
late the  secretion  of  pepsin,  while  the  salts  of  the  alkalies  have  exactly  the  opposite 
effect.  Alcohol  precipitates  the  pepsin,  although  this  is  redissolved  on  addition  of 
water,  so  that  digestion  can  then  proceed  again  undisturbed.  Agents  that  hinder 
thorough  saturation  of  proteids,  as,  for  instance,  binding  them  tightly,  or  concen- 
trated solutions  of  astringent  salts,  retard  digestion. 

The  ingestion  of  half  a  liter  of  cool  water  does  not  disturb  gastric  digestion  in 
the  healthy  individual,  though  it  does  when  the  function  of  the  stomach  is  de- 
ranged, while  the  ingestion  of  a  larger  amount  impairs  the  digestive  activity  of  the 
stomach.  The  same  effect  is  brought  about  by  strong  muscular  action.  In  the 
horse  moderate  movement  (trotting)  assists  the  digestion  of  starches  in  the  first 
hour.  Warm  compresses  over  the  epigastric  region  favor  gastric  digestion 

According  to  Penzoldt,  the  digestibility  of  various  proteid  articles  of  food  by 
the  stomach  is  given  in  the  following  order.  Easily  digestible:  boiled  brain  and 
thymus,  pike,  sea-fish,  carp,  oysters,  chicken,  boiled  pigeon,  raw  scraped  beef  or 
veal,  wheat-bread,  cauliflower,  soft-boiled  egg  (casein,  alkali-albuminate) .  Digest 
ible  with  moderate  ease:  boiled  beef  and  veal,  duck,  goose,  pork,  salt  potatoes,  rye- 
bread,  rice,  tapioca,  asparagus,  rape-cole,  carrots,  raw  egg,  pur6e  of  legumes. 
Digestible  with  difficulty:  salmon,  salt  fish,  highly  salted  caviare,  string  beans,  hard- 
boiled  egg.  The  digestibility  of  the  different  meats,  from  the  more  to  the  less 
readily  digestible,  is  as  follows:  veal,  lamb,  mutton,  pork,  beef,  rabbit,  horse. 


3OO  ACTION    UPON    OTHER    FOODS. 

ACTION  UPON  OTHER  FOODS. 

Milk  coagulates  in  the  stomach,  with  the  liberation  of  heat,  as  a 
result  of  precipitation  of  the  casein,  which  encloses  the  fat  globules. 
The  free  acid  of  the  stomach  is  alone  sufficient  for  precipitation,  the 
alkali  being  withdrawn  from  the  casein,  which  it  holds  in  solution. 

Hammarsten,  in  1872,  discovered  a  special  rennet-ferment  in  the 
gastric  juice,  which  coagulates  the  casein  in  either  neutral  or  alkaline 
solutions.  On  this  fact  depends  the  preparation  of  cheese  by  means  of 
calf's  stomach  rennet. 

The  rennet  is  formed  in  the  chief  cells  of  the  gastric  glands  from  a  rennet-forming 
substance,  by  the  action  of  an  acid.  The  rennet-forming  substance  is  present 
in  the  mucous  membrane  in  much  larger  amount  than  rennet  itself.  One  part 
of  rennet-ferment  is  capable  of  precipitating  800,000  parts  of  casein.  The  addition 
of  calcium  chlorid  hastens,  while  water  retards,  coagulation.  An  excess  of  alkali 
impairs  the  activity  of  rennet.  The  rennet-ferment  is  best  assisted  by  hydro- 
chloric acid,  followed,  in  order,  by  lactic,  acetic,  sulphuric  and  phosphoric  acids. 

The  casein,  as  well  as  the  nucleo-albumin,  is  converted  in  the  process  of  diges- 
tion, mainly  into  peptone  rich  in  phosphorus;  a  residue  poor  in  phosphorus,  para- 
nuclein,  remaining  as  an  insoluble  product. 

The  rennet-ferment  is  destroyed  by  long-continued  artificial  digestion.  To 
obtain  rennet,  Hammarsten  agitates  artificial  gastric  juice  prepared  from  the  calf's 
stomach,  and  after  neutralization,  with  magnesium  carbonate.  The  filtrate  contains 
only  rennet,  which,  after  acidulation  with  acetic  acid,  is  precipitated  by  the  in- 
troduction of  liquid  stearic  acid,  to  which  it  adheres.  The  acid  is  dissolved  in 
ether,  which  can  then  be  readily  separated. 

Finally,  sugar  of  milk  is  converted  in  the  gastric  juice  into  lactic 
acid,  by  fermentative  activity — lactic-acid  ferment.  Further,  the  milk- 
sugar  in  the  stomach  and  intestines  is,  in  part,  transformed  into  grape- 
sugar. 

Cane-sugar  is  gradually  converted  into  grape-sugar,  in  which  process, 
according  to  Uffelmann  the  gastric  mucus,  according  to  Leube  the 
gastric  acid,  plays  the  most  important  part. 

ACTION  ON  THE  DIFFERENT  TISSUES  AND  THEIR  CONSTITUENT 

MATERIALS. 

( i)  The  gelatin-yielding  substance  of  the  various  supporting  structures — connec- 
tive tissue,  fibrous  cartilage  and  the  matrix  of  bone  as  well  as  glutin  itself,  is  pep- 
tonized  and  digested  in  the  gastric  juice.  (2)  The  structureless  membranes  (mem- 
branae  propriae)  of  the  glands,  sarcolemma,  the  nerve-sheath  of  Schwann,  the 
capsule  of  the  crystalline  lens,  the  elastic  layers  of  the  cornea,  the  membranes  of 
the  fat-cells,  are  likewise  digested,  but  scarcely  the  elastic,  fenestrated  membranes 
and  fibers.  (3)  Striated  muscular  tissue  forms  after  digestion  of  the  sarcolemma 
and  breaking  up  of  the  transversely  striated  contents  into  discs  and  fragments  of 
fibrils,  as  well  as  unstriated  muscular  tissue,  a  true  digested  peptone,  in  consequence 
of  hydration  and  the  decomposition  of  the  myosin.  Remains  of  meat,  however, 
always  pass  over  into  the  intestine.  (4)  The  proteid  elements  of  the  soft  cellular 
structures  of  the  glands,  stratified  epithelium,  endothelium  and  lymphoid  cells,  are 
converted  into  peptone,  while  the  nuclein  of  the  nuclei  cannot,  apparently,  be 
digested.  (5)  The  horny  portions  of  the  epidermis,  nails,  hairs,  as  well  as  the  chitin 
and  the  wax  of  lower  animals,  are  indigestible.  (6)  The  erythrocytes  are  digested, 
the  hemoglobin  decomposed  into  hematin  and  a  globulin -like  substance.  The 
latter  is  peptonized;  the  former  remains  unchanged,  and  in  part  appears  in  the 
feces,  and  in  part  is  absorbed  and  transformed  into  the  coloring-matter  of  the  bile. 

(7)  The  fibrin  is  easily  digested  into  propeptone  and  fibrin-peptone  by  the  taking  up 
of  water  and  the  breaking  up  of  the  molecule.     Mucin  is  digested  in  the  stomach. 

(8)  Of  vegetable  articles  of  food,  vegetable  fats  are   not  changed  by  the   gastric 
juice.     The  vegetable  cells  give  up  their  protoplasmic  contents  for  the  production 
of  peptone,  while  the  cellulose  of  the  cell-walls  is  undigestible  in  the  stomach  of 
human  beings. 


THE    GASES    OF    THE    STOMACH. 


301 


That  the  stomach  is  also  capable  of  digesting  parts  of  a  living  body  is  shown 
by  the  fact  that  the  thigh  of  a  living  frog  or  the  ear  of  a  rabbit,  introduced  into  a 
gastric  fistula  in  a  dog,  will  be  partly  digested.  The  edges  of  gastric  ulcers  and 
fistulas  in  human  beings  are  also  eroded  by  the  digestive  activity  of  the  gastric 
juice.  The  question  was  early  asked,  Why  does  the  stomach-wall  not  digest 
itself?  As,  after  death,  the  mucous  membrane  is,  in  fact,  often  rapidly  softened 
by  autodigestion  (gastric  softening),  the  opinion  is  justified  that,  so  long  as  the 
circulation  is  maintained,  the  tissues  are  constantly  protected  against  the  action 
of  the  acid  by  the  alkalinity  of  the  blood.  If  the  reaction  of  the  gastric  juice  be 
alkaline,  digestion  cannot  be  inaugurated.  Ligation  of  the  blood-vessels  of  the 
stomach  resulted,  according  to  Pavy's  investigations,  in  digestive  softening  of  the 
gastric  mucous  membrane.  In  human  beings  morbid  occlusion  of  the  vessels 
causes,  in  an  analogous  manner,  the  development  of  gastric  ulcers.  Also  the  thick, 
firmly  adherent  layer  of  mucus  may  help  to  protect  the  uppermost  layer  of  the 
mucous  membrane  against  autodigestion.  In  general,  however,  the  conditions, 
with  respect  to  all  peptonizing  ferments,  are  such  that  fully  living  protoplasm, 
therefore  also  that  of  the  epithelial  cells  of  the  stomach,  possesses  the  property 
of  being  able  to  resist  the  action  of  enzymes,  as  it  is  capable  of  decomposing  all, 
even  the  most  complicated,  molecules  of  inanimate  substances.  Amcebae,  bacteria, 
worms,  larvae  and  embryonal  vegetable  cells  are  not  affected  by  artificial  digestive 
juices,  not  even  by  trypsin. 

After  extirpation  of  the  stomach,  digestion  is  continued  by  the  pancreas,  the 
liver  and  the  intestines.  The  stomach  is  a  protective  apparatus  with  respect  to 
the  intestine,  as  it  removes  various  injurious  influences,  particularly  of  bacterial 
origin. 

THE  GASES  OF  THE  STOMACH. 

The  stomach  always  contains  gases,  derived  in  part  from  air  directly 
swallowed,  as,  for  example,  with  the  saliva,  and  in  part  from  gases  that 
pass  backward  from  the  duodenum. 

If  the  larynx  and  the  hyoid  bone  are  suddenly  drawn  forcibly  forward  (as  in 
vomiting),  a  considerable  amount  of  air  enters  the  space  behind  the  larynx  and 
when  the  latter  returns  to  its  position  of  rest,  is  carried  down  by  the  peristalsis  of 
the  esophagus.  One  can  feel  distinctly  the  downward  passage  of  such  a  quantity 
of  air.  At  times,  even  without  any  movement  of  deglutition,  a  number  of  small 
air-bubbles  enter  the  stomach. 

These  masses  of  air  constantly  undergo  change,  owing  to  the  absorp- 
tion of  oxygen  into,  and  the  elimination  of  carbon  dioxid  from,  the 
blood.  The  rather  abundant  production  of  carbon  dioxid  in  the 
stomach  depends,  however,  on  chemical  processes  resulting  from  the 
admixture  of  the  pyloric  secretion,  containing  sodium  carbonate,  with 
the  secretion  of  the  fundus,  containing  acid.  According  to  Planer,  the 
amount  of  oxygen  is  extremely  small,  while  that  of  carbon  dioxid  is 
considerable. 

A  portion  of  the  carbon  dioxid  in  the  saliva  is  set  free  by  the  acid  of 
the  gastric  juice.  The  quantity  of  nitrogen  is  indifferent. 

GASES  OF  THE  STOMACH.      VOLUMES  IN  PER  CENT. 

(According  to  Planer.) 


HUMAN  CADAVER  AFTER  VEGETABLE  DIET. 

Doc. 

I. 

n. 

I.  After  a  Meat  diet. 

II.  After  a  Diet  of  Legumes. 

CO3  . 

H  
N  
O  

20.79 
6.71 

72.50 

33-83 
27.58 
38.22 
o-37 

25.2 

32-9 

68.7 
6.1 

66.3 
0.8 

302 


STRUCTURE  OF  THE  PANCREAS. 


Abnormal  development  of  gases,  in  cases  of  gastric  catarrh,  occurs  only  when 
the  reaction  of  the  gastric  contents  is  neutral.  Thus,  in  the  presence  of  butyric- 
acid  fermentation,  hydrogen  and  carbon  dioxid  are  produced,  while  acetic-acid  and 
lactic-acid  fermentation  generate  no  gases.  Marsh-gas  (CH4)  also  is  found;  though 
this  can  reach  the  stomach  only  from  the  intestine,  as  it  can  be  produced  only  in 
the  absence  of  oxygen.  Traces  of  hydrogen  sulphid  generated  by  the  bacterium 
coli  commune  are  formed,  at  times  in  connection  with  benign  dilatation  of  the 
stomach  and  motor  insufficiency.  Yeasts  and  various  bacteria  are  also  found  in 
the  stomach. 

STRUCTURE  OF  THE  PANCREAS. 

The  pancreas  is  a  compound  tubular  gland  with  terminal  alveoli 
which  constitute  the  chief  portions  of  the  gland.  On  the  internal  sur- 
face of  the  membrana  propria,  formed  of  fibrillar  tissue,  lie  the  some- 
what cylindrical-conical  secreting  cells,  which  consist  of  two  layers: 
(i)  the  smaller,  parietal  layer,  which  is  transparent,  lamellated,  stri- 
ated, and  can  be  deeply  stained  by  carmine,  and  (2)  the  internal  layer 
(Bernard's  granular  layer),  which  is  deeply  granular,  and  stains  but 
slightly.  Between  the  two  layers  lies  the  nucleus.  During  the  process 
of  secretion  a  visible  transformation  takes  place  continually  in  the  cell- 
substance  ;  the  granules  in  the  granular  layer  undergo  solution  and  form 
constituents  of  the  secretion,  while  in  the  external  layer  the  homo- 
geneous substance  is  renewed,  and  is  later  again  transformed  into  granu- 
lar matter.  This,  in  turn,  again  moves  inward  toward  the  lumen  of  the 
alveolus. 

In  detail  there  takes  place  in  the  first  stage  of  digestion  (from  the  sixth  to 
the  tenth  hour)  a  consumption  of  the  granular  inner  zone  and  a  growth  of  the 


FIG.  115. — Changes  in  the  Cells  of  the  Pancreas  in  the  Different  Stages  ol  Activity:   i,  in  the  state  of  hunger; 
2,  in  the  first  stage  of  digestion;  3,  in  the  second  stage;  4,  with  paralytic  secretion. 


striated  outer  zone  (Fig.  115,  2).  In  the  second  stage  (from  the  tenth  to  the 
twentieth  hour)  the  inner  zone  of  the  swollen  gland  has  increased  greatly  in  size, 
while  the  outer  zone  is  much  diminished  (Fig.  115,  3).  In  the  state  of  hunger  the 
latter  again  increases  in  size  (Fig.  115,  i).  In  the  pancreas,  yielding  a  para- 
lytic secretion,  and  reduced  in  size,  the  inner  zone  of  shrunken  cells  is  almost 
entirely  lost. 

In  consequence  of  increased  secretion,  some  of  the  secreting  cells  undergo  a 
change,  so  that  the  acini  form  irregular  collections  containing  many  granules,  and 
have  lost  all  resemblance  to  glandular  acini.  Entire  cells  are  also  destroyed  during 
the  activity  of  the  gland  and  new  ones  are  again  formed. 

The  finest  excretory  ducts  of  the  acini  begin  as  intercellular  secretory  spaces. 
With  the  alveolus  there  is  connected  an  intercalary  portion,  constituted  of  flat 
cells,  and  which  develops  in  the  center  of  every  acinus.  Then  a  sort  of  salivary  duct 
follows,  without  striated  epithelium,  as  in  the  salivary  glands.  From  the  micro- 
center  of  the  cells  of  the  excretory-duct  system  a  ciliated  flagellum,  the  "outer 
thread,"  projects  free  into  the  lumen  of  the  canal. 

The  pancreatic  duct,  which  possesses  an  axial  course  and  as  a  rule  empties 
into  the  dtiodenum  in  common  with  the  bile-duct,  while  a  smaller  branch  of  the 
duct  makes  its  entrance  at  a  special  papilla  at  a  higher  level,  consists  of  an  inner, 
denser,  and  an  outer,  looser,  wall  of  connective  and  elastic  tissue,  together  with 


THE    PANCREATIC    JUICE, 


303 


unstnatcd  muscular  fibers  mainly  pursuing  a  circular  course,  and  lined  internally 
by  a  single  layer  of  cylindrical  epithelium.  Small  mucous  glands  lie  in  the  main 
duct  and  in  its  larger  branches.  Medullated  and  non-medullated  nerves  which 
in  their  course  are  connected  with  ganglia,  pass  to  the  glandular  acini'  but  their 
terminations  are  unknown.  Blood-vessels  surround  the  acini,  in  part  of  large 
size  and  in  abundance  in  part  isolated.  The  fresh  pancreas  contains  water  , 
albummates  ferments,  fats  and  salts.  The  resting  gland  contains  much  leucin 
isoleucm  and  tyrosm;  further,  butalanin,  often  xanthin  and  guanhv  lactic  acid' 
formic  acid,  fatty  acids;  most  of  these  from  autodecomposition. 

THE  PANCREATIC  JUICE. 

To  obtain  the  pancreatic  juice  Regner  de  Graaf,  in  1664,  tied  in  the  excretory 
duct  of  a  dog  a  cannula  provided  with  an  empty  bag  at  its  extremity,  in  which 
the  juice  collected  Others  passed  the  tube  through  the  abdominal  walls  exter- 
nally and  thus  made  a  transitory  cannula-fistula,  which  closed  in  the  course  of  a 
tew  days,  with  inflammatory  expulsion  of  the  extremity  of  the  cannula  that  had 
been  tied  m  place.  In  order  to  establish  a  permanent  fistula,  either  a  duodenal 
istula  is  made,  like  a  gastric  fistula,  through  which  the  duct  of  Wirsung  is  cathe- 
tenzed  by  means  of  a  thin  tube ;  or  the  duct  is  opened  in  a  dog  and  drawn  toward 
the  abdominal  wound  and  an  attempt  is  made  to  unite  the  wound  in  the  duct 
with  the  abdominal  wound  so  as  to  form  a  fistula.  Heidenhain  eliminates  the 
portion  of  the  duodenum  in  which  the  duct  opens  from  the  continuity  of  the 
intestine,  incises  it,  and  fixes  it  outside  of  the  abdominal  wound. 

From  such  a  permanent  fistula  an  abundant,  feebly  active,  watery 
secretion,  rich  in  sodium  carbonate,  is  collected.  From  a  freshly  made 
opening  and  before  the  onset  of  inflammatory  processes,  a  scanty  viscid 
fluid  is  obtained  which  exerts  energetic  and  characteristic  physiological 
actions. 

Obviously,  the  scanty,  viscid  secretion  is  normal,  while  the  watery, 
abundant  secretion  is  abnormal  and  derived  from  the  dilated  blood-ves- 
sels, perhaps  in  consequence  of  paralysis  of  the  vasomotor  nerves,  and 
as  a  result  of  increased  transudation.  The  latter  would  thus  in  a  cer- 
tain sense  be  a  paralytic  secretion.  The  amount  must  vary  greatly, 
accordingly  as  viscid  or  watery  secretion  is  produced.  During  digestion 
a  large  dog  secreted  from  i  to  1.5  grams  of  viscid  secretion;  Bidder 
and  Schmidt  obtained  from  a  permanent  fistula  from  35  to  37  grams  of 
watery  secretion  in  twenty-four  hours,  for  each  kilogram  of  weight. 

While  the  resting,  inactive  gland  is  flabby,  yellowish  red  in  color,  the 
secreting  gland  is  turgescent  and  reddened  from  the  dilatation  of  its 
blood-vessels. 

Normal  pancreatic  juice  is  transparent,  colorless  and  odorless,  with  a 
salty  taste,  and  a  strongly  alkaline  reaction  from  the  presence  of  0.4  per 
cent,  sodium  carbonate,  and  therefore  effervescent  from  escape  of  car- 
bon dioxid  on  addition  of  acid.  It  contains  albumin  and  potassium 
albuminate  (9.2  per  cent.);  like  watery  egg-albumin,  it  is  viscid,  flows 
with  difficulty  and  coagulates  at  a  temperature  of  75°  C.  into  a  white 
mass.  On  standing  in  the  cold  a  gelatinous  coagulum  of  albumin  sepa- 
rates, in  which  concentrated  mineral  acids,  metallic  salts,  tannic  acid, 
chlorin-water  and  bromin-water  cause  a  precipitate;  the  precipitate 
produced  by  alcohol  can  be  redissolved  by  water.  The  total  solids  in 
the  pancreatic  juice  of  human  beings  equal  13.6  per  cent.  Among  the 
salts  are  sodium  chlorid,  7.3;  sodium  bicarbonate,  0.4;  sodium  phos- 
phate, 0.45;  sodium  sulphate,  i.i  in  1000,  together  with  some  lime  and 
traces  of  magnesia,  potassium  sulphate  and  ferric  oxid. 

The  more  rapid  and  the  more  profuse  the  flow  of  the  pancreatic 


304  THE    DIGESTIVE    ACTIVITY    OP    THE    PANCREATIC    JUICE. 

juice,  the  more  deficient  is  the  secretion  in  organic  constituents,  the 
inorganic  components  remaining  almost  the  same.  Nevertheless,  the 
total  amount  of  solid  constituents  secreted  is  greater  under  such  circum- 
stances than  when  the  secretion  is  scanty.  The  freshly  discharged  juice 
^contains  traces  of  leucin  and  soaps. 

In  pancreatic  juice  that  is  no  longer  fresh,  chlorin  induces  a  red  color,  as 
does  crude  nitric  acid  in  the  putrefying  juice,  by  the  production  of  indol.  Rarely 
the  juice  forms  concretions  in  the  pancreas,  principally  of  calcium  carbonate.  In 
cases  of  diabetes  dextrose  has  been  found  in  the  pancreatic  juice;  in  cases  of  jaun- 
dice, urea. 

THE   DIGESTIVE   ACTIVITY   OF  THE   PANCREATIC  JUICE. 

The  presence  of  four  hydrolytic  ferments,  or  enzymes  (an  amyloly- 
tic,  a  proteolytic,  a  lipolytic,  and  a  milk-curdling  ferment),  makes  the 
pancreatic  juice  a  most  important  digestive  fluid. 

The  amylolyiic  activity  is  due  to  the  ferment  amylopsin,  which  ap- 
pears to  be  identical  with  the  ptyalin  of  the  saliva,  though  it  acts  more 
energetically,  both  upon  raw  and  upon  boiled  starch  and  glycogen.  At 
the  temperature  of  the  body  almost  immediately,  but  more  slowly  at  a 
lower  temperature,  it  converts  the  substances  named  into  maltose, 
isomaltose  and  dextrin,  as  does  the  saliva.  Even  cellulose  itself  is  said 
to  be  digested  and  gum  to  be  transformed  into  sugar,  but  inulin  remains 
unchanged. 

The  amylopsin  is  precipitated  by  alcohol  and  it  remains  dissolved  in  glycerin 
without  material  enfeeblement.  All  agencies  that  disturb  the  diastatic  activity 
of  the  saliva  also  abolish  that  of  the  amylopsin,  although  admixture  of  acid  gastric 
juice,  as  its  hydrochloric  acid  is  in  combination,  or  of  bile,  is  without  injurious 
effect. 

The  ferment  is  isolated  by  the  same  method  as  that  by  which  salivary  ptyalin 
is  obtained,  but  in  this  process  the  peptic  ferment  is  at  the  same  time  precipitated 
with  it. 

In  addition  to  this  diastase,  the  pancreatic  juice  contains  a  second  diastatic 
ferment,  by  which  maltose  and  isomaltose  are  transformed  into  dextrose.  Saliva 
contains  hardly  a  trace,  and  blood-serum  more  of  this  ferment  than  of  diastase. 

The  addition  of  bile,  as  well  as  of  various  neutral  salts  (in  about  4  per  cent. 
solution),  increases  the  diastatic  activity,  and  in  the  following  order:  potassium 
nitrate,  sodium  chlorid,  ammonium  chlorid,  sodium  nitrate,  sodium  sulphate, 
potassium  chlorate,  ammonium  nitrate  and  ammonium  sulphate. 

The  proteolytic  activity  is  due  to  the  ferment  trypsin,  which  at  the 
temperature  of  the  body  transforms  the  albuminates,  in  the  presence 
of  an  alkaline  medium,  without  previous  swelling,  first  into  albu- 
moses  (hemi-albumose  and  anti-albumose) ,  also  designated  propeptones, 
and  finally  into  true  peptones,  also  designated  tryptones.  Previous 
swelling  of  the  proteids  by  means  of  hydrochloric  acid,  as  well  as  an  acid 
reaction  in  general,  have  a  tendency  to  prevent  this  transformation. 

The  albumoses  of  tryptic  digestion  have  the  character  of  the  deutero- 
albumoses.  Two  kinds  of  peptones  are  formed,  namely  hemi-peptone, 
which  later  breaks  up  into  the  amido-acids,  and  antipeptone,  which  does 
not  undergo  further  decomposition. 

Trypsin  peptonizes  all  proteids,  casein,  vitellin,  elastin,  mucin,  and 
nuclein,  while  neurokeratin,  keratin  and  amyloid  remain  insoluble. 
Glutin  and  the  gelatin-yielding  substance,  swollen  by  acids  are  changed 
into  gelatin-peptone,  and  the  latter  is  not  further  changed.  Oxyhemo- 
globin  decomposes  into  albumin  and  hemochromogen.  Pancreatic  ex- 


THE    DIGESTIVE    ACTIVITY    OF    THE    PANCREATIC    JUICE.  305 

tract  first  affects  milk-casein  in  such  a  manner  that  it  is  coagulated  by 
heat,  after  which  it  is  peptonized.  In  other  respects,  trypsin  has  an 
action  like  that  of  pepsin  upon  tissues  containing  albumin. 

Casein  is  almost  wholly  digested  by  trypsin.  The  tryptic  ferment,  which  is 
also  present  in  the  pancreas  of  new-born  infants,  is  carried  down  mechanically 
from  the  pancreatic  juice  diluted  with  water,  by  the  production  of  a  voluminous 
precipitate,  with  collodion.  The  precipitate  is  washed  and  dried,  and  then  the 
collodion  is  dissolved  out  in  a  mixture  of  ether  and  alcohol.  The  residue  is  soluble 
in  water,  and  represents  the  ferment.  Kuhne  further  separates  with  especial  care 
the  albumin  still  combined  with  the  ferment  in  the  aqueous  extract  of  the  gland, 
and  thus  secures  the  ferment  in  a  purer  form.  It  is  soluble  in  water,  insoluble  in 
alcohol  and  in  pure  glycerin. 

As  trypsin  is  destroyed  by  hydrochloric  acid,  it  is  not  advisable,  as  in  the 
presence  of  weakened  digestion,  to  administer  trypsin  by  the  mouth.  In  a  dried 
state  it  can  be  heated  to  a  temperature  of  140°  C.  without  injury;  in  a  moist 
state,  if  pure,  to  50°  C.;  and  mixed  with  salts  or  with  albumoses  and  peptones, 
to  60°  C. 

Method:  For  testing  trypsin,  gelatin  is  especially  useful,  being  liquefied  in  a 
test-tube  at  the  temperature  of  the  body:  7  grams  of  gelatin  boiled  with  93  grams 
of  an  aqueous  solution  of  thymol.  For  antiseptic  purposes  thymol  should  be 
added  also,  after  nitration,  to  the  fluid  to  be  tested  for  the  presence  of  the  ferment. 

Trypsin  results  through  the  taking  up  of  oxygen  within  the  pan- 
creas, from  a  mother- substance,  zymogen,  which  collects  in  the  interior 
of  the  secreting  cells  in  smallest  amount  between  the  sixth  and  the 
tenth  hour,  and  in  largest  amount,  on  the  other  hand,  sixteen  hours 
after  eating.  It  can  be  extracted  from  fresh  glands  by  glycerin  or  by 
water.  In  aqueous  solution  this  body  yields  the  ferment.  Within  the 
excised  pancreas  the  same  result  occurs  on  treatment  with  strong  alcohol. 

The  addition  of  bile,  sodium  chlorid.  sodium  glycocholate  and  carbonate,  as 
well  as  carbon  dioxid,  increases  the  activity  of  the  ferment,  while  magnesium  sul- 
phate and  sodium  sulphate  enfeeble  its  action. 

With  continued  action  of  the  trypsin  upon  the  hemipeptone  pro- 
duced, this  is  converted  in  part  into  the  amido-acids:  leucin  (C6H13NO2), 
tyrosin  (C9HUNO3),  aspartic  or  amidosuccinic  acid  (C4H7NO4)  in  the  diges- 
tion of  fibrin  and  glutin,  glutamic  acid  (C5H9NO4),  and  butalanin  or 
amidovalerianic  acid  (C5HnNO2).  Gelatin-peptone,  according  to  Nencki, 
on  further  decomposition  yields  glycin  and  ammonia.  The  amido-acids 
produced  may  be  partly  absorbed  as  such  and  may  be  consumed  in  the 
circulation. 

The  following  bases  also  occur:  xant bin-bases ,  lysin,  lysatinin,  argi- 
nin,  together  with  ammonia  and  a  body  that  becomes  reddened  by 
chlorin-water  or  bromin-water. 

If  the  action  be  continued  still  further,  matters  having  a  fecal  odor 
result,  and  with  especial  rapidity  when  the  reaction  is  alkaline,  also  indol 
(C8H7N),  skatol  (C9H9N),  and  phenol  (C6H6O),  volatile  fatty  acids  with 
the  development  of  hydrogen,  carbon  dioxid,  hydrogen  sulphid,  marsh- 
gas  and  nitrogen.  These  products  of  decomposition,  however,  result 
wholly  from  putrefaction  of  the  preparations.  This  can  be  prevented 
by  the  addition  of  salicylic  acid  or  thymol,  which  destroys  the  putre- 
factive organisms  that  are  always  present. 

Prolonged  boiling  of  the  albuminates  with  dilute  sulphuric  acid,  like  the  action 
of  trypsin,  produces  first  peptone,  then  leucin  and  tyrosin,  and  glycin  from  gelatin. 
Hypoxanthin  and  xanthin  result  in  this  way  on  boiling  fibnn,  the  former  als( 
from  long-continued  boiling  of  fibrin  with  wutivr. 

Leucin,  tyrosin,  glutamic  and  aspartic  acids,  together  with  xanthm-bodies, 


306  THE    DIGESTIVE    ACTIVITY    OF    THE    PANCREATIC    JUICE. 

result  also  in  the  germination  of  certain  plants,  by  reason  of  which  there  is  a 
resemblance  between  the  transformation  and  the  consumption  of  nutritive  mate- 
rials in  seeds  and  the  digestive  effects  of  ferments. 

The  lipolytic  activity  depends  on  the  presence  of  a  ferment  termed 
steapsin  or  pialyn,  which  exerts  its  action  more  especially  on  the  neutral 
fats.  This  action  is  two-fold:  (i)  they  are  transformed  into  a  fine, 
permanent  emulsion,  and  (2),  by  taking  up  water,  they  undergo  a  cleav- 
age into  glycerin  and  fatty  acids. 

C57H1100.  +  3H20  =   C3H803  +  3(C«H,A) 

Tristearin    +      Water     =     Glycerin     +      Stearic  Acid. 

The  addition  of  bile  increases  this  action  in  the  rabbit  very  consid- 
erably. This  cleavage  action  is  due  to  a  ferment,  especially  decomposed 
by  acids,  but  which  has  not  yet  been  isolated.  Lecithin  is  split  up  by 
this  ferment  into  glycerinphosphoric  acid,  neurin  and  fatty  acids. 

After  decomposition  is  complete,  the  fatty  acids  are  in  part  united 
with  the  alkalies  of  the  pancreatic  juice  and  the  intestinal  fluid  to  form 
fatty-acid  alkalies,  or  soaps;  and  in  part  emulsified  in  the  alkaline  in- 
testinal juice.  Both  the  emulsion  and  the  soap-solution  are  capable  of 
being  absorbed.  After  extirpation  of  the  pancreas  in  the  dog,  the 
digestion  and  absorption  of  fats  are  correspondingly  diminished. 

If  the  fat  to  be  emulsified  contains  free  fatty  acids,  as  is  the  case  with  all 
of  the  fats  of  the  food,  and  if  the  fluid  at  the  same  time  has  an  alkaline  reaction, 
emulsification  takes  place  with  extraordinary  rapidity.  A  drop  of  cod-liver  oil, 
which  likewise  always  contains  some  free  acid,  placed  in  a  0.3  per  cent,  soda-solu- 
tion, is  at  once  broken  up  into  fine  emulsion-granules.  First  a  hard  soapy  mem- 
brane is  formed  on  the  surface  of  the  oil-drop;  this,  however,  is  quickly  dissolved 
and  small  drops  are  thereby  torn  away.  The  fresh  surface  becomes  again  covered 
with  a  layer  of  soap  and  the  process  is  continually  repeated.  The  soaps  produced 
themselves  in  turn  act  as  emulsifiers.  If  the  amount  of  oleic  acid  contained  in 
the  oil  and  the  concentration  of  the  soda-solution  are  increased,  so-called  "myelin- 
forms"  are  produced,  that  is,  forms  like  those  that  appear  when  fresh  nerve-fibers 
are  teased  in  aqueous  liquids.  Animal  fats  furnish  an  emulsion  more  readily  than 
vegetable  fats,  castor-oil  not  furnishing  any  at  all. 

The  fatty  acids  also  may  undergo  still  further  decomposition  through  the  action 
of  the  fat-splitting  ferment,  with  the  production  of  carbon  dioxid  and  hydrogen 
even,  in  the  absence  of  microorganisms. 

Danilewsky  isolated  the  four  pancreatic  ferments  in  the  following  manner:  If 
an  acid  infusion  of  dog's  pancreas  is  super-saturated  with  magnesium  oxid,  the 
precipitate  carries  the  fat-ferment  down  with  it.  Collodion  added  to  the  filtrate 
precipitates  the  trypsin;  the  precipitate  is  collected;  and  the  collodion  is  dissolved 
out  by  a  mixture  of  ether  and  alcohol.  The  diastatic  ferment  is  contained  in  the 
filtrate  from  the  collodion-precipitate. 

For  testing  the  digestive  activity  of  the  pancreas  an  extract  of  the  swollen 
and  reddened  gland  may  be  prepared  after  trituration  with  the  aid  of  concentrated 
solution  of  sodium  chlorid.  Triturated  pancreas,  which  has  lain  for  a  day,  can 
also  be  extracted  with  glycerin  or  chloroform-water.  Alcohol  precipitates  the  fer- 
ments in  these  extraction-fluids.  Kuhne  renders  the  minced  pancreas  free  from 
water  and  fat  by  means  of  alcohol  and  ether,  and  pulverizes  it.  The  powder,  to 
which  10  parts  of  o.i  per  cent,  salicylic  acid  solution  at  blood-heat  are  added, 
exhibits  the  activity  of  the  ferments.  An  extract  of  the  pancreas,  prepared  rapidly 
and  at  a  high  temperature  with  a  0.7  per  cent,  solution  of  sodium  chlorid,  contains 
almost  alone  the  sugar-forming  ferment,  which  is  absent  from  the  gland  in  the 
state  of  hunger.  After  long-continued  maceration  at  a  later  period  trypsin  prin- 
cipally is  obtained. 

To  demonstrate  the  effects  of  the  pancreas  Setschenow  proceeds  as  follows: 
Minced  calf's  pancreas  is  infused  with  less  than  double  its  volume  of  water  and 
is  kept  at  a  temperature  of  38°  C.  for  five  hours.  The  decanted  fluid  is  strained, 
shaken  with  ether,  and  alcohol  is  added  until  a  precipitate  forms.  The  latter  is 
spread  uniformly  upon  filter-paper  by  filtration,  and  the  paper  is  dried  at  a  tern- 


THE    SECRETION    OF    THE    PANCREATIC    JUICE.  307 

perature  of  40°  C  A  strip  of  this  paper  about  the  length  of  a  finger  immersed 
and  fat4  ^  ^  ^^  ^^  *  L[d  ™P*UQ  °f  ^™%  UP°n  starfhes^umln 
The  pancreas  of  new-born  infants  contains  no  diastatic  ferment,  but  both 
peptic  and  fat-splitting  ferments.  Diseases  of  infants,  diarrhea  at  times  appear 
,°  hVh-ta  Tt  +1  6Ct  °Vhe  aCtivity  °f  the  Pancre*s-  Slight  diastatic  pPower 
of  the  fir^  ear  ^  m  °f  Ufe>  comPlete  activity  only  after  the  lapse 

The  milk-curdling  activity  depends  on  the  presence  of  a  ferment 
according  to  W.  Kuhne  and  W.  Roberts,  which  can  be  extracted  by 
means  of  a  concentrated  solution  of  sodium  chlorid. 

The  pancreas  also  prepares  a  sugar-splitting  ferment.  If  a  solution 
of  sugar  is  digested  with  an  aqueous  or  glycerin  extract  of  pancreas, 
the  amount  of  sugar  diminishes. 

THE   SECRETION   OF   THE   PANCREATIC   JUICE. 

In  the  case  of  the  pancreas,  a  resting  stage,  in  which  the  gland  is  flabby 
and  pale  yellow,  and  a  stage  of  secretory  activity,  in  which  the  organ 
appears  swollen  and  pale  red,  can  be  distinguished.  The  latter  occurs 
only  after  the  ingestion  of  food,  and  results  probably  in  consequence  of 
reflex  excitation  through  the  nerves  of  the  alimentary  canal,  and  ap- 
parently in  consequence  of  the  moistening  of  the  intestinal  mucous  mem- 
brane with  the  acid  gastric  contents,  for  acids  are  the  most  powerful 
excitants  of  this  secretion.  W.  Kiihne  and  Lea  found  that  all  the  lobules 
did  not  take  part  in  the  secretory  activity  at  the  same  time.  The  pan- 
creas in  herbivora  secretes  continuously.  * 

According  to  Bernstein  and  Heidenhain,  the  secretion  begins  to  flow 
with  the  entrance  of  the  food  into  the  stomach,  the  quantity  reaching 
its  maximum  in  the  second  or  third  hour.  After  this  the  amount  de- 
creases between  the  fifth  and  the  seventh  hour;  then,  in  consequence 
of  the  passage  of  all  of  the  dissolved  matters  into  the  duodenum,  it  rises 
again  between  the  ninth  and  the  eleventh  hour,  and  finally  falls  gradually 
between  the  seventeenth  and  the  twenty-fourth  hour,  to  the  point 
of  complete  cessation. 

^  During  the  act  of  secretion  the  blood-vessels  behave  like  those  of  the 
salivary  gland  after  stimulation  of  the  facial  nerve;  they  are  dilated,  the 
venous  blood  being  bright  red.  It  is,  therefore,  probable  that  a  similar 
nervous  mechanism  is  active  here.  In  general,  the  activity  of  the  gland 
is  in  large  measure  dependent  upon  an  adequate  blood-supply;  anemic 
conditions  impair  the  secretory  processes.  The  secretion,  in  the  rabbit, 
is  under  a  secretory  pressure  of  over  17  mm.  of  mercury. 

The  nerves  are  derived  from  the  hepatic,  splenic  and  superior  mesenteric 
plexuses,  to  which  the  pneumogastric  and  splanchnic  nerves  send  branches.  The 
secretion  of  the  gland  is  excited  by  stimulation  of  the  medulla  oblongata,  of  the 
splanchnic  nerves  (feebly),  of  the  peripheral  stump  of  the  pneumogastric  nerve, 
in  consequence  of  which  the  amount  of  ferment  in  the  juice  is  increased,  as  well 
as  of  the  gland  itself  by  means  of  induction-currents.  Reflex  increase  in  the 
secretion  is  brought  about  by  stimulation  of  the  central  stump  of  the  lingual  nerve, 
at  times  also  by  that  of  the  central  stump  of  the  pneumogastric  nerve.  The 
secretion  is  suppressed  by  atropin,  by  excitation  through  the  act  of  vomiting,  as 
well  as  by  stimulation  of  the  pneumogastric  nerve  or  its  central  stump,  as  well  as 
of  other  sensory  nerves,  as,  for  example,  the  crural  and  sciatic  nerves.  Destruction 
of  the  accessible  nerves  of  the  pancreas  surrounding  the  blood-vessels  renders  the 
stimulation  mentioned  ineffective.  On  the  other  hand  the  secretion  of  a  watery, 
paralytic,  slightly  active  secretion  becomes  permanent;  and  the  amount  is  then 
no  longer  modified  by  the  ingestion  of  food. 


308  THE    STRUCTURE    OF    THE    LIVER. 

Fat  and  water,  further  pilocarpin  and  physostigmin,  excite  pancreatic  secre- 
tion. Solutions  of  neutral  and  alkaline  salts  of  the  alkaline  metals  exert  an  in- 
hibitory action.  Animals  tolerate  ligation  of  the  pancreatic  duct.  It  is  a  remark- 
able fact  that  the  duct  may  regenerate  spontaneously.  This  operation  may,  how- 
ever, be  followed  by  cyst-formation  in  the  ducts  and  atrophy  of  the  glandular 
structure.  After  total  extirpation  of  the  pancreas,  the  digestion  of  albumin,  fat 
and  starches  is  impaired.  The  severe  diabetes  that  develops  immediately  after 
extirpation  of  the  pancreas  and  which  has  been  observed  also  in  human  beings 
after  degeneration  of  the  pancreas,  is  of  obscure  origin. 

THE  STRUCTURE  OF  THE  LIVER. 

The  liver  is  included  among  the  compound  tubular  glands.  Its  development 
shows  that  with  its  excretory  ducts  it  evolves  in  the  form  of  a  reticulated  tubular 
gland.  The  globular,  polygonal  hepatic  acini  (lobules,  islands),  flattened  one 
against  the  other,  from  i  to  2  mm.  in  diameter,  are  considered  as  the  ultimate 
macroscopic  units  of  the  gland.  They  show  the  following  histological  peculiarities: 

The  liver  cells  (Fig.  116,  II,  a),  34  or  35  ^in  diameter,  are  irregularly  polyhedral, 
consisting  of  soft,  friable  protoplasm,  filled  with  pigment-grantiles.  They  have 
no  membrane,  and  contain  one  or  more  spherical  nuclei,  with  nucleoli,  and  are  so 
arranged  that  they  radiate  from  the  centre  of  the  acinus  in  longer  or  shorter  con- 
nected lines  toward  the  surface  of  the  lobule.  Thus  arranged  they  are  in  part 
surrounded  by  the  more  delicate  bile-ducts  (Fig.  116,  I,  x),  in  part  separated  one 
from  the  other  in  rows  by  the  coarse  network  of  blood-capillaries  (d  d) .  In  the 
state  of  hunger  the  liver-cells  are  finely  granular  and  deeply  clouded  (Fig.  117,  i). 
About  thirteen  hours  after  suitable  nourishment  the  cells  contain  coarse,  glistening 
flakes  of  glycogen  (2).  At  the  same  time  the  protoplasm  is  condensed  on  the 
surface,  whence  a  network  extends  toward  the  center  of  the  cells,  in  which  the 
nucleus  is  suspended.  The  liver-cells  often  contain  fatty  granules. 

The  Blood-vessels  of  the  Lobule. —  (a)  Ramifications  of  the  venous  system. 
If  the  branches  of  the  portal  vein,  well  supplied  with  muscular  fibers,  and  entering 
through  the  transverse  fissure,  be  followed,  small  vessels  will  finally  be  found, 
after  free  dendritic  branching,  that,  approaching  from  various  directions,  converge  at 
the  limits  of  the  acini,  and  here  enter  into  communication  through  capillary  anasto- 
moses, forming  the  interlobular  veins  (Fig.  116,  V,  i).  From  these  veins  capillary 
vessels  (c  c)  pass  from  the  entire  periphery  of  the  acinus  toward  its  center.  They 
are  relatively  large  (from  10  to  14  //  in  diameter)  and  form  a  longitudinal  network 
in  a  radiating  direction;  and  between  them  rows  of  connected  hepatic  cells, 
liver-cell  columns  (d) ,  are  always  lodged.  The  capillaries  are  so  arranged  that  they 
run  along  the  edges  of  the  rows  of  cells,  and  never  between  the  surfaces  of  two 
adjacent  rows.  The  radiating  course  of  the  capillaries  necessarily  brings  it  about 
that  these  vessels  must  unite  at  the  center  of  the  acinus  to  form  the  beginning 
of  a  larger  vessel.  This  is  the  central  or  intralobular  vein  (V.  c)  which,  m  turn, 
piercing  the  lobule  vertically,  makes  its  exit  at  one  point  and,  reaching  the  surface 
unites,  as  the  sublobular  vein  (V.  a),  with  similar  vessels  from  neighboring  acini, 
to  form  larger  trunks  that  (100  //  in  diameter)  represent  the  roots  of  the  hepatic 
veins.  The  trunks  of  this  great  system  of  venous  radicles  leave  the  gland  at  the 
blunt  edge  of  the  liver. 

(6)  Ramifications  of  the  Hepatic  Artery. — The  branches  of  the  hepatic  artery, 
throughout  their  entire  course,  accompany  the  larger  branches  of  the  portal  vein, 
to  which,  as  well  as  to  the  adjacent  larger  bile-ducts,  they  supply  nutrient  capillaries. 
These  branches  enter  into  numerous  anastomotic  communications  among  them- 
selves. The  small  capillaries  pass  mainly  from  the  periphery  of  the  acinus  into 
the  capillaries  of  the  portal  system  (Fig.  116,  i  i).  Those  arterial  capillaries,  how- 
ever, that  lie  in  the  thicker  connective  tissue  upon  the  larger  venous  and  biliary 
branches  (rr)  pass  over  chiefly  into  two  venous  trunks  that,  accompanying  the 
corresponding  arterial  branches  for  some  distance,  empty  into  branches  of  the 
portal  vein. 

Individual  arterial  branches  pass  up  to  the  surface  of  the  liver,  where  they 
form  a  wide-meshed  nutritive  network,  particularly  under  the  peritoneal  covering. 
The  small  venous  radicles  collecting  from  this  point  also  reach  the  ramifications  of 
the  portal  vein. 

The  Biliary  Passages. — The  finest  biliary  passages,  bile-capillaries,  originate 
from  the  center  of  the  acinus,  and  likewise  within  its  entire  interior,  as  membrane- 
less,  regularly  anastomosing  straight  ducts,  i  or  2  ^  in  diameter.  They  form  a 


THE    STRUCTURE    OF    THE    LIVER. 


309 


polygonal  mesh  about  each  liver-cell  (Fig.  117,  3).  The  ducts  almost  always  lie 
midway  between  the  surfaces  of  two  adjacent  liver-cells  (Fig.  116,  II,  a)  as  true 
intercellular  passages  or  secretory  spaces.  When  the  cells  fall  apart  in  the  process 
of  maceration,  they  retain  only  semicircular  depressions.  The  finest  ducts  of  the 
bile-capillaries  have  been  observed  to  penetrate  the  interior  of  the  liver-cells  and 
to  communicate  here  with  roun 


-s 

to  communicate  here  with  round,  secretory  vacuoles  containing  bile  (Fig    117    7) 

along  the  edges  of  the  rows  of  liver-cells,  while  the 


As  the  blood-capillaries  run  e  rows  o      ver-ces,  we  te 

biliary  ducts  run  along  the  surfaces  of  the  cells,  both  systems  of  ducts  are  always 
at  a  definite  distance  from  one  another  (Fig.   118).    " 

In  human  beings  individual  bile-ducts  sometimes  run  also  along  the  edges  of 
the  cells,  so  that  they  must  then  act  as  intercellular  ducts  of  3  or  4  cells  This 
arrangement  is  said  to  predominate  in  the  embryonal  liver.  In  addition  to  in- 
jection, the  capillaries  can  be  made  visible  by  staining  by  Golgi's  method 


V.i 


V. 


FIG.  116. — I.  Diagrammatic  Representation  of  an  Hepatic  Lobule:  V.  i.,  V.  i,  interlobular  veins;  V.  c,  central  vein; 
c,  capillary  between  the  two;  V.  s,  sublobular  vein;  V.  v,  vascular  vein;  A  A,  branches  of  the  hepatic  artery, 
approaching  the  capsule  of  Glisson  and  the  larger  blood-vessels  at  r  r,  and  forming  the  vascular  vein  further 
on,  entering  the  capillaries  of  the  interlobular  veins  at  i  i;  g,  branches  of  the  bile-duct,  dividing  at  x  x  between 
the  liver-cells;  d  d,  situation  of  liver-cells  in  the  capillary  network.  II.  Isolated  liver-cells,  at  c  lying  upon 
a  capillary  blood-vessel  and  forming  a  fine  bile-duct  at  a. 

Within  the  peripheral,  cortical  portion  of  the  lobule  the  ducts,  without  walls, 
increase  in  size  by  anastomosis  of  neighboring  ducts.  They  then  leave  the  acinus, 
in  order,  from  this  point,  uniting  between  the  lobules  (Fig.  116,  g)  with  adja- 
cent ducts,  to  form  larger  bile-ducts,  with  numerous  anastomoses.  These,  in  com- 
pany with  the  branches  of  the  hepatic  artery  and  the  portal  vein,  finally  leave 
the  transverse  fissure  of  the  liver  as  a  collecting  duct,  the  hepatic  duct.  The  finer 
interlobular  bile-ducts  possess  a  structureless  membrana  propria  with  low  epithe- 
lium. The  larger  (Fig.  119)  exhibit  a  double  membrane  constituted  of  connective 
tissue  and  elastic  fibers,  the  internal  layer  being  c-sjuvially  supplied  with  blood- 
capillaries  and  bearing  a  single  layer  of  cylindrical  epithelium.  Only  in  tin-  largest 
branches,  and  in  the  gall-bladder,  does  this  internal  layer  Kv<>me  an  independent 
mucous  membrane,  with  submucosa.  Unstriped  muscle-fibers  are  found  in  isolated 


3io 


THE    STRUCTURE    OF    THE    LIVER. 


FIG.  117. — A,  Liver-cell,  in  the 
state  of  hunger;  2,  filled  with 
masses  of  glycogen;  3,  sur- 
rounded by  bile-capillaries. 


bundles  in  the  main  ducts  (longitudinal  and  circular  especially  in  the  lower  portions 
of  the  bile-ducts),  as  well  as  in  a  delicate  longitudinal  and  circular  layer  in  the 
gall-bladder.  The  movements  here  are  slowly  rhythmic  and  peristaltic.  The 
mucous  membrane  of  the  gall-bladder  is  provided  with  folds  and  comb-like  de- 
pressions. The  epithelium  is  a  single  layer  of  cylindrical  epithelium  with  a  basal 
membrane  and  intervening  mucous  goblet-cells.  Small  mucous  glands  are  found 
in  the  mucous  membrane  of  the  large  bile-ducts  and  of  the  gall-bladder. 

The  connective  tissue  of  the  liver  enters  the 
portal  fissure  as  a  sheath  (capsule  of  Glisson)  for 
the  vessels,  and,  mixed  with  elastic  tissue,  finally 
reaches  the  periphery  of  the  acini,  where  in  the 
pig,  the  camel  and  the  polar  bear  it  forms  a  clearly 
demonstrable  capsule,  but  in  human  beings  is  in- 
conspicuous. Delicate  elements  can,  however,  be 
followed  even  into  the  acinus,  nucleated  star-cells 
and  a  network  of  delicate  reticular  fibers,  which 
effect  the  fixation  of  the  elements. 

The  connective  tissue  of  the  acini  not  rarely 
undergoes  considerable  increase  in  drunkards,  and 
its  hyperplasia  may  even  cause  destruction  of  the 
contents  of  the  acinus  by  pressure  (cirrhosis  of  the  liver).  In  this  thickened, 
interacinous  connective  tissue  newly  formed  bile-ducts  have  been  found,  and 
likewise  in  the  cicatricial  connective  "tissue  of  the  "corset-liver." 

The  lymph-vessels  begin  as  pericapillary  ducts  in  the  interior  of  the  acinus. 
Further  on  they  run  within  the  walls  of  the  hepatic  veins  and  the  branches  of  the 
portal^vein;  then  they  surround  the  venous  branches.  The  larger  vessels,  formed 

from  the  union  of  the  inter- 
lobular  passages,  leave  the 
organ  in  part  at  the  trans- 
verse fissure,  in  part  with 
the  hepatic  veins,  and  in 
part  at  different  points  on 
the  surface.  At  the  blunt 
edge  of  the  liver  they  form 
a  close  meshwork  and  pass 
through  the  triangular,  he- 
pato-renal  and  suspensory 
ligaments. 

The  nerves  of  the  hepatic 
plexus,  constituted  in  part 


FIG.  118. — Blood-capillaries,  Finest  Biliary  Ducts,  and  Liver- 
cells,  in  Their  Mutual  Relations  in  the  Rabbit's  Liver 
(after  E.  Hering):  B,  blood-vessel;  D,  finest  biliary  duct, 
in  cross-section;  F,  finest  biliary  duct;  K,  nucleus  of 
liver-cell. 


C. 


FIG.  119. — Interlobular  Bile-duct  from 
the  Human  Liver  (after  Schenk) : 
R,  circular  fibrous  layer;  C, 
cylindrical  epithelium. 


of  Remak's  fibers,  in  part  of  medullated  fibers  fiom  the  sympathetic  and  pneu- 
mogastric  nerves,  follow  the  ramifications  of  the  hepatic  artery.  Ganglia  are 
placed  in  their  course  in  the  interior  of  the  organ.  The  nerves  are  in  part 
vasomotor  in  nature.  According  to  Pfliiger,  other  nerve-fibers  enter  into  direct 
connection  with  the  liver-cells,  as  is  the  case  in  the  salivary  glands.  The 
muscle-cells  of  the  bile-ducts  contain  motor  filaments. 


CHEMICAL    CONSTITUENTS    OF    THE    LIVER-CELLS.  311 

The  celiac  plexus  sends  trophic  and  vasomotor  nerves  to  the  liver.  Destruc- 
tion of  this  plexus  therefore  causes  degeneration  of  the  liver-cells,  and  dilatation 
of  the  hepatic  artery.  The  pneumogastric  nerve  supplies  dilator-fibers  to  the 
vessels,  and  the  greater  splanchnic  motor  branches  to  the  muscles  of  the  bile- 
ducts. 

CHEMICAL  CONSTITUENTS  OF  THE  LIVER-CELLS. 

Proteids. — The  fresh,  soft  liver-parenchyma  has  an  alkaline  re- 
action. After  death,  coagulation  takes  place,  with  cloudiness  of  the 
cell-contents ;  the  tissue  becomes  friable  and  gradually  acquires  an  acid 
reaction.  This  process  is  suggestive  of  rigor  mortis,  and  is  due  to 
a  myosin-like,  post-mortem  coagulating  albuminous  substance.  The 
liver  contains,  further,  a  proteid  body  coagulable  at  45°  C.,  another 
coagulable  at  70°  C.,  and  one  slightly  soluble  in  dilute  acids  and  alkalies. 
The  nuclei  contain  nuclein.  The  connective  tissue  yields  gelatin. 

Glycogen,  6C6H1005  + H2O,  or  animal  starch,  from  1.2  to  2.6  per 
cent.,  is  a  carbohydrate  closely  allied  to  inulin,  soluble  in  water,  and 
diffusible  with  difficulty,  which  surrounds  the  nuclei  of  the  liver-cells  in 
amorphous  granules  (Fig.  117,  2),  though  not  always  present  and  not 
always  found  in  equal  amounts  in  all  parts  of  the  liver.  The  glycogen 
in  the  liver  represents  the  excess  of  carbohydrate  material,  which,  after 
the  ingestion  of  suitable  foods,  is  temporarily  stored  like  the  starch  in 
the  plants.  It  is  subsequently  transformed  into  sugar  and  consumed  by 
the  tissues.  t 

Qualitative  Determination. — Glycogen  is  stained  deeply  red  by  iodin  (best  dis- 
solved by  means  of  potassium  iodid  in  a  concentrated  solution  of  sodium  chlorid) , 
like  inulin,  even  in  microscopic  sections  hardened  in  alcohol.  Organs  containing 

?lycogen,  boiled  with  an  excess  of  sodium  sulphate,  yield  an  opalescent  filtrate, 
f  the  organs,  as,  for  example,  the  liver,  still  contain  diastatic  ferment,  the  glycogen, 
after  being  kept  warm  for  several  hours,  will  be  converted  into  sugar,  and,  as 
already  stated,  the  resulting  filtrate  remains  clear. 

Quantitative  Estimation. — According  to  Kulz's  modification  of  Brucke's 
method,  the  coarsely  minced  liver  is  thrown  into  boiling  water  immediately  after 
death  and  boiled  for  half  an  hour.  It  is  then  crushed  and  potassium  hydrate 
(4  grams  to  100  grams  of  liver)  is  added.  Evaporation  over  a  water-bath  to 
double  the  weight  of  the  piece  of  liver  employed  is  permitted  to  take  place  until 
in  the  course  of  three  hours  all  is  dissolved.  After  cooling,  the  mixture  is  neutral- 
ized with  hydrochloric  acid,  and  the  albumin,  together  with  the  lime,  is  precipitated 
by  means  of  hydrochloric  acid,  and  potassio-mercuric  iodid.  Filtration  is  now 
practised,  the  precipitate  being  taken  from  the  filter  four  times,  mixed  with 
a  few  drops  of  hydrochloric  acid  and  potassio-mercuric  iodid  in  water  to  the 
consistency  of  broth  and  filtered.  All  of  the  glycogen  is  now  contained  in  the 
filtrate,  to  which,  with  stirring,  double  the  volume  of  96  per  cent,  alcohol  is  added. 
The  glycogen  deposited  in  the  course  of  twelve  hours  is  placed  upon  the  filter, 
washed  with  62  per  cent,  alcohol,  then  with  absolute  alcohol,  with  ether,  again 
with  absolute  alcohol  and  dried  at  110°  C.  Should  the  fluid  remain  cloudy  after 
addition  of  hydrochloric  acid  and  potassio-mercuric  iodid,  two  parts  of  98  per  cent, 
alcohol  are  added  and  the  filtered  precipitate  is  dissolved  in  2  percent,  potassium 
hydrate,  then  neutralized  with  hydrochloric  acid  and  now  all  of  the  albumin 
can  be  precipitated  by  repeated  addition  of  hydrochloric  acid  and  potassio-mer- 
curic iodid  again. 

According  to  Seegen,  dextrin  is  present  in  the  liver  in  addition  to  glycogen. 
Rabbit's  liver  contains  about  three  times  as  much  glycogen  in  winter  as  in  summer. 

The  following  are  to  be  considered  as  the  sources  of  glycogen  in  the 
liver:  (i)  The  carbohydrates  of  the  food,  after  they  have  been  con- 
verted into  dextrose  in  the  alimentary  canal;  only  the  sugars  ferment- 
able by  yeast  form  glycogen,  and  not  those  incapable  of  fermentation; 


312  CHEMICAL    CONSTITUENTS    OF    THE    LIVER-CELLS. 

and   (2)  the  proteids,  including  gelatin.     If  the  proteids  are  a  source 
of  glycogen,  it  must  result  from  a  non-nitrogenous  derivative  of  them. 

Pfluger  considers  the  formation  of  glycogen  from  albumin  a  synthetic  process. 
The  molecular  group  CH2,  found  in  albumin,  as  well  as  in  the  fatty  acids,  must 
be  transformed  by  oxidation  into  CHOH.  The  cells  taking  part  in  the  formative 
process  may,  however,  also  utilize  this  group  CHOH  wherever  it  is  found  already 
prepared,  as  in  sugar  or  in  glycerin. 

Also  fats  (olive-oil),  glycerin,  taurin  and  glycin  (the  latter  through  decomposi- 
tion into  glycogen  and  urea) ,  have  been  designated  as  the  source  of  glycogen. 

In  rabbits,  the  production  of  glycogen  is  increased  by  the  administration  of 
asparagin,  ammonium  carbonate  or  urea.  The  excessive  production  of  acid  in 
cases  of  diabetes,  demonstrated  by  Stadelmann,  fixes  the  ammonia  and  thus 
materially  diminishes  the  production  of  glycogen. 

Ligation  of  the  common  bile-duct  results  in  diminution  of  the  glycogen  in 
the  liver.  The  liver  after  this  operation  appears  to  have  lost  the  property  of  form- 
ing glycogen  from  suitable  material  brought  to  it.  Also  ligation  of  the  hepatic 
artery  renders  the  liver  free  from  glycogen.  After  excluding  the  portal  circulation 
the  amount  of  sugar  contained  in  the  blood  decreases.  With  reference  to  the  occur- 
rence of  glycogen  elsewhere  reference  may  be  made  to  p.  466. 

If  large  amounts  of  starch,  grape-sugar,  cane-sugar,  levulose  and 
maltose  are  added  to  the  proteids  of  the  food,  the  amount  of  glycogen 
in  the  liver  is  greatly  increased,  while  on  a  pure  albuminous  or  fatty 
diet  it  is  considerably  decreased ;  the  state  of  hunger  may  cause  it  to  dis- 
appear entirely.  Injection  of  grape-sugar  or  of  glycerin  into  a  mesen- 
teric  vein  of  a  fasting  rabbit  causes  the  appearance  of  glycogen  in  a 
liver  previously  free  from  it. 

The  living  liver-cell  is  capable  of  producing  glycogen  in  considerable  quantities 
only  from  the  two  kinds  of  sugar  capable  of  direct  fermentation,  namely  dextrose 
and  levulose.  The  non-fermentable  sugars  are  not  converted  into  glycogen,  and 
cane-sugar  and  maltose  only  in  so  far  as  they  are  transformed  in  the  intestine  into 
dextrose.  As  the  infant  consumes  milk-sugar,  it  must  form  glycogen  from  albu- 
min. 

Forced  muscular  movement  rapidly  renders  the  liver  of  the  dog  free  from 
glycogen.  Reduction  of  temperature  .diminishes  the  amount  of  glycogen  in  the 
liver.  The  rigid  liver  after  death  contains  dextrin  and  grape-sugar.  Glycogen 
is  also  present  in  the  liver  for  a  considerable  time  after  death,  as  well  as  in  the 
muscles. 

Under  normal  conditions,  the  glycogen  in  the  liver  is  gradually 
transformed  in  small  amounts  into  grape-sugar.  The  amount  of  sugar 
normally  present  in  the  blood  is  from  0.5  to  i  in  1000.  The  blood  in 
the  hepatic  veins  may  contain  somewhat  more.  Increased  transforma- 
tion into  sugar  occurs  only  in  connection  with  marked  circulatory  dis- 
turbances in  the  liver,  as  a  result  of  which  the  blood  of  the  hepatic  veins 
comes  to  contain  a  larger  amount  of  sugar.  The  glycogen  undergoes 
this  transformation,  likewise,  soon  after  death,  when  the  liver  is  always 
found  to  contain  a  larger  amount  of  sugar  and  a  smaller  amount  of  gly- 
cogen. 

The  active  ferment  necessary  for  this  process  can  be  obtained  from 
an  extract  of  the  liver-cells,  by  the  method  employed  to  obtain  ptyalin. 
Nevertheless,  it  is  said  not  to  be  formed  in  the  liver-cells,  but  only 
reaches  the  liver  to  be  quickly  stored  up,  through  the  blood,  within 
which  the  ferment  is  always  formed  with  rapidity  so  soon  as  the  move- 
ment of  the  blood  undergoes  marked  disturbance.  This  transforming 
ferment  develops  also  as  a  result  of  the  solution  of  red  blood-corpuscles ; 
and  as  a  constant  slight  destruction  of  red  blood-corpuscles  must  surely 
be  assumed  to  take  place  within  the  liver,  a  source  is  thus  provided 


DIABETES    MELLITUS.  313 

for  the  production  of  the  ferment  through  the  action  of  which  small 
quantities  of  sugar  are  continually  formed  in  the  liver.  As  the  liver  is 
thus  the  seat  for  the  production  of  sugar,  extirpation  of  this  organ  or 
ligation  of  its  vessels  is  followed  by  disappearance  of  the  sugar  con- 
tained in  the  blood. 

The  grape-sugar  formed  in  the  liver  is  destroyed  in  part  in  the  blood- 
stream, on  its  way  through  the  tissues,  in  part  by  a  special  ferment, 
which  appears  to  be  derived  principally  from  the  pancreas,  and  to  be 
carried  by  the  blood-corpuscles.  A  portion  of  the  sugar  in  the  blood  is 
converted  in  the  muscles  into  glycogen. 

According  to  Kiilz  and  Vogel,  the  same  process  takes  place  in  the  liver  in 
the  formation  of  sugar  from  glycogen  as  results  from  the  action  of  the  saliva  and 
the  pancreatic  juice,  with  the  production  likewise  of  maltose  and  isomaltose. 
According  to  E.  Cavazzani,  irritation  of  the  celiac  plexus  causes  the  production 
of  sugar  in  the  liver,  in  connection  with  which  the  liver-cells  undergo  morphologic 
change. 

Further,  /a/5  are  observed  in  the  liver-cells,  in  the  form  of  granules,  as 
well  as  free  in  the  bile-ducts ;  occasionally  when  the  diet  is  rich  in  fat  (in 
greater  amount  in  drunkards  and  tuberculous  patients),  olein,  pal- 
mitin,  stearin  and  volatile  fatty  acids  are  found.  Further,  sarcolactic  acid, 
traces  of  cholesterin,  jecorin,  finally  small  amounts  of  urea  (in  increasing 
amount  in  the  warm,  "surviving"  liver),  uric  acid;  and  leucin,  ty rosin 
(guanin?),  sarcin,  xanthin,  and  cystin  pathologically  in  conjunction  with 
putrefactive  disorders,  may  be  present. 

The  liver-cells  contain  pigments,  which  are  partly  soluble  in  feebly 
alkaline  water,  partly  in  chloroform. 

The  pigment  soluble  in  water,  designated  ferrin,  varies  from  yellow  to  red  in 
color  and  contains  almost  all  o±  the  iron  of  the  liver.  The  latter  can  be  demonstrated 
directly  by  means  of  potassium  ferrocyanid  or  ammonium  sulphid.  The  pigment 
soluble  in  chloroform,  designated  chofechrome,  can  be  extracted  from  pulverized 
dried  liver.  It  stands  midway  between  bile-pigment  and  the  lipochromes. 

The  inorganic  constituents  of  the  liver  are  potassium,  sodium,  calcium, 
magnesium  and  manganese.  Iron  in  organic  combination  with  albumin 
(in  ferratin)  is  present  in  the  liver  to  the  amount  of  about  6  per  cent. 
Abstraction  of  blood  together  with  albumin-hunger  causes  its  disappear- 
ance. It  is  utilized  in  the  production  of  new  blood.  Chlorin,  phosphoric, 
sulphuric,  carbonic  and  silicic  acids  may  also  be  present ;  and  copper,  zinc, 
lead,  mercury  and  arsenic  have  been  found  deposited  in  the  liver  acci- 
dentally. 

DIABETES  MELLITUS. 

The  formation  of  large  amounts  of  grape-sugar  by  the  liver  and  their  entrance 
into  the  blood  and  into  the  urine  (glycosuria,  diabetes  melhtus)  have  been  brought 
into  relation  with  the  normal  conditions  already  mentioned.    Extirpation  of  the 
liver  in. the  frog  or  destruction  of  the  liver-cells  (fatty  degeneration  from  phos 
phorous  or  arsenical  poisoning)  does  not  cause  the  appearance  of  this  phenomenon. 
It  occurs  a  few  hours  after  injury  to  a  particular  spot  (center  for  the  vasomotor 
nerves  of  the  liver)  on  the  floor  of  the  lower  portion  of  the  fourth  ventricle 
Bernard's    sugar-puncture,    piqure) ;    further,    after   division   of   the    vasomot 
paths    in    the^  spinal    cord    from    above    downward   to  the    exi 
for  the  liver  that  is  to  the  lumbar  portion,  in  the  frog  to  the  fourth  vertebra. 

Division  or  paralvsis  of  the  vasomotor  conducting  paths  from  the  ceni 
the  liver  results  in  glvcosuria.     According  to  recent  researches  1  >y  I-  ranjois  I-  ranck 
and  Hallion,  the  vasomotor  nerves  of  the  liver  (for  the  hepatic  artery  anc 
portal  vein)    arise   between  the  sixth  dorsal  and  the  second  lumbar  nerves  am 


314  DIABETES    MELLITUS. 

pass  through  the  communicating  branches  into  the  splanchnic  nerves.  According 
to  the  opinions  of  earlier  investigators,  all  of  the  paths,  however,  do  not  pass 
through  the  spinal  cord  alone.  A  number  of  vasomotor  fibers  for  the  liver  leave 
the  spinal  cord  at  a  higher  level,  and  pass  further  on  in  the  course  of  the  sym- 
pathetic nerve  to  the  liver.  Thus,  destruction  of  the  uppermost,  as  well  as  of  the 
lowest,  cervical  ganglion,  and  of  the  first  dorsal  ganglion,  of  the  abdominal  ganglia, 
often  also  of  the  splanchnic  nerves,  is  followed  by  glycosuria.  The  paralyzed, 
dilated  vessels  render  the  liver  exceedingly  vascular,  and  the  blood-stream  in  them 
is  slowed.  This  disturbance  of  the  circulation  gives  rise  to  the  presence  of  a  large 
amount  of  sugar  in  the  liver,  as  the  blood-ferment  has  time  to  effect  transformation 
of  the  glycogen.  Irritation  of  the  sympathetic  nerve  at  the  last  cervical  and  first 
dorsal  ganglia  causes  contraction  of  the  hepatic  vessels  at  the  periphery  of  the 
acini,  with  anemia.  It  is  a  remarkable  fact  that  glycosuria  when  present  can 
be  removed  by  division  of  the  splanchnic  nerves.  This  is  explained  by  the  cir- 
cumstance that  the  enormous  hyperemia  of  the  intestines  occurring  after  this 
operation  renders  the  liver  anemic. 

Also  a  number  of  poisons  that  paralyze  the  vasomotor  nerves  of  the  liver 
cause  diabetes  in  the  same  manner,  namely  curare,  when  artificial  respiration 
is  not  maintained;  carbon  monoxid,  amyl  nitrite,  orthonitrophenyl-propionic 
acid  and  methyldelphinin ;  less  constantly  morphin,  chloral  hydrate  "and  others. 
The  toxic  products  of  some  of  the  infectious  diseases  also  act  in  the  same  way 
at  times.  Blood-stasis  of  other  sort  in  the  liver  also  appears  capable  of  caus- 
ing glycosuria,  as,  for  example,  after  mechanical  stimulation  of  the  liver.  In 
this  category  probably  belongs  the  glycosuria  following  the  injection  of  dilute 
saline  solutions  into  £he  blood,  as  a  result  of  which  the  changes  in  the  shape 
of  the  red  corpuscles  cause  stasis.  Also  the  fact  that  repeated  venesection 
makes  the  blood  richer  in  sugar  may,  perhaps,  be  explained  by  the  slowing  of  the 
circulation. 

Persistent  irritation  of  peripheral  nerves  may  also  be  active  through  a  reflex 
influence  upon  the  center  for  the  vasomotor  nerves  of  the  liver.  The  appearance 
of  sugar  in  the  urine  has  sometimes  been  observed  as  a  result  of  irritation  of  the 
central  stump  of  the  pneumogastric  nerve,  likewise  after  irritation  of  the  central 
stump  of  the  depressor  nerve.  Even  division  and  central  irritation  of  the  sciatic 
nerve  may  cattse  the  appearance  of  sugar  from  the  urine ;  in  this  way  is  explained 
the  occurrence  of  glycosuria  in  cases  of  sciatica  and  other  nervous  disorders. 

According  to  Schiff,  stagnation  of  the  blood  in  various  extensive  portions 
of  the  body  is  said  to  increase  the  development  of  the  ferment  in  the  blood  to 
such  a  degree  that  diabetes  results.  Qf  this  character  must  be  considered  the 
glycosuria  that  occurs  after  compression  of  the  aorta  or  the  portal  vein,  although 
the  pressure  exerted  under  such  circumstances  may,  perhaps,  paralyze  nerve- 
paths  concerned.  According  to  Eckhard,  injury  to  the  vermis  of  the  cerebellum, 
in  the  rabbit,  is  said  to  bring  about  diabetes.  In  human  beings,  also,  affections 
of  the  nervous  structures  mentioned  may  cause  diabetes. 

Various  explanations  have  been  assigned  in  elucidation  of  the  ultimate  cause 
of  these  symptoms: 

(a)  The  glycogen  of  the  liver  may  without  interference  be  converted  into  sugar, 
as  ferment  may  be  conveyed  to  the  liver-cells  from  the  blood-mass,  in  consequence 
of  its  stagnation.  Therefore  the  normally  functionating  vasomotor  system  of  the 
liver,  and  especially  its  center,  is,  in  a  certain  sense,  to  be  designated  an  inhibitory 
system  controlling  the  production  of  sugar. 

(6)  If  it  be  assumed  that,  under  normal  conditions,  a  certain,  even  though 
small,  amount  of  sugar  flows  continually  from  the  liver  into  the  blood,  through  the 
hepatic  veins,  diabetes  might  be  explained  as  depending  on  the  abolition  of  those 
metabolic  processes  (deranged  combustion  of  sugar)  that  constantly  remove  this 
sugar  from  the  blood  under  normal  conditions. 

The  following  experiments  appear  to  confirm  this  latter  view:  Independently 
of  one  another,  v.  Mering  and  Minkowski,  as  well  as  de  Dominicis,  observed  that 
dogs  become  diabetic  after  total  removal  of  the  pancreas.  According  to  Min- 
kowski, it  is  the  function  of  the  pancreas  to  consume  the  sugar  of  the  blood.  Lepine 
and  Barral  state  that  a  ferment  is  produced  in  the  pancreas  that  destroys  the 
sugar  in  the  blood;  so  that  after  extirpation  of  the  pancreas,  sugar  must  accord- 
ingly accumulate  in  the  blood.  The  ferment  is  contained  in  abundance  within 
the  leukocytes  in  the  portal  vein;  some  is  derived  from  the  lymph,  perhaps  also 
from  other  abdominal  glands.  After  extirpation  of  the  pancreas,  the  blood  con- 
tains little  sugar-destroying  ferment.  Kolisch  and  von  Stejskal  found  much 
jecorin. 


THE    CONSTITUENTS    OF    THE    BILE.  315 

Pfluger  expresses  himself  as  follows  as  to  the  development  of  diabetes  mellitus: 
The  sugar  formed  by  the  liver  in  excessive  amount,  in  consequence  of  abnormalyl 
increased  nervous  excitation,  stimulates  the  pancreas — for  it  is  possible  that  this 
gland  takes  part  in  the  synthetic  production  of  fat  from  sugar — or  the  fat-forming 
organs  to  the  production  of  an  increased  amount  of  fat,  so  that  often  fat-formation 
takes  place  at  the  beginning  of  the  disease.  As  soon  as  the  fat-producing  organs, 
exhausted  and  paralyzed  from  over-activity,  are  no  longer  capable  of  disposing  of 
the  sugar  wholly  or  in  part  (which  may  also  be  the  result  of  excessive  ingestion 
of  sugar) ,  this  is  excreted  by  the  kidneys,  because  even  the  healthy  body  cannot 
assimilate  the  greater  portion  of  the  sugar  as  such,  but  only  after  it  has  been 
transformed  into  fats  or  into  soaps.  The  living  body  strives  to  make  good  the 
resulting  great  loss  in  nutritive  material  by  the  assimilation  of  larger  amounts  of 
albumin  and  fat.  Naturally  a  variety  of  diabetes  is  conceivable  without  hepatic 
disease  as  the  result  of  paralysis  of  the  pancreas,  or  of  the  fat -producing  organs. 
Lepine's  discovery  of  a  glycolytic  ferment  yielded  to  the  blood  by  the  pancreas, 
which  decomposes  the  sugar  in  the  blood  in  some  as  yet  unknown  manner,  and 
which  is  absent  or  diminished  in  cases  of  diabetes,  would  readily  accord  with  the 
foregoing  hypothesis. 

In  the  presence  of  pancreatic  diabetes,  puncture  of  the  floor  of  the  fourth 
ventricle  increases  the  excretion  of  sugar;  likewise,  remarkably,  the  addition  of 
raw  pancreas  to  the  food. 

(c)  Phloridzin,  a  glucosid  from  the  bark  of  the  roots  of  cherry-trees  and  apple- 
trees,  after  ingestion  causes  the  sugar  normally  present  in  the  blood  to  pass  rapidly 
over  into  the  urine,  so  that  the  latter  contains  a  larger  and  the  former  a  smaller 
amount  of  sugar. 

(d)  According  to  Biedl,  diabetes  occurs  after  ligation  of  the  thoracic  duct  in 
the  dog. 

The  enormous  need  of  food  and  drink,  together  with  the  signs  of  consumption 
of  the  bodily  tissues,  is  characteristic  of  diabetic  patients.  Not  rarely,  in  severe 
cases,  collapse-like  coma  is  observed,  which  has  been  designated  also  diabetic  coma, 
and  during  the  existence  of  which  the  breath  often  smells  of  acetone,  which  can 
also  be  demonstrated  in  the  urine.  Diabetic  patients  living  on  an  exclusive  meat- 
diet  exhibit  diacetic  acid  in  the  urine,  in  addition  to  acetone.  Neither  acetone 
nor  its  antecedent,  diacetic  acid  (which  can  be  recognized  by  the  reddening  of  the 
urine  when  dilute  ferric  chlorid  is  added  drop  by  drop) ,  after  the  administration 
of  which  the  urine  contains  much  acetone,  is,  as  direct  feeding-experiments  show, 
the  cause  of  this  coma;  which  is  perhaps  the  result  of  excessive  acid-production 
in  the  body,  therefore  an  acid  intoxication.  To  neutralize  the  acid,  increased 
elimination  of  ammonia  takes  place  from  the  body.  The  urinary  tubules  often  ex- 
hibit signs  of  coagulation-necrosis,  which  can  be  recognized  by  a  bright  and  swollen 
appearance  of  the  necrotic  cells  of  the  tubules,  v.  Frerichs  found,  further,  glyco- 
genic  degeneration  in  Henle's  loops,  in  the  liver,  the  heart,  the  leukocytes  and 
the  lungs.  The  urine  of  diabetic  patients  is  discussed  on  p.  501. 

THE  CONSTITUENTS  OF  THE  BILE. 

The  bile  is  a  transparent  fluid  varying  from  yellowish  brown  to  dark 
green  in  color,  of  a  sweetish,  bitter  taste,  feeble  musk-like  odor,  and 
feebly  acid  or  neutral  reaction.  The  specific  gravity  of  human  bile  from 
the  gall-bladder  is  between  1026  and  1032,  while  that  collected  from 
a  fistula  varies  from  1010  to  ion.  The  constituents  of  the  bile  are  as 
follows : 

Mucus  and  in  addition  a  considerable  amount  of  mucoid  nucleo- 
albumin,  which  together  make  the  bile  ropy,  are  products  of  the  mucous 
glands  and  the  goblet-cells  of  the  mucous  membrane  of  the  bile-ducts. 
They  are  precipitated  by  alcohol,  or  dilute  hydrochloric  acid  or  dilute 
acetic  acid.  They  cause  rapid  putrefaction  of  the  bile. 

The  two  biliary  acids  :  glycocholic  acid  and  taurochplic  acid,  the 
called  conjugate  acids,  combined  with  sodium  (and  with  potassium  in 
traces)  to  form  sodium  glycocholate  and  taurocholate,  have  a  bitter 
taste   and   are   dextrorotatory.     In   human  bile,  as   in  that   of  cattle, 


316  THE    CONSTITUENTS    OF    THE    BILE. 

glycocholic  acid  predominates;   in  carnivora,  the  sheep,  the  goat,  tauro- 
cholic  acid. 

(a)  Glycocholic  acid,  C26H43NO6,  is  decomposed  by  boiling  with  potas- 
sium or  barium  hydrate  or  with  dilute  mineral  acids,  and  by  taking 
up  water  splits  into — 

C2H5N02       +     C24H4005     =     C26H43N06      +      H2O 

Glycin  (glycocoll,    +       Cholalic  or        =     Glycocholic  Acid      -f-       Water, 
gelatin-sugar,  amido-  cholic  Acid 

acetic  acid) 

(b)  Taurocholic  acid,  C26H45NSO7,  decomposes  with  similar  treatment 
and  addition  of  water  into — 

C2H7NS03       +      C24H4005  C26H45NSO?      +      H2O 

Taurin  (amido-ethyl-  +        Cholic  Acid       =       Taurocholic  Acid      +       Water. 
sulphuric  acid,  pris- 
matic crystals) 

Demonstration  of  the  Biliary  Acids. — The  bile  is  evaporated  to  one-fourth  its  vol- 
ume, triturated  to  a  pasty  mass  with  animal  charcoal  to  remove  the  coloring- 
matter,  and  dried  at  100°  C.  The  black  mass  is  extracted  with  absolute  alcohol, 
which  passes  colorless  through  the  filter.  After  a  portion  of  the  alcohol  has  been 
driven  off  by  evaporation,  the  addition  of  an  excess  of  ether  causes  at  first  a 
resinoid  precipitate  of  salts  of  the  biliary  acids,  which  later  pass  over  into  a  crys- 
talline mass  of  brilliant  needles  (Platner's  crystallized  bile) .  The  alkaline  salts  of 
the  biliary  acids  obtained  in  this  way  are  readily  soluble  in  water  or  alcohol,  but 
are  insoluble  in  ether.  From  the  solution  of  both  salts  neutral  lead  acetate  pre- 
cipitates a  portion  of  the  glycocholic  acid  as  lead  glycocholate.  The  latter  is 
collected  on  a  filter,  dissolved  in  hot  alcohol,  and  lead  sulphid  is  precipitated  by 
hydrogen  sulphid.  After  removal  of  the  precipitate,  the  addition  of  water  causes 
separation  of  the  isolated  glycocholic  acid.  If,  after  precipitation  of  the  lead 
glycocholate,  basic  lead  acetate  is  added  to  the  filtrate,  a"  precipitate  of  lead 
taurocholate  forms,  uncontaminated,  however,  by  lead  glycocholate,  from  which 
the  free  acid  is  subsequently  obtained  by  analogous  treatment. 

According  to  Schotten  and  others,  human  bile  contains,  in  addition  to  cholic 
acid,  still  another  acid,  fellic  acid  (C2,HMO4) ;  the  bile  of  cattle  contains  cholic 
acid(C24H4005). 

Of  the  products  of  decomposition  of  the  biliary  acids,  glycin  does  not  occur 
as  such  in  the  body,  but  only  in  the  bile  in  combination  with  cholic  acid,  in  the 
urine  in  combination  with  benzoic  acid  as  hippuric  acid,  and  finally  in  gelatin 
in. complete  combination. 

Cholic  acid  is  dextrorotatory,  insoluble  in  water,  soluble  in  alcohol;  it  is 
soluble  with  difficulty  in  ether,  separating  out  in  prisms.  Its  crystalline  alkaline 
salts  are  readily  soluble  in  water,  like  soap.  With  iodin,  in  direct  light,  it  yields 
a  yellow,  in  transmitted  light  a  blue,  crystalline  combination.  It  occurs  free  only 
in  the  intestine. 

Cholic  acid  is  replaced  in  the  bile  of  some  animals  by  a  related  acid,  as, 
for  example,  in  the  bile  of  swine,  by  hyocholic  acid;  in  the  bile  of  geese,  chenocholic 
acid  is  present. 

By  boiling  with  concentrated  hydrochloric  acid  or  heating,  dry,  to  200°  C., 
cholic  acid  is  changed  into  an  anhydrid  dyslysin. 

Dyslysin  is  only  an  artificial  product  and  never  occurs  in  the  intestines.  When 
fused  with  potassium  hydrate,  it  is  changed  back  to  potassium  cholate. 

Pettenkofer's  Test. — The  biliary  acids,  the  cholic  acids  and  their  anhydrids, 
when  dissolved  or  broken  up  in  water,  and  on  addition  of  two-thirds  concentrated 
sulphuric  acid  (drop  by  drop,  without  permitting  the  temperature  of  the  fluid  to 
rise  above  70°  C.),  and  a  few  drops  of  a  10  per  cent,  solution  of  cane-sugar,  yield 
a  purplish-red  transparent  color,  which  shows  two  absorption-bands  in  the  spec- 
trum, at  E  and  F. 

Before  examining  a  solution  for  the  presence  of  biliary  acids,  the  albumin  must 
always  be  first  removed,  as  the  latter  yields  a  similar  reaction,  although  the  red 
solution  here  is  characterized  by  only  one  absorption-band.  If  only  small  amounts 
of  biliary  acids  are  present,  the  fluid  must  first  be  concentrated  by  evaporation. 
Cholesterin,  stearic  and  oleic  acids,  as  well  as  phenol  and  pyrocatechin,  exhibit 
a  similar  reaction.  Pettenkofer's  test,  therefore,  is  absolutely  reliable  only  when 


THE    CONSTITUENTS    OF    THE    BILE.  317 

the  salts  of  the  biliary  acids  in  alcoholic  extract  are  precipitated  and  thus  isolated. 
It  depends  on  the  production,  from  the  reaction  between  sugar  and  sulphuric 
acid,  of  furfurol,  which  is  stained  red  in  the  presence  of  the  biliary  acids.  Instead 
of  sugar  a  o.i  per  cent,  aqueous  solution  of  furfurol  may  be  employed  with  advan- 
tage for  this  reaction. 

The  biliary  acids  are  formed  in  the  liver,  as  extirpation  of  this  organ 
is  not  followed  by  their  accumulation  in  the  blood. 

The  manner  in  detail  in  which  the  production  of  the  nitrogenous  biliary  acids 
takes  place,  is  unknown,  although  they  are  supposed  to  result  from  albumin.  A 
generous  proteid  diet  increases  the  secretion  of  bile.  Taurin  contains  the  sulphur 
of  the  proteid;  the  biliary  acids  contain  from  4  to  6  per  cent,  of  sulphur.  Probably 
the  substance  of  the  red  blood-corpuscles  broken  up  in  the  liver  takes  part  in 
their  production. 

The  Biliary  Pigments. — Fresh  human  bile  and  that  of  some  animals 
is  yellowish  brown  in  color,  due  to  the  bilirubin  present  which  is 
combined  with  an  alkali.  Under  the  influence  of  oxygen,  heat  and 
light,  bilirubin  is  transformed  by  oxidation  into  a  green  pigment,  biliver- 
din.  This  predominates  in  the  bile  of  herbivora  and  of  cold-blooded 
animals,  and  likewise  often  in  the  state  of  hunger. 

(a)  Bilirubin,  C32H36N4O6,  from  0.15  to  0.25  percent,  in  human  bile, 
according  to  Stadeler  and  Maly  in  combination  with  an  alkali,  crys- 
tallizes in  transparent,  sorrel,  clinorhombic  prisms.  It  is  insoluble  in 
water,  but  soluble  in  chloroform,  by  means  of  which  it  can  be  separated 
from  biliverdin,  which  is  insoluble  in  chloroform.  It  combines  with 
alkalies  as  a  monobasic  acid  and  is  thus  soluble.  It  is  identical  with 
hematoidin. 

It  is  most  easily  prepared  from  red  gall-stones  formed  of  bilirubin  and  lime, 
which  are  triturated,  the  lime  being  dissolved  out  by  means  of  hydrochloric  acid. 
On  agitation  with  chloroform  the  bilirubin  is  taken  up.  The  derivation  of  bilirubin 
from  hemoglobin  is  not  to  be  doubted,  on  account  of  its  identity  with  hematoidin. 
Probably  red  blood-corptiscles  are  broken  up  in  the  liver,  and  their  hemoglobin  is 
converted  into  bilirubin. 

In  normal  bile  from  a  dog,  a  pigment  is  not  rarely  present  having  the  spectral 
properties  of  methemoglobin,  and  which  perhaps  represents  a  body  intermediate  be- 
tween the  hemoglobin  and  the  coloring-matter  of  the  bile. 

'  (b)  Biliverdin,  C32H36N4O8,  is  an  oxidation-stage  of  bilirubin,  from 
which  it  can  be  obtained  by  various  oxidizing  processes.  It  is  readily 
soluble  in  alcohol,  with  great  difficulty  in  ether,  and  not  at  all  in  chlo- 
roform. It  is  present  in  large  amount  in  the  placenta  of  the  dog. 
It  has  not  as  yet  been  possible  to  reconvert  it  into  bilirubin  by  means 
of  reducing  agents. 

Gmelin's  Test. — Bilirubin  and  biliverdin,  which,  in  addition  to  the  bile,  are 
occasionally  found  also  in  other  fluids,  at  times  in  the  urine,  are  demonstrated  by 
Gmelin's  test.  If  to  the  fluid  containing  the  substances  named  are  added  several 
cubic  centimeters  of  nitric  acid  and  one  drop  of  nitrous  acid,  which  are  permitted 
to  flow  carefully  from  the  edge  down  the  sides  of  a  conical  glass,  without  agitation, 
a  play  of  colors  results  as  follows:  green  (biliverdin),  blue,  violet,  red  and  yellow. 

(c)  If  the  addition  of  acid  is  stopped  when  the- color  becomes  1>lue.  thus  pre- 
venting further  oxidation,  a   stable  transformation-product  remains,  name' 
cyanin.       This  has  a  blue  color  in  acid  solution,  a  violet  color  in  alkaline  solution, 
and  it  exhibits  two  ill-defined  absorption-bands  at  D.     Haycraft  and   Schofield 
were  able  to  change  this  back  by  reduction  with  ammonium  sulphid. 

Fluids  containing  biliary  pigment,  if  boiled  for  from  three  to  five  minutes  with 
one-third  formalin,  acquire  an  emerald-green  color,  which  is  changed  to  amethyst 
violet  on  addition  of  hydrochloric  acid. 

(d)  Small  amounts  of  bilijuscin  (bilirubin  +  water)  have  also  been  found  in 
gall-stones  and  putrid  bile. 


318  THE    CONSTITUENTS    OF    THE    BILE. 

(e)  Biliprasin  (bilirubin  +  water  +  oxygen)  has  also  been  found  under  like 
conditions. 

(/)  The  yellow  pigment  finally  obtained  by  the  continued  oxidizing  effect  of 
the  nitric-acid  mixture  upon  all  of  the  biliary  pigments  is  the  choletelin  of  Maly, 
C16H18N2O6;  it  is  amorphous,  and  soluble  in  water,  alcohol,  acids  and  alkalies. 

(g)  With  addition  of  hydrogen  and  water  in  the  intestine  through 
the  agency  of  bacteria  bilirubin  passes  over  into  the  hydrobilirubin  of 
Maly,  C32H40N407.  The  same  result  can  be  brought  about  artificially  by 
treating  an  alkaline  aqueous  solution  of  bilirubin  with  actively  reducing 
sodium-amalgam.  Hydrobilirubin  is  but  slightly  soluble  in  water, 
more  readily  in  salt-solutions  or  alkalies,  alcohol,  ether  and  chloroform, 
and  it  exhibits  an  absorption-band  at  F.  This  body,  which,  according 
to  Hammarsten,  occurs  even  in  normal  bile,  is  a  constant  pigment  of 
the  feces,  from  which,  after  acidulation  with  sulphuric  acid,  it  can  be 
extracted  by  absolute  alcohol.  Probably  it  is  identical  with  the  pigment 
of  the  urine,  the  urobilin  of  JafTe.  Hydrobilirubin  is  formed  in  the 
intestine  from  ingested  bile,  being  in  part  absorbed  and  excreted  from 
the  portal  circulation  through  the  bile. 

Hydrobilirubin  to  which  a  drop  of  sulphuric  acid  and  some  potassium  nitrate 
are  added  again  yields  Gmelin's  reaction.  Fresh  fecal  matter,  broken  up  in  a 
porcelain  dish  in  a  concentrated  solution  of  mercuric  chlorid,  yields  a  red  color  as 
the  reaction  of  hydrobilirubin,  while  admixture  of  bilirubin  causes  a  green  color. 

Cholesterin  forms  transparent  rhomboid  plates  (Fig.  92,  d),  is  in- 
soluble in  water,  but  soluble  in  hot  alcohol,  in  ether  or  chloroform. 
In  the  bile  it  is  kept  in  solution  by  the  salts  of  the  biliary  acids.  Choles- 
terin is  not  a  secretory  product  of  the  liver,  but  a  product  of  the  disinte- 
gration of  the  epithelial  cells  of  the  biliary  passages. 

It  is  most  easily  obtained  from  the  so-called  white  gall-stones,  which  not 
rarely  consist  principally  of  almost  pure  cholesterin,  by  boiling  the  triturated  cal- 
culi with  alcohol.  The  crystals  that  separate  on  evaporation  of  the  alcohol 
become  red  in  color  from  the  edges  on  addition  of  sulphuric  acid  (five  volumes  to 
one  volume  of  water),  and  blue,  like  cellulose,  on  addition  of  sulphuric  acid  and 
iodin.  Dissolved  in  chloroform,  one  drop  of  concentrated  sulphuric  acid  produces 
a  deep-red  color.  Moistened  with  a  deep  wine-yellow,  alcoholic  solution  of  iodin, 
the  crystals  exhibit  green,  blue  and  red  coloration  after  addition  of  sulphuric  apid. 
Dissolved  in  glacial  acetic  acid,  addition  of  sulphuric  acid  produces  first  a  rose- 
red,  then  a  blue  color. 

Other  Organic  Substances. — Lecithin,  or  its  decomposition-products, 
neurin  and  glycerin-phosphoric  acid;  palmitin,  stearin,  olein,  as  well 
as  their  sodium-soaps;  .  diastatic  ferment;  traces  of  urea,  at  times 
ethereal  sulphuric  acids ;  acetic  and  propionic  acids  and  traces  of  myris- 
tinic  acid  in  the  bile  of  cattle. 

Fat  reaches  the  bile  from  the  liver  and,  conversely,  fat  is  in  turn  absorbed 
from  the  bile  in  the  biliary  passages  (epithelial  cells  of  the  gall-bladder).  Fresh 
unboiled  bile  decomposes  hydrogen  dioxid.  Bacteria  introduced  into  the  blood- 
stream are  in  part  eliminated  by  the  bile. 

The  inorganic  constituents  of  the  bile  (from  0.6  to  i  per  cent.)  include 
sodium  chlorid,  potassium  chlorid,  0.2  per  cent,  soda,  alkaline  sodium 
phosphate,  calcium  and  magnesium  phosphate,  and  an  abundance  of  iron. 
The  last  yields  the  usual  reactions  of  iron  even  in  fresh  bile,  so  that 
iron  must  be  present  in  the  bile  in  one  of  its  oxygen-combinations. 
Finally,  some  manganese  and  silica  are  present.  Freshly  secreted  bile 
from  the  dog  contains  more  than  50,  from  the  rabbit  109,  volumes  per 
cent,  of  carbon  dioxid,  in  part  combined  with  alkalies,  in  part  absorbed, 
the  latter  being  almost  completely  absorbed  within  the  bladder. 


SECRETION    OF    BILE. 


319 


Analysis  of  Human  Bile. — Water,  from  82  to  90  per  cent.,  salts  of  the  biliary 
acids,  from  6  to  n  per  cent.,  fats  and  soaps,  2  per  cent.;  cholesterin,  0.4  per  cent.; 
lecithin,  0.5  per  cent.;  mucin,  from  i  to  3  per  cent.;  ash,  0.6  per  cent.  The 
amount  of  sulphur  contained  in  dry  bile  from  a  dog  is  from  2.8  to  3.1  per  cent.;  the 
amount  of  nitrogen,  from  7  to  10  per  cent.  The  sulphur  of  the  bile  is  not  oxidized 
into  sulphuric  acid,  but  it  appears  in  sulphur-containing  compounds  in  the  urine. 

SECRETION  OF  BILE. 

The  secretion  of  bile  is  not  a  simple  nitration  of  already  prepared 
materials  from  the  blood  through  the  liver,  but  a  chemical  production, 
attended  with  oxidation,  of  the  characteristic  biliary  matters  in  the 
liver-cells,  which  exhibit  histological  change  during  the  process  of  diges- 
tion, and  to  which  the  blood  of  the  gland  only  supplies  the  raw  material. 
It  takes  place  continuously,  the  bile  being  in  part  temporarily  stored 
in  the  gall-bladder,  and  only  discharged  in  considerable  amount  at  the 
time  of  digestion.  The  higher  temperature  of  the  blood  in  the  hepatic 
veins,  as  well  as  the  large  amount  of  carbon  dioxid  in  the  bile,  indicates 
the  occurrence  of  oxidation-processes  in  the  liver.  Even  the  water  of 
the  bile  is  not  simply  filtered  out,  since  the  pressure  in  the  biliary  pas- 
sages may  exceed  that  in  the  portal  vein.  It  appears  that  the  bile  is 
derived  from  proteid  only,  and  that  the  excretion  of  carbon  dioxid  in 
the  act  of  respiration  bears  a  certain  relation  to  its  production.  In 
animals  (birds)  deprived  of  their  livers  the  constituents  of  the  bile  are 
not  produced. 

After  an  albuminous  diet  the  liver-cells  undergo  increase  in  size,  and  in  still 
greater  degree  after  administration  of  carbohydrates,  in  connection  with  which 
they  contain  glycogen ;  while  after  ingestion  of  fat  they  likewise  become  larger  and 
contain  fatty  granules,  principally  at  the  periphery  of  the  liver-lobules.  Irritation 
of  the  celiac  plexus  causes  reduction  in  the  size  of  the  cells,  with  deficiency  in 
glycogen,  and  it  appears  to  spur  them  on  to  secretion. 

The  experiments  of  Kallmeyer  and  Jul.  Klein,  performed  under  the  direction 
of  Alex.  Schmidt,  have  yielded  the  interesting  result  that  a  paste  of  fresh,  "sur- 
viving" liver-cells  produces  the  glycin  and  the  taurin  of  the  biliary  acids  from 
a  mixture  of  hemoglobin  (or  serum)  and  glycogen  (or  dextrose)  and  that  addition 
of  soda  or  0.6  per  cent,  sodium-chlorid  solution  favors  this  production.  In  addition 
to  this  production,  a  body  resembling  urea  is  formed.  It  is  now  established  that 
the  source  of  the  latter  is  to  be  referred  to  the  liver. 

Anthen,  under  Alex.  Schmidt's  direction,  found  that  ''surviving"  liver-cells 
possess  the  ability  to  take  up  dissolved  hemoglobin  in  their  cell-bodies,  and,  in 
the  presence  of  glycogen,  to  transform  this  into  a  pigment  closely  related  to  the 
biliary  coloring-matter. 

The  Amount  of  Bile. — Copemann  and  Winston  found  the  amount  of 
bile  to  be  from  700  to  800  cu.  cm.  in  twenty-four  hours,  in  a  small  woman 
with  a  biliary  fistula,  in  whom  the  common  bile-duct  was  completely 
closed,  so  that  no  bile  could  flow  into  the  intestine;  Mayo  Robson  found 
the  amount  to  be  862  cu.  cm.  in  a  similar  case;  Paton  found  it  to  be  as 
much  as  680  grams, with  2.2  per  cent,  solid  matter. 

Older  estimates  are:    533  cu.  cm.  by  v.  !Wittich  ;    from  453   to  566   grams 
by  Westphalen;    652  cu.  cm.  by  Ranke,  in  24  hours.     Analogous  estimates  for 
animals  are,  to  one  kilogram  of  dog  32   grams  (1.2  per  cent,  solid  matter) 
one  kilogram  of  rabbit  137  grams  (2.5  per  cent,  solid  matter);   t 
of  guinea-pig  176  grams  (5.2  per  cent,  solids). 

The  flow  of  bile  into  the  intestine  exhibits  two  maxima  during  a 
digestive  period,  one  from  the  second  to  the  fifth,  and  the  other  from 
the  thirteenth  to  the  fifteenth  hour  after  the  meal.  The  cause  resides 
in  reflex  stimulation  of  the  hepatic  vessels,  which  in  consequence  become 
greatly  distended  with  blood. 


320  SECRETION    OF    BILE. 

The  influence  of  the  food  is  most  striking.  The  most  abundant  secre- 
tion takes  place  after  free  ingestion  of  meat ;  on  addition  of  fat  or  carbo- 
hydrates scarcely  any  more  is  formed.  In  a  state  of  hunger  the  quantity 
is  reduced  from  one-third  to  one-half,  and  even  more  with  a  pure  fat-diet. 
The  ingestion  of  water  increases  the  amount,  with  simultaneous  relative 
reduction  in  the  solid  constituents. 

The  influence  of  the  circulation.  The  portal  vein  furnishes  especially 
the  material  for  the  production  of  the  bile,  and  in  greater  degree  than  the 
hepatic  artery.  The  latter  is  at  the  same  time  the  nutrient  vessel  of 
the  tissues  of  the  liver.  This  is  shown  by  the  following  observations : 

(a)  Simultaneous  ligation  of  the  hepatic  artery  (diameter,   5^  mm.)   and  of 
the  portal  vein  (diameter,  16  mm.)  abolishes  the  secretion  of  bile. 

(b)  If  the  hepatic  artery  is  ligated,  the  portal  vein  alone  maintains  the  secre- 
tion.    According  to  Kottmeier,  Betz,  Cohnheim  and  Litten,  ligation  of  the  artery 
or  of  one  of  its  branches  is  said,  further,  to  result  in  necrosis  of  the  parts  supplied, 
and  possibly  of  the  entire  liver,  as  the  artery  is  the  nutrient  vessel  of  this  organ. 
After  ligation  of   the   artery  the   production  of  urea   diminishes  greatly;    while 
after  ligation  of  the  portal  vein  this  is  said  to  remain  almost  normal. 

(c)  If  the  branch  of  the  portal  vein  for  a  lobule  of  the  liver  is  ligated,  only 
slight  secretion  takes  place  in  this  lobule  through  the  agency  of  the  artery. 

Thus  neither  exclusive  ligation  of  the  hepatic  artery  nor  exclusive  gradual 
obliteration  of  the  portal  vein  (rarely  observed  as  a  morbid  condition)  results  in 
cessation  of  the  secretion.  Only  diminution  in  the  secretion  takes  place.  The 
observation  that  the  secretion  ceases  after  sudden  ligation  of  the  portal  vein 
(which,  besides,  is  rapidly  fatal)  is  to  be  explained  by  the  fact  that,  in  addition 
to  the  diminution  in  the  secretion,  the  enormous  blood-stasis  in  the  abdominal 
viscera  after  this  operation  makes  the  liver  intensely  anemic  and  therefore  unsuited 
for  secretion. 

(d)  If  the  blood  of  the  hepatic  artery  is  introduced  directly  into  the  lumen 
of  the  opened  portal  vein,  ligated  peripherally,  the  secretion  continues. 

(e)  The  passage  as  rapidly  as  possible  of  large  amounts  of  blood  through 
the  liver  acts  most  favorably  upon  the  secretion.     In  this  connection  the  pre- 
vailing blood-pressure  is  not  of  primary  importance,  for  after  ligation  of  the  in- 
ferior cava  above  the  diaphragm,  in  consequence  of  which  the  highest  degree  of 
blood-pressure  due  to  stasis  develops,  the  secretion  ceases.     The  transfusion  of 
considerable  quantities  of  blood  always  increases  the  production  of  bile,  although 
excessive  pressure  in  the  portal  vein,  from  the  introduction  of  blood  from  the 
carotid  artery  of  another  animal  restricts  the  production. 

(f)  Profuse  loss  of  blood  has  a  tendency  to  cause  cessation  of  bile-production 
before  the  function  of  the  muscular  and  nervous  apparatus  is  abolished.     A  more 
abundant  blood-supply  to  other  organs,  as,  for  example,  to  the  muscles  of  the 
body  engaged  in  hard  labor,  diminishes  the  secretion. 

(g)  The   influence  of  the  nerves.     All  procedures  that   cause   contraction   of 
the  arteries  of  the  abdomen,  such  as  irritation  of  the  valve  of  Vieussens,  of  the 
inferior  cervical  ganglion,  the  hepatic  nerves  the  splanchnic  nerve,  the  spinal 
cord,  whether  directly,  as  by  strychnin,  or  reflexly,  by  irritation  of  the  sensory 
nerves,  diminish  the  secretion.    All  procedures  that  induce  stagnation  of  blood  in  the 
hepatic  vessels,  such  as  division  of  the  splanchnic  nerves,  diabetic  puncture,  divi- 
sion of  the  cervical  cord,  have  a  like  effect.     Paralysis   (ligation)  of  the  hepatic 
nerves  is  said  at  first  to  increase  the  secretion  of  bile,  with  reddening  of  the  liver. 

(h)  With  regard  to  the  raw  material  brought  to  the  liver  by  the  blood-vessels 
for  the  production  of  bile,  the  difference  in  the  composition  of  the  blood  in  the 
hepatic  veins  and  that  in  the  portal  vein  is  noteworthy.  The  blood  in  the  hepatic 
veins  contains  somewhat  more  sugar,  lecithin,  cholesterin,  and  blood-corpuscles, 
but,  on  the  contrary,  it  is  deficient  in  albumin,  fibrin,  hemoglobin,  fat,  water  and 
salts.  The  liver  is  capable  of  excreting  unchanged  in  the  bile  biliary  pigments 
circulating  in  the  blood. 

The  production  of  bile  is  dependent  preeminently  upon  the  trans- 
formation of  the  red  blood-corpuscles,  as  they  furnish  the  material  for 
the  formation  of  some  of  the  constituents. 


EXCRETION    OF    BILE.  321 

All  procedures,  therefore,  that  induce  increased  destruction  of  red  blood- 
corpuscles  make  the  liver  rich  in  hemoglobin  and,  as  a  result,  cause  increased 
production  of  bile,  also  pathologically,  as,  for  example,  in  the  presence  of  malaria 
and  blood-degenerations. 

Naturally,  a  normal  condition  of  the  liver-cells  is  necessary  for 
normal  secretion. 

For  observing  the  secretion  of  bile  in  animals,  a  biliary  fistula  is  established, 
the  fundus  of  the  gall-bladder  being  opened  somewhat  to  the  right  of  the  xiphoid 
process,  and  then  being  sutured  into  the  abdominal  wall,  with  the  aid  of  a  cannula 
kept  constantly  open.  As  a  rule,  all  of  the  bile  will  then  be  discharged  externally. 
If  absolute  certainty  in  the  latter  connection  be  desired,  the  common  bile-duct 
should  be  ligated  in  two  places  and  divided.  Soon  after  the  establishment  of  a  fis- 
tula, the  secretion  of  bile  diminishes.  This  is  dependent  upon  the  removal  of 
the  bile  from  the  body.  Introduction  of  bile  in  the  body  from  some  other  source 
again  increases  the  secretion.  Various  investigators  have  been  able  to  observe 
directly  biliary  fistulas  developed  pathologically  in  human  beings.  In  dogs 
regeneration  of  the  divided  bile-duct  may  take  place. 

EXCRETION  OF  BILE. 

This  takes  place : 

1.  Through  the  constant  advance  of  fresh  amounts  of  bile  from  the 
seat  of  production  toward  the  excretory  ducts. 

2.  Through  the  periodic  compression  of  the  liver  by  the  diaphragm 
from  above,  with  each  inspiration.     In  addition,  each  inspiration  accel- 
erates the  blood-current  in  the  hepatic  veins ;  each  respiratory  increase  in 
abdominal  pressure  hastens  the  blood-current  in  the  portal  vein. 

Whether  the  diminution  in  the  secretion  of  bile  following  bilateral  division 
of  the  pneumogastric  nerves  is  to  be  explained  in  this  manner  has  been  decided 
in  the  affirmative.  Nevertheless  it  is  to  be  borne  in  mind  that  the  pneumogastric 
nerve  sends  branches  to  the  hepatic  plexus.  Whether  the  excretion  of  bile  is 
also  decreased  after  paralysis  of  the  phrenic  nerves  and  relaxation  of  the  abdom- 
inal pressure  is  undetermined. 

3.  By  the  peristaltic  contraction,  every  fifteen  or  twenty  seconds,  of 
the  unstriped  muscle-fibers  of  the  large  biliary  ducts  and  the  gall-bladder, 
the  secretion  is  forced  onward.     Stimulation  of  the  region  of  the  spinal 
cord,  from  which  the  motor  nerves  for  these  structures   are   derived 
(through  the  splanchnic  nerves),  for  this  reason  induces   acceleration 
of  the  discharge,  which  is  later  followed  by  retardation.     Under  normal 
circumstances  this  stimulation  appears  to  be  due  to  reflex  action,  ex- 
cited by  the  entrance  of  the  ingesta  into  the  duodenum,  in  conjunc- 
tion with  stimulation  of  the  movement  of  this  portion  of  the  intestine. 

The  movement  of  the  biliary  ducts  can  be  in  part  excited,  in  part  inhibited 
reflexly  by  stimulation  of  the  central  end  of  the  pneumogastric  or  of  the  sciatic 
nerve.  According  to  Oddi,  the  common  bile-duct  is  provided  with  a  sphincter 
at  its  duodenal  orifice,  which  is  affected  by  reflex  influences:  gastro-intestinal 
irritation  is  believed  to  cause  spastic  contraction,  which  would  not  be  unimportant 
in  the  explanation  of  attacks  of  jaundice  of  nervous  origin. 

4.  Direct  stimulation  of  the  liver  or  reflex  stimulation  of  the  spinal 
cord  retards  the  excretion.     On  the  other  hand,  extirpation  of  the  hepatic 
plexus,  as  well  as  injury  to  the  floor  of  the  fourth  ventricle,  has  no  dis- 
turbing influence.     The  splanchnic  nerve  is  the  motor  nerve  of  the  bile- 
ducts  and  the  gall-bladder.     Stimulation  of  its  central  extremity  causes 
relaxation  of  ducts  and  bladder,  while  stimulation  of  the  central  end  of 
the  pneumogastric  nerve  causes  their  contraction,  together  with  relaxa- 
tion of  the  sphincter  of  the  duodenal  orifice. 


322  RESORPTION    OF    BILE. 

5.  Stasis  of  bile  occurs  in  the  bile-ducts  even  from  relatively  slight 
resistance. 

A  manometer  fastened  in  the  gall-bladder  of  a  guinea-pig  balanced  a  column 
of  water  more  than  200  mm.  high.  Up  to  this  pressure,  therefore,  secretion 
took  place.  If  this  pressure  were  increased  or  maintained  for  an  excessively 
long  time,  absorption  of  the  water  of  the  bile  into  the  blood  took  place  on  the  part 
of  the  liver,  up  to  about  four  times  the  weight  of  the  liver,  as  a  result  of  which 
solution  of  red  blood-corpuscles  by  the  bile  absorbed  took  place  at  the  same  time, 
with  the  passage  of  hemoglobin  into  the  urine. 

Various  substances  that  enter  the  circulation  readily  pass  over  into  the  bile, 
particularly  the  metals,  which  are  also  deposited  in  the  hepatic  tissue.  Further, 
potassium  iodid,  bromid,  and  ferrocyanid,  potassium  chlorate,  arsenic,  oil  of 
turpentine,  bile  injected  into  the  blood  (also  that  from  other  animals),  indigo- 
carmine  and  xanthophyllin  pass  over;  less  readily,  cane-sugar  and  grape-sugar, 
sodium  salicylate  and  carbolic  acid.  Sugar  has  been  found  in  cases  of  diabetes, 
leucin  and  tyrosin  in  cases  of  typhoid  fever,  altered  hemoglobin  in  the  presence 
of  blood-degeneration,  lactic  acid  and  albumin  under  other  pathological  con- 
ditions. 

Some  substances  promote  the  secretion  of  bile,  olive-oil  most  intensely; 
further,  oil  of  turpentine,  sodium  salicylate,  alkalies  and  laxatives,  bile  and  salts 
of  the  biliary  acids  (particularly  from  other  species  of  animals),  which,  after  ab- 
sorption, are  again  secreted  by  the  liver.  Pilocarpin  and  atropin  diminish  the 
secretion.  The  so-called  lymphagogues  induce  marked  secretion  of  bile  in  conse- 
quence of  increased  hepatic  activity;  the  increase  of  lymph,  on  the  part  of  the 
liver,  is  thought  to  depend  upon  the  latter. 

RESORPTION  OF  BILE. 

Symptoms  of  Jaundice  (Icterus;  Cholemia). — If  an  obstruction  occurs  to  the  dis- 
charge of  bile  into  the  intestine, — as,  for  example,  a  plug  of  mucus  or  a  gall-stone 
occluding  the  common  bile-duct,  or  a  tumor  or  pressure  from  without,  rendering 
the  duct  impervious, — the  biliary  passages  become  distended,  and,  through  their 
distention,  cause  enlargement  of  the  liver.  The  pressure  in  the  biliary  passages 
is  naturally  increased  under  such  conditions.  As  soon  as  this  pressure  has  reached 
a  certain  point,  in  the  dog  up  to  275  mm.  of  a  column  of  the  excreted  bile — as 
must  soon  take  place  with  the  continued  production  of  bile — resorption  of  the 
bile  from  the  greatly  distended  bile-ducts  of  larger  size  into  the  lymph-vessels 
(not  into  the  blood-vessels)  of  the  liver  occurs.  In  this  way  the  biliary  acids 
and  the  biliary  coloring-matter  enter  the  blood.  Ligation  of  the  thoracic  duct 
therefore  prevents  the  entrance  of  the  substances  into  the  blood.  Also  when 
the  pressure  within  the  portal  vein  is  abnormally  low,  it  is  thought  that  bile  can 
pass  over  into  the  blood  without  occlusion  of  the  bile-ducts.  This  is  said  to 
be  partly  the  case  in  the  presence  of  icterus  neonatorum,  as  blood  no  longer 
enters  the  portal  vein  from  the  umbilical  vein  after  the  umbilical  cord  has  been 
tied;  further,  in  the  presence  of  the  "  hunger  -  icterus "  observed  during  the 
state  of  hunger,  as  in  the  stage  of  inanition,  the  distribution  of  the  portal  vein  is 
relatively  empty,  on  account  of  deficient  absorption  from  the  intestine. 

Cholemia  may,  however,  result  also  from  the  excessive  production  of  bile 
(hypercholia) ,  which  cannot  be  completely  discharged  into  the  intestine,  and 
thus  is  resorbed.  This  takes  place  when  erythrocytes,  which  furnish  the  material 
for  the  manufacture  of  the  bile,  are  destroyed  in  excessive  amount.  From  this 
material  only  the  liver  can  elaborate  bile.  Under  such  circumstances  a  plug 
of  inspissated  secretion  at  times  forms  in  the  bile-ducts,  as  a  result  of  which, 
in  consequence  of  the  stagnation  of  the  bile,  its  resorption  is  in  turn  favored.  The 
transfusion  of  heterogeneous  blood  acts  in  this  way,  in  consequence  of  destruction 
of  the  red  blood-corpuscles.  Therefore  icterus  is  a  frequent  symptom  under 
such  conditions.  The  author  has  encountered  the  same  phenomenon  after  excessive 
transfusion  of  blood  from  the  same  species,  the  blood  being  in  part  likewise  dis- 
solved later.  Such  a  solvent  effect  upon  the  erythrocytes  is  exerted  also  by  the 
injection  of  some  heterogeneous  sera,  of  salts  of  the  biliary  acids,  of  water,  of  vari- 
ous acids,  as,  for  example,  phosphoric  acid,  and  by  the  administration  of  large 
amounts  of  chloral,  chloroform,  and  ether.  Further,  injections  of  hemoglobin  in 
solution  into  the  blood-stream  or  into  the  intestine,  from  which  it  is  absorbed, 
have  the  same  effect.  (The  subject  is  further  considered  on  p.  34 1 .) 


RESORPTION    OF    BILE.  323 

If,  as  a  result  of  compression  of  the  placenta  in  the  uterus,  too  much  blood 
has  been  carried  to  the  new-born  infant,  a  portion  of  this  excess  of  blood  in  the 
body  may  be  dissolved  during  the  first  days  of  life,  the  hemoglobin  being  trans- 
formed into  bilirubin,  with  symptoms  of  icterus.  Under  such  circumstances 
also  there  is  excessive  destruction  of  erythrocytes,  as,  indeed,  of  all  of  the  tissues, 
because  in  the  new-born  infant,  with  insufficient  nourishment  the  metabolic 
processes  must  be  more  active  for  the  maintenance  of  respiration,  heat-production 
and  digestive  activity. 

The  jaundice  that  is  exemplified  by  the  foregoing  symptoms  is  also  designated 
hepatogenic,  or  resorption-icterus,  because  it  is  due  to  the  absorption  of  bile 
already  prepared  in  the  liver. 

Cholemia  is  accompanied  by  a  series  of  characteristic  symptoms: 

1.  Biliary  coloring-matter' and   the   biliary   acids   enter  into   the   tissues   of 
the  body,   giving  rise   to  the  most    striking  objective  symptom  (and  therefore 
designated  also  jaundice).     The  external  integument,  particularly  the  sclera,  ac- 
quires an  exquisitely  yellow  color.     In  pregnant  women  the  fetus  also  is  discolored. 
Hematoidin-crystals  have  been  found  in  the  kidneys,  the  blood  and  the  fatty  tis- 
sue of  icteric  children.     In  exceptionally  rare  cases,  as  in  the  presence  of  hemi- 
plegia,  only  one-half  of  the  body  has  been  found  jaundiced. 

2.  The  biliary  acids  and  the  biliary  coloring-matters  appear  in  the  urine, 
though  not  in  the  saliva,  the  tears  or  in  mucus.     When  the  coloring-matter  is 
present  in  large  amount  the  urine  acquires  a  deep  yellowish-brown  color,  while 
its  foam  is  intensely  lemon-yellow.     Immersed  strips  of  paper  or  linen  are  stained 
the  same  color.     Occasionally  crystals  of  bilirubin  are  present. 

3.  The  feces  become  clay-colored,  because  of  the  absence  of  hydrobilirubin 
derived  from  the  bile-pigment;    extremely  hard,  because  the  diluting  bile  does 
not   reach  the  intestine;    rich  in  fat,   because   the   fats,   particularly  the  more 
solid,  are  not  sufficiently  digested  in  the  intestine  in  the  absence  of  bile  (so  that 
even  as  much  as  78  per  cent,  of  the  fat  ingested  passes  out  in  the  feces;  principally 
fatty  acids  and  soaps  appear  in  the  feces,  and  but  little  neutral  fats) ;    and  highly 
offensive,  because,  under  normal  conditions,  the  bile  poured  out  into  the  intestine 
inhibits   putrid   decomposition    of   the   intestinal   contents.     The   evacuation   of 
the  feces  takes  place  sluggishly,  partly  on  account  of  their  hardness,  partly  because 
of  the  absence   of  bile,  which  excites  peristaltic  movements  in  the  intestines. 

4.  The  heart-beats  are  reduced  to  about  40  in  the  minute.     This  is  due  to 
the  salts  of  the  biliary  acids,  which  at  first  stimulate  the  heart  and  then  enfeeble 
it.     Injection  of  the  salts  of  the  biliary  acids  into  the  heart  causes,  therefore, 
at  first,  transitory  increase  in  the  heart-beats,  followed  by  slowing.     The  same 
result  is  brought  about  if  these  substances  are  injected  directly  into  the  blood, 
although  under  such  circumstances  the  brief  stage  of  stimulation  is  much  less 
marked.     Division  of  the  pneumogastric  nerve  has  no  influence  on  this  phenom- 
enon.    In  addition  to  the  action  on   the   heart,  there  is  marked  dilatation  of 
the  smallest  blood-vessels,  slowing  of  the  respiration  and  lowering  of  the  tem- 
perature. 

5.  An  influence  on  the  nervous  system,  either  through  the  salts  of  the  biliary 
acids  or  through  the  cholesterin  accumulated  in  the  blood,  perhaps  also  upon 
the  muscles,  is  shown  by  the  great  general  relaxation,  fatigue,  weakness  and 
somnolence,  finally  deep  coma;    at  times  by  insomnia,  pruritus,  even  delirium 
and  convulsions.     In  experiments  on  animals  Lowit  observed  symptoms,   after 
injections  of  bile,  indicative  of  stimulation  of  the  respiratory,  cardio-inhibitory 
and  vasomotor  centers.     Direct  application  of  bile  or  its  salts  to  the  cerebrum 
causes  convulsions. 

6.  Jaundice  of  marked  degree  is  attended  with  yellow  vision,  in  consequence 
of  impregnation  of  the  retina  with  yellow  biliary  coloring-matter. 

7.  The  biliary  acids  in  the  blood  dissolve  the  erythrocytes,  and  this  leads 
to  the  further  formation  of  bile.     The  dissolved  hemoglobin  is  transformed  into 
new  bile-pigment,  while  the  globulin-body  of  the  disintegrated  hemoglobin  mav 
form  casts  in  the  renal  tubules,  which  later  are  washed  into  the  urine.     Should 
dissolution  not  take  place,  the  erythrocytes  become  swollen  and  exhibit  increased 
solubility. 

After  ligation  of  the  bile-duct,  the  protoplasm  of  the  liver-cells  disappears, 
and  according  to  some  observers  partial  necrosis  of  the  hepatic  tissue  occurs,  with 
secondary  reactive  inflammation,  connective-tissue  hyperplasia.  cell-multiplica- 
tion of  the  epithelial  cells  of  the  biliary  passages.  The  stagnating  bile  diminishes 
in  amount  and  exhibits  further  an  increase  of  mucus  and  cholestenn,  but  on 
the  other  hand  a  reduction  in  taurocholic  acid  (in  the  dog)- 


324  ACTION    OF    THE    BILE. 


ACTION  OF  THE  BILE. 

The  bile  is  a  metabolic  product  largely  destined  for  excretion,  and 
participating  in  but  small  measure  in  the  digestive  process. 

Bile  plays  an  important  part  in  the  absorption  of  fat.  It  forms  a 
fine  emulsion  of  the  neutral  fats,  in  consequence  of  which  the  fatty 
granules,  in  addition  to  chemical  division,  are  especially  rendered  capa- 
ble of  passing  through  the  cylindrical  epithelium  of  the  small  intes- 
tine. It  does  not  effect  the  chemical  decomposition  of  the  neutral  fats 
into  glycerin  and  fatty  acids,  as  does  the  pancreatic  juice,  but  it  is  capable 
of  dissolving  the  fatty  acids  through  the  salts  of  the  biliary  acids. 

The  soaps  present  in  the  intestine  are  soluble  in  the  bile  and  are  capable 

in  turn  of  greatly  increasing  the  emulsifying  power  of  the  bile.     The  bile  itself, 

however,  is  capable  of  converting  the  fatty  acids  directly  into  an  acid  solution 
that  exerts  an  active  emulsifying  influence. 

As  the  bile,  like  a  soap  solution,  bears  a  certain  relation  to  aqueous 
fluids  as  well  as  to  fats,  it  may  conduce  to  diffusion  between  the  two,  as 
the  membrane  can  be  moistened  and  can  imbibe  both  fluids. 

From  the  foregoing  it  follows  that  the  bile  is  of  great  importance  for  the 
preparation  and  absorption  of  fats.  This  can  also  be  demonstrated  by  experi- 
ments on  animals,  in  which  the  bile  is  entirely  conveyed  externally  through 
a  fistula.  Dogs  thus  treated  absorb,  at  the  most,  40  per  cent,  of  the  fat  ingested, 
while  normal  dogs  absorb  99  per  cent.  The  chyle  of  such  animals  is,  accord- 
ingly, deficient  in  fat,  and  is  not  white,  but  transparent.  The  feces,  however, 
contain  more  fat  and  are  greasy.  The  animals  eat  greedily;  the  tissues  of  the 
body  show  great  deficiency  of  fat,  even  when  the  nutrition  in  general  has  not 
suffered  much.  In  human  beings  suffering  from  derangement  in  the  secretion 
of  bile,  a  diet  rich  in  fat  is,  for  this  reason,  contraindicated. 

Fresh  bile  contains  some  diastatic  ferment,  as  starch  and  glycogen 
are  converted  into  sugar. 

This  ferment  is,  however,  absorbed  from  the  walls  of  the  alimentary  canal 
and  is  then  excreted  as  ptyalin  by  the  bile,  as  by  the  urine  also. 

The  bile  acts  as  a  stimulant  to  the  intestinal  musculature  and 
thus  contributes  to  absorption  in  general. 

Perhaps  through  its  biliary  acids,  acting  as  irritants,  it  causes  the  muscles 
of  the  intestinal  villi  to  contract  from  time  to  time,  in  consequence  of  which 
these  propel  the  contents  of  their  lymph-spaces  into  the  larger  lymph-trunks, 
and  thus  are  capable  of  absorbing  renewed  amounts. 

Also  the  musculature  of  the  intestinal  wall  itself  appears  to  undergo  excita- 
tion, probably  through  the  agency  of  the  myenteric  plexus.  In  favor  of  this 
view  is  the  fact  that  intestinal  peristalsis  is  greatly  impaired  in  animals  with  biliary 
fistulas  and  in  the  presence  of  obstruction  of  the  biliary  passages,  as  well  as  the 
fact  that  the  salts  of  the  biliary  acids,  administered  by  the  mouth,  cause  diarrhea 
and  vomiting.  As,  however,  intestinal  contractions  aid  absorption,  the  bile  is,  in 
this  connection  also,  active  in  taking  up  the  dissolved  food. 

The  presence  of  bile  is  necessary  for  the  normal  vital  activity  of 
the  intestinal  epithelium  in  the  absorption  of  the  fatty  globules. 

Through  its  excretion  the  bile  supplies  a  sufficient  amount  of  water 
for  the  feces.  Animals  with  biliary  fistulae  and  human  beings  with 
obstructed  biliary  passages  are  markedly  constipated.  Besides,  the 
slippery  mucus  of  the  bile  facilitates  the  advance  of  the  ingesta  through 
the  intestinal  canal. 


FINAL    FATE    OF    THE    BILE    IN    THE    INTESTINAL    CANAL.  325 

The  bile  diminishes  putrefactive  decomposition  of  the  intestinal  con- 
tents, especially  with  a  fatty  diet. 

On  the  entrance  of  the  strongly  acid  gastric  contents  into  the  duo- 
denum, the  glycocholic  acid  is  precipitated  by  the  acid  of  the  stomach  and 
carries  the  pepsin  with  it.  Further,  the  albumin  and  the  gelatin,  still 
in  solution,  but  not  the  peptones  and  propeptones,  are  precipitated  by 
the  taurocholic  acid,  salts  of  the  biliary  acids  having  already  been  de- 
composed by  the  acid  of  the  stomach.  If,  however,  the  mixture  is 
again  rendered  alkaline  by  the  pancreatic  and  the  intestinal  juice  and 
the  alkali  of  the  bases  derived  from  the  salts  of  the  biliary  acids,  the 
pancreatic  ferments  enter  energetically  into  action. 

If  bile  enters  the  stomach,  as,  for  instance,  in  the  act  of  vomiting,  the  acid  of 
the  gastric  juice  combines  with  the  bases  of  the  salts  of  the  biliary  acids.  There 
thus  results  principally  sodium  chlorid  and  free  biliary  acids.  At  the  same  time 
the  acid  reaction  is  diminished.  The  biliary  acids  are  not  effective  as  acids 
in  gastric  digestion,  in  place  of  the  combined  hydrochloric  acid,  the  neutralization 
causing  also  precipitation  of  the  pepsin  and  the  mucin.  As  soon,  however,  as  the 
wall  of  the  stomach  secretes  additional  acid,  the  pepsin  is  again  dissolved.  The 
bile  entering  the  stomach  has  a  disturbing  effect  on  gastric  digestion  also,  by 
causing  contraction  of  the  albuminates,  as  these  can  be  peptonized  only  when 
swollen. 

FINAL  FATE  OF  THE  BILE  IN  THE  INTESTINAL  CANAL. 

Of  the  constituents  of  bile,  some  are  evacuated  with  the  feces,  while 
others  are  again  absorbed  through  the  intestinal  walls. 

The  mucin  passes  into  the  feces  unchanged. 

The  biliary  coloring-matters  are  mostly  reduced  in  the  large  in- 
testine and  are  partly  evacuated  with  the  feces  as  hydrobilirubin ;  a 
small  portion  of  them  is  absorbed  and  finds  its  way  into  the  urine  as 
urobilin.  The  reduction  may  proceed  beyond  the  formation  of  hydro- 
bilirubin to  that  of  a  colorless  material,  which  may,  however,  upon  ad- 
mission of  oxygen,  be  again  oxidized  to  hydrobilirubin. 

Hydrobilirubin  is  absent  from  meconium,  but  bilirubin  and  biliverdin  are 
present  together  with  an  unknown  red  oxidation-product  derived  from  them. 
Therefore  the  process  that  takes  place  in  the  fetal  intestine  is  not  a  reducing 
but  an  oxidizing  one. 

Cholesterin  is  in  part  evacuated  with  the  feces;  in  part  it  is  re- 
duced to  the  form  of  hydrocholesterin  (coprosterin),  crystallizing  in 
needles. 

The  biliary  acids  are,  for  the  most  part,  again  absorbed  through  the 
walls  of  the  jejunum  and  the  ileum,  and  are  utilized  anew  in  the  pro- 
duction of  bile.  Tappeiner  found  them  in  the  thoracic  duct;  small 
amounts  find  their  way  from  the  blood  into  the  urine.  Only  a  small 
portion  of  glycocholic  acid  appears  unchanged  in  the  feces.  Taurocholic 
acid,  in  so  far  as  it  is  not  absorbed,  is  readily  decomposed  in  the  intestine 
by  putrefactive  processes  into  cholic  acid  and  taurin.  The  former  is 
found  in  the  feces,  the  latter  is  not  infrequently  absent.  Cholic  acid 
is,  however,  in  part  resorbed  and  may  again  unite  in  the  liver  with 
glycin  or  taurin. 

As  putrefactive  decomposition  is  absent  from  the  fetal  intestine,  unchanged 
taurocholic    acid   is    accordingly    present    in    the    meconium      Grlycocholic    acid, 
when   administered,  is  found   again  in   the  bile  from   animals  (< 
mally  excrete  but  little  thereof. 

The  feces  certainly  contain  merely  traces  of  lecithin. 


326  THE    INTESTINAL    JUICE. 

As,  therefore,  the  largest  part  of  the  biliary  acids  is  returned  to  the  blood, 
it  is  clear  that  animals  from  which  all  the  bile  is  lost  through  a  biliary  fistula, 
without  their  licking  it  up,  lose  considerably  in  weight.  This  is  due  partly  to 
the  impaired  digestion  of  fat,  in  part  to  the  direct  loss  of  the  biliary  acids.  If 
dogs  are  nevertheless  to  maintain  the  same  weight,  they  must  consume  almost 
double  their  former  nourishment.  Under  such  conditions,  carbohydrates  are 
especially  serviceable  as  a  substitute  for  fat  in  the  diet.  If  their  digestive  ap- 
paratus is  in  other  respects  intact,  the  animals  may,  by  reason  of  their  voracity, 
even  gain  in  weight.  Under  such  circumstances,  however,  it  is  the  muscles 
almost  alone  and  not  the  fat  that  is  increased. 

The  fact  that  bile  is  secreted  during  fetal  life,  while  none  of  the 
other  digestive  fluids  are  produced,  indicates  that  the  bile  is  in  part  a 
product  of  retrogressive  tissue-metamorphosis,  and  is  intended  for  the 
constant  elimination  of  certain  excrementitious  matters. 

The  cholic  acid,  which  is  absorbed  through  the  intestinal  wall,  is  finally 
burned  up  in  the  body  into  carbon  dioxid  and  water.  The  glycin  gives  rise  to 
the  production  of  urea,  as  well  as  hippuric  acid,  as,  after  the  ingestion  of  that 
substance,  the  amount  of  urea  is  greatly  increased.  The  fate  of  the  taurin  is 
not  known.  Considerable  amounts  administered  to  human  beings  by  the  stomach 
appear 'again  in  the  urine  principally  as  taurocarbamic  acid,  together  with  a  small 
amount  of  unchanged  taurin.  When  injected  subcutaneously  into  a  rabbit,  it 
almost  all  appears  in  the  urine. 

THE  INTESTINAL  JUICE. 

The  human  intestine  is  ten  times  as  long  as  the  length  of  the  body  from  the 
vertex  to  the  anus.  In  this  it  resembles  that  of  fructivorous  apes.  It  is  relatively 
longer  than  that  of  omnivora.  Its  minimum  length  is  507  cm.;  its  maximum 
length,  1149  cm.  Its  capacity  is  relatively  greatest  in  children,  in  whom  also 
it  is  relatively  longer.  The  intestine  is  somewhat  longer  in  males  than  in  females. 

The  intestinal  juice  is  the  digestive  fluid  secreted  by  the  numerous 
glands  of  the  intestinal  mucous  membrane.  The  largest  amount  is  fur- 
nished by  Lieberkuhn's  glands;  the  duodenum  receives,  besides,  the 
scanty  secretion  of  the  compound  alveolar  grands  of  Brunner. 

B runner's  glands,  which  occur  singly  in  human  beings,  but  in  the  sheep 
constitute  a  continuous  layer  in  the  duodenum,  are  present,  in  part,  at  the 
pylorus.  Their  cylindrical  cells  have  a  middle,  darker  zone';  the  flat  nucleus 
lies  near  the  base  of  the  cell,  with  a  diplosome  nearer  its  free  surface.  During 
the  state  of  hunger,  the  cells  are  turbid  and  small,  and,  like  the  pyloric  glands 
of  the  stomach,  they  contain  fatty  granules,  while  during  digestive  activity 
they  are  large  and  clear.  The  glands  contain  nerve-filaments  from  Meissner's 
plexus  in  the  mucous  membrane. 

The  Secretion  of  Brunner' s  Glands. — The  usually  granular  contents 
of  the  secretory  cells  consist,  in  addition  to  albuminous  materials,  of 
mucin  and  ferment-substances  of  unknown  nature.  It  is  not  improbable 
that  these  glands  are  related  to  the  pancreas,  and  perhaps  are  even  to  be 
regarded  as  detached  portions  of  the  pancreas.  Their  activity  seems  to 
favor  this  view.  An  aqueous  extract  (i)  dissolves  albumin  slowly 
and  feebly,  at  the  temperature  of  the  body.  (2)  It  possesses  diastatic 
activity.  The  secretion  appears  to  have  no  effect  on  fats. 

It  should  be  especially  emphasized  that,  as  on  account  of  the  small  size 
of  the  glands  they  must  be  viewed  individually,  \vith  a  magnifying  glass,  from 
the  under  surface  of  the  intestinal  mucous  membrane,  digestive  experiments 
are  exceedingly  difficult. 

Lieberkuhn's  crypts  or  glands  are  simple  tubular  glands,  resembling  the  finger 
of  a  glove,  that  lie  close  to  one  another  in  the  intestinal  mucous  membrane, 
and  in  greatest  number  in  that  of  the  large  intestine  (on  account  of  the  absence 
of  villi).  They  possess  a  membrana  propria,  constituted  of  most  delicate  fibrils, 


THE    INTESTINAL    JUICE, 


327 


and  a  single  layer  of  cylindrical  protoplasmic  cells,  between  which  goblet-cells 
also  occur,  in  small  number  in  the  small,  and  in  large  number  in  the  large  intes- 
tine. The  glands  in  the  small  intestine  yield  a  watery  secretion  principally; 
those  of  the  large  intestine,  from  their  numerous  goblet-cells,  ropy  mucus.  Both 
kinds  of  gland-cells  multiply  by  mitosis,  and  the  new  products  move  from  situ- 
ations where  active  division  is  going  on  to  places  where  the  production  is  less 
active.  The  mucus  in  the  goblet-cells  encloses  usually  a  single  central  body. 

The  secretion  of  Lieberkiihn's  glands  is,  from  the  duodenum  down- 
ward, the  chief  source  of  the  intestinal  juice. 

The  intestinal  juice  is  obtained, 
by  Thiry's  method,  in  the  following 
manner:  From  a  loop  of  the  in- 
testine of  a  dog,  withdrawn  from 
the  abdomen,  a  piece  of  the  length 
of  a  hand  is  so  divided  by  two  inci- 
sions that  only  the  continuity  of  the 
intestinal  canal  is  severed  but  not 
the  mesentery.  Then  one  end  of  this 
piece  is  ligated;  the  other,  left  open, 
is  sutured  in  the  abdominal  wound, 
after  the  ends  of  the  intestine,  be- 
tween which  the  piece  has  been  re- 
moved, have  been  carefully  united 
by  suture.  Vella  permits  both  ends 
of  this  horseshoe-shaped  portion  of 
intestine  to  open  on  the  abdominal 
wall.  In  this  way,  after  the  opera- 
tion has  been  completed,  the  animal 
can  continue  to  live  with  its  but 
slightly  abbreviated  intestine.  The 
intestinal  fistula,  with  a  free  exter- 
nal opening,  yields,  however,  an  in- 
testinal juice  that  is  not  contamin- 
ated by  any  other  digestive  secretion. 

The  intestinal  juice  derived 
from  such  a  fistula  flows  spon- 
taneously in  very  small  amount ; 
during  digestion  it  is  largely 
increased.  Mechanical,  chemi- 
cal and  electrical  stimulation 
increase  the  secretion,  especi- 
ally of  mucus,  with  reddening 
of  the  mucous  membrane,  so 
that  100  square  centimeters 
yield  from  13  to  18  grams  of 
juice  in  an  hour.  The  adminis- 
tration of  pilocarpin  also  in- 
creases the  secretion.  The  juice 
is  light  yellow  in  color,  opal- 
escent, watery,  strongly  alkaline, 
effervescing  on  addition  of  acids,  and  has  a  specific  gravity  of  1010.  It 
contains,  in  human  beings,  proteid  (0.80  per  cent.),  ferments,  mucin, 
especially  in  the  large  intestine  (0.73  per  cent.),  and  salts  (0.88  per 
cent.),  of  which  0.34  per  cent,  is  soda  and  0.5  per  cent,  sodium  chlorid. 

The  amount  of  intestinal  juice  secreted  is  least  with  the  presence  of  dissolved 
grape-sugar  in  the  intestines,  greater  with  the  presence  of  cane-sugar,  and  still 
greater  with  the  presence  of  starch  and  peptone.  It  increases  in  the  second  hour 
of  digestion. 


G. 


FIG.  120. — Longitudinal  Section  through  the  Small 
Intestine  of  a  Dog:  B,  connective-tissue  layer; 
Z,  intestinal  villi  covered  with  cylindrical  epithe- 
lium; L,  Lieberkiihn's  glands;  Mm,  muscularis 
mucoss;  G,  crowded  lymph-follicles;  Me,  circular 
muscular  layer;  Ml,  longitudinal  muscular  layer. 


328  THE    INTESTINAL    JUICE. 

Biedermann  found  the  production  of  mucus  in  the  goblet-cells  of  the  intestine, 
in  the  frog,  to  take  place  in  such  a  manner  that  droplets  of  mucus  first  appear 
in  the  cell-contents.  These  enlarge  into  vacuoles,  which  soon  become  confluent; 
then  the  mucus  escapes  from  these  and  is  discharged  from  the  cell. 

The  digestive  activity  of  the  juice  of  the  small  intestine  is  still  in 
many  respects  unexplained.  The  juice  has  been  found  most  active  in 
the  dog,  while  it  is  more  or  less  inactive  in  other  animals. 

It  possesses  less  diastatic  activity  than  the  saliva  and  the  pancreatic 
juice.  It  forms  maltose,  which  rapidly  passes  over  into  dextrose.  The 
glands  of  the  large  intestine  are  said  to  be  wanting  in  this  property, 
von  Wittich  has  extracted  the  ferment  by  means  of  glycerin  diluted 
with  water. 

The  intestinal  juice  is  capable  of  transforming  maltose  into  grape- 
sugar.  It,  therefore,  continues  the  diastatic  action  of  the  saliva  and 
the  pancreatic  juice,  which  principally  are  active  only  up  to  the  pro- 
duction of  maltose. 

According  to  Bourquelot,  this  action  is  due  to  intestinal  bacteria,  and  not 
to  the  intestinal  juice  as  such,  nor  to  the  saliva,  the  gastric  juice  or  the  invertin. 
The  larger  part  of  the  maltose,  however,  seems  to  undergo  absorption  unchanged. 

No  action  upon  proteids  is  recognizable,  or,   at  least,  only  traces. 

The  peptonizing  properties  described 
are  in  part  dependent  upon  putre- 
factive processes.  According  to 
earlier  statements,  fibrin  is  slowly 
peptonized  by  trypsin  and  pepsin; 
albumin,  fresh  casein,  raw  or  cooked 
meat  and  vegetable  albumin  less 
readily.  Gelatin  is  probably  also 
brought  into  solution  by  a  special 

FIG.  121. — Transverse    Section    through    Lieber-       ferment. 

kuhn's  Glands:    H,  cavity  of  the  glandular  The    intestinal    JU1C6   is    Capable   of 

tubule;  D,  glandular  epithelium;   B,  connec-  .  %  .   -     .  .  ... 

tive  tissue;  G,  blood-vessels.  acting    on    tat,    which    it     partially 

emulsifies  in  the  presence  of  free  acid. 

Whether  the  neutral  fats  are  also  decomposed,  in  small  measure,  has 
not  as  yet  been  determined  with  certainty. 

The  intestinal  juice  contains  invertin,  an  unorganized  ferment,  which 
decomposes  disaccharids  (cane-sugar,  milk-sugar  and  maltose)  into 
monosaccharids  (dextrose,  levulose  and  galactose),  with  the  taking  up 
of  water  and  the  production  of  heat : 

C12H22On     4-     H20     =     C6H1206        +       C6H1206 

Cane-sugar       +      Water      =        Dextrose  Levulose. 

Milk  (casein)  is  coagulated. 

With  regard  to  the  ferments  of  the  alimentary  canal,  Langley  upholds  the 
view  that  they  undergo  destruction:  the  diastatic  ferment  of  the  saliva  is  de- 
stroyed by  the  hydrochloric  acid  of  the  gastric  juice ;  pepsin  and  the  rennet-ferment 
succumb  to  the  action  of  the  alkaline  salts  of  the  pancreatic  and  intestinal  juices 
and  the  trypsin;  the  diastatic  and  peptic  ferments  of  the  pancreas  are  rendered 
inert  by  the  acid  fermentation  in  the  large  intestine.  Nevertheless  some  ferment 
is  absorbed  and  passes  over  into  the  urine. 

Of  the  influence  of  the  nerves  upon  the  secretion  of  the  intestinal  juice  but 
little  has  been  ascertained  with  certainty.  Stimulation  or  division  of  the  pneumo- 
gastric  nerves  is  without  apparent  effect.  On  the  other  hand,  destruction  of  the 
nerve-filaments  passing  to  the  intestinal  loops  and  accompanying  the  blood-ves- 
sels is  followed  by  distention  of  the  intestinal  canal  with  an  abundance  of  watery 


BACTERIAL    FERMENTATION    IN    THE    INTESTINES.  329 

fluid.  This  result  is  explained  in  part  by  paralysis  of  the  vasomotor  nerves  of 
the  intestinal  tract.  As  the  nerve-filaments  for  a  limited  portion  of  intestine, 
ligated  in  two  places,  can  be  completely  separated,  the  watery  intestinal  contents 
will  be  found  only  in  the  corresponding  loop  of  intestine.  According  to  Hanau, 
the  condition  in  this  experiment  of  Moreau  is  one  of  paralytic  secretion,  which, 
with  regard  to  time,  pursues  a  typical  course. 

The  following  substances  are  after  ingestion  excreted  by  the  intestinal  mucous 
membrane  of  isolated  fistulas :  iodin,  bromin,  lithium,  metallic  ferrocyanogen,  salts 
of  iron  and  others. 

FERMENTATIVE   PROCESSES   IN   THE   INTESTINES   DUE   TO 
MICROBES;    INTESTINAL   GASES. 

Wholly  different  from  the  peculiar  digestive  processes  just  described, 
which  are  brought  about  by  definite  unorganized  ferments  or  en- 
zymes, are  those  processes  which  are  to  be  considered  as  fermentative 
or  putrefactive  decompositions.  These  are  caused  by  microbes,  the  so- 
called  excitants  of  fermentation  or  putrefaction,  or  organized  ferments; 
and  they  may,  therefore,  take  place  outside  of  the  body,  in  suitable 
media.  Lower  forms  of  organisms,  which  maintain  fermentative  pro- 
cesses in  the  intestinal  tract,  are  often  swallowed  with  food  and  drink, 
as  well  as  with  the  buccal  fluid.  Upon  the  introduction  of  these  the 
processes  of  decomposition  begin,  with  simultaneous  production  of  gas. 
On  a  pure  milk-diet  intestinal  putrefaction  is  much  less  marked. 

Fermentation,  therefore,  cannot  occur  in  the  intestine  during  fetal 
life.  For  this  reason  gases  are  always  absent  in  the  intestine  of 
the  new-born.  The  first  bubbles  of  air  reach  the  intestine  through 
frothy  saliva  swallowed,  even  before  food  is  taken.  As,  however,  micro- 
organisms may  enter  the  intestinal  tract  with  the  air  swallowed,  the 
development  of  gas  by  fermentation  must  soon  follow.  The  development 
of  the  intestinal  gases  thus  goes  hand  in  hand  with  the  fermentative 
processes.  As,  however,  gases  from  the  air  swallowed  are  exchanged  in 
the  intestinal  canal,  the  composition  of  the  intestinal  gases  will  be  found 
to  be  dependent  upon  various  factors. 

Kolbe  and  Ruge  collected  intestinal  gases  from  the  human  anus  and 
found  in  100  volumes: 


Food.                                                 C02.  H.  CH4.                                     H,S. 

Milk   .................  16.8  43-3  °-9 

Meat  ................  -.4  ai« 

Peas  .................  21.0  4.0  55.9 


3».3  ) 
18.9  ) 


Moreover,  it  should  be  noted:  i.  That  oxygen  is  rapidly  absorbed  by 
the  walls  of  the  canal  from  the  air-bubbles  swallowed  with  the  food,  so 
that,  in  the  lower  part  of  the  large  intestine,  even  traces  of  oxygen  are 
absent.  In  exchange  the  blood-vessels  of  the  intestinal  wall  give  up 
into  the  intestine  carbon  dioxid,  so  that,  therefore,  a  portion  of  the  car- 
bon dioxid  in  the  intestines  is  derived  from  the  blood  by  diffusion. 

2.  Hydrogen,  carbon  dioxid  and  ammonia,  as  well  as  marsh-gas,  are 
also  developed  from  the  intestinal  contents  by  fermentation,  which  may 
take  place  even  in  the  small  intestine. 

Bacteria  as  Excitants  of  Fermentation.  The  organisms  that  especially  cause 
fermentation,  putrefaction  and  other  forms  of  decomposition  are  bacteria  (schizo- 
mycetes),  namely,  minute,  unicellular  structures,  chiefly  having  the  shape  < 
sphere  (micrococcus) ,  or  a  short  rod  (bacterium) ,  or  a  long  rod  (bacillus) ,  or  a 
spiral  thread  (vibrio,  spirillum,  spirochasta) .  Their  power  of  reproduction  is 
beyond  all  conception.  Through  their  vital  phenomena  they  cause  profound 


330 


BACTERIAL    FERMENTATION    IN    THE    INTESTINES. 


chemical  changes  in  the  matters  containing  them.  As  for  their  growth  and 
metabolism,  they  abstract  certain  substances  from  the  nutritive  fluid  in  which 
they  live,  they  decompose  the  chemicals  contained  therein.  In  this  process 
some  of  them  form  certain  substances  that  may  subsequently  act  as  ferments 
upon  matters  in  the  nutritive  fluid. 

The  microbes  are  destroyed  by  antiseptics,  such  as  carbolic  acid,  salicylic 
acid,  etc.,  although  the  ferments  are  not  destroyed.  Therefore,  these  substances 
afford  a  means  of  distinguishing  and  separating  the  fermentative  from  the  micro- 
biotic  decompositions. 

The  bacteria  consist  of  a  capsule  and  protoplasmic  contents.  Some  possess 
flagella  as  organs  of  locomotion,  which,  perhaps,  are  possessed  by  all  capable 
of  motion.  The  organisms  multiplying  by  division  are  sometimes  collected 
together  in  extensive  colonies,  united  by  a  gelatinous  mass,  often  visible  to  the 
naked  eye,  and  which  are  designated  zoogleae.  These  appear  in  the  form  of 
nodules,  branches,  patches,  flakes,  layers  of  mold,  or  ropy,  creamy  or  greasy 
deposits.  In  the  case  of  some  micro-organisms,  principally  bacteria,  multiplica- 
tion takes  place  by  spore-formation,  especially  if  the  nutritive  fluid  becomes 
deficient  in  nutrient  material.  The  rods  then  grow  into  threads  of  considerable 
size,  which  become  jointed;  and  globular,  strongly  refractive  granules,  from  i  to  2  /u 
in  size,  develop  in  the  individual  parts  (Fig.  122,  8,  9).  In  the  case  of  some,  as 


FIG.  122.— A,  bacterium  aceti,  in  the  form  of  cocci  (i),  diplococci  (2),  short  bacilli  (3),  and  jointed  threads  (4,  5). 
B,  bacillus  butyricus:  i,  isolated  spore;  2,  3,  4,  germinating  stage  of  the  spore;  5,  6,  short  and  long  bacilli; 
7,  8,  9,  spore-formation  in  the  bacteria. 

the  butyric-acid  germ,  the  bacilli,  before  spore-formation,  acquire  the  shape  of 
an  enlarged  spindle,  within  which  the  spores  form.  After  death  of  the  mother- 
cells,  the  spores  become  free,  and  from  them,  transplanted  to  a  suitable  soil, 
the  newly  formed  cells  of  the  microbes  again  germinate.  The  processes  of  spore- 
formation  (7,  8,  9)  and  of  germination  of  the  butyric-acid  micro-organism  (1,2, 
3,  4)  are  illustrated  in  Fig.  122,  B.  The  spores  are  extremely  resistant,  being 
capable,  in  the  dry  state,  of  surviving  for  a  long  time,  and  some  even  withstanding 
boiling. 

Among  bacteria,  a  distinction  is  made  between  those  that  exhibit  their  vital 
activity  in  the  presence  of  oxygen,  aerobes,  and  others  that  thrive  only  when 
oxygen  is  excluded,  anaerobes.  In  accordance  with  the  products  to  which  they 
give  rise  by  decomposition  in  their  nutrient  media,  they  may  be  divided  into 
those  that  induce  decomposition  in  the  form  of  fermentations  (zymogenic  schizo- 
mycetes) ,  those  that  form  pigments  (chromogenic) ,  those  that  generate  bad 
odors,  as  in  the  putrefactive  processes  (bromogenic) ,  and,  finally,  those  that, 
developing  in  the  living  tissues  of  other  organisms,  cause  morbid  conditions, 
even  death  itself  (pathogenic) .  Some  also  elaborate  poisons  (toxicogenic) .  All 
of  these  have  been  found  in  and  upon  the  human  body. 

If  it  be  borne  in  mind  that  a  large  number  of  bacteria  are  introduced  into 
the  alimentary  canal  with  foods  and  drinks,  as  well  as,  in  part,  also  with  the  in- 
spired air;  that,  further,  the  temperature  of  the  intestine  is  especially  favorable 


BACTERIAL    FERMENTATION    IN    THE    INTESTINES.  331 

to  their  development ;  and,  finally,  that  sufficient  material  of  the  most  varied  kind 
not  entirely  disposed  of  by  the  digestive  processes,  furnishes  nutrient  matter  for 
the  vegetation  of  the  germs,  it  is  not  surprising  that  a  rich  formation  of  these 
organisms  is  found  in  the  alimentary  canal  and  that  they  cause  numerous  forms 
o±  decomposition  in  the  intestinal  contents.  Knowledge  of  these  processes  is 
at  the  present  time,  still  highly  deficient;  and  the  formula*  proposed  for  the  de- 
compositions can,  therefore,  only  approximately  explain  the  processes.  For  this 
reason,  the  following  statements  can  only  be  considered  provisionally  as  aphorisms 
in  the  study  of  the  mycotic  intestinal  decompositions. 

Fermentation  of  Carbohydrates,  which  takes  place  principally  in  the 
small  intestine,  i.  Bacillus  acidi  lactici  (bacterium  lacticum),  whose 
biscuit-shaped  ^  cells,  from  1.5  to  3  /^  in  length,  are  arranged  in  groups 
or  rows  or  are  isolated,  causes  fermentative  decomposition  of  sugar  into 


inactive  lactic  acid : 


C6H1206  2(C3H603) 

i  Grape-sugar  =  2  Lactic  acid. 


Milk-sugar  (C12H22On)  may  be  decomposed  by  the  same  bacterium,  with 
the  addition  of  water,  first  into  two  molecules  of  grape-sugar,  2(C6H12O6), 
and  this  in  turn  into  four  molecules  of  lactic  acid,  4(C3H6O3). 

This  micro-organism,  whose  germs  float  in  the  air  everywhere,  causes  the 
spontaneous  souring  and  curdling  of  milk.  It  develops  further  in  sour-crout, 
sour  pickles,  and  the  like.  It  induces  fermentation  of  cane-sugar,  mannite, 
inosite,  and  sorbite,  as  of  the  sugars  mentioned.  In  addition  to  lactic  acid, 
carbon  dioxid  also  results.  There  are,  besides,  other  lactic-acid-producing  bacteria 
that  are  capable  further  of  transforming  starch  into  sugar,  van  de  Velde 
obtained  lactic,  butyric  and  succinic  acids  as  products  of  the  fermentative  activ- 
ity of  the  bacillus  subtilis  (Fig.  123),  and  mannite  as  a  reduction-product. 

2.  Bacillus  butyricus,  which   is  often   stained   blue  by  iodin  in  a 
starch-containing  medium,   transforms   lactic   acid   into   butyric   acid, 
together  with  carbon  dioxid  and  hydrogen. 

2(CSH603)        -         C4H802        +          2CO,         +        4H. 

2  Lactic  Acid         =       i  Butyric  Acid       +       2  Carbon  Dioxid   +    4  Hydrogen. 

This  bacterium  (Fig.  122,  B)  is  a  true  anaerobe,  which  vegetates  only  in  the 
absence  of  oxygen.  The  lactic-acid  bacillus,  which  actively  consumes  oxygen, 
is  therefore  its  natural  predecessor.  Butyric-acid  fermentation  completes  the 
transformation  of  many  carbohydrates,  chiefly  starch,  dextrin  and  inulin.  It 
takes  place  constantly  in  the  feces.  There  are  a  number  of  other  bacteria  with 
similar  activity.  The  butyric-acid  bacillus  produces  also  dextrin  from  starch. 

3.  Certain  micrococci  are  capable  of  developing  alcohol  as  the  chief 
product  from  sugar. 

In  the  human  small  intestine  there  are  present  besides:  bacterium  Bischleri 
(short  rods) ,  which  produces  alcohol,  inactive  lactic  acid  and  acetic  acid  from  sugar; 
bacterium  ilei  (short  rods),  which  transforms  sugar  into  alcohol,  succinic  acid 
and  some  active  paralactic  acid,  together  with  carbon  dioxid  and  hydrogen; 
bacterium  ovale  ilei  (almost  spherical),  which  transforms  sugar  into  alcohol, 
paralactic  acid  and  traces  of  the  fatty  acids;  bacillus  gracilis  ilei  (delicate  long 
rods),  which  has  a  similar  action;  bacterium  lactis  acrogenes,  which  transforms 
sugar  into  alcohol  and  succinic  acid,  together  with  lactic  acid  and  some  acetic 
acid. 

The  presence  of  yeast  also  may  result  in  the  production  of  alcohol 
in  the  intestine,  in  both  instances  likewise  from  milk-sugar,  which  at 
first  passes  over  into  dextrose.  Only  traces  are  found  in  the  intestine. 

4.  Bacterium  aceti  (Fig.  122,  A)  is  capable,  outside  of  the  body,  of 
transforming  alcohol  into  acetic  acid. 

C2H60         +        O         =         C2H40         +         H20 

Alcohol  +         Oxygen        =  Aldehyd  Water. 


332  BACTERIAL    FERMENTATION    IN    THE    INTESTINES. 

Aldehyd  is  changed  by  oxidation  into  acetic  acid  (C2H4O2).  Accord- 
ing to  Nageli,  the  same  micro-organism  is  capable  of  producing  small 
amounts  of  carbon  dioxid  and  water.  As  acetic  fermentation  ceases  at 
35°  C.,  it  will  not  take  place  in  the  intestine,  so  that  the  acetic  acid  con- 
stantly met  with  in  the  feces  must  result  from  other  fermentative  pro- 
cesses. Thus,  it  is  produced  in  considerable  amount  in  herbivora  as  a 
product  of  the  fermentation  of  cellulose;  being,  after  absorption,  burned 
up  in  the  fluids  of  the  body.  Acetic  acid  is  formed  also  as  a  result 
of  the  putrefaction  of  albuminates  with  exclusion  of  air. 

5.  Also  partial  solution  of  starch  and  of  cellulose  is  caused  by  schizo- 
mycetes  (bacillus  butyricus,  bacterium  termo,  vibrio  rugula)  in  the 
intestines;  for  cellulose,  mixed  with  cloacal  discharge  or  the  intes- 
tinal contents,  is  transformed  into  a  sugar-like  carbohydrate,  which 
then  breaks  up  into  equal  volumes  of  carbon  dioxid  and  marsh-gas. 
The  neurin  produced  by  the  pancreas  also  yields  marsh-gas  (CH4),  in 
addition  to  carbon  dioxid. 

The  solution  of  the  cellulose  of  the  cell-walls  then  permits  the  action 
of  the  digestive  juices  upon  the  enclosed  digestible  portions  of  the 


n 


34 


FIG.  123. — Hay-bacillus  (Bacillus  subtilis):  i,  spore;  2,  3,  4,  germination  of  the  spore;  5,  6,  short  bacilli;  7, 
jointed  filament  with  spore-formation  in  each  cell;  8,  short  bacilli,  in  part  with  spore-formation;  9,  spores  in 
individual  short  bacilli;  10,  bacteria  with  flagella. 

vegetable  food.     In  human  beings  the  metabolism  of  cellulose  is  always 
slight,  while  in  herbivora  it  is  digested  in  considerable  amounts. 

6.  Bacillus  subtilis,  cheese-spirilli  and  others  are  capable  of  trans- 
forming starch  into  sugar. 

7.  Micro-organisms  (lactic-acid  bacilli?)  that  produce  invertin  also 
occur  in  the  intestinal  canal.     This  substance  can  be  obtained  also  from 
brewer's  yeast  by  agitation  with  water  and  ether  and  subsequent  fil- 
tration. 

Fermentation  of  Fats.  Putrefaction  is  capable,  with  the  aid  of  as 
yet  unknown  micro-organisms,  of  decomposing  neutral  fats  into  glycerin 
and  fatty  acids,  after  taking  up  water.  Glycerin  is  susceptible  of  varied 
fermentations  with  different  microbes,  as,  for  example,  the  bacillus 
Fitzianus.  When  the  reaction  is  neutral,  hydrogen  and  carbon  dioxid 
are  formed,  together  with  succinic  acid  and  a  mixture  of  fatty  acids. 

Fitz  observed  alcohol,  together  with  caproic,  butyric  and  acetic  acids,  develop 
as  a  result  of  the  action  of  the  hay-bacillus  (bacillus  subtilis,  Fig.  123),  while  in 
other  cases  butyl-alcohol  principally  resulted,  van  de  Velde  found  butyric  and 
lactic  acids,  together  with  traces  of  succinic  acid,  and  also  carbon  dioxid,  water 
and  nitrogen. 


BACTERIAL    FERMENTATION    IN    THE    INTESTINES.  333 

The  fatty  acids  yield,  chiefly  as  calcium-soaps,  material  suitable  for 
fermentation.  Calcium  formate,  in  fermentation  with  cloacal  discharge, 
yields  calcium  carbonate,  carbon  dioxid  and  hydrogen;  calcium  acetate 
yields  calcium  carbonate,  carbon  dioxid  and  marsh-gas.  Of  the  oxy- 
acids,  the  fermentation  of  lactic,  gly eerie,  malic,  tartaric  and  citric  acids 
is  known. 

According  to  Fitz,  lactic  acid,  in  combination  with  calcium,  yields  propionic 
acid,  acetic  acid,  carbon  dioxid  and  water.  Valerianic  acid  in  considerable 
amount  is  produced  by  other  excitants  of  fermentation.  Glyceric  acid  yields 
especially  acetic  acid,  in  addition  to  alcohol  and  succinic  acid.  Malic  acid  forms 
succinic  acid  and  some  acetic  acid;  as  a  result  of  other  fermentative  processes, 
propionic  acid,  and  of  still  other  fermentative  processes,  butyric  acid,  together 
with  hydrogen;  or  it  is  decomposed  into  lactic  acid  and  carbon  dioxid.  Tartaric 
acid  breaks  up  into  acetic  acid,  propionic  acid,  carbon  dioxid  and  water;  as  a 
result  of  the  action  of  other  microbes,  into  butyric  acid;  and  of  that  of  still  others, 
into  acetic  acid,  together  with  some  butyric  and  succinic  acids  and  alcohol.  Citric 
acid  yields  finally  acetic,  with  some  butyric  and  succinic  acids. 

Fermentations  of  Proteids.  In  the  fermentation  of  the  undigested 
proteids  in  the  intestine  and  their  derivatives,  which  takes  place  princi- 
pally in  the  large  intestine,  micro-organisms  likewise  appear  to  take  part. 
In  the  first  place  it  should  be  emphasized  that  some  schizomycetes  are 
capable  of  producing  peptonizing  ferment,  as,  for  example,  the  bacillus 
subtilis,  bacillus  liquefaciens  ilei,  the  cheese-spirilli,  the  micro-organisms 
of  pickled  herring,  etc.,  so  that  assistance  to  the  peptic  enzyme,  even 
though  slight,  on  the  part  of  these  microbes  appears  to  be  not  wholly  ex- 
cluded. 

It  has  been  found  that  pancreatic  digestion  of  albuminates  does  not 
proceed  beyond  the  production  of  amido-acids :  leucin,  tyrosin  and  others. 
Putrefactive  fermentation  in  the  large  intestine  causes  still  further  and 
more  profound  decompositions.  Leucin  (C6H13NO2),  by  taking  up  two 
molecules  of  water,  forms  valerianic  acid  (C5H10O2),  ammonia,  carbon 
dioxid  and  four  molecules  of  hydrogen.  Glycin  behaves  in  a  similar 
manner.  Tyrosin  (CgHuNC^)  breaks  up  into  indol  (C8H7N),  which  is 
constantly  encountered  in  the  intestine,  together  with  carbon  dioxid, 
water  and  hydrogen.  If  the  admission  of  oxygen  is  possible,  still  other 
decompositions  take  place.  These  products  of  putrefaction  are  wanting 
in  the  intestine  of  the  fetus  and  the  new-born.  In  the  putrefactive  de- 
compositions of  proteids,  as  well  as  upon  boiling  them  with  alkalies, 
carbon  dioxid  and  hydrogen  sulphid  develop,  together  with  hydrogen 
and  marsh-gas.  Under  such  circumstances,  gelatin  yields,  in  addition 
to  abundant  leucin,  much  ammonia,  carbon  dioxid,  acetic,  butyric  and 
valerianic  acids  and  glycin.  Mucin  and  nuclein  undergo  no  decomposi- 
tion. Artificial  digestive  experiments  with  the  pancreas  disclose  an 
extraordinary  tendency  to  putrefactive  decomposition. 

The  body  giving  rise  to  the  fecal  odor,  which  likewise  results  from  putre- 
faction, has  not  as  yet  been  discovered.  It  is  intimately  related  to  indol  and 
skatol,  but  these  are  odorless  when  prepared  in  the  pure  state. 

Among  the  solid  matters  in  the  large  intestine  produced  only  by 
putrefaction,  indol  (C8H7N)  is  especially  to  be  pointed  out. 
substance  that  results  also  from  heating  albuminates  with  alkalies,  or 
in  small  amount  by  superheating  them  with  water  to  200°  C. 
forerunner  of  indican  in  the  urine.     If  the  products  of  the  digestion  of 
albuminates,  the  peptones,  are  rapidly  absorbed  in  the  intestine,  only  a 


334  BACTERIAL    FERMENTATION    IN    THE    INTESTINES. 

small  amount  of  indol  is  formed.  If,  on  the  other  hand,  with  a  lesser 
degree  of  absorption,  the  putrefactive  process  can  exert  a  profound  effect 
chiefly  upon  the  products  of  pancreatic  digestion  still  present  in  large 
amount,  considerable  indol  will  be  formed,  and  much  indican  subse- 
quently appears  in  the  urine. 

Thus  Jaffe  found  an  abundance  of  indican  in  the  urine  in  the  presence  of  in- 
carcerated hernia  and  obstruction  of  the  bowel.  After  transfusion  with  hetero- 
geneous blood,  in  connection  with  which  the  walls  of  the  intestine  are  often  the  seat 
of  extravasation  of  blood  and  thrombosis,  and  paralytic  conditions  of  the  intes- 
tinal vessels  and  musculature  itself  are  not  rarely  encountered,  the  author  has 
often  found  the  amount  of  indican  contained  in  the  urine  to  be  large. 

Test  for  indol:  The  fluid  to  be  tested  is  acidulated  with  considerable  hydrochlo- 
ric acid  and  is  well  shaken  after  addition  of  a  few  drops  of  oleoresin  of  turpentine. 
If  an  intense  red  color  results,  the  pigment  is  removed  by  agitation  with  ether. 
The  pigment  resulting  from  fibrin  in  the  process  of  tryptic  digestion,  and  becom- 
ing violet  with  bromin-water,  can  be  isolated  by  agitation  with  chloroform.  In 
addition  to  the  latter  pigment,  there  is  still  a  second  pigment  that  passes  over 
in  the  process  of  distillation,  and  can  be  extracted  from  the  distillate  by  ether. 
Both  appear  to  belong  to  the  indigo-group. 

A.  v.  Bayer  was  able  to  produce  indigo-blue  artificially  from  orthonitrophenol- 
propionic  acid  by  boiling  with  dilute  sodium  hydrate  and  after  addition  of  some 
grape-sugar.  From  indigo-blue  he  obtained  skatol,  in  addition  to  indol.  G. 
Hoppe-Seyler  observed  an  abundance  of  indican  in  the  urine  after  feeding  rabbits 
upon  sodium  orthonitrophenol-propionate. 

Further,  some  phenol  (C6H6O)  is  formed  in  the  intestine  by  the  putre- 
factive process.  Baumann  observed  the  same  substance  as  a  result  of 
the  putrefaction  of  fibrin  with  pancreas  outside  of  the  body,  and  Brieger 
found  it  constantly  in  the  feces.  It  appears  to  undergo  an  increase  under 
conditions  analogous  to  those  attending  an  increase  in  the  amount  of 
indol,  as  an  increase  in  the  amount  of  indican  in  the  urine  is  accompanied 
by  an  increase  in  the  amount  of  phenyl-sulphuric  acid. 

Amidophenyl-propionic  acid  also  can  be  obtained  from  putrefying  meat  and 
fibrin  as  a  product  of  the  decomposition  of  tyrosin.  Part  of  this  is  changed  by 
putrefactive  ferments  into  phenylpropionic  acid  (hydrocinnamic  acid) ,  which  is  com- 
pletely oxidized  in  the  organism  to  benzoic  acid,  and  appears  in  the  urine  as 
hippuric  acid.  In  this  way  is  explained  the  formation  of  hippuric  acid  when  a 
pure  proteid  diet  is  taken. 

Skatol  (C9H9N,  methylindol),  a  constant  constituent  of  human  feces, 
has  been  prepared  artificially  by  Nencki  and  Secretan  by  protracted 
putrefaction  of  egg-albumin  under  water.  In  this  way  results  skatol- 
carbonic  acid,  which,  when  heated,  readily  decomposes  into  skatol  and 
carbon  dioxid.  Skatol  also  appears  in  the  urine  in  combination  with 
sulphuric  acid. 

Milk  inhibits  the  decomposition  of  albumin  and  intestinal  putrefaction  through 
the  presence  of  casein  and  thus  also  diminishes  the  amount  of  ethereal  sulphates 
in  the  urine. 

According  to  the  brothers  Salkowski,  both  skatol  and  indol  result  from  a 
common  substance  preformed  in  albumin,  which,  when  decomposed,  at  one  time 
yields  a  larger  amount  of  indol,  and  at  another  time  a  larger  amount  of  skatol, 
accordingly  as  to  whether  the  hypothetical  indol-bacterium  or  the  skatol-bac- 
terium  active  under  such  conditions  prevails  in  the  development. 

It  is  of  great  importance  in  the  process  of  putrefactive  fermentation  whether 
this  takes  place  with  the  exclusion  of  oxygen  or  not.  In  the  former  case  reduc- 
tion occurs:  oxy-acids  are  reduced  to  fatty  acids,  and  there  are  developed, 
especially  hydrogen,  but  also  marsh-gas  and  hydrogen  sulphid;  the  hydrogen, 
in  turn,  may  cause  further  reduction.  If,  however,  oxygen  is  still  present,  the 
nascent  hydrogen  divides  the  molecule  of  ordinary  free  oxygen  into  two  atoms 
of  active  oxygen;  there  forms,  thus,  on  the  one  hand,  water,  and  on  the  other  hand, 
the  second  atom  of  oxygen  brings  about  active  oxidation. 


PROCESSES    IN    THE    LARGE    INTESTINE.  335 

The  remarkable  fact  should  yet  be  mentioned  here  that  the  putrefactive 
processes,  after  the  development  of  phenol,  indol,  and  skatol,  and  also  of  cresol, 
phenyl-propionic  and  phenylacetic  acids,  are  again  inhibited,  and  after  a  certain 
concentration  in  their  production  cease  completely.  Thus,  the  putrefactive  pro- 
cess itself  generates  antiseptic  substances  even  to  the  point  of  causing  the  death 
of  the  micro-organisms;  for,  as  with  highly  organized  beings,  the  excremen- 
titious  products  of  the  bacteria  themselves  are  poisons  for  them.  It  is,  there- 
fore, to  be  inferred  that,  in  the  intestinal  canal  also,  the  formation  of  the  sub- 
stances mentioned  in  turn  inhibits  the  putrefactive  decompositions  to  some  ex- 
tent. Ptomains  are  not  formed  normally  in  the  intestines. 

The  reaction  of  the  contents  of  the  small  intestine  is  alkaline,  due 
principally  to  carbonates,  and  in  less  degree  to  phosphates.  The  con- 
tents are,  however,  rich  in  carbon  dioxid,  the  presence  of  which  causes, 
on  one  hand,  the  acid  reaction  of  the  indicators  reacting  to  carbon 
dioxid,  while,  on  the  other  hand,  it  ensures  the  maximum  efficiency  on 
the  part  of  the  ferments  in  the  intestine.  In  the  large  intestine' the 
reaction  is  generally  acid,  in  consequence  of  the  acid  fermentation  and 
decomposition  of  the  ingesta  and  the  feces. 

PROCESSES   IN   THE   LARGE   INTESTINE.     FORMATION   OF   THE 

FECES. 

Within  the  large  intestine  the  putrefactive  and  fermentative  decom- 
positions of  the  ingesta  greatly  exceed  the  fermentative  or  true  digestive 
transformations,  as  only  small  amounts  of  the  ferments  of  the  intestinal 
juice  are  found  in  it.  In  addition,  the  absorptive  activity  of  the  walls 
of  the  large  intestine  is  greater  than  the  secretory  activity,  whence  the 
consistency  of  the  contents,  which  at  the  commencement  of  the  large 
intestine  are  still  semi-liquid,  but  become  more  consistent  in  the  further 
course  of  the  intestine.  The  absorption  includes  not  only  the  water  and 
the  products  of  digestion  in  solution,  but  also,  under  certain  circum- 
stances, even  unchanged  fluid  proteids.  Also  toxic  substances  are  de- 
cidedly more  readily  absorbed  here  than  from  the  stomach.  The  feces 
begin  to  be  formed  only  in  the  lower  portion  of  the  large  intestine.  The 
cecum  in  some  animals,  as,  for  example,  the  rabbit,  is  of  considerable 
size ;  fermentative  decompositions  appear  to  take  place  in  it  with  great 
activity,  with  the  development  of  an  acid  reaction.  In  human  beings 
the  cecum  is  principally  an  organ  of  absorption,  as  the  abundance  of 
lymphatic  follicles  indicates.  From  the  lower  portion  of  the  small  in- 
testine and  from  the  cecum  onward,  the  ingesta  acquire  the  fecal  odor. 

Observations  on  Thiry's  intestinal  fistulae  permit  the  conclusion  that 
a  considerable  portion  of  the  feces  is  derived  from  the  secretion  of  the 
mucous  membrane  and  from  epithelial  desquamation. 

The  amount  of  feces  evacuated  equals,  on  an  average,  170  grams  in 
twenty-four  hours  (from  60  to  250  grams),  although,  when  large  amounts 
of  food,  especially  if  difficult  of  digestion,  are  taken,  even  more  than  500 
grams  may  be  discharged.  After  a  diet  of  animal  food  the  amounts  of 
feces  and  of  solid  residue  therein  are  less  than  after  a  vegetable  diet.  The 
consistent  feces  are  broken  up  by  the  development  of  gas,  and  there- 
fore float  on  water. 

The  consistency  of  the  feces  depends  on  the  amount  of  water  con- 
tained in  them,  which  usually  reaches  75  per  cent.  A  pure  meat- 
diet  causes  rather  dry  feces;  food  rich  in  sugar,  rather  watery  feces; 
while  the  amount  of  fluid  ingested  is  without  influence.  The  more 


336 


PROCESSES  IN  THE  LARGE  INTESTINE. 


rapidly  peristalsis  takes  place,  however,  the  more  watery  are  the  feces, 
because  there  is  not  sufficient  time  for  the  absorption  of  fluid  from  the 
rapidly  advancing  ingesta.  Paralysis  of  the  intestinal  blood-vessels  and 
lymph- vessels,  after  transection  of  the  nerves,  is  likewise  accompanied 
by  liquefaction  of  the  feces. 

The  reaction  of  the  feces  is  often  acid,  particularly  in  consequence  of 
lactic-acid  fermentation  of  large  amounts  of  carbohydrates  ingested. 
Numerous  other  acids  generated  by  fermentation  are  also  present. 
If,  however,  considerable  amounts  of  ammonia  are  produced  in  the  lower 
portion  of  the  intestine,  a  neutral  and  even  an  alkaline  reaction  may 
preponderate.  The  secretion  of  large  amounts  of  mucus  in  the  intestine 
favors  a  neutral  reaction. 


E. 


St. 


G. 


SI. 


Mm 


B. 


Lm. 


FIG.  124. — Longitudinal  Section  through  the  Large  Intestine:  E,  epithelium;  St,  mucous  membrane;  G,  blood- 
capillaries;  SI,  solitary  follicles;  C,  circular  muscular  layer;  Ms,  muscular  layers;  Lm,  longitudinal 
muscular  layer;  Ld,  Lieberkiihn's  glands;  Mm,  muscularis  mucosEe;  B,  connective  tissue. 

The  odor  of  the  feces,  which  is  more  pronounced  with  a  meat-diet 
than  with  a  vegetable  diet,  is  dependent  upon  the  fecal-smelling  products 
of  putrefaction  not  yet  prepared  in  an  isolated  state ;  further  upon  the 
volatile  fatty  acids,  as  well  as  upon  traces  of  methylmercaptan.  The 
last-named  substance  can  be  prepared  from  proteid  by  means  of  fused 
potassium  hydroxid,  and  it  develops  in  traces  on  boiling  varieties  of 
cabbage,  and  it  is  also  formed  from  hydrogen  sulphid  (as  from  eggs). 

The  color  of  the  feces  varies  in  accordance  with  the  amount  of  altered 
biliary  pigment  present,  hence  shades  vary  from  light  yellow  to  dark 
brown. 


PROCESSES  OF  THE  LARGE  INTESTINE. 


337 


In  addition,  the  color  of  the  food  has  considerable  effect.  Thus  the  presence 
of  much  blood  in  the  food  renders  the  feces  almost  brownish  black,  from  hematin; 
green  vegetables  render  them  brownish  green,  from  chlorophyll;  bones,  in  dogs, 
render  the  feces  white,  from  the  calcium  contained;  bluish-red  vegetable  juices 
render  them  bluish  black;  iron-preparations  stain  them  black  in  part,  from  the 
production  of  iron  sulphid. 

The  feces  contain  (Fig.  125): 

i.  The  secreted  juice  of  the  intestinal  mucous  membrane,  together 
with  desquamated  and  digested  epithelial  cells.  After  almost  complete 
absorption  of  the  digested  food,  the  feces  still  contain  from  8  to  9  per 
cent,  of  nitrogen,  from  12  to  18  per  cent,  of  ethereal  extract  and  from 
ii  to  15  per  cent,  of  ash.  Certain  articles  of  food  stimulate  these  excre- 
tions more  vigorously  than  others. 

If  a  loop  of  the  lower  portion  of  the  small  intestine  and  the  upper  portion  of 
the  large  intestine  be  excluded,  as  in  a  Thiry's  fistula,  and  it  be  replaced  in  the 


FIG  125.— Feces:  a,  muscle  fibers;  b,  tendon;  c,  epithelial  cells;  d,  leukocytes;  e-i,  various  forms  of  plant-cells, 
among  which  everywhere  large  numbers  of  bacteria  (i)  are  scattered;  between  h  and  b  are  yeast-cells;  *, 
ammoniomagnesium  phosphate. 

abdominal  cavity  after  being  closed  by  a  circular  suture,  a  mass  of  fecal  char- 
acter will  be  found  in  it.  A  loop  of  colon,  thus  excluded,  will  contain  only  a 
watery  transudate,  rich  in  salts. 

2.  The  indigestible  residue  of  the  tissues  of  animal  or  vegetable  food: 
hairs,  horny  tissue,  elastic  tissue;   most  forms  of  cellulose,  wood-fibers, 
fruit-stones,  spiral  vessels  from  plant-cells,  gum. 

3.  Fragments  of  otherwise  readily  digestible  substances,  particularly 
when  they  were  ingested  in  excessive  amount,  or  when  not  sufficiently 
comminuted  by  mastication;  thus,  the  remains  of  meat  (up  to  i  per 
cent.),  pieces  of  ham,  shreds  of  tendon,  bits  of  cartilage,  flakes  of  fatty 
tissue,  small  pieces    of   hard  albumin;    further,  plant-cells,  starch   in 
vegetable  cells,  firm-walled  cells  of  ripe  pulses,  unground  adhesive  cell 
of  grain,  and  the  like.     The  presence  of  meat  and  starch  is  suggestive 
of  an  existing  intestinal  catarrh. 

Of  all  articles  of  food  certain  remnants  pass  over  into  the  feces:  of  wheat- 
bread,  3-7  Per  cent.;  of  rice,  4-1  per  cent.;  of  meat,  4.7  P^  cent.;  of  potc  es, 
9.4  per  cent.;  of  cabbage,  14.9  per  cent.;  of  rye-bread,  15  per  cent.;  of  carrots, 
20.7  per  cent. 


338  PROCESSES  OF  THE  LARGE  INTESTINE. 

4.  The  metabolic  products  of  the  biliary  coloring-matter,  which  are 
especially  abundant  in  all  diseases  that  cause  increased  destruction  of 
erythrocytes,  and  which  now  no  longer  yield  the  Gmelin-Heintz  reaction, 
as  well  as  the  altered  biliary  acids.     In  diarrhea!  stools,  as,  for  example, 
the  green  stools,  the  reaction,  however,  can  often  be  readily  demonstrated. 
It  indicates  accelerated  peristalsis.     The  meconium  contains  unaltered 
bilirubin,  biliverdin,  glycocholic  and  taurocholic  acids. 

5.  Unaltered  mucin  and  nuclein  and,  as  a  metabolic  product  of  the 
latter,  xanthin-bases ;  nuclein  especially  after  a  diet  of  bread ;  in  addition, 
cylindrical  epithelial  cells  from  the  alimentary  tract  in  various  stages  of 
digestion;  further,  fat-globules  at  times.     Crystals  of  cholesterin  and  of 
coprosterin  are  rare.     The  less  intimately  the  mucus  is  admixed  with 
the  feces,  the  lower  down  in  the  intestine  is  its  source. 

6.  After  the  ingestion  of  a  large  amount  of  milk,  as  well  as  after  a 
diet  of  fat,  crystalline  needles  of  calcium-salts  of  the  fatty  acids,  thus 
calcium-soaps,  are  found  constantly  in  the  feces,  even  in  infants.     When 
courses  of  treatment  with  milk  have  been  pursued  undigested  masses  of 
casein  and  fat  have  besides  been  observed  to  be  present.     Further,  com- 
binations of  ammonia  with  the  acids  resulting  from  putrefaction  already 
mentioned  are  among  the  substances  constantly  present  in  the  feces. 
Larger  masses  of  fat  in  the  feces  indicate  accelerated  peristalsis. 

7.  Among  the  inorganic  residue,   the  readily  soluble  salts,   which 
therefore  are  readily  diffused,  are  rare  in  the  feces;  thus  sodium  chlorid 
and  other  alkaline  chlorids,  the  phosphoric  as  well  as  the  sulphuric  com- 
binations.    On  the  other  hand,  the  insoluble  combinations,  principally 
ammoniomagnesium    phosphate,    neutral    calcium    phosphate,    yellow- 
colored   calcium-salts,  calcium   carbonate   and   magnesium  phosphate, 
constitute  70  per  cent,  of  the  ash.     The  large  amount  of  alkalies  and 
earths  contained-  in  the  feces  is  noteworthy,  three-quarters  of  which  are 
in  combination  with  carbon  dioxid  and  organic  acids.     These  are  derived 
only  in  smallest  part  from  the  secretions  of  the  intestinal  mucous  mem- 
brane.    By  far  the  greatest  part  of  the  ash,  however,  is  derived  from 
the  constituents  of  the  food.     According  to  Rey,  from  20  to  50  per  cent, 
of  solutions  of  calcium-salts,  injected  into  the  blood  or  subcutaneously, 
is  excreted  by  the  glands  of  the  large  intestine  in  the  dog;  0.2  gram  of 
iron  is  present  daily. 

In  the  presence  of  a  fistula  in  the  large  intestine,  Robert  and  Koch  observed, 
in  the  feces:  sodium,  calcium,  magnesium,  iron;  phosphoric,  sulphuric,  hydro- 
chloric acids;  soaps,  neutral  fat,  fatty  acids,  mucin,  albumin,  epithelium,  traces 
of  ethereal  sulphates,  together  almost  one  gram  daily.  At  times  the  excretion 
of  inorganic  substances  is  so  abundant  as  to  form  incrustations  upon  other  fecal 
matter.  Under  such  circumstances  either  ammoniomagnesium  phosphate  is 
present  alone,  in  large  crystals,  or  magnesium  phosphate  is  mixed  with  it.  Par- 
ticularly the  ingestion  of  rye-bran,  in  bread,  which  contains  these  substances 
in  large  amount,  causes  this  result.  Charcot's  crystals  are  found  in  the  presence 
of  entozoa. 

8.  Bacteria  are  present  in  abundance;  yeasts  are  seldom  absent. 

For  the  identification  of  the  individual  bacteria,  Escherich  has  developed 
pure  cultures  from  the  intestinal  contents  of  infants,  Bienstock  from  those  of 
adults.  In  the  intestine  of  infants,  fed  upon  mother's  milk  exclusively,  the 
bacterium  lactis  aerogenes  (Fig.  126,2)  produces,  particularly  in  the  upper  portion, 
where  milk-sugar  is  still  unabsorbed,  acetic  acid,  together  with  carbon  dioxid, 
hydrogen  and  marsh-gas.  Lactates  are  transformed  into  butyrates.  The 
bacterium  also  produces  acetic  acid  from  starch.  A  characteristic  feature  of  the 


MORBID    ALTERATIONS    IN    DIGESTIVE    ACTIVITY. 


339 


feces  is  the  slender  bacterium  coli  commune  (Fig.  126,  i),  provided  with  from 
one  to  three  flagella,  which  forms  lactic  and  formic  acids,  together  with  acetic 
acid,  and  at  times  exerts  a  pathogenic  action. 

In  the  feces  of  adults  Bienstock  found  first  of  all  two  varieties  of  large  bacilli 
pig.  126  3,  4)  resembling  the  bacillus  subtilis  in  size  and  appearance,  differing 
from  the  latter  only  in  the  form  of  its  pure  culture,  by  its  manner  of  sporulation 
and  by  an  absence  of  independent  movement.  These  two  bacilli  are  distinguish- 
able macroscopically  only  by  the  form  of  this  culture,  which  takes  the  shape 
A  ^  2  a  £raPe>  or  of  a  mesentery.  Neither  possesses  any  fermentative  activity 
A  third,  micrococcus-hke,  small,  slowly  multiplying  bacillus  (bacillus  coprogenus 
parvus)  was  present  in  three-quarters  of  all  of  the  stools.  The  fourth  variety  is 
the  specific  bacterium  of  proteid  decomposition  (bacillus  putrificus  coli)  which 
is  wanting  in  the  feces  of  infants,  and  which  with  the  production  a  fecal  odor 
gives  rise  to  the  putrefactive  products  of  proteids.  Only  this  and  no  other  causes 
these  processes  in  the  intestine;  yet  it  does  not  decompose  casein  and  alkali- 


% 

3   < 


0    / 


FIG.  126. — i,  Bacterium  coli  commune-,  2,  Bacterium  lactis  aerogenes;  3,  4,  the  two  large  Bienstock  bacilli  with 
partial  endogenous  spore-formation;  5,  the  various  stages  of  development  of  the  bacillus  of  proteid  outre- 
faction. 

albuminate.  The  evolution  of  this  bacterium  is  represented  in  Fig.  126,  5,  a-g; 
of  which  the  stages  c  and  g  are,  however,  wanting  in  the  feces  and  are  encoun- 
tered only  in  artificial  cultures. 

If  the  feces  are  simply  examined  microscopically,  without  special  precautions, 
the  following  are  found  as  normal  saprophytes:  the  bacterium  coli  commune, 
the  staphylococcus  aureus;  frequently,  also,  varieties  of  proteus,  at  times  with 
infective  properties;  in  addition,  other  bacteria,  whose  entrance  in  part  through 
the  anus  is  possible:  the  bacillus  butyricus,  often  staining  blue  with  iodin,  in 
feces  rich  in  starch,  and  other  small,  spherical  and  rod-shaped  schizomycetes, 
staining  similarly.  After  the  ingestion  of  uncooked  food  of  various  kinds,  Lembke 
was  able  to  verify  the  presence  of  as  many  as  73  different  bacteria  in  the  intestine. 

In  human  beings,  with  accidentally  acquired  intestinal  fistulas  or  an  artificial 
anus  (intestinal  fistula  involving  the  colon),  opportunity  is  afforded  to  study 
the  changes  in  the  intestinal  contents  with  greater  precision. 

MORBID  ALTERATIONS  IN  DIGESTIVE  ACTIVITY. 

The  ingestion  of  food  may  be  prevented  by  spasm  of  the  muscles  of  mas- 
tication (usually  as  a  symptom  of  general  convulsions),  by  strictures  of  the 
esophagus,  either  from  corrosive  cicatrices  (after  the  swallowing  of  caustic  fluids) 
or  from  neoplasms,  especially  carcinoma.  Inflammatory  affections  of  any  kind  in 
the  mouth  and  pharynx  may  also  seriously  interfere  with  the  ingestion  of  food. 
Inability  to  swallow  occurs  as  a  symptom  of  disease  of  the  medulla  oblongata, 
in  consequence  of  paralysis  of  the  center  for  the  motor  nerves  (facial,  pneumogastric 
and  hypoglossal)  and  of  that  for  the  sensory  nerves  through  which  pass  reflex 
impulses  (glossopharyngeal,  pneumogastric  and  trigeminal).  Irritation  or  ab- 
normally heightened  stimulation  of  this  area  may  cause  spasmodic  swallowing 
and  a  feeling  of  constriction  in  the  throat  (globu's  hystericus). 

The  secretion  of  saliva  is  diminished  in  conjunction  with  inflammation 
of  the  salivary  glands,  occlusion  of  their  ducts  by  concretions  (salivary  calculi) , 
etc.;  further,  under  the  influence  of  atropin  and  daturin,  in  consequence  of  which 
the  secretory  (not  the  vasomotor)  fibers  of  the  chorda  tympani  appear  to  become 
paralyzed.  Slight  fever  may  increase  the  amount  of  saliva,  though  the  amount 
of  ferment  may  be  lessened;  fever  of  more  marked  degree  diminishes  both,  while 


340  MORBID    ALTERATIONS    IN    DIGESTIVE    ACTIVITY. 

in  the  presence  of  high  fever  no  saliva  at  all  is  secreted.  The  saliva  secreted 
with  lower  grades  of  fever  is  cloudy,  viscous  and  it  usually  becomes  acid.  With 
increase  in  fever  the  inertness  of  the  diastatic  action  also  increases.  After  the 
crisis  the  amount  of  saliva  and  the  activity  of  the  ferment  become  subnormal; 
likewise  in  the  presence  of  diseases  of  the  kidneys.  After  chronic  illness  of  long 
standing  the  production  of  ferment  frequently  diminishes.  The  secretion  of 
saliva  is  increased  by  morbid  irritation  of  the  nerves  of  the  mouth,  as  from  in- 
flammations, ulcers,  trigeminal  neuralgia,  so  that  enormous  quantities  may  be 
poured  out.  Mercury  and  jaborandi-leaves  cause  salivation,  the  former  with  the 
simultaneous  occurrence  of  a  stomatitis  that  induces  reflex  secretion  of  saliva. 
Diseases  of  the  stomach  also  may  increase  the  secretion  of  saliva,  in  conjunction 
with  paroxysms  of  nausea  and  retching.  Viscid,  ropy  saliva,  due  to  irritation 
of  the  sympathetic  nerve,  is  secreted,  together  with  some  vascular  disturbance, 
in  consequence  of  active  sexual  excitement,  but  also  as  a  result  of  certain  psychical 
impressions.  The  reaction  of  the  buccal  secretion  becomes  acid  in  the  presence 
of  catarrhal  conditions  of  the  mouth  and,  further,  as  a  result  of  the  decomposition 
of  accumulated  epithelial  cells  in  the  mouth  during  the  prevalence  of  fever,  as 
well  as  in  cases  of  diabetes  mellitus,  in  consequence  of  acid  fermentation  of 
the  sugar  contained  in  the  saliva.  Diabetic  patients  therefore  suffer  frequently 
from  carious  teeth.  The  secretion  of  the  mouth  in  infants  also  has  a  slightly 
acid  reaction  unless  the  greatest  cleanliness  is  observed. 

Disturbances  in  the  activity  of  the  gastric  musculature  may  appear,  as  a 
paralytic  phenomenon,  with  distention  of  the  stomach,  and  a  protracted  sojourn 
of  the  ingesta.  With  more  marked  grades  of  the  disorder  decomposition  and  the 
production  of  gas  take  place.  Diminution  in  muscular  activity  may  give  rise  to 
dilatation  of  the  entire  stomach.  Incompetency  of  the  pylorus  represents  a 
special  form  of  gastric  paralysis.  Derangement  of  innervation,  central  or  periph- 
eral in  nature,  may  be  the  cause;  further,  actual  paralysis  of  the  pyloric  sphinc- 
ter or  anesthesia  of  the  mucous  membrane  of  the  pylorus,  which  exerts  a  reflex 
effect  upon  the  sphincter  muscle;  finally,  also,  interference  with  the  transmission 
of  the  reflex  within  the  center.  Abnormally  increased  activity  of  the  gastric 
musculature  will,  as  gastric  diarrhea,  hasten  the  ingesta  into  the  intestine;  often 
vomiting  occurs.  In  nervous  individuals  so-called  peristaltic  unrest  of  the  stomach 
is  at  times  present,  in  conjunction  with  dyspeptic  disorders.  Spasm  of  the  cardiac 
orifice  or  paresis  of  the  inhibitory  nerves  of  the  cardia  also  occurs.  Rarely,  in  the 
presence  of  stricture  of  the  pylorus,  true  antiperistalsis  of  the  stomach  has  been 
observed. 

Gastric  digestion  is  delayed  by  all  severe  physical  and  mental  exertion  and,  if 
this  be  of  more  marked  degree,  digestion  may  even  be  inhibited.  Also  sudden 
emotional  disturbance,  as  well  as  reflex  influences  from  other  organs  (uterine 
dyspepsia),  may  have  this  effect.  Probably  these  factors  exert  an  influence  upon 
the  vasomotor  nerves  of  the  stomach.  Impairment  and  abolition  of  the  secretion  of 
the  gastric  juice  may,  under  certain  conditions,  be  purely  nervous  in  nature,  as  in 
cases  of  nervous  dyspepsia  and  gastric  neurasthenia.  Complete  absence  of  the 
gastric  juice  is  found  in  connection  with  atrophy  of  the  mucous  membrane,  prin- 
cipally in  cases  of  pernicious  anemia.  Also  excessive  secretion  of  the  gastric 
juice,  continuous  flow  of  the  juice,  and  likewise  excessive  production  of  acid  may 
depend  upon  derangement  of  nervous  activity:  nervous  gastroxynsis,  chiefly 
observed  in  women.  Excessive  production  of  hydrochloric  acid  occurs  in  asso- 
ciation with  round  ulcer  of  the  stomach. 

Inflammatory  or  catarrhal  affections  of  the  stomach,  as  well  as  ulcers  and 
neoplasms,  disturb  normal  digestive  activity,  as  does  also  the  excessive  ingestion 
of  foods  difficult  of  digestion,  of  sharp  spices  in  considerably  amount,  or  much 
alcohol.  Griitzner  observed  in  a  dog  that  the  mucous  membrane  secreted  con- 
tinuously under  the  influence  of  a  chronic  gastric  catarrh,  but  the  gastric  juice 
was  deficient  in  pepsin,  cloudy,  viscous,  less  acid,  even  alkaline.  The  introduc- 
tion of  food  did  not  modify  the  secretion;  the  stomach,  therefore,  never  actually 
comes  to  rest.  At  the  same  time  the  chief  cells  of  the  gastric  glands  are  turbid. 
Accordingly  it  would  seem  o:  advantage  for  patients  suffering  from  gastric  catarrh 
to  eat  frequently,  but  only  a  little  at  a  time,  and  in  addition  use  a  0.4  per  cent, 
hydrochloric-acid  solution  as  a  beverage.  Small  doses  of  sodium  chlorid  appear 
to  aid  gastric  digestion. 

In  the  presence  of  enfeebled  digestion,  the  cause  may  be  deficient  formation 
either  of  hydrochloric  acid  or  of  pepsin.  Both  substances  may  therefore  be 
administered  as  remedial  agents.  In  the  presence  of  enfeebled  gastric  digestion 


MORBID    ALTERATIONS    IN    DIGESTIVE    ACTIVITY.  341 

and  motor  insufficiency  decomposition  of  the  contents  of  the  stomach  into  lactic, 
butyric  and  acetic  acids  often  takes  place  as  a  result  of  the  action  of  lower  organ- 
isms. Small  doses  of  salicylic  acid  are  advisable  under  such  circumstances, 
together  with  some  hydrochloric  acid  (notwithstanding  possible  heart-burn  or 
acid  eructation).  The  administration  of  pepsin  probably  is  but  rarely  imperative, 
as  this  ferment  is  only  seldom  absent  even  from  the  diseased  gastric  mucous 
membrane.  In  the  presence  of  marked  dilatation  and  a  protracted  sojourn,  the 
proteids  in  the  stomach,  notwithstanding  the  hydrochloric  acid,  undergo  putre- 
faction, which,  however,  does  not  as  a  rule  have  an  injurious  effect.  In  cases  of 
gastric  catarrh  and  cholera,  albumin  has  been  observed  to  appear  in  the  gastric 
juice. 

Gastric  Digestion  in  Patients  with  Fever  and  Anemia. — Beaumont,  from  obser- 
vations made  upon  the  man  with  the  gastric  fistula  examined  by  him,  found 
that  only  scanty  secretion  of  gastric  juice  takes  place  in  the  presence  of  fever. 
The  mucous  membrane  was  deficient  in  secretion,  red  and  irritable.  Dogs, 
which  Manassein  had  made  febrile  from  septicemia  or  profoundly  anemic  by 
venesection,  elaborated  a  fairly  active  gastric  juice,  characterized  especially 
by  a  deficiency  of  hydrochloric  acid.  Hoppe-Seyler  examined  the  gastric  juice 
from  a  patient  with  typhoid  fever — in  which  disease  van  de  Velde  found  no  free 
hydrochloric  acid  (for  the  parietal  cells  are  destroyed  under  such  conditions) ; 
as  well  as  in  cases  of  gastric  carcinoma  also,  in  which  disease  there  is,  as  a  rule, 
no  excess  of  free  hydrochloric  acid — and  found  it  absolutely  inactive  for  artificial 
digestion,  even  after  hydrochloric  acid  had  been  added.  This  investigator  properly 
emphasizes  the  fact  that  the  diminution  in  hydrochloric  acid  after  such  conditions 
favors  the  development  of  a  neutral  reaction  of  the  gastric  contents,  by  reason 
of  which,  on  the  one  hand,  digestion  in  the  stomach  can  no  longer  take  place; 
while,  on  the  other  hand,  abnormal  fermentative  processes  must  take  place, 
with  the  aid  of  developing  micro-organisms  and  sarcinae  ventriculi  (?). 
Uffelmann  found  that,  in  patients  with  fever,  the  secretion  of  a  peptone- 
forming  gastric  juice  ceases  if  the  fever  sets  in  violently,  if  a  condition  of 
great  weakness  develops,  or  if  a  high  temperature  persists  for  a  long  time.  In 
any  event,  also  the  amount  of  gastric  juice  secreted  is  diminished.  In  the  presence 
of  fever  the  irritability  of  the  mucous  membrane  is  increased,  so  that  vomiting 
is  readily  induced.  Also  the  increased  excitability  of  the  vasomotor  nerves  of 
patients  with  fever  is  evidently  detrimental  to  the  secretion  of  active  digestive 
juices.  Gluzinski  found  an  absence  of  hydrochloric  acid  in  the  acute  febrile 
infectious  diseases.  Beaumont  observed  that  fluids  were  rapidly  absorbed  from 
the  stomach  of  a  febrile  patient,  while,  on  the  other  hand,  the  absorption  of  pep- 
tones was  diminished,  on  account  of  the  frequently  accompanying  gastric  catarrh 
and  the  disturbed  activity  of  the  muscularis  mucosas. 

Many  salts  disturb  gastric  digestion,  if  added  in  considerable  amount,  par- 
ticularly the  sulphates.  Of  the  alkaloids,  morphin,  strychnin,  digitalin,  narcotin 
and  veratrin  likewise  have  a  disturbing  influence.  A  small  amount  of  quinin  ac- 
celerates gastric  digestion. 

As  the  digestive  activity  of  the  stomach  can  be  replaced  by  the  pancreas, 
it  is  evident  that  dogs  may  continue  to  live  without  profound  disturbance  of 
nutrition  after  extirpation "  of  the  stomach.  Langenbach  observed  a  similar 
result  in  human  beings  after  operation. 

The  secretion  of  bile  undergoes  a  change  in  the  presence  of  acute  disease, 
as,  for  example,  fever,  in  that  it  becomes  scanty  and  at  the  same  time  more  watery, 
and  that  it  is  poorer  in  its  specific  constituents.  Should  the  liver  undergo 
profound  structural  changes  as  a  result  of  the  morbid  process,  the  secretion  of 
bile  may  cease  completely. 

As  a  result  of  the  decomposition  of  bile  (acid  fermentation?)  gall-stones 
form  within  the  gall-bladder  or  biliary  passages.  These  calculi  may  be  white  or 
brown.  The  former  consist  almost  entirely  of  laminated  cholesterin-crystnls. 
They  are  generally  about  i  cm.  in  diameter,  but  they  may  be  the  size  of  a  walnut 
or  even  larger.  The  brown  gall-stones  consist  of  bilirubin-lime,  together  with 
biliverdin,  bilicyanin  and  choletelin,  and  also  calcium  carbonate  and  phosphate, 
often  mixed  with  iron,  manganese,  copper  and  other  precipitated  heavy  metals. 
All  gall-stones,  like  urinary  calculi,  possess  an  organic  supporting  structure. 
Some  are  rather  spherical,  often  studded  with  mulberry-shaped  nodules.  Those 
packed  together  in  the  gall-bladder  become  polished,  from  mutual  attrition  in 
consequence  of  the  contraction  of  the  walls  of  the  gall-bladder.  The  white  gall- 
stones often  contain  lime  and  biliary  coloring-matter  as  a  nucleus,  together  with 


342  MORBID    ALTERATIONS    IN    DIGESTIVE    ACTIVITY. 

a  nitrogenous  residue,  probably  derived  from  desquamated  epithelium,  mucus, 
salts  of  biliary  acids  and  some  fat.  Gall-stones  may  cause  obstruction  of  the 
bile-ducts  and  then  give  rise  to  symptoms  of  cholemia.  Smaller  stones,  impacted 
in  the  ducts,  may  cause  intense  pain  (biliary  colic)  and,  by  means  of  their  sharp 
edges,  they  may  even  bring  about  fatal  rupture  of  the  ducts.  The  formation  of 
biliary  calculi  is  probably  due  ultimately  to  local  stagnation  and  decomposition 
of  bile  in  the  gall-bladder,  caused,  for  example,  by  tight  lacing,  in  consequence  of 
which  kinking  of  the  gall-bladder  takes  place.  Cholemia  and  jaundice  have 
already  been  discussed. 

In  the  presence  of  high  fever  the  pancreatic  secretion  appears  to  be  dimin- 
ished and  its  activity  enfeebled.  Cessation  of  secretion  is  attended  with  the 
appearance  of  fat  in  the  form  of  globules  and  crystalline  fatty  acids  in  the  feces. 
Degeneration  of  the  pancreas  may  cause  diabetes. 

Among  the  disturbances  in  the  activity  of  the  intestinal  tract,  constipation 
(obstipation)  is  first  to  be  considered.  The  causes  of  this  condition  may  reside  in: 

(1)  Obstructions   that    occlude   the   normal   passage.     In   this   category   belong 
constrictions  of  the  intestinal  canal,  due  to  cicatricial  strictures,  as,  for  example, 
in  the  colon  often  after  dysentery;   neoplasms;   further,  axial  torsion  of  a  loop  of 
intestine    (volvulus),  or  invagination  of    one  portion  into  another  (intussuscep- 
tion) ,  or  into  a  hernial  sac  (hernia) ;   also  the  pressure  of  tumors  or  exudates  from 
without.     Finally,    congenital   absence   of    the   anus    may  constitute  the   cause. 

(2)  Excessive  dryness  of  the  intestinal  contents  may  cause  obstipation.     Under 
such  circumstances  the  following  factors  may  be  operative:    Excessive  dryness 
of  the  food;    further,  diminution  of  the  digestive  juices,  as,  for  example,  of  the 
bile  in  cases  of  icterus ;  or  in  consequence  of  great  loss  of  fluid  through  other  organs 
of  the  body,  as  after  profuse  perspiration  or  secretion  of  milk,  or,  finally,  during 
fever.      (3)  Derangement  of  the  activity  of  the  muscles  and  of  the  motor  nerve- 
apparatus  of  the  intestine  may  induce  constipation  through  insufficient  peristal- 
sis.    This  is  caused  especially  by  paralytic  conditions,  as  in  the  presence  of  in- 
flammation,  degeneration,  chronic  catarrh  and  peritonitis.     Spinal  paralysis  is 
generally    attended    with    sluggish    defecation;     central    affections    often    also. 
Whether  the  phenomena  of  mental  impairment  and  hypochondriasis  are  the  ac- 
companiment  or    the   sequel   of    constipation  has  not   yet  been   demonstrated. 
Spasmodic  contraction  of  certain  portions  of  the  intestine  may  give  rise  to  transi- 
tory retention  of  the  intestinal  contents,  with  great  pain  (colic) ;  as  may  also  spasm 
of  the  anal  sphincter,  which  may  also  take  place  reflexly,  from  irritation  of  the 
lower  portion  of  the  intestine.     The  feces  are  almost  always  hard  and  deficient _in 
water,  when  constipation   exists,   because    during  their  long  sojourn  in  the  in- 
testines fluid  is  absorbed  from  them.     In  consequence,  the  fecal  masses  form  large 
pieces  (scybala)  within  the  large  intestine  and  these  may,  in  turn,  constitute  a 
new  obstacle  to  the  onward  movement  (coprostasis) .     Diminution  in  the  intes- 
tinal and  gastric  secretion  occurs  also  as  a  sign  of  general  nervous  affections  (hys- 
teria, hypochondria,  mental  disorders),  although   increased   secretion   may  also 
take  place  under  such  circumstances. 

The  agents  that  cause  constipation  are,  in  part,  those  that  paralyze  the  motor 
apparatus  temporarily,  such  as  opium  or  morphin;  and,  in  part,  those  that  dimin- 
ish the  secretions  of  the  intestinal  mucous  membrane,  and  exert  a  constringent 
effect  upon  the  blood-vessels  and  the  mucous  membrane,  such  as  tannic  acid, 
alum,  lime,  lead  acetate,  argentic  and  bismuth  nitrates. 

Increase  in  the  intestinal  discharges  is  usually  accompanied  by  a  greater 
degree  of  fluidity  of  the  feces  (diarrhea).  The  causes  are  as  follows: 

1.  Unduly  rapid    propulsion  of    the  contents  through  the  intestinal  canal, 
particularly  through  the  large  intestine,  so  that  absorption  from  this  part  cannot 
take  place  in  a  normal  manner.     The  increased  peristalsis  is  due  to  irritation  of 
the  motor-nerve  apparatus  of  the  intestine,  and  is  principally  reflex  in  character, 
Rapid  passage  of  the  ingesta  through  the  intestinal  canal  results  in  the  presence 
in  the  discharges  of  substances  that  could  not  be  completely  or  at  all  digested 
in  the  short  time  afforded  (lientery) .     This  will  also  occur  if  portions  of  the  in- 
testine,  situated  high  up,   communicate   with   lower  portions   of  the   intestine, 
through  abnormal  openings. 

2 .  The  feces  may  be  of  the  consistency  of  paste  from  the  admixture  of  water, 
mucus  and  fat,  in  considerable  amount;  further,  from  the  residue  of  fruits  and 
vegetables.     In  rare  cases  in  which  the  feces  contain  a  good  deal  of  mucus,  so- 
called  Charcot's  crystals  are  present  (Fig    92,  c).     In  the  presence  of  ulceration 
of  the  intestine,  leukocytes  (pus-cells)  are  found. 


COMPARATIVE    PHYSIOLOGY    OF    DIGESTION.  343 

3.  Diarrhea  may  develop   in  consequence  of  disturbances  of  the  processes 
of  diffusion  through  the  intestinal  walls.     Affections  of  the  epithelial  cells  should 
be  mentioned  in  this  connection:  swelling  in  association  with  catarrhal   or  in- 
flammatory conditions  of  the  mucous  membrane.     As,  further,  in  the  process 
of  absorption  independent  activity  on  the  part  of  the  cylindrical  cells  is  to  be  taken 
into  consideration,  controlled,  perhaps,  by  the  nervous  system,  it  is  plain  how 
sudden  agitation,  from  fright,  anxiety,  etc.,  may  cause  diarrhea. 

4.  Diarrhea  may  be  the  result  of  increased  secretion.     In  its  simplest  form 
this  occurs  through  capillary  transudation,  when  salts,  as,  for  example,  magne- 
sium sulphate,  introduced  into  the  intestine,  remove  water  from  the  blood  by 
endosmosis.     In  this  category  belong  the  copious  watery  discharges  that  take 
place  in  consequence  of  alteration  of  the  intestinal  epithelium,   as  in  cases  of 
cholera,  in  which  such  excessive  transudation  takes  place  into  the  intestine  that 
the    blood    becomes    inspissated    and    may   even    stagnate    in    the    veins.     In 
addition,  transudation  into  the  bowel  may  take  place  in  consequence  of  paralysis 
of  the  yasomotor  nerves  of  the  intestine.     The  diarrhea  due  to  cold  appears  to 
belong  in  this  group.     Certain  substances  appear  directly  to  irritate  the  secretory 
organs  of  the  intestine  or  their  nerves ;   among  these  are  the  drastic  purgatives. 
Pilocarpin  injected  into  the  blood  also  induces  marked  secretion. 

In  the  presence  of  febrile  disorders,  the  secretion  of  the  intestinal  glands 
appears  to  undergo  quantitative  and  qualitative  changes,  with  simultaneous 
derangement  in  the  activity  of  the  intestinal  musculature  and  the  organs  of 
absorption  and  increased  irritability  of  the  mucous  membrane. 

With  respect  to  fermentations  in  the  intestine,  the  fact  should  be  emphasized 
that  all,  in  excess,  as,  for  example,  the  butyric  or  the  acetic,  give  rise  to  patho- 
logical manifestation.  With  regard  to  the  pathogenic  schizomycetes  acting 
from  the  intestinal  canal  (cholera,  typhoid,  dysentery,  and  others)  reference  may 
be  made  to  p.  246  Flagellated  trichomonads  are  exceedingly  rare. 

Finally,  attention  should  be  directed  to  the  fact  that,  in  consequence  of 
abnormal  decompositions  in  the  intestinal  canal,  substances  may  be  formed  that 
exert  a  toxic  effect  upon  the  organism  and  thus  give  rise  to  auto-intoxications. 

COMPARATIVE  PHYSIOLOGY  OF  DIGESTION. 

Among  mammals,  herbivora  possess  larger  salivary  glands  than  carnivora, 
while  omnivora  occupy  an  intermediate  position.  Whales  have  no  salivary 
glands  at  all;  the  pinnipeds  have  a  small  parotid,  the  echidna  none  at  all.  The 
dog,  like  some  carnivora,  has  an  additional  zygomatic  gland  situated  in  the  orbit. 
In  birds  the  salivary  glands  empty  at  the  angle  of  the  mouth;  the  parotid 
gland  is  wanting.  Among  snakes  the  parotid  glands  are  in  some  species 
transformed  into  poison-glands;  tortoises  have  sublingual  glands;  in  addition, 
reptiles  have  labial  glands  at  the  margin  of  the  lips.  Amphibia  and  fish  have 
only  small,  disseminated  buccal  glands.  In  insects  the  salivary  glands  are  widely 
distributed,  partly  unicellular  (as,  for  example,  two  pairs  in  lice),  partly  com- 
pound; several  pairs  of  them  are  usually  present.  In  some  the  secretion  contains 
formic  acid,  for  which  reason  the  stings  of  these  animals  cause  burning  and  in- 
flammation; in  others  the  secretion  is  strongly  alkaline,  as  that  from  the  large 
salivary  glands  of  the  bed-bug.  In  bees  and  ants  the  lower  salivary  glands  secrete 
a  sort  of  cement-substance.  The  web-glands  on  the  lower  lip  of  caterpillars 
secreting  the  silky  material,  principally  those  of  the  silk-worm,  should  not  be 
confounded  with  the  salivary  glands.  Among  vermes,  leeches  have  unicellular 
salivary  glands.  In  snails  the  salivary  glands  are  also  widely  disseminated, 
and  the  saliva  from  dolium  galea  contains  more  than  3^  per  cent,  sulphuric  acid, 
which  also  is  present  in  murex.  cassis,  and  aplysia.  Cephalopods  have  a 
double  set  of  salivary  glands.  In  the  octopus  the  saliva  digests  fibrin,  but  not 
starch,  and  it  is  poisonous. 

Crop-like  formations  are  wanting  in  all  mammals;  the  stomach  appears  to 
be  single,  as  in  human  beings,  or  divided  into  halves,  as  in  many  rodents,  into 
a  cardiac  portion  and  a  pyloric  portion. 

The  stomach  of  ruminants  consists  of  four  portions:  the  first  and  largest 
is  the  paunch  (rumen),  the  next  the  honeycomb-bag  (reticulum).  In  these  two 
portions,  principally  in  the  paunch,  the  ingesta  undergo  maceration  and  fermenta- 
tion. They  are  now  returned  to  the  mouth  by  the  action  of  the  voluntary  mus- 
cular fibers  passing  to  the  stomach,  again  thoroughly  masticated,  and,  by  the 
closure  of  a  special  semicircular  groove  (esophageal  groove),  the  bolus  is  carried 


344  COMPARATIVE    PHYSIOLOGY    OF    DIGESTION. 

into  the  third  stomach,  the  manyplies  (psalterium) ,  which  is  absent  in  camels,. 
and  thence  to  the  true,  fourth  stomach,  the  rennet-stomach  (abomasum).  In 
the  two  first  stomachs  starch  and  cellulose  are  digested,  the  sugar  formed  in  part 
passing  over  into  lactic  acid.  The  third  stomach  performs  chiefly  mechanical 
work,  while  the  fourth  really  digests  albumin.  In  the  small  intestine  proteids 
and  carbohydrates  are  further  digested. 

The  intestine  is  divided  into  the  small  and  the  large  intestine.  It  is  short 
in  carnivora,  and  considerably  longer  in  herbivora.  The  cecum,  which  in  her- 
bivora  attains  considerable  size  as  the  most  important  organ  of  digestion,  and  in 
some  rodents  is  even  multiple,  represents  in  human  beings  an  insignificant, 
typical  remnant,  and  is  wholly  absent  in  carnivora.  In  birds  the  esophagus, 
especially  in  birds  of  prey  and  granivora,  often  possesses  a  diverticular  appendix, 
the  crop,  for  the  maceration  of  the  food.  In  the  crop  of  pigeons  there  occurs, 
at  the  breeding-season,  the  secretion  of  crop-milk,  the  product  of  a  special  gland r 
which  is  also  used  as  food  for  the  young.  The  stomach  consists  of  the  proven- 
triculus  well  supplied  with  glands,  and  the  thick-walled  muscle-stomach,  which, 
with  the  aid  of  the  inner  horny  plates,  effects  the  crushing  especially  of  grain.  In 
the  intestine,  at  the  junction  with  the  short  large  intestine,  there  is  almost  con- 
stantly present  a  pair  of  ceca  shaped  like  a  glove-finger.  The  intestinal  mucous 
membrane  exhibits  principally  longitudinal  folds.  The  alimentary  canal  of  fish 
is  usually  simple.  The  stomach  frequently  represents  only  a  dilatation.  Less 
commonly  the  pylorus  possesses  one,  more  frequently  a  large  number  of  divertic- 
ular appendices,  containing  a  large  number  of  glands  (appendices  pyloricae,  as, 
for  example,  in  the  salmon).  The  mucous  membrane  of  the  usually  short  intes- 
tine exhibits  longitudinal  plication,  as  a  rule,  or  the  so-called  spiral  valve,  as  in 
the  sturgeon,  resulting  from  a  spiral  arrangement.  The  alimentary  canal  of  fish, 
from  the  esophagus  to  the  rectum,  possesses  peptonizing  power.  The  short 
rectum  is  provided,  in  sharks  and  rays,  with  a  diverticular  appendage  (bursa 
entiana). 

In  amphibia  and  reptiles  the  stomach  is  generally  a  simple  dilatation.  The 
intestine  is  longer  in  herbivora  than  in  carnivora.  Especially  interesting  in 
this  connection  is  the  fact  that  the  vegetable-eating  frog-larvas  acquire  a 
much  shorter  intestine  with  the  metamorphosis  that  makes  them  carnivorous, 
terrestrial  animals.  The  intestinal  mucous  membrane  of  reptiles  exhibits 
numerous  plications.  The  liver  is  not  wanting  in  any  vertebrate,  and  is 
especially  large  in  fish.  The  amphioxus  has  only  a  diverticulum  indicative  of 
the  liver.  The  gall-bladder  is  wanting  occasionally  in  all  classes,  in  accord  with 
which  is  the  experimental  observation  that  extirpation  of  the  gall-bladder  is 
unattended  with  appreciable  influence  on  digestion  and  absorption.  The  pan- 
creas is  wanting  only  in  some  fish.  One  opening  (in  the  amphioxus)  or  two  open- 
ings (in  the  shark,  the  ray,  the  sturgeon,  the  eel  and  the  salmon)  lead  from  with- 
out freely  into  the  abdominal  cavity;  the  same  conditions  prevail  also  in  crocodiles. 

Among  the  molluscs,  snails  and  cephalopods  only  have  true  organs  of 
mastication.  Some  herbivorous  land-snails  have  a  movable,  horny  grinding 
plate  situated  in  the  upper  pharyngeal  wall.  Horizontal  maxillary  plates,  with 
hard  edges  working  one  upon  the  other,  are  present  particularly  in  carnivorous 
snails  with  uncovered  gills.  A  horny  grinding  plate,  placed  like  a  tongue,  whose 
peculiar  form  serves  for  the  systematic  differentiation  of  various  snails,  is  fre- 
quently present  in  others.  Cephalopods  possess  a  strong  biting  apparatus  in 
the  form  of  a  large,  horny  pair  of  jaws,  resembling  a  parrot's  beak  in  shape.  They 
also  have  a  grinding  plate  upon  a  tongue-like  prominence,  studded  with  spines. 
The  alimentary  canal  is  divided  into  esophagus,  stomach  and  intestine,  at  times 
provided  with  diverticula.  In  many  mussels  the  rectum  pierces  the  heart  and 
the  pericardium.  In  snails  the  anus  is  usually  in  the  vicinity  of  the  respiratory 
organs.  The  liver  is,  as  a  rule,  large.  The  vineyard-snail  has  a  cellulose- 
splitting  ferment  in  the  secretion  of  the  liver.  In  the  cephalopods  the  ink-bag 
opens  into  the  rectum  or  near  the  anus. 

Among  vertebrates  crustaceans  have  a  masticating  apparatus  transformed 
from  feet;  in  some,  true  masticating  feet  are  still  present;  in  parasitic  crabs  there 
are  also  sucking  mouth-organs.  Among  arachnids  the  mites  have  sucking  mouth- 
organs;  in  true  spiders,  there  are,  in  addition  to  the  sucking  mouth-organs, 
horizontally  acting  clutching  jaws,  in  part  connected  with  poison-glands.  Centi- 
pedes possess  a  strong  pair  of  jaws,  acting  horizontally.  Of  insects,  those  provided 
with  masticating  mouth-organs  possess,  between  the  upper  and  lower  lips,  two 
pairs  of  jaws,  acting  horizontally  against  each  other,  of  which  the  upper  (man- 


COMPARATIVE    PHYSIOLOGY    OF    DIGESTION.  345 

dibulae)  exceed  the  lower  (maxillae)  in  strength.  In  sucking-insects  the  four 
jaws  are  transformed  into  a  long  tube  with  a  longitudinal  slit  (the  stinging  pro- 
boscis of  the  bed-bug),  which  lies  in  the  semicircularly  grooved  lower  lip  as  in 
a  case.  The  proboscis  of  the  butterfly  consists  of  the  greatly  prolonged  lower 
jaws,  lying  side  by  side,  and  capable  of  being  rolled  up,  while  the  development 
of  the  upper  jaws  has  been  arrested.  Bees  have  a  sucking  tongue,  which  lies 
in  a  groove  formed  in  the  lower  jaws;  in  addition,  the  feeble  upper  jaws  still  per- 
sist as  organs  of  mastication. 

In  crustaceans  the  esophagus  is  short;  in  some  the  stomach  is  a  simple  dila- 
tation, in  others  it  possesses  diverticula,  in  which  are  situated  the  bile-producing 
glands.  The  fresh- water  crab  and  its  relatives  possess  a  strong  chitinized  in- 
tima  in  the  stomach,  which  is  capable  of  acting  as  a  masticating  organ.  This 
membrane  is  expelled  when  the  skin  is  shed.  Among  arachnids,  scorpions  have 
a  simple  alimentary  canal.  True  spiders  possess  a  narrow  esophagus  and  a 
circular  stomach;  in  addition  diverticula  on  all  sides,  at  the  base  of  which  liver- 
tissue  is  present,  and  which  may  extend  even  down  into  the  feet.  In  insects, 
in  addition  to  the  esophagus  and  the  chyle-stomach,  generally  rich  in  glands, 
and  at  times  serrated,  there  are  present  various  portions,  such  as  the  crop  in 
the  cricket  for  instance,  the  sucking  stomach  in  the  butterfly,  the  masticating 
stomach  in  the  beetle,  in  varying  manner.  The  intestinal  canal  is  usually  shorter 
in  carnivorous  than  in  herbivorous  insects.  In  the  intestine  of  the  flour- worm 
(tenebrio)  ferments  are  present  resembling  those  of  the  pancreatic  juice.  It 
is  remarkable  that,  in  the  larval  state,  as,  for  example,  of  most  bees,  the  tract  is 
closed  below  the  chyle-stomach.  The  rectum,  with  its  auxiliary  apparatus,  exists 
by  itself  and  empties,  as  an  excretory  duct,  into  the  anus.  Peculiar  long,  tubular 
excretory  organs,  the  Malpighian  vessels,  several  of  which  are  present,  open  at 
the  junction  of  the  small  and  the  large  intestine. 

Of  the  vermes,  tape-worms,  as  well  as  the  acanthocephala  (echinorhynchus) 
among  round  worms,  have  no  special  digestive  organ,  but  are  nourished  byendos- 
mosis,  through  absorption  on  the  part  of  the  skin.  The  anus  is  wanting  in 
trematodes  (distomum),  thread-worms,  and  almost  all  turbellaria.  In  the  first, 
as  well  as  in  leeches  (sanguisuga) ,  the  buccal  orifice  is  surrounded  by  a  sucking- 
cup,  which,  in  leeches,  possesses,  in  its  depth,  three  dentated  cutting  organs. 
Some  leeches,  as  well  as  the  planaria,  have  a  protrusile  proboscis.  The  intestine 
of  turbellaria,  unprovided  with  an  anus,  is  shaped  simply  like  a  glove-finger.  It 
is  variously  branched  in  liver-flukes  (distomum) .  In  the  annulate  worms  the  in- 
testine extends  from  the  anterior  to  the  posterior  extremity  of  the  body;  both 
mouth  and  anus  are  present.  Among  them,  the  earth-worms  possess  a  muscular 
pharynx,  while  leeches  have  a  highly  distensible  stomach,  provided  with  many 
lateral  diverticula,  which,  when  the  animal  has  sucked  itself  full,  can  be  incised 
through  the  skin  of  the  back,  so  that  the  blood  flows  continuously  from  the  wound, 
while  the  animal  continues  to  take  up  blood  through  its  sucking  mouth  (bdel- 
lotomy) .  All  vermes  are  unprovided  with  a  liver. 

All  echinoderms  possess  an  intestinal  canal.  The  mouth  is  often  provided 
with  a  biting  mechanism,  which  appears  in  sea-urchins  in  the  form  of  five  enamel- 
teeth  connected  with  a  movable,  complicated  maxillary  apparatus  (Aristotle's 
lantern) .  Many  of  the  starfish  are  unprovided  with  an  anus ;  a  bile-like  secretion 
is  found  in  diverticula  of  their  stomach.  Salivary  glands  have  been  found  in 
sea-urchins. 

The  aquatic  celenterates  possess  no  intestinal  tract  provided  with  independent 
walls.  The  abdominal  cavity  is  the  digestive  cavity;  mouth  and  anus  are  repre- 
sented by  the  same  central  orifice,  which  often  is  surrounded  by  tentacles  (med- 
usae, polyps)!  A  system  of  canals,  passing  through  the  body  (medusa?),  and  con- 
nected with  the  digestive  cavity,  conveys  the  nutritive  fluid  and,  at  the  same 
time,  the  oxygen-containing  water.  It  is,  therefore,  the  water- vascular-system,  and 
at  the  same  time  the  nutritive,  respiratory  and  excretory  organ. 

Among  the  protozoa,  the  gregarines  are  nourished  by  endosmosis  through 
the  skin.  Infusoria  possess  mouth  and  anus,  although  their  abdominal  cavity 
is  bounded  only  by  the  protoplasm  of  their  body-substance.  Rhizopods  surround 
their  food  with  their  body-substance  and  excrete  the  indigestible  material  at 
another  portion  of  the  body.  In  sponges  this  process  takes  place  from  the  in- 
terior of  their  numerous  canals,  which  penetrate  the  colonies  of  their  protoplasmic 
bodies. 

Digestive  Phenomena  in  Plants. — The  observations  upon  the  digestion  of 
proteid  on  the  part  of  a  number  of  plants  are  highly  remarkable.  The  sundew 


346  HISTORICAL. 

(drosera)  possesses,  upon  the  surface  of  its  leaves,  numerous  tentacle-like  processes, 
provided  with  glands.  As  soon  as  an  insect  lights  upon  the  leaf,  the  former  is 
suddenly  seized  by  the  tentacles.  The  glands  discharge  a  juice  of  acid  reaction 
and  digest  the  animal  with  the  exception  of  its  insoluble  chitinous  remains.  The 
juice  contains  a  pepsin-like  ferment  and  formic  acid.  The  secretion,  as  well  as, 
later,  the  absorption  of  the  dissolved  substances,  takes  place  in  conjunction 
with  movement  of  the  protoplasm  of  the  leaf-cells.  Venus'  fly-trap  (dionea)  and 
butter-wort  (pinguicula)  exhibit  similar  processes,  as  well  as  the  cavities  of  the 
transformed  leaves  of  the  nepenthe.  Altogether,  about  15  species  of  .such 
carnivorous  dichotyles  are  known. 

The  juice  escaping  from  incisions  in  the  green  fruit  of  the  papaw-tree  (carica 
papaya)  possesses  peptonizing  properties  due  to  a  ferment  closely  allied  to  trypsin. 
The  milky  sap  from  the  fig-tree  is  likewise  active,  exerting  a  diastatic  effect  and 
also  coagulating  milk  at  50°  C.  Albumin  is  dissolved  also  by  some  fungi  (boletus, 
tuber) ,  lichens  (parmelia)  and  the  sap  of  taraxacum,  lactuca,  agave  and  portulac. 
Artichokes,  yellow  or  lady's  bedstraw  and  other  plants  contain  rennet-ferment. 
The  sap  of  aloes  and  of  sugar-cane,  as  well  as  dried  figs,  coagulates  milk  and  has 
a  peptonizing  action;  as  does  also  ordinary  flour-dough  on  admixture;  further,  the 
juice  (containing  peptone  at  the  same  time)  from  the  seed  of  wheat,  barley, 
poppy,  beets  and  corn,  after  the  addition  of  organic  acids.  Potatoes  and  rice 
have  feeble,  flour,  grain  and  corn  marked  sugar-forming  activity. 

HISTORICAL. 

Digestion  in  the  Mouth. — The  vessels  of  the  teeth  were  known  to  the  Hippo- 
cratic  school.  Aristotle  ascribed  an  uninterrupted  growth  to  the  teeth.  In 
addition,  he  directed  attention  to  the  fact  that  those  animals  that  exhibit  a  devel- 
opment of  horns  and  antlers,  cloven-hoofed  animals,  possess  an  imperfect  denture 
(absence  of  the  upper  incisor  teeth) .  It  is  a  remarkable  fact  that,  in  human  beings 
with  excessive  formation  of  horny  substance,  in  consequence  of  the  presence 
of  superfluous  hair,  imperfect  development  of  the  teeth  (absence  of  the  incisors) 
has  also  been  observed.  The  muscles  of  mastication  were  recognized  early. 
Vidius  (died  1567)  described  the  maxillary  articulation,  with  the  meniscus.  The 
epiglottis,  according  to  Hippocrates,  prevents  the  entrance  of  food  into  the 
larynx.  The  ancients  considered  the  saliva  only  a  solvent  and  a  means  for 
moistening  the  food.  In  addition,  in  consequence  of  a  knowledge  of  the  saliva  of 
rabid  animals  and  the  parotid  secretion  of  venomous  snakes,  various  poisonous 
properties  were  ascribed  to  the  saliva,  especially  from  fasting  animals — a  view 
that  Pasteur  again  confirmed  in  part,  referring  the  action  to  pathogenic  bac- 
teria in  the  secretions  of  the  mouth.  Aretasus  (81  A.  D.)  emphasizes  the 
muscular  nature  of  the  tongue.  The  salivary  glands  had  been  discovered  in 
ancient  times.  Galen  (131-203  A.  D.)  was  familiar  with  Wharton's  duct  and 
^tius  (270  A.  D.)  with  the  submaxillary  and  sublingual  glands.  Regner  de  Graaf 
established  salivary  fistulas  in  dogs  in  1663,  by  tying  tubes  in  Stenon's  duct. 
Hapel  de  la  Chenaye  obtained  in  1780  for  examination  large  amounts  of  saliva 
from  a  salivary  fistula  established  in  a  horse.  Spallanzani  in  1786  stated  that 
insalivated  articles  of  food  are  more  readily  digested  than  those  moistened  with 
water.  Hamburger  and  Siebold  investigated  the  reaction,  consistency  and 
specific  gravity  of  the  saliva  and  found  mucus,  proteid  and  salts  present.  Ber- 
zelius  introduced  the  term  ptyalin  for  the  characteristic  substance  in  the  saliva, 
though  Leuchs  in  1831  first  discovered  its  diastatic  fermentative  action. 

Gastric  Digestion. — The  ancients  compared  digestion  to  cooking,  through  which 
solution  is  effected.  Aristotle  supposed  that,  through  this  "pepsis"  chyle 
(ichor)  first  developed  from  the  food,  and  then  reached  the  heart.  He  also 
knew  of  the  rennet-action  of  the  stomach.  According  to  Galen,  only  dissolved 
masses  pass  through  the  pylorus  into  the  intestine.  He  described  the 
movement  of  the  stomach  and  the  peristalsis  of  the  intestines.  ^Elian  recognized 
the  four  stomachs  of  ruminants  and  gave  their  names.  Vidius  (died  1567) 
observed  the  numerous  small  glandular  openings  in  the  gastric  mucous  mem- 
brane, van  Helmont  (died  1644)  expressly  mentions  the  acid  of  the  stomach. 
He  as  well  as  Sylvius  (died  1672)  compared  the  action  of  the  stomach  with 
fermentation,  in  connection  with  which,  according  to  Descartes  (died  1650)  and 
Willis  (died  1675),  the  action  of  the  acid  predominates.  Reaumur  (1752) 
recognized  that  a  juice  was  secreted  by  the  stomach  that  effects  solution  and 
with  which,  together  with  Spallanzani  (1777),  he  undertook  digestive  experi- 


HISTORICAL.  347 

ments  outside  of  the  stomach.  Carminati  (1785)  then  found  that  the  stomach 
of  carnivora,  especially  when  engaged  in  digestion,  secretes  an  actively  acid  juice. 
Prout  discovered  in  1824  the  hydrochloric  acid  of  the  gastric  juice  and  Sprott 
and  Boyd  in  1836  found  the  glands  of  the  gastric  mucous  membrane,  among 
which  Wassmann  and  Bischoff  distinguished  the  two  different  kinds.  After 
Beaumont  (1825-1833)  had  made  his  observations  upon  a  man  with  a  gastric 
fistula,  Bassow  (1842)  and  Blondlot  (1843)  established  the  first  artificial  gastric 
fistulae  in  animals.  Eberle  subsequently  (1834)  prepared  artificial  gastric 
juice.  Mialhe  designated  the  albumin  modified  by  digestion  as  albuminose; 
while  Lehmann,  who  examined  this  more  thoroughly,  introduced  the  name  of 
peptone.  Schwann  (1836)  first  prepared  pepsin  and  defined  its  activity  in  com- 
bination with  hydrochloric  acid. 

Pancreas,  Bile,  Intestinal  Digestion. — The  pancreas  was  known  to  the  Hip- 
pocratic  school.  Moritz  Hofmann  demonstrated  in  1641  its  excretory  duct  in 
the  turkey  to  Wirsung,  who  (1642)  described  it  in  human  beings  as  his  dis- 
covery. Regner  de  Graaf  collected  in  1663  pancreatic  juice  from  fistulae,  and  which 
Tiedemann  and  Gmelin  found  to  be  alkaline,  while  Leuret  and  Lassaigne  found 
it  to  resemble  saliva.  Bouchardat  and  Sandras  in  1845  discovered  its  diastatic, 
Eberle  in  1834  its  emulsifying,  Purkinje  and  Pappenheim  in  1836  its  peptic,  and 
Cl.  Bernard  in  1846  its  fat-splitting  properties,  to  the  last  of  which  Purkinje  and 
Pappenheim  had  already  directed  attention. 

Aristotle  designates  the  bile  as  a  useless  excrementitious  product.  Ac- 
cording to  Erasistratus  the  bile  is  conveyed  from  the  liver  to  the  gall-bladder 
through  most  minute,  invisible  ducts.  Aretaeus  attributed  the  cause  of  icterus  to 
occlusion  of  the  bile-ducts.  Benedetti  in  1493  described  gall-stones.  According 
to  Jasolinus  (1573)  the  gall-bladder  is  emptied  by  its  own  contraction.  Sylvius  de 
le  Boe  (1640)  observed  the  hepatic  lymph- vessels,  Walaeus  (1641)  the  connective 
tissue  of  the  so-called  capsule  of  Glisson.  Albr.  v.  Haller  pointed  out  the  utility 
of  the  bile  in  the  digestion  of  fat.  Henle,  Purkinje  and  Dutrochet  (1838)  de- 
scribed the  liver-cells.  Heynsius  discovered  urea,  Cl.  Bernard  (1853)  sugar,  in 
the  liver,  and  with  Hensen  (1857),  ne  found  glycogen  in  the  liver.  Kiernan  (1834) 
described  the  blood-vessels  more  thoroughly.  Beale  injected  the  lymph- vessels, 
Gerlach  (1854)  the  finest  biliary  passages,  Schwann  (1844)  established  the  first 
biliary  fistula.  Gmelin  discovered  cholesterin,  taurin  and  the  biliary  acids. 
Demarcey  pointed  out  the  combination  of  the  biliary  acids  with  sodium  (1838). 
Strecker  found  the  sodium-combinations  of  both  biliary  acids  and  isolated  them. 

Corn.  Celsus  mentioned  nutritive  enemata  (3-5  A.D.).  Laguna  (1533)  and 
Rondelet  (1554)  knew  of  Bauhin's  valve.  Fallopia  (1561)  described  the  folds 
and  villi  of  the  intestinal  mucous  membrane,  as  well  as  the  nerve-plexuses 
of  the  mesentery.  J.  Conrad  Brunner  (1687)  discovered  the  duodenal  glands 
that  bear  his  name.  Severinus  (1645)  knew  of  the  agminated  follicles  (Peyer's 
patches,  1673)  and  Galeati  (1731)  knew  of  Leiberkuhn's  (1745)  glands  in  the 
intestine. 


PHYSIOLOGY  OF  ABSORPTION. 


STRUCTURE  OF  THE  ORGANS  OF  ABSORPTION. 

The  mucous  membrane  of  the  entire  intestinal  tract,  so  far  as  it  is 
lined  by  a  single  layer  of  cylindrical  epithelium,  that  is,  from  the  cardiac 
orifice  to  the  anus,  is  capable  of  absorption.  The  buccal  cavity  and  the 
esophagus  can  take  part  in  this  process  only  to  an  exceedingly  limited 
extent,  on  account  of  their  thick,  many-layered  squamous  epithelium. 
Nevertheless,  poisoning,  as,  for  example,  with  potassium  cyanid,  may 
take  place  by  absorption  from  the  mouth  alone.  The  capillary  blood- 
vessels, as  well  as  the  chyle- vessels,  of  the  mucous  membrane  act  as  the 
absorbing  channels  of  the  intestinal  tract.  The  former  convey  the 
materials  absorbed  almost  wholly  through  the  portal  vein  to  the  liver, 
while  the  latter,  uniting  in  their  further  course  with  lymph- vessels,  dis- 
charge the  absorbed  chyle  or  milky  juice  through  the  thoracic  duct  into 
the  blood  at  the  junction  of  the  subclavian  and  internal  jugular  veins. 

From  the  stomach  are  absorbed  aqueous  salt-solutions  (within  six 
minutes),  sugar  (namely,  grape-sugar,  milk-sugar,  cane-sugar  and  mal- 
tose) in  aqueous  solution  in  moderate  amount,  in  alcoholic  solution  in 
somewhat  larger  amount;  dextrin  and  peptone,  chiefly  in  concentrated 
solutions,  in  lesser  amount;  and  poisons,  especially  when  dissolved  in 
alcohol.  Klemperer  and  Scheurlen  observed  that,  in  the  dog,  neither 
fat  nor  the  fatty  acids  were  absorbed.  The  empty  stomach  absorbs 
more  rapidly  than  that  filled  with  food.  Diseases  of  the  stomach  and 
fever  cause  delayed  absorption. 

In  addition  to  absorption,  an  active  secretion  of  water  into  the  stomach, 
takes  place,  in  general,  in  greater  degree  in  proportion  as  the  amount  of  absorbed 
substances  is  greater. 

The  small  intestine  constitutes  the  principal  field  of  absorption,  pre- 
senting, especially  in  its  upper  half,  through  its  many  folds  of  mucous 
membrane  and  through  the  innumerable  cone-shaped  villi  projecting  from 
them,  an  extraordinary  expanse  of  surface  for  absorption.  The  villi  are 
close  together  at  their  bases,  so  that  the  entire  surface  of  the  mucous 
membrane  appears  to  be  covered  with  them.  In  the  spaces  between 
their  bases  the  numerous  simple  tubules  of  Lieberkiihn's  glands  empty. 
Each  villus  is  to  be  regarded  as  a  projection  of  the  entire  mucous  mem- 
brane, for  it  contains  all  of  the  elements  comprised  within  it. 

The  cloak-like  covering  of  the  villi  consists  of  a  single  layer  of  cylin- 
drical epithelium  with  intervening  isolated  mucous  goblet-cells.  The 
surface  of  the  cells  directed  toward  the  lumen  of  the  intestine  is  poly- 
gonal (Fig.  127,  D)  and,  viewed  from  the  side  (C),  exhibits  a  broad 
seam-like  outline,  which  was  formerly  considered  the  thickened  wall  of 
the  cell-membrane  and  was  designated  by  the  term  "lid-membrane." 
This  seam  exhibits  a  delicate  longitudinal  striation,  which  was  inter- 
preted in  part  as  the  expression  of  the  constitution  of  the  lid,  of  rods 

348 


STRUCTURE    OF    THE    ORGANS    OF    ABSORPTION. 


349 


arranged  as  a  mosaic,  in  part  as  pore-canaliculi,  intended  for  the  passage 
of  the  finest  fat-granules.  As  a  matter  of  fact,  however,  this  seam 
belongs  only  to  the  longitudinal  surfaces  of  the  epithelial  cells  and  is 
comparable  to  the  thickened  edge  of  a  cylindrical  vessel,  open  above. 
The  protoplasmic  cell-contents,  which  enclose  a  large  elliptical  nu- 
cleus with  nucleolus  in  the  lower  portion  of  the  cell,  end  approximately 
on  a  level  with  this  edge,  although  at  the  same  time,  they  contain,  at  the 
level  of  the  thickness  of  this  marginal  seam,  many  pseudopod-like  proto- 
plasmic processes,  which,  standing  side  by  side,  and  arranged  in  bundles, 
are  surrounded  by  the  edge  of  the  marginal  border.  Thus,  when  viewed 
from  the  side,  the  lid-membrane  appears  striated,  while,  as  a  matter 


FIG.  127. — Structure  of  the  Absorption-apparatus  of  a  Villus:  A,  transverse  section  of  a  villus,  in  part ;  a.  cylindrical 
epithelium,  with  thickened  border  (b);  c,  a  goblet-cell;  i,  i,  framework  of  the  adenoid  tissue  of  the  villus; 
d,  d,  cavity  within  this,  in  which  lie  lymphoid  cells  (e,  e);  f,  central  lymph-space  in  transverse  section.  B,  two 
cylindrical  epithelial  cells  with  extended  pseudopod-like  processes  of  the  cell-protoplasm,  participating  in 
absorption  of  the  fat-granules.  C,  cylindrical  epithelium  after  absorption  of  the  fat-granules  has  been  com- 
pleted. D,  cylindrical  epithelium  of  the  villus,  viewed  from  the  surface,  with  a  goblet-cell  in  the  center. 

of  fact,  neither  the  lid  nor  the  mosaic  plates  or  pores  attributed  to  it 
exist.  The  cells  are,  therefore,  open  toward  the  intestinal  surface. 
The  protoplasmic  processes,  standing  close  together,  and  resembling  the 
cilia  of  ciliated  epithelium,  are  directed  from  the  interior  of  the  cell 
toward  the  periphery  of  the  intestine.  In  their  midst,  near  the  free  sur- 
face, lies  a  diplosoma.' 

These  protoplasmic  processes  are  rapidly  extended  from  the  cell-body 
beyond  the  edge  of  the  cell-membrane,  and  in  a  manner  comparable 
to  the  pseudopods  of  amoebae,  they  seize  the  finely  granular  fat  and 
draw  it  into  the  cell-body.  Moistening  with  bile  appears  especially  to 
promote  their  activity,  as  the  movement  is  not  observed  in  villi  not 
moistened  with  bile. 


35° 


STRUCTURE  OF  THE  ORGANS  OF  ABSORPTION. 


In  addition,  the  medulla  oblongata,  the  spinal  cord  or  the  dorsal  nerves  must 
have  been  divided  for  about  a  day  previously.  This  apparently  depends  upon 
the  fact  that,  in  the  preparation  of  an  uninjured  animal  (frog),  the  fresh  division 
of  nerves  that  becomes  necessary  acts  as  an  irritant,  as  a  result  of  which  the 
cells  settle  down  to  rest,  like  irritated  amoeba?  or  like  the  corneal  cells  after  irrita- 
tion of  their  nerves.  This  fact  points  to  an  influence  of  the  nerves  upon  absorp- 
tion. 

When  the  epithelial  cells  are  filled  with  fat -granules,  the  processes 
are  withdrawn  into  the  interior  of  the  cell.  The  border  then  appears 
unstriated,  and  a  transparent  zone  lies  between  it  and  the  cell-proto- 
plasm. The  goblet-cells  appear  to  be  engaged  principally  in  the  secre- 
tion of  mucus;  although  small  fat-granules  are  also  occasionally  seen 
within  them. 

Pathological:    In  cases  of  cholera,  as  well  as  after  poisoning  with  arsenic  and 

muscarin,  enormous  desquamation  of 
intestinal  epithelium  takes  place. 

According  to  the  views  of 
Eimer,  Heidenhain,  v.  Than- 
hoffer  and  others,  the  con- 
stricted root-ends  of  the  epithe- 
lial cells  communicate  with 
anastomosing  connective-tissue 
corpuscles  of  the  villous  tissue. 
Into  these  the  fat-granules  are 
believed  to  migrate  from  the 
interior  of  the  epithelial  cells. 
The  soft  connective-tissue  cells, 
finally,  are  thought  to  com- 
municate with  the  central 
lymph- vessel ;  and  in  this  man- 
ner a  communication  is  estab- 
lished between  the  epithelium 
and  the  latter.  Thus,  the  fat- 
granules  would  migrate  through 
the  body  of  the  connective- 
tissue  cells,  as  through  lymph- 
canaliculi,  to  the  central  lymph- 
vessel.  The  author  is  able  to 
agree  with  this  conception  with  a 
modification,  which  approaches 

the  views  of  His,  Briicke  and  v.  Basch.  As  a  result  of  his  investiga- 
tions he  believes  that  the  epithelial  cell  narrows  toward  its  lower 
extremity,  like  a  funnel;  the  cell-membrane  entering,  in  various  direc- 
tions, directly  into  communication  with  the  supporting  cells  of  the 
adenoid  tissue  of  the  villus,  as  well  as  with  the  subepithelial  branching 
layer  of  the  villus,  which,  accordingly,  must  be  perforated  in  many 
places.  The  supporting  cells  of  the  villous  tissue  surround  a  spongy 
system  of  cavities  within  which  lie  protoplasmic,  nucleated  stroma-cells 
(Fig.  127,  A)  of  varying  appearance.  The  latter  at  times  contain  fat- 
granules  in  suspension.  According  to  v.  Davidoff ,  these  cells  are  formed 
by  constriction  from  the  lower  extremities  of  the  epithelial  cells,  which, 
in  time,  develop  a  nucleus  within  themselves. 

These  cells,  like  ameboid  cells  without  capsules,  communicate  with  one 


A. 


FIG.  128. — Blood-vessels  of  an  Intestinal  Villus:  Cn, 
capillaries;  A,  artery;  Cl,  cylindrical  epithelium;  O, 
surface  of  the  epithelium;  V,  vein. 


ABSORPTION    OF    THE    DIGESTED    FOOD.  351 

another  and  with  the  protoplasm  of  the  epithelial  cells,  and  in  them, 
through  active  movement  of  the  protoplasm,  wander  the  fat-granules, 
which  the  cells  take  up  and  again  give  up  within  the  villus.  Thus,  the 
epithelial  sheath,  with  the  connective-tissue  corpuscles  of  the  villus, 
forms  the  supporting  apparatus ;  the  contents  of  the  epithelial  cells  and 
the  numerous  stroma-cells  are  the  active  propellers  of  the  fat-granules 
taken  up.  Through  appropriate  interstices  in  the  tissues  the  cavities 
containing  the  stroma-cells  communicate  with  the  axial  lymph-vessel, 
which  is  lined  by  endothelial  cells.  It  is  not  improbable  that  leukocytes 
frequently  migrate  from  the  capillary  blood-vessels  of  the  villus  into 
the  tissue  of  the  villus  and,  in  part  containing  absorbed  fat-granules, 
pass  over  into  the  central  lymph-vessel.  According  to  Schafer,  Zawary- 
kin,  Wiedersheim,  Stohr,  Preusse,  Heidenhain  and  others,  the  ameboid 
cells  probably  migrate  from  the  parenchyma  of  the  villi  toward  the 
epithelial  layer  and  perhaps  even  between  the  epithelial  cells,  and  return 
toward  the  axis  of  the  villus,  laden  with  the  substances  absorbed. 

A  small  artery  enters  every  villus  and,  lying  excentrically,  passes 
to  the  summit  of  the  villus  without  division,  to  give  off  branches  from 
this  point.  In  human  beings  this  division  begins  at  the  middle.  The 
ramifications  form  a  dense  capillary  network,  which  lies  superficially 
in  the  parenchyma  of  the  villus,  almost  directly  beneath  the  epithelial 
layer,  and  from  which,  either  at  the  apex  of  the  villus  or  further  downward, 
a  vein,  running  backward,  is  constituted. 

The  villus  is  provided  with  unstriated  muscular  fibers,  both  deep- 
seated,  their  bundles  accompanying  the  central  lymph- vessel  longitu- 
dinally, and  also  superficial,  running  rather  transversely. 

The  connective  tissue  of  the  small  intestine  has  two  layers,  a  deeper,  composed 
of  thick,  interwoven,  mainly  collagenous  fibers  (stratum  fibrosum),  and  lying 
above  this  a  reticular  layer  intermixed  with  elastic  fibers  (stratum  granulosum) , 
entering  into  the  villi  also. 

Nerves  enter  the  villi  from  Meissner's  mucous-membrane  plexus,  are  provided 
with  small,  granular  ganglion-cells  in  their  course,  and  end  in  part  in  the  muscles 
of  the  villi  and  of  the  arteries,  while  in  part  they  appear  to  communicate  with 
the  contractile  protoplasm  of  the  epithelial  cells. 

Nerve-filaments  pass  from  Meissner's  mucous-membrane  plexus  to  the  vessels 
of  the  submucosa.  Meissner's  plexus  communicates,  by  numerous  fibers,  with 
a  nerve-plexus  that  spreads  throughout  the  entire  thickness  of  the  mucous  mem- 
brane, extends  into  the  villi  and  supplies  the  muscularis  mucosae,  the  vessels 
of  the  mucosa  and  Lieberkuhn's  glands. 

The  epithelial  cells  of  the  large  intestine  possess  no  seam-like  mar- 
ginal thickening. 

The  serous  coat  of  the  alimentary  tract  is  provided  with  special 
lymph- vessels,  at  first  distinct  from  the  chyle- vessels. 

ABSORPTION  OF  THE  DIGESTED  FOOD. 
PHYSICAL  FORCES:  ENDOSMOSIS,  DIFFUSION,  FILTRATION. 

Endosmosis  and  diffusion  take  place  between  two  liquids  that  are  capable 
of  admixture,  as,  for  example,  hydrochloric  acid  and  water,  but  never  between 
two  fluids  that  are  opposed  to  admixture,  as,  for  instance,  oil  and  water.  If 
two  miscible  dissimilar  liquids  are  separated  from  each  other  by  a  membrane 
provided  with  physical  pores,  such  as  may  be  present  even  in  apparently  homo- 
geneous membranes,  an  interchange  of  the  constituent  parts  takes  place  through 
the  pores  of  the  membrane,  until  finally  both  fluids  have  the  same  composition. 
This  process  is  designated  endosmosis  or  diosmosis.  The  endosmptic  passage 
of  a  substance  through  the  membrane  takes  place  if  a  solvent  liquid  having  an 
attraction  for  the  substance  is  present  on  the  other  side  of  the  membrane. 


352 


ABSORPTION    OF    THE    DIGESTED    FOOD. 


If  both  miscible  fluids  are  simply  placed  over  one  another  in  a  vessel,  without 
the  intervention  of  a  porous  septum,  an  interchange  of  particles  of  the  liquids  also 
takes  place,  until  the  entire  mass  has  undergone  homogeneous  admixture.  This 
interchange  is  designated  diffusion. 

The  rapidity  of  diffusion  is  influenced:  i.  By  the  nature  of  the  fluids.  Acids 
pass  over  most  rapidly,  alkaline  salts  more  slowly;  liquid  albumin,  gelatin,  gum, 
dextrin,  and  starch-solutions  most  slowly.  The  latter,  in  part,  do  not  crystallize, 
and  also  in  part  do  not  represent  true  solutions,  but  only  suspensions.  2.  The 
more  concentrated  the  solutions,  the  greater  is  the  diffusion.  3.  Heat  promotes, 
cooling  retards,  diffusion.  4.  If  the  solution  of  a  body  difficult  of  diffusion  is 
mixed  with  a  readily  diffusible  solution,  the  former  diffuses  with  even  greater 
difficulty.  5.  Dilute  solutions  of  various  substances  diffuse  into  one  another 
without  difficulty,  while  concentrated  solutions  mutually  retard  diffusion.  6. 
Double  salts,  of  which  one  constituent  diffuses  more  readily,  and  the  other  with 
greater  difficulty,  may  even  be  separated  chemically  by  diffusion. 

In  the  endosmotic  interchange  of  fluids,  the  passage  of  the  fluid-particles 
takes  place  independently  of  the  hydrostatic  pressure. 
Fig.  129  is  a  simple  illustration  of  endosmotic  exchange. 
A  glass  cylinder  is  filled  with  distilled  water  (F).  A  flask 
(J)  is  kept  immersed  in  the  water  to  a  suitable  height,  and 
closed  by  a  membrane  (m)  replacing  its  broken  bottom. 
From  the  neck  of  the  flask,  in  which  it  is  tightly  corked, 
projects  a  glass  tube  (R) .  The  flask  is  filled  with  concen- 
trated salt-solution  up  to  the  level  of  the  lower  extremity  of 
the  tube.  The  flask  is  introduced  into  the  glass  cylinder  to 
such  a  distance  that  both  fluids  stand  at  the  same  level  (x). 
In  a  short  while  the  fluid  rises  in  the  tube  (R),  because 
particles  of  water  pass  through  the  membrane  into  the 
concentrated  salt-solution  in  the  flask,  and  independently 
of  the  hydrostatic  pressure.  The  fluid  rises  in  the  tube  as 
high  as  the  attraction  of  the  water  causes  it  to.  The  height 
of  the  fluid  thus  indicates  the  osmotic  pressure. 

Conversely,  also,  particles  of  the  concentrated  salt- 
solution  pass  from  the  flask  into  the  interior  of  the  cylinder, 
mixing  with  the  water  (F) .  This  interchange  of  current 
continues  until  an  entirely  uniform  mixture  is  present  in 
the  flask  and  in  the  cylinder.  Under  these  circumstances 
the  level  of  the  fluid  will  to  the  last  always  have  risen 
higher  in  the  tube  (to  y). 

The  circumstance  that  the  level  of  the  liquid  within  the 
tube  can  rise  so  high  and  be  kept  at  such  a  height  depends 
upon  the  fact  that  the  pores  of  the  membrane  are  too  fine  to 
permit  of  the  action  of  hydrostatic  pressure  through  them. 
Therefore  endosmosis  is  defined  as  an  interchange  of  par- 
ticles of  fluid  independently  of  the  hydrostatic  pressure. 

Reflection    will  show  that  if,  in  an    endosmosis-experi- 
ment  of  similar  kind,  the  water  in  the  cylinder  is  renewed 
from  time  to  time,  the  solution  in  the  flask  must  become 
progressively    more    dilute,  until,  finally,  the  flask   (J)   and 
the  cylinder  (F)  contain  only  pure  water. 

Endosmotic  Equivalent. — It  has  been  found  that  in  endomosis-experiments, 
equal  parts  by  weight  of  different  fluids  or  soluble  substances  (which  soon  coalesce 
on  the  moist  surface  of  the  membrane  within  the  flask  to  form  concentrated  solu- 
tions, as,  for  example,  sodium  chlorid)  being  present  in  the  flask,  a  varying  amount  of 
distilled  water  passes  through  the  membrane,  so  that,  finally,  if  the  water  in  the 
cylinder  is  constantly  renewed,  a  variable  amount  of  distilled  water  will  be  pre- 
sent in  the  flask.  In  other  words,  it  has  been  found  that  a  definite  part  by  weight 
of  a  soluble  substance  in  the  flask  has  been  exchanged  by  endosmosis  for  a 
definite  part  by  weight  of  distilled  water.  The  figure  that  indicates  how  many 
parts  by  weight  of  distilled  water  pass  over  in  the  endosmosis-flask  for  a 
definite  part  by  weight  of  a  soluble  substance  has  been  designated  by  Jolly  as  the 
endosmotic  equivalent.  For  i  gram  of  alcohol,  4.2  grams  of  water  are  exchanged; 
for  i  gram  of  sodium  chlorid,  4.3  grams  of  water.  The  endosmotic  equivalents 
for  the  following  substances  are: 


FIG.  129. — Apparatus  for 
Diosmosis. 


ABSORPTION    OP    THE    DIGESTED    FOOD.  353 

Acid  potassium  sulphate =  2.3  Magnesium  sulphate ..          .  =  n  7 

Sodium  chlond =  4.3  Potassium  sulphate =  12.0 

Sugar      =  7.1  Sulphuric  acid =  0  T.Q 

Sodium   sulphate    =  n.6  Potassium   hydrate =  215.0 

The  amount  of  the  substance  passing  through  the  membrane  into  the  water 
of  the  cylinder  within  an  equal  time  is  proportional  to  the  degree  of  concentra- 
tion of  the  solution.  If,  therefore,  the  water  within  the  cylinder  is  frequently 
renewed,  the  course  of  the  endosmotic  equalization  is  the  more  rapid.  Further, 
the  larger  the  pores  of  the  membrane  and  the  smaller  the  molecules  of  the  sub- 
stance in  solution,  the  more  quickly  endosmosis  takes  place.  It  thus  results 
that  the  rapidity  with  which  endosmosis  takes  place  varies  for  different  substances. 
Thus  the  rapidity  for  sugar,  sodium  sulphate,  sodium  chlorid  and  urea  is,  as 
i  :  i.i  :  5  :  9.5. 

The  endosmotic  equivalent  for  each  substance,  however,  is  not  constant. 
It  is  influenced  by:  i.  The  temperature,  with  increase  in  which,  in  general,  the 
endosmotic  equivalent  increases.  2.  C.  Ludwig  and  Cloetta  have  demonstrated 
that  the  endosmotic  equivalent  varies  with  the  degree  of  concentration  of  the 
penetrating  solutions;  it  is  larger  for  dilute  solutions  of  substances. 

Should  a  solution  of  another  substance  be  present  in  the  cylinder  instead  of 
water,  an  endosmotic  current  takes  place  from  both  sides,  until  complete  equaliza- 
tion is  effected.  In  this  process  it  is  seen  that  these  counter-currents  of  concen- 
trated solutions  have  a  disturbing  influence  on  each  other.  If,  however,  two  sub- 
stances in,  solution  are  present  in  the  flask  at  the  same  time,  both  diffuse 
toward  the  water,  without  interfering  with  each  other.  3.  The  endosmotic 
equivalent  varies  with  the  employment  of  different  membranes  of  different  porosity. 
Sodium  chlorid,  which  has  an  endosmotic  equivalent  of  4.3  when  pig's  bladder  is 
used,  possesses  an  equivalent  of  6.4  when  a  cow's  bladder  is  employed;  2.9 
with  a  swimming-bladder,  and  20.2  with  a  collodion  membrane. 

There  are  a  number  of  fluids  that,  on  account  of  the  considerable  size  of  their 
molecules,  are  capable  of  passing  with  difficulty,  if  at  all,  through  the  pores  of  a 
membrane  impregnated  with  gelatinous  substances,  diffusible  with  difficulty. 
These  consist  in  part  of  fluids  that  contain  substances,  not  in  true  solution,  but 
in  a  greatly  diluted  state  of  imbibition.  Among  such  substances  are  the  liquid 
albuminates,  solutions  of  starch,  dextrin,  gum,  mucus  and  gelatin.  They  are 
capable  of  gradually  passing  over  into  and  mixing  with  other  fluids  by  diffusion, 
in  the  absence  of  an  intervening  porous  membrane-wall ;  they  pass  by  endosmosis 
with  difficulty,  if  at  all,  through  the  pores  of  membranes  impregnated  with  gelatin. 
Nevertheless,  the  nature  of  the  outside  liquid  must  be  taken  into  consideration; 
egg-albumin,  it  is  true,  passes  through  membranes  into  salt-solutions,  but  not  into 
water;  the  transudate,  under  such  conditions,  becomes  more  concentrated. 
Graham  has  designated  the  substances  in  question  colloids,  because  in  consider- 
able concentration  they  become  gelatinous.  They  also  possess  the  property 
of  not  crystallizing,  as  a  rule,  while  crystalline  substances,  designated  crystalloids, 
are  exchanged  by  endosmosis.  The  endosmotic  apparatus  thus  constitutes  a 
mechanism  for  effecting  a  separation  from  mixtures  of  crystalloids  and  colloids, 
which  by  Graham  is  designated  dialysis.  If  mineral  salts  are  added  to  the  colloid 
substances,  their  ability  to  pass  through  membranes  is  increased. 

That  endosmosis  takes  place  within  the  alimentary  canal,  through 
its  mucous  membrane  and  the  delicate  membranes  of  the  capillary 
blood-vessels  and  lymphatics,  cannot  be  denied.  On  the  one  side  of 
the  membrane,  within  the  tract,  there  are  relatively  concentrated  aque- 
ous solutions  of  salts,  sugar,  soaps,  and  peptones,  all  of  which  possess 
slight  diosmotic  power.  On  the  inner  side  of  the  vessels  is  the  colloid, 
albuminous  solution  of  the  blood  and  the  lymph,  practically  incapable 
of  osmosis,  and  deficient  in  the  matters  in  solution  within  the  ali- 
mentary canal,  particularly  in  the  state  of  hunger.  The  vital  proper- 
ties, however,  probably  in  consequence  of  the  motility  of  the  proto- 
plasmic structure  within  the  membranes,  also  appear  to  exert  some 
influence  upon  endosmosis.  Thus,  Reid  observed  that  the  exfoliated 
frog's  skin  is  less  permeable  than  living  skin,  and  the  latter,  in  turn, 
more  so  after  irritation  had  been  applied. 
23 


354  ACTIVITY    OF    THE    WALL    OF    THE    ALIMENTARY    CANAL. 

Filtration  is  the  passage  of  fluid  through  the  coarser  intermolecular  pores 
of  a  membrane  dependent  upon  pressure.  The  higher  the  latter  and  the 
larger  and  more  numerous  the  pores,  the  more  rapidly  will  the  nitrate  pass  through 
the  pores  of  the  membrane.  Increase  in  temperature  likewise  accelerates  nitra- 
tion. Further,  those  fluids  filter  most  readily  that  most  rapidly  soak  into  the 
membrane  in  question.  Therefore,  different  fluids  vary  in  the  readiness  with 
which  they  pass  through  different  membranes.  Further,  the  greater  the  con- 
centration of  the  solutions,  the  more  slowly,  in  general,  is  their  passage.  The 
filter  has  the  property  of  retaining  in  part  matters  from  the  solutions  passing 
through,  either  substances  dissolved  in  the  fluid  (particularly  colloid  substances) , 
or  water  (from  dilute  solutions  of  potassium  nitrate) .  In  the  former  case  the 
filtrate  is  more  dilute,  in  the  latter  more  concentrated,  than  the  fluid  was  before 
its  passage  through  the  filter.  Other  substances  pass  through  without  material 
change  in  concentration.  Should  the  filtrate  enter  another  fluid,  the  concen- 
tration of  the  transudate  increases  with  the  pressure  under  which  filtration  takes 
place.  Some  membranes  exhibit  a  difference  according  as  filtration  takes  place 
from  their  different  surfaces;  thus  the  membrana  testacea  of  the  egg  per- 
mits of  filtration  only  in  the  direction  from  without  inward.  The  mucous  mem- 
brane of  the  stomach  and  intestine  also  exhibits  a  difference  in  this  respect. 

It  was  formerly  believed  that  filtration  of  substances  in  solution 
could  take  place  from  within  the  digestive  canal  into  the  vessels:  i.  If 
the  intestine  contracted  and  thereby  exerted  pressure  directly  on  the 
contents.  This  alone,  however,  could  scarcely  have  any  noteworthy 
influence,  even  in  case  the  canal  were  contracted  in  two  places  and  the 
intervening  musculature,  through  contraction,  compressed  the  fluid 
intestinal  contents.  2.  Filtration  under  negative  pressure  may  be 
effected  through  the  villi,  which  on  contracting  forcibly  evacuate  the 
contents  of  the  blood-vessels  and  lymphatics  in  a  centripetal  direction. 
The  latter  particularly  will  remain  empty,  as  the  chyle  in  the  fine 
lacteals  is  prevented  from  passing  backward  by  numerous  valves.  When 
the  villi  are  again  relaxed,  they  will  by  suction  be  able  to  fill  themselves 
with  the  fluids  of  the  digestive  tract  capable  of  filtration.  On  the  other 
hand,  the  fact  must  especially  be  emphasized  that,  according  to  Spee 
and  Heidenhain,  the  muscles  of  the  villus  actively  dilate  the  central 
lymph- vessels. 

ABSORPTIVE  ACTIVITY  OF  THE  WALL   OF  THE  ALIMENTARY 

CANAL. 

The  process  of  digestion  prepares  from  the  food  in  part  true  solutions, 
in  part  finely  divided  emulsions,  whose  small  globules  are  surrounded  by 
an  albuminoid  capsule. 

Absorption  of  Solutions. — It  cannot  be  denied  that  true  solutions 
can  pass  over  into  the  blood  and  the  lymph  of  the  intestinal  canal  by 
endosmosis,  but  some  observations  indicate  that  the  cellular  elements  of 
the  digestive  tract  also  participate  in  the  process  of  absorption  through 
the  functional  activity  of  their  protoplasm.  It  has  not  as  yet  been 
possible  to  refer  the  forces  effective  in  this  connection  to  simple  physical  or 
chemical  processes.  When  Heidenhain  introduced  methylene-blue  in 
solution  into  the  intestine,  he  was  convinced  that  the  path  of  its  absorp- 
tion was  in  part  through,  in  part  between,  the  epithelial  cells. 

The  Inorganic  Substances:  Water,  and  the  dissolved  salts  necessary 
for  nutrition,  are  generally  easy  of  absorption,  and  in  large  measure 
by  the  blood-vessels.  In  the  absorption  of  salt-solutions  by  endosmosis, 
water  must  naturally  pass  from  the  intestinal  vessels  into  the  intestine, 
while  the  salt-solutions  enter  the  vessels.  The  amount  of  water,  how- 


ACTIVITY    OF    THE    WALL    OF    THE    ALIMENTARY    CANAL.  355 

ever,  is  but  slight  on  account  of  the  small  endosmotic  equivalent  of  the 
salts  to  be  absorbed.  Salts  are  absorbed  in  larger  amount  from  con- 
centrated than  from  dilute  solutions.  If,  however,  considerable  amounts 
of  salts  with  a  high  endosmotic  equivalent  are  introduced  into  the  in- 
testine, as,  for  example,  magnesium  or  sodium  sulphate,  these  salts 
retain  the  water  for  their  solution,  and  in  addition  more  fluid  escapes 
from  the  vessels  of  the  intestinal  wall,  and  diarrhea  results.  Conversely, 
it  is  evident  that,  on  injecting  these  substances  into  the  blood,  a  large 
amount  of  water  passes  from  the  intestine  into  the  blood,  so  that  con- 
stipation results,  in  consequence  of  the  great  dryness  of  the  interior  of 
the  intestine.  It  should,  however,  especially  be  pointed  out  that  the 
absorption  of  solutions  of  various  salts,  isotonic  with  one  another, 
takes  place  differently.  The  epithelial  cells  of  the  intestine  behave 
like  the  erythrocytes  with  respect  to  the  permeability  of  the  solutions. 
Water  is  absorbed  from  the  stomach  only  in  small  amount. 

The  absorption  of  fluids  takes  place  best  at  moderate  pressure  within  the 
intestinal  canal  (from  80  to  140  cm.  of  water-pressure),  in  connection  with  which 
the  surface  of  the  mucous  membrane  is  best  smoothed  out.  A  greater  degree  of 
pressure  would  compress  the  intestinal  vessels  and  would  accordingly  allow 
absorption  to  diminish.  During  digestion,  on  account  of  the  dilatation  of  the 
blood-vessels,  absorption  takes  place  rapidly.  For  this  reason  warm  solutions 
also  are  more  quickly  absorbed  from  the  stomach  than  cold,  the  latter  causing 
contraction  of  the  vessels. 

The  fact  that  a  0.5  per  cent,  sodium-chlorid  solution  is  better  ab- 
sorbed than  water,  further  a  potassium-solution  less  well  than  sodium- 
solutions,  and  also  the  extensive  absorption  of  dog's  serum  in  the  dog's 
intestine,  are  opposed  to  the  view  that  only  physical  forces  (endosmosis) 
are  concerned  in  absorption. 

Some  other  inorganic  substances  also,  which  are  not,  as  such,  constituents  of 
the  body,  are  absorbed  by  endosmosis:  potassium  iodid,  potassium  chlorate, 
potassium  bromid;  further,  iron-salts,  as  well  as  dilute  sulphuric  acid,  etc. 

Carbohydrates  in  solution  have  their  chief  representatives  in  the 
different  varieties  of  sugar — and  principally  in  dextrose  and  maltose, 
which  have  relatively  high  endosmotic  equivalents,  as  cane-sugar  is  gen- 
erally transformed  by  a  ferment  into  invert-sugar.  Absorption  appears 
to  take  place  relatively  slowly,  as,  at  this  time,  only  small  amounts 
of  grape-sugar  are  found  in  the  intestinal  vessels  and  in  the  portal 
vein.  According  to  v.  Mering,  the  sugar  is  absorbed  from  the  intestine 
by  the  portal  vein.  Dextrin  is  also  present  in  the  blood  of  the  portal 
vein,  as  boiling  with  dilute  sulphuric  acid  increases  the  amount  of  sugar 
in  this  blood.  The  amount  of  sugar  absorbed  depends  upon  the  concen- 
tration of  its  solution  in  the  intestine.  Therefore,  the  amount  of  sugar 
contained  in  the  blood  is  increased  after  a  diet  rich  in  sugar,  so  that 
it  may  even  pass  over  into  the  urine.  To  this  end  approximately  a 
0.6  per  cent,  solution  of  sugar  in  the  blood  is  necessary.  Also  cane- 
sugar  in  small  amount  has  been  found  in  the  blood.  When  a  large 
amount  of  sugar-solution  is  present  in  the  intestine,  a  portion  also  enters 
the  lymph- vessels.  In  a  girl  with  a  fistula  of  the  receptaculum  chyli, 
not  more  than  J  per  cent,  of  the  sugar  introduced  into  the  alimentary 
canal  was  found  to  be  absorbed  by  the  lacteals.  The  sugar  is  in  part 
consumed  in  the  blood  and  in  metabolism,  perhaps  principally  in  the 
muscles. 


356  ACTIVITY    OF    THE    WALL    OF    THE    ALIMENTARY    CANAL. 

Peptones  have  an  endosmotic  equivalent,  more  than  four  times 
smaller  than  that  of  dextrose.  They  can  be  rapidly  absorbed,  on 
account  of  their  ease  of  diffusion  and  filtration.  Absorption  takes 
place  through  the  blood-vessels,  unless  excessive  amounts  are  present  in 
the  intestine,  as  after  ligation  of  the  thoracic  duct,  ingested  proteids  are 
as  well,  absorbed  as  under  normal  conditions.  Peptones  have  been 
recovered  from  the  blood,  with  certainty,  in  small  amounts  only.  It  is, 
therefore,  to  be  inferred  that  they  are  quickly  retransformed  into  true 
proteids.  The  mucous  membrane  possesses  the  property  of  retrans- 
forming  peptone  into  albumin.  Heidenhain  regards  the  epithelial  cells 
of  the  villi  as  the  seat  of  this  transformation.  Peptone  gains  entrance 
into  the  blood  unchanged  only  in  minimal  amount  and  it  disappears 
from  this  after  its  passage  through  the  tissues. 

If  blood  containing  peptone  is  kept  warm  in  the  presence  of  a  small  piece  of 
small  intestine,  while  air  is  passed  through  the  mixture,  the  peptone  soon  disap- 
pears from  the  blood. 

The  peptones  undoubtedly  represent  the  principal  contingent  of  the 
albuminates  destined  for  absorption.  Of  all  the  proteids  they  alone 
suffice  to  maintain  the  body  equilibrium,  as  animals  fed  upon  peptone 
only  (in  addition  to  the  necessary  fat  or  sugar)  are  able  to  maintain 
their  nutrition.  They  can  do  the  same  when  fed  with  propeptone. 

According  to  Pfeiffer,  the  diffusion  of  the  peptones  is  promoted  by  a  i  per 
cent,  solution  of  sodium  chlorid  or  sulphate.  The  absorption  of  grape-sugar  and 
peptone  in  the  stomach  and  intestine  is  increased  by  the  addition  of  certain  sub- 
stances, as,  for  example,  sodium  chorid,  pepper,  alcohol  or  ethereal  oils.  In 
dogs  a  peptone-solution  (5  cu.  cm.  of  a  20  per  cent,  solution  in  0.6  per  cent,  sodium- 
chlorid  for  an  animal  weighing  8  kilograms)  introduced  into  the  blood,  causes 
death. 

Unchanged  Proteids. — In  spite  of  their  slight  power  of  filtration 
and  (on  account  of  their  great  endosmotic  equivalent)  of  diffusion,  it 
has  been  demonstrated  with  certainty  that  unchanged  proteids,  such 
as  liquid  casein  and  the  proteids  of  milk,  meat-juice,  dissolved  myosin, 
alkali- albuminate,  egg- albumin  mixed  with  sodium  chlorid,  syntonin, 
gelatin,  can  be  absorbed;  their  absorption  takes  place,  in  part,  even 
from  the  mucous  membrane  of  the  large  intestine.  The  amount  of 
absorbed  unaltered  albumin  is,  however,  smaller  than  that  of  the 
peptones. 

Egg- albumin  without  sodium  chlorid,  serum-albumin,  hemoglobin  and  fibrin 
are  not  absorbed.  Many  years  ago  the  author  made  the  observation  in  a  young 
man  that  after  the  ingestion  of  the  white  of  between  14  and  20  raw  eggs,  with 
sodium  chlorid,  albumin  was  excreted  in  the  urine  after  from  4  to  10  hours.  The 
amount  of  albumin  thus  excreted  increased  up  to  the  third  day,  then  becoming 
less  and  ceasing  on  the  fifth  day.  The  more  albumin  ingested,  the  earlier  the 
albuminuria  appeared  and  the  longer  it  lasted.  In  this  case  the  condition  was 
evidently  one  in  which  considerable  absorption  of  unchanged  egg-albumin  took 
place  into  the  circulation.  If  egg-albumin  be  injected  directly  into  the  blood- 
stream of  animals,  it  likewise  passes,  in  part,  into  the  urine. 

The  soluble  soaps  form  only  a  part  of  the  fats  absorbed,  the  largest 
portion  of  the  fat  being  taken  up  in  the  form  of  a  finely  granular 
emulsion.  Absorbed  soaps  have,  on  the  one  hand,  been  found  in  the 
chyle;  on  the  other  hand,  from  the  circumstance  that  the  blood  of  the 
portal  vein  is  richer  in  soaps  at  the  time  of  absorption  than  during  the 
state  of  hunger,  it  has  been  inferred  that  absorption  of  the  soaps  takes 
place,  to  some  extent,  through  the  intestinal  capillaries.  Nevertheless, 
only  a  small  portion  of  the  soaps  enters  the  blood. 


ACTIVITY    OF    THE    WALL    OF    THE    ALIMENTARY    CANAL.  357 

The  experiments  of  Lenz,  Bidder  and  Schmidt  render  it  probable  that  the 
organism  can  take  up  only  a  limited  amount  of  fat  within  a  certain  time,  and 
this  may,  perhaps,  bear  a  definite  relation  to  the  quantity  of  bile  and  pancreatic 
juice.  Beyond  that  amount  no  more  fat  is  absorbed.  Thus,  in  cats,  0.6  gram  of 
•fat  an  hour  was  found  to  be  the  greatest  amount  absorbed  for  every  kilogram 
of  body  weight.  I.  Munk  and  Rosenstein  found  the  absorption  of  fat  greatest 
from  5  to  8  hours  after  ingestion,  and  earlier  or  later  accordingly  as  the  fat  was 
more  or  less  readily  liquefiable. 

The  greater  part  of  the  soaps  in  the  intestine,  transformed  into 
neutral  fat,  passes  over  into  the  chyle.  It  seems  as  if  the  soaps  are 
capable  of  uniting  with  glycerin  in  the  parenchyma  of  the  villus  to  form 
neutral  fat.  Perewoznikoff  and  Will  found  neutral  fat  after  the  injection 
of  both  of  these  ingredients  into  the  intestinal  canal,  and  also  C.  A. 
Ewald  observed  fat  to  form  when  he  brought  soap  and  glycerin  in  contact 
with  the  fresh,  living  intestinal  mucous  membrane.  Blood  and  chyle 
contain  no  free  fatty  acids.  In  the  blood  the  fat  is  subsequently  decom- 
posed in  the  presence  of  oxygen. 

Of  other  organic  matters  in  solution  that  are  introduced  into  the  intestinal 
tract,  some  are  absorbed,  as,  for  example,  alcohol,  and  many  others.  Other 
bodies  may  be  in  part  absorbed,  in  part  fermented:  tartaric  acid,  citric  acid,  malic 
acid,  lactic  acid,  glycerin  and  inulin  ;  gum  and  vegetable  mucin,  which  give  rise 
to  the  formation  of  glycogen  in  the  liver;  and  it  is  probable  that  unknown  products 
of  metabolism  are  also  absorbed. 

Of  pigments,  alizarin,  alkanna  and  indigo-carmine  are  absorbed;  others  are 
in  part  absorbed,  such  as  hematin;  chlorophyll  is  not  absorbed.  Metallic  salts 
appear,  in  part,  to  be  held  in  solution  by  an  excess  of  albuminates,  and  to  be 
absorbed  at  the  same  time  with  these  (iron  sulphate  has  been  found  in  the  chyle) , 
and,  in  part,  to  be  conveyed  to  the  liver  through  the  blood  of  the  portal  vein. 
Numerous  poisons  undergo  rapid  absorption,  prussic  acid  in  the  course  of  a  few 
seconds;  potassium  cyanid  has  been  found  in  the  chyle. 

Moreover,  the  purely  physical  conception  of  the  absorption  even  of 
true  solutions  by  endosmosis  and  filtration  alone  is  not  sufficient.  Here, 
also,  the  protoplasm  of  the  cells  takes  at  least  an  active  part,  for  only 
in  this  way  is  it  possible  to  explain  how  even  a  slight  derangement  in 
the  activity  of  these  cells,  as,  for  example,  after  cold  or  excitement, 
may  be  followed  by  sudden  serious  disturbances  of  absorption,  even  the 
escape  of  fluid  into  the  intestine.  Only  in  this  way,  also,  can  the  fact 
be  explained  that  the  presence  of  different  spices,  in  small  amount, 
actively  increases  absorption  in  the  stomach.  If,  further,  absorption 
took  place  solely  and  alone  by  endosmosis,  water  would  pass  over  into 
the  intestine  after  the  injection  of  alcohol;  but  this  never  occurs. 
Further,  salt  is  absorbed  in  the  intestine  from  a  solution  that  has  less 
osmotic  energy  than  blood-plasma.  Moreover,  Brieger  observed,  after 
the  injection  of  from  0.5  to  i  per  cent,  solutions  of  metallic  salts  into 
ligated  loops  of  the  intestine,  that  transudation  of  water  into  the  bowel 
failed  to  take  place;  although  this  occurred  when  injections  of  20  per 
cent,  solutions  were  made. 

Absorption  of  the  Smallest  Granules.— The  largest  amount  of  the 
neutral  fats  and  at  the  same  time  also  of  the  fatty  acids  is  absorbed  in 
the  form  of  a  milky  emulsion  prepared  by  the  bile  and  by  the  pancreatic 
juice  and  composed  of  minute  granules.  The  individual  fat-granules 
appear  to  be  surrounded  by  a  delicate  albuminous  membrane,  the  hap- 
togenic  membrane,  which  is  derived  in  part  from  the  pancreatic  juice. 
In  the  absorption  of  fat-emulsions,  the  villi  of  the  small  intestine  par- 
ticipate primarily  and  in  greatest  degree;  but  the  epithelial  cells  of  the 


358  ACTIVITY    OF    THE    WALL    OF    THE    ALIMENTARY    CANAL. 

stomach  also,  as  well  as  those  of  the  large  intestine,  take  part  in  this 
process.  In  the  villi  the  fat-granules  are  seen:  (i)  Within  the  epithe- 
lial cells,  the  protoplasm  of  which  is  dotted  with  them.  The  nucleus 
remains  free  from  them,  yet  it  is  so  beset  by  the  innumerable  fat-granules 
as  to  escape  observation.  (2)  Within  the  tissue  of  the  villus  itself,  the 
granules  traverse  in  large  numbers  the  intercommunicating  course  of  the 
spaces  in  the  reticular  tissue.  Not  rarely,  when  absorbed  in  smaller 
amount,  the  granules  arrange  themselves  in  connected  reticular  paths. 
At  times  they  appear  to  be  collected  in  undivided,  band-like  lines;  at 
other  times,  the  entire  parenchyma  of  the  villus  is  completely  filled  with 
innumerable  granules.  (3)  At  a  later  period  the  central  lymph- vessel 
in  the  axis  of  the  villus  appears  filled  with  fat-granules. 

The  amount  of  fat  in  the  chyle  varies  in  the  dog,  after  generous 
feeding  of  fat,  from  8  to  10  per  cent.  The  fat  disappears  from  the 
blood  within  thirty  hours.  If  chyle,  rich  in  fat,  is  mixed  with  blood 
(even  if  lake-colored),  and  is  agitated  with  air,  the  amount  of  fat  in 
the  mixture  diminishes  as  a  result  of  the  action  of  a  lipolytic  substance 
present  in  the  blood,  in  consequence  of  which  a  body,  insoluble  in  ether, 
is  formed. 

The  fat-granules  are  taken  up  out  of  the  blood  by  the  various  tissues,  particu- 
larly by  the  liver,  and  in  smallest  measure  by  the  muscles.  The  consumption 
of  fat  in  the  tissues  begins  with  a  division  into  glycerin  and  fatty  acids,  which  is 
followed  by  the  final  combustion. 

With  regard  to  the  forces  that  effect  absorption  of  the  fat-gran- 
ules, it  appeared  conceivable  from  observations  made  by  v.  Wisting- 
hausen  that  moistening  of  the  porous  membranes  with  bile  is  capable 
of  facilitating  the  passage  of  fat-granules ;  but  this  does  not  adequately 
explain  the  abundant  and  rapid  absorption.  It  appears  most  probable 
that  the  protoplasm  of  the  epithelial  cells  of  the  alimentary  tract  seizes 
the  fat-granules  by  an  independent  movement,  and  then  actively  draws 
them  within  itself.  The  protrusion  of  delicate  protoplasmic  filaments 
from  the  cell-body  would  take  place  in  a  manner  similar  to  that 
in  which  the  absorption  and  the  inclusion  of  granular  articles  of  food 
takes  place  in  the  lower  organisms,  the  amoebae.  Absorption  is  possible 
on  the  part  of  the  goblet-cells  also,  because  the  entrance  to  the  cell 
remains  open.  The  protoplasm  of  the  epithelial  cells  communicates 
directly  with  the  protoplasmic  lymphoid  cells  present  in  large  number 
within  the  reticulum  of  the  villus.  Thus,  the  granules  may  be  conveyed 
to  these  cells  and  finally  from  them,  through  the  stomata  between  the 
endothelial  cells,  into  the  central  lymph- vessel  of  the  villus. 

The  process  of  the  absorption  of  granules — and  perhaps  the  same  is  in 
part  true  of  proteids — is  thus  established  as  a  wholly  active,  vital  one. 
This  view  receives  adequate  support  from  the  investigations  of  Briicke 
and  of  v.  Thanhoffer  and  others,  as  well  as  the  observation  of  Griinhagen 
that  the  absorption  of  fat-granules  in  frogs  takes  place  most  rapidly  at 
a  temperature  at  which  the  motile  phenomena  of  the  protoplasm  are 
most  active.  In  fact,  the  conception  of  a  simple  physical  filtration  of 
the  granules  into  the  tissue  of  the  villus  is  scarcely  any  longer  permissible. 
This  is  to  be  concluded  also  from  the  fact  that  the  number  of  fat-granules 
present  in  the  chyle  is  independent  of  the  amount  of  water  present  in 
it.  If  absorption  took  place  essentially  through  filtration,  the  constancy 
of  a  direct  relation  between  the  amount  of  fat  and  the  amount  of  water 


INFLUENCE    OF    THE    NERVOUS    SYSTEM.  359 

present  would  at  least  be  highly  probable.  The  fatty  acids,  in  their 
passage  through  the  intestinal  wall,  are  retransformed  with  fixation  of 
glycerin  into  neutral  fats.  They  pass,  in  part,  through  the  blood-vessels. 

The  intestine  of  distomum  hepaticum  may  be  considered  as  a  truly  classical 
object-lesson  for  a  study  of  the  cells  of  the  intestine  in  their  functional  activity 
and  of  the  manner  in  which  they  accomplish  the  absorption  of  solid  substances 
by  means  of  their  pseudopod-like  processes.  Sommer  has  admirably  depicted 
the  conditions,  and  the  author  convinced  himself  of  the  accuracy  of  the  represen- 
tation by  personal  observation  of  the  preparations.  Metschnikoff  noted  similar 
conditions  in  celenterates,  Du  Plessis  in  turbellaria,  Greenwood  in  earth-worms. 

If  carmine  or  India-ink  is  mixed  with  the  food  of  rabbits,  a  deposition  of 
either  granular  pigment  takes  place  in  Peyer's  patches  and  in  the  lymph-cells. 

Pathological.— In  the  presence  of  severe  intestinal  disease,  injury  to  and  al- 
teration in  the  epithelial  cells  of  the  intestine  appear  to  be  caused  .by  a  poison 
elaborated  in  the  bowel,  as,  for  example,  in  cases  of  cholera  and  cholera  infantum. 

INFLUENCE  OF  THE  NERVOUS  SYSTEM. 

Little  is  known  with  certainty  concerning  the  influence  of  the  nervous 
system  upon  the  processes  of  absorption  in  the  intestinal  tract.  After 
division  of  the  mesenteric  nerve-filaments,  the  intestinal  contents  be- 
come abundant  and  watery.  This  may  be  due,  in  part,  to  deficient 
absorption,  as  well  as  to  an  increased,  paralytic  secretion  of  the  intestinal 
juice,  although  it  is  as  yet  impossible  to  determine  with  certainty  to 
what  extent  transudation  into  the  intestine  on  the  part  of  the  vessels 
participates  in  this  process.  After  extirpation  of  the  sympathetic 
ganglia  of  the  abdomen,  symptoms  of  paralysis  of  the  intestine  appear, 
with  exhausting  diarrhea,  finally  terminating  fatally;  acetone  is  also 
present  in  the  urine.  Of  especial  interest  is  the  observation  of  v.  Than- 
hoffer,  who  noted  the  protrusion  of  filaments  from  the  protoplasm  of 
the  epithelial  cells  of  the  small  intestine  only  when  the  medulla  oblongata 
or  the  dorsal  nerves  had  been  divided  some  time  previously. 

NOURISHMENT    BY    MEANS    OF    "NUTRITIVE    ENEMATA." 

In  those  desperate  cases  in  human  beings  in  which  administration  of  food 
by  the  mouth  is  impossible,  c.  g.,  in  the  presence  of  stenosis  of  the  esophagus 
or  of  persistent  vomiting,  resort  has  been  had  to  the  procedure  adopted  by  Corn. 
Celsus,  namely,  rectal  alimentation.  As  the  large  intestine  is  capable  of  scarcely 
any  digestive  activity  it  is  best  to  introduce  fluid  material  capable  of  absorption, 
which  is  permitted  to  flow  slowly,  by  its  own  weight,  into  the  anus,  preferably 
through  a  long  tube  provided  with  a  funnel.  The  recipient  must  endeavor  to 
retain  the  material  for  as  long  a  time  as  possible.  By  means  of  slow  and  gradual 
injection,  the  fluid  at  times  may  even  pass  beyond  the  ileo-cecal  valve.  Particles 
of  proteid  substances,  saturated  with  a  solution  of  sodium  chlorid,  may  even  pass 
through  the  small  intestine  into  the  stomach,  where  they  may  be  digested. 

Nitrogenous  substances  are  to  be  recommended  for  this  purpose:  eggs  rubbed 
up  into  an  emulsion  with  an  aqueous  solution  of  sodium  chlorid,  peptone  or  pro- 
peptone;  less  well,  milk  and  egg-albumin  with  sodium  chlorid.  The  commercial 
preparations  of  peptone  are  made  by  digestion  with  pepsin,  by  vegetable  ferments 
or  by  superheated  water,  and  they  often  contain  much  propeptone.  An  adult 
should  receive  daily  120  grams,  a  child  50  grams  of  meat-peptone;  Leube  ad- 
vises from  50  to  80  grams  dissolved  in  250  cu.  cm.  of  water.  In  addition,  as  a 
stimulant  and  as  food-sparer,  tea  with  wine  may  be  given.  Leube  introduces 
into  the  rectum  a  pasty  mixture  consisting  of  150  grams  of  meat  with  50  grams 
of  reddened  pancreatic  tissue  and  100  grams  of  water,  and  it  is  believed  that 
proteids  are  peptonized  and  absorbed  here.  In  addition,  as  much  as  50  grams 
of  grape-sugar  dissolved  so  as  to  make  300  cu.  cm.,  or  starch-paste  and  dilute  lake- 
colored  blood  may  be  employed;  also  fat-emulsions  (not  more  than  10  grams  of 
fat  daily) ;  mixed  with  pancreatic  paste,  as  much  as  50  grams  of  fat  can  be  given. 


360  SYSTEM    OF    LACTEAL    AND    LYMPHATIC    VESSELS. 

Whether  thin  soap-solutions  are  advisable,  however,  has  not  as  yet  been  deter- 
mined. This  mode  of  administering  nutriment  by  means  of  nutrient  enemata, 
must,  however,  always  remain  imperfect;  at  best  only  one-quarter  of  the  amount 
of  proteids  necessary  for  the  maintenance  of  the  metabolic  equilibrium  is  absorbed. 

SYSTEM  OF  LACTEAL  AND   LYMPHATIC  VESSELS. 

Within  the  tissues  of  the  body,  and  even  in  those  without  special 
blood-vessels  (cornea)  or  with  but  a  poor  supply,  there  is  present  a 
system  of  vessels  conveying  fluid,  and  within  which  the  movement  is  only 
centripetal.  These  vessels  begin  within  the  parenchyma  of  the  organs 
in  widely  different  ways,  and  unite  in  their  course  to  form  delicate, 
then  thicker  tubes,  which  empty  into  two  trunks  of  considerable  size 
at  the  junction  of  the  common  jugular  and  subclavian  veins:  the  tho- 
racic duct  on  the  left  side,  the  lymphatic  trunk  on  the  right. 

The  importance  of  the  lymph  and  of  its  movement  in  the  various 
organs  is  apparent  in  different  ways  at  different  points,  (i)  In  some 
tissues  the  lymphatics  represent  the  nutrient  channels  through  which 
the  nutrient  fluid  given  off  by  adjacent  blood-vessels  is  distributed,  as 
in  the  cornea  particularly  and  often  within  the  connective  tissues. 
(2)  In  some  tissues,  as  in  the  glands,  for  example  the  salivary  glands 
and  the  testicles,  the  lymph-spaces  constitute  the  chief  reservoirs  for 
fluid,  from  which,  at  the  time  of  secretion,  the  cellular  elements  derive 
their  necessary  fluid.  (3)  In  addition,  the  lymphatic  vessels  everywhere 
have  the  task  of  collecting  the  fluid  with  which  the  tissues  are  saturated 
and  of  conveying  it  back  again  to  the  blood.  If  the  network  of  capillary 
blood-vessels  be  regarded,  from  this  standpoint,  as  an  irrigation-system, 
which  supplies  the  tissues  with  nutrient  fluid,  the  lymphatic  system  can 
be  considered  as  a  drainage-mechanism,  which,  in  turn,  conducts  away 
the  excess  of  the  transuded  fluids.  Metabolic  products  from  the  tissues, 
the  products  of  retrogressive  metamorphosis,  are  added  to  this  return- 
current.  The  lymph-channels  are  thus,  at  the  same  time,  absorbent 
vessels:  substances  that  would  otherwise  be  carried  to  the  parenchyma 
of  the  tissues  are  thus  also  absorbed  by  the  lymphatic  system. 

A  consideration  of  these  circumstances  shows  that  the  system  of  the 
lymph-channels  represents  in  reality  an  appendix  to  the  blood- vascular 
system ;  therefore,  further,  the  lymphatic  system  cannot  be  active  at  all 
if  the  circulation  of  blood  is  totally  interrupted;  it  operates  only  as  a 
part  of  the  whole  and  with  the  whole. 

If  the  lacteals  are  contrasted  with  the  true  lymph- vessels,  this  is 
done  chiefly  for  anatomical  reasons,  because  the  important  and  con- 
siderable paths  of  the  former,  which  are  derived  from  the  entire  intes- 
tinal tract,  have  especially  attracted  the  attention  of  investigators  since 
antiquity  and  are  to  a  certain  extent  an  almost  independent  division 
of  the  lymphatic  system,  with  conspicuous  absorptive  activity.  In  addi- 
tion their  contents,  of  white  color  from  the  generous  admixture  of  fat- 
granules,  as  chyle  or  lacteal  fluid,  appeared  at  first  sight  to  be  essen- 
tially distinct  from  the  clear  and  watery  fluid  of  the  true  lymphatics. 
From  the  physiological  standpoint,  however,  the  lacteals  cannot  be  given 
an  independent  position.  They  are,  functionally  and  structurally,  lym- 
phatics, and  their  contents  are  true  lymph,  mixed  with  a  large  amount 
of  absorbed  materials. 


ORIGIN    OF    THE    LYMPH-CHANNELS.       LYMPHATICS.  361 

ORIGIN  OF  THE  LYMPH-CHANNELS.     LYMPHATICS. 

Development  by  Means  of  Secretory  Spaces.  Within  the  supporting  sub- 
stances (connective  tissue,  bone)  numerous  star-shaped  or  polymorphous  spaces 
are  found  that  are  connected  with  one  another  by  means  of  delicate  tubular 
processes.  This  system  of  communicating  spaces  contains  the  cellular  elements 
of  the  tissues.  The  cells,  however,  by  no  means  completely  fill  the  spaces, 
an  interval  often  existing  between  the  cell-body  and  the  wall  of  the  space, 


FIG.  130.— Origin  of  the  Lymph-channels:  I,  from  the  central  tendon  of  the  rabbit  (semi-diagrammatic);  s, 
secretory  spaces,  communicating  with  the  lymphatic  at  x;  a,  commencement  of  the  lymphatic  fromlthe 
confluence  of  secretory  spaces.  II,  perivascular  lymphatics.  III.  lymph-stomata. 

and  varying  in  size,  in  accordance  with  the  state  of  motility  of  the  protoplasmic 
cells.  These  spaces  are  the  so-called  secretory  spaces,  or  secretory  canals,  and 
they  represent  the  commencement  of  the  lymphatics.  As  adjacent  spaces  inter- 
communicate, the  propulsion  of  the  lymph  is  provided  for.  The  eel 
the  secretory  spaces  are  capable  of  ameboid  movement.  In  part  they  remain 
permanently  in  their  spaces  (fixed  connective-tissue  cells,  bone-corpuscles);  in 
part  they  are  capable  of  engaging  in  active  migration  through  the  secretory  canal- 


362  ORIGIN    OF    THE    LYMPH-CHANNELS.       LYMPHATICS. 

system  (wandering-cells).  At  greater  or  lesser  distances,  these  secretory  clefts 
are  connected  with  minute  tubular  lymphatics,  which  are  designated  lymph- 
capillaries  (Fig.  130,  I,  L).  Their  commencement  results  from  the  more  intimate 
approximation  of  secretory  spaces  (I,  a). 

The  lymph-capillaries,  generally  exceeding  the  capillary  blood-vessels  in 
caliber,  lie  principally  in  the  space  midway  between  the  arched  loops  of  the  blood- 
capillaries  (B).  They  are  composed  of  delicate  nucleated  endothelial  cells  (e), 
whose  characteristic  sinuous  edges  can  be  stained  black  by  means  of  a  solution 
of  silver  nitrate.  Between  the  endothelial  cells  scattered  spaces,  stomata,  are 
present.  The  endothelial  cells  constituting  the  wall  are  often  united  by  bridges 
of  protoplasm.  According  to  Kolossow,  the  cells  may  recede  from  one  another 
at  their  edges,  and  thus  form  spaces  between  them,  while  the  connecting  bands 
of  protoplasm  are  capable,  subsequently,  of  drawing  them  together  again.  Thus, 
the  stomata  would  develop  temporarily  and  again  close. 

It  is  to  be  inferred  that  the  blood-vessel  system  communicates  with 
the  lymph-spaces ;  that  the  blood-plasma  finds  its  way  into  the  lymph- 
spaces  from  the  thin- walled  blood-capillaries  through  their  stomata. 
In  the  lymph-spaces  this  fluid  maintains  the  nutrition  of  the  tissues, 
inasmuch  as  the  necessary  constituents  are  taken  up  independently 
by  the  tissues.  The  materials  consumed  are  returned  to  the  lymph- 
spaces  and  later  reach  the  lymph-capillaries,  which  finally  deliver  them 
to  the  venous  system. 

To  what  extent  the  cellular  elements  within  the  lymph-spaces  exert  any 
action  upon  the  discharge  of  blood-plasma  and  later  upon  its  propulsion  into 
the  lymphatics  can  only  be  surmised.  It  can  be  conceived  that,  through  con- 
traction and  diminution  in  size  of  their  cell-bodies,  as  well  as  through  partial  change 
in  position  from  the  group  of  secretory  spaces  closer  to  the  blood-vessel  to  that 
directed  toward  the  lymph-capillary,  they  might  exert  suction  upon  the  blood- 
plasma  transuded.  If  the  cells,  themselves,  then  take  up  the  transuded  fluid, 
the  conception  is  permissible,  further,  that  by  subsequent  contraction  they  ex- 
press this  fluid  in  a  certain  direction,  namely  from  secretory  space  to  secretory 
space,  toward  the  lymph-capillaries.  In  consequence  of  the  independent  migra- 
tion of  the  cellular  elements  through  the  secretory  spaces  into  the  larger  lymph- 
paths,  small  particles  that  may  be  contained  in  the  secretory  spaces  (as,  for  ex- 
ample, pigment-granules  that  have  been  rubbed  into  the  tissue  of  the  irritated, 
horny  skin  in  the  process  of  tattooing,  and  also  minute  fat-granules,  bacteria  and 
the  like),  and  which  the  lymph-cells  are  capable  of  taking  up  through  ameboid 
movement,  may  be  propelled  onward. 

After  what  has  been  said  concerning  the  migration  of  leukocytes 
from  the  blood-stream  through  the  stomata  between  the  endothelial 
cells  of  the  capillaries,  or  through  the  walls  of  smaller  vessels,  the  migra- 
tion of  cellular  elements  from  the  blood-vessel  system  into  the  com- 
mencement of  the  lymph-channels  may  be  regarded  as  a  normal  process. 
Granular  pigments  pass  from  the  blood  into  the  protoplasmic  bodies  of 
the  cells  in  the  lymph-spaces.  Only  when  the  granular  substance  is 
present  in  large  amount  is  it  distributed  into  the  ramifications  of  the 
lymph-spaces  as  a  granular  injection. 

The  origin  of  the  lacteals  within  the  villi  has  been  outlined  in  their  descrip- 
tion as  organs  of  absorption. 

Commencement  of  the  Lymphatics  in  the  Form  of  Perivascular  Spaces. — In 

the  tissue  of  bony  substance,  of  the  central  nervous  system  and  of  the  liver, 
the  smallest  blood-vessels  are  surrounded  by  wider  lymph- vessels,  so  that  the 
blood-vessels  lie  in  the  lymph- vessels  like  a  finger  in  a  glove.  In  the  brain  these 
lymph- vessels  are  in  part  constituted  of  delicate  connective-tissue  fibrils,  which, 
partly  traversing  the  lumen  of  the  lymph-canal,  are  supported  upon  the  sur- 
face of  the  blood-vessel.  Fig.  130  II,  B  represents  in  transverse  section  a  small 
blood-vessel  (B),  with  a  peri  vascular  lymph-vessel,  from  the  brain;  p  is  the  tra- 
versed lumen  of  the  lymph- vessel.  In  addition  to  these  so-called  peri  vascular 
spaces  of  His,  the  cerebral  vessels  are  provided  also  with  lymph-spaces  within 


THE    LYMPH-GLANDS.  363 

the  adventitia  (Virchow- Robin  spaces).  In  part  these  possess  a  well-developed 
endothelmm.  In  their  further  course,  where  the  vessels  increase  in  caliber,  the 
blood-vessel  penetrates  the  wall  of  the  lymph-vessel  at  one  spot,  and  both  continue 
separately  side  by  side.  Wherever  the  lymph-vessels  serve  as  peri  vascular 
sheaths,  the  passage  of  blood-plasma  and  lymph-cells  into  the  lymph-stream  is 
greatly  facilitated.  It  should  be  especially  mentioned  that,  in  tortoises,  even 
the  larger  vessels  are  often  covered  by  the  lymph- vessels  as  a  sheath.  In  Fig. 
130,  II,  A,  the  bifurcation  of  the  aorta,  with  the  peri  vascular  lymph- vessels,  is 
shown  according  to  Gegenbaur.  The  animals  referred  to  exhibit  macroscopically 
the  same  relations  that  warm-blooded  animals  present  microscopically;  ancl 
thus  the  illustration  may  serve  also  as  the  microscopical  picture  of  small  peri- 
vascular  lymph- vessels  in  warm-blooded  animals. 

Commencement  in  the  Form  of  Interstitial  Spaces  Within  the  Viscera. — In 
the  testicles  the  lymphatics  commence  simply  in  the  form  of  numerous  spaces, 
which  occur  between  the  multifarious  coils  and  convolutions  of  the  seminiferous 
tubules.  They  will,  therefore,  here  present  the  form  of  spaces  bounded  by  the 
arched,  cylindrical  surfaces  of  the  tubules.  The  limiting  surfaces  are,  however, 
lined  with  endothelmm.  The  lymphatics  acquire  independent  tubular  walls 
only  beyond  the  parenchyma  of  the  testicle.  Similar  conditions  are  found  in 
the  kidneys.  In  many  other  glands  the  glandular  substance  is  likewise  sur- 
rounded by  lymph-spaces.  Into  these  the  blood-vessels  first  pour  lymph,  from 
which  the  secreting  cells  remove  the  material  for  the  formation  of  the  glandular 
secretion,  as,  for  example,  the  salivary  glands. 

Commencement  by  Means  of  Free  Stomata  upon  the  Walls  of  the  Larger 
Serous  Cavities  (Fig.  130,  III).  From  the  investigations  of  v.  Recklinghausen , 
C.  Ludwig,  Dybkowsky,  Schweigger-Seydel,  Dogiel  and  others,  it  has  been  found 
that  the  old  view  of  Mascagni,  that  the  serous  cavities  communicate  freely  with 
the  lymphatics,  is  correct.  Upon  examining  serous  membranes  (most  readily 
the  peritoneal  lining  of  the  large  lymph-cavity  in  the  frog) ,  best  after  moistening 
them  with  argentic  nitrate,  followed  by  exposure  to  the  action  of  light,  disseminated, 
relatively  large,  free  openings  of  the  stomata  are  found  lying  between  the  endo- 
thelial  cells.  Groups  of  the  latter  include  a  stoma  among  them.  A  portion 
of  motile  protoplasm  lies  in  the  cells  surrounding  the  stoma,  close  to  the  edge 
of  the  opening.  Upon  the  state  of  contraction  of  this  protoplasm  appears  to 
depend  the  fact  whether  the  stomata  are  widely  open  (a) ,  half  closed  (b) ,  or  com- 
pletely closed  (c).  These  stomata  are  thus  the  beginnings  of  the  lymph-capil- 
laries. Fluids,  introduced  into  the  serous  cavities,  therefore  readily  reach  the 
path  of  the  lymphatics.  The  cavities  of  the  peritoneum,  the  pleurae,  the  peri- 
cardium, and  the  serous  covering  of  the  testicle,  further  the  arachnoid  space,  the 
chambers  of  the  eye,  and  the -labyrinth  of  the  ear  have  shown  themselves  to  be 
true  lymphatic  cavities;  the  fluid  in  them  is  thus  to  be  designated  lymph.  Fluids 
in  the  peritoneal  cavity  are  absorbed,  in  part,  also  by  the  veins.  The  endothelial 
cells  of  the  serous  membranes  are  capable  of  movement  and  communicate  with 
one  another  by  means  of  connecting  bridges  of  protoplasm.  In  the  animal  king- 
dom the  free  surfaces  of  the  cells  are  frequently  provided  with  cilia. 

Even  upon  the  free  surface  of  a  number  of  mucous  membranes,  it  is  stated, 
open  pores  have  been  observed  as  the  commencement  of  the  lymphatics:  in  the 
bronchi,  in  the  nasal  mucous  membrane  and  in  the  larynx. 

The  larger  lymphatics  arising  from  the  lymph-capillaries  closely  resemble 
veins  of  equal  size  in  the  structure  of  their  walls.  Especial  stress  is  to  be  laid 
upon  the  presence  of  a  large  number  of  valves,  which  are  placed  so  closely  behind 
one  another  that  the  distended  lymphatic  is  not  unlike  a  string  of  pearls. 

THE  LYMPH-GLANDS. 

The  so-called  lymph-glands  are  peculiar  to  the  lymphatic  apparatus.  They 
are  inappropriately  designated  glands,  because  they  really  represent  only  many- 
branched,  lacunar,  labyrinthine  spaces,  constituted  of  adenoid  tissue,  interposed 
in  the  course  of  the  lymphatics.  Simple  and  compound  lymph-glands  can  be 
distinguished. 

The  simple  lymph-glands,  more  correctly  designated  simple  lymph-follicles 
or  cutaneous  follicles,  are  present  either  isolated  (solitary  follicle) ,  as  in  the  intes- 
tine, the  bronchi,  the  spleen;  or  collected  in  masses  (conglobate  follicle),  as  in 
the  tonsil,  Peyer's  patches,  the  follicles  of  the  tongue.  They  are  small,  spherical 
vesicles,  attaining  approximately  the  size  of  a  pin's  head,  and  they  consist  through- 


364  THE    LYMPH-GLANDS. 

out  of  delicate  elements  of  the  reticular  connective  tissue  intermixed  with  elastic 
fibrils  and  arranged  in  a  network  (Fig.  131,  C).  In  the  meshes  of  this  network, 
lymph  and  lymph-cells  are  present  in  abundance.  Upon  the  surface  the  tissue 
becomes  condensed  into  a  somewhat  more  independent,  conspicuous  sheath,  which, 
however,  is  variously  traversed  by  small  spongy  spaces  in  the  reticular  tissue. 
Small  lymphatics  advance  everywhere  directly  up  to  these  lymph-follicles,  often 
keeping  considerable  areas  of  their  surface  covered  with  a  rich  network.  Fre- 
quently, also,  the  surface  of  the  follicle  is  incorporated  into  the  wall  of  the  vessel, 
at  times  throughout  a  slight,  at  other  times  throughout  a  considerable,  extent, 
so  that  the  surface  of  the  follicle  is  directly  irrigated  by  the  lymph  of  the  vessel ; 
and,  if  no  direct  canal-orifice  of  considerable  size  leads  from  the  lumen  of  the 
lymphatic  into  the  interior  of  the  spherical  follicle,  a  communication  must,  never- 
theless, be  assumed  to  exist  between  the  small  lymphatic  and  the  lymph-follicle, 
and  this  is  adequately  provided  by  the  innumerable  spaces  between  the  fol- 
licles. Thus,  the  lymph-follicle  is  a  true  lymphatic  structure,  whose  fluid  and 
lymph-cells  can  pass  over  into  the  stream  of  the  adjacent  lymphatics.  The 
follicles  are  provided,  upon  their  surfaces,  with  a  network  of  blood-vessels, 
which  also  send  numerous  delicate  ramifications  and  capillaries  through  the 
interior  of  the  follicle  (A) ,  within  which  they  are  supported  by  the  reticulum  (B) . 
It  is  to  be  inferred  that  leukocytes  can  pass  from  these  capillaries  into  the  follicle. 

It  should  be  mentioned  as  of  special  importance  in  connection  with 
these  follicles  that,  in  the  lymph-glands,  the  solitary  as  well  as  the 


FIG.  131. — A,  blood-vessels  of  the  follicle;    B,  the  reticulum  and  a  branch  of  a  blood-vessel;    C,  lymph-follicle 

with  reticulum  and  sheath. 

conglobate  glands,  an  enormous  migration  of  the  leukocytes  normally 
takes  place  uninterruptedly  during  life  through  the  epithelium  be- 
tween the  cells.  The  leukocytes  insinuate  themselves  between  the 
epithelial  cells,  but,  by  their  enormous  migration,  as  well  as  by  the 
divisions  that  take  place  during  this  process,  they  impair  the  functions 
of  the  epithelium  and  may  even  destroy  it.  Thus,  in  a  measure,  physio- 
logical injuries  result,  which  prepare  the  way  for  invading  microorgan- 
isms. The  cells  that  have  thus  migrated  later  undergo  disintegration. 

The  compound  lymph-glands  (incorrectly  designated  lymph-glands)  repre- 
sent to  a  certain  extent  an  aggregation  of  lymph-follicles  of  altered  shape.  Every 
lymph-gland  is  surrounded  externally  by  a  connective-tissue  capsule  traversed 
by  numerous  unstriated  muscle-fibers,  and  from  whose  inner  surface  numerous 
septa  and  bands  (Fig.  132,  a  a)  penetrate  into  the  interior  of  the  body  of  the  gland, 
and  divide  it  into  a  large  number  of  small  compartments.  The  latter  possess 
within  the  cortical  substance  of  the  gland  a  rather  rounded  shape  (alveoli), 
in  the  medulla,  a  rather  longitudinal  sausage-shaped  form  (medullary  spaces) .  All, 
however,  are  of  the  same  significance  and  all  are  connected  by  communicating 
orifices.  Thus,  a  rich  network  of  cavities,  connected  in  all  directions,  is  formed 
within  the  lymph-gland  by  the  septa.  These  spaces  are  traversed  by  the  so- 


THE    LYMPH-GLANDS. 


365 


called  follicular  bands  (f  f).  The  latter  represent  to  a  certain  extent  the  inner- 
most contents  of  the  spaces,  but  in  such  a  manner  that  they  are  smaller  than  the 
spaces  and  nowhere  touch  the  walls  of  the  cavities  themselves.  If  the  cavities 
of  the  gland  be  conceived  as  injected  with  a  substance  that  at  first  has  filled  them 
all,  but  later,  by  contraction,  is  reduced  to  half  its  size,  one  will  have  an  approxi- 
mate picture  of  the  spatial  relations  of  the  follicular  bands  to  the  cavities  of  the 
gland.  The  follicular  bands  contain  the  blood-vessels  (b)  of  the  gland  within 
them.  About  these  there  is  deposited  a  rather  thick  cortex  of  reticular  connective 
tissue,  whose  meshes  (x)  are  extremely  delicate  and  fine,  whose  spaces  are  rich 
in*lymph-cells  and  whose  surface  (o  o)  is  so  constituted  of  the  condensed  reticulum- 
cells  that  a  communication  between  the  narrow  meshes  is  still  possible. 

Between  the  surface  of  the  follicular  bands  and  the  inner  wall  of  all  the  cavities 


Fio.  132.— Part  of  a  Lymph-gland:  A,  afferent  vessel;  B,  B,  lymph-path  within  the  cavity  of  the  gland;  a,  a, 
column  and  septa  bounding  the  cavity  of  the  gland;  f,  f,  follicular  band  of  the  cavity;  x,  x,  its  reticulum; 
b,  its  blood-vessels;  o,  o,  delicate  reticular  junction  between  the  follicular  band  and  the  lymph-pains. 

of  the  glands  lie  the  paths  of  the  lymphatics  (B  B) .  Perhaps  they  are  lined  by 
an  endothelium;  their  lumina  are  traversed  by  a  rather  coarse  reticulum. 

The  afferent-vessels  (A),  which  spread  out  upon  the  surface  of  the  gland, 
penetrate  the  external  capsule  and  pass  over  into  the  lymph-paths  of  the  glandular 
cavities  (C).  The  efferent  vessels,  which  exhibit  large,  almost  cavernous  anasto- 
moses and  dilatations  in  the  vicinity  of  the  gland,  arise  at  other  parts  of  the  gland 
directly  from  the  lymph-paths.  The  latter,  thus,  to  a  certain  degree  represent 
a  dense  interlacing  network  of  capillary  vessels,  lying  within  the  glandular  cavi- 
ties, arranged  between  the  afferent  and  efferent  vessels. 

The  movement  of  the  lymph  on  its  way  through  the  many-branched  and 
tortuous  lymph-paths  of  the  gland  will  be  retarded  and,  on  account  of  the  resist- 
ance to  the  current  that  the  cellular  elements,  arranged  in  the  paths,  must  offer, 
will  possess  feeble  propulsive  power.  The  lymph-corpuscles,  lying  11 


366  PROPERTIES  OF  THE  CHYLE  AND  THE  LYMPH. 

of  the  reticulum,  are  carried  onward  by  the  lymph-stream,  so  that,  after  flowing 
through  the  glands,  the  lymph  is  richer  in  cells.  The  lymph-cells  lying  in  the 
range  of  the  follicular  bands  may  again  migrate  through  the  narrow  meshes  of  the 
reticulum  (o)  into  the  lymph-paths,  to  make  good  the  loss.  The  formation  of 
the  lymph-cells  in  the  follicular  bands  either  takes  place  locally  by  division,  or 
new  cells  migrate  from  the  capillary  blood-vessels  into  the  follicular  bands. 
Further  on,  the  muscular  activity  of  the  capsule  and  of  the  trabeculae  should 
not  be  underestimated  in  the  movement  of  the  lymph  through  the  glands.  Such 
muscular  contraction  will  express  the  gland  like  a  sponge.  The  direction 
of  the  fluid  thus  discharged  is  governed  by  the  presence  of  valves  within  the 
related  lymphatics. 

Of  the  chemical  substances  in  the  lymph-glands,  in  addition  to  those  of  the 
lymph,  leucin  and  the  xanthin-bodies  are  worthy  of  mention. 

PROPERTIES  OF  THE  CHYLE  AND  THE  LYMPH. 

Both  chyle  and  lymph  are  colorless,  albuminous,  clear  fluids,  contain- 
ing lymph-cells.  The  latter  are  in  reality  the  same  elements  that  enter 
the  circulation  with  the  lymph-stream,  and  within  the  former  are  desig- 
nated white  blood-corpuscles.  The  source  of  the  lymph-cells  is  dis- 
cussed on  p.  370.  As,  in  rare  cases,  isolated  red  blood-corpuscles  also 
pass  out  through  the  walls  of  the  vessels  and  into  the  commencement  of  the 
lymph- vessels  again,  the  presence  of  erythrocytes  in  the  lymph,  rarely 
in  the  chyle,  is  readily  explained.  Red  blood-corpuscles  can  also  pass 
over  from  the  veins  into  the  central  extremities  of  the  large  lymph- 
trunks  when  the  pressure  in  the  veins  is  high.  Lymph  and  chyle  con- 
tain also  molecular  granules,  and  fragments  of  disintegrated  leukocytes; 
chyle  contains,  in  addition,  numerous  fat-granules. 

In  the  lymph  a  distinction  is  made  between  the  lymph-plasma  and 
the  contained  lymph-cells  or  leukocytes,  whose  chemical  constituents 
are  considered  on  p.  64.  The  lymph- plasma  contains  both  of  the  fibrin- 
factors,  derived  from  disintegrated  lymph-cells.  They  cause  coagulation 
of  the  lymph  after  withdrawal  from  the  body,  and  in  this  process  the 
soft,  gelatinous,  scanty  lymph-clot,  which  forms  but  slowly,  includes 
the  still  surviving  lymph-cells  within  it.  The  fluid  remaining,  the 
lymph-serum,  contains  alkali-albuminates,  serum-albumin  and  some 
diastatic  ferment  derived  from  the  blood.  Of  the  coagulable  albumi- 
nates  about  37  per  cent,  consist  of  paraglobulin. 

The  chyle,  which  is  the  sole  fluid  contained  in  the  lymphatic  vessels  of 
the  digestive  tract  (lacteals),  can  be  obtained  only  in  small  amounts, before 
its  admixture  with  the  lymph,  and  it  can,  therefore,  be  examined  only 
with  great  difficulty.  A  small  number  of  lymph-cells  are  already  present 
in  the  first  beginnings  of  the  lacteals  in  the  villi;  beyond  the  intestinal 
wall  and,  still  more,  after  passing  through  the  mesenteric  glands,  their 
number  increases.  On  the  other  hand,  the  amount  of  the  solid  constitu- 
ents of  the  chyle,  which  is  increased  after  abundant  good  digestion,  is 
decidedly  diminished  after  the  chyle  has  become  mixed  with  lymph. 
After  the  ingestion  of  food  rich  in  fat  the  chyle  contains  many  fat-drop- 
lets (from  2  to  4  /*  in  diameter),  which,  however,  decrease  conspicuously 
in  the  further  course  of  the  current.  The  amount  of  fibrin-factors  in 
the  chyle  increases  with  increase  in  the  number  of  lymph-cells.  In  addi- 
tion, chyle  contains  sugar  (up  to  2  per  cent.),  glycogen,  peptone  adherent 
to  the  leukocytes,  diastatic  ferment  absorbed  from  the  intestine,  and 
lactates  after  ingestion  of  starches,  traces  of  urea  and  leucin. 


PROPERTIES  OF  THE  CHYLE  AND  THE  LYMPH.  367 

The  chyle  from  the  body  of   an  executed  person  contained,  together  with 
90.5  per  cent,  of  water: 

(  fibrin  .......     a  trace 


Carl  Schmidt  found  the  following  inorganic  constituents  in  1000  parts  of  chyle 
from  a  horse  : 

Sodium  chlorid  ......  5-84     Sulphuric  acid  .....  0.05     Magnesium  phosphate  0.05 

Sodium  ............  1.17     Phosphoric  acid.  .  .  .0.05     Iron  .............  a  trace 

Potassium  ..........  0.13     Calcium  phosphate.  0.20 

The  lymph,  at  the  beginnings  of  the  lymphatics,  is  likewise  deficient 
in  cells,  and  clear  and  colorless.  The  fluid  from  the  serous  cavities  and 
synovial  fluid  exhibit  similar  features.  A  variation  in  the  lymph,  in 
accordance  with  the  tissues  from  which  it  is  derived,  can  with  certainty 
be  assumed,  although,  up  to  the  present  time,  this  has  not  been  estab- 
lished. After  passing  through  the  lymph-glands,  the  lymph  becomes 
richer  in  cellular  elements  and,  probably  in  consequence  of  this,  also 
richer  in  solid  constituents,  particularly  proteid  and  fat.  In  one  cu.  cm. 
of  lymph  from  a  dog,  8200  lymph-corpuscles  were  counted. 

Hensen  and  Dahnhardt  succeeded  in  collecting  for  examination  pure 
lymph  in  considerable  amount  from  a  lymphatic  fistula  on  the  thigh 
of  a  human  being.  It  had  an  alkaline  reaction  and  a  salty  taste.  The 
relative  composition  of  pure  lymph,  cerebrospinal  fluid  and  pericardial 
fluid  is  as  follows  : 

Pure  Lymph.  Cerebrospinal  Fluid.  Pericardial  Fluid. 

(Hensen  and  Dahnhardt.)  (Hoppe-Seyler.)  (v.  Gorup-Besanez.) 

Water  ................  98.63  98.74  95.51 

Solids  .................  1.37  1.25  4-48 

Fibrin  .................  o.n  0.08 

Albumin  ..............  0.14  0.03  —  0.06  2.46 

Alkali-  albuminate  .......  0.09 

Extractives  ............  —  1-26 

Urea,  leucin  ............  1.05 

Salts  ..................  0.88 

Absorbed  carbon  dioxid,  The  cerebrospinal  lymph  contains  a  substance 

to  70  per  cent,  by  volume,  that  reduces  Fehling's  solution,  and  that  Naw- 

of  which  50  per  cent,  could  ratzki  determined  to  be  dextrose.     This,  how- 

be  obtained  by  extraction  ever,  disappears  soon  after  death. 
and  20  per  'cent,  was  ob- 
tained by  addition  of  acid. 

100  parts  of  lymph-ash  contain: 

Sodium  chlorid  ____  74.48      Calcium  ...........  0.98      Sulphuric  acid  .......  1.28 

Sodium  ...........  10.36      Magnesia  ..........  0.27      Carbon  dioxid  ........  8.21 

Potassium  .........  3.26      Phosphoric  acid  ----  1.09      Iron  oxid  ............  0.06 

Just  as  in  the  case  of  the  blood,  potassium  and  phosphoric  acid, 
of  the  inorganic  constituents,  predominate  in  the  cells;  while  in  the 
lymph-serum,  sodium  preponderates,  principally  as  sodium  chlorid. 
Only  in  the  cerebrospinal  fluid  are  the  potassium-combinations  and  the 
phosphates  said  to  predominate.  The  amount  of  water  in  the  lymph 
rises  and  falls  in  correspondence  with  that  in  the  blood.  Of  gases, 
dog's  lymph  contains  carbon  dioxid  in  abundance  (over  40  per  cent,  by 
volume,  of  which  17  per  cent,  can  be  pumped  out  and  23  per  cent,  can 
be  removed  by  acids),  traces  of  oxygen  and  1.2  volumes  per  cent,  of 
nitrogen. 


368  QUANTITATIVE    RELATIONS    OF    LYMPH    AND    CHYLE. 

QUANTITATIVE  RELATIONS  OF  LYMPH  AND  CHYLE. 

It  is  estimated  that  the  total  amount  of  lymph  and  chyle  introduced 
into  the  circulation  through  the  large  lymph-trunks  in  twenty-four  hours 
equals  the  total  volume  of  the  blood.  Of  this  one-half  will  be  contributed 
by  the  chyle,  the  other  half  by  the  lymph.  The  secretion  of  lymph  in 
the  tissues  takes  place  without  interruption.  From  a  lymphatic  fistula 
on  a  woman's  thigh,  about  6  kilograms  of  lymph  were  collected  in  twenty- 
four  hours.  In  young  horses,  the  amount  of  lymph  collected  from  the 
large  lymph-trunk  of  the  neck  in  from  one  and  one-half  to  two  hours 
measured  between  70  and  more  than  100  grams.  The  following  influ- 
ences affect  the  amount  of  chyle,  as  well  as  that  of  lymph. 

The  amount  of  chyle  increases  considerably  during  digestion,  espe- 
cially if  the  quantity  of  food  taken  has  been  large,  so  that  the  vessels 
of  the  mesentery  and  the  intestine  will  at  this  time  be  constantly  found 
filled  with  white  chyle.  In  the  state  of  hunger  the  vessels  are  collapsed 
and  can  be  recognized  with  difficulty. 

The  amount  of  lymph  increases  especially  with  the  activity  of  the 
organ  from  which  it  flows.  Thus  it  was  found  that  active  and  passive 
muscular  movements  increase  the  amount  of  lymph  considerably,  almost 
five-fold  in  the  horse.  Lesser  obtained  more  than  300  cu.  cm.  of  lymph 
in  this  manner  from  fasting  dogs,  in  consequence  of  which,  with  inspis- 
sation  of  the  blood,  the  animals  became  exhausted,  to  the  point  of  death. 

All  agencies  that  increase  the  pressure  to  which  the  parenchymatous 
fluids  of  the  tissues  are  subjected  increase  the  amount  of  lymph  secreted, 
and  conversely.  Of  this  the  following  observations  are  illustrative : 

(a)  An  increase  in  blood-pressure,  not  alone  in  the  entire  blood-vessel  system, 
but  also  in  the  vessels  of  the  part  in  question,  causes  increase  in  the  amount  of 
lymph,  and  conversely. 

(b)  Ligation  or  compression  of  the  efferent  veins  causes  considerable  increase 
in  the  amount  of  lymph  given  off  by  the  parts  in  question,  even  more  than  double, 
because  the  escape  of  fluid   is  confined  to  the  lymphatic  vessels.     The  applica- 
tion of  tight  bands  is  also  a  cause  for  swelling  of  the  parts  to  the  peripheral  aspect  of 
the  application,  as  copious  effusion  of  lymph  takes  place  into  the  tissues — hypo- 
static  edema. 

(c)  An  increased  supply  of  arterial  blood  acts  in  a  similar  manner,  but  less 
powerfully.     In  this  connection  paralysis  of  the  vasomotor  or  irritation  of  the  vaso- 
dilator fibers  may  cause  an  increase  in  the  amount  of  lymph  by  creating  marked 
hyperemia.    The  process  of  dilatation  favors  the  production  of  lymph  in  greater 
degree  than  permanent  distention  of  the  blood-vessels.     Contraction  of  the  arterial 
paths  as  a  result  of  irritation  of  the  vasomotor  nerves  or  from  other  causes  will 
naturally  have  the  opposite  result;    but  even  after  ligation  of  both  carotids,  the 
lymph-current  in  the  large  cervical  trunk  of  the  dog  by  no  means  ceases,  as  the 
head  is  still  supplied  with  blood  in  small  amount  by  the  vertebral  arteries. 

If,  after  unilateral  division  of  the  sympathetic  nerve,  the  blood-vessels  of 
the  ear  are  dilated,  indigo-carmine,  injected  into  the  blood,  enters  earliest  and 
in  greater  degree  into  the  lymph  of  this  ear;  the  latter  also  becomes  decolorized 
earlier  than  the  healthy  ear.  In  this  way  the  rare  instances  of  unilateral  or 
partial  icterus  are  to  be  explained. 

An  increase  in  the  total  volume  of  blood  as  a  result  of  injection  of 
blood  or  serum  into  the  veins  causes  increased  formation  of  lymph,  as, 
in  consequence  of  the  increased  tension  thus  induced,  blood-plasma 
passes  over  into  the  tissues  in  large  amount.  If  water  or  a  hypotonic 
salt-solution  be  infused,  water  passes  out  into  the  tissues. 

After  death  and  complete  rest  of  the  heart,  the  formation  of  lymph 
still  goes  on  for  some  little  time,  although  in  slight  degree.  If  fresh 


ORIGIN    OF    LYMPH.  369 

blood  be  then  passed  through  the  animal's  body,  still  warm,  increased 
lymph  will  in  turn  flow  from  the  large  lymph-trunks.  It  thus  appears 
that  the  tissues  are  still  capable  of  taking  up  plasma  from  the  blood 
for  the  production  of  lymph  for  some  time  after  cessation  of  the  circula- 
tion. This  fact  may  explain  the  circumstance  that  some  tissues,  as,  for 
example,  _the  connective  tissue,  appear  to  contain  more  fluid  after  death 
than  during  life,  while,  at  the  same  time,  the  blood-vessels  have  after 
death  given  up  much  of  the  plasma  from  their  interior. 

Under  the  influence  of  curare  an  increase  in  the  secretion  of  lymph 
takes  place ;  the  amount  of  the  solid  constituents  of  the  lymph  increasing. 
In  the  frog  large  amounts  of  lymph  collect  in  the  lymph-sacs,  and  this 
may  be  due  in  part  to  the  fact  that  the  lymph-hearts  are  paralyzed  by 
curare.  The  production  of  lymph  is  increased  also  in  the  tissues  of 
inflamed  parts. 

ORIGIN  OF  LYMPH. 
SOURCE  OF  LYMPH-PLASMA. 

The  lymph-plasma  is,  in  part,  a  filtrate  from  the  blood-vessels,  passing 
over  into  the  tissues,  in  accordance  with  the  prevailing  blood-pressure. 
In  this  process,  the  salts  (penetrating  membranes  most  readily)  pass 
through  admixed  in  approximately  the  same  proportions  as  the  salts  in 
the  blood-plasma;  the  fibrin-factors,  to  about  two-thirds;  the  albumin, 
about  one-half.  As  in  the  case  of  filtration  in  general,  the  filtration  of 
lymph  also  must  increase  with  increased  pressure. 

C.  Ludwig  and  Tomsa  were  able  to  demonstrate  this  by  permitting  blood- 
serum  to  pass  through  the  blood-vessels  of  an  excised  testicle  under  varying 
pressure,  with  the  result  that  the  transuded  fluid  from  the  lymph-vessels  was 
increased  or  diminished  in  amount.  This  artificial  lymph  exhibited  a  composi- 
tion similar  to  that  of  natural  lymph.  The  albumin  contained  in  the  lymph 
also  increased  with  increasing  pressure.  In  addition,  the  metabolic  products 
of  the  tissues,  concerning  whose  qualitative  and  quantitative  conditions  little 
is  known,  naturally  undergo  admixture  with  the  lymph-plasma  in  the  different 
tissued. 

In  part,  however,  the  formation  of  lymph  must  be  regarded  as  a 
secretory  process  of  the  cells  of  the  blood-capillaries. 

In  favor  of  this  view  is  the  fact  that  materials  injected  into  the  blood  (sugar, 
egg- albumin,  peptone,  urea  and  sodium  chlorid)  pass  in  concentrated  form  into 
the  increased  lymph  ;  further,  that  the  blood  is  capable  of  maintaining  the 
osmotic  tension  of  its  plasma.  As  a  result  of  this  secretory  property  on  the  part  of 
the  endothelium  of  the  vessels,  substances  that  would  disturb  the  isotonia  between 
the  blood-corpuscles  and  the  blood-plasma  are  quickly  eliminated  from  the  blood, 
including  superfluous  water.  After  the  injection  of  peptone,  the  blood-pressure 
falls  enormously,  so  that  the  passage  into  the  lymph  cannot  be  dependent  upon 
this  pressure.  With  increase  in  the  lymph-current,  the  secretion  of  urine  also  is 
later  increased.  The  lymph-paths  may  thus  be  considered  as  a  reservoir  that 
temporarily  takes  up  out  of  the  blood  the  substances  to  be  eliminated,  whence 
they  are  then  gradually  further  consumed  or  excreted. 

According  to  Heidenhain,  there  are  materials  that  increase  lymph-production, 
lymphagogues,  which  are  in  part  effective  by  causing  the  passage  of  fluid  from  the 
blood  into  the  lymphatic  radicles.  Among  such  agencies  are  injections  into 
the  blood  of  a  decoction  of  leeches,  crab-muscles,  mussels,  solution  of  nuclcin, 
tuberculin,  bacterial  extracts,  bile,  physostigmin ,  pilocarpin  and  extract  of  helian- 
thus.  In  part  they  increase  the  amount  of  lymph  by  causing  the  passage  of  water 
from  the  tissues  into  the  lymph.  In  this  category  belong  injections  into  the 
blood  of  sugar,  urea  and  salts.  Atropin  diminishes  lymph-production. 
24 


370  SOURCE    OF    THE    LYMPH-CELLS. 

Muscular  activity  causes  increased  lymph-production,  as  well  as  a 
more  rapid  escape  of  the  lymph.  The  tendons  and  fasciae  of  the  skeletal 
muscles,  which  possess  numerous  small  stomata,  absorb  lymph  from  the 
muscular  tissue.  With  alternate  contraction  and  relaxation  of  these 
fibrous  tissues,  their  lymph-ducts  suck  themselves  full  and  propel  the 
lymph  onward.  Even  passive  movements  are  effective  in  this  direction. 
If  solutions  are  injected  beneath  the  fascia  lata,  they  can  be  propelled 
onward  by  passive  movements,  contraction  and  relaxation,  into  the 
thoracic  duct. 

SOURCE  OF  THE   LYMPH-CELLS. 

A  considerable  portion  of  the  lymph-cells  are  derived  from  the  lymph- 
glands,  out  of  which  the  lymph-stream  washes  them  into  the  efferent  ves- 
sel. Therefore  it  happens  that  the  lymph-stream,  after  passing  through 
the  lymph-glands,  is  always  found  richer  in  lymph-cells.  Within  the 
lymph-glands  there  are  large  and  small  lymphocytes,  the  -latter  being 
the  daughter-cells  of  the  former,  and  arising  by  mitosis.  In  addition, 
new  leukocytes  are  constantly  migrating  from  the  blood-capillaries  of 
the  follicular  bands  into  the  reticulum.  The  lymphatic  follicles  permit 
cellular  elements  to  enter  through  the  meshes  of  their  limiting  layer  into 
the  adjacent  small  lymph- vessels. 

A  second  seat  of  lymph-cell  production  is  found  in  the  organs  contain- 
ing adenoid  tissue  as  a  basis,  in  the  meshes  of  which  lymph-cells  are  found 
in  large  number,  such  as  the  entire  mucous  membrane  of  the  intestinal 
tract,  the  bone-marrow  and  the  spleen.  The  cells  reach  the  radicles  of 
the  lymph- vessels  in  these  organs  by  ameboid  movement. 

Just  as  the  lymph-cells  reach  the  circulation  through  the  large  trunks 
and  are  there  encountered  as  white  blood-corpuscles,  so,  likewise, 
numerous  leukocytes  migrate  in  turn  from  the  blood-capillaries  into  the 
lymph- vessels,  especially  in  their  small  beginnings,  and  partly  by  active 
ameboid  movement,  partly  by  being  forced  by  filtration-pressure  exerted 
by  the  blood-column.  In  rare  cases  even  a  return  movement  of  lymph- 
cells  from  the  lymph-spaces  into  the  blood-vessels  has  been  observed. 

Also  particles  of  cinnabar  or  milk-globules  introduced  into  the  blood  reach 
the  lymph- vessels  from  the  blood-capillaries  in  a  short  time;  the  nerves  of  the 
vessels  having  no  influence  in  this  condition.  In  case  of  venous  stasis,  in  analogy 
with  the  processes  attending  diapedesis,  this  passage  takes  place  more  freely  than 
when  the  circulation  is  unembarrassed.  Inflammatory  changes  in  the  vessel- 
wall  also  favor  the  passage.  The  vessels  of  the  portal  system  prove  especially 
permeable. 

New  lymph-cells  result  also  through  multiplication  by  division  of  the 
lymph- corpuscles,  and  likewise  of  the  so-called  fixed  connective-tissue 
cells,  as  has  been  demonstrated  with  certainty  especially  in  the  pres- 
ence of  inflammation  of  certain  organs.  If  irritants  which  excite  inflam- 
mation are  applied  to  the  excised  cornea,  kept  in  a  moist  chamber, 
a  large  increase  in  the  wandering  cells  in  the  anastomosing  lymph- 
passages  of  the  cornea  will  be  noted ;  and  as,  in  the  inflamed  cornea,  the 
corneal  cells  permit  the  recognition  of  a  reproduction  of  their  nuclei  by 
division,  the  conclusion  is  probably  justified  that  a  division  of  the  corneal 
corpuscles  (fixed  connective-tissue  cells)  is  responsible  for  the  increase 
in  the  wandering  cells. 

That  a  new-formation  of  leukocytes  must  take  place  by  division,  as  well  as 
by  the  setting  free  of  divided  connective-tissue  cells,  is  shown  by  their  often 


CIRCULATION    OF    CHYLE    AND    LYMPH. 


371 


enormous  production  in  the  presence  of  inflammations  (pus-formation),  particu- 
larly in  the  case  of  extensive  phlegmons  and  purulent  effusions  in  the  serous 
cavities,  when  by  reason  of  their  enormous  number,  they  cannot  be  regarded  as 
having  resulted  solely  by  migration  from  the  circulation. 

The  destruction  of  the  lymph-cells  appears  to  take  place  in  part  at 
the  seats  of  origin  of  the  vessels  and  in  the  vessels  themselves.  The 
occurrence  in  the  lymph  of  the  fibrin-factors,  which  are  derived  from 
disintegrated  leukocytes,  tends  to  support  this  view.  Particularly  in  the 
presence  of  severe  inflammation,  especially  in  connective  tissue,  the 
new-formation  of  numerous  lymph-cells  appears  to  be  attended  with 
their  increased  destruction.  Therefore  the  lymph  under  such  circum- 
stances becomes  especially  rich  in  fibrin,  and,  naturally,  also  the  blood, 
through  the  lymph. 

According  to  Hoyer,  the  lymph-glands  are  also  filtering  apparatus  in  which 
degenerating  leukocytes  are  intercepted  and  subjected  to  a  destructive  meta- 
morphosis. 

CIRCULATION  OF  CHYLE   AND    LYMPH. 

The  cause  for  the  movement  of  the  chyle  and  the  lymph  depends 
ultimately  on  the  difference  in  pressure  prevailing  between  the  lymphatic 
radicles  and  the  points  at  which  the  lymphatics  empty  into  the  venous 
system. 

In  detail  the  following  facts  are  noteworthy : 

In  the  onward  movement  of  the  lymph,  forces  are  primarily  active 
that  are  of  influence  at  the  points  of  origin  of  the  lymphatics.  These 
forces  must  vary  in  accordance  with  the  character  of  the  points  of  origin, 
(a)  The  lacteals  receive  the  first  motile  impulse  through  the  contraction 
of  the  muscles  of  the  villi.  Inasmuch  as  these  grow  shorter  and  smaller, 
they  constrict  the  axial  lymph-space,  whose  contents  must  move  in  a 
centripetal  direction.  With  the  succeeding  relaxation  of  the  villus,  the 
numerous  valves  prevent  the  chyle  from  flowing  backward.  With  con- 
striction7 of  the  lumen  of  the  intestine,  through  contraction  of  the  in- 
testinal muscles,  the  villi  are  forced  more  closely  together  longitudinally, 
the  evacuation  of  the  central  lymph- vessel  being  likewise  favored,  (b) 
Within  those  lymph- vessels  that  originate  as  peri  vascular  spaces,  every 
dilatation  of  the  blood-vessels  must  cause  a  movement  of  the  surrounding 
lymph-stream  in  a  centripetal  direction,  (c)  Lymph  enters  the  open 
lymph-pores  of  the  pleura  with  each  inspiratory  movement,  which 
excites  suction  upon  the  thoracic  duct.  A  similar  condition  exists  at  the 
orifices  of  the  lymph- vessels  on  the  abdominal  aspect  of  the  diaphragm- 
atic peritoneum.  The  blood-vessels  participate  principally  in  absorption 
from  the  abdominal  cavity,  the  lymphatics  relatively  little.  If  serous 
fluid  or  a  solution  of  salt  or  sugar  is  introduced  into  the  abdominal 
or  pericardial  cavity,  it  will  be  absorbed,  and,  if  isotonic  with  the  blood- 
plasma,  without  change;  if  it  is  not  isotonic,  it  will  first  be  made 
isotonic  by  elimination  from  the  blood.  Accordingly,  osmosis  cannot 
be  alone  the  active  agency  in  the  process  of  absorption,  as  imbibition 
contributes  some  influence.  If  the  intra-abdominal  pressure  increases, 
the  blood-vessels  absorb  more  freely,  but  with  excessively  high  pressure 
less  freely,  in  consequence  of  compression  of  the  abdominal  veins.  In 
this  manner  is  explained  the  clinical  observation  that,  in  the  presence  of 
ascites,  absorption  is  often  promoted  after  the  abdominal  tension  is 


372  CIRCULATION    OF    CHYLE    AND    LYMPH. 

diminished  through  removal  of  a  moderate  amount  of  fluid,  (d)  In 
those  vessels  that  arise  by  means  of  fine  secretory  canaliculi,  the  move- 
ment will  depend  directly  on  the  tension  of  the  parenchymatous  fluids, 
and  the  latter,  in  turn,  upon  the  tension  in  the  blood-capillaries.  Thus 
the  blood-pressure  will  still  be  active  as  a  force  from  behinde  ven  into 
the  lymphatic  radicles. 

In  the  lymph-trunks  themselves,  the  contractions  of  their  mus- 
cular walls  propel  the  current  onward.  Heller  noted,  in  the  lymphatics 
of  the  mesentery  of  the  guinea-pig,  that  this  movement  was  peristaltic 
in  an  upward  direction.  The  large  number  of  valves  prevent  a  back- 
ward current.  In  addition,  the  contractions  of  the  surrounding  muscles, 
further,  any  pressure  upon  the  vessels  and  the  tissues  as  the  seat  of 
origin  of  the  lymphatic  radicles  will  force  the  current  onward.  If  the 
escape  of  blood  from  the  veins  is  rendered  difficult,  lymph  is  poured 
out  more  abundantly  from  the  tissues  in  question. 

The  interposed  lymph-glands  offer  considerable  resistance  to  the 
current,  as  the  lymph  must  flow  through  numerous  spaces,  traversed  by 
fine  meshes  and  partially  filled  with  cells.  Nevertheless  the  obstacles 
thus  presented  are  in  part  compensated  for  by  the  numerous  unstriated 
muscles  that  are  present  in  the  sheath  and  the  trabeculae  of  the  glands. 
By  means  of  these,  compression  of  the  glands  (as  of  a  sponge)  can  take 
place,  the  presence  of  the  valves  again  determining  the  centripetal 
direction  of  the  current.  From  this  point  of  view  electrical  stimulation 
of  swollen  lymph-glands  might  be  successful. 

With  the  union  of  the  vessels  into  a  few  of  considerable  size,  and 
finally  to  form  the  main  trunk,  the  sectional  area  of  the  current  becomes 
diminished,  and  the  velocity  of  the  current  correspondingly  increased. 
Nevertheless,  the  velocity  under  such  circumstances  is  always  low, 
reaching  only  from  238  almost  to  300  mm.  in  a  minute  in  the  main 
cervical  lymph-trunk  in  the  horse,  a  fact  that  is  indicative  of  the 
exceedingly  slow  movement  of  the  lymph  in  the  small  vessels.  The 
lateral  pressure  in  the  same  situation  was  from  10  to  20  mm.;  in  the 
dog  only  from  5  to  10  mm.  of  a  dilute  soda-solution,  but  in  the  tho- 
racic duct  of  a  horse  it  was  12  mm.  of  mercury.  . 

The  time  required  for  the  passage  of  the  lymph  through  the  walls  of  the 
capillaries  of  the  abdomen  or  of  the  lower  extremity,  is  about  2  minutes  in  the 
dog;  for  the  propulsion  of  the  lymph  through  the  lymphatics  of  the  lower  ex- 
tremity and  of  the  trunk,  3.2  seconds. 

The  respiratory  movements  have  an  important  influence  upon  the 
lymph-stream  in  the  thoracic  duct  and  the  right  lymphatic  duct,  as  each 
inspiration  conveys  the  current  of  lymph,  together  with  venous  blood, 
to  the  heart,  and  as  a  result  the  tension  in  the  thoracic  duct  may  even 
become  negative. 

Lymph-hearts. — The  lymph-hearts  containing  valves  found  in  some  ani- 
mals, particularly  cold-blooded  animals,  are  deserving  of  consideration.  The  frog 
possesses  two  axillary  hearts  (above  the  shoulder  near  the  vertebral  column) 
and  two  sacral  hearts  (above  the  anus  near  the  apex  of  the  sacrum) .  They  beat, 
though  not  synchronously,  about  60  times  in  the  minute  and  contain  about  10 
cu.  cm.  of  lymph.  They  contain  striated  muscle-fibers  and  are  provided  with 
.special  ganglia.  The  posterior  hearts  pump  the  lymph  into  the  branches  of  the 
communicating  iliac  vein,  the  anterior  into  the  subscapular  vein. 

Their  pulsation  depends  in  part  on  the  spinal  cord,  for,  as  a  rule  rapid  de- 
struction of  trie  cord  causes  cessation  of  the  heart-beat,  but  pulsations  are  not 
rarely  observed  to  continue  after  removal  of  the  cord.  A  second  normal  source 


ABSORPTION    OF    PARENCHYMATOUS    EFFUSIONS.  373 

of  excitation  of  the  lymph-hearts  is  to  be  sought  in  Waldeyer's  ganglia.  Irrita- 
tion of  the  skin,  the  intestine  and  the  blood-heart  gives  rise  to  a  reflex  influence, 
partly  acceleration,  partly  retardation  of  the  beat,  which  does  not  affect  the  sacrai 
heart  if  the  coccygeal  nerve,  which  connects  the  posterior  lymph-heart  with  the 
spinal  cord,  is  divided.  Strychnin-convulsions  accelerate  the  beat,  as  does  also 
irritation  of  the  spinal  cord  by  heat,  while  it  is  diminished  by  cold.  The  heart 
that  has  ceased  to  beat  in  consequence  of  exposure  or  of  the  action  of  muscarin,  but 
not  resting  in  consequence  of  destruction  of  its  nerves,  can  be  excited  to  renewed 
pulsation  by  increased  filling.  Antiar  paralyzes  the  lymph-hearts  and  the  blood- 
heart;  curare,  the  former  only.  In  other  amphibians,  two  lymph-hearts  have 
been  found;  and  one  or  two  in  the  ostrich  and  the  cassowary,  in  some  web-footed 
birds,  as  well  as  in  the  chicken-embryo;  in  fish  they  have  been  found  in  the  tail, 
as,  for  example,  in  the  eel,  where  their  pulsation  visibly  affects  the  adjacent 
veins. 

The  nervous  system  has  a  direct  influence  upon  the  movement  of 
the  lymph  through  innervation  of  the  muscles  of  the  lymphatics,  the 
lymph-glands,  and,  when  they  exist,  the  lymph-hearts.  In  addition, 
there  are  still  other  special  effects  of  the  nerves  upon  the  absorptive 
activity  of  the  lymphatic  radicles.  Kiihne  noted,  after  irritation  of  the 
corneal  nerves,  that  the  corneal  cells  contracted  within  their  secretory 
canaliculi.  The  following  observation  by  Goltz  is  also  interesting  in  this 
connection.  When  this  investigator  injected  a  dilute  solution  of  sodium 
chlorid  subcutaneously  into  the  lymph-spaces,  he  saw  that  it  was  rapidly 
absorbed;  it  remained  unabsorbed,  however,  after  destruction  of  the 
central  nervous  system.  Division  of  the  nerves  to  the  extremities  also 
resulted,  temporarily,  in  retarding  the  absorption. 

If  inflammation  was  excited  in  both  posterior  extremities  of  a  dog,  marked 
edema,  together  with  acceleration  of  the  lymph-stream,  appeared  in  the  one  in 
which  the  sciatic  nerve  had  been  divided. 

If  the  thigh  of  a  frog  is  tightly  constricted  until  the  circulation  ceases,  the 
nerve  being  preserved,  and  the  part  is  immersed  in  water,  it  becomes  greatly 
swollen  (the  dead  thigh  does  not  swell) ;  whence  it  follows  that  absorption  takes 
place  independently  of  the  existence  of  the  circulation.  Division  of  the  sciatic 
nerve  or  crushing  of  the  spinal  cord  (though  not  mere  transverse  section  or  separa- 
tion of  the  brain)  abolishes  absorption. 

ABSORPTION  OF  PARENCHYMATOUS  EFFUSIONS. 

Fluids  that  transude  into  the  tissue-spaces  from  the  blood-vessels,  or  those 
that  are  injected  into  the  parenchyma  through  a  needle,  undergo  absorption. 
In  this  process  the  blood-vessels  participate  primarily,  and  the  lymphatics  also 
secondarily.  Into  the  latter,  there  pass  from  the  clefts  and  secretory  spaces  in 
the  connective  tissue,  even  small  particles,  as,  for  example,  granules  of  cinnabar 
and  India  ink  after  tattooing  of  the  skin,  blood-corpuscles  from  hemorrhagic 
extravasations  and  fat-droplets  from  the  marrow  of  fractured  bones.  If  all  the 
lymphatics  of  a  part  be  ligated,  absorption  still  takes  place  just  as  rapidly  as 
before.  Therefore,  the  absorbed  fluid  must  have  passed  through  the  delicate 
membranes  of  the  blood-vessels.  The  opposite  observation,  that  no  absorption 
of  parenchymatous  fluids  takes  place  after  ligation  of  all  the  blood-vessels,  does 
not  exclude  a  participation  of  the  lymphatics  in  the  process. of  absorption,  because, 
after  ligation  of  all  of  the  blood-vessels,  naturally  all  formation  of  lymph  in  the 
tissues,  and  consequently  any  lymph-current,  must  cease.  The  absorption  of 
fluids  introduced  into  the  tissues  artificially,  particularly  in  the  subcutaneous  cellular 
tissue  (parenchymatous  and  subcutaneous  injection),  generally  takes  place 
rapidly,  as  a  rule  more  rapidly  than  after  administration  by  the  mouth.  There- 
fore, subcutaneous  injections  of  drugs  in  solution  are  much  employed  for  thera- 
peutic purposes.  Naturally  the  substances  to  be  injected  should  not  have  a 
destructive,  corrosive  or  coagulating  effect  upon  living  tissues.  In  addition  to 
the  great  rapidity  of  absorption,  subcutaneous  injection  has  the  further  advantage 
over  the  administration  of  a  drug  by  the  mouth  that  some  agents  that  are  ingested 
undergo  decomposition  in  the  stomach  and  intestine  as  a  result  of  the  digestive 


374  LYMPH-STASIS    AND    SEROUS    EFFUSIONS. 

process,  so  that  they  cannot  at  all  be  absorbed  unchanged.  Thus,  particularly 
poisons  that  act  through  ferments,  such  as  snake-venom,  ptomains  and  putrid 
poisons,  are  destroyed  by  the  stomach.  Emulsin  also  behaves  in  the  same  manner. 
If  this  ferment  is  introduced  into  the  stomach  while  amygdalin  is  injected  into 
a  vein  of  the  same  animal,  poisoning  by  hydrocyanic  acid  does  not  take  place, 
because  the  emulsin  is  destroyed  by  the  digestive  process.  If,  however,  emulsin 
is  injected  into  the  blood  and  amygdalin  into  the  stomach,  hydrocyanic-acid  poison- 
ing takes  place  rapidly,  because  amygdalin  is  absorbed  unchanged  from  the 
stomach.  Amygdalin  is  a  glucosid  (C20H27Npn)  that  breaks  up  as  a  result  of 
the  fermentative  activity  of  fresh  emulsin  with  the  taking  up  of  water,  2  (H,O) , 
into  hydrocyanic  acid  (CHN),  oil  of  bitter  almonds  (C7H6O)  and  sugar,  2(C6H12O6). 
For  observations  on  animals  on  the  absorption  of  solutions  from  the  parenchyma- 
tous  structures,  either  poisons  whose  action  gives  rise  to  conspicuous  tonic  symp- 
toms, or  such  harmless  substances  as  are  readily  discoverable  in  the  blood  and 
subsequently  especially  in  the  urine  are  employed,  as,  for  example,  potassium 
ferrocyanid. 

The  author,  in  1878,  demonstrated  that  serum,  injected  into  the  subcuta- 
neous tissue,  is  rapidly  absorbed.  The  serum,  which  must  be  obtained  from 
an  animal  belonging  to  the  same  species  or  at  least  as  indifferent  as  possible, 
undergoes  decomposition  in  the  circulation,  so  that  the  production  of  urea  in- 
creases. Infusions  of  serum  may,  therefore,  be  given  for  nutritive  purposes. 
Febrile  reaction  is  observed  after  such  injections,  as  in  the  case  of  transfusion. 
Solutions  of  albumin  and  peptone,  oil,  butter,  dextrose,  levulose,  galactose  and 
maltose  in  solution  have  also  been  observed  to  undergo  absorption. 

LYMPH-STASIS  AND  SEROUS  EFFUSIONS. 

If  obstruction  to  the  efferent  venous  and  lymphatic  paths  of  an  organ  arises, 
stasis  results,  and  later  abundant  effusion  of  lymph  into  the  tissues.  This  is  most 
distinctly  recognizable  in  the  skin  and  the  subcutaneous  tissue,  where  the  soft 
parts  become  swollen;  while,  without  redness  and  pain,  tumefaction  develops, 
with  a  doughy  feeling,  and  pressure  with  the  finger  causes  pitting.  These  are  the 
signs  of  lymph-stasis,  which,  if  the  fluid  is  especially  rich  in  water,  is  designated 
by  the  term  edema. 

Also  within  the  serous  cavities,  under  like  conditions,  a  similar  collection 
of  lymph  takes  place.  If  numerous  leukocytes  migrate  from  the  delicate  blood- 
vessels into  such  serous  cavities  and  undergo  multiplication,  the  fluid,  richer 
in  cells,  becomes  more  and  more  like  pus.  The  multiplication  of  these  cells  gives 
rise  to  the  presence  of  a  considerable  amount  of  albumin,  which  may  subsequently 
be  increased  by  absorption  of  water  from  the  effusion.  The  latter  will  be  made 
particularly  easy  when  the  pressure  in  the  fluid  exceeds  that  in  the  small  blood- 
vessels. These  sero-purulent  effusions  not  rarely  undergo  a  change  in  constitu- 
tion later  on,  for  which  no  reason  has  been  found.  The  substances  present  are 
in  part  products  of  the  decomposition  of  albumin,  such  as  leucin  and  tyrosin, 
in  part  products  of  the  retrogressive  metamorphosis  of  nitrogenous  substances, 
such  as  xanthin,  kreatin,  kreatinin  (?),  uric  acid  (?)  and  urea.  Further,  endo- 
thelial  cells  from  the  serous  cavities;  sugar  in  pathological  serous  and  chylous 
effusions  and  edematous  fluid  have  been  found;  in  the  latter  also  diastatic  fer- 
ment, often  cholesterin;  and  in  the  fluid  of  serous  hydrocele  and  echinococcus- 
cysts,  succinic  acid. 

f  Not  only  the  pressure  from  without  upon  the  lymphatics,  but,  in  general, 
resistance  of  any  kind  that  is  present  in  the  lymph-path  may  give  rise  to  lymph- 
stasis  and  serous  effusions.  Thus,  lymph-stasis  results  from  occlusion  of  the  lymph- 
atics in  consequence  m  of  inflammation  and  thrombosis  (lymph-coagulation) ; 
further,  as  a  result  of  impermeable,  swollen,  inflamed  or  degenerated  lymph-glands. 
In  these  cases,  however,  the  formation  of  new  lymph-vessels  is  frequently  ob- 
served,' reestablishing  the  former  communication.  An  effusion  of  lymph  may 
also  take  place  into  the  serous  cavities  of  the  abdomen  or  the  thorax,  from  rup- 
ture of  large  lymph-paths,  especially  of  the  thoracic  duct— chylous  ascites  or 
chylothorax.  Interference  with  or  even  removal  of  all  those  factors  that  have 
been  found  active  in  propelling  the  lymph  onward  will  be  capable  of  inducing 
lymph-stasis. 

If  stagnation  of  lymph  can  develop  in  this  manner  also  on  the  part  of  the 
lymphatic  apparatus,  the  appearance  of  considerable  amounts  of  watery  lymph, 
in  the  form  of  edema  or  anasarca,  as  well  as  of  serous  effusions,  is  often  at  the  same 


COMPARATIVE. 


375 


time  due  to  the  fact  that  a  copious  transudate  is  furnished  on  the  part  of  the  blood- 
vessels. Obstruction  in  the  distribution  of  the  lymph-stream  may  then  further 
increase  such  a  collection  of  fluid.  Particularly  the  vessels  of  the  abdomen  and, 
further,  those  that  furnish  a  watery  exudation  also  under  normal  circumstances 
appear,  above  all  others,  to  be  especially  adapted  to  transudation.  Such  increase 
in  transudation  is  favored  by  (i)  any  considerable  degree  of  venous  stasis.  These 
hypostatic  transudates  are,  as  a  rule,  deficient  in  albumin  and  leukocytes,  but, 
on  the  other  hand,  the  richer  in  erythrocytes  the  greater  the  interference  with  the 
flow  of  venous  blood.  Ranvier  induced  hypostatic  edema  artificially  in  the 
lower  extremity  by  ligation  of  the  inferior  vena  cava  and  simultaneous  division 
of  the  sciatic  nerve.  The  paralytic  dilatation  of  the  vessels  of  the  posterior 
extremity,  induced  by  the  latter,  causes  an  increase  in  the  amount  of  blood  present 
and  a  rise  in  the  blood-pressure,  which,  in  turn,  promotes  edematous  exudation. 
(2)  Further,  as  yet  unknown  physical  changes  in  the  protoplasm  of  the  endothelial 
cells  of  the  blood-vessels  and  capillaries  may  render  these  capable  of  permitting 
the  abnormal  passage  of  albumin,  hemoglobin  and  even  blood-cells.  This  takes 
place  when  foreign  matters  are  present  in  the  blood  in  considerable  amount, 
as,  for  example,  hemoglobin  in  solution;  further,  when  the  blood  is  deficient  in 
oxygen  or  albumin.  Also  after  exposure  to  abnormal  heat,  a  similar  condition 
has  been  observed,  and  the  tumefaction  of  the  soft  parts  in  the  vicinity  of  inflamed 
tissues  likewise  appears  to  be  due  to  an  exudation  of  lymph  through  altered 
vessel-walls.  Perhaps  a  nervous  influence,  which  makes  itself  felt  in  a  certain 
vascular  area  (by  contraction  or  relaxation  of  the  protoplasm  of  the  blood-capil- 
laries ?) ,  may  even  be  capable  of  causing  such  a  transitory  change  in  the  vessel- 
walls.  Lymphatic  transudates  of  this  character  are  generally  rich  in  cells  and 
consequently  also  in  albumin.  (3)  Further,  the  presence  of  a  large  amount  of 
water  in  the  blood  will  increase  its  capacity  for  transudation.  Nevertheless, 
the  fact  should  be  considered  in  this  connection  that  the  large  amount  of  water 
contained  in  the  blood  acts,  in  turn,  by  inducing  changes  in  the  protoplasm  of 
the  endothelium  of  the  blood-vessels  and  capillaries,  so  that  it  is  itself,  when 
long  continued,  a  factor  that  increases  the  permeability  of  the  vessel-walls. 
Debilitated,  poorly  nourished,  flabby  individuals  particularly  exhibit  watery 
lymphatic  exudations  from  watery  blood — cachectic  edema. 

There  is  no  doubt  that  lymph-stasis  (hydrops)  may  develop  also  under  cer- 
tain circumstances,  and  even  through  the  action  of  microorganisms  (bacterium 
lymphagoguni) ,  in  consequence  of  the  fact  that  irritation  of  the  cells  of  the  blood- 
capillaries  (as  by  the  products  of  metabolism  of  that  organism)  gives  rise  to 
increased  exudation  of  fluid. 

COMPARATIVE. 

Extensive  lymph-spaces,  lined  with  endothelium,  are  present  in  the  frog, 
beneath  the  entire  external  integument.  In  addition,  a  large  lymphatic  space,  the 
cysterna  lymphatic  magna  of  Panizza,  extends  in  front  of  the  vertebral  column, 
separated  from  the  abdominal  cavity  by  the  peritoneum.  Tailed  amphibia, 
as  well  as  many  reptiles,  have  large  lymph-spaces  beneath  the  skin,  occupying 
the  entire  length  of  the  trunk  in  the  lateral  regions  of  the  back.  Further,  all 
reptiles  and  the  tailed  amphibia  possess,  in  the  course  of  the  aorta,  large,  longi- 
tudinal lymph-reservoirs.  Tortoises  likewise  have  an  extensive  lymphatic  ap- 
paratus (Fig.  130,  A,  II).  The  bony  fish  have  longitudinal  lymph-trunks 
in  the  lateral  regions  of  the  back,  from  the  tail  to  the  anterior  fins,  and  these  are 
connected  with  dilated  lymph-spaces  at  the  root  of  the  tail  and  the  fins  of  the 
extremities.  Within  the  interior  of  the  body  the  extensive  lymph-sinuses  attain 
their  greatest  development  in  the  region  of  the  gullet.  Many  birds  possess  a 
sinus-like  dilatation  of  a  lymph-space  in  the  region  of  the  tail.  In  the  carnivora 
the  mesenteric  lymph-glands  are  united  to  form  a  large,  compact  mass,  the  so- 
called  pancreas  of  Aselli.  Naturally  the  lymph-spaces  (provided  with  valves) 
always  communicate  with  the  venous  system,  and  usually  with  the  territory 
of  the  superior  vena  cava. 

HISTORICAL. 

Although  the  lymph-glands  were  known  to  the  school  of  Hippocrates,  espe- 
cially through  their  morbid  enlargement,  and  although  Herophilus  and  Erasistratus 
had  observed  the  milk-white  chyle-vessels  in  the  mesentery,  Aselli  (1623)  was  the 


376  HISTORICAL. 

first  to  study  the  mesenteric  chyle-vessels  more  thoroughly,  together  with  their 
valves.  Pecquet  (1648),  as  a  student,  found  the  receptacle  for  the  chyle,  Rudbeck 
and  then  Thorn.  Bartholinus  the  clear,  watery  lymph-vessels  (1650-1652).  Eus- 
tachius  (1562)  was  familiar  with  the  thoracic  duct,  which  Gassendus  (1654) 
later  claimed  to  have  been  the  first  to  discover.  Lister  noticed  that  chyle  was 
colored  blue  after  the  injection  of  indigo  into  the  intestine  (1671).  Rudbeck 
(1652)  observed  the  separation  of  fibrin  in  the  lymph;  Reuss  and  Emmert(iSoy) 
were  the  first  to  observe  the  lymph-corpuscles.  The  chemical  examinations 
date  from  the  first  quarter  of  the  nineteenth  century,  and  were  made  by  Lassaigne, 
Tiedemann,  Gmelin  and  others,  of  whom  the  latter  also  recognized  the  fact  that 
the  white  color  was  dependent  upon  the  fat-granules. 


PHYSIOLOGY  OF   ANIMAL  HEAT. 


SOURCES  OF  HEAT. 

The  heat  of  the  body  is  a  form  of  kinetic  energy  appearing  without 
interruption  and  must  be  conceived  as  depending  upon  vibrations  of 
the  atoms  of  the  body.  In  the  last  analysis  every  source  of  heat  is 
contained  in  the  mass  of  potential  energy  taken  into  the  body  as  food, 
in  combination  with  the  oxygen  obtained  from  the  air  in  the  act  of 
respiration.  The  amount  of  heat  liberated  depends  upon  the  amount  of 
potential  energy  transformed. 

The  potential  energy  of  nutrient  matters  may  be  appropriately  desig- 
nated as  latent  heat,  inasmuch  as  it  may  be  conceived  that  in  their 
consumption  in  the  body,  which  is  essentially  a  process  of  combustion, 
kinetic  energy  is  transformed  only  in  the  form  of  heat.  As  a  matter  of 
fact,  mechanical  energy  and  electricity  are  also  developed  from  the 
potential  energy  supplied.  However,  in  order  to  obtain  a  uniform 
measure  for  the  forces  transformed,  it  is  advisable  to  express  all  potential 
energy  in  terms  of  heat-units.  The  calorimeter  is  an  apparatus  with  the 
aid  of  which  the  amount  of  potential  energy  contained  in  food-stuffs 
can  be  converted  experimentally  into  heat  and  the  units  of  the  latter 
can  at  the  same  time  be  measured. 

Favre  and  Silbermann  employed  the  so-called  water-calorimeter  (Fig.  133). 
A  cylindrical  box,  the  so-called  combustion-chamber  (K),  serves  for  the  recep- 
tion of  the  substance  to  be  burned.  This  box  is  suspended  in  a  larger,  cylindrical 
vessel  (L),  which  is  filled  with  water  (w),  so  that  the  combustion-chamber  is 
completely  surrounded  thereby.  Three  tubes  enter  into  the  upper  portion  of 
the  chamber:  one  (O)  is  intended  for  the  passage  of  air  containing  oxygen, 
which  is  necessary  in  the  process  of  combustion.  The  second  tube  (a)  in  the 
middle  of  the  cover  is  closed  above  with  a  thick  glass  plate,  upon  which  is  mounted 
at  an  angle  a  mirror  (s) ,  which  permits  the  observer  (B)  to  look  into  the  interior 
of  the  chamber  from  a  lateral  point  of  view  in  the  direction  b  b.  in  order  to  observe 
the  process  of  combustion  at  c.  The  third  tube  (d)  is  employed  only  when  it 
is  desired  to  consume  combustible  gases  in  the  chamber  and  through  it  these 
are  then  passed.  Generally  this  tube  is  closed  by  a  cock.  A  lead  pipe  (e  e)  also 
passes  out  of  the  upper  portion  of  the  chamber  and  in  a  convoluted  arrangement 
traverses  the  volume  of  water,  finally  reaching  the  surface  at  g.  Through  this 
the  gases  of  combustion  escape,  being  cooled  in  the  convoluted  tube  to  the  tem- 
perature of  the  water. 

The  cylindrical  vessel  containing  the  water  is  covered  with  a  lid  having  open- 
ings for  the  four  tubes  that  pass  through  it.  The  water-cylinder  stands  upon 
legs  within  a  larger  cylinder  (M),  which  is  filled  with  a  poor  conductor  of  heat. 
Finally  this  is  placed  in  a  still  larger  cylinder  (N),  which  again  contains  water 
(W) .  This  last  layer  of  water  is  intended  to  prevent  any  heat  from  the  exterior 
from  raising  the  temperature  of  the  water  in  the  interior.  A  definite  amount  of 
the  material  to  be  examined  is  burned  in  the  combustion-chamber.  After  com- 
bustion has  been  completed,  during  the  progress  of  which  the  water  in  the  interior 
is  repeatedly  stirred,  the  temperature  of  the  water  is  determined  by  means  of  a 
delicate  thermometer.  If  the  amount  of  increase  in  temperature  is  noted,  and 
if  the  amount  of  water  in  the  inner  cylinder  is  known,  the  number  of  heat-units 
furnished  by  the  combustion  of  the  measured  amount  of  the  substance  under 
examination  can  be  readily  estimated. 

377 


378  SOURCES    OF    HEAT. 

Instead  of  the  water-calorimeter  the  ice-calorimeter  may  be  employed.  In 
this  instrument  the  inner  container  is  surrounded  with  ice  instead  of  with  water. 
Around  this  in  a  second  container  is  still  more  ice,  which  prevents  any  heat 
from  without  acting  upon  the  ice  in  the  interior.  The  body  in  the  interior  cham- 
ber gives  off  heat  and  causes  a  portion  of  the  surrounding  ice  to  melt,  while  the 
ice-water  passes  off  below  through  a  tube  and  is  measured.  In  this  connection 
it  should  be  noted  that  79  heat-units  are  required  to  melt  i  gram  of  ice  into  i 
gram  of  water  at  a  temperature  of  o°  C.  For  animal  experimentation  the  calor- 
imeter has  probably  reached  the  highest  grade  of  perfection  at  the  hands  of  Rubner. 

The  air-calorimeter  of  d'Arsonval  permits  of  measurement  in  human  beings 
within  a  few  minutes.  A  rigid  cylinder  of  woolen  material,  within  which  a  man 
may  stand,  is  provided  above  with  a  chimney.  If  the  man  heats  the  air  in  the 
interior,  this  will  escape  through  the  chimney  and  set  in  motion  a  small  wind- 
mill contained  therein,  whose  revolutions  can  be  counted.  The  amount  of 
heat  given  off  is  proportional  to  the  square  of  the  velocity  of  the  escaping  cur- 
rent of  air.  A  man  in  the  nude  state  yielded  124,  and  in  the  dressed  state  79 
calories  in  an  hour. 

Just  as  in  the  calorimeter,  though  much  more  slowly,  nutrient  mat- 
ters are  consumed  in  the  human  body  with  a  supply  of  oxygen,  and  as  a 
consequence  there  takes  place  a  transformation  of  potential  into  kinetic 
energy,  which  in  a  person  at  rest  appears  almost  wholly  as  heat. 

Favre  and  Silbermann,  Frankland,  Rechenberg,  Stohmann,  B.  Danilewsky, 
Jlubner  and  others  have  made  calorimetric  observations  as  to  the  amount  of  heat 
yielded  by  the  combustion  of  many  nutrient  substances.  One  gram  of  water- 
free  substance  yields  in  heat-units  as  follows: 

CARBOHYDRATES. 

Proteids  on  the  average,  ........  S711  Galactose,   ....................  3722 

Serum-albumin,    ...............  5918  Cane-sugar,   ...................  3955 

Egg-albumin  ..................  5735  Milk-sugar,  ....................  3952 

Syntonin,  .....................  59°8  Maltose,  ......................  3949 

Hemoglobin,  .....  ..............  5885  Glycogen,  .....................  4191 

Milk-casein,  ...................  5858  Starch,  .......................  4183 

Yolk  of  egg,  .  .  .  :  ...............  5841  Cellulose,  .....................  4185 

Vitellin,  .......................  5745  Cow's  milk,    ...................  5613 

M_af  f  5663  Woman's  milk  ..................  5786 

•  \  5641  Rye-bread  .....................  4471 

Peptone,  ......................  5299  Wheat-bread,   .................  43  5  1 

Fibrin,  ........................  5637  Peas  ..........................  4889 

Vegetable  fibrin,  ...............  5942  Buckwheat,  ...................  4288 

Legumin,  .....................  5793  Maize,  ........................  5188 

Conglutin,  ....................  5479  Alcohol,  ......................  6980 

Muscle-extractives,  .............  4400 

Animal  fats  on  the  average,  .....  9500  Liebig's  meat-extract  ...........  3216 

Butter  923i  (Principally    according    to    Stoh- 

Olive-oil,  '.'.'.'.'.'.'.'.'.'.  '.'.'.'.'.'.'.'.'.'.'/   9*7         mann>-  ' 

(       900 


T>  ., 

RaPe-011' 


9627      Urea  .........................    2537 

9759      Glycin,  ...................  .... 


Stearic  acid,  ...................  2712  Leucin,  .......................  6533 

Oleic  acid,    ....................  2682  Hippuric  acid,  .................  5678 

Palmitic  acid,   .................  2398  Kreatinin,  .....................  4275 

Glycerin,    .....................  397  Uric  acid,  ...........  .  .........  274* 

Alcohol,  ......................  7  100 

As  the  proteids  in  the  body  are  not  transformed  beyond  urea  the  amount 
of  heat  resulting  from  the  combustion  of  urea  is  to  be  deducted  from  that  resulting 
from  the  combustion  of  the  proteids.  As  one  gram  of  proteids  (average  calories 
5711)  yields  0.3428  gram  of  urea,  and  i  gram  of  urea  yields  2537  calories,  870 
calories  are  to  be  deducted. 

Isodynamic  food-stuffs,  namely,  those  that  yield  the  same  amount  of  heat 
in  the  process  of  combustion,  are  as  follows:  100  grams  of  animal  proteid,  after 
deduction  of  the  heat  resulting  from  the  combustion  of  urea,  equal  52  grams  of 
fat,  114  grams  of  starch,  128  grams  of  dextrose.  One  hundred  grams  of  fat  are 


SOURCES    OF    HEAT. 


379 


isodynamic  with  243  grams  of  dry  meat  or  225  grams  of  dry  syntonin,  or  with 
256  grams  of  dextrose.  According  to  Pfliiger,  i  gram  of  nitrogen  in  meat  equals 
2.79  grams  of  fat;  i  gram  of  animal  fat  equals  0.364  gram  of  nitrogen  in  meat; 
i  gram  of  starch  equals  0.424  gram  of  fat  or  0.154  gram  of  nitrogen  in  meat;  i  gram 
of  grape-sugar  equals  0.390  gram  of  fat  or  0.42  gram  of  nitrogen  in  meat;  too 
grams  of  vegetable  albumin  likewise  equals  55  grams  of  fat  or  121  grams  of 
starch  or  137  grams  of  dextrose. 

Rubner  estimates  in  human  beings  on  a  mixed  diet  the  available  heat -pro- 
ducing energy  for  i  gram  of  proteid  at  approximately  4100  calories,  for  i  gram 
of  fat  9300  calories,  for  i  gram  of  carbohydrate  4100  calories.  For  the  dog  Rubner 
determined  that  i  gram  of  nitrogen  in  the  excreta  of  the  fasting  animal  had  caused 
the  production  of  25,000  calories;  further,  that  i  gram  of  nitrogen  in  the  excreta 
with  a  meat-diet  had  produced 
26,000  calories;  and  i  gram  of 
carbon,  formed  from  1.3  grams 
of  fat,  had  yielded  12,300  calo- 
ries. 

If  it  be  known,  therefore, 
how  many  parts  by  weight 
of  the  foregoing  substances 
a  human  being  takes  up  with 
his  food  during  twenty-four 
hours,  the  calculation  can  be 
made  as  to  how  many  heat- 
units  he  may  generate  there- 
from through  oxidation.  In 
this  connection  the  utiliza- 
tion of  the  nutrient  materials 
must  be  taken  into  consider- 
ation, in  accordance  with 
which  a  certain,  even  though 
small,  percentage  of  the  food 
cannot  be  disposed  of  by  the 
digestive  and  absorptive  or- 
gans, and  therefore  is  ex- 
creted unused. 


Rubner  found  that,  however 
abundant  the  administration  of 
food,  a  larger  amount  of  heat 
can  be  shown  to  be  produced 
immediately  on  the  first  day  of 
feeding,  as  compared  with  the 
preceding  days  of  fasting.  The  bodily  temperature  under  such  circumstances 
remains  unaltered.  The  greatest  amount  of  heat  is  produced  as  a  result  of 
excessive  administration  of  proteids,  less  from  carbohydrates  and  least  from  fats. 

In  detail  the  sources  of  heat  are  as  follows : 

i.  The  transformation  of  chemical  combinations  of  foods  with  high 
potential  energy  into  those  of  lesser  or  completely  exhausted  potential 
energy.  As  the  organic  articles  of  food,  exclusive  of  the  inorganic 
accompaniments,  consist  of  C,  H,  N  and  O,  it  is  especially  through  (a) 
the  combustion  of  C  into  CO2  and  of  H  into  H2O  that  heat  is  produced. 
In  this  connection  it  is  to  be  noted  that  the  combustion  of  i  gram  of 
C  into  C02  yields  8080  heat-units,  while  that  of  i  gram  of  H  into  H2O 
yields  34,460  heat-units,  though  the  C  and  H  in  the  molecules  of  the 
food-stuffs  must  not  already  be  saturated  with  O.  The  amount  of  0 
necessary  for  this  purpose  is  taken  up  in  the  act  of  respiration.  There- 


FIG.  133. — Water  Calorimeter  (after  Favre  and  Silbermann). 


380  SOURCES    OF    HEAT. 

fore  an  approximate  estimate  may  be  made  as  to  the  quantity  of  heat 
produced  by  an  organism  from  the  amount  of  oxygen  consumed  in  a 
unit  of  time.  An  equal  consumption  of  O  corresponds  with  an  equal 
production  of  heat,  whether  it  served  for  the  oxidation  of  H  or  of  C. 
As  a  matter  of  fact,  a  relation  exists  between  heat-production  in  the 
animal  body  and  the  consumption  of  O,  as  between  cause  and  effect. 
Thus,  cold-blooded  animals,  which  consume  little  O,  have  a  low  bodily 
temperature.  Among  warm-blooded  animals  i  kilogram  of  living  rabbit 
takes  up  0.914  gram  of  O  within  an  hour  and  by  this  means  maintains 
its  bodily  temperature  on  the  average  at  38°  C.;  i  kilogram  of  living 
hen,  on  the  other  hand,  consumes  1.186  grams  of  O  in  an  hour  and 
maintains  as  a  result  an  average  temperature  of  43.9  C.  The  amount  of 
heat  produced  is  equally  large  whether  the  combustion  takes  place 
slowly  or  rapidly.  The  activity  of  metabolism  has,  accordingly,  an  in- 
fluence only  upon  the  rapidity,  but  never  upon  the  absolute  amount,  of 
heat-formation.  Also,  the  combustion  of  inorganic  substances  in  the 
body,  such  as  that  of  sulphur  into  sulphuric  acid,  that  of  phosphorus 
into  phosphoric  acid,  constitutes  a  source  of  heat,  although  it  be  but 
slight.  According  to  Rubner  this  amounts  to  but  0.47  per  cent,  of  the 
heat. 

(b)  In  addition  to  the  processes  of  combustion,  however,  all  of  those 
chemical  processes  in  the  human  body,  as  a  result  of  which  the  total 
amount  of  potential  energy  present  is  diminished,  in  consequence  of 
greater  saturation  of  affinities  of  the  atoms  previously  present,  are 
attended  with  the  development  of  heat.  Wherever  the  atoms  combine 
with  saturated  affinities  for  greater  stability  in  their  ultimate  position 
of  rest,  chemical  potential  energy  is  transformed  into  kinetic  thermal 
energy,  as,  for  instance,  in  the  alcoholic  fermentation  of  grape-sugar 
and  other  similar  processes. 

Heat  is  produced  also  in  the  following  chemical  process : 

(«)  The  union  of  bases  with  acids.  Here  the  character  of  the  base  determines 
the  amount  of  heat  formed,  while  the  character  of  the  acid  is  without  any  influence. 
Only  when  the  acid,  as,  for  instance,  carbon  dioxid,  is  not  capable  of  neutraliz- 
ing the  alkaline  reaction,  is  the  production  of  heat  smaller.  Also,  the  forma- 
tion of  chlorin-combinations,  as  in  the  stomach,  generates  heat. 

(-3)  The  transformation  of  a  neutral  into  a  basic  salt.  In  the  blood  the 
sulphuric  and  phosphoric  acids  resulting  from  the  combustion  of  sulphur  and 
phosphorus  combine  with  the  alkalies  of  the  blood  to  form  basic  salts.  The 
decomposition  of  the  carbonates  of  the  blood  by  lactic  and  phosphoric  acids 
constitutes  a  double  source  of  heat,  namely  through  the  formation  of  a  new  salt, 
as  well  as  through  the  release  of  carbon  dioxid,  which  is  in  part  absorbed  by  the 
blood. 

(>-)  The  combination  of  hemoglobin  with  oxygen.  According  to  Berthelot 
the  amount  of  heat  produced  in  this  way  is  equal  to  one-seventh  of  the  total 
amount  formed  in  the  body. 

In  the  chemical  processes  through  which  the  body  is  provided  with  heat  there 
not  rarely  occur  heat-absorbing  intermediate  transformations  of  the  bodies.  At 
times,  in  order  to  bring  about  more  complete  saturation  of  the  affinities,  inter- 
mediary atom-groups  in  themselves  firmly  united  must  first  be  broken  up.  In  this 
process  thermal  energy  is  consumed.  Also  in  the  breaking  up  of  stable  aggregate 
states  in  processes  of  retrogressive  metamorphosis  heat  is  bound  up.  All  of  these 
intermediary  losses  of  heat,  however,  are  extremely  slight  as  compared  with  that 
due  to  the  development  of  the  end-products. 

2.  Physical  processes  may  be  mentioned  as  a  second  source  of  heat, 
(a)  The  transformation  of  the  kinetic  mechanical  energy  of  the  viscera 
furnishes  heat,  as  the  work  done  cannot  be  conveyed  to  the  outside. 


ANIMALS    WITH    CONSTANT    AND    VARIABLE    TEMPERATURE.  381 

Thus,  all  of  the  kinetic  energy  of  the  heart  is  transformed  into  heat 
through  the  resistance  opposed  to  the  blood-stream.  The  same  may  be 
said  of  the  kinetic  energy  of  certain  muscular  viscera.  Thus,  the 
torsion  of  the  costal  cartilages  and  the  friction  of  the  current  of  air 
in  the  respiratory  organs  and  of  the  contents  of  the  digestive  tract  yield 
a  certain  amount  of  heat. 

Small  amounts  of  the  mechanical  energy  of  the  heart  are  transmitted  through 
the  apex-beat  and  the  superficial  pulse  to  surrounding  parts,  but  these  are  ex- 
ceedingly small.  Also,  in  the  respiratory  movement,  in  the  expulsion  of  the 
respiratory  gases,  the  expectorated  and  other  matters,  a  small  amount  of  energy 
is  conveyed  to  the  outside,  which  is  not  converted  into  heat.  Joule  has 
attempted  to  determine  the  amount  of  heat  generated  in  consequence  of  the 
kinetic  energy  lost  by  a  flowing  fluid.  According  to  him  the  amount  of  heat 
produced  in  this  way  as  a  result  of  the  friction  must  stand  in  a  relation  to  the 
product  of  the  difference  between  the  initial  and  the  terminal  pressure  in  the 
weight  of  the  flowing  fluid  mass.  If  it  be  assumed  that  the  daily  work  of  the 
circulation  equals  more  than  86,000  meter-kilograms,  it  will  be  seen  that  the 
resulting  amount  of  heat  in  23  hours  will  be  about  204,000  calories,  which  is  suffi- 
cient to  raise  the  temperature  of  the  body  of  a  medium-sized  person  about  2°  C. 

(6)  If  the  body  through  muscular  activity  does  work  transmitted  to 
the  outside,  as,  for  instance,  if  an  individual  throws  a  heavy  weight  or 
ascends  a  tower,  a  portion  of  the  kinetic  energy  is  converted  into  heat 
through  the  friction  of  the  muscles,  the  tendons,  the  articular  surfaces, 
further  through  concussion  and  pressure  of  the  ends  of  the  bone  upon 
one  another. 

(c)  The  electrical  currents  generated  in  muscles,  nerves  and  glands, 
apart  from  the  small  amounts  that  pass  outside  of  the  body  with  suitable 
conduction,   are  most  probably  transformed  into   heat.     Thermogenic 
chemical  processes  also  generate   electricity,  which   likewise   is  trans- 
formed into  heat.     This  source  of  heat  is,  however,  quite  insignificant. 

(d)  As  a  further  slight  source  of  heat  from  physical  causes  there  should  yet 
be  mentioned  heat-production  through  absorption  of  carbon  dioxid,  through  the 
condensation  of  water  in  its  passage  through  membranes,  and  in  the  process  of 
imbibition,   the   formation   of  stable   aggregate   states,    as,  for   instance,  of  cal- 
cium in  the  bones.     It  is  true,  heat  is  again  in  part  lost  through  the  involution 
of  solid  parts  at  advanced  age.     After  death,  at  times  also  under  pathological 
conditions  during  life,  coagulation  of  blood  and  the  rigidity  of  muscles  constitute 
in  this  manner  a  source  of  heat. 

ANIMALS  WITH  CONSTANT  AND  WITH  VARIABLE 
TEMPERATURE. 

Instead  of  the  older  division  of  animals  into  cold-blooded  and  warm- 
blooded (mammals  and  birds),  it  is  advisable  to  base  their  classification 
upon  another  characteristic,  namely,  the  uniformity  or  the  variability 
of  the  bodily  temperature  with  respect  to  external  influences.  For  the 
class  of  warm-blooded  animals  the  name  homoiothermic  animals  has  been 
introduced  by  Bergmann,  because  they  are  capable  of  maintaining  their 
bodily  temperature  with  remarkable  uniformity  notwithstanding  consid- 
erable variations  in  the  surrounding  temperature.  He  designated  cold- 
blooded animals  poikilothermic  animals  because  their  bodily  temperature 
rises  and  falls  within  wide  limits  in  accordance  with  the  temperature  of 
the  surrounding  medium.  Accordingly,  heat-production  must  be  in- 
creased in  homoiothermic  animals  if  exposed  for  a  long  time  in  a  cold 
atmosphere  and  diminished  on  exposure  for  a  long  time  in  a  warm 
atmosphere. 


382  METHODS    OP    ESTIMATING    THE    TEMPERATURE. 

An  instance  of  this  great  constancy  of  the  temperature  in  the  human  body 
was  furnished  by  Fordyce,  who  died  in  1792.  After  a  man  had  been  for  ten 
minutes  in  a  room  filled  with  hot,  dry  air,  the  temperature  of  the  interior  of  his 
closed  hand,  the  cavity  of  his  mouth  beneath  the  tongue,  as  well  as  the  urine, 
was  raised  only  a  few  tenths  of  a  degree.  When  Becquerel  and  Brechet  were  inves- 
tigating by  means  of  the  thermo-electric  needle  the  temperature  in  the  middle  of 
the  biceps  muscle  in  a  man  whose  arm  had  been  immersed  for  a  whole  hour  in 
ice-water,  they  found  the  temperature  of  muscular  tissue  reduced  only  0.2°  C. 
The  same  muscle  exhibited  either  no  increase  in  temperature  or  a  reduction  of 
only  0.3°  C.  after  the  man  had  immersed  the  arm  in  water  at  a  temperature  of 
42°  C.  for  a  quarter  of  an  hour. 

If  marked  alteration  in  temperature  be  brought  about  by  powerful 
agents,  namely,  by  vigorous  abstraction  of  heat  or  by  considerable 
addition  of  heat,  great  danger  to  the  continuance  of  life  results. 

Poikilothermic  animals  react  differently,  the  bodily  temperature 
following  in  general  the  surrounding  temperature,  though  with  varia- 
tions. On  the  basis  of  numerous  observations  Soetbeer  therefore  states 
that  the  poikilothermic  vertebrates  have  no  special  temperature  in  the 
ordinary  sense  of  the  term,  but  their  bodily  temperature,  like  that  of 
inanimate  objects,  is  dependent  upon  that  of  the  physical  conditions  of 
their  surroundings. 

The  following  may  suffice  as  illustrations  of  the  bodily  temperature  in  the 
animal  kingdom:  Birds:  sea-gull,  37.8°  C.;  swallow  and  titmouse,  44.03°;  mam- 
mals: dolphin,  35.5°,  mouse,  41.1°,  echidna  from  26.5°  to  36°;  arthropods:  from 
0.1°  to  5.8°  above  the  surrounding  temperature;  in  bees  aggregated  in  the  hive 
from  30°  to  32°,  and  in  bees  in  swarms  as  high  as  40°.  The  following  animals 
raise  their  temperature  above  the  surrounding  temperature:  cephalopods  0.57°, 
molluscs  0.46°,  echinoderms  0.40°,  medusae  0.27°,  polyps  0.21°  C. 

METHODS   OF  ESTIMATING  THE   TEMPERATURE: 
THERMOMETRY. 

Thermometry. — By  means  of  thermometric  apparatus  information  is  obtained 
as  to  the  temperature  of  the  body  subjected  to  examination.  For  this  purpose 
there  are  employed: 

The  thermometer  (Galileo,  1603).  Sanctorius  was  the  first  in  1626  to  make 
thermometric  measurements  in  human  beings.  It  is  advantageous  to  employ 
instruments  ^  graduated  in  100  parts  according  to  Celsius,  each  degree  being 
subdivided  into  ten  parts.  The  apparatus  should  be  compared  with  a  nor- 
mal thermometer  before  being  used.  The  column  of  mercury  should  be  slender 
and  the  spindle  neither  too  small  nor  too  large,  and  preferably  cylindrical  in 
shape.  A  large  bulb  increases  the  sensitiveness  and  also  the  period  of  observation, 
because  the  large  amount  of  mercury  is  influenced  through  and  through  by  heat 
with  greater  difficulty.  If  the  spindle  be  smaller  the  observation  can  be  made 
more  rapidly,  but  it  is  less  trustworthy.  The  scale  should  be  of  porcelain. 

All  thermometers  acquire  an  error  after  use  for  a  considerable  time,  regis- 
tering too  high.  Therefore,  they  should  be  compared  from  time  to  time  with  a 
normal  instrument.  At  every  observation  the  bulb  should  be  completely  sur- 
rounded and  kept  at  rest  for  at  least  fifteen  minutes  and  during  the  last  five 
minutes  no  movement  in  the  column  of  mercury  should  be  noticeable.  Minimal 
and  particularly  maximal  thermometers,  for  the  measurement  of  febrile  tempera- 
ture, are  of  the  greatest  convenience  to  the  physician. 

For  delicate  comparative  measurements  Walferdin's  metastatic  thermometer 
(Fig.  134)  is  especially  useful.  The  tube  is  exceedingly  narrow  in  proportion  to 
the  bulb.  In  order  that  on  this  account  the  instrument  should  not  be  drawn  out 
to  an  extraordinary  length,  an  arrangement  is  provided  by  which  the  necessary 
amount  of  mercury  can  be  increased  or  diminished  at  will.  So  much  mercury  is 
taken  that  at  the  expected  temperature  the  column  reaches  about  to  the  middle 
of  the  tube.  This  end  is  attained  by  having  at  the  upper  extremity  of  the  tube 
an  expansion  in  which  the  superfluous  mercury  is  received.  If,  for  instance,  a 
temperature  is  to  be  taken  that  is  likely  to  be  between  37°  and  40°  C.,  the  bulb 


METHODS    OF    ESTIMATING    THE    TEMPERATURE. 


383 


X 


is  first  heated  to  somewhat  above  40°  C.;  then  it  is  copied  quickly  and  at  the 
same  time  shaken,  so  that  the  column  of  mercury  is  broken 
below  the  upper  expansion.  Thus  the  play  of  the  column  is 
from  about  40°  downward.  The  tube  is  so  fine  that  i°  C.  com- 
prises about  10  cm.  in  length,  and  yi^0  C.  is  still  i  mm.  long. 
A  reading  of  even  as  little  as  T^oo°  C.  has  been  made  possible. 
The  scale  is  graduated  arbitrarily.  The  value  of  the  graduation 
must  be  determined  by  comparison  with  a  normal  thermometer, 
and  also  the  temperature  when  the  column  of  mercury  reaches  a 
certain  level. 

Kronecker  and  Mayer  caused  small  maximal  thermometers 
to  be  passed  through  the  digestive  canal  or  through  vessels  of 
considerable  size.  The  small  instruments  are  so-called  outflow 
thermometers,  whose  mercury  escapes  through  the  short  open 
tube,  and  in  greater  amount  naturally  when  the  temperature  is 
highest.  After  removal,  examination  is  made  by  comparison  with 
a  normal  thermometer  for  the  purpose  of  determining  the  tem- 
perature at  which  the  mercury  rises  exactly  to  the  free  extremity 
of  the  tube. 

The  thermo-electric  apparatus  permits  rapid  and  accurate 
measurement  of  the  temperature  (Fig.  135,  I).  The  thermo-elec- 
tro-galvanometer  of  Meissner  and  Meyerstein  employed  for  this 
purpose  contains  a  circular  magnet  (m)  suspended  from  a  silk 
thread  (c)  to  which  by  means  of  a  hook  a  small  mirror  (s)  is 
attached.  Near  this  magnet  another  bar-magnet  is  fixed,  with 
its  poles  similarly  directed,  and  in  such  proximity  that  the  free 
magnet  is  capable  of  turning  to  the  north  with  the  slightest  de- 
gree of  force.  About  the  latter  a  thick  copper  wire  (b  b)  is  wound 
several  times  (in  the  diagrammatic  representation  but  one  turn 
is  shown),  and  with  the  prolonged  extremities  of  this  two 
needle-like  thermo-elements  (a  f ,  f  a)  made  of  different  metals — 
German  silver  and  iron — and  soldered  together,  are  connected. 
The  free  ends  of  these  needles  of  similar  name  are,  further,  con- 
nected by  means  of  a  wire  (b) .  Thus  the  two  thermo-elements  are 
incorporated  into  the  closed  circuit.  At  a  distance  of  three  meters 
from  the  mirror  a  horizontal  scale  (K  K)  is  fixed,  the  numbers  on 
which  are  reflected  in  the  mirror.  The  scale  itself  is  supported 
upon  a  telescope  (F) ,  which  is  directed  toward  the  mirror.  The 
observer  (B),  looking  through  the  telescope,  sees  in  the  mirror 
the  figures  of  the  scale,  which  can  be  accurately  adjusted.  If  the 
magnet  swings  out  of  the  magnetic  meridian,  and  with  it  the 
mirror,  other  figures  on  the  scale  appear  to  the  observer  in  the 
mirror.  If  one  of  the  thermo-elements  is  heated,  an  electric  cur- 
rent results,  which  is  directed  in  the  warmer  element  from  the 
German  silver  to  the  iron,  and  at  the  same  time  causes  deflection 
of  the  movable  magnet.  If  the  observer  conceive  that  he  is 
swimming  in  the  direction  of  the  current  within  the  conducting 
wire  the  north  pole  of  the  magnet  is  deflected  to  the  left. 

The  tangent  of  the  angle,  through  which  the  freely  movable 
magnet  is  deflected  from  its  position  of  rest  in  the  magnetic  me- 
ridian by  means  of  a  galvanic  current  passed  before  it,  is  equal  to 
the  relation  of  the  galvanic  energy  G  to  the  magnetic  energy. 
Therefore,  the  tangent  is  as  G  is  to  D.  In  order,  thus,  to  keep 
the  tangent  as  large  as  possible,  while  G  remains  the  same,  the 
magnetic  energy  must  be  reduced  as  much  as  possible.  If  the 
magnetism  of  the  swinging  magnet  be  designated  m  and  the  mag- 
netism of  the  earth  T  the  magnetic  energy  D  equals  Tm.  From 
this  it  appears  that  D  can  be  diminished  in  two  ways,  namely 
(i)  by  reduction  of  the  magnetic  force  of  the  swinging  magnet, 
as  may  be  done  through  the  astatic  pair  of  needles  of  the  Nobili 
multiplicator,  and  (2)  by  lessening  the  magnetism  of  the  earth  by 
means  of  a  fixed  auxiliary  magnet  (Hauy  bar)  applied  in  the 
neighborhood  of  the  swinging  magnet  with  the  same  object. 

Of  importance  for  the  rapid  and  accurate  adjustment  of  the 
magnet  is  the  employment  of  the  so-called  damping  arrangement 
of  Gauss,  which  is  not  indicated  in  the  illustration.  This  consists  of  a  thick, 


FIG.  134— Wal- 
ferdin's  Me- 
tastatic  Ther- 
mometer. 


METHODS    OF    ESTIMATING    THE    TEMPERATURE. 


copper,  hollow  cylinder,  upon  which  the  wire  of  the  coil  is  wound.  This  mass  of 
copper  may  be  considered  as  a  closed  multiplicator  of  a  single  winding  with  a  large 
cross-section.  The  magnet  set  into  oscillation  induces  in  this  closed  copper 
mass  a  current  whose  intensity  is  greatest  when  the  rapidity  of  oscillation  of  the 
magnet  is  greatest,  and  which  takes  the  opposite  direction  as  soon  as  the  mag- 
net is  reversed.  In  lesser  degree  the  multiplicator  itself  as  soon  as  it  is  closed 
operates  in  the  same  manner  as  a  damper.  The  currents  thus  induced  cause  a 
reduction  in  the  oscillations  of  the  magnet  in  such  a  way  that  the  arc  of  move- 


FIG.  135. — Diagrammatic  Representation  of  Thermo-electric  Apparatus  for  the  Measurement  of  Temperature. 


ment  diminishes  in  rapid  and  almost  geometric  progression.  The  induced,  damp- 
ing current  is  the  stronger  the  less  the  resistance  in  the  closed  circuit,  in  the 
presence  of  the  damper  therefore  the  greater  the  transverse  section  of  the  copper 
ring.  By  means  of  this  damping  arrangement  the  monotonous  oscillation  of  the 
magnet  to  and  fro  is  limited  and  the  latter  comes  to  rest  rapidly  and  promptly 
after  three  or  four  small  oscillations  while  the  observation  is  sharp  and  made 
without  loss  of  time. 

So-called  Dut rochet  needles  (II)   are  introduced  as  thermo-electric  elements. 
These  consist  of  German  silver  and  iron  and  are  soldered  together  longitudinally 


TEMPERATURE-TOPOGRAPHY.  385 

at  their  points.  Becquerel  needles  (III)  also  may  be  employed.  These  are  made 
of  the  same  metals,  which  are  soldered  together  in  continuity.  The  needles  must 
be  well  covered  upon  their  surface  with  brown  varnish  in  order  that  the  currents 
resulting  from  the  moistening  of  different  metals  with  the  parenchymatous  fluids 
may  not  interfere  with  the  thermo-currents  obtained.  Before  the  investigations 
are  undertaken  the  extent  of  deflection  on  the  scale  to  which  a  definite  difference 
in  temperature  in  the  needles  gives  rise,  thus  about  i°  C.,  must  further  be  deter- 
mined. In  order  to  do  this  a  sensitive  thermometer  is  fastened  by  means  of  a 
loop  to  each  of  the  thermo-needles,  which  are  placed  in  separate  oil-baths  of  a 
constant  temperature,  though  differing  by  i°  C.,  as  can  be  seen  from  the  ther- 
mometers. If  the  circuit  is  now  closed  the  deflection  on  the  scale  will  naturally 
correspond  to  i°.  If,  thus  adjusted,  the  instrument  exhibited  a  deflection  of  150 
mm.,  every  displacement  of  the  scale  of  i  mm.  would  equal  Tiff  °  C.  If  this  has 
been  determined,  either  the  two  thermo-needles  can  be  introduced  into  the  different 
tissues  or  organs  of  animals  at  the  same  time,  and  in  this  way  information  be 
gained  as  to  the  prevailing  differences  in  temperature  in  these  portions  of  the 
body;  or  one  of  the  thermo-needles  is  placed  in  a  bath  of  constant  temperature — 
approximately  that  of  the  body — in  which  at  the  same  time  there  is  a  sensitive  ther- 
mometer, while  the  other  needle  is  introduced  into  the  viscus  to  be  examined. 
In  this  event  the  difference  in  temperature  between  the  tissue  and  the  constant 
source  of  heat  is  learned.  For  slight  differences  in  temperature,  such  as  usually 
exist  in  the  tissues  of  the  body,  the  thermo-electric  energy  is  always  proportionate 
to  the  difference  in  temperature  between  the  two  needle-elements. 

It  is  obvious  that  instead  of  one  pair  of  needles  a  multiplicity  may  be  em- 
ployed. By  this  means  the  delicacy  of  the  apparatus  naturally  is  materially  in- 
creased. Thus,  v.  Helmholtz  was  able  to  increase  the  delicacy  of  the  apparatus 
to  the  detection  of  differences  of  ^Vcr  °  C.  by  the  employment  of  16  antimony- 
bismuth  elements?  Schiffer  constructed  a  thermopile  of  four  pairs  of  needle- 
elements  in  a  simple  manner  (Fig.  135,  IV)  by  soldering  together  alternately 
wires  of  iron  and  German  silver.  It  is  intended  that  four  such  elements  should  be 
introduced  into  two  substances  (A  and  B)  to  be  examined  for  differences  in  tem- 
perature. 

Thermo  palpation  is  the  name  given  by  Benczur  and  J6nas  to  the  following 
method  of  examination :  If  the  finger  be  moved  over  an  uncovered  portion  of  the 
trunk  it  will  be  found  that  the  skin  is  warmer  over  parts  containing  air,  such  as 
lungs  and  intestines,  than  over  parts,  normal  or  pathological,  not  containing  air. 
The  boundaries  are  said  to  agree  with  those  determinable  by  percussion,  but 
this  has  been  disputed.  Naturally  this  difference  can  be  established  also  by 
thermometric  examination. 

TEMPERATURE-TOPOGRAPHY. 

Although  a  •  powerful  influence  must  be  ascribed  to  the  blood,  on 
account  of  its  constant  movement,  in  the  equalization  of  the  temperature 
in  the  different  parts  of  the  body,  nevertheless  an  exact  equalization  is 
never  attained,  but  noteworthy  differences  exist  in  different  parts  of  the 
body. 

The  temperature  of  the  skin  has  been  found  to  be  as  follows : 

In  the  middle  of  the  sole  of  the  foot 32 .26°  C.  J.  Davy  made  these  measure- 
In  the  vicinity  of  the  Achilles  tendon ...  33.85°  C.  ments  immediately  on 
In  the  middle  of  the  anterior  aspect  of  arising  without  dressing, 

the  leg 33-°5°  C.  with  the   temperature   of 

In  the  middle  of  the  calf 33 .85°  C.  the    room    at    21°.     Only 

In  the  popliteal  space 35°       C.  the  inferior  surface  of  the 

In  the  middle  of  the  thigh 34-40°  C.  bulb    of    a    thermometer 

In  the  inguinal  fold 35-8o°  C.  otherwise  covered  came  in 

Over  the  apex-beat  of  the  heart 34-40°  C.  contact  with  the  different 

On  the  face  in  a  man 31°       C.  portions  of  the  skin. 

At  the  tip  of  the  nose  and  on  the  lobule 

of  the  ear from  22°  to  24°  C. 

In  the  closed  axillary  cavity,  the  temperature  ranges,  according  to  Wunderlich, 
from  36.49°  to  37.25°;  according  to  C.  v.  Liebermeister  it  is  36.89°  C. 

25 


386  TEMPERATURE-TOPOGRAPHY. 

The  skin  overlying  muscles  is  warmer  than  that  covering  bones  and  tendons. 
The  cutaneous  temperature  is  somewhat  lower  in  the  aged,  while  in  children  it 
ranges  between  25°  and  29°  C. 

The  skin  of  the  cranial  vault  fcas  a  higher  temperature  in  the  frontal  and 
parietal  regions  than  in  the  occipital  region.  Further,  the  left  side  is  warmer  than 
the  right.  The  temperature  of  the  skin  is  increased  by  dyspnea. 

v.  Liebermeister  employs  the  following  method  in  taking  the  temperature  of 
free  cutaneous  surfaces :  The  bulb  of  the  thermometer  is  heated  to  a  point  slightly 
above  that  of  the  temperature  expected.  Then  the  fall  of  the  column  of  mercury 
is  observed  as  the  instrument  is  held  in  the  air,  and  then  at  the  apparently  appro- 
priate moment  the  bulb  is  applied  to  the  surface  of  the  skin.  If  the  skin  has  the 
same  temperature  as  the  bulb,  the  mercury  must  remain  stationary  for  a  time. 
For  the  measurement  of  the  cutaneous  temperature,  it  is  useful  to  employ  a  spe- 
cially constructed  thermometer  with  a  flat  vessel. 

The  temperature  of  the  cavities  of  the  body : 

Cavity  of  the  mouth  beneath  the  tongue 37-I9°  C. 

Rectum 38.01°  C. 

Vagina   .  .  38.03°  C. 

The  temperature  of  the  uterus  is  somewhat  higher,  while 

that  of  the  cervical  canal  is  somewhat  lower. 
Urine 37.3o°C. 

The  temperature  of  the  stomach  falls  during  the  process  of  digestion. 
Cold  rectal  injections  (11°  C.)  rapidly  lower  the  temperature  of  the 
stomach  i°  C. 

The  temperature  of  the  blood  is  on  the  average  39°  C.  In  the  internal 
portions  of  the  body  venous  blood  is  warmer  than  arterial  blood,  while 
the  reverse  condition  prevails  in  the  peripheral  portions. 

Blood  of  the  right  heart 38.8°    C.  ] 

Blood  of  the  left  heart 38.6°    C.    [  P1       ,     R  A 

Blood  of  the  aorta 38.7°    C.   [Claude  Bernard. 

Blood  of  the  hepatic  veins 39-7°    C.  J 

Blood  of  the  superior  vena  cava 36.78°  C.  1 

Blood  of  the  inferior  vena  cava 38.11°  C.   \  G.  v.  Liebig. 

Blood  of  the  crural  vein 37.20°  C.  J 

The  lower  temperature  of  the  blood  in  the  left  heart  is  due  to  the  fact  that 
the  blood  is  cooled  in  the  lungs  in  the  process  of  respiration.  According  to  Heiden- 
hain  and  Korner  the  temperature  of  the  right  heart  is  somewhat  higher  because 
it  lies  upon  the  warm  liver,  while  the  left  heart  is  surrounded  by  the  air-containing 
lung.  This  fact,  observed  by  Malgaigne  in  1832  and  by  Berger  and  G.  v.  Liebig, 
is  disputed  by  others,  who  attribute  the  somewhat  higher  temperature  of  the  left 
heart  to  the  fact  that  more  active  processes  of  combustion  take  place  in  arterial 
blood  and  that  heat  is  generated  in  the  formation  of  oxyhemoglobin.  In  adjacent 
veins  or  in  those  of  the  same  name  the  temperature  of  the  blood  is  generally  lower 
than  in  the  corresponding  arteries,  on  account  of  the  greater  amount  of  heat 
given  off  in  the  slower  movement.  Thus,  the  temperature  of  the  blood  of  the 
jugular  vein  is  from  0.5°  to  2°  lower  than  that  of  the  carotid;  that  of  the  blood 
of  the  crural  vein  is  from  0.75°  to  i°  lower  than  that  of  the  crural  artery.  Super- 
ficial veins,  particularly  in  the  skin,  give  off  much  heat  and  therefore  the  contained 
blood  has  a  lower  temperature.  The  hepatic  veins  contain  the  warmest  blood, 
39.7°  C.,  not  alone  on  account  of  the  glandular  activity  of  the  liver,  but  also 
on  account  of  the  extraordinarily  protected  situation  of  the  organ. 

The  Temperature  of  the  Tissues. — The  temperature  of  the  individual 
tissues  is  the  higher:  (i)  the  more  they  contribute  to  the  production  of 
heat  through  the  transformation  of  potential  energy,  that  is,  the  greater 
their  metabolic  activity;  (2)  the  more  blood  they  contain;  and  (3)  the 
more  protected  their  situation. 

The  muscles  are  the  chief  seat  of  heat-production,  principally  during 
contraction,  but  also  during  rest.  The  temperature  of  the  blood  in  the 


TEMPERATURE-TOPOGRAPHY.  387 

aorta  is  from  0.1°  to  0.6°  lower  than  that  of  muscle  at  rest.  In  the 
second  place,  the  glands  generate  heat,  especially  during  activity,  par- 
ticularly the  liver,  the  salivary  glands,  the  glands  of  the  stomach  and 
the  intestines. 

Berger  took  the  temperature  of  different  tissues  in  the  sheep  and  obtained 
the  following  results : 

Subcutaneous  connective  tissue 37-35°  C. 

Brain 40.25°  C. 

Liver 4i.25°C. 

Lungs 4i .4o°  C. 

Rectum 40.67°  C. 

The  right  heart 41.40°  C. 

The  left  heart 40.90°  C. 

In  man,  Becquerel  and  Brechet  found  the  temperature  of  the  subcutaneous 
connective  tissue  2 .  i°  C.  lower  than  that  of  the  adjacent  muscles.  The  temperature 
of  the  cornea  and  of  the  aqueous  humor  depends  in  part  upon  the  state  of  the 
iris.  The  smaller  the  pupil,  the  more  heat  must  they  receive  from  the  vessels  of 
the  iris. 

INFLUENCES  AFFECTING   THE  TEMPERATURE   OF  INDIVIDUAL 

ORGANS. 

The  temperature  of  the  individual  organs  is  by  no  means  constant, 
but  there  are  numerous  influences  that  at  times  cause  it  to  rise  and 
at  other  times  cause  it  to  fall. 

i.  The  more  heat  a  portion  of  the  body  generates  independently 
within  itself,  the  higher  will  be  its  temperature.  As  the  production  of 
heat  depends  upon  the  metabolic  changes  in  the  organs,  it  follows  that 
with  the  activity  of  the  latter  the  degree  of  heat-production  must  keep 
pace. 

(a)  The  glands  during  secretion  produce  much  heat,  which  they 
impart  either  to  their  secretion  or  to  the  outflowing  venous  blood. 

C.  Ludwig  found  the  temperature  of  the  escaping  saliva  on  irritation  of  the 
tympanico-lingual  nerve  1.5°  C.  higher  than  that  of  the  blood  passing  through 
the  glandular  artery  to  the  secreting  organ.  The  temperature  of  the  venous  blood 
in  the  secreting  kidney  is  higher  than  that  of  the  arterial  blood.  The  secreting 
liver  in  particular  produces  a  large  amount  of  heat.  Claude  Bernard  studied  the 
temperature  of  the  blood  in  the  portal  vein  and  of  the  blood  in  the  hepatic  veins 
during  hunger,  at  the  beginning  of  digestion  and  at  the  height  of  digestion,  and 
found 

Temperature  of  portal  vein 37 .8°  C. )  After  fasting  for  four  days.     Blood  ot 

hepatic  veins.  .  .  .  38.4°  C.  j       right  heart  during  fasting  38.8°  C. 

Temperature  of  portal  vein .  .       .  .  39.9°  C.  |  A      h    beginning  of  digestion, 
hepatic  veins 39-5    C.  i 

Temperature  of  portal  vein 39.7°  C.  )  At  the  height  of  digestion.     Blood  of 

hepatic  veins.  ...  .41.3°  C.  I       right  heart  during  digestion  39.2°  C. 

In  dogs  feeding  or  chemical  or  mechanical  irritation  of  the  gastric  mucous 
membrane,  and  even  the  holding  of  food  before  the  animal,  brought  about  elevation 
of  temperature  in  the  stomach  and  the  intestines. 

(6)  The  muscles  produce  heat  in  their  contraction.  J.  Davy  found 
the  temperature  of  active  muscle  higher  by  0.7°.  Becquerel  observed  in 
1835,  by  means  of  the  thermo-galvanometer,  an  increase  of  i  °C.  in  the 
temperature  in  the  interior  of  a  contracting  muscle  in  man  after  five 
minutes. 


388  TEMPERATURE-TOPOGRAPHY. 

Therefore  the  temperature  in  fast  runners  may  rise  above  40°.  The  increase 
in  temperature  following  vigorous  muscular  activity  disappears  about  one  and 
a  half  hours  after  the  commencement  of  rest.  The  lower  temperature  of  par- 
alyzed muscles  is  due  only  in  part  to  the  absence  of  muscular  contractions. 

(c)  With  reference  to  the  influence  of  the  sensory  nerves  upon  the 
temperature  it  should  in  the  first  place  be  noted  whether  the  circu- 
lation   is    increased    or   diminished    as    a   result    of   their   stimulation, 
whether  respiration  is  slowed  or  accelerated,  and  whether  the  muscula- 
ture of  the  body  is  relaxed,  or  is  stimulated  to  activity  through  reflex 
influences.     In  the  first  place  the  temperature,  in  the  interior  of  the 
body  and  the  rectum,  will  be  increased,  and  in  the  latter  diminished. 
From  this  point  of  view  the  conflicting  statements  not  rarely  made  can 
be  reconciled. 

(d)  The   bodily  temperature   rises  also   (about   0.3°)  as   the  result 
of  mental  activity.     The  brain  itself  acquires  a  higher  temperature  in 
consequence  of  sensorial  or  sensory  stimulation. 

(e)  The  parenchymatous   fluids,   the  serous   fluids   and  the  lymph 
generate    but    little    heat   within  themselves   by  reason   of  the  slight 
metabolic  changes  that  take  place  in  them,  and  accordingly  their  tem- 
perature is  that  of  their  environment.     The  epidermoidal  and  horny 
tissues  produce  no  heat  at  all,  and  therefore  maintain  their  temperature 
from  the  subjacent  tissues. 

2.  The  temperature  of  an  organ  depends  upon  the  amount  of  blood 
it  contains,  as  well  as  upon  the  time  within  which  the  volume  of  blood 
is  renewed. 

This  is  seen  most  distinctly  in  the  differences  in  temperature  between  cold, 
pale  skin,  and  warm,  reddened  skin. 

When  Becquerel  and  Brechet  compressed  the  axillary  artery  in  a  man,  the 
temperature  in  the  interior  of  the  biceps  muscle  of  the  arm  fell  several  tenths  of 
a  degree.  After  ligation  of  the  crural  artery  and  vein  in  dogs  Landois  observed 
the  temperature  decline  several  degrees.  Long-continued  elevation  of  the  ex- 
tremities deprives  them  of  blood  and  causes  them  to  become  colder. 

Attention  should  be  called  at  this  point  to  a  difference  between  the  internal 
and  external  portions  of  the  body,  which  is  especially  emphasized  by  v.  Lieber- 
meister.  The  external  portions  of  the  body  give  off  more  heat  to  the  exterior 
than  they  generate  within  themselves.  They  will,  therefore,  be  the  cooler  the 
more  slowly  the  blood  flows  into  them ;  and  the  warmer  the  more  rapid  the  blood- 
current.  Acceleration  of  the  blood-current,  therefore,  will  cause  greater  uniformity 
in  temperature  between  the  peripheral  portions  and  the  interior  of  the  body, 
while  retardation  of  the  blood-current  causes  greater  uniformity  in  temperature 
between  the  peripheral  portions  of  the  body  and  the  surrounding  medium.  The 
internal  portions  of  the  body  react  in  exactly  the  opposite  manner.  Here  active 
production  of  heat  takes  place,  while  heat-dissipation  occurs  almost  solely  through 
the  blood-current.  The  temperature  in  these  parts  must,  therefore,  fall  when  the 
blood-current  is  accelerated,  and  the  reverse.  From  this  it  follows  that  the 
greater  the  difference  in  temperature  between  the  periphery  and  the  interior  of 
the  body,  the  less  is  the  rapidity  of  the  circulation. 

3.  If  the  situation  of  an  organ  causes  it  to  lose  much  heat  by  con- 
duction and  radiation,  or  if  other  conditions  bring  about  the  same  result, 
the  temperature  of  the  organ  declines. 

In  the  first  place  the  skin  is  again  to  be  mentioned  in  this  connection,  as  it 
must  exhibit  a  different  temperature  accordingly  as  it  is  exposed  to  colder  or 
warmer  surroundings,  or  is  covered  or  not,  or  is  dry  or  moistened  by  perspiration 
(in  the  evaporation  of  which  heat  is  lost) .  The  ingestion  of  considerable  amounts 
of  cold  food  and  drink  must  cause  the  temperature  of  the  stomach,  and  the  inhala- 
tion of  cold  air  must  cause  that  of  the  respiratory  tract  down  to  the  bronchial 
tree,  to  fall. 


MEASUREMENT    OF    THE    VOLUME    OF    HEAT:    CALORIMETRY.  389 

MEASUREMENT    OF    THE    VOLUME    OF    HEAT:    CALORIMETRY. 

The  calorimeter  furnishes  information  as  to  the  amount  of  heat  that 
the  body  to  be  examined  possesses  or  is  capable  of  producing.  The  heat- 
unit  or  calory,  that  is  the  amount  of  kinetic  energy  that  is  capable  of 
raising  the  temperature  of  one  gram  of  water  i°  C.,  is  employed  as  the 
unit  of  measure. 

Experiment  has  shown  that  equal  amounts  of  different  bodies  require  unequal 
amounts  of  heat  in  order  to  attain  the  same  temperature.  For  instance  i 
kilo  of  water  requires  nine  times  as  much  heat  as  i  kilo  of  iron  to  attain  the  same 
temperature.  Wherever,  therefore,  different  materials  with  equal  temperatures 
are  found,  each  will  be  endowed  with  different  amounts  of  heat.  The  same 
amount  of  heat  imparted  to  different  bodies  will,  thus,  also  produce  different 
temperatures  in  them.  On  the  other  hand,  bodies  naturally  of  different  tempera- 
ture may  possess  equal  amounts  of  heat.  The  amount  of  heat  that  a  definite 
amount  (as,  for  instance,  i  gram)  of  a  body  requires  in  order  to  have  its  tempera- 
ture raised  a  definite  amount  (as,  for  instance,  i°  C.),  is  designated  the  specific 
heat  of  that  body.  The  specific  heat  of  water,  which  possesses  the  greatest  of  all 
bodies,  is  placed  at  i.  Heat-capacity  is  the  term  applied  to  that  property  of 
bodies  by  means  of  which  they  are  required  to  take  up  a  varying  amount  of  heat 
in  order  to  maintain  the  same  temperature. 

Calorimetry  is  employed : 

For  the  determination  of  the  specific  heat  of  the  different  organs 
of  the  body.  But  few  observations  in  this  connection  have  as  yet  been 
recorded. 

The  specific  heat  of  a  number  of  animal  parts,  as  compared  with 
that  of  water  as  i ,  is  as  follows : 

Blood  from  man,  on  the  average .  1.02    (?)  Meat  from  man,  on  the  average .  .  . 0.741 

(it  is  in  proportion  to  the  num-  Compact  bone 0.3 

ber  of  erythrocytes)  Spongy    bone..  ..0.71 

Arterial  blood,  on  the  average.  .  1.031  (?)  Fat    0.712 

Venous  blood,  on  the  average  .  .0.892  (?)  Striated  muscle 0.825 

Cow's  milk,  on  the  average  .  .  .  .0.992  Defibrinated  blood 0.927 

The  specific  heat  of  the  human  body  as  a  whole  is  thus  only  ap- 
proximately that  of  an  equivalent  weight  of  water. 

For  the  method  of  determining  the  specific  heat  of  solid  or  liquid  bodies 
works  on  physics  should  be  consulted. 

More  important  is  the  employment  of  calorimetry  for  the  estima- 
tion of  the  amount  of  heat  that  either  the  entire  body  or  an  individual 
portion  is  capable  of  producing  in  a  definite  period  of  time. 

Lavoisier  and  Laplace  made  the  first  calorimetric  observations  on  animals  in 
1780,  with  the  aid  of  the  ice-calorimeter.  A  guinea-pig  melted  13  ounces  of 
ice  in  10  hours.  Crawford  in  1779  and  later  Dulong  and  Despretz  in  1822 
employed  for  this  purpose  the  water-calorimeter  of  Rumford — after  which  that 
of  Favre  and  Silbermann  (Fig.  133)  is  modeled.  Small  animals  were  placed  in 
the  interior  chamber  (K)  made  of  thin  copper  and  this  was  immersed  in  a  large 
volume  of  water  surrounded  by  a  poor  conductor  of  heat.  The  amount  of  the 
surrounding  water  and  its  initial  temperature  were  known.  From  the  elevation 
of  temperature  at  the  termination  of  the  experiment,  which  lasted  several  hours, 
the  number  of  calories  furnished  could  be  directly  estimated.  The  air  for  breathing 
was  supplied  to  the  animal  through  a  special  tube  from  a  gasometer.  The  expired 
gases  were  examined  chemically  for  carbon  dioxid. 

According  to  Despretz,  a  small  bitch  generated  14,610  heat-units  in  an  hour— 
393,000  in  twenty-four  hours.  The  taking  of  the  temperature  of  the  animal  before 
and  after  the  experiment  was  carelessly  omitted.  Assuming  equal  metabolic 
activity,  a  human  being  about  seven  times  heavier  would,  on  the  basis  of  this 
observation,  produce  in  the  neighborhood  of  2,750,000  calories  in  twenty-four 


39°  HEAT-CONDUCTION    OF    ANIMAL    TISSUES. 

hours.     Senator  found  that  a  dog  weighing  6330  grams  produced  15,370  calories, 
with  a  loss  of  3.67  grams  of  carbon  dioxid. 

An  adult  man  produces  at  rest  in  twenty-four  hours  2,400,000 
calories,  therefore  100,000  in  an  hour.  One  kilogram  of  body-weight 
produces  in  twenty-four  hours  approximately  34,000  calories,  therefore 
1417  in  an  hour.  These  figures  increase  with  increase  in  the  total 
metabolism  and  also  with  functional  activity. 

The  first  calorimetric  observations  on  man  were  made  by  Scharling  in  1849. 
Leyden  introduced  the  leg  alone  into  the  chamber  of  the  calorimeter.  This  raised 
the  temperature  of  6600  grams  of  water  i°  C.  in  an  hour.  If  it  be  assumed  that 
the  total  superficies  of  the  body  is  about  fifteen  times  as  great  as  that  of  the  leg 
the  human  body,  assuming  equal  loss,  would  produce  2,376,000  calories  in  twenty- 
four  hours. 

HEAT-CONDUCTION  OF  ANIMAL  TISSUES. 
EXPANSIBILITY    OF    ANIMAL    TISSUES    BY    HEAT. 

The  heat-conduction  of  animal  tissues  is  principally  of  importance 
in  relation  to  the  arrangement  of  the  external  integument  and  the  sub- 
cutaneous fatty  tissue.  The  latter  especially  serves  as  a  protecting 
shield  in  warm-blooded  animals  living  in  cold  water  (whale,  walrus,  seal) 
and  through  this  abstraction  of  heat  by  means  of  conduction  from  the 
interior  of  the  body  is  practically  impossible.  Few  investigations  have 
been  made  upon  this  question.  Greiss  in  1870  determined  the  con- 
ductivity of  the  following  tissues  by  noting  the  distance  from  a  central 
source  of  heat  introduced  into  the  tissues  at  which  was  melted  a  layer 
of  wax.  He  studied  the  stomach  of  sheep,  the  bladder  of  oxen,  the 
skin  of  cattle,  calves'  feet,  the  hoofs  of  oxen,  the  bones  of  oxen, 
the  horns  of  buffaloes,  the  antlers  of  deer,  ivory,  mother  of  pearl  and 
haliotis-shell  (sea-snail).  He  found  that  fibrous  tissues  conduct 
better  in  the  direction  of  their  fibers  than  at  right  angles  to  their 
course.  The  figures  formed  by  the  melting  wax  upon  tissues  spread 
out  over  a  wide  area  were  therefore  generally  elliptical.  Landois  has 
made  observations  upon  a  number  of  human  tissues  by  determining  the 
melting-distance  of  a  layer  of  paraffin  from  a  thin  test-tube  filled  con- 
stantly with  boiling  water  and  applied  intimately  to  tissues  in  layers 
of  equal  thickness,  and  subsequently  applied  on  the  flat  and  supported 
by  threads.  Desiccation  was  avoided,  and  also  the  effect  of  radiant  heat. 
Landois  was  able  to  confirm  the  fact  of  the  better  conduction  in  the 
direction  of  the  fibers.  Next  to  bone  the  best  conductor  was  found  to  be 
blood-clot;  then  there  followed  successively  spleen,  liver,  cartilage,  ten- 
don, muscle,  elastic  tissue,  nails  and  hair,  anemic  skin,  gastric  mucous 
membrane,  washed  fibrin-fibers.  The  great  thermic  conductivity  of 
the  blood  as  compared  with  the  much  lower  conductivity  of  bloodless 
skin  is  of  particular  interest.  In  this  way  is  explained  the  fact  that  but 
little  heat  is  dissipated  by  anemic  skin,  while  hyperemic  skin  conducts 
and  gives  off  a  much  larger  amount  of  heat. 

Like  all  bodies  the  human  body  undergoes  expansion  at  elevated 
temperatures.  A  man,  weighing  60  kilos,  will  expand  about  62  cu.  cm. 
with  an  increase  of  his  bodily  temperature  from  37°  C.  to  40°  C.  Of 
the  different  tissues,  connective  tissue  (tendon)  is  expanded  by  heat, 
while  elastic  tissue  and  skin  are  contracted  like  rubber. 


VARIATIONS    IN    THE    MEAN    BODILY    TEMPERATURE. 


391 


VARIATIONS    IN    THE    MEAN    BODILY    TEMPERATURE. 

General  Climatic  and  Somatic  Influences. — The  bodily  temperature 
remains  on  the  whole  constant  within  different  climates.  This  is  note- 
worthy if  it  be  considered  that  a  human  being  at  the  equator  and  in 
the  polar  regions  is  exposed  to  surrounding  temperatures  that  differ  from 
each  other  by  more  than  40°  C.  Further,  it  has  been  observed  that  when 
a  person  passes  from  a  warm  to  a  cold  climate  his  temperature  declines 
but  little,  but  that  when  an  individual  passes  from  a  cold  to  a  hot 
region  his  temperature  rises  relatively  in  more  considerable  degree.  In 
the  temperate  zone  the  bodily  temperature  in  the  cold  winter-season  is 
usually  from  o.i°too.3°C.  lower  than  on  hot  summer  days .  The  elevation 
of  a  region  above  the  level  of  the  sea  has  no  demonstrable  influence 
upon  the  temperature.  Race  and  sex  cause  no  difference.  Persons  of 
vigorous  constitution  are  believed  to  have  a  somewhat  higher  tempera- 
ture in  general  than  debilitated,  flabby,  anemic  persons. 

Influence  of  the  General  Metabolism. — As  the  production  of  heat 
is  related  to  the  breaking  up  of  chemical  combinations,  from  which,  in 
addition  to  the  formation  of  water,  carbon  dioxid  and  urea  finally  result 
as  the  most  important  excrementitious  products,  the  amount  of  heat 
generated  will  keep  pace  with  the  total  production  of  those  bodies  formed. 
The  increased  metabolic  activity  that  sets  in  after  a  heavy  meal  causes 
an  elevation  of  several  degrees  in  temperature.  As  the  general  metabol- 
ism is  naturally  much  less  on  days  of  fasting  than  on  days  on  which  a 
normal  amount  of  food  is  taken,  it  is  clear  that  in  human  beings  the 
temperature  will  be  found  to  be  on  the  average  36.6°  on  fasting  days 
and  37.17°  C.  on  ordinary  days. 

Also  Jiirgensen  found  in  human  beings  on  the  first  day  of  inanition  a  reduction 
in  the  temperature,  although  on  the  second  day  a  transitory  elevation  occurred. 
In  experiments  on  fasting  animals  it  was  found  that  the  temperature  declined 
much  at  first,  then  for  a  considerable  time  remained  pretty  constant,  and  finally 
in  the  last  days  declined  still  further.  Schmidt  subjected  a  cat  to  starvation, 
and  found  that  up  to  the  fifteenth  day  the  temperature  was  38.6°  C.;  on  the  six- 
teenth day  it  was  38.3°,  on  the  seventeenth,  37.64°,  on  the  eighteenth,  35.8°,  on 
the  nineteenth,  the  day  of  death,  33°  C.  Chossat  found  the  temperature  of 
mammals  and  birds  16°  C.  lower  on  the  day  of  death  from  starvation  than  under 
normal  conditions. 

Influence  of  Age. — The  activity  of  the  general  metabolism  must  be 
in  part  responsible  for  the  temperature  of  the  body  at  different  ages,  but 
other  influences  of  undetermined  origin  may  also  in  part  be  contributory. 


ACE. 

MEAN      TEMPERA- 
TURE   AT    ROOM- 
TEMPERATURE. 

NORMAL  LIMITS. 

PLACE  OF  MEASUREMENT. 

New-born 

17  4<?°C. 

0_                .0  Q 

Rectum. 

5-  9  years  
15-20 
21-25 
26-30              
31-40 
4  1—  ^o 

37-72°  c. 

37-37°  C. 
37.220C. 
36.91°  C. 
37.io°C. 
?6  87°  C. 

37.870-37.62°  C. 
36.i2°-38.io°  C. 

Mouth  and  rectum. 
Axillary  cavity. 

51—60                                      .  .  . 

36  83°  C. 

" 

-80                

37-46°  c. 

Mouth. 

According  to  Chelmonski  the  bodily  temperature  is  somewhat  lower  in  the 
old,  and  the  evening  temperature  lower  than  the  morning  temperature. 


392 


VARIATIONS    IN    THE    MEAN    BODILY    TEMPERATURE. 


The  temperature  in  the  new-born  exhibits  special  peculiarities,  such 
as  would  be  readily  explicable  from  the  sudden  change  in  the  conditions 
of  life.  Immediately  after  birth  the  temperature  of  the  child  is  on  the 
average  0.3°  higher  than  that  of  the  vagina  of  the  mother,  namely 
37.86°  C.  In  the  first  hours  after  birth  the  temperature  declines  about 
0.9°  C.,  in  conjunction  with  the  reduction  in  gaseous  interchange.  After 
from  nine  to  thirty-six  hours  it  will  again  have  risen  to  the  average 
temperature  of  the  infant,  which  is  about  37.45°  C.  Certain  irregular 
fluctuations  occur  during  the  first  week  of  life.  During  sleep  the  tem- 
perature in  infants  declines  between  0.34°  and  0.56°  C.  Persistent  crying 
may  cause  the  temperature  to  rise  several  tenths  of  a  degree.  Less  heat 
is  produced  in  the  aged  on  account  of  their  lesser  activity  of  metabolism, 
so  that  they  suffer  more  readily  from  cold  and  therefore  need  warmer 
clothing. 

Periodic  variations  in  the  course  of  the  day  are  constant  at  all 
periods  of  life.  In  general,  it  may  be  stated  that  the  temperature  rises 
continuously  by  day,  the  maximum  being  reached  between  5  and  8  p.  m. ; 
while  it  declines  continuously  by  night,  the  minimum  being  reached 
between  2  and  6  a.  m.  The  mean  temperature  of  the  body  is  found  in 
the  third  hour  after  breakfast.  The  average  level  of  all  the  temperatures 
observed  in  a  person  in  the  course  of  a  day  is  designated  the  daily  mean, 
which,  according  to  Jager,  is  37.13°  in  the  rectum.  If  the  daily  mean  is 
above  37.8°  it  must  be  considered  as  febrile,  and  if  below  37°  as  an 
evidence  of  collapse. 

As  the  daily  variations  in  temperature  occur  also  during  the  state  of  hunger, 
although  the  elevations  are  somewhat  less  after  the  time  for  meals,  the  ingestion 
of  food  cannot  alone  be  the  cause  of  the  variations,  but  these  appear  to  reside 
essentially  in  the  varying  degree  of  muscular  activity. 


HOUR. 

v.  BAREN- 

SPRUNG. 

J.  DAVY. 

HALLMANN. 

GlERSE. 

JURGENSEN. 

JAGER. 

a.  m.    5 

36.7 

36.6 

36.9 

6 

36.68 

36.7 

36.4 

37-r 

7 

36.94* 

36-63 

36.98 

36.7* 

36.5* 

37-5* 

8 

37-16* 

36.80 

37.08* 

36.8 

36.7 

37-4 

9 

36.89 

36.9 

36.8 

37-5 

10 

37.26 

ioi  =  37.36 

37-23 

37 

37 

37-5 

ii 

36.89 

37-2 

37-2 

37-3 

m.     12 

36.87 

37-3* 

37-3* 

37-5* 

p.  m.     i 

36.83 

37-13 

37-3 

37-3 

37-4 

p.  m.    2 

37-°5 

37-21 

37.50* 

37-4 

37-4 

37-5 

3 

37-J5* 

37-43 

37-4* 

37-3* 

37-5 

4 

37-J7 

37-4 

37-3 

37-5* 

5 

37.48 

37-05* 

Si  =  37-31 

37-43 

37-5 

37-5 

37-5 

6 

6*  =  36-83 

37-29 

37-5 

37-6 

37-4 

7 

37-43 

7i  =  36.5°* 

37-3i* 

37-5* 

37.6* 

37-3 

8 

37-4 

37-7 

37.1* 

9 

37.02* 

37-4 

37-5 

36.9 

10 

37-29 

37-3 

37-4 

36.8 

ii 

•36.85 

36.72 

36.70 

36.81 

37-2 

37-i 

36.8 

m.     12 

37-1 

36-9 

36.9 

a.-m.     i 

36-85 

36.44 

37 

39.9 

36-9 

2 

36.9 

36.7 

36.8 

3 

36.8 

36.7 

36.7 

4 

36-31 

36.7 

36-7 

36.7 

*  Indicates  ingestion  of  food. 


VARIATIONS    IN    THE    MEAN    BODILY    TEMPERATURE. 


393 


The  excretion  of  carbon  dioxid  from  hour  to  hour,  also  the  daily  variation 
in  the  pulse-frequency,  almost  coincides  with  the  temperature,  v.  Barensprung 
found  that  the  mid-day  maximum  temperature  somewhat  preceded  the  maxi- 
mum pulse. 

If  a  person  sleeps  by  day  and  performs  all  of  his  other  daily  duties 
by  night,  the  typical  course  of  the  temperature-curve  described  may  be 
inverted.  The  variations  are,  therefore,  dependent  upon  the  state  of 
activity.  With  respect  to  the  state  of  activity  or  of  rest  of  the  individual, 
the  temperature  of  persons  active  during  the  day  appears  in  general 
higher  and  during  the  night  in  general  lower  than  in  a  person  at  rest. 

The  peripheral  portions  of  the  body  also  exhibit  more  or  less  regular  variations 
in  temperature.  In  the  palm  of  the  hand  the  course  is  somewhat  as  follows: 
After  a  relatively  high  temperature  during  the  night  a  rapid  fall  sets  in  in  the 
morning  at  six  o'clock,  which  reaches  its  lowest  between  9  and  10  o'clock. 
Then  there  follows  a  slow  ascent,  which  reaches  its  maximum  after  the  midday 
meal.  Between  i  and  3  o'clock  the  temperature  begins  to  decline,  and  the  lowest 
level  is  reached  in  the  course  of  two  or  three  hours.  Between  6  and  8  there  is 
again  a  rise,  and  finally  a  decline  toward  morning.  A  rapid  fall  of  the  temperature 
at  the  periphery  corresponds  with  a  rise  in  the  interior  of  the  body. 


FIG.  136. — Variations  in  the  Bodily  Temperature  during  Health  within  Twenty-four  Hours.     L according 

to  v.  Liebermeister.     J  —      —  according  to  Jiirgensen. 

Certain  operations  upon  the  body  cause  variations  in  temperature. 
After  venesection  the  temperature  at  first  falls.  Then  it  rises  several 
tenths  of  a  degree  with  chilliness.  In  the  first  days  it  falls  again  to  the 
previous  level  and  even  somewhat  below  this.  Profuse  acute  hemor- 
rhage causes  a  reduction  in  temperature  of  from  0.5°  to  2°  C.,  while 
long-continued,  extensive  hemorrhage  may  cause  in  dogs  a  reduction  to 
as  low  as  31°  and  29°  C. 

Here  the  reduction  in  oxidation-processes  in  the  tissues  the  seat  of  lessened 
metabolic  activity  in  consequence  of  the  hemorrhage  and  the  enfeebled  circulation 
obviously  constitute  the  cause  of  the  reduction  in  temperature.  Analogous  condi- 
tions of  diminished  metabolism  can  be  brought  about  if  the  peripheral  extremity 
of  the  divided  vagus  is  irritated  for  about  an  hour,  so  that  the  heart-beat  becomes 
extremely  slow,  and  in  conjunction  with  it  the  entire  circulation.  Thus  Landois 
was  able  to  reduce  the  temperature  in  rabbits  several  degrees  within  a  short  time. 

After  every  transfusion  of  any  considerable  amount  of  blood,  begin- 
ning about  half  an  hour  after  the  operation,  the  temperature  rises  to  a 
marked  febrile  attack,  which  will  have  subsided  in  the  course  of  several 


394  REGULATION    OF    THE    TEMPERATURE. 

hours.     Direct  transfusion  from  an  artery  to  an  adjacent  vein  in  the 
same  animal  excites  the  same  phenomenon. 

Certain  poisons,  particularly  chloroform,  chloral  and  other  anes- 
thetics, as  well  as  alcohol;  further,  digitalis,  quinin  and  others,  cause 
reduction  in  temperature.  These  substances  appear  in  part  to  render 
the  tissues  less  suited  for  the  molecular  decomposition  necessary  for  the 
generation  of  heat.  In  the  case  of  the  anesthetics  it  is  possibly  a  con- 
dition of  the  latter  kind  within  the  structure  of  the  nerve  that  furnishes 
the  cause.  In  part,  however,  they  may  also  have  an  influence  upon 
those  processes  that  control  the  dissipation  of  heat  from  the  body. 
Other  poisons  cause  elevation  of  temperature  from  opposite  causes. 

Strychnin,  nicotin,  picrotoxin,  veratrin,  laudanin,  cause  elevation  of  the 
bodily  temperature.  The  lowest  temperature  terminating  in  recovery  observed 
was  24°  (!)  C.jn  the  rectum  of  a  profoundly  intoxicated  individual. 

Reduction  in  temperature  in  connection  with  disease  is  due  either 
to  diminished  heat-production  (reduction  in  metabolic  activity),  or  to 
increased  heat-dissipation. 

Marked  reduction  in  temperature  in  individual  instances  (between  31°  and 
27.5°  and  down  to  22°  C.  in  the  anus)  has  been  observed  particularly  in  cases  of 
paralysis,  in  one  of  which  Reinhard  found  a  rectal  temperature  of  as  low  as 
22.5°  C.  four  and  one-half  hours  before  death.  The  lowest  temperature  observed 
one  day  before  death  was  23°  C.  in  the  anus  in  a  case  of  hemorrhage  into  the 
medulla  oblongata.  Also  in  cases  of  diabetes  a  reduction  in  temperature  below 
30°  C.  has  been  observed. 

Elevation  of  temperature  is  exhibited  as  a  rule  in  connection  with 
fever,  the  highest  temperature  being  observed  by  Wunderlich  before 
death,  44.65°  C. 

REGULATION  OF  THE  TEMPERATURE. 

As  human  beings  and  other  homoiothermic  animals  are  capable  of 
maintaining  their  bodily  temperature  at  the  same  level  under  varying 
conditions,  the  body  must  possess  special  mechanisms  by  means  of  which 
the  heat-economy  is  subjected  to  constant  regulation.  The  latter  can 
obviously  make  itself  effective  in  two  directions :  either  by  control  of  the 
amount  of  molecular  transformation  through  which  potential  energy  is 
transformed  into  the  kinetic  energy  of  heat,  or  by  influencing  the  dissi- 
pation of  heat  from  the  body  in  accordance  with  the  production  or  the 
effects  of  external  agencies. 

Regulatory  Mechanisms  Governing  He  at- production. 

C.  v.  Liebermeister  estimated  the  heat-production  of  a  medium- 
sized  person  as  1800  calories  per  minute.  It  is  in  the  highest  degree 
probable  that  mechanisms  are  operative  in  the  body  upon  whose  stimula- 
tion the  amount  of  heat-producing  molecular  transformation  is  depen- 
dent. It  should  especially  be  borne  in  mind  that  this  stimulation  is  of 
reflex  origin.  Irritation  from  the  peripheral  extremities  of  the  cutane- 
ous nerves,  through  thermic  excitation,  or  of  the  nerves  of  the  intes- 
tines and  of  the  digestive  glands,  through  mechanical  or  chemical 
stimulation  during  the  process  of  digestion  or  during  inanition,  may 
be  transmitted  to  a  heat-center,  from  which  an  influence  is  exerted 
through  centrifugal  fibers  upon  the  reservoir  for  potential  energy,  for  the 
purpose  of  stimulating  either  increased  or  diminished  metabolism.  Little 
is  as  yet  known,  however,  concerning  the  nervous  apparatus  and  chan- 


VARIATIONS    IN    THE    MEAN    BODILY    TEMPERATURE.  395 

nels  necessary  for  the  maintenance  of  this  hypothesis.     Nevertheless, 
numerous  phenomena  indicate  that  such  a  view  is  not  unjustifiable. 

Investigation  has  as  yet  furnished  no  adequate  evidence  as  to  the  existence 
of  a  heat-center.  Tschetschechin  and  Naunyn,  as  well  as  Ott  and  Wood  recently, 
assume  the  existence  in  the  brain  (according  to  Ott  in  the  anterior  portion  of  the 
optic  thalamus)  of  a  center  that  is  supposed  to  exert  an  inhibitory  effect  upon 
the  combustion-processes  in  the  body  through  fibers  that  descend  through  the 
pons,  medulla  and  cord;  and  accordingly  destruction  of  this  center  or  its  con- 
ducting paths  would  cause  increased  heat-production.  Aronsohn  and  Sachs  ob- 
served transitory  rise  of  temperature,  with  increased  metabolism,  after  deep 
puncture  of  the  rabbit's  brain  several  millimeters  to  one  side  of  and  behind  the 
anterior  fontanel.  Injuries  of  the  caudate  nucleus,  optic  thalamus,  corpus  cal- 
losum,  septum  lucidum  and  trigone  also  cause  similar  phenomena.  Confirmatory 
evidence  is  given  by  Richet,  who  attributes  this  elevation  of  temperature  to  in- 
creased heat-production.  The  animals  eat  more,  yet  lose  flesh.  Repeated  cerebral 
puncture  eventually  induces  marasmus,  reduction  in  temperature,  as  low  as  26°, 
and  death.  Centers  with  an  opposite  function,  namely,  stimulating  heat-produc- 
tion, are  said  to  be  situated  in  the  caudate  nucleus,  in  the  gray  substance  of  the 
septum  lucidum  and  in  the  gray  matter  in  front  of  and  below  the  caudate 
nucleus  and  in  the  tuber  cinereum.  After  high  division  of  the  spinal  cord  heat- 
regulation,  heat-production  and  heat-dissipation  are  disturbed. 

The  regulatory  mechanisms  governing  heat-production  can  be  recog- 
nized from  the  following  phenomena : 

1.  As  a  result  of  the  moderate,  transitory  influence  of  cold  the  bodily 
temperature  rises,  while  as  a  result  of  the  like  influence  of  heat  upon  the 
external  integument  the  temperature  declines. 

2.  Heat-production  is   increased   by   reduction   of  the   surrounding 
temperature,   while  the  excretion  of  carbon  dioxid  and  the  consump- 
tion of  oxygen  are  at  the  same  time   increased.     Heat-production   is 
diminished  by  increase  of  the  surrounding  temperature.     The  produc- 
tion of  carbon  dioxid  takes  place  principally  in  the  muscles,  without 
contraction  necessarily  taking  place  at  the  same  time. 

Human  beings  generate  at  o°  C.  about  twice  as  much  heat  as  at  a  surrounding 
temperature  of  30°  C.  D.  Finkler  found  in  experiments  on  guinea-pigs  that  the 
production  of  heat  is  more  than  doubled  in  vigorous  animals  in  consequence  of 
a  reduction  in  the  surrounding  temperature  of  about  24°  C.  Thus,  during  the 
winter  the  metabolism  of  the  guinea-pig  was  increased  about  23  per  cent,  as  com- 
pared with  the  summer.  It  thus  caused  an  alteration  in  heat-production  in 
general  that  is  entirely  analogous  to  that  resulting  from  lowering  of  surround- 
ing temperature  of  shorter  duration. 

C.  Ludwig  and  Sanders-Ezn  have  observed  in  rabbits,  when  the  surrounding 
temperature  was  reduced  from  38°  C.  to  6°  or  7°,  a  rapid  increase  in  the  elimination 
of  carbon  dioxid.  Conversely,  this  was  diminished  in  animals  as  the  surrounding 
temperature  was  raised  from  between  4°  and  9°  to  from  35°  to  37°.  The  thermic 
stimulation  of  the  surrounding  temperature  must  thus  have  had  an  effect  also 
upon  the  combustion-processes.  In  accordance  with  this  fact  is  the  observation 
of  Pfliiger,  who  found  increased  consumption  of  oxygen  and  increased  elimination 
of  carbon  dioxid  in  rabbits  that  had  been  immersed  in  cold  water.  When  the 
influence  of  the  cold  was  so  profound  that  the  bodily  temperature  fell  as  low  as 
30°,  the  gaseous  interchange  also  diminished,  and  if  the  exposure  continued  until 
the  temperature  fell  to  20°  the  interchange  became  only  half  of  the  normal, 
mammals  are  placed  in  a  warm  bath  whose  temperature  exceeds  that  of  the  body 
by  2°  or  3°  the  elimination  of  carbon  dioxid  and  the  consumption  of  oxygen 
increase  in  consequence  of  a  stimulation  of  the  metabolic  processes.  The  elimina- 
tion of  urea  also  increases  from  the  same  cause. 

3.  The  application  of  cold  to  the  external  integument  causes  in  part 
involuntary  muscular  movement  (shivering),  in  part  voluntary  muscular 
movement.     As  a  result  of  both  heat  is  produced. 


396  VARIATIONS    IN    THE    MEAN    BODILY    TEMPERATURE. 

Cold  thus  stimulates  muscular  activity,  which  is  attended  with  oxidation- 
processes.  In  human  beings  muscular  activity  induces,  in  addition  to  increased 
heat-production,  also  increased  heat-dissipation.  The  latter,  however,  becomes 
less  on  conclusion  of  the  activity  than  it  had  been  before.  After  administration 
of  curare,  which  paralyzes  the  voluntary  muscles,  this  regulation  of  temperature 
falls  to  a  minimum. 

Strychnin  increases  heat-dissipation  and  heat-production,  and  the  bodily  tem- 
perature may  be  either  increased  or  diminished  in  accordance  with  the  prepon- 
derance of  production  (convulsions)  or  of  dissipation.  Cocain  increases  the  bodily 
temperature,  while  the  anesthetics  have  the  reverse  effect. 

4.  Change  in  the  surrounding  temperature  has  an  influence  upon  the 
need,  for  food.  Ingestion  of  food  increases  the  elimination  of  carbon 
dioxid,  principally  in  consequence  of  increased  activity  on  the  part  of 
the  digestive  glands.  In  winter,  as  well  as  in  cold  regions,  the  sense 
of  hunger  and  the  need  for  fats,  whose  combustion  yields  much  heat, 
are  increased. 

Regulatory  Mechanisms  Governing  Heat-dissipation. 

The  average  dissipation  of  heat  from  the  skin  of  a  human  being 
weighing  82  kilos  is  between  2,092,000  and  2,592,000  calories" in  twenty- 
four  hours — therefore,  between  1450  and  1798  calories  in  the  minute. 

i.  Elevation  of  temperature  causes  dilatation  of  the  cutaneous  ves- 
sels. The  skin  becomes  vividly  reddened,  soft,  and  full  of  fluid,  so  that 
it  serves  as  a  better  conductor  of  heat  and  is  swollen.  The  epithe- 
lium becomes  moistened  and  sweat  exudes  from  the  surface.  In  this 
way  provision  is  made  for  augmented  heat  dissipation,  evaporation  of 
the  sweat  playing  an  important  part  in  the  abstraction  of  heat. 

The  greater  the  increase  in  the  moisture  of  the  air,  the  less  becomes  the  evapora- 
tion from  the  skin.  Accordingly,  heat-dissipation  must  be  increased  by  conduc- 
tion and  radiation.  The  same  amount  of  heat  that  is  capable  of  transforming 
i  gram  of  water  at  a  temperature  of  100°  C.  into  steam  is  equal  to  that  which 
will  raise  the  temperature  of  10  grams  from  o°  to  53.67°  C.  The  sweat  secreted 
is  of  the  same  temperature  as  the  body;  if  it  be  completely  converted  into  vapor 
it  will  require  first  sufficient  heat  to  raise  it  to  the  boiling-point  and  then  addi- 
tionally the  amount  of  heat  that  will  convert  it  from  this  point  into  steam.  For 
purposes  of  more  precise  determination  there  would  be  required  a  knowledge  of 
the  heat-capacity  and  of  the  boiling-point  of  the  sweat. 

The  action  of  cold  is  to  cause  contraction  of  the  cutaneous  vessels. 
The  skin  becomes  pale,  less  soft,  deficient  in  fluid  and  collapsed.  The 
epithelium  becomes  dry  and  permits  the  escape  of  no  fluid  for  evapora- 
tion. In  this  way  dissipation  of  heat  through  the  skin  is  diminished. 
Through  the  contraction  of  the  muscles  of  the  skin  and  of  the  cutaneous 
vessels,  with  the  displacement  of  well-conducting  fluid  and  blood  from 
the  skin  and  the  subcutaneous  connective  tissues,  loss  of  heat  from  the 
periphery  is  diminished  and  heat-conduction  transversely  through  the 
tissues  is  rendered  difficult.  The  cooling  of  the  body  is  lessened  through 
the  marked  interference  with  the  flow  of  blood  through  the  skin,  in  the 
same  way  as  is  the  case  with  a  cooling  apparatus  made  of  convoluted 
tubing  if  the  current  passing  through  it  is  greatly  lessened.  If,  however, 
the  cutaneous  vessels  undergo  dilatation,  the.  temperature  of  the  surface 
of  the  body  rises,  and  the  difference  in  temperature  between  it  and  the 
surrounding  cooler  medium  is  increased,  and  thus  the  loss  of  heat  is  aug- 
mented. Tomsa  has  shown  that  anatomically  the  arrangement  of 
the  fibrillation  of  the  skin  is  such  that  every  stretching  of  the  fibers 
effected  by  the  muscles  of  the  skin  gives  rise  to  a  reduction  in  the  thick- 
ness of  the  skin,  as  a  result  of  which  an  influence  is  exerted  principally 


VARIATIONS    OF    THE    MEAN    BODILY    TEMPERATURE.  397 

upon  the  readily  displaceable  blood  present.  When  the  author,  in  con- 
junction with  Hauschild,  ligated  in  dogs  either  the  arteries  alone  or  at 
the  same  time  the  axillary  and  crural  arteries  and  veins,  the  carotids 
and  the  jugular  veins,  the  temperature  of  the  interior  of  the  body  rose 
several  tenths  of  a  degree  within  a  short  time.  Chlorotic  and  anemic 
individuals,  with  pale,  bloodless  skin,  at  times  exhibit,  for  the  same  reason 
of  failing  circulation  through  the  skin,  elevation  of  the  bodily  temperature. 

By  means  of  systematically  employed  stimuli,  which,  like  cold  baths  and  cold 
sponging,  cause  contraction  of  the  muscles  and  vessels  of  the  skin,  the  latter  may 
be  so  invigorated  and  be  maintained  in  such  a  state  of  irritability  as  to  oppose 
vigorously  loss  of  heat  when  the  body  or  individual  parts  thereof  are  threatened 
with  sudden  abstraction  of  heat.  Thus,  cold  spongings  and  baths  constitute  in  a 
measure  gymnastics  for  the  muscles  of  the  skin,  which  under  the  conditions  indi- 
cated are  capable  of  protecting  the  body  against  cold. 

2.  Elevation  of  temperature  accelerates  the  heart-beat,  while  reduc- 
tion of  temperature  diminishes  the  number  of  contractions  of  the  heart. 
Through  the  action  of  the  heart  the  blood  that  is  relatively  the  warmest 
is  pumped  from  the  interior  of  the  body  to  the  surface  of  the  skin ;   and 
in  this  way  it  may^ readily  give  off  heat  upon  the  extensive  surface.     The 
oftener  the  same  amount  of  blood  courses  through  the  skin,  the  more 
will  be  the  amount  of  heat  given  off,  and  the  reverse.     Therefore,  the 
frequency  of  the  heart-beat  is  in  direct  relation  to  the  rapidity  with 
which  cooling  takes   place.      Thus,   the    pulse   has   been  observed   to 
rise  to  more  than  160  per  minute  in  air  of  an  excessively  high  tem- 
perature— above  ioo°C.     This  is  true  not  alone  of  the  range  of  normal 
conditions,  but  also  of  the  pathological  variations  in  temperature  during 
the  febrile  state.     C.  v.  Liebermeister  records  the  following  figures  for 
the  pulse  and  the  temperature  respectively  in  adults  : 

Pulse — in  the  minute:   78.6,  91.2,  99.8,  108.5,  IIO«  T37-5- 

Temperature  in  °C.:      37°,    38°,    39°,    40°,     41°,  42°. 

If  the  number  of  heart -beats  is  permanently  diminished  it  might  be  anticipated 
that  elevation  of  temperature  would  occur.  When  the  author,  in  conjunction  with 
Ammon,  caused  reduction  for  about  one  and  one-half  hours  in  the  number  of  heart- 
beats by  irritation  of  the  peripheral  extremity  of  the  vagus  in  rabbits,  the  tem- 
perature in  the  rectum  fell  on  the  average  from  39°  to  34-5°  C.  The  enfeebled 
circulation  diminishes  also  metabolism  and  oxidation  in  the  body;  in  fact,  this 
diminution  must  therefore  even  over-compensate  for  the  accumulation  of  heat 
resulting  from  the  diminished  circulation. 

3.  Elevation  of  temperature  increases  the  number  of  respirations,  so 
that  a  much  larger  amount  of  air  passes  through  the  lungs  in  a  given 
time  and  in  them  is  raised  almost  to  the  temperature  of  the  body.     In 
addition  a  certain  amount  of  water  undergoes  evaporation  in  the  expired 
air  with  every  respiration,  and  in  this  way  heat  is  taken  up.     Therefore, 
it  is  to  be  borne  in  mind  that  vigorous  respiratory  movement  materially 
sustains  the  circulation,  so  that  the  respiration  operates  indirectly  in 
the  manner  outlined  in  2 .     Forced  respiratory  movement  exerts  a  cooling 
effect  even  if  air  heated  to  a  temperature  of  54°  C.  and  saturated  with 
watery  vapor  is  inhaled. 

4.  Nature  provides  many  animals  with  furs  during  the  winter  and 
with  lighter  covering  in  the  summer.     Many  animals  living  in  air  and 
water  of  a  low  temperature  are  protected  against  excessive  heat-dissipa- 
tion by  heavy  layers  of  fat.     In  the  same  manner  man  provides  for  a 
more  uniform  dissipation  of  heat  on  the  part  of  the  skin  by  means  of 
a  difference  in  clothing  for  winter  and  summer.     The  attitude  of  the  body 


398  CLOTHING. 

also  is  not  without  influence  upon  the  temperature.  Thus,  a  cowering 
position  and  drawing  together  of  the  head  and  the  extremities  help  to 
retain  heat,  while  spreading  of  the  extremities,  erection  of  the  hair, 
ruffling  of  feathers,  permit  the  escape  of  a  greater  amount  of  heat. 
Landois  found  that  in  rabbits  suspended  in  air  with  their  extremities 
spread  out  the  rectal  temperature  declined  from  39°  C.  to  37°  C.  in 
the  course  of  three  hours.  Exposure  in  heated  or  cooled  rooms,  ingestion 
of  hot  or  cold  food  and  drink,  hot  or  cold  baths,  exposure  to  a  quiet 
atmosphere  or  to  air  in  active  motion  (fanning)  are  measures  employed 
by  man  for  regulating  the  temperature  at  will. 

In  the  cooling  of  the  body  from  its  surface,  radiation,  conduction  (also  through 
the  air)  and  convection  (as  the  layer  of  air  in  contact  with  the  body  is  constantly 
being  displaced  by  the  heat)  take  part  in  addition  to  evaporation.  The  radiating 
power  of  the  skin  has  been  carefully  studied  by  Eichhorst  and  Masje.  It  is  in- 
creased after  irritation  and  friction  of  the  skin,  after  muscular  effort,  and  in  still 
greater  degree — up  to  three  or  four  times  the  initial  amount — through  the  action 
of  cold  air  or  after  a  cold  bath.  After  marked  abstraction  of  heat  radiation  be- 
comes small,  while  it  is  increased  during  the  febrile  process  and  after  the  employ- 
ment of  antipyretics.  The  amount  of  heat  radiated  by  a  naked  man  from  each 
square  centimeter  of  superficies  is  equal  to  o.ooi  calory  in  the  second.  This  would 
make  for  the  entire  body,  weighing  82  kilos,  approximately  1,782,000  calories  in 
twenty-four  hours.  Stewart  found  the  loss  of  heat  through  radiation  for  a  clothed 
man,  weighing  70  kilos,  700,000  calories;  for  a  man,  weighing  82  kilos,  820,000 
calories.  In  a  clothed  person  the  radiation,  according  to  Rubner,  with  a  weight 
of  82  kilos  and  a  superficies  of  22,430  square  centimeters,  is  1,181,000  calories. 

In  estimating  the  influence  of  climate  upon  the  regulation  of  heat  of  the  body 
chief  importance  is  to  be  attached  to  the  rapidity  of  evaporation,  which  is  pro- 
portional to  the  square  root  of  the  velocity  of  the  wind. 

CLOTHING. 

The  effect  of  the  clothing  is  yet  to  be  taken  into  consideration.  A  warm 
dress  is  an  equivalent  for  food,  for  as  the  dress  is  intended  to  preserve  the  heat 
of  the  body  generated  by  the  latter  from  the  combustion  of  food,  it  may  be  stated 
that  the  body  has  a  direct  income  through  the  food,  while  by  means  of  clothing 
it  protects  itself  against  unnecessary  expenditure.  The  clothing  thus  at  room- 
temperature  saves  20  per  cent.  From  this  its  importance  in  the  heat-economy  is 
obvious.  Summer-clothing  weighs  from  3  to  4  kilos  and  winter-clothing  from  6 
to  7  kilos.  The  radiation  of  heat  from  the  body  through  a  full  suit  of  clothing 
is  only  about  one-third  of  that  from  the  naked  skin.  At  a  low  temperature  this  re- 
duction in  heat-radiation  is  greater  than  when  the  surrounding  temperature  is  high. 

With  respect  to  the  usefulness  of  clothing  the  following  considerations  are  to 
be  borne  in  mind:  (i)  Its  conductivity.  Those  materials  that  are  the  poorest  con- 
ductors of  heat  keep  the  body  the  warmest.  The  following  is  a  list  of  conductors 
arranged  successively  from  the  poorest  to  the  best:  Hare-skin,  down,  beaver-skin, 
raw  silk,  taffeta,  sheep's  wool,  cotton,  flax,  twisted  silk.  (2)  The  radiating  power. 
Rough  substances  radiate  heat  more  readily  than  smooth  substances.  The  radi- 
ating power  is,  however,  equal  for  different  colors.  (3)  The  relation  to  the  sun's 
rays.  Dark  materials  absorb  more  heat  from  the  sun  than  light  materials.  (4) 
The  degree  in  which  materials  are  hygroscopic  is  of  great  importance,  that  is 
whether  they  are  capable  of  taking  up  much  moisture  from  the  skin,  and  at  the 
same  time  yield  this  up  gradually  by  evaporation,  or  the  reverse.  Wool  of  the 
same  weight  takes  up  twice  as  much  water  as  linen,  but  the  latter  permits  its 
more  rapid  evaporation.  Wool  upon  the  skin,  therefore,  less  readily  permits 
accumulation  of  moisture  and  also  the  development  of  cold  through  rapid  evapora- 
tion, and  therefore  affords  protection  against  catching  cold.  (5)  The  degree  of 
permeability  for  air — ventilation — is  of  importance  with  respect  to  clothing,  but  it 
bears  no  relation  to  heat-conduction.  Thus  the  application  of  a  coat  of  varnish 
to  materials  increases  the  heat-conduction,  but  destroys  the  ventilation.  The  perme- 
ability depends — apart  from  the  thickness  of  the  material — upon  the  specific  gravity 
and  the  character  of  the  thread.  The  following  is  a  list  of  substances  beginning 
with  the  more  permeable  and  passing  to  the  less  permeable:  Flannel,  buckskin, 


HEAT-BALANCE. 


399 


linen,  silk,  leather,  oil-cloth.  (6)  Clothing  that  is  in  direct  contact  with  the  skin 
naturally  also  takes  up  the  excrementitious  products  of  the  skin,  linen  and  cotton 
in  greatest  amount,  and  wool  least  of  all  transmitting  the  waste  matters  to  the 
overlying  clothing.  The  drawers  take  up  the  least  material,  the  shirt  twice  as 
much,  the  socks  eight  times  as  much. 

The  temperature  of  the  surface  of  the  body  beneath  winter-clothing  is  on  the 
average  18°  C.  and  beneath  summer-clothing  20°  C.  Heat  is  given  off  principally 
by  conduction  when  clothing  is  worn.  Clothing  appears  comfortable  when  the 
temperature  of  its  surface  is  5°  or  6°  C.  higher  than  that  of  the  air. 

HEAT-BALANCE. 

As  the  temperature  of  the  body  is  capable  of  remaining  constant 
within  narrow  limits,  it  is  obvious  that  the  amount  of  heat  taken  up 
must  be  equivalent  to  the  amount  of  heat  given  off,  that  is  exactly  so 
much  potential  energy  must  within  a  given  time  be  converted  into  heat 
as  heat  is  given  off  from  the  body.  Attempts  have  been  made  from 
different  points  of  view  to  set  up  heat-balances  which  while  partly  at 
least  without  a  reliable  foundation,  are  nevertheless  of  great  inter- 
est in  the  elucidation  of  the  heat-economy  of  the  animal  organism. 
An  adult  produces  on  an  average  enough  heat  to  raise  the  temperature 
of  his  body  almost  i°  C.  in  half  an  hour.  If  no  heat  were  given  off,  the 
body  would  in  a  short  time  become  enormously  heated — in  thirty-six 
hours  to  the  boiling-point — providing  the  production  of  heat  continued 
uninterruptedly . 

HEAT-BALANCE  ACCORDING  TO  H.  v.  HELMHOLTZ. 

Hermann  von  Helmholtz  was  the  first,  in  1846,  to  determine  numerically  the 
amount  of  heat  produced  by  man. 

1.  Heat-income. — (a)    A  healthy  adult,  weighing  82  kilos, 
expires  in  twenty-four  hours  878.4  grams  of  carbon   dioxid. 
The  combustion    of    the    carbon  thereof    into  carbon    dioxid 

generates 1,730,760  calories 

(6)  The  man,  however,  takes  up  more  oxygen  than  is 
present  in  the  carbon  dioxid  given  off.  This  excess  is  em- 
ployed for  purposes  of  oxidation,  particularly  for  the  forma- 
tion of  water  through  the  combustion  of  hydrogen.  In  conse- 
quence of  the  excess  of  oxygen  thus  taken  up  13,615  grams 
of  hydrogen  can  be  additionally  burned  up,  yielding 318,600 

2,049,360  calories 

(c)  About  25  per  cent,  of   heat   must   be    derived  from 
other   sources   than   combustion-processes,   so   that  in  round 

figures  there  will  be . 2,732,000  calories 

This  amount  would  in  fact  suffice  to  raise  the  temperature  of  a  human  body 
weighing  from  88  to  90  kilos  from  an  average  temperature  of  10°,  28°  or  29°C., 
thus  to  38°  or  39°  C.,  that  is  the  normal  temperature. 

2.  Heat-expenditure. — According  to  v.  Helmholtz  the  following  debits  must  be 
set  against  the  heat-income : 

(a)  For  the  heating  of  food  and  drink, 
which  have  an  average  temperature  of  1 2 °  C . .  .  7  °  - J  5  7  calories  =  2 . 6  per  cent . 

(6)  For  heating  the  inspired  air  =  16,400 
grams,  assuming  the  temperature  of  the  air  to 
be  20°  C r 70,032  =2.6  per  cent. 

[If  the  temperature  of  the  air  were  o°  the 
number  of  calories  would  be  140,064  =  5.2 
per  cent.] 

(c}  656  grams  of  water  evaporated  through 
the  lungs 397-536  =  14.7  per  cent. 

(d)  The  remainder  through  radiation  and 

evaporation  from  the  external  integument  .  .  .   from  77.5  per  cent,  to  80. i  percent. 


4OO  VARIATIONS    IN    HEAT-PRODUCTION. 

ESTIMATION    OF    HEAT-INCOME    ACCORDING    TO    FRANKLAND'S 

METHOD. 

Frankland  in  1866  burned  food  directly  in  the  calorimeter  (Fig.  133)  and 
obtained  the  following  results : 

i  gram  of  proteids  yielded 4998  heat-units  1  These     figures     may    be 

grape-sugar  yielded    3277  r      compared    with    Rub- 
beef-fat  yielded    9069                       J      ner's  results,  p.  379. 

The  proteids  are  decomposed  only  to  the  stage  of  urea ;  therefore  the  heat  yielded 
by  the  combustion  of  the  latter  is  to  be  deducted  from  4998,  thus  leaving  4263 
heat -units  for  i  gram  of  proteids.  If  the  number  of  grams  of  the  individual  foods 
taken  by  man  has  been  determined  by  weight  the  number  of  heat-units  taken  up 
can  be  readily  estimated. 

When  the  amount  of  food  is  sufficient  the  production  of  heat,  under  otherwise 
like  conditions,  is  always  the  same.  If  the  amount  of  food  is  insufficient,  the 
amount  of  heat  produced  is  but  little  diminished,  as  the  body  must  then  consume 
some  of  its  own  tissues.  This  is  naturally  the  case  in  the  state  of  hunger  especially. 
The  character  of  the  food,  providing  it  is  sufficient  in  other  respects,  is  of  subor- 
dinate importance. 

VARIATIONS  IN  HEAT-PRODUCTION. 

According  to  v.  Helmholtz  the  average  heat-production  in  a  healthy  adult, 
weighing  82  kilos,  in  twenty-four  hours  is  2,732,000  calories. 

Influence  of  the  Superficies  of  the  Body. — Rubner  found  that  heat- 
production  is  dependent  not  upon  the  weight  of  the  body,  but  upon 
its  size  and  the  related  superficies.  Small,  and  also  young,  animals 
have  a  relatively  larger  superficies  than  larger,  and  also  older,  animals. 
As,  however,  the  dissipation  of  heat  takes  place  principally  from  the 
external  surface,  accordingly  greater  heat-production  will  have  to  take 
place  in  animals  with  a  greater  superficies — heat-dissipating  surface. 
Thus  a  relatively  greater  consumption  of  oxygen  was  accordingly  ob- 
served in  smaller  animals.  Rubner's  investigations  have  shown  that  for 
dogs  of  various  sizes  the  heat-production  for  each  square  meter  of  body- 
surface  uniformly  equaled  1,143,000  calories.  If  the  body- weight  was 
compared  with  the  body-surface  in  different  animals,  he  found  that  for 
every  kilogram  of  weight  there  was  in  the  rat  1650,  in  the  rabbit  946, 
in  man  287  square  centimeters  of  surface. 

According  to  J.  Rosenthal  the  production  of  heat  is  to  be  estimated  in  the 
following  manner:  If  n  represents  the  amount  of  heat  produced  in  an  animal 
in  one  hour,  g  the  body- weight,  and  A  a  factor  that  remains  nearly  constant  in  the 
same  species  and  under  like  nutritive  conditions  (for  the  body  of  the  child,  11.97  > 
for  that  of  the  adult,  12.31;  for  that  of  the  dog'  49;  for  that  of  the  rabbit,  33), 

then  n  =  A^/g2 . 

Age  and  Sex. — In  the  earliest  period  of  life,  as  well  as  in  old  age,  the  production 
of  heat  is  less  than  at  mature  age.  It  is  likewise  so  in  women  as  compared 
with  men. 

Daily  Variation. — The  production  of  heat  exhibits  a  course  similar  to  that 
of  the  bodily  temperature  at  different  hours  of  the  day. 

Bodily  Functions. — During  waking,  with  physical  and  mental  exertion,  as 
well  as  during  digestion  (on  account  of  the  greater  glandular  activity) ,  the  pro- 
duction of  heat  is  greater  than  under  the  opposite  conditions. 

RELATION  OF  HEAT-PRODUCTION  TO  THE  WORK  PERFORMED 

BY  THE  BODY. 

The  potential  energy  supplied  to  the  body  can  be  transformed  by  the 
latter  into  heat  and  into  kinetic  energy.  In  the  resting  body  almost  the 


RELATION    OF    HEAT-PRODUCTION    TO    BODY   WORK.  401 

entire  amount  of  potential  energy  is  transformed  solely  into  heat,  for 
the  work  of  the  muscles  of  the  circulatory,  digestive,  and  respiratory 
organs  is  transformed  within  the  body  into  heat,  and  therefore  is  not 
work  transmitted  outward.  A  man  at  work,  however,  in  addition  to  the 
production  of  heat,  transforms  potential  energy  into  work.  An  equiva- 
lent measurement  will  serve  for  the  comparison  of  both  activities, 
namely,  i  heat-unit,  that  is,  the  energy  that  will  raise  the  temperature  of 
i  gram  of  water  i°  C.,  which  equals  425.5  grammeters. 

The  following  illustration  will  serve,  first  of  all,  to  make  clear  the  relation 
between  heat-production  and  work.  If  a  small  steam-engine,  in  which  a  given 
amount  of  coal  is  burned,  is  placed  within  the  inner  chamber  of  a  capacious  calor- 
imeter, heat  alone  will  be  produced  from  the  coal  so  long  as  the  engine  is  not 
brought  into  working  activity.  The  water  in  the  calorimeter  will  indicate  exactly 
through  the  elevation  of  its  temperature  the  number  of  heat-units  furnished  by 
the  burning  coal.  If  this  has  been  determined,  the  same  amount  of  coal  is  burned 
in  the  steam-engine  in  a  second  experiment,  but  at  the  same  time  by  means  of  a 
suitable  device  outside  of  the  calorimeter  work  is  performed  by  the  engine,  such 
as  the  raising  of  a  weight.  This  work  must  naturally  be  furnished  by  the  potential 
energy  of  the  fuel  and  be  transformed.  If  now  the  elevation  of  temperature  at 
the  end  of  the  experiment  is  noted  it  will  be  found  that  a  smaller  number  of  heat- 
units  have  been  transmitted  to  the  water  than  in  the  first  experiment,  in  which 
the  engine  was  heated,  but  performed  no  work.  Comparative  experiments  of  this 
kind  have  demonstrated  beyond  doubt  that  in  the  second  experiment  the  useful 
working  effect  is  almost  proportional  to  the  heat-deficit  observed. 

If  the  processes  in  the  organism  be  compared  with  this  illustration 
it  will  be  seen  that  the  resting  human  being  generates  between  2  J  and  2-J 
million  calories  from  the  potential  energy  contained  in  the  ingested 
food,  while  the  amount  of  work  performed  by  a  laborer  is  estimated  at 
300,000  kilogram -meters.  If  the  organism  were  exactly  comparable 
with  the  engine,  just  so  much  less  heat  would  have  to  be  formed  within 
the  body  as  corresponds  to  the  amount  of  work  done.  As  a  matter  of 
fact,  the  organism  naturally  can  transform  only  a  lesser  amount  of  heat 
from  the  same  measure  of  potential  energy  when  work  is  performed. 
One  point,  however,  should  be  taken  into  consideration  in  which  the 
laborer  differs  from  the  working  engine.  The  laborer  consumes  in  the 
same  time  a  far  larger  amount  of  potential  energy  than  the  resting  indi- 
vidual. A  greater  amount  of  combustion  takes  place  in  his  body,  and 
it  therefore  comes  about  that  the  loss  through  the  increased  combustion 
is  not  alone  made  good,  but  is  even  over-compensated.  The  laborer  is, 
by  reason  of  his  greater  muscular  activity,  warmer  than  the  resting 
individual.  The  following  may  serve  as  an  example  of  the  relation  in- 
dicated: Him  in  1858  took  up  at  rest  in  the  calorimeter-chamber  30 
grams  of  oxygen  in  an  hour,  and  produced  155,000  calories.  When 
subsequently  he  undertook  in  the  chamber  work  transmitted  outward, 
to  the  amount  of  27,450  kilogram-meters,  he  consumed  132  grams  of 
oxygen  and  furnished  only  251,000  calories. 

In  estimating  the  amount  of  work  done  only  that  transmitted  outward  as  heat- 
equivalent  is  to  be  considered,  as,  for  instance,  the  lifting  of  a  load,  the  throwing 
of  weights,  the  displacement  of  masses.  Also  the  lifting  up  of  the  body  is  to 
be  included  here.  In  ordinary  walking  the  overcoming  of  the  resistance  of  the 
air  and  the  activity  of  the  muscles  must  be  taken  into  consideration.  In  descending 
from  a  height  an  increase  in  heat  of  the  body  is  not  to  be  looked  for,  for  muscular 
activity  is  required  to  prevent  the  body  from  falling  down  and  from  collapsing, 
and  to  avoid  a  too  precipitate  descent. 
26 


402  ACCOMMODATION    TO    VARIATIONS    IN    TEMPERATURE. 

The  organism  is  superior  to  the  engine  in  the  fact  that  more  work  in 
proportion  to  heat  is  transformed  from  the  same  measure  of  potential 
energy.  While  the  best  gas-engine  is  capable  of  converting  10.82  per 
cent,  of  the  potential  energy  of  illuminating  gas  into  work  and  the 
remainder  into  heat,  the  human  being  is  capable  of  furnishing  35  per 
cent,  of  work — in  making  ascents  and  in  doing  work  of  other  character 
only  25.4  per  cent. — from  the  chemical  transformation  in  its  muscular 
tissue,  Pfluger's  experimental  dog  as  much  as  48.7  per  cent.,  and  an 
excised  bit  of  frog's  muscle  even  50  per  cent.  Work  alone,  without 
simultaneous  production  of  heat,  can  never  be  transformed  from  chem- 
ical potential  energy  in  an  inanimate  or  animate  motor. 

ACCOMMODATION  TO  VARIATIONS  IN  TEMPERATURE. 

All  bodies  possessing  great  heat-conductivity,  when  brought  in  contact 
with  the  skin,  appear  much  cooler  or  warmer  respectively  than  poor 
conductors.  The  reason  for  this  lies  in  the  fact  that  they  abstract  more 
heat  from  the  body  or  supply  more  heat  to  the  body  than  the  latter. 
Thus  the  water  of  a  cold  bath  will  always  feel  colder  than  the  air  at 
the  same  temperature,  because  it  is  a  better  conductor  of  heat.  In  the 
temperate  zone,  for  example: 

AIR  WATER 

At  1 8°  C.  feels  moderately  warm,  Up  to  18°  C.  appears  cold, 

From  25°  to  28°  C.,  hot,  From  18°  to  29°  C.,  cool, 

Above  28°  C.,  extremely  hot.  From  34°  to  35°  C.,  indifferent, 

Above  35.5°  C.,  warm, 
At  37.5°  C.  and  above,  hot. 

So  long  as  the  temperature  of  the  body  is  higher  than  that  of  the 
surrounding  medium,  the  body  gives  off  heat,  and  in  greater  amount 
and  more  rapidly  the  better  the  conductivity  of  the  surrounding  medium. 
As  soon,  however,  as  the  surrounding  temperature  becomes  higher  than 
that  of  the  body,  the  latter  takes  up  heat  and  in  greater  amount  and 
more  rapidly  as  the  medium  is  a  better  conductor.  Therefore,  hot 
water  appears  to  be  of  a  higher  temperature  than  air  at  the  same  tem- 
perature. 

A  human  being  may  remain  for  eight  minutes  in  a  bath  at  a  tempera- 
ture of  4  5 . 5  °  C . ,  but  not  without  risk  to  life .  The  hands  tolerate  immersion 
in  water  of  a  temperature  of  5  o .  5  °  C . ,  but  not  of  a  temperature  of5i.65°C. 
At  a  temperature  of  60°  C.  intense  pain  is  felt  in  the  integument.  On 
the  other  hand,  a  human  being  may  tolerate  air  at  a  temperature  of 
127°  C.  for  eight  minutes.  Girls  have  remained  for  as  long  as  twenty 
minutes  in  air  at  a  temperature  of  132°  C.  Under  these  circumstances 
the  bodily  temperature  rises  but  little,  namely,  to  38.7°  or  38.9°  C. 
This  depends  upon  the  fact  that  the  air,  acting  as  a  poorer  conductor 
of  heat,  does  not  convey  so  much  heat  to  the  body  as  does  water.  Fur- 
ther, and  this  is  the  most  important  fact,  the  body  exposed  to  hot  air 
is  capable  of  losing  heat  at  its  surface  through  abundant  sweating 
and  evaporation,  and  to  this  end  the  increased  evaporation  of  water  due 
to  the  increased  activity  of  the  lungs  contributes.  The  enormous  accel- 
eration of  the  heart-beat — up  to  above  160 — causes  constantly  renewed 
volumes  of  blood  to  be  sent  to  the  skin  through  its  greatly  dilated  blood- 
vessels, for  the  secretion  of  sweat  and  evaporation.  In  the  degree  in 


ACCUMULATION  OF  HEAT  IN  THE  BODY.  403 

which  these  diminish  the  body  becomes  less  capable  of  withstanding 
the  surrounding  heat,  and  thus  is  readily  explained  the  fact  that  the 
human  being  is  by  far  less  able  to  withstand  air  rich  in  watery  vapor 
than  dry  air  at  the  same  temperature,  as  heat  must,  under  such  circum- 
stances, accumulate  within  the  body.  Thus  in  the  Russian  steam -bath 
at  a  temperature  of  from  53°  to  60°  C.  the  normal  rectal  temperature 
rises  to  between  40.7°  and  41.6°  C.  A  human  being  is  just  able  to  work 
in  an  atmosphere  at  a  temperature  of  31°  C.  almost  completely  saturated 
with  watery  vapor. 

In  water  at  the  temperature  of  the  body  the  normal  bodily  temperature  rises 
i  C.  in  one  hour;  about  2°  C.  in  one  and  one-half  hours  .  Gradual  elevation  of  the 
temperature  of  the  water  from  38.6°  to  40.2°  C.  caused  an  increase  in  the  axil- 
lary temperature  to  39°  C.  within  fifteen  minutes. 

ACCUMULATION  OF  HEAT  IN  THE  BODY. 

As  under  normal  conditions  the  constancy  of  the  bodily  temperature 
is  the  result  of  a  constant  relation  between  heat-production  and  heat- 
dissipation  it  is  obvious  that  heat  must  be  stored  up  in  the  body  when 
heat-dissipation  is  lessened.  The  chief  organ  regulating  heat-dissipation 
is  the  external  integument.  Contraction  of  the  skin  and  its  vessels 
diminishes  heat-dissipation,  while  relaxation  with  dilatation  of  the  ves- 
sels increases  heat-dissipation.  Accumulation  of  heat  may,  accordingly, 
be  effected : 

(a)  By  intense  and  extensive  cutaneous  irritation,  through  which  a 
transitory  influence  is  exerted,  causing  contraction  of  the  skin  and  its 
vessels.  (6)  Also  through  other  forms  of  restriction  of  loss  of  heat 
through  the  skin,  (c)  Through  increased  activity  of  the  vasomotor 
center,  as  a  result  of  which  contraction  of  all  vessels,  and  naturally 
also  those  of  the  external  integument,  is  brought  about.  In  thi's 
way  the  elevation  of  temperature  following  transfusion  of  blood  from 
an  animal  of  the  same  species  is  to  be  explained — direct  transfusion 
of  arterial  blood  from  the  crural  artery  into  the  adjacent  vein  in  the 
same  animal  will  suffice,  as  Landois  was  able  to  confirm  by  experiments 
on  the  carotid  and  the  external  jugular  vein — as  well  as  that  following 
venesection  after  a  preceding  decline  in  temperature.  In  both  events 
abnormal  blood-distribution  takes  place.  In  the  first  the  venous  system 
is  abnormally  overloaded,  in  the  second  abnormally  empty.  For  the 
restoration  of  the  normal  distribution  vigorous  activity  on  the  part  of 
the  musculature  of  the  vessels  is  necessary,  excited  through  the  vaso- 
motor center.  The  marked  contraction  of  the  cutaneous  vessels  hereby 
brought  about  exerts  an  inhibitory  influence  on  heat-dissipation  and 
heat-accumulation  thus  takes  place.  The  elevation  of  temperature 
observed  after  sudden  abstraction  of  water  from  the  body  must  appa- 
rently be  explained  in  the  same  way.  The  inspissated  blood  requires 
less  vascular  space  and  the  contracted  vessels  permit  the  escape  of  little 
heat  into  the  skin,  (d)  If  the  circulation  through  the  cutaneous  vessels 
in  considerable  areas  is  retarded  by  mechanical  means,  as  by  occlusion 
of  small  vessels  by  viscous  masses  of  stroma  or  coagula,  which  form 
after  transfusion  of  blood  from  an  animal  of  a  different  species,  accumu- 
lation of  heat  takes  place  likewise  in  consequence  of  diminished  dissipa- 
tion. Perhaps  a  number  of  other  pyrogenic  agents  act  in  the  same 
manner.  In  dogs  in  which  both  carotids  and  both  axillary  and  crural 


404  FEVER. 

arteries  were  ligated  at  one  time,  with  or  without  the  related  veins, 
the  temperature  was  observed  to  rise  almost  i°  C.  within  two  hours. 

It  is  obvious  that  increased  heat-production  in  the  presence  of 
normal  heat-dissipation  must  give  rise  to  accumulation  of  heat.  In 
this  category  belongs  the  elevation  of  temperature  following  muscular 
and  mental  activity,  and  attending  digestion.  Finally,  the  elevation  of 
temperature  that  appears  several  hours  after  a  cold  bath  and  is 
brought  about  by  increased  heat-production  through  reflex  influences 
from  the  cooled  skin  is  probably  of  the  same  character. 

If  the  temperature  of  the  body  as  a  whole  is  raised  about  6°  C. 
death  results,  as  in  the  case  of  heat-stroke  or  sunstroke.  At  this  tem- 
perature molecular  decomposition  of  the  tissues  appears  to  take  place. 
With  long-continued,  though  less  marked,  elevation,  distinct  fatty  de- 
generation of  many  tissues  occurs.  If  animals  whose  temperature  is 
raised  artificially  to  42°  or  44°  C.  are  subsequently  placed  in  a  cooler 
atmosphere,  the  temperature  at  first  becomes  subnormal  (36°  C.)  and  it 
may  remain  so  for  days. 

FEVER. 

In  many  ways  related  to  the  accumulation  of  heat  largely  confined  within 
the  limits  of  physiological  phenomena  fever  occurs  as  the  most  common  patho- 
logical derangement  in  the  bodily  economy  and  to  it  some  reference  may  be  made. 
Fever  consists  essentially  in  increased  metabolism,  chiefly  in  the  muscles,  together 
with  elevation  of  temperature.  Under  these  circumstances  a  disturbance  in  the 
regulation  of  the  heat-balance  must  naturally  take  place,  for  if  provision  be  made 
that  with  the  increased  heat-production  also  increased  heat-dissipation  shall  take 
place,  there  can  then  be  no  elevation  of  temperature,  or  accumulation  of  heat. 
According  to  v.  Liebermeister  heat-regulation  is  placed  upon  a  higher  temperature- 
level  during  the  febrile  process.  As  in  the  state  of  fever  the  body  appears  to  be 
in  large  measure  incapacitated  for  mechanical  activity,  the  transformation  of  this 
larger  amount  of  decomposing  potential  energy  in  the  body  almost  wholly  into 
heat,  and  the  failure  to  utilize  this  for  mechanical  activity,  must  moreover  be 
especially  emphasized  as  characteristic.  Malarial  intermittent  fever  may  be 
considered  as  the  prototype  of  fever.  It  is  attended  with  severe  paroxysms  of 
fever  lasting  several  hours  in  alternation  with  wholly  afebrile  periods,  so  that  its 
symptoms  may  be  readily  analyzed.  Among  the  individual  phenomena  of  fever 
there  are  encountered: 

1.  Elevation  of  bodily  temperature  (to  38°  or  39°  C.  constitutes  mild,  and  from 
39°  to  41°  C.  and  above,  severe  fever) .     Not  only  the  febrile  patient  with  a  burning, 
reddened  skin  (calor  mordax),  but  also  the  shivering  patient  in  a  chill  with  an 
apparently  cold  skin  may  exhibit  elevation  of  temperature.     The  reddened  skin, 
however,  is  a  good  conductor,  the  pale  skin  a  much  poorer  conductor  of  heat. 
Therefore,  the  former  appears  the  warmer  to  the  touch. 

2.  Increased  heat-production,  which  had  already  been  assumed  by  Lavoisier  and 
Crawford,  can  be  recognized  indubitably  by  calorimetric  measurement.     This  can 
be  attributed  only  in  smallest  part  to  transformation  of  the  increased  circulatory 
activity  into  heat,  but  in  largest  part  it  is  dependent  upon  heat  generated  in  the 
processes  of  combustion. 

3.  Increased  metabolism,  to  which  the  wasting  character  of  fever  is  due.     This 
was  known  to  Hippocrates  and  Galen  and  was  thus  described  by  v.  Barensprung  in 
1852 :   "All  so-called  fever-symptoms  indicate  that  during  the  febrile  process  tissue- 
consumption  is  abnormally  increased.     The  increased  metabolism  is  evidenced  by 
augmented    carbon-dioxid   elimination    (from  70  to  80  per  cent.)-     In     addition 
to  carbon-dioxid  elimination  there  is  increased   absorption  of   oxygen,  at  most 
20    per    cent,  in    a  patient    with    acute    fever,    while    the    respiratory  quotient 
remains  unchanged.     According  to  D.  Finkler  the  production  of  carbon  dioxid  is 
susceptible  of  greater  variation  than  the  consumption  of  oxygen.     The  state  of  the 
nutrition  is  an  index  of  the  size  of  the  respiratory  quotient.     The  increase  in 
gaseous  interchange  is  not  the  result,  but  the  cause,  of  the  increased  bodily  tem- 
perature.    The  former  takes  place  also  when  the  bodily  temperature  is  reduced  by 


FEVER. 


405 


a  cold  bath.  The  elimination  of  urea  is  increased  between  one-third  and  two- 
thirds.  In  dogs  suffering  from  septic  fever  Naunyn  observed  increased  elimina- 
tion of  urea  even  before  the  temperature  rose — prefebrile  elevation.  At  times, 
however,  the  urea  is  in  part  retained  during  the  febrile  process  and  is  eliminated 
in  large  amount  after  the  termination  of  the  febrile  attack — epicritical  elimination 
of  urea.  The  uric  acid  also  is  increased.  At  the  same  time  the  urinary  pigment 
derived  from  the  hemoglobin  may  be  increased  twenty  times  and  the  elimination 
of  calcium  be  increased  seven  times.  The  urinary  water  is  diminished  (in  typhoid 
fever)  and  is  excreted  in  greater  amount  during  convalescence.  The  fact  that  the 
combustion-processes  in  the  body  of  the  febrile  patient  are  exceptionally  increased 
if  he  be  placed  in  a  warmer  atmosphere  appears  especially  noteworthy.  During 
the  febrile  process  there  is  also  an  increase  in  oxidation-processes  under  the  influ- 
ence of  colder  surroundings,  but  the  increase  of  combustion  in  warm  surroundings 
is  much  greater  than  in  cold. 

4.  Diminished  Heat-dissipation. — That  in  some  cases  febrile  temperature  may 
actually  result  from  diminished  heat-dissipation  is  shown,  for  instance,  by  the 
sudden  attacks  of  fever  that  occur  after  catheterization  or  with  the  passage  of  a 
gall-stone  through  tire  bile-duct.     These  are  brought  about  solely  through  reflex 
irritation  of  the  vasomotor  center,  which  greatly  interferes  with  heat-dissipation 
in  consequence  of  contraction  of  the  cutaneous  vessels.     In  other  forms  of  fever 
in  man  diminished  heat-dissipation  is  only  in  part  a  causative  factor,  as  the  fol- 
lowing analysis  will  show: 

(a)  The  Stage  of  Chill,  or  the  Cold  Stage. — Here  the  loss  of  heat  through  the 
pale,  anemic  skin,  by  conduction,  radiation  and  evaporation  of  water,  is  diminished 
in  greatest  degree,  but  also  heat-production  is  from  one  and  one-half  to  two  and 
one-half  times  greater.  The  rise  of  temperature  in  the  febrile  stage,  which 
often  is  rapid  and  marked,  alone  establishes  the  fact  that  the  diminished  heat- 
dissipation  is  not  the  sole  cause  of  the  elevation  of  temperature.  (6)  In  the  hot 
stage  loss  of  heat  from  the  reddened,  hyperemic  skin  is  increased,  but  the  in- 
creased heat-production  still  preponderates,  v.  Liebermeister  estimates  that  a 
temperature-elevation  of  i°,  2  ,  3°  or  4°  C.  corresponds  with  an  increase  in  heat- 
production  of  6  per  cent.,  12  per  cent.,  18  per  cent.,  or  24  per  cent.,  respectively. 
(c)  In  the  sweating- stage  heat-dissipation  from  the  reddened,  moist  skin,  and 
evaporation,  are  most  pronounced,  being  more  than  two  or  three  times  the  normal 
loss.  Under  these  circumstances  he  at -production  is  either  increased  or  normal 
or  subnormal,  so  that  under  such  conditions  the  temperature  of  the  body  likewise 
may  become  subnormal,  down  to  36°  C.  In  case  of  fatal  collapse  the  produc- 
tion has  fallen  to  three-fourths  or  one-half  of  the  normal,  without  simultaneous 
increase  in  heat-dissipation. 

Plethysmographic  examinations  of  the  vessels  of  the  arm  in  febrile  patients 
have  shown,  in  accordance  with  the  temperature- variations  during  the  febrile 
process,  that  the  blood-vessels  begin  to  contract  before  any  elevation  of  tem- 
perature is  evident.  With  the  progress  of  the  contraction  the  temperature  then 
rises,  and  both  reach  their  maximum  at  the  same  time.  The  decline  in  tempera- 
ture is  subsequently  preceded  by  dilatation  of  the  vessels,  and  with  marked  dilata- 
tion of  the  vessels  the  temperature  again  falls  to  the  normal  level. 

5.  Deranged   Heat-regulation. — High  surrounding   temperature   may  increase 
that  of  the  febrile  patient  more  than  that  of  a  non-febrile  individual.     The  reduc- 
tion in  heat-production  that  permits  normal  animals  to  maintain  their  normal 
temperature  in  warm  surroundings  is  far  less  during  fever. 

Among  the  accessory  phenomena  of  fever  the  following  are  especially  note- 
worthy: Increase  in  the  intensity  and  number  of  the  heart-beats,  and  respiration — 
in  adults  to  40,  in  children  to  60  in  the  minute.  Both  are  compensatory  phenomena 
of  the  elevated  temperature.  There  are,  further,  diminished  digestive  activity  and 
intestinal  movement,  derangement  of  cerebral  activity,  of  the  secretions,  of  muscu- 
lar activity,  interference  with  elimination,  as  for  instance  of  water,  or  of  admin- 
istered potassium  iodid,  through  the  urine.  Febrile  pyrexia  is  by  some  con- 
sidered as  having  a  curative  influence  on  the  body,  it  being  reasoned  that  the 
body  is  cleansed  and  purified  by  the  heat  of  the  fever.  In  the  presence  of 
high  fever  molecular  degeneration  of  the  tissues  has  often  been  found. 

With  respect  to  the  blood-corpuscles  during  fever  reference  may  be  made  to 
p.  50,  i,  to  the  amount  of  carbon  dioxid  in  the  blood  on  p.  81,  to  the  vascular 
tension  on  p.  142,  to  the  saliva  on  p.  339,  to  the  digestion  on  p.  341  D.  The  utiliza- 
tion of  the  food  throughout  the  entire  tract  has  not  been  found  interfered  with  in 
marked  degree. 

In  experiments  on  animals  Krehl  and  Mathes  found  an  increase  of  10  per 


406  ARTIFICIAL    ELEVATION    OF    THE    BODILY    TEMPERATURE. 

cent,  in  heat-production  in  conjunction  with  elevation  of  temperature,  and  diminu- 
tion in  heat-dissipation.  At  the  height  of  the  fever  heat-production  was  likewise 
increased,  while  heat-dissipation  was  increased  only  when  heat-production  was 
considerable.  With  decline  of  temperature  heat-production  is  generally  diminished 
while  heat-dissipation  varies. 

According  to  Filehne,  Hildebrand,  Richter,  Stern,  and  others,  antipyretics  act 
by  restoring  heat-regulation  to  a  lower  level.  Quinin  reduces  temperature  by 
limiting  heat-production.  Toxic  doses  of  metallic  salts  act  similarly,  diminished 
carbon-dioxid  formation  being  at  the  same  time  demonstrable.  According  to 
others  the  influence  of  antipyretics  is  exerted  principally  upon  the  increase  of 
heat-dissipation  through  the  dilatation  of  the  vessels,  while  heat-production  is  but 
little  diminished — about  15  per  cent. 

The  course  of  heat-production  in  infected  cold-blooded  animals  follows  that 
in  febrile  warm-blooded  animals.  It  rises  at  the  height  of  the  disease  and  falls 
during  collapse.  Even  in  plants — injured  bulbs — Pfeffer  observed  phenomena 
analogous  to  fever. 

ARTIFICIAL   ELEVATION   OF   THE   BODILY   TEMPERATURE. 

Elevation  of  the  bodily  temperature,  in  addition  to  causing  disturb- 
ances of  the  general  condition,  influences,  first  of  all,  consciousness,  so 
that  mental  confusion,  vertigo,  insomnia  and  loss  of  consciousness  occur. 
The  functions  of  the  medulla  oblongata  and  the  spinal  cord  are  affected 
only  later. 

If  mammals  are  kept  constantly  in  air  at  a  temperature  of  40°  C. 
escape  of  heat  from  the  body  ceases,  and  accordingly  accumulation  of 
the  heat  produced  must  take  place.  At  first  the  bodily  temperature 
declines  somewhat  for  a  short  time,  but  later  a  distinct  elevation  sets  in. 
Respiration  and  pulse  are  accelerated  and  the  latter  becomes  weaker 
and  irregular.  Absorption  of  oxygen  and  elimination  of  carbon  dioxid 
diminish  in  the  course  of  from  six  to  eight  hours,  and  death  takes  place 
amid  signs  of  great  exhaustion,  convulsions,  salivation  and  loss  of  con- 
sciousness, even  when  the  temperature  of  the  body  is  not  increased  more 
than  4°  or  at  most  6°  C.  Death  is  due  not  to  the  rigidity  of  the  muscles, 
as  the  coagulation  of  their  myosin  does  not  take  place  in  mammals  at 
a  temperature  below  49°  or  50°  C.,  in  birds  at  a  temperature  of  53°  C., 
in  frogs  at  a  temperature  of  40°  C.,  but  probably  to  a  derangement  of 
the  heat-regulating  functions  of  the  nerves.  If  mammals  are  exposed 
suddenly  to  air  of  a  high  temperature,  100°  C.,  death  takes  place 
amid  similar  phenomena,  but  much  more  rapidly — in  fifteen  or 
twenty  minutes.  The  temperature  of  the  body  rises  only  4°  or  5°  C. 
under  such  circumstances.  Under  like  conditions  a  loss  of  i  gram  in 
body- weight  is  observed  in  rabbits  within  a  minute.  Birds  tolerate  the 
high  temperature  somewhat  better,  dying  only  after  the  temperature  of 
their  blood  reaches  48°  or  50°  C.  Man  also  is  capable  of  surviving  for  a 
short  time  in  air  having  a  temperature  between  100°  and  132°,  although 
the  greatest  danger  to  life  sets  in  in  the  course  of  ten  or  fifteen  minutes. 
At  the  same  time  the  skin  becomes  burning  red,  copious  sweating  takes 
place,  and  the  cutaneous  veins  are  greatly  distended  and  of  a  brighter 
red  appearance.  Pulse  and  respiration  are  greatly  accelerated.  Severe 
headache,  vertigo,  exhaustion  and  failure  of  sensor}7  activity  are  in- 
dicative of  great  danger.  At  the  same  time  the  temperature  taken  in 
the  rectum  will  have  risen  but  i°  or  2°  C.  According  to  the  observations 
of  C.  A.  Koch,  v.  Voit  and  Simanowsky,  artificial  elevation  of  tempera- 
ture in  man  and  animals  is  not  followed  by  increased  proteid  metabolism, 
whence  it  is  to  be  concluded  that  the  increased  proteid  metabolism 


EMPLOYMENT    OF    HEAT.  407 

attending  the  febrile  process  cannot  be  dependent  upon  the  elevation  of 
temperature,  but  must  be  brought  about  by  the  inadequate  nutritive 
state  of  the  tissues,  or  by  bacterial  poisons.  Fever  may  also  endanger 
life  through  elevation  of  the  bodily  temperature.  If  the  temperature  re- 
mains at  42.5°  C.  for  a  considerable  time  death  is  unavoidable.  If  the 
artificial  elevation  of  temperature  is  not  increased  to  the  point  of  causing 
death,  beginning  in  from  thirty-six  to  forty-eight  hours  fatty  infiltration 
and  degeneration  will  take  place  in  the  liver,  the  heart,  the  kidneys  and 
the  muscles. 

In  cold-blooded  animals  the  temperature  can  be  raised  from  6°  to  10°  C. 
within  a  short  time,  by  exposure  to  hot  water  as  well  as  to  hot  air.  As  the  heart 
of  the  frog  ceases  to  beat  at  a  temperature  of  40°,  and  as  the  muscles  in  the  interior 
of  the  body  begin  to  become  rigid  at  the  same  temperature,  the  maximum  tempera- 
ture for  the  continuance  of  Hfe  is  in  this  animal  considerably  lower.  Actual 
death  is  preceded  by  a  condition  of  apparent  death,  from  which  resuscitation  is 
possible.  Insects  live  in  the  desert  at  a  temperature  of  64°  R.  and  arctisca  and 
anguillulae  die  in  water  at  a  temperature  of  45°,  while  in  a  dry  medium  they  can 
be  heated  to  a  temperature  of  70°,  and  rotifers,  after  careful  desiccation,  can  be 
heated  to  125°  C.  Most  juicy  plants  die  after  exposure  for  half  an  hour  to  air 
at  a  temperature  of  52°  C.  or  to  water  at  a  temperature  of  46°  C.  Desiccated 
seeds  (oats)  may  retain  their  germinating  activity  after  exposure  for  a  considerable 
time  to  air  at  a  temperature  of  120°  C.  Lowly  organized  plants,  such  as  the 
algse,  can  live  in  warm  springs  at  temperatures  up  to  60°  C.  Some  bacteria 
tolerate  the  boiling  temperature. 

EMPLOYMENT  OF  HEAT. 

Brief  and  not  intense  heat  applied  to  the  surface  of  the  body  causes  at  first 
a  transitory,  slight  reduction  in  the  bodily  temperature,  partly  because  the  pro- 
duction of  heat  is  thereby  diminished  through  reflex  influences,  partly  because 
more  heat  is  given  off  in  consequence  of  dilatation  of  the  cutaneous  vessels  and 
expansion  of  the  skin.  Baths  at  a  temperature  above  that  of  the  blood  cause  at 
once  elevation  of  the  bodily  temperature.  Following  the  bath  a  slight  reduction 
in  temperature  takes  place  after  a  time.  Apart  from  the  changes  in  bodily  tem- 
perature brought  about  by  changes  in  circulation  and  in  respiration,  Oppenheimer 
estimates  the  elevation  of  temperature,  t,  brought  about  by  a  bath  of  400  liters 
(kilos)  at  a  temperature  of  40  C.  and  of  half  an  hour's  duration  (the  time  required 
to  warm  the  body  thoroughly),  in  a  man  weighing  75  kilos,  with  a  bodily  tem- 
perature of  37°  C.,  assuming  equal  heat-capacity  for  the  body  and  the  water  of 
the  bath : 

(400  +  75)  t  =  400.40  +  75,37;  therefore  t  =  *    !/_°  =  39.5. 

The  temperature  of  the  body,  thus,  rises  from  37°  to  39.5°  C.,  an  increase  of  2.5° 
C.,  representing  187,500  heat-units. 

General  application  of  heat  to  the  entire  body  is  indicated  when  the  bodily 
temperature  has  fallen  extremely  low,  or  when  danger  is  threatened  thereby,  as 
in  the  algid  stage  of  cholera,  and  in  the  case  of  a  premature  human  fetus.  General 
supply  of  heat  is  effected  by  means  of  warm  baths,  packs  (beds) ,  vapors,  insolation, 
and  copious  hot  drinks.  Heat  is  applied  locally  by  means  of  hot  compresses, 
partial  baths,  placing  of  a  part  in  hot  earth  or  sand,  introduction  of  a  part  into 
the  body  of  a  recently  killed  animal  (animal  bath) ,  introduction  of  injured  parts 
into  receptacles  containing  heated  air.  After  removal  of  the  heating  agent,  the 
greater  amount  of  heat-dissipation  caused  by  the  dilatation  of  the  vessels  is  to  be 
taken  into  consideration. 

POST-MORTEM  ELEVATION  OF  TEMPERATURE. 

R.  Heidenhain  found  as  a  constant  phenomenon  in  dogs  that  were  killed  that 
a  transitory  elevation  of  temperature  took  place  before  the  cooling  of  the  cadaver 
set  in,  and  this  slightly  exceeded  the  normal  temperature  of  the  body. 
Similar,  and  in  part  remarkable,  elevations  of  temperature  had  been  observed 


408  THE    INFLUENCE    OF    COLD    UPON    THE    BODY. 

previously  in  human  bodies  immediately  after  death,  particularly  when  this  re- 
sulted from  violent  muscular  spasm.  Thus,  for  instance,  Wunderlich  found  a 
temperature  of  45.375°  C.  in  a  body  fifty-seven  minutes  after  death  from  tetanus. 
The  causes  of  post-mortem  elevation  of  temperature  reside : 

1.  In   a  transitory  increase  in  heat-production   after  death,   and  especially 
through  the  conversion  of  the  viscid  contents  of  the  muscles  (myosin)  into  the 
solid  form  of  coagulation  (muscular  rigidity).     The  muscle  in  the  process  of  be- 
coming rigid  produces  heat.     All  causes  that  excite  rapid  and  intense  muscular 
rigidity — including  transitory  spasm — therefore  favor  post-mortem  elevation   of 
temperature.     Rapid  coagulation  of  the  blood  must  also  contribute  to  the  produc- 
tion of  heat. 

2.  Further,  a  series  of  chemical  processes  take  place  in  the  interior  of    the 
body  soon  after  death   that  produce  heat.     When  Valentin  placed  dead  rabbits 
in  a  chamber  at  the  temperature  of  the  body,  and  in  which  loss  of  heat  from 
the  body  was  impossible,  the  internal  temperature  of  the  body  rose  constantly. 
The  processes  that  thus  give  rise  to  the  production  of  heat  after  death  take  place 
more  rapidly  in  the  first  hour  than  in  the  second.     The  higher,  further,  the  bodily 
temperature  at  the  moment  of  death,  the  more  considerable  will  be  the  post-mortem 
generation  of  heat. 

3.  Diminished  heat-dissipation  after  death  is  a  third  cause.     As  the  circulation 
is  abolished  within  a  few  minutes,  but  little  heat  is  given  off  from  the  cutaneous 
surface  of  the  cadaver,  because  in  order  that  rapid  loss  of  heat  should  take  place 
constantly  renewed  filling  of  the  cutaneous  vessels  with  warm  blood  is  necessary. 

THE  INFLUENCE  OF  COLD  UPON  THE  BODY. 

Transitory  slight  cooling  of  the  external  integument  causes  either  no  change 
in  the  bodily  temperature  or  a  slight  elevation.  The  latter  is  dependent  upon  the 
fact  that  both  through  reflex  influences  a  more  rapid  molecular  transformation 
for  purposes  of  heat-production  is  stimulated,  as  well  as  through  contraction 
of  the  small  cutaneous  vessels  and  the  skin  itself  heat-dissipation  is  diminished. 
The  long-continued  action  of  more  intense  cold,  however,  causes  reduction  in 
temperature,  particularly  through  conduction,  in  spite  of  increased  heat-production 
at  the  same  time.  Thus,  after  cold  baths  the  temperature  may  be  34°  or  32°  C., 
and  even  as  low  as  30°  C.  Cold  baths  at  a  temperature  below  25°  cause  the 
cutaneous  temperature  to  fall  as  low  as  19°.  Within  the  interior  of  the  body 
the  temperature,  after  remaining  stationary  for  a  moment,  declines  in  proportion 
to  the  intensity  of  the  cooling.  If  the  cooling  be  continued  the  body  is  placed 
in  the  condition  of  that  of  a  cold-blooded  animal. 

As  an  after-effect  of  marked  abstraction  of  heat,  it  is  found  that  the  bodily 
temperature  remains  for  some  time  lower  than  it  had  been  before — primary  after- 
effect. It  was,  for  example,  only  22°  C.  in  the  rectum  at  the  end  of  an  hour. 
The  designation  secondary  after-effect  is  applied  to  the  elevation  of  temperature 
that  takes  place  after  the  primary  after-effect  has  been  neutralized.  This  begins — 
after  cold  baths — at  the  end  of  from  five  to  eight  hours,  and  reaches  in  the  rectum 
about  0.2°  C.  In  an  analogous  manner  Hoppe-Seyler  observed  in  the  course  of 
a  short  time  a  decline  in  the  bodily  temperature  after  the  action  of  heat  upon 
the  body. 

Catching  Cold. — If  the  body  of  a  rabbit  is  suddenly  cooled  after  exposure  to 
a  surrounding  temperature  of  35"°  C.  transitory  diarrhea  occurs  at  times,  in  addition 
to  shivering.  In  the  course  of  one  or  two  days  the  temperature  rises  1.5°  C.  and 
albuminuria  sets  in.  Kidneys,  liver,  lungs,  heart,  nerve-sheaths,  exhibit  micro- 
scopic traces  of  interstitial  inflammation;  the  dilated  arteries,  particularly  in  the 
liver  and  the  lungs,  contain  thrombi,  and  the  adjacent  veins  migrated  leukocytes. 
In  pregnant  animals  even  the  fetus  exhibited  the  same  conditions.  In  explanation 
of  the  phenomenon  the  question  may  be  discussed  whether  increased  destruction 
of  the  cellular  elements  does  not  take  place  in  the  greatly  cooled  blood. 

Freezing. — As  a  result  of  the  long-continued  action  of  high  degrees  of  cold 
upon  the  skin ,  the  musculature  of  the  skin  and  its  vessels  contracts  at  first ,  in  con- 
sequence of  the  stimulating  influence  of  the  cold,  and  pallor  of  the  integument 
develops.  If  the  action  be  maintained,  paralysis  of  the  walls  of  the  vessels  takes 
place,  and  the  skin  becomes  reddened,  with  dilatation  of  the  vessels.  As  the  pas- 
sage of  fluids  through  the  capillaries  is  seriously  embarrassed  in  consequence  of 
the  action  of  the  cold,  stagnation  of  the  blood  results.  This  soon  makes  itself 
manifest  as  livid  discoloration,  as  the  oxygen  is  almost  consumed  in  the  small 


ARTIFICIAL    REDUCTION    OF    BODILY    TEMPERATURE    IN    ANIMALS.     409 

vessels  in  consequence  of  the  slowness  of  the  current.  Thus  the  circulation  at 
the  periphery  is  slowed.  If  the  intense  effect  of  the  freezing  be  continued  the 
movement  of  blood  at  the  periphery  ceases  entirely  and  principally  in  the  thinnest 
parts,  namely  the  ears,  the  nose,  the  toes  and  the  fingers.  The  functions  of  the 
sensory  nerves  become  impaired,  and  numbness  and  anesthesia  develop.  Later 
there  may  be  even  complete  freezing  throughout.  If  the  peripheral  parts  become 
anemic,  the  internal  organs  naturally  become  hyperemic  and  the  heart  is  distended 
with  blood. 

As  the  retardation  of  the  circulation  must  naturally  be  transmitted  from  the 
surface  of  the  body  to  the  other  circulatory  areas,  increased  venosity  of  the  blood 
develops  in  consequence  of  diminished  circulation  through  the  lungs,  notwith- 
standing the  larger  amount  of  oxygen  in  the  cold,  dense  air,  and  as  a  result  the 
activity  of  the  nerve-centers  is  affected.  Great  disinclination  to  movement,  a 
distressing  feeling  of  fatigue,  a  peculiar  irresistible  tendency  to  sleep,  an  inability 
to  think  logically,  uncertainty  in  sensorial  activity,  and  finally  complete  loss  of 
consciousness  are  the  symptoms  of  this  condition.  At  a  temperature  of  — 0.56°  C. 
the  blood  freezes,  while  the  fluids  of  the  superficial  portions  of  the  body  become 
rigid  somewhat  earlier.  The  protoplasm,  as,  for  instance,  of  the  muscles,  may 
be  cooled  on  careful^ experimentation  down  to  a  temperature  of  18°  C.  without 
becoming  solid.  In  making  attempts  at  resuscitation  or  at  thawing,  all  bending 
or  breaking  movements  of  the  rigid  parts  is  to  be  avoided,  in  order  that  the  crystals 
of  ice  do  not  perforate  the  tissues.  Further,  too  rapid  heating  is  to  be  avoided, 
as  hereby  sudden  expansion  of  the  tissues  might  be  brought  about,  and  give  rise 
to  their  molecular  destruction.  Simple  rubbing  with  snow  in  order  if  possible 
to  set  the  blood  gradually  in  motion  from  the  parts  that  are  not  frozen  toward 
those  that  are  rigid,  with  gradual  warming,  will  yield  the  best  results.  Often 
complete  freezing  is  followed  by  partial  death  of  the  affected  part. 

ARTIFICIAL    REDUCTION    OF    THE    BODILY    TEMPERATURE    IN 

ANIMALS. 

In  consequence  of  reduction  of  the  temperature  of  the  body  the 
activity  of  the  most  highly  developed  nerve-centers  (cerebrum)  is 
diminished  first  and  only  later  that  of  the  medulla  oblongata.  If  "the 
functions  of  the  latter  are  beyond  restoration  death  must  result. 

Artificial  reduction  of  the  temperature  in  warm-blooded  animals  by 
exposure  to  a  cold  atmosphere,  or  to  cold-mixtures,  is  followed  by  a 
series  of  characteristic  phenomena.  If  the  temperature  of  the  animals — 
rabbits — is  lowered  to  18°  C. — rectal  temperature — they  are  overcome  by 
great  prostration,  without  abolition,  however,  of  voluntary  and  reflex 
movements,  although  these  are  lost  at  a  temperature  of  17°  C.  The 
pulse  is  reduced  in  frequency  from  100  or  150  to  20  beats  in  a  minute, 
and  at  the  same  time  the  blood-pressure  falls  to  a  few  millimeters  of 
mercury.  Respirations  are  infrequent  and  superficial,  and  breathing, 
therefore,  becomes  inadequate  (at  25°  C.,  in  rabbits).  Asphyxia  is  no 
longer  capable  of  exciting  convulsions ;  the  secretion  of  urine  ceases ;  and 
the  liver  exhibits  excessive  hyperemia.  In  this  condition  the  animal 
may  remain  for  twelve  hours;  then,  after  the  muscles  and  the  nerves 
exhibit  signs  of  paralysis,  coagulation  of  the  blood  has  taken  place  fol- 
lowing the  destruction  of  large  numbers  of  blood-corpuscles,  and  the 
eye-ground  has  become  pale,  death  takes  place  amid  symptoms  of 
paralysis  of  the  heart,  convulsions  and  asphyxia. 

If  left  to  itself,  an  animal  whose  temperature  has  been  reduced  to 
1 8°  C.  is  incapable  of  recovery  when  the  surrounding  temperature  is  the 
same.  If,  however,  artificial  respiration  is  practised  the  bodily  tem- 
perature rises  10°.  If  in  conjunction  with  the  latter,  heat  is  in  addition 
supplied  from  without,  the  animals  recover  completely,  even  when 
they  have  been  apparently  dead  for  about  forty  minutes.  Walther  was 


4IO     ARTIFICIAL    REDUCTION    OF    BODILY    TEMPERATURE    IN    ANIMALS. 

in  this  way  able  to  resuscitate  full-grown  animals  whose  temperature 
had  been  reduced  to  9°  C.  and  Howarth  young  animals  even  when  the 
temperature  had  been  reduced  to  5°  C.  Mammals  born  blind  and 
birds  born  without  feathers,  if  left  to  themselves,  suffer  reduction  in 
temperature  more  rapidly  than  others.  Morphin,  and  in  still  greater 
degree  alcohol,  accelerate  the  reduction  in  the  temperature  of  mam- 
mals, the  gaseous  interchange  at  the  same  time  falling  considerably, 
and  for  this  reason  drunken  persons  are  more  readily  exposed  to  the 
danger  of  death  from  freezing. 

Knoll  lowered  the  temperature  of  rabbits  by  means  of  intravenous  infusion 
of  an  ice-cold  indifferent  solution  of  sodium  chlorid.  He  found  reduction  in 
pulse-frequency,  prolonged  systole,  paralysis  of  the  cardiac  branches  of  the  vagus, 
primary  increase  -and  secondary  reduction  in  blood-pressure,  accelerated,  super- 
ficial breathing  and  later  diminished  frequency  of  breathing. 

Cl.  Bernard  made  the  remarkable  discovery  that  the  muscles  of 
animals  whose  temperature  had  been  reduced  maintain  their  irritability 
for  a  longer  time,  with  respect  to  direct  stimuli,  as  well  as  to 
stimulation  through  the  nerve.  He  found  the  same  condition  when  the 
animals  were  asphyxiated  through  deficiency  of  oxygen.  Artificial 
cold-bloodedness,  that  is,  a  condition  in  which  the  temperature  of  warm- 
blooded animals  is  reduced,  with  preservation  of  the  irritability  of 
muscles  and  nerves,  can  be  developed  in  warm-blooded  animals  also  by 
division  of  the  cervical  cord  while  artificial  respiration  is  maintained, 
and  further  by  application  of  a  cool  solution  of  sodium  chlorid  to  the 
peritoneum. 

Hibernation,  which  is  due  essentially  to  the  lowering  of  the  temperature  of  the 
animals,  exhibits  a  series  of  analogous  phenomena.  Valentin  found  that  the 
marmot  begins  to  be  only  half  awake  when  the  bodily  temperature  reaches  28°  C. ; 
at  a  temperature  of  18°  C.  it  is  soporose;  at  6°  it  exhibits  shallow  and  at 
1 6°  C.  deep  sleep.  At  the  same  time  the  heart-beats  fall  to  8  or  10  in  a  minute, 
with  reduction  in  the  blood-pressure.  The  respirations  and  the  movements  of  the 
bladder  and  the  intestine  cease  entirely,  and  only  the  cardio-pneumatic  movement 
maintains  the  slight  diffusion  of  gases  in  the  lungs.  The  temperature  does  not 
fall  as  low  as  o°,  but  the  animals  awaken  before  the  temperature  has  fallen  to 
this  level.  At  a  temperature  of  o°  C.  no  further  dissociation  of  the  oxy hemo- 
globin would  take  place.  Hibernating  animals,  indifferently  whether  in  the 
waking  or  in  the  sleeping  state,  may,  however,  survive  an  artificial  reduction  of 
temperature  down  to  — 1°  C.  and  recover  spontaneously.  Hibernating  animals, 
therefore,  submit  to  a  greater  reduction  of  temperature  than  other  mammals. 
Under  such  circumstances,  they  yield  up  their  heat  rapidly  and  they  are  able  to 
renew  their  heat  with  rapidity  even  spontaneously.  Newborn  mammals  more 
closely  resemble  hibernating  animals  in  this  respect  than  do  adult  animals.  The 
animals  can  be  awakened  from  their  winter's  sleep  by  sensory  stimulation  and  in- 
creasing temperature  through  the  agency  of  the  nerve-centers. 

In  cold-blooded  animals  exposed  to  great  cold  the  temperature  can  be  reduced 
almost  to  the  freezing-point — tenches  can  be  frozen  into  ice.  In  the  state  of  cold 
their  metabolism  is  greatly  lowered  and  the  animals  are  apparently  dead,  although 
they  recover  rapidly  when  exposed  to  warmer  surroundings.  Under  favorable  con- 
ditions animals  frozen  into  a  mass  of  ice  may  be  resuscitated — the  frog.  If,  for 
example,  however,  the  fluids  throughout  the  body  have  been  frozen  into  ice,  the 
animals  will  die,  for  the  reason  that  with  the  formation  of  ice  in  the  tissues,  the 
gases  are  expelled  in  the  form  of  bubbles  and  the  salts  separate  in  the  form  of 
crystals.  The  germs  and  ova  of  lower  forms  of  animal  life,  as,  for  instance,  the 
eggs  of  insects,  survive  long-continued,  severe  cold.  A  moderate  degree  of  cold 
only  retards  their  development.  Snakes  tolerate  an  external  temperature  of 
— 25°,  frogs  a  temperature  of  — 28°,  myriapods  and  infusoria  a  temperature  of 
— 50°,  snails  for  days  a  temperature  of  — 120°.  Germs,  grains  of  seed  and  spores 
of  fungi  exposed  to  a  temperature  of  — 200°  are  capable  of  germinating  after 


EMPLOYMENT    OF    COLD.  4H 

being  again  warmed,  and  also  the  seeds  of  wheat,  oats,  peas,  etc.,  exposed  for  four 
or  five  days  to  a  temperature  of  — 192°  C. 

The  application  of  a  coat  of  varnish  to  the  skin  gives  rise  to  a  series  of  condi- 
tions similar  to  those  due  to  reduction  in  temperature.  The  varnished  skin  readily 
gives  off  heat  outward  through  radiation,  particularly  as  the  blood-vessels  of  the 
skin  are  enormously  dilated.  Therefore  the  temperature  of  the  animals  falls 
greatly  and  some  even  die.  If  the  reduction  in  temperature  be  prevented 
by  applications  of  heat  and  of  external  coverings  the  animals  survive.  The  blood 
of  such  animals  as  die  contains  no  toxic  substances  and  no  retained  excremen- 
titious  matters  that  might  have  caused  death,  for  other  animals  injected  with 
such  blood  remain  healthy.  In  human  beings  varnishing  of  the  skin  appears 
to  have  no  injurious  effect. 

EMPLOYMENT  OF  COLD. 

Applications  of  cold  to  a  large  part  of  the  surface  of  the  body  may  be  made 
from  the  following  points  of  view : 

(a)  By  means  of  cold  baths  or  packs  of  considerable  duration  to  remove  large 
amounts  of  heat  from  the  surface  of  the  body  when  the  temperature  in  the  presence 
of  fever  has  attained  a  dangerous  elevation.  This  effect  can  be  produced  in  a 
most  lasting  manner  if  the  temperature  of  the  bath  is  at  first  moderate  and  is 
gradually  reduced,  because  the  skin  is  rendered  anemic  and  becomes  contracted 
in  consequence  of  low  degrees  of  temperature,  so  that  a  marked  obstacle  to  the 
dissipation  of  heat  at  once  arises.  Also,  the  gradually  cooled  bath  is  borne  for  a 
considerable  time.  The  addition  of  stimulating  substances,  as,  for  instance, 
salt,  which  effects  dilatation  of  the  cutaneous  vessels,  favors  heat-dissipation, 
chiefly  because  the  salt-water  acts  as  a  better  conductor  of  heat.  The  reduction 
in  temperature  is  favored  by  simultaneous  administration  of  alcohol  internally. 
Also,  evaporation  of  water  from  the  skin,  through  spraying  with  aqueous  vapor, 
is  adapted  for  the  reduction  of  the  bodily  temperature. 

(6)  Local  external  reduction  of  temperature,  as  by  means  of  an  ice-bag,  serves 
in  the  first  place  to  cause  contraction  of  the  vessels  and  of  the  tissues,  as  in  case 
of  inflammation,  with  simultaneous  local  abstraction  of  heat.  Whether,  under 
such  circumstances,  the  heat-generating  molecular  disintegration  of  potential 
energy  is  retarded  locally  or  not  is  as  yet  undetermined. 

(c)  Local  abstraction  of  heat  through  the  rapid  evaporation  of  volatile  sub- 
stances, such  as  ether  and  carbon  disulphid,  causes  anesthesia  of  sensory  nerves. 
The  introduction  of  media  of  low  temperature  into  the  interior  of  the  body,  such 
as  the  inhalation  of  cold  air,  the  ingestion  of  cold  drinks,  cold  injections  into  the 
intestine,  the  bladder  or  the  genital  tract,  in  part  acts  locally  and  in  part  may 
cause  general  abstraction  of  heat  if  the  action  be  long  continued  and  intense.  In 
connection  with  the  action  of  cold  it  should  be  borne  in  mind  that  the  contraction 
of  the  vessels  and  the  collapse  of  the  tissues  after  cessation  of  the  effect  are  usually 
followed  by  increased  fulness  and  turgescence. 

THE  TEMPERATURE  OF  INFLAMED  PARTS. 

Heat  is  considered  one  of  the  fundamental  phenomena  of  inflammation,  in 
conjunction  with  redness,  swelling  and  pain.  Nevertheless,  the  apparent  increase 
in  the  temperature  of  inflamed  parts  is  by  no  means  dependent  upon  increase 
in  the  temperature  above  that  of  the  blood,  a  condition  that  has  never  been 
observed.  In  consequence  of  the  dilatation  of  vessels,  which  causes  redness,  and 
the  increased  amount  of  blood  flowing  through  the  inflamed  parts,  as  well  as 
through  tumefaction  of  the  tissues  with  well-conducting  fluid,  the  external 
portions  of  the  body,  such  as  the  skin,  are  usually  of  a  higher  temperature  than 
normal,  and  at  the  same  time  they  more  readily  give  off  heat  through  conduction. 
Whether  or  not  increased  heat-production  takes  place  in  the  inflammatory  focus 
itself,  perhaps  in  accordance  with  the  character  of  the  inflammatory  process,  in 
consequence  of  accelerated  molecular  disintegration,  has  not  as  yet  been  de- 
termined. 

HISTORICAL.     COMPARATIVE. 

Hippocrates — born  460  B.  C. — considered  the  indigenous  heat  as  the  cause  of 
life.  According  to  Aristotle  the  heart  prepares  heat  within  itself  and  distributes 
it  to  all  parts  of  the  body,  together  with  the  blood.  This  doctrine,  which  is  pre- 


412  HISTORICAL.       COMPARATIVE. 

sented  in  a  similar  manner  also  in  the  writings  of  Hippocrates  and  Galen,  was  for 
a  long  time  the  dominating  one,  and  is  found  last  in  the  writings  of  Cartesius  and 
Bartholinus  (1667,  "Flammula  cordis").  The  iatromechanical  school  attributed 
the  heat  to  the  friction  of  the  blood  in  the  walls  of  the  vessels.  The  iatrochemical 
school,  on  the  other  hand,  looked  for  the  source  of  heat  in  fermentative  processes 
taking  place  in  the  blood  through  the  entrance  of  absorbed  articles  of  food. 
Lavoisier  was  the  first,  in  1777,  to  make  the  combustion  of  carbon  in  the  lungs 
the  source  of  heat.  After  the  invention  of  the  thermometer  by  Galileo,  Sanctorius 
in  1626  made  the  first  thermometric  observations  on  the  sick,  while  the  first 
calorimetric  observations  were  made  by  Lavoisier  and  Laplace  in  1780.  Compara- 
tive observations  have  already  been  recorded  on  p.  382,  and  also  with  respect  to 
hibernation  on  p.  410. 


PHYSIOLOGY  OF  METABOLISM. 


SCOPE  OF  METABOLISM. 

By  metabolism  is  understood  the  phenomenon  common  to  all  living 
organisms,  sharply  differentiating  the  organized  from  the  unorganized, 
and  consisting  in  the  power  of  incorporating  into  their  own  tissues 
the  substances  obtained  from  food  (in  animals  by  means  of  digestion) 
and  of  forming  them  into  component  parts  of  their  own  animate 
bodies.  This  division  of  metabolism  is  designated  assimilation.  More- 
over, out  of  these  assimilated  substances,  which  constitute  a  reservoir  of 
potential  energy,  the  organism  is,  by  means  of  transformation-processes, 
able  to  develop  activities  in  the  form  of  kinetic  energy,  which  are  mani- 
fested most  strikingly  among  the  higher  animals  as  muscular  work  and 
heat.  The  resulting  transformation  of  tissue-constituents,  which  ter- 
minates in  the  formation  of  excrementitious  substances,  is  thus  an  in- 
direct object  in  the  study  of  metabolism. 

Normal  metabolism  requires,  accordingly,  food-material  suitable 
both  qualitatively  and  quantitatively;  a  storing  up  within  the  body,  in 
proportion  to  the  consumption ;  a  regulated  chemical  transformation  of 
the  tissues ;  and  the  preparation  of  the  waste-products  to  be  thrown  off 
by  the  organs  of  excretion. 


SYNOPSIS   OF   THE   MOST   IMPORTANT   SUBSTANCES 

USED  AS  FOOD. 

WATER.     EXAMINATION  OF  DRINKING-WATER. 

When  it  is  considered  that  the  body  contains  in  all  of  its  tissues  about  58.5 
per  cent,  of  water,  that  water  is  constantly  being  thrown  off  with  the  urine  and 
the  feces,  as  well  as  by  the  skin  and  the  lungs,  and  that  in  the  processes  of  digestion 
and  absorption  most  substances  must  be  dissolved  in  water,  and  likewise  that 
numerous  waste-products,  especially  in  the  urine,  must  leave  the  body  in  aqueous 
solution,  the  importance  of  a  constant  supply  and  continual  renewal  of  water  will 
be  at  once  obvious.  Hoppe-Seyler  epitomized  admirably  the  importance  of  water 
to  life  in  the  following  words:  "All  organisms  live  in  water,  and  indeed  in  running 
water,"  a  saying  that  deserves  a  place  by  the  side  of  the  old  one  of  "Corpora  non 
agunt  nisi  fluida." 

Leaving  out  of  consideration  its  presence  as  a  constituent  of  fluid  food,  water 
is  used  as  a  drink  in  different  forms:  (i)  As  rain-water  (in  some  countries,  where 
it  is  collected  in  suitable  reservoirs,  cisterns,  etc.) ,  which  most  closely  approximates 
distilled  (chemically  pure)  water,  although  it,  nevertheless,  always  contains  small 
amounts  of  carbon  dioxid,  ammonia,  nitrous  and  nitric  acids.  (2)  As  well-water  or 
spring-water,  which  is  ordinarily  rich  in  mineral  matter,  it  results  from  atmos- 
pheric precipitations,  which  filter  through  the  layers  of  earth  rich  in  carbon  dioxid, 
and  with  the  aid  of  the  absorbed  carbon  dioxid  it  is  capable  of  dissolving  out 
the  alkalies,  the  alkaline  earths  and  metals.  These  substances  enter  into  solution 
as  bicarbonates,  for  instance  calcium  carbonate  and  ferric  carbonate.  The  water 
is  either  drawn  from  the  wells  by  mechanical  appliances  or  it  gushes  from  the 


414  EXAMINATION    OF    DRINKING-WATER. 

surface  of  the  earth  in  certain  localities  in  the  form  of  springs.  (3)  The  running 
water  of  streams,  rivers  and  brooks  is  generally  much  poorer  in  mineral  matter 
than  that  of  wells  or  springs. 

Flowing  on  the  surface  spring- water  soon  gives  off  much  of  its  carbon  dioxid. 
As  the  solution  of  many  minerals  is  possible  only  in  the  presence  of  carbon  dioxid, 
insoluble  precipitates  of  these  substances  must  result.  The  water  of  wells  and 
springs  is  poor  in  oxygen,  and  on  the  other  hand  rich  in  carbon  dioxid.  The  latter 
gives  it  its  refreshing  and  stimulating  properties.  For  the  same  reason  a  generous 
vegetable  life  is  possible  about  springs,  while  on  the  other  hand  the  existence  in 
spring-water  and  well-water  of  animal  organisms  requiring  oxygen  is  extremely 
limited.  Freely  running  water,  however,  absorbs  oxygen  from  the  air,  while  giving 
off  carbon  dioxid,  and  thus  supplies  the  necessary  conditions  for  existence  to  fishes 
and  other  aquatic  animals.  River- water  contains  about  from  ^  to  oV  °f  its 
volume  of  absorbed  gases,  which  may  be  driven  off  by  boiling  or  freezing. 

The  water  from  wells  and  springs  chiefly  is  used  for  drinking-purposes.  River- 
water  (with  which,  unfortunately,  some  large  cities  must  yet  content  themselves) 
demands  first  a  careful  removal  of  the  clay  and  other  accidental  impurities  sus- 
pended in  it.  It  may  be  cleared  and  purified  by  means  of  large  filter-beds  made 
of  thick  layers  of  sand  mixed  with  charcoal.  On  a  small  scale  the  commercial 
charcoal-filter  can  be  used  with  advantage  to  clarify  the  water,  the  charcoal  being 
in  addition  disinfectant.  In  this  connection  it  is  a  noteworthy  fact  that  alum  in 
a  dilution  of  o.oooi  per  cent,  is  able  to  clarify  turbid  water. 

EXAMINATION  OF  DRINKING-WATER. 

Drinking-water  (even  when  viewed  in  thick  layers)  should  be  perfectly  color- 
less and  clear,  also  without  odor,  which  is  best  perceived  by  heating  to  50°  C., 
with  or  without  addition  of  sodium  hydroxid.  Moreover,  it  should  not  be  too 
hard,  that  is,  not  unduly  rich  in  salts  of  calcium  and  magnesium. 

By  the  term  degree  of  hardness  is  designated  the  content  of  compounds  of  cal- 
cium and  magnesium  in  100,000  parts  of  water.  A  water  of  20  degrees  of  hardness 
contains,  therefore,  in  100,000  parts,  20  parts  of  calcium  (calcium  oxid)  in  com- 
bination with  carbon  dioxid,  sulphuric  and  hydrochloric  acids  (the  small  amounts  of 
magnesium  need  not  be  taken  into  consideration) .  A  good  drinking-water  should 
not  greatly  exceed  20  degrees  of  hardness.  To  determine  the  degree  of  hardness 
a  titrated  soap-solution  may  be  used.  This  is  shaken  with  the  water  to  be  exam- 
ined, and  the  later  that  foam  appears  the  harder  is  the  water.  The  degree  of 
hardness  exhibited  by  unheated  water  is  designated  its  total  hardness;  that  of 
heated  water  its  permanent  hardness.  By  means  of  boiling,  the  calcium  carbonate 
principally  is  precipitated,  as  a  result  of  the  escape  of  the  carbon  dioxid.  It  is 
on  this  account  that  boiled  water  becomes  softer. 

Turbidity  of  the  water  following  the  addition  of  hydrochloric  acid  and  barium- 
chlorid  solution  indicates  the  presence  of  sulphuric  acid,  usually  in  combination 
with  calcium. 

As  chlorin  (always  in  combination  with  a  metal)  appears  only  in  small  quanti- 
ties in  pure  spring-water,  and  as  its  presence  in  large  amounts  (apart  from  saline 
springs,  the  vicinity  of  the  sea,  or  factory-sewers)  generally  indicates  a  commu- 
nication with  water-closets  or  manure-heaps,  the  estimation  of  this  is  of 
especial  interest.  For  purposes  of  demonstration,  20  cu.  cm.  of  water  are  mixed 
with  a  few  drops  of  nitric  acid,  and  silver  nitrate  is  added;  a  precipitate  of  silver 
chlorid  results.  For  quantitative  estimation  by  titration  there  are  necessary  a 
solution  A  of  17  grams  of  crystallized  silver  nitrate  in  i  liter  of  water  (i  cu.  cm. 
of  this  solution  precipitates  3.55  mgm.  of  chlorin  as  silver  chlorid) ;  and  also  a  cold 
saturated  solution  B  of  neutral  potassium  chromate.  In  testing,  50  cu.  cm.  of  the 
water  to  be  examined  are  placed  in  a  beaker,  2  or  3  drops  of  the  solution  B  are 
added,  and  then  from  a  buret  solution  A  is  permitted  to  flow  drop  by  drop  until 
the  precipitate,  at  first  white,  remains  red,  even  after  stirring.  If  the  number 
of  cubic  centimeters  of  A  used  be  multiplied  by  7.1,  the  amount  of  chlorin  con- 
tained in  100,000  parts  of  water  will  be  obtained.  Example:  if  50  cu.  cm.  required 
2.9  cu.  cm.  of  silver-solution,  then  100,000  parts  of  water  contain  2.9  X  7-*  = 
20.59  parts  of  chlorin.  In  good  drinking-water  the  chlorin  should  not  exceed 
15  mgm.  in  i  liter. 

If  50  cu.  cm.  of  water  are  acidulated  with  a  little  hydrochloric  acid,  then 
ammonia  added  in  excess,  and  to  this  a  solution  of  ammonium  oxalate,  the  white 
precipitate  obtained  is  calcium  oxalate.  According  as  the  resulting  turbidity  is 
only  slightly  cloudy  or  markedly  milky  it  is  known  whether  the  water  is  soft 


EXAMINATION    OF    DRIXKIXG-WATER.  415 

(poor  in  calcium)  or  hard  (rich  in  calcium).  After  this  calcium-precipitate  has 
settled,  the  clear  fluid  is  poured  off  and  mixed  with  a  solution  of  sodium  phos- 
phate and  a  little  ammonia;  the  crystalline  precipitate  that  now  forms  indicates 
the  presence  of  magnesia. 

The  feebler  the  reactions  for  sulphuric  acid,  chlorin,  calcium  and  magnesium, 
the  better  is  the  water.  Good  drinking-water,  should,  moreover,  contain  only 
traces  of  nitrates,  nitrites  and  ammonium-compounds,  as  their  presence  points  to 
organic  substances  containing  nitrogen  in  a  state  of  decomposition. 

Nitricacid  is  indicated  when  100  cu.  cm.  of  water  are  acidulated  with  two  or  three 
drops  of  concentrated  sulphuric  acid,  some  bits  of  zinc  are  added  and  then  a  solu- 
tion of  iodin,  zinc  and  starch,  and  a  blue  tint  appears.  The  following  test  is  exceed- 
ingly sensitive :  some  fragments  of  brucin  sulphate  along  with  a  drop  of  the  water 
to  be  examined  are  to  be  placed  in  a  watch-glass;  then  a  few  drops  of  concentrated 
sulphuric  acid  are  added.  A  rose-red  color  appears.  Diphenylamin  sulphate 
mixed  with  a  few  drops  of  concentrated  sulphuric  acid  yields  in  the  presence  of 
nitrates,  even  when  in  great  dilution,  a  blue  color.  This  test  is,  therefore,  recom- 
mended for  the  demonstration  of  well-water  in  milk. 

Demonstration  of^nitrous  acid:  To  100  cu.  cm.  of  water  a  few  drops  of  pure 
concentrated  sulphuric  acid  and  a  solution  of  zinc  iodid  and  starch  are  added: 
a  blue  color  appears.  In  addition  naphthionic  acid  and  pure  /3-naphthol,  thor- 
oughly mixed  in  a  mortar,  are  recommended  as  a  reagent.  To  10  cu.  cm.  of  the 
fluid  to  be  examined  for  nitrites  two  drops  of  a  concentrated  solution  of  hydro- 
chloric acid  and  as  much  of  the  mixture  mentioned  as  can  be  taken  up  on  the 
point  of  a  knife  are  added  and  the  whole  is  thoroughly  shaken.  If  ammonia  is 
added  in  a  layer  on  top  of  this  mixture  a  red  ring  appears.  This  test  has  a  sensi- 
tiveness of  i  :  100  millions. 

Ammonium-compounds  in  considerable  amount  render  the  water  suspicious. 
To  150  cu.  cm.  of  water  0.5  cu.  cm.  of  solution  of  sodium  hydrate  and  i.o  cu.  cm. 
of  solution  of  sodium  carbonate  are  added  and  the  precipitate  is  allowed  to  settle. 
Of  the  supernatant  clear  fluid  a  column  15  cm.  high  is  introduced  into  a  narrow 
graduated  cylinder  and  mixed  with  Nessler's  reagent  (a  solution  of  mercuric 
iodid  and  potassium  iodid  in  an  excess  of  potassium  hydroxid) :  Traces  of  ammo- 
nia in  water  thus  yield  a  color  between  yellow  and  red,  large  amounts  a  brown 
precipitate  of  mercuric -ammonium  iodid. 

The  contamination  of  water  by  decomposed  animal  substances  will  be  recog- 
nized by  the  amount  of  contained  nitrogen.  In  most  cases  it  is  sufficient  to 
determine  the  amount  of  nitric  acid.  For  this  two  solutions  are  necessary:  A, 
containing  1.871  gin.  of  potassium  nitrate  to  a  liter  of  water;  i  cu.  cm.  of  this 
contains  i  gram  of  nitric  acid;  B,  a  dilute  solution  of  indigo;  i  part  of  pulverized 
indigotin  is  slowly  added  with  stirring  to  6  parts  of  fuming  sulphuric  acid;  the 
mixture  is  allowed  to  settle,  the  blue  liquid  is  poured  into  40  times  its  amount 
of  distilled  water  and  then  filtered.  Finally,  the  fluid  is  diluted  with  distilled 
water  until  it  begins  to  be  transparent  in  layers  of  from  12  to  15  mm.  thick.  To 
test  the  efficiency  of  B,  i  cu.  cm.  of  A  is  mixed  with  24  cu.  cm.  of  water,  some 
table-salt  and  50  cu.  cm.  of  concentrated  sulphuric  acid  are  added,  and  so  much 
of  B  is  now  allowed  to  flow  from  a  buret  until  a  faint  green  tint  appears.  The 
number  of  cubic  centimeters  of  B  used  corresponds  to  i  mgm.  of  nitric  acid. 
Twenty-five  cubic  centimeters  of  the  water  to  be  examined  are  mixed  with  50 
cu.  cm.  of  concentrated  sulphuric  acid  and  titrated  with  B  until  the  green  color 
appears.  This  titration  must,  however,  be  repeated,  and  in  the  second  observa- 
tion the  number  of  cubic  centimeters  of  indigo-solution  be  permitted  to  flow  in  a 
stream;  a  somewhat  larger  amount  of  fluid  may  be  required  to  produce  the  green 
color.  The  number  of  cubic  centimeters  of  solution  B  thus  used  (in  proportion 
to  the  previously  ascertained  strength)  indicates  the  amount  of  nitric  acid  present 
in  25  cu.  cm.  of  water.  In  well-water  as  much  as  10  mgm.  nitric  acid  is  found 
in  the  liter. 

Hydrogen  sulphid  is  recognized,  apart  from  its  odor,  through  the  brown  color 
imparted  to  a  piece  of  filter-paper  that  has  been  saturated  in  an  alkaline  solution 
of  lead,  and  is  held  over  the  water  boiling  in  a  flask.  If  hydrogen  sulphid  is 
present  in  combination  in  the  water,  some  sodium  hydroxid  and  a  dilute  solution 
of  sodium  nitro-prussid  are  added;  a  reddish- violet  color  appearing 

It  is  of  the  greatest  significance  with  respect  to  the  excellence  of  drinking- 
water  that  it  should  be  free  from  putrefying  or  decomposing  organic  matter.  _  The 
latter,  in  conjunction  with  the  lower  organisms  always  to  be  found  in  it, 
when  ingested  with  drinking-water,  expose  the  body  to  serious  dangers,  as  a 
number  of  infectious  diseases,, especially  cholera  and  typhoid  fever,  can  be  spread 


416  EXAMINATION    OF    DRINKING-WATER. 

in  this  manner.  The  latter  is  especially  the  case  if  the  wells  in  use  lie  near  water- 
closets  and  manure-heaps,  so  that  the  products  of  decomposition  can  filter  through 
into  the  reservoir  for  the  water. 

Qualitative  Demonstration. — (i)  A  fairly  large  amount  of  water  is  evaporated 
in  a  porcelain  dish  to  dryness,  and  is  then  subjected  to  greater  heat.  If  large 
amounts  of  organic  matter  are  present  a  discoloration  between  brown  and  black 
takes  place.  If  the  matters  contain  nitrogen  the  odor  of  'burning  hair  appears 
at  the  same  time.  Good  water,  so  treated,  yields  but  a  faint  brown  color.  Micro- 
scopic examination  may  also  be  made  to  determine  the  presence  of  microorganisms 
in  water.  About  i  cu.  cm.  of  water  is  allowed  to  evaporate  upon  a  slide  having 
an  up-turned  edge  and  kept  in  a  place  free  from  dust,  and  the  dry  spot  is  examined. 
(2)  A  solution  of  gold-pota%ssium  chlorid  added  to  water  produces,  after  stand- 
ing for  a  long  time,  a  black  muddy  precipitate.  (3)  A  solution  of  potassium  per- 
manganate added  to  the  water  placed  under  cover  is  gradually  decolorized,  with 
the  formation  of  a  brown  muddy  deposit.  The  precipitates  from  2  and  3  are 
the  more  abundant  the  greater  the  amount  of  organic  substances  present  in  the 
drinking-water. 

Quantitatively  the  amount  of  organic  substances  is  determined,  according  to 
Kubel,  as  follows.  Two  solutions  are  required:  A,  containing  0.63  gram  of 
pure  crystalline  oxalic  acid  in  i  liter  of  distilled  water;  B,  containing  0.33 
gram  of  potassium  permanganate  in  i  liter  of  purest  distilled  water.  For  the 
determination  of  the  efficiency  of  the  latter  100  cu.  cm.  of  distilled  water  are 
placed  in  a  wide-necked  bottle  of  300  cu.  cm.  capacity,  together  with  5  cu.  cm. 
of  dilute  sulphuric  acid  (i  volume  of  acid  to  3  volumes  of  water)  and  heated  to 
boiling.  Into  this  from  3  to  4  cu.  cm.  of  solution  B  are  allowed  to  flow  from  a  buret 
provided  with  a  glass  stop-cock.  The  mixture  is  boiled  for  ten  minutes,  the 
heat  is  then  removed  and  10  cu.  cm.  of  solution  A  are  added.  Finally,  the  fluid, 
which  has  become  colorless,  is  mixed  with  solution  B  until  a  faint  red  tint  appears. 
The  number  of  cubic  centimeters  used  corresponds  to  6.3  mgm.  of  oxalic  acid, 
which  are  present  in  the  10  cu.  cm.  of  solution  A,  and  contains  exactly  3.16  mgm. 
of  potassium  permanganate,  or  0.8  mgm.  of  oxygen  available  for  oxidation, 
which  is  necessary  for  the  transformation  of  the  6.3  mgm.  of  oxalic  acid  into 
carbon  dioxid. 

In  order  to  test  a  given  water  for  the  amount  of  organic  matter  present, 
100  cu.  cm.  of  the  sample  are  placed  in  a  flask  of  300  cu.  cm.  capacity,  5  cu.  cm. 
of  dilute  sulphuric  acid  are  added  and  so  much  of  solution  B  that  the  fluid  becomes 
an  intense  red  and  remains  so  even  when  heated.  After  five  minutes'  boiling, 
10  cu.  cm.  of  solution  A  are  added.  The  fluid,  thus  made  colorless,  is  then  titrated 
with  solution  B  until  a  faint  red  tint  appears. 

For  purposes  of  calculation  as  many  cubic  centimeters  of  solution  B  as  are 
necessary  for  the  oxidation  of  10  cu.  cm.  of  solution  A  are  subtracted  from  the 
total  number  of  cubic  centimeters  of  solution  B  used  in  the  experiment.  The 
difference  in  cubic  centimeters  is  multiplied  by  3.16  :  x  if  the  proportion  of  potas- 
sium permanganate,  by  0.8  :x  if  the  proportion  of  oxygen,  necessary  for  the 
oxidation  of  the  organic  substances  present  in  100,000  parts  of  water  is  desired 
(x  represents  the  number  of  cubic  centimeters  of  solution  B  that  corresponds  to 
10  cu.  cm.  of  solution  A). 

Example. — Nine  and  nine-tenths  cubic  centimeters  of  solution  B  correspond  to 
10  cu.  cm.  of  solution  A.  After  acidulation  with  sulphuric  acid,  100  cu.  cm.  of  the 
water  under  examination  is  mixed  with  15  cu.  cm.  of  solution  B  and  boiled.  The 
red  fluid  is  decolorized  by  the  10  cu.  cm.  of  solution  A.  To  restore  a  faint  red 
tint  4.4  cu.  cm.  of  solution  B  must  be  added.  Estimation:  15  +  4.4  =  19.4; 
19.4  —  9.9  =  9.5.  Therefore,  for  the  oxidation  of  the  organic  Substances  in 
100,000  parts  of  water  (9.5  X  3-i6)  :  9.9  =  3.008  of  potassium  permanganate,  or 
(6.5  X  0.8)  :  9.9  =  0.77  part  of  oxygen  are  necessary.  Bad  drinking-water,  espe- 
cially when  it  contains  much  organic  matter,  should  never  be  used  in  its  native 
state,  but  particularly  not  at  a  time  when  epidemics  of  typhoid  fever,  of  cholera 
or  of  dysentery  prevail  or  threaten.  It  should  be  urgently  advised  that  the 
water  be  thoroughly  boiled  previously,  as  by  this  means  the  germs  of  infection 
are  destroyed.  The  resulting  insipid  taste  can  be  readily  improved  by  means  of 
effervescent  powder,  sugar  or  fruit- juice. 


STRUCTURE  AND  SECRETORY  ACTIVITY  OF  MAMMARY  GLANDS.        417 


STRUCTURE    AND    SECRETORY    ACTIVITY    OF    THE    MAMMARY 

GLANDS. 

About  twenty  milk-ducts  open  separately  on  the  tip  of  the  nipple,  and  just 
in  advance  of  their  mouth  present  an  oval  dilation,  the  lacteal  sinus,  generally  ex- 
panded laterally.  Each  undergoes  dendritic  ramification  and  passes  to  a  spe- 
cial lobe  of  the  gland,  which  is  bound  together  by  loose  interstitial  connective 
tissue.  Only  at  the  time  of  lactation  do  all  of  the  terminal  branches  of  the  milk- 
ducts  lead  to  round  glandular  acini  arranged  in  groups.  Each  vesicle  has  a 
membrana  propria,  upon  which  externally  is  a  network  of  star-shaped  connective- 
tissue  cells,  and  internally  a  single  layer  of  somewhat  flattened,  polyhedral  and 
nucleated  secretory  cells.  According  to  the  degree  of  secretory  activity  of  the 
acinus  its  lumen,  at  times  narrow,  at  other  times  wide,  is  filled  with  a  fluid  in 
which  float  round,  shining  fat-granules  (milk).  Fibrillary  connective  tissue, 
principally  arranged  in  a  circular  manner,  and  transversed  externally  by  fine 
elastic  fibers,  forms  the  wall  of  the  glandular  ducts,  which  are  lined  by  cylindrical 
epithelium.  In  the  smallest  of  these  a  membrana  propria  can  yet  be  recognized, 
which  is  continuous  with  that  of  the  terminal  vesicle. 

During  the  first  days  following  delivery  (as  well  as  before  it),  the  breasts 
secrete  little  milk  of  considerable  consistency  and  yellowish  color  (colostrum) ,  in 
which  large  cells  completely  filled  with  fat-granules  are  present  (colostrum-corpus- 
cles). The  latter  appear  also  later  on,  when  the  discharge  of  the  milk  has  for 
a  time  been  discontinued.  Sometimes  a  nucleus  is  recognizable  in  the  cells, 


FIG.  137. — /,  Acinus  of  the  mammary  gland,  inactive;   II,  during  the  formation  of  milk:   a,  b,  milk-globules; 
c  d  e,  colostrum-corpuscles;  /,  pale  cells  (from  the  dog). 

rarely  ameboid  movement  (Fig.  137,  c,  d,  e).  The  normal  secretion  of  milk, 
appearing  in  the  course  of  three  or  four  days,  is  a  productive  activity  of  the  gland- 
cells. 

Heidenhain  and  Partsch  found  the  secretory  cells  in  the  inactive  gland  (Fig. 
137,  7)  to  be  flat,  polyhedral  and  mononuclear;  on  the  other  hand,  in  the  active 
gland  often  polynuclear,  cylindrical,  higher,  and  richer  in  albumin  and  granules 
(Fig.  137,  //).  The  free  edge,  turned  toward  the  cavity  of  the  acinus,  undergoes 
characteristic  changes  during  secretion.  There  are  formed  in  this  part  of  the 
cells  fat-granules,  which  are  thrown  off  during  secretion,  together  with  the  de- 
tached cell-margin.  In  part  the  nuclei  also,  degenerate,  their  product  likewise 
passing  over  into  the  milk  (nuclein-content  of  milk).  The  same  cells  appear 
to  be  able  to  perform  the  secretory  process  repeatedly,  undergoing  regeneration 
during  the  period  of  rest.  According  to  Bizzozero,  Benda,  Michaelis  and  Unger, 
the  cells  actively  produce  the  fat-granules  and  throw  them  off. 

Leukocytes  containing  fat-granules  are,  further,  found  in  milk,  representing 
colostrum-corpuscles,  and  isolated,  pale  cells  (/).  Some'  milk-globules  still  have 
shreds  of  cell-substance  on  their  surface  (6) .  With  respect  to  the  formation  of  the 
individual  constituents  of  milk,  H.  Thierfelder,  who  exposed  fresh  mammary 

t lands  to  digestive  processes  immediately  after  death,  found  that  during  the 
igestion  of  the  gland  at  the  temperature  of  the  body  a  reducing  substance, 
probably   milk-sugar,   was   formed   as   a  result    of    fermentative    activity.     The 
mother-substance  (saccharogen)  is  soluble  in  water,  but  not  in  alcohol  or  ether; 
it  is  not  destroyed  by  boiling  and  is  not  identical  with  glycogen.     The  ferment 
forming  milk-sugar  seems  to  be  fixed  in  the  glandular  cell,  as  it  does  not  pass 
over  into  the  milk  or  into  a  watery  extract  of  the  gland.     During  the  digestion 
27 


418        STRUCTURE  AND  SECRETORY  ACTIVITY  OF  MAMMARY  GLANDS. 

of  the  mammary  gland  at  the  temperature  of  the  body  casein  also  is  formed 
as  a  result  of  a  fermentative  process,  and  probably  from  serum-albumin.  This 
ferment  is  present  in  the  milk. 

The  mammillary  areola  and  the  nipple  are  characterized  by  pigmentary  deposits 
in  the  cells  of  the  rete  Malpighii  (during  pregnancy  more  abundant  and  of  greater 
extent)  and  by  large  papillae  in  the  cutis,  some  of  which  contain  tactile  corpuscles. 
Numerous  unstriated  muscle-fibers  in  the  deep  layers  of  the  corium  and  in  the 
subcutaneous  tissue  (always  free  from  fat)  surround  the  milk-ducts  of  the  nipples 
and  in  part  also  pass  longitudinally  to  the  tip  of  the  nipple.  The  glands  of  Mont- 
gomery, about  the  size  of  a  millet-seed,  situated  during  lactation  in  the  mam- 
millary  areola,  are  small,  nodular,  prominent,  subcutaneous  milk-glands,  with 
a  special  duct  of  evacuation  at  the  summit  of  each  nodule. 

Arteries  enter  the  mammary  gland  from  different  directions.  Their  branches 
do  not  accompany  the  glandular  ducts.  Capillaries  arranged  in  a  network  sur- 
round the  glandular  acini  and  anastomose  by  means  of  small  arteries  and  veins 
with  those  of  the  neighboring  vesicles.  In  the  mammillary  areola  the  veins  are 
arranged  in  the  form  of  rings  (circles  of  Haller) . 

The  nerves  of  the  mammary  gland  arise  from  the  supra-clavicular  and  the 
second,  fourth  and  sixth  intercostals.  They  pass  in  part  to  the  skin  of  the  gland 
and  of  the  highly  sensitive  nipple,  in  part  to  the  vessels,  and  in  part  to  the 
unstriated  muscle-fibers  of  the  nipple  and  to  the  glandular  vesicles  themselves,  in 
which  their  mode  of  termination  is,  however,  as  yet  unknown.  In  connection 
with  the  investigations  of  the  mammary  glands  great  credit  belongs  to  C. 
Langer. 

Lymphatics  are  found  close  about  the  alveoli,  often  distended  to  their  utmost, 
and  from  them  material  for  the  formation  of  milk  appears  to  be  derived. 

Comparative. — From  ten  to  twelve  nipples  are  found  in  rodents,  insectivora 
and  carnivora ;  others  among  these  animals  have  only  four.  Pachyderms  and  rumi- 
nants generally  possess  from  two  to  four  on  the  abdomen ;  the  carnivorous  whale 
has  two  at  the  side  of  the  vulva.  Apes,  bats,  herbivorous  whales,  elephants  and 
sloths  resemble  man;  the  half-apes  have  from  two  to  four  nipples.  The  duck-bill 
(ornithorhynchus  paradoxus)  possesses  tubes  arranged  in  groups  (similar  to  skin- 
glands)  ,  which  open  without  nipples  upon  a  hairless  flat  area  of  skin.  The  mar- 
supials carry  their  undeveloped  young  in  a  muscular  duplicature  of  the  skin  of 
the  abdomen,  in  which  the  nipples  are  situated.  In  them  and  in  the  duck-bill 
there  is  a  compressor  muscle  of  the  mammary  gland,  which  promotes  the  evacua- 
tion of  milk. 

Development  of  the  Breast. — The  first  indication  of  the  breasts  consists  on  each 
side  in  a  transitory  elevation  passing  downward  on  the  lateral  aspect  of  the  thorax, 
and  of  which  subsequently  there  remain  only  punctate  and  nodular  formations,  the 
precursors  of  the  breasts.  The  further  development  of  the  latter  begins  in  both 
cases  as  early  as  the  third  month;  between  the  fourth  and  fifth  a  number  of 
simple  tube-like  glandular  ducts  arranged  radially  are  already  present  beneath 
the  hairless,  excavated  mammillary  areola.  In  the  new-born  the  ducts  already 
exhibit  two  or  three  branches,  and  they  are  provided  with  dilated  extremities. 
In  both  sexes  the  ducts  divide  in  a  dendritic  manner  until  the  twelfth  year,  though 
without  the  development  of  actual  acini.  In  girls  who  have  reached  puberty  this 
Branching  proceeds  rapidly  and  extensively,  although  also  in  them  the  gland,  rich 
in  connective  tissue,  exhibits  the  formation  of  acini  only  at  ,the  periphery,  while 
only  with  the  occurrence  of  pregnancy  do  characteristic  acini  develop  also  in  the 
center  of  the  body  of  the  gland  along  with  relaxation  of  the  connective  tissue. 

In  the  climacteric  period  all  of  the  acini  and  numerous  small  milk-ducts  dis- 
appear. In  the  adult  man  the  mammary  gland  usually  resembles  that  of  the  new- 
born, having  undergone  involution  after  puberty.  Supernumerary  nipples  on  the 
breast  are  of  interest  as  representing  independent  openings  of  individual  milk-ducts . 
Supernumerary  glands  and  nipples  (hypermastia  and  hyperthelid)  arranged  in  part 
irregularly  and  in  part  regularly  in  rows,  like  the  dugs  of  the  sow,  point  to  their 
original  multiple  beginning  and  are  worthy  of  note  as  points  of  resemblance 
among  animals. 

The  situation  of  a  breast  in  the  axilla,  on  the  back,  on  the  acromion  or  on 
the  tibia  is  a  curiosity.  A  slight  secretion  from  the  breast  of  the  new-born  (witches' 
milk)  is  normal.  On  the  other  hand,  suckling  performed  by  a  man  is  to  be  included 
among  the  greatest  rarities.  According  to  Aristotle  buck- goats  sometimes  give 
milk  (noted  also  by  Schlossberger) ,  as  do  also  calves  after  their  dugs  have  been 
frequently  sucked,  and  goats  that  have  not  been  covered,  when  their  udders  are 
irritated  by  nettles. 


MILK    AND    MILK-PREPARATIONS.  419 

The  evacuation  of  milk  (from  500  to  1500  cu.  cm.  in  twenty-four  hours)  is 
due  not  alone  to  the  purely  mechanical  act  of  suction,  but  also  to  the  functional 
activity  of  the  mammary  gland.  The  latter  consists  primarily  in  erection  of  the 
nipple,  the  smooth  muscle-fibers  of  which  exerting  pressure  on  the  sinuses  of  the 
ducts,  so  that  the  milk  may  spurt  forth  in  a  stream.  Moreover,  the  glandular 
structure  itself  is  reflexly  stimulated  to  more  active  secretion  through  irritation 
of  the  sensory  nerves  of  the  nipple. 

From  the  suddenly  dilated  glandular  vessels  a  transudate  pours  abundantly 
into  the  gland,  by  which,  admixed  with  the  milk-corpuscles  and  transformed  into 
milk,  it  is  discharged.  The  amount  of  the  secretion  depends  thus  upon  the  degree 
of  blood-pressure.  Accordingly,  not  only  the  milk  stored  up  in  the  breast  is  sucked 
out,  but  during  the  process  of  suction  secretion  is  accelerated.  "The  breast  is 
willing, ' '  as  the  nursing  women  say.  Only  in  this  manner  can  be  explained  the  speedy 
arrest  of  the  secretion  of  milk  in  connection  with  sudden  emotional  excitement  .which 
(as  anger,  fright,  etc.)  acts,  as  is  known  from  experience,  on  the  vasomotor  nerves. 
Laffont  saw,  following  stimulation  of  the  mammary  nerve  of  a  bitch,  erection  of 
the  nipples,  dilatation  of  the  vessels  and  secretion  of  milk.  After  section  of  the 
external  spermatic  nerve  in  goats,  Eckhard  noted  absence  of  erection  of  the 
dugs,  although  the  formation  of  milk  suffered  no  interruption,  which  appeared 
only  after  section  of  the  nerves  on  both  sides.  Continued  stimulation  of  sensory 
nerves  diminishes  the  secretion.  The  rarely  observed  condition  of  galactorrhea 
is  perhaps  to  be  considered  as  a  sort  of  paralytic  secretion  similar  to  the  analogous 
secretion  of  saliva.  Heidenhain  and  Partsch  noted  increased  secretion  in  dogs 
when,  following  section  of  the  glandular  nerves,  strychnin  or  curare  was  in- 
jected. Atropin  decreases  the  amount  of  milk. 

The  slight  milk-fever  appearing  with  the  commencement  of  the  secretion  of 
milk  is  probably  due  to  increased  stimulation  of  the  vasomotors,  whose  activity 
must  further  be  considered  in  relation  with  the  transposition  of  the  mass  of  blood 
out  of  the  pelvic  cavity  after  birth. 

MILK  AND  MILK-PREPARATIONS. 

Milk  must  be  designated  a  complete  food,  in  which  all  of  the  constitu- 
ents are  present  in  such  proportion  that  the  body  can  thrive  upon  it.  Ac- 
cording to  Johannessen  the  proportions  in  human  milk  are  as  follows:  Albumin 
i,  fat  2,  sugar  4.2;  in  cow's  milk:  albumin  i,  fat  i,  sugar  1.43.  Of  the  milk 
relatively  more  fat  is  absorbed  in  the  intestine  than  albuminates.  Human  milk 
is  utilized  up  to  91.6  per  cent.,  cow's  milk  to  90  per  cent. 

Milk  is  opaque,  bluish  white,  with  a  sweetish  taste  and  a  characteristic  odor, 
probably  due  to  peculiar  odoriferous  bodies  in  the  cutaneous  secretion  of  the 
gland.  It  has  a  specific  gravity  of  from  1.030  to  1.032.  On  standing  numerous 
butter- globules  collect  on  the  surface  as  cream,  beneath  which  is  a  watery  bluish 
layer.  Human  milk  has  always  an  alkaline  reaction;  cow's  milk  is  at  times  alka- 
line, sometimes  acid,  tand  sometimes  amphoteric.  The  milk  of  carnivora  is 
always  acid. 

Milk  consists  of  the  fluid  (milk-plasma,  plasma  lactis)  and  the  morphological 
constituents  suspended  in  it,  among  which  the  milk-globules  predominate.  If  the 
milk  be  clotted,  the  cheese-cake  (placenta  lactis),  which  consists  of  coagulated 
casein,  containing  milk-globules,  separates  from  the  whey  (serum  lactis).  The 
latter  contains  some  dissolved  albumin,  milk-sugar  and  most  of  the  salts. 

Milk-globules  or  Butter-globules. — Microscopically,  milk  contains  innumerable 
small  globules  (Fig.  137).  Colostrum-corpuscles  and  epithelium  from  the  milk- 
ducts  are  not  common  in  mature  milk.  The  milk-globules  and  the  swollen  casein 
cause,  on  account  of  the  reflection  of  light,  the  white  color  and  the  opacity  of 
milk.  The  milk-corpuscles  consist  of  butter-fat  and  are  apparently  surrounded 
by  a  thin  layer  of  casein  (haptogenic  membrane) . 

That  the  milk-corpuscles  are  actually  surrounded  by  a  capsule  of  casein  has 
lately  been  definitely  denied.  Formerly,  the  following  observations  were  offered 
in  support  of  the  presence  of  the  capsule:  if  acetic  acid,  which  dissolves  the  casein- 
capsule,  be  added  to  a  microscopic  preparation,  the  milk-globules  run  together 
in  fat-droplets.  Further,  if  cow's  milk  be  shaken  with  potassium  hydroxid, 
which  destroys  the  casein-capsule,  and  then  be  mixed  with  ether,  the  milk  becomes 
clear  and  transparent,  as  the  ether  dissolves  all  of  the  fat-granules.  Previously 
to  the  treatment  with  potassium  hydroxid  or  acetic  acid,  the  ether  is  incapable 
of  setting  free  the  fat  in  cow's  milk  from  its  capsule;  in  the  case  of  human  milk 
the  addition  of  ether  and  shaking  alone  suffice.  Other  investigators,  however, 


420  MILK    AND    MILK-PREPARATIONS. 

deny  the  presence  of  the  casein-capsule ;  according  to  them  milk  is  a  simple  emul- 
sion, permanently  maintained  as  such  by  means  of  the  colloid  casein,  which  is 
simply  swollen  in  milk-plasma.  The  treatment  of  milk  with  potassium  and  ether 
renders  the  casein  of  the  plasma  unfitted  to  maintain  the  emulsion  of  the  milk 
permanently. 

The  fats  of  the  milk- globules  (human)  are  the  triglycerids  of  stearic,  palmitic 
and  oleic  acids,  in  lesser  amount  of  myristic,  capric,  caprylic,  caproic  and  butyric 
acids.  In  addition  there  are  found  traces  of  formic  acid  and  cholesterin. 

By  means  of  long-continued  beating  of  milk  (churning) ,  and  even  more  readily 
of  cream,  the  fat  of  the  milk-globules  (after  rupture  of  the  casein-capsule)  is  ob- 
tained as  butter  in  coherent  masses.  Butter  is  soluble  in  alcohol  and  ether,  and 
is  purified  by  melting  at  60°  C.,  or  by  washing  with  water  at  40°.  On  standing 
in  the  air  it  becomes  rancid,  from  the  glycerin  of  the  neutral  butter-fats  being 
decomposed  by  the  action  of  germs  into  acrolein  and  formic  acid,  which,  with  the 
volatile  fatty  acids,  give  the  odor. 

The  milk-fluid  (plasma  lactis)  is  clear,  somewhat  opalescent  and  contains 
proteids,  chief  among  which  is  casein,  together  with  a  small  amount  of  lact- 
albumin  and  lacto globulin  and  the  opalescent  opalisin,  a  little  nuclein,  phospho- 
carnic  acid  and  a  trace  of  diastatic  ferment  (in  human  milk) . 

Casein  is  retained  in  the  filtration  of  milk  by  means  of  fresh  animal  membrane 
or  by  means  of  clay  cylinders.  It  can  also  be  completely  precipitated  out  of 
human  milk  by  means  of  saturation  with  magnesium  sulphate,  from  cow's  milk 
by  means  of  a  little  acetic  acid. — Quantitative  Determination  in  Cow's  Milk: 
Twenty  cubic  centimeters  of  cow's  milk  are  diluted  with  60  cu.  cm.  of  water,  and 
30  cu.  cm.  of  a  i  in  1000  sulphuric-acid  solution  are  added  with  stirring,  precipi- 
tating the  casein  of  cow's  milk.  After  five  hours  filtration  is  practised,  the  filter  is 
washed  with  water,  twice  with  alcohol  and  fifteen  times  with  ether,  and  it  is  then 
dried  and  weighed.  The  casein  can  be  completely  precipitated  by  addition  of 
alum  at  a  temperature  of  37°  C.  Magnesium  sulphate  then  precipitates  the  globu- 
lin in  the  filtrate.  Globulin  and  albumin  together  are  precipitated  from  the  filtrate 
by  means  of  tannic  acid. 

The  albumin  in  milk  coagulates  on  boiling;  in  addition  the  free  surface  be- 
comes covered  with  a  skin  of  insoluble  casein. 

The  plasma  contains,  further,  milk-sugar,  a  carbohydrate  resembling  dextrin, 
lactic  acid?,  lecithin  (if  times  as  much  as  in  cow's  milk), urea,  traces  of  kreatin, 
kreatinin,  xanthin-bodies  (potassium  sulphocyanid  in  cow's  milk) ;  sodium  chlorid, 
potassium  chlorid,  alkaline  phosphates,  calcium  and  magnesium  sulphates,  alkaline 
carbonates  and  in  addition  traces  of  iron,  metallic  fluorids  and  silica,  carbon  dioxid, 
nitrogen,  oxygen  and  ammonia.  Human  milk  contains  numerous  staphylococci. 

The  curdling  of  milk  consists  of  a  coagulation  of  the  casein.  The  latter  is 
combined  in  the  milk  with  calcium  phosphate,  and  is  therefore  soluble.  Acids, 
which  remove  the  calcium  phosphate  from  the  casein,  cause  coagulation  of  the  casein ; 
lactic  acid  acts  most  readily  in  this  connection,  then  hydrochloric,  nitric,  sulphuric, 
acetic  and  phosphoric  acids.  Acetic  and  tartaric  acids,  when  added  in  excess,  re- 
dissolve  the  precipitated  casein.  Human  milk  is  not  curdled  by  all  acids,  but  only  by 
means  of  two  or  more  drops  of  o.i  per  cent,  hydrochloric  or  2  per  cent,  acetic 
acid.  Heating  above  130°  C.  coagulates  the  milk,  acids  being  formed  from  milk- 
sugar  as  a  result  of  the  action  of  heat  and  the  contained  casein  becoming  more 
coagulable.  The  spontaneous  curdling  of  milk  after  standing  for  some  time, 
especially  in  the  heat,  results  from  the  formation  of  lactic  acid  by  the  bacillus 
acidi  lactici,  which  transforms  the  neutral  alkaline  phosphate  into  acid  phosphate, 
removes  the  calcium  phosphate  from  the  casein  and  thus  precipitates  it.  The 
sugar  is  transformed  into  lactic  acid  and  carbon  dioxid.  The  bacillus  furnishes 
the  stimulation  for  this  decomposition,  while  the  casein  of  the  milk  is  the  actual 
fermenting  body. 

By  means  of  the  lab-ferment  milk  of  alkaline  reaction  may  be  coagulated 
(sweet  whey) .  This  ferment  decomposes  the  casein  in  the  precipitated  cheese  and 
the  scanty  but  readily  soluble  whey-albumin.  The  lab-coagulation  is  then  quite 
different  from  the  others.  It  takes  place  only  when  calcium-salts  are  dissolved 
in  the  milk.  If  these  are  precipitated  by  means  of  potassium  oxalate,  the  lab- 
ferment  no  longer  causes  coagulation  in  the  fluid;  this  latter,  however,  occurs 
again  as  soon  as  calcium  chlorid  is  added. 

Boiling  (by  destroying  lower  organisms) ,  sodium  bicarbonate  (TVo  o) »  ammonia, 
salicylic  acid  GfiW),  also  glycerin  and  ethereal  oil  of  mustard,  prevent  spontaneous 
coagulation.  Fresh  milk  renders  tincture  of  guaiac  blue;  boiled  milk  does  not. 
After  standing  for  some  time  in  the  air  milk  gives  off  carbon  dioxid  and  absorbs 


MILK    AND    MILK-PREPARATIONS.  421 

oxygen.  At  the  same  time,  as  a  result  of  the  activity  of  germs  that  develop 
rapidly  in  the  milk(?),  an  increase  of  the  fat,  together  with  that  of  the  alcoholic 
and  ethereal  extracts  at  the  expense  of  the  casein,  is  brought  about.  Accord- 
ing to  Schmidt-Mulheim  some  casein  is  transformed  into  peptone  but  onlv  in 
unboiled  milk. 

Milk-analysis. — Every  100  parts  of  milk  contain: 

HUMAN.  Cow.  GOAT.  Ass. 

Water 88.3  88.0  86.25  89.01 

Casein 0.9-1.2  \  3.0            2.53  ) 

Albumin 0.3-0.5  f  I'1  03             i  26  /  3>s? 

jitter    3-21  3-5  4-34  1.85 

Milk-sugar 4.67  4.c  *  78  1 

Salts   0.2  0.7  0.65}  5-05 

Colostrum  contains  much  serum-albumin  and  little  casein,  but,  on  the  other 
hand,  all  other  solid  substances  in  larger  amount,  especially  the  butter. 

Pfliiger  and  Setschenow  found  in  100  volumes  of  milk  the  following  substances 
by  volume:  carbon  dioxid  from  5.01  to  7.60;  oxygen  from  0.09  to  0.32;  nitrogen 
from  0.70  to  1.41.  The  carbon  dioxid  can  in  part  be  displaced  only  by  means 
of  phosphoric  acid. 

Among  the  salts,  those  of  potassium  preponderate  over  those  of  sodium  (as 
in  the  red  blood-corpuscles  and  in  meat) ;  also  a  considerable  amount  of  calcium 
phosphate  is  present,  for  the  formation  of  the  bones  of  the  infant.  Wildenstein 
found  in  100  parts  of  ash  from  human  milk  sodium  chlorid  10.73;  potassium 
chlorid  26.33,  potassium  21.44,  calcium  18.78,  magnesium  0.87,  phosphoric  acid  19, 
ferric  phosphate  0.21,  sulphuric  acid  2.64,  silica  a  trace.  The  amount  of  salts  is 
influenced  by  that  in  the  food. 

Milk  exhibits  no  difference  in  the  amount  of  albumin  before  and  after  nursing. 
The  amount  of  sugar,  however,  diminishes  after  nursing,  while  the  fat  increases  con- 
siderably. With  the  progress  of  lactation,  albumin  appears  most  abundantly 
in  the  first  six  months,  in  lesser  amount  in  the  second  six  months,  and  after  the 
first  year  it  decreases  still  more.  The  amount  of  fat  varies,  but  rather  increases 
after  the  first  year.  The  sugar  exhibits  a  pretty  uniform,  inconsiderable  increase. 
In  primiparae  the  amount  of  solid  constituents  (9.67  per  cent.)  is  greater  than  in 
multipart  (8.56  per  cent.).  Young  mothers  form  more  albumin  and  fat,  older 
mothers  more  sugar.  A  starchy  diet  yields  a  fatter  milk,  while  with  a  proteid 
and  fatty  diet  the  amount  of  albumin  and  of  sugar  increases.  Camerer  and 
Spldner  found  in  milk  a  body  resembling  the  basis  of  bone,  together  with 
hitherto  unknown  bodies  consisting  of  carbohydrates  combined  with  proteids. 

If  it  be  necessary  to  employ  the  milk  of  animals,  it  should  be  noted  that  cow's 
milk  (best  when  containing  much  fat)  must  be  diluted  with  water  and  mixed  with 
milk-sugar.  Heubner  and  Hofmann  recommend  for  children  from  one  to  nine 
months  old,  as  a  general  rule,  only  one  mixture,  consisting  of  i  part  of  cow's  milk 
and  i  part  of  a  solution  containing  69  grams  of  milk-sugar  in  i  liter  of  water. 
Soxhlet  recommends  a  mixture  of  2  parts  of  cow's  milk  and  i  part  of  a  12.3  per 
cent,  solution  of  milk-sugar.  The  casein  of  cow's  milk  varies  qualitatively; 
further,  it  appears  in  larger  flakes  and  is,  there  fore,  more  difficult  of  digestion  than 
the  small-flaked  casein  of  human  milk.  The  casein  of  human  milk  does  not  split 
off  paranuclein  in  the  process  of  digestion,  as  does  that  of  cow's  milk.  Boiled  cow's 
milk  is  somewhat  more  difficult  of  digestion  than  unboiled  cow's  milk,  but,  never- 
theless, because  sterilized,  is  to  be  preferred.  The  milk  should  be  boiled  for  ten 
minutes,  be  cooled  quickly  to  below  18°  C.  and  be  kept  cool.  In  the  case  of  chil- 
dren more  than  nine  months  old,  the  addition  of  water  is  progressively  diminished. 
Cow's  milk  may  also  be  diluted  with  advantage  with  beef-tea.  For  children  that 
cannot  take  milk,  v.  Liebig  has  recommended  especial  soups  prepared  from  cow's 
milk,  water,  wheat-flour,  hop-flour  and  sodium  bicarbonate.  The  starch  is  trans- 
formed, in  the  course  of  preparation,  into  sugar  and  dextrin.  The  more  rapid 
the  growth  exhibited  by  mammals  the  richer  is  their  milk  in  albumin. 

Milk-tests. — The  amount  of  cream  is  measured  by  permitting  the  milk  to  stand 
for  twenty-four  hours  in  a  cool  place  in  a  high  glass  cylinder  graduated  into  100 
parts.  The  cream  that  collects  on  the  surface  should  amount  to  from  10  to  14 
volumes  per  cent.  The  specific  gravity  of  whole  cow's  milk  is  between  1029  and 
1034,  of  skimmed  milk  between  1032  and  1040.  It  is  determined  by  means  of 
the  areometer  at  a  temperature  of  15°  C.  Every  degree  Celsius  more  or  less 
makes  a  difference  of -0.1°  or  +  0.2°  on  the  areometer.  Should  only  an  approximative 


422  MILK    AND    MILK-PREPARATIONS. 

estimation  be  desired,  the  amount  of  sugar  both  in  the  whey  as  well  as  in  the  whole 
milk  diluted  with  water  can  be  titrated  directly  by  means  of  Fehling's  solution 
(i  cu.  cm.  of  which  corresponds  to  0.0067  gram  of  milk-sugar) ;  or  the  amount 
in  the  whey  may  be  determined  by  means  of  the  polarization-apparatus.  If  the 
estimation  is  to  be  made  with  exactness,  the  proteid  must  be  removed  from  the 
whey;  and  in  addition  the  fat-globules  dissolved  out  of  the  whole  milk,  and  the 
fat  extracted.  The  amount  of  water,  as  compared  with  the  amount  of  milk-cor- 
puscles (fat) — the  latter  should  not  be  less  than  3  per  cent,  in  whole  milk,  and 
i$  per  cent,  in  half-skimmed  milk— is  determined  by  means  of  the  lactoscope  (the 
diaphanometer  of  Donne,  modified  by  Vogel  and  Hoppe-Seyler) .  This  consists  of 
a  glass  vessel  i  cm.  in  diameter  with  plane  parallel  walls.  A  measured  quantity  of 
milk  is  introduced  into  the  vessel  and  water  added  from  a  graduate  until  the  flame 
of  a  lighted  candle  placed  about  a  meter  behind  the  apparatus  can  be  distinctly 
seen  outlined  (in  a  dark  room)  with  the  eye  placed  directly  in  front  of  the  appara- 
tus. In  such  an  experiment  from  70  to  85  cu.  cm.  of  water  are  needed  for  each 
cubic  centimeter  of  good  cow's  milk.  Feser's  galactoscope  also  is  serviceable  in 
the  examination  of  milk,  even  in  the  hands  of  the  laity. 

The  following  substances  pass  into  the  milk:  fat  taken  with  the  food, 
numerous  odorous  substances  (anise,  vermouth,  garlic,  etc.) ;  chloral  hydrate, 
opium,  indigo,  salicylic  acid,  iodin,  iron,  zinc,  mercury,  lead,  bismuth  and  anti- 
mony. In  cases  of  osteomalacia  the  amount  of  calcium  in  the  milk  is  increased. 
Potassium  iodid  diminishes  the  secretion  of  milk. 

Abnormal  admixtures  include  hemoglobin,  biliary  pigments,  mucin,  blood- 
corpuscles,  pus,  fibrinous  clots,  tubercle-bacilli  and  other  bacilli.  Numerous 
germs  develop  in  evacuated  milk,  of  which  the  bacillus  cyanogenus,  which  occurs 
rarely,  gives  the  milk  a  sky-blue  color.  It  is  the  milk-serum  that  is  blue,  not 
the  germ.  There  are  also  schizomycetes  that  produce  bluish-black  and  green 
colors.  Red  and  yellow  milk  are  also  observed  as  a  result  of  similar  action  by  other 
chromogenic  schizomycetes.  Red  milk  is  due  to  the  notorious  micrococcus 
prodigiosus,  which  is  itself  colorless,  and  also  to  the  bacterium  erythrogenes ; 
yellow  milk,  to  the  bacillus  synxanthus.  Some  of  the  pigments  formed  seem  to 
be  related  to  the  aniline  dyes  and  others  to  those  belonging  to  the  phenol-group. 
As  the  possibility  of  the  entrance  also  of  other  pathogenic  germs  cannot  be  ex- 
cluded, the  milk  should  be  sterilized  by  boiling. 

The  rennet-like  activity  of  bacteria  is  widespread,  so  that  they  coagulate 
and  peptonize  casein  and  finally  cause  further  decompositions.  Thus  the  butyric- 
acid  bacilli  first  cause  the  coagulation  of  the  casein,  which  they  then  peptonize 
and  later  decompose,  with  the  development  of  ammonia.  Milk  becomes  viscous 
from  the  action  of  the  bacillus  lactis  viscosus,  perhaps  in  other  ways,  just  as  beer 
and  wine  may  become  "long." 

Preparations  of  Milk. — i.  Condensed  Milk.  Eighty  grams  of  cane-sugar  are 
added  to  each  liter  of  milk,  the  mixture  evaporated  to  one-fifth  its  volume  and 
then  sealed  in  tin  cans  while  hot.  For  the  use  of  nursing  infants  a  teaspoonful 
is  dissolved  in  a  pint  of  cold  water  and  then  boiled. 

2.  As  a  food  replacing  albumin  A.  Salkowski  recommends  the  following  prep- 
aration of  casein:    Casein  20  parts,  sodium  phosphate  2  parts,  water  200  parts, 
or    the    soluble    ammonia-compound    prepared    by  conducting    ammonia    over 
casein  (eucasin) ;    Rohmann  advises  acid  casein-calcium  3  grams,  milk-sugar  4.5 
grams,  di-sodium  phosphate  0.375  gram,  monopotassium  phosphate  0.153  gram, 
calcium  chlorid  0.04  gram,  potassium  chlorid  0.3  gram,  magnesium  acetate  o.oi 
gram,  water  100  grams. 

3.  Koumiss  and  Kefyr.     The  Kirghese  are  accustomed  to  produce  alcoholic 
fermentation  in  mare's  milk,  and  the  Caucasian  mountaineers  do  the  same  with 
cow's  milk.     As  a  result  of  the  addition  of  sour  milk,  which  contains  the  bacterium 
lacticum  and  the  bacillus  caucasicus,  the  unfermentable  milk-sugar  is  transformed 
into  fermentable  glucose,  and  by  the  action  of  yeast,  which  is  present  in  an  ad- 
dition of  completed  koumiss,  alcoholic  fermentation  of  the  glucose  takes  place, 
the  mixture  being  vigorously  stirred.     Koumiss  contains  from  two  to  three  per 
cent,  of  alcohol.     The  casein,  which  is  precipitated  at  first  and  later  is  partly 
dissolved  again,  is  transformed  into  acid-albumin  and  peptone.     The  kefyr-fungus 
(dispora  caucasica)    also  gives  rise  to  a  similar  preparation,  in  part  containing 
peptones.     In   addition  to  the  kefyr-fungus,  there  is  also  found  the  bacterium 
lacticum  and  a  schizomycete  that  peptonizes  casein,  as  well  as  a  streptococcus 
that  forms  lactic  acid  and  another  organism  that  ferments  milk-sugar.     Koumiss 
and  kefyr  are  also  prepared  at  some  health-resorts. 

4.  Cheese  is  prepared  by  coagulating  skim-milk  (poor  cheese),  or  whole  milk 


EGGS.  423 

(fat  cheese),  by  means  of  rennet,  permitting  the  whey  to  run  off  and  well  salting 
the  coagulated  mass.  After  some  time  the  cheese  ripens,  the  casein,  probably 
with  the  formation  of  sodium  albuminate,  becoming  soluble  in  water  once  more. 
In  some  kinds  of  cheese  liquefaction  occurs,  with  the  formation  of  peptone  and 
diastatic  ferment  as  a  result  of  the  action  of  the  cheese-spirillum  (spirillum 
tyrogenum).  On  further  decomposition,  leucin  and  tyrosin  appear.  The  amount 
of  fat  in  the  cheese  increases,  while  that  of  casein  diminishes.  Later  on,  the  fats 
decompose;  the  volatile  fatty  acids  yield  the  characteristic  odor.  The  formation 
of  peptone,  leucin,  and  tyrosin  and  the  splitting  up  of  the  fats  suggest  the 
digestive  processes.  Cheese  contains  also  saprophytic  microbes. 

EGGS. 

Eggs  also  must  be  looked  upon  as  a  complete  food,  as  the  organism 
of  the  young  bird  is  capable  of  developing  from  them.  The  yolk  contains, 
as  the  characteristic  albuminous  body,  vitellin;  also  an  albuminate  in  the 
capsules  of  the  yellow  yolk-globules,  the  egg-casein,  which  is  precipitated 
by  means  of  a  one  per  cent,  solution  of  sodium  chlorid,  on  combining 
with  oxygen;  nuclein  from  the  white  yolk;  fats  in  the  yellow  yolk 
(palmitin  and  olein) ;  cholesterin,  much  lecithin,  and,  as  a  product  of 
decomposition,  glycerophosphoric  acid,  grape-sugar;  pigments  (lutein), 
including  one  containing  iron  and  related  to  hemoglobin;  finally  salts, 
qualitatively  as  in  the  blood,  quantitatively  as  in  the  blood-corpuscles; 
gases. 

The  white  of  the  egg  contains  egg-albumin  as  the  principal  con- 
stituent, in  addition  to  some  globulin,  mucin-matter  and  albumose,  also 
small  amounts  of  palmitin  and  olein,  partly  saponified  by  sodium;  grape- 
sugar  ;  extractives ;  finally  salts  that  resemble  qualitatively  those  of  the 
blood  and  quantitatively  those  of  the  serum.  There  are,  besides,  traces 
of  fluorin.  On  a  diet  of  eggs  and  also  on  a  diet  of  roast  meat,  relatively 
more  of  the  nitrogenous  constituents  are  absorbed  than  of  the  fats. 

MEAT  AND   MEAT-PREPARATIONS. 

In  the  form  in  which  it  is  consumed,  meat  contains,  in  addition  to 
the  proper  muscular  tissue,  an  admixture  in  greater  or  lesser  amount  of 
the  elements  of  fatty,  connective  and  elastic  tissues.  Beef  freed  from  fat 
and  dried  contains,  according  to  Argutinsky,  carbon  49.6,  nitrogen  15.3, 
hydrogen  6.9,  ash  5.2,  oxygen  and  sulphur  23  per  cent.  According  to  H. 
Schulz  the  amount  of  sulphur  present  is  i.i  per  cent,  of  the  dried  muscle. 
The  chemistry  of  muscle  is  fully  discussed  on  p.  548.  The  proteids  of 
muscle  are  contained  in  the  contractile  substance  and  in  part  in  the 
saturating  fluid.  The  fats  are  derived  for  the  greater  part  from  the 
inter-fibrillary  fat-cells,  the  lecithin  and  cholesterin  chiefly  from  the 
muscle-nerves.  The  gelatin-yielding  substance  is  supplied  by  the  con- 
nective-tissue fibers  of  theperimysium,  the  perineurium,  the  vessel- walls 
and  the  tendinous  parts.  The  red  coloring-matter,  which  is  present  in 
varying  amount  even  in  the  muscles  of  the  same  animal  (red  muscles 
and  white  muscles),  is  hemoglobin.  In  addition,  some  muscles,  for 
example  the  heart,  contain  the  related  substance,  myohematin.  Elastin 
is  present  in  the  sarcolemma,  the  neurilemma  and  the  elastic  fibers  of 
the  perimysium  and  the  vessel- walls.  Keratin,  in  small  amount,  is  de- 
rived from  the  endothelium  of  the  vessels.  The  following  are  to  be  con- 
sidered as  end-products  of  the  retrogressive  metamorphosis  of  the  muscle- 
substance  proper,  in  which  also  they  occur  in  greatest  amount:  k;reatin 


424 


MEAT    AND    MEAT-PREPARATIONS. 


25  per  cent.,  kreatinin,  sarcin,  xanthin  (especially  in  fasting  pigeons), 
carnin  (oxidizable  into  xanthin,  present  in  meat-extract),  uric  acid 
(urea  o.oi  per  cent.).  There  are  present  further  inosite  (abundant  in 
the  muscles  of  alcoholics),  inosinic  acid  (inconstant),  phospho-carnic 
acid,  resembling  nuclein  and  decomposing  into  carnic  acid  (C10N3O5H15), 
and'  a  carbohydrate,  and  also  some  non-coagulable  albumin,  taurin 
(especially  in  cold-blooded  animals),  some  grape-sugar,  glycogen  (0.43 
per  cent.)  abundantly  in  fetal  muscles.  Further,  meat  contains  lactic 
acids  together  with  volatile  fatty  acids.  Among  the  salts  the  potassium- 
compounds  with  phosphoric  acid  predominate;  magnesium  phosphate 
predominates  over  calcium  phosphate. 

According  to  Schlossberger  and  v.  Bibra  100  parts  of  meat  contain 
the  following: 


Ox. 

CALF. 

DEER. 

PIG. 

MAN. 

CHICKEN. 

CARP. 

FROG. 

Water  
Solids  
Soluble      albu-  ] 

77-5° 
22.50 

78.20 
21.80 

74.63 
25-37 

78.30 
21.70 

74-45 
25-55 

77-30 
22.70 

79.78 

20.22 

80.43 
*9>S7 

min   .                ! 

Coloring-  mat-  f 

2.  2O 

2.6o 

1.94 

2.40 

*-93 

3-° 

2-35 

1.86 

ter.    .......  J 

Glutin  

I.  3O 

1.  60 

o  ^o 

0.80 

o    A  *T 

i  .  20 

1.98 

2    A8 

Alcoholic  extract 

*  '  O 

1.50 

1.40 

W'OW 

4.75 

1.70 

^.U/ 

3-71 

1.40 

3-47 

4  .q.0 

3.46 

Fats 

I    3O 

o    o  n 

i  ii 

O   I  O 

Insoluble      albu- 

*«JV 

2.30 

min,      vessels, 

etc  

17    CQ 

16.  20 

16.81 

16.81 

T  C?     £  A 

1  6  ^o 

T  T     2  T 

II    67 

/  *DW 

-1  JO4 

1  x  •6i 

zoo  parts  of  meat-ash  contain  the  following: 


HORSE. 

Ox. 

CALF. 

PIG. 

Potassium  carbonate  
Sodium. 

39-40 
4  86 

35-94 

34.40 

37-79 

Magnesium 

3  88 

•35 

4  81 

Calcium  
Potassium  

i.  80 

•o1 
i-73 
e.  e.6 

x-4o 

1.99 

7-54 

Sodium  ) 
Chlorin  f 
Iron  oxid  
Phosphoric  acid 

1.47 

1.  00 
4.6   1  A. 

oou 

4.86  j 
0.98 

10.59 
0.27 

A&    I? 

0.40 
0.62 
0-35 

Sulphuric  acid.  .  .  . 

O    3O 

o4-3u 

44-47 

Silicic  acid  
Carbon  dioxid 

•61 

2.07 

Q       fNrt 

0.81 

Ammonia 

*   " 

*  * 

0.15 

Potassium  and  sodium  may  partially  replace  each  other.  The  flesh  of  the 
pike  contains  almost  twenty  times  as  much  calcium  as  does  beef. 

The  amount  of  fat  in  meat  is  exceedingly  variable  in  accordance  with  the 
state  of  nutrition  of  the  animal.  In  100  parts  of  human  flesh,  after  the  visible 
fat  has  been  cut  away,  it  is  from  7  to  15;  in  beef  from  11  to  12;  in  veal  10.4;  in 
mutton  3.90;  in  wild  goose  8.80;  in  chicken  2.50. 

The  amount  of  extractives  is  most  abundant  in  the  flesh  of  those  animals 
that  exhibit  vigorous  muscular  activity,  therefore  especially  in  game.  After 
severe  muscular  exertion  the  extractives  increase,  and  at  the  same  time  sarco- 
lactic  acid  is  formed,  the  meat  as  a  result  becoming  tender  and  more  pleasant 


MEAT    AND    MEAT-PREPARATIONS.  425 

to  the  taste.  Among  the  extractives  there  are  some  that  have  a  stimulating 
influence  on  the  nervous  system,  such  as  kreatin,  kreatinin,  etc.,  and  some  that 
give  to  the  flesh  the  pleasant  characteristic  taste  (osmazome).  The  latter  is 
due  in  part  also  to  the  various  fats  in  the  meat,  and  at  times  it  appears 
distinctly  only  on  preparation.  In  100  parts  of  meat  the  amount  of  extractives 
is  in  man  and  in  pigeons  3,  in  deer  and  in  ducks  4,  in  swallows  7. 

Preparation  of  Meat. — As  a  general  rule  the  flesh  of  younger  animals  is  more 
tender  and  more  easily  digested  than  that  of  older  animals,  because  the  sarcolemma. 
the  connective  tissue  and  the  elastic  constituents  are  less  tough.  Further,  after 
being  allowed  to  hang  for  a  while,  the  flesh  is  still  more  tender,  because  the  inosite 
is  converted  into  sarcolactic  acid,  the  glycogen  into  sugar,  and  the  latter  into 
lactic  acid,  so  that  the  constituents  of  the  meat  undergo  a  sort  of  maceration. 
Meat  is  further  always  more  easily  attacked  by  the  digestive  juices  when  in  a 
finely  divided  state  than  when  in  large  pieces;  and,  finally,  it  should  be  noted  that 
adequately  boiled,  steamed,  broiled  or  roasted  meat  is  easily  digestible,  although 
not  so  rapidly  as  raw  meat.  In  the  preparation  the  heat  should  not  be  too  in- 
tense or  too  long  continued,  because  in  such  an  event  the  muscle-fibers  become 
hard  and  much  shrunken.  On  the  other  hand,  those  pieces  of  meat  that  are 
heated  to  about  60°  or  70°  C.,  such  as  the  pieces  from  the  middle  of  a  large  roast 
that  yet  have  a  rosy  but  not  bloody  appearance,  are  most  easily  digested,  as  this 
temperature  is  quite  sufficient  with  the  aid  of  the  acid  in  the  meat  to  transform 
the  connective  tissue  into  gelatin. 

Thus,  the  meat  falls  apart  and  the  separate  fibers  are  readily  isolated  in  the 
stomach.  To  obtain  a  piece  of  good,  readily  digestible  meat,  a  large  cubical 
block  is  taken  and  its  surface  is  suddenly  exposed  to  strong  heat  by  frying  in  fat 
or  immersion  in  boiling  water.  In  this  manner  a  firmly  coagulated  layer  of  albumin 
forms  on  the  surface,  which  no  longer  allows  the  juices  of  the  meat  to  escape 
from  the  interior.  The  reddish,  juicy  parts  from  the  interior  of  a  piece  of  meat 
thus  prepared  are  the  most  nutritious  and  the  most  readily  digested,  while  the 
hard  and  much  shrunken  outer  crust  resists  the  digestive  juices  for  some  time. 

Meat-broth  is  most  suitably  prepared  by  permitting  thoroughly  chopped 
meat  to  stand  for  some  hours  in  cold  water  and  then  boiling,  v.  Liebig  found 
that  out  of  100  parts  of  chopped  beef  thus  treated,  but  6  parts  pass  over  into 
the  cold  water.  Of  these,  2.95  parts  are  again  precipitated  as  coagulated  albumin 
and  for  the  greater  part  skimmed  off  and  thrown  away,  so  that  only  3.05  parts 
remain  dissolved.  Of  100  parts  of  chicken  8  parts  are  extracted,  of  which  4.7 
are  coagulated  and  3.3  parts  dissolved  in  the  broth.  By  protracted  boiling  a 
part  of  the  coagulated  albumin  may  again  pass  into  solution.  The  dissolved 
substances  are:  i.  Inorganic  salts  of  the  meat,  of  which  82.27  Per  cent,  pass  over 
into  the  broth.  The  boiled-out  meat  retains  principally  the  earthy  phosphates. 
2.  Kreatin,  kreatinin,  lactates  and  inosinates,  which  give  to  the  meat-broth  its 
stimulating  and  nerve-strengthening  power,  as  well  as  a  small  amount  of  extract- 
ives of  pleasant  taste  and  some  glycogen.  3.  Gelatin,  which  is  obtained  in  consid- 
erable amount  from  the  flesh  of  younger  animals. 

In  accordance  with  the  facts  and  figures  presented,  meat -broth  is  thus  to 
be  considered  really  as  merely  a  highly  valuable  stimulant,  acting  as  a  re- 
storative to  the  muscles,  but  not  as  a  food  in  the  ordinary  sense  of  the  word, 
for  the  constituents  of  the  meat-extract  and  the  kreatin  leave  the  body  in  the 
urine  in  a  practically  unchanged  condition.  From  larger  pieces  of  meat  cooked 
in  the  broth  even  fewer  constituents  are  obtained.  Such  cooked-out  meat  ac- 
cordingly, provided  it  is  not  much  shrunken  by  excessive  boiling  and  therefore 
rendered  difficult  of  digestion,  possesses  a  high  nutritive  value,  which  is  usually 
underestimated  by  the  laity.  On  the  other  hand,  the  preparation  of  meat-broth 
at  home  is  a  real  luxury,  its  so-called  strength  in  the  sense  of  the  laity  being 
a  pure  illusion. 

J.  v.  Liebig' s  Meat-extract  is  a  fat-free  meat-broth  containing,  however,  some 
gelatin  and  glycogen,  and  also  about  30  per  cent,  of  albumoses  and  peptone.  It 
is  prepared  from  finely  chopped  beef  or  mutton,  in  parts  of  South  America  and 
Australia  where  beef  is  plentiful,  and  is  evaporated  in  wide  dishes  on  a  water- 
bath  to  the  consistency  of  an  extract.  By  solution  in  water  a  cheap  meat-broth 
can  thus  be  readily  obtained:  i  kilogram  of  beef  yields  31  grams..  By  boiling 
the  solution  with  bones  (gelatin),  some  beef-fat,  pot-herbs  and  addition  of  salt 
a  beverage  completely  replacing  fresh  broth  is  obtained.  The  so-called  "bouillon- 
tablets"  on  sale  consist  almost  entirely  of  desiccated  gelatin,  which  is  obtained 
to  the  extent  of  about  28  per  cent,  from  bones  boiled  in  Papin's  pots  under  high 
pressure.  These  alone,  when  dissolved  in  hot  water,  naturally  cannot  replace 


426  VEGETABLE    FOODS. 

meat-broth;  they  can,  however,  be  advantageously  employed  in  conjunction 
with  v.  Liebig's  meat-extract.  In  boiling,  meat  loses  weight,  principally  through 
loss  of  water,  as  follows:  beef  15  per  cent.,  mutton  _io  per  cent.,  chicken  13.5 
per  cent.  In  roasting  the  same  kinds  of  meat  the  loss  is  respectively  19  per  cent., 
24  per  cent.,  24  per  cent. 

J.  v.  Liebig's  " Infusum  carnis  jrigide  paratum"  is  prepared  by  mixing  finely 
chopped  meat  with  i  :  1000  hydrochloric  acid  (3  cu.  cm.  of  fuming  hydrochloric 
acid  to  1000  cu.  cm.  of  water),  stirring  frequently  and  expressing  after  some 
hours.  The  almost  tasteless  fluid,  which,  in  addition  to  the  constituents  of 
the  broth,  is  also  rich  in  albumin,  is  often  useful  in  cases  with  enfeeble  digestion. 
Albumin  is,  however,  precipitated  by  the  addition  of  sodium  chlorid  or  by 
boiling.  Leube  and  J.  Rosenthal  reduced  such  a  mixture  of  hydrochloric  acid 
and  meat  to  a  gelatinous  spongy  condition  (containing  but  little  peptone)  by 
heating  under  high  pressure  in  hermetically  sealed  vessels.  The  meat-solution 
thus  obtained  is  employed  advantageously  in  cases  of  weak  stomach. 

Of  other  methods  of  preservation  there  are  yet  to  be  mentioned:  the  canning 
in  its  own  juices  of  meat  boiled  at  a  temperature  of  100°;  the  drying  of  fat-free 
meat  cut  into  long  narrow  strips  (the  pemmican  of  the  Indians) ;  dried,  powdered, 
salted  beef  (carne  pura).  C.  v.  Voit  discovered  that  the  nutritive  value  of 
meat  is  not  impaired  to  any  great  degree  in  the  process  of  pickling.  He  found  in 
pickled  meat,  in  addition  to  increase  in  sodium  chlorid,  a  loss  of  water  of  10.4 
per  cent.,  of  organic  matters  2.1  per  cent.,  of  albumin  i.i  per  cent.,  of  extractives 
13.5  per  cent.,  of  phosphoric  acid  8.5  per  cent.  The  practice  of  smoking  is  based 
upon  the  antiseptic  action  of  the  smoke. 

Poor  quality  and  decomposition  of  meat  may  result  from  the  development 
of  the  alkaloids  of  putrefaction  (ptomains) ,  as  well  as  from  the  action  of  bacteria. 
Such  a  condition  should  always  cause  rejection  of  the  meat.  Although  it  is  often 
enough  consumed  without  bad  result,  as  the  popularity  of  the  "haut  gout"  or 
"gamey  taste"  demonstrates.  At  least,  the  meat,  before  being  eaten,  should 
always  be  thoroughly  boiled.  The  decomposition  of  sausages  and  similarly  pre- 
pared meat  at  times  results  in  the  development  of  a  peculiar  and  even  fatal 
poison,  the  sausage-poison.  Occasionally  the  decomposition  of  meat,  particu- 
larly also  of  fish,  gives  rise  to  a  peculiar  actively  phosphorescent  light,  due  to 
the  development  of  lower  organisms.  The  use  of  such  meat,  however,  does 
not  seem  to  be  directly  injurious.  A  knowledge  of  the  occurrence  of  the  trichina 
spiralis  in  pork  is  highly  important;  also  of  bladder-worms  varying  in  size  from  a 
pea  to  a  bean  in  pork  and  beef,  the  development  of  which  into  tapeworms  is  dis- 
cussed under  Reproduction.  The  cysticercus  of  bothriocephalus  latus  is  found  in 
the  pike. 

VEGETABLE  FOODS. 

The  nitrogenous  constituents  of  plants  are  less  readily  absorbed  than  those 
of  animal  foods.  Nevertheless  the  former  may  completely  replace  the  animal 
proteids,  provided  they  contain  an  equal  amount  of  nitrogen.  Carbohydrates, 
starch  and  sugar  are  quite  completely  absorbed  and  even  some  cellulose  is  digested. 
The  greater  the  amount  of  fat  in  vegetable  food  the  less  the  carbohydrates  are 
digested  and  absorbed. 

Among  the  vegetable  articles  of  food  the  cereals  occupy  the  first  place.  They 
contain  proteids,  starch,  and  salts,  together  with  water  to  about  14  per  cent. 
The  nitrogenous  gluten  is  most  abundant  beneath  the  capsule,  so  that  the  use 
of  finely  ground  bran  in  coarse  bread  seems  plausible  for  good  digestive  organs; 
although  the  varieties  of  bread  that  contain  a  considerable  amount  of  bran  are 
digested  with  appreciably  greater  difficulty,  as  the  cellulose-membrane  of  the 
gluten-layer  is  scarcely  dissolved  in  the  process  of  digestion.  Rye-bread  is  assimi- 
lated with  greater  difficulty  than  wheat-bread.  For  commercial  bread  a  mixture 
of  both  kinds  of  flour  is  advisable.  Quantitative  composition: 

ioo  parts  of  dry  flour  contain:  100  parts  of  cereal  ash  contain: 

Albuminates.       Starch.  Red  Wheat.                                               White  Wheat. 

Wheat 16.52%     56.25%  27.87     Potassium  carbonate     33.84 

Rye 11.92         60.91  15-75                Sodium                  .... 

Barley 17.70         38.31  1.93                Calcium                   3.09 

Corn 13-65         77-74  9.60             Magnesium             13. 54 

Rice 7.40          86.21  1.36               Iron  oxid                 0.31 

Buckwheat    6.8-10.5     65.05  49-36         Phosphoric  acid         49.21 

0.15  Silica  .... 


VEGETABLE    FOODS. 


427 


It  is  remarkable  that  in  white  wheat  sodium  is  wanting  and  is  replaced  by 
other  alkalies.  Rye  contains  more  cellulose  and  dextrin  than  wheat,  but  less 
sugar.  Rye-bread  is,  as  a  rule,  less  porous.  Barley  and  oats  are  much  used  as 
gruel,  and  in  the  North  also  mixed  in  bread. 

Oats  contain  a  crystalline  globulin  (avenalin) ,  and  a  proteid  soluble  in  alcohol 
and  another  soluble  in  alkalies.  By  admixture  with  water  or  neutral  salts  three 
other  proteids  are  obtained  as  products  of  transformation.  Rye  and  wheat 
yield  one  globulin  (edestin) ;  one  albumin  (leukosin) ;  gliadin,  forming  gluten, 
and  soluble  in  dilute  alcohol;  and  glutenin  (absent  from  rye),  soluble  in  dilute 
acids  and  alkalies.  Barley  contains  leukosin,  edestin,  hordein,  corresponding  to 
gliadin,  and  also  other  proteids. 

In  the  preparation  of  bread,  flour  is  kneaded,  together  with  water,  to  form 
dough,  in  which  the  gluten  acts  as  a  cementing  substance,  and  to  which  salt  and 
also  yeast  (saccharomyces  cerevisiae)  are  added.  Under  the  influence  of  heat  the 
albuminates  of  the  flour  begin  to  undergo  decomposition  and  the  ferments  act 
upon  the  swollen  starch,  which  is  partially  transformed  into  sugar.  The  sugar 
undergoes  further  decomposition  into  carbon  dioxid  and  alcohol,  of  which  the 
first,  forming  bubbles  in  the  stiff  dough,  causes  this  to  become  spongy.  Certain 
bacteria  also  cooperate  with  the  yeast  to  the  same  end.  By  the  baking  at  200° 
C.  the  alcohol  is  driven  off  and  the  dough  is  done.  Much  readily  soluble  dextrin 
is  formed  in  the  crust .  In  the 
preparation  of  sour  bread,  old 
sour  dough,  in  which  the  sugar 
has  partially  undergone  lactic- 
acid  fermentation,  is  added 
instead  of  yeast,  and  as  a  re- 
sult, in  addition  to  the  alco- 
holic fermentation,  the  lactic- 
acid  fermentation  of  the 
grape-sugar  in  the  dough  is 
also  initiated.  As  in  the 
transformation  of  starch  into 
sugar,  and  the  latter  into  car- 
bon dioxid  and  alcohol 
(which  eventually  escape) , 
material  is  directly  lost;  am- 
monium carbonate,  which  es- 
capes during  the  process  of 
baking  with  the  expansion  of 
the  dough,  is  added.  This 
loss  amounts  to  about  one 
per  cent.;  with  an  average 
daily  consumption  of  bread 
for  each  individual  of  256 
grams,  the  daily  loss  for  1,000,000  persons  should  equal  2500  kilograms  of  bread, 
or  sufficient  for  10,000  persons.  J.  v.  Liebig  proposes  the  use  of  sodium  bicarbon- 
ate and  hydrochloric  acid  for  the  same  purpose ;  then  the  dough  will  not  have  to 
be  salted,  because  of  the  formation  of  sodium  chlorid.  Horsford's  baking-powder 
(calcium  phosphate  and  sodium  bicarbonate)  is  also  used.  It  permits  the  escape 
from  the  dough  of  the  expanding  carbon  dioxid,  the  phosphoric  acid  of  which  is 
also  useful  to  the  body. 

The  legumes  contain  much  albumin.  Beans  contain  two  globulins  readily 
soluble  in  salt-solutions — the  phaseolin  of  Ritthausen  and  phaselin.  Peas  and 
vetches  yield  in  considerable  amount  a  globulin,  designated  legumin  by  Braconnot, 
which  is  soluble  in  a  solution  of  sodium  chlorid,  and  also  three  other  proteids. 
Legumes  contain  also  starch,  lecithin,  and  cholesterin,  together  with  from  9  to 
19  per  cent,  of  water.  Peas  contain  28.02  per  cent,  of  albumin  and  38.81  of  starch; 
beans  28.54  and  37.50;  lentils  29.31  and  40  respectively.  The  last  are  richer  in 
cellulose.  Because  of  the  deficiency  in  gluten  no  dough  can  be  made  from  them, 
and  therefore  no  bread.  As  a  food  for  the  mass  of  the  people,  these  plants  deserve 
the  greatest  consideration,  because  of  the  large  amount  of  albumin  they  contain, 
although  they  may  be  a  source  of  intestinal  discomfort  in  consequence  of  the  devel- 
opment of  gas,  as  well  as  of  the  presence  of  indigestible  cellulose.  Leguminous 
flour,  when  mixed  in  different  proportions  with  the  flour  of  cereals  (for  instance 
in  the  form  of  Hartenstein's  leguminose) ,  can  be  used  with  advantage  in  the  feed- 
ing of  children  and  debilitated  persons. 


FIG.  138. — Section  through  a  Grain  of  Wheat:  p,  epidermis,  with 
c,  cuticula,  m  middle  layer,  qu  transverse,  sch  tubular  cells,  br 
and  n  seed-membrane,  Kl  gluten,  /  starch. 


428 


CONDIMENTS. 


Maize  contains  three  globulins,  several  albumins,  and  a  proteid — zein — soluble 

in  alcohol. 

Potatoes  contain  from  70  to  81   per  cent,   of  water.     In  the  juicy  cellular 

tissue,  which  yields  an  acid  reaction  when  fresh,  from  the  presence  of  phos- 
phoric, malic  and  hydrochloric 
acids,  there  is  present  from  16 
to  23  per  cent,  of  starch,  2.5 
per  cent,  of  dissolved  prpteids, 
consisting  of  one  globulin  (tu- 
berin),  soluble  in  potato-juice, 
and  some  albumin,  together 
with  a  trace  of  asparagin. 
The  cell-capsules  become  swol- 
len when  boiled,  and  are 
changed  by  dilute  acids  into 
sugar  and  gum.  The  "eyes" 
contain  the  poisonous  sub- 
stance solanin.  One  hundred 
parts  of  potato-ash  contain: 
potassium  carbonate  46.96,  so- 
dium chlorid  2.41,  potassium 
chlorid  8.1 1,  magnesia  13.58, 
calcium  3.35,  phosphoric  acid 
11.91,  sulphuric  acid,  derived 
from  burned  albuminates,  6.50, 
silica  7.17. 

Fruits  contain  as  the  prin- 
cipal food-constituents  sugar 
and  salts.  Their  characteristic 
taste  is  due  to  the  organic  acids. 
The  gelatinizing  substance  of 
fruit-jellies  is  the  soluble  so- 
called  pectin  (CgjH^Og;;) ,  which 
can  also  be  obtained  artifici- 
ally by  cooking  from  the  pec- 
tose  of  unripe  fruit,  which 
is  soluble  with  difficulty,  and 
from  carrots. 
Green  vegetables  are  especially  rich  in  salts  that  resemble  the  salts  in  the  blood. 

For  instance,  unseasoned  lettuce  contains   23  per  cent,   of  salts,  spinach  much 

iron.     Of  less  importance  in  them  are  starch,  dextrin,  sugars  and  small  amounts 

of  albumin. 


FIG.  139. — Section  through  Potato:  k,  cork;  pi,  plasma-containing 
cells,  with  small  starch-granules;  cr,  protein  crystalloid;  s, 
starch. 


CONDIMENTS. 
COFFEE,  TEA,  CHOCOLATE,  ALCOHOLIC  DRINKS  AND  SPICES. 

Since  the  time  of  v.  Bibra  the  term  condiment  has  been  applied  to  such  articles 
of  food  as  are  used  less  because  of  their  direct  nutritive  properties,  than  because 
of  their  agreeable  action  and  stimulation,  in  part  upon  the  organs  of  taste  and  in 
part  also  upon  the  nervous  system.  Coffee,  tea  and  chocolate  are  prepared  as 
infusions  or  decoctions  of  the  familiar  vegetables.  They  contain  respectively 
an  active  constituent,  caffein  or  thein  (C8H10N4O2  +  H2O — trimethylxanthin) 
or  the  closely  related  theobromin  (C7H8N4O2 — dimethylxanthin) ,  which  are  classi- 
fied among  the  alkaloids,  or  vegetable  bases.  These  have  recently  been  prepared 
artificially  from  xanthin. 

These  alkaloids  and  similar  bodies  in  many  other  plants  are  present  in  the 
plants  preformed.  Their  behavior  is  similar  to  that  of  ammonia.  They  have 
an  alkaline  reaction  and  with  acids  form  crystalline,  well-defined  salts.  All 
of  these  vegetable  bases  affect  the  nervous  system,  some  feebly,  as  the  preceding, 
or  more  actively  stimulating,  as  quinin;  others  have  a  more  powerful  stimulating 
effect,  to  the  point  of  paralysis,  including  active  poisons,  such  as  morphin,  atropin, 
strychnin,  curarin,  nicotin,  etc. 

The  alkaloids  of  coffee,  tea  and  chocolate  confer  upon  the  infusions  of  these 
substances  generally  used  as  popular  beverages  the  pleasantly  stimulating  effect 
upon  the  nervous  system,  refreshing  the  mind,  animating  movement  and  stimu- 


CONDIMENTS. 


429 


lating  to  increased  activity.  In  this  respect  they  resemble  the  stimulating 
extractives  of  beef-broth.  Coffee  contains  about  £  per  cent,  of  caffein,  which  is 
partially  first  set  free  in  the  process  of  roasting.  Tea  contains  6  per  cent,  of 
thein,  green  tea  also  i  per  cent,  of  ethereal  oil,  black  tea  \  per  cent.;  green  tea 
1 8  per  cent.,  black  tea  15  per  cent,  of  tannic  acid.  Green  tea  yields  on  the 
whole  about  46  per  cent.,  black  tea  scarcely  30  per  cent.,  of  extract. 

In  addition  the  inorganic  substances  in  these  beverages  are  to  be  considered, 
Tea  contains  3.03  per  cent,  of  salts,  including  considerable  amounts  of  soluble 
compound  of  iron  and  manganese,  which  are  important  in  the  formation  of 
hemoglobin! ,  and  also  sodium-salts.  In  coffee,  which  yields  3.41  per  cent, 
of  ash,  potassium  preponderates.  In  all  three  beverages,  however,  the  remaining 
inorganic  substances  that  are  found  in  the  blood  are  present  in  suitable  propor- 
tions. Cocoa  is  only  inadequately  utilized  as  a  nutritive  agent:  of  50  grams 
only  5  grams  of  albumin,  16  grams  of  fat  and  6  grams  of  starch. 

Alcoholic  beverages  owe  their  activity  primarily  to  the  alcohol  they  contain. 
With  regard  to  the  latter  the  following  is  to  be  noted:  i.  Alcohol  is  decomposed 
in  the  body,  principally  into  carbon  dioxid  and  water.  In  this  respect  it  does  not 
differ  essentially  from  other  articles  of  food,  and  it  is  thus  to  be  regarded  as 
a  source  of  heat.  As  alcohol  readily  undergoes  this  combustion  in  the  body, 
its  use  can,  therefore,  diminish  to  a  certain  degree  the  consumption  of  the  con- 
stituents of  the  body  itself.  It  has,  however,  been  shown  that  with  a  mixed 
diet  alcohol  is  not  capable  of  protecting  the  albumin  from  decomposition,  but 
solely  the  fat.  With  a  mixed  diet  alcohol  is  not  able  to  replace  any  of  the  carbo- 
hydrate of  the  food.  Only  from  i  to  2.5  per  cent,  of  the  alcohol  passes  over  into 
the  urine,  from  5  to  6  per  cent,  into  the  breath.  The  odor  of  the  breath  is  due, 
in  addition,  to  other  volatile  substances  in  the  alcoholic  beverage,  such  as  fusel-oil 
and  others.  Traces  pass  into  the  cutaneous  secretions.  2.  In  small  amounts 
alcohol  has  a  stimu- 
lating effect,  in  large 
doses,  through  over- 
stimulation,  a  para- 
lyzant  effect  upon  the 
nervous  system.  By 
means  of  this  stimu- 
lating effect  it  is 
therefore  capable  of 
spurring  the  body 
temporarily  to  greater 
functional  activity  for 
achievement,  at  the 
expense,  it  is  true,  of  a  subsequent  depression.  3.  When  taken  in  small  suitable 
doses  before  or  after  meals,  it  aids  the  digestion,  while  larger  doses  interfere  with 
digestion.  4.  It  diminishes  the  sensation  of  hunger.  5.  It  induces  more  active 
respiratory  movements,  and  stimulates  the  heart  and  the  vascular  system,  and 
thus  accelerates  the  circulation  of  bright-red  blood,  so  that  muscles  and  nerves 
become  more  capable  of  action.  It  also  causes  a  subjective  sensation  of  heat. 
In  a  larger  dose,  however,  it  paralyzes  the  vessels  by  overstimulation  and  they 
become  dilated,  for  example,  in  the  external  integument.  As  a  result  heat  is 
radiated  in  greater  degree  through  the  skin  than  it  is  generated  in  the  body,  and 
therefore  the  bodily  temperature  is  lowered.  Large  doses  also  diminish  the  activity 
of  the  heart  by  the  excitation  of  smaller,  weaker  and  more  rapid  beats.  In  ele- 
vated regions  the  power  of  alcohol  is  greatly  enfeebled,  as,  on  account  of  the  low 
atmospheric  pressure,  the  alcohol  is  rapidly  given  off  from  the  blood. 

From  the  foregoing  remarks  it  is  clear  that  alcohol,  when  taken  in  small 
amounts,  can  be  of  incalculable  benefit  in  conditions  of  temporary  privation  and 
want  of  food,  in  conjunction  with  which  resistance  to  fatigue  and  an  extraordinary 
amount  of  work  are  yet  required.  In  a  similar  manner  it  is  capable  of  protecting 
the  tissues  of  the  sick  from  too  rapid  consumption,  with  the  exception  of  the  al- 
bumin. When  taken  habitually,  however,  and  especially  in  large  amounts, 
it  causes  derangement  of  the  nervous  system  by  overstimulation,  and  undermines 
the  forces  of  mind  and  body,  partly  in  consequence  of  its  poisonous  properties, 
chiefly  due  to  its  volatile  constituents  (fusel-oil) ,  affecting  the  nervous  system 
permanently,  partly  through  its  direct  action  in  causing  injurious  catarrhal  and 
inflammatory  conditions  in  the  digestive  organs,  and  partly  finally  through  inter- 
ference with  and  impairment  of  the  normal  metabolism. 

Alcoholic  beverages  are  prepared  by  fermentation  of  the  sugar  obtained  from 


FIG.  140. — i,  Isolated  yeast-cells;  2,  3,  formation  of   buds;    4,  5,  endogenous 
cell-formation:  6,  germination  and  bud-formation. 


43°  METABOLIC    EQUILIBRIUM. 

various  carbohydrates,  especially  starch.  Alcoholic  fermentation  is  a  result 
of  the  vital  activity  of  a  low  order  of  fungus,  namely  the  yeast-fungus — the  sac- 
charomyces  cerevisiae  (in  the  fermentation  of  beer)  and  the  saccharomyces  ellip- 
soideus  (in  the  fermentation  of  wine),  the  fungus  removing  directly  from  the 
saccaharine  mixture  the  substances  necessary  for  its  existence,  namely  carbo- 
hydrates, albuminates  and  salts,  chiefly  calcium  phosphate,  potassium  phosphate 
and  magnesium  sulphate  and  causing  their  decomposition  into  alcohol  and  car- 
bon dioxid,  together  with  some  glycerin  (from  3.2  to  3.6  per  cent.)  and  succinic 
acid  (from  0.6  to  0.7  per  cent.)-  The  yeast-liquor  alone,  in  the  absence  of  yeast- 
cells,  also  causes  fermentation,  through  the  presence  of  a  ferment  known  as  zymase, 
which  acts  like  a  chemical  agent.  Yeast  belongs  to  the  budding  fungi,  which 
multiply  both  by  budding  and  by  sporulation  (ascospores) .  It  is  added  directly 
to  the  fluids  to  be  fermented,  or  its  spores,  which  constantly  float  about  in  the  air, 
fall  into  the  uncovered  mixture.  Perfect  exclusion  of  yeast-cells,  or  their  destruc- 
tion, as  by  boiling  the  syrup  in  sealed  vessels,  therefore,  prevents  the  occurrence 
of  fermentation.  Alcoholic  fermentation  is,  therefore,  a  result  of  the  vital  activity 
of  a  lower  form  of  organism. 

Wine  contains  on  an  average  from  89  to  90  per  cent,  of  water,  from  7  to  8 
per  cent,  of  alcohol,  together  with  the  ethyl-alcohol,  propyl-alcohol  and  butyl- 
alcohol.  The  color  of  red  wine  is  derived  from  the  skins  during  fermentation. 
If  the  skins  be  previously  removed  red  grapes  will  yield  whitish  wine.  The  fine 
taste  (flower,  bouquet)  develops  during  the  storing  of  the  wine.  Enanthic  ether 
is  said  to  give  rise  to  the  characteristic  odor  of  wine.  The  value  of  wine  depends 
upon  the  as  yet  unknown  stimulating,  volatile  substances  that  confer  upon  each 
wine  its  special  character.  Of  great  importance  are,  further,  the  salts,  which  in 
their  composition  resemble  those  of  the  blood. 

Beer  contains  from  75  to  95  per  cent,  of  water,  alcohol  from  2  to  5  per  cent, 
(porter  and  ale  as  much  as  8  per  cent.),  carbon  dioxid  from  o.i  to  0.8  per  cent., 
sugar  from  2  to  8  per  cent.,  gum,  dextrin  from  2  to  10  per  cent.,  cholin,  the  con- 
stituents of  hops,  some  residue  of  protein-substances  (gluten),  fat,  lactic  acid, 
ammonia-compounds,  the  salts  of  barley  and  of  hops. 

In  the  ash  the  enormous  amount  of  phosphoric  acid  and  potassium  carbon- 
ate, so  important  in  the  formation  of  blood,  is  noteworthy;  one  hundred  parts  of 
ash  contain  of  potassium  carbonate  40.8,  phosphorus  20,  magnesium  phosphate 
20,  calcium  phosphate  2.6,  silica  16.6  per  cent.  The  favorable  influence  of  beer 
on  the  formation  of  blood,  muscles  and  other  tissues  is  due  to  the  abundance  of 
phosphoric  acid  and  potassium  carbonate.  The  obesity  of  the  beer-drinker  de- 
pends chiefly  on  the  fat-sparing  action  of  the  alcohol.  The  potassium  carbonate 
present  in  beer  has  a  fatiguing  effect  after  heavy  drinking. 

Spices  are  not  consumed  because  of  their  nutritive  value,  but  in  part  on  account 
of  their  taste,  in  part  because  of  their  stimulating  effect,  through  which  they  arouse 
the  digestive  organs  to  increased  activity.  In  a  certain  sense  sodium  chlorid 
must  also  be  regarded  as  a  spice,  being  withheld  at  present  apparently  from  only 
a  few  savage  tribes.  A  similar  fact  was  recorded  by  Homer.  Also  certain  as 
yet  unknown  substances  that  have  a  marked  effect  on  the  organs  of  taste,  and 
that  develop  only  in  the  course  of  preparation  of  some  dishes,  as  in  the  crust 
of  a  roast,  and  in  the  crust  of  pastry,  may  be  included  among  spices. 


PHENOMENA  AND  LAWS  OF  METABOLISM. 

METABOLIC  EQUILIBRIUM. 

By  metabolic  equilibrium  is  understood  that  normal  condition  in 
which  precisely  the  same  amount  of  material  for  the  maintenance  and 
growth  of  the  organism  is  taken  up  and  assimilated  from  the  digested 
nourishment  as  is  removed  from  the  body  through  the  excretory  organs 
in  the  form  of  waste-materials  or  end-products  of  retrogressive  tissue- 
metamorphosis.  The  income  must  always  balance  the  expenditure. 
During  the  period  of  growth  of  the  body  a  certain  excess  of  formative 
activity  corresponding  to  the  increase  in  size  of  the  body  must  pre- 
dominate. Thus,  growing  portions  of  the  body  exhibit  from  2.5  to  6.3 


METABOLIC    EQUILIBRIUM.  431 

times  as  active  a  metabolism  as  parts  of  the  body  already  formed.  On 
the  other  hand,  in  the  years  of  senile  debility  a  certain  excess  of  bodily 
expenditure  is  to  be  considered  as  a  normal  phenomenon. 

Method. — The  normal  metabolic  equilibrium  in  the  organism  may  be  recog- 
nized: i.  By  determining  chemically  that  the  sum  of  all  the  egesta,  given  off  by 
the  body  within  a  certain  period  of  investigation,  corresponds  to  the  sum  of  the 
ingesta  furnished  by  the  food.  In  this  connection  the  amount  of  carbon,  nitrogen, 
hydrogen,  oxygen,  and  salts,  together  with  the  water  of  the  food  and  the  oxygen 
of  the  inspired  air,  must  be  equal  to  the  carbon,  nitrogen,  hydrogen,  oxygen,  the 
salts  and  the  water  in  the  excretions  (urine,  feces,  expired  air,  evaporated  water) 
of  the  organism.  2.  The  physiological  equilibrium  of  metabolism  may  further 
be  recognized  in  a  purely  empirical  way  from  the  fact  that  with  a  suitably  selected 
diet,  the  body  performing  its  ordinary  functions  is  able  to  maintain  its  normal 
weight.  Thus,  this  simple  procedure  of  weighing  makes  it  possible  for  the  phy- 
sician to  inform  himself  quickly  and  with  certainty  concerning  the  metabolism 
of  his  patient  or  convalescent.  The  tedious  method  of  elementary  metabolic 
analysis  was  first  successfully  undertaken  particularly  by  the  Munich  investi- 
gators, v.  Bischoff,  v.  Voit,  v.  Pettenkofer  and  others.  It  was  soon  apparent 
that  of  all  the  elements  the  greatest  importance  was  to  be  assigned  to  the  passage 
through  the  body  of  carbon  and  nitrogen. 

The  total  amount  of  carbon  taken  with  the  food  (which  is  ascertained  by 
elementary  analysis  of  a  sample  of  each  article  of  diet,  or  is  calculated  from  re- 
liable analyses  of  the  articles  of  food)  must,  in  complete  metabolic  equilibrium, 
correspond  to  the  carbon  in  the  carbon  dioxid  contained  in  the  expired  air  (90 
per  cent.)  from  the  lungs  and  the  skin.  To  this  there  should  also  be  added  the 
relatively  small  amount  of  carbon  in  the  organic  excrementitious  matters 
of  the  urine  and  the  feces  (10  per  cent.),  which  is  to  be  determined  by  ele- 
mentary analysis.  As  all  organic  food  and  all  the  constituents  of  the  body 
contain  carbon,  an  increased  loss  of  carbon  (as  compared  with  the  income)  in- 
dicates that  organic  matter  in  excess  is  being  decomposed  in  the  body;  on 
the  other  hand,  diminished  excretion  of  carbon  necessarily  indicates  an  ad- 
dition to  the  substance  of  the  body.  For  the  exact  determination  of  the  car- 
bon dioxid  in  the  expired  air  the  Munich  investigators  employed  v.  Petten- 
kofer's  respiratory  apparatus. 

With  regard  to  the  nitrogen,  which  should  be  determined  in  the  ingesta 
as  well  as  the  excreta  by  the  method  of  Kjeldahl,  it  was  found  that  almost 
all  the  nitrogen  of  the  ingested  food  is  excreted  again  in  the  urine  within  24 
hours,  principally  in  the  form  of  urea.  The  remaining  nitrogenous  urinary 
constituents  (uric  acid,  kreatinin,  etc.)  furnish  only  about  2  per  cent,  of  the 
nitrogenous  elimination.  In  addition,  the  nitrogen-content  of  the  feces  is 
to  be  taken  into  account  (from  4  to  5  per  cent,  in  dogs).  A  small  amount  of 
nitrogen  also  escapes  from  the  organism  in  the  expired  air;  also  a  portion  with 
the  desquamated  epidermal  structures  (about  50  mg.  of  hair  and  nails  daily) 
and  in  the  sweat. 

The  opinion  that  practically  all  the  nitrogen  ingested  with  the  food  is 
excreted  in  the  urine  and  the  feces  was  established  for  carnivora  by  v.  Voit 
and  Gruber;  for  ruminants  by  Henneberg,  Stohmann  and  Grouven,  and  for 
man  by  Ranke.  Contrary  to  this  view  a  number  of  the  older  as  well  as  more 
recent  investigators  have  made  the  assertion  that  the  total  amount  of  nitrogen 
cannot  be  recovered  from  the  excretions  mentioned,  but  that  an  appreciable 
nitrogen-deficit  exists. 

According  to  Leo  about  0.55  per  cent,  of  the  albumin  decomposed  in  the 
body  yields  its  nitrogen  (which  may  be  assumed  to  amount  to  15  per  cent.) 
in  the  gaseous  state.  In  making  exact  analyses  of  metabolism  this  gaseous 
excretion  of  nitrogen  must  naturally  be  taken  into  account. 

In  the  food  nitrogen  occurs  almost  exclusively  as  a  constituent  of  albu- 
minous substances.  In  the  excretions  it  indicates  decomposition  of  'the 
albuminous  constituents  of  the  body.  As  proteids  contain  on  the  average 
1 6  per  cent,  of  nitrogen  the  amount  of  albumin  corresponding  to  the  amount 
of  nitrogen  excreted  is  determined  by  multiplying  the  latter  figure  by  6.25. 
Nitrogenous  equilibrium  thus  indicates  that  the  albuminous  substances  in 
the  body  are  unchanged.  If  nitrogen  is  retained  gain  in  weight  takes  place, 
principally  in  the  form  of  muscle ;  if  there  is  an  excess  of  nitrogenous  excre- 
tion, consumption  of  the  albuminous  constituents  of  the  body  must  ensue. 


432  METABOLIC    EQUILIBRIUM. 

The  relative  amount  of  nitrogen  and  carbon  in  albumin  may  be  expressed 
as  i  :  3.3.  Of  the  amount  of  carbon  decomposed  in  the  process  of  metabolism 
there  are  3.3  parts  for  every  part  of  nitrogen  in  the  proteids  subjected  to  the 
process.  The  excess  is  to  be  attributed  to  the  decomposition  of  non-nitrogenous 
substances  (fats  or  carbohydrates). 

It  is  believed  that  the  greater  portion  of  the  'proteids  are  decomposed 
in  the  tissues  into  carbamic  acid,  which  is  then  transformed  in  large  amounts, 
in  the  liver,  into  urea. 

The  excretion  of  nitrogen  after  the  taking  of  food  is,  in  animals,  not 
uniform  from  hour  to  hour,  but  it  increases  rapidly  at  once,  reaches  its  maxi- 
mum after  5  or  6  hours  and  then  gradually  declines.  The  excretion  of  sulphur 
and  phosphorus  pursues  a  similar  course,  though  the  maximum  excretion,  on 
a  meat  diet,  occurs  as  early  as  the  fourth  hour.  On  addition  of  fat  to  a  meat- 
diet  the  excretion  of  nitrogen  and  of  sulphur  is  more  evenly  distributed  through- 
out the  hours  of  the  day.  In  human  beings  Rosemann  found  during  the  day 
an  increase  between  9  and  n  a.  m.,  as  a  result  of  breakfast  and  the  stimu- 
lation of  all  of  the  functions  in  the  morning;  a  second  increase  between  3  and 
4  p.  m.,  as  a  result  of  dinner;  a  third,  smaller  one  between  7  and  9  p.  m.,  fol- 
lowing supper;  and  a  final  increase  between  9  and  n  p.  m.  The  excretion 
diminishes  during  the  night. 

The  nitrogenous  constituents  of  the  body  become  poorer  in  carbon  as 
a  result  of  the  processes  of  metabolism,  but  richer  in  nitrogen  and  oxygen ; 
for  there  are,  in  the  albumins,  4  atoms  of  carbon  for  each  atom  of  nitrogen, 
in  gelatin  3^  atoms  of  carbon,  in  glycocoll  2  of  carbon,  in  kreatin  i^  of  carbon, 
in  uric  acid  i£  of  carbon,  in  allantoin  i  of  carbon,  in  urea,  finally,  only  \  atom 
of  carbon. 

The  oxygen  furnished  by  respiration  is  either  determined  directly  from 
the  reduction  in  its  amount  in  the  air  supplied  to  the  animal,  or  it  is  calculated 
from  other  data.  This  inspired  oxygen,  as  well  as  the  oxygen  of  the  food, 
makes  its  appearance  principally  in  the  form  of  carbon  dioxid  and  water; 
a  small  amount  leaves  the  body  in  the  excrementitious  products.  The  amount 
of  oxygen  absorbed  in  respiration  is  the  measure  of  the  entire  process  of 
combustion  in  the  body,  by  which  carbon  is  oxidized  into  carbon  dioxid  and 
hydrogen  into  water.  The  respiratory  quotient  indicates  the  amount  of 
inspired  oxygen  that  is  required  alone  for  the  combustion  of  the  carbon. 
If  the  volume  of  carbon  dioxid  produced  by  the  combustion  of  pure  carbon 
is  exactly  the  same  as  the  volume  of  oxygen  consumed  for  this  purpose,  the 
respiratory  quotient  is  i.  This  is  the  case  in  the  decomposition  of  carbo- 
hydrates. As  hydrogen  and  oxygen  are  present  in  these  compounds  in  the 
proportion  necessary  to  form  water  by  combustion,  practically  all  the  oxygen 
is  utilized  for  the  oxidation  of  the  carbon  of  the  carbohydrates.  For  albumin 
the  respiratory  quotient  is  0.8,  for,  on  a  purely  albuminous  diet,  only  800  cu. 
cm.  of  carbon  dioxid  are  excreted  for  every  1000  cu.  cm.  of  oxygen.  For 
fats  the  respiratory  quotient  is  0.7,  for,  on  a  diet  of  fat,  only  700  cu.  cm.  of 
carbon  dioxid  are  excreted  for  every  1000  cu.  cm.  of  oxygen  consumed.  Thus 
for  fats  and  albumin  the  respiratory  quotient  is  smaller  than  for  carbohydrates, 
the  volume  of  carbon  dioxid  excreted  is  less  than  that  of  oxygen  inspired, 
because  in  the  combustion  of  albumin  or  fat  a  part  of  the  oxygen  taken  up 
must  be  employed  for  the  oxidation  of  hydrogen  into  water. 

In  case  a  larger  volume  of  carbon  dioxid  is  excreted  than  the  amount  of 
oxygen  absorbed,  the  respiratory  quotient  rises  above  i.  This  happens 
if,  in  addition  to  the  inspired  oxygen,  a  portion  of  the  oxygen  from  the  con- 
stituents of  the  food  is  converted  into  carbon  dioxid  in  the  process  of  com- 
bustion in  the  body.  This  is  the  case,  for  example,  when  nutritive  materials 
rich  in  oxygen  (for  example,  carbohydrates)  are  transformed  in  the  body  into 
those  poor  in  oxygen  (for  example,  fats). 

The  respiratory  quotient  may  also,  under  certain  circumstances,  become 
even  smaller  than  it  is  after  an  exclusive  fat-diet,  if,  for  instance,  a  portion 
of  the  inspired  oxygen  is  employed  in  the  body  for  the  formation  and  deposi- 
tion in  the  tissues  of  compounds  rich  in  oxygen  (for  example,  in  the  formation 
of  glycogen) .  ^ 

The  respiratory  quotient  may,  however,  exhibit  certain  periodic  varia- 
tions independently  of  the  character  of  the  diet.  As  the  oxygen  taken  up 
is  not  always  used  in  the  formation  of  carbon  dioxid  immediately  upon  its 
entrance  into  the  body,  but  as  certain  intermediate  predecessors  of  carbon 
dioxid,  rich  in  oxygen,  may  accumulate  in  the  body  and  be  excreted  only 


NOURISHMENT    FOR    A    HEALTHY    ADULT.  433 

later  completely  oxidized  into  carbon  dioxid,  it  may  happen  that  during 
one  part  of  a  period  of  dieting  more  oxygen  may  be  taken  up  than  is  given 
off  as  carbon  dioxid. 

Hydrogen  leaves  the  body  principally  oxidized  into  water,  but  it  may 
also  leave  the  body  combined  with  organic  excreta.  The  water  is  given  off 
with  the  urine,  the  feces,  through  the  lungs  and  by  evaporation  from  the  skin. 
As  hydrogen  is  oxidized  into  water  the  amount  of  water  given  off  is  naturally 
greater  than  that  taken  up.  The  salts  are  excreted  in  various  ways,  the  most 
soluble  of  them  passing  out  with  the  urine,  a  few,  particularly  potassium-salts, 
and  those  that  are  soluble  with  difficulty,  with  the  feces,  and  some,  like  com- 
mon salt,  in  part  also  with  the  sweat.  The  salts  contained  in  the  ingesta 
and  excreta  are  estimated  by  weight  after  incineration. 

If  the  sulphur  and  the  phosphorus  are  to  be  estimated  separately  the 
amount  of  each  in  the  ingested  food  is  oxidized  by  combustion,  by  addition  of 
sodium  hydroxid  and  potassium  nitrate  into  sulphuric  and  phosphoric 
acids  respectively.  The  same  method  is  followed  for  their  estimation  in  the 
feces,  as  well  as  for  sulphur  in  the  epidermal  structures.  The  sulphuric  and 
phosphoric  acids  so  obtained,  as  well  also  as  the  sulphur  and  the  phosphorus 
excreted  in  the  urine  in  an  already  oxidized  form,  are  estimated  according  to 
the  method  described  on  p.  491.  The  sulphur  is  derived  principally  from 
the  albuminous  food;  about  half  of  it  is  excreted  with  the  urine  as  sulphuric 
acid,  half  with  the  feces  (as  taurin)  and  through  the  epidermal  structures. 

For  every  body,  there  is,  according  to  its  weight  and  activity,  a 
minimum  and  a  maximum  limit  of  metabolic  balance.  If  less  food  is 
supplied  than  is  necessary  for  the  first,  loss  of  body- weight  results.  If, 
on  the  other  hand,  an  excess  of  food  is  supplied,  any  amount  exceeding 
the  maximum  limit  will  be  passed  unabsorbed  as  superfluous  ballast 
with  the  feces,  provided  it  cannot  be  utilized  for  increase  of  flesh.  The 
more  the  body  gains  in  weight  on  a  generous  diet,  the  higher  the  mini- 
mum limit  rises.  With  marked  increase  of  flesh,  therefore,  the  necessary 
supply  of  food  must  be  relatively  much  greater  than  in  the  case  of  thin 
persons,  in  order  to  cause  a  like  increase  in  the  tissues  of  the  body. 
With  continued  increase  in  flesh  there  finally  results  a  condition  in  which 
the  digestive  organs  are  able  to  prepare  only  sufficient  material  for  the 
maintenance,  but  not  for  increase,  of  weight. 

QUALITY  AND  QUANTITY  OF    NOURISHMENT    FOR    A  HEALTHY  ADULT. 

The  question  as  to  the  substances  that  are  needed  by  man  for  his 
satisfactory  nourishment,  and  the  amount  required,  has  naturally  been 
answered  in  a  purely  empirical  way  by  observation  of  the  manner  of 
nourishment  of  healthy  individuals  at  different  ages  and  with  varying 
degrees  of  activity.  As,  for  example,  the  infant  flourishes  and  grows  on 
a  diet  of  milk,  milk  must  undoubtedly  include  in  its  composition  nutrient 
matter  qualitatively  and  quantitatively  appropriate. 

In  accordance  with  his  entire  organization  man  beldngs  to  the 
omnivora,  that  is,  to  the  class  of  beings  that  is  adapted  to  a  mixed  diet. 
He  possesses  the  canine  tooth  of  the  carnivora,  but  his  intestine  is 
shorter  than  that  of  the  herbivora. 

For  his  continued  existence  man  requires  the  following  four  principal 
nutritive  substances,  none  of  which  can  be  spared  from  the  diet  for  any 
length  of  time : 

i.  Water;  for  an  adult  from  2700  to  2800  grams  daily  in  food  and 
drink. 

Withdrawal  of  water  increases  the    disintegration  principally  of    the   albu- 
minous tissues.      If  thirsting  cats  are  kept  for  a  long  time  in  hot  air,  a  con- 
centration of  the   blood   becomes  manifest,  which,  through   chemical   injury, 
leads  to  a  fatal  central  narcosis  by  poisoning  of  the  vital  centers. 
28 


434  NOURISHMENT    FOR    A    HEALTHY    ADULT. 

2.  Inorganic  matters  as  integral  parts  of  all  of  the  tissues,  without 
which  their  structure  could  not  be  formed.     These  substances  are  present 
in  sufficient  amount  in  all  the  usual  articles  of  diet,  so  that  it  is  unneces- 
sary to  supply  them  separately  (as  the  nutrition  of  animals  shows). 
Increase  in  the  supply  of  salt  causes  increase  in  the  consumption  of 
water,  and  this  in  turn  causes  increase  of  nitrogenous  decomposition  in 
the  body.     Withdrawal  of  certain  necessary  salts  causes  disturbances  in 
the  nutrition  of  the  tissues  containing  them.     Thus,  the  use  of  food  free 
from   calcium  is  followed  by  disturbance  in    normal    bone-formation ; 
withholding  common  salt  causes  albuminuria.     The  body  absorbs  the 
iron  required  for  the  formation  of  blood  in  part  in  the  form  of  complex 
organic  compounds  from  the  vegetable  and  animal  kingdoms,  but  in 
part  also  in  an  inorganic  form;  phosphorus  principally  from  proteids 
containing  phosphorus.     The  alkaline  salts  derived  from  vegetable  food 
serve  to  neutralize  the  sulphuric  acid  formed  by  oxidation  of  the  sulphur 
of  the  proteids.     Food  that  has  been  artificially  deprived  of  all  salts 
causes  rapid  death  in  animals  by  acid  intoxication. 

Only  as  a  matter  of  necessity  does  man  occasionally  resort  to  the  use  of 
considerable  amounts  of  inorganic  matter  in  order  to  obtain  the  organic 
nutrient  material  mixed  with  it,  as  A.  v.  Humboldt  relates  of  the  inhabitants 
along  the  shores  of  the  Orinoco  and  the  Meta,  and  who,  in  times  of  scarcity, 
when  the  catch  of  fish  is  low,  are  compelled  to  eat  a  certain  kind  of  rich  clay, 
containing  an  abundance  of  infusoria. 

3.  At  least  one  animal  or  vegetable  proteid.      The  albuminates  are 
utilized  to  replace  the  consumed  nitrogenous  tissues,  particularly  the 
muscles.     In  addition,  they  are  used  as  sources  of  energy  and  heat.     The 
latter  function  of  albuminous  food  can  be  fulfilled  by  non-nitrogenous 
food;  the  first,  however,  can  not.     The  albuminates  contain  from  15  to 
1 8  per  cent,  of  nitrogen. 

Different  tissues  of  the  body  contain  proteids  in  the  following  proportions: 
Blood  20.56  per  cent.,  muscles  19.9  per  cent.,  liver  11.74  per  cent.,  brain  8.63 
per  cent.,  blood-plasma  9.0  per  cent.,  milk  3.8  per  cent.,  lymph  2.4  per  cent. 
According  to  Pfluger  and  Bohland  a  growing  youth  weighing  62  kilos  decom- 
poses 89.9  grams  of  albumin  daily. 

It  is  a  remarkable  fact  that  asparagin — a  nitrogenous  amido-body,  which 
is  formed  in  sprouting  plants  from  albumin  and  under  certain  circumstances 
may  be  again  transformed  into  this  in  the  plant — combined  with  gelatin  is 
capable  of  replacing  the  albumin  of  the  food.  Asparagin  alone  is  capable 
(only  in  herbivora)  of  diminishing  the  decomposition  of  albumin.  Salts  of 
ammonia,  glycocoll,  sarcosin  and  benzamid  increase  the  destruction  of  proteid. 

4.  At  least  one  form  of  fat  or  digestible  carbohydrate.     These  serve 
principally  for  the  replacement  of  the  decomposed  fat  and  non-nitrog- 
enous  constituents   of  the   body.      On   account   of  the   large  amount 
of  carbon  they  contain,  they  are,  through  their  oxidation,  the  chief 
sources  of  heat-production.     Fats  and  carbohydrates  can  replace  each 
other  in  the  diet  in  reciprocal  amounts  corresponding  to  the  quantity  of 
heat  that  they  are  able  to  produce  by  their  combustion  in  the  body. 
In  the  same  way,  the  portion  of  the  albumin  of  the  food  that  does  not 
serve  for  the  restoration  of  the  tissues  can  be  replaced  by  equivalent 
amounts  of  fat  or  carbohydrates.     In  this  connection  100  parts  of  fat 
are  equivalent  to  256  of  grape-sugar,  243  of  milk-sugar,  234  of  cane- 
sugar,  221  of  dry  starch.     In  general  the  same  amounts   correspond  to 
227  parts  of  carbohydrate,  as  well  as  to  227  of  albumin. 


NOURISHMENT    FOR    A    HEALTHY    ADULT. 


435 


The  compound  sugars  in  the  organism  must  first  be  decomposed  into 
monosaccharids  before  they  are  oxidized,  just  as  they  are  decomposed  into 
monosaccharids  in  the  process  of  fermentation.  If  the  organism  is  unable  to 
split  a  compound  sugar  into  its  components,  it  cannot  oxidize  the  sugar.  This 
splitting,  for  example,  of  cane-sugar  and  milk-sugar,  is  carried  out  in  the 
intestine.  If  these  substances  are  introduced  subcutaneously  they  are  not 
split  up,  and  therefore  are  not  made  use  of;  that  is,  they  are  excreted  again 
in  the  urine. 

It  is  a  remarkable  fact  that  butter  can  be  injected  subcutaneously  in 
considerable  amounts  and,  thus  introduced,  is  utilized  either  for  combustion 
or  for  the  deposition  of  fat. 


With  regard  to  the  relative  proportions  in  which  these  various  nutri- 
tive materials  should  be  combined,  experience  has  taught  that  for  man, 
a  diet  in  which  the  nitrogenous  and  non-nitrogenous  elements  are  mixed 
in  the  proportion  of  one  nitrogenous  to  3^,  or  at  the  most  4^,  parts  of  the 
non-nitrogenous  elements,  must  be  considered  as  the  most  advantageous. 
If  the  customary  articles  of  diet  be  considered  according  to  this  standard, 
it  can  easily  be  seen  to  what  degree  they  conform  with  the  requirement 
mentioned,  and,  furthermore,  that  a  suitable  diet  may  often  be  formed 
by  a  mixture  of  several  of  them. 

The  following  table  shows  the  proportion  of  nitrogenous  and  non- 
nitrogenous  matters  in  various  articles  of  food  : 


Nitrog-  Non-nitrog- 


enous. 

1.  Veal, 10 

2.  Hare, 10 

3.  Beef, 10 

4.  Lentils, 10 

5.  Beans, 10 

6.  Peas,   10 

7.  Mutton  (fattened),  10 

8.  Pork 10 

9.  Cow's  milk, 10 


to 


enous. 

I 
2 

21 
22 
23 

27 


Nitrog-  Non-nitrog- 

enous. enous. 

TO.  Human  milk,  .....    10  to       37 

11.  Wheat-flour,  .....    10  46 

12.  Oat-meal,   .......    10  50 

13.  Rye-flour,  .......    10  57 

14.  Barley-flour,  .....    10  57 

15.  White  potatoes,.  .  .    10  86 

16.  Blue  potatoes,  .  .  .  .    10  115 

17.  Rice  ,  ............    10  123 

1  8.  Buckwheat-flour,  ..    10  130 


This  survey  shows  that  in  addition  to  human  milk,  wheat-flour  lies  within 
the  normal  limits  with  regard  to  its  proportional  composition.  On  the  other 
hand  the  articles  of  diet  from  i  to  9  require  an  addition  of  non-nitrogenous,  those 
from  12  to  1  8  of  nitrogenous,  substances  in  order  to  maintain  the  proportions 
from  10:35  to  10  :  45.  A  man  who  attempted  to  live  on  meat  alone  would,  there- 
fore, be  just  as  irrational  as  one  who  took  potatoes  alone  as  food.  Experience  long 
ago  impressed  upon  the  mind  of  the  people  the  fact  that  milk  and  eggs  will  indeed 
support  life,  but  that  a  meal  of  meat  requires  potatoes  or  bread;  a  dish  of  beans 
a  portion  of  bacon. 

It  should  also  be  especially  mentioned  that  the  proportions  of  the  diet  vary 
in  accordance  with  climate  and  season.  As  with  a  considerable  degree  of  cold 
the  organism  must  produce  more  heat,  the  inhabitants  of  higher  latitudes  take 
relatively  more  non-nitrogenous  food  (fat  and  sugar  or  starches)  ,  which,  on  account 
of  its  richness  in  carbon,  is  especially  suited  for  the  generation  of  heat  in  the  body. 

The  graphic  representation  of  the  composition  of  the  most  important 
articles  of  food  in  Fig.  141  (after  A.  Fick)  is  especially  clear. 

If  it  be  borne  in  mind  that  the  nitrogenous  bodies  in  the  food  must 
be  in  the  proportion  of  i  :  3$  to  4^  of  the  non-nitrogenous,  a  glance 
will  show  at  once  what  articles  of  diet  are  suited  for  food  without  addi- 
tion, as  well  as  which  of  them  may  be  suitably  combined  to  supplement 
one  another. 

The  absolute  amount  of  food  that  an  adult  needs  during  twenty-four 
hours  is  influenced  by  various  factors.  As  food  represents  the  reservoir 


436 


NOURISHMENT  FOR  A  HEALTHY  ADULT. 


of  chemical  potential  energy  from  which  the  body  generates  on  the  one 
hand  heat  and  on  the  other  kinetic  energy,  the  absolute  amount  of  food 


Explanation  of  the  figures: 


Water. 


Proteids. 


ANIMAL  FOOD. 


Albuminoids.  Non-nitrogenous 

organic  matter. 


Human  milk 


89 


VEGETABLE  FOOD. 


Explanation  of  the  figures: 


Salts. 


Potatoes 


White  tur- 
nips 


Water.  Proteids.  Digestible          Undigestible 

Non-nitrogenous 
organic  matter. 


75 


90,5 


Salts. 


0-5 


Cauliflower 


Beer 


80 


90 


FIG.  141. 


must  be  increased  when  the  loss  of  heat  from  the  body  (winter)  or  its 
muscular  activity  (work)  increases.  On  the  average  a  man  requires  130 
grams  of  proteids,  84  grams  of  fat,  and  404  grams  of  carbohydrates. 


NOURISHMENT    FOR    A    HEALTHY    ADULT.  437 

The  following  figures  are  average  values  derived  from  many  individual  ob- 
servations : 

An  adult  requires  in  24  hours: 

Resting          Moderate  Work  Hard  Work    (v.  Pettenkofer 
Air.ount  of  Food  in  Grams.  (Playfair).  (Moleschott).     (Playfair).       and  v.  Voit.) 

Proteids, 70-87  130          155.92  137 

Fats,   28.35  84  70.87  117 

Carbohydrates  (sugar,  starch,  etc.) ,       310.20  404          567.50  352 

In  an  analogous  example  taken  from  C.  v.  Vierordt  the  elementary  matters 
in  the  food  will  be  estimated  and  at  the  same  time  the  amounts  ingested  be  com- 
pared with  those  excreted. 

An  adult  with  moderate  activity  consumes: 

C  H  N                    O 

120  grams  of  albumin,  containing, 64.18  8.60  18.88           28.34 

90  grams  of  fats,                               70.20  10.26  9-54 

330  grams  of  starch,                          146.82  20.33  162.85 

281.20       39.19          18.88         200.73 

In  addition:    744.11  grams  of  oxygen  from  the  air  by  respiration. 
2818        grams  of  water. 

32         grams  of  inorganic  compounds  (salts). 

The  whole  amounts  to  about  3.2  kg.  or  about  ^  of  the  body-weight.  Over 
6  per  cent,  of  the  water,  about  6  per  cent,  of  the  fat, "about  i  per  cent,  of  the  albu- 
min and  about  0.4  per  cent,  of  the  salts  in  the  body  are  thus  daily  replaced. 

An  adult  with  moderate  activity  excretes : 

Water                C  H  N  O 

With  respiration, 330  248.8  .  .  ?  651.15 

By  transpiration, 660               2.6  .  .  .  .  7.2 

In  the  urine, 1700               9.8  3.3  15.8  n.i 

In  the  feces, 128  20.0  3.0  3.0  12.0 

2818          281.2          6.3  18.8        681.45 

In  addition  296  grams  of  water — not  included  in  the  2818  grams  of  water  in- 
gested— are  formed  in  the  body  by  oxidation  of  the  hydrogen  of  the  food.  These 
296  grams  of  water  contain  34.89  grams  of  hydrogen  and  263.31  grams  of  oxygen. 
Further,  26  grams  of  salts  are  passed  with  the  urine  and  2  grams  with  the  feces. 

An  adult  at  rest  consumes  during  twenty-four  hours  96.5  grams  of 
proteid — equivalent  to  1.46  grams  for  each  kilogram;  at  hard  work, 
107.6  grams — equivalent  to  1.6  grams  for  each  kilogram.  Three  or  four 
times  as  much  fat  as  albumin  is  transformed  daily. 

Investigations,  principally  by  the  Munich  school,  have  determined  the  fol- 
lowing minimum  figures  for  the  diet  at  various  ages: 

Age.  Nitrogenous.  Fat.  Carbohydrate. 

For  a  child  up  to  i£  years, 20-36  gms.     30-45  gms.     60-90  gms. 


250—400 
500 
400 
350 
260 


For  a  child  from  6  to  15  years, 70-80  27-50 

For  a  man,  with  moderate  activity, 1 18  56 

For  a  woman,  with  moderate  activity,  ...  92  44 

For  an  old  man 100  68 

For  an  old  woman, 80  50 

It  is  frequently  asserted  that,  in  case  of  necessity,  a  considerably  smaller 
amount  of  proteid  (55  gms.  for  a  man)  would  suffice,  providing  that  the  amount 
of  food  were  sufficient  to  supply  the  requisite  number  of  calories  for  the  body, 
that  is,  45,000  calories  for  each  kilogram  of  body- weight.  The  diet  of  the  Japanese 
contains,  for  example,  a  much  smaller  amount  of  nitrogen  than  that  of  the  Euro- 
pean. Numerous  experiments  have  demonstrated,  however,  that  an  adult 
weighing  70  kilograms  can  be  sufficiently  nourished  only  temporarily,  and  not 
for  any  length  of  time,  on  less  than  80  grams  of  proteid. 


438 


NOURISHMENT    FOR    A    HEALTHY    ADULT. 


The  minimum  amount  of  proteid  requisite  for  preserving  the  nutrition  must 
be  so  large  that  the  nitrogen  it  contains  will  be  equal  to  the  nitrogen  excreted  by 
the  individual  in  question  in  a  fasting  condition. 

Small  animals  consume  for  each  unit  of  body-weight  decidedly  more  than 
large  ones.  This  depends  not  so  much  on  the  fact,  as  was  formerly  believed, 
that  the  metabolism  is  more  active  in  small  animals,  as  on  the  fact  that  small 
animals,  in  proportion  to  their  body-weight,  possess  a  larger  body-surface,  and 
are,  therefore,  more  exposed  relatively  to  external  influences,  and  especially  to 
the  cooling  effect  of  the  surrounding  air.  If  the  amount  of  the  substances  de- 
composed is  compared,  not  to  the  body- weight  but  to  the  body-surface,  for 
example  to  one  square  meter,  almost  the  same  values  will  be  obtained  for  small 
is  for  large  animals  of  the  same  species.  On  the  other  hand,  the  values  for  animals 
of  different  species  are  different. 

The  absolute  amount  of  food  that  an  adult  requires  in  twenty-four 
hours  is  most  conveniently  expressed  in  the  form  of  units  of  energy 
that  it  is  capable  of  supplying,  that  is,  in  calories.  An  adult,  with  a 
moderate  amount  of  fat,  requires  daily,  for  each  kilogram  of  body- 
weight  : 

At  complete  rest from  32,000  to  38,000  calories. 

At  light  work 35,ooo   "   45,000 

At  hard  work 50,000   "   70,000 

Therefore,  a  man  weighing  70  kilograms  at  light  work  would  require 
in  the  neighborhood  of  70  X  40,000,  or  2,800,000  calories.  Any  diet 
containing  2,800,000  calories  is  sufficient;  but  the  diet  must  always 
contain  proteid — and  in  no  event  less  than  80  grams  daily.  As  i 
gram  of  proteid  yields  4100  calories,  i  gram  of  carbohydrate  4100 
calories  and  i  gram  of  fat  9300  calories,  the  following  dietetic  combina- 
tions may  be  considered  as  sufficient: 


Grams.  Calories. 

80  of  proteid =      328,000 

300  of  carbohydrate  ....  =  1,230,000 

113  of  fat =  1,237,000 


2,795,000 


80  of  proteid =      328,000 

265  of  fat =  2,465,000 


100  of  proteid 

280  of  carbohydrate 
133  of  fat 


2,793,000 

=  410,000 
=  1,148,000 
=  1,237,000 

2,795,000 


Grams.  Calories. 

80  of  proteid =      328,000 

200  of  carbohydrate  ....    =      820,000 
177  of  fat =  1,646,000 

2,794,000 

328,000 
1,640,000 
828,000 


80  of  proteid 

400  of  carbohydrate  .  .  . 
89  of  fat  


For  a  short  time  also: 

60  of  proteid 

320  of  carbohydrate  . 
133  of  fat 


2,796,000 

246,000 
1,212,000 
1,237,000 

2,795,000 


In  most  of  the  ordinary  articles  of  food  nitrogenous  and  non-nitrog- 
enous substances  occur  together,  but,  as  the  statements  on  page  435 
show,  in  widely  different  proportions.  Man  requires  a  diet  in  which 
the  proportion  between  nitrogenous  and  non-nitrogenous  substances  is 
between  1:3^  and  i  :  4^.  If  a  person  takes  food  in  which  this  propor- 
tion does  not  hold,  he  must  consume  an  excessive  amount  of  it,  in  order 
to  obtain  a  sufficient  quantity  of  that  substance  in  which  the  article 
of  diet  is  relatively  deficient.  This,  it  is  clear,  must  necessarily  cause 
waste  of  the  preponderating  substance.  Moleschott  has,  in  this  con- 
nection, grouped  the  principal  articles  of  diet  together.  In  order  to 


METABOLISM    IN    THE    STATE    OF    STARVATION  439 

obtain  the  necessary  130  grams  of  proteid  a  laborer  must  consume  the 
following  amounts  of  various  foods : 

Cheese 388  gms.       Beef 614  gins.       Rice 2562  gms. 

Lentils 491  Eggs 968  Rye-bread...    2875     " 

Peas .582  Wheat-bread.  .  1444  Potatoes 10000     " 

It  is  quite  evident  that,  in  using  the  last-named  substances,  the 
laborer  must  consume  a  useless  excess  of  non-nitrogenous  food.  In 
order  to  obtain  from  his  food  the  necessary  448  grams  of  carbohydrate 
(or  the  equivalent  amount  of  fat)  required  for  his  subsistence,  such  a 
laborer  would  have  to  eat : 

Rice 572  gms.       Peas 819  gms.       Cheese 2011  gms. 

Wheat-bread.  .  .625  Eggs 902  Potatoes 2039     " 

Lentils 806  Rye-bread 930  Meat    2261     " 

Thus,  particularly  with  the  exclusive  use  of  cheese  or  meat,  the 
laborer  would  be  compelled  to  consume  enormous  quantities,  which 
would  be  equivalent  to  a  waste  of  nitrogenous  material. 

Finally,  attention  should  be  drawn  to  the  fact  that  not  all  of  the 
food  is  digested  or  absorbed  in  the  digestive  tract,  but  that  there  is 
always  a  certain  residue  that  is  unutilized  and  is  voided  with  the  feces. 
Calculated  as  dry  substance  this  amounts  in  percentages:  in  rice  to  4.1, 
in  white  bread  to  4.5,  in  meat  to  5.2,  in  eggs  to  5.2,  in  milk  to  9,  in 
potatoes  to  9.4,  in  peas  to  n.8,  in  beans  to  18.3,  in  black  bread  to  15. 
It  is  more  advantageous  to  administer  the  amount  of  food  required 
daily  in  several  portions  than  to  give  it  at  infrequent  intervals  or  all  at 
once ;  the  distribution  of  the  food  over  several  meals  diminishes  proteid 
decomposition. 

For  the  herbivora  a  diet  suffices  containing  one  part  of  nitrogenous  to  eight 
or  nine  parts  of  non-nitrogenous  material. 


METABOLISM  IN  THE  STATE  OF  STARVATION. 

If  a  warm-blooded  animal  is  deprived  of  all  food,  it  must,  naturally, 
decompose  and  utilize  the  energy  stored  in  its  own  tissues  in  order  to 
generate  its  bodily  heat  and  to  perform  any  mechanical  labor  demanded 
of  it.  Its  body- weight,  accordingly,  steadily  decreases  till  death  from 
starvation  occurs,  the  tissues  and  organs  meanwhile  becoming  richer  in 
water. 

Method. — For  an  exact  investigation  of  the  state  of  inanition  (i)  the  starving 
man  or  animal  is  weighed  daily.  (2)  All  of  the  carbon  and  nitrogen  in  the  expired 
air,  the  urine  and  the  feces  is  estimated  daily.  The  nitrogen  found  can  be  derived 
only  from  the  consumed  proteids  of  the  body,  especially  the  muscles,  and  from  the 
same  source  also  a  varying  amount  of  carbon,  in  accordance  with  the  composition 
of  the  muscles.  The  amount  of  carbon  remaining  after  subtracting  this  amount 
is  to  be  attributed  to  the  decomposition  of  the  non-nitrogenous  tissues  of  the 
body,  principally  the  fat.  After  the  amount  of  muscle  and  fat  broken  down  has 
been  thus  computed,  the  subtraction  of  this  amount  from  the  total  loss  of  body- 
weight  will  yield  the  amount  of  water  lost. 

The  following  example,  which  deals  with  a  cat  starved  to  death  by  Bidder 
and  Schmidt,  shows  the  various  excretions  on  the  successive  days  of  starvation: 


44° 


METABOLISM    IN    THE    STATE    OF    STARVATION. 


DAY. 

BODY- 
WEIGHT. 

AMOUNT 

OF 

WATER 

TAKEN. 

AMOUNT 

OF 

URINE. 

UREA. 

INORGANIC 
CONSTITU- 
ENTS OF 
THE  URINE. 

DRY 

FECES. 

EXPIRED 
CARBON. 

WATER 

IN 

URINE  AND 
FECES. 

i    .... 

2464 

98 

7-9 

J-3 

1.2 

13-9 

91.4 

2     .... 

2297 

n-5 

54 

5-3 

0.8 

1.2 

12.9 

50-5 

3   .... 

2210 

45 

4.2 

0.7               I.I 

13 

42.9 

4  .... 

2172 

68.2 

45 

3-8 

0.7               I.I 

12.3 

43 

5  .... 

2129 

55 

4-7 

0.7 

i-7 

II.9 

54-1 

6   

2O24 

44 

4-3 

0.6 

0.6 

ii.  6 

41.1 

7  .... 

1946 

40 

3-8 

o-5 

0.7 

ii 

37-5 

8  .... 

1873 

42 

3-9 

0.6 

i.i 

10.6 

40 

9  

1782 

!5-2 

42 

4 

o-5 

!-7 

10.6 

41.4 

10  .... 

1717 

35 

3-3 

0.4 

!-3 

10.5 

34 

ii   .... 

1695 

4 

32 

2.9 

o-5 

I.I 

IO.2 

3°-9 

12     .... 

1634 

22.5 

30 

2.7 

0.4 

I.I 

19-3 

29.6 

I3     

!57o 

7-1 

40 

3-4 

°-5 

0.4 

IO.I 

36.6 

I4    

1518 

3 

4i 

3-4 

°-5 

o-3 

9-7 

38 

15     

1434 

4i 

2.9 

0.4 

o-3 

9-4 

38.4 

16  

1389 

48 

3 

0.4 

O.2 

8.8 

45-5 

17  — 

J335 

28 

1.6 

0.2 

°-3 

7-8 

26.6 

i8f  ... 

1267 

13 

0.7 

O.I 

0.3 

6.1 

12.9 

-1197 

i3i-5 

775 

65-9 

9.8 

15.8 

190.8 

734-4 

The  cat  before  death  had  lost  1197  grams  in  weight.  This  loss  may  be  dis- 
tributed, according  to  what  has  been  said,  as  follows:  Proteid  204.43  grams,  or 
17.01  per  cent.;  fat  132.75  grams,  or  11.05  Per  cent.;  water  863.82  grams,  or 
7 1.91  per  cent,  of  the  total  loss  of  weight. 

With  regard  to  the  general  phenomena  of  inanition  it  is  worthy  of  remark 
that  strong,  well-nourished  dogs  die  of  starvation  only  after  four  weeks,  while 
man  succumbs  in  twenty-one  or  twenty-two  days.  Six  persons  suffering  from 
melancholia,  who  had  taken  water,  lived  for  forty-one  days,  however.  In  recent 
years  voluntary  exhibitions  of  starvation  have  become  the  fashion.  The  most 
striking  of  these  was  given  by  the  Italian  painter,  Merlatti,  who,  it  is  alleged, 
withstood  starvation  for  a  period  of  fifty  days  with  the  use  of  water  only.  Succi, 
according  to  unexceptionable  testimony,  fasted  for  thirty  days. 

Under  such"  conditions  the  regulation  of  temperature,  the  circulation,  the 
respiration,  the  muscular  and  the  nervous  activity  were  found  to  be  within  limits 
of  normal  variation;  the  secretions  necessary  for  digestion  were,  on  the  other 
hand,  almost  abolished. 

Small  mammals  and  birds  succumb  within  nine  days,  but  frogs  only  after 
nine  months.  Full-grown,  vigorous  mammals,  on  the  contrary,  have  lost  as  much 
as  T^  of  their  weight  (from  i  to  |)  before  death.  In  man  the  decrease  in  weight 
is  relatively  greatest  during  the  first  few  days.  Young  individuals  die  much 
earlier  than  adults.  To  outward  appearance  the  emaciation  is  striking.  The  mouth 
is  dry,  the  walls  of  the  alimentary  tract  become  remarkably  thin,  the  digestive 
juices  are  no  longer  secreted,  the  action  of  the  heart  is  enfeebled,  the  pulse, 
smaller  and  of  lower  tension,  is  less  frequent,  the  respirations  are  increased  in  fre- 
quency and  more  superficial,  the  urine  is  highly  acid  on  account  of  increase  in 
sulphuric  and  phosphoric  acids,  and  its  chlorin-compounds  soon  disappear  almost 
entirely.  The  blood  is  poorer  in  water,  the  plasma  in  albumin;  the  gall-bladder 
is  greatly  distended,  a  fact  that  points  to  uninterrupted  destruction  of  red  blood- 
cells  in  the  liver.  The  liver  is  small  and  extremely  dark.  The  muscles  tire 
readily.  Finally,  great  weakness  of  the  wasted  and  friable  muscles  develops  and 
death  follows  amid  signs  of  the  greatest  prostration  and  coma. 

The  conditions  of  metabolism  are  apparent  from  the  foregoing  table,  accord- 
ing to  which  the  decrease  in  the  excretion  of  urea  is  much  greater  than  that 
of  carbon  dioxid.  From  this  it  may  be  concluded  that  a  correspondingly 
greater  breaking-down  of  fats  than  of  proteids  takes  place.  According  to  the 
calculations  a  tolerably  constant  amount  of  fat  is  broken  down  daily,  while  the 
proteids  undergo  much  slighter  destruction  with  the  progress  of  the  days  of 
fasting.  Drinking  of  water  hastens  the  destruction  of  the  proteids. 


METABOLISM    IN    THE    STATE    OF    STARVATION.  441 

In  the  case  of  the  fasting  virtuoso,  Cetti,  Zunty  and  Lehmann  found  that 
the  consumption  of  oxygen  and  the  production  of  carbon  dioxid,  as  calculated 
for  the  unit  of  body- weight,  rapidly  reach  minimal  values,  below  which  they  did 
not  fall  with  continued  starvation.  On  the  average,  the  consumption  of  oxygen 
from  the  third  to  the  sixth  day  of  fasting  amounted  to  4.65  cu.  cm.  for  each  kilo- 
gram of  body- weight  and  for  each  minute.  Absolutely,  as  regards  the  individual, 
the  respiratory  interchange  decreased  slowly,  but  this  decrease  failed  to  keep 
pace  with  the  decrease  in  the  weight  of  the  body.  At  the  beginning  of  starvation 
the  amount  of  carbon  dioxid  diminished  more  than  the  consumption  of  oxygen. 
The  respiratory  quotient  was  0.67.  The  urea  from  the  first  to  the  tenth  day  of 
starvation  decreased  from  29  to  20  grams. 

In  the  case  of  another  faster,  Succi,  Luciani  found  that  a  nitrogenous  excretion 
of  16.23  grams  had  decreased  on  the  first  day  of  fasting  to  13.8  grams,  on  the 
seventeenth  day  to  7.8  grams,  on  the  twenty-second  to  4-75  grams,  on  the  twenty- 
eighth  day  to  5.6  grams.  Also  Johannson,  Landgren,  Sonden  and  Tigerstedt 
found  that  metabolic  activity  at  first  declined  quickly  and  to  a  large  degree,  later 
slowly  and  slightly. 

A  consideration  of  the  relative  loss  of  weight  of  the  various  organs  is  also 
of  great  interest,  as  shown  by  comparison  with  a  similar  animal  killed  without 
preliminary  starvation.  It  should  be  stated,  however,  in  this  connection,  that 
many  organs  lose  weight  proportionately,  for  example,  the  bones  (and  as  a  result 
phosphoric  acid,  calcium,  and  magnesium  increase  in  the  urine),  while  other  parts 
exhibit  a  disproportionately  marked  decomposition,  for  example  the  fat.  The 
latter  are  broken  down  with  especial  rapidity  and  from  them  other  organs  are 
in  part  nourished  during  starvation.  Finally,  certain  organs,  like  the  heart  and 
the  nerves,  suffer  slight  loss,  as  they  are  able  to  maintain  themselves  on  the  de- 
composition-products of  other  tissues.  In  the  breaking  down  of  the  tissues  the 
nuclei  also  suffer  and  certain  glands  undergo  fatty  degeneration. 

A  starved  male  cat  lost,  according  to  v.  Voit: 

Percentage  of  the  Percentage  of  the 

Amount   Originally  Total  Loss  of  the 

Present.  Body. 

1.  Fat    97  26.2 

2.  Spleen 66.7  0.6 

3-  Liver 53.7  4-8 

4.  Testicles 40.0  o.i 

5.  Muscles 30.5  42.2 

6.  Blood 27.0  3.7 

7.  Kidneys 25.9  0.6 

8.  Skin 20.6  8.8 

9.  Intestines 18.0  2.0 

10.  Lungs 17.7  0.3 

n.  Pancreas 17.0  o.i 

12.  Bones 13.9  5.4 

13.  Central  nervous  system 3.2  o.i 

14.  Heart   2.6  0.02 


15.   Remainingportions  of  the  body  together  36.8  5.0 

The  average  resistance  of  the  hemoglobin  is  increased  by  inanition. 

Allusion  should  be  made  also  to  an  important  difference  between  animals  that 
have  been  liberally  fed  with  meat  or  fat  before  the  beginning  of  the  period  of 
inanition,  and  those  that  have  been  kept  on  a  barely  sufficient  diet.  Liberally 
fed  animals  suffer  much  greater  loss  in  weight  in  the  early  days  of  starvation  than 
in  the  later.  Furthermore,  fat  individuals  exhibit  from  the  first  a  greater  decom- 
position of  fat  in  proportion  to  proteids  than  thinner  individuals.  Animals  liber- 
ally fed  with  proteid  continue  to  decompose  much  albumin  in  the  early  days  of 
fasting.  Animals  fed  with  little  proteid,  on  changing  to  a  liberal  albuminous  diet, 
likewise  continue  to  decompose  only  a  limited  quantity  of  albumin  in  the  first 
few  days. 


442          METABOLISM    ON    A    DIET    OF    MEAT,    ALBUMIN    OR    GELATIN. 


METABOLISM   WITH  AN  EXCLUSIVE  DIET  OF  MEAT,    ALBUMIN 

OR  GELATIN. 

According  to  Pfliiger  the  higher  animal  (as  has  been  demonstrated  experi- 
mentally for  the  dog)  can  be  nourished  and  maintained  almost  exclusively  on 
proteids,  without  impairment  of  its  functional  activity.  Proteids  are,  therefore, 
to  be  designated  as  foods  of  the  first  order,  as  fundamental  foods.  Pfliiger  applies 
the  term  nutritive  requirement  to  the  smallest  amount  of  lean  meat  that  is  capable 
of  maintaining  the  metabolic  equilibrium,  without  fat  or  carbohydrate  of  the  body 
being  utilized  for  decomposition.  The  amount  of  this  nutritive  requirement  is 
determined  by  the  weight  of  the  flesh  of  the  animal  and  increases  with  this  on 
addition  of  flesh  to  the  body.  The  decomposition  of  proteids  increases  also  with 
the  supply  of  proteid  if  the  latter  exceeds  the  nutritive  requirement.  Under  such 
circumstances,  however,  a  certain  portion  of  the  excess  of  proteid  is  conserved 
and  deposited  as  flesh.  The  nutritive  requirement  of  the  dog  is  for  i  gram  of 
animal  nitrogen  0.0636  gram  of  nutrient  nitrogen;  or  i  kilogram  of  nitrogenous 
animal  tissue  requires  2.099  grams  of  nitrogen  in  the  food. 

Human  beings  provided  exclusively  with  meat  free  from  fat  are,  however, 
not  able  to  maintain  the  metabolic  equilibrium.  Compelled  to  adhere  to  such  a 
diet  permanently  they  would  certainly  succumb.  The  reason  for  this  is  obvious. 
In  beef  the  proportion  of  nitrogenous  to  non-nitrogenous  elementary  nutritive 
constituents  is  as  i  to  1.7.  The  healthy  person  gives  off  daily  in  the  carbon  dioxid 
of  the  respiration,  in  the  feces  and  in  the  urine,  about  280  grams  of  carbon. 
If  he  desired  to  obtain  these  280  grams  of  carbon  from  the  carbon  of  an  exclusively 
meat-diet,  he  would  be  compelled  to  digest  and  assimilate  more  than  2  kilos  of 
pure  meat  in  twenty-four  hours.  His  organs,  however,  would  by  no  means  suffice 
to  accomplish  this  permanently.  The  man  would  under  such  conditions  soon  be 
compelled  to  consume  less  meat.  This  result  would  require  the  decomposition  of 
the  constituents  of  his  own  body,  first  of  all  the  fat  and  then  also  the  proteids. 

Also  in  the  following  manner  it  can  be  clearly  shown  that  a  human  being  is 
unable  to  maintain  himself  on  a  meat-diet  exclusively.  A  man  weighing  70  kilo- 
grams and  doing  a  moderate  amount  of  work  requires  40,000  calories  daily  for  each 
kilo  of  body-weight,  therefore  a  total  of  2,800,000  calories.  One  thousand  grams 
of  lean  beef  yield  95,000  calories.  Such  a  person  would,  therefore,  be  compelled 
to  consume  about  3  kilograms  of  beef,  or  2,850,000  calories,  daily,  and  this,  natur- 
ally, is  impossible. 

The  carnivora  (dog) ,  whose  digestive  organs  are  especially  adapted  to  the 
digestion  of  meat,  by  reason  of  the  short  intestine  and  actively  solvent  in- 
fluence of  the  digestive  fluids  upon  proteids,  cannot  be  maintained  permanently  on 
chemically  pure  albumin,  although  this  is  possible  with  the  leanest  meat,  which, 
however,  always  contains  not  less  than  0.59  per  cent,  of  fat.  Under  such  circum- 
stances the  animal  consumes  large  amounts  of  meat,  and  as  a  result  the  elimina- 
tion of  urea  is  increased  correspondingly.  If  it  eat  still  larger  amounts,  it  may 
even  put  on  flesh,  and  then,  in  accordance  with  the  maintenance  of  the  newly 
deposited  flesh,  it  requires  naturally  a  constantly  increasing  amount  of  meat. 

The  herbivora  are  under  no  circumstances  capable  of  subsisting  upon  a  meat- 
diet  exclusively,  as  their  digestive  apparatus,  which  is  adapted  for  vegetable  food, 
would  by  no  means  suffice  for  the  disposal  of  the  necessary  amounts  of  meat. 

Of  gelatin  it  has  been  shown  that  it  may  replace  the  proteids  in  the  food, 
in  so  far  as  these  serve  as  sources  of  energy  and  heat,  but  not  if  bodily  tissue  is 
to  be  replaced.  Under  such  circumstances  two  parts  of  gelatin  take  the  place  of 
one  part  of  proteid.  The  carnivora,  which  can  maintain  their  metabolic  equilib- 
rium with  large  amounts  of  meat,  are  capable  of  doing  this  with  less  meat  and 
a  corresponding  addition  of  gelatin.  According  to  Munk  the  dog  is  capable  for 
a  few  days  of  replacing  £  of  its  proteid  requirement  by  gelatin.  A  diet  of  gelatin 
exclusively  is,  however,  inadequate.  In  addition  the  animals  soon  lose  their 
appetite  for  such  food. 

In  consequence  of  its  solubility  the  addition  of  gelatin  (calf's-foot  jelly)  to 
the  food  of  convalescents  has  been  recommended.  The  absorbed  products  of  the 
digestion  of  gelatin  are  conveyed  to  the  connective  tissues,  which  constitute  a  re- 
pository for  it.  After  a  long-continued  diet  of  chondrin,  together  with  meat, 
glucose  has  been  found  in  the  urine. 


LAWS    GOVERNING    METABOLISM.  443 


AN  EXCLUSIVE  DIET  OF  FATS  OR  CARBOHYDRATES. 

If  fat  alone  is  supplied,  the  body  is  unable  to  maintain  itself.  In  consequence 
of  the  deficiency  of  nitrogen,  the  animal  must  necessarily  perish.  The  symptoms 
occurring  with  this  form  of  diet  are  as  follows :  The  animal  in  question  secretes  less 
urea  than  in  a  state  of  hunger.  Therefore,  the  consumption  of  fat  must  restrict 
that  of  the  flesh  of  the  animal  itself.  This  is  due  to  the  fact  that  the  fat,  being 
a  readily  combustible  substance,  is  more  readily  oxidized  in  the  body  than  the 
less  readily  combustible  nitrogenous  albuminates.  If  the  amount  of  fat  taken 
is  exceedingly  large,  not  all  of  the  carbon  of  the  fat  can  be  recovered  in  the  excreta, 
or  as  carbon  dioxid  in  the  expired  air.  Accordingly  the  body  must  accumu- 
late fat,  while  naturally  it  destroys  proteids  in  corresponding  amount.  The 
animal  thus  becomes  fatter  and  at  the  same  time  poorer  in  flesh. 

The  result  of  administration  of  carbohydrates  alone,  which  must  first  be  con- 
verted into  sugar  by  the  digestive  processes,  exhibits  marked  similarity  to  that 
obtained  with  a  pure  fat-diet.  It  should,  however,  be  noted  that  the  sugar  in 
the  body  more  readily  undergoes  destruction  than  the  fat,  and,  further,  that  with 
reference  to  the  nutritive  value,  256  parts  of  glucose  are  the  equivalent  of  100 
parts  of  fat.  Accordingly,  a  carbohydrate-diet  restricts  the  decomposition  of 
proteids  even  more  readily  than  a  pure  fat-diet. 

Just  as  it  is  necessary  outside  of  the  body  for  the  fermentation  of  disaccharids 
and  polysaccharids  that  these  be  first  decomposed  into  monosaccharids,  so  also 
the  combustion  of  sugar  in  the  body  can  occur  only  on  condition  that  a  trans- 
formation into  monosaccharids  has  previously  taken  place. 

LAWS   GOVERNING   METABOLISM  ON  A  MIXED   DIET  OF   MEAT 
AND  FAT  OR  CARBOHYDRATES. 

If  a  dog  in  a  state  of  metabolic  equilibrium  be  given  an  amount  of  fat  and 
starch  exceeding  its  requirements,  elimination  through  metabolism  is  not  in- 
creased, but  the  excess  of  these  non-nitrogenous  foods  administered  is  deposited 
in  the  body  of  the  animal  as  fat. 

If  a  dog  fed  with  the  leanest  possible  meat,  and  in  a  state  of  metabolic  equilib- 
rium, be  given  an  additional  amount  of  meat  exceeding  its  requirements,  the 
elimination  through  metabolism  increases  almost  proportionately  to  the  addi- 
tional amount  administered  beyond  the  requirements.  Only  a  small  portion  of 
the  addition  is  conserved  and  increases  the  body-weight  as  a  deposition  of  flesh. 
This  augmentation  of  metabolism  not  only  causes  an  increase  in  the  nitrog- 
enous excretion  in  general  proportional  to  the  supply  of  proteid,  but  also  the 
carbon  contained  in  the  supply  of  proteid  is  again  excreted,  for  of  the  proteid 
fed  no  portion  is  deposited  in  the  body  as  fat  or  carbohydrate.  From  both  of 
these  statements  it  follows  that  neither  fat  nor  carbohydrate  is  capable  of  in- 
creasing metabolism  beyond  the  requirements,  although  proteid  is. 

The  seat  of  active  proteid  metabolism  after  a  diet  rich  in  proteids  is, 
according  to  Pfliiger,  not  in  the  increased  flow  of  fluid,  but  within  the  proteid- 
containing  cells  which  have  undergone  a  marked  alteration  (saturation)  as  a 
result  of  the  entrance  of  the  proteid  into  them.  This  view  is  confirmed  by  the 
experiments  of  Schondorff,  who  found  that  if  the  blood  of  a  fasting  animal  be 
forced  through  the  tissues  of  a  generously  nourished  animal  the  urea  in  the  blood 
of  the  latter  increases,  while,  on  the  contrary,  if  the  blood  of  a  well-nourished 
animal  be  forced  through  the  tissues  of  a  fasting  animal  the  urea  in  the  blood 
of  the  latter  diminishes.  As,  on  providing  an  adequate  amount  of  proteid,  mus- 
cular activity  takes  place  only  at  the  expense  of  proteid,  and  as  in  the  decomposi- 
tion of  this  proteid  neither  fat  nor  carbohydrate  results,  fat  or  carbohydrate 
cannot  be  the  source  of  muscular  activity  (Pflugcr).  Other  investigators  are 
of  the  opinion,  however,  that  with  adequate  nitrogenous  nourishment  energy  as 
well  as  heat  can  be  generated  from  fat  and  carbohydrate. 

Nourishment  with  Carbohydrates  and  Meat. — The  organism  is  capable  of  gen- 
erating fat  from  carbohydrates.  A  deposition  of  fat  in  the  body  thus  brought 
about  takes  place  only  if  in  addition  to  the  proteid  of  the  meat  a  nutritive  excess 
of  carbohydrates  is  present.  Such  an  excess  of  starch  may  be  present  even  when 
the  supply  of  starch  itself  is  small,  while  the  excess  may  even  be  wanting  when 
the  supply  of  starch  is  large.  The  result  depends  upon  the  character  of  the  food 
that  is  supplied  in  addition  to  the  starch.  The  larger  the  amount  of  proteid,  in 


444  ORIGIN    OF    THE    FAT    IN    THE    BODY, 

addition  to  the  starch,  contained  in  the  food,  the  more  readily  is  an  excess  of 
starch  to  be  attained  without  the  necessity  of  supplying  too  much  starch.  If 
this  condition  of  such  an  excess  is  not  fulfilled,  fat  does  not  result  even  with 
generous  administration  of  carbohydrates.  The  newly  formed  fat  possesses  the 
same  potential  energy  as  the  nutritive  excess  resulting  from  the  carbohydrates 
administered. 

Deposition  of  fat  in  the  body  does  not  take  place,  however  large  the  excess 
of  proteid  food,  if  carbohydrates  or  fat  be  not  supplied  at  the  same  time.  On 
feeding  with  meat  and  starch,  or  in  general  with  a  mixed  diet,  the  amount  of 
newly  formed  fat  depends  in  no  wise  upon  the  amount  of  proteid  decomposed, 
but  only  upon  the  amount  of  nutritive  excess  due  to  carbohydrates.  Deposition 
of  fat  from  carbohydrates  takes  place  even  when  no  proteid  at  all  is  supplied 
and  the  metabolism,  therefore,  must  be  maintained  in  part  at  the  expense  of  a 
portion  of  the  body-proteid. 

While  for  the  maintenance  of  the  metabolic  equilibrium  on  a  pure  meat-diet 
an  enormous  consumption  (from  2V  to  ^  of  the  body-weight  in  the  dog)  is  required, 
a  third  of  the  amount  of  meat  suffices  with  an  adequate  addition  of  fat  or  carbo- 
hydrate. For  100  parts  of  fat,  added  to  the  meat,  245  parts  of  dry  meat  or  227 
of  syntonin  can  be  conserved.  If  carbohydrates  are  selected  instead  of  additional 
fat,  100  parts  of  fat  correspond  to  from  230  to  250  parts  of  carbohydrate.  It 
should,  however,  be  borne  in  mind  that,  at  least  for  a  short  time,  the  carbohy- 
drates are  superior  to  fat  as  a  proteid-sparer,  as  the  fat  is  less  completely 
utilized  in  the  process  of  metabolism  than  the  carbohydrates. 

It  appears  that,  instead  of  fat,  a  corresponding  amount  of  fatty  acids  has  the 
same  effect  in  the  process  of  metabolism. 

Glycerin  is  not  capable  of  lessening  the  destruction  of  bodily  proteid,  although 
recently  I.  Munk  has  stated  that  moderate  amounts  of  glycerin  introduced  into 
the  circulation  are  consumed  in  the  body  and  through  their  oxidation  protect  a 
portion  of  the  bodily  fat  against  oxidation.  According  to  Lebedeff,  v.  Voit  and 
Arnschink,  glycerin,  however,  diminishes  the  decomposition  of  bodily  fat  and  is 
therefore  a  food-material. 

ORIGIN   OF  THE    FAT   IN   THE    BODY. 

A  portion  of  the  bodily  fat  is  derived  directly  from  the  food,  being  simply 
deposited  in  the  tissues  after  absorption.  In  favor  of  this  view  is  the  observation 
that  with  a  scanty  proteid  diet  a  generous  addition  of  meat  causes  the  deposition 
of  large  amounts  of  fat  in  the  body.  The  administration  of  fatty  acids  alone  may 
also  contribute  to  the  formation  of  fat,  inasmuch  as  glycerin,  formed  by  the 
body,  must  combine  with  them  in  the  process  of  metabolism. 

As  a  result  of  fattening  experiments  with  different  warm-blooded  animals 
(pig,  goose,  dog),  in  which,  in  addition  to  a  large  excess  of  starch,  only  a  small 
amount  of  fat  and  proteid  is  supplied,  the  conclusion  has  been  reached  that  a 
direct  transformation  of  the  absorbed  carbohydrates,  rich  in  oxygen,  into  fatty 
tissue,  poor  in  oxygen,  takes  place.  Pfluger  found  that  the  sugar-molecule  of  the 
food,  given  in  excess  of  the  requirements  for  the  development  of  fat  in  the  animal, 
is  in  part  oxidized  and  in  part  reduced,  so  that,  on  the  one  hand,  carbon  dioxid, 
and,  on  the  other  hand,  the  group  of  atoms  concerned  in  the  formation  of  fat, 
result,  inasmuch  as  the  molecular  groups  CH  OH  are  reduced  to  CH3.  The  carbon 
dioxid  that  is  exhaled  when  fat-formation  takes  place  in  consequence  of  the 
administration  of  starch  is  thus  derived  from  two  sources,  namely,  in  part  from 
the  process  of  decomposition  described,  and  in  part  from  the  total  combustion 
of  starch.  The  excessive  elimination  of  carbon  dioxid  in  this  process  of  fat- 
formation  in  consequence  of  an  excessive  starchy  diet  must  naturally  cause  an 
increase  in  the  respiratory  quotient,  even  above  1.2. 

If  the  carbohydrates  be  considered  as  decomposing  into  fat,  carbon  dioxid 
and  water,  100  grams  of  starch  or  in.i  grams  of  sugar  will  yield  at  most  41.1 
grams  of  fat,  47.5  grams  of  carbon  dioxid  and  11.4  grams  of  water.  Also  the 
circumstance  that  bees  utilize  the  sugar  of  honey  in  the  formation  of  wax  is  in 
favor  of  the  production  of  fat  from  carbohydrates.  According  to  Pasteur  and 
E.  Voigt,  glycerin  can  be  formed  from  carbohydrates. 

Does  fat  result  from  proteid  metabolism  ?  v.  Pettenkofer  and  v.  Voit  reached 
the  conclusion,  as  a  result  of  their  experiments,  that  fat  can  be  formed  in  the  ani- 
mal body  from  proteids.  They  fed  a  dog  with  large  amounts  of  meat,  and  although 
all  of  the  nitrogen  thereof  was  excreted  in  the  urine  and  the  feces,  a  portion  of 


DEPOSITION    OF    FAT    AND    FLESH    IN    THE    BODY.  445 

the  carbon  of  the  meat  could  not  be  recovered  from  the  excreta.  They  concluded, 
therefore,  that  this  carbon  had  been  transformed  into  fat  for  accumulation  in 
the  body. 

This  statement  is  contradicted  by  Pfluger  on  the  basis  of  his  own  investiga- 
tions, which  lead  him  to  the  conclusion  that  the  doctrine  of  the  development 
of  fat  from  proteids  in  the  bodies  of  animals  is  entirely  groundless.  If  it  were 
assumed  that  fat  could  be  formed  from  proteid,  such  formation  is  not  possible 
through  simple  decomposition  of  the  proteid  molecule,  but  rather  it  w^ould  be 
necessary  for  decomposition  first  to  take  place  and  then  synthesis  of  the  decom- 
posed parts. 

Earlier  investigators,  who  accepted  the  formation  of  fat  from  proteids,  be- 
lieved that  the  proteids  administered  broke  up  into  a  non-nitrogenous  and  a 
nitrogenous  atom-complex.  The  former,  in  case  it  did  not  leave  the  body  com- 
pletely decomposed  into  carbon  dioxid  and  water  when  a  rich  proteid  diet  was 
taken,  was  believed  to  furnish  the  material  for  the  formation  of  fat,  while  the 
latter  was  supposed  to  leave  the  body  oxidized  principally  into  urea. 

The  following  experiments  support  the  view  that  fat  can  develop  from  proteid 
furnished  as  food:  (i)  Ssubotin  and  Kemmerich  fed  nursing  bitches  with  meat 
almost  free  from  fat,  and  found  that  the  greater  the  amount  of  meat  eaten,  the 
greater  was  the  amount  of  milk  produced  and  thus  also  of  fat.  In  these  experi- 
ments, however,  the  possibility  is  not  excluded  that  the  bitches  utilized  the  fat 
of  their  own  bodies  in  the  preparation  of  the  milk.  (2)  Radziejewski  gave  a 
lean  dog  meat  almost  free  from  fat  and  in  addition  pure  rape-oil,  one  of 
whose  constituents,  erucic  acid,  does  not  occur  normally  in  the  animal  body. 
When  the  animal,  after  a  period  of  feeding  of  considerable  length,  had  accumulated 
fat,  chemical  examination  demonstrated  that  the  tissues  contained,  in  addition 
to  erucin,  also  fat  which  otherwise  is  normally  present  in  the  dog.  In  an  analogous 
manner  Lebedeff  found  in  a  dog  after  feeding  with  lean  meat  and  linseed-oil  con- 
siderable amounts  of  linoleic  acid,  together  with  normal  dog's  fat.  In  both  experi- 
ments, however,  the  normal  dog's  fat  could  have  been  derived  from  the  fat  of  the 
meat  fed.  (3)  The  fat  found  within  organs  in  a  state  of  pathological  fatty  degenera- 
tion had  previously  often  been  considered  as  derived  from  the  proteid  protoplasm 
of  the  tissues.  Even  though  it  be  admitted,  says  Pfluger,  that  the  fat  of  the  de- 
generated organs  has  developed  within  them,  and  has  not  gained  entrance  from 
without,  it  would  still  first  be  necessary  to  believe  that  the  cells  everywhere  con- 
tain carbohydrates  or  their  derivatives,  which  it  is  known  with  certainty  can  be 
transformed  into  fat  by  synthetic  processes.  Also  the  fatty  degeneration  produced 
in  the  animal  body  by  phosphorus-poisoning  affords  no  support  for  the  view  that 
fat  is  developed  from  proteid,  for  although  a  small  amount  of  fat  is  found  in  the 
body  after  such  poisoning,  its  development  from  proteid  has  not  yet  been  demon- 
strated. In  the  case  of  fatty  degeneration,  there  is  primarily  an  injury  of  proteid 
bodies  and  in  place  of  these  fat  from  other  sources  appears  in  the  cells  in  a  certain 
measure  as  a  reparative  procedure.  (4)  Nageli  showed  that  lower  forms  of  fungi, 
like  other  plants,  are  able  to  form  proteid,  fat  and  carbohydrates  synthetically 
from  various  matters,  in  part  exceedingly  simple.  Thus,  for  example,  fungi 
generate  fat  synthetically  in  ripening  cheese  probably  from  the  products  of  de- 
composed proteid.  In  the  decomposition  of  entire  cadavers  and  their  transforma- 
tion into  a  mass  consisting  almost  wholly  of  palmitic  and  stearic  acids  (adippcere) 
in  the  presence  of  fungi,  it  cannot  be  concluded  that  a  simple  transformation  of 
albumin  into  these  fats  takes  place. 

DEPOSITION   OF   FAT   AND    FLESH   IN    THE   BODY   (HYPER- 
NUTRITION). 

CORPULENCE  AND  THE  MEANS  FOR  ITS  CORRECTION. 

Hypernutrition  results  if  more  food  is  supplied  than  the  body  is  capable  of 
decomposing  and  again  eliminating.  The  digestive  apparatus  (collectively  and 
in  common  activity)  is  probably  capable  of  digesting  twice  as  much  as  the  re- 
quirements demand.  The  absorbed  excess  of  food  that  is  not  decomposed  is 
accumulated  and  forms  the  superfluous  tissue.  Higher  animals  are  capable, 
although  not  in  the  strict  sense,  of  surviving  on  an  almost  exclusively  proteid  diet. 
Pfluger  was  able  to  keep  a  dog  engaged  in  hard  work  alive  for  an  indefinite  time 
on  a  diet  exclusively  of  meat  and  almost  free  from  fat.  All  of  the  vital  phenomena, 
therefore,  can  be  carried  on  by  means  of  proteid  alone.  Albumin  may,  accordingly, 


446  DEPOSITION    OF    FAT    AND    FLESH    IN    THE    BODY. 

wholly  replace  fat  in  the  process  of  metabolism.  The  smallest  amount  of  lean  meat 
that  thus  maintains  the  metabolic  equilibrium  is  designated  by  Pfluger  as  the 
nutritive  requirement.  The  supply  of  fat  or  carbohydrates  exclusively  is  never 
capable  of  maintaining  life,  as  the  animal  under  such  circumstances  is  compelled 
to  consume  its  own  flesh.  Therefore,  a  certain  indispensable  amount  of  proteid 
must  absolutely  be  present  in  every  diet. 

If  an  amount  of  proteid  be  added  to  the  food  that  is  sufficient  in  itself  to. 
fulfil  the  requirement  and  if  any  desired  amount  of  fat  is  added,  almost  all  of 
the  proteid  will  be  decomposed  and  almost  all  of  the  fat  will  be  deposited  as  such. 
The  conditions  are  much  the  same  if  carbohydrate  is  supplied  instead  of  fat, 
except  that  in  this  case  the  carbohydrate  is  transformed  in  the  body  into  fat 
and  is  deposited  as  such.  The  greater  the  amount  of  non-nitrogenous  food  that 
is  supplied  in  addition  to  the  nutritive  requirement  of  proteid  the  more  favorable 
are  the  conditions  for  fattening,  because  all  of  the  non-nitrogenous  matters  are 
transformed  into  bodily  fat. 

If  proteid  is  not  supplied  in  sufficient  amount  the  deficiency  may  be  made 
good  by  fat  or  carbohydrate,  and  in  such  proportion  that  two-thirds  of  the  nutritive 
requirement  may  be  supplied  by  non-nitrogenous  matters.  Under  such  circum- 
stances the  latter  replace  the  deficiency  of  proteid  in  accordance  with  the  amount 
of  their  potential  energy  as  indicated  by  the  number  of  calories  yielded  in  their 
combustion.  From  these  facts  it  follows  that  the  greater  or  smaller  amount  of 
albumin  supplied  with  such  food  is  decomposed  almost  wholly  in  the  process  of 
metabolism,  indifferently  whether  much  or  little  fat  or  carbohydrate  is  sup- 
plied at  the  same  time.  In  direct  contrast  to  the  proteid,  the  amount  of  fat  or 
carbohydrate  that  is  consumed  in  the  process  of  metabolism  is  in  nowise  dependent 
upon  the  amount  thereof  contained  in  the  food.  Generally,  the  amount  of  carbo- 
hydrate or  fat  that  undergoes  decomposition  is  the  smaller  the  larger  the  amount 
of  proteid  supplied.  The  nutritive  requirement  is  satisfied  first  and  foremost  by 
proteid,  but  if  the  amount  of  proteid  supplied  is  not  sufficient,  the  fats  and  the 
carbohydrates  are  also  utilized  in  so  far  as  the  requirements  demand.  In  order 
to  comprehend  the  laws  of  fattening  by'  means  of  proteid  and  starch,  it  should 
be  borne  in  mind  that  for  the  satisfaction  of  the  nutritive  requirement,  in  addition 
to  almost  the  entire  amount  of  proteid  supplied,  so  much  carbohydrate  is  decom- 
posed as  will  wholly  suffice  for  the  nutritive  requirement.  The  amount  of  carbo- 
hydrate left  over  is  deposited  as  fat.  In  accordance  with  the  foregoing  statements, 
on  supplying  equal  amounts  of  carbohydrate  a  proportionately  larger  amount 
will  be  conserved  the  larger  the  amount  of  proteid  furnished. 

The  amount  of  nutritive  requirement,  that  is,  the  smallest  amount  of  fat-free 
meat  that  alone  establishes  metabolic  equilibrium,  is  governed  by  the  flesh-weight 
of  the  animal  and  increases  in  direct  proportion  to  this.  A  fat  animal  has,  there- 
fore, apparently  a  smaller  nutritive  requirement  only  because  the  total  amount 
of  fat,  acting  as  a  similar  amount  of  dead  matter,  consumes  nothing. 

The  decomposition  in  the  process  of  metabolism  of  the  proteid  taken  with 
the  food  increases  with  the  supply,  even  when  this  far  exceeds  the  requirement, 
but  a  portion  of  the  excess  is  always  conserved.  In  this  manner  there  is  a  gradual 
deposition  of  flesh  in  the  body. 

As  the  amount  of  proteid  supplied  with  the  food  has  practically  no  influence 
upon  the  deposition  of  fat  in  the  body,  and  the  carbohydrates  are  generally  not 
so  useful  as  proteid,  fat  will  be  produced  most  advantageously  with  the  smallest 
amount  of  proteid  possible,  but  with  the  largest  possible  amount  of  starch  in 
the  food.  If  an  animal  on  a  mixed  diet  in  a  moderate  state  of  fattening  be  given 
a  further  supply  of  proteid,  this  will  at  once  satisfy  a  portion  of  the  nutritive 
requirement,  which  theretofore  had  been  satisfied  by  non-nitrogenous  matters. 
These  therefore  can  be  dispensed  with  and  are  deposited  as  fat. 

With  a  diet  of  meat  exclusively  deposition  of  flesh  is  possible  only  when  the 
proteid  of  the  food  exceeds  the  requirement.  The  largest  portion  of  the  excess 
of  proteid  is  decomposed  and  some  is  deposited.  With  increase  in  the  weight  of 
flesh,  the  consumption  of  proteid  soon  increases,  and,  accordingly,  the  amount  of 
excess  diminishes.  It  is,  therefore,  one  of  the  properties  of  proteid  food  that  it 
tends  speedily  to  neutralize  the  conditions  necessary  for  the  deposition  of  flesh 
if  these  are  present. 

With  a  mixed  diet  deposition  of  flesh  can  be  attained  only  if  the  supply  of 
proteid  exceeds  the  amount  indispensable.  Under  such  circumstances  only  from 
7  to  9  per  cent,  on  the  average,  at  most  16  per  cent.,  of  the  proteid  supplied,  is 
conserved  by  the  non-nitrogenous  articles  of  food.  The  deposition  of  flesh  is  then 
the  greater  the  larger  the  amount  of  proteid  contained  in  the  food.  Of  the  proteid 


CORPULENCE    AND    THE    MEANS    FOR    ITS    CORRECTION.  447 

consumed  the  body  can  deposit  only  one  part  of  proteid,  while  nine  parts  are 
decomposed.  In  addition,  for  two  parts  of  decomposing  proteid  one  part  of  fat 
is  formed  from  the  carbohydrate  supplied  in  excess. 

Excessive  deposition  in  the  body  of  man,  corpulence,  is  to  be  considered  an 
abnormal  manifestation  of  metabolism,  which  to  the  subject  may  be  a  source 
not  alone  of  inconvenience,  but  also  of  disorders  or  even  of  serious  danger.  With 
reference  to  the  causes  of  obesity,  a  certain  degree  of  congenital  predisposition 
(in  from  33  to  56  per  cent,  of  the  cases)  cannot  be  denied,  inasmuch  as  members 
of  certain  families  increase  more  readily  in  weight  (as  is  likewise  true  of  certain 
breeds  of  animals) ,  while  others,  even  when  supplied  with  an  abundance  of  food, 
which  may  reach  enormous  amounts,  remain  thin.  The  principal  cause,  however, 
is  an  habitually  excessive  supply  of  food  beyond  the  normal  metabolic  average, 
although  almost  every  corpulent  person  will  with  complacent  self-deception  main- 
tain that  he  really  eats  remarkably  little. 

The  mistake  should  be  avoided  of  considering  the  corpulent  individual  as 
always  excessively  fat.  The  process  of  overfeeding  results  at  first  in  the  deposition 
both  of  fat  and  of  flesh.  On  continuance  of  the  process  the  development  of 
muscular  tissue  diminishes,  because  in  consequence  of  his  clumsiness  and  helpless- 
ness the  corpulent  individual  is  rendered  inactive.  As  a  result,  the  nutrition  of 
the  muscular  structures  is  secondarily  impaired.  Some  active  corpulent  individ- 
uals, however,  retain  their  large  deposition  of  flesh  throughout  life.  If,  however, 
those  factors  become  especially  operative  later  on  that  favor  the  production  of 
fat,  corpulence  may  be  transformed  into  obesity  exclusively,  as,  naturally,  is  fre- 
quently the  case. 

The  following  influences  favor  the  development  of  corpulence:  (i)  An  excessive  diet 
of  proteid,  with  a  corresponding  addition  of  fat  or  carbohydrate.  The  proteid  of 
the  food  serves  for  the  deposition  of  albuminates  in  the  body,  while  the  fat  is 
produced  by  the  ingestion  of  fat  and  carbohydrates.  (2)  Diminished  consump- 
tion of  nitrogen  in  the  body,  in  consequence  of  (a)  lessened  muscular  activity  (little 
movement,  much  sleep),  (b)  Enfeeblement  of  the  sexual  functions,  as  shown  by 
the  fattening  of  castrated  animals,  as  well  as  the  circumstance  that  women  readily 
become  corpulent  after  cessation  of  menstruation,  probably  in  consequence  princi- 
pally of  withdrawal  of  the  stimulating  influence  of  vascular  activity,  (c)  Dimin- 
ished mental  activity  (obesity  of  idiocy),  phlegmatic  temperament,  probably  for 
the  foregoing  reason.  Conversely,  vigorous  mental  activity,  an  excitable  tem- 
perament, anxiety  and  grief  counteract  the  fattening  process,  (d)  The  corpu- 
lent individual  need  consume  relatively  less  material  for  the  generation  of  heat 
in  his  body,  partly  because  his  compact  body,  in  consequence  of  the  greater 
concentration  of  mass,  gives  off  less  heat  from  the  external  integument  than  a 
delicate  slender  body,  and  partly  because  of  the  thick  layer  of  fat  as  a  poor  con- 
ductor of  heat  prevents  direct  loss  of  heat  by  conduction.  As  a  result  of  the 
relatively  lessened  production  of  heat  in  the  body  thus  required,  there  may  be  an 
increased  deposition  of  tissue,  (e)  A  reduction  in  the  number  of  red  blood-cor- 
puscles, which  stimulate  oxidation-processes  in  the  body,  is  generally  followed  by 
an  increase  in  the  amount  of  fat.  Corpulent  persons  are,  therefore,  not  rarely 
fat  because  they  are  anemic.  Women  with  a  reduced  number  of  red  blood-cor- 
puscles are  generally  fatter  than  men.  (/)  The  use  of  alcohol  favors  the  conserva- 
tion of  fat  in  the  body,  because,  on  account  of  the  readiness  with  which  it  is 
oxidized,  it  protects  the  fat  in  the  body  from  combustion  (the  obesity  of  drunkards) . 

In  addition  to  the  great  inconvenience  due  to  the  weight  of  the  body,  cor- 
pulence, and  particularly  obesity,  is  attended  with  certain  disadvantages  and 
dangers.  Among  these  are  dyspnea,  readiness  of  fatigue,  the  development  of 
intertrigo  in  the  folds  of  the  skin  and  of  so-called  fat-hernia,  and  finally  the  danger 
of  fatty  degeneration,  of  cardiac  paralysis  and  of  apoplexy. 

For  the  correction  of  obesity  the  following  measures  should  be  adopted:  (i) 
Uniform  reduction  of  all  of  the  articles  of  food  to  the  proportions  of  the  normal 
diet.  The  obese  patient  should  weigh  himself  and  his  daily  amount  of  food  from 
week  to  week.  So  long  as  he  observes  no  reduction  in  body- weight,  the  amount 
of  food  (in  spite  of  the  appetite)  should  be  gradually  and  uniformly  reduced. 
This  course  should  be  pursued  slowly,  without  unduly  sudden  limitation.  Almost 
all  good  resolutions  fail  in  the  face  of  the  excellent  appetite.  A  moderate  reduction 
of  the  fat  and  the  carbohydrates  in  the  normal  diet  would  at  the  same  time  result 
in  consumption  of  the  fat  of  the  body  itself.  Such  individuals  as  are  still  capable 
of  muscular 'activity  may  be  permitted  156  grams  of  proteid,  43  grams  of  fat, 
114  grams  of  carbohydrates.  Those  in  whom  hypostasis,  hydremia,  and  respira- 
tory difficulty  have  developed  may  be  permitted  170  grams  of  proteid,  125  grams 


448  THE    METABOLISM    OF    THE    TISSUES. 

of  fat  and  170  grams  of  carbohydrates.  It  is,  however,  not  advisable  to  restrict 
a  corpulent  person  excessively  as  to  fats  and  carbohydrates  alone,  as  is  customary 
in  the  so-called  cure  of  Banting.  Such  a  violent  modification  of  the  normal  diet 
is  often  attended  with  profound  derangement  of  the  entire  metabolism.  Many 
persons  have  suffered  greatly  in  health  as  a  result  of  this  procedure.  Every  long- 
continued  limitation  of  diet  in  one  direction  is  deleterious  and  will  accordingly 
result  in  emaciation,  but  not  without  danger,  for  it  has  a  disturbing  influence  upon 
the  entire  metabolism  and  thus  in  a  given  sense  is  pathological.  (2)  It  is  advisable 
during  the  principal  meals  to  avoid  as  much  as  possible  the  use  of  fluids  of  all 
kind  (until  about  three-quarters  of  an  hour  later) ,  because  by  this  means  the 
absorption  and  the  digestive  activity  in  the  intestine  are  rendered  less  effective. 
(3)  Muscular  activity  should  be  increased  by  vigorous  work,  and  also  mental 
activity  should  be  encouraged.  (4)  Heat-dissipation  should  be  favored  by  cold 
baths  of  long  duration,  followed  by  vigorous  friction  of  the  skin  to  the  point  of 
bright  redness.  At  the  same  time  the  clothing  should  be  light.  The  patient 
should  sleep  in  a  cool  room  and  for  not  too  long  a  time.  In  this  manner  the 
increased  ingestion  of  tea  and  coffee  also  is  useful,  actively  stimulating  the  cuta- 
neous circulation  and  thereby  the  dissipation  of  heat.  (5)  Mild  laxatives,  such  as 
acid  fruits,  cider,  alkaline  carbonates  (Marienbad,  Carlsbad,  Vichy,  Neuenahr,  Ems, 
etc.),  have  a  favorable  influence  in  the  correction  of  obesity  by  increasing  the 
evacuations  from  the  intestines  and  diminishing  absorption.  (6)  If,  in  the  pres- 
ence of  marked  deposition  of  fat,  there  is  already  danger  of  enfeeblement  of  the 
action  of  the  heart  an  attempt  should  be  made,  with  caution,  by  means  of  in- 
creased muscular  activity  (mountain-climbing  and  the  like),  to  stimulate  the 
heart  and  to  strengthen  its  musculature.  By  this  means  the  circulation  is  improved 
and  metabolism  becomes  more  active,  so  that  recovery  may  even  yet  be  brought 
about  with  the  aid  of  a  sensible  diet. 

Entirely  different  from  the  process  of  fattening,  which  consists  in  the  deposi- 
tion of  large  droplets  of  fat  in  the  fat-cells  of  the  panniculus  and  about  the  viscera, 
as  well  as  in  the  bone-marrow  (but  never  in  the  subcutaneous  connective  tissue 
of  the  eyelids,  the  penis,  the  red  margin  of  the  lips,  the  ears,  the  nose),  is  the  con- 
dition of  fatty  atrophy  or  fatty  degeneration,  which  occurs  in  the  form  of  fatty 
granules  in  the  albuminous  tissues,  for  example,  in  muscle-fibers  (of  the  heart), 
glandular  cells  (liver,  kidneys),  cartilage-cells,  lymph-corpuscles  and  pus-corpus- 
cles, as  well  as  in  divided  nerves.  If  this  process  increases  in  the  tissues  to  such 
a  degree  that  the  albumin  is  as  a  result  made  to  disappear  without  being  again 
restored,  the  fatty  atrophy  or  degeneration  is  marked.  It  is  observed  after  severe 
fevers,  marked  (artificial)  heating  of  the  tissues,  diminished  absorption  of  oxygen 
into  the  body  (as  has  been  observed  especially  after  phosphorus-poisoning),  also 
in  drunkards,  after  certain  forms  of  intoxication  (arsenic),  and  in  connection  with 
disorders  of  circulation  and  innervation.  Finally,  some  organs  exhibit  fatty  de- 
generation in  connection  with  special  diseases.  In  rare  cases  in  the  new-born  the 
entire  body  may  rapidly  undergo  fatty  atrophy. 

THE  METABOLISM  OF  THE  TISSUES. 

All  tissues  require  for  their  normal  existence  and  for  their  functional 
activity  the  process  of  metabolism.  The  chief  medium  for  this  is  the 
blood-current,  which,  acting  as  the  principal  traffic-carrier  in  the  metab- 
olic process,  conveys  the  material  for  the  restoration  of  the  tissues  and  re- 
moves the  products  of  their  vital  activity.  Those  tissues  that,  like  the 
cornea  and  cartilage,  possess  no  vessels  in  their  structure,  must  receive  the 
nutritive  plasmatic  fluid  from  the  adjacent  capillaries  through  their 
cellular  elements,  which  thus  act  as  channels  for  the  conveyance  of  the 
fluid.  Therefore,  interference  with  the  normal  circulation  in  the  tissues, 
as,  for  example,  through  constriction  or  calcification  of  the  walls  of  the 
vessels  and  the  like,  is  attended  with  derangement  of  nutrition;  com- 
plete occlusion,  as,  for  example,  by  thrombosis,  total  compression,  or 
artificially  by  ligature  of  all  the  afferent  vessels,  is  followed  by  certain 
destruction  of  the  tissues,  which  soon  appears  in  the  form  of  gangrene 
(necrosis). 


THE    METABOLISM    OF    THE    TISSUES.  449 

Atrophy  resulting  from  reduction  in  the  normal  supply  of  blood  gradually  dis- 
appears in  the  further  course  of  time. 

In  accordance  with  what  has  been  stated  a  double  current  can  be 
recognized  in  the  fluids  of  the  tissues,  the  afferent  current,  which  brings 
the  materials  for  the  restoration  of  the  tissues,  and  the  efferent  current, 
which  removes  the  effete  products  of  metabolic  activity.  The  former 
will  convey  the  albuminates,  fats,  carbohydrates,  as  well  as  the  salts 
in  solution,  as  they  are  taken  up  by  the  organs  of  absorption,  for  the 
formation  of  the  tissues.  It  is  clear  that  obstruction  of  any  sort  in  the 
arterial  system  of  the  tissue  in  question  will  diminish  this  supply.  The 
metabolism  is  as  a  result  restricted,  in  consequence  of  deficient  formative 
activity. 

This  current  can  be  recognized  from  the  circumstance  that  after  injection  of 
a  relatively  indifferent,  readily  demonstrable  substance,  for  instance  potassium 
ferrocyanid,  into  the  blood,  that  substance  will  be  found  in  the  blood  within  the 
tissues,  whither  it  has  been  conveyed  with  the  afferent  current. 

The  efferent  current  removes  the  products  of  metabolism,  particu- 
larly urea,  carbon  dioxid,  water  and  salts,  in  order  to  convey  these  with 
the  utmost  rapidity  to  the  excretory  organs. 

This  current  can  be  recognized  from  the  circumstance  that  if  a  soluble  sub- 
stance be  introduced  into  the  tissues  themselves,  as  with  a  syringe  for  subcutaneous 
injection,  for  example  potassium  ferrocyanid,  this  will  be  found  in  the  urine  in 
the  course  of  a  few  (from  two  to  five)  minutes. 

If  the  efferent  current  from  the  tissues  is  so  strong  and  so  large  that 
the  excretory  organs  are  unable  to  eliminate  the  waste  matters  from  it, 
these  may  again  wander  through  the  tissues.  Such  a  condition  is  ob- 
served after  subcutaneous  injection  of  considerable  doses  of  poisonous 
substances,  which  often  enter  the  blood  in  such  large  amount  that, 
before  they  can  be  eliminated,  they  are  conveyed  to  other  tissues,  for 
example  the  nervous  system,  upon  which  they  exert  their  effects  before 
any  considerable  degree  of  elimination  has  taken  place.  If  large  amounts 
of  foreign  substances  are  injected  they  may  even  be  temporarily  de- 
posited partly  in  other  tissues,  particularly  in  the  liver  and  the  bone- 
marrow.  As  the  afferent  current  traverses  two  canal-systems,  the  veins 
and  the  lymphatics,  it  is  clear  that  obstruction  of  these  paths  will  disturb 
the  metabolism  as  a  result  of  interference  with  the  normal  removal  of 
effete  matters.  On  tight  constriction  of  a  peripheral  portion  of  the 
body,  in  consequence  of  which  veins  and  lymphatics  are  compressed, 
stagnation  of  the  current  takes  place  to  so  marked  a  degree  that  even 
swelling  of  the  tissues  may  result. 

In  the  propagation  of  the  currents  in  the  tissues  the  activity  of  the 
muscles  is  of  great  importance,  inasmuch  as  not  only  do  they  favor  the 
movement  of  the  fluid  in  the  vessels  by  pressure  within  the  yielding 
tissues,  but  also  where  they  are  attached  to  the  periosteum,  the  peri- 
chondrium  and  the  joints  they  cause  changes  in  the  form  of  the  inter- 
stices and  thereby  influence  the  movement  of  the  fluid  within  the  latter 
by  alternate  contraction  and  relaxation. 

H.  Nasse  found  the  specific  gravity  of  the  blood  in  the  jugular  vein  0.225 
in  a  thousand  higher  than  that  of  the  blood  in  the  carotid  artery,  and  contain- 
ing 0.9  part  more  by  weight  in  1000  of  solids.  One  thousand  cu.  cm.  of  blood 
yield  in  circulating  through  the  head  more  than  5  cu.  cm.  of  transudate  to  the 

tissues. 

29 


450  THE    METABOLISM    OF    THE    TISSUES. 

The   activity   of   metabolism  in   the   tissues   and   at   the   same  time   the   in- 
tensity in  the  varying  currents  depends  upon  diverse  factors : 

1.  Upon  the  activity  of  the  tissues  themselves.     The  increased  activity  of  an 
organ  can  be  recognized  from  the  larger  amount  of  blood  contained  in  it  and  the 
increased  activity  of  the  circulation,  which  in  turn  are  the  media  for  the  metab- 
olism.    If  an  organ  is  subjected  to  complete  inactivity,  for  example  a  paralyzed 
muscle  or  the  peripheral  extremity  of  a  divided  nerve,  the  amount  of  blood  an'd  its 
interchange  soon  diminish.     The  organism  sends  its  fluids  only  to  active  tissues. 
The  affected  part  becomes  pale  and  flaccid  and  finally  undergoes  fatty  degenera- 
tion.    For  some  organs  increased  metabolism  in  association  with  their  activity 
has   been   demonstrated,    for  example   the  muscles.     Langley  and   Sewall   have 
been     able    to    observe    microscopically    the    metabolism    in    thin    lobules    of 
glands  during  life.     The  cells  both  of  the  serous  and  of  the  mucous  and  peptic 
glands  become  filled  in  the  state  of  rest  with  coarse  granules,  dark  in  transmitted 
and  white  in  reflected  light,  which  are  consumed  during  the  period  of  activity. 
During  sleep,  in  which  most  of  the  organs  are  at  rest,  metabolism  is  restricted. 
It  is  likewise  diminished  by  darkness,  while  it  is  stimulated  by  light  (obviously 
through    nervous    influences).     The    variations    in    total    metabolism    will    be 
reflected  in  the  elimination  of  carbon  dioxid  and  urea,  which  in  conformity  with 
the  activity  of  the  organism  yields  a  curve  that  is  fairly  parallel  with  that  for 
the  daily  variations  in  respiration,  pulse  and  temperature. 

2.  Also  the  state  of  the  blood  has  a  distinct  influence  upon  the  currents  in  the 
tissues  on  which  the  metabolism  depends.     A  highly  concentrated  blood  deficient 
in  water  (such  as  is  observed  after  profuse  sweating,  copious  diarrhea,  for  example 
in  cases  of  cholera)  renders  the  tissues  dry;  while,  conversely,  the  taking  up  into 
the  blood  of  large  amounts  of  water  renders  the  tissue  more  succulent,  even  to 
the  point  of  dropsy.     The  presence  of  a  considerable  amount  of  sodium  chlorid 
in  the  blood  and  a  reduction  in  the  amount  of  oxygen  in  the  red  blood-corpuscles, 
the  latter  in  association  with  muscular  exertion  causing  dyspnea,  give  rise  to 
increased  disintegration  of  albuminates  and  thus  to  increased  production  of  urea. 
Therefore,  exposure  to  rarefied  air  causes  increased  elimination  of  urea.     Certain 
abnormal  changes  in  the  blood  are  noteworthy:    Thus,  carbon-monoxid  blood  is 
not  capable  of  abstracting  oxygen  from  the  air  and  conveying  carbon  dioxid  from 
the  tissues.     The  presence  of  hydrocyanic  acid  in  the  blood  immediately  interrupts 
the  chemical  oxidation-processes  carried  on  through  the  blood;    the  tissues  no 
longer  remove  oxygen  from  the  bright-red  blood  overladen  with  oxygen,   and 
there  thus  results  asphyxia  from  interference  with  the  internal  respiration.     Fer- 
mentative processes  also  are  interfered  with  in  the  same  way  by  hydrocyanic  acid. 
A  reduction  in  the  total  volume  of  blood  causes,  on  the  one  hand,  the  passage  of 
a  larger  amount  of  water  from  the  tissues  into  the  vessels,  while,  on  the  other  hand, 
it  retards  the  absorption  of  substances  from  the  tissues  (for  example,  poisons  or 
pathological  exudates)   or  from  the  surface  of  the  intestine.     If  the  substances 
derived  from  the  tissues  are  rapidly  eliminated  from  the  blood,  or  transformed 
therein,  subsequent  absorption  takes  place  the  more  rapidly. 

3.  The  blood-pressure  has  an  influence  upon  the  fluid-current,  inasmuch  as 
marked  increase  of  pressure  renders  the  tissues  richer  in  fluid,  but  the  blood  itself 
more  concentrated  (up  to  from  3  to  5  in  1000).     That  pressure  upon  the  afferent 
vessels  causes  the  escape  of  blood-plasma  through  the  walls  of  the  capillaries  can 
be  demonstrated  on  a  surface  of  corium  denuded  of  its  epidermis,  as,  for  example, 
in  a  blister.     Reduction  of  the  blood-pressure  will  have  the  opposite  effect.     After 
administration  of  phosphorus,  copper,  ether,  chloroform,  and  chloral,  the  oxidation- 
activity  in  the  animal  body  is  diminished. 

4.  Elevation  of  the  temperature  of  the  tissues  (for  several  hours  during  the  day) 
does  not  cause  increased  destruction  of  proteid  and  fat.     This  subject  is  discussed 
also  on  pp.  404,  406  and  409. 

5.  An  influence  of  the  nervous  system  upon  the  tissue-metabolism  has  also  been 
observed.     Doubtless  this  influence  is  a  double  one.     In  the  first  place  it  may  be 
exerted  indirectly  through  the  intermediation  of  the  vessels,  the  vascular  nerves 
causing  contraction  or  dilatation  of  the  vessels,  and  thus  increasing  or  diminishing 
the  amount  of  blood  passing  through  the  vessels.      In  this  connection  attention 
should  be  called  especially  to  pathological  conditions,  abnormal  stimulation  or 
paralysis  of  the  vascular  nerves  or  their  centers.     Independently  of  the  vessels, 
however,  certain  special  nerves  that  have  been  designated  trophic  control  the 
metabolism  in  the  tissues.     Atrophy  caused  by  nerve-paralysis  increases  the  longer 
it  persists.      Examples  of  metabolism  in  tissues  excited  directly  through  the  nerves 
are  the  secretion  of  saliva  on  nerve-irritation  after  exclusion  of  the  circulation 


REGENERATION.  451 

and  metabolism  on  contraction  of  bloodless  muscles.     Increased  respiration  and 
apnea  are  not  followed  by  increased  oxidation. 

REGENERATION. 

The  power  of  regenerating  parts  that  have  been  lost  varies  widely  in  different 
organs  and  tissues.  It  is  much  more  marked  in  the  lowrer  animals  than  in  warm- 
blooded animals.  Division  of  the  fresh-water  polyp  (hydra)  is  followed  by  the 
development  of  two  new  individuals.  An  entire  being  may  even  develop  from 
every  excised  portion  of  the  trunk  of  the  body;  only  exceedingly  small  pieces  give 
rise  to  incomplete  reproduction.  No  animal  regenerates  portions  of  the  arm. 
Also  the  planaria  exhibit  similar  powers  of  regeneration.  From  every  portion  of 
the  umbrella  of  certain  medusae  (thaumantiades) ,  if  it  contain  only  a  portion  of 
the  margin,  a  new  medusa  may  develop.  From  the  surface  of  a  piece  of  the  trunk 
of  a  turbellaria  directed  downward  a  pedal  extremity  develops,  from  the  upper 
surface  a  cephalic  extremity,  and  if  attached  horizontally  heads  develop  at  both 
extremities.  Artificial  division  is  possible  also  in  rhizopods  and  infusoria. 
Divided  infusoria  regenerate  only  if  the  divided  portion  contains  a  part  of  the 
nucleus.  Transversely  divided  earthworms  (lumbriculus  variegatus)  regenerate 
entirely  to  whole  individuals.  The  decapitated  head  has  been  observed  to  re- 
generate five  times.  In  starworms  the  excised  snout,  together  with  the 
pharyngeal  ring  of  the  central  nervous  system,  regenerates.  Spiders  and  crabs 
regenerate  feelers,  legs  and  claws;  snails,  parts  of  the  head,  including  feelers  and 
eyes,  providing  the  central  nervous  system  is  uninjured.  Some  fish  are  capable 
of  replacing  repeatedly  destroyed  fins,  principally  the  caudal  fin.  Salamanders 
and  lizards  exhibit  regeneration  of  the  entirely  lost  tail,  with  bones,  muscles  and 
even  the  posterior  extremity  of  the  spinal  cord.  In  young  frogs  amputated 
legs  regenerate,  but  only  when  the  bones  also  are  divided,  and  not  after  ex- 
articulation.  In  tritons  the  lower  jaw  regenerates.  In  order,  however,  that  this 
regeneration  shall  take  place  a  stump  at  least  must  be  left.  Total  extirpation 
of  the  parts  mentioned  destroys  the  power  of  regeneration. 

Loeb  designates  as  heteromorphosis  the  phenomenon  that  occasionally  after 
injuries  supernumerary  parts  appear  that  otherwise  do  not  belong  in  such  situa- 
tions. Thus,  for  example,  in  young  lizards  lateral  notching  of  the  tail  may  cause 
the  growth  of  a  second  tail  from  the  wound;  likewise  supernumerary  extremities 
develop  in  tailed  amphibia  after  amputation.  Planaria  injured  on  the  head  exhibit 
the  growth  of  a  second  head. 

In  amphibia  and  reptiles  the  regeneration  of  organs  and  tissues  follows,  on 
the  whole,  the  type  of  embryonal  development,  and  the  histological  processes  in 
the  growing  caudal  extremity  and  in  regenerating  portions  of  the  body  of  earth- 
worms take  place  in  the  same  manner.  In  amphibia  and  reptiles  only  tissue  of 
the  same  kind  develops  from  injured  tissue.  The  spinal  cord  regenerates  from 
the  epithelial  cells  of  the  central  canal.  In  the  process  of  tissue-formation  the 
leukocytes  assume  only  the  function  of  nutrition  and  conveyance  of  material.  It 
is  a  remarkable  fact  that  tadpoles  develop  after  destruction  of  the  brain  and  the 
medulla  and  functional  exclusion  of  the  spinal  cord. 

The  power  of  regeneration  is  much  more  restricted  in  warm-blooded  animals 
and  in  man.  In  these  also  it  is  confined  principally  to  early  life.  True  regenera- 
tion is  exhibited  by — 

1.  The  blood;   first  the  plasma,  then  the  white  and  finally  also  the  red  blood- 
corpuscles. 

2.  The  epidermal  structures  and  the  epithelium  of  the  mucous  membrane  re- 
generate by  cell-division  in  the  deepest  layers  after  previous  nuclear  division. 
After  direct  loss  they  regenerate  so  long  as  the  normal  matrix  upon  which  they 
grow  and  the  deepest  layer  of  cell-protoplasm  capable  of  development  is  not  also 
destroyed.     In  the  latter  event,  regeneration  ceases  and  restoration   must  take 
place  from  the  margins  of  the  deficiency.     In  the  process  of  regeneration,  there- 
fore, growth  takes  place  always  either  from  the  deep  layers,  or,  after  their  de- 
struction, from  the  margins.     There   develop  under  such  circumstances  proto- 
plasmic   wandering   cells  that  in  part  become  detached   and   help   to  close  the 
deficiency,  and  in  part  the  deepest  layer  of  cells  develops  into  large,  multinu- 
cleated  protoplasmic  cells,    which  multiply   by  division  into  polygonal  flat  nu- 
cleated cells. 

The  nail  grows  from  the  posterior  fold  forward,  on  the  fingers  in  the  course 
of  from  four  to  five  months,  on  the  great  toe  in  about  twelve  months  (and  more 


452  REGENERATION. 

slowly  in  extremities  with  fractured  bones).  Its  matrix  extends  as  far  as  the 
lunula,  and  its  total  or  partial  destruction  causes  corresponding  loss  of  the  nail. 
The  eyebrows  are  changed  in  from  one  hundred  to  one  hundred  and  fifty  days,  the 
remaining  hairs  more  slowly.  Destruction  of  the  papilla  in  a  hair-follicle  prevents 
regeneration.  Cutting  accelerates  the  growth  of  the  hair,  although  cut  hair  does 
not  grow  longer  than  uncut  hair.  •  After  attaining  a  certain  length  the  hair  falls 
out.  The  hair  never  grows  at  its  free  extremity.  The  epithelial  cells  of  the 
mucous  membranes  and  the  glands  appear  to  be  subjected  to  a  regular  cycle 
in  their  utilization  and  in  the  regeneration  of  new  cells.  In  the  mammary  gland 
and  likewise  in  the  sebaceous  glands  partial  desquamation  of  secretory  cells,  and 
also  their  regeneration,  are  evident.  The  regeneration  of  spermatozoa  takes  place 
through  spermatoblasts.  In  catarrhal  conditions  increased  desquamation  and 
regeneration  of  epithelial  cells  take  place  upon  the  mucous  membranes,  together 
with  the  appearance  of  indifferent  cell-forms  (leukocytes)  in  large  number.  The 
crystalline  lens,  which  represents  an  invaginated  epidermal  sac  that  has  become 
independent,  regenerates  like  epithelial  structures.  Its  matrix  is  the  anterior  wall 
of  the  capsule,  with  the  single  layer  of  cells  present  in  this  situation.  If  the  lens 
is  removed,  but  with  preservation  of  these  cells,  regeneration  takes  place,  the 
cellular  elements  becoming  elongated  into  lenticular  fibers  and  filling  the  entire 
cavity  of  the  empty  capsule.  The  removal  of  large  amounts  of  water  from  the 
body  may  cause  turbidity  of  the  lens. 

3.  The  blood-vessels  exhibit  extensive  regeneration,  which  takes  place  in  the 
same  way  as  the  formation  of  the  vessels,  but  this  has  already  been  discussed. 
There  always  develop  at  first  capillaries,  about  which,  later  on,  the  characteristic 
tissue-elements  are  deposited  from  without  in  places  that  subsequently  are  to 
become  arteries  or  veins.     In  case  of  injury  or  permanent  occlusion  of  a  vessel, 
at  least  the  portion  to  the  next  collateral  vessel  is  always  wholly  obliterated, 
derivatives  of  the  endothelial  cells,  connective-tissue  corpuscles  from  the  vessel- 
wall  and  wandering  cells  being  transformed  into  the  spindle-cells  of  the  obliterating 
cicatrix.     On  the  blood-vessels  of  young  and  adult  animals  blind  and  solid  pro- 
cesses are  present  as  an  evidence  of  constant  obliteration  and  regeneration  of  the 
vessels.     The  lymphatics  behave  in  the  same  way  as  the  blood-vessels.     After 
removal  of  lymphatic  glands  regeneration  may  take  place,  especially  when  stasis 
of  lymph  is  present. 

4.  The  contractile  substance  of  the  muscular  -fibers  may  undergo  regeneration 
if  destroyed  by  injury  or  degenerative  processes.     The  contractile,  transversely 
striated  contents  of  the  sarcolemma  undergo  granular  or  fibrillar  degeneration, 
or  break  up  into  discs  or  plates,  the  latter  being  observed   in    connection  with 
waxy  degeneration  of  the  abdominal  muscles  in  cases  of  typhoid  fever.     At  the 
same  time  nuclei  in  large  number  appear  within  the  sarcolemma,  as  well  as  in 
this  itself,  and  the  previously  contractile  contents  are  converted  into  cell-proto- 
plasm.    In  the  course  of  a  few  days  mitotic  cell-division  is  observed.     The  proto- 
plasm exhibits  at  first  fine  fibrillary  longitudinal  striation.     From  this  fibrous 
tissue  of  myogenous  origin,  transversely  striated,  nucleated  fibers  may  be  devel- 
oped in  the  course  of  months.     In  case  of  considerable  loss  of  muscular  tissue  or 
gaping  wounds  a  fibrous  cicatrix  forms.     In  fibers  injured  through  subcutaneous 
wounds  Neumann  observed,  after  from  five  to  seven  days,  a  budhke  prolongation 
of  the  divided  extremities,  at  first  without  transverse  striation,  which,  however, 
appeared,  later.     Unstriated  muscle-fiber  may  regenerate  after  injury.     The  nuclei 
of  the  injured  fibers  divide  by  karyokinesis  and  about  each  newly  formed  nucleus 
a  new  muscle-fiber  develops  in  consequence  of  the  differentiation  of  the  surrounding 
protoplasm.     The  fibers  divide  in  the  middle  of  their  length. 

5.  Immediate  reunion  of  a  divided  nerve  never  takes  place  with  immediate 
restoration  of  function.     If  a  portion  of  a  nerve- trunk  be  excised,  the  peripheral 
extremity  of   the  nerve  degenerates  first,  the  medullary  sheath  and  the  axis- 
cylinder  being  transformed  into  cells.     The  deficiency  is  soon  filled  with  juicy 
connective  tissue.     The  process  pursued  later  in  the  regeneration  of  nerve-fibers 
is  fully  considered  on  p.   636.     It  is  an  especially  noteworthy  fact  that  in  the 
peripheral  nerves  a  constant  loss  by  fatty  degeneration,  associated  with  consecutive 
regeneration  of  fibers,  takes  place.     Regeneration  of  peripheral  ganglion-cells  does 
not  occur.     On  the  other  hand,  v.  Voit  observed  in  a  decerebrated  pigeon,  after 
the  lapse  of  five  months,  a  regenerated  nerve-mass  in  the  skull,  consisting  of 
medullated  fibers  and  central  ganglia.    Also,  Vitzou  has  reported  the  regeneration 
of  destroyed  cerebral  ganglion-cells  after  the  appearance  of  karyokinesis  in  the 
adjacent  cells.     Eichhorst  and  Naunyn  found  in  young  dogs  in  which  the  spinal 
cord  was  divided  between  the  thoracic  and  the  lumbar  portion  that  an  anatomical 


REGENERATION.  453 

and  functional  regeneration  takes  place,  so  that  voluntary  movements  again 
occur.  Vaulair  observed  in  frogs  and  Masius  in  dogs  first  motility,  then  sensi- 
bility, return.  Regeneration  of  the  spinal  ganglia  did  not  take  place.  According 
to  Stroebe  a  formation  of  fibers  takes  place  in  a  small,  limited  area  at  the  site 
of  injury  to  the  spinal  cord  of  the  rabbit,  but  not  complete  regeneration  of  the 
actual  spinal  tissue. 

6.  In  some  glands  the  regeneration  of  their  cells  during  normal  activity  is 
exceedingly  active,  for  example  the  sebaceous  glands,  the  mucous  follicles  of  the 
stomach,  the  glands  of  Lieberkuhn,  the  uterine  glands,  the  mammary  glands 
during  pregnancy;   in  others  regeneration  is  less  active.     The  removal  of  consider- 
able portions  of  various  glands  is  not  followed,  as  a  rule,  by  regeneration,  while 
after  injury  of   glands  regeneration  of  the  affected  parts  does  not  take  place  if 
suppuration  occurs.     Regeneration  of  the  biliary  passages,  the  bile-duct,  and  of 
the  pancreatic  duct,  is  remarkable.     After  injury  of  the  liver  Tizzoni  and  Colluci, 
as  well  as  Griffini,  observed  the  regeneration  of  liver-cells  and  biliary  passages 
even  beyond  the  normal  limits  of  the  liver.     Pisenti  reports  similar  observations 
upon  the  kidney. 

After  injury  to  the  liver  Podwisotzky  observed  the  deficiency  disappear  com- 
pletely through  partial  multiplication  of  the  liver-cells  and  partial  hyperplasia  of 
the  epithelial  cells  of  the  biliary  passages,  which  are  likewise  transformed  into  true 
liver- tissue  (resembling  the  embryonal  development  of  the  liver) .  Ponfick  extir- 
pated even  three-quarters  of  the  liver,  and  regeneration  set  in  within  a  few  days 
after  the  operation  and  was  complete  in  the  course  of  a  few  weeks. 

According  to  Philippeaux  and  Griffini  regeneration  may  take  place  after  partial 
removal  of  the  spleen,  according  to  Laudenbach,  in  the  dog,  even  after  almost 
complete  removal.  After  mechanical  injury  to  the  secretory  cells  of  certain  glands 
(liver,  kidney,  salivary,  mammary,  Meibomian)  hyperplasia  and  division  of  adja- 
cent cells  take  place  for  the  purpose  of  regeneration.  The  nipple  of  which  half 
has  been  extirpated  undergoes  regeneration. 

7.  Of  the  connective  tissues,  cartilage,  providing  its  perichondrium  remains 
intact,  appears  to  regenerate  by  division  of  the  cartilage-cells,  although,  probably, 
loss  of  tissue  is  most  frequently  replaced  by  connective  tissue. 

8.  After  incised  wounds  of  tendons  reunion  takes  place  through  the  agency  of 
the  tendon-cells  themselves.     These  multiply  considerably  by  utilizing  the  matrix 
for  the  formation  of  cells  and  by  mitotic  division  of  the  latter.     If  the  extrem- 
ities of  the  divided  tendon    are   widely  separated,  granulation-tissue   forms   for 
the  development  of  a  cicatrix,  as  a  result  of  marked  reaction  in  the  surrounding 
connective-tissue  tendon-sheath. 

9.  The  regeneration  of  bone  is  remarkable.     If  the  articular  extremity,  together 
with  the  adjacent  portion  of  the  bone,  be  resected,  it  may  be  regenerated,  although 
an  appreciable  shortening  results.     Pieces  of  bone  that  have  been  broken  or  sawed 
off  reunite  if  replaced;    likewise  teeth  that  have  been  removed  and  replaced  in 
the  alveolus.     An  isolated  piece  of  periosteum,  even  if  transplanted  to  another 
bone,  gives  rise  to  a  piece  of  bone  of  corresponding  size.     Defects  in  bone  are 
readily  filled  by  bony  tissue  if  the  periosteum  be  preserved.     For  this  reason  the 
surgeon  in  resecting  diseased  bones  carefully  preserves  the  periosteum,  in  the  hope 
that  the  bone  will  regenerate  from  it.     The  medulla  of  bone  may  also  regenerate. 
The  internal  medullary  membrane  is  capable,  if  transplanted,  of  producing  bony 
tissue  in  small  amount  from  the  osteoblasts  present. 

If  a  bone,  for  example  a  long  bone,  has  been  fractured,  a  circular  thickened 
deposit,  at  first  of  rather  gelatinous,  vascular  and  cellular,  later  of  firmer  car- 
tilaginous, character,  forms  from  the  periosteum  upon  the  external  surface  at  the 
site  of  fracture — the  external  callus.  A  similar  process  takes  place  at  the  same 
time  within  the  medullary  cavity,  which  is  thereby  diminished  in  size — internal 
callus.  These  formations  are  due  to  cell-multiplication,  in  part  from  the  perios- 
teum, in  part  from  the  medulla  and  the  bone-tissue  itself.  The  callus  generally 
resembles  tissue,  and  is  often  cartilaginous. 

In  the  external  and  internal  callus  calcification  of  the  cartilage  later  takes 
place,  as  well  as  the  deposition  of  osseous  lamellae,  which,  acting  as  rings,  fix  the 
fractured  extremities.  Later  (up  to  the  fortieth  day)  a  thin  layer  of  the  same 
material  forms  between  the  fractured  extremities,  and  this  subsequently  under- 
goes ossification — intermediate  callus.  With  the  final  solidification  of  the  latter, 
the  bony  matter  of  the  external  and  internal  callus  gradually  disappears.  Ex- 
ternally, the  swelling  disappears,  internally  the  medullary  canal  becomes  again  of 
uniform  size  and  the  intermediate  callus  eventually  acquires  the  same  archi- 
tecture as  the  adjacent  portions.  Bone-fractures  toward  which  the  course  of  the 


454  TRANSPLANTATION    AND    ADHESION. 

nutritive  vessels  of  the  bone  is  directed  are  said  to  heal  relatively  more  readily 
and  more  rapidly. 

With  reference  to  the  growth  and  the  metabolism  of  bones  a  number  of  in- 
teresting observations  may  be  recorded:  (i)  Exceedingly  small  amounts  of  phos- 
phorus or  arsenous  acid,  added  to  the  food,  cause  marked  thickening  of  the  bones. 
This  appears  to  be  due  to  the  fact  that  the  portions  of  bone  that  undergo  absorp- 
tion in  the  process  of  normal  growth — for  example,  the  walls  of  the  medullary 
cavity — are  not  absorbed,  but  persist,  while  new  growth  continues  to  take  place. 
Small  doses  of  phosphorus  are  employed  for  the  correction  of  rachitic  softening 
of  bone.  In  cases  of  osteomalacia  Neumann  found  an  increased  elimination  of 
phosphoric  acid  with  the  urine.  (2)  Complete  exclusion  of  lime  from  the  food 
does  not  impair  the  growth  of  the  bones,  but  makes  them  thinner,  all  parts,  even 
the  organic  matrix  of  the  bone,  undergoing  uniform  atrophy.  (3)  The  ingestion 
of  madder  (rubia  tinctorum)  makes  the  bones  red,  the  pigment  being  deposited 
in  the  osseous  tissue  together  with  the  calcium-salts.  In  birds  the  egg-shell  like- 
wise is  stained.  (4)  Long-continued  administration  of  lactic  acid  has  a  solvent 
influence  upon  the  osseous  tissue.  The  ashy  constituents  of  the  bones  are  dimin- 
ished. The  changes  in  the  bones  in  youth  induced  by  the  withdrawal  of  calcium- 
salts  are  increased  by  administration  of  lactic  acid.  The  bones  resemble  rachitic 
bones.  Osteomalacia  in  women  can  be  relieved  by  castration.  (5)  Artificial 
hypostatic  hyperemia  is  capable  of  increasing  the  growth  of  bone.  The  normal 
growth  of  bone  is  considered  in  connection  with  its  embryological  development. 

At  all  portions  of  the  body  where  considerable  amounts  of  tissue  have  been 
lost,  with  secondary  inflammation,  such  defects  heal  by  the  formation  of  a  cicatrix 
of  the  structure  of  connective  tissue  that  fills  the  defect. 

After  injury  to  permanent  connective  tissue  there  occurs  in  the  course  of 
three  hours  an  abundant  multiplication  of  the  nuclei,  which  are  derived  from  the 
matrix,  followed  by  the  formation  of  cells  (awakened  slumbering  cells) ,  while  the 
fixed  connective-tissue  corpuscles  undergo  increase  in  size.  After  the  formation 
of  the  previously  slumbering  cells  from  elastic  and  gelatinous  fibers  has  continued 
for  one  or  two  days,  mitotic  division  is  observed  particularly  early  in  the  cells 
of  the  adjacent  capillaries,  then  also  in  the  tissue-cells  themselves.  This  often  per- 
sists for  more  than  eight  days.  The  spindle-cells  form  blood-vessels,  which  bridge 
over  the  wound-defect,  and  soon  also  bundles  of  fibers,  that  is,  a  young  cicatrix. 
The  larger  the  number  of  cells  that  become  fibers,  the  firmer  becomes  the  cicatrix; 
the  vessels  atrophy  and  the  old  cicatrix  is  firm  and  deficient  in  vessels. 

The  formative  process  described  occurs  in  all  situations  where  lost  tissue 
is  replaced  by  connective  tissue.  On  the  free  surface  of  the  body  the  newly 
formed  vascular  tissue  not  rarely  grows  (from  wounds  and  ulcers)  above  the 
adjacent  level — proud  flesh.  This  soon  returns,  however,  to  the  normal  level  (after 
the  application  of  astringents  to  the  vessels),  becoming  pale,  and,  finally,  after  a 
protecting  layer  of  epidermal  cells  has  developed  upon  the  free  surface,  forms  the 
cicatrix. 

If  the  continuity  of  a  tissue  has  been  severed  by  a  wound,  as,  for  example, 
an  incision,  the  divided  surfaces  may,  after  careful  apposition,  unite  directly, 
without  inflammation — union  by  primary  intention.  The  surfaces  are  at  first  held 
together  by  blood-plasma,  and  later  on  direct  union  of  the  parts  takes  place. 
Divided  blood-vessels,  however,  never  reunite  to  form  a  blood-channel.  The  cut 
surfaces  of  nerves  often  unite  directly,  but  direct  physiological  restoration  does 
not  take  place.  Wherever  direct  union  does  not  take  place,  cicatricial  connective 
tissue  forms  in  the  sequence  of  inflammation  and  suppuration — union  by  secondary 
intention. 

TRANSPLANTATION  AND  ADHESION. 

Parts  of  the  body,  such  as  the  nose,  the  ears,  and  even  the  fingers,  if  severed 
by  means  of  a  sharp  and  clean-cutting  surface,  may  unite,  even  after  the  lapse 
of  hours,  an  evidence  that  the  life  of  severed  tissues  may  persist  for  a  time.  As 
a  matter  of  fact,  some  tissues  detached  from  the  body  may  continue  to  live  for 
a  considerable  time,  for  example  leukocytes  for  three  weeks,  ciliated  epithelium 
for  eighteen  days. 

The  transplantation  of  flaps  of  skin  is  often  practised  by  surgeons  to  effect 
closure  of  existing  defects.  The  flap  of  skin  intended  for  transplantation,  and 
detached  from  the  subjacent  tissues,  is  permitted  to  remain  for  a  time  attached 
by  means  of  a  pedicle  in  its  original  position,  and  its  margins  are  united  accurately 


INCREASE  IN  SIZE  AND  WEIGHT  IN  THE  PROCESS  OF  GROWTH.        455 

by  suture  to  the  freshened  margins  of  the  deficiency,  the  pedicle  being  divided 
only  after  the  approximated  margins  have  united  firmly.  In  this  way,  a  new 
cutaneous  covering  for  the  nose  can  be  formed  from  the  skin  of  the  back  from 
another  person,  or  from  the  skin  of  the  patient's  own  arm,  or  from  the  skin  of 
the  forehead.  It  is  possible  also  to  transplant  even  large,  entirely  detached  flaps 
of  skin,  without  a  pedicle,  even  after  they  have  been  preserved  for  fifty  hours 
in  0.6  per  cent,  sodium-chlorid  solution  at  room-temperature. 

To  form  a  cutaneous  covering  for  large  granulating  (previously  carefully 
cleansed)  ulcerous  surfaces  Reverdin  and  Thiersch  apply  under  pressure  numer- 
ous rapidly  detached  bits  of  cutis  the  size  of  beans  upon  the  granulations,  or 
after  removal  of  the  latter  upon  the  freshened  wound-surface,  where  they  become 
adherent.  From  the  margins  of  these  fragments  newly  formed  layers  of  epidermis 
extend  over  the  entire  surface  of  the  ulcer.  Enderlin  was  able  to  employ 
successfully  such  fragments  after  preservation  for  four  days  moistened  with 
physiological  salt-solution.  The  excised  spur  of  the  cock  can  be  made  to  grow 
upon  the  comb.  Bert  transplanted  the  denuded  tails  and  feet  of  rats  beneath 
the  skin  of  the  back  of  other  rats.  The  transplanted  parts  became  adherent  and 
formed  vascular  communications  with  adjacent  tissues,  and  even  their  bony  parts 
increased  in  size.  Parts  excised  as  long  as  three  days  previously  exhibited  similar 
phenomena.  Detached  portions  of  periosteum  transplanted  to  other  situations 
likewise  heal  in  place  and  even  develop  bone.  Extracted  teeth  may  be  replaced 
and  even  in  a  second  person,  v.  Hippel  transplanted  successfully  a  piece  of  a 
rabbit's  cornea  4  mm.  square  in  a  defect  in  a  human  eye,  the  clear  membrane 
of  Descemet  being  preserved  as  a  foundation,  but  the  transplanted  structure  sub- 
sequently became  turbid.  Also  blood  and  lymph  can  be  transfused. 

All  of  the  transplantations  mentioned  succeed  almost  solely  between 
individuals  of  the  same  species.  Most  tissues,  however,  are  not  susceptible  of 
transplantation,  for  example  muscles,  nerves,  glands  and  organs  of  special  sense. 
In  the  lower  animals,  even  entire  parts  can  be  transplanted;  for  example  two 
pieces  of  different  earthworms  may  unite,  and  also  of  hydra. 

The  union  of  two  higher  animals  (rats  and  others)  was  successfully  effected 
first  by  Bert  in  1862,  who  divided  the  skin  of  the  trunk  and  united  the  margins 
of  the  wounds  in  the  respective  animals  by  suture.  Union  had  taken  place  in 
the  course  of  five  days.  When  atropin  was  administered  to  one  of  the  animals 
the  pupils  of  both  dilated.  Post-mortem  injection  demonstrated  the  exist- 
ence of  anastomoses  between  the  vessels  of  both.  That  such  union  may  take 
place  also  in  man  is  shown  by  the  experiments  related  on  p.  454.  The  procedure 
might  be  of  therapeutic  significance,  as  the  possibility  does  not  appear  excluded 
that  the  union  of  the  skin,  for  example  along  the  extensor  aspect  of  the  two  fore- 
arms, might  result  in  an  influence  of  the  one  individual  upon  the  other,  whether 
to  the  end  of  conveying  nutritive  juices,  or  for  the  removal  of  certain  substances 
from  the  body  of  the  one  (as  for  example  in  case  of  insufficiency  on  the  part  of 
certain  excretory  organs),  or  for  the  transmission  of  antitoxins  and  the  like. 

INCREASE    IN    SIZE    AND    IN  WEIGHT    IN    THE    PROCESS    OF 

GROWTH. 

In  the  first  period  after  birth  the  length  of  the  body,  which  on  the  average 
is  -1—  of  that  of  an  adult,  exhibits  the  most  rapid  increase;  in  the  first  year  about 
20  cm.,  in  the  second  10  cm.  more,  in  the  third  about  7  cm.;  from  the  fifth  to 
the  sixteenth  year  the  annual  increase  (about  5^  cm.)  is  pretty  much  the  same. 
From  the  twentieth  year  on,  only  slight  growth  takes  place.  From  the  fiftieth 
year  on,  the  size  of  the  body  diminishes,  principally  in  consequence  of  attenuation 
of  the  intervertebral  discs.  The  reduction  may  reach  6  or  7  cm.  up  to  the  eightieth 
year. 

The  weight  of  the  body  (about  ^  of  tnat  of  the  adult)  diminishes  constantly 
in  the  first  five  days  or  week  after  birth  in  consequence  of  evacuation  of  meconium 
and  of  the  small  amount  of  food  taken  at  first,  together  with  increased  functional 
activity  (generation  of  heat,  respiration,  digestive  activity),  as  a  result  of  which 
the  metabolic  products  are  considerably  augmented.  Not  before  the  tenth  day 
does  the  weight  of  the  child  again  equal  that  of  the  newborn.  Later  on,  the 
increase  in  weight  exceeds  that  of  the  increase  in  length  of  the  body  during  corre- 
sponding periods.  In  the  first  year  the  weight  is  trebled.  In  man,  the  maximum 
is  reached  at  about  the  fortieth  vear.  At  about  the  sixtieth  year  reduction  in 


456      SUMMARY  OF  THE  CHEMICAL  CONSTITUENTS  OF  THE  ORGANISM. 

weight  sets  in,  in  consequence  of  the  retrogressive  nutritive  processes  of  age,  and 
this  may  reach  about  6  kilos  up  to  the  eightieth  year.  The  detailed  figures  are 
given  in  the  following  table : 


Age. 

Length 
Male. 

(cm.) 
female. 

Weight 
Male. 

(kilos) 
Female. 

Age. 

Length 
Male. 

(cm.) 
Female. 

Weight 
Male. 

(kilos) 
Female. 

0 

49.6 

48.3 

3-20 

2.9I 

15 

155-9 

I47-5 

46.41 

41.30 

I 

69.6 

69.0 

IO.OO 

9.30 

16 

161.0 

150.0 

53-39 

44-44 

2 

79.6 

78.0 

12.  OO 

11.40 

*7 

167.0 

154-4 

57-40 

49.08 

3 

86.0 

85.0 

13.21 

12.45 

18 

170.0 

156.2 

61.26 

53-10 

4 

93-2 

91.0 

I5-°7 

14.18 

*9 

170.6 

— 

63-32 

5 

99.0 

97.0 

16.70 

I5-5° 

20 

171.1 

I57-° 

65.00 

54.46 

6 

104.6 

103.2 

18.04 

16.74 

25 

172.2 

157-7 

68.29 

55-o8 

7 

III.  2 

109.6 

20.  16 

18.45 

3° 

172.2 

*57-9 

68.90 

55-I4 

8 

II7.0 

II3-9 

22.26 

19.82 

40 

!7J-3 

IS6-5 

68.81 

56-65 

9 

122.7 

120.0 

24.09 

22.44 

50 

167.4 

153-6 

67-45 

58.45 

10 

128.2 

124.8 

26.12 

24.24 

60 

163.9 

151.6 

65-50 

56.73 

ii 

I32-7 

I27-5 

27-85 

26.25 

70 

162.3 

i5r-4 

63-03 

53-72 

12 

J35-9 

132.7 

31.00 

30-54 

80 

161.3 

150.6 

61.22 

51-52 

13 

140.3 

138.6 

35.32 

34.65 

90 

— 

— 

57.83 

49-34 

14 

148.7 

144.7 

48.50 

38.10 

In  the  first  three  days  the  newborn  child  loses  from  170  to  222  grams  in  weight. 
Nourished  with  mother's  milk,  the  child  doubles  its  weight  in  the  first  five  months 
and  trebles  it  in  the  first  year.  The  weight  of  a  five-year-old  child  is  double  that 
of  a  child  one  year  old,  and  that  of  a  twelve-year-old  child  double  that  of  a  child 
five  years  old.  Between  the  twelfth  and  the  fifteenth  year,  the  weight  and  the 
size  of  girls  are  greater  than  those  of  boys,  on  account  of  the  earlier  advent  of 
puberty  in  girls.  Growth  is  most  rapid  in  the  last  months  of  fetal  life;  then  from 
between  the  sixth  and  the  ninth  year  to  between  the  thirteenth  and  the  sixteenth 
year.  At  about  the  thirtieth  year  the  length  of  the  body  is  complete,  while  the 
weight  is  not. 

Normally  developed  individuals  weigh  as  many  kilos  as  their  length  measures 
in  centimeters  after  subtraction  of  the  first  meter.  As  compared  with  the  growth 
of  the  entire  body,  the  individual  parts  exhibit  wide  variations.  The  brain  grows 
least,  namely,  only  to  the  third  year,  and  from  this  time  on  scarcely  at  all.  Also 
the  liver  and  the  intestines  grow  little,  while  the  heart,  the  spleen  and  the  kidneys 
grow  only  in  slightly  lesser  measure  than  the  entire  body.  Fat,  and  particularly 
muscles,  grow  more  than  the  entire  body. 


SUMMARY  OF  THE  CHEMICAL  CONSTITUENTS 

THE  ORGANISM. 
INORGANIC  CONSTITUENTS. 


OF 


Water  constitutes  58.5  per  cent,  of  the  entire  body  and  is  present  in  the 
different  tissues  in  widely  varying  amounts.  The  tissues  of  the  kidneys  contain 
the  largest  amount  of  water,  namely  82.7  per  cent.,  while  the  bones  contain  22 

Eer  cent.,  the  teeth  10  per  cent,  and  the  enamel  at  least  0.2  per  cent.  Schonbein 
Dund  some  hydrogen  dioxid  in  the  urine. 

Gases:  Oxygen,  ozone,  hydrogen,  nitrogen,  carbon  dioxid,  methane,  am- 
monia, hydrogen  sulphid. 

Salts:  Sodium  chlorid,  potassium  chlorid,  calcium  chlorid,  ammonium 
chlorid,  calcium  fluorid,  sodium  carbonate,  sodium  bicarbonate,  calcium  carbonate, 
sodium  phosphate,  alkaline  disodium  phosphate,  acid  monosodium  phosphate, 
neutral  potassium  phosphate,  acid  potassium  phosphate,  tribasic  calcium  phos- 
phate, acid  calcium  phosphate,  magnesium  phosphate,  neutral  sodium  sulphate, 
potassium  sulphate,  calcium  sulphate. 

Free  acids:  Hydrochloric  acid  (and  sulphuric  acid  in  the  saliva  of  some 
snails,  for  example  dolium  galea). 

Silicon  (as  silicic  acid),  manganese,  iron  in  the  blood  (and  combined  with 
a  proteid  as  ferratin,  which  aids  in  blood-formation),  iodin  (in  the  thyroiodin  of 
the  thyroid  gland,  diminished  in  the  presence  of  goiter,  increased  after  administra- 
tion of  iodid) ,  copper  ( ?) . 


THE    TRUE    ALBUMINOUS    BODIES.  457 

On  the  whole,  a  man  weighing  70  kilograms  consists  of  thirteen  elementary 
substances,  namely,  44  kilograms  of  oxygen,  7  kilograms  of  hydrogen,  1.72  kilo- 
grams of  nitrogen,  0.8  kilogram  of  chlorin,  o.i  kilogram  of  fluorin,  22  kilograms 
of  carbon,  800  grams  of  phosphorus,  100  grams  of  sulphur,  1750  grams  of  calcium, 
80  grams  of  potassium,  70  grams  of  sodium,  50  grams  of  magnesium,  45  grams 
of  iron. 

ORGANIC  CONSTITUENTS. 

THE  PROTEID   BODIES  OR  PROTEIN-SUBSTANCES. 
THE  TRUE  ALBUMINOUS  BODIES. 

The  albuminous  or  proteid  bodies,  consisting  of  C,  H,  N,  O  and  S,  are  the 
fundamental  and  principal  constituents  of  the  animal  body,  to  which  they  are 
supplied  through  vegetable  food.  They  are  present  in  almost  all  animal  and 
vegetable  fluids  and  tissues,  partly  in  liquid  form,  partly  in  more  consistent,  semi- 
solid  form  as  constituents  of  the  tissues.  Their  chemical  constitution  is  unknown; 
their  percentage-composition  is  described  on  p.  26.  The  nitrogen  is  combined  in 
them  in  two  different  ways,  in  part  loosely,  in  which  form  it  can  be  separated  on 
treatment  with  dilute  hot  potassium  hydroxid,  with  the  formation  of  ammonia; 
and  in  part  firmly.  According  to  Pfliiger  a  portion  of  the  nitrogen  of  the  living 
proteid  portions  of  the  body  is  combined  in  the  form  of  cyanogen.  Also  the 
sulphur  in  the  proteid  molecule  is  combined  in  part  firmly,  in  part  loosely.  The 
loosely  combined  sulphur  can  be  split  off  by  hot  potassium  hydroxid  as  potassium 
sulphid.  With  lead  acetate  it  forms  lead  sulphid.  The  firmly  combined  sul- 
phur can  be  prepared  only  after  destruction  of  the  albumin.  In  serum-albumin 
the  proportion  of  the  loosely  to  the  firmly  combined  sulphur  is  as  3  to  2 . 

The  proteid  molecule  is  exceedingly  large,  and  is  probably  complex.  A 
small  portion  of  it  belongs  to  the  group  of  aromatic  substances  (which  appear 
especially  in  connection  with  putrefaction) ;  the  larger  portion  of  the  molecule 
to  the  series  of  fatty  bodies  (in  the  oxidation  of  proteids,  fatty  acids  especially 
develop).  Also  carbohydrates  may  appear  as  decomposition- products,  not 
being  entirely  wanting  in  any  form  of  albumin  studied  by  Krukenberg.  The 
decompositions  in  the  process  of  digestion  that  are  of  physiological  interest  are 
discussed  on  p.  304,  those  occurring  in  the  putrefactive  processes  on  p.  333. 

The  proteids  form  a  large  group  of  related  substances,  which  perhaps  represent 
only  modifications  of  the  same  body.  If  it  be  borne  in  mind  that  the  infant  pre- 
pares from  the  casein  of  milk  the  majority  of  all  the  proteids  of  its  own  body 
this  last  view  will  be  clear.  The  proteids  are  generally  soluble  in  water  or  dilute 
salt-solutions,  but  with  the  exception  of  the  peptones,  are  incapable  of  diffusing 
through  membranes  on  account  of  the  large  size  of  their  molecule.  They  are  in- 
soluble in  alcohol  or  ether.  They  are  in  general  not  crystallizable,  so  that  they 
can  be  prepared  in  a  pure  state  only  with  difficulty.  They  rotate  the  plane  of 
polarized  light  to  the  left  and  in  the  flame  they  yield  the  odor  of  burned  horn. 
They  are  transformed  into  a  solid  modification,  that  is  coagulated,  by  heat  and 
the  long-continued  action  of  alcohol,  and  are  then  insoluble  in  neutral  sol- 
vents. Coagulated  albumin  is  soluble  only  (i)  in  dilute  alkalies,  alkali-albuminate 
resulting,  having  lost  a  portion  of  nitrogen  and  sulphur;  (2)  in  dilute  mineral  or 
strong  organic  acids,  acid-albumin  (syntonin)  developing;  and  (3)  by  the  process 
of  digestion,  albumoses  and  peptones  being  formed.  By  neutralization  of  alkali- 
albuminate  and  acid-albuminate,  these  substances  are  rendered  insoluble.  As  a 
result  of  long-continued  boiling  with  dilute  mineral  acids  or  alkalies,  as  well  as 
of  the  action  of  steam  under  high  tension,  the  proteids  take  up  water  and  break 
up  into  amido-acids,  with  the  formation  of  ammonia  and  hydrogen  sulphid;  on 
boiling  with  alkalies,  splitting  off  also  carbon  dioxid,  oxalic  acid  and  acetic  acid. 

Color-reactions:  (i)  Coagulated  and  heated  with  nitric  acid  proteids  are  stained 
yellow— xanthoproteic  acid.  Supersaturation  with  ammonia  makes  the  color 
orange.  (2)  If  heated  above  60°  with  Millon's  reagent  (mercuric  nitrate  with 
nitrous  acid)  a  red  color  results.  (3)  Boiled  with  potassium  hydroxid,  then 
cooled  and  copper  sulphate  added,  proteids  become  deep  violet-blue.  (4)  Concen- 
trated hydrochloric  acid  (pure)  dissolves  them  on  boiling  and  produces  a  violet 
color.  (5)  Solid  proteids  are  made  blue  by  sulphuric  acid  containing  molybdic 
acid.  (6)  The  solution  of  thoroughly  desiccated  albumin  in  glacial  acetic  acid  is 
made  violet  by  concentrated  sulphuric  acid  and  exhibits  the  absorption-band  of 
hydrobilirubin.  (7)  lodin  may  be  employed  as  a  microscopic  reagent,  staining 


458  THE    TRUE    ALBUMINOUS    BODIES. 

proteids  brownish-yellow;  also  sulphuric  acid  and  cane-sugar,  which  stain  them 
purple- violet. 

Precipitation:  (i)  By  boiling.  (2)  By  strong  alcohol.  (3)  By  "salting." 
Most  proteids  are  precipitated  by  the  addition  of  neutral  salts  to  their  solutions 
to  the  point  of  complete  saturation,  especially  if  the  reaction  be  acid.  If  the 
addition  of  salt  be  made  gradually,  some  of  the  albumin  can  thus  be  separated  in 
crystalline  form.  (4)  Nitric  acid  precipitates  albumin,  as  does  also  metaphos- 
phoric  acid.  (5)  Further  precipitants  are  the  salts  of  the  heavy  metals  (iron 
chlorid,  lead  acetate,  copper  sulphate,  platinum  chlorid,  mercuric  chlorid  in  solu- 
tion with  hydrochloric  acid).  (6)  Precipitation  is  caused  by  acetic  acid  and 
potassium  ferrocyanid,  also  by  tannic  acid,  picric  acid  or  trichloracetic  acid.  (7) 
Mercuric-iodid,  potassium-iodid  on  addition  of  hydrochloric  acid,  phosphotungstic 
and  phosphomolybdic  acids  also  precipitate  albumin. 

Animal  proteids. 

Albuminous  bodies  can  be  divided  into  several  characteristic  groups :  The  first 
group  comprises  albuminous  substances  in  the  strict  sense,  designated  genuine 
albuminous  substances  or  proteins,  which  are  soluble  in  water  or  in  dilute  saline 
solutions  and  are  levorotatory.  This  first  group  comprises  the  albumins  and  the 
globulins. 

The  albumins  are  soluble  in  water  and  precipitable  by  complete  saturation 
with  ammonium  sulphate,  but  not  by  means  of  sodium  chlorid  or  magnesium 
sulphate. 

Serum-albumin  has  been  prepared  in  crystalline  form  by  Giirber.  By 
diffusion  almost  all  of  its  salts,  and  thereby  its  coagulability  by  heat,  can  be  re- 
moved. It  is  precipitated  by  strong  alcohol.  It  is  readily  soluble  in  concen- 
trated hydrochloric  acid,  acid-albumin,  which  is  soluble  in  water,  being  precipitated 
on  addition  of  water. 

Egg-albumin,  C80H122N20SO24  +  H2O,  has  been  prepared  in  crystalline  form 
by  Hofmeister.  It  occurs  in  the  white  of  birds'  eggs  and  exhibits  a  specific  rotation 
of  polarized  light  of  — 37.8°.  After  injection  into  the  veins  or  beneath  the  skin, 
or  even  after  introduction  into  the  intestine  in  large  amount,  it  appears  partly 
unchanged  in  the  urine.  It  is  precipitated  by  agitation  with  ether.  Its  composi- 
tion is  C^.zgHy.aeNisSj.og. 

Lactalbumin. 

Muscle-albumins,  that  is,  the  proteid  bodies  in  the  aqueous  extract  of  muscle. 

The  globulins  are  insoluble  in  water,  the  majority  soluble  in  dilute  salt- 
solutions.  They  contain  less  sulphur  and  yield  a  more  marked  xanthoproteic 
reaction  than  the  albumins.  In  solution  they  are  coagulated  by  a  temperature  of 
75°  C.  and  they  are  precipitated  by  abundant  addition  of  water.  Dilute  acids  con- 
vert them  into  acid- albumins.  They  are  precipitated  by  saturation  of  the  solu- 
tion with  magnesium  sulphate  and  also  by  semisaturation  with  ammonium 
sulphate,  by  very  dilute  acids,  as  well  as  by  carbon  dioxid.  The  globulins  include : 

Serum- globulin,  the  presence  of  which  in  the  urine  is  described  on  p.  496. 

Fibrinogen,  from  which  fibrin  results.  The  substances  from  which  this  is 
produced  are  described  on  p.  69.  Stroma-fibrin  is  considered  on  p.  72. 

Myosinogen. 

Vitellin,  which  occurs  in  the  yolk  of  birds'  eggs  and  likewise  in  the  crystalline 
lens,  perhaps  also  in  the  chyle  and  in  the  amniotic  fluid,  is  not  precipitable 
by  saturation  of  a  neutral  salt-solution  with  sodium  chlorid.  Crystalline  vitellins 
occur  as  yolk-plates  in  the  eggs  of  fish,  frogs,  tortoises.  In  the  eggs  of  birds  and 
in  tissues  the  vitellins  are  amorphous. 

Alkali-albuminates. — Potassium  and  sodium,  also  calcium  hydroxid  and 
barium  hydroxid,  form  combinations  with  proteids,  and  the  more  rapidly  the  more 
concentrated  the  alkaline  solution  and  the  higher  the  temperature.  These  com- 
binations are  designated  alkali-albuminates.  They  exhibit  especially  marked  cir- 
cumpplarization,  are  not  coagulated  on  boiling  and  are  precipitated  from  solutions 
by  acids,  which  combine  with  the  alkali.  If,  for  example,  egg-albumin  be  mixed 
with  a  solution  of  potassium  hydroxid,  potassium  albuminate  is  formed  as  a 
gradually  developing  jelly,  which  is  soluble  in  boiled  water. 

Acid-albuminates. — If  proteids  are  dissolved  in  strong  acids,  for  example 
hydrochloric  acid,  they  acquire  the  properties  of  so-called  acid-albumin,  which  ex- 
hibits great  similarity  to  alkali-albuminate  (also  the  specific  rotation) .  This  body 
is  insoluble  in  water  and  neutral  salt-solutions,  readily  soluble  in  dilute  hydrochloric 
acid.  They  are  thrown  out  of  solution  by  the  addition  of  much  salt  (sodium 
chlorid  or  sodium  sulphate).  Also  neutralization  by  alkali  causes  precipitation, 
though  boiling  does  not.  On  cooling,  the  boiled  (concentrated)  fluid  becomes 


VEGETABLE    PROTEIDS.  459 

gelatinous  and  again  fluid  when  heated.  The  syntonin  from  muscle  is  an  acid- 
albuminate.  It  is  converted  into  myosin  by  milk  of  lime  and  ammonium  chlorid. 

The  second  group  comprises  the  complex  albuminous  bodies.  These  are  pro- 
teins combined  with  bodies  of  complex  composition  and  they  are  also  designated 
proteids.  They  are  precipitated  by  alcohol,  which  coagulates  them  after  long- 
continued  action.  Heat  does  not  cause  coagulation.  They  are  generally  pre- 
cipitated from  their  solutions  by  slight  acidulation.  They  are  readily  soluble  in 
dilute  alkalies.  The  second  group  comprises: 

Chromoproteids,  that  is  combinations  of  protein  with  pigment.  These  in- 
clude : 

Hemoglobin,  whose  combinations  and  derivatives  are  described  on  pp.  55-63. 

Glycoproteids,  that  is  combinations  of  protein  with  carbohydrates.  These 
include : 

Mucin,  probably  present  in  various  slightly  different  modifications.  It  is 
richer  in  oxygen,  but  poorer  in  nitrogen  and  carbon,  than  albumin,  free  from 
phosphorus,  and  contains  up  to  1.79  per  cent,  of  sulphur  and  up  to  13.5  per 
cent,  of  nitrogen.  It  is  liquefied  in  water  into  a  ropy  mucous  mass,  but  it  is 
insoluble  in  water.  On  addition  of  alkali  it  is  converted  into  a  neutral  ropy 
solution.  It  serves  as  a  protecting  substance  against  the  entrance  of  injurious 
agents.  It  is  precipitated  by  a  small  amount  of  acetic  acid  and  is  redissolved  by 
a  larger  amount  of  the  same  acid.  It  is  precipitated  also  by  alcohol,  the  resulting 
precipitate  being  soluble  in  water.  Acetic  acid  and  potassium  ferrocyanid  cause  no 
precipitation,  although  nitric  acid  and  other  mineral  acids  do.  Mucin  yields  all 
the  color-reactions  of  the  albuminous  bodies.  It  is  present  in  saliva,  bile,  the 
mucous  glands,  the  secretions  from  mucous  membranes,  in  "mucous"  tissue 
and  in  the  tendons.  In  addition  it  is  occasionally  found  pathologically  in 
cysts  (in  the  lower  animals,  especially  in  snails  and  in  the  skin  of  holothurians) . 
On  boiling  with  water  or  on  standing  in  alcohol  it  is  transformed  into  coagulated 
albumin.  Alkalies  and  lime-water  transform  it  into  alkali-albuminate,  acids  into 
acid-albuminate.  On  decomposition  it  yields  leucin  and  7  per  cent,  of  tyrosin. 
The  mucins  react  like  glucosids.  At  high  temperatures  they  break  up  under  the 
influence  of  dilute  mineral  acids  into  a  proteid  and  a  carbohydrate,  namely,  animal 
gum. 

Peptone  and  propeptone  are  discussed  on  p.  298;  their  demonstration  in  the 
urine  on  p.  496.  Peptone  is  found  also  in  dry  lupins,  in  oats,  etc.,  and  less  in 
germinating  seed.  There  may  yet  be  mentioned  proteic  acid,  precipitated  from 
the  meat-juice  of  animals  (fish)  by  Limpricht  with  the  aid  of  acids;  and 
finally  amyloid,  encountered  partly  in  the  form  of  laminated  granules  on  the  brain 
and  in  the  prostate  gland,  partly  (pathologically)  as  a  glistening  infiltration  of  the 
liver,  spleen,  kidneys,  coats  of  the  vessels,  and  recognizable  from  the  blue  dis- 
coloration on  addition  of  iodin  and  sulphuric  acid  (like  cellulose),  and  the  red 
discoloration  on  adding  iodin.  It  can  with  difficulty  be  converted  into  albuminate 
by  alkalies  and  acids. 

APPENDIX:  VEGETABLE  PROTEIDS. 

Plants  contain,  although  in  distinctly  smaller  amount  than  animals,  proteids 
of  various  kinds.  These  occur  either  in  liquid  (swollen)  form,  particularly  in  the 
juices  of  living  plants,  or  in  solid  form.  They  resemble  the  animal  albuminates 
in  composition  and  reaction.  There  are  distinguished: 

I.  The  vegetable  albumins. 

II.  The  vegetable  globulins.     Of  the  globulins  forming  crystals  or  spheroids 
that  were   formerly  grouped   together  under  the   names    conglutin  and  vitellin, 
together  with  legumin,  the  following  may  be  mentioned:  Edestin  in  grain,  amandin 
in  almonds,  corylin  in  nuts,  excelsin  in  the  Para  nut,  avenalin  in  oats,    conglutin 
in  lupins.     The  globulins  include  as  a  decomposition-product  glutin,  an  important 
constituent  of  wheat,  whose  glutinous  property  makes  it  possible  to  convert  a 
mixture  of  flour  and  water  into  a  coherent  dough.     Gluten  can  be  obtained  from 
wheat-flour,  which  may  contain  as  much  as  17  per  cent.,  by  washing  the  dough 
repeatedly  with  water.     Thus  prepared,  it  is  viscid,  gray,  insoluble  in  water  and 
alcohol,  soluble  in  dilute  acids  (for  example  i  in  1000  parts  of  hydrochloric  acid) 
and  in  alkalies.     Gluten  results  from  a  myosin-like  globulin-substance,  which  is 
transformed  by  a  ferment  in  the  presence  of  water  into  gluten. 

III.  The  nucleins,  which  comprise   a  special   group   of  readily  decomposed 
complex  proteids,  containing  phosphoric  acid  in  firm  combination.     They  form  the 
chromatin-substance  of  the  cell-nucleus  (whence  the  name) ,  as  well  as  the  tingible 


460  THE    ALBUMINOID    BODIES. 

constituents  of  the  cell-body,  and  accordingly  they  are  widely  distributed  in  the 
animal  and  vegetable  kingdoms.  The  nucleins  have  a  strongly  acid  character. 
They  are  divided  into  the  following  two  groups : 

1.  Paranucleins,  which  consist  of  albumin  plus  phosphoric   acid.     If  more 
albumin  is  added  to  paranuclein,  nucleoalbumin  is  formed.     Casein  is  such  a 
body,  in  which,  besides,  calcium,  is  present  for  the  neutralization  of  the  acid.    It 
occurs  in  solution  in  the  milk  of  all  mammals,  from  which  it  can  be  precipitated 
by  addition  of  acid  or  of  rennet,  but  not  by  heat.     In  the  process  of  gastric  diges- 
tion nuclein  is  gradually  separated  from  casein.     On  boiling  casein  with  hydro- 
chloric acid  and  stannous  chlorid  lysatin,  C6B.13N3O2,  results,  which    yields  urea 
when  boiled  with  baryta-water. 

2.  The  true  nucleins,  which  consist  of  albumin  plus  nucleinic  acid.     Nucleinic 
acids    are    decomposed   by   hydration   into   phosphoric    acid    and   xanthin-bases 
(nuclein-bases) .     The  latter  include  xanthin,  guanin,  adenin,  hypoxanthin,  cyto- 
sin.     The  true  nucleins  may    combine    with    more    albumin    and  yield   nucleo- 
proteids.     A  carbohydrate  is  derived  from  nucleinic  acid,  namely  pentose. 

The  nucleins  are  insoluble  in  water  or  dilute  acids,  readily  soluble  in  dilute 
alkalies,  with  which  they  unite  by  reason  of  their  acid  character  to  form  neutral 
combinations.  They  swell  in  solution  of  sodium  chlorid,  and  yield  all  the  color- 
reactions  of  albumin.  In  alkaline  solution  they  are  readily  decomposed  into 
proteids  and  nucleinic  acids  (or  phosphoric  acid) .  The  nucleins  resist  the  solvent 
action  of  the  gastric  juice,  which  is  capable  of  dissolving  and  digesting  only  the 
proteids  of  the  nucleoalbumins  and  nucleoproteids.  Upon  the  latter  property 
depends  the  possibility  of  isolating  the  nucleins.  The  nucleinic  acids  occur  also 
uncombined  with  albumin  in  certain  cellular  structures  of  the  animal  kingdom 
(salmon-spawn).  Nuclein-bases  have  been  found  free  in  animal  and  vegetable 
tissues. 

The  yolk  of  the  egg  contains  a  nuclein-like  body  containing  iron  that  is 
utilized  in  the  formation  of  blood  from  the  yolk  (hematogen),  and  that  also 
aids  in  hemogenesis  on  a  diet  of  eggs.  From  a  body,  phosphosarcic  acid,  closely 
related  to  the  paranculeins,  can  be  prepared  a  ferruginous  body,  carniferrin, 
which  contains  iron  in  similar  firm  combination  as  in  hematogen. 

Nucleohiston,  a  combination  of  nuclein  and  histon,  which  can  be  prepared 
from  the  erythrocytes  of  the  goose,  is  readily  decomposed  into  nuclein  and  histon. 
The  latter  prevents  coagulation  of  the  blood. 

Nucleoalbumin  is  prepared  by  Halliburton  in  the  following  manner:  Kidneys 
are  rubbed  up  with  powdered  sodium  chlorid  and  some  water.  The  expressed 
extract  is  poured  into  distilled  water,  in  which  the  remains  of  tissue  and 
the  globulins  fall  to  the  bottom,  while  the  mucoid  nucleoalbumin  floats  on  the 
surface.  This  is  collected  and  washed  repeatedly  with  distilled  water. 

Injected  into  the  veins  nucleoalbumin  causes  coagulation.  According  to  Pekel- 
haring,  the  zymogen  of  the  fibrin-ferment  is  a  nucleoalbumin.  Histon,  a  base 
consisting  of  protamin  and  albumose,  is  present  in  the  nuclei  of  the  erythrocytes 
of  birds  and  in  leukocytes,  thymus,  spleen,  testicles,  in  combination  with  nuclein. 
It  is  coagulable  by  ammonia,  not  by  boiling,  and  can  be  extracted  by  means  of 
dilute  acids.  Reticulin,  the  ground-substance  of  reticular  connective  tissue,  is  a 
related  body.  It  contains  phosphorus  and  sulphur,  is  indigestible  and  insoluble, 
and  on  heating  with  alkalies  splits  off  the  phosphorus-containing  group,  and  is 
then  soluble  with  difficulty.  With  hydrochloric  acid  it  splits  off  amidovalerianic 
acid  (but  no  tyrosin).  Plastin  is  similar  to  nuclein  and  occurs  in  the  nuclei  and 
in  the  protoplasm  of  spermatozoa.  It  is  formed  in  the  process  of  peptic  digestion, 
and  is  insoluble  in  sodium  carbonate  as  well  as  in  hydrochloric  acid  4  to  3  of  water. 

THE  ALBUMINOID  BODIES. 

These  resemble  the  true  albuminous  bodies  with  reference  to  their  composition 
and  source.  They  are  uncrystallizable ;  some  of  them  are  free  of  sulphur;  while 
most  cannot  be  prepared  in  an  ash-free  state.  Their  reactions  and  decomposi- 
tion-products resemble  those  of  the  albuminous  bodies.  Some  of  them  yield,  in 
addition  to  much  leucin  and  tyrosin,  also  glycin  and  alanin  (amidopropionic  acid), 
although  in  physiological,  chemical  and  physical  respects  they  exhibit  considerable 
differences  from  albuminous  bodies.  They  occur  in  the  tissues  both  as  organized 
constituents  as  well  as  in  liquid  form.  Whether  they  are  formed  by  oxidation 
from  the  albuminous  bodies  or  by  synthesis  is  not  known.  They  are  in  part 
indigestible,  in  part  digestible,  although  the  products  of  their  digestion  can  replace 
the  decomposed  albumin  in  the  body  not  at  all  or  but  incompletely.  They  are 


THE    ALBUMINOID    BODIES.  461 

contained  principally  in  the  connecting  and  protecting  structures  of  the  body. 
They  can  enter  into  combination  with  acids  or  alkalies. 

1.  Keratin  is  present  in  all  horny  and  epidermal  structures.     It  is  soluble  only 
in  boiling  caustic  alkalies,  while  it  swells  in  cold  alkalies  and  in  concentrated 
acetic  acid.     It  contains  from  2  to  5  per  cent,  of  sulphur,  a  large  part  of  which 
can  be  split  off  by  alkalies.     It  is  indigestible;   decomposed  by  hydrolysis  it  yields 
10  per  cent,  of  leucin  and  3.6  per  cent,  of  tyrosin.     Neurokeratin  is  described  on 
p.  627. 

2.  Fibroin  is  soluble  in  strong  alkalies  and  mineral  acids,  as  well  as  in  cupric- 
ammonium  sulphate.     Boiled  with  sulphuric  acid  it  yields  5  per  cent,  of  tyrosin, 
leucin  and  glycin.     It  is  the  principal  ingredient  of  the  web  of  insects  and  spiders. 
By  long  boiling  silk-gelatin  (sericiri)  is  obtained  from  silk.     This  body  is  richer  in 
oxygen  and  water  than  fibroin.     Treated  with  sulphuric  acid  it  yields,  in  addition 
to  leucin  and  tyrosin,  also  serin,  a  crystalline  amidoacid. 

3.  Spongin,  a  body  resembling  fibroin,  and  derived  from  sponges,  yields  leucin 
and  glycin  as  decomposition-products. 

4.  Elastin,  the  ground-substance  of  all  elastic  tissue-elements,  is  soluble  only 
when  boiled  in  concentrated  potassium  hydroxid.     It  yields  from  36  to  45  per 
cent,  of  leucin,  together  with  one-half  per  cent,  of  tyrosin.     It  yields  the  reactions 
of  albumin  and  its  decomposition-products.     It  contains  sulphur  only  in  loose 
combination.     It  is  peptonized  by  trypsin,  but  not  by  the  gastric  juice. 

5 .  Glutin  or  bone-gelatin  can  be  prepared  from  all  connective  or  gelatin-yielding 
substances  (which  contain  collagen)  in  the  form  of  gelatin  by  boiling  with  water. 
This  gelatin  on  cooling  forms  a  jelly.     Collagen  is  soluble  by  boiling  with  acids 
or  alkalies.     Glut  in  is  strongly  levorotatory.     It  is  transformed  by  long  boiling 
and  digestion  into  a  peptone-like  state,  in  which  it  does  not  become  gelatinous. 
A  glutin-like  body  is  present  in  leukemic  blood  and  in  splenic  juice.     Glycin, 
leucin    and    ammonia,    but    no    tyrosin,    result    on    hydrolytic    decomposition. 
Glutin  contains  0.7  per  cent,  of  sulphur. 

6.  Chondrin  or  cartilage-gelatin  is  obtained  by  boiling  hyaline  cartilage.     It 
becomes  gelatinous  in  the  cold.     It  is  precipitated  by  acetic  acid  and  by  small 
amounts  of  mineral  acids.     It  is  dissolved  in  an  excess  of  the  latter  as  well  as  by 
neutral  salts. 

The  true  characteristic  substance  of  hyaline  and  elastic  cartilage  is  a  mono- 
basic acid,  namely,  chondroitin  (Ci8H27Npi4) ,  which  as  an  ethereal  sulphate,  namely, 
as  chondroitin-sulphuric  acid,  is  contained  in  cartilage.  This  acid  is  present  in 
cartilage  only  in  exceedingly  loose  combination  with  albuminous  or  gelatinous 
substances.  Alkalies  separate  the  albuminous  bodies  from  the  chondroitin-sul- 
phuric acid  by  forming  alkaline  salts  with  the  latter.  The  chondrin  (of  the  earlier 
writers)  is  a  gelatinizing  solution  consisting  of  a  mixture  of  ordinary  gelatin  and 
the  last-mentioned  chondroitin-sulphates  of  the  alkalies.  It  can,  therefore,  be 
prepared  artificially  from  gelatin  and  potassium  or  sodium  chondroitin-sulphate. 
True  hyaline  cartilage  is,  therefore,  distinguished  from  (gelatin-yielding)  osseous 
cartilage  by  the  circumstance  that  the  ground-substance  of  the  former  contains 
chondroitin-sulphates. 

On  decomposition  of  chondroitin  (as  well  as  of  chitin)  glycosamin  (C6HnO5NH2) 
is  formed,  the  latter  on  treatment  with  nitrous  acid  being  transformed  into  glucose 
— an  example  of  the  manner  in  which  non-nitrogenous  carbohydrates  may  be 
derived  from  nitrogenous  albuminous  bodies. 

7.  The  hydrolytic  ferments,  also  designated  enzymes  (in  order  to  distinguish 
them  from  the  organized  ferments,  for  example  yeast  and  bacteria).     The  charac- 
teristic of  all  organized  ferments  is  that  they  are  active  only  in  the  presence  of 
water  and  in  such  a  manner  that  they  cause  a  decomposition  of  the  body  upon 
which  they  act  as  a  result  of  which  the  latter  takes  up  water.     All  of  the  ferments 
likewise  decompose  hydrogen  dioxid  into  water  and  oxygen.     Their  activity  is 
greatest  at  a  temperature  between  30°  and  35°  C.     They  are  destroyed  by  boiling. 
In  the  dry  state  they  may  tolerate  exposure  to  a  temperature  of  100°  C.  without 
attenuation.     The  addition  in  considerable  amount  of  antiseptics  that  destroy 
lower  organisms  does  not  check  their  activity.     During  periods  of  protracted  in- 
activity their  solutions  undergo  destruction  in  greater  or  lesser  degree.     The  fol- 
lowing hydrolytic  ferments  are  distinguished: 

(a)  Sugar-forming  ferments  in  the  saliva,  the  pancreatic  juice,  the  intestinal 
juice,  the  bile,  the  blood,  the  lymph,  the  chyle,  the  liver,  the  urine,  the  milk, 
and  invertin  in  the  intestinal  juice. 

Almost  all  dead  tissues,   organic  fluids,   and  even  albuminous  bodies,  may 


462  FATS. 

exert  a  feeble  diastatic  action.     Diastatic  ferment  is  found  also  in   grain  and 
leguminous  fruits,  in  hay  and  other  vegetable  foods. 

(6)  Proteolytic  ferments:  In  the  gastric  juice  (pepsin),  the  muscles,  also  in 
germinated  seeds,  for  example  vetches,  malted  barley,  and  in  the  myxomycetes; 
in  the  pancreatic  juice  (trypsin),  the  intestinal  juice,  the  urine.  Pepsin  and 
trypsin  diffuse  through  membranes  like  peptone. 

(c)  Fat-splitting  ferments:  in  the  pancreatic  juice. 

(d)  Milk-coagulating  -ferments:  in  the  stomach,  the  pancreatic  juice,  the  urine. 

NITROGENOUS  GLUCOSIDS. 

The  following  nitrogenous  glucosids,  which  on  hydrolytic  treatment  take  up 
water  and  are  decomposed  into  sugar  and  other  atom-groups,  may  be  considered 
here: 

Cerebrin,  C57H110N2O25. 

Protagon  in  the  medullary  substance  of  nerves  (C66.30N2.39H10.69P1.068  per  cent.) 

Chitin,  2  (C15H26N2O10) ,  a  nitrogenous  glucosid  or  amin  of  a  carbohydrate  in  the 
cutaneous  covering  of  all  arthropods,  also  in  the  intestine  and  the  trachea  of  these 
animals;  soluble  in  concentrated  hydrochloric  or  nitric  acid.  The  hyalin  of  the 
bladder-worms  is  closely  allied  to  chitin.  Among  the  glucosids  of  the  vegetable 
kingdom  are  also  solanin,  amygdalin  and  salicin. 

NITROGENOUS  PIGMENTS. 

These  are  of  unknown  constitution  and  occur  only  in  animals.  In  all  proba- 
bility they  are  all  derivatives  of  hemoglobin.  They  are:  (i)  Hematin  and  hema- 
toidin.  (2)  The  biliary  pigments.  (3)  The  urinary  pigments.  (4)  Melanin  or 
the  black  pigment  contained  partly  in  epithelial  cells  (choroid,  iris,  deep  epidermal 
cells  in  colored  races) ,  partly  in  connective-tissue  corpuscles  (lamina  fusca  of  the 
choroid) ,  in  hairs  and  in  pathological  neoplasms.  Schmiedeberg  produced  melanin 
by  boiling  albumin  for  a  long  time  with  concentrated  mineral  waters.  The  melanin 
>repared  from  a  melanosarcoma  had  the  following  composition:  C68H64N10SO26 + 


ORGANIC  NON-NITROGENOUS  ACIDS. 

The  fatty  acids,  constructed  according  to  the  formula  CnH2n-1O(OH)f  are 
present  in  the  body  in  part  free,  in  part  combined.  In  the  free  state  the  volatile 
fatty  acids  are  found  in  decomposing  cutaneous  secretions  (sweat) ,  also  in  the 
large  intestine.  In  combination,  acetic  acid  and  caproic  acid  will  appear  as 
amido-combinations  in  glycin  (amido-acetic  acid)  and  leucin  (amido-caproic  acid) . 
Particularly,  however,  the  fatty  acids  are  combined  with  glycerin  to  form  neutral 
fats,  from  which,  in  the  process  of  pancreatic  digestion,  the  fatty  acids  are  again 
decomposed. 

The  acids  of  the  acrylic-acid  series,  constructed  according  to  the  formula 
CnH2n-3(HO),  yield  the  animal  organism  but  one  acid,  namely  oleic  acid.  This, 
also,  forms  with  glycerin  the  neutral  fat,  olein.  It  will  be  advisable  at  this 
point  to  discuss  the  neutral  fats,  in  the  formation  of  which  both  the  fatty  acids 
and  oleic  acid  are  utilized. 

THE  FATS. 

The  fats  occur  abundantly  in  the  animal  body,  but  probably  also  in  all  plants, 
in  the  latter  particularly  in  the  seeds  (nuts,  almond,  cocoanut,  poppy),  less 
commonly  in  the  pericarp  (olive) ,  or  in  the  root.  They  are  obtained  by  expression, 
by  melting  or  by  extraction  with  ether  or  boiling  alcohol.  They  contain  a  smaller 
amount  of  oxygen  than  the  carbohydrates.  On  paper  they  produce  characteristic 
fat-spots;  agitated  with  colloidal  substances  they  yield  an  emulsion.  If  neutral 
fats  are  superheated  with  water  or  are  heated  with  certain  ferments  or  are  permitted 
to  undergo  decomposition,  they  take  up  water  and  break  up  into  glycerin  and 
free  fatty  acids,  of  which  the  latter,  if  volatile,  diffuse  a  rancid  odor.  Treated 
with  caustic  alkalies  they  likewise  take  up  water  and  are  decomposed  into  glycerin 
and  fatty  acids.  The  fatty  acids  form  salt-like  combinations  (soaps)  with  the 
alkali,  while  the  glycerin  is  set  free.  The  soap-solutions  in  turn  dissolve  fats. 
Glycerin,  a  triatomic  alcohol,  C3H5(OH)3,  combines  (i)  with  the  following  mono- 
basic fatty  acids: 


FATS. 


463 


Formic  acid,  CH2O2, 
Acetic  acid,  C2H4O2 


i. 

2.  ,     242, 

3.  Propionic  acid,  C3H6O2, 

4.  Butyric  acids,  C4H8O2, 
5. 

6. 
7. 
8. 
9. 
10. 


Valerianic  acid,  C5Hi0O2, 
Caproic  acids,  C6H12O2, 
Enanthylic  acids,  C7H14O2, 
Caprylic  acids,  C8H16O2, 
Pelargonic  acid,  C9H18O2, 
Capric  acid,  C]0H20O2, 
Undecylic  acids,  CnH^O^ 


12.  Laurostearic  acid,  C12H24Ofl, 


A  j  •  J.  \S±L  \>CL*~L\^^y  iiv*    CU^XVl0f    V^iciJ. 

1 6.  Palmitic  acids,  C,6H32O2, 

17.  Margaric  acids,  C17H34O2, 

1 8.  Stearic  acids,  C18H36O2, 

19.  Arachinic  acid,  C^H^Oj, 

20.  Hyenic  acid,  C25H50O2, 

21.  Cerotic  acid,  C27H34O2, 

22.  Melissic  acid,  C30H60O2,  etc. 


The  acids  form  an  homologous  series  according  to  the  formula  CnH2n-1O(pH). 
With  each  additional  CH2  the  boiling-point  is  raised  19°.  The  acids  containing  a 
larger  amount  of  carbon  are  consistent  and  do  not  volatilize;  those  containing  a 
lesser  amount  of  carbon  (to  10  inclusive)  are  oleaginous  and  volatile,  with  a 
pungent  acid  taste  and  a  rancid  odor.  The  earlier  may  be  produced  from  the 
later  in  the  series  by  oxidation,  CH2  disappearing,  with  the  formation  of  CO2 
and  H2O:  for  example,  butyric  acid  results  from  propionic  acid.  Human  and 
animal  fat  contain  16  and  18,  in  smaller  amount  and  inconstantly  14,  12,  6,  8, 
10,  4.  Some  are  contained  in  the  sweat  and  in  the  milk.  Many  develop  from 
albumin  and  gelatin  in  the  process  of  putrefaction.  The  majority,  with  the  ex- 
ception of  those  from  19  to  22,  are  present  in  the  contents  of  the  large  intestine. 

2.  In  addition,  glycerin  combines  with  the  monobasic  oleic  acids,  which  like- 
wise form  a  series  and  stand  in  an  intimate  relation  to  the  fatty  acids.     Their 
general  formula  is    CnH2n-3O(OH) ;    they  all   thus  possess  2H  less  than  the  cor- 
responding members  of  the  fatty-acid  series.      By  suitable  procedures  the  cor- 
responding fatty  acids   can   be    obtained   from   the   oleic   acids,  and  conversely 
oleic  acids  develop  from  the  corresponding  fatty  acids.       Oleic  acid  (elaic  acid) , 
C}8H34O2,  is  the  only  member  found  in  the  organism;    combined  with  glycerin  it 
yields  fluid  olein.     The  fat  in  the  new-born  contains  more  glycerids  of  palmitic 
and  stearic  acids  than  that  of  the  adult,  which  contains  more  glycerids  of  oleic 
acid.     In  addition,  oleic  acid  occurs  in  combination  with  alkalies  (in  soaps),  and, 
like  a  number  of  fatty  acids,  in  the  lecithins.     Lecithin  is  considered  as  a  glycero- 
phosphate  of  neurin,  in  which  two  atoms  of  H  in  the  radicle  of  glycero-phosphoric 
acid  are  replaced  by  two  atoms  of  stearic,  palmitic,  or  oleic  acid.     If  barium 
hydrate  is  added  to  lecithins,  insoluble  barium  stearate  or  oleate  or  palmitate 
+  oleate  is  produced,  together  with  neurin  in  solution  and  barium  glycero-phos- 
phate.     There  appear  to  be  different  lecithins,  of  which  those  combined  with  the 
stearic-acid  and  that  with   the  palmitic-acid  +   oleic-acid  radicle   are   the  most 
frequent.     Lecithin  is  present  in  the  blood-corpuscles,  in  larger  amount  in  the 
semen,  in  the  yolk  of  birds,  in  the  nervous  tissue,  in  traces  in  all  animal  cells. 
Neurin  also  is  a  constant  constituent  of  bacteria  and  of  the  seeds  of  vetch  and  peas. 

The  neutral  fats,  the  glycerids  of  the  fatty  acids  and  of  oleic  acid,  are  triple 
ethers  of  the  triatomic  alcohol,  glycerin.  Fat  in  the  ordinary  sense  of  the  word 
consists  of  palmitin  (with  a  melting-point  of  62°),  stearin  (71.5°),  olein  (o°). 
Related  to  the  neutral  fats  is  glycero-phosphoric  acid,  an  acid  glycerin-ether, 
resulting  from  the  combination  of  glycerin  with  phosphoric  acid,  with  the  giving 
off  of  i  molecule  of  water — C3HflPO6;  it  is  a  product  of  the  decomposition  of 
lecithin.  Spermaceti  (cetaceum) ,  obtained  from  the  cranial  cavity  of  certain 
whales,  contains  principally  palmitic-acid  cetyl-ether. 

3.  The  glycolic  acids,  acids  of  the  lactic-acid  series,  are  constructed  according 
to  the  formula   CnHn-2O(OH)2.      They  result  from  the  fatty  acids  by  oxidation, 
if  i  atom  of  H  in  the  fatty  acids  is  replaced  by  OH  (hydroxyl).     Conversely  also 
fatty  acids  can  be  obtained  from  the  glycolic  acids.     Those  fatty  acids  that  (from 
propionic  acid  downward)   contain  more  than  2   atoms  of  C  may  form  various 
isomeric  glycolic  acids,  in  accordance  with  the  C-atom  in  which  the  other  hydroxl- 
group  enters.     There  occur  in  the  body 

(a)  Carbonic  acid,  hydrooxyformic  acid,  CO(OH)2,  in  this  form,  however, 
forming  only  salts.  Free  carbonic  acid  is  the  anhydrid,  namely  CO2. 

(6)  Glycolic  acid,  oxyacetic  acid,  C2H2O(OH)2,  does  not  occur  in  the  body 
in  the  free  state.  A  combination  of  this,  glycin — glycocol,  amido-acetic  acid, 
gelatin-sugar—occurs  as  a  conjugate  acid,  namely  as  glycocholic  acid  in  the  bile 
and  as  hippuric  acid  in  the  urine.  Glycin  exists  in  gelatin  in  complex  combination. 

(c)  Lactic  acid,  oxypropionic  acid,  C3H4O(OH)2,  is  contained  in  the  body 
in  two  isomeric  forms:  (i)  Ethylidene  lactic  acid,  which  occurs  in  two  modifica- 


464  THE    ALCOHOLS. 

tions,  namely  as  dextrorotatory  sarcolactic  acid,  paralactic  acid,  a  metabolic 
product  of  muscle  and  also  in  the  thymus  and  thyroid  glands ;  it  develops  also 
from  the  action  of  bacteria  on  grape-sugar,  and  as  ordinary  optically  inactive  or 
fermentation-lactic-acid,  which  is  present  in  the  gastric  juice,  in  sour  milk,  sour- 
crout,  sour  pickles,  and  can  also  be  obtained  from  sugar  by  fermentation.  (2)  The 
isomer  ethyl ene  lactic  acid  is  likewise  present  in  muscle  in  small  amounts. 

(rf)  Leucic  acid,  oxycaproic  acid,  C6H12O3,  does  not  occur  independently,  but 
only  as  a  derivative,  namely  as  leucin,  amidocaproic  acid,  as  a  metabolic  product 
in.  certain  tissues,  as  well  as  a  product  of  pancreatic  digestion.  By  treatment 
with  nitrous  acid  leucic  acid  can  be  produced  from  leucin,  and  glycolic  acid  from 
glycin. 

4 .  A  cids  of  the  oxalic-acid  or  succinic-acid  series ,  with  the  formula  CnH2n-4O2  (O  H)  2 , 
dibasic  acids,  which  develop  from  fatty  acids  and  glycolic  acids  as  completed 
oxidation-products  by  taking  up  oxygen  and  giving  off  water.     Their  development 
from  bodies  rich  in  carbon,  particularly  fats,  carbohydrates  and  proteids,  is,  there- 
fore, noteworthy. 

(a)  Oxalic  acid,  C2O2(OH)2,  results  by  oxidation  from  glycol,  glycin,  cellulose, 
sugar,  starch,  glycerin  and  many  vegetable  acids,  and  occurs  normally  in  the 
urine  in  combination  with  calcium. 

(6)  Succinic  acid,  C4H4O2(OH)2,  has  been  found  by  some  in  small  amounts 
in  dead  animal  tissues  and  fluids,  urine,  echinococcus-fluid,  hydrocephalus-fluid, 
hydrocele-fluid.  It  is  present  in  large  amount  in  the  urine  of  the  dog  after  a 
diet  of  fat  and  meat,  in  the  urine  of  the  rabbit  when  fed  with  carrots.  It  is  gen- 
erated by  micro-organisms  and  is  wanting  in  fresh,  living  tissues.  It  develops  in 
small  amounts  in  the  process  of  alcoholic  fermentation. 

5.  The  cholalic  acids  are  present  in  bile  and  in  the  intestine. 

6.  Aromatic  acids,  containing  the  benzol-nucleus:    benzoic  acid  (phenylformic 
acid)  occurs  in  the  urine  in  conjunction  with  glycin  as  hippuric  acid. 

THE  ALCOHOLS. 

Alcohols  are  bodies  that  develop  from  carbohydrates  by  the  substitution  of 
hydroxyl  (HO)  for  one  or  more  atoms  of  hydrogen.  They  can  also  be  viewed 
as  water,  §}O,  in  which  half  of  the  hydrogen  is  replaced  by  a  CH-combination. 
Thus,  for  instance,  C2H6,  ethyl  hydrid,  is  transformed  into  C2g5}O,  ethyl-alcohol. 

(a)  Cholesterin,  cJ^j-O,  is  a  levorotatory  alcohol  that  occurs  in  blood,  yolk' 
brain  and  bile,  and,"  besides,  quite  generally  in  vegetable  cells.  It  is  present 
also  in  tissues  of  man  and  animals  containing  keratin.  Liebreich  considers  choles- 
terin  as  a  necrobiotic  fat.  By  oxidation  cholesteric  acid  (C8H10O5)  is  developed 
from  cholesterin,  appearing  also  as  an  oxidation-product  of  cholic  acid. 

(  OFT 

(6)   Glycerin,  C,H,O^  OH,  is  considered  as  a  triatomic  alcohol.     It  occurs  in 

I  OH 

combination  with  fatty  and  oleic  acids  in  neutral  fats.  It  is  formed  in  the  process 
of  pancreatic  digestion  by  decomposition  of  the  neutral  fats.  It  is  developed 
in  small  amount  as  a  result  of  the  fermentation  of  fats  in  the  intestine,  as  well 
as  in  the  process  of  alcoholic  fermentation. 

(c)  Phenol  (phenylic  acid,  carbolic  acid,  oxybenzol). 

(d)  Pyrocatechin  (dioxybenzol) . 

(e)  The  sugars  may  be  considered  advantageously  in   connection  with   the 
alcohols,  as  they  behave  like  polyatomic  alcohols.     Their  exact  constitution  is  as 
yet  unknown.     The  sugars  form,  together  with  a  series  of  closely  related  bodies, 
the  large  group  of  carbohydrates,  which  will  be  considered  collectively.     Although 
many  of  these  do  not  occur  in  the  animal  body,  their  consideration  is  justified  by 
the  fact  that  they  occur  largely  as  constituents  of  vegetable  food. 

THE  CARBOHYDRATES. 

These  bodies  occur  in  the  animal  and  vegetable  kingdoms  and  have  received 
their  designation  because  they  contain  in  their  molecules,  in  addition  to  at  least 
six  atoms  of  C,  the  atoms  of  H  and  O  always  in  the  proportions  present  in  water, 
namely,  H2O.  All  are  solid,  chemically  indifferent,  without  odor.  They  either 
have  a  sweet  taste  (sugars)  or  may  at  least  be  readily  transformed  into  sugar 
by  the  action  of  dilute  acids.  They  deflect  the  ray  of  polarized  light  either  to 


THE    CARBOHYDRATES.  465 

the  right  or  to  the  left.  Heated  dry  they  give  off  the  odor  of  caramel.  They  stain 
red  with  thymol  and  sulphuric  acid.  According  to  their  constitution,  they  may  be 
considered  as  fatty  bodies,  as  hexatomic  alcohol  in  which  2  atoms  of  H  are  wanting. 
In  small  amounts  the  carbohydrates  are  constituents  of  almost  all  animal  tissues. 
In  the  presence  of  special  nutritive  disturbances  decomposition  of  complex  organic 
constituents  of  the  viscera  appears  to  take  place.  Nitrogenous  products  that  are 
readily  decomposed  into  urea  are  split  off  from  the  albuminates,  and  in  addition 
to  these  the  non-nitrogenous  portion  appears  as  carbohydrate.  The  formation  of 
carbohydrates  (sugar)  from  fats  occurs  in  the  germination  of  seeds  containing  oil, 
with  the  taking  up  of  oxygen. 

The  carbohydrates  can  be  divided  into  the  following  groups : 

1.  The  monosaccharids  or  glucoses,  which  contain  only  one  molecule  of  simple 
sugar:   C6H12O6.      i.  Grape-sugar  (glucose,  dextrose,  lump-sugar,  starch-sugar,  liver- 
sugar  or  urinary  sugar)  has  been  produced  synthetically  by  E.  Fischer.     It  occurs 
in  the  animal  body  in  small  amounts  in  the  blood,  chyle,  muscle,  liver,  urine; 
in  large  amounts  in  the  urine  in  cases  of  diabetes  mellitus.     It  is  formed  in  the 
process   of   digestion   by  diastatic   ferments  from   other  carbohydrates.     In   the 
vegetable  kingdom  it  is  distributed  in  the  sweet  juices  of  many  fruits  and  flowers, 
and  thence  into  honey.     It  is  formed  from  cane-sugar,  maltose,  dextrin,  glycogen 
and  starch  on  boiling  with  dilute  acids.     It  crystallizes  in  cauliflower-like,  warty 
masses,  with  one  molecule  of  water  of  crystallization,  combines  with  bases,  salts, 
acids  and  alcohols,  but  is  readily  decomposed  by  bases.     It  exerts  a  reducing 
action  on  many  metallic  oxids.     Phenylglucosazone  melts  at  a  temperature  of 
204°  C.     As  a  result  of  its  oxidation  there  develop  first  the  monobasic  glyconic 
acid  and  then  the  monobasic  glucic  acid.     A  fresh  solution  has  a  rotatory  power 
of  +106°,  which  falls  to  +56°.     On  fermentation  with  yeast    it    is    decomposed 
into  alcohol  and  carbon  dioxid;    by  putrefactive  bacteria  it  is  broken  up  into 
two  molecules  of  lactic   acid.     The   qualitative  and  quantitative  estimation  of 
grape-sugar  is  discussed  on  pp.  267,  268,  and  501.     In  alcoholic  solution  it  enters 
into    almost   insoluble    combinations    with  calcium,  barium  or  potassium;     also 
with  sodium  chlorid  it  crystallizes  into  a  combination. 

2.  Galactose  is  formed  by  hydrolytic  decomposition  of  milk-sugar  (lactose), 
but  also  by  hydrolysis  of  gum  and  mucoid  substances;    and  as  a  decomposition- 
product  of  the  glucosid,  cerebrin.     It  forms  needles  and  plates,  soluble  in  water, 
is  dextrorotatory  +  88.08°  and  fermentable  and  yields  the  reactions  of  dextrose. 
Its  phenylosazone  melts  at  193°  C.     When  oxidized  it  forms  galactonic  acid  and 
later  mucic  acid. 

3.  Levulose  (levorotatory  fruit-sugar,  invert-sugar  or  mucous  sugar)  is  formed 
from  inulin  by  the  action  of  acids  together  with  levulin,  which  is  the  analogue  of  dex- 
trin.  It  occurs  in  the  acid  juices  of  some  fruits  and  in  honey  as  a  colorless  syrup,  crys- 
tallizable  with  difficulty,   fermentable  with   greater  difficulty,  insoluble  in  cold 
alcohol,  with  a  rotatory  power  of  — 106°.     It  reduces  like  dextrose  and  has  the 
same  osazone.     It  is  formed  normally  in  the  intestine  and  is  rarely  found  abnor- 
mally in  the  urine. 

II.  Disaccharids  or  saccharoses  contain  two  molecules  of  simple  sugar,  and  hav- 
ing the  formula  C12H22OU,  are  the  anhydrids  of  the  members  of  the  first  division. 

1.  Milk-sugar  (lactose  =  dextrose  +  galactose)  occurs  only  in  milk,  crystal- 
lizes in  crusts,  with  i  molecule  of  water,  from  whey  evaporated  to  a  syrupy  con- 
sistence, is  dextrorotatory  +52.5°,  soluble  with  greater  difficulty  than  grape-sugar 
in  water  and  particularly  in  alcohol.     On  boiling  with  dilute  mineral  acids  it  is 
decomposed  into  galactose  and  dextrose;    it  can  be  transformed  directly  into 
lactic  acid  only  by  fermentation,  and  the  resulting  galactose  is,  however,  sus- 
ceptible of  alcoholic  fermentation  with  yeast  (preparation  of  koumiss).     Its  quan- 
titative estimation  is  discussed  on  p.  422.     It  occurs  rarely  in  the  urine.     Lacto- 
sazoiie  melts  at  200°  C. 

2.  Maltose  (malt-sugar),  C12H22O12  +  H2O,  contains  one  molecule  of  water  less 
than  two  molecules  of  grape-sugar  (C12H24O12)  and  results  in  the  diastatic  decomposi- 
tion of  starch.     It  is  soluble  in  alcohol",  but  is  precipitated  from  an  alcoholic  solution 
by  ether  in  the  form  of  needles  (dextrose  is  not).     It  is  dextrorotatory  138.4°  and 
crystallizable,  and  100  parts  reduce  equally  with  66  of  dextrose.     Dextrose  reduces 
cupric  acetate,  while  maltose  does  not.     Maltosazone  melts  at  208°  C.     Isomaltose 
is  not  susceptible  of  fermentation. 

3.  Saccharose  (cane-sugar  or  beet-sugar  =  dextrose  +  fruit-sugar)  is  present 
in  cane-sugar  and  a  number  of  plants,  but  it  does  not  reduce  copper.     It  is  soluble 
in  alcohol  with  difficulty,  is  dextrorotatory  and  not  fermentable.     In  the  intestine, 
and  also  when  boiled  with  dilute  acids,  it  is  transformed  into  a  mixture  of  glucose 

30 


466  THE    CARBOHYDRATES. 

and  levulose.     Oxidized  with  nitric  acid  it  is  decomposed  into  glucic  acid  and 
oxalic  acid. 

III.  Polysaccharids  or  amyloses,  result,  as  anhydrids  of  members  of  the  first 
division,  from  the  union  of  many  molecules  of  the  monosaccharids.  Many  of 
them  do  not  undergo  fermentation.  They  yield  colloid  solutions,  do  not  diffuse 
and  do  not  crystallize. 

1.  Glycogen,  with   a  rotatory  power  of  +211°,   devoid  of    reducing    action, 
occurs  in  the  liver,  the  muscles,  many  embryonal  tissues,  the  fetal  membranes, 
the  rudimentary  embryo  of  the  chick  and  in  part  in  normal  and  pathological 
epithelium.      It  is  present  in  small  amounts  in  many  organs:    testicle,  lung,  skin, 
and  in  pus  and  inflammatory  foci.     It  has  been  found  in  considerable  amount  in 
the  body  of  the  diabetic,  in  the  brain,  the  pancreas,  and  cartilage.     It  occurs  also 
in  oysters  and  other  molluscs,  but  it  may  be  present  in  the  cells  of  all  of  the  tissues 
and  of  all  classes  of  animals.     Errera  found  glycogen  in  yeast. 

2.  Dextrin   is    dextrorotatory  +138°,    forms    a   viscid    solution   with   water, 
from  which  it  is  precipitable  by  alcohol  and  acetic  acid,  and  is  discolored  feebly 
red  by  iodin.     It  results  from  scorched  starch  (and  is  therefore  abundant  in  bread- 
crusts)  through  the  action  of  dilute  acids,  and  in  the  body  through  the  action 
•of  ferments.     It  is  formed  from  cellulose  by  treatment  with  dilute  sulphuric  acid. 
It  occurs  also  in  beer.     In  the  vegetable  kingdom  it  is  present  in  most  vegetable 
juices. 

3.  Starch  is  present  in  the  mealy  portion  of  many  vegetables,  partly  con- 
sisting of  organized  granules  in  layers  forming  within  the  vegetable  cells,  with  a 
generally  excentric  nucleus,  and  partly,  though  less  commonly,  occurring  unformed 
in  vegetables.     The  diameter  of  the  starch-granule  varies  considerably  in  different 
plants.     It  is,  for  instance,  from  0.14  to  0.18  mm.  in  the  potato  and  only  0.004 
mm.  in  the  seed  of  the  red  beet.     In  water  at  a  temperature  of  72°  C.  it  swells 
as  a  paste.     It  is  stained  blue   by  iodin   only  in   the  cold.     The   starch-granules 
contain  further  always  more  or  less  cellulose,  as  well  as  a  body  stained  red  by 
iodin  (erythrogranulose) .     The  transformation  of  starch  and  glycogen  takes  place 
through  the  action  of  the  saliva,  the    pancreatic  and  the  intestinal  juice;  both 
are  transformed  into  dextrose  by  dilute  sulphuric  acid. 

4.  Gum,  C10H20O10,   occurs  in  man  in  organs  containing  mucus,  such  as  the 
salivary  glands,  the  mucoid  tissues,  the  lungs,  and  in  bile,  occasionally  in  albuminous 
fluids,  and  in  small  amounts  in  the  urine.      It  is  susceptible  of  fermentation  and  is 
decomposed  by  boiling  with  dilute  acids  into  a  body  reducing  copper  oxid.     In 
the  vegetable  kingdom  gum  is  found  in  the  juices  particularly  of  acacias  and 
mimosas,  partly  soluble  in  water  (arabin),  partly  swelling  up  like  mucus  (bassorin). 
It  is  precipitated  by  alcohol.     Wood-gum  (pentosan,  C5HSO4)  occurs  abundantly 
in  fibrous  vegetable  matters  consumed  by  herbivora  as  food.     On  heating  with 
dilute  acids  there  result  by  hydration  pentoses,  in  the  same  way  as  dextrose  is 
formed  from  starch.     There  are  two  pentosans:  xylan,  which  yields  xylose,  and 
araban,  from  which  arabinose  results.     Pentosan  results  from  the  oxidation  of 
cellulose  and  starch,  i  atom  of  C  being  transformed  into  CO2. 

5.  Inulin,  a  crystalline  powder  present  in  the  root  of  chicory  and  dandelion, 
and  in  the  bulbs  of  dahlia  variabilis,  is  not  stained  blue  by  iodin. 

6.  Lichenin,  lichen-starch,  the  intercellular  substance   of  lichens,  especially 
of  Iceland  moss  (cetraria  Icelandica),  and  of  algae.     It  can  be  transformed  into 
glucose  by  dilute  sulphuric  acid. 

7.  Cellulose,  C6H10O5,  the  cellular  tissue  of  all  vegetables,  is  found  also  in  the 
integument  of  tunicates,  the  exoskeleton  of  arthropods  and  the  skin  of  snakes. 
It  is  soluble  only  in  ammoniated  cupric  oxid  and  is  colored  blue  by  sulphuric 
acid  and  iodin.     On  boiling  with  dilute  sulphuric  acid  dextrin  and  glucose  are 
formed.      It   is   transformed    (cotton)    by   concentrated   nitric    acid   mixed   with 
sulphuric   acid  into  nitro-cellulose    (gun-cotton,  C6H7(NO2)3p5)),  which,   dissolved 
in  a  mixture  of  ether  and  alcohol,  forms  collodion.      Tunicin,  a  body  similar  to 
cellulose,  occurs  in  the  integument  of  tunicates  (molluscs).     Cellulose  is  dissolved 
in  the  intestine  of  herbivora  with  the  aid  of  bacteria. 

For  the  sake  of  completeness,  inosite,  C6H12O6,  hexahydrohexaoxybenzol, 
muscle-sugar,  phaseomannite,  bean-sugar,  may  be  discussed  at  this  point.  This  is 
not  a  true  sugar,  but  it  has  a  sweet  taste.  It  occurs  in  the  muscles,  the  lungs, 
the  liver,  the  spleen,  the  kidneys,  the  brain  of  the  ox,  and  the  kidneys  of  man; 
pathologically  in  the  urine  and  in  echinococcus-fluid.  It  is  widely  distributed  in 
the  vegetable  kingdom,  especially  in  beans  (Leguminosae)  and  in  grape-juice.  It  is 
optically  inactive,  generally  crystallizes  like  cauliflower,  with  two  molecules  of 
water,  in  long  monoclinic  crystals,  insoluble  in  alcohol  or  ether;  it  does  not  re- 


AMMONIA-DERIVATIVES    AND    THEIR    COMBINATIONS.  467 

spond  to  Trommer's  test  and  is  susceptible  only  of  sarcolactic-acid  fermentation. 
Evaporated  to  dryness  with  nitric  acid,  then  with  ammonia  and  calcium  chlorid, 
it  leaves  a  rosy-red  stain. 

AMMONIA-DERIVATIVES  AND  THEIR  COMBINATIONS. 

The  ammonia-derivatives  are  products  of  proteids,  decomposition-products 
of  the  tissue-metamorphosis  of  proteids. 

1.  Amins,  that  is  compound  ammonias,  which  may  be  derived  from  ammonia 
(NH3)    or  from  ammonium  hydroxid   (H4N,  OH)   by  replacing  one  or  all  of  the 
atoms  of  H  by  carbohydrate-groups  (alcohol-radicles) .     The  amins  derived  from  a 
single  molecule  of  ammonia  are  designated  monamins.  Among  these  are  methylamin, 

H  IN,  and  trym'ethalamin,   CH^N,  known    only   as    decomposition-products   of 
CH3 }  CH3  f 

cholin  (neurin)  and  of  kreatin.  Neurin  occurs  in  lecithin  in  complex  combination. 
The  lecithins  are  described  on  p.  463  and  the  diamins  are  discussed  on  p.  305. 

2.  Amids,  that  is  derivatives  of  acids  in  which  NH2  is  substituted  for  the 
hydroxyl  (HO)  of  the  acids.      Urea,  CO(NH2)2,  the  diamid  of  CO2  is  the  principal 
end-product  of  the  tissue-metamorphosis  of  the  nitrogenous  constituents  of  the 
body.     Carbon  dioxid    containing  water  is   CO(OH)2,  in  which  both  OH-atoms 
are  replaced  by  NH2,  thus  CO(NH2)2. 

3.  Amido-acids,    that    is    nitrogenous    combinations    exhibiting    partly    the 
character  of  an  acid,  and  partly  that  of  a  feeble  base,  in  which  H-atoms  of  the 
acid-radicle  are  replaced  by  NH2  or  substituted  ammonia-groups. 

(a)  Glycin  (amido-acetic  acid,  glycocol,  gelatin-sugar)  results  on  boiling  gelatin 
with  dilute  sulphuric  acid.  It  is  present  in  the  cornea,  which  contains,  besides, 
chondrin.  It  has  a  sweet  taste  (gelatin-sugar),  behaves  like  a  feeble  acid,  but 
unites  also  as  an  amin-base  with  acids.  It  occurs  as  glycin  +  benzoic  acid  =  hippuric- 
acid  in  the  urine  (it  has  also  been  prepared  artificially) ,  and  as  glycin  +  cholic 
acid  =  glycocholic  acid  in  the  bile.  (6)  Leucin  (amidocaproic  acid)  has  been  found 
pathologically  in  pus  and  in  the  atheromatous  matter  of  sebaceous  cysts,  generally 
in  combination  with  tyrosin.  (c)  Serin  (amidolactic  acid)  is  obtained  from  silk- 
gelatin,  (d)  Blood-alinin  (amidovalerianic  acid) .  (e)  A spartic  acid  (amidosuccinic 
acid) .  (/)  Glutamic  acid  (amidopyrotartaric  acid)  is  obtained  in  the  decomposition 
of  albuminates.  Aspartic  acid  can  be  obtained  from  asparagin  by  boiling  with 
acids  and  the  splitting  off  of  ammonia.  Asparagin  is  formed  largely  in  the  vegetable 
kingdom  from  albumin  and  has  been  prepared  artificially,  while  in  the  animal 
body  it  is  transformed  into  urea  and  uric  acid,  (g)  Cystin  (amidolactic  acid),  in 
which  O  is  replaced  by  S,  is  strongly  levorotatory.  (h)  Taurin  (amido-ethyl- 
sulphuric  acid)  occurs,  besides  in  a  number  of  glands,  particularly  in  combination 
with  cholic  acid  as  taurocholic  acid  in  bile.  It  has  also  been  prepared  artificially. 
(i)  Tyrosin  (paraoxyphenylamidopropionic  acid,  prepared  synthetically)  occurs 
together  with  leucin  in  the  presence  of  pancreatic  digestion.  It  may  occur  patho- 
logically in  the  urine.  It  is  abundant  in  dahlia-bulbs. 

There  are  related  to  the  amido-acids  further:  (a)  Kreatin,  methylguanidin- 
acetic  acid,  CH9N3O2,  which  is  present  in  muscle,  brain,  blood,  and'  urine,  and 
has  been  prepared  artificially.  Boiled  with  baryta-water  it  takes  up  water 
and  is  decomposed  into  urea;  (6)  Sarcosin  (C3H7NO2,  methylamido-acetic  acid). 
When  boiled  with  water  or  heated  with  strong  acids  in  the  presence  of  decomposing 
substances  kreatin  is  transformed  into  kreatinin  with  the  loss  of  water;  kreatinin 
occurs  in  the  urine.  This  strong  base  can  be  retransformed  into  kreatin  by  the 
action  of  alkalies. 

4.  Ammonia-derivatives  in  Part  of  Unknown  Constitution. — Uric  acid.    Allan- 
loin  results  from  the  oxidation  of  uric  acid  by  means  of  potassium  permanganate. 
It  has  been  found,  together  with  guanin  and  sarcin,  also  in  the  buds  of  Platanaceae. 
Cyanuric  acid  has  been  found  in  dog's  urine.     Inosinic  acid  is  present  in  muscle. 
Guanin  (C5H5N5O),  together  with  adenin,  xanthin  and  hypoxanthin,  a  decomposi- 
tion-product of  nuclein,  occurs  in  traces  in  normal  blood,  in  larger  amount  in 
leukemic   blood,   and  in  considerable   amount   in   embryonal  muscle,  as  well  as 
in  the  liver,  the  spleen  and  the  pancreas.     It  occurs,  pathologically,  in  rapidly 
growing  neoplasms  rich  in  nuclei,   and  in  the  muscles  of  swine  suffering  from 
guanin-gout.     It  is  transformed  by  nitrous  acid  into  xanthin,  by  oxidation  into 
urea  and  when  fed  to  animals  it  increases  the  elimination  of  urea.     It  occurs, 
further,  in  guano,  in  the  excrement  of  spiders,  in  the  skin  of  amphibia  and  reptiles, 
in  the  silver  gloss  of  some  fish  (for  example  the  herring) .     Hypoxanthin  or  sarcin 


468  HISTORICAL. 

in  association  with  xanthin  occurs  in  many  organs  and  in  urine.  Kossel  suc- 
ceeded in  preparing  hypoxanthin  from  nuclein  b)^  prolonged  boiling.  It  can  be 
obtained  from  fibrin  by  putrefaction  and  the  action  of  gastric  and  pancreatic 
juice.  Xanthin  can  be  produced  from  hypoxanthin  by  oxidation  and  is  con- 
vertible into  caffein.  Xanthin  and  guanin  have  been  produced  synthetically  by 
Gautier.  Paraxanthin  and  heteroxanthin  occur  in  the  urine;  carnin,  which  re- 
sembles them,  in  meat.  An  intermediate  stage  between  nuclein.  and  hypoxanthin 
is  represented  by  the  adenin  (C3H5N5)  of  Kossel,  which  has _  been  found  in  the 
spleen,  the  pancreas,  the  thymus,  the  seminal  fluid,  and  also  in  tea  and  in  yeast. 
It  appears  to  occur  as  an  amorphous  powder,  or  in  six-sided  columns  disintegrating 
in  the  air,  and  as  a  decomposition-product  of  nuclein  in  all  animal  and  vegeta- 
ble cell-tissues. 

AROMATIC  BODIES. 

i.  M anatomic  phenols:  (a)  The  phenol  (hydroxl  or  benzol)  in  the  intestine; 
phenylsulphuric  acid  in  the  urine.  (b)  Kresol  in  the  form  of  orthokresol,  meta- 
kresol  and  parakresol  combines  with  sulphuric  acid  in  the  urine.  (2)  Diatomic 
phenols:  (a)  Pyrocatechin  combined  with  sulphuric  acid  in  the  urine.  (3)^  Aro- 
matic oxy acids:  (a)  Hydroparacumanc  acid;  (6)  Paroxyphenylacetic  acid  in  the 
urine.  (4)  Substituted  carbohydrates:  (a)  Indol  (also  prepared  artificially)  and 
(b)  skatol  both  occur  in  the  intestine  and  combined  with  sulphuric  acid  in  the 
urine.  Stoehr  has  prepared  skatol  artificially  by  distillation  of  strychnin  with 
calcium. 

HISTORICAL. 

According  to  Aristotle  the  body  requires  food  for  three  purposes,  namely 
for  growth,  for  the  generation  of  heat  and  to  compensate  for  loss  from  the  body. 
The  generation  of  heat  was  thought  to  take  place  in  the  heart  by  a  process  of 
concoction,  the  heat  being  carried  with  the  blood  to  all  parts  of  the  body,  while 
the  act  of  respiration  was  considered  as  a  means  for  dissipating  the  excess  of  heat 
generated  in  the  process  of  combustion.  In  a  somewhat  modified  form  also  Galen 
held  this  view.  According  to  him  the  metabolism  is  comparable  to  the  conception 
of  a  lamp,  the  blood  representing,  to  a  certain  degree,  the  oil,  the  heart  the  wick, 
and,  finally,  the  lungs  the  draft.  According  to  the  view  of  the  iatrochemical 
school,  metabolism  takes  place  in  the  body  in  the  form  of  fermentative  processes 
in  which  the  substances  introduced  are  decomposed  in  conjunction  with  the 
bodily  juices.  There  thus  result  refined,  useful  juices,  and  fermentative  waste 
products  intended  for  excretion.  Since  the  middle  of  the  seventeenth  century 
knowledge  of  the  metabolic  processes  has  progressed  hand  in  hand  with  the  devel- 
opment of  chemistry.  A.  v.  Haller  ascribed  the  heat  to  chemical  processes.  He 
believed  that  the  nourishment  must  make  good  to  the  body  the  constant  loss 
of  excrementitious  matter.  Anabolism  takes  place  through  a  lymphatic  fluid, 
which  is  poured  out  for  the  reconstruction  of  the  used-up  animal  fibers  between 
the  latter.  Mayow  believed  in  1679  that  metabolism  was  essentially  a  process 
of  combustion,  the  blood  becoming  bright  red  in  the  lungs.  After  the  discovery 
of  oxygen  Lavoisier  formulated  the  theory  of  combustion  in  the  lungs,  in  which 
he  believed  carbon  dioxid  and  water  were  formed.  He  compared  the  relatively 
slow  course  of  physiological  combustion  with  the  heating  of  dung  that  takes 
place  at  a  lower  temperature.  Mitscherlich  compared  the  metabolic  processes  in 
the  living  body  directly  with  putrefactive  phenomena.  Magendie  first  pointed 
out  the  difference  between  nitrogenous  and  non-nitrogenous  foods  and  showed 
that  the  latter  alone  are  not  capable  of  sustaining  life.  Also  gelatin  alone  is 
insufficient  for  this  purpose.  His  results  were  less  precise  with  respect  to  the 
nutritive  value  of  albuminates,  which  he  nevertheless  gave  foremost  rank,  and 
among  which  he  was  willing  to  recognize  only  meat  as  adequate  as  nutritive 
material. 

The  greatest  advance  in  the  principles  of  nutrition  is  due  to  J.  Liebig,  who 
laid  the  foundation  of  the  present  knowledge  of  metabolism.  According  to  his 
view  food-stuffs  subserve  two  purposes,  namely  as  plastic,  for  the  growth  of  the 
body,  and,  as  respiratory,  for  the  generation  of  heat.  The  former  includes  espe- 
cially the  albuminates,  the  latter  especially  the  non-nitrogenous  carbohydrates 
and  fats. 

Among  recent  investigators  the  Munich  school  deserves  especial  mention  as 
advancing  knowledge:  v.  Bischoff,  v.  Pettenkofer,  v.  Voit  and  others.  Most 
recently  Pfliiger  has  made  important  contributions. 


THE    SECRETION    OF    URINE.  469 

THE  SECRETION  OF  URINE. 

STRUCTURE  OF  THE  KIDNEY. 

The  kidneys  are  compound  tubular  glands  (Fig.  142). 

All  of  the  urinary  tubules  arise  within  the  cortex  of  the  kidney  from  Bow- 
man's capsules,  which  are  globular  in  shape,  measure  from  200  to  300  fi  in  diameter, 
are  constituted  of  endothelioid  cells  (k),  and  whose  inner  surface  is  lined 
with  a  single  layer  of  epithelial  cells  (Fig.  142,  II).  In  the  interior  of  the 
capsule  lies  the  convolution  of  vessels  known  as  the  glomerulus  or  Malpighian  body. 
Each  capsule  passes  by  means  of  a  narrowed  portion  into  the  convoluted  urinary 
tubule,  which  has  a  diameter  of  45  p  (I,  x).  This  possesses  a  membrana  propri'a 
constituted  of  extremely  fine  fibers  and  passes  through  the  cortical  structure 
in  a  devious  course.  It  is  lined  by  characteristic  epithelium,  the  cells  contain- 
ing a  turbid  protoplasm  that  swells  readily  and  is  occasionally  filled  with 
fat-globules.  That  portion  of  the  protoplasm  which. is  directed  toward  the  rela- 
tively narrow  lumen  of  the  tubule  contains  a  distinct  globular  nucleus,  while 
the  portion  adjacent  to  the  membrana  propria,  and  different  also  chemically, 
presents  a  fibrillated  appearance,  as  if  constituted  of  rods.  Where  the  rods 
are  in  direct  contact  with  the  membrane  they  diverge  like  the  bristles  of  a  brush 
pressed  against  a  surface.  The  free  extremities  of  the  rods  of  adjacent  cells 
touch  one  another,  so  that  the  attached  surface  of  the  cells  acquires  an  irregular 
radiating  appearance.  When  secretion  takes  place  the  free  surface  has  a  brush- 
like  margin. 

Landauer  describes  the  cells  of  the  convoluted  tubules  and  of  the  wider  portion 
of  Henle's  loop  as  provided  with  lateral  folds  (and  not  with  the  rod-like  structure) , 
by  means  of  which  adjacent  cells  are  brought  in  direct  contact  with  one  another. 

At  the  junction  of  the  medullary  and  the  cortical  tissue  the  convoluted 
tubule  becomes  suddenly  constricted  and  passes  over  as  Henle's  loop  in 
the  form  of  an  elongated  arch  into  the  medullary  structure  (t,  t).  A  distinction 
is  made  in  the  loop  between  the  small  descending  limb,  with  a  relatively  large 
lumen  (14  //)  and  clear,  flat  epithelium  arranged  in  alternating  order  and  bulged 
out  at  the  middle  by  its  nucleus  (IV,  S),  and  the  wider,  ascending  limb.  The 
transition  from  the  one  to  the  other  takes  place  in  man,  as  a  rule,  in  the  lowermost 
portion  of  the  descending  limb.  The  ascending  limb  becomes  dilated  to  a  diameter 
of  from  20  //.  to  26  u,  its  lumen  is  relatively  large  and  its  epithelium  is  essentially 
the  same  as  that  of  the  convoluted  tubules,  except  that  the  rods  are  shorter. 
Where  the  ascending  limb  penetrates  into  the  cortical  structure  the  canal  at  first 
becomes  smaller  again.  It  then  passes  into  the  intercalated  portion  (n,  n), 
which  has  a  diameter  of  40  u.  and  in  structure  most  nearly  resembles  the  con- 
voluted tubules,  than  which,  however,  it  is  shorter,  though  lined  with  similar 
cells.  After  a  second  constriction  the  intercalated  portions  pass  over  into  the 
collecting  tubules  (o) ,  which  within  the  medullary  rays  projecting  into  the  cortex 
have  a  diameter  of  about  45  //.  In  their  further  course  downward  in  the  papilla 
adjacent  collecting  tubules  unite  and  form  tubes  having  a  diameter  of  from  200 
to  300  //,  the  papillary  ducts  or  excretory  tubes  (O),  of  which  from  24  to  80 
open  at  the  apex  of  each  of  the  1 2  or  15  papillae  (foramina  papillaria  or  cribrum 
benedictum). 

In  the  lowermost  and  widest  portion  the  membrana  propria  of  the  duct  is 
surrounded  and  fortified  by  a  layer  of  delicate  connective-tissue  fibers.  The  cells 
are  large  cylindrical  epithelia,  with  well-defined,  spherical  nuclei  (VI)  and  dip- 
losomata.  Further  upward  the  constricted  portion  of  the  collecting  tubules  is 
lined  by  low,  cylindrical,  rather  cubical  cells,  with  large  nuclei  (V)  supported  upon 
a  structureless  membrana  propria.  Within  the  cortical  structure  the  cells  assume 
an  inclined  position,  so  that  they  overlie  one  another  like  the  shingles  on  a  roof. 
In  the  cells  of  all  of  the  urinary  tubules,  excepting  those  of  the  collecting  tubules, 
a  ciliated  process  projects  from  the  centrosoma  into  the  lumen  of  the  tubule. 
The  same  peculiarity  is  present  in  the  epithelium  of  the  seminal  vesicles. 

The  Blood-vessels  of  the  Kidney. — The  renal  artery  with  its  branches 
reaches  the  junction  of  the  medullary  and  the  cortical  structure  after  repeated 
division.  From  this  point  the  interlobular  arteries  (a)  arise  at  equal  distances 
apart  and  traverse  the  cortex  vertically.  Throughout  their  entire  course  they 
give  off  laterally  the  afferent  vessels  (i) ,  each  of  which  enters  into  a  capsule  formed 
by  the  urinary  tubule  at  a  point  exactly  opposite  to  that  from  which  the  tubule 


470 


STRUCTURE    OF    THE    KIDNEY. 


itself  passes  off.  By  breaking  up  into  numerous  capillary  loops  the  vascular  tuft 
or  glomerulus  is  formed  within  the  interior  of  the  capsule.  The  glomerulus  is 
provided  toward  the  wall  of  the  capsule  with  a  covering  of  flat,  nucleated  cells 


FIG.  142. — Structure  of  the  Kidneys:  i,  the  vessels  and  urinary  tubules  in  semi-schematic  arrangement;  A,  cortical 
capillaries;  B,  medullary  capillaries;  a,  interlobular  artery;  i,  afferent  vessel;  2,  efferent  vessel;  r  e,  straight 
arterioles;  c,  straight  venules;  v  v,  interlobular  veins;  S,  origin  of  a  stellate  vein;  i  i,  capsule  enclosing  a 
glomerulus;  x  x,  convoluted  tubule;  t  t,  Henle's  loops;  n  n,  intercalated  portion;  o,  collecting  tubules; 
O,  excretory  duct;  II,  capsule  and  glomerulus:  a,  afferent  vessel;  e,  efferent  vessel;  c,  capillary  network  of 
the  cortex;  k,  endothelioid  structure  of  the  capsule;  h,  origin  of  the  convoluted  tubule;  III,  rod-cells  from 
the  convoluted  tubules;  2,  viewed  from  the  side  (g,  internal  area  containing  the  nuclei);  i,  viewed  from  the 
surface;  IV,  cellular  lining  of  Henle's  loop;  V  cells  in  collecting  tubule;  VI,  section  of  the  excretory  duct. 

(Fig.  142,  II),  which  are  present  also  between  the  capillary  loops  of  the  tuft. 
From  the  loops  there  passes,  from  the  center  of  the  tuft,  the  efferent  vessel  (2), 
which  is  always  of  smaller  size  and  makes  its  exit  from  the  capsule  close  by 


STRUCTURE    OF    THE    KIDNEY.  471 

the  side  of  the  afferent  vessel  and  in  structure  and  further  course  resembles  a 
small  artery.  Throughout  the  entire  cortex  all  of  the  efferent  vessels  enter  into 
the  formation  of  a  line  capillary  network  (A  and  II,  c),  which  surrounds  the 
urinary  tubules.  Within  the  range  of  the  medullary  rays  of  the  cortex  the  fibers 
of  the  network,  in  accordance  with  the  straight  course  of  the  urinary  tubules,  are 
arranged  rather  longitudinally,  while  in  the  remainder  of  the  cortex  their  ar- 
rangement is  polygonal.  From  this  capillary  network  of  the  cortex  venous 
radicles  arise  to  form  the  interlobular  veins  (v).  These  originate  just  beneath 
the  fibrous  capsule  of  the  kidney  from  the  union  of  the  radicles  of  the  smallest 
venules  arranged  in  a  stellate  manner  (stellulae  Verheynii  or  stellate  veins)  and 
then  pass  each  in  the  company  of  an  interlobular  artery  to  the  junction  of  the 
medulla  and  the  cortex. 

The  vessels  of  the  medullary  structure  arise  from  the  straight  arterioles.  These 
either  begin  at  the  junction  of  the  cortical  and  the  medullary  structure  of  the 
kidney  as  individual,  direct  branches  (r)  of  the  interlobular  arteVies,  still  provided 
with  muscular  fibers,  or  they  are  formed  from  those  efferent  vessels  (e)  that  lie 
adjacent  to  the  medullary  structure  of  the  kidney.  The  latter  are  said  to  be  un- 
provided with  muscular  fibers.  Finally  it  is  stated  that  a  number  of  these  vessels 
are  formed  from  the  union  of  the  capillaries  of  the  medullary  rays.  All  of  the 
straight  arterioles,  accompanying  the  straight  urinary  tubules,  pass  into  elongated 
brush-like  capillary  bundles,  which  surround  the  urinary  tubules.  From  these 
capillaries  there  collect  throughout  the  entire  extent  of  the  medulla  loops  curving 
upward  and  downward,  representing  the  beginning  of  the  veins.  The  latter  pass 
back  toward  the  junction  between  the  medullary  and  the  cortical  structure  and 
gradually  constitute  the  straight  venules  (c),  which  empty  into  the  lower  portion 
of  the  interlobular  veins.  On  the  papillae  the  capillaries  of  the  medulla  communi- 
cate with  vascular  branches  in  garland-like  arrangement  surrounding  the  papil- 
lary ducts. 

The  vessels  of  the  fibrous  capsule  of  the  kidney  are  derived  in  part  from  pene- 
trating branches  arising  from  the  extremity  of  the  interlobular  arteries  and  in 
part  from  branches  of  the  suprarenal,  phrenic  and  lumbar  arteries,  between  which 
anastomoses  take  place.  The  capillary  network  is  a  simple  mesh-arrangement. 
The  venous  radicles  pass  over  in  part  into  the  stellate  veins  and  in  part  into  veins 
of  the  same  name  as  the  arteries.  A  number  of  venous  radicles  also  pass  out  of 
the  cortex.  The  communication  between  the  distribution  of  the  renal  artery  and 
other  arteries  in  the  capsule  explains  the  fact  that  after  ligation  of  the  renal 
artery  within  the  kidney  the  blood-stream  may  enter  from  the  capsule.  Arterial 
blood  also  is  sent  to  the  kidney  and  this  may  even  give  rise  to  a  slight  secretion. 

Lymphatics  are  present  within  the  fibrous  capsule  as  a  wide-meshed 
network  and  beneath  the  capsule  in  the  form  of  spaces  of  considerable  size. 
In  the  parenchyma  of  the  kidney  itself  the  lymph  is  said  to  circulate  between 
the  urinary  tubules  and  the  blood-vessels,  in  tissue-spaces  without  walls  which 
are  found  in  larger  number  around  the  convoluted  tubules  than  around  the 
straight  tubules.  The  spaces  reach  to  the  surface  of  the  kidney  and  are  dis- 
tributed extensively  beneath  the  capsule.  Marked  distention  of  the  lymph-spaces 
compresses  the  urinary  tubules  and  the  vessels.  Large  lymphatics,  provided 
with  valves,  are  visible  at  the  hilus  of  the  kidney,  while  others  pass  through 
the  fibrous  capsule,  both  communicating  with  the  lymph-spaces  of  the  capsule 
of  the  kidney. 

Of  the  nerves,  branches  provided  with  ganglia  accompany  the  afferent  vessels. 
Non-medullated  fibers  penetrate  to  the  surface  of  the  capsule  and  between  the 
urinary  tubules.  It  is  established  physiologically  that  motor  fibers  are  present 
for  the  unstriated  muscular  fibers,  also  vasomotor  fibers  and  sensory  branches  in 
the  capsule  and  the  pelvis  of  the  kidney.  The  existence  of  vasodilator  and 
secretory  fibers  is  also  probable. 

The  connective  tissue  of  the  kidney  forms  in  the  papillae  fibrillated,  con- 
centric layers  about  the  excretory  ducts  (VI).  Further  upward  star-shaped  cells 
of  reticular  tissue  appear  in  addition  and  these  are  found  alone  in  the  cortex. 
The  outer  layers  of  the  fibrous  capsule  of  the  kidney  are  formed  of  dense  bundles 
of  fibrils,  while  the  inner  layers  are  looser  and  send  processes  into  the  cortical 
layer.  The  fatty  capsule  of  the  kidney  is  connected  with  the  organ  itself,  in  part 
through  vessels  and  in  part  through  bands  of  connective  tissue. 

Unstriated  muscular  fibers  are  contained  in  the  kidney  in  three  forms:  (i) 
A  sphincter-like  layer  surrounding  each  papilla;  (2)  a  wide-meshed  net- 
work on  the  surface  of  the  kidney;  (3)  fibers  that  arise  from  the  depth  of  the 
pelvis  of  the  kidney  and  pass  through  the  pyramids  with  the  blood-vessels 


472  THE    URINE. 

H.  Kostjurin  found  at  the  junction  of  the  cortical  and  the  medullary  structure, 
in  the  dog,  a  layer  of  muscle-fibers  from  which  bundles  pass  in  each  direction. 


THE  URINE.* 

THE  PHYSICAL  CHARACTERS  OF  THE  URINE. 

The  amount  of  urine  in  men  is  between  1000  and  1500  cu.  cm.  in 
twenty-four  hours;  in  women  between  900  and  1200.  There  is  a  min- 
imum between  2  and  4  a.  m.,  a  maximum  in  the  morning  and  a  second 
maximum  between  2  and  4  p.  m. 

The  amount  of  urine  is  diminished  by  profuse  perspiration,  diarrhea,  thirst, 
food  deficient  in  nitrogen,  reduction  in  the  general  blood-pressure,  after  profuse 
hemorrhage,  as  a  result  of  the  action  of  certain  poisons,  such  as  atropin  and  mor- 
phin,  and  in  the  presence  of  certain  diseases  of  the  structure  of  the  kidney.  The 
minimum  that  may  still  be  considered  normal  is  between  400  and  500  cu.  cm. 

The  amount  is  increased  by  increase  in  the  blood-pressure  in  general,  or  in  the 
distribution  of  the  renal  artery  alone,  by  copious  drinking,  contraction  of  the 
cutaneous  vessels  from  the  action  of  cold,  the  elimination  of  soluble  diuretic 
substances,  such  as  urea,  salts,  and  sugar  through  the  urine,  a  diet  rich  in  nitrogen, 
as  well  as  by  certain  medicaments,  such  as  digitalis,  juniper,  squill,  alcohol,  etc. 
Carbonated  beverages  increase  the  urine  in  the  succeeding  hour. 

The  direct  influence  of  the  nervous  system  upon  the  amount  of  urine  is  also 
familiar.  In  this  category  belongs  the  polyuria  suddenly  developed  after  nervous 
perturbation,  as,  for  instance,  in  hysterical  persons,  following  epileptic  attacks, 
and  also  after  pleasurable  excitement,  and  finally  the  remarkable  increase  in 
urinary  secretion  after  injury  of  the  floor  of  the  fourth  ventricle  of  the  brain. 
Nocturnal  polyuria  occurs  in  persons  suffering  from  disease  of  the  heart  and  the 
kidneys,  in  cachectic  states  and  in  the  presence  of  arterio-sclerosis.  Neurasthenic 
anuria  of  neurotic  origin  lasting  from  twelve  to  fifty-six  hours  is  extremely 
rare.  The  urine  can  be  measured  in  graduated  cylinders  or  flasks. 

The  specific  gravity  of  the  urine  varies  between  1015  and  1025. 
The  minimum  is  observed  after  abundant  ingestion  of  water,  1002;  the 
maximum  after  profuse  sweating  and  marked  thirst,  1040.  In  the  new- 
born the  specific  gravity  falls  considerably  in  the  first  few  days,  in 
conformity  with  the  progressive  increase  in  the  amount  of  nourishment 
taken.  The  adult  discharges  per  diem  on  the  average  i  gram  of  solids 
through  the  urine  for  every  kilogram  of  body-weight. 

The  determination  of  the  specific  gravity  is  made,  with  the  urine  at  a  tem- 
perature of  16°  C.,  by  means  of  the  urinometer  (Fig.  144).  If  but  a  small  amount 
of  urine  is  obtainable  and  it  does  not  sufficiently  fill  the  urinometer-cylinder  the 
urine  is  diluted  with  twice  or  thrice  its  volume  of  distilled  water,  and  then  the 
last  two  figures  on  the  urinometer  are  multiplied  by  two  or  three  respectively.  By 
means  of  the  formula  of  Trapp  or  Haeser  the  amount  of  solids  contained  in  1000 
parts  of  urine  can  be  estimated  approximately  from  the  specific  gravity.  Of  the 
number  indicating  the  specific  gravity,  as,  for  instance,  1018,  the  last  two  figures 
are  taken,  in  this  instance  therefore  18,  and  multiplied  by  2.33.  The  estimation 
of  the  total  solids  can  be  made  in  a  more  trustworthy  manner  by  evaporating 
about  15  cu.  cm.  of  urine  in  a  weighed  porcelain-dish  over  the  water-bath  and 
subsequent  complete  drying  in  the  air-bath  at  a  temperature  of  100°  C.  and  cooling 
over  concentrated  sulphuric  acid.  In  this  way  some  urea  is  decomposed  into 
carbon  dioxid  and  escaping  ammonia,  in  consequence  of  which  the  result  is  some- 
what too  low. 

The  specific  gravity  depends  naturally  upon  the  amount  of  water  in  the 
urine.  The  urine  of  the  morning  (urina  noctis)  is  most  concentrated,  that  is, 
heaviest,  because  water  is  absorbed  from  the  bladder  after  the  urine  has  been 


*  The  illustrations  are  taken  in  part  from  Ultzmann  and  Hoffmann's  Atlas  of 
Urinary  Sediments. 


THE    PHYSICAL    CHARACTERS    OF    THE    URINE. 


473 


....  1000 
.._10U 

....  mo 

.._1080 
__J040 


\ 


present  for  a  considerable   time   during  sleep  and    the    urine  thus   becomes  in- 
spissated.    The  most  dilute  urine  is  encountered  after  copious  drinking  (urina 
potus).     Hunger  and  laxatives  diminish,  while  physical  exertion  increases,  the 
amount  of  solids  in  the  urine.     Among  pathological  conditions,  highly  concentrated 
and  copious  urine,  up  to  10,000  cu.  cm.,  is  observed  in  cases  of  diabetes  mellitus 
(p.  313),  when  the  specific  gravity  may  be  from  1030  to  1060.     Concentrated, 
scanty  urine  is  encountered  in  the  presence  of  fever.     Simple,  for  instance,  ner- 
vous, polyuria  is  characterized  by  ex- 
tremely dilute  and  copious  urine,  and  the 
specific  gravity  may  be  as  low  as  1001. 

The  color  of  the  urine  exhibits 
various  gradations  principally  in 
accordance  with  the  amount  of 
water  contained.  Highly  diluted 
urine  is  likely  to  be  pale  yellow  in 
color.  Urine  of  watery  clearness 
has  even  been  observed  in  associa- 
tion with  sudden  polyuria — as,  for 
instance,  the  spastic  urine  of  the 
hysterical.  Concentrated  urine, 

particularly  after  a  generous  meal,  lo  > 

varies  from  dark  yellow  to  brown- 
ish red  in  color.  Urine  of  similar 
tint  in  association  with  fever  is 
commonly  designated  high-colored. 

Fetal  urine,  as  well  as  that  passed 
immediately  after  birth,  is  as  clear  as 
water.  Admixture  of  blood  gives  rise, 
in  accordance  with  the  degree  of  disinte- 
gration of  hemoglobin,  to  a  color  vary- 
ing from  red  to  deep  brownish-red;  bili- 
ary pigment  to  a  deep  yellowish-brown 
color,  with  an  intense  yellowish  foam; 
senna,  taken  by  the  mouth,  causes  the 
urine  to  have  a  deep-red  color,  rhubarb 
a  brownish-yellow  color,  carbolic  acid  a 
black  color.  Urine  in  a  state  of  am- 
moniacal  decomposition  may  present  a 
dirty-blue  appearance  from  the  forma- 
tion of  indigo.  For  uniform  estimation 
of  the  color  of  the  urine  a  urinary  color- 
scale  has  been  devised  empirically. 

The  urine,  especially  if  in  a  state  of 
ammoniacal  decomposition,  exhibits 
fluorescence,  which  disappears  on  addi- 
tion of  acid,  and  reappears  on  addition  of  alkali.  Normal  urine  precipitates  in  the 
course  of  a  few  hours  a  cloud  or  nubecula  of  vesical  mucus  that  settles  slowly. 
The  froth  of  normal  urine  is  white  and  it  disappears  rather  quickly,  though  persist- 
ing for  a  longer  time  when  albumin  is  present.  Not  rarely  the  urine  contains  a 
number  of  epithelial  cells. 

Normal  urine  flows  in  a  limpid  stream  like  water. 

The  presence  of  considerable  amounts  of  sugar,  albumin  or  mucus  diminishes 
its  fluidity.  So-called  chylous  urine  from  patients  in  the  tropics  may  even  present 
a  white,  gelatinous  appearance. 

The  taste  of  urine  is  saline  and  bitter,  the  smell  characteristically 
aromatic,  approximating  that  of  beef-broth,  particularly  after  the  inges- 
tion  of  roast  meat. 


FIG.  143.  —  Graduated 
cylinder  and  Flask 
for  measuring  the 
Amount  of  Urine. 


FIG.  144. — Urino  meter. 


474  THE    PHYSICAL    CHARACTERS    OF    THE    URINE. 

Urine  in  a  state  of  ammoniacal  fermentation  exhibits  the  odor  of  ammonia. 
Of  substances  taken  by  the  mouth,  turpentine  gives  rise  to  the  odor  of  violets, 
copaiba  and  cubebs  to  an  aromatic  odor,  and  asparagus  to  a  disgusting  odor  due 
to  methylmercaptan.  Valerian,  garlic  and  castor  yield  up  some  of  their  odorous 
constituents  to  the  urine. 

The  reaction  of  normal  urine  is  acid  from  the  presence  of  acid  salts, 
especially  acid  monosodium  phosphate  (PO4H2Na).  The  latter  re- 
sults from  alkaline  disodium  phosphate  (PO4HNa2),  uric  acid,  hippuric 
acid,  sulphuric  acid  and  carbon  dioxid  each  taking  up  one  atom  of  so- 
dium, so  that  the  phosphoric  acid  must  be  displaced  to  form  the  acid 
salt.  After  a  meat-diet  acid  potassium  phosphate  especially  causes  the 
acid  reaction.  That  the  urine  contains  no  free  acid  is  shown  by  the  fact 
that  no  precipitate  takes  place  on  addition  of  sodium  hyposulphite. 

•  Night-urine  exhibits  the  highest,  morning-urine  the  lowest  degree  of  acidity. 
Sometimes  the  reaction  of  the  morning- urine  is  alkaline. 

The  acid  reaction  becomes  increased  after  ingestion  of  acids,  such  as  hydro- 
chloric acid  and  phosphoric  acid;  as  well  as  of  ammonium-salts,  which  are  trans- 
formed in  the  body  into  nitric  acid;  after  active  muscular  exercise;  after  a  milk- 
diet;  and  pathologically  in  the  presence  of  hyperacidity  of  the  gastric  juice. 
The  absolute  elimination  of  acid  is  increased  by  marked  diuresis,  while  the  relative 
elimination  is  diminished. 

The  acidity  of  the  urine  is  lessened  and  its  reaction  may  even  be  rendered 
alkaline:  (i)  By  the  ingestion  of  caustic  alkalies,  alkaline  carbonates,  or  alkaline 
salts  of  the  vegetable  acids — the  last  being  oxidized  in  the  body  into  alkaline 
carbonates.  (2)  By  the  presence  of  calcium  or  magnesium  carbonate.  (3)  By 
admixture  of  blood  or  pus  of  alkaline  reaction.  (4)  By  drainage  of  the  acid  gastric 
juice  outside  the  body  through  a  fistula;  further,  in  from  one  to  three  hours 
after  digestion,  in  consequence  of  the  formation  of  acid  in  the  stomach.  (5)  By 
the  absorption  of  alkaline  transudates,  such  as  serum  or  blood.  (6)  In  con- 
sequence of  profuse  secretion  of  sweat  and  hot  baths.  If  the  surface  of  the 
body  is  kept  at  a  temperature  of  31°  C.  and  30  per  cent,  of  relative  humidity, 
alkaline  urine  will  be  excreted  in  the  morning-hours,  on  account  of  the  fixed 
alkaline  carbonates,  while  the  evening-urine  exhibits  a  strongly  acid  reaction. 
(7)  The  urine  has  rarely  been  observed  to  be  alkaline  in  anemic  persons,  from 
deficiency  of  phosphoric  and  sulphuric  acids. 

The  reaction  is  tested  by  means  of  strips  of  violet  litmus-paper,  which  become 
red  when  dipped  in  acid  urine  and  blue  in  alkaline  urine.  In  order  to  determine 
the  degree  of  acidity  of  the  urine  it  is  necessary  to  learn  the  amount  of  sodium 
hydroxid  required  to  render  exactly  neutral  the  reaction  of  100  cu.  cm.  of  urine. 
For  this  purpose  a  solution  of  sodium  hydroxid  is  employed  of  which  each  cubic 
centimeter  contains  0.0031  gram  of  sodium;  i  cu.  cm.  of  this  solution  neutralizes 
exactly  0.0063  gram  of  oxalic  acid.  From  a  graduated  buret  (Fig.  145)  the  sodium- 
solution  is  permitted  to  escape  drop  by  drop  into  a  beaker  containing  100  cu.  cm. 
of  urine,  with  constant  stirring,  until  violet  litmus-paper  no  longer  becomes  either 
red  or  blue.  The  amount  of  sodium-solution  in  cubic  centimeters  is  read  from 
the  scale  of  the  buret,  and  as  each  cubic  centimeter  corresponds  to  0.0063  gram 
of  oxalic  acid,  the  amount  of  oxalic  acid  that  is  the  equivalent  of  the  acid  in  the 
100  cu.  cm.  of  urine  can  be  readily  estimated.  The  degree  of  acidity  of  the  urine 
is  therefore  expressed  in  terms  of  the  equivalent  amount  of  oxalic  acid  that  is 
fully  neutralized  by  the  same  amount  of  sodium  hydrate. 

The  urine  of  carnivora  varies  in  color  from  pale  to  golden  yellow.  It  has 
a  high  specific  gravity  and  exhibits  a  strongly  acid  reaction.  The  urine  of 
herbivora  has  an  alkaline  reaction  and  therefore  exhibits  precipitates  of  earthy 
carbonates  (so  that  it  effervesces  on  addition  of  acid)  and  of  earthy  basic  phos- 
phates. In  the  state  of  hunger  it  acquires  the  character  of  the  urine  of  carnivora, 
as  under  these  conditions  the  animal  in  a  certain  measure  lives  upon  its  own 
tissues. 


THE    ORGANIC    CONSTITUENTS    OF    THE    URINE. 


475 


THE  ORGANIC  CONSTITUENTS  OF  THE  URINE. 
UREA:  CO(NH2)2. 

Urea,  the  diamid  of  CO2  or  carbamid  must  be  considered  as  the 
principal  end-product  of  the  oxidation  of  the  nitrogen-containing  consti- 
tuents of  the  body.  It  has  the  following  extremely  simple  composi- 
tion: i  atom  of  carbon  dioxid 
-f-  2  atoms  of  ammonia  —  i 
atom  of  water.  It  crystallizes 
in  silky-glistening,  four-sided 
prisms,  with  oblique  ends,  be- 
longing to  the  rhombic  system 
(Fig.  146,  i,  2),  without  water  of 
crystallization ;  when  rapidly 
crystallized  it  forms  delicate, 
white  needles.  It  has  no  in- 
fluence upon  litmus,  is  odorless, 
and  of  a  feeble  bitter,  cooling 
taste  like  that  of  potassium  ni- 
trate. It  is  readily  soluble  in 
water  and  in  alcohol,  but  almost 
insoluble  in  ether.  It  is  isomeric 
with  ammonium  cyanate,  from 
which  it  develops  on  evapora- 
tion through  atomic  displace- 
ment. Numerous  other  modes 
of  artificial  preparation  are 
known. 

Heated  to  a  temperature  above 
120°  it  is  decomposed,  with  the  de- 
velopment of  vapors  of  ammonia, 
and  leaving  a  vitreous  mass  of  biuret 
and  hydrocyanic  acid.  In  the  pro- 
cess of  ammoniacal  putrefaction  and 
as  a  result  of  treatment  with  strong 
mineral  acids,  of  boiling  with  alka- 
line hydrates  and  of  heating  with 
water  at  a  temperature  of  240°  C., 
it  takes  up  two  atoms  of  water 
and  yields  ammonium  carbonate: 
CO(NH2)2  +  2H2O  =  CO(ONH42). 
Brought  in  contact  with  nitrous  acid 
it  is  decomposed  into  water,  carbon 
dioxid  and  nitrogen.  The  last  two 
forms  of  decomposition  have  been  employed  for  the  quantitative  estimation  of  urea. 

The  amount  of  urea  in  normal  urine  is  between  2.5  and  3.  2  per  cent. 
Adults  excrete  daily  about  from  30  to  40  grams;  women  less;  children 
relatively  more.  In  accordance  with  the  more  active  metabolism  in  the 
latter,  the  amount  of  urea  furnished  by  the  weight-unit  of  the  child's 
body,  as  compared  with  that  of  the  adult,  is  as  1.7  to  i.  If  the  body  is 
in  a  condition  of  metabolic  equilibrium  almost  as  much  nitrogen  is 
eliminated  in  the  form  of  urea  as  is  introduced  into  the  body  with  the 
food. 

The  amount  of  urea  increases  with  the  amount  of  proteids  in  the  food, 


FIG.  145. — Graduated  Buret. 


476 


UREA. 


as  well  as  with  the  degree  of  disintegration  of  the  nitrogen-containing 
tissues  in  the  body.  As  the  latter  is  increased  by  withholding  oxygen 
and  by  hemorrhage,  these  also  cause  an  increase  in  the  amount  of  urea. 
The  administration  of  large  amounts  of  water — by  more  thorough 
washing  out  of  the  tissues — and  also  of  salts,  frequent  micturition  and 
exposure  to  compressed  air  likewise  increase  the  amount  of  urea.  In 
diabetics  who  partake  of  large  amounts  of  food,  the  amount  of  urea 
occasionally  exceeds  100  grams  daily,  while  in  the  state  of  hunger  it 
falls  to  5.6  grams.  In  the  state  of  inanition  a  maximum  of  elimination 
has  been  observed  toward  noon,  and  a  minimum  toward  morning. 

Daily  variations  in  the  amount  of  urea  pursue  a  course  parallel  with 
the  amount  of  urine.  Three  or  four  hours  after  digestion  begins  the  forma- 
tion of  urea  reaches  its  maximum,  subsequently  falling  again  and  reaching 
its  minimum  during  the  night.  The  excretion  of  urea,  and  in  the  same 
proportion  that  of  the  total  nitrogen,  with  the  urine  is  materially  aug- 
mented in  consequence  of  increased  muscular  activity.  This  excretion 


FIG.  146. — i,  2,  Prisms  of  pure  urea;   3,  rhombic  plates;   4,  hexagonal  tablets;   5,  6,  irregular  scales  and  plates 

of  urea  nitrate. 


is  less  on  the  first  working  day,  as  observed  in  dogs,  than  on  the  second 
and  third,  but  it  is  still  increased  on  the  two  resting  days  succeeding 
the  work. 

Pathological. — In  the  presence  of  acute  febrile  inflammatory  processes  and  of 
fever  in  general,  the  excretion  of  urea  increases  to  the  height  of  the  morbid  process, 
in  association  with  which  it  again  declines.  After  the  cessation  of  the  process 
the  excretion  is  often  subnormal.  At  times  the  formation  of  urea  may  be  in- 
creased in  association  with  high  fever,  but  the  excretion  may  be  checked  and 
retention  of  urea  takes  place.  In  the  further  course  of  the  disorder  the  excretion 
may  be  greatly  increased.  In  chronic  diseases  the  amount  of  urea  varies  with 
the  state  of  the  nutrition,  the  metabolism  of  the  patient  and  in  accordance  with 
the  height  of  the  accompanying  fever.  Degenerative  disorders  of  the  liver,  as, 
for  instance,  from  phosphorus-poisoning,  may  be  attended  with  diminished  excre- 
tion of  urea  and  increased  excretion  of  ammonia. 

Substances  that  increase  the  proteid  disintegration  in  the  body,  as,  for  instance, 
arsenic,  antimony-combinations,  and  small  amounts  of  phosphorus,  increase  the 
formation  of  urea;  while  those  that  conserve  proteids,  as,  for  instance,  quinin, 
diminish  the  production.  Increased  formation  of  bile  in  the  liver  gives  rise  at  the 
same  time  to  increased  formation  of  urea. 


UREA. 

Urea  represents  the  end-product  of  the  metabolism  of  proteids.  Next  in 
order  there  stand,  as  lower  stages  of  oxidation,  uric  acid,  guanin,  xanthin,  hypo- 
xanthin,  alloxan  and  allantoin.  Uric  acid  administered  as  urates  appears  in  the 
urine  as  urea,  being  transformed  by  the  liver,  with  increase  in  the  secretion  of 
bile.  Muscle-extractives  have  the  same  effect,  and  in  general  increased  formation 
of  bile  is  attended  with  augmented  formation  of  urea.  After  administration  of 
leucin,  glycin,  aspartic  acid  or  of  ammonium-salts  an  increase  in  the  excretion  of 
urea  takes  place. 

The  liver  is  the  principal,  but  not  the  sole  seat  of  the  formation  of 
urea.  The  correctness  of  the  supposition  of  Schmiedeberg  that  the  urea 
is  derived  from  ammonium  carbonate  through  loss  of  water  was  demon- 
strated by  v.  Schroder,  who  found  urea  in  large  amount  in  blood  to 
which  ammonium  carbonate  had  been  added,  and  made  to  pass  through 
a  recently  removed  liver.  It  is,  therefore,  to  be  concluded  that  am- 
monium-combinations derived  from  nitrogen-containing  tissues  as  meta- 
bolic products  pass  over  into  the  circulation,  through  which  they  are 
conveyed  to  the  liver  for  the  formation  of  urea.  The  organism  is 
capable  of  converting  considerable  amounts  of  ammonia,  as,  for  instance, 
in  the  form  of  lactate  or  acetate,  into  urea.  The  liver  forms  urea  also 
from  the  ammonia  in  the  blood  of  the  portal  vein.  In  the  metabolism 
especially  of  proteids  there  is  formed  in  many  organs  by  oxidation  car- 
bamic  acid,  CO2NH3,  which  likewise  is  transformed  principally  in  the 
liver  into  urea,  and  also  the  amido-acids.  If  acids  are  taken  into  the 
body  before  the  ammonium-combinations  are  transformed  into  urea, 
there  result  ammonium-salts,  with  a  corresponding  reduction  in  the 
amount  of  urea  in  the  urine.  Under  pathological  conditions  the 
urea-forming  activity  of  the  liver  may  be  diminished. 

After  extirpation  of  the  liver,  the  urine  no  longer  contains  urea,  and  likewise 
after  exclusion  of  the  hepatic  circulation,  but  on  the  other  hand  large  amounts 
of  ammonium- salts. 

Eck,  in  the  dog,  diverted  the  blood  of  the  portal  vein  directly  into  the  inferior 
vena  cava,  by  establishing  an  artificial  communication  between  the  two  vessels, 
and  then  ligated  the  portal  vein  close  to  the  liver.  The  dogs  were  seized  with 
severe  nervous  attacks  and  convulsions.  As,  according  to  v.  Schroder,  ammonium- 
salts  are  transformed  in  the  liver  into  urea,  this  transformation  is  thus  almost 
wholly  prevented,  and  the  substances  named  now  exert  a  toxic  effect  upon  the 
nervous  system. 

By  injection  of  a  6.2  per  cent,  solution  of  sulphuric  acid  into  the  bile  duct, 
in  the  dog,  all  of  the  liver-cells  became  necrotic,  and  the  animal  died  in 
one  or  two  days  with  signs  of  prostration,  mental  derangement,  loss  of  sensibility, 
central  narcosis  and  finally  convulsions.  From  this  it  has  been  concluded  that 
the  liver  serves  the  purpose  of  converting  a  toxic  metabolic  product,  carbamic 
acid,  into  an  innocuous  one,  urea. 

In  birds  the  liver  thus  produces  the  largest  amount  of  uric  acid  from  the 
ammonium  supplied.  As  birds  readily  tolerate  ablation  of  the  liver,  Minkowski 
observed  after  this  operation  reduction  in  the  amount  of  uric  acid  and  in- 
crease in  the  amount  of  ammonium-salts  in  the  urine. 

Urea  is  present  in  the  following  parts  of  the  body:  Blood  (i  :  10,000) ;  lymph, 
chyle  (2  :  1,000);  liver,  lymphatic  glands,  spleen,  lungs,  brain,  eye,  bile,  saliva, 
amniotic  fluid;  by  Schondorff  it  was  found  in  the  muscles  and  the  erythrocytes 
and  in  almost  all  of  the  organs  of  the  dog;  besides,  pathologically,  in  the  sweat, 
as,  for  instance,  in  cases  of  cholera,  as  well  as  in  the  vomitus  and  in  dropsical 
fluids  of  uremic  patients. 

The  preparation  of  urea  can  be  accomplished  directly  from  dogs'  urine,  after 
generous  feeding  with  meat,  the  fluid  being  evaporated  to  a  syrupy  consistency, 
extracted  with  alcohol,  the  filtered  extract  again  evaporated,  the  crystals  thus 
separated  freed  of  the  adherent  extractives  by  means  of  alcohol  and  then  dis- 
solved in  absolute  alcohol.  Filtration  is  practised  again  and  evaporation  is  per- 
mitted to  take  place  until  crystallization  occurs.  A  given  volume  of  human  urine 


478  QUALITATIVE    AND    QUANTITATIVE    ESTIMATION    OF    UREA. 

is  evaporated  to  one-sixth  of  its  original  volume,  is  reduced  to  a  temperature 
of  o°  and  an  excess  of  strong,  pure  nitric  acid  is  added.  Urea  nitrate  contaminated 
with  coloring-matter  is  precipitated.  The  precipitate  is  filtered,  expressed,  dis- 
solved in  a  little  boiling-water,  mixed  with  animal  charcoal  for  the  removal  of 
the  coloring-matter,  and  filtered  hot.  On  cooling,  decolorized  crystals  of  urea 
nitrate  separate  from  the  filtrate.  These  are  again  dissolved  in  hot  water,  and 
barium  carbonate  is  added  so  long  as  effervescence  takes  place.  Barium  nitrate 
and  free  urea  are  thus  formed.  Evaporation  to  dryness  is  now  practised,  fol- 
lowed by  exhaustion  with  absolute  alcohol,  filtration  and  evaporation,  after  which 
the  urea  separates  in  crystals. 

Combinations  of  Urea. — Urea  is  capable  of  entering  into  combination  with 
acids,  as  nitric,  oxalic  or  phosphoric,  or  with  bases,  or  with  salts,  as  sodium 
chlorid,  mercuric  nitrate.  The  most  important  combinations  are: 

1.  Urea  nitrate:    CH4N2O.NO3H,  whose  mode  of  preparation  from  the  urine 
has  just  been  described.     The  preparation  of  urea  nitrate  is  employed  with  advant- 
age for  the  microscopic   demonstration   of  urea.     If  there  are  but  a  few  drops 
of  watery  fluid  in  which  the  presence  of  urea  is  suspected — and  this  must  be  so 
prepared  that  the  urea  present  is  in  concentrated  watery  solution— one  drop  of  this 
fluid  is  placed  upon  a  glass  slide,  a  thread  is  laid  through  the  middle  of  the  drop 
and  over  both  is  placed  a  cover-slip.     From  the  extremity  of  the  thread  a  drop 
of  concentrated  nitric  acid  is  permitted  to  find  its  way  beneath  the  cover-slip. 
The  characteristic  crystals  appear  upon  either  side  of  the  thread  (Fig.  146,  3,  4, 
5,  6).     Urea  nitrate  is  readily  soluble  in  water,  soluble  with  difficulty  in  water 
acidulated  with  nitric  acid.     Less  commonly,  when  crystallization  takes  place 
slowly,  it  yields  six-sided  prisms. 

2.  Mercuric-nitrate  urea  is  obtained  in  the  form  of  a  white,  cheesy  precipitate, 
when  mercuric  nitrate  is  introduced  into  a  solution  of  urea.     If,  on  the  develop- 
ment of  the  precipitate,  the  nitric  acid  set  free  is  neutralized  by  sodium  carbonate, 
all  of  the  urea  eventually  combines  with  the  mercuric  salt.     When  this  point  has 
been  reached,  all  excess  of  mercuric  nitrate  gives  rise,  on  addition  of  sodium 
carbonate,  to  the  production  of  sodium  nitrate  and  yellow  basic  mercuric  carbo- 
nate.    The  titration-method  of  J.  v.  Liebig  for  urea  is  based  upon  this  reaction. 

QUALITATIVE   AND    QUANTITATIVE    ESTIMATION    OF    UREA. 

The  qualitative  estimation  of  urea  aims  (i)  at  the  preparation  of  this  substance 
directly  as  such.  If  its  presence  be  suspected  in  an  albuminous  fluid  mixed  with 
blood  or  pus,  the  following  course  is  pursued:  Three  or  four  times  its  volume  of 
alcohol  are  added  to  the  fluid,  and  filtration  is  practised  after  the  lapse  of  several 
hours.  The  filtrate  is  evaporated  over  the  water-bath,  and  the  residue  is  dis- 
solved in  a  few  drops  of  water.  (2)  This  aqueous  solution  is  employed  for  the 
microchemic  preparation  of  urea  nitrate,  which  has  important  diagnostic  signifi- 
cance. (3)  By  means  of  a  solution  of  sodium  hypobromite,  the  urea  in  the  fluid 
submitted  to  examination  is  decomposed  into  carbon  dioxid,  water,  and  nitrogen. 
The  nitrogen  rises  in  the  mixture  in  the  form  of  small  bubbles.  The  Knop- 
Hiibner  method  of  quantitative  estimation  is  based  upon  this  reaction.  (4)  A 
crystal  of  urea  is  cautiously  fused  in  a  dry  test-tube,  and  yields  an  odor  of  am- 
monia. On  cooling,  it  is  dissolved  in  a  small  amount  of  water,  and  sodium  hy- 
drate, together  with  one  drop  of  dilute  copper  sulphate,  is  added,  with  the  develop- 
ment of  a  red-color — biuret-reaction. 

Quantitative  estimation  of  urea  in  the  urine,  according  to  the  method  of 
Morner  and  Sjoqvist: 

To  2.5  cu.  cm.  of  urine  are  added  2.5  cu.  cm.  of  baryta-mixture  (i  volume 
of  a  cold  saturated  solution  of  barium  hydrate  and  2  volumes  of  cold  saturated 
barium  nitrate)  and  75  cu.  cm.  of  ether-alcohol  (the  alcohol  must  be  70  per  cent.). 
The  mixture  is  preserved  for  a  day  sealed.  It  is  now  filtered,  and  the  filtrate, 
which  contains  of  the  nitrogenous  substances  only  the  urea,  is  evaporated  at 
a  temperature  of  55°  C.  after  the  addition  of  0.5  gram  of  magnesium  oxid. 
After  the  addition  of  10  cu.  cm.  of  sulphuric  acid  it  is  further  evaporated  upon 
a  boiling  water-bath,  until  no  further  reduction  in  volume  takes  place.  Then 
it  is  placed  in  a  Kjeldahl  boiling-flask,  and  the  examination  is  continued  according 
to  the  Kjeldahl  method. 

The  method  of  Kjeldahl  is  employed  for  the  estimation  of  the  total  amount 
of  nitrogen  in  the  urine.  It  is  based  upon  the  fact  that  all  of  the  nitrogen  is 
transformed  into  ammonia,  and  this  is  estimated  quantitatively.  Five  cu.  cm. 
of  urine  of  moderate  concentration  are  measured  by  means  of  a  pipet  and  intro- 


URIC    ACID. 


479 


duced  into  a  flask  having  a  capacity  of  about  200  cu.  cm.,  with  20  cu.  cm.  of 
pure  English  sulphuric  acid  (to  one  liter  of  which  200  grams  of  phosphoric  anhydrid 
are  added) ,  and  one  drop  of  metallic  mercury ;  and  this  is  boiled  over  the  sand- 
bath  until  the  fluid,  which  at  first  was  dark,  is  entirely  decolorized.  On  cooling, 
the  fluid  is  rinsed  with  about  200  cu.  cm.  of  water  into  a  flask 
having  a  capacity  of  half  a  liter,  and  100  cu.  cm.  of  sodium  hy- 
drate (of  a  sp.  gr.  of  1.34),  a  few  cu.  cm.  of  an  aqueous  solution 
of  potassium  sulphid,  and  some  powdered  zinc  are  added.  The 
flask  is  then  quickly  closed  with  a  stopper  and  the  ammonia  set 
free  is  distilled  into  a  receiver  containing  50  cu.  cm.  of  one- 
tenth  normal  sulphuric  acid.  The  extremity  of  the  tube  from 
which  the  ammonia  escapes  must  be  immersed  in  the  normal 
sulphuric  acid.  In  order  to  determine  whether  all  of  the  am- 
monia is  present  in  the  receiver,  the  stopper  of  the  receiver  is 
cautiously  removed,  a  strip  of  litmus-paper  is  placed  by  means 
of  a  pair  of  forceps  in  front  of  the  tube  conveying  the  ammonia.  . 

and  note  is  made  whether  the  escaping  distillate  causes  the  strip 
to  turn  blue.  The  amount  of  sulphuric  acid  in  the  receiver  not 
saturated  by  ammonia  is  determined  by  titration  with  one-tenth 
normal  sodium  hydrate. 

According  to  Pfliiger  and  Bohland,  the  amount  of  nitrogen 
in  the  urine  can  be  estimated  approximately  by  the  following 
simple  method:  To  10  cu.  cm.  of  urine,  Liebig's  urea-titrating 
solution  is  added  from  a  buret,  and  the  mixture  is  tested  upon 
a  dark  glass  plate  with  sodium  bicarbonate  drop  by  drop,  as  in 
the  estimation  of  urea.  If  the  stirred  stain  remains  yellow,  the 
number  of  cubic  centimeters  of  titration-fluid  employed  is  mul- 
tiplied by  0.04  and  in  this  way  the  percentage  of  nitrogen  present 
is  obtained.  The  total  amount  of  nitrogen  in  the  urine  is  to  the 
nitrogen  in  the  urea  approximately  as  5  to  4. 


FIG.    147.  —  Gradu- 
ated Pi  pet. 


URIC  ACID— C5H4N403. 

Next  to  urea,  the  greatest  amount  of  nitrogen  is 
eliminated  as  uric  acid,  namely,  0.5  gram  in  24  hours 
(in  the  state  of  hunger,  0.24  gram ;  after  a  generous  meat- 
diet,  2. ii  grams).  The  amount  of  uric  acid  is  to  that  of 
urea  on  the  average  as  i  to  46,  though  with  many  varia- 
tions. In  the  mammalian  body  the  uric  acid  is  formed 
from  the  nuclein  of  the  disintegrating  leukocytes.  With 
increase  in  the  latter,  there  is  increase  in  the  amount  of 
uric  acid  formed.  Ingestion  of  nuclein — as,  for  instance,  after  the  eating 
of  thymus  gland — increases  the  number  of  leukocytes  in  the  blood  and 
the  excretion  of  uric  acid.  Xanthin-bases  (guanin,  xanthin,  hypoxan- 
thin)  occur  in  the  intestines  as  products  of  the  digestion  of  nucleins.  If 
they  be  increased  in  amount,  an  increase  in  the  amount  of  uric  acid 
results. 

In  birds,  reptiles  and  insects,  uric  acid  is  the  principal  nitrogenous  excrementi- 
tious  product;  while  it  appears  in  but  small  amount  in  the  urine  of  herbivora. 

The  products  of  the  decomposition  of  leukocytes  present  in  surviving  splenic 
pulp  (nuclein)  yield,  when  treated  with  fresh  blood  at  the  temperature  of  the 
body,  an  abundance  of  uric  acid,  together  with  xanthin  and  hypoxanthin.  Also 
the  nuclein  of  the  nuclei  of  many  other  tissues  has  also  shown  itself  to  be  a  source 
of  uric  acid.  In  addition  to  uric  acid,  xanthin-bodies  are  formed  in  the  same 
way.  When  animals  are  fed  with  nucleinic  acid  and  hypoxanthin,  the  elimination 
of  uric  acid  is  increased. 

Uric  acid  fed  to  mammals  passes  into  the  urine  in  part  further  oxidized  into 
urea,  together  with  an  increase  in  the  amount  of  oxalic  acid.  In  hens  there  is 
increased  elimination  of  uric  acid  after  the  administration  of  leucin,  glycin, 
aspartic  acid,  hypoxanthin,  or  ammonium  carbonate.  The  urea  administered  to 
hens  is,  however,  eliminated  chiefly  reduced  to  uric  acid. 


48o 


URIC    ACID. 


Uric  acid  is  dibasic,  tasteless,  odorless,  and  colorless,  soluble  with 
great  difficulty  in  water  (in  15,000  parts  of  warm,  or  18,000  parts  of  cold 
water,  though  in  2,000  parts  of  a  2  per  cent,  solution  of  urea),  insoluble 
in  alcohol  or  ether.  It  crystallizes  in  various  forms  (Fig.  148),  the 
basic  type  of  which  is  the  rhombic  plate  (i).  Enlargement  of  the  op- 
posed larger  angles  causes  the  formation  of  the  whetstone-shape  fre- 
quently observed  (2).  If  the  longer  sides  of  the  latter  are  flattened, 
six-sided  plates  result.  Large,  golden-yellow  crystalline  resets  (6,  8) 
often  separate  spontaneously  from  diabetic  urine.  Precipitated  by 
addition  of  hydrochloric  acid  (25  cu.  cm.)  to  urine  (one  liter)  or  of 
acetic  acid,  the  crystals  usually  assume  the  form  of  a  barrel  (9)  or  a 
bundle  of  spears  that  are  tinged  brownish  violet  by  adherent  urea. 

Uric  acid  is  readily  soluble  in  alkaline  carbonates,  borates,  phosphates,  lactates, 
and  acetates.  Removing  a  portion  of  the  base  from  these  salts,  there  result, 
on  the  one  hand,  acid  urates;  and  on  the  other  hand,  acid  salts  from  the  neutral 


FJG.  148. — Different  Forms  of  Uric  Acid:  i,  rhombic  plates;  2,  whetstone-shape;  3,  quadratic  shape;  4,  5.  elon- 
gated forms  with  two  pointed  extremities;  6,  8,  arrangement  of  several  crystals  in  the  form  of  a  roset;  7, 
crystals  drawn  out  into  the  shape  of  a  lance;  9,  so-called  barrel-shape  obtained  from  human  urine  by  means 
of  hydrochloric  acid,  in  part  darkly  discolored. 


salts.     Among  alkalies,  lithium  (citrate)  is  especially  noteworthy  as  a  solvent  of 
uric  acid. 

According  to  v.  Noorden  and  Strauss,  a  favorable  composition  of  the  urine 
will  be  obtained  if  calcium  carbonate  or  calcium-salts  of  the  vegetable  acids  (from 
2  to  10  grams)  are  administered.  Phosphoric  acid  leaves  the  body  with  the  cal- 
cium through  the  intestines.  In  consequence,  the  monosodium  phosphate  in  the 
urine  is  diminished,  as  it  gives  up  the  phosphoric  acid  and  thus  disodium  phos- 
phate results.  The  latter,  however,  is  capable  of  dissolving  uric  acid,  inasmuch 
as  sodium  urate  and  monosodium  phosphate  are  formed.  Uric  acid  is  soluble  in 
concentrated  sulphuric  acid,  from  which  it  is  reprecipitated  by  water.  Plumbic 
oxid  converts  it  into  urea,  allantoin,  oxalic  acid  and  carbon  dioxid;  ozone  pro- 
duces the  same  substances,  together  with  alloxan.  Reduced  by  hydrogen  in  a 
nascent  state,  xanthin  and  sarcin  are  produced.  Horbaczewski  has  prepared 
uric  acid  synthetically  by  fusing  one  part  of  glycin  and  seven  parts  of  urea. 

In  the  urine,  the  uric  acid  is  dissolved  principally  in  the  form  of  acid 
sodium  and  potassium  urate.  These  salts  are  present  also  in  urinary 


URIC    ACID.  481 

sediments,  urinary  sand,  and  urinary  calculi.  Ammonium  urate  is  con- 
tained in  lateritious  sediment  in  but  small  amount,  being  formed  in  large 
amount  only  as  a  result  of  ammoniacal  decomposition  of  the  urine  (Fig. 
154).  Free  uric  acid  occurs  in  normal  urine  only  in  the  smallest  amount . 
It  is,  however,  not  rarely  precipitated  subsequently  on  standing  (Fig. 
153).  and  it  is  present,  further,  also  in  urinary  sand  and  calculi.  De- 
ficiency of  neutral  phosphates  in  the  urine  favors  the  formation  of  uric- 
acid  sediment. 

The  urine  of  the  new-born  is  rich  in  uric  acid  (uric-acid  infarct  of  the  kidneys) . 
The  uric  acid,  together  with  its  salts,  is  increased  by  marked  muscular  activity 
attended  with  perspiration,  also  in  the  presence  of  catarrhal  and  rheumatic  fevers 
and  such  as  are  attended  with  derangement  of  respiratory  activity;  further,  in 
cases  of  leukemia  with  increased  leukocyte-destruction  and  splenic  tumor,  granular 
liver;  and,  finally,  quite  generally  in  connection  with  gastric  and  intestinal  catarrh 
following  excessive  indulgence  in  alcohol,  after  generous  ingestion  of  cheese  and  salt 
fish  or  salt  meat,  after  administration  of  glycerin,  and  a  diet  containing  nuclein. 
Hypoxanthin  fed  to  birds  is  eliminated  in  part  transformed  into  uric  acid. 

The  amount  of  uric  acid  is  diminished  after  generous  ingestion  of  fresh  fruits 
(strawberries,  cherries,  grapes)  or  of  quinic  acid  or  alkaline  salts  of  the  vegetable 
acids  contained  in  them;  further,  after  hot  baths;  also  after  ingestion  of  proteids 
in  large  amount  and  after  the  administration  of  caffein,  potassium  iodid,  sodium 
chlorid,  sodium  carbonate,  lithium  carbonate,  sodium  sulphate,  inhalations  of 
oxygen,  gentle  muscular  exercise,  though  not  after  copious  ingestion  of  water.  In 
cases  of  gout  in  which  uric  acid  is  deposited  in  the  gouty  nodules,  its  elimination 
is  slight.  In  the  presence  of  chronic  splenic  tumor,  anemia,  and  chlorosis,  it  is 
diminished,  particularly  if  no  respiratory  disorder  is  at  the  same  time  present; 
and  likewise  in  cases  of  epilepsy  in  advance  of  an  attack. 

The  Urates. — With  various  bases  uric  acid  forms  principally  acid 
urates,  which  are  soluble  with  difficulty  in  cold  water  and  readily  in 
hot  water.  Neutral  urates  are  transformed  by  carbon  dioxid  into  acid 
salts.  Hydrochloric  and  acetic  acids  dissolve  the  combinations  and 
the  uric  acid  separates  in  the  form  of  crystals. 

Acid  sodium  urate,  sodium  biurate,  has  a  neutral  reaction,  and  ap- 
pears as  a  uratic  sediment  (lateritious  sediment)  generally  of  a  brick- 
red  color  from  uroerythrin  (according  to  Hoppe-Seyler  from  urobilin) — 
less  commonly  it  is  between  light  gray  and  whitish  in  color — in  the 
presence  of  catarrhal  digestive  disorders  and  of  rheumatic  and  febrile 
affections.  Microscopically  it  appears  as  amorphous  granules  (Fig. 
153,  b).  The  sediment  is  dissolved  by  heating  the  urine.  Not  rarely 
the  sediment  contains  also  the  potassium-salt,  which  is  entirely  similar 

Acid  ammonium  urate  is  soluble  with  difficulty  in  water,  is  always 
present,  as  a  sediment,  in  ammoniacal  urine,  appears  in  reflected  light 
in  the  form  of  yellowish  spheres  of  thorn-apple  or  morning-star  shape- 
in  transmitted  light  of  a  darker  color — and  is  frequently  accompanied 
by  triple  phosphates  (Fig.  154,  a). 

Acid  sodium  urate  and  acid  ammonium  urate  are  recognized  by 
the  separation  of  free  uric-acid  crystals  in  microscopic  preparations,  after 
addition  of  a  drop  of  hydrochloric  acid. 

Acid  calcium  urate,  occasionally  present  in  urinary  calculi,  is  a  white 
amorphous  powder  soluble   with   difficulty  in   water.     Fused  upon   a 
platinum    plate,    it    leaves    a   residue    of   calcium    carbonate.     Rarely 
magnesium  urate  occurs  in  urinary  calculi. 
31 


482         QUALITATIVE  AND  QUANTITATIVE   ESTIMATION   OF  URIC  ACID. 


QUALITATIVE  AND  QUANTITATIVE  ESTIMATION  OF  URIC  ACID. 

Qualitative  Estimation. — i.  The  microscopic  demonstration  of  uric  acid  and  the 
urates  is  based  upon  the  characteristics  that  have  been  described.  Uric  acid  is 
precipitated  from  urine  by  addition  of  acetic  or  hydrochloric  acid. 

2.  The  murexid  test.     Uric  acid  or  urates  are  heated  in  a  shallow  dish  with 
nitric  acid  at  a  low  temperature.     Decomposition  takes  place,  with  the  develop- 
ment of  a. yellow  color.     Nitrogen  and  carbon  dioxid  escape,   while  urea  and 
alloxan     (C4H2N2O4)    remain    behind.      Evaporation    is    now    cautiously    carried 
further,  and  the  resulting  yellowish-red  stain  is  permitted  to  cool.     The  addition 
of  a  drop  of  dilute  ammonia  produces  a  purple-red  color  (murexid  =  ammonium 
purpurate:    alloxantinamid) .     This  red  color  becomes  blue  on  further  addition  of 
potassium  hydrate.     If,  at  the  outset,  potassium  or  sodium  hydrate  is  added  to 
the  stain,  instead  of  ammonia,  a  violet  color  results. 

3.  If  upon  a  strip  of  filter-paper  saturated  with  a  solution  of  silver  nitrate 
is  dropped  uric  acid  or  urate  dissolved  in  an  alkaline   carbonate,   a  black  stain 
at  once  appears  through  reduction  of  the  silver. 

Quantitative  Estimation. — i.  The  method  of  Hopkins,  by  means  of  which  the 
uric  acid  is  precipitated  as  ammonium  urate.  If  100  cu.  cm.  of  urine  are  thor- 
oughly saturated  with  ammonium  chlorid  (about  30  grams  are  necessary),  all  of 
the  uric  acid  is  precipitated  as  ammonium  urate,  particularly  if  some  ammonia 
is  added  besides.  After  the  lapse  of  two  hours  the  precipitate  is  collected  upon  a 
filter,  where  it  is  washed  several  times  with  a  saturated  solution  of  ammonium 
chlorid.  The  precipitate  is  now  rinsed  from  the  filter  with  boiling  water,  and 
exposed  to  the  action  of  hydrochloric  acid  with  heat.  The  uric  acid  that  sepa- 
rates is  collected  upon  a  dry  filter,  and  is  again  dried  and  weighed. 

2.  The  method  of  Salkowski,  modified  by  E.  Ludwig,  is  based  upon  the  pre- 
cipitation of  the  uric  acid  by  silver  nitrate  and  its  subsequent  separation  and 
weighing.  The  following  solutions  are  necessary :  A .  Twenty-six  grams  of  silver 
nitrate  dissolved  in  water,  and  admixed  with  ammonia,  until  complete  solution 
takes  place;  then  addition  of  water  to  make  i  liter.  B.  Magnesia-mixture:  100 
grams  of  crystallized  magnesium  chlorid  dissolved  in  water;  ammonia  added  until 
a  strong  odor  is  developed;  then  ammonium  chlorid  to  the  solution;  and, 
finally,  addition  of  water  to  make  i  liter.  C.  Ten  grams  of  pure  sodium  hydrate 
dissolved  in  i  liter  of  water.  One-half  of  this  is  completely  saturated  with  hydro- 
gen sulphid,  and  then  both  halves  are  mixed. 

Mode  of  Procedure. — One  hundred  cubic  centimeters  of  filtered  non-albumin- 
ous urine  (if  necessary  freed  of  albumin)  are  placed  in  a  beaker.  In  another  glass, 
10  cu.  cm.  of  the  solution  A  are  mixed  with  10  cu.  cm.  of  the  solution  B,  and 
ammonia  is  added,  if  necessary  also  ammonium  chlorid  to  the  point  of  complete 
saturation.  This  solution  is  poured  with  stirring  into  the  urine,  and  the  mixture 
is  permitted  to  stand  for  one  hour.  The  precipitate  is  then  collected  upon  a 
filter,  is  washed  with  water  containing  ammonia,  and  is  brought,  by  means  of  a 
pipette  and  a  glass  rod,  without  injury  to  the  filter,  back  again  into  the  beaker. 
Now  10  cu.  cm.  of  the  solution  C,  diluted  with  10  cu.  cm.  of  water,  are  heated  to 
the  boiling-point,  and  this  solution  is  passed  through  the  used  filter  into  the  beaker 
which  contains  the  silver-precipitate;  the  filter  is  then  washed  with  hot  water, 
and  the  beaker  is  heated  for  some  time  over  the  water-bath  with  stirring.  On 
cooling,  the  solution  is  filtered  into  a  dish;  the  filter  is  washed  with  hot  water; 
the  filtrate  is  acidulated  with  hydrochloric  acid;  and  the  product  is  evaporated  to 
about  15  cu.  cm.,  when  15  drops  of  hydrochloric  acid  are  added,  and  the  solution 
is  permitted  to  stand  for  twenty-four  hours.  The  uric  acid  separated  out  is  col- 
lected upon  a  previously  weighed  filter,  washed  with  water,  alcohol,  ether,  and 
hydrogen  sulphid;  dried  at  a  temperature  of  100°  and  weighed.  For  every  10  cu. 
cm.  of  the  watery  filtrate,  0.00048  gram  of  uric  acid  are  to  be  added. 

KREATININ,  XANTHIN-BASES,  OXALURIC,  OXALIC,  AND  HIPPURIC 

ACIDS. 

Kreatinin  (C4H9N3O2)  is  derived  in  part  from  the  kreatin  present  in 
the  muscles  by  loss  of  water,  and  in  part  from  the  meat  in  the  food.  Its 
amount  daily  is  from  0.6  to  1.3  grams. 

The  amount  of  kreatinin  is  diminished  in  cases  of  progressive  muscular  atrophy, 
of  tetanus,  and  of  marantic,  anemic,  or  paralytic  conditions  of  the  musculature. 


KREATININ,    XANTHIN    BASES,    OXALURIC    AND    OXALIC    ACIDS.       483 

It  is  increased  particularly  by  greatly  augmented  muscular  activity,  after  the 
ingestion  of  food  rich  in  nitrogen.  It  is  wanting  in  the  urine  of  infants. 

Kreatinin  yields  an  alkaline  reaction,  is  readily  soluble  in  water  and  in  hot 
alcohol,  and  it  forms  colorless,  oblique  rhombic  columns.  It  combines  with  acids, 
but  also  with  salts.  Kreatinin-zinc  chlorid  is  prepared  for  the  detection  of  krea- 
tinin. 

Demonstration. — A  few  drops  of  a  slightly  brown,  watery  solution  of  sodium 
nitroprussid  and  then  dilute  sodium  hydrate  added  to  5  cu.  cm.  of  urine  cause 
a  Burgundy-red  color  that  soon  disappears.  Addition  of  acetic  acid  changes  the 
color  to  yellow.  Acetone  yields  a  similar  reaction,  though  in  the  case  of  this 
substance  the  red  color  becomes  still  darker,  almost  purple,  after  addition  of 
acetic  acid.  Acetone  can  first  be  driven  off  from  the  urine  by  boiling,  and  then 
the  reaction  of  kreatinin  is  certain. 

Xanthin-bases  :  Alloxuric  Bases. — Under  the  names  xanthin-bases  or  nuclein- 
bases,  or  alloxuric  bases,  are  comprised  a  group  of  bodies,  including  xanthin, 
hypoxanthin,  adenin,  guanin,  carnin,  which  are  related  genetically  to  uric  acid, 
and,  together  with  it,  are  also  designated  alloxuric  bodies.  The  mother-substance 
of  all  alloxuric  bodies,  including  uric  acid,  is  purin  (C5N4H4),  from  which  are 
derived:  hypoxanthin,  as  oxypurin;  xanthin,  as  dioxypurin;  uric  acid,  as  trioxy- 
purin;  adenin,  as  6-aminopurin;  guanin,  as  2-amino-6-oxypurin.  By  the  en- 
trance of  one  methyl-group  into  the  xanthin-molecule,  there  result  the  isomers, 
i-methylxanthin,  3-methylxanthin,  y-methylxanthin  (heteroxanthin) .  If  two 
methyl-groups  enter,  there  are  formed  theobromin,  paraxanthin,  and  theophyllin. 
If  3  methyl-groups  enter,  caffein  is  formed. 

Salomon  and  Kruger  found  in  the  urine  hypoxanthin,  xanthin,  adenin,  hetero- 
xanthin, paraxanthin,  i-methylxanthin,  y-methylguanin;  and  of  the  foregoing, 
respectively,  in  10,000  liters  of  urine,  8.5  grams,  10.1  grams,  3.5  grams,  22.3 
grams,  15.3  grams,  31.3  grams,  3.4  grams. 

Alloxuric  bases  are  prepared  from  the  urine  as  combinations  with  silver  or 
copper,  and  these  are  decomposed  by  hydrogen  sulphid.  The  crude  bases,  treated 
with  dilute  hydrochloric  acid,  exhibit  varying  solubility.  The  vegetable  alkaloids 
of  coffee,  tea,  and  cocoa  are  the  antecedents  of  heteroxanthin.  Paraxanthin  is 
derived  from  caffein.  Studies  of  the  alloxuric  bodies,  therefore,  are  of  value  only 
after  protracted  abstinence  from  the  beverages  named. 

Xanthin,  C5H4N4O2,  is  present  in  small  amounts  only;  according  to  E.  Sal- 
kowski,  it  may,  however,  under  some  circumstances,  be  as  much  as  one-eighth 
of  the  weight  of  uric  acid.  It  is  an  amorphous,  yellowish-white  powder,  quite 
readily  soluble  in  boiling  water.  It  is  said  to  be  present  in  the  urine  in  somewhat 
greater  amount  after  courses  of  treatment  with  sulphur,  in  leukemic  patients  and 
in  conjunction  with  nephritis  in  children.  Rarely  it  forms  urinary  calculi.  It 
represents  an  intermediate  link  between  sarcin  and  uric  acid.  Guanin  and  hypo- 
xanthin can  be  converted  into  xanthin.  In  contact  with  water  and  ferments, 
xanthin  is  transformed  into  uric  acid.  Evaporated  with  nitric  acid,  it  leaves  a 
yellow  stain  that  becomes  yellowish  red  with  potassium  and  violet  red  when 
further  heated. 

Hypoxanthin,  sarcin,  C5H4N4O,  can  be  prepared  in  the  form  of  needles  or 
exfoliating  scales  from  meat,  milk,  bone-marrow,  liver,  blood  from  the  cadaver. 
It  is  present  in  normal  urine  in  smaller  amount.  Hypoxanthin  exhibits  great 
resemblance  to  xanthin,  into  which  it  can  be  transformed  by  oxidation.  Hydrogen 
in  the  nascent  state  conversely  reduces  uric  acid  to  xanthin  and  hypoxanthin. 
Evaporated  with  nitric  acid,  it  yields  a  light-yellow  stain,  which  becomes  more 
intense  on  addition  of  sodium  hydrate,  but  not  reddish  yellow.  It  is  more  readily 
soluble  in  water  than  xanthin,  and  a  means  of  differentiating  the  two  is  thus  af- 
forded. Guanin  is  wholly  insoluble  in  water. 

Paraxanthin  has  proved  toxic  in  moderate  amount  to  dogs.  Rachford  found 
it  in  the  urine  in  considerable  amount  in  cases  of  severe  migraine  with  convulsive 
conditions. 

Oxaluric  acid,  C3H4N2O4,  occurs  in  the  urine  in  but  small  amount  as  an  ammo- 
nium-salt, is  but  slightly  soluble  in  water  and  appears  as  a  loose  white  powder. 
Ammonium  oxalurate  can  be  prepared  from  uric  acid.  Perhaps  there  is  a  physio- 
logical connection  between  uric  acid  and  oxaluric  acid. 

Oxalic  acid,  C2H2O4,  occurs,  though  not  constantly,  as  calcium  oxalate,  to 
an  amount  varying  from  10  to  25  mg.  daily.  It  is  recognizable  from  its  envelop- 
shaped  clear  octahedra  (Fig.  153,  J),  which  are  insoluble  in  acetic  acid;  biscuit- 
shaped  or  hour- glass  shaped  crystals  (Fig.  159,  c)  are  less  common.  The  genetic 
relation  between  oxalic  acid  and  uric  acid  appears  demonstrated  by  the  fact  that 


OXALIC    ACID,    HIPPURIC    ACID. 


dogs  after  being  fed  with  uric  acid  excrete  much  calcium  oxalate.  It  should,  how- 
ever, be  pointed  out  that  the  oxalic  acid  may  also  result  as  an  oxidation-product 
from  derivatives  of  the  fatty-acid  series.  Oxalic  acid  is  formed  from  oxaluric  acid 
by  the  taking  up  of  water,  together  with  the  appearance  of  urea. 

Oxalic  acid  is  wanting  on  a  pure  milk-diet.  Almost  all  vegetable  articles 
of  food  contain  it.  The  ingestion  of  substances  that  contain  a  considerable  amount 
of  calcium  oxalate,  such  as  sorrel  and  tea,  increases  the  excretion.  Citric  acid, 
treated  with  ozone,  yields  carbon  dioxid  and  oxalic  acid.  The  presence  of  calcium 
oxalate  after  the  use  of  lemons  is  thus  explained.  Increased  elimination  of  oxalic 
acid  in  the  urine  is  designated  oxaluria,  and  is  considered  in  part  a  sign  of  retarded 
metabolism,  as,  for  instance,  from  deficiency  of  oxygen,  in  the  dog;  and  in  part 

as  dependent  upon  hyperacid- 
ity of  the  gastric  juice.  It  may 
become  dangerous  in  conse- 
quence of  the  formation  of  cal- 
culi. In  conjunction  with  oxa- 
luria, the  uric  acid  has  often 
been  found  increased.  The 
amount  of  oxalic  acid  is  in- 
creased in  the  urine  of  jaun- 
diced persons.  According  to 
Neubauer,  dissolved  calcium 
oxalate,  held  in  solution  by 
acid  sodium  phosphate,  also 
occurs  in  the  urine.  The  elim- 
ination of  this  substance  takes 
place  in  crystalline  form  the 
more  completely,  the  more 
nearly  the  urine  approaches  a 
neutral  reaction. 

Hippuric  acid,  C9H9NO3, 
benzoylamidoacetic  acid,  oc- 
curs in  the  urine  of  herbivora, 
and  as  the  principal  represen- 
tative of  the  nitrogenous  prod- 
ucts of  metabolism;  and  in 
human  urine  only  in  small 
amount — from  0.3  to  3.8  grams 

in  a  day.  It  is  an  odorless,  monobasic  acid,  with  a  bitter  taste,  crystallizing  in  color- 
less four-sided  prisms;  and  it  is  readily  soluble  in  alcohol,  but  only  in  600  parts  of 
water.  It  is  a  conjugate  acid  and  results  in  the  body  from  benzoic  acid  (or  from 
the  cuticular  substance  of  plants,  which  is  closely  related  to  it) ,  or  from  oil  of  bitter 
almonds,  cinnamic  acid,  quinic  acid  (in  hay),  which  are  readily  transformed  by 
reduction  (quinic  acid)  or  by  oxidation  (cinnamic  acid)  into  benzoic  acid,  with 
which  glycin  combines  with  the  giving  up  of  water. 

C7H6O2     +     C2H5NO2     =     C9H9NO3     +     H2O 

Benzoic  Acid  Glycin  Hippuric  Acid  Water. 

The  formation  of  hippuric  acid  is,  accordingly,  dependent  principally  upon 
the  food.  It  is,  therefore,  wanting  in  the  urine  of  nursing  calves,  as  well  as  after 
the  ingestion  of  such  vegetables  as  possess  no  cuticula;  as,  for  instance,  earthy 
bulbs  and  peeled  vegetables.  Similar  syntheses  of  glycin  occur  in  the  organism 
also  after  ingestion  of  many  other  substances,  as,  for  instance,  after  administration 
of  substituted  benzoic  acids  or  of  aromatic  acids.  As  the  albuminates  also  are 
capable  of  yielding  benzoic  acid  and  oil  of  bitter  almonds  through  oxidizing  agents, 
the  hippuric  acid  may  be  formed  in  the  body  from  disintegrating  albuminates. 
This  explains  the  fact  that  it  is  found  also  in  the  urine  of  fasting  persons. 

In  the  dog,  the  conjugation  of  hippuric  acid  takes  place  in  the  kidneys;  in 
frogs,  also  outside  these  organs.  Kuhne  and  Hallwachs  refer  the  formation  to 
the  liver,  Jaarsfeld  and  Stokvis  to  the  kidney,  the  liver  and  the  intestines.  The 
observation  of  Salomon  that  hippuric  acid  was  present  in  the  blood  and  in  the 
liver  of  nephrectomized  rabbits  after  injection  of  benzoic  acid  into  the  blood 
indicates  that  the  formation  does  not  take  place  exclusively  in  the  kidneys.  Fur- 
ther, the  hippuric  acid  formed  in  human  beings  may,  under  pathological  condi- 
tions, particularly  when  the  reaction  is  alkaline  and  albuminuria  is  present,  be 
again  decomposed  in  the  urine,  in  consequence  of  a  fermentative  process.  Whether 


FIG.  149. — Kreatinin-zinc  Chlorid:  a,  spherical  aggregations  with 
radiate  striation;  b,  groups  after  crystallization  out  of  water;  c, 
less  common  form  from  alcoholic  extract. 


ALLANTOIN,    COLORING-MATTERS    OF    THE    URINE. 


485 


the  hippuric  acid  formed  is  already  decomposed  in  the  blood  and  the  tissues 
of  man  is  doubtful.  In  the  kidneys  of  swine  and  of  the  dog,  fermentative  decom- 
position of  hippuric  acid  takes  place. 

After  ingestion  of  pears,  prunes,  cranberries,  unpeeled  apples,  the  amount  of 
hippuric  acid  increases  greatly.  It  is  increased  also  in  the  presence  of  jaundice, 
diseases  of  the  liver,  and  diabetes.  If  it  be  contained  in  the  urine  in  large  amounts, 
it  appears  in  the  sediment,  from  which  it  can  be  isolated  by  boiling  with  alcohol. 
Boiled  in  strong  acids  or  alkalies,  or  in  combination  with  putrid  substances  or 
the  micrococcus  ureae,  it  is  decomposed  again  into  benzoic  acid  and  glycin,  with 
the  taking  up  of  water. 

The  urine  of  the  dog  contains,  in  addition  to  uric  acid,  kynuric  acid, 
C10H14N3O6  +  H2O,  and  uroprotic  acid,  C66H116N2rtSO54  +  H2O. 

Allantoin,  C4H6N4O3,  a  constituent  of  the  amniotic  fluid  of  the  cow,  in  lesser 
degree  of  that  of  human  beings,  is 
normally  present  in  the  urine  in 
traces,  especially  after  the  eating  of 
meat;  in  larger  amount  in  the  first 
week  of  life  and  in  pregnant  women, 
as  well  as  after  administration  of 
thymus  gland  and  pancreas.  The 
amount  increases  after  the  ingestion 
of  considerable  amounts  of  tannic 
acid;  in  the  dog,  from  the  oxidation 
of  uric  acid  fed. 

Allantoin  forms  glistening,  pris- 
matic crystals.  It  crystallizes  in 
transparent  prisms  from  the  urine  of 
nursing  calves  on  evaporation  to  a 
sirupy  consistence,  and  standing  at 
rest  for  a  day.  It  is  decomposed  by 
ferments  into  urea,  ammonium  oxa- 
late  and  carbonate,  and  another  sub- 
stance whose  identity  has  not  yet 
been  established.  It  is  readily  sol- 
uble in  water,  with  difficulty  in  alco- 
hol, and  not  at  all  in  ether.  For  its 
preparation,  the  urine  is  precipitated 
by  means  of  basic  lead  acetate,  the 
lead  being  removed  from  the  nitrate 
by  means  of  hydrogen  sulphid.  The  fluid  is  then  evaporated  to  a  sirupy  consist- 
ence, and  the  crystals  separate  in  the  course  of  days.  These  are  washed  with  water 
and  recrystallized  out  of  hot  water. 

Oxyproteic  acid  is  an  oxidation-product  of  albumin  containing  nitrogen  and 
sulphur.  It  can  be  prepared  as  a  baryta-combination,  is  soluble  in  water  but 
not  in  alcohol,  and  is  precipitable  by  mercuric  nitrate  and  sulphate.  On  a 
mixed  diet,  it  constitutes  from  2  to  3  per  cent,  of  the  total  nitrogen,  thus  some- 
what more  than  the  uric  acid.  It  is  greatly  increased  in  cases  of  phosphorus-poison- 
ing, and  perhaps  also  in  conjunction  with  other  forms  of  proteid  decomposition. 


FIG.  150. — Hippuric  Acid. 


COLORING-MATTERS  OF  THE  URINE. 

Urobilin  is  present  in  considerable  amount  in  highly  colored  febrile 
urine,  often  also  in  normal  urine,  particularly  after  the  ingestion  of 
readily  digestible  food  and  after  the  termination  of  gastric  digestion; 
in  small  amount  in  the  state  of  hunger  and  during  the  process  of  gastric 
digestion.  It  is  a  derivative  of  hematin,  or  of  the  biliary  coloring- 
matter  resulting  therefrom.  It  closely  resembles  the  hydrobilirubin  of 
Maly,  from  which,  however,  it  differs  in  the  greater  amount  of  nitro- 
gen it  contains.  It  gives  the  urine  a  red  or  reddish-yellow  color,  which 
becomes  yellow  after  admixture  with  ammonia. 

Urobilin  can  be  extracted  from  some  urine  by  agitation  after  addition  of 
an  equal  volume  of  ether  or  chloroform.  The  urobilin  passes  over  into  the  latter, 


486 


COLORING-MATTERS    OF    THE    URINE. 


and  if  this  be  permitted  to  evaporate,  it  remains  as  a  residue.  It  is  soluble  in 
ammonia-water  or  in  dilute  soda-solution.  If  urobilin  be  dissolved  in  dilute 
sodium  hydrate  and  a  small  amount  of  calomel  be  added,  the  yellow  solution 
becomes  rose-red  (urorosein).  If  a  chloroform-extract  be  prepared  by  agitation 
of  urine  containing  urobilin,  and  if  iodin  be  added,  and  be  combined  by  agitation 
with  dilute  potassium-solution,  the  solution  acquires  a  color  varying  from  yellow 
to  brownish  yellow,  with  a  beautiful  fluorescence  in  green.  This  reaction  can  also 
be  applied  directly  to  any  urine  containing  urobilin.  At  times  the  urobilin,  on 
standing,  undergoes  a  modification,  and  then  the  usual  reactions  fail. 

If  sodium  or  potassium  carbonate  be  added  to  the  urine,  the  characteristic  ab- 
sorption-band at  F  approaches  b  and  becomes  much  darker  and  more  sharply  de- 
fined. According  to  Hoppe-Seyler  and  Saillet,  urobilin  develops  in  the  urine  only 
after  evacuation  by  the  taking  up  of  oxygen  on  the  part  of  another  body  forming 
urobilin  (Jaffe's  chromogen).  If  acetic  ether  be  added  to  recently  discharged 
urine  acidulated  with  acetic  acid  and  agitation  be  practised,  the  chromogen  passes 
over  into  the  ether.  If  the  acetic  ether  be  agitated  in  sunlight  with  water,  uro- 
bilin is  formed;  and  this  can  be  again  shaken  out  by  means  of  chloroform.  If 
zinc  chlorid  be  added  to  urine  containing  urobilin  and  rendered  alkaline  by  addition 
of  ammonia,  the  urine  exhibits  marked  fluorescence,  with  a  distinct  green  luster, 
particularly  in  reflected  rays  of  sunlight.  The  isolated  urobilin  is  fluorescent  also 
without  addition  of  zinc  chlorid.  Phosphotungstic  acid  precipitates  all  urobilin 
as  a  rose-colored  deposit,  which  is  soluble  in  water,  and,  after  addition  of  hydro- 


Red.     Orange.  Yellow. 

_-~~ 

B 
40 


Green. 


70         SO         9O        10O        110 


FIG.  151. — Spectrum  of  Urobilin  in  Acid  Urine. 

Red.     Orange.  Yellow.  Green.  Cyan-blue. 

'    -^ 

110 


A  a  JB   C 

40        50 


D 
60 


El)  F 

70         80         00        100 


FIG.  152. — Spectrum  of  Urobilin  in  Alkaline  Urine. 

chloric  acid,  also  in  chloroform.  By  the  employment  of  reducing  agents  (sodium- 
amalgam)  a  colorless  reduction-product  is  formed  from  urobilin;  but  this,  on 
standing  in  the  air,  is  retransformed  into  urobilin,  with  the  taking  up  of  oxygen. 
The  colorless  body  is  identical  with  the  chromogen  that  Jaffe  found  in  urine. 
In  many  cases  of  jaundice,  in  which,  at  times,  Gmelin's  test  for  biliary  pigment 
fails  to  develop,  urobilin  is  present,  particularly  when  incomplete  biliary  stasis 
exists.  This  urobilin-icterus  occurs  especially  after  the  absorption  of  considerable 
extravasations  of  blood.  According  to  Cazeneuve,  the  urobilin  is  increased  in  all 
diseases  that  are  attended  with  increased  destruction  of  red  blood-corpuscles. 

Urochrome  is  considered  by  Thudichum  as  the  peculiar  yellow  coloring-matter 
of  the  urine.  It  can  be  isolated  in  yellow  crusts  that  are  soluble  in  water,  as 
well  as  in  dilute  acids  and  alkalies.  The  watery  solution  oxidizes  in  the  air,  with 
the  development  of  a  red  color  through  the  formation  of  uroerythrin.  Treated 
with  acids,  further  decomposition-products  appear;  among  them,  uromelanin. 
The  uroerythrin  often  gives  the  urates  a  red  color,  the  urochrome  a  yellow  color. 
The  latter,  however,  is  by  many  not  considered  a  well-characterized  chemical 
body.  Human  urine  saturated  with  ammonium  sulphate  yields,  on  agitation  with 
90  per  cent,  phenol,  all  of  its  coloring-matter  to  the  latter.  If  this  solution  of 
phenol  be  mixed  with  ether  and  water,  the  water  is  stained  yellow  (urochrome), 
the  phenol-ether  mixture  red  (urobilin  and  hematoporphyrin) . 


INDICAN.  487 

In  the  presence  of  melanotic  neoplasms,  black  urine  has  from  time  to  time 
been  observed,  due  to  melanin  or  a  pigment  containing  iron. 

A  brown  pigment  containing  iron  is  carried  down  by  the  uric  acid  precipitated 
on  addition  of  hydrochloric  acid.  By  repeated  addition  of  sodium  urate  to  urine 
and  precipitation  of  the  uric  acid  by  hydrochloric  acid,  this  pigment  can  be 
obtained  in  considerable  amount. 


SUBSTANCES  FORMING  INDIGO,  PHENOL,  KRESOL,    PYROCATE- 
CHIN,  AND  SKATOL.       OTHER  SUBSTANCES. 

Indican,  or  the  indigo-forming  substance,  is  derived  from  indol, 
C8H7N,  the  mother-substance  of  indigo,  which  is  formed  in  the  intestine 
as  a  result  of  the  pancreatic  digestion  of  proteids,  and  as  a  putrefactive 
product.  The  indol,  conjugated  with  the  sulphuric-acid  residue,  SO3H, 
and  combined  with  potassium,  represents  the  indican,  or  indigogen  of 
the  urine  (C8H6NSO4K,  potassium  indoxylsulphate).  It  forms  white 
glistening  tables  and  plates,  readily  soluble  in  water,  slightly  in  alcohol. 
By  oxidation  it  forms  indigo-blue : 

2  indican  -f-  O2  =  C16H10N2O2  (indigo-blue)  -j-  sHKSO4  (acid  potassium  sulphate). 

Jaffe  found  between  4.5  and  19.5  mg.  of  indigo  in  1500  cu.  cm.  of  normal 
human  urine.  Indigo  is  more  abundant  in  the  urine  of  inhabitants  of  the  tropics, 
less  abundant  on  a  milk-diet,  and  it  is  wanting  in  the  new-born.  The  urine  of 
horses  contains  23  times  as  much  as  human  urine.  Subcutaneous  injections  of 
indol  increase  the  amount  of  indican  in  the  urine.  E.  Ludwig  obtained  indican 
by  heating  hematin  or  bilirubin  with  potassium  hydrate  and  powdered  tin.  It 
has  been  found  also  in  the  sweat. 

Demonstration. — One-half  of  a  test-tubeful  of  urine  is  mixed  with  an  equal 
amount  of  hydrochloric  acid,  and  2  drops  of  a  freshly  prepared  solution  of  chlorin- 
ated lime  are  added.  The  mixture  becomes  at  first  clear,  then  grayish  blue. 
Now  a  few  drops  of  chloroform  are  added,  and  the  mixture  is  persistently  agitated, 
the  pigment  being  dissolved  by  the  chloroform.  If  the  mixture  is  permitted 
to  stand,  the  blue  chloroform-layer  is  deposited  at  the  bottom.  For  quantitative 
estimation,  the  indican  is  transformed  into  indigo  and  further  into  sulphoindigotic 
acid,  and  this  is  titrated  with  a  solution  of  potassium  permanganate.  Certain 
bacteria  may  produce  indigo-blue  in  the  evacuated  urine,  but  also  in  the  urinary 
passages;  therefore,  a  lustrous  bluish-red  coating  of  microscopic  rhombic  crys- 
tals of  indigo-blue  upon  the  surface  of  putrid  urine,  or  a  precipitate  thereof,  is 
occasionally  observed  (Heller's  uroglaucin) . 

Pathological. — Indican  is  increased  in  the  urine  when  the  formation  of  indol 
is  increased  in  the  intestines  in  consequence  of  active  putrefactive  fermentation; 
as,  for  instance,  in  cases  of  typhoid  fever,  lead-colic,  trichinosis,  gastro-intestinal 
catarrh,  hemorrhage  from  the  stomach  or  bowel,  diseases  of  the  small  intestine, 
cholera  nostras,  carcinoma  of  the  liver  and  the  stomach,  strangulated  hernia, 
peritonitis.  As  indican  is  developed  as  a  result  of  the  decomposition  of  pus,  an 
increased  amount  in  the  urine  may  indicate  the  presence  of  suppuration,  when 
the  intestinal  conditions  are  normal. 

Urine  boiled  with  hydrochloric  acid  yields  to  the  ethereal  extract,  together  with 
indigo-blue,  a  garnet-red  pigment,  crystallizing  in  rhombic  plates,  namely  indigo- 
red,  urorubin,  urorosein,  which  is  developed  by  oxidation  from  an  unknown 
chromogen.  Its  amount  depends  upon  the  same  conditions  as  does  that  of 
indican.  The  urine  thus  extracted  yields  a  brownish-black  pigment  to  amylic 
alcohol,  namely,  uromelanin.  All  urinary  pigments  that  are  produced  through  the 
activity  of  acids  are  contaminated  by  dark-colored,  nitrogenous  humin-sub- 
stances,  which  are  formed,  in  part,  from  the  carbohydrates  of  the  urine. 

Reaction  for*  Indigo-red. — One- quarter  of  a  test-tubeful  of  urine  is  boiled  con- 
tinuously, with  addition  of  nitric  acid,  drop  by  drop,  until  a  red  color  is  produced; 
it  is  then  cooled  and  rendered  alkaline  with  ammonia.  If  now  it  be  gently 
agitated  with  2  cu.  cm.  of  ether,  indigo-red  dissolved  in  the  ether  passes  over. 
The  red  reaction  takes  place  in  the  presence  of  insufficiency  of  the  intestine  and 
its  glands,  in  conjunction  with  severe  diarrhea  and  most  profound  nutritive 
disorders. 


488          PHENOL,  KRESOL,  PYROCATECHIN,  AND  SKATOL. 

Phenol,  C6H6O,  carbolic  acid,  occurs,  according  to  Baumann,  like- 
wise united  with  sulphuric  acid,  as  phenol-sulphuric  acid,  C6H5OSO3H, 
which  is  found  in  the  urine  in  combination  with  potassium.  It  is 
present  in  large  amount  in  horses'  urine. 

Phenol  results  from  the  decomposition  of  albuminates  through  pancreatic  di- 
gestion, and  especially  through  putrefactive  processes.  The  mother-substance  is 
tyrosin.  -  The  formation  of  phenol-sulphuric  acid  is,  therefore,  entirely  analogous 
to  the  formation  of  indican.  Phenol,  as  well  as  kresol,  is  increased  in  the  urine  in 
the  presence  of  infectious  and  suppurative  diseases,  as  well  as  of  diabetes,  If 
phenol  is  employed  internally  or  externally,  the  amount  of  phenol-sulphuric  acid 
in  the  urine  increases  greatly.  Therefore,  sulphuric  acid  must  unite  with  it. 
For  this  reason,  alkaline  sulphate  is  decomposed  in  the  body,  so  that  it  may  be 
entirely  wanting  in  the  urine.  Living  muscular  structure  or  liver,  digested  for 
seven  hours  in  a  current  of  air  with  blood,  with  addition  of  phenol  and  sodium 
sulphate,  forms  phenol-sulphuric  acid.  Likewise,  under  these  circumstances, 
pyrocatechin  forms  ether-sulphuric  acid. 

The  dark  discoloration  of  the  urine  often  observed  in  human  beings  after 
the  internal  or  external  employment  of  phenol  depends  upon  oxidation  of  the 
phenol  into  hydroquinone  (orthodioxybenzol,  C6H6O2),  which  appears  in  the  urine 
in  large  part  as  ether-sulphuric  acid. 

Parakresol  (hydroxyltoluol,  C7H8O)  is  present  in  larger  amount 
than  phenol,  together  with  the  isomers,  orthokresol  and  metakresol, 
the  latter  in  traces;  also  these,  combined  with  sulphuric  acid  as  kresol- 
sulphuric  acids. 

For  the  demonstration  of  phenol,  and  also  of  kresol,  150  cu.  cm.  of  urine 
are  distilled  with  dilute  sulphuric  acid.  The  distillate  yields,  with  bromin-water, 
a  precipitate  of  tribrom-phenol,  which  soon  crystallizes;  as  well  as  a  red  color  with 
Millon's  reagent.  The  hydroxylbenzols — pyrocatechin  and  hydroquinone — are 
given  off  after  protracted  heating  of  urine  to  which  hydrochloric  acid  is  added. 
Resorcin,  which  is  isomeric  with  hydroquinone,  leaves  the  body  in  the  urine  as 
ether-sulphuric  acid  when  ingested.  Toluol  and  naphthalin  react  in  a  similar 
manner.  When  benzol  is  administered,  it  is  first  oxidized  into  phenol. 

Pyrocatechin,  C6H6O2,  metadihydroxylbenzol,  is  formed,  together 
with  hydroquinone,  from  phenol;  and  it  is  likewise  isomeric  with  hy- 
droquinone. In  an  analogous  manner  to  indol  and  phenol,  it  is  united 
with  sulphuric  acid.  Infinitesimal  amounts  occur  normally.  It  has 
been  observed  in  larger  amount  by  Ebstein  and  Miiller  in  the  urine  of  a 
dyspeptic  child.  It  can  be  recognized  by  the  dark  discoloration  of  the 
urine  that  results  from  putrefaction. 

Possibly  pyrocatechin  is  formed  in  the  body  from  decomposed  carbohydrates, 
from  which  Hoppe-Seyler  observed  it  to  develop  by  heating  with  water  under 
high  pressure,  as  well  as  by  treatment  with  alkalies. 

Skatol,  which  appears  in  crystalline  form  in  the  presence  of  in- 
testinal putrefaction,  likewise  appears  in  the  urine  as  an  ethereal  sul- 
phate. Brieger  found  potassium  skatoxyl-sulphate  after  feeding  dogs 
with  skatol. 

Demonstration.— -The  skatol-combination  can  be  recognized  by  addition  of 
dilute  nitric  acid,  in  consequence  of  which  a  violet  color  results;  or  of  fuming 
nitric  acid,  in  consequence  of  which  red  flakes  are  precipitated.  Its  amount  varies 
with  the  same  causes  as  does  that  of  indican. 

Also  hydroparacumaric  acid  and  paraoxyphenylacetic  acid,  which  belong  to  the 
aromatic  oxyacids,  are  encountered  in  the  urine  in  increased  amount,  together 
with  a  large  amount  of  indican,  in  the  presence  of  urticaria,  acne,  and  senile  pruri- 
tus, as  signs  of  increased  intestinal  putrefaction.  The  first  is  a  putrefactive 
product  of  meat,  while  the  second  has  been  obtained  by  E.  and  G.  Salkowski 
from  putrid  albumin. 

Demonstration. — If  the  urine,   to  which  a  mineral  acid  has  been  added,   is 


SKATOL,    OTHER    ORGANIC    CONSTITUENTS.  489 

agitated  with  ether,  the  latter  then  evaporated,  and  the  residue  dissolved  in 
water,  it  will  yield  a  red  color  with  Millon's  reagent.  This  is  the  reaction  of  the 
aromatic  oxyacids. 

Baumann  has  named  the  following  list  of  substances  that  result  from  tyrosin 
by  decomposition  and  oxidation,  of  which  most  members  develop  both  as  a 
result  of  the  putrefaction  of  proteids  in  the  intestine,  and  pass  thence  into  the 
urine. 

Tyrosin,  CftHuNO3-fH2  =  C9H10O3  (hydroparacumaric  acid)  +NH3. 

C9H10O3  =  C8H10O  (parethylphenol,  not  yet  demonstrated)  +CO  . 

C8HinO+O3  =  C8H8O3  (paraoxyphenylacetic  acid)  +H2O. 

C8H803  =  C7'H80  (parakresol)+CO2. 

C7H8O+O3  =  C7H6O3  (paraoxybenzoic  acid,  not  yet  demonstrated)  +H2O. 

C7H6O3  =  C6H6O  (phenol) +CO2. 

Potassium  sulphocyanate  or  sodium  sulphocyanate  is  present  in  the 
urine  in  the  proportion  of  from  0.02  to  0.08  gram  to  the  liter,  in  larger 
amount  in  the  urine  of  smokers.  It  is  derived  from  the  saliva  and  can 
be  recognized  by  the  ferric-chlorid  test  after  acidulation  with  hydro- 
chloric acid. 

Succinic  acid,  C4H6P4,  occurs  particularly  after  the  ingestion  of 
meat  and  fat,  and  in  infinitesimal  amounts  after  the  taking  of  vegetable 
food.  It  occurs  in  considerable  amount  as  a  product  of  the  decom- 
position of  asparagin,  after  the  eating  of  asparagus.  Also,  as  a  product 
of  alcoholic  fermentation,  it  finds  its  way  into  the  urine  through  in- 
gestion of  spirit;  or,  administered  internally,  it  passes  undecomposed 
into  the  urine. 

Lactic  acid,  C3H6O3,  is  a  constant  constituent  of  the  urine.  Fermen- 
tation lactic  acid  has  been  found  principally  in  cases  of  diabetes,  sarco- 
lactic  acid  in  cases  of  phosphorus-poisoning  and  of  trichinosis. 

Traces  of  volatile  fatty  acids  are  inconstant.  They  occur  par- 
ticularly in  connection  with  destructive  diseases  of  the  liver. 

Ferments. — Diastatic,  peptic,  and  rennet-like  ferments  have  been  found  by 
Griitzner  principally  in  urine  of  high  specific  gravity.  Fat-splitting  ferment  is 
not  present  normally.  Trypsin  is  much  attenuated. 

Traces  of  grape-sugar  occur  up  to  between  o.oi  and  0.05  per  cent. 
After  the  ingestion  of  milk-sugar,  cane-sugar,  or  grape-sugar  (50  grams 
and  more),  these  varieties  of  sugar  appear  unchanged  in  the  urine  in 
small  amounts.  Baisch  found  some  isomaltose. 

Reducing  substances  (yielding  Trommer's  reaction)  are  always  present  in  the 
urine.  Normal  human  urine  effects  reduction  almost  like  a  0.3  or  0.4  per  cent. 
solution  of  grape-sugar,  in  larger  measure  in  the  presence  of  fever.  Almost  five- 
sixths  of  these  substances  are  probably  combinations  of  glycuronic  acid,  while 
one-sixth  "consists  of  uric  acid  and  kreatinin.  There  is  present  a  dextrin-like 
carbohydrate  and  one  soluble  in  alcohol,  as  well  as  some  animal  gum.  Bechamp's 
nephrozymose  consists  principally  of  gum.  This  substance  is  prepared  by  pre- 
cipitating the  urine  with  thrice  its  amount  of  90  per  cent,  alcohol.  It  is  not  a 
simple  body,  and  it  transforms  starch  into  sugar  at  a  temperature  of  between  60° 
and  70°  C. 

Acetone,  C3H6O,  appears  after  an  exclusive  diet  of  meat  and  fat,  according 
to  v.  Noorden  only  on  digestion  of  the  flesh  of  the  body.  As  soon  as  carbohydrates 
are  taken,  it  is  no  longer  observed.  Also  the  digestion  of  the  muscle  and  fat 
of  the  body  occasions  its  appearance.  Vicarelli  found  it  in  pregnant  women  with 
dead  fetuses. 

Demonstration. — One-half  liter  of  urine  is  acidulated  with  hydrochloric  acid 
and  is  distilled.  On  addition  of  tincture  of  iodin  and  ammonia,  iodoform  appears 
in  the  distillate  as  a  cloudiness  and  is  recognizable  by  its  peculiar  odor. 

Optically  inactive  urine  that  becomes  discolored  brown  or  black  on  exposure 
to  the  air  after  addition  of  alkali,  with  the  taking  up  of  oxygen  and  a  powerful 
reducing  activity,  contains  alkapton,  homogentisic  acid,  which  occurs  but  rarely, 


4QO  THE    INORGANIC    CONSTITUENTS    OF    THE    URINE. 

and    is  produced  from  tyrosin   (by  the   action  of    microorganisms?)   within  the 
body  and  then  passes  over  into  the  urine. 


THE  INORGANIC  CONSTITUENTS  OF  THE  URINE. 

The  inorganic  constituents  of  the  urine  either  are  taken  into  the 
body  as  such  with  the  food  and  pass  unchanged  into  the  urine,  or  they 
are  formed  independently,  inasmuch  as  the  sulphur  and  the  phosphorus 
of  the  food  are  consumed  and  unite  with  bases  to  form  salts.  From 
9  to  25  grams  of  salts  are  eliminated  daily. 

During  sleep,  the  chlorin,  potassium,  and  sodium  in  the  urine  are  greatly 
reduced,  sulphuric  acid  and  the  solid  constituents  of  the  urine  generally  are  some- 
what reduced,  while  the  acidity  is  considerably  increased. 

Sodium  Morid,  table-salt,  12  grams  (from  10  to  13  grams)  daily, 
is  increased  after  meals  as  the  result  of  movement,  of  the  copious  drink- 
ing of  water,  of  increase  in  the  amount  of  urine  generally,  of  generous 
administration  of  sodium  chlorid,  but  also  of  potassium-salts.  It  is 
diminished  principally  under  the  reverse  conditions. 

Under  abnormal  conditions  the  elimination  of  sodium  chlorid  is  diminished 
in  large  measure  in  association  with  pneumonia  and  other  affections  attended 
with  inflammatory  exudation;  further,  in  conjunction  with  most  febrile  disorders, 
except  malaria,  as  well  as  with  persistent  diarrhea  and  sweating;  constantly  also 
when  the  urine  contains  albumin  and  when  dropsy  is  present.  Destruction  of  red 
blood-corpuscles  increases  the  chlorids  in  the  urine,  while,  on  the  contrary,  the 
amount  of  chlorin  in  the  urine  (as  well  as  in  the  gastric  juice)  is  diminished  in 
the  presence  of  anemia,  although  the  blood  contains  more  chlorin  than  normal. 

Qualitative  Estimation. — Urine  is  acidulated  in  a  test-tube  with  nitric  acid, 
and  a  solution  of  silver  nitrate  is  added,  with  the  result  that  a  white,  cheesy  deposit 
of  silver  chlorid  takes  place.  The  albumin  must  first  be  removed  from  albuminous 
urine  by  boiling.  On  microscopic  examination,  attention  should  be  given  in  the 
evaporated  preparation  to  the  terrace-like  arrangement  of  the  cubes  of  sodium 
chlorid;  and,  at  the  same  time,  also  to  the  rhombic  prisms  of  sodium-chlorid  urea. 

Quantitative  Estimation,  according  to  the  method  of  Habel  and  Fernholz: 
15  cu.  cm.  of  the  mixture  of  urine  and  baryta  are  acidulated,  after  neutralization, 
with  10  drops  of  dilute  nitric  acid  having  a  specific  gravity  of  1 1 19,  and  a  solution 
of  silver  nitrate,  of  which  i  cu.  cm.  fixes  10  mg.  of  sodium  chlorid  or  6.065  of 
chlorin,  is  added  so  long  as  a  precipitate  of  silver  chlorid  is  observed  to  take 
place.  Then  a  small  portion  is  filtered  into  a  test-tube,  and  a  test  is  made  to 
determine  whether  turbidity  results  from  addition  of  one  or  two  drops  of  the 
silver-solution.  If  this  be  marked,  the  whole  amount  is  poured  back  into  the 
beaker,  p.i  cu.  cm.  of  the  silver-solution  is  added,  and  the  test  is  repeated  until 
the  turbidity  produced  by  two  drops  of  the  silver-solution  is  no  longer  particularly 
distinct.  Now  an  equal  amount  is  filtered  into  a  second  test-tube,  and  two  drops 
of  a  one  per  cent,  solution  of  sodium  chlorid  are  added.  If  the  turbidity  is  equally 
marked  with  that  produced  by  two  drops  of  the  silver-solution,  the  correct  point 
has  been  reached.  Next,  exactly  so  many  cubic  centimeters  of  the  silver-solution 
are  added  to  a  new  specimen  acidulated  with  10  drops  of  the  nitric  acid;  and  the 
intensity  of  the  turbidity  in  the  filtrate  induced  by  two  drops  of  silver-solution 
is  compared  with  that  induced  by  two  drops  of  the  one  per  cent,  solution  of  sodium 
chlorid.  If  the  turbidity  caused  by  the  sodium  chlorid  is  the  greater,  0.05  cu.  cm. 
less  of  the  silver-solution  is  added,  and  the  turbidity  of  the  filtrates  is  compared. 
Then  so  much  more  or  less  of  the  silver-solution  is  aclded  as  represents  the  differ- 
ence between  the  two  points  last  found;  and  this  is  continued  until  an  equal 
amount  of  silver  nitrate  and  sodium  chlorid  produce  equal  turbidity  in  the  filtrate. 

Titration  of  the  chlorids  according  to  the  Freund-Topfer  modification  of 
Mohr's  method:  Ten  cubic  centimeters  of  urine  are  diluted  to  25  cu.  cm.,  and  2.5 
cu.  cm.  of  a  mixture  of  3  parts  of  acetic  acid,  10  parts  of  sodium  acetate,  and  100 
parts  of  water  are  added.  Next,  a  few  drops  of  a  10  per  cent,  solution  of  potas- 
sium bichromate  are  added,  and  titration  is  practised  with  the  silver-solution 
(14.63  grams  in  500  cu.  cm.  of  water),  until  the  well-stirred  yellow  fluid  retains 


THE    INORGANIC    CONSTITUENTS    OF    THE    URINE.  491 

a  reddish  tint.     Every  cubic  centimeter  of  silver-solution  used  corresponds  to  10 
mg.  of  sodium  chlorid,  or  0.00607  gram  of  chlorin. 

Phosphoric  acid,  about  2  grams  daily,  occurs  in  the  form  of  mono- 
potassium  and  monosodium  phosphate,  and  acid  potassium  and  mag- 
nesium phosphate.  It  is  present  in  larger  amount  after  the  ingestion  of 
animal  than  of  vegetable  food.  Its  amount  increases  from  the  mid- 
day meal  till  evening,  and  it  then  declines  in  the  night  until  the  next 
morning.  It  is  increased  by  muscular  activity.  It  is  derived  in  largest 
part  from  the  alkaline  and  earthy  phosphates  of  the  food;  and  it  is  in 
part  a  metabolic  product  of  lecithin  and  nuclein. 

In  the  presence  of  fever,  the  increased  elimination  of  potassium  phosphate  is 
indicative  of  consumption  of  blood  and  muscle.  When  abnormal  destruction  of 
blood  takes  place  suddenly  in  the  body,  the  phosphoric  acid,  together  with  the 
urea,  is  greatly  increased.  In  the  state  of  hunger,  the  phosphoric  acid  is  derived 
principally  from  the  breaking  down  of  the  bones,  which  contain  thirty  times  as 
much  as  the  muscles.  Also  in  the  presence  of  cerebral  meningitis,  softening  of 
the  bones,  diabetes  and  oxaluria,  the  elimination  of  phosphorus  is  said  to  be  in- 
creased; likewise,  after  administration  of  lactic  acid,  morphin,  chloral,  or 
chloroform.  It  is  diminished  during  pregnancy,  on  account  of  the  formation  of 
bone  in  the  fetus.  It  is  diminished  also  in  consequence  of  the  ingestion  of 
ether  and  alcohol,  and  likewise  of  inflammation  of  the  kidney. 

Qualitative  Estimation.— Potassium  hydrate  is  added  to  urine  in  a  test-tube, 
and  heat  is  applied.  The  earthy  phosphates  are  thus  precipitated  in  a  cloud, 
while  the  alkaline  phosphates  remain  in  solution.  For  qualitative  estimation, 
there  are  necessary  a  titrated  solution  of  uranic  acetate,  of  which  i  cu.  cm.  unites 
with  exactly  0.005  gram  of  phosphoric  acid.  To  50  cu.  cm.  of  urine  are  added 
5  cu.  cm.  of  a  solution  of  sodium  acetate  containing  100  grams  of  the  latter  salt 
and  100  cu.  cm.  of  strong  acetic  acid  diluted  to  i  liter  with  water;  and  the  mixture 
is  heated.  The  titrating  solution  is  permitted  to  flow  with  stirring  so  long  as 
precipitation  is  apparent.  As  soon  as  free  uranium  oxid  is  present  in  the  fluid, 
one  drop  of  the  mixture,  to  which  a  solution  of  potassium  ferrocyanid  is  added 
upon  a  porcelain  plate,  yields  a  brownish-red  reaction  of  uranium  ferrocyanid. 

In  addition  to  phosphoric  acid,  phosphorus  occurs  in  the  urine  in  an  incom- 
pletely oxidized  form,  namely  as  glycerin-phosphoric  'acid,  about  0.05  gram 
daily,  in  larger  amount  in  the  presence  of  nervous  diseases  and  after  chloroform- 
narcosis. 

Sulphuric  acid  is  united  in  part  with  alkaline  metals,  in  part  with 
indol,  phenol,  skatol,  and  pyrocatechin,  in  the  form  of  aromatic  ethe- 
real sulphates,  both  in  the  proportion  of  i  to  0.1045  on  the  average. 
All  factors  that  favor  the  formation  of  indol,  phenol,  skatol,  or  pyro- 
catechin increase  the  conjugate  ethereal  sulphates.  The  total  amount 
of  sulphuric  acid  eliminated  is  from  2.5  to  3.5  grams  daily.  It  is  in- 
creased after  the  ingestion  of  sulphur.  The  sulphuric  acid  is  derived 
principally  from  the  decomposition  of  albuminates.  It  is  increased 
by  muscular  activity;  and,  therefore,  its  amount  is  always  parallel  to 
that  of  the  urea  eliminated.  The  amount  of  alkaline  sulphates  ad- 
ministered with  the  food  is,  as  a  rule,  exceedingly  small. 

Increased  excretion  of  sulphuric  acid  in  febrile  urine  indicates  increased 
tissue-metabolism  in  the  body.  In  the  presence  of  inflammation  of  the  kidney 
a  diminution  has  been  observed,  in  cases  of  eczema  a  marked  increase  in  the 
amount  of  sulphuric  acid  in  the  urine.  In  rabbits,  but  not  in  carnivora  and 
human  beings,  administration  of  taurin,  which  contains  sulphur,  causes  the  pres- 
ence of  an  increased  amount  of  sulphuric  acid  in  the  urine.  According  to  Ziilzer, 
the  relative  amount  of  sulphuric  acid  in  the  urine  is  small  when  the  secretion 
of  bile  in  the  intestine  is  large. 

The  qualitative  demonstration  is  made  by  addition  of  barium  chlorid  to  the 
urine,  which  yields  a  fine,  white,  insoluble  precipitate  of  barium  sulphate. 

For  quantitative  estimation,  50  cu.  cm.  of  urine  are  strongly  acidulated  with 
acetic  acid  and  an  equal  volume  of  water  and  barium  chlorid  is  added.  After 


492  THE    INORGANIC    CONSTITUENTS    OF    THE    URINE. 

three-quarters  of  an  hour's  warming  upon  the  water-bath,  the  precipitate  will 
have  been  deposited.  This  is  collected  upon  an  ash-free  filter,  first  washed  out 
with  water,  then  with  warm  dilute  hydrochloric  acid,  and  finally  again  with  water. 
The  barium  sulphate  thus  purified  is  fused  and  weighed.  It  contains  all  of  the 
sulphuric  acid  united  with  salts.  The  filtrate  and  the  wash-water  contain  besides 
the  conjugate  sulphates.  The  combined  fluid  is  mixed  with  one-eighth  of  its 
volume  of  concentrated  hydrochloric  acid  and  heated  for  a  considerable  time. 
Barium  sulphate  and  a  resinous  mass  separate  out.  The  fluid  is  filtered,  and 
the  resinous  mass  is  dissolved  and  washed  from  the  filter  with  hot  alcohol,  and 
finally,  again  washed  with  hot  water,  then  dried  and  fused.  One  part  of  barium 
sulphate  corresponds  to  0.3433  sulphuric  acid. 

In  addition  to  sulphuric  acid,  sulphur  (one-fifth)  occurs  in  the  urine  in  an 
incompletely  oxidized  form  (potassium  sulphocyanate,  cystin,  and  a  sulphurous 
substance  derived  from  the  bile).  Sulphurous  acid,  constant  in  carnivora,  occurs 
in  normal  human  urine  only  when  hydrogen  sulphid  is  formed  in  the  intestine 
in  considerable  amount.  Hydrogen  sulphid,  which  is  less  commonly  observed, 
is  abnormal.  It  is  recognizable  by  the  black  discoloration  of  paper  moistened 
with  lead  acetate  and  ammonia  when  held  over  the  urine.  It  results  principally 
through  fermentation  by  bacteria  (bacterium  coli) ,  and  is  rarely  absorbed  from 
the  intestine  or  from  pathological  putrid  foci. 

Small  amounts  of  silicic  acid  and  nitric  acid,  derived  from  drinking- 
water,  the  latter,  however,  in  part  produced  in  the  body  itself,  are 
present.  In  the  fermentation  of  urine,  the  nitrates  are  reduced  to 
nitrites.  After  the  administration  of  salts  of  the  vegetable  acids,  car- 
bonates appear  in  the  urine,  which  then  effervesces  upon  addition  of 
an  acid. 

Sodium  in  the  urine  is  principally  united  with  chlorin,  and  in  lesser 
degree  with  phosphoric  acid  and  uric  acid.  Potassium,  equaling  about 
one-third  of  the  sodium,  is  combined  principally  with  chlorin.  During 
fever,  more  potassium  is  excreted  than  sodium,  while  the  reverse  occurs 
during  convalescence.  Calcium  and  magnesium  are  present  in  normal 
acid  urine  dissolved  as  chlorids  or  acid  phosphates.  If  the  urine  be- 
comes neutral,  neutral  calcium  phosphate  and  magnesium  phosphate 
are  precipitated.  The  latter  has  been  found  also  in  alkaline  urine  in 
association  with  disorders  of  the  stomach,  in  the  form  of  large,  trans- 
parent, four-sided  prisms.  If  the  urine  becomes  alkaline,  calcium  car- 
bonate (Fig.  172,  a), or  amorphous  tribasic  calcium  phosphate  is  pre- 
cipitated, the  magnesium,  however,  in  the  form  of  ammonio-magnesium 
phosphate  (triple  phosphate).  The  calcium  is  derived  from  food,  and 
its  amount  varies  in  accordance  with  the  digestive  and  absorptive 
capability  of  the  digestive  tract.  In  the  presence  of  pulmonary  tuber- 
culosis and  diabetes,  the  excretion  of  calcium  is  increased. 

Free  ammonia,  from  0.06  to  0.88  gram  in  the  day,  occurs  also  in 
quite  fresh  urine,  and  in  larger  amount  with  animal  than  with  vegetable 
food.  After  administration  of  mineral  acids,  the  excretion  of  com- 
bined ammonia  likewise  increases.  The  appearance  of  an  increased 
amount  of  ammonia  indicates  a  predominance  of  acids  in  the  body  and  a 
deficiency  of  alkalies.  Demonstration:  A  strip  of  red  litmus-paper  held 
over  a  mixture  of  urine  and  milk  of  lime  in  a  covered  glass  becomes 
blue.  The  alkaline  combinations  of  the  organic  acids  diminish  the 
excretion  of  ammonia.  Inorganic  ammonia-combinations  are  trans- 
formed into  organic  combinations,  perhaps  into  an  ammonium  albu- 
minate. 

Iron  is  never  wanting  in  the  urine,  from  2.5  to  10  mg.  being  excreted 
daily.  Further,  some  hydrogen  dioxid  is  present,  and  is  recognized 
by  discoloration  of  a  solution  of  indigo  on  addition  of  an  iron  sulphate. 


ACID    AND    AMMOXIACAL    URINARY    FERMENTATION. 


493 


One  liter  of  urine  contains  24.4  cu.  cm.  of  gases;  TOO  volumes  of 
urinary  gases  obtained  by  exhaustion  contain  65.40  volumes  of  carbon 
dioxid,  2.74  volumes  of  oxygen,  and  31.86  volumes  of  nitrogen.  After 
vigorous  muscular  activity  the  amount  of  carbon  dioxid  may  be  doubled. 
The  act  of  digestion  also  causes  an  increase,  while  drinking  in  large 
amount  causes  a  reduction. 


SPONTANEOUS    ALTERATIONS    IN    THE    URINE    ON    STANDING; 
ACID  AND  AMMONIACAL  URINARY  FERMENTATION. 

When  kept  in  a  cool  place,  normal  urine  often  exhibits  a  forma- 
tion of  newly  developed  acid — acid  urinary  fermentation.  This  results 
in  consequence  of  the  development  of  peculiar  fermentative  microor- 
ganisms, both  budding-fungi,  as  well  as  fission-fungi,  and  is  ac- 
companied by  excretion  of  uric  acid  (Fig.  153,  c),  acid  sodium  urate 
(b),  and  calcium  oxalate 
(d).  The  nature  of  the 
fermentative  process  is  not 
as  yet  entirely  known.  Ac- 
cording to  Briicke,  lactic 
acid  is  formed  from  the  /vg*&  ^/l  •-*£/§'$ '  yj.?;  \^~ 

•S-ftA*  '*    £    •<X-£*lf^ 


d    - 


...    b 


FIG.  153. — Sediment  due  to  Acid  Urinary  Fermentation:  a,  fer- 
mentative budding-fungi;  b,  amorphous  acid  sodium  urate: 
c,  uric  acid;  d  calcium  oxalate. 


sugar  of  the  urine ;  accord- 
ing to  Scherer,  the  germs 
decompose  the  vesical  mu- 
cus and  some  urinary  pig- 
ment into  lactic  and  acetic 
acids.  According  to  Roh- 
mann,  who  observed  acid 
fermentation  develop  only 
exceptionally,  this  is  due  to 
acids  that  result  from  the 
decomposition  of  sugar 
and  of  alcohol  accidentally 
present.  Also  the  occur- 
rence of  butyric  and  formic 

acids  as  products  of  the  decomposition  of  other  constituents  of  the  urine 
has  been  observed.  These  newly  formed  acids  expel  the  uric  acid  from 
the  simple  sodium  urate,  so  that  free  uric  acid  and  neutral  sodium  biurate 
(acid  sodium  urate)  must  be  formed.  With  the  commencement  of  acid 
fermentation,  the  urine  appears  to  absorb  oxygen.  Even  while  the  urine 
has  an  acid  reaction,  it  becomes  turbid  and  exhibits  the  presence  of  nitrous 
acid,  whose  source  is  as  yet  undetermined.  The  presence  of  nitrites  is  dis- 
closed by  the  development  of  an  intensely  yellow  color  on  addition  of 
potassium  ferrocyanid  and  acetic  acid.  According  to  v.  Voit  and  Hoff- 
mann, phosphoric  acid  is  detached  from  acid  sodium  phosphate,  with  the 
formation  of  the  basic  salt,  and  partly  displaces  uric  acid  from  sodium 
urate  and  partly  causes  its  transformation  into  biurate. 

On  standing  for  some  time,  and  more  readily  when  exposed  to  heat, 
the  urine  eventually  undergoes  ammoniacal  fermentation  (Fig.  154), 
the  urea  being  decomposed,  with  addition  of  water,  into  carbon 
dioxid  and  ammonia,  as  a  result  of  the  development  of  the  micrococcus 
and  the  bacterium  urese  (Fig.  155),  at  times  arranged  like  a  string  of 


494 


ALBUMIN    IN    THE    URINE. 


pearls.  The  ammonia  is  recognizable  both  from  its  odor  and  from  the 
vapor  that  forms  when  a  rod  moistened  with  hydrochloric  acid  is  held 
over  the  urine. 

The  capability  of  decomposing  urea  is  possessed  besides  by  various  other 
bacteria,  including  the  staphylococci  and  the  pulmonary  sarcinae,  whose  germs 
float  everywhere  in  the  air.  These  organisms  produce  a  soluble  ferment  that 
decomposes  urea.  Miquel  describes  ten  microorganisms  that  decompose  urea 
and  uric  acid. 

In  consequence  of  the  presence  of  the  ammonia  formed  in  the  urine, 
the  latter  becomes  turbid  because  substances  are  precipitated  that  are 
no  longer  capable  of  being  held  in  solution,  namely  amorphous  tribasic 
calcium  phosphate;  acid  ammonium  urate  (Fig.  154,  a)  in  the  form  of 
thorn-apple  or  morning-star  spherules;  and,  finally,  the  large,  clear, 
coffin-lid  shaped  crystals  of  ammonio-magnesium  phosphate  (6).  There 
are  formed,  also,  volatile  fatty  acids,  principally  acetic  acid  (from  the 
carbohydrates  of  the  urine).  In  the  presence  of  catarrhal  and  inflam- 
matory conditions  of  the  bladder,  the  fermentative  process  may  take 

place  within  this  viscus.  Under 
such  circumstances,  however, 
leukocytes  (pus-corpuscles,  Fig. 
1 60),  and  desquamated  epithe- 
lial cells  are  admixed  in  con- 
siderable amount.  When  pus  is 
present  in  large  amount,  the 
urine  becomes  albuminous. 
Rarely,  free  gases  form  in  the 
bladder  (pneumaturia),  as,  for 


FIG.  154. — Sediment  due  to  Ammoniacal  Urinary  Fermen- 
tation: a,  acid  ammonium  urate;  b,  ammonio-mag- 
nesium phosphate. 


FIG.  155. — Micrococcus  ureae. 


instance,  in  consequence  of  the  entrance  of  the  bacterium  lactis  aero- 
genes  (Fig.  126,  2).  A  bacillus  generating  hydrogen  sulphid  (bacterium 
coli  commune)  and  one  generating  methylmercaptan,  have  also  been 
found. 


ALBUMIN  IN  THE  URINE:   PROTEINURIA,  ALBUMINURIA. 

For  the  physician,  albumin  is  a  most  important  abnormal  constituent  of  the 
urine. 

(i)  Serum-albumin  (whose  properties  are  described  on  pp.  73  and  458)  may 
appear  in  the  urine  in  the  absence  of  anatomical  alteration  in  the  structure  of 
the  kidney,  and  the  condition  has  been  designated  by  Leube  as  physiological  albu- 
minuria.  Albumin  has  often  been  found  normally  in  the  urine  in  minute  traces, 
particularly  in  consequence  of  the  presence  of  a  considerable  amount  of  albumin 
in  the  blood-plasma  (as,  for  instance,  when  the  secretion  of  milk  is  suppressed) 
and  after  a  meal  containing  an  excess  of  proteid.  Albumin  is  common,  also,  in 
the  urine  of  the  fetus  and  the  new-born.  (2)  When  the  pressure  in  the  distribution 
of  the  renal  vessels  is  increased  (as,  for  instance,  after  a  cold  bath  or  after  excessive 


ALBUMIN    IN    THE    URINE.  495 

drinking  of  fluids),  either  for  a  considerable  time  or  as  a  transitory  phenomenon, 
particularly  in  association  with  hypostatic  hyperemia  attending  diseases  of  the 
heart,  emphysema,  chronic  pleural  effusions,  infiltrations  of  the  lungs;  and  after 
compression  of  the  chest  that  causes  stasis  in  the  pulmonary  circulation,  and 
finally  extends  into  the  renal  veins.  (3)  After  division  or  paralysis  of  the  vaso- 
mptor  nerves  of  the  kidney,  in  consequence  of  which  intense  hyperemia  of  the 
kidney  is  brought  about.  In  this  category  belongs  the  albuminuria  following 
severe  and  protracted  painful  affections  of  the  abdominal  viscera,  as,  for  instance, 
strangulated  hernia,  in  consequence  of  which  reflex  paralysis  of  the  nerves  of  the 
renal  vessels  is  induced.  After  severe  muscular  exertion,  as  in  marches,  parturi- 
tion, or  convulsive  seizures,  in  cases  of  epilepsy,  eclampsia,  the  convulsions  attend- 
ing suffocation  and  strychnin-poisoning.  The  albuminuria  observed  in  conjunc- 
tion with  concussion  of  the  brain,  apoplexy,  and  spinal  paralysis,  severe  emotional 
disturbances,  excessive  mental  activity,  and  morphinism,  is  possibly  attributable 
to  a  disorder  of  the  vasomotor  centers.  (4)  Inability  en  the  part  of  the  epithelial 
cells  to  restrain  the  albumin  may  cause  albuminuria;  and,  as  it  appears,  in  conse- 
quence of  defective  nutrition  and  functional  debility  of  the  secretory  elements. 
In  this  category  belongs  the  albuminuria  attending  ischemia,  and  that  following 
hemorrhage  and  attending  anemic  conditions,  scorbutus,  icterus,  diabetes,  and 
the  death-agony.  (5)  In  association  with  many  acute  febrile  diseases,  especially 
the  acute  exanthemata  (as,  for  instance,  scarlet  fever);  further,  typhoid  fever, 
pneumonia,  and  pyemia.  It  is  probable  that  under  such  circumstances  the  secre- 
tory apparatus  of  the  kidney  has  undergone  changes  (cloudy  swelling  of  the  epithe- 
lial cells  of  the  urinary  tubules,  inflammation  of  the  glomeruli) ' that  render  these 
incapable  of  preventing  the  escape  of  the  albumin.  (6)  Degeneration  of  the  kidneys, 
such  as  contraction  of  the  kidneys,  amyloid  degeneration,  further  inflammatory 
processes  in  their  various  stages,  are  generally  attended  with  albuminuria.  Sem- 
mola  has  shown  that  the  albuminuria  attending  nephritis  is  not  rarely  dependent 
rather  upon  the  state  of  the  blood  than  upon  the  disease  of  the  kidneys.  He 
believed  that  the  renal  lesion  occurs  in  general  as  a  secondary  phenomenon,  while 
the  albuminuria  is  primary,  except  the  form  that  is  a  result  of  the  inflammation 
of  the  kidney  itself.  (7)  Finally,  inflammatory  and  suppurative  processes  in  the 
tirinary  passages,  from  the  pelvis  of  the  kidney  to  the  extremity  of  the  urethra, 
may  cause  albuminuria.  Under  such  circumstances,  however,  leukocytes  are 
always  found  in  the  urine;  not  rarely,  also,  erythrocytes  or  the  products  of  their 
solution,  and  fibrin-coagula.  Certain  substances  that  give  rise  to  irritation  and 
inflammation  of  the  urinary  apparatus  should  finally  be  mentioned,  such  as  can- 
tharides  and  carbolic  acid.  (8)  The  appearance  of  albumin  in  the  urine  after 
sodium  chlorid  has  been  entirely  eliminated  from  the  food  is  noteworthy.  The 
albumin  disappears  when  the  salt  is  resumed. 

Demonstration  of  Albumin  in  the  Urine. — (a)  After  strong  acidulation  with 
acetic  acid,  a  few  drops  of  a  concentrated  solution  of  potassium  ferrocyanid  causes 
a  precipitate. 

(b)  Urine  to  which  is  added  one-third  its  volume  of  pure  nitric  acid  exhibits 
a  precipitate.     A  resulting  turbidity  may  be  due,  apart  from  albumin,  to  the 
precipitation  of  urates.     Slight  heat,  however,  causes  solution  of  the  latter,  while 
albumin  remains  turbid. 

(c)  Urine  to  which  a  few  drops  of  acetic  acid  are  added  and  which  is  then 
mixed  with  an  equal  volume  of  concentrated  sodium  sulphate  and  boiled  yields  a 
precipitate. 

(d)  The  urine  is  acidulated  with  a  few  drops  of  concentrated  acetic  acid,  and 
filtration  is  practised  for  the  removal  of  mucin.     The  urine  is  then  cautiously 
overlaid,  drop  by  drop,  in  a  test-tube  held  obliquely,  by  the  following  mixture: 
Mercuric  chlorid,  8;    tartaric  acid,  4;   glycerin,  20;  water,  200.     Turbidity  results 
at  the   line  of   contact.     Albumose  is  disclosed  by  the  same  reaction,  but  it  is 
redissolved  by  heat.     Jolles  recommends  the  following   mixture:    Ten   parts    of 
mercuric  chlorid,  20  parts  of  succinic  acid,   10  parts  of  sodium  chlorid,  and  500 
parts  of  water.     Five  cubic  centimeters  of  filtered  urine  are  acidulated  with    i 
cu.  cm.  of  30  per  cent,  acetic  acid  and  4  cu.  cm.  of  the  reagent  described  are 
added. 

(e)  A  few  drops  of  30  per  cent,  sulphosalicylic  acid  are  added  to  filtered  urine. 
This  reaction  discloses  also  the  presence  of  albumoses,  but  the  precipitate  due  to 
the  latter  is  cleared  up  on  heating. 

Boiling,  by  driving  off  the  carbon  dioxid.  may  cause  a  precipitate  of  earthy 
phosphates  in  alkaline  urine,  and  this  may  simulate  albumin.  If.  however,  a 
small  amount  of  acetic  acid  be  added,  the  phosphates  are  redissolved,  while  albu- 


496 


ALBUMIN    IN    THE    URINE. 


min  would  be  coagulated.  Only  small  amounts  of  clear  urine  should  be  employed 
in  making  the  tests  for  albumin.  Turbid  urine,  therefore,  should  first  be  filtered. 
The  quantitative  estimation  of  albumin  is  made  as  follows:  100  cu.  cm.  of 
urine,  if  necessary  after  addition  of  a  small  amount  of  acetic  acid,  are  heated 
in  a  dish  to  the  boiling-point,  with  the  result  that  the  albumin  is  precipitated 
as  a  flocculent  deposit.  The  precipitate  is  collected  upon  a  weighed,  ash-free 
filter,  dried  at  110°,  and  it  is  washed  repeatedly  with  hot  water,  then  with  alcohol, 
and  is  thoroughly  dried  in  the  air-bath  at  110°.  The  dried  filter  is  now  weighed, 
and  the  weight  of  the  filter  is  deducted.  Finally,  the  filter  with  the  albumin  is 
reduced  to  ash  in  a  weighed  platinum  crucible,  and  the  weight  of  the  ash  is  sub- 
tracted. 

For  the  estimation  by  the  polarization-apparatus,  reference  may  be  made 
to  p.  268. 

By  means  of  Esbach's  albuminimeter.  A  glass  cylinder  is  filled  with  urine 
to  the  mark  U,  and  with  the  albumin-precipitating  reagent  (20  parts  of  citric 
acid,  10  parts  of  picric  acid,  970  parts  of  water)  to  the  mark 
R,  and  is  then  closed  with  a  stopper  and  agitated.  After  the 
lapse  of  twenty-four  hours  (at  room-temperature)  the  coagu- 
lated albumin  will  have  settled  to  the  bottom.  The  divisions 
of  the  scale  on  the  glass  indicate  the  number  of  grams  of  albu- 
min in  1000  grams  of  urine.  The  urine  must  have  an  acid 
reaction,  be  fresh,  and  its  specific  gravity  should  not  be  too 
high.  The  presence  of  an  excessive  amount  of  albumin  also 
may  therefore  require  dilution  of  the  urine  with  from  2  to  4 
times  as  much  water.  The  amount  of  albumin  obtained  is 
then  naturally  to  be  multiplied  by  2  or  4. 

Globulin  has  been  found  almost  exclusively  in  albuminous 
urine;  and,  indeed,  in  the  majority  of  cases.  To  demonstrate 
its  presence,  50  cu.  cm.  of  albuminous  urine  are  rendered 
feebly  alkaline  with  potassium  hydrate,  and  powdered  magne- 
sium sulphate  is  added  to  an  amount  approximating  some- 
what more  than  24.11  per  cent.  If  exposed  to  a  warm  tem- 
perature, all  of  the  globulin  is  precipitated  in  the  course  of 
twenty-four  hours,  and  it  can  be  filtered  out,  dried,  and 
weighed.  With  this  the  total  amount  of  albumin  should  be 
compared.  The  presence  of  globulin  is  of  unfavorable  prog- 
nostic significance.  Its  amount  is  diminished  by  favorable 
circulatory  conditions  in  the  kidney. 

Propeptone  (Albumose). — Peptone  does  not  occur  in  the 
urine.  What  has  previously  been  described  as  such  is  pro- 
peptone.  The  latter  occurs  sometimes  in  acid,  albuminous 
urine;  rarely,  also,  in  urine  free  from  albumin.  Maixner 
found  it  constantly  in  connection  with  all  suppurative  dis- 
orders, empyema,  peritonitis,  pneumonia,  meningitis,  ulcer- 
ative  affections  of  the  digestive  tract,  etc. — pyo genie  propcp- 
tonuria.  Albumose  is  always  present  also  in  pus,  and  propep- 
tonuria  is  a  sign  of  the  destruction  of  pus-corpuscles.  It  oc- 
curs further  in  connection  with  increased  retrogressive  or  de- 
structive processes  in  tissues  rich  in  albumin;  as,  for  instance, 
in  the  presence  of  carcinoma  and  of  fever.  In  the  same  category  probably  belongs 
also  its  constant  occurrence  in  the  puerperium;  often,  also,  during  pregnancy,  when 
the  fetus  has  died  and  is  undergoing  putrefaction — puerperal  propcptonuria.  Pro- 
peptone  is  found,  also,  when  the  urine  contains  semen. 

Demonstration. — Ten  cu.  cm.  of  urine  are  heated  with  8  grams  of  ammo- 
nium sulphate  until  the  latter  is  dissolved.  Then  the  hot  fluid  is  centrifugated 
for  a  minute.  The  fluid  is  decanted,  the  residue  rubbed  up  with  97  per  cent, 
alcohol  for  the  removal  of  the  urobilin,  then  dissolved  in  a  small  amount  of  water, 
and  boiled  and  filtered.  The  filtrate  is  subjected  to  the  biuret-test.  When  the 
urine  contains  hematoporphyrin,  it  is  advisable  to  precipitate  this  first  with  barium 
chlorid. 

Egg-albumin  appears  after  generous  ingestion  of  fluid  egg- albumin,  as  well 
as  after  injection  into  the  tissues  or  into  the  blood-stream. 

Mucus  is  present  in  association  with  catarrhal  conditions  of  the  urinary  organs, 
particularly  of  the  bladder.  Microscopically,  the  presence  of  numerous  leukocytes 
is  noteworthy.  As  these  contain  albumin  the  intensity  of  the  reaction  for  albumin 
will  vary  with  their  abundance.  The  characteristic  reagent  for  mucus,  however, 


FIG.   156. — Esbach's   Al- 
buminimeter. 


BLOOD    AND    HEMOGLOBIN    IN    THE    URINE.  497 

is  acetic  acid,  which  produces  a  flocculent  sediment  also  in  clear  filtered  urine. 
Mucin,  however,  is  not  precipitated  by  boiling.  The  mucoid  substance,  nucleo- 
albumin,  which  is  precipitated  by  an  excess  of  acetic  acid  in  dilute  urine,  occurs 
as  a  sign  of  renal  irritation. 

In  the  presence  of  disorders  of  the  bladder,  there  rarely  occurs  in  the  urine 
an  admixture  of  a  peculiar  ropy,  gum-like  substance,  consisting  of  transformed 
mucus,  which  is  thought  to  be  the  product  of  an  anaerobic  bacterium  gliscro- 
genum.  Nucleoalbumin  also  has  been  found,  derived  partly  from  the  bladder, 
partly  from  the  urinary  tubules  of  the  medullary  structure;  it  is  precipitable  by 
acetic  acid.  Kolisch  and  Burian  found  histon  in  a  case  of  leukemia,  and  Jolles 
nucleohiston.  According  to  Morner,  the  urine  contains  substances  that  precipitate 
albumin,  such  as  chondroitin-sulphuric  acid,  nucleinic  acid,  rarely  taurocholic  acid, 
in  larger  amount  in  association  with  jaundice.  If  acetic  acid  be  added  to  normal 
urine,  these  substances  are  eventually  precipitated  out. 

BLOOD  AND  HEMOGLOBIN  IN  THE  URINE:  HEMATURIA, 
HEMOGLOBINURIA. 

In  case  of  hematuria  the  blood  may  be  derived  from  any  portion  of  the  urinary- 
apparatus.  ( i)  In  case  of  hemorrhage  from  the  kidney,  the  blood  is  generally  admixed 
with  the  urine  in  small  amount  and  is  well  distributed.  The  erythrocytes  under 
such  circumstances  often  exhibit  peculiar  alterations  in  shape,  and  processes  of 
division,  which  may  be  brought  about  by  the  action  of  the  urea,  and  which  have 
been  attributed  by  Friedreich  to  independent  ameboid  movement  (Fig.  159). 
The  blood-cylinders  present  in  the  sediment  are  pathognostic  of  renal  hemorrhage, 
that  is,  elongated  microscopic  coagula  of  blood,  which  must  be  considered  as 
actual  casts  of  the  collecting  tubules  of  the  kidneys,  and  which  are  washed  thence 
into  the  urine  (Fig.  166).  (2)  In  case  of  hemorrhage  from  the  ureters,  long,  worm- 
like  strings  of  coagulated  blood  are  occasionally  observed  in  the  urine  as  casts 


0 


o 


o*r 

FIG.    157. — Thorn-apple   shaped   Blood-corpuscles   in        FIG.  158.— Peculiar  Changes  in  the  Shape  of  the  Rod 
the  Urine.  Blood-corpuscles    in    Case    of   Renal    Hematuria 

(after  Friedreich). 

of  the  ureter.  (3)  Relatively  the  largest  coagula  of  blood  occur  in  cases  of  hemor- 
rhage from  the  bladder.  (4)  Blood  is  present  in  the  urine  as  an  admixture  at  every 
menstrual  period. 

Urine  containing  blood  should  always  be  examined  microscopically  for  blood- 
corpuscles.  In  addition,  attention  should  be  given  to  ribrin-coagula.  In  acid 
urine,  erythrocytes  can  be  recognized  for  as  long  as  two  or  three  days;  though 
never  arranged  in  rouleaux.  If  the  hemorrhage  has  been  considerable,  the  cor- 
puscles are  generally  normal  in  shape.  If,  however,  the  urine  is  concentrated, 
they  appear  mulberry  or  thorn-apple  shaped  (Fig.  157). 

The  blood-corpuscles  always  settle  gradually  to  the  bottom  in  urine  at  rest. 
If  the  blood  is  slowly  admixed  with  the  urine  and  in  small  amount  from  ruptured 
capillaries,  the  erythrocytes  appear  of  variable  size,  some  not  larger  than  between 
one-eighth  and  one-half  of  the  normal  (Fig.  159).  At  the  same  time,  their  pig- 
ment has  become  brownish  yellow  in  color  (methemoglobin) .  If,  in  a  case  of 
hemorrhage  of  this  kind,  there  exists  catarrhal  inflammation  of  the  bladder, 
numerous  leukocytes,  at  times  adherent  to  one  another  (Fig.  160),  which, 
32 


498 


BLOOD    AND    HEMOGLOBIN    IN    THE    URINE. 


FlO.  159. — Red  and  White  Blood-corpuscles  of  Varying  Size. 


in  fresh  preparations,  often  exhibit  distinct  ameboid  movement,  are  found  among 
the  erythrocytes,  which  often  are  greatly  shrunken.     If  the  urine,  as  is  usual, 

is  of  alkaline  reaction,  crystals 
of  ammonio -magnesium  phos- 
phate will  be  present  (Fig.  160) . 
If  the  erythrocytes  have  al- 
ready become  pale,  they  are 
not  rarely  rendered  more  dis- 
tinct by  addition  of  a  wine- 
yellow  solution  of  iodin  and 
potassium  iodid. 

Hemoglobinuria,  that  is, 
the  elimination  of  hemoglobin 
through  the  urine,  is  entirely 
distinct  from  true  hematuria. 
It  occurs  only  when  a  consider- 
able amount  of  hemoglobin  has 
already  been  set  free  in  the 
vessels  from  dissolved  red 
blood-corpuscles  (hemocytoly- 
sis).  This  is  observed  in  its 
purest  form  after  transfusion 
of  blood  from  an  animal  of  a 
different  species,  and  also  from 
lambs'  blood  in  human  beings. 
The  foreign  blood-corpuscles 
are  dissolved  in  the  blood- 
stream of  the  recipient  and  the 
hemoglobin  appears  in  the 
urine .  In  addition ,  microscopic 

casts  of  the  urinary  tubules  of  coagulated  globulin-like  substance,  stained  yellow 
by  hemoglobin,  are  present.  Hemoglobin  has  been  found  in  the  urine,  also,  after 
extensive  burns;  after  decomposition  of  blood  in  the  body  in  cases  of  pyemia, 
scorbutus,  purpura,  severe  ty- 
phoid fever ;  after  the  ingestion 
of  unboiled  toad-stools,  and  of 
lupins  by  sheep;  after  inhala- 
tion of  hydrogen  arsenid ;  after 
the  entrance  of  azobenzol, 
naphthol,  pyrogallic  acid,  to- 
luylendiamin,  potassium  chlor- 
ate, chloral,  phosphorus,  or  car- 
bolic acid,  into  the  circulation, 
as  these  bodies  dissolve  the 
erythrocytes;  and,  finally, 
periodically  in  attacks  (in  the 
horse  also)  of  as  yet  unex- 
plained nature,  in  which  the 
condition  appears  to  depend 
upon  undue  solubility  of  the 
erythrocytes,  particularly  from 
the  action  of  external  cold  upon 
the  skin. 

Demonstration  of  Blood  in 
the  Urine. — i.  The  color  of 
urine  containing  blood  has 
been  observed  to  be  of  all 
shades,  from  light  red  to  dark 


FIG.  160. — Greatly  Shrunken  Red  Blood-corpuscles  in  the  Urine 
from  a  Case  of  Catarrh  of  the  Bladder,  in  the  midst  of  numer- 
ous Leukocytes  and  small  Crystals  of  Triple  Phosphates. 


brownish-black,  in  accordance 
with  the  amount  of  blood 
present.  Often  the  urine  is 
turbid. 

2.  Urine  containing  blood  or  hemoglobin  must  always  exhibit  the  reactions 
of  album^n. 

3.  Heller's  blood-test:  To  urine  in  a  test-tube,  one-third  potassium  hydrate  is 
added  and  moderate  heat  is  applied.     The  earthy  phosphates  are  precipitated, 


BLOOD    AND    HEMOGLOBIN    IN    THE    URINE. 


499 


and  carry  down  with  them  hemochromogen,  so  that  garnet-red  flakes  are  de- 
posited. When  the  urine  contains  but  a  small  amount  of  blood,  these  flakes 
appear  red  in  reflected  light  and  greenish  in  transmitted  light,  the  distinction 
being  clear  when  as  little  as  one  part  of  hemoglobin  is  present  in  a  thousand. 
If  the  earthy  phosphates  are  already  precipitated  in  alkaline  urine,  deposition 
is  effected  artificially  by  addition  of  a  few  drops  of  magnesium  sulphate  and 
ammonium  chlorid,  and  the  same  change  in  color  is  apparent. 

4.  From  the  earthy  phosphates  thus  obtained,  containing  hemoglobin,  and 
collected  upon  a  filter,  hemin-crystals  can  be  prepared.     For  this  purpose  the  same 
procedure  may  be  followed  as  is  described  on  p.  62. 

5.  The  reaction  may  be  tested,  also,  with  tincture  of  guaiac  and  oil  of  tur- 
pentine, the  blood  acting  as  a  carrier  of  ozone.     The  urine  should  not  lose  the 
property  of  developing  a  blue  color  as  a  result  of  previous  heating. 

6.  Urine    containing    blood   when    examined    with    a    spectroscope    exhibits 
characteristic  appearances.     The  arrangement  of  the  apparatus  is  shown  in  Fig. 
161.     The  urine  is  placed  in  the  chamber  D  (hematinometer)   i  cm.  thick,  with 
parallel  glass  walls.     Through  this  pass  the  rays  of  light  from  a  lamp,  E,  while 


FIG.  161. — Spectroscope  for  Examination  of  the  Urine  as  to  the  Presence  of  Hemoglobin. 


another,  F,  illuminates  a  scale,  and  the  observer  makes  his  observation  through 
the  telescope,  A.  The  examination  yields  the  following  results: 

(a)  Fresh  urine  containing  blood  exhibits  the  spectrum  of  oxyhemoglobin  (Fig. 
15).  Under  some  circumstances,  it  is  necessary,  in  this  connection,  to  dilute  the 
urine  with  distilled  water  and  to  secure  perfect  clearness  by  filtration.  To  con- 
firm the  observation,  the  oxyhemoglobin  may  be  exposed  to  the  action  of  reducing 
substances,  which  produce  reduced  hemoglobin. 

(6)  If  concentrated  urine  containing  blood  is  permitted  to  stand  for  a  some- 
what longer  time,  especially  at  the  temperature  of  the  blood,  it  acquires  a  deep, 
dark-brown  color,  like  coffee-grounds,  in  the  presence  of  an  acid  reaction.  The 
hemoglobin  is  thus  converted  into  methemoglobin.  Methemoglobin  in  solution  is, 
in  contradistinction  from  oxyhemoglobin,  precipitable  by  lead  acetate.  The  acid 
solution  of  methemoglobin  in  urine  thus  resulting  exhibits  in  the  spectroscope  a 
close  resemblance  to  hematin  in  acid  solution  (Fig.  15).  If  the  urine  is  now 
rendered  alkaline,  the  absorption-bands  of  methemoglobin  in  alkaline  solution 
appear.  The  spectra  of  oxyhemoglobin  and  methemoglobin  are  also  found  com- 
bined in  the  urine.  When  treated  with  reducing  substances  methemoglobin  is 
transformed  into  hemoglobin.  Later  on,  also  hematin  is  present  in  acid  solution 
in  the  urine.  If  such  urine  is  treated  with  reducing  substances,  alkaline  hematin 
appears. 


500  BILIARY    CONSTITUENTS    IN    THE    URINE. 

Traces  of  hematoporphyrin  are  constant  in  the  urine,  btit  in  considerable 
amount  this  substance  is,  however,  rare  (in  cases  of  lead-poisoning,  intestinal 
hemorrhage,  administration  of  sulfonal). 

Demonstration. — To  500  cu.  cm.  of  urine  are  added  100  cu.  cm.  of  a  ten  per 
cent,  sodium-hydrate  solution.  The  precipitate  is  washed  upon  a  filter,  dissolved 
in  hydrochloric-acid  alcohol,  and  exhibits  spectroscopically  acid  hematoporphyrin. 

(c)  If  urine  containing  blood  is  coagulated  by  boiling  and  the  brownish-black 
coagulum  is  washed  out  and  dried,  and  then  extracted  at  gentle  heat  with  alcohol 
containing  sulphuric  acid,  a  brown  fluid  is  obtained,  which,  if  sufficiently  concen- 
trated, proves  on  spectroscopic  examination  to  be  hematin  in  acid  solution  (Fig. 
15,5). 

BILIARY  CONSTITUENTS  IN  THE  URINE:  CHOLURIA. 

The  physiological  factors  that  are  of  importance  in  connection  with  the  pres- 
ence of  biliary  matters  in  the  urine  have  been  in  part  already  discussed  (p.  319). 
If  bilirubiii  is  formed  from  hemorrhagic  extravasations  through  the  activity  of  the 
connective-tissue  cells,  bile-pigment  may  pass  over  into  the  urine,  while  the  tissues 
acquire  a  yellow  color.  Cases  presenting  this  peculiarity  have  been  designated 
instances  of  hematogenous  or  anhepatogenous  icterus. 

The  biliary  coloring-matters  are  demonstrated  by  the  Gmelin-Heintz  test 
(P  3J7-) !  the  appearance  of  the  green  color-ring  of  biliverdin  can  be  considered  as 
characteristic.  The  method  has  received  several  modifications,  (i)  If  a  consid- 
erable amount  of  icteric  urine  is  passed  through  filter-paper,  one  drop  of  nitric 
acid  with  nitrous  acid  yields  the  color-rings  upon  the  inner  surface  of  the  yellow- 
colored,  and,  if  necessary,  warmed,  filter.  (2)  If  50  cu.  cm.  of  icteric  urine,  acidu- 
lated with  acetic  acid,  be  agitated  with  10  cu.  cm.  of  chloroform,  bilirubin  passes 
over  into  the  latter.  If  bromin-water  be  added,  beautiful  color-rings  appear.  If 
to  the  chloroform-extract  oil  of  turpentine  containing  ozone  be  added,  together 
with  a  little  dilute  potassium  hydrate,  a  green  color  due  to  biliverdin  appears  in 
the  watery  solution.  (3)  Tincture  of  iodin  diluted  ten  times  with  alcohol  and 
overlaid  on  the  urine  gives  rise  to  a  grass-green  ring.  (4)  According  to  Jolles, 
the  following  procedure  yields  the  most  distinct  results:  To  50  cu.  cm.  of  urine 
are  added  5  cu.  cm.  of  a  ten  per  cent,  solution  of  barium  chlorid  and  5  cu.  cm. 
of  chloroform,  agitation  being  practised  for  four  minutes  in  a  vessel  closed  with 
a  glass  stopper.  After  the  lapse  of  ten  minutes  chloroform  and  precipitate  are 
pipetted  into  a  dish,  placed  over  the  water-bath  at  a  temperature  of  80°  until 
evaporation  takes  place.  The  mixture  is  then  permitted  to  cool.  Now  one  or 
two  drops  of  concentrated  nitric  acid  are  permitted  to  flow  upon  the  precipitate 
at  several  places,  and  the  color- rings  appear.  (5)  The  urine  is  rendered  alkaline 
with  soda,  and  calcium  chlorid  is  added  drop  by  drop  until  the  fluid  overlying 
the  precipitate  appears  normal.  The  precipitate  is  filtered  off  and  washed,  over 
it  is  poured  alcohol,  and  it  is  dissolved  by  means  of  hydrochloric  acid.  If  the 
solution  be  boiled,  a  color  varying  between  green  and  blue  develops.  When 
cooled,  it  yields  a  play  of  colors  from  blue  to  violet  to  red  with  nitric  acid. 

In  the  presence  of  protracted  high  fever,  the  urine  at  times  contains  only 
biliprasin.  If  it  contains  only  choletelin,  the  urine,  to  which  hydrochloric  acid 
has  been  added,  is  examined  with  the  spectroscope,  and  a  pale  absorption-band 
will  be  found  between  b  and  F. 

Hematoidin-crystals  (Fig.  92,  b)  are  present  in  the  urine  when  erythrocytes 
are  destroyed  in  the  blood-stream  in  large  number.  After  these  had  been  found 
first  by  v.  Recklinghausen  and  Landpis,  after  transfusion  of  heterogeneous  blood, 
they  were  observed  in  conjunction  with  various  infectious  diseases  that  exercise  a 
destructive  effect  upon  the  erythrocytes;  in  cases  of  scarlet  fever;  in  lesser  degree 
in  cases  of  typhoid  fever;  '  and  Landois  with  Strubing  observed  them  in  the  urine 
in  association  with  attacks  of  periodic  hemoglobinuria.  Landois  refers  the  biliary 
acids  often  observed  by  him  in  the  urine  after  solution  of  the  erythrocytes  to 
the  hemoglobin  of  the  destroyed  corpuscles.  If  old  collections  of  blood  rupture 
into  the  urinary  passages,  as  in  cases  of  pyonephrosis  or  in  conjunction  with  the 
perforation  of  necrotic  areas,  the  appearance  of  the  crystals  is  comparable  to 
that  in  the  sputa  in  analogous  cases.  In  cases  of  hypostatic  icterus,  bilirubin, 
which  is  identical,  was  found  in  crystalline  form. 

The  biliary  acids,  which  Dragendorff  demonstrated  to  the  extent  of  0.8  gram 
in  100  liters  of  normal  urine,  appear  in  larger  amount  in  connection  with  resorption- 
icterus,  although  even  under  such  circumstances  never  in  considerable  amount. 


SUGAR    IN    THE    URINE.  501 

Landois  observed  them,  also,  in  association  with  the  passage  of  biliary  matters 
in  consequence  of  marked  destruction  of  erythrocytes.  Their  properties  and 
reaction  have  already  been  described  (p.  315),  a  solution  of  cane-sugar  0.5  gram 
to  one  liter  of  water  being  employed  for  the  latter.  Urine  of  low  specific  gravity 
should  be  concentrated  upon  the  water-bath.  To  insure  absolute  certainty,  a 
portion  of  urine  is  evaporated  over  the  water-bath  almost  to  dryness,  and  the 
residue  extracted  with  alcohol.  The  alcoholic  extract  is  again  carefully  evaporated 
in  a  porcelain  dish,  and  the  residue  dissolved  in  a  few  drops  of  water  and  sub- 
jected to  Pettenkofer's  test.  If  the  test  is  applied  directly  to  the  urine,  one 
must  previously  have  convinced  himself  that  the  urine  is  free  from  albumin,  as 
this  substance  yields  a  similar  reaction.  In  such  an  event  the  albumin  should 
be  removed  by  boiling  and  filtration.  If  filter-paper  is  dipped  into  urine  to 
which  cane-sugar  has  been  added,  and  the  paper  is  dried  and  brought  in  contact 
with  sulphuric  acid,  a  violet-red  color  results,  which  is  particularly  pretty  in 
transmitted  light. 

SUGAR  IN  THE  URINE:  GLYCOSURIA. 

Normal  urine  contains  traces  of  dextrose.  Small  amounts  of  sugar  are  present 
after  ingestion  of  sugar  in  large  amounts  (alimentary  glycosuria) ,  and  also  in  the 
presence  of  fever,  after  the  drinking  of  beer  supplemente'd  by  alcohol,  occasionally 
in  the  exceedingly  obese,  in  neurasthenics,  in  association  with  cerebral  disease, 
and  in  advanced  age.  Glycosuria  occurs  also  as  a  result  of  failure  in  intestinal 
activity  in  ill-nourished  individuals;  and,  artificially,  after  ligation  of  the  mesen- 
teric  arteries.  Dextrosuria  of  considerable  degree  is  a  sign  of  diabetes  mellitus. 
In  this  connection,  the  large  amount  of  urine,  up  to  10,000  cu.  cm.,  as  well  as 
the  high  specific  gravity,  from  1030  to  1040,  are  striking.  The  diabetic  patient 
excretes  a  relatively  larger  amount  of  water  through  the  kidneys;  and,  on  the 
other  hand,  a  relatively  smaller  amount  through  the  skin  (and  the  lungs?)  than 
a  healthy  person.  Also  the  elimination  of  the  water  ingested  takes  place  later 
and  more  uniformly  than  in  health.  The  urine  is  pale  yellow  in  color,  although 
the  amount  of  coloring-matter  is,  in  the  aggregate,  by  no  means  diminished;  and 
the  nitrogenous  matters  are  increased.  A  diet  of  carbohydrates  generally  in- 
creases the  excretion  of  sugar;  while  a  proteid  diet  may  reduce  it.  Uric  acid 
and  calcium  oxalate  are  often  found  increased  at  the  commencement  of  the  disease. 
On  standing  for  a  considerable  time  yeast-cells  constantly  develop  in  the  urine. 

For  quantitative  estimation  the  tests  for  sugar  already  described  (p.  268) 
are  appropriate,  although  the  urine  must  be  free  from  albumin  or  be  rendered 
so.  The  following  tests  are  most  to  be  recommended: 

(a)  The  fermentation-test  is  the  most  reliable.     A  test-tube  inverted  over 
mercury  is  filled  with  the  saccharine  urine  and  a  piece  of  yeast,  living  and  free 
from  sugar,  as  large  as  a  pea,  and  also  one  drop  of  tartaric  acid,  are  added,  and 
the  mixture  is  kept  in  a  warm  place.     Carbon  dioxid  collects  at  the  bottom  of 
the  inverted  tube,  and  disappears  after  the  introduction  of  potassium  hydrate. 

(b)  A  2.5  per  cent,  solution  of  copper  sulphate  and  a  solution  containing  10 
parts  of  sodiopotassic  tartrate  in   100  parts  of  a  4  per  cent,  solution  of  sodium 
hydrate  are  employed.     Five  cubic  centimeters  of  urine  are  boiled  in  a  test-tube, 
and  from  i  to  3  cu.  cm.  of  the  copper-solution  and  2.5  cu.  cm.  of  the  tartaric- 
acid  solution  in  a  second  test-tube.     The  boiling  of  both  fluids  is  interrupted 
simultaneously,  and  after  the  lapse  of  from  20  to  25  seconds,  the  contents  of  the 
one  tube  are  poured  without  agitation  into  the  other;  reduction  then  takes  place 
spontaneously . 

(c)  Bottger's  test  with  Nylander's  modification  (p.  267). 

(d)  In  the   application  of  the  phenylhydrazin-test,   5  cu.  cm.   of    urine  are 
diluted  with  5  cu.  cm.  of  water,  and  0.5  of  phenylhydrazin  hydrochlorate  and  i 
gram  of  sodium  acetate  are  added.     The  mixture  is  boiled  for  two  minutes  over 
the  water-bath,  is  permitted  to  cool  slowly  and  to  stand  for  four  hours  in  the 
cold.     Combinations  of  glycuronic  acid  form  similar,  though  plumper,  crystals, 
more  like  thorn-apples. 

(e)  In  applying  Molisch's  test,  «-naphthol  dissolved  in  chloroform,  instead  of 
in  alcohol,  is  employed.     The  test  discloses  the  presence  of  all  of  the  carbohy- 
drates in  the  urine,  under  normal  circumstances  0.96  per  cent,  altogether,  of  which 
o.  i  is  grape-sugar.     Urine  containing  sugar  should  be  diluted  100  times. 

(/)  If  to  10  cu.  cm.  of  diabetic  urine  in  a  test-tube  0.5  mg.  of  powdered  gentian- 
violet  are  added,  the  urine  is  colored,  while  normal  urine  is  not. 


502 


SUGAR    IN    THE    URINE. 


Quantitative  estimation  is  made  by  fermentation  or  by  the  titration-method. 
The  estimation  by  circumpolarization  is,  according  to  Worm-Muller,  almost  value- 
less for  the  estimation  of  the  amount  of  sugar  in  diabetic  urine,  as  the  urine 
often  contains  in  part  as  yet  unknown  optically  active  substances.  If,  however, 
it  be  desired  to  employ  this  method,  the  urine  must  be  previously  agitated  with 
commercial  animal  charcoal  and  filtered,  in  consequence  of  which  it  becomes 
colorless.  Small  amounts  of  glycogen  derived  from  urinary  tubules  that  have 
undergone  glycogenic  degeneration  have  been  found  by  Leube  in  diabetic  urine. 

After  ingestion,  the  sugars  that  are  most  readily  decomposed  pass  with  greatest 
difficulty,  while  those  that  are  not  at  all  decomposable  pass  most  readily,  into 
the  urine.  If,  therefore,  considerable  amounts  of  dextrose  are  administered,  a 
portion  thereof  passes  into  the  urine;  and  a  larger  amount  in  cases  of  diabetes 
than  in  health.  Ingested  levulose  does  not  increase  the  amount  of  sugar  in  the 
urine  of  a  diabetic  patient.  The  use  of  starch  in  considerable  amounts  never 
gives  rise  to  the  presence  of  sugar  in  the  urine  in  health,  although  it  increases 
the  amount  of  sugar  in  cases  of  diabetes.  The  ingestion  of  cane-sugar  or  of  milk- 
sugar  in  considerable  amount  causes  the  passage  of  small  amounts  of  each  into 
the  urine  during  health.  The  diabetic,  under  such  circumstances,  excretes  an 
increased  amount  of  dextrose.  According  to  Kulz,  the  cane-sugar  ingested  by 
a  diabetic  patient  is  decomposed  into  grape-sugar  and  fruit-sugar;  the  latter  is 

consumed  in  the  body,  the 
former  in  part  excreted.  The 
same  takes  place  with  milk- 
sugar. 

Levulose  is  rarely  present 
in  the  urine,  constituting  levu- 
losuria. 

In  severe  cases  of  diabetes 
mellitus,  Kulz  found  levorota- 
tory  fi-oxybutyric  acid,  the  next 
higher  analogue  of  lactic  acid, 
in  the  urine,  from  the  oxida- 
tion of  which  diacetic  acid  is 
produced.  The  latter,  in  its 
turn,  is  readily  decomposed 
into  carbon  dioxid  and  acetone. 
/3-oxybutyric  acid  is  never 
wanting  when  diabetic  coma  is 
present.  Acetone  is  present  in 
the  urine  of  diabetics  often  in 
considerable  amount,  princi- 
pally in  association  with  pro- 
gressive loss  of  strength,  and 
often  even  in  spite  of  admin- 
istration of  carbohydrates. 
From  oxybutyric  acid  there 
results,  by  dehydration,  a-cro- 
tonic  acid,  which  Stadelmann  found  in  diabetic  urine.  As  albuminuria  results  from 
administration  of  acetone,  the  complication  of  albuminuria  with  diabetes  is  clear. 
Milk-sugar — lactosuria — is  present  in  the  urine  of  puerperal  women,  together 
with  glucose  and  isomaltose,  chiefly  in  connection  with  milk-stasis.  The  condition 
is  thus  due  to  absorption  from  the  breasts.  Milk-sugar  likewise  appears  in  the 
urine  of  infants  with  derangement  of  digestion. 

Pentose  has,  on  several  occasions,  been  observed  in  the  urine:  pentosuria. 
This  substance  contains  5  atoms  of  carbon,  is  not  susceptible  of  fermentation, 
and  is  capable  of  causing  reduction.  It  may  possibly  be  due  to  disease  of  the 
pancreas.  Phloroglucin  and  hydrochloric  acid  yield  a  red  color.  Pentose  is 
present  in  coffee,  in  many  wines,  and  in  varieties  of  milk  and  sugar.  Ingested 
pentoses — arabinose,  xylose — pass  over  into  the  urine. 

Reichart  has  called  attention  to  the  simultaneous  appearance  of  dextrin  in 
urine  containing  sugar.  Inosite  has  been  found  both  in  cases  of  diabetes  and 
in  cases  of  polyuria  and  albuminuria.  Traces  of  it  are  contained  even  in  normal 
urine.  _ Occasionally,  "sugar-puncture"  in  animals  is  followed  by  the  appearance 
of  inosite  instead  of  dextrose  in  the  urine.  For  the  detection  of  inosite,  the 
dextrose  is  removed  by  fermentation,  and  albumin  by  boiling  after  addition  of 
a  few  drops  of  acetic  acid  and  sodium  sulphate.  Of  the  filtrate,  a  few  cubic 


FIG.  162. — A,  crystals  of  cystin;  B,  of  calcium  oxalate;  c,  hour- 
glass shaped  crystals  of  calcium  oxalate. 


CYSTIN,    LEUCIN,    TYROSIN. 


503 


centimeters  are  evaporated  in  a  porcelain  dish. down  to  a  few  drops;  then  2  drops 
of  a  solution  of  mercuric  nitrate  (titration-solution  according  to  J.  v.  Liebig) 
are  added.  A  yellow  precipitate  takes  place.  If  this  is  spread  out  and  further 
carefully  heated  to  a  point  beyond  desiccation,  a  dark-red  color  appears,  which 
on  cooling  gradually  disappears. 

The  sugar  may,  in  rare  cases,  also  give  rise  to  pneumaturia,  fermentation  by 
microbes  causing  the  development  of  carbon  dioxid. 


CYSTIN. 

Cystin,  C6H12N2S2O4,  is  a  levorotatory  body  that  occurs  normally  in  [traces 
in  the  urine  and  but  rarely  in  considerable  amount.  It  appears  in  the  form  of 
colorless,  six-sided  plates  (Fig.  162,  A),  in  children  also  forming  concretions. 
Cystin  is  insoluble  in  water,  alcohol,  and  ether;  readily  soluble  in  ammonia,  after 
the  evaporation  of  which  it  crystallizes  out.  According  to  Baumann  and  Preusse, 
there  exist  intermediary  products 
of  metabolism  that  contain  the 
material  necessary  for  the  forma- 
tion of  cystin.  When  the  metab- 
olism is  normal,  these,  however, 
undergo  further  change ;  and  their 
sulphur  appears  in  the  urine  ox- 
idized as  sulphuric  acid.  In  rare 
cases  this  oxidation  fails  to  take 
place;  and  then  the  sulphur  ap- 
pears in  the  urine  as  cystin.  In 
cases  of  phosphorus-poisoning  the 
cystin  is  increased. 


LEUCIN,  C6H13NOo,  AND  TY- 
ROSIN, C9HnN03. 

Both  of  these  bodies,  whose 
development  has  been  referred  to 
in  the  consideration  of  pancreatic 
digestion,  are  present  in  traces  in 
normal  urine.  They  occur  to- 
gether in  somewhat  larger  amount 
in  association  with  derangements 
in  the  function  of  the  liver-cells 
(acute  yellow  atrophy  of  the  liver,  phosphorus-poisoning) .  As  the  elimination  of 
urea  is  generally  diminished  at  the  same  time,  it  may  be  concluded  that  the  liver 
is  the  seat  of  the  formation  of  urea. 

Leucin,  which  separates  either  spontaneously  in  the  precipitate  or  only  after 
evaporation  of  an  alcoholic  extract  of  the  inspissated  urine,  appears  in  the  form 
of  yellowish-brown  spheres  (Fig.  163,  a  a) ,  occasionally  with  concentric  radiation 
or  provided  with  fine  points  at  the  periphery.  When  heated  dry  leucin  sublimes 
without  fusing. 

Tyrosin  forms  silky,  colorless  sheaves  of  needles  (Fig.  163,  b  6).  If  a  solution 
of  tyrosin  be  boiled  with  Millon's  reagent,  there  results  at  first  a  pretty  red  color, 
and  shortly  afterward  a  deep  brownish-red  precipitate.  If  tyrosin  is  gently 
heated  with  a  few  drops  of  concentrated  sulphuric  acid,  it  is  dissolved  with  the 
development  of  a  transitory  deep-red  color.  If  it  now  be  diluted  with  water,  and 
barium  carbonate  be  added  to  the  point  of  neutralization,  the  mixture  boiled 
and  filtered,  and  dilute  iron  chlorid  added  to  the  filtrate,  a  violet  color  appears. 
Dissolved  in  hot  water,  addition  of  quinone  produces  a  red  color. 


FIG.  163. — a  a,  Lcucin-spheres;  b  b,  tyrosin-sheaves;  c,  double 
spheres  of  ammonium  urate. 


SEDIMENTS  IN  THE  URINE. 

Both  in  normal,  as  well  as  in  pathological  urine,  precipitates  may  form  at 
the  bottom  of  the  vessel;  and  these  are  designated  sediments.  They  are  either 
organized  or  unorganized. 


5°4 


ORGANIZED    SEDIMENTS. 


ORGANIZED  SEDIMENTS. 

(A)  Sediment  of  blood:  derived  from,  erythrocytes  and  leukocytes  (Figs.  157, 
158,  159,  160),  occasionally  also  shreds  of  tibrin  (Figs.  6,  7). 

(B)  Pus-corpuscles,  in  greater  or  lesser  amount  in  association  with  catarrhal 
or  inflammatory  processes  in  the  urinary  passages,  entirely  resemble  the  leukocytes 
(Figs.  6,   7).     Marked,   persistent    admixture    of  pus   is   indicative    of    profound 
parenchymatous   suppuration;   numerous   mononucleated   leukocytes,    of   disease 
of  the  kidneys.     Demonstration. — If  the  supernatant  fluid  be  poured  off  and  a  bit 
of  potassium  hydrate  be  dissolved  in  the  sediment,  the  pus  is  converted  into  a 
vitreous,  ropy  mass,  later  becoming  more  consistent   (alkali-albuminate) .    Mucus 
treated  in  this  manner  is  dissolved  into  a  thin  fluid  admixed  with  flakes. 

(C)  Epithelial  cells  of  varied  shape  and  not  always  distinguishable  as  to  the 
source  whence  they  are  derived.     They  are  more  abundant  in  the  presence  of 
catarrhal  conditions  in  the  parts  in  question.     In  the  urine  of  women,  pavement 
epithelial  cells  from  the  vagina  are  also  present.     The  spermatozoids  likewise  are 
included  among  epithelial  structures. 

(D)  Lower  forms   of  organisms.     The   freshly   collected  urine   from   healthy 


FIG.  164.-^,  Molds;  /,  budding-fungi  (yeast);  d  g, 
bacteria  (micrococci  and  bacilli);  a  b  c,  uric  acid 
(after  v.  Jaksch). 


FIG.  165. — Epithelial  Tube-casts. 


persons  always  contains  many  microorganisms,  which,  however,  have  probably 
been  washed  away  from  the  urethral  mucous  membrane.  They  are  principally 
large  or  small  diplococci.  In  cases  of  gonorrhea,  gonococci  thus  gain  entrance 
into  the  urine.  Lower  forms  of  organisms  may  also  appear  in  the  urinary  pas- 
sages, as,  for  instance,  in  the  bladder,  when  their  germs  have  been  introduced  by 
means  of  unclean  catheters.  The  following  varieties  may  be  distinguished: 

1.  Schizomycetes    (fission-fungi).     In    pathological    cases    bacteria   may    gain 
entrance  into  the  urinary  tubules  and  the  urine  from  the  blood.     Bacterial  cul- 
tures injected  artificially  into  the   vessels   are  in  part   eliminated  through  the 
kidneys.     In  urine  undergoing  alkaline  fermentation,  both  micrococci  and  rod- 
shaped  bacteria  or  bacilli   appear  (Fig.  164).     The   sarcinae   are  further  included 
among  schizomycetes. 

2 .  Saccharomycetes  (fermentative  germs) :    (a)    The  germ  of  acid  fermentation 
of  urine  (saccharomyces  urinas) :    small  vesicular  cells,  arranged  partly  in  groups, 
partly  in  rows  (Figs.  153,  a;    Fig.  164,  /).      (6)   Yeast  (saccharomyces  fermentum, 
Fig.  140)  is  present  in  diabetic  urine. 

3.  Phycomycetes  (molds)  appear  in  putrid  urine  as  mold-formations  (Fig.  164,  r). 
They  are  without  significance. 

(E)  Of  great  significance  in  the  diagnosis  of  certain  diseases  of  the  kidney  is 
the  occurrence  of  so-called  urinary  cylinders,  that  is,  casts  of  the  urinary  tubules. 
If  these  structures  are  relatively  thick  and  rather  straight,  they  are  probably 


ORGANIZED    SEDIMENTS. 


505 


derived  from  the  collecting  tubules  of  the  kidney;    while  if  they  are  thinner  and 
tortuous,  their  source  is  suspected  to  be  the  convoluted  tubules. 

^  Various  kinds  of  tube-casts  can  be  distinguished:  i.  Epithelial  casts  (Fig.  165), 
which  consist  of  coherent  and  desquamated  cells  of  the  urinary  tubules.  They 
indicate  that  no  profound  change  has  as  yet  taken  place  within  the  kidney,  but 
that,  as  in  catarrhal  inflammatory  states  of  mucous  membranes,  the  epithelial 
cells  are  in  process  of  desquamation.  2.  Hyaline  tube-casts  (Fig.  171)  are  com- 
pletely homogeneous  and  transparent.  They  are  most  readily  demonstrated  by 
addition  of  a  solution  of  iodin  to  the  preparation.  They  are  generally  long  and 
narrow;  occasionally,  they  present  fine  disseminated  points,  or  fat-granules  (finely 
granular  tube-casts,  Fig.  169).  They  appear  not  to  be  derived  from  a  transud.a- 
tion  from  the  blood,  but  as  a  result  of  the  secretory  activity  of  the  epithelial 


FTG.  166. — Blood-casts. 


FIG.    167. — Casts  of   Leukocytes 
(after  v.  Jaksch). 


FIG.  168. — Acid  Sodium  Urate  in 
the  Form  of  Tube-casts. 


FIG.  169. — Finely  Granular  Tube- 
casts. 


FIG.     170. — Coarsely     Granular 
Tube-casts  (after  v.  Jaksch) 


FIG.  171. — a.  Hyaline  tube-cast: 
b,  hyaline  tube-cast  with 
leukocytes;  c,  hyaline  tube- 
cast  with  renal"  epithelium 
(after  v.  Jaksch). 


cells  of  the  urinary  tubules.  3.  Darkly  granular  tube-casts  (Fig.  170),  brownish 
yellow,  opaque,  and  consisting  wholly  of  a  granular  mass,  are  usually  somewhat 
wider  than  hyaline  tube-casts.  Marked  variations  of  the  latter  occur.  Not 
rarely,  they  exhibit  fattily  degenerated  or  atrophic  epithelial  cells  of  the  urinary 
tubules.  4.  Amyloid  tube-casts  occur  in  cases  of  amyloid  degeneration  of  the 
kidneys.  They  have  a  waxy  luster,  are  completely  homogeneous  (Fig.  171,  u) 
and  yield,  with  sulphuric  acid  and  solution  of  iodin,  the  blue  color  of  amyloid 
reaction.  5.  Blood-casts,  consisting  entirely  of  coagulated  blood,  with  distinct 
blood-corpuscles,  occur  in  association  with  capillary  hemorrhage  into  the  tissue 
of  the  kidney  (Fig.  166).  These  are  allied  to  the  casts  found  in  connection  with 
hemoglobinuria ;  as,  for  instance,  after  transfusion  of  heterogeneous  blood.  They 
consist  of  hemoglobin  or  of  its  globulin  tinged  with  hematin.  The  tube-casts 
stained  yellow  that  have  been  observed  in  conjunction  with  icterus  probably  also 
result  from  the  albumin  of  dissolved  blood-corpuscles.  Urine  containing  tube- 
casts  is  always  albuminous. 


506  SEDIMENTS    IN    THE    URINE. 

Tube-casts  of  leukocytes  are  observed  in  connection  with  suppurative  pro- 
cesses in  the  urinary  tubules  (Fig.  167).  U rates  arranged  in  the  shape  of  tube- 
casts  are  without  significance  (Fig.  168);  as  well  as  cylindroids,  formed  of  mucus, 
with  which  short  strands  of  mucus  arising  in  the  ureter,  the  bladder,  the  prostate, 
the  uterus,  and  the  vagina,  may  be  confounded. 

UNORGANIZED  SEDIMENTS. 

The  unorganized  sediments,  in  part  crystalline,  in  part  amorphous,  have  already 
received  consideration  in  the  discussion  of  the  individual  constituents  of  the 


SCHEMATIC  RESUME  FOR  THE  RECOGNITION  OF  ALL  OF 
THE  SEDIMENTS  IN  THE  URINE. 

I.  In  acid  urine  there  may  be  found — • 

i.  An  amorphous  crumbling  sediment, 

(a)  Which  is  soluble  in  the  heat  and  is  again  precipitated  in  the  cold,  and 
which,  on  addition  of  a  drop  of  acetic  acid  to  the  microscopic  preparation,  forms 
crystals  of  uric  acid,  which  often  has  a  reddish  color  (brick-dust  powder) . 

This  sediment  consists  of  sodium  or  potassium  biurate  (Fig.  153). 

(6)  The  sediment  is  not  dissolved  by  heat,  but  on  addition  of  acetic  acid, 
and  without  effervescence.  This  is  probably  tribasic  calcium  phosphate. 

(c)    Highly  refracting  granules,  occurring  occasionally  and  soluble  in  ether. 


$ 


FIG.  172. — a,  Finely  granular  calcium  carbonate;  b  and  c,  crystalline  neutral  calcium  phosphate. 

are  fat-globules.  Fat  occurs  in  the  urine  particularly  in  conjunction  with  the 
presence  of  a  round-worm  (filaria  sanguinis  hominis)  in  the  blood  (only  in  for- 
eigners or  travelers) ;  further,  occasionally  together  with  sugar  in  the  urine,  in 
tuberculous  patients;  in  cases  of  phosphorus-poisoning,  of  yellow  fever,  of  pyemia; 
after  protracted  suppuration;  and,  finally,  after  injections  of  fat  or  milk  into  the 
circulation.  Fatty  degeneration  in  some  portion  of  the  urinary  apparatus,  ad- 
mixture of  pus  from  old  abscesses,  and  severe  injuries  to  bones,  should  further 
be  taken  into  consideration.  In  this  connection,  attention  should  be  given  also 
to  cholesterin  and  lecithin.  Rarely,  the  amount  of  fat  in  the  urine  may  be  so 
marked  as  to  give  rise  to  a  creamy  appearance — chyluria. 

2 .  A  sediment  consisting  of  crystals : 

(a)    Uric  acid  (Fig.  148  and  Fig.  153 — whetstone-shaped  crystals). 

(6)  Calcium  oxalate  (Fig.  153,  Fig.  162,  B} — envelop-shaped  crystals,  insolu- 
ble on  addition  of  acetic  acid. 

(c)  Cystin — extremely  rare  (Fig.  162,  A). 

(d)  Leucin  and  tyrosin — of  great  rarity  (Fig.  163). 
II.   In  alkaline  urine  there  may  be  present: 

1.  The  sediment  is  wholly  amorphous  and  crumbling;    it  consists  of  tribasic 
calcium  phosphate.     It  is  soluble  on  addition  of  acids  without  effervescence. 

2.  The  sediment  is  crystalline,  or,  at  least,  of  characteristic  form. 


URINARY    CONCRETIONS. 


507 


(a)  Ammonia-magnesium  phosphate  (Figs.  173,  160,  154):  Large  coffin-lid 
crystals,  immediately  soluble  on  addition  of  acids. 

(6)  Small  globules,  yellowish  in  reflected  light,  dark  in  transmitted  light, 
often  provided  with  points;  thorn-apple  or  morning-star  shaped,  together  with 
amorphous  granules  (Figs.  154  and  175).  These  consist  of  acid  ammonium  urate. 

(c}  Calcium  carbonate:  Small  whitish  globules,  biscuit-shaped  or  arranged 
side  by  side  in  irregular  masses,  together  with  amorphous  granules.  Efferves- 


ft  %.* 

FIG.  173. — Ammonio-magnesium  Phosphate. 


V  # 


FIG.    174. — Imperfectly   Developed    Crystals   of   Am- 
monio-magnesium Phosphate. 


FIG.  175. — Acid  Ammonium  Urate  (after  v.  Jaksch).  FIG.  176. — Basic  Magnesium  Phosphate. 


cence  takes  place  on  addition  of  acids,  also  in  the  microscopic  preparation  (Fig. 
172,  a). 

(d)  Leucin  and  tyrosin  are  extremely  rare  (Fig.  163).  Crystals  of  neutral 
calcium  phosphate  (Fig.  172,  c),  with  their  spear-shaped  extremities  in  contact, 
are  also  rare,  as  well  as  plates  of  basic  magnesium  phosphate  (Fig.  176). 

Organic  sediments  may  occur  both  in  acid,  as  well  as  in  alkaline,  urine.  Among 
them,  pus-corpuscles  are  present  especially  in  alkaline  urine,  and  the  lower  forms 
of  vegetable  organisms  likewise  predominate  under  such  circumstances. 


URINARY  CONCRETIONS. 

Urinary  concretions  vary  in  size  from  that  of  a  grain  of  sand  or  a  pebble  to 
that  of  a  fist.  They  are  encountered  in  the  bladder,  also  in  the  pelvis  of  the  kid- 
ney, in  the  ureters,  and  in  the  prostatic  sinus.  All  urinary  concretions  contain  a 
framework  of  organic  structure  uniting  the  particles  of  the  formation  into  a 
coherent  mass.  They  are  divided,  according  to  Ultzmann,  as  follows: 

1.  Concretions  whose  nucleus  consists  of  the  sediment  formed  in  acid  urine — 
primary  calculus-formation.     All  of  these  arise  primarily  in  the  kidney  and  pass 
thence  into  the  bladder,  where  they  undergo  enlargement  in  accordance  with  the 
development  of  the  crystals  in  the  urine. 

2.  Calculi  that  have  for  a  nucleus  either  the  sediments  found  in  alkaline  urine 


508  URINARY    CONCRETIONS. 

or  a  foreign  body — secondary  calculus-formation.  These  develop  in  the  bladder 
itself. 

Primary  calculus-formation  takes  place  from  free  uric  acid  in  the  form  of 
sheaves  as  a  nucleus  (Fig.  148,  7),  and  surrounded  by  layers  of  calcium  oxalate. 
Secondary  calculus- format-ion  takes  place  in  neutral  urine  from  calcium  carbonate 
and  crystalline  calcium  phosphate,  in  alkaline  urine  from  acid  ammonium  urate, 
ammonio-magnesium  phosphate,  and  amorphous  calcium  phosphate. 

Chemical  examination  next  determines  whether  or  not  the  particles  of  the 
concretion  are  combustible  upon  a  platinum  plate. 

I.  Combustible  concretions  can  consist  only  of  organic  matter. 

(a)  If  the  murexid-test  yields  a  positive  reaction,  the  concretion  contains 
uric  acid.     Uric-acid   calculi   are   common,   often   of  considerable   size,    smooth, 
rather  hard,  and  in  color  from  yellow  to  reddish  brown. 

(b)  If  another  specimen  on  boiling  with  potassium  hydrate  yields  an  odor 
of  ammonia,  and  if  moist  turmeric-paper  held  in  the  vapor  becomes  brown,  or  a 
glass  rod  moistened  with  hydrochloric  acid  and  held  over  the  vapor  yields  fumes 
of   ammonium  chlorid,  the    concretion   contains   ammonium    urate.      If  this  test 
yields   a  negative    result,  the    concretion    contains   pure    uric    acid.     Calculi  of 
ammonium  urate   are  rare,   generally  small,  of  earthy  consistence,  and  in  color 
between  clay- yellow  and  whitish. 

(c)  Should  the  xanthin-reaction  be  positive,  this  substance  is  present,  though 
it  is  rare.     In  one  instance,  indigo  has  been  found  in  a  calculus. 

(d)  If  cystin-crystals  (Fig.   162,  .4)  are  developed  after  solution  in  ammonia 
and  evaporation  of  the  latter,  the  presence  of  this  rare  substance  is  demonstrated. 

(e)  Concretions  composed  of  blood-coagula  or  fibrinous  flakes,  without   any 
crystallization  whatever,   are    rare.     If  burned,  they  yield    an    odor  of    singed 
hair.     They  are  insoluble  in  water,  alcohol,  and  ether.    They  are  soluble  in  potas- 
sium hydrate,  out  of  which  they  are  reprecipitable  by  acids. 

(f)  Urostealith  is  the  name  that  has  been  given  to  the  substance  composing 
rarely    found  concretions    which    in   the    fresh    state    are    soft    and    elastic,    re- 
sembling India  rubber.     On  drying,  they  become  brittle  and  hard,  and  in  color 
between  brown  and  black.     Warmth  causes  them  to  become  softer  again,  and 
they  melt  when  heated.     Solution  takes  place  in  ether,  the  residue  of  the  evapo- 
rated ethereal  solution  becoming  violet  in  color  on  further  heating.     Urostealith 
is  dissolved  by  heated  potassium-hydrate  solution,  with  saponification.     Concre- 
tions containing  fat  or  cholesterin  are  rare. 

II.  If  concretions  are  only  in  part  combustible,  with  a  residue,  they  contain 
organic  and  inorganic  matters. 

(a)  A  portion  of  the  calculus  is  reduced  to  powder,  and  this  is  boiled  with 
water  and  filtered  hot.     Urates  that  may  be  present  undergo  solution.     In  order 
to  determine  whether  the  uric  acid  is  combined  with  sodium,  potassium,  calcium, 
or  magnesium,  the  filtrate  is  evaporated  and  fused.     The  ash  is  examined  spectro- 
scopically  (flame-spectra) ,  and  by  this  means  sodium  and  potassium  are  recognized. 
Magnesium  urate  and  calcium  urate  are  transformed  by  fusing  into  carbonates.     In 
order  to  separate  the  two,  the  ash  is  dissolved  in  dilute  hydrochloric  acid,  and 
filtration  is  practised.     The  filtrate  is  neutralized  with  ammonia;  then  again  dis- 
solved with  a  few  drops  of  acetic  acid.     Addition  of  ammonium  oxalate  precipi- 
tates calcium  oxalate.     Filtration  is  now  practised,  and  to  the  filtrate  are  added 
sodium  phosphate  and  ammonia.       By  this  means  the  magnesia  is  separated  as 
ammonio-magnesium  phosphate. 

(b)  Calcium  oxalate  occurs  principally  in  children,  either  as  small,  smooth, 
pale   hempseed-calculi,    or  in   dark,  nodular,   hard  mulberry-calculi.       It   is  not 
affected  by  acetic  acid,  is  soluble  in  mineral  acids,  without  effervescence;    and  is 
reprecipitated  by  ammonia.     When  fused  upon  a  platinum  plate,  the  specimen 
becomes  black;  it  is  then  burned  white  to  calcium  carbonate,   which  undergoes 
effervescence  upon  addition  of  acid. 

(c)  Calcium   carbonate  occurs   generally  in  whitish-gray,   earthy,   chalk-like, 
rather  rare  calculi  that  usually  are  multiple.    It  is  soluble  in  hydrochloric  acid  with 
effervescence.   .  When  fused,  it  becomes  at  first  black,  from  admixture  of  mucus; 
but  soon  afterward  white. 

(d)  Ammonio-magnesium  phosphate  and  basic  calcium  phosphate  are  usually 
united  in  soft,  white,   chalky  stones,  which   at  times  attain   quite  considerable 
size.     Such  calculi  imply  a  long  sojourn  in  ammoniacal  urine.     The  first  substance 
yields  an  odor  of  ammonia  when  heated,  and  more  distinctly  when  heated  with 
potassium  hydrate.      It   is   soluble  in   acetic   acid  withotit   effervescence,   and   is 
precipitated  in  crystalline  form  from  this  solution  on  addition  of  ammonia.     When 


PHYSIOLOGICAL    PROCESS    OF    URINARY    SECRETION.  509 

fused,  the  specimen  melts  to  a  white,  porcelain-like  mass.  Basic  calcium  phos- 
phate does  not  effervesce  with  acids.  The  solution  in  hydrochloric  acid  is  pre- 
cipitated by  ammonia.  The  solution  in  acetic  acid  yields  calcium  oxalate  on 
addition  of  ammonium  oxalate.  In  order  to  isolate  calcium  and  magnesium  from 
such  stones,  the  process  described  in  paragraph  (a)  should  be  followed. 

(e)  Neutral  calcium  phosphate  is  rarely  found  in  calculi,  but,  on  the  other 
hand,  not  rarely  in  urinary  sand.  Such  concretions  resemble  the  earthy  phos- 
phates in  physical  and  chemical  properties,  except  that  they  contain  no  magnesia. 

THE  PHYSIOLOGICAL  PROCESS  OF  URINARY  SECRETION. 

The  two  older  and  most  important  theories  of  secretion  will  be 
mentioned:  (i)  Bowman  held  that  the  glomeruli  secrete  only  water, 
and  that  the  epithelial  cells  of  the  urinary  tubules  through  their  glandu- 
lar activity  furnish  the  specific  urinary  elements,  which  the  onflowing 
urinary  water  washes  out  of  the  cells.  (2)  C.  Ludwig  assumed  that  a 
dilute  urine  is  secreted  in  the  capsules.  Passing  through  the  urinary 
tubules,  this,  by  endosmosis,  returns  water  to  the  blood,  which  is  more 
deficient  therein,  and  to  the  lymph  of  the  kidney,  and  thus  becomes 
reduced  to  normal  consistence. 

The  secretion  of  the  urine  in  the  kidneys  depends,  however,  not  alone 
upon  physically  definable  influences,  but  it  must  rather,  in  accordance 
with  a  series  of  acquired  facts,  be  assumed  that  in  addition  the  vital 
activity  of  special  secretory  cells  plays  a  prominent  role.  The  physical 
or  chemical  forces  obviously  underlying  the  latter  have  not  as  yet  been 
determined.  The  secretion  includes  (i)  the  urinary  water,  and  (2)  the 
urinary  elements  dissolved  therein.  Both  together  constitute  the 
totality  of  the  secretion.  The  amount  of  urinary  water  secreted  in  the 
glomeruli  determines  principally  the  amount  of  urine,  while  the  amount 
of  substances  dissolved  in  the  urinary  water  determines  the  concen- 
tration of  the  urine. 

The  amount  of  urinary  water,  which  is  secreted  principally  in  the 
capsules,  depends,  in  the  first  place,  upon  the  blood-pressure  in  the 
distribution  of  the  renal  artery;  and,  accordingly,  is  governed  by  the 
laws  of  filtration.  The  amount  of  urinary  water  furnished  is,  however, 
not  dependent  upon  the  hydrostatic  pressure  alone,  but  the  functional 
activity  of  the  cells  lining  the  glomerulus  is  also  of  influence.  In  ad- 
dition to  the  water,  a  certain  amount  of  the  salts  occurring  in  the  urine 
is  secreted  in  the  glomerulus;  albumin,  however,  is  retained.  In 
consideration  of  the  functional  activity  of  the  cells,  the  amount  of 
urinary  water  must  depend  also  in  part  upon  the  rapidity  with  which 
new  blood  conveying  the  material  for  secretion  passes  to  the  glomeruli; 
and,  in  part,  upon  the  amount  of  urinary  elements  and  water  contained 
in  the  blood. 

The  independent  activity  of  the  secretory  cells  is  present  only  when  their 
vitality  is  intact.  It  is  paralyzed  in  consequence  of  transitory  occlusion  of  the 
renal  artery.  For  this  reason,  the  kidney  no  longer  secretes  under  such  circum- 
stances, even  when  the  circulation  is  restored  after  removal  of  the  compression. 
The  observation  that  the  urine  is  not  rarely  found  to  have  a  higher  temperature 
than  the  arterial  blood  is  also  indicative  of  this  activity. 

The  dependence  of  the  secretion  upon  the  blood-pressure  will  be 
made  clear  by  the  following  observations : 

i.  Increase  of  the  total  contents  of  the  vessels,  in  consequence  of 
which  the  tension  in  the  -vascular  system  must  increase,  increases  the 


510  PHYSIOLOGICAL    PROCESS    OF    URINARY    SECRETION. 

amount  of  filtered  urinary  water.  Injections  of  water  directly  into  the 
vessels,  or  the  ingestion  of  considerable  quantities  of  fluid,  operates  in 
this  direction.  If  the  increase  in  blood-pressure  exceeds  a  certain 
level,  albumin  may  even  pass  into  the  urine.  Conversely,  loss  of  water 
in  consequence  of  profuse  sweating  or  diarrhea,  or  copious  venesection, 
as  well  as  prolonged  thirst,  will  cause  diminution  in  the  amount  of 
urinary  secretion.  The  circumstance  that  the  blood-pressure  does  not 
rise  constantly  after  free  drinking  is  evidence  of  the  functional  activity 
of  the  cells  of  the  glomeruli,  as  is  also  the  fact  that  the  amount,  of  urine  is 
not  increased  after  large  transfusions. 

2.  Diminution  in  the  vascular    capacity  will    operate   in  a  similar 
manner:   contraction  of   the    cutaneous  vessels  under  the  influence  of 
cold,  stimulation  of  the  vasomotor  center  or  of  considerable  areas  of 
the  vasomotor  nerves,  ligation  or  compression  of  arteries  of  large  size, 
envelopment  of  the  extremities  in  tight  bandages.     Naturally  the  op- 
posite conditions  will  be  followed  by  a  reduction  in  the  amount  of  urine  : 
the  influence  of  heat  upon  the  skin  to  the  point  of  redness  and  dila- 
tation of  the  vessels,  enfeeblement  of  the  stimulation  of  the  vasomotor 
center,  or  paralysis  of  considerable  areas  of  the  vasomotor  nerves. 

3.  Increased  cardiac  activity,  in  consequence  of  which  the  tension 
and  the  rapidity  of  the  current  in  the  arterial  distribution  are  increased, 
augment  the  amount  of  urine.     Conversely,  enfeeblement  of  the  heart's 
action  (paresis  of  the  motor  nerves  of  the  heart,  disease  of  the  heart- 
muscle,  valvular  lesions)   diminishes  the  amount  of  urine.     Artificial 
irritation  of  the  vagi,  in  consequence  of  which,  with  slowing  of  the  heart- 
beats, the  average  blood-pressure  fell  in  animals  from  130  to  100  mm. 
of  mercury,  with  slowing  of  the  pulse,  was  followed  by  a  reduction  in 
the  amount  of  urine  to  about  one-fifth.      At  40  mm.  of  aortic  pressure 
the  secretion  of  urine  ceases. 

4.  The  amount  of  urine  secreted  rises    or  falls  with    increasing  or 
diminishing  fulness  of  the  renal  artery.     Even  moderate  compression 
of  the  artery  in  animals  is  followed  by  distinct  reduction. 

Pathological. — In  the  presence  of  fever,  there  is  diminished  fulness  of  the 
renal  vessels,  with  consecutive  reduction  in  the  amount  of  urine.  The  observation 
is  of  especial  significance  for  the  pathogenesis  of  certain  diseases  of  the  kidney 
that  ligature  of  the  renal  artery,  even  if  continued  for  only  two  hours,  causes 
necrosis  of  the  epithelium  of  the  urinary  tubules.  In  case  of  arterial  anemia  of 
longer  duration,  necrosis  of  the  entire  renal  structure  takes  place.  Ribbert  found 
the  epithelial  cells  of  the  convoluted  tubules  greatly  altered  after  compression  of 
the  renal  artery  for  some  time. 

Most  diuretic  medicaments  act  in  one  or  another  of  the  directions 
indicated.  In  case  of  increased  diuresis,  the  lumen  of  the  urinary 
tubules  is  increased. 

The  pressure  within  each  afferent  vessel  must  be  relatively  large,  because  (i) 
the  duplicate  capillary  arrangement  in  the  kidney  offers  considerable  resistance, 
and  because  (2)  the  efferent  vessel  has  a  much  narrower  lumen  than  the  afferent 
vessel.  In  accordance  with  these  facts,  an  excretion  from  the  blood  into  the 
capsules  of  the  urinary  tubules  will  take  place  from  the  capillary  loops  of  the 
glomerulus  in  consequence  of  the  filtration-pressure.  Dilatation  of  the  afferent 
vessels,  as,  for  instance,  from  the  action  of  the  nerves  upon  the  unstriated  muscular 
fibers,  will  increase  the  filtration-pressure;  while  constriction  will  diminish  the 
secretion.  If  the  reduction  in  the  pressure  has  become  so  considerable  that  the 
blood-current  in  the  renal  vein  is  distinctly  slowed,  the  secretion  of  urine  begins 
to  diminish.  It  is  a  remarkable  fact  that  occlusion  of  the  renal  veins  completely 
suppresses  the  secretion.  C.  Ludwig  has  concluded  from  this  that  the  secretion 


PHYSIOLOGICAL    PROCESS    OF    URINARY    SECRETION  511 

of  fluid  accordingly  can  not  take  place  from  the  true  renal  capillaries,  because 
the  blood-pressure  in  these  must  be  increased  by  occlusion  of  the  veins,  and  this 
would  cause  increased  nitration.  On  the  other  hand,  the  observation  mentioned 
would  indicate  that  the  secretion  takes  place  from  the  capillaries  of  the  glomerulus. 
The  venous  stasis  in  the  efferent  vessel  distends  this  vessel,  which  arises  in  the 
center  of  the  convolution,  to  such  a  degree  that  the  capillary  loops  are  pushed 
together  against  the  wall  of  the  capsule  and  compressed,  so  that  no  nitration  can 
take  place  from  them.  Whether  some  fluid  is  given  off  through  the  urinary 
tubules,  especially  the  convoluted  tubules,  is  as  yet  undecided. 

The  amount  of  urine  and  the  amount  of  contained  urea  are  diminished  by 
venous  stasis  in  the  kidneys.  The  amount  of  sodium  chlorid  remains  constant, 
while  that  of  albumin  in  pathological  urine  increases. 

As  the  blood-pressure  in  the  renal  artery  equals  between  120  and 
140  mm.  of  mercury,  and  the  urine  in  the  ureter  is  propelled  under 
exceedingly  slight  pressure,  so  that  it  is  no  longer  capable  of  escaping 
against  a  counter-pressure  of  from  10  to  40  mm. — provided  by  a  manome- 
ter introduced  into  the  ureter  divided  transversely — it  must  be  clear  that 
the  blood-pressure  is  also  capable,  as  a  vis  a  tergo,  of  forcing  the  stream 
of  urine  through  the  ureter. 

The  degree  of  concentration  of  the  urine  depends  upon  the  amount 
of  the  constituents  in  solution  passing  out  of  the  blood  into  the 
urinary  water.  The  cells  of  the  convoluted  urinary  tubules  appear  to 
take  up  these  substances  from  the  blood  by  means  of  an  independent 
activity.  The  urinary  water  passing  through  the  urinary  tubules  from 
the  glomerulus,  and  containing  only  readily  diffusible  salts,  later  takes 
up  these  substances  out  of  the  cells  of  the  convoluted  tubules  by  a  pro- 
cess of  extraction.  The  independent  activity  of  the  cells  is  indicated 
by  the  following  facts : 

i.  Sulphindigotate  of  sodium  (indigocarmin),  which,  when  injected 
into  the  blood,  passes  into  the  urine,  can  be  recognized  in  the  interior  of 
the  cells  of  the  urinary  tubules,  but  not  in  the  capsules.  Further  on, 
this  substance  is  visible  in  the  lumen  of  the  urinary  tubules,  whither  it 
is  washed  by  the  current  of  urinary  water  from  the  glomerulus.  If, 
in  such  an  experiment,  the  cortical  layer  containing  the  capsules  has 
been  removed  two  days  previously  by  cauterization  or  with  the  knife, 
the  blue  pigment  will  have  remained  in  the  convoluted  tubules.  It 
will  not  have  advanced  onward,  as  the  current  of  water  from  the  de- 
stroyed glomeruli  is  wanting.  This  observation  thus  indicates  that 
the  glomeruli  furnish  principally  the  urinary  water,  and  the  convoluted 
tubules  the  specific  urinary  elements.  Heidenhain  and  Sauer  observed 
also  urates  (injected  into  the  blood)  secreted  by  the  convoluted  tubules. 
Nussbaum  has  also  demonstrated  that  urea  is  not  secreted  by  the  cap- 
sules, but  by  the  urinary  tubules.  Mobius  found  the  same  with  respect 
to  the  biliary  pigment,  Glaevecke  with  respect  to  the  iron  salts  of  the 
vegetable  acids  when  injected  subcutaneously,  and  Landois  first 
described  the  same  condition  with  respect  to  hemoglobin.  After  in- 
fusion of  milk  into  the  vessels,  Landois  encountered  numerous  fat- 
globules  within  the  cells  of  the  urinary  tubules. 

It  appears  that  the  capsules  may  also  take  part  in  the  process  only  after 
abundant  secretion.  After  infusion  of  large  amounts  of  sodium  sulphindigotate 
and  after  the  observation  has  been  continued  for  some  time,  the  epithelium  of  the 
Malpighian  capsules  also  exhibits  the  blue  discoloration.  Likewise  in  the  presence 
of  albuminuria,  the  abnormal  elimination  of  albumin  takes  place  first  in  the  urinary 
tubules  and  later  in  the  capsules.  Also  hemoglobin  occurs  in  part  in  the  capsules. 
Egg-albumin  is  believed  by  Nussbaum  to  be  excreted  through  the  capsules. 


512  PHYSIOLOGICAL    PROCESS    OF    URINARY    SECRETION. 

Disse  studied  the  alterations  in  the  secretory  cells  during  their 
activity.  With  the  commencement  of  this  activity  the  cells  become 
larger,  and  bright  areas  of  the  protoplasm,  infiltrated  with  secretion, 
appear  as  halos  about  the  nucleus.  The  discharge  of  the  secretion  into 
the  lumen  of  the  tubules  takes  place  through  filtration.  The  brush- 
border  indicates  only  the  empty  cell ;  it  disappears  while  the  cell  is  being 
filled  with  secretion. 

Henle,  H.  Meckel,  Leydig,  and  Bial  observed  in  snails  constituents  of  the 
urine  (guanin)  within  the  cells  of  the  kidney. 

2.  Also  when,  either  after  ligation  of  the  ureter  or  in  consequence  of 
marked  reduction  in  blood-pressure  in  the  renal  artery  (after  division 
of  the  cervical  cord  or  venesection),  urinary  water  is  no  longer  secreted, 
the  substances  named  are,  nevertheless,  after  introduction  into  the 
blood,  seen  to  pass  over  into  the  urinary  tubules.  Injection  of  urea 
likewise  again  stimulates  the  secretion.  This  indicates  that  the  secre- 
tory activity  takes  place  independently  of  the  filtration-pressure. 

The  independent  vital  activity  of  the  glandular  cells  of  the  urinary  tubules 
not  explainable  by  physical  processes  makes  it  impossible  to  consider  the  glandular 
tubules  as  a  simple  apparatus  resembling  physical  membranes.  This  is  shown 
also  by  the  following  experiment:  Abeles  permitted  the  circulation  of  arterial 
blood  to  continue  artificially  through  fresh,  living,  extirpated  kidneys.  Pale 
urinous  fluid  escaped  from  the  ureter  drop  by  drop.  If  urea  or  sugar  were  added 
to  the  circulating  blood,  the  vessels  became  dilated  and  the  secretion  contained 
the  admixed  substances  in  greater  concentration.  Thus,  also  the  surviving  kid- 
ney excretes,  in  concentrated  form,  substances  that  circulate  in  the  blood  in  a 
dilute  state.  The  same  observation  was  made  by  I.  Munk  in  analogous  experi- 
ments with  sodium  chlorid,  potassium  nitrate,  caffein,  grape-sugar,  and  glycerin, 
with  an  increase  in  the  total  amount  of  the  secretion.  Addition  of  caffein  or 
theobromin  to  the  circulating  blood  induces  an  increase  in  the  secretion,  stimu- 
lates, thus,  the  secretory  cells  themselves  to  increased  activity.  The  assumption 
of  vital  activity  alone  explains,  also,  why  the  serum-albumin  of  the  blood  does 
not  pass  into  the  urine,  although  egg- albumin  or  dissolved  hemoglobin,  intro- 
duced into  the  blood,  does  so  rapidly. 

Among  the  salts  that  occur  in  the  total  blood,  also  in  the  blood-corpuscles, 
naturally  only  those  in  solution  can  pass  over  into  the  urine.  Those  that  are 
united  to  proteids  or  in  the  cellular  elements  cannot  pass  over,  or  at  least  only 
after  decomposition.  This  fact  explains  the  difference  between  the  salts  of  the 
total  blood  and  those  of  the  urine.  The  urine  can,  likewise,  take  up  only  the 
gases  absorbed  into  the  blood;  and  not  those  in  chemical  combination. 

Should  stagnation  of  the  secretion  take  place  in  the  ureter,  as  after  ligation, 
and,  later,  in  the  urinary  tubules,  a  return  of  the  secretion  into  the  tissue  of  the 
kidney  and,  later,  into  the  blood  will  be  observed.  The  kidney  becomes  edem- 
atous,  in  consequence  of  distention  of  its  lymph-spaces.  The  secretion  is  altered, 
inasmuch  as,  first,  water  is  reabsorbed  into  the  blood;  then  the  sodium  chlorid 
in  secretion  is  diminished,  likewise  sulphuric  acid  and  phosphoric  acid,  and,  finally, 
also  the  urea.  Kreatinin  will  still  be  present  in  considerable  amount.  A  true 
secretion  of  urine,  later  on,  no  longer  takes  place. 

The  circumstance,  further,  is  noteworthy  that  the  two  kidneys  never  secrete 
symmetrically.  The  condition  is  one  of  alternation  in  activity  and  hyperemia. 
The  one  kidney  secretes  a  fluid  containing  a  larger  amount  of  water,  and, 
at  the  same  time,  more  sodium  chlorid  and  urea.  It  may  even  be  more 
acid.  v.  Wittich  observed  that  the  excretion  of  uric  acid  in  the  kidneys  of 
birds  does  not  take  place  uniformly  in  all  of  the  urinary  tubules,  but  only  in 
varying  areas.  The  extirpation  of  one  kidney  or  its  morbid  destruction  in  human 
beings  does  not  diminish  the  secretion.  There  occurs  increased  activity,  with 
enlargement  of  the  remaining  organ;  and  this  is  due  to  the  increased  functional 
demands  upon  the  secretory  cells  of  this  kidney. 


THE    PREPARATION    OF    THE    URINE.  513 


THE  PREPARATION  OF  THE  URINE. 

The  question  has  often  been  raised,  whether  the  urine  is  really  se- 
creted through  the  kidney,  or  whether  the  urinary  constituents  are  not 
in  part  prepared  by  the  kidney  itself.  The  following  experiments  will 
shed  light  upon  this  subject: 

1.  The  blood  already  contains  one  part  of  urea  in  from  3000  to  5000 
parts ;  but  the  blood  in  the  renal  vein  contains  less  urea  than  that  of  the 
artery.     This  fact  indicates  that  urea  is  excreted  from  the  blood. 

2.  After  extirpation  of  the  kidney — nephrectomy — or  ligation  of  its 
vessels,  urea  accumulates  in  the  blood  and  progressively  with  the  lapse 
of  time  to  between  ^-g-  and  -g-J-g-.     At  the  same  time,  fluids  containing 
urea  and  ammonia  are  vomited  and  discharged  with  the  stools.      Ani- 
mals die  after  such  profound  operations,  moreover,  within  from  one  to 
three  days. 

3.  If  the  ureters  are  ligated,  the  actual  secretion  of  the  kidneys  soon 
ceases.     After  this,  the  accumulation  of  urea  in  the  blood  likewise  in- 
creases, and,  indeed,  as  it   appears,  not   in  greater   amount  than   after 
nephrectomy.     Nevertheless,  it  is  possible  that  the  kidney,  in  its  meta- 
bolic activity,  does,  like  other  portions  of  the  body,  prepare  some  urea  in 
its  tissues. 

4.  The  blood  of  birds  contains  uric  acid  even  under  normal  con- 
ditions.    Ligation  of  the  ureters,  as  well  as  of  the  renal  vessels,  or 
gradual  destruction   of    the   secreting  renal    epithelium    by  means   of 
subcutaneous  injections  of  neutral  potassium  chromate,  is  followed  in 
birds  by  a  deposition  of  uric  acid  in  the  joints  and  tissues;  so  that  the 
serous   membranes   particularly  acquire    a  whitish  incrustation  there- 
from.    The  brain  remains  free.     Also  acid  combinations  of  uric  acid 
with  ammonia,    sodium,   and  magnesium   are   thus   deposited.     Extir- 
pation of  the  kidneys  in  serpents  gives  rise  to  the  same  phenomena  in 
lesser  degree. 

From  these  experiments  it  may  be  concluded  that  the  urea,  and  with 
it  probably  most  of  the  organic  constituents  of  the  urine,  are  excreted 
principally  through  the  kidneys,  but  are  not  prepared  in  them.  The 
seat  for  the  formation  of  all  of  these  substances  is  probably  to  be  re- 
ferred to  the  tissues.  The  urea  is  formed  from  decomposed  proteid,  and 
principally  in  the  liver.  As  a  result  of  experiments  with  birds  and 
serpents,  v.  Schroder  and  Colasanti  come  to  the  conclusion  that  the 
formation  of  uric  acid  cannot  be  assumed  to  take  place  exclusively  in 
any  definite  organ.  Urobilin  is  formed  from  hemoglobin. 

Little  is  known  concerning  the  physiological-chemical  processes  in  the  kidneys 
themselves.  Hippuric  acid  is  formed  in  part  in  the  kidney,  for  the  blood  of 
herbivora  contains  no  trace  thereof;  but  the  synthesis  of  this  substance  in  rabbits 
takes  place  also  in  other  tissues.  If  blood  to  which  sodium  benzoate  and  glycin 
have  been  added  is  passed  through  the  vessels  of  a  fresh  kidney,  hippuric  acid 
is  formed.  If,  further,  phenol  and  pyrocatechin  are  digested  with  fresh  renal 
tissue,  the  corresponding  sulphuric-acid  combinations  that  occur  in  the  urine  are 
formed.  The  latter,  it  is  true,  are  formed  also  by  similar  digestion  with  hepatic 
and  pancreatic  tissue  and  with  muscle.  From  these  observations  it  may  be  con- 
cluded that  in  the  body  the  substances  in  question  are  prepared  w'ithin  the 
kidneys  and  the  organs  named. 

The  kidneys  are  extremely  rich  in  water,  and  they  yield  an  alkaline  reaction. 
In  addition  to  serum-albumin,  globulin,  iiucleo-albumin,  albumin  soluble  in  sodium 
carbonate,  a  gelatin-yielding  substance,  fat  in  the  epithelial  cells  (principally  after 
33 


514  PASSAGE    OF    VARIOUS    SUBSTANCES    INTO    THE    URINE. 

the  ingestion  of  milk  and  meat) ,  the  elastic  sarcolemma-like  substance  of  the 
membrana  propria  of  the  urinary  tubules,  and  the  tissue-elements  of  the  vessels 
and  their  unstriated  muscles,  the  kidneys  contain  leucin,  xanthin,  hypoxanthin, 
kreatin,  taurin,  inosite,  cystin  (the  last  is  present  in  no  other  tissue) ;  and  of  these, 
the  majority  pass  into  the  urine  either  not  at  all  or  only  in  small  amount.  The 
presence  of  these  substances  indicates,  probably,  active  metabolism  in  the  kidneys; 
and  this  is  suggested  also  by  the  great  vessels  of  the  kidney.  During  the  secretion 
of  the  kidneys,  the  blood  of  the  renal  vein  is  said  to  become  bright  red,  and  to 
be  deprived  of  its  fibrin.  If  alkaline  blood-serum  be  filtered  through  a  layer  of 
nucleo-albumin  or  lecithin-albumin,  an  acid  filtrate  passes  through.  Liebermann 
explains  in  a  similar  manner  the  development  of  acid  urine  on  passing  blood- 
plasma  through  the  renal  epithelium  containing  lecithin-albumin. 


THE  PASSAGE  OF  VARIOUS  SUBSTANCES  INTO  THE  URINE. 

The  following  substances  pass  unchanged  into  the  urine:  Alkaline  sulphates, 
borates,  silicates,  nitrates,  carbonates;  alkaline  chlorids,  bromids,  and  iodids; 
potassium  sulphocyanate,  potassium  ferrocyanid;  salts  of  the  biliary  acids;  urea, 
kreatinin;  cumaric,  oxalic,  camphoric,  pyrogallic,  sebacylic  acids;  further,  many 
alkaloids,  as,  for  instance,  morphin,  strychnin,  curarin,  quinin,  caffein;  among  the 
pigments,  sodium  sulphindigotate,  carmine,  gamboge,  madder,  logwood,  the  color- 
ing-matter of  huckleberries,  mulberries,  cherries,  rhubarb;  further,  santonin;  and, 
finally,  the  salts  of  gold,  silver,  mercury,  arsenic,  bismuth,  antimony,  iron  (but 
no  lead) ,  which,  however,  pass  in  largest  amount  into  the  bile  and  into  the  feces. 

Inorganic  acids  appear  in  human  beings  and  carnivora  as  neutral  ammo- 
nium-salts; in  herbivora,  as  neutral  alkaline  salts. 

Certain  substances  that  generally  undergo  decomposition,  even  when  they 
gain  entrance  into  the  blood  in  small  amounts,  pass  in  part  into  the  urine  when 
they  accumulate  in  the  blood  in  considerable  amount,  because  they  are  not  com- 
pletely decomposed,  such  as  sugar,  hemoglobin,  egg- albumin,  alkaline  salts  of  the 
vegetable  acids,  alcohol,  chloroform. 

Many  substances  appear  in  the  urine  as  oxidation-products:  moderate 
amounts  of  alkaline  salts  of  the  vegetable  acids  as  alkaline  carbonates;  uric  acid 
in  part  as  allantoin;  sodium  sulphite  acid  and  hyposulphite  in  part  as  sodium 
sulphate;  potassium  sulphid  as  potassium  sulphate.  Many  oxids  appear  as  sub- 
oxids,  benzol  as  phenol. 

Those  bodies,  such  as  glycerin  and  the  resins,  that  are  completely  con- 
sumed, exhibit  no  special  derivatives  in  the  urine. 

Some  substances  undergo  synthesis  with  metabolic  products,  and  appear 
in  the  urine  as  conjugated  combinations.  In  this  category  belongs  the  develop- 
ment of  hippuric  acid  by  conjugation,  the  formation  of  the  conjugate  sulphates, 
as  well  as  the  formation  of  urea  by  synthesis  from  carbamic  acid  and  ammonia. 
After  administration  of  camphor,  or  of  chloral  and  butyl-chloral,  a  conjugated 
combination  with  glycuronic  acid,  an  acid  closely  allied  to  sugar,  appears  in  the 
urine.  Taurin  and  sarcosin  undergo  conjugation  with  sulphamic  or  carbamic  acid. 
Phenyl  bromid,  when  administered,  enters  into  conjugation  with  mercapturic  acid, 
a  body  allied  to  cystin. 

Tannic  acid,  C14H10O9,  takes  up  water,  and  is  thus  decomposed  by  hydro- 
lysis into  two  molecules  of  gallic  acid  —  2C7H6O5. 

Potassium  iodate  and  bromate  are  reduced  to  potassium  iodid  and  bromid; 
malic  acid,  C4H6O5,  in  part  to  succinic  acid,  C4H6O4;  indigo-blue,  C16Hi0N2O2, 
takes  up  hydrogen  to  form  indigo-white,  C16H12N2O2. 

Finally,  many  substances  do  not  pass  into  the  urine  at  all,  such  as  serum- 
albumin,  oils,  insoluble  metallic  salts,  and  metals. 


INFLUENCE   OF  THE   NERVES   UPON    THE  SECRETION  OF   THE 

KIDNEYS. 

As  yet,  only  the  influence  of  the  vasomotor  nerves  upon  the  ni- 
tration of  the  urine  from  the  renal  vessels  is  known,  and  these  nerves 
appear  to  be  derived  from  both  halves  of  the  spinal  cord  for  each  kidney. 
In  general,  it  should  be  borne  in  mind  that  dilatation  of  the  branches  of 


INFLUENCE  OF  NERVES  UPON  SECRETION  OF  KIDNEY.      515 

the  renal  arteries,  particularly  of  the  afferent  vessels,  must  increase 
the  pressure  in  the  glomeruli,  and  therefore  the  amount  of  filtered 
fluid  increases.  The  greater  the  measure  in  which  the  dilatation  of 
the  vessels  is  confined  to  the  distribution  of  the  renal  artery  alone, 
the  greater  will  be  the  amount  of  urine.  The  lower  dorsal  nerves,  in  the 
dog  principally  the  twelfth  and  thirteenth,  contain  the  largest  number 
of  the  vasomotor  fibers  for  the  kidney. 

Division  of  the  renal  plexus  is,  as  a  rule,  followed  by  increase  in  the 
amount  of  urine.  Occasionally,  in  consequence  of  the  increased  pres- 
sure, albumin  is  observed  to  pass  into  the  Malpighian  capsules;  and  with 
rupture  of  the  vessels  of  the  glomeruli  even  blood  may  appear  in  the 
urine.  The  center  for  these  renal  vasomotor  fibers  is  situated  on  the 
floor  of  the  fourth  ventricle,  in  front  of  the  origin  of  the  vagus.  In- 
jury, as  by  puncture,  in  this  situation  is,  therefore,  followed  by  increase 
in  the  amount  of  urine  (diabetes  insipidus),  occasionally  with  the  simul- 
taneous appearance  of  albumin  and  blood.  Naturally,  any  injury  of 
the  active  nerve-path  from  the  center  to  the  kidney  has  a  similar  effect. 
The  center  for  the  vasomotor  nerves  of  the  liver  is  situated  close  to 
this  center,  and  injury  of  the  former  gives  rise  to  the  production  of 
sugar  in  the  liver.  Eckhard  observed  hydruria  develop  after  irritation 
of  the  vermiform  process  of  the  cerebellum  lying  upon  the  medulla. 
A  similar  result  is  brought  about  in  human  beings  also  as  a  result  of  irrita- 
tion in  this  situation  by  tumors,  inflammatory  processes,  and  the  like. 

If,  in  addition  to  the  distribution  of  the  renal  artery,  an  adjacent 
extensive  vascular  area  be  paralyzed  simultaneously,  the  blood-pressure 
in  the  distribution  of  the  renal  artery  will  be  less  high;  as,  at  the  same 
time,  much  blood  finds  its  way  into  the  other  paralyzed  area.  Under 
such  conditions,  therefore,  either  a  slight  or  only  a  transitory  polyuria 
will  be  observed.  In  this  way,  there  results  a  moderate  increase  in 
the  amount  of  urine  for  a  few  hours  after  division  of  the  splanchnic 
nerve,  which  contains  the  vasomotor  fibers  for  the  kidney.  These 
leave  the  spinal  cord  in  part  through  the  first  dorsal  nerve,  and  pass 
into  the  sympathetic  nerve.  The  splanchnic  contains,  at  the  same 
time,  also  the  fibers  for  the  extensive  distribution  of  the  intestinal 
vessels.  Irritation  of  this  nerve  is,  naturally,  attended  with  the  op- 
posite effect. 

If,  with  paralysis  of  the  renal  nerves,  the  overwhelming  majority  of 
all  of  the  vasomotors  of  the  body  are  at  once  paralyzed,  the  pressure 
throughout  the  entire  arterial  distribution  falls  in  accordance  with  the 
extensive  dilatation  of  all  of  these  vascular  paths.  In  consequence, 
the  secretion  of  urine  diminishes,  even  to  the  point  of  complete  cessation. 
This  last  effect  is  seen  after  division  of  the  cervical  cord  down  to  the 
seventh  cervical  vertebra.  This  fact  explains  the  observation  that  the 
polyuria  that  occurs  after  injury  to  the  floor  of  the  fourth  ventricle  dis- 
appears as  soon  as  the  spinal  cord  down  to  the  twelfth  dorsal  nerve 
is  divided. 

The  presence  of  a  large  amount  of  urea  in  the  blood  causes  con- 
traction of  the  vessels  of  the  body,  but  dilatation  of  the  renal  vessels. 

Contraction  of  the  vessels,  and,  therefore,  at  the  same  time  of  the  volume 
of  the  kidney,  are  caused  by  asphyxia  and  strychnin-poisoning;  also  irritation  of 
sensory  nerves  has  a  similar  reflex  effect.  Extirpation  of  the  nerves  of  the  kidney 
has  the  opposite  effect.  During  fever,  the  vessels  of  the  kidney  are  contracted, 
probably  in  consequence  of  irritation  of  the  center  by  the  abnormally  heated  blood. 


5i 6  UREMIA;  AMMOXIEMIA;   URIC-ACID  DYSCRASIA. 

Repeated  inhalation  of  carbon  monoxid  is  said  occasionally  to  be  attended 
with  polyuria,  perhaps  in  consequence  of  paralysis  of  the  center  for  the  vasomotor 
nerves  of  the  kidneys. 

According  to  Cl.  Bernard,  irritation  of  the  vagus  at  the  cardia  causes  increased 
secretion  of  urine,  with  reddening  of  the  blood  in  the  renal  veins.  Possibly  this 
nerve  contains  vasodilator  fibers  that  behave  similarly  to  the  corresponding  fibers 
in  the  facial  nerve  for  the  salivary  glands.  The  vagus  innervates  the  intrinsic 
unstriated  musculature  of  the  kidney. 

According  to  Arthaud  and  Butte  and  others,  irritation  of  a  peripheral  ex- 
tremity of  the  vagus,  conversely,  diminishes  the  secretion  of  urine  and  the  circu- 
lation in  both  kidneys.  Atropin  renders  the  experiment  impossible.  The  vagus 
thus  appears  to  be  the  vasomotor  nerve  of  the  kidney.  According  to  Boeri,  it 
possesses  trophic  functions,  as  albuminuria  occurs  after  division  of  the  vagus. 
Irritation  of  the  cervical  sympathetic  likewise  diminishes  the  secretion.  This 
irritation  appears  to  be  reflex,  being  transmitted  through  the  spinal  cord  to  the 
splanchnic  nerve. 

UREMIA;  AMMONIEMIA;  URIC-ACID  DYSCRASIA. 

After  extirpation  of  the  kidneys,  nephrectomy,  or  ligation  of  the  ureters,  which 
renders  further  secretion  of  urine  impossible;  further,  also,  in  human  beings,  as 
a  result  of  extreme  urinary  stasis,  as  well  as  in  consequence  of  morbid  alterations 
in  the  kidneys  (inflammation,  fatty  degeneration,  and  desquamation  of  the  epithe- 
lial cells  of  the  urinary  tubules,  cicatricial  contraction  of  the  kidney,  amyloid 
degeneration) ,  there  develop  a  series  of  characteristic  phenomena  that  resemble 
an  intoxication,  and,  if  of  marked  degree,  cause  death,  with  degeneration  of  the 
ganglia  in  the  cerebral  cortex  and  the  spinal  cord.  This  condition  is  designated 
uremic  intoxication  or  uremia.  Among  the  phenomena,  the  following  are  con- 
spicuous: Mental  prostration,  somnolence,  even  loss  of  consciousness  to  the  point 
of  deep  coma,  and,  in  addition,  from  time  to  time,  the  occurrence  of  twitching 
or  even  widespread,  severe  convulsions.  Occasionally,  there  are  delirium  and 

feneral  excitement.  At  the  same  time,  the  occurrence  of  the  so-called  Cheyne- 
tokes  respiratory  phenomenon  is  often  observed.  Occasionally,  transitory^  in- 
variably bilateral,  blindness  occurs,  from  toxic  paralysis  of  the  psycho-optic 
center.  There  may,  however,  take  place,  quite  independently,  hemorrhagic 
extravasations  into  the  retina,  causing,  rarely  permanent,  blindness — apoplectic 
retinitis.  Also  impairment  of  hearing  is  observed.  Vomiting  and  diarrhea  are 
common.  Ammonium  carbonate,  formed  in  the  digestive  tract  from  urea,  as  well 
as  kreatin,  causes  uremip  diarrhea.  Also  the  breath  and  the  emanation  from  the 
skin  may  exhale  the  odor  of  ammonia.  The  alkalinity  of  the  blood  and  the 
amount  of  oxygen  in  the  blood  are  diminished.  The  retention  of  substances  that 
are  normally  excreted  by  the  urine  must  be  considered  as  the  cause  of  these 
symptoms,  although  it  has  not,  as  yet,  been  possible  to  designate  with  certainty 
the  substances  that  must  be  considered  as  the  agents  upon  which  the  toxic 
phenomena  depend. 

Suspicion  was  first  directed  to  urea.  v.  Voit  observed  that  even  healthy 
dogs  exhibited  uremic  manifestations  when  they  partook  of  urea  for  a  considerable 
time  with  their  food  if.  at  the  same  time,  the  use  of  water,  which  would  have 
carried  off  the  urea  rapidly  through  the  kidneys,  was  prevented.  Further,  Meissner 
found  that  death  amid  uremic  manifestations  could  be  hastened  in  nephrectomized 
animals,  if  urea  was  at  the  same  time  injected  into  the  blood.  An  injection  of 
moderate  amounts  of  urea  into  the  blood  of  entirely  healthy  animals  was  not, 
it  is  true,  followed  by  uremic  symptoms,  although  one  or  two  grams  caused  a 
comatose  state  in  rabbits.  Dogs  died  after  subcutaneous  injection  of  urea  to  an 
amount  equaling  one  per  cent,  of  the  bodily  weight.  Hippuric  acid  is  said  to 
have  an  entirely  similar  effect  in  frogs.  Although  urea,  when  introduced  into  the 
blood  in  large  amounts,  causes  death  with  convulsions,  this  condition  should  not 
be  confounded  with  uremic  attacks  of  intermittent  occurrence. 

As  injection  of  ammonium  carbonate  causes  symptoms  similar  to  those  of 
uremia,  v.  Frerichs  and  Stannius  believed  that  the  decomposition  of  urea  in  the 
blood  causes  the  intoxication — ammoniemia.  However,  after  nephrectomy  or 
ligation  of  the  ureters,  even  on  simultaneous  injection  of  urea  into  the  blood, 
careful  chemical  investigation  fails  to  disclose  the  presence  of  ammonia  in  the 
blood.  Therefore,  spontaneous  formation  of  ammonia  in  the  blood  cannot  be  the 
cause  of  the  uremic  symptoms. 


STRUCTURE    AND    FUNCTIONS    OF    THE    URETERS.  517 

As  in  birds  and  reptiles,  which  eliminate  principally  uric  acid,  ligation  of  the 
ureters  likewise  induces  a  comatose  state,  it  was  necessary  to  think  of  other  sub- 
stances as  possibly  causing  the  toxic  symptoms.  Meissner  observed  prostration 
and  twitchings  develop  in  dogs  after  injection  of  kreatinin.  Cl.  Bernard,  Traube, 
Ranke,  Astaschewsky,  Feltz  and  Ritter,  and  others  attribute  the  phenomenon 
to  an  accumulation  of  the  neutral  potassium-salts;  Schottin  and  Oppler  suggest 
the  accumulation  of  normal  or  abnormally  decomposed  extractives,  Thudichum 
that  of  the  oxidation-stages  of  the  urinary  pigment.  Possibly  many  substances 
and  their  decomposition-products  act  in  conjunction.  R.  Fleischer  found  a  reduc- 
tion in  the  elimination  of  sulphuric  and  phosphoric  acids  in  advance  of  the  ure- 
mic  attack  in  man. 

On  placing  various  substances  occurring  in  the  urine — kreatinin,  kreatin,  acid 
potassium  phosphate,  uratic  sediment  from  human  urine — directly  upon  the  sur- 
face of  the  cerebrum,  Landois  observed  the  development  of  all  signs  of  uremia. 
There  occurred,  particularly,  fully  developed  convulsive  seizures,  with  intervals 
of  rest,  in  dogs,  with  subsequent  coma.  Also,  many  other  secondary  phenomena 
of  uremic  eclampsia  could  be  thus  induced.  Urea  is  inactive  in  this  direction, 
ammonium  carbonate,  leucin,  sodium  carbonate,  sodium  chlorid,  potassium 
chlorid,  feebly  active. 

After  long-continued  excessive  ingestion  of  food,  together  with  the  use  of 
spirit,  and  slight  activity,  there  occurs,  principally  in  conjunction  with  respiratory 
disorders,  derangement  of  metabolism,  and  not  rarely  a  marked  accumulation  of 
uric  acid  in  the  blood.  The  latter  is  deposited  in  the  joints  and  their  ligaments 
and  cartilages,  principally  of  the  foot  and  the  hand,  and  gives  rise  to  inflammatory 
and  painful  attacks — gouty  nodules,  uric  arthritis.  Rarely,  the  kidneys,  the 
heart,  and  the  liver  are  involved.  In  the  vicinity  of  the  foci,  the  tissues  undergo 
necrosis.  Food  containing  nuclein  is  to  be  avoided;  also  meat-broths,  meat- 
extract,  sodium  chlorid;  while  cheese,  peptone,  legumins,  and  aleuronat  are  to 
be  commended.  As  to  the  amins,  piperazin,  lysidin,vlycetol,  urotropin,  the  in- 
vestigations are  not  as  yet  concluded.  As  uric  acid  is  more  readily  soluble  in 
solutions  of  urea,  the  administration  of  this  substance  has  been  advised.  Uric 
acid  introduced  into  the  blood  or  into  the  lymphatic  system  causes  changes  in 
the  renal  epithelium,  in  the  form  of  uric-acid  spheroliths  between  and  within 
the  cells  of  the  convoluted  tubules.  Administration  of  adenin,  while  it  does  not 
increase  the  excretion  of  uric  acid,  favors  its  deposition  in  the  kidney  amid  in- 
flammatory symptoms.  In  birds,  long-continued  administration  of  oxalates, 
sugar,  acetone,  phenol,  gives  rise  to  deposition  of  urates  in  the  urinary  tubules, 
as  well  as  in  the  serous  and  the  synovial  membranes,  and  these  have  disappeared 
after  administration  of  piperazin. 

Human  urine,  when  injected  beneath  the  skin  or  into  the  veins  of  animals, 
has  a  toxic  and  even  fatal  effect,  particularly  in  the  case  of  infectious  diseases, 
diseases  of  the  liver,  carcinoma,  exophthalmic  goiter,  and,  in  accordance  herewith, 
after  extirpation  of  the  thyroid  gland.  The  toxic  properties  are  due  to  organic 
(toxins)  and  inorganic  constituents,  principally  potassium-salts.  Pregnant  ani- 
mals are  especially  susceptible  to  this  poison. 

STRUCTURE   AND    FUNCTIONS    OF   THE    URETERS. 

The  pelvis  of  the  kidney  and  the  ureter  possess  a  mucous  membrane  con- 
stituted of  delicate  connective-tissue  fibers  with  many  embedded  cells,  upon 
which  a  laminated  transitional  epithelium  is  situated.  The  deepest  layer  of  the 
latter  is  provided  with  small,  round,  soft  cells.  Then  follows  a  layer  of  more 
nearly  vertical,  club-shaped  and  bulbous  colls,  whose  attenuated  extremities 
ramify  between  the  cells  of  the  deepest  layer;  the  free  surface  is  covered  by  cubical 
cells,  which  finally  are  surmounted  by  a  homogeneous  cuticular  border.  Beneath 
the  epithelium  there  is  a  layer  of  adenoid  tissue,  containing  disseminated  lymph- 
follicles.  In  the  pelvis  of  the  kidney,  the  mucous  membrane  contains  isolated 
small  grape-like  mucous  glands,  which  are  present  also  in  the  ureter.  The  muscular 
coat  consists  of  an  internal  somewhat  thicker  longitudinal  layer  and  an  external 
circular  layer,  to  which,  in  its  lower  third,  a  number  of  disseminated  bundles  of 
longitudinal  fibers  are  added.  All  of  these  layers  are  rather  freely  interwoven 
with  connective  tissue.  The  external  connective-tissue  sheath  forms  a  sort  of 
adventitia,  in  which  the  larger  vessels  and  the  nerves,  together  with  the  ganglia, 
are  situated.  The  layers  of  the  ureter  may  be  followed  upward  to  the  pelvis  of 
the  kidney  and  to  the  calices.  They  finally  line  the  pelvis  itself  only  with  mucous 


STRUCTURE    AND    FUNCTIONS    OF    THE    URETERS. 


membrane,  passing  over  upon  the  base  of  the  pyramids,  while  the  muscle-fibers 
cease  at  the  foot  of  the  pyramids,  where  they  form  a  sort  of  sphincter  about  the 
pyramids  by  means  of  circular  bundles.  The  blood-vessels  supply  the  various 
layers  and  form  a  capillary  network  beneath  the  epithelium.  The  relatively 
scanty  medullated  nerves,  in  the  vicinity  of  which  ganglia  are  found,  in  part 
supply  the  muscles  as  motor  fibers,  while  in  part  they  penetrate  toward  the  epithe- 
lium. These  are  reflex  and  sensory,  as  indicated  by  the  severe  pain  attending 
impaction  of  calculi.  The  ureter  penetrates  the  thickness  of  the  bladder- wall, 
passing  obliquely  through  it  for  a  considerable  distance.  The  internal  opening 
is  a  slit  in  the  mucous  membrane  directed  obliquely  inward  and  downward,  and 
provided  with  a  sharp,  valve-like  process  (Fig.  177) . 

The  propulsion  of  the  urine  through  the  ureter  takes  place  (i)  in 
consequence  of  the  fact  that  the  urine  constantly  secreted  in  the  kidney 

under  considerable 
pressure  forces  on- 
ward the  urine  in  the 
ureter,  which  is  under 
lower  pressure.  (2)  In 
the  erect  posture,  the 
urine  flows  by  gravity 
d  own  the  ureter .  ( 3 ) 
The  muscles  of  the 
ureter  through  their 
peristaltic  movement 
propel  the  urine  into 
the  bladder.  This 
movement  occurs  on- 
ly as  a  reflex  phenom- 
enon in  response  to 
the  entrance  of  the 
urine,  a  few  drops 
every  three-quarters 
of  a  minute,  or  in  con- 


FIG.  177.— Lower  Portion  of  the  Male  Bladder,  with  the  Commencement  of 


the  Ureter,  Opened  through  a  Median  Incision  in  the  Anterior  Wall, 
and  spread  out  (after  Henle).  The  clear  lines  of  the  trigone,  the  slit- 
like  openings  of  the  ureters,  the  ureters  divided  above  and  the  seminal 
vesicles  can  be  recognized.  On  the  colliculus  seminalis  there  appear 
in  the  middle  the  large  opening  of  the  prostatic  sinus,  and  on  either 
side  the  small  circular  orifice  of  the  ejaculatory  duct,  and  below  both 
the  numerous  punctate  openings  of  the  excretory  ducts  of  the  prostate 
gland. 


sequence  of  direct  ir- 
ritation. It  always 
passes  downward 
with  a  velocity  of 
from  20  to  30  mm.  in 

a  second.  The  greater  the  distention  of  the  ureter  by  the  urine,  the 
more  rapidly  does  this  peristaltic  movement  take  place.  Asphyxia, 
venous  hyperemia,  and  irritation  of  the  splanchnic  increase  the  number 
of  contractions;  while  rapid  ligation  of  the  renal  vessels,  as  well  as 
ligation  of  the  ureter,  diminishes  them. 

In  case  of  local  irritation,  the  contraction  takes  place  in  both  directions. 
As  Engelmann  observed  these  movements  also  in  excised  portions  of  ureter 
in  which  neither  nerve-fibers  nor  ganglia  were  visible,  he  believes  that  the  move- 
ments are  due  to  direct  muscular  conduction  in  the  unstriated  muscles,  just  as 
takes  place  in  the  heart. 

The  stagnation  of  urine  toward  the  kidney  is  prevented  (i)  by  the 
fact  that  the  secretion  collecting  in  the  pelvis  of  the  kidney  and  in  the 
calices  under  high  pressure  presses  upon  the  pyramids  from  all  sides,  so 
that  the  urine  cannot  pass  back  into  the  urinary  tubules  closed  by  pres- 
sure. (2)  If  when  the  urine  has  accumulated  in  the  ureter  in  consid- 
erable amount,  as  from  occlusion  by  concretions,  the  musculature  en- 


STRUCTURE    OF    URINARY    BLADDER    AND    URETHRA.  519 

gages  in  increased  activity  for  the  propulsion  of  the  urine,  the  portion  of 
the  muscular  fibers  surrounding  the  pyramids  so  compresses  the  urinary 
tubules  that  the  urine  cannot  pass  back  into  the  excretory  ducts  of  the 
tubules.  The  return  of  urine  from  the  bladder  into  the  ureter  is  ren- 
dered difficult  in  part  by  the  fact  that  with  marked  stretching  of  the 
bladder-wall  the  ureter,  in  so  far  as  it  is  contained  therein,  is  likewise  com- 
pressed ;  and  in  part  by  the  fact  that  the  stretching  of  the  mucous  mem- 
brane of  the  bladder  firmly  approximates  the  margins  of  the  slit -like 
openings  of  the  ureters  (Fig.  177). 

In  case  of  retention  of  urine  in  the  bladder,  a  return  of  urine  into  the  ureters 
may,  it  is  true,  take  place. 

STRUCTURE  OF  THE  URINARY  BLADDER  AND  THE  URETHRA. 

The  mucous  membrane  of  the  bladder  is  not  unlike  that  of  the  ureter.  The 
laminated  epithelium  exhibits  flatter  cells  in  the  upper  layer.  When  the  bladder 
is  distended,  the  epithelial  cells  become  stretched  and  thinner.  The  unstriated 
muscular  fibers  are  arranged  in  bundles  that  form  an  external  longitudinal  layer 
and  an  internal  circular  layer.  In  addition,  fibers  pass  in  various  directions  and 
cross  one  another,  forming  a  wide-meshed  trabecular  network.  Between  the  mus- 
cular coat  and  the  mucous  membrane  there  is  a  layer  of  delicate,  fibrillar,  cellular 
connective  tissue,  with  an  intermixture  of  elastic  fibers.  An  excessively  minute 
dissection  of  the  individual  layers  and  bands  of  the  musculature  of  the  bladder 
has  given  rise  to  erroneous  physiological  interpretations.  In  this  category  belongs 
the  establishment  of  a  special  detrusor  urinas  muscle,  which  is  said  to  consist  of 
fibers  pursuing  a  vertical  direction  from  the  vertex  to  the  fundus,  principally 
upon  the  anterior  and  posterior  surfaces.  The  conception  of  a  special  internal 
sphincter  vesicse  is  likewise  unjustified  as  constituted  of  a  circular  layer  of  un- 
striped  muscles,  from  6  to  12  mm.  thick,  surrounding  the  commencement  of  the 
urethra,  and  in  its  form  helping  to  give  rise  to  the  funnel-shape  of  the  outlet  of 
the  bladder.  This  layer,  also  designated  annulus  urethralis  vesicae,  is  no  sphincter 
at  all.  In  the  trigone  of  Lieutaud  there  are,  at  times,  between  the  orifices  of 
the  ureters,  numerous  muscular  bundles,  attached  in  part  to  the  circular,  in  part 
to  the  longitudinal  fibers  of  the  wall  of  the  bladder.  Waldeyer  believes,  par- 
ticularly of  the  trigone,  that  it  facilitates  the  distention  of  the  bladder,  favors  its 
complete  evacuation  and  aids  its  closure. 

From  the  physiological  standpoint,  it  should  be  borne  in  mind  that 
the  entire  musculature  of  the  bladder  represents  a  continuous  hollow 
muscle  whose  sole  function  it  is,  in  contracting,  to  diminish  the  cavity 
of  the  bladder  from  all  directions  and  to  expel  its  contents. 

The  vessels  of  the  bladder  resemble  those  of  the  ureter  in  their  distribution. 
The  nerve-fibers  are  provided  with  ganglia,  as  is  the  case  generally  at  all  parts 
of  the  urinary  passages  outside  the  kidney.  These  are  situated  in  part  in  the 
mucosa,  in  part  in  the  muscularis,  and  they  communicate  with  one  another  by 
means  of  filaments.  In  the  mucous  membrane  and  its  epithelium,  the  nerves 
terminate  in  end-bulbs.  In  accordance  with  their  functions,  the  nerves  are  motor, 
sensory,  reflex,  and  vascular. 

In  women,  the  urethra  serves  only  as  the  excretory  duct  of  the  urinary 
bladder.  The  mucous  membrane,  formed  of  a  large  amount  of  fibrillary  con- 
nective and  elastic  tissue  and  supplied  with  papillae,  is  lined  by  laminated  pavement 
epithelium.  In  addition,  a  number  of  Littre's  mucous  glands  are  embedded  in  it. 
Next  to  the  mucous  membrane  is  a  layer  of  longitudinal  unstriated  muscular 
fibers,  and  next  to  the  latter  a  layer  of  circular  fibers.  These  layers  contain  an 
abundance  of  connective-tissue  and  elastic  fibers,  and,  besides,  extensive  venous 
plexuses,  suggestive  in  their  structure  of  cavernous  spaces. 

The  true  sphincter  muscle  of  the  bladder  is  a  striated  muscle,  which 
undergoes  contraction  and  relaxation  under  the  influence  of  the  will,  and 
consists  in  part  of  transverse,  completely  circular  fibers,  which  extend 


520  EVACUATION    OF    THE    URINE. 

downward  to  the  middle  of  the  urethra  and  lie  next  to  the  unstriated  cir- 
cular fibers,  and  in  part  of  longitudinal  fibers,  which  pass  upward  to  the 
base  of  the  bladder  only  on  the  posterior  wall  of  the  urethra,  and  down- 
ward between  the  circular  fibers.  Additional  circular  fibers  are  situated 
below  the  middle  of  the  urethra,  and  only  in  isolated  distribution  on  its 
anterior  surface. 

In  the  male  urethra,  the  epithelium  of  the  prostatic  portion  still  resembles 
that  of  the  bladder,  in  the  membranous  portion  it  becomes  laminated,  and  in 
the  cavernous  portion  a  simple  cylindrical  epithelium.  The  mucous  membrane 
beneath  the  laminated  epithelium,  provided  with  papillae,  contains,  principally  in 
the  posterior  portion,  the  mucus-secreting  glands  of  Littre.  Unstriated  muscle- 
fibers  are  present  in  the  prostatic  portion  as  a  longitudinal  layer,  especially  at 
the  colliculus  seminalis;  while  the  membranous  portion  contains  principally  cir- 
cular fibers,  with  intervening  longitudinal  fibers.  The  cavernous  portion  contains 
posteriorly  delicate  circular  fibers,  anteriorly  only  isolated  insignificant  oblique 
and  longitudinal  fibers. 

With  respect  to  the  mechanism  for  closure  of  the  male  urethra,  it 
should  be  pointed  out  that  the  so-called  internal  sphincter  vesicse  of  the 
anatomists,  which  consists  of  unstriated  muscular  fibers,  and,  as  an  integ- 
ral portion  of  the  musculature  of  the  bladder  surrounds  the  commencement 
of  the  urethra  down  to  within  the  prostatic  portion  of  the  urethra, 
above  the  colliculus  seminalis,  is  not  a  sphincter  muscle  at  all.  The  true 
striated  sphincter  of  the  urethra,  or  external  sphincter  of  the  bladder,  is 
situated  below  the  former.  It  is  a  completely  circular  muscle,  surround- 
ing the  urethra,  just  above  the  entrance  of  the  urethra  into  the  urogen- 
ital  septum,  at  the  apex  of  the  prostate  gland,  where  its  fibers  anasto- 
mose with  those  of  the  subjacent  deep  transverse  peroneal  muscle. 

This  sphincter  muscle  includes,  also,  longitudinal  fibers,  which  pass  downward 
from  the  bladder  along  the  upper  border  of  the  prostate.  Isolated  transverse 
bundles  are  derived  anteriorly  from  the  surface  of  the  neck  of  the  bladder. 
The  sphincter  muscle  includes,  besides,  certain  transverse  fibers  that  lie  within 
the  prostate  even  opposite  the  apex  of  the  colliculus  seminalis,  passing  like  a 
thick  transverse  column  in  advance  of  the  commencement  of  the  urethra  into  the 
structure  of  the  prostate — prostatic  muscle. 

In  the  male  urethra,  the  blood-vessels  form  a  rich  capillary  network  beneath 
the  epithelium,  in  the  midst  of  which  a  wide-meshed  lymphatic  vascular  net- 
work is  situated. 


COLLECTION  AND  RETENTION  OF  THE  URINE  IN  THE  BLADDER. 
EVACUATION  OF  THE  URINE. 

After  the  evacuation  of  the  bladder,  urine  reaccumulates,  with  grad- 
ual distention  of  the  viscus.  As  long  as  the  amount  of  urine  is  but  mod- 
erate, the  elasticity  of  the  elastic  fibers  surrounding  the  urethra  and  of 
the  sphincter  muscle  of  the  urethra — in  men,  in  addition,  that  of  the 
prostate — suffices  perfectly  to  retain  the  urine  in  the  bladder.  This  is 
indicated  by  the  fact  that  in  the  cadaver  the  urine  does  not  escape  from 
the  bladder.  The  movements  for  the  evacuation  of  the  bladder,  as 
well  as  for  the  retention  of  the  urine  in  the  bladder,  exhibit,  in  many 
respects,  an  agreement  with  the  motor  mechanism  at  the  rectum.  In 
the  first  place,  it  should  be  pointed  out  that  the  walls  of  the  bladder  are 
capable  of  independent  contraction.  Whether  these  are  due  to  the 
ganglion-cells  in  the  bladder  that  are  found  in  the  course  of  the  nerves 
has  not  been  demonstrated.  It  is  rather  more  likely  that  the  muscula- 
ture of  the  bladder  is  capable  of  rhythmic  movement  without  nervous  aid. 


EVACUATION    OF    THE    URIXE.  521 

The  urinary  bladder,  especially  when  considerably  distended,  exhibits  the 
occurrence  of  intermittent  slight  contractions,  which  can  be  compared  with  the 
peristaltic  movements  of  the  intestines.  Even  the  excised  frog's  bladder,  and  even 
portions  thereof  without  ganglia,  exhibit  similar  rhythmic  contractions,  which 
can  be  increased  by  heat.  After  division  of  all  of  the  nerves  of  the  bladder, 
bleeding  with  asphyxia  is  still  followed  by  contractions  as  a  result  of  direct  stimu- 
lation of  the  muscles  of  the  bladder.  The  contractions  occur,  further,  more 
actively  in  the  presence  of  derangement  of  the  circulation  in  the  bladder,  or  of 
venosity  of  the  blood,  in  the  same  way  as  the  movements  of  the  intestine  are 
brought  about  in  marked  degree  by  like  influences.  In  this  category  belongs  the 
evacuation  of  the  urine  when  the  action  of  the  heart  ceases  in  cases  of  sudden 
asphyxia  or  protracted  suppression  of  respiration.  As  emotional  disturbances 
also  influence  the  contraction  of  the  walls  of  the  bladder,  the  evacuation  of  the 
urine  in  connection  with  sudden  fear  can  be  explained  in  this  manner.  In  the 
state  of  apnea,  as  well  as  in  apneic  intervals  after  persistent  deep  respiratory 
movements,  the  independent  contractions  of  the  bladder  cease. 

In  order  to  comprehend  the  mechanism  of  the  retention  of  the  urine 
in  the  bladder,  as  well  as  of  its  evacuation,  a  description  is  necessary  of 
the  following  nervous  apparatus  which  participates  in  these  processes : 

T  .  The  sensory  nerves  of  the  walls  of  the  bladder  are  derived  from  the 
first,  second,  third,  and  fourth  posterior  sacral  roots.  A  number  of 
sensory  fibers  pass  into  the  spinal  cord  through  the  intermediation  of  the 
hypogastric  plexus.  The  sensory  nerves  pass  upward  in  the  cord  to  the 
cerebral  cortex. 

2.  The  center  for  reflex  stimulation  of  the  unstriated  musculature  of 
the  wall  of  the  bladder — vesicospinal  center — is  situated  in  the  neigh- 
borhood of  the  fourth  lumbar  vertebra,  in  the  dog. 

3 .  The  motor  tracts  pass  from  this  center  to  the  unstriated  muscula- 
ture of  the  wall  of  the  bladder  through  the  nerves  between  the  second 
lumbar — by   way    of   communicating   branches    of   the    sympathetic — 
and  the  fourth  sacral  by  way  of  the  nervi  erigentes.      Irritation  of  the 
sensory  nerves  of  the  wall  of  the  bladder  causes  reflex  contraction  of  the 
bladder-wall. 

In  addition  to  the  sensory  nerves  of  the  bladder,  the  reflex  described 
may  be  excited  also  by  irritation  of  other  sensory  nerves;  thus,  active 
tickling,  or  warming  of  the  region  of  the  knee  during  sleep  at  times  causes 
evacuation  of  urine,  likewise  the  hearing  of  splashing  and  whistling 
sounds.  In  animals,  stimulation  of  certain  sensory  nerves  likewise 
causes  contractions  of  the  bladder. 

Omitting  consideration  of  the  sphincter  muscle  of  the  urethra,  the 
sensation  of  a  distended  bladder  will  become  apparent  as  soon  as  the 
bladder  is  moderately  distended.  Then  the  mechanical  irritation  of  the 
sensory  nerves  of  the  bladder  in  the  mucous  membrane  excites  in*  the 
vesicospinal  center  the  reflex  through  the  motor  nerves  of  the  unstriated 
musculature  of  the  bladder,  and  in  consequence  of  this  the  walls  of  the 
bladder  undergo  contraction .  This  constitutes  the  process  as  it  takes  place , 
for  instance,  normally  always  in  infants,  who  do  not  as  yet  have  control 
of  the  urethral  sphincter.  Also  voluntary  evacuation  of  the  bladder, 
whatever  the  degree  of  distention,  is  always  effected  only  through  exci- 
tation of  the  reflex  described.  The  will  is  incapable  of  influencing  di- 
rectly the  unstriated  musculature  of  the  bladder ;  and  this  is  emphasized 
particularly  by  the  author,  in  opposition  to  the  statements  of  many  other 
observers.  To  induce  reflex  stimulation  of  this  movement  of  the  bladder, 
principally  in  the  presence  of  considerable  degrees  of  distention,  the 
direction  of  the  attention  to  the  sensations  in  the  urinary  apparatus 


522  EVACUATION    OF    THE    URINE. 

alone  suffices.  When  the  distention  of  the  bladder  is  only  moderate  or 
slight,  the  sensory,  excito-reflex  nerves  of  the  bladder  must  first  be  stimu- 
lated, and  either  through  irritation  of  the  sensory  nerves  by  voluntary 
contraction  of  the  striated  muscles  of  the  urethra  and  the  floor  of  the 
pelvis,  or  of  the  nerves  of  the  bladder  as  a  result  of  abdominal  pressure. 

As  electric  stimulation  from  the  cerebral  peduncle  downward  through 
the  motor  paths  of  the  spinal  cord  to  the  motor  nerves  of  the  unstriated 
musculature  of  the  bladder  causes  contraction  of  the  bladder,  many 
investigators  have  concluded  that  the  will  is  capable  of  exciting  spon- 
taneous contractions  of  the  bladder  directly  in  this  way.  The  author  con- 
siders this  view  as  incorrect.  In  his  opinion,  voluntary  evacuation  of 
urine  is  always  induced  by  reflex  influences,  in  the  excitation  of  which 
the  will  participates  only  in  a  secondary  manner.  With  the  vesical 
center  situated  in  the  spinal  cord  still  other  nervous  apparatus  cooper- 
ates. As  painful  irritation  of  sensory  nerves  in  different  parts  of  the 
body  also  is  capable  of  causing  reflex  contraction  of  the  bladder — the 
involuntary  discharge  of  urine  that  occurs  frequently  in  children  suffer- 
ing from  disorders  of  dentition  may  be  of  this  character;  as,  further,  as 
has  already  been  pointed  out,  sensory  nerves  situated  at  a  higher  level, 
even  cerebral  nerves,  are  capable  of  exciting  the  vesical  reflex,  it  must  be 
concluded  that  the  vesical  center  extends  for  a  considerable  distance  up- 
ward, perhaps  to  the  anterior  portion  of  the  optic  thalamus,  and  that 
from  these  higher  levels  descend  motor  paths  that  are  susceptible  of— 
possibly  reflex — stimulation  in  the  spinal  cord.  Irritation  of  the  medulla 
from  the  cerebral  peduncle  downward  causes  contraction  of  the  walls 
of  the  bladder. 

With  respect  to  the  mechanism  for  the  retention  of  the  urine  in  the 
bladder  through  the  sphincter  muscle  of  the  urethra,  consideration 
should  be  given  to  the  following  facts : 

4.  The   motor  nerves  for  the   striated   sphincter   muscle   are   con- 
tained in  the  pudendal  nerve,   derived  from  the  anterior  roots  of  the 
third  and  fourth  sacral  nerves.      Irritation  causes   contraction  of  the 
muscle;   paralysis,  inability  to   close  the  urethra,  with  the  result  that 
dribbling  or  incontinence  of  urine  takes  place.     The  nerves  maybe  both 
stimulated — voluntary  interruption  of  the    stream  of   urine — and    in- 
hibited through  the  action  of  the  will. 

5.  The   sensory  nerves   of   the  urethra  pass    into   the    spinal  cord 
through  the  posterior  roots  of  the  third,  fourth,  and  fifth  sacral  nerves. 
These  stimulate,  on  the  one  hand,  the  reflex  for  the  urethral  sphincter,  so 
that  as  soon  as  urine  escapes  from  the  bladder  into  the  commencement 
of  the  urethra  the  sphincter  muscle  contracts;  as,  for  instance,  in  adults, 
during  sleep,  when  the  bladder  becomes  distended.     On  the  other  hand, 
they  transmit  sensory  impressions   from  the  urethra,  particularly  also 
when  urine  forces  its  way  into  the  canal. 

6.  The  center  for  the  urethral -sphincter  reflex — urethrospinal  cen- 
ter— is  situated,  in  the  dog,  at  the  level  of  the  fifth,  and,  in  the  rabbit, 
at  the  level  of  the  seventh  lumbar  vertebra. 

7.  From  the  cerebral  cortex  the  voluntary  motor  paths  course  down- 
ward through  the  spinal  cord  to  the  sphincter  muscle  of  the  urethra, 
within  the  pyramidal  tracts. 

8.  The  inhibitory  paths  for  this  muscle  likewise  pass  from  the  brain 
through  the  spinal  cord,  and  through  them  the  muscle  may  voluntarily 


DERANGEMENT    OF    URINARY    RETENTION    AND    MICTURITION.         523 

be  relaxed  into  inactivity.     It  has  not  yet  been  possible  to  stimulate 
this  center  experimentally. 

With  respect  to  the  mutual  relations  between  the  activity  of  the  mus- 
culature of  the  bladder — expulsion  of  urine — and  of  the  sphincter  of  the 
urethra — retention  of  urine — the  action  of  the  sphincter  muscle  pre- 
ponderates, as  a  rule,  when  the  distent  ion  of  the  bladder  is  not  excessive. 
In  other  words,  as  soon  as  urine  is  forced  into  the  urethra  by  contraction 
of  the  musculature  of  the  bladder,  reflex  closure  of  the  urethra  takes 
place.  The  action  of  the  sphincter  muscle,  however,  predominates 
only  to  a  certain  degree;  and  neither  the  reflex  nor  the  voluntary  con- 
traction of  the  sphincter  is  capable  of  resisting  strong  pressure  by  the 
urine.  In  the  act  of  micturition,  as  it  takes  place  when  the  bladder  is 
moderately  distended,  the  sphincter  of  the  urethra  must  always  be  vol- 
untarily inhibited  in  its  contraction  during  the  contraction  of  the  walls 
of  the  bladder. 

The  foregoing  description  of  the  innervational  conditions  of  the  bladder  is 
based  upon  the  published  experiments  of  Budge,  all  of  which  were  performed  in 
collaboration  with  Landois.  Division  of  the  sacral  nerves,  in  the  dog,  causes 
degeneration  of  the  nerves  of  the  bladder  and  of  the  rectum,  but  not  of  the  internal 
genitalia — some  fibers  of  the  urethral  and  vulvar  nerves  undergo  degeneration. 
Bilateral  division  renders  micturition  an'd  defecation  impossible,  while  unilateral 
division  renders  these  difficult.  In  addition,  there  is  complete  anesthesia  at  the 
anus,  of  the  vagina,  and  on  the  posterior  aspect  of  the  thigns,  together  with  weak- 
ness at  the  ankle-joint. 

Normally,  the  bladder  is  completely  evacuated.  The  residual  urine  that  col- 
lects abnormally  in  greater  or  lesser  amount  is  a  source  of  danger,  on  account  of 
the  tendency  to  decomposition.  The  urine  undergoes  alterations  during  its 
sojourn  in  the  bladder.  According  to  Kaupp,  retention  is  attended  with  an 
increase  in  the  amount  of  sodium  chlorid,  and  a  diminution  in  the  amount  of 
urea  and  of  water.  The  reduction  in  the  latter  is  much  more  marked  in  con- 
junction with  simultaneous  sweating.  The  question  whether  the  mucous  mem- 
brane of  the  bladder  absorbs  soluble  matters  has  been  answered  in  the  affirmative 
by  Cl.  Bernard,  for  the  dog.  Under  such  circumstances,  water  is  again  excreted 
into  the  bladder.  Maas  and  Pinner  noted  absorption  also  on  the  part  of  the 
urethral  mucous  membrane,  Lewin  and  Goldschmidt  also  on  the  part  of  the 
ureter,  and  the  pelvis  of  the  kidney,  as  well  as  the  prostatic  vesicle  (strychnin). 

As  the  ureters  empty  rather  toward  the  base  of  the  bladder,  the  urine  most 
recently  secreted  is  always  the  lowermost.  Under  varying  conditions  of  secretion 
the  urine  may  therefore  (in  a  resting  posture)  form  layers  in  the  bladder,  so  that 
when  evacuated  the  different  layers  may  be  clearly  distinguishable.  In  quiet 
dorsal  decubitus,  the  pressure  in  the  bladder  is  from  13  to  15  cu.  cm.  of  a  column 
of  water.  The  pressure  is  naturally  increased  by  increase  of  the  intra-abdominal 
pressure,  especially  in  consequence  of  coughing  and  expulsive  efforts.  The  erect 
posture  has  a  similar  effect,  in  consequence  of  the  pressure  of  the  viscera  from 
above.  In  the  evacuation  of  the  urine,  the  amount  expelled  is  at  first  small;  this 
increases  later  in  the  same  interval  of  time,  and  toward  the  end  of  the  act  it  again 
diminishes.  In  men,  the  last  portions  are  expelled  from  the  urethra  through 
voluntary  contraction  of  the  bulbo-cavernous  muscle.  Adult  dogs  constantly 
accelerate  the  stream  of  urine  rhythmically  through  the  action  of  this  muscle. 

MORBID  DERANGEMENT  OF  URINARY  RETENTION  AND    OF 

MICTURITION. 

Derangement  in  the  mechanism  of  retention  and  evacuation  of  urine  may  be 
referred  by  the  physician  to  its  cause  from  a  consideration  of  the  physiological 
conditions  described.  Retention  of  urine — ischuria — results  (i)  from  occlusion  of 
the  urethra  by  foreign  bodies,  concretions,  strictures,  prostatic  enlargement;  (2) 
from  paralysis  or  exhaustion  of  the  musculature  of  the  bladder,  the  latter  also 
following  parturition  in  consequence  of  the  pressure  of  the  child's  parts  against 
the  bladder;  (3)  primarily,  after  division  of  the  spinal  cord.  Under  such  circum- 


524  COMPARATIVE.       HISTORICAL. 

stances,  retention  of  urine  takes  place  (a)  because  the  division  of  the  spinal  cord 
gives  rise  to  increased  reflex  activity  on  the  part  of  the  urethral  sphincter,  and  (b) 
because  inhibition  of  this  reflex  cannot  take  place.  If,  with  increasing  distention 
of  the  walls  of  the  bladder,  the  urethral  orifice  is  finally  dilated  mechanically, 
dribbling  of  urine  takes  place.  Nevertheless,  the  urine  escapes  only  drop  by 
drop,  as  it  overcomes  the  maximum  tension  at  which  the  urethra  still  closes. 
Therefore,  the  bladder  becomes  more  and  more  distended,  as  the  tone  of  the 
continuously  stretched  walls  lessens  progressively,  and  the  bladder  may  be 
distended  to  an  enormous  size.  In  consequence  of  the  entrance  of  bacteria  into 
the  bladder,  ammoniacal  decomposition  of  the  long-retained  urine  may  readily 
take  place;  and,  as  a  result,  catarrhal  and  inflammatory  conditions  of  the  bladder 
may  be  excited.  (4)  From  interference  with  the  voluntary  control  of  the 
inhibition  of  the  reflex  of  the  urethral  sphincter,  as  well  as  from  increased  reflex 
excitability  of  the  urethral  center. 

Incontinence  of  urine — stillicidium  urinas — occurs  as  a  result  (i)  of  paralysis 
of  the  urethral  sphincter;  (2)  of  anesthesia  of  the  urethra,  in  consequence  of 
which  the  reflex  of  the  sphincter  must  be  lost;  (3)  incontinence  of  urine  is,  sec- 
ondarily, always  a  result  of  division  of  the  spinal  cord  or  of  abnormal  degeneration. 
Strangury  is  observed  as  an  excessive  reflex  of  the  walls  of  the  bladder  and  the 
sphincter  muscle,  in  consequence  of  irritation  of  the  bladder  and  the  urethra,  as 
observed  in  association  with  inflammation,  irritation,  and  neuralgia.  So-called 
nocturnal  enuresis,  nocturnal  involuntary  discharge  of  urine,  may  be  a  result  of 
increased  reflex  activity  of  the  walls  of  the  bladder,  or  of  enfeeblement  of  the 
reflex  of  the  sphincter  muscle.  Nothing  of  a  definite  nature  is  known  as  to  the 
influence  of  deranged  action  of  the  will,. principally  in  connection  with  unilateral 
injury,  apoplexy,  and  the  like.  In  patients  suffering  from  disease  of  the  spinal 
cord,  there  is  impairment  of  the  sensation  of  a  distended  bladder,  as  well  as  of 
the  contractile  power  of  the  walls  of  the  bladder.  In  neurasthenic  patients,  the 
latter  is  diminished,  while  the  sensation  of  distention  is  increased.  In  patients 
with  prostatic  disease,  there  is,  at  first,  likewise  increased  sensitivity  with  a  dis- 
tended bladder. 


COMPARATIVE.      HISTORICAL. 

In  vertebrates,  with  exception  of  the  bony  fishes,  there  is  often  a  union  of  the 
urinary  and  the  generative  organs.  The  primitive  kidney  (Wolffian  body),  which 
serves  during  the  first  period  of  embryonic  life  as  an  excretory  organ,  assumes 
this  function  throughout  life  in  fish  and  amphibia.  The  myxenoids  (cyclostomata) 
possess  the  simplest  kidneys :  On  either  side  there  is  a  long  ureter,  upon  which  are 
situated  capsules  with  short  pedicles  containing  glomeruli,  and  arranged  in  rows. 
Both  ureters  empty  into  the  genital  pore.  In  the  remaining  fishes,  the  kidneys 
often  extend  longitudinally,  lying  as  more  compact  masses  on  either  side  of  the 
vertebral  column.  The  two  ureters  unite  to  form  the  urethra,  which  always 
opens  behind  the  anus,  either  united  with  the  genital  orifice  or  behind  this.  In 
the  sturgeon  and  the  shark  the  anus  and  the  urethral  orifice  together  form  a 
cloaca.  Bladder-like  formations,  which,  however,  do  not  resemble  the  urinary 
bladder  of  mammalia  morphologically,  occur  in  fish,  either  at  each  ureter  (ray, 
shark)  or  at  the  junction  of  the  two. 

In  amphibia,  the  efferent  vessels  of  the  testicles  unite  with  the  urinary  tubules. 
The  testicular-renal  duct  unites,  in  the  frog,  with  that  of  the  other  side;  and  both, 
united,  open  into  the  cloaca,  while  the  capacious  urinary  bladder  opens  through 
the  anterior  wall  of  the  cloaca. 

From  the  reptiles  upward,  the  kidney  in  all  vertebrates  is  no  longer  the  per- 
sisting Wolffian  body,  but  a  newly  formed  organ.  In  reptiles,  it  is  generally 
flattened  longitudinally.  The  ureters  open  separately  into  the  cloaca.  Saurians 
and  tortoises  possess  a  bladder  opening  into  the  anterior  wall  of  the  cloaca.  In 
birds,  the  ureters  remain  separate  and  open  into  the  urogenital  sinus  emptying 
into  the  cloaca  internally  to  the  excretory  ducts  of  the  generative  glands.  The 
bladder  is  constantly  wanting.  In  mammalia,  the  kidneys  often  consist  of  many 
small  lobules,  reniculi,  as,  for  instance,  in  the  seal,  the  dolphin,  the  ox. 

Among  invertebrate  animals,  molluscs  possess  excretory  organs  in  the  form 
of  canals  provided  with  an  external  opening  and  an  internal  opening,  communi- 
cating with  the  cavity  of  the  body,  and  occasionally  functionating  also  as  oviducts. 
In  mussels,  this  canal  is  expanded  into  a  spongy  organ  (organ  of  Bojanus) ,  situated 
at  the  base  of  the  gills,  often  possessing  a  central  cavity  of  considerable  size,  and 


FUNCTIONS    OF    THE    EXTERNAL    INTEGUMENT.  525 

provided  with  ciliated  secretory  cells.  The  internal  (ciliated)  excretory  duct  opens 
into  the  pericardial  cavity;  the  outer,  occasionally  united  with  the  sexual  orifices, 
opens  upon  the  external  surface  of  the  body.  In  the  analogous,  generally  un- 
paired, often  contractile  organ  of  snails,  guanin  has  been  demonstrated.  The  organ 
is  capable,  in  a  remarkable  manner,  not  alone  of  excreting  water  from  the  blood, 
but  also  of  conveying  water  into  the  blood.  Cephalopods  possess  sacculated  ex- 
cretory organs,  provided  with  glands  and  opening  into  the  mantel-cavity  lying 
on  the  vascular  trunks  of  the  gills. 

Insects,  spiders,  and  centipedes  have  so-called  Malpighian  vessels,  partly  as 
uric-acid  forming  excretory  organs;  partly,  also,  as  biliary  organs.  These  vessels 
are  long  tubes  that  open  into  the  commencement  of  the  large  intestine.  In 
crabs,  the  blind  tubes  of  the  digestive  tract  probably  have  similar  functions.  In 
cestodes,  the  excretory  organs  are  longitudinal  tubes;  in  tape-worms  two  that 
extend  throughout  the  entire  chain,  in  the  teniag  anastomosing  at  the  junction  of 
the  segments  by  means  of  a  large  communication.  In  trematodes  (distomum) 
the  branching  organ  opens  at  the  posterior  extremity  of  the  body.  Also  in  most 
round-worms  the  excretory  organ  is  formed  of  tubes,  which,  united,  open  at  a 
pore  in  the  abdominal  line.  Earth-worms  possess,  almost  in  all  segments  of  the 
body  in  pairs,  the  so-called  nephridia-canals,  that  is,  tubes,  often  much  con- 
voluted, that  commence  in  the  abdominal  cavity  with  an  inner,  ciliated  orifice, 
and  communicate  upon  the  ventral  aspect  of  the  body  with  the  external  surface . 
In  the  sea-urchin,  the  star-fish,  and  the  medusae,  the  water- vascular  system  is,  at 
the  same  time,  the  excretory  organ.  Also  in  sponges,  the  canals  passing  through 
the  body  and  conveying  water  may  be  considered  as  such. 

Historical. — According  to  Aristotle  the  urine  is  derived  from  the  blood  passing 
through  the  kidneys,  and  then  flows  through  the  ureters  into  the  bladder;  the 
venous  blood  of  the  kidneys  does  not  undergo  coagulation.  He  pointed  out  the 
relatively  large  size  of  the  human  bladder.  Berengar  (1521)  observed,  on  injecting 
water  into  the  renal  vessels,  that  fluid  escaped  from  the  papilla?.  Massa  (1552) 
discovered  lymphatic  vessels  in  the  kidneys.  Eustachius  (died  1580)  ligated  the 
ureters  and  subsequently  found  the  bladder  empty.  Cusanus  (1450)  studied 
the  color  and  the  specific  gravity  of  the  urine.  Rousset  (1581)  pointed  out  the 
muscular  nature  of  the  walls  of  the  bladder,  in  which  Sanctorius  (1631)  was  un- 
able to  recognize  any  special  sphincter  muscle;  while  Vesling  (1641)  had  already 
described  the  trigone  of  Lieutaud  (1753).  The  first  more  important  chemical 
investigations  were  made  by  van  Helmont  in  1644.  He  demonstrated  the  solid 
constituents  of  the  urine,  and  found  among  them  sodium  chlorid.  He  noted  the 
higher  specific  gravity  of  febrile  urine,  and  explained  the  development  of  urinary 
calculi  from  the  solid  constituents  of  the  urine.  With  respect  to  the  discovery 
of  individual  urinary  constituents,  it  may  be  noted  that  Scheele,  in  1776,  dis- 
covered uric  acid;  Bergmann  calcium  phosphate;  Brand  and  Kunckel  phosphorus; 
Rouelle,  in  1773,  urea,  which  was  named  by  Fourcroy  and  Vauquelin  in  1799; 
Berzelius  lactic  acid;  Seguin  albumin  in  pathological  urine;  J.  v.  Liebig  hippuric 
acid;  Heintz  and  v.  Pettenkofer  kreatin  and  kreatinin;  Wollaston,  in  1810, 
cystin;  Marcet,  in  1817,  xanthin;  Lindbergson  magnesium  carbonate.  The  more 
recent  histological,  physiological,  and  chemical  investigations  are  discussed  in  the 
text. 


FUNCTIONS  OF  THE  EXTERNAL  INTEGUMENT. 
STRUCTURE  OF  THE  SKIN. 

The  external  integument,  from  2.3  to  2.7  mm.  thick,  with  a  specific  gravity  of 
1057,  is  constituted  of  the  cults  rcni,  corium,  cutis,  and  the  overlying  epidermis. 

The  corium  (Fig.  178,  I,  C)  forms  upon  the  entire  surface  numerous  papillae, 
from  o.i  to  0.5  mm.  high,  of  which  the  largest  are  encountered  upon  the  palmar 
aspect  of  the  hand  and  the  plantar  aspect  of  the  foot,  as  well  as  upon  the  nipple 
and  the  glans  penis.  The  majority  of  the  papillae  contain  loops  of  capillary 
blood-vessels  (g) ,  and  in  circumscribed  areas  of  the  skin  also  so-called  tactile 
corpuscles  (Fig.  179,  a).  The  papillae  are  arranged  upon  the  skin  in  groups  in 
the  small  areas  bounded  by  the  delicate  furrows  in  the  skin  that  are  still  macro- 
scopically  visible.  On  the  palmar  aspect  of  the  hand  and  the  plantar  aspect  of 
the  foot  they  follow  the  characteristic  cutaneous  lines.  The  horny  skin  consists 


526 


STRUCTURE    OF    THE    SKIN. 


of  a  dense,  uniformly  woven  network  of  elastic  fibers,  more  delicate  in  the  papillae, 
and  coarser  in  the  deeper  layers,  with  which  fibrillary  connective  tissue,  with 
connective-tissue  corpuscles  and  lymphoid  cells,  are  intermixed.  In  the  deepest 
layers,  the  connective  tissue  predominates,  and,  by  the  interlacing  of  its  bundles, 
forms  longitudinal-rhombic  reticular  spaces  (a  a),  generally  filled  with  fatty  tissue, 
whose  longitudinal  expansion  corresponds  with  that  of  the  greatest  degree  of 


FIG.  178. — Histology  of  the  Skin  and  the  Epidermoidal  Structures:  I,  transverse  section  through  the  skin,  with 
hair  and  sebaceous  glands  (T),  corium  and  epidermis  are  shown  in  reduced  size;  i,  external,  2,  internal  fibrous 
layer  of  the  hair-follicle;  3,  cuticula  of  the  hair-follicle;  4,  external  root-sheath;  5,  Henle's  layer  of  the  inner 
root-sheath;  6,  Huxley's  layer  of  the  inner  root-sheath;  p,  hair-root  attached  to  the  vascular  hair-papilla; 
A,  arrector  pili  muscle;  C,  corium;  a,  subcutaneous  fatty  tissue;  b,  horny  layer;  d,  Malpighian  mucous 
layer  of  the  epidermis;  g,  vessels  of  the  cutaneous  papillae;  v,  lymphatics  of  the  cutaneous  papillae;  h,  horny 
substance;  i,  medullary  canal;  k,  epidermis  of  the  hair;  K,  sudoriferous  gland;  E,  epidermal  scales  from 
the  horny  layer,  viewed  partly  from  the  side,  partly  from  the  surface;  R,  prickle-cells  from  the  Malpighian 
layer;  n,  superficial,  deep  nail-cells;  H,  hair,  more  highly  magnified;  e,  epidermis;  c,  medullary  canal  with 
medullary  cells;  f  f,  fiber  cells  of  the  hair-substance;  x,  cells  of  Huxley's  layer;  i,  cells  of  Henle's  layer;  S, 
transverse  section  through  a  sudoriferous  gland  of  the  axillary  cavity;  a,  adjacent  unstriated  muscular  fibers; 
t,  cells  of  a  sebaceous  gland,  in  part  with  fatty  contents. 


tension  of  the  skin  at  the  part  of  the  body  in  question.  Beneath  the  corium 
lies  the  subcutaneous  connective  tissue,  which,  however,  is  without  fat-cells  in 
some  places.  At  certain  points,  firm  fibrous  bands  of  connective  tissue  unite  the 
skin  to  the  underlying  fascia,  ligaments,  or  bones  (tenacula  cutis).  In  other 
situations,  principally  over  projecting  bony  parts,  there  are  subcutaneous  mucous 
bursae  filled  with  a  synovial-like  fluid,  their  interior  partly  lined  by  endothelium. 


THE    NAILS    AND    THE    HAIR.  527 

Unstriated  muscle-fibers  are  present  in  the  uppermost  layers  of  the  corium, 
principally  on  the  extensor  aspects;  further,  particularly  on  the  nipple,  the  mam- 
millary  areola,  the  prepuce,  the  perineum,  and  in  especial  abundance  in  the  tunica 
dartos  of  the  scrotum. 

The  arteries  of  the  skin  in  the  palm  of  the  hand  and  the  sole  of  the  foot,  which 
must  sustain  the  greatest  amount  of  pressure,  possess  the  thickest  walls  for  the 
propulsion  of  the  blood-stream.  In  silver- workers,  the  elastic  fibers  of  the  skin 
of  the  hands  are  discolored  black  in  places  from  the  deposition  of  reduced  silver, 
and  the  same  condition  exists  in  cases  of  medicamentous  argyria. 

The  epidermis  is  a  layer  of  pavement  epithelium,  from  0.08  to  0.12  mm.  thick, 
united  by  cement-substance.  The  deepest  layer,  the  mucous  layer  (d),  rete  Mal- 
pighii,  consists  of  several  layers  of  protoplasmic  nucleated  prickle-cells  (R) ,  without 
membrane,  pigmented  in  the  colored  races,  as  well  as  on  the  scrotum  and  at  the 
anus,  and  of  which  the  deepest  are  rather  cylindrical  and  vertical.  Among  these 
cells  scattered  lymphatic  wandering  cells  are  encountered,  which  convey  important 
constructive  and  nutrient  material  to  the  epithelial  cells.  On  high  -magnification 
the  cells  are  found  to  be  provided  with  a  fibrillar  structure.  The  interstices 
between  the  prickles  serve  as  lymph-paths.  The  more  superficial  layers  (b), 
stratum  corneum,  consist  of  flat,  horny,  non-nucleated,  epidermic  scales  (E)  that 
swell  up  in  sodium  hydrate.  The  division  between  these  two  layers  is  constituted 
by  a  layer  especially  distinct  when  the  epidermis  is  thick — of  bright  transitional 
forms  of  cells — stratum  lucidum  (between  b  and  d) .  The  uppermost  layers  of  the 
epidermis  are  being  continually  desquamated,  while  new  layers  of  cells  resulting 
from  division  of  the  rete  cells  are  constantly  brought  up  from  the  depth.  In  this 
process,  the  cells  that  are  elevated 
acquire  the  microscopic  and 
chemical  character  of  the  horny 
layer,  inasmuch  as  the  nucleus  un- 
dergoes atrophy. 

Wherever  pigment  is  present 
in  the  epidermis  itself  and  likewise 
in  the  epidermoidal  structures,  it 
is  conveyed,  in  many  situations, 
from  the  underlying  connective 
tissue  by  the  stellate  wandering 
cells.  In  this  way  is  explained  the 
fact  that  pieces  of  epidermis  trans- 
planted from  a  white  person  to  a  FlG-  '  TO-— Cutaneous  Papillae  Deprived  of  their  Epidermis 
r^crrn  cnrm  Wv-nrnP  rlarV  TTI  rpr  and  the  Vessels  Injected:  a  a  a,  tactile  papillae,  each  con- 

taining a  Meissner  corpuscle. 

tain  other  situations,  however — 
as,   for  instance,    on    the    mam- 
milla— it  can  be  shown  that  the  pigment  is  formed  in  the  deep  epidermal  cells 
themselves.     Finally,  the  pigment  in  connective-tissue  cells  is  said  to  be  derived 
in  part  from  that  formed  in  the  epidermal  cells. 

In  the  layer  of  the  epidermis  in  which  the  process  of  cornification  takes  place, 
therefore,  from  the  upper  layers  of  prickle-cells  down  to  the  actual  cornified 
epidermis,  the  cells  contain  two  varieties  of  granules — the  albuminoid,  intracellular, 
hyaline  granules,  and  the  fat-like,  extracellular  granules  of  eleidin,  which  are 
exhibited  in  an  analogous  manner  by  all  horny  structures  at  the  boundary  of  the 
process  of  cornification.  The  granules  of  eleidin  can  be  stained  with  henna,  the 
hyaline  granules  with  hematoxylin.  Both  structures  are  said  to  be  allied  to 
chitin. 

Between  the  prickle-cells  of  the  epidermis,  and  between  the  laminated  epithelial 
cells  of  the  mucous  membrane,  Herxheimer  observed  peculiar,  spiral,  solid  fibers, 
which  appeared  to  consist  of  fibrin-like  masses.  The  elastic  fibers  of  the  horny 
.skin  undergo  hyaline  swelling  and  scaly  or  granular  disintegration  as  a  phenom- 
enon of  age. 

THE  NAILS  AND  THE  HAIR. 

The  nails  consist  of  numerous  layers  of  firmly  united  cornified  prickly  epi- 
dermal cells,  which  can  be  isolated  by  caustic  alkalies,  and  at  the  same  time 
undergo  swelling  and  display  a  nucleus  (Fig.  178,  n,  m).  The  entire  inferior 
surface  of  the  nail  rests  upon  the  nail-bed.  The  posterior  and  the  lateral  borders 
are  situated  in  a  deep  groove,  the  nail-fold  (Fig.  180,  <?).  The  corium  beneath 


528 


THE    NAILS    AND    THE    HAIR. 


FIG.  180. — Transverse  Section  of  One-half  of  a  Nail,  through  the  True 
Nail-bed  (after  Biesiadecki) :  a,  nail-substance;  b,  subjacent  loose 
horny  layer;  c,  mucous  layer;  d,  nail-ridge  divided  transversely;  e, 
nail-fold  without  papillae;  /,  the  horny  layer  of  the  nail-fold,  which 
has  pushed  itself  over  the  nail;  g,  papillae  of  the  skin  of  the  dorsum 
of  the  finger. 


the  nail  is  provided  throughout  the  entire  extent  of  the  nail-bed  with  longitudinal 
rows  or  bands  of  papillae  (Fig.  180,  d).  Immediately  above  these,  as  upon  the 
skin  in  other  situations,  is  the  laminated,  prickle-cell  layer  of  the  Malpighian 

mucous  network  (Fig.  180, 
c).  Over  this  the  nail  is 
spread,  thus  representing 
the  horny  layer  of  the  nail- 
bed  (Fig.  1 80,  a).  The  pos- 
terior nail-fold  and  the 
semilunar,  brighter  portion 
of  the  nail,  the  lunula,  con- 
stitute the  root  of  the  nail. 
With  the  exception  of  a 
small  surrounding  area, 
they  form  at  the  same 
time  the  matrix,  from  which 
the  growth  of  the  nail  takes 
place.  The  whitish  cres- 
cent, present  also  on  iso- 
lated nails,  is  due  to  the 
lessened  translucence  of  this 
posterior  portion  of  the  nail, 
and  this  is  a  result  of  the 
special  thickness  and  the 
uniform  distribution  of  the 
cells  of  the  mucous  layer  in 
this  situation. 

Growth  and  Develop- 
ment.— According  to  Unna,  working  under  Waldeyer,  the  matrix  of  the  nail  is 
formed  only  by  the  floor  and  not  also  by  the  roof  of  the  fold  up  to  the  anterior 
border  of  the  lunula.  The  nail  grows  continuously 
from  behind  forward,  and  it  is  formed  in  layers 
by  separation  of  the  matrix.  These  layers  are 
parallel  with  the  surface  of  the  matrix,  though 
not  with  that  of  the  nail.  They  pass  obliquely 
from  above  and  behind,  downward  and  forward, 
through  the  thickness  of  "the  nail-structure.  The 
nail  is  of  uniform  thickness  from  the  anterior 
border  of  the  lunula  to  the  free  margin.  It,  there- 
fore, no  longer  grows  in  thickness  in  this  area,  ex- 
cept by  the  deposition  of  new  cornified  layers  of 
cells  from  the  mucous  layer  on  the  under  surface  of 
the  nail.  In  the  course  of  a  year,  the  fingers  yield 
about  2  grams,  the  hands  and  feet,  3.43  grams  of 
nail-substance — in  the  summer  relatively  more 
than  in  the  winter. 

In  the  development  of  the  nail,  Unna  observed 
the  following  stages:  (i)  Between  the  second  and 
the  eighth  month  of  fetal  life,  the  situation  of 
the  nail  is  occupied  by  a  partial  increase  of  the 
cornification  of  the  epidermis  on  the  dorsal  aspect 
of  the  terminal  phalanx — the  eponychium.  As 
the  remains  of  this,  there  persists  throughout  the 
whole  of  life  the  normally  formed,  epidermal, 
horny  layer  that  separates  the  subsequently  de- 
veloped, definitive  nail  from  the  roof  of  the  fold. 
(2)  The  definitive  nail  develops  in  the  fourth 
month  beneath  the  eponychium.  The  base  of  the 
nail  is  situated,  at  first,  at  the  extremity  of  the 
terminal  phalanx,  and  subsequently  moves  fur- 
ther toward  the  dorsum.  In  the  seventh  month, 
the  actual  thin  nail,  itself  still  covered  with 
eponychium,  covers  the  entire  extent  of  the  nail- 
bed,  and  in  the  eighth  month  it  penetrates  the 
fold  wholly.  (3)  When,  subsequently,  the  eponychium  is  exfoliated,  the  nail  is 
disclosed.  After  birth,  the  papillae  develop  upon  the  nail-bed,  and,  at  the  same 
time,  the  matrix  extends  to  the  most  posterior  portion  of  the  fold. 


FIG.  181. — Transverse  Section  of  a  Hair 
below  the  Neck  of  the  Hair-follicle: 
a,  external  sheath  of  the  hair-follicle, 
with  (b)  blood-vessels  in  transverse 
section;  c,  internal  sheath  of  the  hair- 
follicle;  d,  vitreous  layer  of  a  hair- 
follicle;  e,  external,  g,'  internal  root- 
sheath;  /,  external  layer  (Henle's 
sheath);  g,  inner  layer  of  the  latter 
(Huxley's  sheath);  h,  cuticula;  /, 
hair. 


THE    NAILS    AND    THE    HAIR.  529 

The  Hair. — With  the  exception  of  the  palm  of  the  hand,  the  sole  of  the  foot, 
the  dorsal  aspect  of  the  third  phalanges  of  the  fingers  and  toes,  the  external 
surface  of  the  eyelids,  the  glans  penis,  the  inner  surface  of  the  prepuce,  a  portion 
of  the  labia,  and  the  lips,  the  skin  of  the  entire  body  is  covered  with  in  part  large 
and  in  part  small  hairs  (lanugo) .  The  hair  is  embedded  by  means  of  its  root  in  a 
depression  in  the  skin — hair- follicle  (Fig.  178,  I) — which  passes  obliquely  through 
the  thickness  of  the  skin,  at  times  down  into  the  subcutaneous  connective  tissue.  In 
the  hair-follicle  the  following  parts  are  distinguished:  (i)  The  external  fibrous  layer 
(Fig.  178,  i,  and  Fig.  181,  a),  constituted  of  nucleated  connective-tissue  bun- 
dles pursuing  principally  a  longitudinal  course,  and  in  which  the  vessels  and 
nerves  are  distributed.  (2)  The  inner  fibrous  layer  (Fig.  178,  2,  and  Fig.  181,  c), 
which  contains  connective-tissue  fibers  pursuing  especially  a  transverse  course. 
Toward  the  orifice  of  the  hair- follicles,  this  layer  passes  over  into  the  portion  of 
the  cutis  vera  forming  the  papillae.  At  the  bottom  of  the  hair-follicle  there  is 
formed  from  the  inner  fibrous  sheath  the  bulbous,  vascular  hair-papilla — compara- 
ble to  a  papilla  of  the  cutis — the  matrix  of  the  hair,  from  which  the  growth  of 
the  hair  takes  place.  (3)  The  innermost  layer  of  the  hair-follicle  proper  forms,  be- 
sides, a  vitreous  layer  (Fig.  178,  3,  and  Fig.  181,  d).  It  terminates  at  the  neck 
of  the  hair-papilla;  above,  its  prolongation  passes  to  the  junction  between  the 
cutis  vera  and  the  epidermis.  In  addition  to  these  layers,  the  hair-follicle  has 
an  epithelial  lining,  which  must  be  looked  upon  as  related  to  the  epidermis.  Thus, 
the  external  root-sheath  (Fig.  178,  4,  and  Fig.  181,  e),  consisting  of  several  layers 
of  soft  cells  of  fibrillar  appearance,  separated  by  spaces,  and  lying  in  contact 
with  the  vitreous  layer,  appears  as  a  direct  continuation  of  the  Malpighian  mucous 
layer,  and  its  outermost  layer  exhibits  cells  stretched  laterally.  At  the  bottom 
of  the  hair-follicle  it  becomes  narrower,  and  on  fully  developed  hairs  it  is  delimited 
from  the  root  of  the  hair  itself.  The  horny  layer  of  the  epidermis,  passing  down 
into  the  hair- follicle  to  the  orifice  of  the  sebaceous  glands,  retains  the  properties 
that  it  possesses  upon  the  external  skin.  Below  the  orifice,  however,  its  con- 
tinuation forms  the  so-called  internal  root-sheath.  This  consists  (i)  of  the  outer 
single  layer  (Fig.  178,  5,  and  Fig.  181,  /)  of  longitudinal,  flat,  homogeneous, 
nucleated  cells  (Fig.  178,  magnified  at  i) — Henle's  layer — lying  next  to  the  outer 
root-sheath.  Internal  to  this,  there  lies  (2)  the  layer  of  Huxley  (Fig.  178,  6, 
and  Fig.  181,  g),  constituted  of  nucleated,  rather  longitudinal,  polygonal  cells 
(Fig.  178,  x) ;  and,  finally  (3)  the  cuticula  of  the  inner  root-sheath,  a  layer  formed 
of  cells  in  a  manner  analogous  to  the  superficial  covering  of  the  hair,  separates 
the  inner  root-sheath  from  the  hair  itself.  Toward  the  ha*lr-bulb,  this  triple  layer 
becomes  ill  defined,  its  cells  mingling  with  those  of  the  hair-bulb,  without  distinct 
limitation.  All  hair-bulbs  are  provided  with  nerve-cells  and  nerve-fibers,  the 
latter  having  a  bifid  termination. 

The  arrector  pili  muscle  (Fig.  178,  A)  is  a  flat,  expanded  layer  of  unstriped 
muscle-fibers  passing  from  the  outer  fibrous  layer  of  the  bottom  of  the  hair- 
follicle  to  the  upper  layer  of  the  true  skin,  and  always  subtending  the  obtuse 
angle  formed  by  the  obliquely  directed  hair-follicle  with  the  surface  of  the  skin. 
Therefore,  its  contraction  must  cause  the  hair  to  become  erect  (goose-flesh).  As 
a  sebaceous  follicle  is  usually  present  in  the  angle  mentioned,  the  contraction 
may,  by  pressure,  cause  evacuation  of  the  secretion  of  the  gland.  In  addition, 
the  muscle  exerts  a  compressing  effect  upon  the  vessels  of  the  papillary  body. 
Goose-flesh  never  occurs  upon  the  ear,  the  hand,  or  the  foot.  Occasionally  it 
is  only  unilateral  or  confined  to  circumscribed  areas.  The  pilomotor  nerves  are 
described  on  p.  719. 

The  arrectores  pilorum  receive  their  nerves  (pilomotor  nerves)  from  branches 
that  pass  from  the  spinal  cord  and  thence  into  the  sympathetic.  The  irritation 
of  certain  ganglia  of  the  sympathetic  has  caused  erection  of  the  hair  in  definite 
circumscribed  areas  of  the  skin  in  the  ape.  The  muscles  are  stimulated  by  reflex 
influences,  which  either  extend  over  the  entire  body  or  remain  strictly  unilateral 
or  local. 

The  hair,  which  remains  firmly  attached  to  the  surface  of  the  hair-papilla  by 
means  of  its  swollen,  lowermost  portion,  the  head  of  the  hair,  consists  of  three 
parts:  (i)  The  medullary  substance  (Fig.  178,  I,  i),  which  is  wanting  in  the 
lanugo  and  in  the  hair  of  early  childhood,  consists  of  a  central  row  of  cells,  from 
two  to  eight  in  number,  lying  side  by  side  (H,  c).  (2)  Surrounding  this  is  the 
thicker  cortical  layer  (h) ,  which  consists  of  long,  rigid,  cornified  hair-fiber  cells 
(H,  f,  f),  containing  the  pigment-granules  of  the  hair.  Nevertheless,  the  hair- 
fibers  at  times  possess,  besides,  a  diffuse  tint.  These  fibers  consist  of  minute 
longitudinal  horn-fibrils,  and  exhibit  a  longitudinal  nucleus  when  boiled  with 
34 


530 


THE    NAILS    AND    THE    HAIR. 


..1 


caustic  alkalies.  (3)  Upon  the  surface  of  the  hair  is  the  cuticula  (k),  consisting 
of  laminated  and  non-nucleated  scales  arranged  like  the  shingles  on  a  roof  (H,  e). 
The  graying  of  the  hair  in  late  life  is  dependent  upon  a  deficiency  in  pigment- 
formation  in  the  cortical  structure.  The  silvery  luster  of  white  hair  is  further 
increased  by  the  development  of  numerous  air-bubbles,  in  large  number  in  the 
medulla,  but  also  in  small  number  in  the  cortex,  which  reflect  the  light.  Occa- 
sionally pigment  develops  in  the  growing  hair,  at  times  not,  so  that,  accordingly, 

it  appears  discolored  in  places  and  not  so  in 
others.  Sudden  graying  of  the  hair,  of  which 
well-authenticated  records  exist,  and  which 
has  also  been  observed  upon  one  side  of  the 
body,  was  found  by  Landois  in  the  case  of  a 
man  who  during  an  attack  of  delirium  tremens 
was  harassed  by  frightful  hallucinations  and 
became  gray  during  a  single  night,  to  be  de- 
pendent upon  the  presence  of  many  air-bub- 
bles throughout  the  entire  medulla  of  the 
blond  hair,  and  in  smaller  numbers,  also,  in 
the  cortical  structure,  while  the  pigment  was 
preserved.  These  air-bubbles  imparted  an 
exquisite  gray  luster  to  the  hair.  In  rare 
cases,  intermittent  graying  of  the  hair  of  the 
scalp  has  been  observed;  so  that  the  hair  ex- 
hibited alternately  light  and  dark  curls  at  in- 
tervals of  about  i  mm.  In  such  a  case,  Lan- 
dois found  the  bright  areas  to  be  due  to  an 
abundant  development  of  small  air-bubbles  in 
the  medullary  canal  and  the  surrounding  corti- 
cal area,  while  the  pigment  was  well  preserved. 
As  to  the  development  of  the  hair,  Kolliker 
has  discovered  that,  first,  about  the  twelfth  or 
thirteenth  week,  depressions  like  the  finger  of 
a  glove  take  place  from  the  epidermis  into  the 
corium.  They  are  bounded  externally  by  a 
vitreous  membrane,  and  internally  are  occu- 

Eied  by  soft  homogeneous  cells  of  the  Malpig- 
ian  mucous  network.  As  these  depressions 
subsequently  enlarge  downward  and  acquire  a 
flask-like  shape,  the  cells,  arranged  axially,  ac- 
quire a  rather  longitudinal  form  and  constitute 
a  conical  body,  rising  from  the  bottom  of  the 
recess.  On  this  body  there  can  be  recognized 
an  inner,  darker  portion,  the  primitive  hair; 
and  a  thin,  light,  overlying  cover,  the  inner 
root-sheath.  The  outermost  cells,  in  contact 
with  the  wall  of  the  fold,  become  the  external 
root-sheath.  Even  before  this,  the  papilla 
grows  from  below  toward  the  hair-root ;  while, 
at  the  same  time,  the  fibrous  layers  of  the  hair- 
follicle  develop  externally.  Later  on,  the  apex 
of  the  hair  grows  toward  the  horny  layer  of 
the  epidermis.  Here  the  apex  penetrates  the 
inner  root-sheath,  which  is  reflected  upon  the 
constantly  growing  hair  like  a  sleeve.  In  the 
nineteenth  week  the  hairs  appear  upon  the 
forehead  and  the  brow;  between  the  twenty- 
third  .  and  the  twenty-fifth  week  the  lanugo- 
hair  appears  free,  having  a  characteristic 
direction  or  grain  on  all  parts  of  the  body, 

just  as  is  the  case  in  animals.     According  to  Kolliker,  children  are  born  only  with 
lanugo-hair. 

Of  the  physical  properties  of  the  hair,  its  great  elasticity  (tension,  0.33  of  its 
length) ,  marked  cohesion  (traction  of  from  i  \  to  3  ounces) ,  great  resistance  to 
putrefaction,  as  well  as  its  high  hygroscopic  power,  should  be  pointed  out.  The 
last  property  is  possessed,  also,  by  the  epidermal  cells,  as  indicated  by  the  pains 
of  clavi  and  cicatrices  in  damp  weather. 


FIG.  182. — Longitudinal  Section  through  a 
Hair-follicle,  with  the  Hair  in  Process  of 
Change  (after  v.  Ebner):  a,  external  and 
middle  hair-follicle  sheaths;  b,  vitreous 
layer;  c,  hair- papillae  with  vascular  loop; 
d,  external,  e,  internal  root-sheath  (differ- 
entiated into  Henle's  and  Huxley's  layer); 
/,  cuticula  of  the  inner  root-sheath;  g, 
cuticula  of  the  hair;  h,  young,  non-medul- 
lated  hair;  i,  conical  tip  of  the  new  hair; 
/,  hair  polyp  of  the  exfoliated  hair  with,  k, 
the  remains  of  the  exfoliated  external 
root-sheath. 


THE    GLANDS    OF    THE    SKIN.  531 

The  growth  of  the  hair  takes  place  by  the  constant  formation  by  cellular 
division  of  new  cells,  at  first  soft,  upon  the  surface  of  the  papilla,  which  represents 
the  matrix  of  the  hair.  These  cells  are  situated  upon  the  lower  surface  of  the 
hair-bulb,  acquire  the  shape  characteristic  of  the  different  portions  of  the  hair  to 
which  they  become  attached,  and  eventually  undergo  cornification.  Thus,  every 
newly  formed  layer  raises  the  hair  to  a  higher  level  out  of  the  follicle.  Human 
beings,  between  the  eighteenth  and  twenty-sixth  year,  produce  daily  0.20  gram  of 
hair-tissue — corresponding  to  a  loss  of  nitrogen  represented  by  0.0615  gram  of 
urea — and  even  more  in  summer;  and  when  frequently  cut,  according  to  Beneke, 
14.6  grams  of  hair-tissue  from  the  scalp  annually.  lodin  or  bromin,  ingested 
into  the  body,  passes  into  the  tissue  of  the  hair. 

As  to  changes  in  ike  hair,  the  statements  made  are  by  no  means  unanimous. 
According  to  one  view,  after  the  hair  has  attained  its  typical  length,  the  formative 
process  upon  the  surface  of  the  hair-papilla  is  uninterrupted.  The  hair-bulb  rises 
from  the  papilla,  becomes  cornified,  remains  generally  free  from  pigment,  and  is 
finally  raised  more  and  more  from  the  surface  of  the  papilla,  while  its  bulbous 
lower  extremity  becomes  fibrillated  like  a  broom  (Fig.  182).  The  lower  portion 
of  the  hair-follicle,  thus  made  empty,  diminishes  in  size;  and  upon  the  old  papilla 
a  new  hair  is  formed  through  resumption  of  the  formative  processes,  while  the 
old  soon  becomes  detached  and  falls  out.  In  opposition  to  this  view,  Steinlein, 
Stieda,  and  others,  contend  that  the  papilla  of  the  old  hair  is  destroyed,  while  a 
new  one  forms  in  the  hair-follicle,  from  whose  surface  the  formation  of  the 
new  hair  takes  place.  Finally,  Kolliker  and  Waldeyer  believe  both  that  new  hair 
forms  upon  the  old  papilla  and  that  its  formation  may  take  place  upon  a  new 
papilla.  The  statement  that  hairs  may  be  newly  formed  in  adults,  as  in  the  fetus, 
is  denied  by  v.  Ebner. 

THE  GLANDS  OF  THE  SKIN. 

The  sebaceous  glands  (Fig.  178,  I,  T)  are  simple  acinous  glands  that  in  the 
case  of  large  hairs  empty  laterally  by  from  one  to  three  openings  into  the  hair- 
follicle,  while  in  the  case  of  small  hairs  the  follicle  projects  free  through  the  ex- 
cretory duct  of  the  gland  (Fig.  183).  The  glands  upon  the  labia  minora,  the 
glans  penis,  the  prepuce  (Tyson's  glands),  and  those  upon  the  red  surface  of  the 
lips  bear  no  relation  to  hair- follicles.  The  largest  are  present  upon  the  nose  and 
the  labia;  they  are  entirely  wanting  upon  the  palm  of  the  hand  and  the  sole  of 
the  foot.  The  glands  contain  polyhedral  or  circularly  flat,  nucleated,  secre- 
tory cells  (Fig.  178,  t),  through  whose  proliferation  several  layers  of  epithelium 
result,  the  elements  of  which  undergo  fatty  degeneration  as  they  advance  toward 
the  lumen  of  the  gland,  where  they  are  broken  up  into  fatty  detritus.  The 
membrane  that  gives  form  to  the  gland- vesicle  is  a  structureless  vitreous  skin. 

The  sudoriferous  glands  (Fig.  178,  I,  K),  also  designated  sweat-glands,  each 
consist  of  a  long,  intestine-like,  diverticular  tube,  whose  extremity  is  rolled  into  a 
convoluted  mass  in  the  subcutaneous  connective  tissue ;  while  the  somewhat  smaller 
excretory  extremity  passes  through  the  corium  and  the  epidermis  in  a  spiral 
manner — in  the  illustration  it  is  shown  in  abbreviated  form.  The  cells  of  the 
sweat-glands  are  more  compact,  and  are  provided  with  intercellular  and  intra- 
cellular  secretory  passages  and  a  rod-shaped  central  body.  The  glands  are 
numerous  and  large  on  the  palm  of  the  hand,  the  plantar  surface  of  the  foot, 
in  the  axilla,  the  groin,  the  forehead,  and  about  the  nipple;  scanty  on  the  dorsum 
of  the  trunk;  and  are  wanting  on  the  glans  penis,  the  prepuce,  and  the  margin 
of  the  lips.  Modifications  are  seen  in  the  glands  about  the  anus,  the  wax-glands 
of  the  ears  (ceruminous  glands),  and  the  glands  of  Moll  at  the  margin  of  the 
lids  (which  empty  into  the  hair-follicles  of  the  eyelashes) . 

The  glandular  tube  is  lined  within  the  convolution,  in  the  smaller  part  of  the 
tube  by  a  single  layer  of  nucleated  pavement-epithelium,  and  in  the  larger  part 
by  cylindrical  epithelial  cells  (Fig.  178,  S)  without  membrane,  and  in  part  con- 
taining fatty  granules.  The  membrana  propria  is  structureless  and  surrounded 
by  delicate  connective-tissue  fibrils.  Unstriated  muscular  fibers  pass  in  a  longi- 
tudinal direction  on  the  larger  glands  (Fig.  178,  S,  a).  The  excretory  duct 
(sweat-canal)  contains  no  muscular  fibers  and  is  lined  by  a  laminated  epithelium 
of  flat  cells,  whose  surface  possesses  a  thick,  cuticular  border.  Within  the  epider- 
mis, the  canal  pursues  an  intercellular  course,  without  an  independent  mem- 
brane, between  the  epidermal  cells.  A  network  of  capillaries  surrounds  the  con- 
volution. Before  the  vessels  become  capillary,  the  arteries  form  an  intricate  net- 


532 


THE    SKIN    AS    AN    EXTERNAL    COVERING. 


work  surrounding  the  convolution.  This  bears  a  remarkable  re  emblance  to  the 
network  forming  the  glomerulus  in  the  Malpighian  capsule  of  the  kidney.  Finally, 
a  plexus  of  nerves  passes  to  the  glands. 

The  total  number  of  sudoriferous  glands  may  be  about  two  and  one-half 
millions,  representing  a  secretory  superficies  of  approximately  1080  square 
meters.  With  respect  to  their  function,  it  should  be  borne  in  mind  that  they 
secrete  sweat.  Nevertheless,  an  oily  fat  is  admixed  with  their  secretion,  possibly 
from  special  cells,  and  this  may  predominate  in  the  secretion  in  animals,  as  in 
the  hoof-glands  of  the  frog  of  a  horse's  foot,  the  glands  on  the  sole  of  the  dog's 
foot,  and  those  of  birds'  feet.  Meissner  attributes  only  a  secretion  of  fat  to  the 
convoluted  glands,  and  Unna  also  believes  that  the  sweat  is  produced  from  the 

intercellular  spaces  of  the  prickle-cells,  which 
communicate  with  the  penetrating  sweat- 
/  ducts. 

Tubular  and  reticular  lymphatics  without 
valves  (Fig.  178, 1,  v)  are  present  in  the  cutis, 
in  part  with  blind  terminations  in  the  papillae. 
Neumann  observed  them  arranged  in  the  form 
of  a  network  about  the  hair-follicles  and  their 
glands.  A  coarser  network  of  larger  lymph- 
trunks  is  found  in  the  subcutaneous  tissue. 

The  blood-vessels  appear  principally  in 
two  layers;  namely,  in  a  superficial  layer, 
from  which  the  loops  for  the  cutaneous  papillae 
arise;  and  a  deep  subcutaneous  layer.  Both 
vascular  areas  anastomose  by  means  of  pro- 
cesses. In  addition,  the  glands  of  the  skin  are 
surrounded  by  a  network  of  vessels. 


THE  SKIN  AS  AN   EXTERNAL 
COVERING. 

It  is  the  function  of  the  subcutaneous 
fatty  tissue  to  fill  the  depressions  be- 
tween the  different  parts  of  the  body,  as 
well  as  to  round  off  projecting  portions, 
so  that  the  rounded  fulness  of  the  body- 
form,  agreeable  to  the  eye,  results.  The 
fatty  tissue  acting  as  a  soft  cushion,  also 
affords  protection  from  excessive  pres- 
sure, as  on  the  sole  of  the  foot,  in  the 
palm  of  the  hand,  on  the  buttocks;  and 
it  encloses  various  more  important  parts 
that  may  be  readily  injured,  as,  for  in- 
stance, the  vessels  and  nerves  in  the 

axilla,  the  inguinal  fold,  and  the  popliteal  space.  As  a  poor  con- 
ductor of  heat,  the  subcutaneous  fat  shields  the  body  against  ex- 
cessive loss  of  heat ;  the  cutis  vera  and  the  epidermis  exert  a  similar 
influence  The  firm,  elastic,  readily  movable  cutis  is  capable  of  afford- 
ing protection  against  external  mechanical  injuries,  and  in  this  it  is 
aided  by  the  epidermis,  whose  dry,  impervious,  horny  tissue,  without 
nerves  and  vessels,  is  especially  adapted  to  afford  protection  against 
poisons  in  solution;  and  is  capable  of  offering  considerable  resistance 
even  to  thermic  and  chemical  influences.  A  thin  layer  of  sebum  pro- 
tects the  free  surface  of  the  epidermis  from  maceration  by  fluids  and 
from  the  destructive  action  of  the  air.  The  epidermal  layer  is,  further, 
important  in  the  fluid-economy  of  the  body.  It  exerts  pressure  upon  the 
cutaneous  capillaries,  and  thus  affords  protection  against  excessive  loss 


FIG.  183. — Sebaceous  Gland  with  a  Lanugo- 
hair:  a,  glandular  epithelium;  b,  rete 
Malpighii.  continued  into  the  glandular 
epithelium;  c,  fat-containing  cells  and 
free  fat  as  glandular  contents;  d,  acini; 
e,  root  sheath  with  the  hair. 


CUTANEOUS    RESPIRATION.       CUTANEOUS    SECRETION:  533 

of  fluid  from  the  vessels  of  the  skin.  Portions  of  skin  deprived  of  epi- 
dermis, therefore,  appear  reddened,  and  exude  droplets  of  moisture. 
Large  weeping  areas  of  skin  are  capable  of  impairing  considerably  the 
nutritive  state  of  the  body  through  loss  of  albumin.  The  epidermis  and 
the  epidermoidal  structures  are,  further,  when  dry,  poor  conductors  of 
electricity.  The  passage  of  a  strong  current  diminishes  this  resistance 
to  one-thirtieth,  in  consequence  of  cataphoric  infiltration.  Finally,  it 
may  be  stated  that  the  presence  of  the  uninjured  epidermis  protects 
adjacent  parts  against  adhesion. 

As  the  epidermis  is  but  slightly  extensible,  it  is  drawn  tensely  over  the  folds 
and  papillae  of  the  corium,  which  are  obliterated  on  stretching  the  skin.  Even 
the  papillae  disappear  in  this  way,  if  the  tension  is  considerable. 

The  hairs  serve  in  various  situations  as  tactile  organs — eye-lashes,  lanugo- 
hair  of  the  face;  and  upon  the  head,  as  a  poor  conductor  of  heat,  they  regulate  the 
taking  up  and  the  giving  off  of  heat  and  afford  protection  against  direct  radia- 
tion from  the  sun. 


CUTANEOUS  RESPIRATION.     CUTANEOUS  SECRETION. 

SEBUM.      SWEAT.      PIGMENT-FORMATION. 

The  secretory  activity  of  the  external  integument,  whose  extent  ex- 
ceeds more  than  one  and  a  half  square  meters,  comprises  (i)  the  respi- 
ratory excretion;  (2)  the  secretion  of  the  cutaneous  fat;  and  (3)  the 
secretion  of  sweat. 

Cutaneous  respiration  has  already  been  discussed  (p.  241). 

Suppression  of  the  activity  of  the  skin,  by  varnishing  is  followed,  in  warm- 
blooded animals,  at  first  by  no  reduction  in  the  total  gaseous  interchange.  Proba- 
bly increased  respiratory  activity  on  the  part  of  the  lungs  compensates  for  the 
loss  of  the  respiratory  activity  of  the  skin.  In  certain  mammals,  especially  in 
rabbits,  death  results  from  varnishing  of  the  skin,  probably  in  consequence  of 
excessive  loss  of  heat.  Strong  animals  die  later  than  weak;  horses  only  in  the 
course  of  several  days,  with  trembling  and  emaciation.  The  greater  the  area  of 
skin  that  is  not  varnished,  the  later  does  death  take  place.  Rabbits  die  after 
one-eighth  of  the  surface  of  their  body  has  been  varnished ;  and  after  total  covering 
of  the  skin  the  temperature  at  once  declines,  to  as  low  as  19°.  Pulse  and  respira- 
tion generally  become  less  frequent ;  but  with  circumscribed  varnishing,  increased 
respiratory  frequency  and  increased  excretion  of  urea  have  been  observed.  Swine, 
dogs,  and  horses  are  said  to  exhibit  only  transitory  depression  of  temperature 
and  languor  after  one-half  of  the  surface  of  the  body  has  been  varnished,  though 
life  is  preserved.  Varnishing  of  the  skin  is  not  injurious  to  human  beings. 

The  sebum  of  the  skin.  The  fat  secreted  by  the  sebaceous  glands 
is  fluid  when  discharged,  but  stagnating  within  the  excretory  duct  of  the 
gland  it  is  transformed  into  a  white,  tallowy  mass,  which,  principally 
on  the  alae  of  the  nose,  can  be  expressed  in  sausage-shaped  comedones. 
Its  function  is  to  keep  the  epidermis  and  the  hair  pliable  and  to  pro- 
tect the  skin  against  excessive  desiccation.  Microscopically,  the  secre- 
tion contains  innumerable  fat -globules,  a  few  gland-cells  filled  with  fat 
and  rendered  visible  on  addition  of  sodium  hydrate,  and  in  almost  all 
human  beings  microscopic  mite-like  animals — demodex  folliculorum. 

Chemical  examination  demonstrates  the' presence  principally  of  fats,  particu- 
larly olein  (fluid)  and  palmitin  (solid),  together  with  fatty  soaps,  and  some  choles- 
terin;  in  addition,  a  small  amount  of  albumin  and  unknown  extractives.  Among 
the  inorganic  constituents,  the  insoluble  earthv  phosphates  preponderate;  while 
the  alkaline  chlorids  and  phosphates  are  subordinate.  There  is  some  doubt  as  to 
the  occurrence  of  sodium  and  ammonium  phosphate  and  of  ammonium  chlorid. 


534  CUTANEOUS    RESPIRATION.       CUTANEOUS    SECRETION. 

The  vernix  caseosa,  which  covers  the  skin  of  the  new-born,  is  a  greasy  mixture 
of  cutaneous  fat  and  macerated  epidermis.  It  contains  35  per  cent,  of  water 
and  14  per  cent,  of  ethereal  extracts,  together  with  traces  of  albumin,  chlorin, 
calcium,  magnesium,  and  phosphoric  acid.  Examination  for  fats  disclosed  the 
presence  of  cholesterin,  isocholesterin,  oleic  and  palmitic  acids  (salts  of  fatty  acids) , 
together  with  glycerin.  The  preputial  smegma  (52.8  per  cent,  fat)  is  a  similar 
product,  in  which  an  ammonium-soap  occurs.  Ear-wax  is  a  mixture  of  the  secre- 
tion of  the  ceruminous  glands,  which  resemble  the  sudoriferous  glands,  and  of 
the  glands  of  the  hair-follicles  of  the  auditory  canal.  It  contains,  in  addition  to 
the  constituents  of  the  cutaneous  fat,  a  brown  pigment,  soluble  in  alcohol  and 
fat;  a  bitter  yellow  extractive ;  albumin;  lecithin;  cholesterin;  potassium-soaps; 
and  a  special  fat.  The  secretion  of  the  Meibomian  glands  is  cutaneous  fat.  The 
production  of  the  fatty  coating  necessary  for  the  oiling  of  the  epidermis  takes 
place,  together  with  the  formation  of  keratin,  in  part  within  the  epidermis  itself. 
The  presence  of  cholesterin-fats  in  this  situation  has  also  been  demonstrated  in 
the  layer  of  beginning  cornification. 

The  sweat  is  secreted  by  the  convoluted  glands,  the  nuclei  of  the 
secretory  cells  acquiring  a  more  nearly  circular  outline,  and  the  cells,  in 
the  horse,  becoming  granular.  So  long  as  the  secretion  is  confined  with- 
in narrow  limits,  the  water  secreted,  together  with  the  volatile  constitu- 
ents, evaporates  at  once  from  the  surface  of  the  skin.  As  soon,  however, 
as  the  secretion  increases  or  evaporation  is  inhibited,  the  sweat  appears 
in  pearly  drops  at  the  orifices  of  the  sweat-glands.  The  former  has  been 
designated  insensible,  the  latter  sensible  perspiration. 

The  insensible  perspiration  varies  widely.  Generally,  the  right  side  of  the 
body  perspires  more  freely  than  the  left.  The  palm  of  the  hand  sweats  in  greatest 
measure.  Then,  in  order,  follow  the  sole  of  the  foot,  the  cheek,  the  breast,  the 
thigh,  and  the  forearm.  Sweating  increases  slowly  from  the  morning  onward,  in 
greater  degree  in  the  afternoon,  and  declines  after  the  evening  meal;  then, 
increasing,  it  reaches  its  maximum  before  midnight.  The  presence  of  a  large 
amount  of  moisture  in  the  surrounding  air  diminishes  the  perspiration,  as  do  also 
copious  sweating  previously  and  increased  diuresis.  Children  have  a  relatively 
greater  insensible  perspiration.  Ingestion  of  water  increases,  and  withholding  of 
water  diminishes,  the  sweat;  alcohol  also  diminishes  it.  The  smallest  measure  of 
dissipation  of  watery  vapor  takes  place  at  15°  C.,  while  both  above  and  below 
this  temperature-level  the  dissipation  increases.  The  ordinary  temperature  be- 
neath the  clothing  is  about  32°  C.  At  this  temperature  the  insensible  perspiration 
equals  1500  grams  of  water.  When  the  temperature  of  the  surrounding  atmos- 
phere is  33°  C.  and  above,  sweating  begins.  Generous  nutrition,  warm  clothing, 
and  work  cause  greater  excretion  of  water. 

Pathological. — The  insensible  perspiration  is  increased  in  the  presence  of  dis- 
eases of  the  skin,  principally  the  acute  erythemata.  It  is  diminished  in  cases  of 
scarlet  fever,  especially  in  association  with  uremia. 

Sweat  can  be  collected  in  largest  amount  from  human  beings  by  exposure 
in  the  steam-bath  at  a  high  temperature  in  a  metallic  tub  in  which  the  subject 
lies  and  into  which  the  secretion  of  the  skin  flows.  In  this  way  Favre  collected 
2560  grams  of  sweat  in  one  and  a  half  hours.  It  is  convenient,  also,  to  obtain 
thus  the  partial  secretion  of  sweat  from  the  arm,  which  is  placed  in  a  glass  cylinder 
hermetically  sealed  by  rubber  bandages  about  the  arm. 

In  animals,  sweating  takes  place  in  the  horse,  less  in  cattle,  on  the  palm  and 
the  sole  of  the  foot  of  the  ape,  the  cat,  the  hedgehog.  Swine  sweat  (?)  on  the 
snout,  cattle  about  the  mouth  (?),  while  goats,  rabbits,  rats,  mice,  and  dogs  do 
not  sweat  at  all. 

Microscopically,  sweat  contains  epidermal  scales  and  fatty  granules 
from  the  glands  of  the  skin  accidentally  present.  The  sweat  is  colorless 
and  slightly  turbid,  with  a  specific  gravity  of  1005.  It  has  a  salty  taste 
and  a  characteristic  odor  in  different  portions  of  the  body,  due  to 
volatile  fatty  acids. 

The  moist  epidermis,  including  the  hair  and  the  nails,  has  an  acid 
reaction,  while  the  cutis  has  an  alkaline  reaction.  The  sweat  secreted 


CUTANEOUS    RESPIRATION.       CUTANEOUS    SECRETION.  535 

during  rest  has  an  acid  reaction,  while  if  the  secretion  is  increased,  the 
acidity  diminishes  and  the  reaction  may  even  become  alkaline.  The 
sweat  is  composed  of  a  glandular  secretion  having  an  alkaline  reaction 
and  an  acid  epidermal  secretion.  The  reaction  will  vary  in  accordance 
with  the  preponderance  of  the  one  or  the  other  of  these  constituents. 
The  constituents  of  the  sweat : — Water,  together  with  volatile  sub- 
stances, and  it  increases  after  copious  drinking,  991  parts  in  1000. 
E.  Harnack  found  the  solids  on  the  average  8.5  in  the  thousand,  includ- 
ing organic  matters,  2  in  the  thousand,  and  inorganic  matters,  6.5  in  the 
thousand.  Among  the  organic  substances  there  should  be  mentioned 
some  neutral  fats,  palmitin,  stearin,  found  also  in  the  sweat  of  the  palm  of 
the  hand,  which  contains  no  sebaceous  glands;  in  addition,  cholesterin, 
volatile  fatty  acids,  principally  formic  acid,  together  with  acetic,  bu- 
tyric, proprionic,  caproic,  and  capric  acids,  probably  varying  qualitatively 
and  quantitatively  in  different  portions  of  the  body.  They  are  present 
in  largest  amount  in  the  acid  sweat  first  secreted.  Further,  there  are 
traces  of  sulphocyanid-combinations,  of  albumin  (resembling  casein), 
considerable  urea,  more  than  o.i  per  cent.,  and  also  ammonium-salts 
as  decomposition -products  of  the  latter  in  the  air.  Also  sulphuric  acid, 
in  conjugation  with  skatol  and  phenol,  and  oxyacids  were  found  by 
Kast  in  the  sweat,  uric  acid  by  Tichborne.  In  the  uremic  state — anuria 
attending  cholera — urea  is  even  found  upon  the  skin  in  crystalline 
form. 

Marked  increase  in  the  secretion  of  sweat  in  healthy  persons  and  in  uremic 
patients  diminishes  the  amount  of  urea  in  the  urine.  The  reddish-yellow  pigment 
that  alcohol  extracts  from  the  residue  of  sweat  and  that  is  colored  green  by  oxalic 
acid,  is  of  unknown  composition. 

Among  the  inorganic  substances,  those  that  are  readily  soluble  pre- 
ponderate over  those  that  are  soluble  with  difficulty.  There  have  been 
found  sodium  chlorid,  0.2;  potassium  chlorid,  0.02;  sulphates,  o.oi  in 
1000,  together  with  traces  of  earthy  phosphates  and  sodium  phosphate. 
Of  gases,  the  sweat  contains  carbon  dioxid  absorbed  together  with  some 
nitrogen. 

Of  ingested  substances,  the  following  appear  again  in  the  sweat:  readily, 
benzoic  acid,  according  to  H.  Meissner,  also  hippuric  acid;  cinnamic,  tartaric, 
succinic  acids;  with  greater  difficulty,  quinin,  potassium  iodid,  mercuric  chlo- 
rid, arsenous  and  arsenical  acids,  potassium  and  sodium  arsenate.  After  the 
ingestion  of  iron  arsenite,  iron  is  found  in  the  urine  and  arsenous  acid  in  the 
sweat.  Mercuric  iodid  is  found  transformed  into  chlorid,  the  iodin  passing  over 
into  the  saliva.  When  ingested,  sweat  has  toxic  effects. 

Pigment- formation  takes  place  in  the  form  of  a  granular  deposition, 
principally  in  the  deeper,  and  less  in  the  upper  layers  of  the  Malpighian 
network.  It  thus  occurs  particularly  in  the  anal  fold,  on  the  scrotum, 
and  the  nipple;  as  well  as  universally  in  the  colored  races.  The  horny 
layer  of  the  epidermis  contains  a  diffuse  yellowish-white  pigment,  which 
becomes  darker  in  old  age.  This  pigment -format  ion  is  supposed,  like 
the  process  of  cornification,  to  depend  upon  a  chemical  process,  in  con- 
sequence of  which  reduction  takes  place.  This  process  is  increased  by 
light.  In  addition,  the  prickle-layer  contains  granular  pigment.  The 
dark  discoloration  of  the  epidermis  can  be  removed  and  the  process 
of  cornification  can  be  prevented  by  means  of  free  oxygen. 

Among  pathological  pigment-formations  is  that  which  occurs  in  liver-spots, 
freckles,  and  in  conjunction  with  Addison's  disease. 


536  INFLUENCES    AFFECTING    THE    SECRETION    OF    SWEAT. 


INFLUENCES  AFFECTING  THE  SECRETION  OF  SWEAT. 

The  secretion  of  the  skin,  which  on  the  average  equals  about  -g^  of  the 
weight  of  the  body,  or  twice  the  elimination  through  the  lungs,  may 
be  increased  or  diminished  as  a  result  of  various  influences.  The  tendency 
to  sweating  varies  greatly  in  different  individuals.  Among  the  influences 
affecting  the  secretion  of  sweat  the  following  are  known :  i .  Elevation 
of  the  surrounding  temperature  causes  marked  redness  of  the  skin  and 
profuse  secretion  of  sweat.  Cold  and  a  temperature  of  the  skin  above 
50°  C.  suppress  the  secretion.  2.  The  presence  of  an  increased  amount 
of  water  in  the  blood,  principally  after  the  ingestion  of  warm  fluid  in 
large  amount,  increases  the  sweat.  3.  Marked  activity  on  the  part  of 
the  heart  and  the  vessels,  in  consequence  of  which  the  blood-pressure  in 
the  capillaries  of  the  skin  is  increased,  has  a  similar  effect.  In  this 
category  belongs,  also,  the  increased  sweating  in  consequence  of  violent 
muscular  activity.  Under  such  circumstances  the  excretion  of  nitro- 
gen through  the  sweat  is  increased.  4.  Certain  agents — hydrotics — 
increase  sweating,  such  as  pilocarpin,  physostigma,  strychnin,  picro- 
toxin,  muscarin,  nicotin,  camphor,  and  ammonium-combinations. 
Others,  such  as  atropin  and  morphin  in  large  doses,  diminish  the 
sweat.  5.  The  antagonism  that  exists  between  the  secretion  of  sweat 
and  the  secretion  of  urine  and  the  intestinal  discharges,  probably  in 
consequence  principally  of  mechanical  influences,  is  especially  note- 
worthy in  so  far  as  abundant  micturition,  as,  for -instance,  in  cases  of 
diabetes,  and  thin  stools  are  associated  with  dryness  of  the  skin. 

If  the  amount  of  sweat  is  increased,  the  proportion  of  salts,  urea  and 
albumin  present  increases;  while  the  remaining  organic  substances 
diminish.  The  more  saturated  the  air  with  watery  vapor,  the  more 
readily  does  the  secretion  appear  in  drops  upon  the  surface;  while  in 
dry  air  in  active  motion  the  secretion  appears  as  fluid  later  in  conse- 
quence of  the  rapid  evaporation. 

NERVOUS  CONTROL  AFFECTING  THE  SECRETION  OF  SWEAT. 

As  in  the  secretion  of  saliva,  vascular  nerves  are  principally  active 
in  the  secretion  of  sweat,  in  addition  to  the  true  secretory  nerves;  and 
most  frequently  the  vasodilators,  as  indicated  by  the  sweating  when  the 
skin  is  reddened.  The  observation  of  sweating  when  the  skin  is  pale 
(the  sweating  of  fear  and  of  death)  shows,  however,  that  also  in  the 
presence  of  vasoconstriction,  the  sweat -fibers  may  at  the  same  time 
be  active. 

Under  certain  conditions  an  increase  in  the  amount  of  blood  present  appears 
alone  to  be  sufficient  for  the  occurrence  of  sweating.  In  favor  of  this  view  is  the 
observation  of  Dupuy,  who  noted  unilateral  sweating  of  the  neck  in  a  horse 
after  division  of  the  cervical  sympathetic;  and  in  opposition  to  this  view  is  the 
statement  of  Nitzelnadel,  who  observed  diminution  of  sweating  in  human  beings 
after  percutaneous  galvanization  of  the  cervical  sympathetic. 

Independently  of  the  circulation,  sweat -nerves  of  independent  activ- 
ity control  the  secretion  from  the  surface  of  the  body.  Irritation  of  the 
appropriate  nerve-trunk  still  causes  transitory  secretion  of  sweat  even  if 
the  extremity  has  been  previously  amputated ;  and  therefore  the  circula- 
tion no  longer  exists.  In  addition,  the  secretion  of  sweat  may  take  place 
under  higher  pressure  than  that  of  the  blood.  In  the  healthy  body,  pro- 


NERVOUS    CONTROL    AFFECTING    THE    SECRETION    OF    SWEAT.         537 

fuse  secretion  of  sweat,  it  is  true,  appears  usually  to  be  associated  with 
vascular  dilatation,  like  the  secretion  of  saliva  after  irritation  of  the 
facial  nerve.  Indeed,  the  sudoriferous  and  the  vascular  nerves  appear 
to  pursue  almost  identical  paths. 

For  the  hind  extremity,  in  the  cat,  these  fibers  are  contained  in  the  sciatic 
nerve.  Luchsinger  was  able  to  excite  constantly  renewed  secretion  of  sweat  for 
half  an  hour  by  irritation  of  the  peripheral  stump,  if  the  paw  was  constantly 
kept  dry.  This  nervous  activity  is  destroyed  by  atropin.  If  a  young  cat,  whose 
sciatic  nerve  on  one  side  has  been  divided,  is  placed  in  a  room  filled  with  hot  air, 
the  three  intact  members  soon  sweat,  but  not  that  with  the  divided  nerve,  not 
even  when  excessive  hyperemia  of  the  member  is  induced  by  ligation  of  the  veins. 
The  sweat-fibers  pass  centripetally  from  the  sciatic  nerve,  in  the  abdominal  sym- 
pathetic, in  order  to  reach  the  upper  lumbar  and  lower  dorsal  cord  (twelfth  dorsal 
and  first,  second,  and  third  lumbar  roots  in  the  cat),  through  the  communicating 
branches  of  the  sympathetic  and  through  the  anterior  roots.  The  center  for  the 
secretion  of  sweat  in  the  hind  extremities  is  situated  in  the  ganglia  of  the  anterior 
horns  in  the  lower  dorsal  and  upper  lumbar  portions  of  the  spinal  cord.  According 
to  Langley,  non-medullated  sweat-fibers  pass  in  the  cat  to  the  nerves  from  the 
eleventh  dorsal  to  the  fifth  lumbar,  and  are  derived  from  the  sixth  and  seventh 
lumbar  and  the  first  and  second  sacral  ganglia  of  the  sympathetic.  The  origin 
and  course  of  the  vasomotors  are,  on  the  whole,  the  same. 

This  spinal  center  may  be  irritated  directly  (i)  through  marked 
venosity  of  the  blood;  therefore  through  dyspneic  stimulation.  In 
this  category  belongs  probably  also  the  sweat  of  the  death-agony.  (2) 
Through  overheated  blood  (45°  C.)  passing  through  the  center.  (3) 
By  certain  poisons  (see  p.  536).  Reflex  stimulation  of  this  center  is 
effected,  though  with  varying  result,  through  irritation  of  the  crural  or 
peroneal  nerve  of  the  same  side,  as  well  as  of  the  sciatic  nerve  of  the  op- 
posite side. 

For  the  fore-paws,  in  the  cat,  the  sweat-fibers  pass  in  the  ulnar  and  median 
nerves.  These  pass  from  the  dorsal  roots  between  the  fourth  and  the  tenth  to 
the  dorsal  division  of  the  sympathetic,  and  then  pass  downward  through  the 
stellate  ganglion,  and  thence  into  the  nerves  of  the  anterior  limb. 

An  analogous  center  for  the  anterior  extremities  is  situated  in  the 
lower  half  of  the  cervical  cord.  Irritation  of  the  central  stump  of  the 
brachial  plexus  causes  reflex  sweating  of  the  paw  of  the  opposite  side. 
Under  such  circumstances,  the  hind  paws  also  sweat  at  the  same  time. 

Pathological. — Degeneration  of  the  motor  ganglia  of  the  anterior  horns  of  the 
spinal  cord  induces  loss  of  the  secretion  of  sweat,  together  with  paralysis  of  the 
striated  muscles  of  the  trunk.  Perspiration  is  increased  in  enfeebled  as  well  as  in 
edematous  extremities.  Nephritic  patients  exhibit  great  variations  in  the  amount 
of  water  given  off  by  the  skin.  Dieffenbach  observed  that  sweating  reappeared 
in  transplanted  bits  of  skin  only  after  the  return  of  sensitivity. 

The  sweat-fibers  for  the  head  (man,  horse;  snout  in  swine)  are  derived  from 
the  upper  dorsal  sympathetic,  pass  through  the  stellate  ganglion  and  ascend  in 
the  cervical  sympathetic.  The  observation  is  probably  appropriate  here  that  in 
human  beings  percutaneous  galvanization  of  the  cervical  sympathetic  causes 
sweating  on  the  same  side  of  the  face  and  the  arm,  as  well  as  the  pathological 
observation  that  in  association  with  unilateral  sweating  of  the  head,  neck,  and 
upper  extremity,  the  corresponding  pupil  is  dilated  and  the  skin  is  pale.  In  the 
cephalic  portion  of  the  sympathetic  the  sweat-fibers  enter  the  branches  of  the 
trigeminus,  and  this  fact  explains  the  circumstance  that  irritation  of  the  infra- 
orbital  nerve  excites  the  secretion  of  sweat.  Some  fibers,  however,  arise  directly 
from  the  trigeminal  roots  and  the  facial  nerve. 

Undoubtedly,  the  cerebrum  must  also  exert  a  direct  influence  either 
upon  the  vasomotor  nerves  or  upon  the  sweat -fibers,  as  is  shown  by  the 
sweating  that  attends  emotional  disturbances,  fright,  etc. 


538  PHYSIOLOGICAL    CARE    OF    THE    SKIN. 

An  observation  of  Adamkiewicz  and  Senator  tends  to  support  this  view. 
They  noted  that  in  a  human  being  with  an  abscess  in  the  motor  area  of  the  cerebral 
cortex  for  the  arm,  convulsions  and  sweating  occurred  in  this  member. 

According  to  Adamkiewicz,  all  of  the  four  paws  of  the  cat  sweat  on 
irritation  of  the  medulla  oblongata,  in  which  the  dominating  center  for 
the  secretion  of  sweat  appears  to  be  situated,  even  three-quarters  of  an 
hour  after  death. 

Nerve-fibers  that  pass  to  the  unstriated  muscular  fibers  of  the  sudorif- 
erous glands,  and  are  wanting  in  the  smaller  glands,  must  have  an  influ- 
ence upon  the  discharge  of  the  secretion. 

Pilocarpin  and  other  diaphoretics,  when  injected  subcutaneously,  even  after 
division  of  the  nerves,  cause  sweating  first  at  the  site  of  injection.  Atropin,  in 
the  same  way,  causes  first  local  suppression  of  sweat-secretion.  If  the  sweat- 
nerves  are  divided,  in  the  cat,  the  irritability  of  the  fibers  (sciatic)  to  electrical 
stimulation  is  lost  in  the  course  of  four  days.  In  cats  operated  on,  delayed 
sweating  after  injection  of  pilocarpin  occurs  during  the  course  of  three  days,  and 
this  may  be  prolonged,  after  the  lapse  of  six  days,  even  to  a  delay  of  ten  min- 
utes. At  a  later  period,  the  sweating  may  remain  entirely  in  abeyance.  The 
familiar  phenomenon  of  the  dry  skin  of  paralyzed  members  is  in  accord  with  this 
observation. 

If  in  man,  a  motor  nerve,  such  as  the  tibial,  median,  or  facial,  be  irritated, 
sweat  appears  in  the  distribution  of  the  active  musculature  and  in  the  corre- 
sponding distribution  on  the  unirritated  half  of  the  body ;  and  both  when  the  cir- 
culation is  free,  as  well  as  when  it  is  arrested.  On  sensory  and  thermic  irritation 
of  the  skin,  there  likewise  occurs  reflex  sweating  always  upon  both  sides,  inde- 
pendently of  the  circulation.  The  seat  of  the  sweating  is  independent  of  the 
site  of  cutaneous  irritation.  In  the  case  of  the  author  himself,  cold  sweat  appeared 
immediately  upon  the  forehead  as  soon  as  the  mucous  membrane  of  the  mouth  was 
irritated  by  strong  vinegar. 


PHYSIOLOGICAL  CARE  OF  THE  SKIN. 

PATHOLOGICAL   ABNORMALITIES    IN    THE    SECRETION    OF    SWEAT    AND 

SEBUM. 

In  order  to  maintain  the  normal  secretion  of  the  skin,  the  care  of  this  organ 
by  means  of  frequent  ablution  and  baths,  soap  being  used  to  remove  the  fatty 
accumulation  upon  the  skin,  is  of  the  greatest  significance,  as  in  this  way  the 
pores  are  kept  open.  By  friction  of  the  epidermis,  baths  aid  metabolism,  by  an 
action  upon  the  cutaneous  vessels  influence  the  circulation  and  the  heat-economy 
of  the  body,  and  have  a  stimulating  effect  upon  the  nervous  system.  The  estab- 
lishment of  public  bath-houses  must  be  considered  among  the  most  beneficent 
measures  for  the  preservation  of  the  public  health. 

Diminution  in  the  secretion  of  sweat,  anidrosis,  occurs  in  cases  of  diabetes  and 
carcinomatous  cachexia;  further,  together  with  other  nutritive  disorders  of  the 
skin,  in  connection  with  certain  nervous  diseases,  as,  for  instance,  paralytic  de- 
mentia. It  has  been  observed  in  circumscribed  areas  of  the  skin  as  one  of  the 
phenomena  of  certain  trophoneuroses ;  as,  for  instance,  unilateral  atrophy  of  the 
face,  and  in  paralyzed  parts.  In  some  of  these  cases  there  may  be  paralysis  of 
the  nerves  in  question,  or  of  their  spinal  centers. 

Increase  in  the  secretion  of  sweat,  hyperidrosis,  occurs  in  part  in  readily  excit- 
able persons,  in  consequence  of  irritation  of  the  nerves  in  question.  In  this  cate- 
gory belongs  the  sweating  that  attends  debilitated  states,  and  that  occurs  also  in 
hysterical  persons,  principally  upon  the  head  and  the  hands;  and  the  so-called  epilep- 
toid  sweats  that  occur  paroxysmally.  Unilateral  sweating,  principally  of  the  head, 
long  known  to  earlier  physicians,  is  especially  noteworthy.  This  has  been  ob- 
served in  conjunction  with  other  nervous  disorders,  in  part  among  the  symptoms 
of  irritation  of  the  cervical  sympathetic — dilatation  of  the  pupils,  exophthalmos. 
Landois  has,  however,  observed  unilateral  sweating  without  other  evidence  of 
sympathetic  disorder,  probably  as  a  manifestation  of  irritation  of  the  true  sweat- 
fibers. 

Qualitative   alterations  in  the  secretion  of  sweat,  paridrosis.     In   this   cate- 


ABSORPTION    THROUGH    THE    SKIN.  539 

gory  belong  the  rare  cases  of  blood-sweating,  hematidrosis ,  which  may  also  be  uni- 
lateral, and  in  which,  at  times,  the  bloody  discharge  from  the  pores  of  the  skin 
appears  to  take  place  vicariously  for  absent  menstruation.  More  commonly,  how- 
ever, the  condition  has  been  one  of  the  symptoms  of  a  profound  nervous  disorder, 
especially  convulsive  seizures.  Blood-corpuscles,  rarely  blood-crystals,  have  been 
found  in  the  escaping  drops  of  red  sweat.  Yellow  fever  also  is,  at  times,  attended 
with  bloody  sweats.  Biliary  pigment  has  been  found  in  the  sweat  of  jaundiced 
persons;  a  bluish-black  discoloration,  further  a  blue  color  from  indigo,  from  pyo- 
cyanin  (the  rare  blue  pigment  of  pus),  produced  by  the  bacillus  pyocyaneus,  or 
from  ferric  phosphate,  are  among  the  rarest  exceptions.  Such  colored  sweating 
is  designated  chrornidrosis. 

Between  the  epidermal  scales  and  upon  the  hair  there  live  numerous  micro- 
organisms, which,  however,  must  be  designated  as  innocuous:  Two  varieties  of 
saccharomyces ;  the  leptothrix  epidermidis  and  various  bacteria  on  surfaces  the 
seat  of  intertrigo,  namely,  five  varieties  of  micrococci;  and  between  the  toes,  the 
bacterium  graveolens  and  bacillus  saprogenes,  which  generate  the  odor  of  the  sweat 
of  the  foot.  Yellow,  blue,  and  red  sweat  are  likewise  caused  by  bacteria,  the  last 
by  the  micrococcus  haematodes.  Red  sweat  and  black  sweat  may  be  caused  also 
by  a  variety  of  torula.  Within  the  lesions  of  acne  and  in  comedones,  there  vegetates 
a  thick  bacillus,  which  Hodara  considers  as  the  cause  for  the  formation  of  the 
pustule. 

Grape-sugar  has  been  found  in  the  sweat  in  cases  of  diabetes;  rarely  uric 
acid,  in  individuals  with  calculi;  cystin,  in  cases  of  cystinuria.  In  the  fetid  sweat 
of  the  feet,  leucin,  tyrosin,  valerianic  acid,  and  ammonia  are  present.  This  con- 
dition can  be  corrected  only  by  the  most  systematic  and  scrupulous  cleanliness. 
To  the  foot-baths,  anti-fermentative  and  bactericidal  substances  should  be  added, 
such  as  salicylic  acid  or  potassium  permanganate.  Odorous  secretion  of  sweat  is 
designated  as  osmidrosis,  fetid  sweating  as  bromidrosis.  In  the  sweating  stage  of 
intermittent  fever,  considerable  calcium  butyrate  has  been  found;  in  cases  of 
puerperal  fever,  lactic  acid.  The  viscid  sweat  of  acute  articular  rheumatism  is 
said  to  contain  a  greater  amount  of  albumin,  as  does  also  the  sweat  attending 
enforced  diaphoresis. 

With  respect  to  abnormalities  in  the  secretion  of  the  cutaneous  sebum,  there 
should  be  mentioned  the  pathological  increase  in  secretion — seborrhea — which 
occurs  either  locally  or  disseminated  over  the  entire  skin.  In  cases  of  premature 
baldness,  there  is  increased  production  of  sebum  on  the  scalp.  Diminished  secre- 
tion of  sebum — asteatosis  of  the  skin — causes  the  skin  to  become  brittle  and  rough, 
in  part  locally  and  in  part  extensively.  Often,  as  upon  the  bald  head  in  the 
aged,  the  sebaceous  glands  undergo  atrophy.  If  the  excretory  ducts  of  the  seba- 
ceous glands  become  obstructed,  the  sebum  accumulates,  in  greater  or  lesser 
amount.  Not  rarely,  the  excretory  ducts  are  occluded  by  particles  of  dirt,  gran- 
ules of  ultramarine  derived  from  washing  blue,  and  vegetable  fibers  from  the 
clothing.  By  pressure,  the  fatty,  worm-like  comedo  is  discharged. 


ABSORPTION  THROUGH  THE  SKIN.     GALVANIC   CONDUC- 
TIVITY. 

After  prolonged  exposure  to  water,  the  epidermis  becomes  moist  and 
swollen..  On  the  other  hand,  the  skin  is  incapable  of  absorbing  sub- 
stances, either  salts  or  vegetable  poisons,  from  watery  solutions,  such  as 
baths.  This  inability  is  due  to  the  fat  normally  present  in  the  epi- 
dermis and  the  pores  of  the  skin.  If,  therefore,  substances  dissolved 
in  such  fluids  as  dissolve  and  extract  the  cutaneous  sebum,  as  al- 
cohol, ether,  and  particularly  chloroform,  are  applied  to  the  skin, 
they  may  be  absorbed  in  small  amounts — in  larger  measure  in  rabbits. 
Volatile  substances,  such  as  carbolic  acid,  that  exert  a  corrosive  effect 
upon  the  epidermis,  are  capable  of  absorption  through  the  injured  areas. 
Absorption  does  not  take  place  from  ointments  applied  simply  to  the 
skin.  In  the  case  of  persistent  vigorous  inunction,  there  occurs,  at  times, 
a  forcible  introduction  into  the  pores  of  the  skin,  not  rarely  in  association 
with  mechanical  lesions  in  the  continuity  of  the  layers  of  epidermis. 


540  COMPARATIVE.       HISTORICAL. 

Under  such  circumstances,  absorption,  as  of  potassium  iodid,  may  take 
place  from  ointments.  Thus,  v.  Voit  observed  globules  of  mercury  be- 
tween the  layers  of  epidermis  and  even  in  the  corium  of  an  executed  in- 
dividual, to  whom,  while  still  warm,  he  had  given  vigorous  inunctions. 

In  courses  of  treatment  with  inunctions  of  mercurial  ointment,  globules  of 
mercury  penetrate,  on  rubbing,  also  into  the  hair-follicles  and  excretory  ducts  of 
the  glands,  where  under  the  influence  of  the  glandular  secretion  they  may  be 
transformed  into  a  combination  susceptible  of  absorption.  In  addition,  mercury, 
in  the  form  of  vapor,  reaches  the  respiratory  mucous  membrane,  where,  likewise, 
it  is  transformed  into  an  absorbable  combination.  The  inflamed  skin,  especially, 
however,  when  covered  with  fissured  or  injured  epidermis,  absorbs  rapidly,  like 
a  wound-surface.  As  all  substances  that  irritate  the  skin  sever  the  continuity  of 
the  latter  when  the  effect  is  long  continued,  it  can  readily  be  understood  that 
they  are  eventually  absorbed  from  the  wounded  areas. 

As  the  skin,  under  normal  conditions,  absorbs  oxygen  from  the 
atmosphere,  it  may  also  absorb  gases,  such  as  hydrocyanic  acid,  hydro- 
gen sulphid,  carbon  monoxid,  carbon  dioxid,  vapors  of  ether  and  chloro- 
form. From  a  bath  that  contains  absorbed  hydrogen  sulphid,  this  gas 
is  absorbed;  conversely,  carbon  dioxid  is  given  off  to  the  bath-water. 

In  frogs,  active  absorption  of  watery  solutions  takes  place  through  the  skin, 
the  epidermal  cells  undergoing  enlargement  and  exhibiting  motor  phenomena. 
These  phenomena  may  also  be  induced  artificially  by  electric  stimulation.  The 
frog  also  absorbs  much  water  through  the  skin  even  when  the  circulation  is  elimi- 
nated and  the  central  nervous  system  is  destroyed;  though  more,  however,  when 
the  circulation  is  maintained.  The  skin  of  the  frog  exhibits,  in  the  process  of 
absorption,  a  vital  cellular  activity,  in  consequence  of  which  penetration  takes 
place  from  without  inward. 

The  transfer  of  watery  solutions  through  the  skin  by  means  of  the  constant 
galvanic  current,  cataphoric  action,  is  a  matter  of  especial  interest.  Both  elec- 
trodes are  impregnated  with  a  watery  solution  of  the  substance  in  question,  and 
the  direction  of  the  current  is  altered  from  time  to  time.  Thus,  H.  Munk  was 
able  to  introduce  through  the  skin  of  rabbits  within  several  minutes  strychnin, 
from  the  effects  of  which  they  died.  In  man,  the  introduction  of  quinin  and  po- 
tassium iodid  into  the  body  was  thus  effected,  these  substances  being  subsequently 
demonstrated  in  the  urine.  In  the  introduction,  the  compound  bodies  are 
(always?)  decomposed  by  the  current;  thus,  for  instance,  the  positive  pole  of  the 
current  introduces  the  calcium  of  calcium  chlorid;  the  negative,  only  chlorin. 


COMPARATIVE.     HISTORICAL. 

In  all  vertebrates,  the  skin  consists  of  corium  and  epidermis.  In  reptiles, 
the  cornification  of  the  epidermis  occurs  in  large  plates  (scales  of  the  snake, 
shell  of  the  tortoise).  Among  mammals,  the  armadillo  exhibits  a  similar  forma- 
tion. In  addition  to  hair  and  nails,  there  occur  in  animals,  as  epidermoidal  struc- 
tures, prickles,  bristles,  feathers,  claws,  hoofs,  horns  (the  antlers  of  the.  deer  are 
bony  formations  arising  from  the  frontal  bone) ,  spurs  (cock) ,  the  horny  covering 
of  the  beak  of  turtles  and  of  birds,  and  the  horn  of  the  rhinoceros.  The  scales  of 
fish,  on  the  other  hand,  consist  of  ossified  portions  of  skin.  Some  fish  possess 
considerable  portions  of  bone  upon  the  skin. 

The  skin  is  provided  with  a  large  variety  of  glands.  In  the  amphibia,  they 
secrete  either  mucus  alone  or  poisonous  substances.  Serpents  and  tortoises  possess 
no  cutaneous  glands  at  all.  In  lizards,  the  thigh-glands  extend  from  the  anus  to 
the  popliteal  spaces.  In  crocodiles  the  glands  open  beneath  the  margin  of  the 
cutaneous  osseous  scales.  Birds  have  no  cutaneous  glands.  The  coccygeal  gland, 
situated  above  the  coccygeal  vertebra,  furnishes  a  secretion  for  lubricating  the 
feathers. 

The  civet-glands  at  the  anus  of  the  civet-cat,  the  preputial  glands  on  the 
musk-bag  of  the  musk-deer,  the  inguinal  glands  of  the  hare,  the  pedal  glands  of 
ruminants  are  peculiarly  developed  sebaceous  glands.  The  strongly  odorous 
castoreum  is  the  secretion  of  the  prepuce  in  both  sexes  of  the  beaver. 


COMPARATIVE.       HISTORICAL.  541 

In  molluscs,  the  skin,  consisting  of  epidermis  and  corium,  is  intimately  united 
with  the  underlying  muscles  to  form  the  musculo-cutaneous  tube  of  the  body. 
Cephalopods  have,  in  their  skin,  the  so-called  chromatophores;  that  is,  round 
cells  filled  with  granular  pigment,  at  the  periphery  of  which  muscular  fibers  are 
attached  in  a  radiate  manner,  so  that  their  contraction  must  increase  the  colored 
surface.  Through  the  play  of  these  muscles  there  result  the  color-variations 
observed  in  cuttle-fish.  Chromatophores  are  present,  also,  in  other  classes  of 
animals,  such  as  amphibia  (frog)  and  fish  (pike).  In  these  animals,  they  appear 
as  connective-tissue  cells,  within  which  pigment-granules  either  collect  toward 
the  center  or  swarm  toward  the  periphery,  while  the  processes  of  the  cells  them- 
selves do  not  change  their  place.  Every  cell  is  provided  with  numerous  nerve- 
endings,  which  surround  the  pigment-mass  in  the  form  of  garlands,  with  free 
terminal  radiations.  Special  glands  furnish  the  material  for  the  formation  of  the 
scales  of  the  snails.  In  all  invertebrates,  the  development  of  the  scales  takes 
place  from  a  portion  of  the  surface  of  the  body  of  the  animal  that  has  been  desig- 
nated the  mantle. 

In  articulates,  the  entire  surface  of  the  body  is  covered  by  a  more  or  less 
solid  shield,  which  is  to  be  considered  as  a  cuticular  structure  consisting  of  chitin, 
which  is  separated  from  the  underlying  matrix.  It  extends  for  some  distance 
into  the  digestive  tube  and  the  trachea.  In  the  formation  of  the  skin  it  is  thrown 
off  and  replaces  itself  anew7  from  the  matrix.  This  shield,  which  affords  protection 
to  the  body,  serves,  at  the  same  time,  for  the  attachment  of  the  muscles.  It 
thus  becomes  a  passive  motor  organ  comparable  to  the  skeleton  of  the  vertebrates. 

The  echinoderms  exhibit  deposits  of  lime  in  their  skin,  in  consequence  of 
which  they  often  acquire  a  cutaneous  skeleton.  The  deposits  of  lime  are  either 
united  to  form  large  immovable  plates,  as  in  the  scale  of  the  sea-urchin,  or  united 
together  in  segments,  as  in  the  arms  of  the  star-fish.  In  holothurians  alone,  the 
significance  of  calcification  with  respect  to  the  cutaneous  skeleton  is  of  subordinate 
importance.  In  them,  only  isolated  plates  of  lime  have  remained  in  various 
forms.  In  worms,  the  skin  forms  with  the  underlying  muscles  the  musculo- 
cutaneous  tube.  The  epidermis  is,  in  some,  provided  with  cilia;  in  others  (tape- 
worms) it  is  traversed  by  pores;  while  in  still  others  it  is  without  any  appendage. 
The  hooklets  on  the  head  of  teniae,  the  rod-shaped  motor  bristles  on  the  body 
of  earth-worms,  are  cuticular  formations.  Cutaneous  glands  are  present  in  the 
more  highly  developed  worms,  such  as  the  leech. 

The  integument  of  ccelentrates  (zoophytes)  is  characterized  by  the  forarunners 
of  disseminated  nettle-cells;  that  is,  cells  provided  with  whip-like  processes,  which 
contain  a  corrosive  fluid  and  serve  as  organs  of  capture.  Cilia  are  present  in  many; 
in  some  a  tubular,  external,  chitin-like  skeleton  is  formed.  The  integument  of 
sponges  is  suggestive  of  that  of  zoophytes.  Infusoria  possess  numerous  cilia,  which 
in  part  are  even  subject  to  voluntary  stimulation.  Rhizopods  are  wholly  unpro- 
vided with  a  true  skin.  Nevertheless  under  these  circumstances  the  formation  of 
silicious  (radiolaria)  or  calcareous  structures  (monothalamia  and  polythalamia) 
is  noteworthy. 

Historical:  Hippocrates  (born  460  B.  C.)  and  Theophrastus  (born  371  B.  C.) 
distinguished  perspiration  from  sw-eat.  According  to  the  latter  the  secretion  of 
sweat  stands  in  a  certain  antagonistic  relation  to  the  secretion  of  urine  and  to 
the  amount  of  water  in  the  feces.  Individuals  suffering  from  fright  were  believed 
to  sweat  more  freely  from  the  feet.  Father  Augustinus  stated  that  he  knew  an 
individual  who  was  able  to  sweat  voluntarily.  According  to  Cassius  Felix  (97 
A.  D.)  the  skin  absorbs  water  in  the  bath.-  He  made  investigations  into  the 
evaporation  from  the  skin.  Sanctorius  (1614)  measured  more  accurately  the 
insensible  perspiration  and  the  loss  of  weight  on  the  part  of  a  fasting  individual. 
The  hair-follicle  and  the  root  of  the  hair  are  mentioned  in  the  Talmud.  Alberti 
(1581)  recognized  the  hair-bulb.  Donatus  (1588)  made  the  first  report  of  sudden 
graying  of  the  hair.  Riolan  (1626)  discovered  the  cutaneous  pigment  of  the 
negro  in  the  epidermis.  De  Heyde  (1684)  and  Leeuwenhoeck  described  the 
ciliated  movement  on  the  beard  of  mussels  (1694). 


PHYSIOLOGY  OF  THE  MOTOR 
APPARATUS. 


STRUCTURE  AND  ARRANGEMENT  OF  THE  MUSCLES. 

The  striated  (voluntary)  muscles  are  covered  on  their  outer  surface  by  a 
connective-tissue  sheath,  the  external  perimysium.  From  this  sheath  septa  extend 
into  the  interior  of  the  muscle,  the  internal  perimysium,  carrying  vessels  and 
nerves,  and  dividing  the  muscle  into  bundles  of  fibers,  which  are  sometimes  finer 
(eye  muscles)  and  sometimes  coarser  (gluteals).  Each  compartment  thus 
formed  contains  a  number  of  muscle-fibers  lying  close  together. 

Each  muscle-fiber  is  surrounded  by  a  rich  meshwork  of  blood-capillaries,  with 
neighboring  lymphatics;  it  also  has  a  nerve-fiber  leading  to  it.  These  structures 
are  held  on  the  surface  of  the  muscle-fiber  by  means  of  an  extremely  delicate 
connective  tissue  with  a  scarcely  recognizable  fibrillar  structure,  representing  to  a 
certain  extent  a  perimysium  for  each  separate  fiber. 

The  individual  muscle-fibers  or  primitive  muscular  bundles  may  be  isolated  by 
means  of  a  35  per  cent,  solution  of  potassium  hydroxid,  or  of  nitric  acid  containing 
an  excess  of  potassium  chlorate.  They  are  from  10  to  100  fj.  in  diameter,  and 
are  of  limited  length,  in  man  from  5.3  to  9.8  cm.  Within  short  muscles  (the  sta- 
pedius  among  others  and  the  small  muscles  of  the  frog)  the  fibers,  therefore, 
traverse  the  entire  length  of  the  muscle;  within  longer  muscles,  however,  each 
fiber  tapers  to  a  point  and  is  attached  obliquely  by  cement-substance  to  the 
succeeding,  similarly  pointed  fiber.  Each  muscular  spindle  is  completely  en- 
closed in  a  structureless,  transparent  sheath,  the  sarcolemma  (Fig.  184,  i,  S). 

The  muscle-fiber  exhibits  at  intervals  of  from  2  to  2.8  //  a  transverse  striation 
due  to  alternate  light  and  dark  layers  (i,  Q).  As  a  result  of  the  action  of  hydro- 
chloric acid  (i  :  1000)  or  of  the  gastric  juice,  or  after  freezing,  the  fiber  not  rarely 
undergoes  a  solution  of  continuity  in  the  region  of  the  light  bands,  so  that  it 
breaks  up  into  plates  or  discs  (5)  resembling  an  overthrown  pile  of  coins,  the 
discs  always  corresponding  to  the  dark  parts  of  the  fiber.  In  addition  to  the 
transverse  striation,  a  longitudinal  striation  may  be  observed  in  the  fiber.  This 
is  due  to  the  fact  that  the  muscle-fiber  is  made  up  of  numerous,  fine,  contractile 
threads  (from  i  to  1.7  //in  diameter),  the  primitive  fibrils  (Fig.  184,  i,  F),  lying 
side  by  side.  Each  separate  fibril  is  striated  transversely,  and  all  are  bound 
together  by  a  small  amount  of  a  fluid,  finely  granular,  cement-substance  (Rollet's 
sarcoplasm) ,  in  such  manner  that  the  transverse  striations  of  all  fibrils  are  situated 
at  the  same  level.  The  sarcoplasm  embeds  all  of  the  fibrils  uniformly,  and  occurs 
also  in  a  thin  layer  between  the  sarcolemma  and  the  muscle-substance ;  it  contains 
minute  interstitial  granules  (fat  and  lecithin).  The  fibrils  are  prismatically  flat- 
tened against  one  another;  hence,  a  cross-section  of  a  fresh  frozen  muscle  exhibits 
a  design  consisting  of  polygonal  figures — Cohnheim's  fields  (2). 

The  study  of  an  isolated  fibril  under  high  magnification  shows  it  to  be  a 
columnar  structure,  made  up  of  numerous  parts  superposed  in  layers.  These 
sections,  which  may  be  termed  muscular  elements,  exhibit  individually  a  com- 
plicated structure.  Each  muscular  element  (4)  is  a  prismatic  body,  from  2  to 
2.8  fj-  in  height,  with  plane  terminal  surfaces.  The  entire  middle  layer  is  occupied 
by  the  darker  and  more  highly  refractive,  true  contractile  substance,  the  trans- 
verse disc  (Bowman's  sarcous  elements,  Kuhne's  muscle-prisms).  This  is  doubly 
refractive  (anisotropic)  and  contains  a  bright  layer,  the  median  disc  (4  c), 
which  can  be  recognized  as  a  bright  line  bisecting  the  dark  field.  On  the  upper 
and  lower  surfaces  of  the  darker,  contractile  substance  is  a  layer  of  light,  singly 
refractive  (isotropic)  substance  (4  d).  Where  this  lighter  disc  comes  in  contact 
with  that  of  the  adjacent  element,  a  dividing  band  can  be  recognized,  the  terminal 
or  intermediate  disc  (4  a) ,  which  appears  as  a  dark  line. 

542 


STRUCTURE    AND    ARRANGEMENT    OF    THE    MUSCLES. 


543 


In  the  muscles  of  arthropods  there  lies  within  the  isotropic  layer,  at  a  short 
distance  from  the  terminal  disc,  still  another  narrow  layer  of  doubly  refractive 
substance,  the  accessory  disc,  which  contains  chromatin.  Every  muscle-fiber  is 
closed  off  toward  its  extremity  by  a  layer  of  singly  refractive  substance.  When 
the  tube  of  the  microscope  is  lowered,  the  doubly  refractive  discs  appear  dark, 
the  singly  refractive,  light;  when  the  tube  is  raised,  the  conditions  are  reversed. 

The  fibrils  are  readily  obtained  singly  from  the  muscles  of  insects;  in  mamma- 
lian muscles  they  may  be  isolated  after  the  action  of  dilute  alcohol  or  Muller's 
fluid,  especially  at  the  torn  ends  of  the  fibers  (Fig.  184,  3). 


12 


FIG.  184. — Histology  of  Muscular  Tissue:  i,  Diagrammatic  representation  of  the  parts  of  a  striated  muscle- 
fiber:  S,  sarcolemma;  Q,  transverse  striation;  F,  fibrils,  further  on  giving  rise  to  longitudinal  striation; 
K,  nuclei  of  the  muscle-fiber;  N,  motor  nerve  leading  to  the  fiber,  with  the  axis-cylinder  a,  which  passes 
over  into  the  motor  end-plate,  seen  in  profile,  the  latter  lying  upon  a  nucleated,  protoplasmic  layer  e.  2, 
Part  of  a  cross-section  of  a  striated  muscle-fiber  with  Cohnheim's  fields  c;  K,  a  muscle-nucleus  in  contact 
with  the  sarcolemma.  3,  Isolated  fibrils  from  a  striated  muscle-fiber.  4,  Part  of  a  fibril  from  an  insect's 
muscle,  highly  magnified:  a,  Krause-Amici  line  limiting  the  muscular  elements;  b,  the  dark,  doubly  refrac- 
tive substance;  c,  Hensen's  line;  d,  the  singly  refractive  substance.  5,  Striated  muscle-fiber  breaking  up 
into  discs.  6,  Striated  muscle-fiber  from  the  heart  of  the  frog.  7,  Structure  of  a  striated  muscle-fiber 
from  a  three-months'  human  embryo.  8,  Reticulated  muscle-fibers  of  the  heart.  9,  Cross-section  of  the 
heart-muscle:  c,  capillaries;  b,  connective-tissue  corpuscles.  10,  Unstriated  muscle-fibers,  n,  Unstriated 
muscle-fibers  in  cross-section.  12,  Striated  muscle-fibers  with  the  related  tendon  S  (detached). 


In  all  fibers  there  are  encountered  several  nuclei,  from  9  to  13  u  long  and 
from  3  to  4  n  wide,  directed  longitudinally,  which  become  more  evident  on  addition 
of  dilute  acetic  acid.  They  are  surrounded  by  a  thin  layer  of  protoplasm  or  sar- 
coplasm  (i  and  2  K),  and  are  designated  'muscle-corpuscles.  Each  nucleus  contains 
one  or  two  nucleoli;  the  protoplasm  sends  to  adjacent  corpuscles  distinct,  delicate 
processes,  at  times  containing  refractive  granules,  so  that  a  continuous  network  of 
cells  is  formed  beneath  the  sarcolemma. 

Histogenetically  the  muscle-corpuscles  are  the  remains  of  cells,  from  the  body 
of  which  the  muscle-fibers  were  formed  (7) ;  the  striated  substance  is  the  differen- 
tiated parietal  or  intracellular  substance  that  has  separated  from  the  corpuscles. 


544 


STRUCTURE    AND    ARRANGEMENT    OF    THE    MUSCLES. 


The  latter  probably  represent  the  natural  source  of  nutrition  for  the  muscle- 
fibers.  In  amphibia,  birds,  fish,  and  insects,  the  muscle-corpuscles  are  situated  in 
the  axis  of  the  fiber  between  the  fibrils. 

The  protoplasm  of  the  muscle-corpuscles  is  further  connected  with  the  proto- 
plasm that  throughout  the  entire  muscle-fiber  forms  longitudinally  and  trans- 
versely a  network  of  fibers  on  the  fibrils — the  sarco plasm.  The  transverse  fibers 
follow  the  course  of  Hensen's  and  the  Krause-Amici  lines;  the  longitudinal  fibers 
pass  in  the  interstices  between  Cohnheim's  fields.  The  amount  of  sarcoplasm  is 
greater  in  the  lower  than  in  the  higher  animals. 

The  relation  of  the  muscle-fibers  to  the  tendons  varies.  According  to  Toldt,  the 
delicate  connective-tissue  elements  that  surround  the  individual  muscle-fibers 
pass  over  the  extremity  of  the  latter  directly  into  the  elements  of  the  tendon. 
Apart  from  this  it  may  happen  that  the  extremities  of  the  muscle-fibers  are  at- 
tached by  a  special  cement-substance  to  the  plane  surface  or  in  shallow  depressions 
at  the  extremity  of  the  independently  formed  tendon  (Fig.  184,  12  S).  In  arthro- 
pods there  is  doubtless  also  a  direct  transition  of  the  sarcolemma  into  the  substance 
of  the  tendon. 

The  tendons  consist  of  parallel  bundles  of  fibrillar  connective  tissue,  containing 
connective-tissue   corpuscles   and   elastic   fibers.     They   are   covered   by   a   loose 
sheath  of  connective  tissue,  the  peritendinemn,  which  contains  the  blood-vessels, 
the  lymphatics,  and  the  nerves.     The  tendons  pass  through  sheaths,  whose  slip- 
pery   synovial    fluid  fa- 
vors   the  gliding  move- 
ment.     In    some    situa- 
tions the  extremities  of 
the  muscle-fibers  are  at- 
tached   directly    to  the 
fixed  point ;  in  other  sit- 
uations, such  as  the  face, 
they    terminate    among 
the     tissue-elements     of 
the  skin  or  the  fasciae. 

Motor  Nerves. — The 
trunk  of  the  nerve,  as  a 
rule,  enters  the  muscle 
at  its  geometrical  center ; 
hence,  the  point  of  en- 
trance in  long  muscles 
with  parallel  fibers  or  in 
spindle-shaped  muscles 
is  situated  near  the  mid- 
dle. If  the  muscle  with 
parallel  fibers  is  more 

than  2  or  3  cm.  wide,  several  branches  enter  side  by  side  at  its  middle.  In  tri- 
angular muscles  the  point  of  entrance  of  the  nerve  is  displaced  toward  the  tendin- 
ous point  of  convergence  of  the  muscle-fibers,  the  amount  of  displacement  varying 
with  the  degree  of  convergence  and  the  consequent  thickness  of  the  pointed  ex- 
tremity of  the  muscle.  In  general,  the  entrance  of  the  nerve-trunk  into  a  muscle 
may  be  suspected  to  take  place  at  that  point  where  the  least  displacement  of  mus- 
cular tissue  occurs  during  the  contraction  of  the  muscle. 

The  motor  nerve  destined  for  a  certain  muscle  does  not  originally  contain  as 
many  fibers  as  there  are  muscle-fibers;  in  the  eye-muscles  of  man  about  seven 
muscle-fibers  correspond  to  three  nerve-fibers  in  the  trunk;  in  other  muscles,  in 
the  dog,  there  is  one  nerve-fiber  to  from  forty  to  eighty-three  muscle-fibers.  Hence, 
it  is  necessary,  in  the  course  of  their  ramification  in  the  muscle,  for  the  separate 
nerve-fibers  to  subdivide  dichotomously. 

In  warm-blooded  animals  each  muscle -spindle  has  only  one  point  of  innerva- 
tion,  while  the  longer  spindles  of  cold-blooded  animals  have  several.  The 
medullated  fiber  enters  the  muscle-fiber  and  forms  at  its  point  of  entrance  a 
nodular  prominence,  the  nerve  end-bulb  (Fig.  184,  i,  e).  In  this  transition  the 
neurilemma  fuses  directly  with  the  sarcolemma,  the  medullary  substance  disap- 
pears, and  the  axis-cylinder  becomes  transformed  into  a  flattened  ramification, 
the  nerve  end-plate,  or  nerve-arborization,  which  rests  upon  a  finely  granular 
accumulation  of  sarcoplasm  (Fig.  185),  in  which  nuclei  are  present.  Accord- 
ing to  Kiihne  the  connection  of  the  nerve  with  the  muscle-fiber  is  established 
only  through  the  coalescence  of  the  end-plate  with  the  substratum  of  sarco- 


Nerve. 


Muscle 
nucleus. 


FIG.   185. — Muscle-fibers   with   Nerve-ending,  from  the  lizard 
(after  W.  Kiihne). 


STRUCTURE    AND    ARRANGEMENT    OF    THE    MUSCLES.  545 

plasm,  and  through  the  connection  of  the  latter  with  the  interstitial  rows  of  nuclei 
in  the  sarcoplasm,  or  with  the  protoplasm  surrounding  the  muscle-nuclei,  and  further 
with  the  interstitial  cement-substance  of  the  fibrils. 

In  the  arthropods  (crawfish)  each  muscle-fiber  possesses  two  nerve-termina- 
tions, arising  from  separate  axis-cylinders.  There  are  no  end-plates  at  the  point 
of  entrance;  but  the  nerve-fibrils  are  distributed  for  a  great  distance  between  the 
muscle-fibrils,  and  the  nerve-endings  appear  to  extend  as  far  as  the  terminal  or 
intermediate  discs.  Some  investigators  have  assumed  the  existence  of  a  similar 
arrangement  in  higher  animals  also. 

The  muscle  is  supplied  also  with  sensory  fibers,  which  subserve  the  muscular 
sense.  Their  existence  is  demonstrated  physiologically  by  the  fact  that  stimula- 
tion of  a  muscle  will  cause  reflex  variations  in  the  blood-pressure  and  dilatation 
of  the  pupil,  also  an  increase  in  the  respiratory  movements  and  muscular  reflexes; 
and,  further,  by  the  fact  that  inflamed  muscles  are  painful. 

At  first  slender  and  medullated,  these  fibers  finally  become  non-medullated. 
It  appears  that  they  are  distributed  on  the  outer  surface  of  the  sarcolemma, 
as  they  wind  around  the  muscle-fibers  after  undergoing  dendritic  ramifications. 
According  to  others,  the  sensory  nerves,  after  branching  dichotomously,  terminate 
only  in  the  overlying  connective  tissue  or  in  the  aponeuroses,  either  abruptly  or 
by  means  of  a  small  swelling.    Bremer  designates  their  termination  as  unbellif erous ; 
while  according  to  Landauer  they  pass  longitudinally  along  the  muscle-fibers, 
in  the  frog,  in  the  form  of  filaments  pro- 
vided with  oval ,  nuclear  formations .  Ac- 
cording to  still  other  observers,  they  ter- 
minate as  muscular  buds  or  muscular 
spindles,  or  as  free  endings.     In  the  horse 
the  sterno-maxillary  muscle  receives  sen- 
sory branches  from  a  separate  nerve. 

Red  and  Pale  Muscles. — In  some 
fish,  such  as  the  sturgeon;  birds,  such 
as  the  turkey;  and  mammals,  such  as 
rabbits,  two  kinds  of  striated  muscles 
can  be  distinguished,  namely  red  or 
dark,  for  example  the  soleus  and  semi- 
ten  dinosus  of  the  rabbit,  and  pale  or 
light,  for  example  the  crural  of  the  rab- 
bit. The  fibers  of  pale  muscle  are  usu- 
ally wider,  and  poorer  in  protoplasm 
than  those  of  red  muscle;  their  trans- 
verse striation  is  closer,  and  their  longi- 
tudinal striation  less  prominent;  their 
fibrils  are  placed  at  regular  intervals;  FIG.  186. — Cross-section  through  the  Gastrocnemius 
their  muscle-nuclei,  lying  directly  in  ^t&Sf  ^L^l^T^'' W' ^  ^ 

contact  with    the  sarcolemma,  are  less 
numerous  than  those  of  the  fibers  of  red 

muscle,  within  which  they  are  situated  between  the  fibrils;  and  they  contain  less 
glycogen,  myosin,  and  water. 

Julius  Arnold  found  in  man  white  fibers  extensively  distributed  among  the 
red.  Even  in  the  same  muscle,  in  fact  in  almost  every  muscle,  in  the  frog  and 
in  mammals,  red  and  white  fibers  are  intermingled  (Fig.  186).  Nevertheless  it 
should  be  pointed  out  that  their  color  is  not  always  clearly  differentiated.  The 
physiological  differences  are  considered  on  p.  563. 

The  heart  of  the  frog,  as  well  as  that  of  invertebrates,  contains  transition- 
forms  between  striated  and  unstriated  muscle-fibers  (Fig.  184,  6).  The  spindle- 
shaped,  mononuclear  cells  have  the  form  of  unstriated  fibers,  but  the  transverse 
striation  of  voluntary  muscles. 

Development. — Each  striated  muscle-fiber  develops  from  a  mononuclear, 
mesodermal  cell  without  a  wall,  which  becomes  elongated  in  the  form  of  a  spindle. 
As  it  progressively  increases  in  length,  the  nuclei  multiply  by  mitosis.  At  a  more 
advanced  stage  the  peripheral  or  parietal  substance  of  this  structure  is  transformed 
into  the  fibrillar,  striated  mass  of  the  fiber  (Fig.  184,  7),  while  the  nuclei  with  a 
scanty  covering  of  protoplasm  (muscle-corpuscles)  form  a  continuous  line  in  the 
axis  of  the  fiber,  where  they  remain  permanently  in  some  animals.  In  man  the 
nuclei  advance  later  toward  the  surface  of  the  fiber,  where  a  structureless  cuticle, 
the  sarcolemma,  separates.  The  muscle-corpuscles  serve  in  a  certain  sense  as 
trophic  centers  for  the  striated  parietal  substance ;  they  may  bring  about  degenera- 
35 


546 


STRUCTURE    AND    ARRANGEMENT    OF    THE    MUSCLES. 


tion,  or  restitution  of  the  latter  may  arise  from.  them.  The  muscles  of  the  young 
have  fewer  fibers  than  those  of  the  adult,  although  the  former  are  on  the  whole 
smaller.  In  growing  muscles,  both  in  the  new-born  and  in  later  life,  the 
number  of  fibers  is  increased  by  the  separation  from  a  fiber  of  a  band  of  sarco- 
plasm,  together  with  a  continuous  row  of  muscle-corpuscles.  This,  as  a  "myo- 
blast,"  develops  into  a  new  fiber  according  to  the  embryonal  type.  The  new  fiber 
also  receives  its  nerve-fiber,  which  develops  from  the  nuclei  of  the  sheath  of 
Schwann.  The  individual  fibers  increase  in  thickness  by  an  increase  in  the 
number  of  fibrils.  In  the  growth  of  the  muscle  as  a  result  of  continuous  in- 
creased exertion,  the  individual  fibers  become  thicker,  but 
not  more  numerous;  the  sarcoplasm  is  increased,  while  the 
fibrils  and  the  nuclei  are  not  changed. 

Degeneration. — An  active  degeneration  of  fibers  prob- 
ably takes  place  in  the  muscles,  in  accordance  with  their 
active  metabolism.  As  an  introduction  to  this  process 
(rigid  ?)  muscular  substance  accumulates  on  the  fibers  in 
the  form  of  nodules  or  rings;  at  such  situations  the  fiber 
disintegrates  into  fragments,  termed  sarcolytes,  which  un- 
dergo absorption. 

Comparative. — In  addition  to  the  parts  of  vertebrates 
analogous  to  human  muscuiar  tissues,  striated  muscle- 
fibers  are  found  also  in  the  iris  and  the  choroid  of  birds. 


FIG.  187. — Unstriated  Mus- 
cle-fibers, isolated  by 
means  of  Diluted  Alco- 
hol: i,  from  the  intes- 
tine; 2,  from  the  radial 
artery  of  man. 


FIG.  188. — Special  Forms  of  Unstri- 
ated Muscle-fibers  from  the  Mus- 
cular Coat  of  the  Aorta  (after  v. 
Ebner):  i,  from  man;  2,  from  the 
hog;  3,  from  the  ox.  (The  pro- 
cesses at  the  sides  are  cell-bridges 
that  have  been  torn  off.) 


FIG.  189. — Muscle-cells  from  the 
Frog's  Stomach  with  Distinct  Fi- 
brils (after  Engelmann):  i,  por- 
tion of  a  fiber  treated  with  am- 
monium bichromate;  2,  cross- 
section  of  cells  that  have  been 
treated  with  8  per  cent,  sodium- 
chlorid  solution. 


Arthropods  have  only  striated  muscle-fibers,  while  molluscs,  worms,  and  echino- 
derms  have  chiefly  unstriated  fibers.  The  latter  possess  also  special,  energetically 
contracting  fibers  with  double  oblique  striation,  formed  of  crossed,  oblique  lines. 
In  cephalopods  the  muscle-fibers  exhibit  spiral  lines  at  the  periphery.  Among 
vertebrates  fish  have  the  thickest  muscle-fibers,  then  follow  with  decreasing  width, 
toads,  lizards,  mammals,  and  birds. 

The  unstriated,  involuntary  muscle-fibers,  or  contractile  fiber-cells,  can  be 
isolated  by  means  of  a  35  per  cent,  solution  of  potassium  hydroxid.  They  are 
unencapsulated,  unicellular,  spindle-shaped,  flattened  fibers,  in  some  places  pre- 
senting an  appearance  of  longitudinal  fibrillar  striation,  from  45  to  230  //  long, 
and  from  4  to  10  //  wide.  They  are  occasionally  forked  at  one  or  both  extremities, 
and  contain  at  the  middle  a  solid,  rod-shaped  nucleus,  which  may  be  sharply 
brought  out  by  the  addition  of  dilute  acetic  acid.  The  nucleus  is  surrounded  by 
a  small  amount  of  protoplasm,  and  encloses  one  or  two  bright  nucleoli  within  a 
rich  network  (Fig.  184,  10  and  n).  The  fibers  either  lie  singly,  or  are  joined 
together  in  continuous  layers  or  reticular  columns,  being  arranged  longitudinally 


STRUCTURE    AND    ARRANGEMENT    OF    THE    MUSCLES. 


547 


with  their  tapering  extremities  in  contact  with  one  another.  The  fibers  are  not 
held  together  by  a  viscid  interstitial  cement-substance,  as  was  formerly  supposed, 
but  they  are  universally  connected  by  so->called  cell-bridges.  The  conduction  of 
stimuli  through  unstriated  muscles  is  at  the  same  time  thus  explained. 

Where  fibrils  are  visible  in  the  fiber-cell  (Fig.  189),  they  lie  embedded  in  a 
rather  homogeneous,  granular  substance,  the  sarcoplasm.  According  to  Engel- 
mann,  the  disintegration  of  the  substance  of  unstriated  muscle  into  the  separate 
spindle-shaped  elements  is  a  postmortem  change  in  the  tissue.  The  transverse, 
thickened  areas  occasionally  observed  are  not  due  to  transverse  striation,  but  to 
partial  contraction  or  fold-formation  (Fig.  184,  10).  Unstriated  muscle-fibers  also 
have  tendinous  insertions  at  times.  The  blood-capillaries  pass  in  longitudinal 
meshes  between  the  fibers,  as  do  also  the  numerous  lymph-capillaries  that  surround 
the  cells. 

The  motor  nerves,  according  to  J.  Arnold,  form  a  plexus  of  medullated  and 
non-medullated  fibers,  partially  supplied  with  ganglion-cells,  and  situated  in  the  con- 
nective-tissue of  the  envelop  surrounding  the  unstriated  muscle-fibers — the  ground 
plexus.  From  this  arises  a  second  non-medullated  plexus,  with  nuclei  at  the  nodal 
points — the  intermediate  plexus.  This  is  situated  either  immediately  upon  the 
musculature  or  in  the  connective  tissue  between  the  individual  bundles.  The 
delicate  fibrils  (from  0.2  to  0.3  u)  given  off  by  this  plexus  unite  to  form  still  an- 


FIG.  190. — Sensory  Nerve  in  a  Tendon.     One  fiber  terminates  in  a  Pacinian  corpuscle  (P),  the  other  in  a  tendon- 
spindle  of  Golgi  (G). 

other  network,  the  intermuscular  plexus,  and  pass  to  each  fiber,  running  along  its 
border  and  terminating  in  a  pear-shaped  thickening.  According  to  Franken- 
hauser  the  fibrils  terminate  in  the  nucleolus;  according  to  Lustig,  in  the  vicinity 
of  the  nucleus;  according  to  J.  Arnold  they  traverse  both  fiber  and  nucleus  and 
re-enter  the  plexus.  P.  Schultz  describes  also  sensory  nerves,  connected  with 
ganglion  cells  and  provided  with  terminal  nodules. 

In  tendons  the  sensory  nerves,  after  subdividing  repeatedly,  become  non- 
medullated  fibers  (Fig.  190,  a),  which  at  the  junction  of  muscle  and  tendon  twine 
around  or  spread  out  over  the  bundles.  This  situation  is  covered  with  endothe- 
lium.  The  non-medullated  fibers  terminate  finally  in  a  tuft  of  delicate  ramifica- 
tions, designated  Golgi 's  tendon-spindle.  Terminations  in  the  form  of  Pacinian 
corpuscles  (P)  or  end-bulbs  are  also  found  in  the  tendons. 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  MUSCULAR  TISSUE. 

The  consistency  of  muscular  tissue  is  similar  to  that  of  living  proto- 
plasm; it  is  semi-solid,  that  is,  not  fluid  to  such  a  degree  as  to  be  diffluent, 
nor  is  so  solid  that  confluence  of  separated  parts  would  not  be  possible. 
The  consistency,  therefore,  may  be  compared  to  that  of  a  jelly  at  the 
moment  of  liquefaction. 


548         PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  MUSCULAR  TISSUE. 

The  view  expressed  is  supported  by  the  following  facts:  (i)  The  analogy  be- 
tween the  function  of  the  muscle-substance  and  that  of  the  contractile  protoplasm 
of  cells,  the  latter  surely  possessing  this  semi-solid  property,  as  must  be  inferred 
from  the  movement  of  the  protoplasm.  (2)  The  observation  of  the  course  of  the 
contractile  wave-movement  through  the  length  of  the  muscle-fiber.  In  the  same 
category  belongs  the  wave-like  movement  first  observed  by  W.  Kiihne,  when  a 
strong,  constant  current  is  passed  through  the  muscle.  The  phenomenon  depends 
upon  the  occurrence  of  slow  contraction-waves  within  the  fibers  in  the  direction 
of  the  galvanic  current,  which  are  increased  by  heat,  and  disappear  when  the 
muscle  is  tightly  stretched,  or  when  its  extremities  are  forcibly  pushed  together. 
(3)  Under  the  microscope,  the  progression  of  a  parasitic  round-worm  (Myoryctes 
Weismanni)  has  been  observed  to  fake  place  by  means  of  the  serpentine  move- 
ments through  the  contractile  substance,  the  separated,  semi-solid  masses  becom- 
ing again  confluent  behind  it. 

Refraction  of  Light. — The  contractile  substance  refracts  the  light  doubly 
(anisotropic) ,  while  the  ground-substance  is  singly  refractive  (isotropic).  The 
contractile  substance  behaves  like  a  doubly  refractive,  positively  uniaxial  body, 
whose  optical  axis  corresponds  with  the  longitudinal  axis  of  the  fiber.  Under  the 
polarization-microscope,  with  the  Nicol's  prisms  crossed  and  the  fiber  so  placed 
that  the  longitudinal  axis  intersects  the  vibration-planes  of  the  Nicol's  prisms 
at  an  angle  of  45°,  the  doubly  refractive  substance  can  be  recognized  by  its  ap- 
pearing bright  in  a  dark  field  of  vision,  while  in  a  colored  field  (purple-red  from 
the  interposition  of  a  mica  plate)  it  appears  of  another  color  (blue,  yellowish-red, 
to  yellow).  Although  the  doubly  refractive  contractile  substance  undergoes 
change  in  form  during  contraction,  its  double  refraction  nevertheless  persists 
unaltered.  Catherine  Schipiloff,  A.  Danilewsky,  and  O.  Nasse  believe  that  the 
contractile,  anisotropic  mass  consists  of  myosin.  According  to  the  observations 
of  Engelmann  all  contractile  elements  possess  the  property  of  double  refraction, 
and  the  direction  of  shortening  always  corresponds  with  that  of  the  optical  axis. 
With  respect  to  the  actual  cause  of  the  anisotropy,  the  comprehensive  investiga- 
tions of  v.  Ebner  have  demonstrated  that  as  a  result  of  the  processes  of  growth 
in  the  tissue,  tensions  are  produced  (for  example,  the  tension-phenomena  of  bodies 
subject  to  imbibition)  that  give  rise  to  double  refraction. 

During  sustained  contraction  in  degenerating  muscle-fibers  the  refractive  index 
of  the  muscle-substance  is  increased  as  a  result  of  loss  of  water  from  the  tissue 
and  the  consequent  increased  concentration  of  the  dissolved  parts  of  the  muscle. 

The  chemical  composition  of  muscle  undergoes  rapid  and  profound 
changes  after  death.  As,  however,  the  muscles  of  the  frog,  when  thawed 
after  freezing,  again  become  capable  of  contracting,  they  are,  therefore, 
not  altered  chemically  by  the  freezing.  W.  Kiihne  cooled  to  10°  C.  frogs' 
muscles  rendered  bloodless  by  means  of  a  i  per  cent,  sodium-chlorid 
solution,  triturated  them  in  an  ice-cold  mortar,  and  expressed  the  juice 
(which  thaws  at  — 3°)  through  linen.  The  fluid  thus  expressed  is  filtered 
in  the  cold  and  appears  as  a  slightly  opalescent  juice  of  a  neutral  or 
generally  alkaline  reaction  and  light  yellowish  tint,  and  designated 
muscle-plasma.  In  common  with  blood-plasma  it  coagulates  spon- 
taneously. The  muscle-plasma  becomes  at  first  uniformly  gelatinous. 
Later,  turbid,  opaque,  doubly  refractive  flakes  and  threads  undergo  con- 
traction in  the  jelly,  and  like  the  fibrin  of  the  contracting  blood-clot 
express  a  juice,  muscle-serum,  which  has  an  acid  reaction.  Cold  prevents 
the  coagulation  of  muscle-plasma;  above  o°  it  takes  place  but  slowly, 
then  more  rapidly  with  increasing  temperature,  finally  with  great  rapidity 
at  40°  C.  for  the  muscles  of  cold-blooded  animals,  or  at  55°  C.  for  those 
of  warm-blooded  animals.  The  addition  of  water  or  of  a  little  acid  to 
the  muscle-plasma  causes  immediate  coagulation.  This  coagulated 
proteid,  the  most  abundant  in  the  muscles,  is  derived  from  the  doubly 
refractive  substance,  and  is  designated  myosin.  Its  chemical  formula 
is  C108H172N30S033. 

Myosin  forms  from  3  to  n  per  cent,  of  moist  muscular  tissue.     It  can  be 


METABOLISM  IN  MUSCLE.  549 

extracted  from  muscle-juice  by  means  of  a  5  to  10  per  cent,  solution  of  ammon- 
ium chlorid.  Myosin  belongs  to  the  globulins;  Halliburton  has  prepared  it  also 
from  the  muscles  of  warm-blooded  animals.  It  is  precipitated  from  its  solutions 
by  saturation  with  sodium  chlorid  or  magnesium  sulphate.  When  dissolved 
in  a  10  per  cent,  solution  of  sodium  chlorid,  it  is  coagulated  by  heat.  It  is 
dissolved  by  2  per  cent,  hydrochloric  acid,  with  the  formation  of  acid-albumin 
(syntonin),  and  by  alkalies  or  alkaline  carbonates,  with  the  formation  of  alkali- 
albuminate.  Like  fibrin,  myosin  actively  decomposes  hydrogen  dioxid.  A. 
Danilewsky  has  succeeded  in  reconverting  syntonin  in  part  into  myosin.  Myosin 
is  not  present  in  unstriated  muscles. 

Muscle-serum  contains  further  small  amounts  of  myoalbumin  (C114- 
H174N30SO30),  which  is  coagulable  at  73°  C.,  but  is  not  precipitated  by  sat- 
uration of  the  serum  with  magnesium  sulphate ;  also  my o globulin,  which  is 
precipitated  by  this  last  procedure,  and  is  coagulable  at  63°  C.;  and  a 
little  nucleoalbumin. 

Halliburton  distinguishes  the  following  proteids  in  muscle:  (i)  Paramyosino- 
gen,  or  musculin,  a  globulin-like  body,  forming  20  per  cent,  of  the  total  proteids, 
and  coagulating  at  47°  C.  (2)  Myosinogen,  forming  77  per  cent,  of  the  total 
proteids,  coagulating  at  55°.  Both  of  these  bodies  are  coagulable  spontaneously, 
forming  myosin.  (3)  According  to  v.  Furth  myosinogen  gives  rise  to  myogen- 
fibrin,  which  is  soluble,  is  coagulable  at  35°,  and,  like  paramyosinogen,  is  readily 
transformed  into  a  fibrin-like  modification  that  is  dissolved  with  difficulty.  Cer- 
tain salts  or  organic  substances  (caffein,  veratrin)  accelerate  this  process,  while 
it  is  inhibited  by  blood-serum,  and  also  by  egg-albumin.  (4)  Myoalbumin,  which  is 
similar  to  serum-albumin.  The  coloring-matter  of  muscle  (myohematin)  appears 
to  be  different  from  hemoglobin.  The  absorption-bands  are  situated  somewhat 
nearer  to  the  red  end  of  the  spectrum.  According  to  Levy,  myohematin  is  identical 
with  hemochromogen.  There  is  an  oxidized  and  a  reduced  myohematin  (by  am- 
monium sulphid).  The  muscle-nuclei  yield  some  nuclein.  The  sarcolemma  con- 
tains a  substance  resembling  keratin.  Several  ferments  are  present  in  traces: 
pepsin,  diastatic,  lactic-acid  (?),  glycolytic,  and  coagulating  (fibrin-) ferments. 
Proteic  acid  is  a  proteid  substance  in  the  flesh  of  fish. 

The  other  chemical  constituents  of  muscle  have  already  been  mentioned  in 
the  consideration  of  meat  (p.  423).  It  will  suffice  to  add  a  little  more  here,  (i) 
In  addition  to  volatile  fatty  acids  (formic,  acetic,  and  butyric  acids),  two  isomeric 
lactic  acids  are  found  in  muscle  having  an  acid  reaction :  (a)  Ethylidene-lactic  acid 
in  the  modification  of  dextrorotatory  paralactic  or  sarcolactic  acid,  (b)  Ethylene- 
lactic  acid  in  small  amount,  which  Maly  also  observed  develop  as  an  occasional 
fermentation-product  of  carbohydrates  (glycogen,  etc.).  The  formation  of  lactic 
acid  during  the  rigidity  of  death  is  discussed  on  p.  552.  Acid  potassium  phosphate 
also  contributes  to  the  acid  reaction.  (2)  Glycogen  is  found  to  the  amount  of 
i  per  cent,  after  an  abundant  meat-diet,  and  of  0.5  per  cent,  during  fasting. 
During  digestion  it  is  stored  up  in  the  muscles,  as  well  as  in  the  liver,  but  it  dis- 
appears in  the  state  of  hunger.  It  is  formed  in  the  muscles  themselves,  probably 
from  albuminates.  (3)  Dextrose,  0.02  per  cent.  (4)  Of  gases,  there  are  present 
carbon  dioxid  (from  15  to  18  vol.  per  cent.,  partly  absorbed,  partly  in  chemical 
combination,  the  latter  probably  being  formed  as  a  result  of  decomposition), 
some  absorbed  nitrogen;  but  no  oxygen,  although  muscle  continually  absorbs 
oxygen  from  the  blood.  The  muscles  contain  a  substance  that  yields  carbon 
dioxid  on  decomposition;  exercise  consumes  this  substance,  so  that  muscles  that 
are  greatly  fatigued  are  capable  of  generating  less  carbon  dioxid. 

METABOLISM  IN  MUSCLE.     THE  SOURCE  OF  MUSCULAR 

ENERGY. 

The  resting  muscle  continuously  abstracts  oxygen  from,  and  returns 
carbon  dioxid  to,  the  capillary  blood  passing  through  it.  Nevertheless, 
the  muscle  excretes  less  carbon  dioxid  than  corresponds  to  the  amount 
of  oxygen  it  absorbs.  Excised  muscles  deprived  of  blood  exhibit  an 
analogous  but  diminished  interchange  of  gases.  Further,  as  such  muscles 


550  THE    SOURCE    OF    MUSCULAR    ENERGY. 

retain  their  irritability  longer  in  oxygen  or  in  air  than  in  indifferent 
gases  free  from  oxygen,  it  is  to  be  assumed  that  this  gaseous  interchange 
is  a  vital  phenomenon  connected  with  normal  metabolism,  and  to  which 
the  functional  activity  of  the  muscle  is  due. 

The  excised,  resting,  surviving  muscle  gives  off  carbon  dioxid,  which  in  part 
has  been  present  in  the  muscle  preformed,  and  in  part  is  subsequently  generated 
by  processes  of  decomposition  that  accompany  the  development  of  rigidity.  A 
small  part  of  this  carbon  dioxid  arises  only  when  oxygen  is  supplied.  Bacterial 
putrefaction  of  the  muscles  causes  marked  excretion  of  carbon  dioxid. 

In  active  muscle  the  blood-vessels  are  always  dilated,  and  the  amount 
of  blood  passing  through  them  is  increased  three  or  four  times,  a  cir- 
cumstance that  obviously  indicates  increased  metabolic  activity.  Ac- 
cordingly, active  is  distinguished  from  passive  muscle  by  a  series  of 
chemical  changes: 

1.  The  contents  of  living  passive  muscle  have  an  alkaline,  or,  more 
correctly,  a  neutral  reaction,  changing  red  litmus  to  blue,  but  acid  to 
turmeric  paper.     The  reaction  becomes  acid  in  active  muscle  (not  of 
the  unstriated  variety),  and,  indeed,  the  degree  of  acidity  increases,  to 
a  certain  limit,  in  proportion  to  the  amount  of  work  performed.     The 
acidity  is  due  to  phosphoric  acid  resulting  from  the  decomposition  of 
lecithin  and  nuclein. 

The  earlier  view,  that  the  acidity  is  due  to  the  development  of  lactic  acid 
produced  from  glycogen,  has  not  been  substantiated.  Pfliiger  and  Warren,  and 
also  Astaschewsky  and  Heffter,  even  found  the  quantity  of  lactic  acid  in  active 
muscles  diminished,  as  compared  with  passive  muscles.  Other  investigators,  how- 
ever, still  adhere  to  the  theory  of  lactic-acid  formation,  especially  if  there  is  a 
deficiency  of  oxygen  during  the  work. 

2.  The  active  muscle  excretes  considerably  more  carbon  dioxid  than 
the  resting  muscle:     (a)  Active  muscular  exertion  in  man  or  animals 
increases  considerably  the  excretion  of  carbon  dioxid   from  the  body, 
(b)  Venous  blood  flowing  from  the  tetanized  muscles  of  an  extremity 
contains  an  increased  quantity  of  carbon  dioxid;  and,  indeed,  under 
these  conditions  more  carbon  dioxid  is  excreted  than  corresponds  to  the 
amount  of  oxygen  simultaneously  absorbed,     (c)  Also,   excised,  con- 
tracted muscles  excrete  an  increased  amount  of  carbon  dioxid. 

3.  Active  muscle  consumes  a  greater  amount  of  oxygen:     (a)  During 
work  the  entire  body  takes  up  much  more  oxygen,  even  four  or  five 
times  as  much,     (b)  Venous  blood  flowing  from  the  active  muscles  of 
an  extremity  contains  a  diminished  amount  of  oxygen.     Nevertheless, 
the  increase  in  the  consumption  of  oxygen  by  an  active  muscle  is  not  so 
great  as  the  increase  in  the  excretion  of  carbon  dioxid.     The  increase  in 
the  interchange  of  gases  continues  in  the  period  of  rest  immediately 
following  the  activity. 

The  consumption  of  oxygen  can  also  be  demonstrated  volumetrically 
in  excised  muscles  deprived  of  blood.  It  is  true,  oxygen  is  not  absolutely 
necessary  for  muscular  activity  of  short  duration,  as  the  excised  muscle 
is  capable  of  contracting  for  some  time  in  a  vacuum  or  in  a  gaseous  mixture 
free  from  oxygen,  and  no  free  oxygen  can  be  obtained  from  its  tissue. 
The  muscle  must,  therefore,  contain  a  supply  of  oxygen  in  chemical 
combination,  which  is  consumed  during  activity.  Frogs'  muscles  ab- 
stract the  oxygen  from  easily  reducible  substances;  thus,  they  may  de- 
colorize a  solution  of  indigo.  Muscles  that  have  rested  act  less  energet- 
ically than  those  that  have  been  active. 


THE  SOURCE  OF  MUSCULAR  ENERGY.  551 

4.  An  active  muscle  contains  less  extractives  soluble  in  water,  but, 
on  the  other  hand,  more  of  those  soluble  in  alcohol.     It  also  contains  less 
of  the  substances  that  form  carbon  dioxid,  less  fatty  acids,  kreatin,  krea- 
tinin,  and  sarcophosphoric  acid. 

5.  During  contraction  the  amount  of  water  in  muscular  tissue  is  in- 
creased, while  that  in  the  blood  is  correspondingly  diminished.     The 
solid  matters  of  the  blood  are  increased,  while  those  of  the  lymph  (al- 
bumin) are  diminished. 

6.  The  question  as  to  the  extent  to  which  the  proteids  of  muscular 
substance  generate  the  kinetic  energy  of  muscular  activity,  by  the  trans- 
formation of  their  chemical  potential  energy,  has  been  answered  by 
Pfliiger  with  the  statement  that  albumin,  if   given  in   sufficiently  large 
amounts,  may  be  the  exclusive  source  of  muscular  force. 

This  albumin  represents  a  special  variety,  and  is  thought  to  be  formed  syn- 
thetically from  ordinary  living  albumin  by  the  absorption  of  alcohol-radicals, 
which  may  be  withdrawn  either  from  another  proteid,  or  from  fat  and  sugar 
if  there  is  a  deficiency  of  proteids.  The  living  albumin  is  transformed  into  a 
readily  decomposable,  living  proteid,  which  contains  a  greater  amount  of  carbon, 
and  represents  the  immediate  source  of  muscular  energy. 

If  a  lean  dog,  fed  only  with  lean  meat  and  in  a  state  of  metabolic  equilibrium 
during  muscular  rest,  is  subjected  to  a  period  of  several  days'  work,  it  must  receive 
a  definite  excess  of  lean  meat  in  order  to  maintain  its  bodily  weight.  During  the 
period  of  activity,  the  animal,  therefore,  decomposes  more  proteid,  in  accordance 
with  the  extent  of  the  activity,  and  the  metabolic  equilibrium  is  thus  maintained. 
Undoubtedly  the  work  performed  is  accomplished  at  the  expense  of  an  increased 
consumption  of  proteids.  If  the  dog  does  not  receive  an  increased  quantity  of 
proteids  on  beginning  to  work,  it  loses  in  bodily  weight. 

Even  though  sufficient  quantities  of  fat  and  carbohydrates,  in  addition  to  the 
proteid,  be  administered  to  the  active  dog,  there  will  still  be  an  increased  con- 
sumption of  proteids  during  work. 

As  on  administration  of  a  sufficient  amount  of  proteid  the  muscular  work  is 
performed  with  the  aid  of  this  alone,  and  as  in  the  decomposition  of  this  proteid 
neither  fat  nor  carbohydrate  results,  the  fat  and  carbohydrate  cannot  be  the  true 
source  of  muscular  force  (Pfliiger) . 

The  carbon  dioxid  resulting  from  the  decomposition  of  proteid  leaves  the 
body  quickly  through  the  pulmonary  respiration;  while  the  nitrogenous  products 
of  decomposition  are  excreted  slowly,  even  for  as  long  as  two  days  after  the  com- 
pletion of  the  work. 

One  and  the  same  readily  decomposable  proteid  is  thus  oxidized 
slowly  and  continuously  in  the  muscular  tissue,  with  the  generation  of 
heat,  while  under  the  influence  of  innervation  it  is  consumed  rapidly  and 
in  larger  amount,  and  is  then  the  source  not  only  of  heat,  but  also  of 
kinetic  energy. 

Pfliiger  estimated  that  in  his  experimental  dog  one  gram  of  nitrogen  in  the 

Sroteid,  decomposed  within  the  body,   produced   7456   kilogrammeters  of  work. 
f  the  total  supply  of  energy  contained  in  the  proteid  (measured  by  means  of 
the  calorimeter  in  calories),  the  dog  converted  48.7  per  cent,  into  kinetic  energy, 
the  remainder  being  transformed  into  heat.     This  48.7  per  cent,  represents  the 
mechanical  equivalent  of  the  proteid. 

At  an  earlier  period  Fick  and  Wislicenus,  as  well  as  v.  Voit  and  v.  Pettenkofer, 
had  reached  the  conclusion  as  a  result  of  their  experiments  that  the  daily 
excretion  of  nitrogen  is  not  increased  to  any  considerable  extent  by  forced  work, 
whereas  the  consumption  of  oxygen  and  the  excretion  of  carbon  dioxid  are 
increased,  provided  that  the  body' has  at  its  disposal  sufficient  material  containing 
carbon,  such  as  glycogen  and  fat,  in  its  tissues  or  in  the  food.  Hence,  the  proteid 
cannot  be  the  source  of  muscular  energy.  Increased  elimination  of  nitrogen 
takes  place  only  when  the  activity  gives  rise  to  dyspnea,  for  deficiency  in  oxygen 
causes  decomposition  of  albuminates. 

Also  the  increased  excretion  of  sulphuric  acid  resulting  from  work  is  indicative  of 


552  MUSCULAR    RIGIDITY. 

a  more  active  decomposition  of  albuminates.  The  excretion  of  sulphur  is  increased 
by  muscular  exertion,  and  indeed  the  non-oxidized  sulphur  is  at  first  excreted 
more  rapidly  than  the  oxidized.  The  excretion  of  phosphoric  acid  also  is  in- 
creased. 

7.  In  the  muscles  of  animals  the  amount  of  glycogen  (0.43  per  cent.) 
has  been  observed  to  diminish  as  a  result  of  activity,  and  even  to  dis- 
appear completely  in  consequence  of  strychnin-convulsions.  The  same 
observation  has  been  made  with  respect  to  the  glycogen  of  the  liver. 
Luchsinger  maintains  that  muscles  can  still  contract  when  completely 
free  from  glycogen;  so  that  the  latter  cannot  be  the  source  of  muscular 
energy.  Also,  the  sugar  of  the  blood  undergoes  a  decrease  in  the  muscles 
as  a  result  of  activity. 

There  is  a  difference  of  opinion  as  to  whether  the  muscle-glycogen  is  carried 
by  the  circulation  from  the  liver  into  the  muscles,  or  whether  it  is  produced  in 
the  muscular  tissue  itself  as  the  result  of  an  as  yet  unknown  decomposition  of 
the  albuminates.  Ktilz  observed  an  increase  in  the  amount  of  glycogen  in  the 
muscles  of  frogs  that  had  been  deprived  of  their  livers  after  subcutaneous  injections 
of  sugar.  Likewise,  the  muscles  retained  their  glycogen  for  a  much  longer  time 
than  the  liver  during  the  state  of  hunger.  These  facts  indicate  the  formation  of 
glycogen  in  the  muscular  substance  itself.  In  any  event,  the  normal  circulation 
is  a  requisite  for  the  production  of  glycogen  in  muscle,  for  this  diminishes  after  liga- 
ture of  all  of  the  vessels.  Surviving  muscle  converts  glycogen  into  sugar. 

Some  investigators,  however,  assume  also  that  not  only  proteid 
but,  in  part,  also  fat  and  carbohydrate  may  be  the  source  of  muscular 
energy  in  the  body. 

MUSCULAR  RIGIDITY  (CADAVERIC  RIGIDITY,  RIGOR  MORTIS). 

Excised  muscles,  striated  as  well  as  unstriated,  and  also  the  muscles 
of  the  intact  body  some  time  after  death,  pass  into  a  state  of  rigidity, 
described  more  fully  later  on,  that  is  designated  muscular  rigor.  If 
the  muscles  of  the  dead  body  become  involved,  the  entire  cadaver  be- 
comes completely  stiff  (cadaveric  rigidity).  The  cause  of  this  phenome- 
non resides  in  a  spontaneous  coagulation  of  the  myosin  within  the  muscle- 
fibers,  with  the  development  of  a  small  amount  of  acid.  During  this 
process  of  coagulation,  heat  is  liberated  owing  to  the  transition  of  the 
fluid  myosin  into  the  solid  condition,  and,  also,  owing  to  the  thickening 
of  the  tissue  that  takes  place  at  the  same  time. 

Myosin,  dissolved  in  a  5  per  cent,  solution  of  magnesium  sulphate  diluted  with 
water,  separates  after  a  time  in  the  form  of  solid  flakes,  with  the  development 
of  an  acid  reaction.  Warming  hastens  this  process. 

_  The  rigid  muscle  exhibits  the  following  properties:  It  is  shortened, 
thickened,  and  somewhat  denser;  stiff,  firm  and  solid;  turbid  and  opaque, 
in  consequence  of  the  coagulation  of  the  myosin;  incompletely  elastic, 
less  extensible,  and  less  readily  torn.  It  is  completely  unresponsive  to 
stimuli,  and  its  electrical  potential  has  disappeared.  The  amount  of 
glycogen  present  is  diminished.  Striated  muscle  has  an  acid  reaction, 
on  account  of  increased  formation  of  the  two  varieties  of  lactic  acid  (un- 
striated has  not),  and  it  develops  free  carbon  dioxid.  If  incisions  be 
made  into  rigid  muscles,  a  fluid  exudes  spontaneously,  the  muscle- 
serum. 

The  view  was  formerly  held  that  during  rigidity,  partial  or  complete  trans- 
formation of  the  glycogen  occurred,  first  into  sugar  and  then  into  lactic  acid. 
This  view,  however,  has  been  contested  by  Bohm,  who  asserted  that  during 


MUSCULAR    RIGIDITY.  553 

digestion  a  transitory  accumulation  of  large  amounts  of  glycogen  takes  place  in 
the  muscles,  as  in  the  liver;  so  that  approximately  as  much  can  be  found  in  the 
former  as  in  the  latter.  Rigidity  causes  no  diminution  of  glycogen,  provided 
putrefaction  is  prevented;  <  hence,  the  lactic  acid  of  rigid  muscles  cannot  arise 
from  glycogen,  but  probably  from  decomposition  of  albuminates.  Heffter  main- 
tains that  lactic  acid  is  not  formed  at  all  during  postmortem  rigidity. 

The  amount  of  acid  does  not  vary,  whether  the  rigidity  develops  slowly  or 
rapidly.  With  the  onset  of  acidification,  the  rigidity  becomes  more  marked, 
on  account  of  the  coagulation  of  the  alkali-albumin  in  the  muscle.  The  less 
carbon  dioxid  there  is  generated  by  the  rigid  muscle  the  more  it  had  already 
given  off  previously  during  activity. 

Fibrin-ferment  is  present  in  muscle  in  a  state  of  cadaveric  rigidity.  It  is  in 
general  a  product  of  protoplasm,  and  is  never  wanting  where  the  latter  is  present. 
There  is  thus  an  analogy  between  coagulation  of  blood  and  muscular  rigidity. 

Two  stages  of  rigidity  are  to  be  distinguished:  In  the  first  stage 
the  muscle  is  already  somewhat  stiff,  but  still  excitable;  the  myosin  in 
this  stage  acquires  a  gelatinous  consistency.  Restitution  is  still  possible 
from  this  stage.  In  the  second  stage  the  rigidity  is  fully  developed  in 
all  of  the  characteristics  mentioned. 

Rigidity  appears  in  man  in  from  ten  minutes  to  seven  hours;  the  duration  is 
likewise  variable,  from  one  to  six  days.  After  its  disappearance,  the  muscles 
again  become  soft,  owing  to  the  onset  of  further  decomposition  and  an  alkaline 
reaction;  the  rigidity  yields.  The  onset  of  rigidity  is  always  preceded  by  a  dis- 
appearance of  nervous  activity.  Therefore,  the  muscles  of  the  head  and  the  neck 
are  first  affected,  and  then  the  others  in  a  descending  order.  Likewise  those 
muscles  that  usually  degenerate  earliestaare  the  first  to  become  rigid;  for  example, 
in  the  frog  the  flexors  before  the  extensors.  Rigidity  disappears  earliest  also  in 
those  muscles  that  first  became  rigid.  Great  muscular  activity  before  death,  for 
example  during  the  convulsions  of  tetanus,  cholera,  strychnin-poisoning,  or  opium- 
poisoning,  causes  rapid  and  intense  rigidity.  Therefore,  the  heart  becomes 
strongly  rigid  and  with  relative  rapidity.  White  muscles  become  rigid  later  than 
red  muscles.  Wild  animals,  hunted  to  death,  may  become  rigid  in  a  few  minutes. 
Usually  the  rigidity  lasts  the  longer  the  later  it  sets  in.  Rigidity  never  occurs 
in  the  fetus  before  the  seventh  month.  Frogs'  muscles  cooled  to  o°  C.  become 
rigid  only  after  from  four  to  seven  days. 

Stenson's  Experiment. — The  influence  of  the  amount  of  blood  in  the  muscles 
upon  the  onset  of  rigidity  is  especially  worthy  of  notice.  Ligation  of  the  muscular 
arteries  in  warm-blooded  animals  causes  first  increased  irritability  of  the  muscular 
tissue,  lasting  a  few  minutes,  then  rapid  diminution  in  the  irritability,  followed 
by  the  onset  of  both  stages  of  rigor  in  succession.  If  the  arteries  of  the  muscles 
were  ligated,  Stannius  observed  that  the  irritability  of  the  motor  nerves  disap- 
peared in  the  course  of  an  hour,  that  of  the  muscular  tissue  itself  in  from  four 
to  five  hours;  then  rigidity  sets  in. 

Pathological. — Thrombotic  occlusion  of  the  muscular  vessels  will  also  cause 
rigidity.  Excessively  tight  bandaging  may  give  rise  to  true  rigidity  in  man  by 
cutting  off  the  circulation.  The  muscles  become  paralyzed  and  stiff,  and  later  break 
up  into  flakes,  and  the  contents  of  the  fibers  are  subsequently  absorbed.  The  circu- 
latory disturbances,  arising  in  muscles  under  the  influence  of  cold,  also  cause 
paralyses  that  are  often  designated  rheumatic.  Also  in  cases  of  trichinosis  the 
affected  muscle-fibers  are  the  seat  of  rigidity,  and  the  stiffness  in  the  muscles 
is  thus  explained.  The  contractures  occurring  in  cases  of  cholera  should  probably 
be  included  in  the  class  of  muscular  contractions  resulting  from  circulatory  dis- 
turbances, the  inspissated  blood  giving  rise  to  stagnation;  as  should  also  certain 
contractions  occurring  in  the  presence  of  atheroma  and  in  the  agonal  period. 
The  sensory  nerves  in  completely  anemic  extremities  retain  their  irritability  for 
from  five  to  ten  hours. 

If  the  circulation  be  restored  in  the  first  stage  of  rigidity,  the  muscle  soon 
recovers.  If,  however,  the  second  stage  has  set  in,  restitution  is  impossible.  In 
cold-blooded  animals  rigidity  does  not  set  in  for  several  days  after  ligature  of 
the  vessels.  Brown-Sequard,  by  the  injection  of  fresh  blood  containing  oxygen, 
succeeded  in  restoring  softness  and  irritability  to  a  human  cadaver  in  the  first 
stage  of  rigidity  even  four  hours  after  death.  Heubel  obtained  the  same  result 
with  the  frog's  heart  as  long  as  fourteen  and  one-half  hours  after  death.  On  pass- 


554  MUSCULAR    RIGIDITY. 

ing  blood  containing  oxygen  through  excised  muscles,  C.  Ludwig  and  Al.  Schmidt 
found  that  the  onset  of  rigidity  was  retarded  for  a  long  time;  this  did  not  occur, 
however,  with  blood  deprived  of  oxygen.  After  considerable  loss  of  blood,  rigidity 
sets  in  relatively  early.  If  an  artificial  circulation  be  kept  up  in  the  dead  muscles 
of  a  frog  by  means  of  feebly  alkaline  fluids,  rigidity  does  not  occur. 

Previous  section  or  paralysis  of  the  motor  nerves  results  in  delayed  onset  of 
rigidity  in  the  relaxed  muscles.  The  reason  is  found  in  the  greater  abundance  of 
blood  in  these  muscles,  in  consequence  of  associated  paralysis  of  the  vasomotors, 
the  alkaline  blood  remaining  in  the  muscles  even  after  death,  while  the  arteries 
in  other  parts  of  the  body  become  empty.  This  view  is  supported  by  the  fact 
that  rigidity  appears  much  later  in  fish  whose  medulla  oblongata  is  suddenly 
destroyed  than  in  those  that  die  slowly.  According  to  Ewald  and  Willgerodt  the 
labyrinths  of  the  ear,  as  organs  controlling  tone,  likewise  have  an  influence  on  the 
course  of  rigidity. 

Freezing  and  thawing  cause  rigidity  to  set  in  more  rapidly,  and  it  is 
favored  likewise  by  mechanical  injury. 

Continuous  passive  movements  may  retard  the  onset  of  rigidity,  but  on  their 
cessation  their  rigidity  sets  in  all  the  more  rapidly.  Rigidity  that  has  already 
developed  may  be  overcome  by  forced  movements,  but  it  may  set  in  again. 

Rigidity  may  be  induced  artificially: 

1 .  By  heat  (heat-rigor) ,  which  causes  coagulation  of  the  myosin  in  cold-blooded 
animals  at  40°,  in  mammals  at  from  45°  to  47°  C.,  and  in  birds  at  about  53°  C. 
Under  such  circumstances  there  is  marked  excretion  of  carbon  dioxid,  but  less 
after  previous  tetanization.     Protoplasm,  for  example  of  the  amoeba,  is  similarly 
subject  to  heat-rigor. 

The  degree  of  heat  required  to  bring  about  rigidity  is  the  higher  the  longer 
the  muscles  have  been  excised.  If  the  muscles  of  a  frog  in  a  state  of  cadaveric 
rigidity  be  heated,  the  remaining  proteids  undergo  coagulation  successively,  and 
the  muscle  becomes  still  more  rigid  as  a  result  of  these  coagulative  processes. 

2.  Saturation  with  water  induces  water-rigor,  with  the  development  of  an 
acid  reaction,  in  consequence  of  the  coagulation  of  the  globulin-substances,  the 
excretion  of  carbon  dioxid  not  being  increased. 

If  the  thigh  of  a  frog  be  ligated,  and  the  muscles,  deprived  of  their  skin,  be 
immersed  in  warm  water,  they  will  become  rigid.  On  loosening  the  ligature  a 
slight  degree  of  rigidity  may  disappear  through  restoration  of  the  circulation.  On 
the  other  hand,  a  more  marked  degree  of  rigidity  can  be  removed  only  by  placing 
the  leg  in  a  10  per  cent,  solution  of  sodium  chlorid,  which  will  dissolve  the  myosin- 
coagulum. 

3.  Acids,  even  weak  acids  such  as  carbon  dioxid,  induce  rapid  acid-rigor. 
This  is  probably  different  from  normal  rigidity,  as  the  muscle  does  not  develop 
free  carbon  dioxid.     Injection  of  from  o.i  to  0.2  per  cent,  solutions  of  lactic  or 
hydrochloric  acid  into  the  vessels  of  frogs'  muscles  causes  immediate  rigidity, 
which  can  be  overcome  by  0.5  per  cent,  acid,  and  also  by  a  neutralizing  solution 
of  sodium  bicarbonate,  or  13  per  cent,  solution  of  ammonium  chlorid.     The  acids 
enter  into  combination  with  the  myosin. 

4.  Among  poisons    and   other   substances,    the    following   promote    rigidity: 
Caffein,  quinin,  digitalin,  veratrin,  hydrocyanic  acid,  also  oils  of  mustard,  fennel, 
and  anise,  and,  when  placed  in  direct  contact  with  the  muscles,  potassium  sulpho- 
cyanid,  ammonia,  metallic  salts,  alcohol,  ether,  chloroform.     Chloroform,  acetic 
acid,  and  heat  induce  rigidity  with  shortening;    ammonia,  on  the  other  hand, 
rigidity  without  shortening. 

The  position  of  the  entire  body  during  rigidity  is  usually  that  which  it  occupied 
at  death.  The  position  of  the  limbs  corresponds  to  the  resultant  of  the  various 
degrees  of  muscle-tension.  If  the  limbs  occupied  another  position  before  death, 
they  are  frequently  seen  to  move  during  the  onset  of  rigidity.  The  arms  and 
fingers  especially  are  readily  flexed.  If  the  rigidity  develops  with  especial  firmness 
and  rapidity  in  certain  groups  of  muscles,  an  unusual  position  may  be  assumed, 
for  example  the  fencing  attitude  of  cholera-cadavers.  If  the  rigidity  occurs  rap- 
idly, the  body  at  times  remains  in  the  same  position  that  it  occupied  at  the  moment 
of  death,  for  example  on  the  battle-field.  Under  such  circumstances,  however, 
the  contracted  muscle  never  passes  immediately  into  a  condition  of  rigidity,  a 
period  of  relaxation  intervening,  even  though  short. 

Muscles  scalded  by  immersion  in  boiling  water  do  not  become  rigid;  neither 
do  they  become  acid,  nor  evolve  free  carbon  dioxid.  Muscles  coagulated  by 
concentrated  alcohol  or  by  immersion  in  concentrated  solutions  of  sodium  chlorid , 
potassium  nitrate,  sodium  and  magnesium  sulphate,  do  not  yield  an  acid  reaction. 


IRRITABILITY    AND    STIMULATION    OF    THE    MUSCLE.  555 

Attention  has  repeatedly  been  directed  to  the  analogies  between  muscle  in 
active  contraction  and  in  the  state  of  rigidity-  The  form  of  the  contracted  and 
of  the  rigid  muscle  is  shortened  and  thickened;  both  are  denser,  of  changed  elas- 
ticity, and  evolve  heat;  the  contents  of  the  contracted  as  of  the  rigid  muscle  are 
negative  electrically  as  compared  with  resting  or  non-rigid  contents;  both  evolve 
free  carbon  dioxid  and  the  remaining  acid  from  the  same  source.  A  contraction 
may,  therefore,  be  regarded  as  a  temporary  rigidity,  disappearing  physiologically, 
just  as  earlier  investigators,  and  recently  Bernstein,  designated  rigidity  as  being, 
to  a  certain  extent,  the  final  vital  act  of  the  muscles. 

A  muscle  in  process  of  becoming  rigid  will  lift  a  weight,  like  a  living,  con- 
tracting muscle.  The  height  to  which  the  weight  is  lifted  by  a  rigid  muscle  is 
greater  in  the  case  of  small  weights  and  less  for  heavy  ones  than  if  the  living 
muscle  be  stimulated  to  a  maximum  degree.  If  a  muscle,  in  which  heat-rigor  has 
been  induced,  be  at  first  prevented  from  contracting1,  and  if  later  (for  example 
after  ten  minutes)  it  be  set  free,  its  elastic  energy  will  cause  it  to  contract,  and 
it  must  lose  heat  at  the  same  time. 

The  disappearance  of  cadaveric  rigidity  takes  place  at  first  as  a  result  of 
increased  formation  of  acid  in  the  muscle,  by  which  the  myosin  is  redissolved. 
Subsequently,  with  the  development  of  micro6rganisms  putrefaction  sets  in,  with 
the  associated  evolution  of  ammonia,  hydrogen  sulphid,  nitrogen,  and  carbon 
dioxid. 

The  loss  of  irritability  in  the  muscles  that  precedes  the  onset  of  rigidity  occurs 
in  the  following  order  in  man  (beheaded  criminal):  Left  ventricle,  stomach,  intes- 
tine (fifty-five  minutes),  urinary  bladder;  right  ventricle  (sixty  minutes);  iris 
(one  hundred  and  five  minutes) ;  muscles  of  the  face  and  the  tongue  (one  hundred 
and  eighty  minutes) ;  the  extensors  of  the  extremities  about  one  hour  before  the 
flexors ;  the  muscles  of  the  trunk  (from  five  to  six  hours) .  The  esophagus  remains 
irritable  for  a  long  time. 

IRRITABILITY,  STIMULATION,  AND  DEATH  OF  THE  MUSCLE. 

By  the  irritability  of  a  muscle  is  understood,  its  ability  to  contract  in 
response  to  stimuli  applied  directly  to  it  (not  to  its  nerves).  Stimu- 
lation is  the  state  of  functional  activity  in  which  a  muscle  is  placed  by 
stimuli.  At  the  moment  of  activity  the  stimulation  causes  the  chemical 
potential  energy  of  the  muscle  to  be  converted  into  work  and  heat; 
stimuli  thus  act  as  liberating  forces.  The  mean  temperature  of  the 
body  is  most  favorable  for  the  manifestation  of  irritability.  Each 
muscle  appears  to  possess  a  special  degree  of  irritability  peculiar  to  it- 
self, as  do  likewise  the  nerves. 

So  long  as  the  current  of  blood  in  the  muscle  is  uninterrupted,  stimu- 
lation first  causes  an  increase  in  its  functional  activity,  partly  because 
the  circulation  becomes  more  active  in  association  with  dilatation  of  the 
vessels;  later,  however,  the  functional  activity  diminishes. 

This  diminution  in  functional  activity  is  a  sign  of  fatigue.  If  the  same  stimu- 
lation be  continued,  the  muscular  activity  will  exhibit  a  periodic  variation,  in 
such  manner  that  after  a  series  of  weaker  contractions  stronger  ones  will  again 
set  in,  followed  in  turn  by  weaker,  and  so  on.  This  phenomenon  depends  upon 
periodically  recurring  improvement  in  the  nutrition  of  the  muscle,  as  a  result  of 
analogous  variations  in  its  circulation. 

In  excised  muscles  also,  especially  if  the  large  nerve-trunks  have  al- 
ready undergone  degeneration,  the  irritability  is  at  first  somewhat  in- 
creased after  each  stimulation,  so  that  with  a  uniform  series  of  stimuli 
the  contractions  at  first  exhibit  an  increase  in  extent.  Thus,  it  may 
happen  that,  while  the  first  weak  stimulus  is  still  ineffectual,  the  second 
will  give  rise  to  a  contraction.  The  unstriated  muscles  exhibit,  under 
certain  conditions,  automatic  and  rhythmic  movements  without  the 
intervention  of  nerves. 


556  IRRITABILITY    AND    STIMULATION    OF    THE    MUSCLE. 

Frogs'  muscles  that  have  been  cooled,  or  those  in  which  desiccation  has 
begun,  exhibit  an  excessively  increased  irritability,  especially  to  mechanical 
stimuli.  This  fact  may  explain  the  remarkable  muscular  movements  that  often 
take  place  in  cholera-cadavers.  Cooled  muscles  from  the  frog  or  the  tortoise 
may  preserve  their  irritability  for  as  long  as  ten  days,  but  the  muscles  of  warm- 
blooded animals  often  degenerate  in  from  one  and  one-half  to  two  and  one-half 
hours.  The  irritability  of  the  heart-muscle  is  considered  on  p.  118.  Curarized, 
isolated  frogs'  muscles  exhibit  the  least  amplitude  of  contraction  at  o°,  the  greatest 
at  30°;  if  heated  beyond  the  latter  temperature,  the  contraction  gradually  dimin- 
ishes, until  the  point  is  reached  where  rigor  sets  in.  The  duration  of  contraction 
and  the  latent  period  are  also  shortest  at  30°. 

Since  the  time  of  Alb.  v.  Haller  (1743)  it  has  been  thought  necessary  to 
attribute  to  muscle  a  peculiar  irritability  (even  without  the  intermediation  of  the 
motor  nerve) .  In  more  recent  times  attempts  have  been  made  to  adduce  further 
support  in  favor  of  this  specific  muscular  irritability:  (i)  There  are  chemical 
irritants  that  induce  no  movement  when  applied  to  the  motor  nerves,  but  cause 
contraction  when  applied  directly  to  the  muscle;  for  example  ammonia,  lime- 
water,  carbolic  acid.  (2)  The  extremities  of  the  sartorius  muscle  of  the  frog,  in 
which  no  nerve-endings  can  be  demonstrated  by  means  of  the  microscope,  never- 
theless react  to  direct  stimulation  by  contractions.  (3)  Curare  paralyzes  the 
motor  nerves,  while  the  muscle  itself  remains  irritable.  The  action  of  cold,  or 
the  arrest  of  the  circulation  in  the  muscle  of  an  animal,  will  likewise  abolish  the 
irritability  of  the  nerve,  but  not  of  the  muscle  at  the  same  time.  In  general, 
the  directly  stimulated  muscle  will  still  contract  for  some  time  after  its  motor 
nerve  has  degenerated.  (4)  After  section  of  the  nerves,  the  muscles  still  remain 
irritable,  even  though  the  nerves  have  undergone  total  fatty  degeneration.  (5)  At 
times  electrical  stimuli  act  only  upon  the  nerves,  and  not  upon  the  muscles  them- 
selves. 

In  lower  animals  (hydra,  medusa)  unicellular  structures,  neuro-muscular  cells, 
have  been  found  in  which  nervous  and  muscular  tissue  are  represented  in  one 
and  the  same  cellular  structure. 

With  regard  to  the  stimuli  that  act  upon  the  muscles,  the  following  are  to 
be  noted: 

1.  The  normal  stimulus  under  ordinary  circumstances  acts  upon  the  muscle 
by  way  of  its  nerve,  as  in  voluntary  movement,  the  automatic  motor  impulse, 
reflex  excitation.     Its  nature  is  unknown.     The  irritation  of  a  muscle  through  the 
intermediation    of   its   nerve    is    designated   indirect    stimulation.     Pseudomotor 
effects  are  considered  on  p.  559. 

2.  Chemical  Stimuli. — All  chemical  agents  that  alter  the  chemical  constitution 
of  muscular  tissue  with  sufficient  rapidity  act  as  muscle-stimuli.     According  to 
Kuhne,  the  mineral  acids  (o.i  per  cent  hydrochloric  acid),  acetic  and  oxalic  acids, 
the  salts  of  iron,  zinc,  copper,  silver,  and  lead,  bile,  all  act  as  stimuli  to  the  muscle 
in  dilute  solution,  and  only  on  the  nerves  in  much  stronger  solutions.     Lactic 
acid  and  glycerin,  when  concentrated,  excite  only  the  nerve  (?) ;  when  dilute,  only 
the  muscle.     The  neutral  alkaline  salts  act  equally  on  muscle  and  nerve.     Alcohol 
and  ether  both  act  feebly.     Water,  especially  if  injected  into  the  muscular  vessels, 
causes  fibrillary  contractions.     Solutions  of  sodium  chlorid,  from  0.6  to  0.9    per 
cent.,   or  normal  solutions  of  other  sodium-salts,   act  indifferently  toward    the 
muscular  substance,  even  after  the  latter  is  exposed  to  their  influence  for  days; 
this  is  especially  true  after  the  addition  of  a  trace  of  calcium  chlorid  or  calcium 
phosphate.     A  6  per  cent,  solution  of  sodium  chlorid  causes  the  sartorius,  when 
deprived  of  its  nerve,  to  contract  much  more  strongly  than  when  its  nerve  is 
preserved,  and  especially  in  its  active,  thick  fibers.     Acids,  potassium-salts,  and 
meat-extract  diminish  the  irritability  of  the  muscle,  while  other  muscle-stimuli, 
such  as  alcohol,  sodium-salts,  some  metallic  salts,  in  small   doses  increase  the 
irritability.     Gases  and  vapors  also  have  a  stimulating  influence  on  the  muscles, 
either  exciting  simple    contractions  or  immediately  causing    contracture.     Pro- 
tracted exposure  to  the  gases  causes  rigidity.     Only  the  vapor  of  carbon  disulphid 
has  an  irritating  effect  on  the  nerves,  while  most  vapors  (for  example,  of  hydro- 
chloric acid)  destroy  without  causing  excitation. 

In  comparative  observations  on  the  influence  of  chemically  related  substances, 
only  chemically  equal  quantities,  for  example  normal  solutions,  should  be  employed. 
Thus,  among  the  halogens,  sodium  iodid,  with  its  high  molecular  weight,  has  the 
strongest  effect;  while  sodium  chlorid,  with  its  low  molecular  weight,  has  the 
feeblest  effect.  The  combinations  of  the  metals  act  in  like  manner;  also  the  salts 
of  the  alkaline  earths.  Those  with  the  highest  molecular  weight  cause  the 


IRRITABILITY    AND    STIMULATION    OF    THE    MUSCLE.  557 

greatest  excitation  and  the  least  injury.  The  following  substances  cause  injury 
in  the  order  of  their  sequence,  arranged  from  those  with  stronger  to  those  with 
weaker  effects:  ammonia,  potassium,  sodium,  hydrochloric  acid,  nitric  acid, 
sulphuric  acid,  phosphoric  acid  (in  accordance  with  their  avidity) ;  the  fatty  acids 
with  larger  molecules  as  compared  with  those  with  smaller;  the  higher  alcohols 
as  compared  with  the  lower. 

In  making  experiments  upon  the  chemical  irritation  of  "muscles,  it  is  inad- 
visable to  immerse  the  transverse  section  of  the  muscle  in  the  solution.  The 
substance  in  solution  should  rather  be  applied  to  a  limited  area  on  the  uninjured 
surface  of  the  muscle.  The  stimulation  will  then  be  manifested  in  a  few  seconds 
by  contraction  or  fibrillary  motion  of  the  superficial  muscular  layers. 

If  the  sartorius  of  a  curarized  frog  be  immersed  in  a  solution  of  5  grams  of 
sodium  chlorid,  2  grams  of  alkaline  sodium  phosphate,  and  0.5  gram  of  sodium 
carbonate  in  i  liter  of  water  at  10°  C.,  the  muscle  will  be  thrown  into  rhythmic 
contractions,  which  may  persist  even  for  days.  These  contractions  suggest,  to  a 
certain  degree,  the  rhythmic  action  of  the  heart  (Biedermann). 

The  following  act  as  chemical  irritants  upon  unstriated  muscles:  ergot,  aloes, 
colocynth,  the  alkalies;  atropin  and  nicotin  paralyze  the  nervous  elements  in 
such  muscles,  as  does  also  ether;  chloroform  also  destroys  the  muscle-fibers  them- 
selves. Carbon  dioxid  in  small  amounts  acts  as  an  irritant  to  the  nerves,  in 
larger  amounts  as  a  paralyzant,  and  in  still  larger  amounts  it  irritates  and  finally 
paralyzes  the  muscle-fibers  themselves. 

3.  Thermal  Stimuli. — If  a  frog's  muscle  be  rapidly  heated,  a  gradually  in- 
creasing contraction  begins  at  about  28°  C.,  becomes  more  pronounced  at  30°  C., 
and    attains   its   maximum   at   45°   C.;   following   this,    further  heating   rapidly 
leads  to  heat-rigor.     Local  cooling  of  the  muscle  increases  its  irritability  for  all 
kinds  of  stimuli.     Frog's  muscle  cooled  to  o°  is  exceedingly  responsive  to  me- 
chanical irritation,  and  it  may  be  stimulated  by  degrees  of  cold  below  o°,  until 
freezing  takes  place.     Heat  has  a  relaxing  effect  on  unstriated  muscle    (frog), 
while  cold  has  a  moderately  stimulating  effect.     Variations  in  temperature,  how- 
ever, also  affect  the  nerves  of  these  muscles,  each  fluctuation  causing  reflex  con- 
traction, which  does  not  occur  if  the  nerves  are  paralyzed. 

Cl.  Bernard  made  the  remarkable  observation  that  the  muscles  of  artificially 
cooled  animals  retain  their  irritability  for  many  hours  after  death.  Heat  causes 
rapid  disappearance,  with  temporary  increase  of  the  irritability. 

4.  Mechanical  stimuli  of  all  kinds  cause  a  contraction  at  each  separate,  sudden 
blow;  and  tetanus  if  repeated.     Strong,  local  stimuli  induce  an  elevated  contrac- 
tion of  considerable  duration  at  the  point  of  application.     Moderate  stretching  of 
a  muscle  increases  its  irritability.     Mechanical  stimulation  of  a  muscle  poisoned 
with  veratrin  causes  a  heaving  movement  of  its  fibers,  which  may  persist  for  as 
long  as  one  minute. 

5.  Electrical  stimuli  are  discussed  in  conjunction  with  nerve-stimuli  (p.  631). 
Curare,  the  arrow-poison  of  the  South  American  Indians,  is  the  dried  juice 

of  the  root  of  Strychnos  Crevauxi.  When  introduced  into  the  blood  or  injected 
subcutaneously,  it  first  causes  paralysis  of  the  intramuscular  termination  of  the 
motor  nerves,  the  muscles  themselves  retaining  their  irritability,  while  the  sensory 
nerves  and  those  of  the  central  organs  and  the  viscera  (heart,  intestine,  and  ves- 
sels) remain  for  a  time  unaffected.  In  warm-blooded  animals  the  paralysis  of 
the  respiratory  muscles  naturally  causes  early  asphyxia,  which  is  unattended  with 
convulsions.  Frogs,  whose  skin  is  their  most  important  respiratory  organ,  on 
receiving  a  suitable  dose,  may  recover  completely,  after  remaining  motionless  for 
days,  during  which  the  poison  is  eliminated  through  the  urine.  Larger  doses  paralyze 
also  the  cardiac  inhibitory  and  vasomotor  nerves.  In  electrical  fish  paralysis  of 
the  nerve  transmitting  the  electrical  shock  occurs.  In  frogs  the  lymph-hearts  also 
are  paralyzed.  If  the  doses  that  are  fatal  when  administered  subcutaneously  be 
given  by  mouth,  poisoning  does  not  result,  because  the  poison  is  eliminated  by 
the  kidneys  at  the  same  rate  that  it  is  absorbed  by  the  gastric  mucous  membrane. 
For  the  same  reason  the  flesh  of  an  animal  killed  by  a  poisoned  arrow  is  harm- 
less. If,  however,  the  ureters  be  ligated,  the  poison  accumulates  in  the  blood, 
and  intoxication  results.  Large  doses,  however,  will  kill  uninjured  animals  also 
by  way  of  the  intestinal  tract. 

Atropin  appears  to  be  a  specific  poison  for  unstriated  muscle-fibers,  although 
different  muscles  are  variously  affected  by  it. 

The  irritability  of  the  muscles  after  lesions  of  the  nerves  deserves  especial 
attention.  After  three  or  four  days  the  irritability  of  the  paralyzed  muscle  is 
diminished  for  direct  or  indirect  (nerve)  stimuli.  There  then  follows  a  stage  in 


558  CHANGE    OF    SHAPE    IN    ACTIVE    MUSCLE. 

which  a  constant  current  has  an  abnormally  excessive  effect,  while  induced  cur- 
rents are  almost  or  completely  without  effect;  irritability  to  direct,  mechanical 
stimuli  is  also  increased.  This  increased  irritability  is  observed  at  about  the 
seventh  week.  It  then  diminishes  gradually,  until  it  completely  disappears  at 
about  the  sixth  or  seventh  month.  Beginning  with  the  second  week,  the  muscle 
begins  to  undergo  progressive  fatty  degeneration,  to  the  point  of  complete  atrophy. 
In  experiments  on  animals  Schmulewitsch  found,  immediately  after  section  of  the 
sciatic  nerve,  that  irritability  was  increased  in  the  muscles  innervated  by  it. 

After  death  the  muscles  degenerate  (excised  muscles  more  rapidly), 
and  the  earlier  if  they  have  been  exhausted  and  exposed  to  stimuli  of 
considerable  intensity.  Thick  muscles  "survive  longer  (in  their  inte- 
rior) than  thin  muscles.  It  would  appear  that  there  is  a  definite  stage  of 
early  or  late  death  for  each  individual  muscle;  for  example,  the  extensors 
in  man  degenerate  earlier  than  the  flexors. 

The  muscles  of  the  frog  degenerate  in  twenty-four  hours  at  summer  tem- 
perature, in  the  course  of  two  or  three  days  at  moderate  temperature,  and  only 
after  about  twelve  days  at  o°.  The  muscles  of  warm-blooded  animals  degenerate 
on  an  average  in  the  course  of  from  one-sixth  to  twelve  hours.  The  degeneration 
of  the  heart  is  considered  on  p.  113. 

CHANGE  OF  SHAPE  IN  ACTIVE  MUSCLE. 

Macroscopic  Phenomena. — i.  Active  muscle  becomes  shorter  and  at 
the  same  time  increases  in  thickness. 

The  degree  of  shortening,  which  in  exceedingly  irritable  frogs  may  amount 
to  as  much  as  from  65  to  85  per  cent,  (on  an  average  72  per  cent.)  of  the  entire 
length  of  the  muscle,  depends  upon  various  factors:  (a)  To  a  certain  degree  an 
increase  in  the  strength  of  the  stimulus  gives  rise  to  a  greater  amount  of  shortening. 
(6)  With  increasing  exhaustion  after  continuous,  vigorous  activity,  the  same 
strength  of  stimulus  causes  less  shortening,  (c)  Elevation  of  temperature  up  to 
30°  C.  causes  stronger  contractions  in  the  frog's  muscles.  If  the  temperature  be 
further  elevated  the  degree  of  shortening  is  again  diminished. 

2.  The  contracting  muscle  is  somewhat  diminished  in  volume.     Con- 
sequently, the  specific  gravity  of  contracting  muscle  is  somewhat  in- 
creased, the  ratio  to  that   of  non-contracting  muscle  (in  the  marmot) 
being  as  1062  : 1061.     The  diminution  in  volume  amounts  to  only  T^T¥- 

Method. — Swammerdam  placed  a  frog's  muscle  in  a  glass  tube  containing  air 
and  drawn  out  into  a  thin  tubule  containing  a  small  drop  of  fluid.  The  nerve  was 
conducted  to  the  exterior  through  a  small  lateral  opening.  Mechanical  stimulation 
of  the  exposed  nerve  caused  contraction  of  the  muscle  and  descent  of  the  small 
drop.  In  an  analogous  manner  Ermann  placed  irritable  fragments  of  an  eel 
in  a  similar  tube,  filled  with  an  indifferent  fluid.  The  fluid  rises  to  a  certain 
level  in  a  thin  tubule  communicating  with  the  glass  container.  When  the  muscu- 
lature of  the  eel  was  made  to  contract,  the  fluid  sank.  Landois  demonstrated 
the  diminution  in  volume  of  contracted  muscle  by  means  of  the  manometric 
flame.  The  cylindrical  glass  vessel  containing  the  muscle  receives  two  electrodes 
passing  through  its  walls  in  an  air-tight  manner.  It  communicates  at  one  point 
with  a  gas-supply  pipe,  and  at  another  point  it  gives  off  a  thin  tubule,  at  the 
extremity  of  which  a  small  flame  is  ignited  at  low  gas-pressure.  The  muscular 
contraction  following  each  electrical  stimulus  causes  a  reduction  in  the  size  of  the 
flame.  If  a  pulsating  heart,  naturally  containing  no  air,  be  placed  in  the  gas- 
chamber,  each  pulsation  will  be  attended  with  a  reduction  in  the  size  of  the  flame. 

3.  Under  normal  conditions,  all  stimuli  applied  to  the  muscle,  as 
well  as  to  the  motor  nerve,  will  cause  contraction  in  all  of  its  fibers.    The 
muscle  thus  conducts  to  all  of   its    fibers  the  impulses  communicated 
to  it.     Deviations  from  this  rule  are  observed,  however,  in  two  direc- 
tions:   (a)  When  the  muscle  is  greatly  exhausted,  or  when  it  is  about 


CHANGE    OF    SHAPE    IN    ACTIVE    MUSCLE.  559 

to  degenerate,  a  violent  mechanical,  and  also  a  chemical  or  electrical 
stimulus,  applied  to  a  circumscribed  portion  of  the  muscle  will  cause 
contraction  in  this  portion  alone;  so  that  an  elevated  thickening  of 
the  fibers  (Scruff's  idiomuscular  contraction]  is  observed  at  this  point. 
The  same  phenomenon  may  be  induced  in  the  muscles  of  a  healthy 
person,  and  especially  in  weakened  and  poorly  nourished  individuals, 
if  the  fibers  be  struck  with  a  blunt  edge  at  right  angles  to  their  course, 
(b)  Under  certain  conditions,  as  yet  not  fully  known,  the  muscles  will 
be  seen  to  exhibit  so-called  fibrillary  contractions,  that  is  the  various 
bundles  of  fibers  in  the  muscle  are  from  time  to  time  traversed  by  short 
contractions.  Such  a  condition  is  observed  in  the  tongue -muscles  of 
the  dog  after  section  of  the  hypoglossal  nerve,  and  in  the  face-muscles 
after  section  of  the  facial  nerve. 

According  to  Bleuler  and  Lehmann,  section  of  the  hypoglossal  nerve  in  the 
rabbit  is  followed  in  the  course  of  from  sixty  to  eighty  hours  by  fibrillar  con- 
tractions that  persist  for  months,  even  when  stimulation  of  the  healed  nerve 
above  the  point  of  union  again  excites  movements 
in  the  corresponding  half  of  the  tongue.  Stimu- 
lation of  the  lingual  nerve  increases  the  fibrillar 
contractions.  This  nerve  contains  vasodilator 
fibers  from  the  chorda  tympani.  Schiff  believes 
that  the  cause  of  the  contractions  resides  in  the 
increased  blood-supply  to  the  tongue.  Sigm. 
Mayer  also  observed  contractions  in  the  facial 
muscles  in  rabbits,  after  restoration  of  the  cir- 
culation  in  the  carotids  and  subclavians,  pre- 
viously  compressed.  Section  of  the  motor  nerves 
in  the  face  does  not  abolish  the  phenomenon, 
while  repeated  compression  of  the  arteries  does  FIG.  191.— The  Microscopic  Phenomena 

SO.      The  Cause   Of   the   contractions    resides,    ac-  of  Muscular  Contraction  in  the  Indi- 

cordingly,  in  the  musculature  itself.     This  motor  EnSSLS?*8  °f  the  Fibrils  (after 

phenomenon  is  designated  pseudomotor.     It  may 

be   compared  to  the   paralytic   secretion  of  the 

salivary   glands.      Similar  phenomena  have  been   observed  also   in    man   under 

pathological  conditions,  but  at  times  fibrillar  contractions  may  be  observed  even 

in  the  absence  of  other  evidence  of  pathological  disturbances. 

Microscopic  Phenomena. — i.  The  separate  fibrils  of  the  muscle 
exhibit  the  same  phenomena  as  does  the  entire  muscle,  in  that  they  be- 
come shorter  and  thicker.  2 .  The  observation  of  the  individual  muscle- 
elements  is  attended  with  especial  difficulties.  In  the  first  place,  it  is 
certain  that  during  contraction  they  become  collectively  shorter  and 
thicker,  so  that  the  transverse  striations  appear  to  be  pushed  more  closely 
together.  3.  Opinions  are  not  fully  in  accord  as  to  the  behavior  of  the 
constituent  parts  of  each  muscle-element  during  contraction. 

Fig.  191,1  represents,  according  to  Engelmann,  on  the  left  a  muscular  element 
at  rest;  from  c  to  d  extends  the  doubly  refractive,  contractile  substance,  in  the 
middle  of  which  the  median  disc  a  b  is  situated;  h  and  g  are  the  terminal  discs. 
In  addition,  there  is  in  each  singly  refractive  light  layer  an  accessory  disc,  f  and 
e,  which  is  doubly  refractive  in  but  slight  degree,  and  occurs  only  in  the  muscles 
of  insects.  Fig.  i  shows  on  the  right  the  same  element  in  polarized  light,  the 
middle  portion  of  the  element,  so  far  as  the  actual  contractile  substance  extends, 
appearing  light  on  account  of  the  double  refraction;  while  the  remainder  of  the 
muscle-element  appears  black  on  account  of  the  single  refraction.  Fig.  191,  2 
represents  the  transition-stage,  and  3,  the  actual  contractile  stage  of  the  muscle- 
element,  both  on  the  left  as  viewed  in  ordinary  light,  and  on  the  right  in  polarized 
light. 

According  to  Engelmann,  during  contraction  (3)  the  singly  refractive 
layer  becomes  on  the  whole  more  highly  refractive,  and  the  doubly  re- 


560  THE  TIME  RELATIONS  OF  MUSCULAR  CONTRACTION. 

fractive  layer  less  so.  As  a  result,  the  fiber  may  with  a  certain  degree 
of  shortening  (2)  appear  homogeneous  and  only  faintly  striated  when 
observed  in  ordinary  light,  the  homogeneous  or  transitional  stage  (Mer- 
kel's  stage  of  dissolution).  If  the  shortening  be  more  pronounced  (3), 
distinct  dark  striae  again  appear,  corresponding  to  the  singly  refractive 
discs.  At  every  stage  of  shortening,  including,  therefore,  the  transition- 
stage,  the  singly  and  doubly  refractive  layers  may  be  demonstrated,  by 
means  of  the  polarizing  apparatus,  as  sharply  defined,  regularly  alternat- 
ing layers  (in  i,  2,  3,  to  the  right).  They  do  not  exchange  places  in  the 
muscle-compartment  during  contraction.  The  height  of  both  layers  is 
diminished  during  contraction,  that  of  the  singly  refractive  much  more 
rapidly  than  that  of  the  doubly  refractive  layer.  The  total  volume  of 
each  element  is  not  appreciably  changed  during  contraction.  There- 
fore, the  doubly  refractive  layers  increase  in  volume  at  the  expense  of  the 
singly  refractive  layers.  Hence  it  follows  that  during  contraction  fluid 
passes  from  the  singly  into  the  doubly  refractive  layer;  the  former 
shrinks,  the  latter  swells. 

Method. — The  phenomena  described  can  be  best  observed  by  instantaneously 
coagulating  the  living  muscle-fibrils  of  insects  in  the  various  stages  of  rest  or 
contraction  by  suddenly  applying  alcohol  or  dilute  perosmic  acid  to  the  muscles, 
and  thus  fixing  the  different  stages.  The  movement  itself  may  be  followed  under 
the  microscope,  either  by  stimulating  the  thin,  outspread  muscle  electrically,  or, 
still  better,  by  observing  the  independent  muscular  contractions  in  the  trans- 
parent parts  of  an  insect,  for  example  in  the  head  of  the  gnat's  larva. 

A  thin,  extended  muscle,  for  example  the  sartorius  of  the  frog,  yields  a  double 
spectrum  (like  a  Nobert's  glass  screen),  if  light  be  allowed  to  pass  through  a 
narrow  slit,  held  closely  in  front  of  the  fibers  and  at  right  angles  to  them.  If  the 
muscle  be  made  to  contract,  for  example  by  mechanical  stimulation,  the  spectrum 
broadens,  an  evidence  that  the  intervals  between  the  transverse  stria?  become 
smaller.  At  the  same  time  the  transparency  of  the  muscle  becomes  greater  than 
during  rest. 

THE    TIME-RELATIONS    OF    MUSCULAR    CONTRACTION. 

MYOGRAPHY.    SIMPLE  CONTRACTION.     TETANUS. 

ISOTONY.     ISOMETRY. 

Isotonic  muscular  activity  is  the  term  applied  to  the  contraction  in 
which  the  tension  of  the  muscle  remains  the  same,  while  the  fibers  be- 
come shorter. 

Method. — The  time-relations  of  the  contraction  in  the  isotonic  muscular  act 
may  be  shown  by  v.  Helmholtz's  myograph  (Fig.  192).  The  suspended  muscle 
(M),  fastened  at  its  upper  extremity  (K),  is  attached  by  its  lower  extremity  to 
a  lever  constructed  like  a  balance,  which  can  be  weighted  by  means  of  the 
weights  (W)  as  desired,  and  is  raised  by  the  shortening  of  the  muscle.  From  the 
free  extremity  of  the  arm  of  the  lever  is  suspended  by  means  of  a  hinge- joint 
a  style  (F),  which  records  the  movement  of  the  lower  extremity  of  the  muscle 
on  the  smoked  surface  of  a  cylinder  made  by  means  of  clockwork  to  rotate  at  a 
uniform  speed  in  front  of  the  style.  In  this  way  the  contracting  muscle  itself 
records  its  contraction-curve,  in  which  the  abscissas  represent  the  units  of  time 
calculated  from  the  known  rapidity  of  rotation  of  the  cylinder,  and  the  ordinates 
represent  the  degree  of  shortening  at  any  particular  moment. 

Fick  improved  the  myograph  materially  by  making  the  writing  lever  ex- 
ceedingly light,  and  applying  the  weight  close  to  the  rotation-axis  of  the  balance. 
In  this  way  the  swinging  movement  accompanying  the  muscular  contraction  is 
reduced  to  a  minimum,  as  is  also  the  change  in  tension  brought  about  by  such 
movements. 

The  surface  intended  for  the  reception  of  the  myogram  must  be  moved  rapidly, 
as  the  process  of  movement  takes  place  rapidly.  Therefore,  either  a  plate  fastened 


ISOTONIC  MUSCULAR  CONTRACTION. 


to  the  rod  of  a  pendulum  (Pick's  pendulum-myograph) ,  or  a  surface  set  in  motion 
by  gravity  (Jendrassik's  gravity-myograph)  or  by  means  of  a  spring  (Du  Bois- 
Reymond)  or  a  rotating  convex  surface  (Rosenthal's  rotating  myograph) ,  may  be 
employed.  Under  the  myogram  a  time-curve  is  traced  by  means  of  a  vibrating 
tuning-fork.  The  apparatus  is,  in  addition,  provided  with  an  arrangement  for 
indicating  in  the  tracing  the  moment  of  stimulation. 

The  curve  may  be  traced  advantageously  on  the  vibrating  plate  of  a  tuning- 
fork  (Fig.  194,  I).  The  time-units  are  thus  registered  in  all  parts  of  the  curve, 
each  complete  vibration  being  equal  to  0.01613  second.  The  moment  of  stimula- 
tion coincides  with  the  beginning  of  the  vibration  of  the  fork,  which  is  at  first 
moved  to  one  side  for  a  time,  without  vibrating.  This  is  accomplished  by  re- 
leasing a  clamp,  which  at  the  same  time  opens  a  galvanic  circuit,  and  sends  an 
induction  (opening)  shock  of  the  secondary  coil  through  the  muscle.  The  tuning- 
fork  can  also  be  set  in  vibration  by  a  blow  on  one  of  its  prongs.  If  under  such 
circumstances  the  nerve  is  so  placed  upon  the  fork  as  to  be  struck  by  the  blow, 
the  latter  acts  at  the  same  time  as  a  mechanical  nerve-stimulus. 

The  balance,  together  with  the  imposed  weights,  is  jerked  upward   at  the 
commencement  of  the  contraction.     As  a  result  the  curve  is  distorted,  because  the 
muscle  is  no  longer  weighted  after  the  moment  of  occurrence  of  the  jerk.     For 
this  reason  the  muscle  has  been 
made  to  draw  up  an  elastic  spring. 
In  this  way,  however,  a  stronger 
pull  must  be  made  on  the  muscle 
as  the  spring  is  raised  higher  and 
higher.     To  avoid  this  Grutzner 
constructed  a  spring  that  exerts 
a  steadily  diminishing  tension  on 
the  apparatus  as  the  muscle  pro- 
gressively contracts. 

If  it  be  desired  to  record  only 
the  extent  (height)  of  the  contrac- 
tion, the  tracing  is  made  on  a 
stationary  surface,  which  is  dis- 
placed slightly  after  each  move- 
ment (Pfliiger's  myograph) . 

Muscular  contractions  may 
also  be  recorded  in  the  case  of 
man.  It  is  best  to  transfer  the 
increase  in  thickness  attending 
contraction  either  to  a  lever  or 
to  a  drum  covered  with  rubber, 
for  example  that  of  Brondgeest's 
pansphygmograph  (p.  101). 


FIG.  192. — Diagrammatic  Representation  of  v.  Helmholtz's 
Myograph:  M,  the  muscle,  fastened  at  K;  F,  the  writing- 
style,  suspended  from  the  arm  of  the  lever  that  is  to  be 
raised;  P,  a  counter-weight  for  maintaining  equilibrium; 
W,  scale-pan  for  weighting  the  muscle  as  desired;  S  S,  posts 
supporting  the  balancing  lever. 


If  a  single  stimulus  of 
momentary  duration  be  ap- 
plied to  a  freely  movable  mus- 
cle, the  latter  executes  a  simple  contraction,  that  is  it  shortens  rapidly 
and  also  returns  quickly  to  the  relaxed  condition.  Under  such  circum- 
stances the  internal  tension  of  the  muscle  remains  the  same  during  the 
course  of  the  entire  contraction,  and  for  this  reason  the  resulting  curve 
is  designated  an  isotonic  myogram. 

The  following  details  can  be  noted  in  an  isotonic  contraction-curve 
described  by  a  muscle  that  has  to  lift  only  the  light  writing  lever,  and  is 
not  overweighted  by  any  other  attached  weights:  i.  The  stage  of 
latent  stimulation  (Fig.  193,  a  b),  which  arises  from  the  fact  that  the  con- 
traction of  the  muscle  does  not  begin  at  the  moment  of  stimulation,  but 
always  somewhat  later.  If  the  momentary  stimulus,  for  example  an 
induction-shock,  be  applied  directly  to  the  entire  muscle,  the  latent  period 
is  about  o.oi  second. 


In  man  the  stage  of  latent  stimulation  varies  from  0.004  to  o.oi   second. 
36 


562  ISOTONIC  CONTRACTION  CURVE. 

If  provision  is  made  in  the  experiment  for  the  muscle  to  contract  immediately, 
so  that  no  time  is  lost  between  the  act  of  the  relaxed  muscle  becoming  tense  and 
the  commencement  of  the  contraction,  the  latent  stage  may  fall  below  0.004  second. 
For  the  excised  frog's  muscle,  Bernstein  and  Engelmann  found  the  shortest 
period  to  be  0.0048  second.  If  the  animal's  muscle  remains  attached  to  the 
body,  protected  as  well  as  possible  from  external  injuries  and  supplied  with  circu- 
lating blood,  then  the  latent  stimulation  may  be  shortened  to  0.0033  second,  and 
even  to  0.0025  second. 

Influences  Affecting  the  Duration  of  the  Latent  Period. — The  latent  period  is 
diminished  by  increase  in  the  strength  of  the  stimulus  and  by  heat,  and  increased  by 
fatigue,  cooling,  and  increase  in  the  weight.  The  latent  period  of  an  opening 
contraction  is  also  longer  (even  0.04  second)  than  that  of  a  closing  contraction. 
Before  the  muscle  contracts  as  a  whole,  individual  muscle-elements  within  it 
must  already  have  undergone  contraction.  It  is,  therefore,  assumed  that  the 
latent  period  of  the  individual  muscle-elements  is  shorter  than  that  of  the  entire 
muscle.  The  latent  period  is  shorter  after  direct  muscle-stimulation  than  after 
indirect  stimulation  through  the  nerve,  as  the  transference  of  the  stimulus  through 
the  motor  end-organ  requires  some  time.  The  transmission  of  the  nerve-stimulus 
is  considered  on  p.  667. 

2 .  From  the  beginning  of  the  contraction  to  the  height  of  the  short- 
ening (b  d),  the  muscle  contracts  at  first  somewhat  slowly,  then  more 
rapidly,  and  finally  toward  the  end  of  the  shortening  more  slowly  again; 

so  that  the  ascending  limb  of  the  curve  has  the  form  of  an  j  .     This    is 

«./ 
termed  the  stage  of  increasing  energy;  it  lasts  about  0.03  or  0.04  second. 


FIG.  193. — Myogram  of  an  Isotonic  Contraction. 

Its  duration  is  the  shorter  the  smaller  the  contraction  (weaker  stimulus), 
the  smaller  the  weight  to  be  raised,  and  the  less  fatigued  the  muscle. 

3.  After  the  height  of  contraction  has  been  reached,  the  muscle  again 
becomes  extended,  at  first  slowly,  then  more  rapidly,  and  finally  more 
slowly  again ;  so  that  the  descending  limb  has  the  form  of  an  inverted 

J  .    This  is  the  stage  of  diminishing  energy  (d  e) ;  it  is  usually  of  shorter 

duration  than  that  of  increasing  energy. 

4.  After  the  descending  limb  of  the  curve  has  been  recorded,  there  fol- 
low several  after-vibrations  (from  e  to  f),  due  to  the  elasticity  of  the 
muscle,  and  disappearing  gradually.     These  constitute  the  stage  of  elastic 
after-vibrations.     The  latter  are,  however,  regarded  as  factitious,  and 
due  to  the  after-vibrations  of  Helmholtz's  apparatus. 

If  the  stimulus  is  applied  to  the  motor  nerve  instead  of  the  muscle, 
the  contraction  is  the  greater  and  lasts  the  longer  the  nearer  to  the 
spinal  cord  the  nerve  is  stimulated. 

It  has,  until  now,  been  assumed  that  the  muscle  is  weighted  only  with  the 
light  writing  lever  that  it  has  to  raise  in  recording  the  curve.  If,  however,  it 
be  after-loaded,  that  is  if  additional  weights  be  hung  on  the  lever  that,  sup- 
ported during  rest,  must  be  lifted  during  contraction,  then  the  commencement  of 
the  contraction  is  delayed  as  the  after-loading  is  increased.  This  is  due  to  the 


ACTION  OF  POISONS  ON  MUSCLE.  563 

fact  that  the  muscle,  from  the  moment  of  stimulation  on,  must  first  accumulate 
so  much  contractile  force  as  is  necessary  to  raise  the  weight.  The  greater  the 
weight  the  longer  is  the  period  of  time  that  must  elapse  before  the  act  of  lifting 
begins.  Finally,  a  degree  of  after-loading  is  reached  at  which  it  is  no  longer 
possible  to  raise  the  weight.  This  indicates  the  limit  to  which  the  lever-force 
may  operate. 

If  a  muscle,  during  contraction,  be  subjected  to  a  temporary  increase  in 
tension,  it  will  be  found  that  a  short,  quick,  and  considerable  increase  in  tension 
immediately  diminishes  the  contraction ;  while  a  more  prolonged  and  slow  increase 
somewhat  later  increases  the  contraction. 

The  temperature  of  the  muscle  also  has  some  influence.  The  duration  of  the 
contractile  force  diminishes  with  increasing  temperature,  increasing  with  increase 
in  weighting.  The  rapidity  with  which  the  contractile  force  develops  increases 
with  increasing  temperature,  diminishing  with  increased  weighting.  The  height 
to  which  an  unweighted  muscle  may  lift  a  weight  increases  with  its  temperature. 
A  frog's  muscle,  supplied  with  circulating  blood,  exhibits  the  greatest  contraction 
in  response  to  stimuli  at  o°  C.  As  the  temperature  rises,  the  extent  of  contraction 
•diminishes  progressively. 

If  the  muscle  becomes  fatigued  as  a  result  of  repeated  stimulation,  the  stage 
of  latent  stimulation  becomes  longer  and  the  curve  remains  lower,  because  the 
•contraction  of  the  muscle  is  less;  while  the  abscissa  becomes  longer,  because 
the  muscle  contracts  more  slowly  (Fig.  194,  I).  Cooling  of  a  muscle  has  like 
effects.  Also  the  muscles  of  the  new-born  behave  in  a  similar  manner.  The  con- 
traction-curve has  a  flat  apex,  and  is  considerably  prolonged,  especially  in  the 
descending  limb. 

If  the  nerve  of  the  muscle  is  stimulated  by  the  closing  or  opening  of  a  constant 
current,  the  muscular  contraction  corresponds  exactly  to  that  already  described. 
If,  however,  the  current  is  applied  directly  to  the  muscle  itself,  and  is  closed 
and  opened,  a  certain  degree  of  persistent  contraction,  though  often  but  slight, 
takes  place  during  the  period  of  closure,  so  that  the  curve  assumes  the  form 
shown  in  Fig.  194,  IV,  in  which  the  current  was  closed  at  S  and  opened  at  O. 

According  to  Cash  and  Kronecker,  the  individual  muscles  have  a  special 
form  of  contraction-curve.  Thus,  the  omohyoid  of  the  tortoise  contracts  more 
rapidly  than  the  pectoral.  The  flexors  of  the  frog  contract  more  quickly  than  the 
extensors.  The  muscles  of  tortoises,  the  adductors  of  mussels,  the  muscles  of  the 
bat,  and  the  heart  contract  slowly.  The  muscles  of  flying  insects  contract  with 
great  rapidity,  those  of  the  fly  350  times,  and  of  the  bee  400  times  in  a  second. 
There  are,  however,  slowly  contracting  muscles  among  beetles  also,  for  example 
in  the  water-beetle,  hydrophilus. 

White  muscle-fibers  are  more  irritable,  have  a  shorter  latent  period,  and  are 
more  readily  fatigued  than  red  fibers ;  their  contraction -period  is  shorter.  They 
are  therefore  more  active,  and  the  contraction -wave  is  propagated  more  rapidly 
in  them.  They  also  produce  more  acid  and  heat  during  their  activity.  The  red 
fibers  execute  protracted,  continuous  movements;  hence,  moderate,  physiological 
tetanus.  They  intermediate  the  adjustment  of  the  muscular  force  to  the  resistance 
to  be  overcome.  Red  fibers,  or  those. rich  in  protoplasm,  are  further  present, 
especially  in  the  continuously  active  muscles — respiratory,  masticatory,  ocular, 
and  cardiac.  The  white  fibers  execute  the  rapid,  single  movements.  Muscles 
that  contain  principally  white  fibers  have  a  greater  lifting  capacity  and  a  more 
marked  absolute  power  in  the  single  contraction,  but  they  are  inferior  to  the  red 
muscles  in  tetanic  contraction.  The  contraction-curves  of  a  mixed  muscle  con- 
taining white  and  red  fibers  may  exhibit  two  elevations  in  the  ascending  limb, 
the  first  being  due  to  the  contraction  of  the  active  white  fibers,  and  the  second 
to  that  of  the  more  sluggish  red  fibers.  These  are  observed  especially  after  the 
action  of  veratrin  on  the  muscle-substance.  The  nerves  supplying  the  white  and 
red  muscles  also  exhibit  differences  in  their  irritability. 

Action  of  Poisons. — Small  doses  of  curare,  as  well  as  quinin  and  cocain,  in- 
crease the  size  of  the  contractions  induced  by  stimulation  of  the  nerve;  larger 
doses  reduce  the  size  to  the  point  of  complete  paralysis.  Suitable,  small  doses 
of  veratrin  likewise  increase  the  size  of  the  contractions,  while  the  stage  of  re- 
laxation is  conspicuously  lengthened.  Acids  accelerate  the  relaxation.  Veratrin, 
antiarin,  and  digitalin  in  large  doses  induce  such  changes  in  the  muscle-substance 
that  the  contractions  become  greatly  prolonged  and  similar  to  a  continuous, 
tetanic  contraction.  In  muscles  poisoned  with  veratrin  or  strychnin,  the  latent  stage 
of  contraction  is  at  first  shortened,  but  later  lengthened.  The  gastrocnemius  of  a 
frog  will  contract  more  rapidly  if  supplied  with  circulating  blood  containing 
sodium  bicarbonate.  Kunkel  believes  that  the  essential  factor  in  the  action  of 


564 


THE  DURATION  OF  A  MUSCLE  CONTRACTION. 


the  muscle-poisons  consists  in  their  control  of  the  imbibition  of  water  by  the 
muscle-substance.  As  the  muscular  contraction  depends  on  imbibition,  the  form 
of  contraction  of  the  poisoned  muscle  will  be  influenced  by  the  state  of  imbibition 
produced  in  it  by  the  poison. 

The  contraction-curves  of  unstriated  muscles  are  similar  to  those  of  striated 
muscles,  but  the  contraction  takes  place,  after  a  latent  period  of  as  much  as 
several  seconds,  visibly  later  and  more  slowly. 

The  contraction  in  a  preparation  of  a  frog's  stomach  lasts  600  times  as  long 
as  that  of  a  striated  muscle,  and  the  latent  stage  amounts  to  1.5  seconds.  The 
curve  ascends  more  steeply  than  it  descends,  and  its  apex  is  flattened.  Warming 
increases  the  height  of  the  curve,  and  shortens  the  latent  period  and  the  duration 
of  contraction;  above  39°  C.,  however,  the  conditions  are  reversed. 

A  muscle  contracted  as  a  result  of  stimulation  returns  to  its  original  length 
only  if  a  sufficient  extending  force  is  applied  to  it,  as  by  weights  suspended  from 
it.  Otherwise  it  will  remain  somewhat  shortened  for  a  considerable  time,  the 
resulting  condition  being  designated  contracture  or  contraction-remainder.  This  is 
especially  well  marked  in  muscles  that  have  been  previously  subjected  to  strong, 
direct  stimulation,  or  are  greatly  fatigued,  or  more  strongly  acid,  or  approaching 


FIG.  194. — I,  Contraction  of  a  fatigued  calf-muscle  from  the  frog,  recorded  on  a  v: 

fork.  Each  dentation  represents  0.01613  second;  a  b,  latent  irritation;  b  c,  stage  of  increasing  energy,  c 
stage  of  diminishing  energy.  II,  The  most  rapid  writing  movement  of  the  right  hand,  recorded  on  the  vibrating 
plate  of  a  tuning-fork.  Ill,  The  most  rapid  tetanic  tremor-movement  of  the  right  forearm,  recorded  on  the 
same  plate.  IV,  Myographic  curve  on  closing  and  opening  a  current  applied  to  the  muscle  itself  (after  Wundt). 

a  condition  of  rigor,  or  have  been  obtained  from  animals  poisoned  with  veratrin. 
The  phenomenon  of  contracture  is  also  observed  in  man. 

In  man,  single  twitching  movements  of  the  muscles  may  be  executed  with 
great  rapidity.  The  determination  of  the  time-relations  of  such  movements  may 
be  made  most  simple  by  recording  the  movement  in  question  upon  the  vibrating 
plate  of  the  tuning-fork.  Fig.  194,  II,  represents  the  most  rapid  movement  that 
Landois  could  execute  voluntarily  with  the  right  hand  in  writing  the  letters  n  n 
in  succession.  Each  ascending  and  descending  part  of  the  movement  comprises 
3.5  vibrations  (i  =  0.01613  second)  =  0.0564  second.  In  III  the  right  arm  was 
made  to  vibrate  laterally  to  and  fro  on  the  tuning-fork  plate  in  tetanic  tremor; 
here  the  to-and-fro  movement  comprised  from  2  to  2.5  vibrations — from  0.0323 
to  0.0403  second. 

v.  Kries  found  that  a  simple  muscular  contraction  excited  by  an  induction- 
shock  lasts  longer  than  a  single,  momentary,  voluntary  movement.  The  direct 
registration  of  the  muscular  thickening  during  a  single  voluntary  contraction 
shows  that  the  contraction  within  the  muscle  lasts  longer  than  the  movement 
developed  in  the  passive  motor  organ  itself.  This  shorter  duration  of  the  resulting 
movement,  which  at  first  appears  paradoxical,  is  due  to  the  fact  that,  shortly 
after  the  primary  voluntary  muscular  contraction,  a  contraction  of  antagonists 
takes  place,  and  as  a  result  a  part  of  the  intended  movement  is  cut  off.  Even 
with  the  most  rapid  voluntary  movements  in  man,  v.  Kries  found  that  about 


THE    EFFECT  OF  TWO   SUCCESSIVE  STIMULI.  565 

four  impulses  in  the  muscle  were  effective,  so  that  they  really  represented  short 
tetanic  contractions. 

Pathological. — In  the  presence  of  secondary  degeneration  of  the  spinal  cord 
following  apoplexy,  of  atrophic  muscles  associated  with  ankylosed  extremities,  of 
muscular  atrophy,  of  progressive  ataxia,  and  of  paralysis  agitans  of  long  standing, 
the  latent  period  is  increased.  On  the  other  hand,  it  is  diminished  in  the  presence 
of  the  contractures  attending  senile  chorea  and  spastic  tabes.  The  entire  curve 
appears  to  be  lengthened  in  cases  of  icterus  and  diabetes.  In  cases  of  cerebral 
hemiplegia  in  the  stage  of  contracture  the  muscular  contraction  resembles  the 
veratrin-curve,  as  it  does  likewise  in  cases  of  spastic  spinal  paralysis  and  amyo- 
trophic  lateral  sclerosis.  In  cases  of  pseudohypertrophy  of  the  muscles,  the  as- 
cending limb  is  short  and  the  descending  limb  greatly  lengthened.  In  the  presence 
of  muscular  atrophy  following  cerebral  hemiplegia  and  tabes,  the  height  of  the 
curve  is  reduced,  ascent  and  descent  take  place  gradually,  and  the  contraction  of 
the  atrophic  muscle  resembles  that  of  a  fatigued  muscle.  In  cases  of  chorea  the 
curve  is  short.  The  reaction  of  degeneration  is  described  on  p.  669.  According 
to  Goldscheider  contraction  takes  place  sluggishly  also  in  conjunction  with  affec- 
tions of  the  nerves,  without  any  change  in  the  irritability  of  the  muscles  them- 
selves. In  rare  cases  the  observation  has  been  made  in  man  that  spontaneous 
motor  stimuli  give  rise  to  prolonged  muscular  contractions,  followed  by  after- 
contractions  (Thomsen's  disease).  The  muscle-fibers  of  such  patients  are  broad, 
the  nuclei  increased  in  number,  and  the  fibrils  hypertrophied ;  it  has  been  sug- 
gested that  the  white  fibers  are  wanting.  Fr.  Schultze  and  others  have  observed 
a  peculiar  muscular  undulation. 

If  two  momentary  shocks  be  applied  successively  to  the  muscle  in 
such  a  way  that  each  would  alone  have  induced  a  maximal  contraction, 
that  is  the  greatest  possible  contraction,  the  effect  will  vary  in  accordance 
with  the  time  that  elapses  between  the  two  shocks.  If  the  second  shock 
be  applied  after  the  muscle  has  already  become  relaxed  from  the  contrac- 
tion of  the  first  stimulus,  then  a  second  maximal  contraction  simply 
results.  If,  however,  the  muscle  is  still  in  a  phase  of  contraction  or  re- 
laxation from  the  influence  of  the  first  stimulus,  the  second  shock  gives 
rise  to  a  new  maximal  contraction  from  the  phase  of  contraction  existing 
at  that  time.  If,  finally,  the  second  shock  follows  so  quickly  upon  the 
first  that  both  occur  during  the  period  of  latent  stimulation,  only  one 
maximal  contraction  results. 

If  both  stimuli  are  only  of  moderate  strength,  not  sufficient  to  induce 
maximal  contraction,  a  summation  of  the  effects  of  both  takes  place. 
At  whatever  stage  of  contraction  the  muscle  may  be  as  a  result  of  the 
first  stimulus  (Fig.  195,  7,  6),  the  second  shock  will  have  an  effect  (b  c)  as 
if  the  phase  of  contraction  brought  about  by  the  first  shock  were  the 
natural  passive  form  of  the  muscle.  Thus,  under  favorable  conditions, 
the  contraction  may  be  even  twice  as  large  as  that  induced  by  the  first 
stimulus  alone.  The  most  favorable  condition  is  the  application  of  the 
second  stimulus  ^V  second  after  the  first.  The  effects  of  both  are  also 
produced  if  the  second  shock  is  applied  within  the  period  of  latent  stimu- 
lation. 

The  second  contraction  of  a  summated  contraction  reaches  its  height  in  a 
shorter  period  of  time  than  the  first  contraction  alone  would  have  done.  The 
time  for  b  c  (Fig.  195,  /)  is,  thus,  shorter  than  that  for  a  b. 

If  a  series  of  shocks  be  applied  to  the  muscle  in  rather  rapid  succession, 
the  muscle  will  have  no  time  to  relax  in  the  intervals.  It,  therefore, 
in  accordance  with  the  rapidity  with  which  the  stimuli  follow  one  another, 
remains  in  a  state  of  continuous,  shock-like,  tremulous  contraction  that 
is  designated  tetanus.  The  condition  of  tetanus,  or  rigid  spasm,  is,  thus, 
not  a  state  of  continuous,  uniform  contraction,  but  a  discontinuous 


566  TETANUS. 

form  of  movement,  resulting  from  accumulated  contractions.  If  the 
stimuli  succeed  one  another  with  only  moderate  rapidity,  the  separate 
shocks  may  still  be  recorded  in  the  curve  (//).  If,  however,  the  stimuli 
are  applied  in  more  rapid  succession,  the  curve  has  an  uninterrupted  ap- 
pearance (///).  As  a  single  contraction  takes  place  more  slowly  during 
fatigue,  it  is  obvious  that  a  fatigued  muscle  will  be  more  readily  thrown 
into  tetanus  by  a  smaller  number  of  single  stimuli  than  a  fresh  muscle. 

All  movements  of  considerable  duration  excited  in  the  human  body  are  thus 
to  be  regarded  as  tetanic,  for  they  are  constituted  of  a  series  of  single  contractions 
in  rapid  succession.  Accordingly,  every  movement,  however  steady,  will  on  close 
observation  be  found  to  exhibit  intermittent  vibration,  which  reaches  its  climax 
in  tremor  and  becomes  so  conspicuous  in  cases  of  paralysis  agitans. 

The  number  of  single  impulses  sent  to  the  muscles  of  the  body  in  the  execution 
of  voluntary  movements  varies  considerably — when  the  contractions  are  slow 
from  8  to  14  in  a  second,  when  the  contractions  are  rapid  from  1 8  to  20,  the  average 
being  12.5  in  a  second.  Fig.  196,  I,  represents  a  myogram  of  the  left  flexor  brevis 
pollicis  and  the  abductor  pollicis  during  a  continuous  contraction  of  moderate 
intensity,  recorded  on  the  vibrating  plate  of  a  tuning-fork.  The  wave-like  eleva- 
tions indicate  the  separate  impulses,  each  dentation  being  equal  to  0.01613  second. 
II  represents  a  similarly  recorded  curve  made  by  the  extensor  digiti  tertii. 


n 


FlG.  195. — /,  Two  successive  submaximal  contractions.     77,  A  series  of  contractions  induced  by  12  induction- 
shocks  in  a  second.    777  Marked  tetanus  induced  by  rapid  shocks. 


By  the  summation  of  single  stimuli,  the  muscle  voluntarily  excited  slowly  to 
contraction  is  gradually  brought  to  the  desired  degree  of  shortening.  It  is  cus- 
tomary to  effect  an  exact  adjustment  of  the  extent  of  movement  by  the  develop- 
ment of  resistances  through  antagonistic  muscles,  as  observations  on  lean,  mus- 
cular persons  show. 

The  tetanic  contraction  that  occurs  under  normal  conditions  in  the  intact 
body  has  also  been  shown  to  be  composed  of  single,  successive  contractions,  as 
secondary  tetanus  may  result  from  it;  the  latter  may  be  induced  also  from  a 
muscle  in  a  state  of  strychnin-tetanus. 

If  a  muscle  be  connected  with  a  telephone  whose  wires  are  attached  to  two 
pins,  one  of  which  is  inserted  into  the  tendon  and  the  other  into  the  tissue  of 
the  muscle,  a  sound  will  be  heard  when  the  muscle  is  thrown  into  tetanus,  indi- 
cating that  periodic  motor  processes,  that  is,  successive  contractions,  are  taking 
place  in  the  muscle.  The  sound  is  most  distinct  when  the  tetanizing  Neef's 
hammer  vibrates  about  fifty  times  a  second. 

The  rapidity  with  which  the  successive  stimuli  must  follow  one  another  in 
order  to  induce  tetanic  contraction  varies  for  the  different  muscles  of  the  body, 
as  well  as  for  those  of  different  animals. 

In  the  case  of  the  muscles  of  the  frog  15  successive  shocks  in  a  second  are 
required  on  an  average  to  induce  tetanus  (in  the  hyoglossus  muscle  only  10, 
in  the  gastrocnemius  27  shocks).  If  the  shocks  are  feeble,  more  than  20  in  a 
second  are  required.  The  muscles  of  the  tortoise  are  thrown  into  a  state  of  tetanus 
by  only  2  or  3  shocks  in  a  second;  the  red  muscles  of  the  rabbit  by  10,  the  white 


TETANUS. 


567 


muscles  by  more  than  30,  human  muscles  by  from  8  to  12,  the  sluggish  abductor 
minimi  digiti  of  man  by  6  shocks  in  a  second.  The  muscles  of  birds  are  not 
thrown  into  a  state  of  tetanus  even  by  70  shocks,  and  the  muscles  of  insects  not 
even  by  from  350  to  400  in  a  second.  In  the  muscles  of  the  crab's  claw,  rhythmic 
contractions  or  rhythmically  interrupted  tetanus  (in  the  astacus  and  hydrophilus) 
are  observed  as  a  result  of  tetanic  stimulation. 

O.  Soltmann  found  that  the  white  muscles  of  new-born  rabbits  are  tetanized 
by  1 6  shocks  in  a  second,  and  that  the  tetanus  thus  induced  resembles  that  of 
fatigued  adult  muscles.  This  fact  explains  the  readiness  with  which  tetanus 
occurs  in  the  new-born. 

Curarized  muscles  are  at  times  thrown  into  a  state  of  tetanic  contraction 
by  a  momentary  stimulus. 

The  extent  of  shortening  in  a  muscle  in  a  state  of  tetanic  contraction  is, 
within  certain  limits,  dependent  upon  the  strength  of  the  individual  stimuli,  and 
also  upon  their  frequency.  The  steepness  of  the  tetanus-curve  increases  with 
increase  in  the  strength  of  the  stimuli  rather  than  with  increase  in  the  frequency 
of  the  individual  stimuli.  With  feeble  stimuli  the  muscle  exhibits  greater  con- 
tinuity in  its  contraction;  intensification  of  the  stimuli  then  causes  a  greater 
discontinuity  in  the  curve  (tendency  to  clonic  spasm) ;  and  if  the  intensity  of 
the  stimuli  be  still  further  increased  the  curve  becomes  again  more  nearly  con- 
tinuous. The  contracture  that  may  remain  after  tetanus  is  the  more  marked  the 
stronger  and  longer  the  stimulation  and  the  weaker  the  muscle.  The  height  of 
the  contraction  and  that  of  tetanus  are  the  same  for  an  unweighted  muscle.  Only 
in  the  case  of  the  weighted  muscle  is  the  height  of  the  single  contraction  less 


FIG.  196. — I,  Fluctuations  during  a  continuous  contraction  of  the  flexor  brevis  pollicis  and  the  abductor  pollicis. 

II,  of  the  extensor  digiti  tertii. 

than  that  of  the  tetanic  contraction.  At  times  a  stimulus  applied  immediately 
after  tetanus  has  a  greater  effect  than  one  applied  before  tetanus. 

The  tetanized  muscle  cannot  maintain  the  same  degree  of  contraction  in- 
definitely if  the  succession  of  shocks  remains  the  same.  On  the  contrary,  it  will 
lengthen  somewhat  as  fatigue  sets  in,  at  first  rapidly,  but  later  more  slowly. 
If  the  tetanizing  stimulus  is  withdrawn,  the  muscle  does  not  immediately  regain 
its  natural  length,  but  a  certain  contraction-remainder  persists  for  some  time, 
especially  after  long-continued  induction-shocks. 

Muscle  may  also  enter  into  a  state  of  permanent  contraction,  which  has  not 
been  definitely  determined  to  be  due  to  fusion  of  single  contractions ;  for  example 
the  transient  contraction  induced  by  certain  chemical  agents  (such  as  ammonia 
and  others),  the  elevations  attending  idiomuscular  contraction,  and  that  induced 
by  the  passage  of  a  constant  current. 

If  rapid,  weak  induction-shocks  (more  than  224  and  360,  even  as  many  as 
5000  in  a  second  for  frogs'  muscles)  be  applied  to  the  muscle  or  its  motor  nerve, 
the  tetanus  may  cease  after  the  initial  contraction.  This  occurs  with  the  least 
frequency  of  stimulation  when  the  nerve  is  cooled;  the  higher  the  temperature 
of  the  nerve  the  greater  the  frequency  of  stimulation  that  may  still  be  effective 
in  inducing  a  long-continued  tetanus. 

This  initial  contraction  is  a  short  tetanus;  increase  in  the  strength  of  the 
current  renders  the  tetanus  continuous.  On  the  other  hand,  Kronecker  and 
Stirling,  however,  observed  tetanus  occur  with  more  than  24,000  shocks  in  a 
second.  According  to  these  investigators,  the  upper  limit  of  frequency  for  the 
muscle  that  will  still  cause  tetanus  appears  to  lie  near  the  limit  at  which  fluctua- 
tions in  the  current  can  no  longer  be  appreciated,  even  with  other  rheoscopes. 


568 


ISOMETRIC  MUSCULAR  CONTRACTION. 


Isometric  Muscular  Activity. — While  the  experiments  discussed  in 
the  foregoing  are  concerned  with  the  determination  of  the  changes  in  the 
length  of  a  muscle  on  stimulation  and  the  movement  of  a  weight  sup- 
ported by  it,  Pick  has  investigated  the  changes  that  take  place  in  the 
tension  of  a  muscle  under  the  influence  of  stimuli,  when  its  length  is  kept 
constant.  Pick  designates  this  process  the  isometric  muscular  act. 

The  following  apparatus  will  serve  to  demonstrate  the  isometric  muscular 
act  (Fig.  197) :  The  angular  frame  R  is  provided  at  its  base  with  a  long  writing- 
lever  S  (abbreviated  in  the  illustration),  which  is  movable  at  the  hinge- joint  p. 
The  muscle  M,  suspended  from  above,  is  connected  with  the  writing-lever 
near  its  point  of  attachment.  A  strong  spiral  spring  F  is  connected  with  the 
other  arm  of  the  writing-lever,  and  during  the  activity  of  the  muscle,  permits 
only  the  slightest  degree  of  shortening  to  take  place.  This,  however,  is  sufficiently 
magnified  by  the  great  length  of  the  lever.  A  momentary  electric  stimulus  is 

applied  to  the  muscle 
by  means  of  two  elec- 
trodes (r  r),  and  the 
writing-lever  records 
the  isometric  curve. 

The         isometric 

.      ,  x  -  -  |>s»  contraction-curve    is, 

X  on  the  whole,  similar 

to  the  isotonic  curve, 
as  a  comparison  of  the 
curves  in  Fig.  197  will 
show.  Nevertheless, 
the  following  differ- 
ences exist:  (i)  The 
contracting  muscle 
attains  its  maximum 
tension  in  the  isome- 
tric muscular  act 
more  rapidly  than  it 
attains  its  maximum 
shortening  in  the  iso- 
tonic act.  (2)  The 
FIG.  197.— Isometric  Muscular  Act.  contracting  muscle  in 

the  isometric  act 
maintains  the  degree 

of  highest  tension    somewhat  longer,  while    in  the  isotonic  act  it  recedes   more 
rapidly  from  the  highest  degree  of  shortening. 

In  the  isometric  muscular  act  in  man,  voluntary  excitation  gives  rise  to  a 
higher  degree  of  tension  than  electric  stimulation.  In  the  frog,  the  tension  of 
the  muscle  in  a  state  of  tetanus  is  about  twice  as  great  as  it  is  in  a  maximal  con- 
traction; in  human  muscle  it  may  be  even  ten  times  as  great.  During  extension 
of  the  tetanized  muscle,  as  during  its  contraction,  equal  degrees  of  tension  cor- 
respond to  smaller  lengths. 

In  the  case  of  unstriated  muscles,  the  entire  curve  is  much  shorter  in  the 
isometric  act  than  during  the  isotonic  act,  and  its  form  is  almost  symmetrical. 


RAPIDITY  OF  PROPAGATION  OF  MUSCULAR  CONTRACTION. 

If  a  muscle  of  considerable  length  is  stimulated  at  one  extremity  a 
contraction  occurs  at  that  point,  and  rapidly  traverses  in  a  wave-like 
manner  the  entire  length  of  the  muscle  to  its  other  extremity.  The 
excitation  is  therefore  communicated  to  each  successive  part  of  the 
muscle  by  virtue  of  a  special  conductive  capacity  on  the  part  of  the 
muscle  to  enter  into  a  state  of  contraction.  In  the  frog  the  wave  of 
contraction  has  an  average  velocity  of  from  3  or  4  to  6  meters  in  a  second, 
in  the  rabbit  of  from  4  to  5  meters,  in  the  lobster  of  only  i  meter,  in 


MUSCULAR    WORK.  569 

unstriated  muscles  and  in  the  heart  of  only  from  10  to  15  millimeters. 
These  figures,  however,  apply  only  to  excised  muscles,  for  in  the  striated 
muscles  of  living  human  beings  the  rapidity  of  propagation  is  much 
greater,  namely  from  10  to  13  meters. 

Method. — For  the  demonstration  of  this  motor  phenomenon,  Aeby  placed  a 
writing-lever  transversely  across  the  origin  of  a  muscle  of  considerable  length 
and  another  across  its  insertion.  Both  were  raised  by  the  thickening  resulting 
from  the  contraction  of  the  respective  parts  of  the  muscle,  and  the  movements 
were  recorded  one  above  the  other  on  the  drum  of  a  kymograph.  If  one  ex- 
tremity of  the  muscle  is  now  stimulated,  the  contraction-wave  that  rapidly  traverses 
the  muscle  lifts  first  the  proximal  and  then  the  distal  lever.  As  the  velocity 
with  which  the  drum  revolves  is  known,  the  rapidity  with  which  the  contraction- 
wave  is  propagated  through  the  portion  of  muscle  under  examination  can  readily 
be  calculated  from  the  distance  between  the  elevations  of  the  two  levers. 

The  time  corresponding  to  the  length  of  the  abscissa  of  the  curve  in- 
scribed by  each  recording  lever  is  equal  to  the  duration  of  the  contraction 
in  that  part  of  the  muscle;  according  to  Bernstein  this  is  from  0.053  "to 
0.098  second.  By  multiplying  this  value  by  the  ascertained  rapidity  of 
propagation  of  the  contraction-wave  through  the  muscle,  the  wave- 
length of  the  contraction-wave  is  obtained;  this  equals  from  206  to  380 
millimeters. 

The  rapidity  and  the  height  of  the  contraction-wave  are  diminished 
by  cold,  fatigue,  gradual  degeneration,  and  some  poisons.  On  the  other 
hand,  the  strength  of  the  stimulus  and  the  extent  to  which  the  muscle 
may  be  weighted  have  no  influence  on  the  rapidity  of  the  wave.  In  ex- 
cised muscle  the  wave  diminishes  in  size  during  its  course  through  the 
muscle,  but  not  in  the  muscles  of  a  living  human  being  or  animal.  The 
contraction-wave  never  passes  from  one  fiber  to  an  adjacent  fiber; 
neither  does  it  leap  over  an  interposed  tendon  or  a  transverse  tendinous 
septum. 

If  a  muscle  of  considerable  length  be  stimulated  locally  at  its  middle, 
a  contraction-wave  is  propagated  from  the  point  of  stimulation  toward 
both  extremities,  and  in  other  respects  possesses  the  properties  pre- 
viously described.  If  two  or  more  points  in  the  muscle  are  stimulated 
at  the  same  time,  the  wave-movement  sets  out  from  each,  and  one 
may  even  pass  over  another. 

If  a  stimulus  be  applied  to  the  motor  nerve  of  a  muscle,  it  will  be 
conducted  to  each  muscle-fiber,  whose  contraction-wave  must  develop 
at  the  motor  end-plate  and  be  propagated  thence  in  both  directions  along 
the  fiber,  which  is  only  from  5  to  9  centimeters  in  length.  In  accord- 
ance with  the  obvious  inequality  in  the  length  of  the  motor  fibers  from 
the  nerve-trunk  to  the  end-plates,  the  contraction  will  not  commence  at 
absolutely  the  same  moment  in  all  of  the  muscle-fibers,  as  the  conduction 
through  the  motor  nerves  likewise  occupies  a  certain  amount  of  time. 
The  difference,  however,  is  so  small  that  the  muscle,  stimulated  through 
its  nerve,  appears  to  contract  simultaneously  as  a  whole. 

An  absolutely  simultaneous,  momentary  contraction  of  all  of  the 
fibers  of  a  muscle  can  occur  only  if  all  are  stimulated  at  the  same  time. 


MUSCULAR  WORK. 

The  muscles  are  most  perfect  machines  not  only  because  they  utilize 
most  completely  the  substances  consumed  in  their  activity,  but   be- 


570  MUSCULAR    WORK. 

cause  they  are  distinguished  from  all  machines  of  human  construction  by 
the  fact  that,  as  a  result  of  repeated  exercise,  they  become  stronger, 
better  developed,  and  capable  of  increased  activity. 

According  to  the  usual  method  of  estimation,  the  amount  of  work 
performed  by  a  muscle  is  equal  to  the  product  of  the  weight  lifted  (P) 
and  the  height  to  which  it  is  lifted  (s);  hence,  A  =  s  P.  From  this  it 
follows,  first, that  if  the  muscle  is  not  at  all  weighted,  therefore,  if  P  equals 
o,  then  A  must  equal  o ;  that  is,  no  work  is  performed  if  there  is  no  weight- 
ing. Further,  if  the  muscle  is  burdened  with  an  excessively  heavy 
weight  so  that  it  is  no  longer  able  to  contract,  therefore,  s  equals  o,  then, 
likewise,  no  work  is  performed.  Between  these  two  extremes  the  active 
muscle  is  able  to  execute  work. 

Strictly  speaking,  the  contracting  muscle  lifts,  in  addition  to  the  suspended 
weight  P,  half  of  its  own  weight  p,  which  should  be  added  to  P  as  %  p;  hence, 
A=(P  +  ip)  S. 

With  the  strongest  possible  stimulation,  or  maximal  stimulus,  that 
is,  a  strength  of  stimulus  that  causes  the  maximum  degree  of  contraction 
in  the  unweighted  muscle,  the  work  performed  increases  progressively 
with  each  contraction  as  the  weight  increases  to  a  certain  maximum. 
If,  as  the  weight  is  increased,  the  muscle  can  raise  it  to  a  gradually  dimin- 
ishing height,  the  amount  of  work  diminishes  progressively;  and,  finally, 
as  already  noted,  it  becomes  o,  when  no  elevation  is  effected. 

The  following  table  will  illustrate  the  work  performed  by  a  frog's  muscle, 
according  to  Edward  Weber: 

Weight  Lifted,  Height  in  Milli-  Amount  of  Work  Performed 

in  Grams.  meters.  in  Gram-millimeters. 

5  27.6  138 

i5  25.1  376 

25  11.45  286 

30  6.3  189 

If  the  weight  be  increased  at  any  given  moment  during  the  contraction  of 
the  muscle,  more  work  can  be  performed,  but  only  if  the  stimulus  applied  does 
not  fall  below  a  certain  minimum.  The  duration  of  the  contraction  is  longer. 

If  a  muscle  has  contracted  as  much  as  possible  for  the  purpose  of  lifting  a 
heavy  weight,  it  can  be  made  to  perform  still  more  work  by  gradually  diminishing 
the  weight.  It  contracts  still  further  and  performs  additional  new  work  by 
raising  the  diminished  weight. 

If  the  amount  of  work  performed  by  the  muscle  be  diminished  by  raising  the 
weight  before  the  contraction  to  a  part  of  the  height  to  which  it  would  have 
been  lifted  by  the  muscle  stimulated  to  the  maximum,  then  the  muscle  will  raise 
the  weight  to  a  still  higher  level. 

The  investigations  concerning  muscular  work  yield  the  following 
results : 

1.  The  muscle  is  capable  of  lifting  a  greater  weight  the  larger  its 
transverse  section,  that  is  the  more  fibers  it  contains  arranged  side  by 
side. 

2.  The  muscle  is  capable  of  lifting  a  weight  the  higher  the  longer  it  is, 
that  is  the  more  muscle-fibers  it  contains  arranged  in  succession. 

3.  The  muscle  is  capable  of  lifting  the  greatest  weight  at  the  com- 
mencement of  contraction;  as  the  contraction  progresses,  it  is  capable  of 
lifting  only  a  progressively  smaller  weight,  and  near  the  maximum  con- 
traction only  a  relatively  light  weight. 

4.  By  the  term  absolute  muscular  energy  is  meant,  according  to  Ed. 
Weber,  the  weight  that  the  muscle  stimulated  to  the  maximum  is  no 


MUSCULAR    WORK.  571 

longer  capable  of  raising  while  in  its  natural  passive  form,  without  being 
stretched  by  the  weight  at  the  moment  of  stimulation. 

In  order  to  obtain  a  standard  for  the  comparison  of  the  absolute  muscular 
energy  in  different  muscles  and  also  in  different  animals,  an  estimation  is  made 
of  the  absolute  muscular  force  for  one  square  centimeter  of  cross-section.  The 
mean  cross-section  of  a  muscle  is  determined  by  dividing  its  volume  by  its  length. 
The  volume  is  equal  to  the  absolute  weight  of  the  muscle  in  question  divided 
by  the  specific  gravity  of  muscle-substance  (1058).  Thus,  the  absolute  muscular 
energy  for  one  square  centimeter  of  a  frog's  muscle  is  from  2.8  to  3  kilos;  for 
one  square  centimeter  of  human  muscle  from  7  to  8  or  even  from  9  to  10  kilos. 
Analogous  figures  for  crustaceans  are  from  1.8  to  3.2;  for  beetles  from  3.4  to  6.9; 
for  mussels  from  4.5  to  12.4  kilos.  The  transverse  section  of  the  muscles  tested 
in  man  is  estimated  from  cadavers  having  the  same  constitution  and  muscular 
development  as  the  person  under  observation. 

In  conformity  with  proposition  3  it  is  evident  that  a  muscle  during  contraction 
will  develop  the  greater  absolute  muscular  energy  the  more  it  is  extended  before 
contraction. 

5.  If  a  muscle  in  a  state  of  tetanic  contraction  maintains  a  weight 
in  an  elevated  position,  it  performs  no  work  during  the  time,  but  only  in 
the  act  of  elevation.  Nevertheless,  the  muscle  in  the  state  of  tetanus 
requires  continued  stimuli,  and  it  exhibits  metabolic  changes  and  fatigue. 
The  transformation  of  its  potential  energy  is  applied  to  the  generation 
of  heat. 

When  the  maximal  stimulus  is  applied,  a  muscle  is  not  capable  of  lifting  as 
heavy  a  weight  at  one  contraction  as  when  tetanic  stimulation  is  applied.  During 
tetanic  stimulation,  moreover,  the  muscle  develops  the  greater  energy  (even  as 
much  as  twice  the  ordinary)  the  more  frequent  the  stimulation,  as  has  been  ob- 
served with  increasing  frequency  up  to  100  stimuli  in  a  second. 

If  only  moderate  stimuli  that  do  not  excite  the  maximal  contraction 
are  applied  to  the  muscle  two  possibilities  present  themselves.  If  the 
feeble  stimulus  remains  constant,  while  the  weight  changes,  the  amount 
of  work  performed  follows  the  same  law  that  is  operative  during  maxi- 
mal stimulation.  If  the  weight  remains  the  same,  while  the  strength 
of  the  stimulus  varies,  then,  according  to  Pick,  the  height  to  which  the 
weight  is  raised  varies  in  direct  proportion  to  the  strength  of  the 
stimulus. 

The  stimulus  that  sets  a  muscle  into  activity  must,  naturally,  attain  a  certain 
strength  before  it  becomes  effective — liminal  intensity  of  the  stimulus.  This  is 
independent  of  the  weight  attached  to  the  muscle.  With  a  minimal  stimulus  a 
small  weight  is  raised  to  a  higher  level  than  a  large  one;  but  as  the  stimulus  is 
increased,  the  contractions  increase  in  greater  proportion  with  a  heavy  weight. 

A  contracting  muscle  is  capable  of  performing  considerably  more 
work  if  the  weight  to  be  lifted  is  attached  to  an  inert  mass  that  acts 
like  a  fly-wheel,  or  if  the  weight  is  swung  to  a  considerable  height. 
Starke  was  able  almost  to  quadruple  the  work  corresponding  to  a  maxi- 
mal contraction  by  a  proper  selection  of  materials  for  this  purpose. 
Also  the  production  of  heat  is  increased  under  such  conditions,  although 
in  much  less  degree,  and  it  is  much  more  quickly  diminished  on  fatigue. 

If  the  resistance  applied  to  prevent  the  movement  of  a  limb  whose  muscles, 
strained  to  the  utmost  degree,  be  suddenly  removed,  the  limb  will,  with  the  greatest 
energy  and  rapidity,  assume  the  position  brought  about  by  the  muscles.  Such 
springing  movements  are  observed  especially  in  grasshoppers,  leaping  beetles,  and 
cheese-mites. 

Under  special  conditions  a  muscle  may  perform  considerable  work  through 
its  increase  in  thickness. 

In  the  intact  body  the  vessels  of  a  muscle  dilate  during  muscular  contraction, 


572  THE    ELASTICITY    OF    PASSIVE    AND    ACTIVE    MUSCLE. 

so  that  the  amount  of  blood  circulating  through  it  is  increased.  Evidently  the 
vasodilator  nerve-fibers  contained  in  the  same  nerve-trunks  as  the  motor  nerves 
are  stimulated  at  the  same  time  as  the  latter. 

In  estimating  the  absolute  muscular  energy  of  single  muscles  or  groups  of 
muscles  in  man,  close  attention  should  always  be  paid  to  the  physical  relations, 
for  example  leverage,  effects,  direction  of  the  traction,  degree  of  shortening,  and 
the  like. 

The  absolute  energy  of  certain  groups  of  muscles  may  practically  be  measured 
readily  by  means  of  the  dynamometer.  This  is  constructed  in  part  on  the  principle 
of  the  spring-scales,  upon  which  the  pressure  or  pull  of  the  muscles  in  question 
is  allowed  to  act.  Quetelet  has  determined  statistically  the  strength  of  certain 
groups  of  muscles.  The  pressure  of  both  hands  in  man  equals  70  kilos.  The 
pull  amounts  to  double  this  weight.  The  strength  of  the  hands  of  a  woman  is 
about  one-third  less.  Further,  a  man  can  carry  more  than  twice  his  own  weight, 
a  woman  only  half  her  weight ;  boys  are  able  to  carry  about  one-third  more  than 
girls. 

In  estimating  the  work  done  by  man,  not  only  the  amount  of  work  he  is 
able  to  perform  in  any  one  moment  should  be  taken  into  consideration,  but  also 
the  number  of  times  in  succession  he  can  perform  this  work.  In  accordance  with 
practical  experience,  the  mean  value  of  the  daily  work  performed  by  a  man  during 
eight  hours'  activity  has  been  estimated  at  from  6.3  to  10  (at  most  from  10.5 
to  n)  kilogrammeters  in  a  second,  hence  a  daily  usefulness  of  288,000  (in  round 
numbers  300,000)  kilogrammeters.  The  work  performed  by  a  horse  in  a  second 
is  assumed  to  be  75  kilogrammeters — horse-power  or  dynamic  horse. 

This  average  performance  of  work  may,  it  is  true,  be  temporarily  increased, 
but,  the  organism  then  requires  a  prolonged  rest  after  the  work  is  done,  so  as  not 
to  suffer  in  health  as  a  result  of  the  overexertion.  The  amount  of  work  performed 
in  walking  and  in  bicycling  is  discussed  on  p.  595. 

Some  substances,  when  introduced  into  the  body,  impair  and  eventually 
abolish  muscular  activity;  for  example  mercury,  digitalin,  helleborin,  potassium- 
salts,  apomorphin,  and  others.  Others  have  been  shown  to  increase  the  functional 
activity  of  muscular  tissue;  for  example  caffein.  theobromin,  veratrin,  muscarin 
in  small  doses,  glycogen,  kreatin,  and  hypoxanthin;  extract  of  meat  likewise 
causes  rapid  recovery  of  the  muscles  after  fatigue. 

Unstriated  muscles  are  capable  of  performing  a  great  amount  of 
work,  for  example  the  uterus  during  labor,  the  craw  of  granivorous 
animals.  The  longitudinal  musculature  of  the  earth-worm  is  capable 
of  raising  more  than  15  kilos,  the  frog's  intestine  of  overcoming  the  pres- 
sure of  a  column  of  water  of  i  meters. 


THE  ELASTICITY  OF  PASSIVE  AND  ACTIVE  MUSCLE. 
MYOTONOMETRY. 

Preliminary  Physical  Considerations. — Every  elastic  body  has  its  natural 
form,  that  is  the  outer  form  that  it  possesses  when  no  external  force  (traction  or 
pressure)  operates  upon  it.  Thus,  the  passive  muscle  also  possesses  a  natural  form, 
when  no  traction  or  pressure  is  exerted  upon  it.  If  traction  in  a  longitudinal 
direction  be  made  on  a  muscle  its  connected  parts  must  be  somewhat  separated 
from  one  another,  and  the  natural  form  will  be  stretched  under  the  influence  of 
the  elastic  energy.  If  the  extending  force  be  removed,  the  elastic  body  will 
return  to  its  natural  form.  A  body  is  said  to  be  completely  elastic  if  it  returns 
entirely  to  its  natural  form  after  the  tension  ceases.  By  amount  of  elasticity 
(modulus)  is  meant  the  weight,  expressed  in  kilograms,  by  which  an  elastic  body 
having  a  cross-section  of  one  square  millimeter  would  be  stretched  the  equivalent 
of  its  own  length,  provided  it  did  not  previously  rupture,  as,  naturally,  often 
it  does.  For  passive  muscle  this  equals  0.2734,  for  bone  2294,  for  tendon  1.6693, 
for  nerves  1.0905,  for  the  coats  of  the  arteries  0.0726.  The  amount  of  elasticity 
of  "passive  muscle  is,  thus,  small,  as  the  latter  yields  readily  to  tractile  force; 
hence  its  elasticity  is  not  great.  The  coefficient  of  elasticity  is  that  fraction  of 
the  length  of  an  elastic  body  to  which  it  is  stretched  by  the  unit  of  weight  applied 
to  it.  This  is  large  for  muscle  at  rest.  When  the  traction  reaches  a  certain 
degree  the  elastic  body  finally  ruptures.  The  carrying  capacity  of  muscular  tissue, 


THE    ELASTICITY    OF    PASSIVE    AND    ACTIVE    MUSCLE.  573 

just    short  of  the  point  of  rupture,  varies  for  youth,  middle  and  advanced  age 
approximately  in  the  proportions  7  13  12. 

In  the  case  of  unorganized  elastic  bodies  the  amount  of  extension  is  always 
directly  proportional  to  the  extending  weight.  In  that  of  organized  bodies, 
therefore  also  of  muscle,  this  is  not  the  case,  however,  as  with  continued  increase 
in  weight  in  equal  amount  they  are  extended  less  and  less  in  the  further  course 
of  observation  than  at  first.  At  the  same  time,  they  may  for  days  or  even  weeks 
gradually  undergo  a  still  further  increase  in  length  after  the  primary  extension, 
corresponding  to  the  suspended  weight,  has  been  attained,  if  the  same  weight 
be  continued.  This  is  designated  elastic  after-effect. 

The  elasticity  of  passive  muscle  is  small  but  complete,  and  is  com- 
parable to  that  of  India  rubber.  The  muscle  can  be  greatly  elongated 
by  means  of  small  weights.  With  the  uniform  addition  of  further  units 
of  weight,  uniform  extension,  however,  no  longer  takes  place,  but 
a  slighter  increase  in  length  corresponds  with  equal  increments  of 
weight  the  greater  the  load.  This  phenomenon  may  also  be  expressed 
as  follows :  the  amount  of  elasticity  of  passive  muscle  increases  with  its 
increased  extension. 

Method. — For  the  purpose  of  studying  elasticity,  the  muscle  is  suspended 
free  from  a  support  provided  with  a  scale,  and  the  lower  extremity  is  loaded 
successively  with  different  weights  placed  in  a  small  attached  weighing-pan.  The 
resulting  elongation  is  measured  in  each  instance.  To  construct  a  curve  of  elonga- 
tion, the  units  of  weight  added  successively  are  taken  as  abscissas,  and  the  lengths 
corresponding  to  each  load  as  ordinates.  The  following  is  an  example  from  the 
hyoglossus  of  the  frog: 

Weight  in 
Grams. 

0-3 
i-3 
2-3 
3-3 
4-3 
5-3 

The  curve  of  elongation  is  not  a  straight  line,  as  in  the  case  of  unorganized 
bodies,  but  it  resembles  a  hyperbola  in  form.  The  stretched  muscle  has  a  some- 
what diminished  volume,  as  have  the  contracted  and  the  rigid  muscle. 

Muscles  permitted  to  retain  their  connections  in  the  living  animal  with 
their  vessels  and  nerves  are  more  extensible  than  excised  muscles.  Perfectly 
fresh  muscles  elongate  at  first  proportionately  to  the  weight  if  the  increase  in 
the  latter  be  uniform  and  be  kept  within  narrow  limits,  therefore  like  unor- 
ganized bodies.  If  the  weights  be  heavy  the  observations  are  not  made  without 
consideration  of  the  elastic  after-effect. 

Dead,  and  especially  rigid,  muscle  possesses  a  greater  elasticity  than  fresh, 
living  muscle;  that  is  a  greater  weight  is  required  to  stretch  the  former  than  is 
needed  to  stretch  the  latter  to  the  same  length.  On  the  other  hand,  the  elas- 
ticity of  dead  muscle  is  less  complete;  that  is,  after  being  stretched,  it  regains  its 
natural  form  only  within  narrow  limits. 

In  contradistinction  from  the  elastic  after-extension  of  muscle  when  weighted, 
after  the  tension  has  become  constant,  Blix  recognizes  an  after-contraction  of 
muscle,  which  comes  into  play  after  removal  of  the  weight.  Further,  he  dis- 
tinguishes an  after-relaxation  in  muscle  that  has  been  stretched,  its  tension  in- 
creasing with  the  increase  in  length,  but  diminishing  when  the  length  has  become 
constant;  and,  finally,  an  after-tension  in  a  previously  stretched  muscle,  whose 
length  is  diminished,  the  previously  low  tension  again  increasing,  when  the  length 
has  become  constant. 

In  the  intact  body  the  muscles  are  already  stretched  to  a  slight  extent,  as 
indicated  by  the  moderate  retraction  that  usually  takes  place  when  the  muscular 
insertion  is  detached.  This  slight  degree  of  extension  is  of  importance  with  the 
occurrence  of  contraction;  as  otherwise  the  muscle  would  first  have  to  contract, 
without  immediately  entering  into  activity,  before  it  could  exert  traction  upon 
the  bones.  The  elasticity  of  the  muscles  becomes  evident  on  the  contractions  of 


Muscle-length  in 
Millimeters. 

Elongation  in 
Millimeters. 

Elongation  in 
Percentages. 

24.9 

— 

— 

30.0 

5-i 

20 

32.3 

2-3 

7 

33-4 

i.i 

3 

34-2 

0.8 

2 

34-6 

0.4 

I 

574 


THE    ELASTICITY    OF    PASSIVE    AND    ACTIVE    MUSCLE. 


its  antagonists.     The  position  of  a  passive  limb  depends  upon  the  resultant  of 
the  elastic  traction  of  the  various  muscle-groups. 

The  elasticity  of  active  muscle  is  diminished  as  compared  with  that  of 
passive  muscle;  that  is  it  is  lengthened  by  the  same  weight  to  a  greater 
extent  than  is  resting  muscle.  For  this  reason  active  muscle  is  softer, 
as  can  be  demonstrated  in  an  excised,  contracted  muscle.  The  appar- 
ently increased  hardness  of  tense,  contracted  muscles  is  due  only  to  their 
tension.  When  an  active  muscle  becomes  fatigued,  its  elasticity  is  still 
further  diminished.  During  the  latent  period,  in  which  the  develop- 
ment of  electrical  phenomena  and  of  heat  points  to  metabolic  activity  in 
the  muscle,  no  change  in  elasticity  has  as  yet  been  demonstrated. 

Method. — Ed.  Weber  made  observations  in  the  following  manner.  The  hyo- 
glossus  muscle  of  the  frog  was  suspended  vertically,  and  its  length  was  measured 
in  the  passive  state.  The  muscle  was  then  tetanized  by  induction-shocks  and 
again  measured.  Progressively  increasing  weights  were  then  attached  to  it,  in 
succession,  and  the  amount  of  stretching  of  the  passive  and  then  the  length 


FIG.  198. — Blix's  Elasticity  Recorder. 

of  the  tetanized  muscle  (supporting  the  same  weight)  ascertained.  The  extent 
to  which  the  active,  weighted  muscle  contracted  from  the  passive,  weighted 
condition  is  termed  the  height  of  the  lift.  This  becomes  steadily  less  as  the  weight 
increases,  until  finally  the  heavily  weighted,  tetanized  muscle  can  no  longer  con- 
tract; that  is  the  height  of  the  lift  is  zero.  Indeed,  if  the  weight  be  exceedingly 
heavy  it  may  happen  that  the  muscle,  when  stimulated,  not  only  can  contract 
no  further,  but  it  may  even  elongate.  According  to  Wundt,  however,  the  elas- 
ticity of  the  muscle  does  not  change  under  such  conditions.  In  these  observations 
the  length  of  the  active,  weighted  muscle  is  equal  to  the  length  of  the  equally 
weighted,  passive  muscle,  minus  the  height  of  the  lift. 

Tracings  of  the  length-curves  recorded  by  passive  or  contracting  muscle 
stretched  by  weights  can  be  conveniently  made  by  means  of  the  apparatus  of 
Blix,  as  shown  in  Fig.  198.  The  rectangular  piece  (A  B  C)  is  movable  hori- 
zontally between  two  strips  (R  R).  To  the  vertical  portion  of  the  former  is 
attached  the  freely  suspended  muscle  (m),  which  is  connected  with  the  writing- 
lever  (S  S),  the  latter  being  attached  to  the  horizontal  portion  near  C  by  means 
of  a  hinge- joint.  The  writing-lever  is  provided  with  a  small  movable  rod  (dd), 
from  which  a  weight  is  suspended.  When  the  rectangular  piece  (A  B  C)  is 
moved  in  the  direction  of  the  arrow,  the  weighted  rod  (d  d)  more  closely  ap- 
proaches the  muscle,  which  thus  becomes  constantly  more  and  more  heavily 
weighted. 

With  the  muscle  at  rest  (m)  the  curve  o  a  b  c  e  is  first  recorded  by  means 
of  the  displacement  described.  Then  a  similar  curve  is  recorded  while  the  muscle 


THE    ELASTICITY    OF    PASSIVE    AND    ACTIVE    MUSCLE.  575 

is  tetanized  (M)  by  electrical  stimulation;  and  the  curve  h  i  k  is  thus  traced. 
With  the  aid  of  the  apparatus  both  the  extension-curve  with  increasing  weight 
and  the  contraction-curve  with  diminishing  weight  can  be  recorded.  Both  curves 
are  necessarily  analogous,  except  that  their  form  is  reversed. 

The  elasticity  of  muscle  may  also  be  measured  by  its  rate  of  oscillation  when 
twisted  about  its  longitudinal  axis.  Kaiser  found  that  the  elasticity  of  active 
muscle  depends  upon  its  length  at  the  time.  It  is  least  when  the  muscle  has 
the  same  length  in  the  active  as  in  the  passive  state.  If  shortening  occurs  in 
a  muscle  stretched  by  a  weight,  its  elasticity  is  diminished,  and  this  reaches  its 
minimum  when  the  muscle  becomes  of  the  same  length  as  the  passive,  unweighted 
muscle.  If  the  active  muscle  contracts  still  further,  its  elasticity  increases. 

Under  the  influence  of  certain  poisons  the  elasticity  of  the  muscles  is  altered 
as  a  result  of  changes  in  the  condition  of  the  contractile  substance.  Potassium 
causes  shortening  of  the  muscle,  with  simultaneous  increase  in  its  elasticity. 
Digitalin  causes  elongation  of  the  muscle,  together  with  increased  elasticity. 
Physostigmin  also  increases  the  elasticity,  while  veratrin  diminishes  it  and  inter- 
feres with  its  completeness.  Tannic  acid  renders  the  muscles  less  extensible,  but 
more  elastic. 

Ligation  of  the  vessels  causes  first  a  diminution,  and  later  an  increase  in  the 
elasticity.  Separation  of  the  nerves  from  the  muscle  results  in  a  diminution  of  the 
elasticity.  The  influence  of  temperature  on  the  extensibility  is  as  follows:  As  the 
temperature  increases — from  o°  to  30° — the  muscle  elongates,  as  its  extensibility 
increases.  The  increase  in  length  is  proportional  to  the  load.  At  34°  contraction 
occurs  as  a  result  of  the  thermal  stimulation;  above  47°  the  muscle-proteid 
coagulates. 

Unstriated  muscles  possess  an  exceedingly  small  amount  of  elasticity;  at  the 
same  time  the  elastic  after-effect  lasts  much  longer,  and  immediately  follows  the 
primary  stretching.  Fibrous  connective  tissue  possesses  the  greatest  elasticity, 
elastic  tissue  less,  and  unstriated  muscular  tissue  the  least.  The  elasticity  of  a 
complex  organ,  made  up  of  these  tissues,  depends,  accordingly,  upon  the  relative 
abundance  of  these  elements. 

As  a  result  of  his  experiments  Edward  Weber  has  reached  the  following  con- 
clusions as  to  the  nature  of  the  contractile  energy  of  muscle.  He  assumes  the 
existence  of  two  states  in  muscular  tissue — the  passive  and  the  active.  Each  of 
these  is  characterized  by  a  special  natural  form.  The  passive  muscle  possesses 
the  longer,  thinner  form;  the  active  muscle  the  shorter,  thicker  form.  Both  the 
active  and  the  passive  muscle  tend  to  maintain  their  respective  form.  If,  now, 
the  passive  muscle  be  thrown  into  activity,  the  passive  form  suddenly  changes 
into  the  active  form,  by  virtue  of  its  elastic  energy.  It  is  this  latter  that  is  capable 
of  performing  the  work  of  the  muscle.  Schwann  has  already  alluded  to  the  simi- 
larity between  the  energy  of  an  active  muscle  and  that  of  a  long,  elastic,  tense  spiral 
spring.  Both  are  able  to  lift  the  greatest  weight  only  from  the  form  in  which 
they  are  most  stretched.  The  greater  the  shortening  they  have  already  undergone, 
the  smaller  is  the  weight  that  they  are  further  able  to  raise. 

Observations  on  elasticity  can  also  be  made  on  the  muscles  of  living  human 
beings.  Under  such  circumstances,  however,  not  alone  the  simple  physical  law 
of  elongation  is  to  be  taken  into  consideration,  for  the  elongation  at  the  same 
time  causes  in  the  muscle  changes  in  its  irritability  and  in  the  blood-supply,  as 
well  as  direct  or  reflex  stimuli,  all  of  which  must  necessarily  modify  its  extensi- 
bility. If  the  extremity  of  the  foot  in  man  be  raised  vertically  by  means  of  a 
cord  passing  over  a  pulley  and  having  weights  attached  to  it,  the  muscles  of 
the  calf  will  be  stretched.  Mosso  and  Benedicenti  found  that,  as  the  weight 
increased,  the  muscles  became  longer  at  the  same  or  at  an  increasing  rate,  if 
the  weight  were  continuous  and  increasing.  If,  however,  the  muscle  is  completely 
released,  before  the  new,  heavier  weight  is  applied,  then  the  length  of  the  stretched 
muscle  diminishes  as  the  weight  is  increased.  Further,  the  curve  of  elongation 
exhibits  individual  differences;  it  exhibits  fluctuations  in  association  with  the 
respiratory  curves;  it  may  exhibit  after-extensions  and  after-contractions;  it 
changes  with  frequent  repetition,  with  heat  and  cold.  Strong,  sudden  stretching, 
and  previous  voluntary  contraction  and  fatigue  likewise  have  an  effect.  Investi- 
gations of  this  sort  are  designated  myotonometry. 


576  HEAT-PRODUCTION    IN    ACTIVE    MUSCLE. 

HEAT-PRODUCTION  IN  ACTIVE  MUSCLE. 

Method. — The  increased  temperature  of  a  muscle  during  contraction  may  be 
determined  either  by  means  of  delicate  thermometers  introduced  between  the 
muscles,  or  thermo-electrically.  The  passive  muscle  on  the  opposite  side  of  the 
body,  or  the  blood  within  a  vein,  will  serve  for  purposes  of  comparison.  As  the 
resistance  to  conduction  in  metals  (platinum  wire,  lead  strips)  is  increased  by 
heat,  the  observation  may  also  be  made  in  this  way. 

After  Bunzen,  in  1805,  had  observed  the  development  of  heat  during 
muscular  activity,  v.  Helmholtz  demonstrated  in  1848  that  also  ex- 
cised frogs'  muscles,  tetanized  for  two  or  three  minutes,  exhibit  a  rise 
in  temperature  of  from  0.14°  to  0.18°  C.  R.  Heidenhain  even  succeeded 
by  thermo-electrical  means  in  demonstrating  an  increase  in  temperature 
of  from  0.001°  to  0.005°  C.  for  each  individual  contraction.  A  similar 
condition  exists  in  the  beating  heart,  whose  temperature  rises  with  each 
systole.  The  production  of  heat  in  the  muscle  exhibits  a  latent  stage, 
which  is,  however,  of  shorter  duration  than  the  latent  period  of  move- 
ment. 

A  contraction  of  a  frog's  muscle,  weighing  one  gram,  will  produce  an  amount 
of  heat  equal  to  about  three  microcalories,  which  will  raise  the  temperature  of 
three  milligrams  of  water  from  o°  to  i°  C. 

The  following  facts  have  been  ascertained  concerning  heat -produc- 
tion: 

T  .  //  bears  a  relation  to  the  amount  of  work  performed,  (a)  If  the 
muscle  during  contraction  carries  a  weight  that  during  rest  extends 
it  again,  it  performs  no  work  that  is  communicated  externally.  All 
of  the  transformed,  chemical,  potential  energy  is,  therefore,  converted 
into  heat  during  this  movement.  Under  these  conditions  the  genera- 
tion of  heat  corresponds  with  the  activity;  that  is  it  increases  at  first 
with  the  weight  and  the  height  of  the  lift  to  the  maximum  point ,  and  then, 
as  the  weight  is  further  increased,  the  generation  of  heat  diminishes.  The 
heat-maximum,  however,  is  attained  with  a  smaller  weight  than  the 
maximum  of  work. 

(6)  If  the  muscle  at  the  height  of  its  contraction  is  relieved  of  its 
weight,  then  it  will  have  performed  some  active  work  communicated 
externally.  Under  such  circumstances  the  amount  of  heat  generated  is 
less  than  in  the  previous  case ;  and,  indeed,  the  amount  of  work  performed 
and  the  lesser  amount  of  heat  evolved,  are  the  same  in  accordance  with 
the  law  of  the  conservation  of  energy. 

(c)  If  the  same  amount  of  work  is  performed  in  the  one  case  by  many 
small  contractions,  and  in  the  other  by  fewer  but  larger  contractions, 
the  amount  of  heat  generated  is  greater  in  the  latter  instance.     This  fact 
indicates  that  large  contractions  are  attended  with  a  relatively  greater 
metabolism  than  smaller  ones,  and  experience  is  in  accordance  with  it. 
Thus,  the  ascent  of  a  tower  by  steps  with  a  high  tread  causes  much  more 
fatigue  (that  is  requires  more  metabolism)  than  ascent  by  steps  with  a 
low  tread. 

(d)  If  a  weighted  muscle  executes  single  contractions  in  succession, 
by  means  of  which  it  performs  work,  the  amount  of  heat  thus  generated 
is  greater  than  if  it  carries  the  weight  constantly  in  tetanic  contraction. 
The  transition  of  the  muscle  into  the  shortened  form  thus  develops  a 
greater  amount  of  heat  than  the  maintenance  of  that  form.     Also  sum- 


HEAT-PRODUCTION    IN    ACTIVE    MUSCLE.  577 

mated  contractions  are,  accordingly,  attended  with  the  generation  of  a 
smaller  amount  of  heat  than  corresponds  to  that  developed  by  two  single 
successive  contractions. 

As  the  stimulus  becomes  stronger,  heat-production  increases,  in  the  case  of 
isometric  contractions  proportionately  to  the  degree  of  tension;  that  of  isotonic 
contractions  at  first  more  rapidly  than  the  height  of  the  lift,  but  with  strong 
stimuli  proportionately  to  the  latter.  Even  if  the  height  of  the  lift,  the  strength 
of  the  stimulus,  and  the  tension  of  the  contracting  muscle  remain  the  same  during 
successive  contractions,  the  muscle  nevertheless  generates  more  heat  during  the 
first  than  during  the  following  contractions.  The  amount  of  heat  generated  also 
depends  upon  the  character  of  the  stimulus  employed;  thus,  a  muscle  tetanized 
by  slow  shocks  generates  more  heat  than  one  contracted  by  rapid  shocks. 

2.  The  development  of  heat  depends  upon  the  tension  of  the  muscle;  it 
increases  with  increase  in  tension.     If  the  muscle  be  prevented  from  con- 
tracting by  fixation  of  its  extremities,  the  maximum  of  heat-production 
takes  place  during  stimulation,  and  the  more  quickly  the  more  rapidly 
the  stimuli  succeed  one  another.     Such  a  condition  arises  during  tetanus, 
in  which  the  violently  contracted  muscles  mutually  oppose  each  other. 
Therefore,  a  marked  development  of  heat  has  been  observed  in  con- 
nection with   this  disease.     Dogs  thrown  into  a  state   of    continuous 
tetanus  by  electrical  stimulation  or  by  the  induction  of  spasm  die  in 
consequence  of  elevation  of  their  bodily  temperature  to  a  fatal  height 
(44°  or  45°  C.).     This  large  production  of  heat  is  attended  with  a  con- 
siderable degree  of  acidity  and  the  formation  of   alcoholic  extractives 
in  the  muscular  tissue. 

In  the  case  of  isometric  tetanus  the  metabolism  and  heat-production  increase 
more  rapidly  than  the  tension  as  the  stimulus  becomes  stronger.  The  continuous 
maintenance  of  tension  in  the  muscle  on  the  one  hand,  as  well  as  the  contraction 
of  the  muscle  with  a  small  amount  of  work  without  considerable  tension,  never- 
theless requires  only  relatively  little  metabolism  for  the  generation  of  heat,  as 
compared  with  the  work,  which  is  essentially  proportional  to  the  consumption  of 
combustible  material.  If  the  stimulated  muscle  be  so  fixed  that  it  cannot  con- 
tract, and  if  it  then  by  releasing  its  lower  extremity  be  permitted  to  contract 
and  lift  a  weight,  an  additional  amount  of  chemical  potential  energy  will  be  trans- 
formed for  the  performance  of  this  latter  task. 

3.  Heat -production  diminishes  as  fatigue  increases,  and  it  again  in- 
creases  during  recovery.     The  muscle  becomes  fatigued  earlier  in  its 
production  of  heat  than  in  its  performance  of  work. 

4.  In  a  muscle  normally  supplied  with  circulating  blood  the  produc- 
tion of  heat,  and  also  the  mechanical  performance  of  work,  takes  place 
much  more  energetically  than  in  a  muscle  whose  circulation  is  inter- 
rupted.    Recovery  following  fatigue  also  takes  place  under  such  con- 
ditions more  rapidly  and  completely. 

The  total  amount  of  work  and  heat  in  a  muscle  must  always  be  equivalent  to 
the  transformation  of  a  corresponding  amount  of  chemical  potential  energy.  Of  this 
the  portion  that  is  transformed  into  work  will  be  the  larger  the  greater  the  force  that 
is  opposed  as  a  result  of  the  contraction  of  the  muscle.  In  the  latter  event  this 
equals  about  one-fourth  of  the  transformed  potential  energy.  If  the  resistance  be 
less,  the  work  performed  is  a  smaller  fraction  of  the  transformed  potential  energy. 

At  a  high  temperature,  therefore  probably  in  the  febrile  state,  muscle  exhibits 
greater  metabolism  for  the  generation  of  increased  amounts  of  heat,  without 
increase  in  the  work  performed. 

In  man,  the  production  of  heat  in  muscles  made  to  contract  by  electrical 
stimulation  can  be  appreciated  through  the  skin.  It  was  observed  by  Landois 
also  when  voluntary  movements  were  executed.  Venous  blood  flowing  from 
a  contracting  muscle  acquires  a  higher  temperature  than  the  arterial  blood — by 
as  much  as  0.6°  C. — as  a  result  of  energetic  action. 
37 


578  THE    MUSCLE-MURMUR. 

The  statement  made  by  some  that  a  rise  in  temperature,  amounting  to  about 
3^°  C.,  occurs  also  in  a  nerve  in  action  is  denied  by  others;  but  an  increase  in 
temperature  does  occur  in  a  nerve  in  process  of  degeneration. 

5.  As  the  muscle  is  an  elastic  body,  thermal  phenomena  will  occur  in 
it  as  a  result  of  purely  physical  influences,  as  in  inanimate,  elastic  bodies, 
such  as  India  rubber.  Thus,  heat  is  set  free  on  stretching  living  or  dead 
muscle;  and,  conversely,  the  temperature  of  the  muscle  falls  on  elastic 
shortening. 

THE  MUSCLE-MURMUR. 

If  a  contracted  muscle  be  at  the  same  time  maintained  in  a  state  of 
tension  by  the  application  of  resistance  to  it,  a  sound  or  murmur  will 
be  audible,  arising  from  intermittent  variations  in  tension  within  the 
muscle. 

Method. — For  purposes  of  observation,  auscultation  is  practised  either  by 
means  of  the  ear  applied  directly,  or  with  the  aid  of  a  stethoscope,  over  a  tetani- 
cally  contracted  muscle  in  another  person.  Some  individuals  are  able  to  appre- 
ciate the  murmurs  of  their  own  muscles  of  mastication  on  closing  the  external 
auditory  canals,  and  pressing  the  jaws  forcibly  together. 

If  one  external  auditory  canal  be  closed,  and  into  the  other  there  be  inserted 
a  small  rod  from  the  end  of  which  is  suspended  a  tetanized,  weighted  frog's  muscle, 
the  sound  of  this  isolated  muscle  can  be  readily  heard. 

If  the  contracting  muscle  is  attached  to  an  elastic  spring,  whose  rate  of  vibra- 
tion can  be  varied,  and  if  the  rate  of  vibration  is  determined  that  must  be  im- 
parted to  the  spring  in  order  that  it  shall  be  energetically  set  into  vibration  by 
the  sounding  muscle,  the  rate  of  vibration  of  the  muscle-sound  can  be  readily  deter- 
mined for  each  case  after  a  few  trials.  A  writing-style  may  be  fastened  to  the 
tip  of  the  vibrating  spring,  and  record  the  vibrations  upon  a  smoked  surface. 

A  muscle,  thrown  into  contraction  by  the  will,  vibrates  from  19.5  to  20 
times  a  second.  The  deep  tone  corresponding  to  such  a  small  number  of  vibra- 
tions is,  however,  not  audible,  but  the  first  overtone,  corresponding  to  twice 
this  number,  is  heard.  The  sound  has  the  same  rate  of  vibration  when  the  muscle 
is  contracted  in  animals,  by  stimulation  of  the  spinal  cord,  and  also  when  the 
motor  nerve  of  a  muscle  is  irritated  by  chemical  means.  If,  however,  the  motor 
center  in  the  cerebral  cortex  be  stimulated,  the  contracting  muscle  will  generate 
a  tone  that  is  the  higher  the  stronger  the  stimulus. 

If  a  tetanizing  induced  current  be  applied  to  the  muscle  (also  in  man),  the 
rate  of  vibration  of  the  muscular  sound  corresponds  exactly  with  the  rate  of 
vibration  of  the  spring-hammer  in  the  induction-apparatus.  The  sound  can, 
therefore,  be  raised  or  lowered  by  changing  the  tension  of  the  spring. 

Loven  found  that  the  muscle-sound  is  relatively  the  strongest  when  the 
weakest  current  is  employed  that  will  induce  tetanus.  The  sound  will  then  have 
the  vibration-rate  of  the  next  lower  octave.  As  the  current  is  increased  in  strength, 
the  muscle-sound  disappears,  and  with  a  strong  current  it  reappears  with  the 
same  rate  of  vibration  as  that  of  the  interrupter  of  the  induction-apparatus. 

If  the  induction-shocks  are  sent  through  the  nerve,  the  sound  is  not  so  loud, 
but  otherwise  it  is  of  the  same  vibratory  duration.  By  means  of  rapid  induction- 
shocks  sounds  have  been  produced  up  to  704  and  1000  vibrations  in  a  second. 

The  first  sound  of  the  heart  is  in  part  a  muscle-sound. 

Landois,  in  1873,  first  reported  the  observation  that  the  rumbling  murmurs 
emitted  by  many  fish  (Cottus,  sea-scorpion)  are  due  to  the  loud  sounds  generated 
by  the  spasmodically  contracted  muscles  of  the  shoulder-girdle,  and  still  fur- 
ther intensified  by  the  resonance  of  their  large  oropharyngeal  cavity  sur- 
rounded by  a  firm  bony  framework.  He  found  at  that  time  that  even  a  single 
induction-shock  that  excited  the  muscles  was  able  to  generate  the  muscle-sound. 
Herroun,  Yeo,  and  Mac  William  also  noted  a  like  condition  in  the  contracting  mus- 
cles of  man.  It  must,  accordingly,  be  considered  as  doubtful  whether  the  muscle- 
sound  can  be  regarded  as  evidence  that  tetanus  is  made  up  of  a  series  of  fluctua- 
tions in  the  density  of  the  muscle.  According  to  Bernstein,  the  sound  heard 
during  contraction  occurs  in  the  latent  period.  Hence,  the  cause  of  the 
muscle-sound  is  not  to  be  sought  in  a  displacement  of  the  mass  of  the  muscle. 


FATIGUE    OF    MUSCLE.  579 

which  is  stationary  during  the  latent  stage,  but  in  molecular  processes  that  are 
responsible  also  for  the  process  of  negative  variation  in  the  current. 

FATIGUE  OF  MUSCLE. 

The  term  fatigue  is  applied  to  that  condition  of  diminished  functional 
capacity  in  which  the  muscle  is  placed  as  a  result  of  prolonged  activity. 
This  condition  is  recognized  during  life  by  a  peculiar  sensory  perception 
localized  in  the  muscles.  In  the  intact  body  the  fatigued  muscle  is 
capable  of  recovery,  as  is  also  the  excised  muscle  to  a  slight  degree.  A 
muscle  is  more  readily  fatigued  than  its  motor  nerve. 

The  cause  of  fatigue  is  the  accumulation  in  the  muscular  tissue  of  the 
products  of  metabolism,  fatigue-bodies,  that  are  formed  as  a  result  of  mus- 
cular activity.  Among  these  products  are :  phosphoric  acid,  free  or  com- 
bined in  acid  salts;  acid  potassium  phosphate;  glycerin-phosphoric 
acid  ( ?) ;  and  carbon  dioxid.  The  accuracy  of  the  foregoing  explanation  is 
indicated  by  the  fact  that  the  fatigued  muscle  becomes  again  more  capa- 
ble of  activity  if  the  substances  named  are  washed  away  by  the  passage 
of  a  normal  solution  (0.6  per  cent.)  of  sodium  chlorid  or  of  a  weak  solu- 
tion of  sodium  carbonate  through  the  blood-vessels  of  the  muscle.  The 
consumption  of  oxygen  on  the  part  of  the  active  muscle  also  promotes 
fatigue;  for  the  passage  of  arterial  (but  not  venous)  blood  through  the 
vessels  removes  the  fatigue  by  replacing  substances  that  have  been  con- 
sumed by  the  muscle.  Conversely,  a  muscle  that  is  capable  of  activity 
may  be  rapidly  fatigued  by  the  injection  of  dilute  phosphoric  acid,  acid 
potassium  phosphate,  or  dissolved  meat-extract  into  its  vessels.  An 
animal  may  be  fatigued  also  by  the  transfusion  of  blood  from  a  com- 
pletely fatigued  animal.  A  muscle  fatigued  by  work  absorbs  less  oxy- 
gen while  in  this  condition,  and  it  also  generates  only  a  small  additional 
amount  of  acid  and  of  carbon  dioxid.  The  activity  that  gave  rise  to 
fatigue  has  thus  induced  considerable  metabolic  activity  in  the  muscle. 

The  fatigued  muscle  requires  a  stronger  stimulus  than  the  fresh 
muscle  in  order  to  perform  the  same  amount  of  work,  that  is,  to  lift  a 
weight  the  same  distance.  The  fatigued  muscle  is  no  longer  able  to  raise 
heavy  weights;  its  absolute  muscular  energy  is  therefore  diminished. 
If  the  muscle  is  loaded  with  the  same  weight  throughout  the  experiment, 
and  if  the  stimulus  is  a  maximal  one  (strong  induced  opening  shock), 
then,  from  one  contraction  to  the  other,  the  height  of  the  lift  steadily 
diminishes  by  a  constant  fraction  of  the  shortening.  The  fatigue-trac- 
ing is,  thus,  a  straight  line.  The  more  rapidly  the  contractions  follow 
one  another,  the  more  marked  is  this  diminution  in  the  height  of 
the  lift,  and  conversely.  The  excised  muscle  becomes  fatigued  to  the 
point  of  exhaustion  after  a  certain  number  of  contractions.  Under 
such  circumstances  it  is  a  matter  of  indifference  whether  the  stimuli 
follow  one  another  in  rapid  or  in  slow  succession.  Analogous  conditions 
are  also  observed  in  connection  with  submaximal  stimuli. 

The  fatigued  muscle  requires,  further,  a  longer  period  of  time  for  its 
contraction,  which,  therefore,  takes  place  more  sluggishly.  Finally, 
the  period  of  latent  stimulation  is  also  lengthened  in  a  state  of  fatigue. 
The  fatigued  muscle  is  said  to  be  more  extensible. 

If  the  muscle  is  loaded  with  a  weight  so  heavy  that  it  cannot  be 
lifted  at  all  when  contraction  takes  place,  the  muscle,  nevertheless,  be- 
comes fatigued,  and,  indeed,  in  a  still  higher  degree  than  if  it  were  able 


580  FATIGUE    OF    MUSCLE. 

to  lift  the  weight.  The  metabolism  and  the  formation  of  acid  are,  thus, 
greater  in  a  stimulated  muscle  maintained  in  an  extended  position 
than  in  one  that  contracts  when  stimulated.  If  a  muscle  loaded  with 
no  weight  is  made  to  contract  by  stimulation,  it  becomes  fatigued  but 
gradually.  If  the  muscle  is  weighted  only  during  the  contraction,  but 
not  during  the  extension,  it  tires  more  slowly  than  if  it  were  continuously 
weighted;  as  it  does  also  if  it  is  required  to  lift  its  weight  only  in  the 
course  of  its  contraction,  instead  of  raising  it  at  once  at  the  beginning  of 
the  contraction.  The  suspension  of  weights  from  a  muscle  that  is  con- 
tinually at  rest  does  not  cause  fatigue. 

If  the  arteries  of  a  warm-blooded  animal  are  ligated,  complete  fatigue  will 
result  after  from  120  to  240  contractions,  in  from  two  to  four  minutes,  on  irritation 
of  the  nerve.  Direct  irritation  of  the  muscle,  however,  will  still  be  able  to  excite 
an  additional  series  of  contractions.  The  fatigue-tracings  in  both  cases  are  straight 
lines. 

If  the  circulation  in  the  muscles  of  a  warm-blooded  animal  be  uninterrupted, 
the  contractions  first  increase  in  height,  and  then  diminish,  to  pursue  a  straight 
line  on  stimulation  of  the  nerve.  Accordingly,  it  is  found  in  persons  that  have 
used  their  muscles  to  the  point  of  fatigue  that  the  muscles  and  their  nerves 
respond  more  actively  to  galvanic  and  faradic  stimulation  in  the  beginning,  but 
to  a  steadily  diminishing  degree  in  the  further  course  of  the  work. 

Novi  has  demonstrated  with  greater  detail  the  course  of  the  contraction  to 
the  point  of  fatigue.  According  to  him,  the  isolated  muscle  stimulated  to  the 
point  of  fatigue  exhibits  several  phases  in  its  action.  The  first  phase  exhibits  a 
period  in  which  the  contractions  occur  rapidly  and  increase  in  size — an  indication 
that  the  repetition  of  the  stimulus  causes  an  increase  in  the  irritability  of  the 
muscle.  In  the  second  phase,  of  longer  duration,  the  rapidity  of  the  contractions 
is  maintained,  but  their  height  diminishes — a  sign  that  the  irritability  of  the 
muscle  is  now  decreasing.  The  third  phase,  again  shorter,  embraces  contractions 
of  slower  course,  the  height  remaining  unchanged.  In  a  fourth  phase  the  con- 
tractions become  still  slower,  but  again  increase  in  height.  Finally  the  fifth  phase 
exhibits  uniform  diminution  in  the  height  of  the  contractions  and  increase  in 
their  duration,  until  exhaustion  occurs.  Only  this  last  phase  corresponds  to 
Kronecker's  law. 

According  to  v.  Kries  a  fatigued  muscle  tetanized  in  maximum  degree  behaves 
like  a  fresh  muscle  tetanized  in  submaximum  degree.  Both  exhibit  an  incom- 
plete transition  from  the  passive  to  the  active  state. 

Recovery  from  the  condition  of  fatigue  may  be  brought  about  by  the 
passage  of  a  constant  galvanic  current  through  the  entire  length  of  the 
muscle,  likewise  by  the  injection  of  fresh  arterial  blood  into  its  vessels, 
or  of  small  doses  of  veratrin. 

Relatively  small  amounts  of  sugar  (30  grams)  increase  the  muscular  energy. 
Cocoa,  coffee,  tea,  and  other  substances  exert  a  stimulating  influence  on  muscular 
activity. 

^  Among  the  poisons,  curare  and  the  putrefaction-toxins  (ptomains)  cause  the 
fatigue-curve  to  pursue  an  irregular  course. 

A.  Mosso  and  Maggiora  made  observations  on  living  persons,  by  having  a  weight 
lifted  by  the  flexors  of  the  middle  finger,  with  the  arm  in  a  fixed  position.  Mosso 
found  that  the  muscle  tires  sooner  when  stimulated  directly  than  when  excited 
indirectly  through  its  nerve.  Only  for  medium  weights  is  the  fatigue-tracing  a 
straight  line;  for  smaller  weights  it  is  S~shaped,  and  for  larger  ones  hyperbolic. 
If  a  tetanizing,  electrical  stimulus  be  continued  until  the  muscular  power  is  ex- 
hausted, there  will  still  be  left  in  the  muscle  a  residue  of  energy  that  can  be  utilized 
by  the  will;  and,  conversely,  a  muscle  finally  exhausted  by  voluntary  contractions 
can  still  perform  some  work  when  impelled  by  an  electrical  stimulus.  If  both 
forms  of  excitation  be  employed  in  immediate  succession,  they  will  exhaust  the 
muscle  completely.  Mental  exertion  diminishes  the  muscular  energy  in  a  marked 
degree,  as  do  likewise  hunger  and  high  temperature,  especially  in  conjunction  with 
marked  humidity  and  diminution  of  atmospheric  pressure;  also  local  artificial 
elevation  or  diminution  of  the  muscle-temperature.  The  strongest  muscular  con- 


MECHANISM  OF  THE  BONES  AND  THEIR  ATTACHMENTS.      581 

traction  induced  by  the  will  cannot  be  further  increased  by  strong  electrical 
stimulation  of  the  motor  nerve.  On  the  other  hand,  if  the  motor  nerve  be  stimu- 
lated so  that  a  less  powerful  contraction  results,  the  will  is  unable  to  strengthen 
this  contraction.  The  work  performed  by  a  muscle  already  fatigued  is  much  more 
exhausting  than  a  greater  amount  of  work  performed  when  it  has  been  rested. 
Anemia  gives  rise  to  symptoms  similar  to  those  of  fatigue,  up  to  the  point  of 
inability  to  contract;  while  an  abundant  supply  of  blood  rapidly  refreshes  the 
muscle.  Fatigue  of  the  legs,  as  after  marching,  hastens  fatigue  in  the  arms.  Long- 
continued  watching  and  fasting  favor  fatigue.  Massage  exerts  a  favorable  in- 
fluence on  fatigued  muscles. 

If  a  muscle  be  completely  exhausted  by  voluntary  movement,  and  if,  never- 
theless, the  will  be  allowed  to  act  as  if  to  excite  a  contraction,  the  muscle  will 
actually  begin  to  contract  again  after  a  period  of  rest,  until  it  becomes  again 
exhausted,  and  so  on.  Mosso  and  Brandis  assume  that  involvement  of  the  central 
nervous  system,  including  the  psychic  centers,  is,  in  part,  to  betaken  into  account 
in  connection  with  fatigue  in  man.  If  a  sensory  stimulus  be  applied  at  the  com- 
mencement of  a  voluntary  contraction,  the  movement  will  be  intensified  and 
accelerated. 

Pathological. — In  rare  cases  a  morbid  increase  in  the  liability  to  muscular 
fatigue  (myasthenia)  has  been  observed  without  muscular  atrophy  or  sensory  or 
reflex  disturbances. 

MECHANISM  OF  THE  BONES  AND  THEIR  ATTACHMENTS. 

The  bones  exhibit  in  their  spongy  structure  an  internal  architecture,  consisting 
of  lamellae  arranged  for  pressure  and  traction  exactly  in  accordance  with  those 
lines  that  would  be  constructed  by  graphic  statics  in  the  representation  of  the 
forces  in  weighted  beams  of  the  same  form.  This  architecture  is,  therefore,  so 
completely  adapted  to  the  function  of  bone  that  it  combines  the  greatest  capa- 
bility as  a  supporting  apparatus  with  the  least  expenditure  of  material. 

The  joints  are  covered  with  a  layer  of  cartilage,  which  moderates,  by  means 
of  its  elasticity,  the  concussions  communicated  to  the  bones.  The  surface  of  the 
articular  cartilage  is  smooth,  and  thus  permits  the  articular  extremities  to  move 
freely  upon  each  other.  At  the  outer  boundary  of  the  cartilage  arises  the  capsule 
of  the  joint,  which  encloses  the  cartilaginous  extremities  like  a  sac.  The  inner 
surface  of  the  capsule  is  lined  by  synovial  membrane,  which  secretes  the  viscid, 
slippery  synovial  fluid,  and  this  facilitates  considerably  the  free  movement  of 
the  surfaces.  The  outer  surface  of  the  capsule  of  the  joint  is  covered  with  numer- 
ous fibrous  bands,  which  act  partly  as  fortifying  and  partly  as  restraining  liga- 
ments. The  bony  processes  also  are  included  among  the  restraining  contrivances, 
for  example  the  coronoid  process  of  the  ulna,  which  permits  the  forearm  to  be 
flexed  only  to  an  acute  angle;  also  the  olecranon,  which  prevents  hyperextension 
at  the  elbow-joint.  The  continuous  apposition  of  the  articular  surfaces  is  made 
possible  (i)  by  the  adhesion  of  the  smooth  cartilaginous  surfaces,  covered  with 
synovial  fluid  and  sliding  on  each  other;  (2)  by  the  external  capsular  ligament; 
and  (3)  by  the  elastic  tension  and  the  contraction  of  the  muscles. 

The  articular  cavities  must  be  regarded  as  cleft  spaces,  bounded  by  free  con- 
nective-tissue surfaces,  and  unprovided  with  endothelium.  The  articular  carti- 
lage and  also  the  adjacent  connective  tissue  are  bare.  The  intima  of  the  synovial 
membrane  does  not  consist  of  endothelium,  but  of  protoplasmic  cells  provided 
with  processes,  together  with  a  fibrous  interstitial  substance.  It  is  almost  every- 
where separated  from  the  articular  cavity  by  a  thin  layer  of  fibrillar  tissue. 

The  synovial  membrane  is  composed  of  delicate  bundles  of  connective  tissue 
intermixed  with  elastic  fibers;  it  is  provided  on  its  inner  surface  in  part  with 
folds  containing  fatty  tissue  and  in  part  with  villi  containing  blood-vessels.  The 
internal  articular  ligaments  or  cartilages  are  not  lined  by  synovial  membrane. 
The  points  of  attachment  of  the  synovial  membrane  to  the  bones  are  termed 
insertion-zones. 

The  colorless,  stringy,  synovial  fluid  has  an  alkaline  reaction  and  the  compo- 
sition of  transudates.  In  addition,  it  contains  a  substance  resembling  mucin,  as 
well  as  albumin  and  traces  of  globulin,  lecithin,  cholesterin,  fat,  soaps,  lutein, 
and  also  salts.  Excessive  movement  diminishes  its  amount  and  increases  its  density 
and  also  the  amount  of  mucin,  but  diminishes  the  amount  of  salts. 

With  regard  to  the  mode  of  movement,  joints  may  be  divided  into  the  fol- 
lowing classes : 


582  MECHANISM    OF    THE    BONES    AND    THEIR    ATTACHMENTS. 

1.  Joints  with  a  Rotatory  Movement  about  One  Axis. — (a)    The  hinge-joint  or 
ginglymus.     The  one  articular  surface  represents  a  section  of  a  cylinder  or  cone, 
about  one  axis  of  which  the  other  surface,  with  a  corresponding  concavity,  moves 
on  flexion  or  extension  at  the  joint.      Examples:    the  joints  of  the  fingers  and 
the  toes.     Strong  lateral   supporting  ligaments  are   always  present,  to  prevent 
lateral  flexion  of  the  joint. 

The  screw-hinge  joint  is  a  modification  of  the  hinge- joint.  The  humero-ulnar 
articulation  belongs  to  this  class.  Strictly  speaking,  simple  flexion  and  extension 
do  not  take  place  at  the  elbow-joint;  but  the  ulna  is  rotated  on  the  trochlea  of 
the  humerus  like  a  nut  on  a  bolt;  on  the  right  humerus  the  screw  is  wound  to 
the  right,  and  on  the  left  humerus  to  the  left.  The  ankle-joint  also  belongs  to 
this  class;  the  nut  is  the  articular  surface  of  the  tibia;  the  right  joint  resembles 
a  left-handed  screw,  the  left  joint  the  reverse. 

(6)  The  pivot- joint  (rotatio) ,  with  a  cylindrical  articular  surface ;  for  example , 
the  articulation  between  the  atlas  and  the  odontoid  process  of  the  axis,  which 
represents  the  axis  of  rotation.  The  axis  of  rotation  of  the  articulation  at  the 
elbow- joint  for  pronation  and  supination  extends  from  the  middle  of  the  cotyloid 
cavity  on  the  head  of  the  radius  to  the  styloid  process  of  the  ulna.  Accessory 
joints  for  this  pivot- joint  are,  above,  the  articulation  between  the  articular  cir- 
cumference of  the  head  of  the  radius  and  the  lesser  sigmoid  cavity  of  the  ulna; 
and,  below,  the  articulation  between  the  head  of  the  ulna  and  the  sigmoid  cavity 
of  the  radius. 

2.  Joints  with  a  Rotatory  Movement  about  Two  Axes. — (a)   The  joints  exhibit 
in  the  two  axes,  which  intersect  at  right  angles,  a  curvature  that  is  different  in 
degree,  but  the  same  in  direction:  for  example,  the  atlanto-occipital  articulation, 
or  the  wrist-joint,  in  which  both  flexion  and  extension,  as  well  as  lateral  inclination, 
are  possible.     (6)  The  joints  have  a  surface  of  curvature  that  pursues  a  different 
direction  in  the  two  axes,  which  intersect  at  right  angles.     To  this  class  belongs 
the  saddle- joint,  the  surface  of  which  is  concave  in  the  direction  of  the  one  axis, 
and  convex  in  that  of  the  other;    for  example,  the'  articulation  between  the  tra- 
pezium and  the  metacarpal  bone  of  the  thumb.     The  principal  movements,  here 
are  (i)  flexion  and  extension,  and  (2)  abduction  and  adduction.     Further,  move- 
ment is  possible  to  a  limited  degree  in  all  other  directions,  and  a  cone-shaped 
space  can  be  circumscribed  by  the  thumb.     In  this  manner  the  saddle- joint  re- 
sembles a  limited  arthrodial  joint. 

3.  Joints  with  a  Movement  on  a  Spiral  Articular  Surface  (Spiral  Joints}. — To 
this  class  belongs  above  all  the  knee-joint.     The  condyles  of  the  femur,  curved 
from  before  backward,  exhibit,  on   sagittal   section   of  their  articular  surface,  a 
spiral  the  center  of  which  lies  toward  the  posterior  portion  of  the  condyle,  and 
whose  radius  vector  increases  from  behind  downward  and  forward.      The  joint 
permits,  first  of  all,  extension  and  flexion.     The  strong  lateral  ligaments  on  both 
sides  arise  from  the  condyles  of  the  femur,  at  a  point  corresponding  to  the  center 
of  the  spiral,  and  are  inserted  on  the  head  of  the  fibula  and  the  internal  condyle 
of  the  tibia  respectively.     When  the  knee-joint  is  strongly  flexed,  the  lateral  liga- 
ments are  relaxed;  they  become  tense  as  extension  increases,  and  in  complete 
extension  they  form  tense  bands,  which  ensure  lateral  fixation  of  the  knee-joint. 
In  accordance  with  the  spiral  form  of  the  articular  surface,  flexion  and  extension 
do  not  occur  about  one  axis,  but  the  axis  constantly  shifts  with  the  points  of 
contact;  the  axis  traverses  a  path  that  likewise  is  sp'iral.     The  greatest  flexion 
and  extension  cover  about   145°.     The  anterior  crucial  ligament  is  made  more 
tense  during  extension,  and  acts  as  a  check-ligament  for  excessive  extension;  the 
posterior  crucial  ligament  is  made  more  tense  during  flexion,   and  is  a  check- 
ligament  for  excessive  flexion.     The  movements  of  extension  and  flexion  at  the 
knee  are,  however,  rendered  more  complex  by  the  screw-like  movement  of  the 
joint,  with  the  result  that  the  leg  deviates  outward  during  extreme  extension. 
Accordingly,  the  thigh  must  be  rotated  outward  during  flexion,  if  the  leg  is  fixed. 
Pronation  and  supination  further  are  observed  in  the  knee-joint,  amounting  to 
41°  in  extreme  flexion,  but  being  entirely  absent  in  extreme  extension.     They  are 
due  to  rotation  of  the  external  condyle  of  the  tibia  about  the  internal  condyle. 
In  all  positions  of  flexion  the  crucial  ligaments  exhibit  a  fairly  uniform  degree 
of  tension,  as  a  result  of  which  the  articular  extremities  are  held  in  apposition. 
It  is  owing  to  their  arrangement  that  with  increase  in  the  tension  of  the  anterior 
ligament  during  extension  the  condyles  of  the  femur  must  roll  more  on  the  anterior 
portion  of  the  articular  surface  of  the  tibia;  while  with  increase  in  the  tension 
of  the  posterior  ligament  during  flexion  they  must  roll  more  on  the  posterior 


FUNCTION    OF    THE    MUSCLES    IN    THE    BODY.  583 

portion.  Braune  and  Fischer  found  in  the  course  of  their  investigations  that 
flexion  at  the  knee-joint  is  attended  with  rotation  of  the  tibia.  The  transition 
from  a  position  of  extension  to  one  of  flexion  of  20°  is  attended  with  an  internal 
rotation  of  6°.  From  this  point  further  flexion  is  attended  with  an  external 
rotation,  which  amounts  to  6°  at  a  flexion  of  90°. 

4.  Joints  with  Rotation  about  One  Fixed  Point. — These  are  the  freely  movable 
ball-and-socket  joints  (arthrodia).     Movement  is  possible  about  innumerable  axes, 
all  of  which  intersect  at  the  point  of  rotation.     The  one  articular  surface  has  an 
approximately  spherical  shape,  while  the  other  has  that  of  a  hollow  sphere.     The 
shoulder- joint  and  the  hip- joint  are  types  of  this   articulation.     Instead  of  the 
numerous  axes,  about  which  movement  is  possible,  three  may  be  substituted, 
intersecting  at  right   angles  in   space.     Therefore,   these  joints  have   also  been 
designated  tri-axial.     The  movements  possible  are :   (i)  pendulum-like  movements 
in  any  desired  plane;   (2)  rotation  about  the  longitudinal  axis  of  the  extremity; 
(3)  movements  circumscribing  the  surface  of  a  cone,   the   apex  of  which  corre- 
sponds to  the  center  of  rotation  of  the  joint,  and  whose  surface  is  circumscribed 
by  the  extremity  itself. 

Limited  artkrodial  joints  are  ball-and-socket  joints  with  a  more  limited  range 
of  movement,  and  in  which,  moreover,  rotation  about  the  longitudinal  axis  is 
wanting;  for  example,  the  metacarpo-phalangeal  joints. 

5.  Rigid  joints  (amphiarthrosis)  are  characterized  by  the  fact  that  movement 
is  possible  in  all  directions,  but  is  limited  in  extent,  owing  to  short  and  unyielding 
external  articular  ligaments.     The  articular  surfaces  are  usually  of  the  same  size, 
and  are  almost  flat.     Examples  are  afforded  by  the  articulations  of  the  carpal  and 
tarsal  bones  with  one  another. 

With  regard  to  the  mechanical  origin  of  the  articular  forms  of  two  bones 
movable  upon  each  other,  it  is  to  be  noted  that  the  articular  extremity  to  which 
the  muscles  are  inserted  near  the  joint  becomes  the  acetabulum;  while  that  ex- 
tremity to  which  the  muscles  are  inserted  at  a  greater  distance  becomes  the  head. 

Symphyses,  synchondroses,  and  syndesmoses  represent  the  junction  of  bones 
without  the  formation  of  an  articular  cavity.  They  are  movable  in  all  directions, 
but  only  to  an  extremely  limited  extent.  Physiologically,  they  are  thus  closely 
related  to  the  amphiarthroses. 

Sutures  unite  bones  without  permitting  any  yielding.  The  physiological 
significance  of  sutures  resides  in  the  fact  that  the  bones  may  grow  at  their  mar- 
gins, so  that  distention  of  the  cavity  enclosed  by  the  bones  is  possible. 

ARRANGEMENT  AND  FUNCTION  OF  THE  MUSCLES  IN  THE 

BODY. 

The  muscles  form  45  per  cent,  of  the  total  mass  of  the  body.  The 
musculature  on  the  right  side  of  the  body  is  heavier  than  that  on  the 
left.  If  the  muscles  are  considered  with  regard  to  their  function  from 
the  mechanical  standpoint,  the  following  categories  may  be  distin- 
guished : 

A.  Muscles  without  Definite  Origin  and  Insertion. 

T.  The  hollow  muscles,  enclosing  spherical,  oval,  or  irregular  cavities, 
such  as  the  urinary  bladder,  the  seminal  -vesicle,  the  gall-bladder,  the 
uterus,  the  heart;  or  forming  the  walls  of  more  or  less  cylindrical  canals, 
such  as  the  intestinal  tract,  the  muscular  ducts  of  glands,  the  ureters, 
the  oviducts,  the  vasa  deferentia,  the  blood-vessels,  and  the  lymphatics. 
Under  such  circumstances  the  muscle-fibers  frequently  are  arranged  in 
several  layers,  for  example  in  longitudinal,  circular,  and  oblique  direc- 
tions. During  activity  all  of  the  layers  contract  to  effect  diminution  in 
the  size  of  the  enclosed  cavity.  It  is  inadmissible  to  ascribe  different 
individual  mechanical  effects  to  the  various  layers,  for  example  to  main- 
tain that  the  circular  fibers  of  the  intestine  narrow  the  tube,  while  the 
longitudinal  fibers  dilate  it.  Both  sets  of  fibers  rather  act  together  in 
diminishing  the  enclosed  cavity,  namely  by  narrowing  and  shortening  it. 
If,  however,  the  wall  of  a  hollow  organ  is  pushed  or  folded  inward  either 


584  FUNCTION    OF    THE    MUSCLES    IN    THE    BODY. 

by  pressure  from  without  or  by  partial  contraction  of  a  number  of  circu- 
lar fibers,  muscle-fibers  that  pass  through  the  valley  of  the  excavation 
to  the  surrounding  borders  may  obliterate  the  depression  by  partial 
contraction,  thus  partially  dilating  the  enclosed  cavity,  and  converting 
the  concave  aspect  of  the  depression  into  a  smaller,  plane  one.  The 
various  layers  are  innervated  from  the  same  motor  source,  a  fact  that 
likewise  supports  the  view  of  their  homologous  action. 

2.  The  sphincters  encircle  an  opening  or  a  short  canal,  which  is  either 
narrowed  or  firmly  closed  by  their  action;  for  example  the  iris,  orbicu- 
laris  palpebrarum,  orbicularis  oris,  sphincter  pylori,  sphincter  ani, 
sphincter  vulvae,  sphincter  urethrae. 

B.  Muscles  with  Definite  Origin  and  Insertion. 

1.  The  origin  is  completely  fixed  when  the  muscle  is  in  action.     The 
course  of  the  muscle-fibers  to  their  insertion  is  such  that   during  con- 
traction the  insertion  approaches  the  origin  in  a  straight  line;  for  ex- 
ample the  attollens,  attrahens,  and  retrahens  auriculse,  and  the  rhom- 
boids.    In  the  case  of  some  of  these  muscles,  the  insertion  is  lost  in  soft 
structures,  which  then  follow  the  line  of  traction;  for  example  the  azygos 
uvulae,  the  elevator  of  the  soft  palate,  most  of  the  facial  muscles  arising 
from  the  bones  and  inserting  into  the  skin,  the  styloglossus,  stylophar- 
yngeus,  and  others. 

2.  Both  Origin   and   Insertion    are    Movable. — Under  such    circum- 
stances the  movements  of  both  points  are  inversely  as  the  resistances 
that  have  to  be  overcome  by  the  movement.     In  this  connection  it 
should  be  borne  in  mind  that  these  resistances  can  often  be  voluntarily 
increased  either  at  the  origin  or  at  the  insertion.     Thus,  for  example,  the 
sterno-cleido-mastoid  may  act  either  as  a  depressor  of  the  head,  or,  if  the 
head  be  fixed,  as  an  elevator  of  the  chest ;  the  pectoralis  minor  may  act 
either  as  an  adductor  and  depressor  of  the  shoulder  or,  if  the  shoulder 
be  fixed,  as  an  elevator  of  the  third,  fourth,  and  fifth  ribs. 

3.  Some  muscles  with  a  fixed  origin  undergo  a  deviation  from  the 
straight  line  in  the  further  course  of  their  fibers  or  their  tendons.     This 
may  be  merely  a  slight  curving,  as  in  the  occipito-frontal  or  the  elevator 
of  the  upper  eyelid;  or  it  may  be  an  angular  deflection  of  the  tendon 
around  a  firm  prominence,  so  that  the  muscular  traction  is  made  in  an 
entirely  different  direction,  namely  as  if  the  muscle  acted  from  this  pro- 
cess directly  on  its  insertion.     Examples  of  the  latter  are  the  superior 
oblique  muscle  of  the  eyeball,  the  tensor  tympani,  tensor  veli  palatini, 
obturator  internus. 

4.  Many  muscles  of  the  extremities  act  upon  the  long  bones  as  upon 
levers:     (a)  The  muscle   may  act  upon  a  lever  with  a  single  arm,  the 
insertion  of  the  muscle  and  the  weight  being  situated  upon  the  same  side 
of  the  point  of  support,  or  fulcrum,  for  example  the  biceps,  the  deltoid. 
The  point  of  application  of  the  force,  under  such  circumstances,  is  often 
situated  close  to  the  fulcrum.     By  this  means,  the  rapidity  of  the  move- 
ment during  contraction  of  the  muscle  is  greatly  increased  at  the  ex- 
tremity of  the  arm  of  the  lever;  for  example,  in  throwing,  the  hand  may 
move  at  a  rate  exceeding  22  meters  a  second;  but  force  is  lost.     This 
arrangement,  however,  has  the  advantage  that  with  lesser  contraction 
of  the  muscle  its  force  is  diminished  less  than  it  would  be  if  the  contrac- 
tion were  more  marked,     (b)  The  muscles  may  act  upon  the  bones  as 
upon  levers  with  two  arms,  the  point  of  application  of  the  force  (muscu- 
lar insertion)  being  situated  upon  the  other  side  of  the  fulcrum  than  the 


FUNCTION    OF    THE    MUSCLES    IN    THE    BODY. 


585 


point  of  application  of  the  weight;  for  example  the  triceps,  the  muscles 
of  the  calf.  In  both  instances  the  muscular  force  necessary  to  overcome 
a  given  resistance  is  calculated  according  to  the  laws  of  the  lever.  Equi- 
librium will  be  established  when  the  static  factors — that  is  the  product 
of  the  force  in  its  vertical  distance  from  the  fulcrum — are  equal;  or 
when  the  force  and  the  weight  are  inversely  proportional  to  their  ver- 
tical distances  from  the  fulcrum. 

In  determining  the  amount  of  muscular  force  and  the  weight ,  especial 
attention  should  be  given  to  the  direction  in  which  these  act  on  the  arms 
of  the  lever.  Thus,  it  often  happens  that  the  direction  that  was  perpen- 
dicular to  the  arm  of  the  lever  in  a  certain  position  may  act  obliquely 
upon  it  during  movement.  The  static  factor  of  a  force  or  weight  acting 
obliquely  on  the  arm  of  the  lever  is  obtained  by  multiplying  the  force  by 
the  perpendicular  dropped  from  the  fulcrum  upon  the  line  of  direction 
in  which  the  force  is  acting. 


I. 


11 


IK. 


p 

i 

p, 

V 

ft) 

I 

FIG.  199.  —  Diagrammatic  Representation  of  the  Action  of  Muscles  on  the  Bones. 


In  Fig.  199,  I,  B  x  represents  the  humerus,  and  x  Zthe  radius;  A  y  the  direc- 
tion of  traction  of  the  biceps.  If  the  biceps  acted  only  in  the  rectangular  position, 
as  in  holding  horizontally  a  weight  (P)  attached  to  the  forearm  or  the  hand,  then 
the  force  exerted  by  the  biceps  (A)  could  be  determined  by  the  formula  A  .  y  x  = 
P  .  x  Z;  whence  A  =  (P  .  x  Z)  :  y  x.  It  is  evident  that  in  the  depressed  position 
of  the  radius  x  C,  the  conditions  are  different;  then  the  force  of  the  biceps  Aj 
=  (P!  .  v  x)  :  o  x. 

In  Fig.  199,  II,  T  F  represents  the  tibia,  F  the  ankle-joint,  M  C  the  foot  in 
the  horizontal  position.  The  force  (a)  of  the  calf  -muscles  necessary  to  neutral- 
ize a  force  p  directed  from  below  against  the  anterior  extremity  of  the  foot  would 
be:  a  =  (p  .  M  F)  :  F  C.  If  the  position  of  the  foot  is  changed  to  the  direction 
R  S,  then  the  force  of  the  calf-muscles  at  =  (pj  .  m  F)  :  F  c. 

From  the  foregoing  the  amount  of  force  with  which  muscles  that,  like 
the  coraco-brachialis,  are  stretched  over  the  angle  of  a  hinge-joint,  act 
on  the  arms  of  their  levers  is  also  evident.  Here  also  the  static  factor  is 
equal  to  the  force  multiplied  by  the  perpendicular  dropped  from  the 
fulcrum  upon  the  line  of  direction  of  the  force. 

In  Fig.  199,  III,  H  E  represents  the  humerus,  E  the  elbow-joint,  E  R  the 
radius,  B  R  the  coraco-brachialis  muscle.  The  factor  in  this  position  is  A  .  b  E. 


586  FUNCTION    OF    THE    MUSCLES    IN    THE    BODY. 

If  the  radius  is  raised  to  the  position  E  Rlf  the  factor  is  A  .  a  E.  It  should,  how- 
ever, be  noted  here  also  that  B  Rt  <  B  R;  hence  the  absolute  muscular  energy 
must  be  less  in  the  more  flexed  position,  as  every  muscle  is  able  to  lift  less  weight 
with  increasing  contraction.  What  is  thus  lost  in  energy  is  made  up  in  elongation 
of  the  arm  of  the  lever. 

5.  Some  muscles  have  a  double  motor  effect,  which  they  usually  exe- 
cute combined;   for   example,  the  biceps  muscle  is  a  flexor  and  a  supi- 
nator  of  the  forearm.     If  one  of  these  movements  is  prevented  by  other 
muscles,  the  muscle  does  not  participate  in  the  execution  of  the  other 
movement. 

Examples. — If  the  forearm  be  strongly  pronated  and  then  flexed,  the  biceps 
does  not  participate;  or  if  the  elbow  be  tensely  extended,  supination  is  effected  by 
the  supinator  brevis  alone,  not  by  the  biceps.  The  muscles  of  mastication  furnish 
another  example.  The  masseter  raises  the  lower  jaw  and  at  the  same  time  pulls 
it  forward.  If  the  depressed  jaw,  however,  be  kept  drawn  strongly  backward,  the 
masseter  does  not  participate  in  the  succeeding  elevation  of  the  jaw.  The  tem- 
poral muscle  raises  the  jaw,  and  at  the  same  time  draws  it  backward.  If  the  de- 
pressed jaw  be  raised  when  drawn  forcibly  forward,  the  temporal  does  not  par- 
ticipate in  its  elevation.  The  muscles  of  this  group  execute  this  partial  movement 
only  on  the  strongest  exertion,  or  when  the  position  of  the  bones  is  specially  in- 
fluenced by  other  mechanical  factors.  The  flexors  of  the  leg  also  exhibit  interesting, 
analogous  relations. 

A  muscle  connected  with  one  joint  as  a  rule  causes  in  a  neighboring  joint  a 
movement  opposite  to  that  to  which  it  gives  rise  in  the  joint  over  which  it  passes. 
For  example,  the  brachialis  anticus  causes,  in  addition  to  flexion  at  the  elbow- 
joint,  also  backward  extension  at  the  shoulder- joint. 

6.  Diarticular  or  poly  articular  muscles  are  those  that  pass  over  two  or 
more  joints  in  their  course  from  origin  to  insertion.     In  these  muscles  the 
tendons  may  deviate  from  a  straight  line  in  certain  positions,  for  example 
the  extensors  and  flexors  of  the  fingers  and  toes  in  flexion  of  the  latter ; 
or  the  direction  remains  constantly  straight,  for  example  the  gastroc- 
nemius.     The  muscles  of  this  group  exhibit  also  the  following  interest- 
ing conditions:     (a)  The  phenomenon  of  so-called  active  insufficiency. 
If  the  origin  and  insertion  of  a  muscle  are  too  closely  approximated  as  a 
result  of  certain  positions  of  the  joints  over  which  it  passes,  it  may  happen 
that  the  muscle  is  compelled  to  contract  to  such  a  degree  before  its  action 
becomes  effective  that  further  active  contraction  is  not  possible  beyond 
the  point  at  which  its  effect  may  first  become  manifest.     For  example, 
when  the  knee  is  flexed  at  an  acute  angle,  the  gastrocnemius  is  no  longer 
able  to  accomplish  plantar  flexion  of  the  foot ;  the  traction  on  the  Achil- 
les tendon   is  made   by  the   soleus   alone,     (b)  Passive  insufficiency  is 
exhibited  by  the  polyarticular  muscles  under  the  following  conditions: 
In  certain  positions  of  the  joints  a  muscle  may  already  be  so  stretched 
and  made  tense   as  from  this  position  to  limit  certain  movements  of 
other  muscles  like  a  rigid  restraining  band.     For  example,  the  gastroc- 
nemius is  too  short  to  permit  complete  dorsal  flexion  of  the  foot  when  the 
knee  is  extended.     The  long  flexors  of  the  leg  arising  from  the  tuber- 
osity  of  the  ischium  are  too  short  to  permit  complete  extension  at  the 
knee-joint  when  the  hip-joint  is  flexed  at  an  acute  angle.     The  extensor- 
tendons  of  the  fingers  are  too  short  to  permit  complete  flexion  of  the 
joints  of  the  fingers  when  the  wrist -joint  is  completely  flexed. 

In  the  dependent  upper  extremity  movement  of  the  forearm  at  the 
elbow-joint  is  attended  with  a  change  in  the  position  of  the  upper  arm. 
The  long  head  of  the  biceps  tends  to  rotate  the  upper  arm  backward  with 
the  elbow-joint  in  a  position  between  extension  and  flexion  at  a  right 


GYMNASTIC    EXERCISES    AND    THERAPEUTIC    GYMNASTICS.  587 

angle;  with  the  elbow-joint  in  a  position  of  greater  flexion,  however, 
the  rotation  is  forward. 

A  diarticular  muscle  when  sufficiently  contracted  will  move  the  bone 
situated  between  the  two  joints  in  the  same  manner  as  that  on  which  it  is 
inserted.  This  associated  movement  impairs  the  strength  of  the  princi- 
pal movement;  and,  conversely,  the  latter  is  strongest  when  the  former  is 
inhibited.  The  muscles  that  effect  this  inhibition  have  been  designated 
by  H.  E.  Hering  pseudo-antagonists.  They  take  part  involuntarily  in 
every  movement,  in  order  to  limit  the  associated  movement. 

7.  Syner gists  is  the  designation  applied  to  those  muscles  that,  collec- 
tively, serve  to  exercise  a  certain  kind  of  movement;  for  example  the 
flexors  of  the  leg,  the  calf -muscles,  and  others.  Also  the  abdominal 
muscles,  including  the  diaphragm,  in  contracting  to  diminish  the  size 
of  the  abdominal  cavity,  as  in  the  act  of  straining;  also  the  inspiratory 
and  the  expiratory  muscles  may  be  regarded  as  synergists.  The  dif- 
ferent heads  of  a  muscle,  or  the  two  bellies  of  a  digastric  muscle,  may 
also  be  considered  from  this  point  of  view. 

Antagonists,  on  the  other  hand,  is  the  designation  applied  to  those 
muscles  that  in  contracting  have  an  effect  opposite  to  that  of  other 
muscles.  Thus,  flexors  and  extensors,  pronators  and  supinators,  ad- 
ductors and  abductors,  elevators  and  depressors,  sphincters  and  dilators, 
inspirators  and  expirators,  are  antagonists. 

When  it  is  desired  to  develop  the  action  of  a  muscle  in  its  full  force, 
it  is  customary  to  place  it  involuntarily  first  in  a  state  of  greatest  pos- 
sible extension,  as  it  is  from  this  condition  that  the  muscle  is  really 
capable  of  developing  the  greatest  amount  of  force.  Conversely,  in 
the  execution  of  delicate  movements,  requiring  the  smallest  possible 
amount  of  force,  a  position  is  chosen  in  which  the  muscle  in  question  is 
already  contracted  to  a  considerable  extent. 

All  of  the  fascias  of  the  body  are  attached  to  muscles,  and  are  made  tense  by 
corresponding  movements  of  the  latter  (tensors  of  fasciae). 

GYMNASTIC  EXERCISES  AND  THERAPEUTIC  GYMNASTICS. 
PATHOLOGICAL  VARIATIONS  IN  THE  MOTOR  FUNCTIONS. 

Gymnastic  exercises  are  of  great  importance  in  the  development  of  muscular 
function  and  of  strength,  and  they  should  be  practised  by  both  sexes  from  early 
youth.  The  systematic  activity  increases  the  size  of  the  muscles,  and  renders  them 
capable  of  doing  more  work;  in  addition,  the  bodily  fat  is  consumed  in  greater 
degree.  With  the  increase  in  the  size  of  the  muscles  the  amount  of  blood  is  in- 
creased, and  at  the  same  time  the  bones,  tendons,  and  ligaments  are  rendered 
more  resistent.  As  the  circulation  is  greatly  increased  in  active  muscle,  exercise 
causes  a  general  improvement  in  the  circulation  and  in  cardiac  activity.  As  a 
result  a  favorable  influence  is  exerted  on  the  movement  of  the  fluids  of  the  body 
in  persons  especially  of  sedentary  habits,  who  suffer  from  stagnation  of  blood  in 
the  abdominal  organs  (hemorrhoids,  etc.).  As,  further,  active  muscle  consumes 
a  good  deal  of  oxygen  and  generates  much  carbon  dioxid,  respiration  is  thus 
actively  stimulated  by  gymnastic  exercises.  The  general  increase  of  metabolism 
gives  rise  to  the  feeling  of  well-being  and  of  vigor,  limits  abnormal  irritability 
and  the  tendency  to  fatigue.  The  whole  body  becomes  more  solid,  firmer,  and 
of  heavier  specific  gravity. 

Swedish  therapeutic  gymnastics  are  employed  to  strengthen  systematically 
the  muscles  in  persons  suffering  from  weakness  of  certain  muscles  or  muscle- 
groups,  and  in  consequence  not  infrequently  exhibiting  deformities  in  the  position 
of  the  skeleton.  The  movements  of  these  muscles  are  practised  especially,  being 
opposed  by  suitable  resistance,  which  should  be  overcome  by  the  subject,  or 
be  opposed  by  him  without  overcoming  them. 


588  GYMNASTIC    EXERCISES    AND    THERAPEUTIC    GYMNASTICS. 

Kneading,  pressing,  and  stroking  the  muscles  (massage)  also  promote  the 
circulation  of  blood  through  them.  These  procedures  may,  therefore,  be  applied 
with  advantage  to  muscles  that  are  so  enfeebled  by  disease  that  independent, 
systematic  training  by  exercises  or  gymnastics  can  no  longer  be  successfully  pur- 
sued. 

Derangement  of  normal  movements  may  occur  in  the  apparatus  concerned  in 
passive  movements,  namely  the  bones,  joints,  ligaments,  and  aponeuroses,  or  in 
apparatus  concerned  in  active  movements,  namely  the  muscles  with  their  ten- 
dons and  motor  nerves. 

Fractures,  caries,  and  necrosis,  and  also  inflammatory  processes,  which  render 
movements  of  the  bones  painful,  impair  such  movements  or  even  render  them  wholly 
impossible.  A  similar  result  is  caused  by  dislocations  or  inflammations  of  the 
joints,  relaxation  of  the  articular  ligaments,  or  firm  adhesions  between  the  articular 
surfaces  (ankylosis)  or  between  the  ligaments  and  soft  parts  surrounding  the 
joint.  Deviations  from  the  normal  function  may  further  be  caused  by  abnormal 
curvatures  of  the  bones,  enlargements  (hyperostosis) ,  or  outgrowths  (exostosis). 
Among  the  abnormal  positions  of  the  skeletal  parts  that  occur  frequently  are  to 
be  included  curvature  of  the  spinal  column  laterally  (scoliosis) ,  backward  (kypho- 
sis) ,  or  forward  (lordosis) .  These  also  give  rise  to  disturbances  of  the  respiratory 
movements.  In  the  lower  extremities,  which  have  to  bear  the  weight  of  the  body, 
genu  valgum  (knock-knee)  develops,  especially  in  flabby,  tall,  young  persons 
engaged  in  trades  requiring  much  standing.  The  opposite  curvature  of  the  legs, 
genu  varum  (bowlegs),  is  usually  the  result  of  rachitic  disease.  Flat-foot  (pes 
valgus)  is  due  to  depression  of  the  arch  of  the  foot,  which  then  no  longer  rests 
upon  its  three  normal  points  of  support.  This  condition  is  often  due  to  the  same 
causes  as  genu  valgum.  The  ligaments  of  the  small  tarsal  joints  are  stretched, 
and  the  longitudinal  axis  of  the  foot  is  usually  directed  outward  in  marked  degree. 
The  inner  border  of  the  foot  is  brought  closer  to  the  ground.  Pains  in  the  foot 
and  the  malleoli  render  walking  and  standing  difficult.  Club-foot  (pes  varus) 
is  the  condition  in  which  the  inner  border  of  the  foot  is  raised,  and  the  point  of 
the  foot  is  turned  upward  and  inward;  it  is  caused  by  a  fetal  arrest  of  develop- 
ment. All  children  are  born  with  a  slight  degree  of  this  position.  Pointed  toe 
(pes  equinus)  is  the  condition  in  which  the  point  of  the  foot  touches  the  ground; 
pes  calcaneus,  that  in  which  the  heel  touches  the  ground.  Both  are  usually  de- 
pendent upon  contracture  of  the  muscles  causing  these  positions,  or  upon  paralysis 
of  their  antagonists. 

Persistent  absence  of  earthy  salts  from  the  food  results  in  a  deficiency  of 
these  in  the  skeleton;  the  bones  become  thin,  transparent,  and  even  flexible. 
Rickets  in  children  and  the  identical  lameness  in  young  domestic  animals  are 
caused  by  the  fact  that  the  calcium-salts  of  the  food  cannot  be  absorbed,  on 
account  of  persistent  disturbances  of  digestion.  Analogous  disturbances  of  the 
motor  functions  develop  if  the  fully  developed  bones  subsequently  lose  their 
calcium-salts  to  the  extent  of  one-third  or  one-half  (halisteresis) ,  and  thus  become 
brittle  and  soft — osteomalacia.  A  certain  minor  degree  of  fragility  of  the  bones 
and  halisteresis  occurs  in  old  age. 

With  regard  to  pathological  alterations  in  the  muscles,  it  should  first  be 
pointed  out  that  the  normal  nutrition  of  muscular  tissue  can  only  take  place 
if  a  sufficient  supply  of  sodium  chlorid  and  of  potassium-salts  is  provided  in  the 
food,  as  these  are  integral  constituents  of  muscular  tissue.  Otherwise,  the  muscles 
atrophy,  and  their  reconstruction  is  prevented.  Under  such  conditions,  further, 
the  central  nervous  system  and  the  digestive  apparatus  also  suffer,  and  the  animals 
perish.  The  extent  to  which  the  muscles  suffer  in  a  state  of  inanition  is  described 
on  page  440.  Muscles  and  bones  that  for  any  reason  are  thrown  out  of  function 
also  undergo  atrophy.  In  the  atrophic  muscles  associated  with  ankylosis  there 
is  often  found  an  enormous  proliferation  of  the  muscle-corpuscles,  occurring  as  an 
"atrophic  proliferation"  at  the  expense  of  the  contractile  substance.  A  certain 
degree  of  muscular  atrophy  takes  place  normally  in  old  age. 

The  great  reduction  (from  1000  to  350  grams)  in  the  muscular  structure  of 
the  uterus  after  parturition  is  especially  noteworthy.  This  is  due  in  part  to 
the  diminished  vascularization  of  the  organ.  In  cases  of  lead-poisoning  the 
extensors  and  interossei  especially  undergo  atrophy.  Atrophy  and  degeneration 
of  the  muscles  give  rise  to  secondary  shortening  and  thinning  of  the  bones  to 
which  they  are  attached. 

Section  and  paralysis  of  the  motor  nerves  cause  inactivity  and  finally  de- 
generation of  the  muscles.  Inflammation,  softening,  and  sclerosis  of  the  ganglion- 


STANDING.  589 

cells  in  the  anterior  horns  or  in  the  motor  nuclei  of  the  medulla  oblongata  also 
give  rise  to  atrophy  of  the  muscles  connected  with  them.  Spinal  paralysis  and 
acute  bulbar  palsy  (paralysis  of  the  medulla  oblongata)  thus  have  an  acute  onset, 
while  progressive  muscular  atrophy  and  progressive  bulbar  paralysis  pursue  a 
chronic  course.  Under  these  conditions  the  muscles  and  their  nerves  become  thin 
and  wasted.  The  muscles  exhibit  many  nuclei,  their  contractile  substance  is 
partly  in  a  state  of  fatty  degeneration,  and  later  disappears  altogether.  The 
intramuscular  connective  tissue  is  increased,  often  also  the  interstitial  fat.  Ac- 
cording to  Charcot,  the  central  nerve-cells  are  also  the  trophic  centers  for  the 
nerves  arising  from  them  and  for  the  related  muscles.  According  to  Friedreich, 
however,  progressive  muscular  atrophy  is  a  primary  disease  of  the  muscles,  a 
primary  interstitial  myositis  resulting  in  atrophy  and  degeneration,  the  central 
nervous  system  becoming  involved  in  the  degenerative  processes  only  secondarily ; 
just  as  after  amputation  of  an  extremity  corresponding  parts  of  the  spinal  cord 
degenerate  secondarily. 

Finally,  mention  should  be  made  of  pseudo-hypertrophy  or  lipomatous  mus- 
cular atrophy,  in  which  the  muscle-fibers  are  completely  atrophied,  in  association 
with  an  abundant  development  of  fat  between  the  fibers,  without,  however, 
degeneration  of  the  nerves  or  the  spinal  cord.  The  muscular  substance  may  also 
undergo  amyloid  degeneration,  the  amyloid  substance  penetrating  and  infiltrating 
the  tissue.  At  times  atrophic  muscles  exhibit  a  deep  brownish-red  color,  probably 
due  to  alteration  of  the  muscle-pigment.  Muscles  constantly  compelled  to  per- 
form a  large  amount  of  work,  such  as  the  heart-muscle,  the  bladder,  the  intestine, 
undergo  hypertrophy.  If  the  mechanism  of  the  skeleton  becomes  altered,  for 
example  as  a  result  of  rigidity  of  a  number  of  joints,  the  muscles  adapt  them- 
selves more  or  less  completely  to  the  altered  mechanical  conditions  by  changes 
in  their  growth,  expenditure  of  energy,  and  manner  of  movement. 


SPECIAL  MOVEMENTS. 
STANDING. 

Standing  is  the  vertical  position  of  equilibrium  of  the  body,  secured 
by  muscular  action,  in  which  the  line  of  gravitation — that  is  a  perpen- 
dicular dropped  from  the  center  of  gravity  of  the  body — strikes  the  ground 
within  the  supporting  area  of  the  soles  of  both  feet.  Of  the  various  posi- 
tions, that  of  "standing  erect"  will  be  analyzed  here.  In  this  position, 
muscular  activity  is  exercised  in  two  directions :  ( i )  to  fix  the  articulated 
body  into  an  inflexible  column  (to  "stiffen");  and  (2)  in  case  of  a 
variation  of  the  equilibrium  to  neutralize  the  disturbance  by  suitable 
muscular  contractions. 

The  following  muscular  activities  are  observed  in  standing: 
i.  Fixation  of  the  head  on  the  vertebral  column.  The  occiput  may 
move  in  various  directions  on  the  atlas,  whose  two  concave  articular 
surfaces  converge  anteriorly.  The  act  of  nodding  is  the  most  readily 
performed.  As  the  center  of  gravity  of  the  head  lies  in  front  of  the 
supporting  points  on  the  atlas,  relaxation  of  the  muscles,  as  in  sleep  or  in 
death,  causes  the  chin  to  fall  upon  the  chest.  The  strong  muscles  of  the 
neck,  which  pull  from  the  spinal  column  upon  the  occiput,  fix  the  head 
on  the  vertebral  column. 

In  addition  to  the  nodding  movement  directly  forward,  a  similar  movement 
is  also  possible  obliquely  forward  and  to  the  side.  Rotation  of  the  head  in  the 
articulations  of  the  atlas  is  possible  only  to  an  inappreciable  extent  around  the 
sagittal  axis,  likewise  around  the  vertical  axis,  the  latter  occurring  only  when 
the  head  is  flexed.  No  special  muscular  activity  is  necessary  to  prevent  these 
movements  in  standing.  When  the  head  is  rotated  to  the  side,  the  contralateral 
vertebral  artery  is  compressed  in  the  vertebral  sulcus,  while  that  on  the  same 
side  is  enabled  to  carry  more  blood. 

The  chief  rotatory  movement  of  the  head  occurs  about  the  vertical  axis  of 


590  STANDING. 

the  odontoid  process  of  the  axis.  The  articular  surfaces  on  the  pedicles  of  the 
first  and  second  vertebrae  are  convex  toward  each  other  in  the  middle,  becoming 
somewhat  lower  anteriorly  and  posteriorly.  The  head  is,  therefore,  highest  in 
the  erect  position;  if  it  is  rotated  on  the  odontoid  process,  it  undergoes  a  slight 
spiral  movement  downward.  In  this  way  distortion  of  the  medulla  is  avoided 
when  the  head  is  strongly  rotated.  In  standing,  no  muscular  action  is  required 
to  fix  these  vertebrae,  as  rotation  cannot  occur  when  the  muscles  of  the  neck  and 
the  flexors  and  extensors  of  the  head  are  at  rest. 

2.  The  vertebral  column  requires  fixation  by  muscles  in  those  sec- 
tions where  its  mobility  is  the  greatest ;  these  are  the  cervical  and  lumbar 
regions.     Here  fixation  is  secured  by  the  numerous  and  strong  muscles  of 
the  cervical  vertebrae,  especially  those  of  the  neck,  and  the  lumbar  mus- 
cles, especially  the  strong  origins  of  the  extensor  dorsi  communis,  sup- 
ported by  the  quadratus  lumborum. 

The  least  movable  vertebras  are  those  from  the  third  to  the  sixth  dorsal;  the 
sacrum  is  completely  immovable.  For  a  definite  length  of  the  column  the  mo- 
bility depends  upon  the  following  factors:  (a)  The  number  and  the  thickness  of 
the  elastic  intervertebral  discs.  These  are  most  numerous  in  the  cervical  region, 
and  are  thickest  in  the  lumbar  region  and  relatively  also  in  the  lower  cervical 
region.  They  permit  movement  in  every  direction.  The  intervertebral  discs 
together  form  one-fourth  the  entire  length  of  the  spinal  column.  They  are  com- 
pressed somewhat  by  the  weight  of  the  body;  hence,  the  body  is  longest  in  the 
morning  and  after  recumbency  of  some  duration.  The  smaller  circumference  of 
the  bodies  of  the  cervical  vertebrae  must  be  more  favorable  for  their  movement 
on  the  discs  than  is  the  greater  size  of  the  lower  vertebrae.  (6)  The  position  of 
the  processes  also  materially  influences  the  mobility.  The  greatly  depressed 
spines  of  the  dorsal  vertebras  prevent  hyperextension.  The  articular  processes 
of  the  cervical  vertebrae  are  so  situated  that  their  surfaces  are  directed  obliquely 
from  before  and  above  backward  and  downward.  By  this  means  relatively  free 
movement  is  rendered  possible  in  rotation,  lateral  inclination,  and  flexion.  In 
the  dorsal  region  the  articular  surfaces  of  the  superior  articular  processes  are 
directed  vertically  and  directly  forward,  while  those  of  the  inferior  articular 
processes  are  directed  directly  backward;  in  the  lumbar  region  the  corresponding 
position  is  almost  vertical  and  sagittal.  In  the  act  of  bending  backward  as  far 
as  possible,  the  most  movable  points  of  the  spinal  column  are  the  lower  cervical 
vertebrae,  from,  the  eleventh  dorsal  to  the  second  lumbar  vertebra,  and  the  two 
lower  lumbar  vertebrae. 

3.  The  center  of  gravity  of  the  part  of  the  body  thus  stiffened  (the 
head  and  the  trunk  with  the  arms)  is  situated  on  the  anterior  border  of 
the  inferior  surface  of  the  eleventh  dorsal  vertebra.     The  perpendicular 
line  dropped  from  the  center  of  gravity  passes  behind  a  line  joining  both 
hip-joints.     Hence,  the  trunk  would  fall  backward  at  the  hip-joints;  but 
this  is  prevented  by  the  ilio-femoral  ligament,  14  mm.  thick,  stretched 
between  the  anterior  inferior  spine  and  the  anterior  intertrochanteric 
line,  and  also  by  the  anterior  tense  layer  of  the  fascia  lata.     As  ligaments 
alone  are  never  able  to  withstand  continuous  traction,  they  are  mate- 
rially supported  by  the  ilio-psoas  muscle,  which  is  inserted  on  the  lesser 
trochanter,  and  also  in  part  by  the  rectus  femoris,  whose  origin  extends 
upward  over  the  acetabulum  to  the  anterior  inferior  spine.     A  lateral 
movement  of  the  hip-joint,  in  which  one  thigh  would  be  abducted  and 
the   other  adducted,  is  prevented  especially  by  the  large  mass  of  the 
gluteal  muscles,  which  fix  the  thigh  on  the  pelvis  posteriorly  and  lat- 
erally.    When  the  thigh  is  extended,  the  ilio-femoral  ligament  also  is 
able  to  prevent  adduction,  aided  by  the  tense  fascia  lata. 

4.  The  part  of  the  body  that  has  thus  far  been  made  rigid,  including 
the  head  and  the  trunk,  with  the  arms  and  the  thighs,  and  whose  center  of 
gravity  is  situated  somewhat  lower  and  only  to  such  a  slight  degree  further 


STANDING.  591 

forward  that  the  line  of  gravity  passes  through  the  line  connecting  the 
posterior  borders  of  the  knee-joints,  must  now  be  fixed  at  the  knee- 
joints.  Falling  backward  is  prevented  by  the  strength  of  the  quad- 
riceps femoris,  supported  by  the  tension  of  the  fascia  lata.  Indirectly, 
the  ilio-femoral  ligament  is  believed  also  to  aid  in  preventing  falling 
backward,  because  in  this  act  the  thigh  must  be  rotated  outward,  and  this 
is  prevented  by  the  tension  of  the  ligament  named  in  the  upright  posi- 
tion. Lateral  flexion  at  the  knee-joint  is  impossible  on  account  of  the 
arrangement  of  the  hinge -joint,  strengthened  by  the  strong  lateral  liga- 
ments of  the  knee.  Rotation  at  the  knee-joint  is  impossible  in  the  ex- 
tended position. 

5.  The  center  of  gravity  of  the  entire  body  is  situated  4.5  cm.  in  a 
vertical  line  below  the  promontory  of  the  sacrum.     A  perpendicular 
dropped  from  this  point  strikes  the  ground  a  little  in  front  of  the  line 
connecting  both  ankle-joints.     The  body  would,  therefore,  fall  forward 
at  the  latter  joints.     This  is  prevented  by  the  muscles  of  the  calf,  aided 
by  the  muscles  of  the  deep  layer,  namely  the  tibialis  posticus,  the  flexors 
of  the  toes,  and  the  peroneus  longus  and  brevis. 

The  following  additional  factors  have  also  been  considered  worthy  of  mention : 
(a)  As  the  longitudinal  axes  of  the  feet  form  an  angle  of  50°  at  the  heels,  falling 
forward  can  take  place  only  if  the  feet  have  taken  a  position  more  nearly  parallel 
to  their  longitudinal  axes.  (6)  Falling  forward  is  opposed  also  by  the  form  of 
the  articular  surfaces  of  the  foot,  as  under  such  circumstances  the  anterior,  broader 
part  of  the  astragalus  would  have  to  be  pressed  between  the  two  condyles.  This 
last  factor  is  actually  of  little  importance,  as  falling  forward  does  not  require 
such  a  marked  change  of  position  as  would  be  necessary  to  bring  this  mechanism 
into  play. 

6.  The  tarsal  and  metatarsal  bones,  united  by  tense  ligaments,  form 
the  arch  of  the  foot.     This  touches  the  ground  at  three  points,  the  tuber- 
osity  of  the  os  calcis,  the  head  of  the  first  metatarsal,  and  the  head  of  the 
fifth  metatarsal  bone.     Between  the  last  two  points,  however,  the  heads 
of  the  other  metatarsal  bones  also  form  points  of  support.    .The  weight 
of  the  body  falls  upon  the  highest  point  of  the  arch,  the  head  of  the  as- 
tragalus.    The  arch  of  the  foot  is  maintained  only  by  ligaments.     The 
toes  are  able  materially  to  aid  in  balancing  the  body  by  means  of  their 
muscle-play.     Standing  erect  causes  more  fatigue  than  walking. 

Braune  and  Fischer  have  recently  distinguished  the  following  varieties  of 
station,  for  which,  in  contradistinction  from  the  foregoing  older  exposition,  a 
different  form  of  muscular  activity  is  required,  (i)  The  "normal  position"  is 
characterized  by  the  fact  that  the  line  of  gravity  passes  downward  through  the 
lines  connecting  the  central  points  of  both  hip- joints,  knee-joints,  and  ankle- 
joints,  and  passes  upward  through  the  centers  of  gravity  of  the  trunk  and  the 
head.  Accordingly,  the  body  need  only  be  stiffened;  no  muscular  activity  at  all 
is  required  to  prevent  falling  forward  or  backward.  (2)  In  the  "comfortable 
position"  the  line  of  gravity  strikes  the  ground  in  front  of  the  line  connecting 
the  centers  of  both  ankle-joints  at  a  point  corresponding  approximately  to  the 
anterior  border  of  the  ankle-joint.  Hence,  muscular  action  is  necessary  to  prevent 
falling  forward  at  the  ankle-joints.  (3)  In  the  "military  position"  the  line  of 
gravity  falls  in  front  of  the  knee-joints  and  ankle-joints,  striking  the  ground  at 
a  point  corresponding  approximately  to  the  middle  of  the  sole.  Hence,  falling 
forward  must  be  prevented  at  both  joints,  and  this  induces  great  fatigue  on  account 
of  the  considerable  and  continuous  muscular  exertion. 

The  position  of  the  center  of  gravity  in  the  living  person  is  determined  as 
follows:  The  body  is  placed  on  a  narrow  board  the  length  of  the  body.  A  balanc- 
ing edge  is  placed  beneath  the  board,  and  first  the  upper  and  lower  halves  are 
balanced,  then  the  right  and  left  halves.  Finally,  the  body  is  balanced  when 
standing  upright  on  a  small  'board.  The  center  of  gravity  is  situated  at  the 


592  SITTING,    WALKING,    RUNNING,    JUMPING. 

intersection  of  the  three  planes,  passing  in  each  instance  at  right  angles  to  and 
along  the  balanring  edge.  The  center  of  gravity  of  individual  parts  of  the  body 
may  be  determined  in  a  similar  manner  on  sections  of  a  frozen  cadaver. 

Pathological. — The  security  of  firm  station  is  recognized  from  the  swaying  of 
the  body,  which  may  be  easily  registered  with  the  aid  of  a  small  rod  placed  verti- 
cally on  the  top  of  the  head,  the  swaying  being  recorded  by  means  of  a  pen  or 
a  brush  on  a  surface  stretched  horizontally  above  the  head.  Disturbances  of 
sensation,  such  as  occurs  in  tabes  and  the  like,  cause  marked  swaying;  as  do 
also  muscular  weakness,  tremor,  fatigue,  coldness  of  the  feet,  the  action  of  an- 
esthetics on  the  soles  of  the  feet. 

SITTING. 

Sitting  is  the  position  of  equilibrium  in  which  the  body  is  supported 
on  the  tuberosities  of  the  ischia,  on  which  a  to-and-fro  rocking  movement 
can  take  place,  as  upon  the  rockers  of  a  rocking-horse.  The  head  and 
the  trunk  together  are  made  rigid  so  as  to  form  an  immovable  column,  as 
in  standing.  The  essential  purpose  of  sitting  is  to  place  the  lower  ex- 
tremities out  of  service  from  time  to  time,  in  order  that  their  muscles  may 
recover  from  fatigue.  The  following  varieties  of  the  sitting  posture 
have  been  distinguished:  i.  The  forward  sitting  posture,  in  which 
the  line  of  gravity  passes  in  front  of  the  tuberosities.  In  this  position 
the  body  is  supported  either  against  a  firm  object,  for  example  by  means 
of  the  arms  on  a  table,  or  on  the  upper  surface  of  the  thigh,  which  is 
either  held  horizontally  or  is  flexed  to  an  acute  angle  at  the  hip  by  a 
support  placed  under  the  feet.  2.  The  backward  sitting  posture  is 
characterized  by  the  passage  of  the  line  of  gravity  behind  the  tuberosi- 
ties. Falling  backward  is  prevented  under  such  circumstances  by  the 
back  of  a  chair  (if  the  latter  extends  upward  as  far  as  the  head  the  neck- 
muscles  also  may  undergo  relaxation  during  rest),  or  by  the  counter- 
weight of  the  legs,  kept  extended  by  muscular  action.  In  the  latter 
event  the  sacrum  may  serve  as  a  further  point  of  support,  while  the 
trunk  is  fixed  on  the  thigh  by  the  ilio-psoas  and  the  rectus  femoris,  and 
the  leg  is  kept  extended  by  the  extensor  quadriceps.  Usually  the  center 
of  gravity  is  so  situated  that  the  heels  form  additional  points  of  support. 
This  latter  sitting  posture  is  naturally  not  adapted  for  resting  the  mus- 
cles of  the  lower  extremities.  3.  In  the  median  sitting  posture  (sitting 
erect)  the  line  of  gravity  passes  between  the  tuberosities.  The  muscles 
of  the  lower  extremities  are  relaxed ;  the  rigid  trunk  requires  only  slight 
muscular  action  to  balance  it,  falling  backward  being  prevented  by  the 
ilio-psoas  and  the  rectus  femoris,  and  falling  forward  by  the  lumbar 
portion  of  the  strong  dorsal  muscles.  Usually,  the  balancing  of  the 
head  is  sufficient  to  maintain  equilibrium. 

WALKING,  RUNNING,  JUMPING. 

By  walking  is  understood  horizontal  progression  effected  with  the 
least  possible  muscular  exertion  by  alternate  activity  of  the  two  legs. 

Method.— The  brothers  William  and  Edward  Weber,  in  1836,  analyzed  the 
various  positions  of  the  body  during  the  movements  of  walking,  running,  and 
jumping,  and  recorded  these  positions  in  continuous  series,  which  thus  represent 
a  true  picture  of  all  the  successive  phases  of  locomotion.  Marey,  in  1872,  deter- 
mined the  time-relations  attending  change  of  position  by  connecting  the  motor 
organs  in  man  and  animals  with  apparatus  that  registered  by  means  of  air-trans- 
ference. He  also  further  developed  Weber's  original  idea,  and  has  recorded  the 
various  phases  of  movement  in  walking,  running,  and  jumping,  and  in  moving 
animals  by  means  of  complete  series  of  instantaneous  photographs  taken  by  a 
camera  working  on  the  principle  of  the  revolver.  The  duration  of  exposure  in 


WALKING,    RUNNING,    JUMPING. 


593 


each  instantaneous  photograph  equals  T-ffV(j  of  a  second.  When  placed  in  a 
stroboscope,  these  series  reproduce  the  natural  movements;  and  by  projection 
with  the  aid  of  a  kinematograph  they  may  also  be  shown  as  "moving  pictures." 
Figs.  201,  202,  and  203  represent  such  series  of  instantaneous  photographs  ob- 
tained in  the  manner  described.  Braune  and  O.  Fischer,  between  1895  ano^  I&99> 
introduced  a  new  method  of  recording  the  motor  process  in  walking  by  means 
of  bilateral  chronophotographic  exposures  on  an  extensive  coordinating  system. 

In  the  act  of  walking  the  legs  are  alternatively  active.  While  one, 
the  "supporting"  or  "active"  leg,  carries  the  body,  the  other,  the  "hang- 
ing," "swinging,"  or  "passive"  leg,  is  inactive.  Thus,  each  leg  in  regu- 
lar alternation  goes  through  an  active  and  a  passive  phase.  The  motion 
of  walking  may  be  divided  into  the  following  acts : 

First  Act  (Fig.  200,  2). — The  active  leg  is  vertical,  slightly  flexed  at 
the  knee,  and  supports  alone  the  center  of  gravity  of  the  body.  The 
passive  leg  is  fully  extended,  and  touches  the  ground  only  with  the  tip  of 
the  great  toe  (z).  This  position  of  the  legs  corresponds  to  a  right-angle 
triangle,  in  which  the  active  leg  and  the  ground  form  the  two  sides 
(catheti),  and  the  passive  leg  the  hypothenuse. 


FIG.  200. — Phases  of  the  Movement  of  Walking.  The  thick  lines  represent  the  active,  the  thin  lines  the  passive 
leg:  h,  hip- joint;  k  a,  knee-joint;  /  b,  ankle-joint;  c  d,  heel;  m  e,  ball  of  the  metatarso-phalangeal  joint; 
z  g,  tip  of  the  great  toe. 

Second  Act. — To  advance  the  trunk,  the  active  leg  tilts  from  its  ver- 
tical position  (cathetus)  into  an  oblique  position  (3)  inclined  forward 
(hypothenuse).  In  order  that  the  trunk  may  remain  at  the  same  height, 
it  is  necessary  for  the  active  leg  to  be  lengthened.  This  is  accomplished 
first  by  complete  extension  of  the  knee  (3,  4,  5),  then  by  elevation  of  the 
heel  from  the  ground  (4,  5),  so  that  the  foot  rests  on  the  ball  formed  by 
the  heads  of  the  metatarsal  bone,  and  finally  by  elevation  of  the  foot  on 
the  joint  of  the  great  toe  (2,  thin  line).  As  both  sections  of  the  foot  are 
successively  raised  from  the  ground,  like  the  links  of  a  measuring  chain 
that  is  lifted  from  the  ground  ("unwound"),  the  elevation  of  the  foot 
from  the  ground  has  also  been  termed  "unwinding"  of  the  foot.  .  During 
the  extension  and  forward  inclination  of  the  active  leg  the  tips  of  the 
toes  of  the  passive  leg  have  been  compelled  to  leave  the  ground  (3). 

While  this  leg  now  becomes  slightly  flexed  at  the  knee  for  the  pur- 
pose of  shortening,  it  executes  at  the  same  time  a  "pendulum-like" 
movement  (4,  5),  by  means  of  which  its  foot  is  moved  just  as  far  in  front 
of  the  active  foot  as  it  was  previously  behind  the  latter. 

When  it  attains  this  position,  the  foot  is  placed  flat  upon  the  ground 
38 


594 


WALKING,    RUNNING,    JUMPING. 


(i,  2,  thick  line).  The  center  of  gravity  is  transferred  to  this,  the  hence- 
forth active  leg,  which  at  the  same  time  assumes  a  vertical  position, 
somewhat  flexed  at  the  knee.  The  first  act  is  now  begun  again. 

In  walking,  the  trunk  also  exhibits  some  characteristic  secondary  movements : 
(i)  It  inclines  each  time  toward  the  active  leg,  as  a  result  of  traction  of  the  glu- 
teal  muscles  and  the  tensor  vaginae  femoris,  with  the  object  of  transferring  the 
center  of  gravity.  In  heavy,  short  persons  with  broad  pelves  this  produces  the 
"waddling"  gait.  (2)  In  order  to  overcome  the  resistance  of  the  air,  especially 


FIG.  201. — Slow  Walking,  Photographed  in  Instantaneous  Pictures  (after  Marey).  Only  the  side  direct  toward 
the  observer  is  represented.  From  the  vertical  position  of  the  right  active  leg  (7)  the  entire  phase  of  the 
movement  of  this  leg  follows  in  six  pictures  (from  /  to  VI);  after  VI  the  vertical  position  is  again  reached. 
The  Arabic  numerals  denote  the  simultaneous  corresponding  positions  of  the  left  leg,  thus  i  =  /,  2  =  77, 
etc.,  so  that,  for  example,  during  position  IV  of  the  right  leg  the  left  leg  at  the  same  time  has  the 
position  7. 


FIG.  202.  —  Instantaneous  Photographs  of  a  Runner  (after  Marey).     Ten  pictures  in  a  second; 
sents  the  distance  traversed  in  meters. 


the  base  line  repre- 


in rapid  walking,  the  trunk  is  balanced  at  a  forward  inclination.  (3)  During  the 
"  pendulum. "-motion  the  trunk  rotates  slightly  about  the  head  of  the  active 
femur.  This  rotation  is  compensated,  especially  in  rapid  walking,  by  the  arm 
on  the  same  side  as  the  oscillating  leg  swinging  in  the  opposite  direction;  while 
that  on  the  other  side  at  the  same  time  swings  in  the  same  direction  as  the  oscil- 
lating leg. 

O.  Fischer  has  accurately  determined  the  movement  of  the  center  of  gravity 
of  the  body.  The  external  forces  to  be  considered  are  the  weight,  the  resistance 
of  the  ground,  the  friction  on  the  latter,  and  the  resistance  of  the  air. 

The  time-relations  of  walking  are  influenced  by  the  following  conditions:  (i) 
The  duration  of  the  step.  As  the  rapidity  of  the  pendulum-motion  depends  upon 


WALKING,    RUNNING,    JUMPING.  595 

the  length  of  the  leg,  it  is  evident  that  each  individual,  in  accordance  with  the 
length  of  his  leg,  has  a  certain  natural  time  of  oscillation,  which  especially  in- 
fluences his  accustomed  rate  of  walking.  In  addition,  however,  the  duration  of 
the  step  depends  upon  the  length  of  time  during  which  both  feet  touch  the  ground 
simultaneously.  Naturally,  this  can  be  increased  voluntarily.  With  a  "rapid 
pace"  the  period  of  time  is  zero;  that  is,  at  the  same  moment  that  the  active  leg 
is  placed  on  the  ground  the  passive  leg  is  raised.  (2)  The  length  (or  stretch)  of 
the  step,  which  amounts  to  six  or  seven  decimeters  on  the  average,  must  be  the 
greater,  the  more  the  length  of  the  hypothenuse  of  the  passive  leg  exceeds  the 
cathetus  of  the  active  leg.  Hence,  in  the  longest  steps  the  active  leg  is  markedly 
shortened  by  flexion  at  the  knee,  so  that  the  trunk  is  carried  at  a  lower  level. 
Similarly,  long  legs  are  especially  able  to  make  greater  steps. 

According  to  Marey,  Carlet,  and  H.  Vierordt  the  pendulum-movement  of  the 
passive  leg  cannot  be  regarded  as  a  true  pendulum-oscillation,  because  it  possesses 
a  more  nearly  uniform  rapidity,  owing  to  muscular  action.  During  the  pendulum- 
movement  of  the  whole  limb,  the  leg  oscillates  independently  at  the  knee-joint, 
as  is  especially  evident  in  women.  According  to  Ed.  and  Wm.  Weber  the  head 
of  the  femur  of  the  passive  leg  is  held  in  the  acetabulum  chiefly  by  air-pressure, 
so  that  no  muscular  activity  is  necessary  to  carry  the  whole  extremity.  If  all 
the  muscles  and  the  joint-capsule  be  divided,  the  head  still  remains  attached 
to  the  acetabulum.  By  pulling  on  the  thigh  the  borders  of  the  cartilaginous 
rim  of  the  acetabulum  are  closely  applied  in  a  valve-like  manner  to  the  margin 


FIG.  203. — Instantaneous  Photographs  of  a  High  Jump  (after  Marey).  The  pictures  partly  overlap  as  soon  as 
the  velocity  of  the  forward  movement  diminishes  on  the  descent  after  the  jump.  In  the  upper,  left-hand 
corner  is  a  dial,  the  white  radius  of  which  has  moved  forward  one  division  in  one-twelfth  of  a  second.  The 
base  line  represents  the  distance  traversed,  in  meters. 

of  the  cartilage  on  the  head  of  the  femur.  According  to  the  statements  of  the 
brothers  Weber,  the  thigh  is  released  from  the  acetabulum  as  soon  as  air  is  allowed 
to  penetrate  the  articular  cavity  by  perforating  the  bottom  of  the  socket. 

The  brothers  Weber  showed  that  in  walking  on  level  ground  an  appreciable 
amount  of  mechanical  work  is  performed,  as  the  weight  of  the  body  must  be 
lifted  several  centimeters  with  every  step.  Marey  and  Demery  estimated  that 
the  work  performed  by  a  person  weighing  64  kilos,  when  walking  slowly,  is  equal 
to  six  kilogrammeters  in  a  second;  when  running  rapidly,  it  amounts  to  56  kilo- 
grammeters. The  performance  consists  in  raising  the  whole  body  and  extremities, 
in  imparting  rapidity  of  motion  to  them,  and  in  maintaining  the  center  of  gravity. 
According  to  Rziha  the  work  performed  in  each  second  in  walking  slowly  is  3.5 
kilogrammeters,  in  walking  at  a  medium  gait  5.46,  in  walking  rapidly  7.87,  in  a 
short  run  21.87,  in  a  brisk  run  42.87,  and  in  a  fast  run  87.50  kilogrammeters. 

A  bicycle-rider  going  at  the  rate  of  two  meters  in  a  second,  performs  1.12 
kilogrammeters,  at  a  four-meter  pace  4.51  kilogrammeters,  at  a  five-meter  pace 
7.05,  and  at  a  six-meter  pace  10.15  kilogrammeters.  The  normal  capability  of 


596  COMPARATIVE    STUDY    OF    MOTION. 

a  bicycle-rider  is  three  and  one-half  minutes  for  each  kilometer,  or  a  rate  of  4.73 
meters  a  second,  with  a  daily  capability  of  from  90  to  100  kilometers.  The  normal 
capability  of  a  workman  is  in  this  connection  assumed  by  comparison  to  be  6.3 
kilogrammeters  a  second.  A  bicycle-rider,  going  at  an  average  rate,  traverses 
the  same  distance  in  half  the  time  and  with  half  the  expenditure  of  energy  that 
a  pedestrian  requires.  With  the  same  metabolic  consumption  of  muscular  tissue, 
the  exertion  and  the  degree  of  fatigue  are  greater  in  walking  than  in  cycling. 
In  long-continued  cycling,  likewise  in  long  marches,  there  is  an  increase  in  the 
consumption  of  energy  for  the  successive  units  of  distance  covered;  at  a  moderate 
pace  this  increase  amounts  to  about  20  per  cent. 

The  pressure  on  the  ground  in  walking  is  distributed  in  the  following  manner: 
The  supporting  leg  always  presses  more  firmly  on  the  ground  than  the  other; 
the  longer  the  step  the  stronger  the  pressure.  The  heel  attains  the  maximum 
pressure  more  rapidly  than  the  point  of  the  foot. 

The  length  of  the  step  varies  not  inconsiderably  even  when  a  voluntary 
attempt  is  made  to  have  the  steps  of  equal  length ;  as  do  also  the  degree  of  spread- 
ing of  the  legs  and  the  duration  of  the  various  phases  of  walking. 

Running  (Fig.  202)  differs  from  rapid  walking  in  the  fact  that  a  mo- 
ment exists  in  which  both  legs  are  off  the  ground,  so  that  the  body  hovers 
in  the  air.  The  active  leg,  in  being  forcibly  extended  from  a  more  flexed 
position,  must  each  time  give  the  body  the  necessary  impetus. 

In  jumping  (Fig.  203)  the  body  is  suddenly  raised  by  the  most  rapid 
and  powerful  contraction  possible  of  the  muscles  in  the  lower  extremi- 
ties, care  being  taken  at  the  same  time  to  maintain  the  equilibrium  by 
appropriate  muscular  action. 

Pathological.— Variations  in  the  walking  movements  depend  primarily  upon 
diseases  of  the  bones,  joints,  ligaments,  muscles,  and  tendons.  Then  the  motor 
nerves  must  be  taken  into  consideration,  irritation  and  paralysis  of  which  give 
rise  to  disturbances  of  the  normal  movements.  The  extent  to  which  the  sensory 
nerves  and  the  reflex  apparatus  in  the  spinal  cord  influence  the  gait  is  pointed  out 
on  pages  716  and  728. 

H.  Vierordt  has  applied  the  graphic  method  to  the  analysis  of  pathological 
varieties  of  gait.  Among  these  are,  for  example,  the  spastic,  the  oscillating  or 
zig-zag  gait,  the  gait  of  tabes  and  that  of  paralysis  agitans.  Abasia  and  astasia 
are  the  terms  applied  by  Blocq  in  1888  to  the  inability  to  walk  and  stand,  arising 
from  cerebral  affections  (hysteria,  hypochondria,  violent  emotions,  imperative 
conceptions,  vertigo),  while  all  other  movements,  even  those  of  the  legs,  can  be 
executed  with  full  force  and  coordination. 


COMPARATIVE  STUDY  OF  MOTION. 

The  absolute  muscular  energy  in  animals  is  not,  generally  speaking,  appreciably 
different  from  that  of  man.  The  greater  exhibitions  of  force  encountered  in  the 
animal  kingdom  arise  from  the  thickness  and  number  of  the  muscles,  as  well  as 
from  differences  in  the  arrangement  of  their  leverage  or  in  the  means  for  the 
transference  of  force.  Thus,  for  example,  insects  are"  capable  of  exerting  a  great 
amount  of  force;  some  of  them  being  able  to  drag  67  times  their  own  weight, 
while  a  horse  can  scarcely  drag  its  own  weight.  While  further,  for  example,  a 
man,  by  pressure  on  a  dynamometer  with  one  hand,  overcomes  a  weight  equal 
to  0.70  time  his  own  body-weight,  a  dog  by  lifting  his  lower  jaw  can  overcome 
a  weight  8.3  times  that  of  his  body;  a  crab  by  closing  its  claw  overcomes  28.5 
times  its  weight;  a  mussel  in  closing  its  shell,  382  times  its  body-weight. 

Standing  is  made  easier  in  quadrupeds  by  reason  of  the  much  greater  sup- 
porting surface;  the  springing  animals  assume,  besides,  more  of  a  sitting  position, 
and  often  use  the  tail  as  an  additional  support  (kangaroo,  squirrel).  Birds  possess 
a  mechanical  arrangement  by  means  of  which,  in  perching,  their  toes  are  flexed; 
in  this  way  they  are  able  to  retain  their  grasp  on  twigs  when  asleep.  In  the 
stork  and  the  crane,  prolonged  standing  on  one  leg  is  made  easy  by  the  fact  that 
no  muscular  action  is  required  to  render  the  leg  rigid;  fixation  is  secured  by  a 
process  of  the  tibia  fitting  into  a  depression  on  the  articular  surface  of  the  femur. 

In  walking,  a  gait  can  be  distinguished  in  quadrupeds ;  the  four  feet  are  moved 


COMPARATIVE    STUDY    OF    MOTION.  597 

at  different  times,  and  always  diagonally  one  after  the  other;  for  example,  in  the 
horse,  right  fore,  left  hind;  left  fore,  right  hind.  In  trotting  there  is  an  accelera- 
tion of  this  gait,  so  that  the  legs  are  moved  together  diagonally  at  two  different 
times,  while  the  body  is  at  the  same  time  raised  higher.  In  the  interval  between 
both  hoof-beats  the 'body  is  in  the  air  half  the  time  in  ordinary  trotting,  longer 
in  an  extended  trot. 

The  gallop:  When  a  (right)  galloping  horse  moves  horizontally  through 
the  air,  the  left  hind  foot  comes  down  first.  Shortly  afterward  the  left  fore 
foot  and  the  right  hind  foot  come  down  simultaneously;  the  right  fore 
foot  has  not  yet  reached  the  ground,  and  is  directed  far  forward.  Up  to  this 
point  the  body  has  maintained  its  horizontal  position.  When,  however,  a 
few  moments  later,  the  left  hind  foot  leaves  the  ground,  it  is  at  a  higher  level 
than  the  fore  foot;  at  the  same  time,  the  right  fore  foot  is  also  brought  down  and 
placed  far  forward;  the  right  hind  leg  and  the  left  fore  leg  are  in  extreme  exten- 
sion. At  the  next  moment  these  limbs  also  leave  the  ground,  and  the  hind  foot 
acquires  such  an  ascendency  over  the  fore  foot  that  it  comes  to  be  situated  much 
higher  than  the  latter.  The  body,  therefore,  is  thrown  forward  and  downward 
until  the  right  fore  leg,  which  alone  still  touches  the  ground,  contracts  actively, 
and  pushes  the  body  forcibly  from  the  ground.  When  this  has  occurred,  the 
horse  again  soars  in  air  with  the  body  directed  horizontally.  In  galloping  the 
longitudinal  axis  of  the  horse's  body  is  placed  obliquely  to  the  direction  of  the 
movement,  forming  an  acute  angle.  In  an  extended  gallop  (carriere),  which  is 
really  a  continuous  jumping  motion,  the  right  hind  leg  and  the  left  fore  leg,  for 
example,  do  not  reach  the  ground  simultaneously,  the  former  striking  first.  The 
rapidity  of  this  movement  in  the  horse  is  82 £  feet  a  second.  Most  beasts  of  prey, 
hares,  etc..  employ  only  the  carriere  for  rapid  movements. 

The  amble  is  a  modification  of  the  gait  that  is  peculiar  to  many  animals, 
for  example  the  camel,  the  giraffe,  the  elephant.  It  occurs  also  in  dogs  and  in 
horses,  but  it  is  not  a  favorite  gait  with  the  latter.  It  consists  in  advancing 
both  feet  on  the  same  side  simultaneously  or  almost  so. 

I.Iarey  fastened  compressible  ampullae  under  the  hoofs  of  the  horse,  connecting 
them  with  registering  apparatus;  and  thus  accurately  recorded  the  time-relations 
of  the  various  gaits.  Muybridge,  in  1872 ,  was  the  first  to  obtain  series  of  instanta- 
neous photographs  of  running  horses,  which  Schmidt-Mulheim  placed  together  in 
the  stroboscope. 

In  snakes  the  progression  of  the  body  is  secured  by  elevation  and  depression 
of  the  ribs  in  a  manner  resembling  rowing. 

Swimming  is  an  acquired  art  on  the  part  of  man.  The  specific  gravity  of 
the  whole  body  is,  on  an  average,  somewrhat  higher  than  that  of  river-water, 
though  somewhat  lower  than  that  of  sea-water.  In  the  quiet  dorsal  decubitus, 
with  only  the  mouth  and  the  nose  above  the  surface  of  the  water,  sinking  can 
be  prevented  by  slight  downward  pressing  movements  of  the  hands ;  sometimes  no 
movement  at  all  may  be  necessary.  In  this  position  progression  may  be  accom- 
plished by  simple  extension  and  adduction  of  the  legs.  The  movement  may  be 
accelerated  by  oar-like  strokes  with  the  arms.  Swimming  on  the  abdomen  is 
more  difficult,  because  the  head,  being  held  above  water,  increases  the  specific 
weight  of  the  body.  The  body  is  advanced  and  held  above  water  by  movements 
divided  into  the  following  three  phases:  First  phase,  horizontal  rowing  movement 
of  the  extended  arms  from  before  backward  to  the  horizontal  position  (forward 
movement) ;  second  phase,  downward  pressure  of  the  arms  toward  the  depth, 
with  subsequent  adduction  of  the  elbows  to  the  bod}''  (elevation  of  the  body) , 
together  with  a  drawing  up  of  the  extended  legs;  third  phase,  forward  thrust  of 
the  arms,  in  contact  with  each  other,  and  at  the  same  time  extension  and  ad- 
duction of  the  legs  obliquely  backward  and  toward  the  depth,  as  a  result  of  which 
both  elevation  of  the  body  and  forward  progression  are  effected.  Unduly  rapid 
movements  are  exhausting  and  defeat  their  own  purpose.  Special  attention  should 
be  paid  to  suitable  respiratory  movements. 

Many  land  mammals,  whose  bodies  are  specifically  lighter  than  water,  move 
through  it  with  a  walking  motion,  especially  of  the  hind  legs;  at  the  same  time 
the  feet,  being  directed  downward,  assure  the  normal  position  of  the  body,  as 
they  are  specifically  the  heaviest  parts  of  the  body.  Those  mammals  that  live 
much  in  the  water,  as  well  as  reptiles  and  amphibia,  possess  webbed  feet  and 
a  propelling  tail  partly  resembling  that  of  fish.  Whales  resemble  fish  in  the 
external  appearance  of  their  bodies. 

Fish  primarily  make  use  of  their  tail  as  a  motor  organ,  which  is  moved  by 


598  COMPARATIVE    STUDY    OF    MOTION. 

the  powerful  lateral  muscles.  Usually  the  caudal  fin  is  bent  in  two  opposite 
directions  above  and  below;  in  slight  movements  it  is  bent  only  in  one  direction. 
By  sudden  extension  of  the  tail,  the  fish  exerts  a  pressure  against  the  water, 
and  thrusts  itself  forward.  Many  fish,  such  as  the  salmon,  can  thus  hurl  them- 
selves up  out  of  the  water.  The  dorsal  and  anal  fins  maintain  the  vertical  posi- 
tion. The  pectoral  and  abdominal  fins,  corresponding  to  the  extremities,  effect 
the  smaller  movements,  especially  upward  and  downward;  during  sleep  the  ab- 
dominal fins  are  spread  out.  Most  fish  possess  a  swimming-bladder.  This  is 
wanting,  however,  in  many  cartilaginei  (cyclostomi) ,  or  is  rudimentary,  as  in 
the  shark.  It  either  opens  into  the  alimentary  tract  through  the  air-passage,  or 
the  latter  is  only  a  temporary  structure  that  is  later  obliterated.  The  swimming- 
bladder  is,  in  part,  to  be  regarded  as  a  respiratory  organ  with  afferent  and  efferent 
vessels,  while  in  part  it  serves  for  hydrostatic  purposes.  In  the  dipnoi  the  bladder 
is  transformed  into  a  lung.  The  body  of  swimming  birds  has  a  much  lighter 
specific  gravity  than  has  water,  while  their  feathers  are  lubricated  by  the  coccygeal 
glands.  They  propel  themselves  forward  with  their  webbed  feet. 

Flying,  in  mammals,  is  confined  to  the  bat  and  its  allied  species.  The  bones 
of  the  upper  extremities,  including  the  phalanges,  are  greatly  lengthened.  Be- 
tween the  latter,  as  well  as  the  hind  limbs  (except  the  feet) ,  is  stretched  a  thin 
membrane,  which  also  partially  includes  the  tail.  The  flying  movement  of  this 
membrane  is  effected  by  the  powerful  pectoral  muscles,  which  arise  in  part  from 
a  ridge-like  elevation  of  the  sternum  and  the  strong  clavicles.  The  so-called 
flying  lemurs,  squirrels,  and  opossums  have  merely  a  duplication  of  the  skin, 
stretched  laterally  between  the  larger  bones  of  the  extremities,  and  serving 
as  a  parachute  in  jumping. 

Man  is  unable  to  imitate  flying  movements  successfully,  for  even  though  he 
were  able  to  construct  artificial  wings,  he  would  still  lack  the  strength  of  the 
pectoral  muscles  that  is  necessary  to  effect  elevation  of  the  body. 

In  birds  the  body  specifically  is  exceedingly  light.  Large  air-sacs  extend  from 
the  lungs  into  the  thoracic  and  abdominal  cavities ;  even  the  bones  are  connected 
with  the  lungs  by  special  canals,  so  that  all  the  spaces  in  the  bones  of  the  cranium, 
spinal  column,  bill,  and  extremities  are  filled  with  air  instead  of  marrow.  The 
upper  extremities,  transformed  into  wings,  are  supported  by  the  powerful  coracoid 
bone  and  the  clavicles  (furcula),  the  latter  being  fused  in  the  middle.  The  wings 
are  operated  by  the  powerful  pectoral  muscles,  which  arise  from  the  large  crest 
of  the  sternum. 

In  flying  upward  the  wings  are  half  closed,  and  are  moved  with  the  anterior 
border  directed  obliquely  forward  and  upward.  The  plane  of  the  wings,  without 
offering  resistance  to  the  air,  follows  in  the  same  direction  as  the  edge  of  the 
wings.  Then  the  latter  are  spread  out  in  a  large  arc  downward  and  backward, 
with  their  surfaces  pressed  downward.  While  the  under  surfaces  of  the  wings 
press  against  the  air  from  above  and  forward,  downward  and  backward,  the  bird 
moves  forward  and  upward.  Birds  can  rise  only  against  the  wind,  partly  because 
the  wind  striking  horizontally  against  their  backs  would  press  them  down,  and 
partly  because  it  would  disarrange  their  feathers.  By  means  of  a  revolving  photo- 
graphic camera,  arranged  in  an  apparatus  resembling  a  musket,  Marey  obtained 
complete  series  of  pictures  of  flying  birds  at  which  he  directed  the  apparatus. 

Among  invertebrates,  all  insects  possess  six  legs.  In  addition  some  of  them 
(butterflies,  bees)  have  two  pairs  of  wings  on  the  second  and  third  thoracic 
segments.  In  beetles  and  earwigs  the  first  pair  is  merely  a  covering;  in  the 
strepsiptera  it  is  entirely  rudimentary.  Conversely,  in  the  flies  the  second  pair 
of  wings  is  reduced  to  small  swinging  bulbs.  Lice,  fleas,  and  bedbugs  have  no 
wings  at  all.  All  spiders  have  eight  legs,  the  moths  having  six  in  their  youth. 
In  the  centipedes  the  first  three  body-rings  carry  each  one  pair  of  legs,  while 
all  the  rest  have  either  one  or  two  pairs.  The  crustaceans  also  possess  numerous 
feet,  as  a  rule,  some  of  them  undergoing  peculiar  transformations,  for  example 
in  the  river-crawfish  into  mandibles,  claws,  ambulatory  feet,  abdominal  swimming 
feet  and  fin-foot.  In  the  arthropods  all  of  the  muscles  are  inserted  on  the  inner 
surface  of  the  chitinous  covering.  The  muscles  themselves  are  highly  developed 
and  capable  of  a  great  amount  of  energy  and  rapidity  of  movement. 

Molluscs  lack  internal  supporting  organs,  while  external  ones  (shells)  of  simpler 
construction  are  present.  The  muscles,  which  are  partly  striated •,  form  a  musculo- 
cutaneous  tube  about  the  body  that  causes  the  changes  in  the  form  of  the  body. 
In  mussels  the  strong  single  or  double  sphincter-muscle  of  the  shells  is  noteworthy. 
In  the  pecten  (scallops)  this  muscle  effects  a  springing  movement  in  the  water 


VOICE    AND    SPEECH.  599 

by  rapidly  bringing  the  shells  together.  The  molluscs  provided  with  shells  possess 
strong  retractors. 

In  the  worms  likewise  the  integument  forms  with  the  muscles  a  musculo- 
cutaneous  tube.  The  unstriated  muscle-fibers  pass  either  longitudinally  only 
(round-worms) ,  or  longitudinally  and  transversely  (scratching  worms) ,  or  finally 
longitudinally,  transversely  and  vertically  through  the  body  (flat-worms).  Some 
worms  possess  muscular  suckers,  and  others  one  or  two  pairs  of  motile  stump- 
like  feet.  In  round-worms  the  epidermal  cells,  and  in  some  bristle-worms  the 
intestinal  epithelium,  pass  directly  over  into  muscle-cells,  both  together  being  called 
"epithelio-muscular  cells."  In  the  echinoderms  also  the  muscles  are  united  with 
the  integument;  in  the  holothurians  there  is  an  external,  continuous  layer  of 
circular  fibers,  beneath  which  is  a  longitudinal  musculature,  arranged  in  five 
separate  bands. 

In  the  star-fish  and  the  hair-stars  special  muscles  move  the  limbs  of  the 
radiating  parts  of  the  body.  The  sea-urchin,  surrounded  by  a  firm  lime-capsule, 
has  special  muscles  that  move  its  spines,  and  by  means  of  which  it  is  capable  of 
locomotion.  The  ambulacral  feet  also  aid  in  locomotion. 

In  the  celenterates  the  muscle-fibers  are  transformed  sections  of  epithelial 
cells.  Hence,  there  are  present  "epithelio-muscular  cells,"  which  are  striated  in 
the  medusa,  and  unstriated  in  the  anemone  and  hydroid  polyp.  The  free  epithelial 
part  may  be  provided  with  cilia.  In  the  medusa  these  elements  lie  partly  on 
the  umbrella  and  partly  on  the  tentacles.  Among  the  polyps,  the  actinia  have 
a  strong  muscular  base,  and,  in  addition,  longitudinal  and  circular  fibers  on  the 
body  and  on  the  tentacles.  In  some  polyps  muscles  also  accompany  the  gastro- 
vascular  apparatus. 

Among  the  protozoa,  striated  muscle-fibers  have  been  found  in  some  infusoria, 
for  example  in  the  pedicle  of  the  vorticella;  while,  in  addition,  the  movements  are 
executed  by  the  movable  protoplasm  of  the  body,  or  by  voluntarily  motile  cilia. 


VOICE  AND  SPEECH. 

SCOPE    OF    THE   VOICE.      PRELIMINARY    PHYSICAL    CONSIDERATIONS 
CONCERNING  THE  PRODUCTION  OF  SOUND  IN  REED-APPARATUS. 

The  current  of  expired  air,  and  under  certain  circumstances  also 
that  of  inspired  air,  can  be  employed  to  throw  the  tense  true  vocal  bands 
of  the  larynx  into  regular  vibration,  as  a  result  of  which  a  sound  is  pro- 
duced. This  is  termed  the  human  voice. 

The  true  vocal  bands  of  the  larynx  are  elastic,  "membranous  reeds."  By 
"reeds"  are  meant  elastic  plates  that  almost  completely  fill  the  space  (frame) 
in  which  they  are  spread  out,  leaving,  however,  a  small  space  for  their  movement. 
If  air  be  blown  against  the  reeds  from  a  tube  below  them  (air-tube),  they  will 
yield  at  the  mcment  that  the  tension  of  the  air  overcomes  the  elastic  tension  of 
the  reeds.  In  this  way  a  considerable  quantity  of  air  suddenly  escapes,  its  tension 
rapidly  diminishes,  and  the  reeds  return  to  their  former  position,  to  repeat  again 
the  movement  described.  From  the  foregoing  it  results  that — 

1.  During  the  vibration  of  the  reeds,  alternate  condensation  and  rarefaction 
of  the  air  must  take  place.     It  is  chiefly  this  that  (as  in  the  siren)  produces  the 
sound,  not  so  much  the  reeds  themselves. 

2.  The  "air-tube,"  which  conducts  the  air  to  the  membranous  reeds,  consists 
in  the  human  voice-apparatus  of  the  lower  section  of  the  larynx,  the  trachea, 
and,  below,  the  entire  bronchial  tree.     The  bellows  is  the  thorax,  diminished  in 
size  during  expiration  by  muscles. 

3.  The  air-passage  above  the  reeds  is  called  a  "reinforcing  tube,"  and  consists 
of  the  upper  section  of  the  larynx,  the  pharynx,  and  also  the  oral  and  nasal  cavities, 
which  are  arranged  in  two  stories  one  above  the  other,  and  can  be  closed  alternately. 

The  pitch  of  the  tone  depends  upon  the  following  factors: 

(a)  The  length  of  the  elastic  plates.  The  pitch  is  inversely  proportional  to 
the  length  of  the  elastic  plates;  that  is  the  fewer  the  units  of  length  that  enter 
into  the  elastic  plates  the  more  numerous  will  be  the  units  of  time  (vibrations) 
entering  into  the  tone  produced.  For  this  reason  the  pitch  of  the  shorter  vocal 
bands  in  children  and  in  women  is  higher  than  that  in  adults  and  in  men. 

(6)   The  pitch  of  the  tone  is,  further,  directly  proportional  to  the  square  root 


600  ARRANGEMENT  OF  THE  LARYNX. 

of  the  elasticity  of  the  elastic  plates.  In  the  case  of  membranous  reeds,  and  also 
in  that  of  silk,  it  is  directly  proportional  to  the  square  root  of  the  extending  weight, 
which  in  the  larynx  corresponds  to  the  force  of  the  tensor  muscles. 

(c)  In  the  case  of  membranous  reeds  a  more  powerful  blast  not  only  strengthens 
the  tone  by  increasing  the  amplitude  of  vibration,  but  it  also  raises  the  pitch  of 
the  tone,  because  the  greater  amplitude  of  vibration  increases  the  mean  tension 
of  the  elastic  membrane. 

Among  physical  influences  the  following  further  are  to  be  noted: 

(d)  The  reinforcing  tube,  which  is  exceedingly  variable  in  form,  also  resounds 
when  the  larynx  is  intonated ;    its  primary  tone  is  mingled  with  the  sound  of  the 
elastic  reeds,  and,  thus,  it  is  able  to  reinforce  certain  overtones  of  the  latter. 
This  subject  will  be  discussed  in  greater  detail  in  the  section  on  voice-formation. 
The  individual  characteristics  of  the  voice  depend  essentially  upon  the  form  of 
the  reinforcing  tube.     In  reed-instruments  the  pitch  of  the  tones  can  undoubtedly 
be  influenced  by  varying  lengths  of  the  reinforcing  tube;  but  this  is  not  taken 
into  consideration  in  the  case  of  the  larynx. 

(e)  During  intonation  of  the  reeds  the  strongest  resonance  takes  place  in  the 
air- tube,  as  the  latter  contains  compressed  air.     This  causes  the  vocal  resonance 
that  is  heard  when  the  ear  is  applied  to  the  chest-wall.     Strong  intonation  may 
even  cause  an  accompanying  vibration  of  the  thoracic  wall.     In  weak  individuals, 
and  in  cases  of  falsetto  voice,  the  vocal  resonance  is  exceedingly  slight. 

(/)  Narrowing  or  widening  of  the  glottis  has  no  effect  on  the  pitch  of  the 
tone;  but  with  the  glottis  wide  open,  disproportionately  more  air  must  pass 
through  it,  thus  materially  increasing  the  work  of  the  thorax. 

ARRANGEMENT  OF  THE  LARYNX. 

Cartilages  and  Ligaments  of  the  Larynx. — The  fundamental  framework  of  the 
larynx  is  formed  by  the  cricoid  cartilage,  which  is  shaped  like  a  seal-ring.  The 
inferior  cornu  of  the  thyroid  cartilage  articulates  with  the  cricoid  in  its  postero- 
lateral  region.  This  joint  allows  the  plate  of  the  thyroid  cartilage  to  tilt  forward, 
the  inclination  occurring  as  a  rotatory  movement  about  a  horizontal  axis  connecting 
the  two  joints,  the  upper  border  of  the  cartilage  moving  forward  and  downward. 
The  joints  also  permit  a  slight  shifting  of  the  thyroid  cartilage  on  the  cricoid 
upward  and  downward,  forward  and  backward.  The  triangular,  pyramidal 
arytenoid  cartilages  articulate  on  the  upper  border  of  the  plate  of  the  cricoid 
cartilage  to  one  side  of  the  median  line,  forming  approximately  a  saddle-shaped 
joint  with  oval  articular  surfaces.  The  latter  permit  a  double  movement  on  the 
part  of  the  arytenoids,  namely  rotation  on  their  base  about  their  vertical,  some- 
what oblique,  longitudinal  axis,  by  which  the  vocal  process  directed  forward  is 
rotated  outward  and  upward,  and  the  muscular  process  directed  outward  and 
overlapping  the  border  of  the  cricoid  cartilage  posteriorly  is  rotated  inward  and 
downward,  or  conversely.  In  addition,  the  arytenoid  cartilages  may  be  displaced 
somewhat  inward  or  outward  on  their  bases. 

The  true  vocal  bands,  or  vocal  ligaments,  are  composed  principally  of  elastic 
fibers.  They  arise  close  together  from  about  the  middle  of  the  internal  angle  of 
the  thyroid  cartilage,  and  are  inserted  on  the  vocal  processes  of  the  arytenoid 
cartilages  directed  forward.  The  "ventricles  of  Morgagni"  allow  free  play  for 
the  vibrations  of  the  bands,  and  separate  them  from  the  upper  "false"  bands, 
or  ventricular  ligaments,  which  are  covered  by  a  fold  of  mucous  membrane.  The 
latter  take  no  part  in  phonation.  Numerous  mucous  glands  of  the  mucous  mem- 
brane keep  the  vocal  bands  moist. 

In  accordance  with  the  functions  of  the  laryngeal  cartilages  in  connection 
with  the  voice-apparatus,  C.  Ludwig  has  called  the  cricoid  the  "foundation-carti- 
lage," the  thyroid  the  "tension-cartilage,"  and  the  arytenoids  the  "position- 
cartilages." 

Owing  to  the  oblique  downward  inclination  of  their  under  surfaces  the  vocal 
bands  readily  come  together  when  the  glottis  is  narrowed  during  inspiration  (for 
example  in  sobbing) ;  and  if  the  glottis  is  already  closed,  inspiration  makes  this 
closure  still  firmer.  The  false  vocal  bands  exhibit  the  opposite  relation,  for  when 
in  mutual  contact  they  are  readily  separated  during  inspiration;  while  during 
expiration  they  readily  close,  owing  to  the  inflation  of  the  ventricles  of  Morgagni. 

Action  of  the  Laryngeal  Muscles. — Dilatation  of  the  glottis  is  effected 
by  the  posterior  crico-arytenoid  muscles.  In  drawing  the  muscular 


ARRANGEMENT    OF    THE    LARYNX. 


601 


processes  of  the  arytenoid  cartilages  backward,  downward,  and  toward 
the  median  line  (Fig.  208),  these  muscles  cause  the  corresponding  vocal 
processes  (/,  /)  to  separate  and  move  upward  (77,  77).  A  large  isosceles 
triangle  is  thus  formed  between  the  vocal  bands,  and  another  between 
the  inner  borders  of  the  arytenoid  cartilages,  having  their  bases  in  con- 
tact, so  that  the  aperture  assumes  a  rhomboidal  form. 

Pathological. — Paralysis  of  these  muscles  may  cause  intense  inspiratory 
dyspnea,  on  account  of  the  failure  of  the  glottis  to  dilate.  The  voice  remains 
unchanged.  In  a  freshly  excised  larynx  the  dilators  first  lose  their  excitability. 


FIG.  204. — Anterior  View  of  the  Larynx,  with  its  Liga- 
ments and  Muscular  Insertions:  O.  h,  hyoid  bone; 
C.  th.,  thyroid  cartilage;  Corp.  trit.,  corpus  triti- 
ceum;  C.  c.,  cricoid  cartilage;  C.  tr.,  tracheal 
cartilages;  Lig.  thyr.-hyoid.  med.,  median  thyro- 
hyoid  ligament;  Lig.  th.-h.  Int.,  lateral  thyrp-hyoid 
ligament;  Lig.  cric.-thyr.  med.,  median  crico-thy- 
roid  ligament;  Lig.  eric,  track.,  crico-tracheal  liga- 
ment; M.  sl.-h.,  sterno-hyoid  muscle;  M.  th.- 
hyoid,  thyro-hyoid  muscle;  M.  st.-th.,  sterno-thy- 
roid  muscle;  M.  cr.-lh.,  crico-thyroid  muscle. 


FIG.  205. — Posterior  View  of  the  Larynx,  after  Re- 
moval of  the  Muscles:  £,  epiglottis  with  the  cush- 
ion (IF);  L.  ar.-ep.,  ary-epiglottic  ligament;  M.m., 
mucous  membrane;  C.  W.,  cartilage  of  Wrisberg; 
C.  S.,  cartilages  of  Santorini;  C.  aryt.,  arytenoid 
cartilages;  O.  c.,  cricoid  cartilage;  P.  m.,  mus- 
cular process  of  the  arytenoid  cartilage;  L.  cr. 
ar.,  crico-arytenoid  ligament;  C.  s,  superior  cornu, 
C.  i.,  inferior  cornu  of  the  thyroid  cartilage;  L.  ce.- 
cr.  p.  i.,  postero-inferior  kerato-cricoid  ligament; 
C.  tr.,  tracheal  cartilages;  P.  m.  tr.,  membranous 
portion  of  the  trachea. 


Also  in  the  presence  of  organic  disease  in  the  distribution  of  the  recurrent  nerve, 
the  branch  to  the  posterior  crico-arytenoid  muscle  is  the  first  to  be  paralyzed. 
Likewise,  in  cooling  the  exposed  recurrent  nerve,  this  branch  is  always  the  first 
to  fail  in  its  function. 

The  constrictor  of  the  entrance  to  the  larynx  is  the  transverse  arytenoid 
muscle,  which  connects  the  two  outer  borders  of  the  arytenoid  carti- 
lages by  transverse  fibers  throughout  their  length  (Fig.  209).  On  the 
posterior  surface  of  this  muscle  are  situated  the  crossed  bundles  of  the 
oblique  arytenoid  muscles  (Fig.  206),  which  have  a  similar  action. 

Pathological. — Paralysis  of  these  muscles  renders  the  voice  feeble  and  hoarse, 
as  much  air  escapes  between  the  arytenoid  cartilages  during  phonation. 


6O2 


ARRANGEMENT  OF  THE  LARYNX. 


The  intimate  approximation  of  the  vocal  bands  is  effected  by  bringing 
the  vocal  processes  of  the  arytenoid  cartilages  close  together.  To  this 
end  the  latter  must  be  rotated  inward  and  downward  by  a  forward 
and  upward  movement  on  the  part  of  the  muscular  processes  affected 
through  the  vocal  or  internal  thyro-arytenoid  muscles.  These  muscles, 
which  are  applied  to  the  elastic  borders  of  the  vocal  bands,  and  in  fact 
are  embedded  in  their  substance  and  whose  fibers  extend  to  the  outer 
borders  of  the  arytenoid  cartilages,  rotate  the  latter  so  that  their  vocal 


Corn 


Corn 
inf. 


FIG.  206. — Posterior  View  of  the  Larynx,  with  the 
Muscles:  E,  epiglottis  with  the  cushion  (WO; 
C.-W.,  cartilages  of  Wrisberg;  C.-S.,  cartilages  of 
Santorini;  Cart,  eric.,  cricoid  cartilage;  Cornu 
sup.,  superior  cornu,  Cornu  inf.,  inferior  cornu  of 
the  thyroid  cartilage;  M.  ar.  tr',  transverse  aryte- 
noid muscle;  Mm.  ar.  obi.,  oblique  arytenoid  mus- 
cles; M.  cr.  aryt.  post.,  posterior  crico-arytenoid 
muscle;  Pars  cart.,  cartilaginous  portion  of  the 
trachea;  Pars  memo.,  membranous  portion  of  the 
trachea. 


FIG.  207. — Nerves  of  the  Larynx:  O.  h.,  hyoid  bone; 
C.  th.,  thyroid  cartilage;  C.  c.,  cricoid  cartilage; 
Tr.,  trachea;  M.  th.-ar.,  thyro-arytenoid  muscle; 
M.  cr.  ar.  p.  posterior  crico-arytenoid  muscle; 
M.  cr.  ar.  1.,  lateral  crico-arytenoid  muscle;  M .  cr. 
lh.,  crico-thyroid  muscle;  N.  LAR.  SUP.  V.,  supe- 
rior laryngeal  branch  of  the  vagus;  R.  I.,  internal 
branch;  R.  E.,  external  branch;  N.  L.  R.  V., 
recurrent  laryngeal  branch  of  the  vagus;  R.  I.  N. 
L.  R.,  its  internal  branch;  R.  E.  N.  L.  R.,  its  ex- 
ternal branch. 


processes  must  move  inward.  The  glottis  between  the  vocal  bands  is 
thus  narrowed  to  a  slit,  while  a  broad,  triangular  opening  remains  be- 
tween the  bases  of  the  arytenoid  cartilages  (Fig.  210). 

The  lateral  crico-arytenoid  muscle  is  inserted  into  the  anterior  border 
of  the  articular  surface  of  the  arytenoid  cartilage;  hence,  it  can  only 
draw  the  cartilage  forward.  Some  investigators,  however,  believe  that 
it  also  can  effect  a  rotation  of  the  arytenoid  cartilage  similar  to  that 
of  the  vocal  or  internal  thyro-arytenoid  muscle,  with  the  difference  that 
the  vocal  process  are  not  brought  so  close  together. 

Pathological. — Paralysis  of  the  muscles  effecting  approximation  of  the  vocal 
bands  results  in  loss  of  voice. 


ARRANGEMENT  OF  THE  LARYNX. 


603 


The  tension  of  the  vocal  bands  is  effected  by  the  action  of  muscles  in 
separating  their  two  points  of  attachment  from  each  other.  To  this 
end  the  thyroid  cartilage  is  drawn  forward  and  downward  chiefly  by  the 
crico-thyroid  muscles,  the  angle  of  this  cartilage  being  at  the  same  time 
somewhat  enlarged.  One  can  readily  convince  himself  of  this  move- 
ment by  feeling  his  own  larynx  during  the  emission  of  high  tones. 
The  same  muscles  also  approximate  the  anterior  arch  of  the  cricoid 
cartilage  to  the  inferior  border  of  the  thyroid  cartilage ;  and  as  a  result 
the  posterior  plate  of  the  cricoid  cartilage  undergoes  a  backward  in- 
clination. At  the  same  time  the  posterior  crico-arytenoid  muscles 
must  draw  both  arytenoid  cartilages  somewhat  backward,  and  hold 
them  in  that  position.  The  tense  vocal  bands  become  longer  and  nar- 
rower. 


FIG.  208. — Diagrammatic  Horizontal  Section  through 
the  Larynx:  7,  /,  Position  of  the  arytenoid  carti- 
lages during  respiration,  in  horizontal  section; 
from  their  anterior  angles  run  the  convergent  vocal 
bands  to  the  internal  angle  of  the  thyroid  cartilage. 
The  arrows  indicate  the  direction  of  traction  of  the 
posterior  crico-arytenoid  muscles.  //,  //,  Posi- 
tion of  the  arytenoid  cartilages  as  a  result  of  the 
action  of  these  muscles. 


FIG.  209. — Diagrammatic  Horizontal  Section  through 
the  Larynx,  to  Illustrate  the  Action  of  the  Aryte- 
noid Muscle :  /,  /,  Position  of  the  arytenoid  carti- 
lages during  quiet  respiration.  The  arrows  indi- 
cate the  direction  of  traction  of  the  muscle.  II,  II, 
Positions  of  the  arytenoid  cartilages  produced  by 
the  action  of  this  muscle. 


The  tension  of  the  vocal  bands  is  aided  by  the  genio-hyoid  and  hyo-thyroid 
muscles,  which  together  draw  the  hyoid  bone,  and  thus  indirectly  the  thyroid 
cartilage,  upward  and  forward  in  the  direction  of  the  chin. 

According  to  Harless,  Schech,  Kiesselbach,  Hooper,  and  others,  the  crico-thyroid 
muscle  effects  elevation  of  the  arch  of  the  cricoid  cartilage  toward  the  thyroid 
cartilage.  In  this  way  the  plate  of  the  cricoid  cartilage  is  directed  backward  and 
downward,  thus  causing  increased  tension  of  the  vocal  bands. 

Pathological. — Paralysis  of  the  crico-thyroid  muscles  renders  the  voice  harsh 
and  deeper,  on  account  of  insufficient  tension  of  the  vocal  bands. 

The  tension  thus  induced  is  of  itself  by  no  means  sufficient  for  pho- 
nation,  for  on  the  one  hand  the  triangular  aperture  of  the  glottis  between 
the  arytenoid  cartilages  that  would  result  from  the  isolated  action  of 
the  internal  thyro-arytenoid  muscles  must  be  closed.  This  is  brought 
about  by  the  transverse  and  oblique  posterior  arytenoid  muscles.  Then 
the  vocal  bands  themselves,  which,  with  the  action  of  the  crico-thyroid 
and  posterior  crico-arytenoid  muscles,  retain  their  concave  border,  so 


604 


ARRANGEMENT    OF    THE    LARYNX. 


that  the  glottis  between  them  appears  as  a  space  having  the  form  of 
a  myrtle  leaf,  must  be  fully  stretched,  so  that  the  glottis  assumes  the 
shape  of  a  linear  slit  (Fig.  214).  This  compensation  likewise  is  brought 
about  by  the  internal  thyro-arytenoid  muscle.  It  is  this  muscle, 
moreover,  that  effects  those  delicate  gradations  of  tension  in  the  vocal 
band  itself  that  are  necessary  for  the  production  of  tones  of  slightly 
different  pitch.  It  is  especially  adapted  for  this  purpose,  as  it  comes 
close  to  the  edge  of  the  vocal  band  and  is  firmly  inserted  into  the  elastic 
tissue  of  the  latter.  The  contracting  muscle  in  addition  gives  to  the 
vibrating  vocal  band  the  resistance  necessary  for  its  vibrations.  As 
some  of  the  fibers  of  the  vocal  muscle  terminate  in  the  elastic  tissue  of 
the  vocal  band  itself,  they  may  impart  increased  tension  to  individual 
segments  of  the  vocal  band,  as  a  result  of  which  modifications  in  tone- 
formation  are  possible.  It  must,  therefore,  be  assumed  that  the  coarser 
variations  in  tension  are  caused  by  separation  of  the  thyroid  cartilage 
from  the  arytenoid  cartilages,  while  the  finer  gradations  of  tension  are 

induced  by  the  vocal  muscle. 
The  usefulness  of  the  elastic 
tissue  in  the  vocal  bands  does 
not  consist  so  much  in  its  ex- 
tensibility, as  in  its  property 
of  shortening  without  forming 
folds  or  creases. 

Pathological.  —  When  these 
muscles  are  paralyzed  the  voice 
can  be  produced  only  by  powerful 
blasts,  as  much  air  escapes  through 
the  glottis.  At  the  same  time  the 
tones  are  deep  and  impure.  Uni- 
lateral paralysis  results  in  napping 
of  the  corresponding  vocal  band. 

Relaxation  of  the  vocal 
bands  occurs  spontaneously 
when  the  stretching  forces 
cease  to  act,  the  thyroid  car- 
tilage drawn  forward  and  the 
arytenoid  cartilages  fixed  pos- 
teriorly returning  to  the  posi- 
tion of  rest  in  consequence  of  the  elasticity  that  is  peculiar  to  their 
arrangement.  Relaxation  of  the  vocal  bands  may  result  also  from  the 
action  of  the  thyro-arytenoid  and  lateral  crico-arytenoid  muscles. 

From  the  foregoing  it  follows  that  tension  of  the  vocal  bands  and 
narrowing  of  the  glottis  are  necessary  for  phonation. 

The  epiglottis,  which  becomes  more  erect  with  high  tones  and  falls 
with  low  ones,  has  an  influence  on  the  timbre  (clear  or  muffled)  of  the 
voice,  but  has  no  effect  on  the  pitch. 

The  mucous  membrane  of  the  larynx,  as  well  as  the  submucosa,  is  rich  in 
delicate,  elastic  networks  of  fibers.  The  submucosa  is  loose  and  yielding  in  the 
region  of  the  entrance  to  the  larynx  and  the  ventricles  of  Morgagni,  a  fact  that 
explains  the  enormous  swelling  that  often  occurs  in  connection  with  so-called 
edema  of  the  glottis.  A  clear,  even,  limiting  layer  lies  beneath  the  epithelium. 
The  epithelium  is  stratified,  cylindrical,  and  ciliated,  interspersed  with  goblet-cells, 
except  on  the  true  vocal  bands  and  the  upper  surface  of  the  epiglottis,  where  a 
stratified,  squamous  epithelium  covers  the  mucous  membrane,  which  in  this  situa- 


FIG.  210. — Diagrammatic  Horizontal  Section  through  the 
Larynx,  to  Illustrate  the  Action  of  the  Internal  Thyro- 
arytenoid  Muscles  in  Narrowing  the  Glottis:  //,  //,  Po- 
sition of  the  arytenoid  cartilages  during  quiet  respiration. 
The  arrows  indicate  the  direction  of  traction  of  the  mus- 
cles. /,  /,  Position  of  the  arytenoid  cartilages  brought 
about  by  action  of  these  muscles. 


ARRANGEMENT    OF    THE    LARYNX. 


605 


tion  bears  papillae.  Racemose  mucous  glands  are  present  in  groups  on  the  carti- 
lages of  Wrisberg,  the  cushion  of  the  epiglottis,  and  in  the  ventricles  of  Morgagni; 
and  are  scattered  in  the  other  situations,  especially  on  the  posterior  wall  of 
the  larynx.  The  blood-vessels  form  a  dense,  capillary  network  under  the  limiting 
layer  of  the  mucous  membrane;  beneath  this  are  two  more  layers  of  vascular  net- 
works. The  lymphatics  form  a  superficial,  narrower  network  beneath  the  blood- 
capillaries,  and  a  deeper,  coarser  network.  The  medullated  nerves,  which  have 


B 


FIG.  211. — -.4,  Vertical  section  through  the  head  and  neck  as  far  as  the  first  dorsal  vertebra:  a  shows  the  position 
of  the  laryngoscope  in  order  to  see  the  posterior  part  of  the  glottis,  the  arytenoid  cartilages,  the  upper  surface 
of  the  posterior  laryngeal  wall,  etc.;  b  shows  the  position  of  the  laryngoscope  in  order  to  obtain  a  view  of  the 
anterior  angle  of  the  glottis.  B,  Large  (6)  and  small  (a)  laryngeal  mirrors. 


ganglia  on  their  branches,  are  numerous  in  the  mucous  membrane;  their  termina- 
tions are  unknown.  The  cartilage  is  hyaline  in  the  thyroid,  the  cricoid,  and 
almost  in  the  entire  arytenoid  cartilage,  with  a  tendency  to  ossification.  Fibro- 
cartilage  is  found  toward  the  apex  and  the  vocal  process  of  the  arytenoid  cartilage, 
and  also  in  all  the  remaining  laryngeal  cartilages. 

The  larynx  grows  until  about  the  sixth  year,  then  rests,  but  rapidly  increases 
in  size  again  at  puberty. 


6o6 


EXAMINATION    OF    THE    LARYNX. 


EXAMINATION  OF  THE  LARYNX. 
LARYNGOSCOPY.    EXAMINATION   OF   THE   EXCISED    LARYNX. 

After  Bozzini,  in  1807,  had  given  the  first  impulse  toward  illuminating  and 
examining  the  internal  cavities  of  the  body  by  means  of  the  mirror,  and  Babington, 
in  1829,  had  viewed  the  glottis  in  this  way,  the  singing- teacher,  Manuel  Garcia, 
in  1854,  made  investigations,  by  means  of  the  laryngoscopic  mirror,  on  himself 
and  other  singers,  concerning  the  movements  of  the  vocal  bands  during  respiration 
and  phonation.  Turck  and  Czermak  rendered  the  greatest  service  in  the  applica- 


FIG.  212. — Method  of  Making  a  Laryngoscopic  Examination. 

tion  of  the  laryngoscope  to  medical  purposes,  the  latter  being  the  first  to  use 
artificial  light  for  illumination.  Rhinoscopy  was  first  attempted  by  Baumes  in 
1838,  and  was  systematically  developed  by  Czermak. 

The  laryngoscope  consists  of  a  small  mirror,  attached  to  a  handle  at  an  angle 
(Fig.  211,  B),  the  instrument  being  introduced  with  the  mouth  wide  open  and 
the  tongue  drawn  out  (Fig.  211,  A).  The  position  of  the  mirror  must  be  changed 

in  accordance  with  the  region  to  be  reflected ; 
and  it  may  at  times  even  be  necessary  to  ele- 
vate the  soft  palate  by  means  of  the  mirror 
(b) .  The  mirror  receives  the  picture  of  the 
larynx  in  the  direction  of  the  dotted  line,  and 
reflects  it  at  the  same  angle  through  the  oral 
cavity  to  the  eye  of  the  observer,  which  has 
taken  its  position  in  the  line  of  the  reflected 
rays.  The  illumination  of  the  larynx  is  ac- 
complished by  collecting  either  sunlight  or 
light  from  an  artificial  source  in  a  concave 
mirror,  and  permitting  the  concentrated  bun- 
dle of  rays  to  fall  on  the  laryngoscopic  mirror 
held  in  the  throat.  The  latter  reflects  the 
light  against  the  larynx,  which  is  thus  illumi- 
nated. The  observer  looks  in  the  same  direc- 
tion as  the  rays  of  light,  either  under  the  edge 
of  the  illuminating  mirror,  or  through  a  cen- 
tral  perforation  in  the  latter. 
The  laryngoscope  received  an  important  improvement  at  the  hands  of  Oertel, 
who  showed  how  the  movements  of  the  vocal  bands  could  be  followed  directly 
with  the  eye  by  means  of  rapidly  intermittent  illumination  through  the  disc  of 
a  stroboscope  (laryngo-stroboscope) .  By  replacing  the  eye  by  a  photographic 
camera,  Ssimanowsky  was  able  to  photograph  the  movements  of  the  vocal  bands 
in  an  artificial  larynx. 


FIG.  213. — The  Laryngoscopic  Image  During 
Respiration. 


EXAMINATION    OF    THE    LARYNX. 


607 


v.  Ziemssen  showed  that  long,  thin  electrodes  could  be  introduced  as  far  as 
the  larynx  under  the  guidance  of  the  laryngoscope,  and  that  the  vocal  bands 
could  be  stimulated  to  activity  by  irritation  of  the  muscles.  Rossbach  succeeded 
in  stimulating  the  muscles  and  nerves  of  the  larynx  externally  through  the  skin. 


FIG.  214. — Image  of  the  Larynx  when  a  Sound  is 
Begun. 


FIG.  215. — View  of  the  Trachea  as  far  as  the  Bifurca- 
tion. 


In  this  way  physiological  information  may  be  gained,  or  therapeutic  applications 
may  be  made  to  the  parts. 

Autolaryngoscopy  was  first  employed  by  Garcia,  and  then  by  Czermak  espe- 
cially for  the  study  of  the  movements  of  the  larynx.  If  one  introduce  an  illumi- 
nated laryngoscopic  mirror  into  his  own  throat,  while  placing  the  mouth  opposite 
a  plane  mirror,  he  may  easily  see 
the  picture  of  his  own  larynx  re- 
fleeted  in  the  latter. 

The  laryngoscopic  picture 
(Fig.  213)  exhibits  the  follow- 
ing details :  L,  the  root  of  the 
tongue,  from  the  middle  of 
which  the  glosso-epiglottic 
ligament  passes  downward ; 
on  each  side  of  the  latter  are 
the  so-called  valleculae  (V  V). 
The  epiglottis  (E)  appears  as 
an  arch,  shaped  like  the  upper 
lip;  beneath  it  in  quiet  res- 
piration is  seen  the  lancet- 
shaped  chink  of  the  glottis 
(R),  and  on  either  side  the 
bright,  yellowish  vocal  liga- 
ment (L.  v.).  This  vocal  band 
is  from  6  to  8  mm.  long  in  chil- 
dren, from  10  to  15  mm.  long 
in  women  when  relaxed,  and 
from  1 5  to  20  mm.  when  tense. 
In  men  it  measures  from  15 
to  20  mm.  and  from  20  to  25 
mm.  respectively.  The  whole 
chink  of  the  glottis  is  23  mm. 
long  in  men  and  17  mm.  in  women;  when  the  vocal  bands  are  tense 
27.5  and  20  mm.  respectively. 

The  width  of  the  vocal  bands  varies  from  2  to  5  millimeters.  Ex- 
ternal to  the  vocal  band  is  the  entrance  (rima  vestibuli)  to  the  sinus  of 
Morgagni  (S.  M.),  represented  by  a  dark  band.  Still  further  outward, 
and  on  a  higher  plane,  may  be  seen  the  fold  of  mucous  membrane  (plica 


FIG.  216. — Position  of  the  Laryngeal  Mirror  in  the  Practice  of 
Rhinoscopy. 


608  EXAMINATION    OF    THE    LARYNX. 

.ventricularis)  covering  the  false  vocal  band  or  the  ventricular  ligament 
(L.  v.  s.).  On  the  lower,  lip-shaped  border  of  the  entrance  to  the  larynx 
may  be  distinguished  the  posterior  lower  notch  of  the  ostium  pharyn- 
geum  laryngis  (above  P.);  and  on  either  side  of  this  the  apices  of  the  car- 
tilages of  Santorini  (5.  S.)  are  visible,  resting  on  the  apices  of  the  aryten- 
oid  cartilages;  immediately  behind  is  the  adjacent  pharyngeal  wall  (P.). 
In  the  ary-epiglottic  ligaments  (W .  W.)  are  the  cuneiform  cartilages  of 
Wrisberg,  and  finally,  external  to  these,  may  be  recognized  the  depres- 
sions of  the  sinus  piriformes  (5.  p.). 

Special  attention  should  be  given  to  the  condition  of  the  glottis  and 
the  vocal  bands  during  respiration  and  phonation.  During  quiet  respira- 
tion the  chink  of  the  glottis  (Fig.  213)  appears  as  a  lancet-shaped  slit, 
which  is  wider  during  life  than  in  the  cadaver.  If  deep  respirations  are 
taken,  the  chink  widens  considerably  (Fig.  215),  and  if  the  mirror  is 
favorably  placed,  it  may  be  possible  to  see  the  rings  of  the  trachea,  and 
even  the  bifurcation.  When  the  voice  is  produced,  the  glottis  closes 
each  time  to  a  narrow  slit  (Fig.  214). 

Appendix. — Rhinoscopy. — The  nasal  cavity  has  important  relations  to  speech 
and  to  respiration.  By  the  introduction  of  a  mirror  bent  at  an  angle,  with  the 

reflecting  surface  directed  upward,  it  is  pos- 
sible gradually  to  survey  a  field  such  as  is 
reproduced  in  Fig.  217. 

In  the  middle  appears  the  nasal  septum 
(5.  ».) ,  on  either  side  the  longitudinally  oval 
choanae  (CTt.),  and  further  below  the  soft 
palate  (P.  m.}  with  the  pendant  uvula  (£/.)• 
On  the  borders  of  the  choanal  openings  may 
be  recognized  the  posterior  portions  of  the 
inferior  (C.  i.),  middle  (C.  m.)  and  superior 
(C.  s.}  turbinated  bones,  with  the  corre- 
sponding nasal  meatus  beneath  each  one. 
Least  distinct  are  the  upper  turbinated  bone 
and  the  lower  meatus.  At  the  uppermost 
part  a  strip  of  the  roof  of  the  pharynx 
(O.  R.)  may  yet  be  seen,  with  the  more  or 
less  developed  pharyngeal  tonsil.  This 
s  !f  te,r  <rtn»tu«  is  composed  of.  lymphatic 

a  repeated  shifting  of  the  mirror  is  necessary      glandular  tissue,  and  extends  in  an  arch- 
in  order  to  obtain  the  entire  image  as  is  given      like  manner  over  the  roof  of  the  pharynx 

between  the  openings  of  the  two  Eustachian 
tubes  (T.  T.~).  External  to  the  mouth  of 
the  Eustachian  tube  on  each  side  is  the  so-called  tubal  eminence  (W.),  and  still 
more  external  the  fossa  of  Rosenmuller  (R.). 

For  the  study  of  the  larynx  experimentation  on  the  excised  larynx  is  further 
of  importance,  as  carried  out  by  Ferrein  in  1741  and  especially  by  Johannes 
Muller  in  1839.  The  latter  conducted  the  air  into  an  excised  human  larynx 
through  a  tracheal  tube  the  air-tension  of  which  was  measured  by  a  communicating 
mercurial  manometer.  The  bases  of  the  arytenoid  cartilages  were  held  in  a  fixed 
position  against  each  other  by  means  of  a  suture;  while  a  cord  passing  over  a 
pulley  and  carrying  weights  drew  the  thyroid  cartilage  forward.  By  increasing 
the  tension  the  tones  could  be  raised  about  z\  octaves.  When  the  tension  re- 
mained the  same,  stronger  blasts  of  air  raised  the  tone  to  the  fifth.  The  tone 
was  not  lowered  by  placing  tubes  over  the  larynx  to  increase  its  length,  but  these 
measures  modified  the  timbre  and  increased  the  resonance  of  the  note. 

Landois  employed  the  fresh,  living,  excised  larynx  from  the  dog  or  the  sheep; 
the  muscles  being  stimulated  by  various  pairs  of  electrodes,  while  a  bellows  supplied 
the  air  through  a  tracheal  tube.  In  this  way  the  most  reliable  information  con- 
cerning the  action  of  the  various  muscles  can  be  obtained. 

The  Rontgen  rays  have  recently  been  applied  with  success  to  the  study  of 
the  position  of  the  laryngeal  cartilages  and  the  hyoid  bone,  and  also  of  the  soft 
palate. 


THE    SOUNDS    OF    THE    VOCAL    APPARATUS.  609 

CONDITIONS  INFLUENCING  THE  SOUNDS  OF  THE  VOCAL 

APPARATUS. 

The  pitch  of  the  voice-tone  depends  upon  the  following  factors: 

1.  The  tension  of  the  vocal  bands;   hence  upon  the  degree  of  contrac- 
tion of  the  crico-thyroid  and  posterior  crico-arytenoid  muscles,  with  the 
assistance  of  the  vocal  or  internal  thyro-arytenoid  muscles. 

2.  The  length  of  the  vocal  bands.     In  this  connection  it  should  be 
noted:     (a)  That  children  and  women,  with  shorter  vocal  bands,  pro- 
duce higher  tones.     The  voices  of  women  are  about  one  octave  higher 
than  those  of  men.     (b)  If  the  arytenoid  cartilages  are  pressed  tightly 
together  by  the  action  of  the  transverse  and  oblique  posterior  arytenoid 
muscles,  so  that  only  the  vocal  bands  themselves  can  vibrate,  while  the 
intercartilaginous  parts  between  the  vocal  processes  cannot,  then  the 
tone  will  be  higher.     To  produce  deeper  tones,  the  vocal  bands,  and  also 
the  margins  of  the  arytenoid  cartilages,  must  vibrate.     At  the  same 
time  the  space  above  the  exit  of  the  larynx  enlarges,  so  that  the  throat 
becomes  more  prominent,     (c)  Each  individual  has  a  certain  medium 
pitch  of  voice,  which  corresponds  to  the  least  possible  muscular  tension 
within  the  larynx. 

3.  The  strength  of  the  blast.     That  the  strength  of  the  blast  is  able 
to  raise  the  pitch  of  the  tone  in  the  human  larynx  is  shown  by  the  fact 
that  the  highest  tones   can  be  emitted   only  in  a  loud  voice.     With 
medium  tones  the  air-tension  in  the  trachea  amounts  to  160  mm.,  with 
high  tones  to   200  mm.,  with  exceedingly  high  notes  to  945  mm.,  in 
whispering  only  to  30  mm.  of  water  measured  through  a  tracheal  fistula. 
In  changing  the  intensity  of  a  tone  from  loud  to  soft,  or  conversely, 
while  maintaining  the  same  note,  the  muscular  action  must  undergo 
a  change  in  force.     When  the  note  is  loud  the  force  diminishes,  while 
it  increases  as  the  tone  becomes  soft.     J.  Muller  called  this  process  the 
"compensation  of  energy  in  the  larynx." 

The  following  accessory  phenomena  have  been  observed  in  the  production  of 
high  notes,  but  no  certain  interpretation  of  them  has  been  given:  (a)  As  the  pitch 
of  the  note  increases,  the  larynx  becomes  elevated,  partly  because  the  elevating 
muscles  of  the  larynx  are  brought  into  activity,  and  partly  because  the  intra- 
tracheal  air-pressure  lengthens  the  trachea  to  such  an  extent  that  the  larynx  is 
raised  up.  The  uvula  also  is  raised  higher  and  higher.  (6)  The  upper  vocal 
bands  approach  each  other  more  and  more,  without  touching  or  participating  in 
the  vibrations,  (c)  The  epiglottis  inclines  more  and  more  backward  over  the 
glottis.  In  explanation  of  c  and  b  it  is  supposed  that,  in  the  production  of  high 
tones,  all  of  those  muscles  are  active  that  aid  in  shortening  the  vibrating  section 
of  the  rim  of  the  glottis  and  in  constricting  its  opening.  In  this  act  the  edge  of 
the  (external)  thyro-arytenoid  muscle  displaces  the  upper  vocal  band  inward; 
while  the  epiglottis  is  drawn  downward  by  those  fibers  that  pass  upward  toward 
it  laterally — the  thyro-ary-epiglottic  muscle. 

4.  So-called  registers  can  be  distinguished  in  the  voice.     There  is 
generally  the   chest-register,  the  thorax   vibrating   (pectoral   fremitus), 
and  the  voice  appearing  to  come  from  the  depths  of  the  chest ;   and  also 
the  head-register,  the  voice  apparently  coming  from  the  throat.     The 
latter,  with  its  soft  timbre  and  lack  of  resonance  in  the  air-tube,  is 
designated  also  a  falsetto  voice  or  shriek.     Oertel  observed  under  such 
circumstances  that  the  vocal  bands  vibrated  so  as  to  form  nodal  lines 
across  their  width;    at  times  only  one  nodal  line  is  formed,  so  that  the 
free  border  of  the  vocal  band  and  the  basal  border  vibrate,  and  are  sepa- 
rated from  each  other  by  a  nodal  line  parallel  to  the  edge  of  the  vocal 

39 


6io 


RANGE    OF    THE    VOICE. 


band.  In  high  falsetto  notes,  as  many  as  three  such  nodal  lines  may 
arise  in  succession.  The  formation  of  the  nodal  lines  must  be  occasioned 
by  a  partial  contraction  of  the  fibers  of  the  internal  thyro-arytenoid  mus- 
cle. At  the  same  time  the  vocal  bands  must  be  stretched  into  the  thinnest 
possible  plates  by  the  combined  action  of  the  crico-thyroid ,  posterior  ary- 
tenoid,  thyro-hyoid,  and  genio-hyoid  muscles.  The  glottis  is  elliptical  in 
form,  while  with  the  chest-voice  it  is  bounded  by  the  straight  lines  of 
the  vocal  bands.  In  the  latter  case  more  air  passes  out  of  the  larynx. 

Oertel  found,  moreover,  that  with  the  falsetto  voice  the  epiglottis  assumes  a 
vertical  position.  The  apices  of  the  arytenoid  cartilages  are  inclined  somewhat 
backward;  the  entire  larynx  appears  longer  in  its  sagittal  diameter  and  narrower  in 
its  transverse  diameter;  the  ary-epiglottic  folds  are  stretched  tensely,  with  sharp 
edges;  the  entrance  to  the  ventricles  of  Morgagni  is  constricted.  The  vocal 
bands  are  longer  than  in  the  production  of  the  same  tone  with  the  chest-voice; 
further,  they  are  narrower,  and  the  vocal  processes  are  in  contact  with  each  other. 
The  rotation  of  the  arytenoid  cartilages  necessary  for  this  is  brought  about  solely 
by  the  lateral  crico-arytenoid  muscle,  while  the  thyro-arytenoid  is  to  be  regarded 
only  as  an  accessory,  aiding  muscle.  Elevation  of  the  pitch  with  the  falsetto  voice 
is  effected  exclusively  by  increasing  the  tension  of  the  vocal  bands.  In  addition 
to  the  characteristic  modification  in  the  vibration  of  the  vocal  bands  already 
described,  still  another  series  of  partly  transverse  and  partly  longitudinal  partial 
vibrations  are  superposed  upon  the  former.  In  the  case  of  the  chest-voice  a 
narrower  edge  of  the  vocal  band  vibrates  than  in  that  of  the  falsetto  voice;  in 
the  production  of  the  latter  there  is  a  feeling  of  less  muscular  exertion  in  the 
larynx.  The  uvula  is  raised  horizontally.  In  the  so-called  chest-register  the 
entire  width  of  the  vocal  band  vibrates,  in  the  middle  register  only  the  inner 
narrower  border.  In  the  chest-voice  the  overtones  in  the  note  are  richest  and 
strongest,  while  in  the  falsetto  voice  they  are  less  numerous  and  feebler. 

Pathological. — By  means  of  Oertel's  laryngo-stroboscope  important  informa- 
tion can  be  obtained  concerning  variations  in  the  vibrations  of  the  vocal  bands, 
such  as  unequal  amplitude  of  vibration  in  the  two  vocal  bands  (laryngeal  catarrh) , 
with  or  without  alternating  vibrations;  the  formation  of  vibration-nodes  in  one 
band;  the  absence  of  vibrations  in  one  or  both  bands. 

In  order  that  the  voice  may  be  produced,  the  following  processes  are 
necessary :  ( i )  The  required  amount  of  air  is  accumulated  in  the  thorax ; 
(2)  the  larynx  and  its  parts  are  fixed  in  the  appropriate  position;  (3) 
then  follows  the  "onset"  of  the  voice,  either  the  closed  glottis  being 
forced  open  by  means  of  an  expiratory  effort,  or  some  air  being  per- 
mitted to  pass  almost  noiselessly  through  the  glottis,  and  the  vocal 
bands  being  then  thrown  into  vibration  as  the  blast  of  air  is  gradually 
increased. 

RANGE  OF  THE  VOICE. 

The  range  of  the  human  voice  for  the  chest -register  is  shown  in  the 
.accompanying  diagram: 

256  Soprano.  1024 

T 


171 


Alto. 


684 


E  F  G  A  B        c  d  e  f  g  a  b       c/  d'  ex  f f  v'  a'  b/ 


•fSfT-— 

aci 

_ 

W1                     HT 

T?                   1 

_^     |__ 

< 

3//d//e//f  //g//a/y  b//'c/// 

80                     Bass.                              342 

128 


Tenor. 


SPEECH.       THE    VOWELS.  6ll 

The  figures  indicate  the  number  of  vibrations  in  a  second  for  the 
corresponding  tone.  It  will  be  readily  seen  that  the  notes  from  c'  to 
f  are  common  to  all  voices;  nevertheless,  each  has. a  different  timbre. 
The  lowest  note,  which  exceptionally  is  sung  by  bass  singers,  is  the 
contra-F  with  only  42  vibrations;  the  highest  note  of  the  soprano  voice 
is  a'"  with  1708  vibrations. 

Hensen  devised  an  especially  ingenious  method  for  determining  with  exactness 
the  pitch  of  a  sung  note.  The  note  is  emitted  against  a  Konig's  capsule,  with 
a  gas-flame.  Opposite  this  is  a  tuning-fork,  vibrating  horizontally,  and  provided 
at  the  extremity  of  one  prong  with  a  mirror,  in  which  the  flame  is  reflected.  If 
the  pitch  of  the  voice  is  the  same  as  that  of  the  fork,  the  flame  appears  in  the 
mirror  as  a  single  jet;  at  the  octave  two  jets  appear,  at  the  twelfth  three  jets, 
and  at  the  double  octave  four. 

Each  individual  has  his  characteristic  voice-timbre,  which  depends 
upon  the  configuration  of  all  of  the  cavities  belonging  to  the  vocal 
organ.  The  so-called  palatal  tones  arise  from  the  approximation  of  the 
soft  palate  to  the  posterior  pharyngeal  wall.  In  the  production  of  nasal 
tones  the  air  in  the  nasal  cavities  vibrates  more  forcibly,  as  access  to 
these  cavities  must  be  freer. 


SPEECH.     THE  VOWELS. 

The  motor  processes  concerned  in  speech  are  carried  out  in  the 
reinforcing  tube — the  pharyngeal,  oral,  and  nasal  cavities;  they  are 
directed  toward  the  production  of  tones  and  noises.  If  the  latter  alone 
are  developed,  the  voice-apparatus  being  passive,  "whispering"  results 
(vox  clandestina) ;  if,  however,  the  vocal  bands  vibrate  at  the  same 
time,  "audible  speech"  results.  Whispering  itself  may  be  made  quite 
loud,  but  to  bring  about  this  result  a  strong  blast  is  required;  hence  it 
is  fatiguing.  It  can  be  practised  during  both  inspiration  and  expira- 
tion, in  contradistinction  to  audible  speech,  which  sounds  transient 
and  indistinct  when  produced  during  inspiration.  Whispering  results 
from  the  sound  that  is  generated,  when  the  glottis  is  moderately  nar- 
rowed, by  the  passage  of  the  air  over  the  blunt  margins  of  the  vocal 
bands.  In  the  production  of  audible  speech  the  vocal  processes  are  so 
placed  that  the  sharp  margins  of  the  vocal  bands  are  directed  toward 
the  air-current,  and  are  thrown  into  vibration  by  it. 

The  soft  palate  always  participates  in  the  production  of  speech.  It  is  raised 
with  every  word,  Passavant's  transverse  ridge  being  at  the  same  time  formed 
in  the  pharynx.  The  palate  is  raised  highest  during  the  utterance  of  u  (oo)  and 
i  (ee) ;  less  high  with  o  and  e  (a) ,  and  least  high  with  a  (ah) .  During  the  enuncia- 
tion of  in  and  n  the  palate  is  stationary;  with  the  explosives  it  is  about  as  high 
as  with  n;  and  it  is  lower  with  the  fricatives.  With  /,  s,  and  especially  with  the 
guttural  r,  it  is  thrown  into  a  tremulous  movement. 

Speech  is  made  up  of  vowels  and  consonants. 

Vowels. — (Analysis   and  artificial  formation  are  considered  on  page 

9°5-) 

In  whispering,  a  vowel  is  the  sound  produced,  during  either  expira- 
tion or  inspiration,  by  the  inflated  characteristically  shaped  oral  cavity, 
the  sound  having  not  only  a  definite  pitch,  but  also  a  characteristic 
timbre.  The  characteristically  shaped  oral  cavity  may  be  designated 
the  "vowel-cavity." 


6i2  SPEECH.       THE    VOWELS. 

The  pitch  of  the  vowels  may  be  determined  musically,  either  by  paying  close 
attention  to  one's  own  whispered  vowels,  or  in  the  case  of  another  by  blowing 
by  means  of  a  suitable  air-tube  from  the  opening  of  the  mouth  into  its  cavity 
placed  in  the  position  peculiar  to  the  vowel  in  question.  It  is  a  remarkable  fact 
that  the  fundamental  tone  of  the  "vowel-cavity"  is  almost  constant  for  various 
ages  and  sexes.  The  differences  in  the  internal  capacity  of  the  mouth  can  be  com- 
pensated for  by  varying  the  size  of  the  opening  of  the  mouth.  The  pitch  of  the 
vowel-cavity  may  also  be  estimated  by  holding  a  series  of  vibrating  tuning-forks  of 
varying  pitch  in  front  of  the  mouth.  When  the  one  is  found  that  corresponds 
with  the  fundamental  tone  of  the  vowel-cavity,  the  note  of  the  tuning-fork  will 
be  strengthened  considerably  by  resonance  from  the  oral  cavity.  Finally,  a  mem- 
brane having  the  same  'rate  of  vibration  as  the  vowel-tone  may  be  held  in  front 
of  the  mouth,  and  the  vibrations  of  the  vowel-tone  may  be  transferred  to  the 
membrane,  the  vibrations  of  the  latter  being  recorded  on  smoked  paper,  as  in 
the  "  phonautograph  "  of  Bonders. 

Konig  found  the  fundamental  tones  of  the  vowel-cavities  to  be  as 
follows:     U  (oo)=b,    O  =  b',  A   (ah)  ==  b",  E    (a)  =  b'",  I    (ee)    = 
b"". 

If  the  vowels  be  whispered  in  this  series,  their  pitch  will  at  once  be 
heard  to  increase.  Otherwise,  these  fundamental  tones  of  the  mouth 
in  the  vowel-positions  may  vary  within  certain  limits ;  hence  it  is  better 
to  speak  of  the  region  of  a  characteristic  tone-position.  This  may  be 
best  demonstrated  by  placing  the  mouth  in  the  characteristic  position 
and  percussing  the  cheeks.  The  sound  of  the  vowel  will  then  be  heard, 
and  its  pitch  will  vary  within  certain  limits  in  accordance  with  the 
position  of  the  mouth. 

In  pronouncing  A  (ah),  the  mouth  has  the  shape  of  a  funnel  dilating 
anteriorly  (Fig.  218,  A).  The  tongue  lies  on  the  floor  of  the  mouth; 
the  lips  are  wide  open.  The  soft  palate  is  raised  moderately;  being 
successively  more  elevated  with  O,  E  (a),  U  (oo),  I  (ee).  The  hyoid  bone 
is  in  a  position  of  rest  when  A  (ah)  is  being  uttered;  but  the  larynx  is 
somewhat  raised,  being  higher  than  with  U  (oo),  but  lower  than  with 
I  (ee). 

When  a  transition  is  made  from  A  (ah)  to  I  (ee),  the  larynx  and  the  hyoid 
bone  retain  their  relative  positions,  but  both  ascend.  During  the  transition  from 
A  (ah)  to  U  (oo),  the  larynx  sinks  to  the  lowest  possible  level.  At  the  same 
time  the  hyoid  bone  moves  slightly  forward.  In  pronouncing  A  (ah),  the  space 
between  the  larynx,  the  posterior  pharyngeal  wall,  the  soft  palate  and  the  root 
of  the  tongue  is  only  moderately  dilated;  it  becomes  larger  with  E  (a)  and  espe- 
cially with  I  (ee) ,  and  is  smallest  with  U  (oo) . 

In  sounding  U  (oo),the  shape  of  the  mouth  is  that  of  a  capacious 
flask  with  a  short,  narrow  neck.  The  entire  reinforcing  tube  is  under 
such  conditions  longest.  Accordingly,  the  lips  are  protruded  as  far  as 
possible,  are  corrugated,  and  are  brought  together  so  as  to  form  a  small 
opening.  The  larynx  is  at  its  lowest  level.  The  root  of  the  tongue 
is  approximated  to  the  posterior  palatine  arch. 

In  sounding  0,  the  mouth,  as  with  U  (oo),  resembles  a  wide-bellied 
flask  with  a  short  neck.  The  latter,  however,  is  shorter  and  at  the  same 
time  more  widely  open,  the  lips  approaching  more  closely  to  the  teeth. 
The  larynx  is  somewhat  higher  than  with  U  (oo).  The  entire  reinforcing 
tube  is,  therefore,  shorter  than  with  U  (oo). 

In  sounding  /  (ee),  the  mouth  has  the  shape  of  a  flask  with  a  small 
belly  in  the  posterior  part,  and  a  long,  narrow  neck.  The  belly  has 
the  fundamental  tone  f ,  while  the  neck  has  that  of  d"".  The  reinforcing 
tube  is  shortest  with  I  (ee),  as  the  larynx  is  raised  as  far  as  possible,  and 


SPEECH.       THE    VOWELS. 


the  mouth  is  bounded  anteriorly  by  the  teeth,  the  lips  being  retracted. 
The  oral  canal  between  the  hard  palate  and  the  back  of  the  tongue  is 
greatly  constricted  to  a  median,  narrow  channel.  Hence,  the  air  can 
pass  through  only  with  a  clear,  whistling  sound,  and  even  the  vertex 
of  the  skull  may  be  set  into  perceptible  vibration;  if  the  ears  are  stopped 
up,  a  shrill  sound  may  be  audible  in  them.  It  is  impossible  to  pro- 
nounce I  (ee)  when  the  larynx  is  depressed  and  also  when  the  lips  are 
protruded,  as  for  U(oo). 

In  pronouncing  E  (a),  which  stands  next  to  I  (ee),  the  cavity  has 
likewise  the  form  of  a  flask  with  a  small  belly  (fundamental  tone  f) 
and  a  long,  narrow  neck  (fundamental  tone  b'").  The  neck,  however, 
is  wider,  so  that  it  does  not  give  rise  to  a  whistling  sound.  The  larynx 
is  somewhat  lower  for  E  (a)  than  for  I  (ee),  but  higher  than  for  A  (ah). 

Fundamentally,  Briicke  is  right  in  assuming  that  there  are  only  three  funda- 
mental vowels,  namely  /  (ee),  A  (ah),  U  (oo),  between  which  the  others,  as  well 
as  the  so-called  diphthongs,  are  interpolated.  The  hieroglyphic,  Indian,  old 
Hebraic,  and  Gothic  writings  contain  only  these  three  vowels. 


2 


FIG.  218.— Sagittal  Section  through  the  Human  Larynx  in  the  Vowel-positions  A  (ah),  I  (ee)  and  U  (oo) :  Z,  tongue; 
p,  soft  palate;  e,  epiglottis;  #,  glottis;  h,  hyoid  bone;  i,  thyroid  cartilage;  2,  3,  cricoid  cartilage;  4,  arytenoid 
cartilage. 


Diphthongs  occur  during  the  utterance  of  a  sound,  by  passing  from 
the  position  of  one  vowel  into  that  of  another.  Distinct  diphthongs 
are  sounded  only  on  passing  from  a  vowel  with  a  wider  oral  opening 
to  one  with  a  narrower  opening;  if  the  reverse  occurs,  the  vowels  appear 
separated  to  the  ears. 

Landois  was  especially  successful  in  producing  the  vowels  artificially.  In 
the  two  halves  of  a  head  sawn  through  in  a  sagittal  plane  he  arranged  all  of  the 
parts  in  the  positions  that  they  would  have  to  assume  in  enunciating  a  certain 
vowel,  and  then  the  entire  space  from  the  trachea  to  the  lips  was  filled  with  paraffin. 
Both  halves  were  then  welded  together.  A  paraffin  cast  was  thus  obtained  of 
the  vowel-cavity.  The  cast  was  covered  with  plaster-of- Paris,  and  then  the 
paraffin  was  removed  by  melting.  In  this  way  a  plaster  reproduction  of  the 
vowel-cavity  was  obtained.  A  vocal  apparatus  was  then  introduced  into  the 
trachea  from  below.  This  apparatus  was  made  of  a  thin,  ivory  reed,  set  in  a 
wide  frame,  and  having  its  pitch  accurately  adjusted  to  the  fundamental  tone 
of  the  plaster  cavity.  All  the  vowels,  even  I  (ee),  were  thus  produced  with  sur- 
prising success. 

In  addition  to  the  pitch  the  characteristic  timbre,  or  tone-color,  of 
the  vowel  is  worthy  of  notice.  In  this  connection  the  mouth,  charac- 
teristically shaped  for  the.  utterance  of  a  vowel,  may  be  compared  to  a 


614  SPEECH.       THE    VOWELS. 

musical  instrument,  which  not  only  gives  forth  its  sound  in  a  certain 
pitch,  but  also  allows  it  to  ring  with  a  characteristic  timbre. 

Thus,  the  vowel-sound  U  (oo),  when  whispered,  has,  besides  its  fundamental 
tone  b,  a'soft,  whistling  timbre;  I  (ee),  with  its  fundamental  tone  b"",  a  hissing, 
whistling  timbre;  A,  with  its  tone  b",  an  open,  blowing  timbre.  This  timbre 
depends  upon  the  number  and  the  pitch  of  the  overtones  peculiar  to  the  vowel- 
sound,  which  are  considered  in  the  section  on  analysis  of  the  vowels  (auditory 
apparatus,  p.  905). 

The  timbre  of  the  vowels  may,  further,  be  modified  in  a  special 
manner  when  they  are  uttered  with  a  "nasal"  twang,  as  is  prevalent 
in  the  French  language.  The  nasal  timbre  is  produced  when  the  soft 
palate  does  not  close  off  the  nasal  cavity,  as  happens  during  utterance 
of  the  pure  vowels,  so  that  the  air  in  the  nasal  cavity  is  set  into  sym- 
pathetic vibration.  When  a  vowel  is  spoken  with  a  nasal  timbre,  the 
air  thus  escapes  through  both  the  mouth  and  the  nose ;  when  the  vowel 
is  spoken  purely,  the  air  escapes  only  through  the  mouth.  Hence r 
in  the  former  case,  a  light  held  in  front  of  the  nostrils  will  flicker,  or  a 
cold  glass  or  metal  will  be  moistened;  but  not  in  the  latter  case. 

In  closure  of  the  nasal  cavity  the  soft  palate  is  raised,  in  smallest  measure 
when  A  (ah)  is  pronounced;  then  follow  O,  E  (a),  U  (oo),  I  (ee).  High  and 
loud  tones  require  more  marked  elevation,  during  which  the  velum  presents  a 
notch  in  the  situation  of  the  elevators  of  the  palate.  The  opening  of  the  Eusta- 
chian  tube  is  constricted,  but  never  entirely  closed,  by  the  elevation  of  the  palate. 

In  uttering  the  pure,  non -nasal  vowels,  the  nasal  cavity  is  so  firmly  closed 
off  from  the  mouth  that  it  can  be  sprung  open  only  by  an  artificial  increase  in 
the  pressure  within  the  nose  of  from  30  to  100  mm.  of  mercury,  with  the  develop- 
ment of  a  gurgling  rhonchal  sound. 

The  nasal  twang  occurs  as  a  result  of  resonance  in  the  naso-pharyngeal  cavity ; 
at  the  same  time  a  portion  of  the  cavity  of  the  mouth  is  excluded  by  elevation 
of  the  dorsum  of  the  tongue  and  depression  of  the  palate. 

Especially  the  vowels  a  (ah),  a  (&),  6  (ce),  o,  e  (a),  are  employed 
with  a  nasal  accent.  The  nasal  i  (ee),  however,  does  not  appear  to  occur 
in  any  language.  At  all  events  it  is  hard  to  form,  because  in  sounding 
it  the  oral  canal  is  so  narrow  that  if  the  nasal  cavity  be  open  at  the  same 
time  the  air  will  escape  almost  completely  through  the  latter,  while 
the  small  amount  passing  through  the  mouth  is  hardly  sufficient  to 
produce  a  sound. 

In  pronouncing  the  vowels  it  should  also  be  observed  whether  they 
are  uttered  through  a  previously  closed  glottis,  as  is  the  case  in  German 
with  all  vowels  placed  at  the  beginning  of  words.  Thus,  the  glottis 
is  at  first  closed,  but  it  is  sprung  open  simultaneously  with  the  intona- 
tion at  the  moment  of  commencing  the  word.  Pronunciation  of  vowels 
in  this  manner  was  termed  by  the  Greeks  spiritus  lenis.  If,  however, 
the  vowel  is  pronounced  after  a  preliminary  breath  has  passed  through 
the  open  glottis,  and  the  sound  of  the  vowel  follows  immediately,  then 
the  aspirate  vowel  results,  corresponding  to  the  spiritus  asper  of  the 
Greeks. 

If  the  vowels  are  pronounced  audibly,  therefore  with  a  simultaneous 
sound  of  the  voice,  the  fundamental  tone  of  the  vowel-cavity,  with  its 
constant,  absolute  pitch,  strengthens  in  a  characteristic  manner  the 
corresponding  partial  tone  present  in  the  sound  of  the  voice.  Accord- 
ingly, the  vowels  are  intonated  most  purely  from  a  musical  point  of 
view  when  the  pitch  of  the  tone  is  so  adjusted  as  to  contain  overtones 


THE    CONSONANTS.  615 

that  correspond  harmonically  with  the  fundamental  tone  of  the  vowel- 
cavity  when  blown  upon. 

THE  CONSONANTS. 

The  consonants  are  noises  that  are  generated  at  certain  parts  of 
the  reinforcing  tube.  They  are  classified  as  follows:  I.  According 
to  their  acoustic  properties  into  (i)  sounding  or  liquid  consonants,  that 
is  those  that  are  audible  even  without  vowels  (m,  n,  I,  r,  s);  (2)  mutes, 
including  all  the  rest,  which  cannot  be  distinctly  heard  without  the 
simultaneous  pronunciation  of  a  vowel.  II.  According  to  the  mechan- 
ism of  their  formation,  as  well  as  the  parts  of  the  speech-apparatus  by 
which  they  are  produced. 

1.  Mutes,  stops,  checks,  or  explosives,  the  air  being  forced  through  an 
existing  closure,  with  the  production  of  more  or  less  noise;    or,  con- 
versely, the  current  of  air  may  be  suddenly  interrupted,  while  at  the 
same  time  the  nasal  cavity  is  closed  off  by  elevation  of  the  soft  palate. 

2.  Fricatives  or  spirants  or  sibilants,  the  canal  being  constricted  at 
one  point,  so  that  the  air  is  forced  through  with  a  hissing  noise,  while 
the  nasal  cavity  is  closed  off. 

L  and  similar  .consonants  are  closely  related  to  the  fricatives,  differ- 
ing, however,  from  these  in  that  the  narrow  passage  through  which  the 
air  is  forced  is  not  situated  in  the  middle  line,  but  to  either  side  of  the 
closed  middle.  The  nasal  cavity  is  closed  off. 

3.  Vibratives,  which  result  when  air  is  forced  through  a  narrow  part  of 
the  canal,  so  that  the  margins  of  the  constriction  are  thrown  into  vibra- 
tion.    The  nasal  cavity  is  closed  off. 

4.  Resonants,  also  designated  nasals  or  semi-vowels.     The  nasal  cavity 
is  entirely  open,  but  the  mouth  is  tightly  closed  anteriorly  at  one  point. 
In  accordance  with  the  position  of  this  closure  of  the  mouth,  the  air  in  a 
larger  or  smaller  portion  of  the  oral  cavity  may  be  set  into  sympathetic 
vibration. 

In  addition  to  these  possible  forms  of  origin  of  the  sounds  the  points 
at  which  they  may  be  produced  must  be  taken  into  consideration.  These 
points  may  be  designated  articulation-positions.  They  are:  A,  between 
the  lips;  B,  between  the  tongue  and  the  hard  palate;  C,  between  the 
tongue  and  the  soft  palate;  D,  between  both  true  vocal  bands. 

(A)  Consonants  of  the  First  Articulation-position. 

1 .  Explosive  Labials. — 6  (bay) :  the  voice  is  sounded  before  the  soft 
explosion  occurs ;  p  (pay) :  the  voice  is  sounded  only  after  the  much 
stronger  explosion  has  taken  place. 

2.  Fricative  Labials. — /:  between  the  upper  incisor  teeth   and  the 
lower  lip  (labio-dental) ;  it  is  absent  from  all  true  slavic  words  \v  (fow) : 
between  the  two    lips   (labial);   w   (vay):    results  when  the  mouth  is 
adjusted  as  for  /  (labial,  as  well  as  labio-dental),  but  instead  of  merely 
blowing  air  out,  the  voice  is  also  sounded.     There  are  really  two  different 
forms  of  w  (vay),  namely,  one  corresponding  to  the  labial  /,  as  in  Wurde 
(pronounced  veerde) ,  and  the  labio-dental,  as  in  Quelle  (pronounced  kwelle) . 

3.  Vibrative  Labials. — The  "burring"  sound  of  drivers, not  employed 
in  civilized  languages. 

4.  Resonant  Labial. — m  is  formed  when  the  voice  is  sounded,  and  the 
air  in  the  oral  and  nasal  cavities  is  thrown  into  resonance. 


6l6  THE    CONSONANTS. 

(B)  Consonants  of  the  Second  Articulation-position. 
Method. — In  order  to  determine  the  extent  to  which  the  tongue  and  the 
palate  are  in  contact  in  the  formation  of  consonants  in  the  second  and  third  articu- 
lation positions,  the  tongue  is  sprinkled  with  a  powdered  dye,  while  the  mouth  is  held 
wide  open.  When  the  consonant  is  formed,  the  palate  receives  a  colored  impres- 
sion at  those  points  where  contact  has  taken  place.  Also  in  the  case  of  the  con- 
sonants, with  the  exception  of  m,  n,  ng,  the  soft  palate  is  elevated. 

1.  The  explosives,  which  are  produced  between  the  tongue  and  the 
hard  roof  of  the  oral   cavity,  are  the   hard  7^-sounds  (also  dt    and  tt), 
when    enunciated    sharply  and  without    the  voice;   the   soft  .D-sounds 
when  uttered  softly  with  simultaneous  intonation  of  the  voice.     Vari- 
ously designated  and  uttered  modifications  of  these  consonants  occur  in 
various  languages,  accordingly  as  the  tip  or  the  back  of  the  tongue,  on 
the  one  hand,  and  the  teeth  or  the  alveolar  process  or  the  hard  palate,  on 
the  other  hand,  are  employed  in  their  formation. 

2.  The  fricatives  embrace  the  consonants   allied  to  5,  including  the 
sharp  s  (also  written  55  and  sz),  which  is  produced  without  the  sound  of 
the  voice,  and  the  soft  s,  which  can  be  produced  only  with  intonation  of 
the  voice.     Modifications  occur  also  here,  in  accordance  with  the  regions 
between  which  the  aspirate  consonant   is  formed.     Thus,  to  the  sharp 
aspirates  belong  also  the  sharp  Sch  and  the  hard   English  Th;  to  the 
soft  aspirates  the  soft  French  J  and  the  soft  English  Th.     The  sound  L 
likewise   belongs  to  this   class,-  occurring  in  manifold  modifications  in 
various  tongues,  for  example  the  soft  L  of  the  French.     The  sound  L 
may  also  be  uttered  softly  with  the  voice,  or  sharply  without  it. 

3.  The  vibratives  of  the  second  articulation-position,  or  the  lingual 
^-sounds,  are  usually  enunciated  with  the  sound  of  the  voice,  although 
they  may  also  be  formed  without  it. 

4.  The  resonants   are  the   A7-sounds,  which  likewise   may  occur  in 
various  modifications. 

(C)  Consonants  of  the  Third  Articulation-position. 

1.  The  explosives  are  the  AT-sounds,  if  hard  and  without  the  sound 
of  the  voice;  or  the  ^-sounds  (gay),  if  the  voice  is  also  given.     There 
are  various  modifications  of  both;  for  example,  the  explosive  position  of 
G  (gay)  and  K  preceding  e  (a)  and  i  (ee)  is  situated  farther  forward  on 
the  palate  than  that  of  G  (gay)  and  K  before  a  (ah),  o,  u  (oo). 

2.  The  aspirates  of  these  positions  are  the  CTz-sounds,  hard  and  with- 
out the  voice ;  and  J  (y),  if  soft  and  without  the  voice.     Following  a  (ah), 
o,  u  (oo),  these  consonants  are  formed  farther  back  on  the  palate  than 
those  that  follow  e  (a)  and  i  (ee). 

3.  The  vibrative  is  the  palatal  R,  which  results  from  vibration  of  the 
uvula. 

4.  The  resonant  is  the  palatal  N.     After  e  (a)  and  i  (ee)  the  closure  is 
displaced  further  forward,  after  a  (ah),  o,  u  (oo),  further  back.     The 
nasal  N  of  the  French  is,  however,  not  a  consonant  at  all,  but  only  the 
nasal  timbre  of  the  vowel  that  results  from  the  patulousness  of  the  nasal 
cavity. 

According  to  Saenger  the  participation  of  the  nasal  cavities  in  the  production 
of  m,  n,  and  ng  consists  chiefly  in  affording  a  passage  for  the  air  expired  during 
phonation. 


PATHOLOGICAL    VARIATION    IN    VOICE    AND    SPEECH.  617 

(D)  Consonants  of  the  Fourth  Articulation-position. 
Logically,  the  glottis  itself  may  further  be  considered  as  a  fourth 
articulation-position . 

1.  An  explosive  consonant  is  not  produced  by  forcing  open  the  glottis, 
if  a  vowel  has  been  loudly  intonated  from  a  previously  closed  glottis. 
If  this  occurs  during  whispering,  a  feeble,  short  sound  may  undoubtedly 
be  heard,  arising  from  the  sudden  opening  of  the  glottis.     As  already 
noted,  the  Greeks  applied  the  term  spiritus  lenis  to  the   utterance  of 
vowels  from  a  previously  closed  glottis. 

2.  The  aspirates  of  the  glottis  are  represented  by  the  //-sound  (hah), 
which  is  produced  with  a  moderately  wide  glottis.     The  Arabic  Hha  is 
emitted  with  especial  sharpness  from  a  still  narrower  glottis. 

3.  A  glottis -vibrative  occurs  in  the  so-called  laryngeal  R  of  lower 
Saxony,  and  in  the  Arabic  Ain.     It  can  be  produced  by  pronouncing  a 
vowel  with  the  deepest  possible  voice.     This  is  followed  by  a  distinct, 
shock-like,  resounding  vibration  of  the  vocal  bands,  which  represents  the 
laryngeal  -R.     The  sound  is  represented  especially  in  the  low  German 
dialect  of  Hither  Pomerania,  for  example  in  Coarl  (Carl),  Wuort  (Wort). 

4.  A  laryngeal  resonant  cannot  be  produced. 

The  combination  of  different  consonants  is  accomplished  by  the  rapid, 
successive  execution  of  the  movements  necessary  for  each  one.  Com- 
pound consonants  are  those  that  are  formed  by  adjusting  the  parts  of  the 
mouth  for  two  different  consonants  at  the  same  time,  so  that  a  mixed 
sound  is  formed  from  the  simultaneous  production  of  both  sounds.  Ex- 
amples: Sch,  tsch,  tz,  ts,  Ps  (0),  Ks  (X,  c). 


PATHOLOGICAL  VARIATION  IN  VOICE  AND  SPEECH. 

Paralysis  of  the  motor  nerves  of  the  larynx  (from  the  vagus)  as  a  result  of 
wounds  or  of  pressure  by  tumors  results  in  loss  of  voice  or  aphonia.  In  the 
presence  of  aneurysm  of  the  arch  of  the  aorta  the  left  recurrent  laryngeal  nerve 
is  often  paralyzed  in  consequence  of  being  greatly  stretched.  Rheumatism,  over- 
exertion,  and  hysteria  may  cause  transitory  paralysis  of  the  laryngeal  nerves. 
Serous  effusions  into  the  laryngeal  muscles  in  con- 
sequence of  inflammatory  processes  will  also  cause 
paralysis  of  these  muscles  and  thus  aphonia.  If 
the  tensors  chiefly  are  paralyzed,  monotonia  of 
the  voice  develops.  The  disturbances  of  respira- 
tion attending  paralysis  of  the  larynx  are  worthy 
of  special  notice.  There  may  be  no  disturbance 
so  long  as  the  respiration  is  quiet,  but  as  soon  as 
the  respiration  becomes  more  active,  a  high  de- 
gree of  dyspnea,  such  as  Landois  has  observed 
also  in  dogs,  may  set  in,  owing  to  the  inability  to 
dilate  the  glottis. 

If  only  one  vocal  band  is  paralyzed,  the  voice      FIG.  219. — Tumors  of  the  Vocal  Cords, 
becomes  impure   and  falsetto-like.     The  dimin- 
ished vibration  on  the  paralyzed  side  of  the  larynx 

may  even  be  felt  externally,  but  it  may  be  still  better  recognized  by  means  of  the 
sensitive  flame.  It  has  been  observed  that  unequal  tension,  from  unequal  innervation 
of  the  tensor-muscles,  may  give  rise  to  alternating  vibrations  of  the  two  bands, 
with  opposite  phases  of  movement.  At  times  the  vocal  bands  are  paralyzed  only 
to  such  an  extent  as  not  to  move  during  phonation,  but  only  on  forced  respiration 
and  on  coughing  (phonetic  paralysis).  Mogiphonia,  or  premature  fatigue  of  the 
voice,  is  the  name  given  by  Frankel  to  a  condition  of  paralysis  of  the  laryngeal 
musculature  that  consists  in  failure  of  certain  coordinated  movements  that  have 
been  acquired  by  practice.  This  corresponds  to  the  paralytic  form  of  writer's 
cramp. 


618  COMPARATIVE.        HISTORICAL. 

Incomplete,  unilateral  paralysis  of  the  recurrent  laryngeal  nerve  results  at 
times  in  double  tone  (diphthongia)  of  the  voice,  on  account  of  the  unequal  tension 
of  the  two  vocal  bands.  According  to  Tiirck  and  Schnitzler,  diphthongia  may 
develop  also  when  the  vocal  bands  are  in  contact  at  one  point  in  their  course 
(perhaps  by  reason  of  deposits  or  tumors) ,  so  that  the  glottis  is  divided  into  two 
sections,  each  of  which  produces  the  sound  of  the  voice  in  a  different  pitch.  If 
the  glottis  is  suddenly  closed  by  muscular  spasm  while  the  voice  is  being  sounded, 
the  rare  condition  of  spastic  aphonia  results.  In  tabetic  patients  ataxic  phenom- 
ena have  been  observed  occasionally  in  the  laryngeal  musculature.  Hoarseness  is 
caused  by  accumulation  of  mucus  on  the  vocal  bands,  or  by  roughness,  swelling, 
or  relaxation  of  the  bands.  If  the  bands  suddenly  come  in  contact  while  closely 
approximated  during  speaking,  the  voice  "breaks,"  on  account  of  the  formation 
of  nodal  points. 

Diseases  of  the  pharynx,  nasopharynx,  and  uvula  may  cause  reflex  nervous 
disturbances  of  the  voice. 

The  reestablishment  of  audible  voice  and  speech  has  been  observed  even 
after  total  extirpation  of  the  larynx,  the  individual  breathing  through  a  tracheal 
tube  and  no  air  escaping  through  the  cavity  of  the  mouth.  The  subject  under 
such  circumstances  fills  with  air  the  cavity  left  by  the  removal  of  the  larynx, 
and  forces  the  air  through  a  narrowed  space  above  into  the  cavity  of  the  mouth, 
thus  producing  a  monotonous  sound  of  stenosis  that  is  remarkably  like  the  voice. 

Paralysis  of  the  soft  palate,  as  well  as  perforation  or  congenital  fissure,  gives 
a  nasal  timbre  to  all  vowels;  the  former  also  causes  difficulty  in  the  normal  forma- 
tion of  consonants  of  the  third  articulation-position.  The  resonants  are  well 
marked,  while  the  explosives  are  enfeebled,  on  account  of  the  escape  of  air  through 
the  nose. 

Paralysis  of  the  tongue  causes  difficulty  in  the  pronunciation  of  I  (ee) ;  E  (a) , 
and  A  (ah)  also  are  less  easily  pronounced.  In  addition,  the  formation  of  con- 
sonants of  the  second  and  third  articulation-positions  is  disturbed.  However, 
persons  having  even  considerable  defects  of  the  tongue  have  reacquired  intelligible 
speech.  Aphthongia  is  that  condition  in  which  each  attempt  to  speak  results 
in  spasmodic  movements  of  the  tongue. 

In  the  presence  of  paralysis  of  the  lips  (facial  nerve)  the  extent  to  which  the 
consonants  of  the  first  articulation-position  can  be  pronounced  should  be  observed. 
Hare-lip  also  must  be  taken  into  consideration  in  this  connection.  In  case  of  nasal 
obstruction  speech  assumes  the  so-called  "obstructed  oral  tone."  The  formation  of 
the  resonants  in  the  normal  way  is  prevented.  After  extirpation  of  the  larynx, 
an  artificial  larynx  has  been  inserted  between  the  trachea  and  the  mouth,  con- 
sisting of  a  metallic  reed  in  a  tube.  All  disturbances  in  the  formation  of  conso- 
nants may  be  designated  as  "stammering"  (dysarthria  litteralis).  Speech-de- 
rangements of  cerebral  origin  are  considered  on  p.  796. 


COMPARATIVE.     HISTORICAL. 

Speech  may  be  included  among  the  "movements  of  expression."  Psychic 
excitement  arouses  in  man  characteristic  movements,  in  which  special  groups  of 
muscles  constantly  participate ;  for  example  laughing,  crying,  facial  expression,  and 
gestures  in  fear,  anger,  shame,  discouragement,  ambition,  disgust,  abhorrence,  desire, 
joy,  merriment,  etc.  Such  movements  constitute  a  medium  by  means  of  which 
related  beings  are  enabled  to  communicate  their  inner  thoughts  to  one  another. 
In  their  origin  these  movements  of  expression  are  reflex  motor  phenomena;  but 
when  reproduced  for  purposes  of  explanation,  they  are  voluntary  imitations  of 
these  reflexes.  In  addition  to  emotional  movements,  impressions  on  the  sense- 
organs  also  call  forth  characteristic  reflexes,  which  are  converted  into  movements 
of  expression;  for  example,  stroking  or  painful  stimulation  of  the  skin,  movements 
following  the  perception  of  pleasant  or  unpleasant  odors,  likewise  the  influence 
of  sound,  also  of  light  (bright  or  dark,  and  of  colors),  and  the  perception  of  objects 
of  all  kinds. 

In  their  simplest  form  movements  of  expression  are  manifested  in  sign- 
language.  In  a  narrower  sense  speech  may  be  designated  as  "sound-pantomime," 
the  accompanying  motor  phenomena  often  taking  the  form  of  facial  expression 
and  gesture.  Thus,  articulate  sound  is  caused,  in  the  first  place,  by  characteristic, 
reflex  motor 'phenomena  in  the  speech-forming  organs. 

A  second  means  of  expression  lies  in  the  imitation  of  sound-phenomena  by 


COMPARATIVE.       HISTORICAL.  619 

the  organ  of  speech  (onomatopoesis) ;  for  example  the  hissing  of  flowing  water, 
the  roaring  of  the  storm,  the  rolling  of  thunder,  ringing,  howling,  whistling,  etc, 
If  a  further  attempt  is  made  to  transform  impressions  depending  on  excitation 
of  other  senses  into  somewhat  corresponding  sound-perceptions,  the  term  indirect 
onomatopoesis  may  be  employed;  for  example  the  attempt  to  represent  a  sudden 
stab  or  a  blinding  flash  of  lightning  by  a  short,  shrill,  whistling  sound  (Heise's 
principle  of  sound-metaphor). 

Therefore,  the  primitive  speech  of  man  may  have  been  a  series  of  reflex  sound- 
pantomimes  and  onomatopoetic  imitations. 

Moreover,  expression  in  language  is  naturally  related  to  the  process  of  apper- 
ception. No  idea  can  be  expressed  in  language  or  gesture  unless  it  be  first  apper- 
ceived,  that  is  raised  from  the  mass  of  ideas  that  fill  the  conscious  mind  to  the 
psychic  view-point. 

Many  different  sounds  occur  in  the  various  languages.  Some  tongues,  for 
example  that  of  the  Hurons,  have  no  labials;  on  some  South  Sea  Islands  no  laryn- 
geal  consonants  are  spoken;  f  is  wanting  in  Sanskrit,  Finnish,  etc. ;  the  short  e  (a), 
o,  and  the  soft  sibilants  in  Sanskrit;  d  in  Chinese  and  Mexican;  s  in  many  Poly- 
nesian tongues,  r  in  Chinese;  etc. 

Movements  of  expression  occur  also  among  animals,  especially  the  higher 
ones.  The  vocal  organ  of  mammals  is  essentially  like  that  of  man.  In  some 
apes  (orang-outang,  mandril,  pavian,  macacus,  mycetes)  large  sacs,  which  can  be 
inflated  with  air,  and  which  open  between  the  larynx  and  the  hyoid  bone,  serve 
as  special  resonance-organs.  The  whale  has  no  voice. 

Birds  possess  two  larynxes,  of  which  the  lower  is  situated  at  the  bifurcation 
of  the  trachea  and  is  capable  of  producing  the  voice.  Two  folds  of  mucous  mem- 
brane (in  singing  birds  three)  project  one  into  each  bronchus;  they  are  rendered 
tense  and  are  approximated  by  from  one  to  five  or  six  pairs  of  muscles,  and  they 
serve  for  the  production  of  the  voice. 

Among  reptiles,  the  tortoise  can  produce  only  a  snorting  noise,  because  it 
possesses  no  vocal  bands ;  in  the  emys  this  may  be  increased  to  a  peculiar  whistling. 
The  blind  snakes  are  wholly  voiceless;  the  chameleon  and  the  lizard  exhibit 
feeble  voice-formation;  the  alligator  and  the  crocodile  are  able  to  emit  a  roar, 
but  in  the  adults  of  some  species  of  crocodile  the  voice  is  lost,  owing  to  changes 
in  the  larynx.  Snakes  lack  special  apparatus  for  voice-formation;  in  the  act  of 
forcing  the  air  from  their  capacious  lung  through  the  entrance  of  the  larynx, 
they  produce  a  hissing  sound,  which  at  times  may  be  surprisingly  loud  and  harsh 
(puffing  adder,  hooded  snake). 

Among  the  amphibia,  frogs  possess  a  larynx  with  vocal  bands  and  muscles. 
By  blowing  gently  through  this  without  muscular  action,  they  produce  deep, 
intermittent  sounds;  by  blowing  more  forcibly  and  contracting  the  constrictors 
of  the  larynx,  they  produce  a  clear,  continuous  sound.  The  males  of  Rana  escu- 
lenta  possess  at  the  angle  of  the  mouth  on  each  side  a  sounding-bag,  which  can 
be  inflated  and  which  intensifies  the  sound.  In  the  tree-toad  these  sacs  are  united 
in  the  middle  line  to  form  a  single  laryngeal  sac.  Among  toads,  the  sounds  pro- 
duced are  usually  weaker,  and  of  these  the  bell-like  note  of  the  bombinator  is 
worthy  of  notice;  true  toads  emit  feeble  tones.  The  vocal  organ  of  the  Surinam 
toad  (pipa)  is  peculiar:  two  cartilaginous  rods  project  into  the  lumen  of  a  large 
larynx;  these  are  set  into  vibration  by  the  current  of  air,  and  sound  like  vibrating 
rods  or  the  branches  of  a  tuning-fork.  The  salamander  occasionally  emits  a 
sound  resembling  "uik."  Among  fish,  utterance  of  sound  occurs,  as  a  result  of 
friction  of  the  upper/ and  lower  pharyngeal  bones  against  each  other,  or  of  vibration 
of  fins  induced  by  muscular  action,  or  of  the  escape  of  gas  from  the  swimming- 
bladder,  mouth,  or  anus.  Finally,  muscular  sounds  may  be  observed  in  fish. 

Among  invertebrates,  insects  are  able  to  produce  sounds  partly  by  forcing 
the  expired  air  through  their  stigmata,  which  are  provided  with  reeds  supplied 
with  muscles  (for  example  bees,  many  diptera,  etc.).  In  addition,  the  wings 
often  generate  sounds  by  the  rapid  movement  of  their  muscles  (as  in  flies,  beetles, 
bees).  The  death-head  (Sphinx  atropos)  produces  sound  by  forcing  air  from  its 
sucking  stomach.  In  others  sounds  are  generated  by  rubbing  the  legs  on  the 
wing-cases  (acridium),  or  the  wing-cases  on  each  other  (gryllus,  locust),  or  the 
breast  (cerambyx),  the  leg  (geotrupes),  further  the  abdomen  (necrophorus)  on  the 
margin  of  the  wings,  or  the  lower  wing  on  the  wing-case  (pelobius) .  hi  the  cicadas 
drum-membranes,  pulled  upon  by  muscles,  are  caused  to  vibrate.  In  some 
spiders  (theridium)  friction-sounds  are  produced  between  the  cephalothorax  and 
the  abdomen,  in  some  crabs  (palinurus)  also  by  the  claws.  In  certain  snails  (helix) 


620  COMPARATIVE.        HISTORICAL. 

the  escape  of  air  produces  a  kind  of  voice.  Finally,  some  mussels  (pecten)  are 
able  to  produce  sounds  by  beating  their  shells  on  each  other.  In  the  animal 
world  the  utterance  of  sounds  serves  principally  as  a  decoy. 

Historical. — The  Hippocratic  school  was  aware  of  the  fact  that  division  of 
the  trachea  abolishes  the  voice.  Aristotle  made  numerous  contributions  regarding 
the  voice  and  the  venting  of  air  in  animals.  The  true  insight  into  the  cause  of 
voice-formation  was,  however,  hidden  from  him,  as  well  as  from  Galen.  The 
latter  compared  the  vocal  bands  with  the  reeds  of  a  shepherd's  pipe.  Loss  of 
voice  in  conditions  of  extreme  weakness,  especially  after  hemorrhage,  was  known 
to  the  ancients.  Galen  observed  loss  of  voice  after  establishment  of  double 
pneumothorax,  further  after  section  of  the  intercostal  muscles  or  their  nerves, 
also  after  destruction  of  the  lower  portion  of  the  spinal  cord,  even  when  the  dia- 
phragm still  performed  its  functions.  He  gave  the  laryngeal  cartilages  the  names 
that  they  still  bear,  recognized  some  of  the  laryngeal  muscles,  and  asserted  that 
the  voice  sounds  only  when  the  glottis  becomes  narrowed.  Dodart  (1700)  first 
attributed  the  development  of  the  voice  to  the  vibration  of  the  vocal  bands  as 
a  result  of  the  air  passing  through  the  glottis ;  as  the  tension  of  the  bands  becomes 
greater  the  pitch  of  the  voice  increases.  The  Paris  professor  Ferrein  first  de- 
clared correctly  in  1741  that  the  width  of  the  glottis  is  without  influence  on  the 
pitch  of  the  voice;  he  was  the  first  to  produce  sounds  in  the  excised  larynx  by 
blowing  air  through  it. 

The  study  of  phonetics  was  practised  already  by  the  ancient  inhabitants  of 
India,  less  by  the  Greeks,  but  later  by  the  Arabians.  Pietro  Ponce  (died  1584) 
was  the  first  to  give  instruction  in  speech  to  deaf-mutes.  Later,  Bacon  (1638) 
studied  the  configuration  of  the  mouth  in  the  utterance  of  the  various  sounds; 
Johann  Wallis  (1653)  did  the  same,  partly  for  the  instruction  of  deaf-mutes,  and 
likewise  Conrad  Ammann  (1692).  Kratzenstein  (1781)  first  produced  artificial 
vowels  by  fastening  variously  shaped  resonators  to  a  freely  vibrating  reed-appa- 
ratus. Wolfgang  v.  Kempelen,  of  Vienna  (1769-1791),  constructed  the  first 
talking  machine.  The  voice-apparatus  consisted  of  an  ivory  reed  moved  by 
means  of  a  bellows  and  striking  upon  leather.  On  the  whole,  the  consonants 
were  well  produced;  the  aspirates  were  produced  by  whistling  and  hissing  reso- 
nating tubes,  the  explosives  by  valve-like  arrangements,  R  by  a  small  rod  dancing 
on  the  ivory  reed,  etc.  The  vowels  were  produced  by  a  megaphone,  the  cavity  of 
which  was  altered  by  hand;  A  (ah),  O,  U  (oo)  were  readily  produced,  E  (a)  with 
more  difficulty,  I  (ee)  incompletely.  Air  was  forced  through  the  entire  apparatus 
by  means  of  a  bellows,  while  the  machine  was  "played  upon"  by  the  right  hand 
raising  valves  and  the  left  hand  changing  the  megaphone;  Wolfgang  v.  Kempelen 
stated  correctly  that  tension  of  the  vocal  bands  and  narrowing  of  the  glottis 
take  place  together;  he  is  to  be  credited  with  many  other  accurate  observations 
concerning  the  formation  of  articulate  sounds.  F.  H.  du  Bois-Reymond  gave,  in 
1812,  a  natural  system  of  consonants.  Robert  Willis  (1828)  found  that  an  elastic, 
vibrating  spring  yields  the  vowels  in  the  series  U  (oo),  O,  A  (ah),  E  (a),  I  (ee), 
in  accordance  with  the  pitch  of  its  tone;  also  that  the  vowel-like  sounds  can 
be  produced  in  the  same  order  by  lengthening  or  shortening  an  artificial  resonating 
tube  attached  to  a  voice-apparatus. 


GENERAL    PHYSIOLOGY   OF    THE    NER- 
VOUS SYSTEM  AND  ELECTRO- 
PHYSIOLOGY. 


GENERAL   CONCEPTION   OF   THE   NERVOUS   SYSTEM. 

STRUCTURE    AND    ARRANGEMENT    OF    THE    ELEMENTS    OF    THE 
NERVOUS   SYSTEM. 

With  relation  to  the  general  comprehension  of  the  structure  and  function  of 
the  nerve-elements,  two  opposed  views  are  held  at  the  present  time.  According 
to  the  one  the  neuron,  that  is  a  ganglion-cell  with  all  of  its  processes,  is  to  be 
considered  as  the  independent  physiological  unit  of  nervous  tissue.  The  various 
neurons  are  not  in  immediate  and  direct  connection  with  one  another.  The  axis- 
cylinders  of  all  nerve-fibers  arise  from  ganglion-cells,  and  not  from  a  network  of 
fibers.  All  nerve-fibers  terminate  finally  by  means  of  terminal  arborescences  or 
telodendrites.  It  is  only  through  these  terminal  filaments  that  the  nerve-elements 
are  connected  by  contact,  the  minute  radicles  being  applied  to  one  another.  The 
nerve-cells  and  the  nerve-fibers  have  each  a  distinct  physiological  importance,  the 
cells  acting  as  the  physiological  centers  (for  automatic  or  reflex  movement,  for 
sensation,  perception,  for  trophic  and  secretory  functions),  the  fibers,  which 
always  originate  from  the  nerve-cells  as  processes,  representing  a  conducting 
apparatus. 

The  more  recent  view  rejects  the  neuron  as  the  physiological  unit  and  con- 
siders the  fibrillary  substance  or  the  neuropile  as  the  medium  of  nervous  activity. 
The  fibrillary  substance  is  present  in  the  great  mass  of  gray  matter,  which  repre- 
sents a  fine  lacework  or  network  of  nerve-fibrils.  It  can  be  seen  further  in  the 
nerve-cells  and  in  the  fibers  passing  off  from  them.  The  higher  the  plane  of  devel- 
opment in  the  animal  scale  the  less  numerous  are  the  nerve-cells  in  proportion  to 
the  fibrillary  structure,  the  ganglion-cells  serving  only  as  nutritional  centers  for 
the  metabolism  of  the  nerve-tissue.  As  Bethe  has  shown  that  reflex  activity 
persists  in  crabs  even  after  the  ganglion-cells  have  been  extirpated,  conduction 
must  obviously  take  place  in  the  mass  of  fibers  exclusively.  The  neuron  thus 
loses  its  significance  in  the  physiological  sense  and  also  from  the  histological 
standpoint. 

The  nerve-fibers  are  of  several  varieties: 

1.  The  simplest  form  of  nerve-fibers  are  the  primitive  fibrils  or  axis- fibrils 
(Fig.   220,    i),  distinguishable  only  with  high  powers  of  the  microscope.     They 
occur  as  delicate  fibers,  presenting  at  varying  intervals  slightly  varicose  or  spindle- 
shaped  thickenings   (postmortem  change),  and    they  can  be  recognized  by  the 
brown  color  that  develops  after  the  application  of  gold.chlorid.     They  appear  in 
part  in  the  vicinity  of  tne  terminal  distribution  of  the  nerves,  resulting  from  the 
fibrillation  of  the   axis-cylinders,  as,  for  example,  in  the  layer  of  fibers  of  the 
optic  nerve  in  the  retina,  in  the  terminal  distribution  of  the  olfactory  fibers,  in 
the  net-like  connection  at  the  terminal  distribution  in  unstriped  muscle,  and  in 
part  in  the  gray  substance  of  the  brain  and  the  spinal  cord  as  the  most  delicate 
processes  of  divided  dendrites. 

2.  Naked  axis-cylinders  (Fig.   220,  2)  represent  bundles  of  primitive   fibrils, 
which  are  characterized  by  most  delicate  longitudinal  striation,  separated  by  a 
number  of  fine  granules.     They  are  encountered  in  most  exquisite  form  as  neurites 
of  central  ganglion-cells  (Fig.  220,  I,  z). 

3.  Axis-cylinders  surrounded  by  neurilemma  or  the  sheath  of  Schwann,  from 
3.8  to  6.8  [i  in  thickness,  and  designated  non-medullated  or  gray  nerve-fibers.     The 
sheath  of  these  fibers  is  a  delicate,  elastic  cylinder  composed  of  flattened  cells 

621 


622        STRUCTURE    AND    ARRANGEMENT    OF    THE    NERVE    ELEMENTS. 

and  covered  here  and  there  with  oval  nuclei.  Dilute  acids  clear  the  fibers, 
without  swelling.  They  are  stained  brownish  red  by  gold  chlorid.  They  occur 
in  large  numbers  in  the  sympathetic  nerves.  In  embryonal  life  all  nerves,  as 
well  as  the  nerves  of  many  invertebrates,  are  of  this  variety.  In  some  situations 
several  axis-cylinders  are  present  within  one  sheath.  These  are  designated  Re- 
mak's  fibers.  They  occur  chiefly  in  the  sympathetic  system  and  in  the  olfactory 
nerves. 

4.  Axis-cylinders  or  nerve-fibrils  surrounded  only  by  a  medullary  sheath  are 
present  in  the  white  and  gray  substance  of  the  central  nervous  system,  also  in 
the  optic  and   auditory  nerves.     After  death  they  exhibit  a  tendency  to  undergo 
varicose  and  nodular  thickening  in  certain  areas  in  consequence  of  the  coagulation 
of  the  medullary  substance ;  hence  they  are  also  designated  varicose  -fibers.     Osmic 
acid  acts  upon  these  fibers  only  imperfectly;    otherwise  the  medulla  exhibits  the 
same  characteristics  as  the  fibers  of  the  following  category. 

5.  The  medullated  fibers,  with  a  sheath  of  Schwann  (Fig.  220,  5,  6),  occurring 
principally  in  the  cerebrospinal  nerves,  but  also  in  small  number  in  the  sympa- 
thetic nerves,  exhibit  the  most  complicated  structure.     They  vary  in  width  from 
i  to  22.6  n.     The  essentially  nervous  element  of  these  fibers  is  the  axis-cylinder 
(Fig.  220,  6,  a) ,  which  occupies  from  one-fourth  to  one-sixth  of  the  width  and  is  sur- 
rounded by  nerve-marrow  like  the  wick  of  a  candle.     Generally  it  is  somewhat 
flattened,  and  at  times  it  is  somewhat  eccentric  (Fig.  220,  7).     Otherwise  the  axis- 
cylinder  is  composed  of  fibrils.     Its  consistence  during  life  is  that  of  semiliquid 
protoplasm  or  even  more  fluid.     According  to  Kupffer  a  fluid  (neuroplasm)  is  pres- 
ent between  the  fibrils. 

Chloroform  and  collodion  render  the  axis-cylinder  visible.  It  is  most  readily 
isolated  by  means  of  nitric  acid  with  an  excess  of  potassium  chlorid.  On  treat- 
ment with  silver  nitrate,  Frommann  noted  the  appearance  in  places  of  striation 
transverse  to  the  axis-cylinder  (Fig.  220,  8),  the  significance  of  which  could  not 
be  determined. 

The  axis-cylinder  is  surrounded  by  the  medullary  sheath,  which  in  the  fresh 
state  is  homogeneous  and  strongly  refracting.  It  is  at  the  same  time  of  fluid 
consistence,  so  that  it  exudes  in  globular  drops  (x)  from  the  cut  surfaces  of  the 
fibers.  After  death,  however,  or  under  the  influence  of  heterogeneous  fluids,  the 
medullary  substance  at  first  retracts  somewhat  from  the  sheath,  and  as  a  result 
the  fiber  exhibits  a  double  contour.  Then  the  substance  by  a  process  of  emulsifi- 
cation  breaks  up  into  larger  and  smaller  globules,  which  tend  to  lie  close  together. 
Peculiar  broken-up  masses  are  thus  formed  in  the  nerve-fiber,  giving  it  its  charac- 
teristic appearance  (Fig.  220,  6). 

The  medullary  sheath  is  strongly  refracting  and  positively  uniaxially  doubly 
refracting.  The  optically  active  body  is  lecithin.  The  substance  of  the  medul- 
lary sheath  is  especially  rich  in  cerebrin  and  lecithin,  which  swell  up  in  warm 
water  and  assume  similar  forms,  which  have  been  well  named  myelin  forms. 
Ether,  chloroform,  and  benzine  increase  the  transparency  of  the  fibers  (with  disap- 
pearance of  the  double  refraction)  by  solution  of  the  fat-like  constituents.  Osmic 
acid  stains  them  black. 

Immediately  surrounding  the  medullary  sheath  is  the  sheath  of  Schwann  or 
neurilemma  (Fig.  220,  6,  c),  a  delicate,  structureless  membrane,  resembling  the 
sarcolemma.  It  contains  disseminated  oblong  readily  stained  nuclei.  On  addition 
of  acetic  acid,  and  in  chromic-acid  preparations,  this  sheath  appears  in  part 
isolated. 

The  sheath  of  Schwann  exhibits,  in  the  case  of  thick  fibers  at  intervals  of 
considerable  length,  in  that  of  thin  fibers  at  somewhat  shorter  intervals,  the 
nodes  of  Ranvier  (Fig.  220,  6,  t  t,  and  Fig.  221,  f  s}.  These  are  annular  con- 
strictions, about  which  the  myelin  is  wanting.  Between  each  two  constrictions 
is  a  nucleus,  so  that  such  a  segment  of  the  fiber  is  equivalent  to  a  cell  from 
which  it  may  be  considered  to  have  originated.  At  the  annular  constrictions  the 
nutritive  plasma  probably  enters  the  fiber  for  the  axis-cylinder,  as  stains  are  able 
to  penetrate  at  this  point  (8) ;  probably  also  the  products  of  metabolism  are  re- 
moved by  the  same  channels.  Apparently  two  segments  of  the  sheath  of 
Schwann  are  united  by  cement-substance  at  the  annular  constriction. 

The  axis-cylinder  exhibits  at  the  situation  of  the  annular  constriction  regu- 
lar preexisting  interruptions,  as  can  best  be  demonstrated  by  treatment  with 
silver  nitrate.  And  although  the  discoverer  Engelmann  does  not  believe  that  in 
the  living  fiber  a  dividing  layer  of  microscopic  thickness  is  interposed  in  the  an- 
nular constriction  between  each  two  adjacent  segments  of  axis-cylinder,  yet  such 


STRUCTURE    AND    ARRANGEMENT    OF    THE    NERVE    ELEMENTS.         623 

an  observation  obviously  gives  material  support  to  the  view  that  the  nerve-fiber 
is  a  chain  of  individual  cells. 

In  the  spinal  nerves  those  fibers  are  the  thickest  that  are  the  longest  to  their 


FIG.  220.— i,  Primitive  fibrils;  2,  axis-cylinder;  3,  fibers  of  Remak;  4,  meduUated  varicose  fibers;  5,  6,  medul- 
lated  fibers,  with  sheath  of  Schwann;  c,  neurilemma;  t  t,  the  annular  constrictions  of  Ranvier;  b,  the  medul- 
lary substance;  d,  cells  of  the  endoneurium:  a,  axis-cylinder;  x,  medullary  drop  or  myelin-globule;  7,  trans- 
verse section  of  a  nerve  with  distinct  axis-cylinders,  medullary  sheaths  and  endoneurium;  8,  nerve-fiber  treated 
with  silver  nitrate;  the  axis-cylinder  striated  transversely  (after  Frommann).  I,  Multipolar  ganglion-cell  of 
the  spinal  cord;  z,  neurite;  y,  dendrites;  to  the  right  a  bipolar  ganglion-cell.  II,  Peripheral  sympathetic 
ganglion-cell  with  connective-tissue  capsule.  Ill,  Ganglion-cell  with  surrounding  fibers;  m,  capsule;  n, 
cellulifugal,  o,  cellulipetal  fiber. 


end-organ;    and   those   ganglion-cells   are   the   largest   that   give  off  the   longest 
nerves. 

According  to  Ewald  and  W.  Kiihne  both  the  axis-cylinder  and  the  medullary 
sheath  are  further  surrounded  by  an  exceedingly  delicate  horny  sheath  consisting 
of  neurokeratin.  Both  are  connected  through  the  substance  of  the  myelin  by 


624        STRUCTURE    AND    ARRANGEMENT    OF    THE    NERVE    ELEMENTS. 

means  of  transverse  or  oblique  fibers  that  divide  the  myelin  between  two  annular 
constrictions  into  a  number  of  successive  segments.  In  this  way  are  formed  the 
oblique  clefts  or  indentations  of  Schmidt,  Lantermann,  and  Kuhnt  in  the  myelin, 
as  shown  in  Fig.  221. 

According  to  Leydig  and  Joseph  the  axis-cylinders  contain  a  delicate  reticular 
framework,  in  the  midst  of  which  the  fibrils  of  the  axis-cylinder  are  embedded. 

The  nerve-fibers  are  undivided  in  their  course  in  the  nerve-trunk.  As  they 
approach  their  terminal  distribution,  they  divide  usually  into  two,  less  commonly 
into  several,  fibers  that  undergo  no  further  change. 

In  animals  the  nerve-sheaths  are  sometimes  still  more  complex.  Thus,  in  the 
electrical  nerve  of  the  electrical  catfish  the  sheath  of  Schwann  of  the  individual 
nerve-fiber  is  constituted  of  such  a  large  number  of  layers  that  the  fiber  may 
attain  the  thickness  of  a  knitting  needle.  In  the  invertebrates  the  nerve-fibers  as 


FIG.  221. — Medullated 
Nerve-fiber  Stained 
Black  by  Osmic 
Acid :  fs,  annular 
constriction  of  Ran- 
vier;  sch,  sheath  of 
Schwann  (after  Eich- 
horst). 


FIG.  222. — Transverse  Section  through  a  Portion  of  the  Median    Xcrvi 
neurium;  pe,  perineurium ;  ed,  endoneurium  (after  Eichhorst). 


a  rule  have  no  medullary  sheath.  Retzius  found  them  present,  however,  in  the 
shrimp. 

The  connective  tissue  mixed  with  elastic  fibers  that  surrounds  a  nerve-trunk 
is  designated  epineurium  (Fig.  222,  <?/?)•  The  individual  nerve-fibers  are  united 
in  the  nerve-trunk  into  bundles  and  each  of  the  latter  is  surrounded  by  the  peri- 
neurium (pe) ,  from  which  the  endoneurium  (cd)  passes  inward  between  the  nerve- 
fibers.  These  sheaths  are  at  the  same  time  provided  with  concentric  layers 
constituted  of  smooth  connective-tissue  cells  that  can  be  stained  with  silver 
nitrate.  Even  the  individual  nerve-fiber,  which  results  from  the  breaking  up  of 
a  bundle  of  fibers,  is  further  surrounded  by  a  sheath  composed  of  flat  connective- 
tissue  cells  in  mutual  contact  (Henle's  sheath).  The  longitudinal  network  of 
blood-vessels  of  the  nerve-fibers  is  supported  by  the  connective  tissue  of  the 
latter.  The  lymphatics  form  spaces,  which  reach  to  the  individual  fibers. 

In  their  development  the  nerve-fibers  first  consist  of  fibrils  that  become  sur- 
rounded by  connective-tissue  and  finally  by  medullary  sheaths.  At  birth  the 
cerebral  motor  nerves  and  the  auditory  nerve  alone  are  medullated.  The  longi- 


STRUCTURE    AND    ARRANGEMENT    OF    THE    NERVE    ELEMENTS.        625 

tudinal  growth  of  the  fibers  takes  place  through  elongation  of  the  individual 
interannular  segments  and  at  the  same  time  by  the  formation  of  new  segments. 

The  ganglia  have  been  considered  partly  as  cells,  partly  as  more  complex 
structures.  There  are  to  be  distinguished: 

i.  Central  ganglia  (Fig.  220,  I),  occurring  partly  as  large  cells  (up  to  150  //  in 
diameter,  visible  to  the  naked  eye,  in  the  anterior  horns  of  the  spinal  cord), 
partly  as  small  cells  (from  4  to  9  //  in  diameter,  deficient  in  protoplasm,  in  the  pos- 
terior horns,  in  many  parts  of  the  cerebrum  and  cerebellum  and  in  the  retina), 
spherical,  ovoid,  or  pear-shaped,  with  numerous  processes  that  often  give  to  the  cells 
a  star-shaped  appearance.  The  brothers  Landois  found  the  ganglia  of  young  insects 
much  smaller  than  those  of  adult  insects.  A  similar  statement  is  made  also  by 
Schwalbe  with  respect  to  these  cells  and  their  nuclei.  The  cell-body  is  without 
a  capsule,  of  soft  consistence  and  exhibiting  a  reticular  structure,  or  a  finely 
fibrillar  structure  which  extends  into  the  processes.  Between  the  fibrillae.  is 
everywhere  distributed  yellow  or  brown  finely  granular  pigment  either  heaped 
up  at  some  particular  part  of  the  cell  or  disseminated  throughout  the  entire  cell. 
The  relatively  large  nucleus  is  clear,  granular  or  reticular,  and  in  early  life  without 
a  membrane.  It  contains  little  or  no  chromatin-substance.  The  nucleus  contains  a 
nucleolus,  which  in  the  fresh  state  is  angular  and  motile,  and  after  death  is  spheri- 
cal, highly  refractile,  staining  feebly,  and  often  in  turn  contains  a  smaller  granule. 

On  treatment  with  precipitating  and  coloring  materials  (alcoholic  methylene- 
blue)  the  cell-substance  can  be  demonstrated  to  contain  chromophilic  granular 
masses,  so-called  Nissl  bodies,  which  are  discernible  with  greater  difficulty  in  the 
fresh  and  living  state,  and  which  appear  with  varying  degrees  of  distinctness  in 
different  nerve-cells.  In  the  motor  ganglion-cells  these  bodies  are  arranged  in 
concentric  parallel  layers.  Electrical  irritation  induces  contraction  of  the  cell, 
causes  it  to  appear  darker  and  brings  about  a  closer  approximation  of  the  Nissl 
bodies.  Section  of  the  motor  fiber  emanating  from  the  ganglion-cell  leads  to 
granular  degeneration  and  diminution  in  the  number  of  the  bodies.  If  the  nerve- 
fiber  undergoes  regeneration  the  cell  again  acquires  its  normal  appearance.  Ac- 
cording to  Lugaro  the  cells  of  the  spinal  ganglia  become  altered  and  finally 
degenerate  after  division  of  their  peripheral  fibers,  the  nucleus  becomes  smaller, 
while  the  Nissl  bodies  increase  in  number  and  size  and  become  grouped  about  the 
nucleus.  Various  poisons  (strychnin,  alcohol,  tetanus,  also  uremia,  autointoxica- 
tions, inanition,  anemia,  prolonged  high  fever,  heat-stroke,  etc.)  cause  various 
changes  in  the  ganglion-cells,  mainly  affecting  the  Nissl  bodies.  The  cells  of  the 
cerebral  cortex  are  affected  in  a  peculiarly  specific  manner  by  each  poison. 

Of  the  processes  given  off  by  the  ganglion-cells  there  are  a  large  number  that 
break  up  soon  after  their  origin,  like  an  intricately  branching  root,  into  numer- 
ous, delicate  fibers  presenting  a  varicose  appearance,  and  designated  den- 
drites  or  protoplasmic  or  secondary  processes  (Fig.  220,  I,  y).  These  dendrites 
conduct  cellulipetally  and  form  an  intricate  terminal  network.  The  dendrites 
of  adjacent  cells  do  not  anastomose  with  one  another,  but  lie  in  close  rela- 
tion, entering  merely  into  contact.  Neither  do  the  fibers  of  the  dendrites 
give  rise  to  nerve-fibers  passing  in  a  peripheral  direction.  The  group  of  terminal 
filaments  of  a  dendrite  is  designated  a  terminal  network  or  a  telodendron.  In 
addition  to  the  dendrites,  the  ganglion-cell  gives  off  a  process  of  considerable 
length,  arising  by  a  conical  base,  then  pursuing  a  uniformly  simple  course,  and 
conducting  in  a  cellulifugal  direction.  This  process  is  designated  an  axone  or 
a  neurite  (an  axis-cylinder  or  principal  process)  (I,  z).  The  neurite  is  often  con- 
tinued peripherally  into  a  nerve-fiber.  Within  the  central  nervous  system  it  gives 
off  here  and  there  delicate  branches  that  are  designated  collaterals.  These 
break  up  into  a  fine  terminal  network,  the  radicles  of  which  penetrate  between 
the  elements  of  the  central  organs.  The  neurites  from  the  ganglion-cells  of  the 
cerebral  and  cerebellar  cortex  divide  after  a  short  course  in  a  complex  manner. 
Also  these  fine  divisions  come  in  contact  with  other  nerve-elements  in  the  central 
organ.  Thus  nerve-cells  are  connected  only  by  the  contact  of  their  delicate 
processes.  Moreover,  a  nerve-fiber  never  passes  directly  over  into  the  histological 
elements  of  a  nerve  end-organ,  the  conducting  fiber  being  only  in  telodendritic 
contact  with  that  organ.  If  certain  nerve-tracts  are  especially  used  and  exercised, 
the  altered  function  of  the  ganglion-cells  in  question  may  perhaps  be  explained 
by  a  further  penetration  of  the  dendrites  into  additional  areas  of  the  interstitial 
tissue,  into  which  they  had  hitherto  not  penetrated.  Demoor  and  Heger  ob- 
served changes  in  the  dendrites  and  neurites  of  the  brain  after  irritation,  cocain- 
anesthesia  and  the  application  of  cold. 
40 


626  CHEMISTRY    OF    NERVOUS    TISSUE. 

2.  Ganglia   with  connective-tissue  capsules    (sheaths  of   Schwann)    (II)    occur 
(about  50  u  in  diameter)  in  the  peripheral  nerve-nodes.     The  soft  cell-body,  pos- 
sessing two  or  more  cell-processes,  is  surrounded  by  a  firm  capsule  of  cells  closely 
applied  to  one  another.     The  cell-body  of  the  spinal  ganglion  cells  is  traversed 
by  fine  fibers ;  the  capsule  is  later  on  connected  with  that  of  the  nerve-fiber. 

3.  Bipolar  ganglia  are  best  seen  in  fish,  for  example  in  the  spinal    ganglia 
of  the  ray  and  the  shark,  as  well  as  in  the  Gasserian  ganglion  of  the  pike.     They 
appear  as  nucleated  spindle-shaped  swellings  of  the  axis-cylinder  (on  the  right, 
next  to  I).     The  nerve-marrow  is  often  absent  where  the  ganglion  is  interposed 
in  the  course  of  the  fiber.     Occasionally,  however,  the  marrow,  and  always  the 
sheath  of  Schwann,  is  continued  over  the  ganglion. 

4.  Ganglia  surrounded  with  fibers  occur  in  the   sympathetic   system  of  the 
frog.     From  the  pear-shaped  cell  (III,  n)  a  process  that  remains  non-medullated 
extends  in  one  direction,  and  perhaps  further  on  divides  into  two  branches.     In  ad- 
dition, on  the  surface  of  the  cell,  a  second  nerve-fiber  is  connected  with  an  extremely 
delicate  network  of  fine  fibers.     The  second  nerve-fiber  winds  around  the  first 
in  a  spiral  manner  and  then  proceeds  in  another  direction   (o)  as  a  medullated 
fiber.     Both  cell  and  process  are  enclosed  in  a  nucleated  capsule  (m) .     The  straight 
fiber  has  been  thought  to  conduct  in  a  cellulifugal  direction,  the  spiral  fiber  in  a 
cellulipetal  direction.     It  is  possible,  however,   that  the  spiral  fiber  is  derived 
from  another  ganglion-cell. 

The  cells  in  the  peripheral  ganglia  are  deserving  of  special  consideration.  They 
may  be  divided  into  two  kinds:  (i)  the  cells  of  the  sensory  ganglia,  including 
the  spinal  ganglia,  and  on  the  cerebral  nerves  the  Gasserian  ganglion,  the  petrosum 
glosso-pharyngei,  the  jugular  ganglion,  and  the  nodose  plexus  of  the  vagus,  the 
auditory  ganglion,  the  geniculate  ganglion.  From  the  pear-shaped  cells  extend 
short  prolongations  that  become  gradually  thinner  and  divide  into  two  processes 
diverging  in  the  shape  of  the  letter  T  and  becoming  medullated  nerve-fibers. 
Only  the  ganglia  of  the  auditory  nerve  have  cells  with  bipolar  processes.  The  pro- 
cess from  the  peripheral  sensory  area  to  the  ganglion  is  the  cellulipetal-  dendrite. 
The  neurite  of  the  cell  passes,  however,  in  a  cellulifugal  direction  into  the  cen- 
tral nervous  system  (in  the  case  of  the  spinal  ganglia  it  passes  through  the 
posterior  roots  into  the  spinal  cord)  and  breaks  up  in  a  dendritic  manner. 

Every  cell  of  the  spinal  ganglia  has  a  connective-tissue  capsule  lined  by  a 
single  layer  of  epithelium.  The  cell-body  exhibits  a  granular  chromophilic  de- 
position and  always  pigment,  while  the  ground-substance  of  the  protoplasm  has 
a  reticular  structure,  and  the  nucleus  is  without  chromatin. 

2.  The  second  group  of  peripheral  ganglia  contains  sympathetic  ganglion-cells. 
It  includes  in  the  course  of  the  cerebral  nerves  the  sphenopalatine,  the  otic,  sub- 
maxillary,  and  ciliary  ganglia,  and  all  ganglia  in  the  distribution  of  the  sympa- 
thetic system.  The  cells  of  the  sympathetic  system  have  numerous  dendrites 
and  a  single  neurite.  The  latter  becomes  a  non-medullated  nerve-fiber  with  neu- 
rilemma,  and  it  leaves  the  ganglion  to  surround  the  nerve-cells  of  other  ganglia 
with  a  network  or  to  terminate  on  a  blood-vessel,  while  the  dendrites  ramify 
within  the  ganglion.  The  nerve-fibers  passing  from  the  central  nervous  system 
to  the  sympathetic  ganglia  surround  the  cells  with  a  delicate  network. 

Numerous  blood-capillaries  surround  the  individual  ganglion-cells,  which  also 
are  provided  with  large  lymph-spaces. 


CHEMISTRY  OF  NERVOUS  TISSUE. 
MECHANICAL  PROPERTIES  OF  NERVES. 

Proteids. — Of  the  solid  constituents  of  the  gray  matter  about  one- 
half  are  proteids;  of  the  white  matter  one-third.  There  are  present 
two  phosphorus-free  globulins  and  a  nucleoalbumin  (almost  absent  from 
the  white  matter). 

One  of  the  globulins  is  precipitable  by  a  little  neutral  salt,  and  coagulates 
at  47°  C.  It  is  present  also  in  leukocytes,  muscles,  and  the  liver.  The  other 
globulin  is  precipitated  only  on  saturation  with  magnesium  sulphate  and  coagu- 
lates at  70°.  It  is  present  also  in  liver-cells.  The  nucleoalbumin,  containing  0.5 
phosphorus,  coagulates  between  55°  and  60°  and  is  precipitated  from  a  watery 
extract  of  brain-material  by  acetic  acid. 


MECHANICAL    PROPERTIES    OF    NERVES.  627 

Neurokeratin,  a  phosphorus-free  substance  rich  in  sulphur  and  closely 
related  to  keratin,  occurs  in  the  horny  sheaths  of  the  nerve-fibers,  remain- 
ing after  artificial  digestion  of  the  gray  nervous  substance  by  trypsin; 
treatment  of  the  resulting  product  with  potassium  hydroxid  yields  pure 
neurokeratin.  The  material  of  the  sheath  of  Schwann  closely  resembles 
elastin,  although  it  is  more  readily  soluble  in  alkalies.  The  connective 
tissue  of  the  nerves  yields  gelatin. 

Fats  and  fat-like  substances  soluble  in  ether  occur  principally  in  the 
white  matter  as  follows: 

(a)  Liebreich's  protagon,  which  resembles  cerebrin,  is  readily  de- 
composed, contains  nitrogen  and  phosphorus,  doubtfully  sulphur,  is  the 
principal  constituent  of  the  brain-mass,  but  is  wanting  in  the  ganglion- 
cells,  as  well  as  in  their  decomposition-products. 

It  can  be  extracted  from  the  white  central  nerve-mass  by  treatment  with 
85  per  cent,  alcohol  at  45°  C.  It  is  readily  soluble  in  ether,  glacial  acetic  acid, 
and  benzol,  scarcely  soluble  in  alcohol,  and  crystallizes  in  plates.  It  swells 
in  water  and  becomes  opalescent.  When  heated  to  50°,  the  glucosid-like,  phos- 
phorus-free body,  cerebrin,  is  separated.  Boiled  with  baryta  it  yields  the  de- 
composition-products of  lecithin.  Protagon  was  considered  by  Diakonow  and 
Hoppe-Seyler  as  a  mixture  of  lecithin  and  cerebrin. 

(6)  Cerebrin  occurs  as  a  decomposition-product  of  protagon. 

It  is  a  white  powder,  consisting  of  spherical,  transparent,  smooth  granules 
containing  nitrogen,  but  free  from  phosphorus,  soluble  in  hot  alcohol,  chloroform, 
and  benzol,  insoluble  in  ether  or  water.  Boiled  with  dilute  sulphuric  acid  it 
is  decomposed  into  galactose  and  a  fat.  Parkus  has  separated  from  cerebrin 
homocerebrin  (kerasin) ,  a  homologous  readily  soluble  body,  crystallizing  in 
needles,  and  encephalin,  which  swells  up  in  hot  water  like  starch  and  contains 
an  additional  molecule  of  water. 

(c)  Lecithin  is  chemically  combined  in  protagon.     In  addition  there 
are  present  decomposition-products  of  lecithin,  such  as  glycerophosphoric 
acid,  oleophosphoric  acid. 

Lecithin  is  an  ether-like  combination  of  neurin  in  which  the  latter  takes  the  place 
of  the  alcohol.  It  is  of  waxy  consistence  and  it  swells  in  water  in  myelin-f orms ; 
it  is  soluble  in  alcohol  or  ether.  Neurin,  C5H15NO2,  is  a  strongly  alkaline,  colorless 
fluid,  forming  crystalline  salts  with  acids.  It  can  be  produced  synthetically 
from  glycol  and  trymethylamin ;  it  is  soluble  in  water  and  in  alcohol.  Neurin 
results  by  reduction  from  cholin;  muscarin  results  by  oxidation  from  cholin. 
Cholin  is  non-toxic,  while  neurin  and  muscarin  are  toxic.  Cephalin  closely  re- 
sembles lecithin;  it  is  precipitable  from  an  ethereal  solution  by  alcohol  and  is 
stained  black  by  osmium. 

(d)  Cholesterin  occurs  partly  free  and  partly  in  combination  in  the 
ganglia  and  in  larger  quantities  in  the  white  matter. 

Whether  neutral  fat  or  fatty  acids  occur  has  not  been  positively  de- 
termined. 

3.  The  following  products  of  retrogressive  tissue-metamorphosis  can 
be  extracted  by  water:  xanthin,  guanin,  and  hypoxanthin,  (?)  adenin, 
kreatin,  urea  (in  larger  amount  in  case  of  retention  of  urine),  (?)  uric 
acid,  jecorin,  neuridin,  a  diamin  occurring  in  connection  with  putrefac- 
tion. Further,  W.  Miiller  has  found  formic  and  acetic  acids,  taurin, 
much  inosite,  and  in  cattle  leucin;  v.  Bibra,  fermentation  lactic  acid, 
and  Jaffe,  a  starch-like  substance  in  human  brains. 

Nervous  tissue  in  a  state  of  rest  has  a  neutral  or  slightly  alkaline 
reaction,  while  when  active  and  also  when  dead  the  reaction  is  acid. 

The   cerebral   cortex   in   the   fresh   state   yields   an   alkaline   reaction,  which 


628  METABOLISM    IN    NERVES. 

is  quickly  changed  to  an  acid  reaction  after  death  (?by  fermentation  lactic  acid). 
The  reaction  of  the  nerve-fibers  during  life  is  variable.  After  the  ingestion  of 
methylene-blue  Ehrlich  found  in  living  animals  that  the  substance  of  the  axis- 
cylinders  stains  blue,  especially  in  those  nerves  that  yield  an  alkaline  reaction 
(cerebral  cortex,  cardiac  nerves,  the  sensory  and  motor  fibers  of  the  unstriped 
muscles,  gustatory  and  olfactory  nerve-endings) ,  while  the  endings  of  the  voluntary 
motor  nerves,  which  he  considers  have  an  acid  reaction,  remain  unstained.  Ac- 
cording to  Flesch  the  ganglion-cells  exhibit  differences  in  their  reactions  to  stains, 
in  accordance  with  their  functions.  The  irritated  nerve  develops  carbon  dioxid. 

As  dead  nerves  exhibit  increased  consistence,  it  is  probable  that  a 
condition  of  rigidity  develops  in  them  after  death  comparable  to  mus- 
cular rigidity  and  attended  with  the  development  of  free  acid.  Fresh 
brain  rapidly  scalded  at  100°  C.  remains  alkaline  (as  do  the  muscles). 

The  gray  matter  contains  more  water  (from  83  to  84  per  cent.)  than  the 
white  (from  68  to  70  per  cent.).  The  dried  material  contains  albumin  (in  the 
gray  matter  30.89  per  cent.,  without  nuclein),  partly  soluble,  partly  insoluble 
(in  the  white  matter  19.33  per  cent.,  without  nuclein  and  neurokeratin) ;  lecithin 
17.2  per  cent.  (9.9  per  cent.);  cholesterin  and  fats  18.7  per  cent.  (51.9  per  cent.); 
cerebrin  0.5  per  cent.  (9.5  per  cent.);  extracts  insoluble  in  ether  6.7  per  cent. 
(3.3  percent.);  salts  1.5  per  cent.  (0.6  per  cent.);  the  gray  matter  contains 
more  phosphoric  acid;  neurokeratin  (0.3  per  cent,  in  moist  peripheral  nerves, 
2.9  per  cent,  in  moist  white  brain-matter).  Breed  found  in  100  parts  of  ash: 
potassium  32,  sodium  n,  magnesium  2,  calcium  0.7,  sodium  chlorid  5,  iron  phos- 
phate 1.2,  combined  phosphoric  acid  39,  sulphuric  acid  o.i,  silicic  acid  0.4. 

Among  the  mechanical  properties  of  nerve-fibers  the  absence  of  elastic  tension 
in  the  various  positions  of  the  body  is  noteworthy.  This  is  recognized  from  the 
fact  that  divided  nerves  do  not  retract  and  that  the  nerve  breaks  up  on  its  surface 
into  delicate  macroscopically  visible  transverse  folds  (Fontana's  transverse  stria- 
tion) . 

The  marked  cohesive  resistance  of  the  nerves  to  traction  is  responsible  for 
the  fact  that  when  a  part  of  the  body  is  forcibly  torn  from  the  trunk,  as  in  machin- 
ery accidents,  the  nerve-trunks  often  resist.  The  nerve,  however,  readily  breaks 
up  into  its  individual  fibers. 

If  a  constant  electrical  current  be  passed  through  an  excised  (or  even  dead) 
nerve  there  is  a  motor  reaction  of  the  contents  of  the  fibers  to  the  anode,  of  the 
sheath  to  the  kathode. 


METABOLISM  IN  NERVES. 

Little  is  at  present  known  concerning  metabolism  in  nerves.  The 
occurrence  of  various  extractives  has  been  determined,  and  these  must  be 
considered  as  decomposition -products.  On  the  other  hand,  it  has  not 
yet  been  possible  to  demonstrate  with  certainty  an  interchange  of  oxygen 
and  carbon  dioxid.  That,  however,  anabolism  from  the  blood  must  take 
place  in  the  nervous  tissue  is  indicated  by  the  fact  that  the  irritability 
of  the  nerves  diminishes  after  compression  of  the  blood-vessels,  and 
returns  on  restoration  of  the  circulation.  Thus,  compression  of  the 
abdominal  aorta  is  followed  by  paralysis  of  motion  and  sensation  in 
the  lower  half  of  the  body;  occlusion  of  the  cerebral  vessels  gives  rise 
to  almost  immediate  abolition  of  the  functions  of  the  cerebrum.  Under 
such  Circumstances,  the  poverty  of  the  nerve-trunks  in  blood-vessels  is 
striking.  As,  however,  the  central  nervous  organs,  especially  the  brain, 
undoubtedly  receive  a  larger  blood-supply  the  opinion  seems  justified 
that  they  are  the  seat  of  more  active  metabolism  than  the  simple 
conducting  apparatus.  The  ganglia  form  much  lymph. 

Hodge,  Vas,  Nissl,  Mann,  Beek,  F.  Pick,  and  others  have  studied  the  changes 
in  the  ganglion-cells  that  take  place  as  a  result  of  activity  and  exhaustion.  It 


IRRITABILITY    OF    NERVES.  629 

has  been  found  that  during  rest  the  chromatic  substance  accumulates  in  the 
cells,  while  it  is  consumed  during  activity.  Actively  functionating  cells  are 
enlarged,  as  are  also  their  nuclei  and  nucleoli.  Exhaustion  is  indicated  by 
contraction  of  the  nucleus,  probably  also  of  the  cell,  and  by  the  formation  of 
a  diffusely  staining  substance  in  the  nucleus.  The  clearing  up  in  the  vicinity  of 
the  nucleus  is  due  to  disappearance  of  the  chromatic  substance.  According  to 
Levi  numerous  granules  appear  in  the  chromatic  substance  in  rabbits  as  a  result 
of  activity  of  the  spinal  ganglia.  These  granules  were  wanting  in  the  state  of 
rest.  Pick  found  the  Nissl  bodies  in  the  spinal  cord  reduced  in  size.  Demoor 
maintains  that  the  active  cells  of  the  visual  area  stain  less  intensely,  are  diminished 
in  size,  and  have  an  irregular  nucleus.  Poisoning  with  morphin  gives  rise  to  a 
granular  condition  of  the  protoplasmic  processes  of  the  cortical  cells.  The  cells 
of  the  motor  area  of  the  cortex  are  shrunken  after  long-continued  irritation,  and 
their  processes  are  granular. 


IRRITABILITY  OF  NERVES.     STIMULI. 

Nerves  possess  the  property  of  being  thrown  into  a  condition  of 
irritability  by  stimuli,  and  they  are,  therefore,  spoken  of  as  irritable. 
Stimuli  may  be  effective  if  applied  at  any  point  in  the  course  of  a  nerve. 
An  entirely  uninjured  and  normally  nourished  nerve  possesses  the  same 
degree  of  irritability  at  all  points  in  its  course.  In  new-born  animals 
and  in  human  beings  up  to  the  sixth  week  the  nerves  (and  muscles) 
react  less  readily  to  electrical  stimuli;  the  resulting  contractions  are 
slower  and  more  extensive.  The  cause  appears  to  reside  in  the  incom- 
plete development  and  evolution  of  these  tissues.  All  stimuli,  if  power- 
ful and  long  continued,  soon  cause  paralysis  by  over-irritation  of  the  nerve 
at  the  site  of  application.  The  nerve,  therefore,  loses  its  irritability  at 
this  point.  Further  on,  toward  the  periphery,  however,  its  irritability 
is  still  retained. 

Mechanical  stimuli  affect  the  nerve  when  they  induce  a  change  in  the  form 
of  the  nerve-particles  with  a  certain  degree  of  rapidity;  for  example,  a  blow, 
pressure,  crushing,  traction,  puncture,  section,  concussion,  sudden  release  of  ten- 
sion. In  the  case  of  sensory  nerves  pain  occurs  as  a  result  ("falling  asleep"  of 
the  extremities ;  pain  on  striking  the  ulnar  nerve  in  its  groove  at  the  elbow) ; 
in  the  case  of  motor  nerves,  muscular  contraction.  If  the  mechanical  injury  to 
the  fibers  has  resulted  in  interference  with  the  continuity  of  their  conducting 
elements  (the  axis-cylinders),  the  conductivity  of  the  nerve  ceases.  If  the 
molecular  arrangement  of  the  nerve-particles  is  permanently  disturbed  (for 
example  by  concussion) ,  the  irritability  of  the  nerve  is  lost. 

A  light  blow  on  the  musculo-spiral  nerve  in  the  arm,  on  the  brachial  plexus 
in  the  supraclavicular  fossa,  causes  in  normal  individuals  contraction  in  the  muscles 
supplied.  The  mechanical  irritability  of  nerves  may  be  abnormally  increased 
under  pathological  conditions. 

Tigerstedt  discovered  that  the  minimal  value  of  the  mechanical  stimulation 
(induced  by  the  falling  of  a  weight  upon  the  isolated  nerve)  is  900  milligram- 
millimeters,  the  maximal  value  from  7000  to  8000.  More  powerful  stimulation 
causes  exhaustion,  but  this  does  not  extend  beyond  the  irritated  area.  The 
mechanically  irritated  nerve  does  not  acquire  an  acid  reaction.  A  lesser  degree 
of  pressure  or  tension  increases  the  irritability,  which  again  diminishes  after  a 
short  time.  The  work  done  by  the  irritated  muscle  as  a  result  of  this  irritation 
was  as  much  as  100  times  greater  than  the  kinetic  energy  of  the  mechanical  nerve- 
irritation. 

If  a  mechanical  influence  acts  gradually  the  nerve  may  lose  its  conductivity 
or  its  irritability  without  any  manifestation  of  irritation  in  the  process.  This  class 
of  phenomena  includes  the  paralysis  in  the  distribution  of  the  brachial  plexus  as 
a  result  of  long-continued  pressure  by  a  crutch  and  the  paralysis  of  the  recurrent 
laryngeal  nerve  by  aneurysms. 

As  a  result  of  pressure  upon  nerves  by  gradually  increasing  the  weight  applied 
there  was  observed  at  first  a.n  increase  and  then  a  diminution  in  the  irritability. 


630  IRRITABILITY    OF    NERVES. 

In  mixed  nerves  the  reflex-conducting  power  is  abolished  earlier  than  the  motor 
power. 

Nerve-stretching  is  a  mechanical  procedure  that  has  been  employed  for  thera- 
peutic purposes.  If  the  exposed  nerve  is  stretched,  the  tension  acts  as  an  irritant 
when  it  reaches  a  certain  degree.  After  slight  stretching  the  reflex  irritability  is 
at  first  increased ;  stronger  stretching  causes  for  a  time  diminution  of  irritability, 
as  well  as  of  reflex  activity,  and  even  temporary  paralysis.  The  most  extreme 
degree  of  stretching  finally  gives  rise  to  permanent  paralysis.  It  appears  that 
the  centripetal  fibers  (sciatic  nerve)  lose  their  conductivity  earlier  than  the  cen- 
trifugal fibers.  In  the  process  of  stretching  mechanical  changes  are  induced  in 
the  nerve-tubes  or  in  the  end-organs  that  bring  about  alteration  in  irritability. 
The  effect  of  the  stretching  may  be  propagated  also  to  the  central  nervous  system. 
Paralysis  following  forced  stretching  may  undergo  a  marked  degree  of  recovery. 
If,  therefore,  a  nerve  is  in  a  state  of  excessive  irritability,  for  example  in  a  case 
of  neuralgia,  if  this  be  due  to  inflammatory  fixation  or  constriction  of  a  nerve 
in  its  course,  nerve-stretching  may  be  useful  partly  by  diminishing  the  irritability 
of  the  nerve,  partly  by  breaking  up  the  inflammatory  adhesions.  Nerve-stretching 
may  be  useful  also  in  cases  in  which  irritation  of  a  centripetal  nerve  gives  rise 
to  reflex  or  epileptic  convulsions  by  diminishing  the  peripheral  irritability  (in 
addition  to  the  action  described).  In  the  case  also  of  diseases  of  the  spinal  cord 
that  have  not  yet  advanced  to  a  state  of  gross  degeneration  nerve-stretching  is 
not  to  be  neglected  as  a  therapeutic  agent. 

For  physiological  purposes  R.  Heidenhain's  tetanomotor  is  employed  to 
induce  mechanical  nerve-stimulation.  This  consists  of  a  vibrating  ivory  hammer 
attached  to  an  extension  of  the  Neef  's  hammer  of  the  induction-apparatus,  which 
by  a  rapid  succession  of  blows  upon  the  underlying  nerve  develops  a  condition 
of  tetanus  lasting  up  to  two  minutes. 

Naturally,  other  mechanical  stimuli  of  a  similar  nature  will  yield  analogous 
results,  such  as  contact  with  a  vibrating  tuning-fork,  or  with  a  sounding  string, 
stroking  with  a  bow-like  apparatus,  rhythmic  stretching  of  the  nerve  (longitudinal 
traction) . 

Thermal  Stimuli. — If  a  frog's  nerve  be  heated  to  45°  C.  its  irritability  at  first 
increases  and  then  declines.  The  higher  the  temperature  the  greater  is  the 
increase  in  irritability,  but  the  shorter  is  its  duration.  Heated  for  a  short  time 
to  50°  C.  the  irritability  and  the  conductivity  of  the  nerve  are  abolished;  but  on 
cooling,  the  frog's  nerve  is  capable  of  recovering  its  irritability.  Heat  increased 
above  65°  C.  destroys  the  irritability,  without  preceding  contraction,  with  degenera- 
tion of  the  myelin.  A  gradually  frozen  nerve  retains  its  irritability  when  thawed. 
The  cooled  nerve  retains  its  irritability  for  a  long  time.  In  motor  nerves  the  irri- 
tability is  increased,  but  the  contractions  are  slighter  and  more  prolonged  and 
the  conduction  in  the  nerve  continues  for  a  longer  time.  Sudden  cooling  of  nerves 
by  a  temperature  of  — 5°  C.  and  below  excites  contraction,  as  does  also  sudden 
warming  by  a  temperature  of  from  40°  to  45°  C.  and  above.  At  still  higher  tem- 
peratures persistent  tetanus  occurs  instead  of  the  contraction.  All  such  irritat- 
ing variations  in  temperature  if  continued  rapidly  destroy  the  nerve,  and  probably 
give  rise  to  chemical  and  mechanical  alterations  in  the  nerve-substance. 

Of  the  nerves  of  mammals  only  the  centripetal  fibers  and  the  dilators  of 
the  blood-vessels  exhibit  the  effects  of  irritation  by  temperatures  between  45° 
and  50°  C.  The  remainder  exhibit  merely  a  change  in  irritability.  Cooling 
to  +5°  C.  diminishes  the  irritability  of  all  of  the  nerve-fibers.  Cooling  of  the 
ulnar  nerve  by  immersion  of  the  elbow-ioint  in  cold  water  causes  pain  and  con- 
traction in  the  peripheral  distribution  of  the  nerve,  such  as  is  brought  about  by 
prolonged  pressure.  Local  cooling  of  nerves  increases  the  irritability  to  the 
constant  current  lasting  for  a  considerable  time  (at  least  for  ^o  second) ,  and  to 
mechanical  and  some  chemical  stimuli.  A  marked  lowering  of  the  temperature 
locally  may  abolish  the  conductivity  of  a  nerve  at  the  point  of  application. 
Local  heating  of  the  nerve  to  35°  C.  increases  its  irritability  to  the  faradic  cur- 
rent, as  well  as  to  constant  currents  of  shorter  duration  (of  less  than  ^  second). 

According  to  Howell  the  extremes  at  which  irritability  is  still  present  in 
motor  nerves  are  4°  (cat),  in  the  inhibitory  nerve  of  the  heart  below  15°,  in  vaso- 
motor  nerves  between  2°  and  51°,  in  the  sweat-nerves  between  3°  and  45°,  in 
the  respiratory  fibers  of  the  vagus  7°,  and  in  the  pressor  fibers  of  the  sciatic  in 
rabbits  about  2°  C. 

Chemical  stimuli  (chemical  muscle-stimuli  are  discussed  on  p.  556)  give  rise 
to  irritation  in  nerves  when  they  cause  alteration  in  the  constitution  of  the  latter 


IRRITABILITY    OF    NERVES.  631 

with  a  certain  degree  of  rapidity.  As  a  result  of  the  action  of  most  of  these 
irritants  the  irritability  of  the  nerves  is  at  first  increased ;  then  follows  diminution 
to  the  point  of  abolition.  Chemical  irritants  have,  as  a  rule,  less  effect  on  sensory 
nerve-fibers  than  on  motor  fibers;  so  that  chemical  and  thermal  stimuli  have  to 
a  certain  degree  opposite  effects  upon  motor  and  sensory  nerves.  According  to 
Griitzner  the  failure  of  chemical  stimuli  to  exert  any  effect  on  sensory  nerves 
observed  in  most  cases  may,  however,  be  due  for  the  most  part  to  want  of  simul- 
taneousness  of  irritation  of  the  individual  fibers;  and  this  view  is  supported  by 
the  circumstance  that  substances  having  a  rapid  and  powerful  action  are  capable 
under  certain  conditions  of  stimulating  also  centripetal  fibers.  Potassium  and  its 
salts  exert  a  stronger  action  upon  the  sensory  nerves  (causing  pain)  than  sodium; 
ammonium  causes  the  most  intense  irritation.  The  painful  effect  of  acids  is 
proportionate  to  their  degree  of  acidity.  Of  the  monatomic  alcohols  the  higher 
have  a  more  intense  action  than  the  lower.  Among  stimuli  of  the  motor  nerves 
are:  (a)  rapid  dehydration  either  by  dry  air  (surrounding  the  nerve  with  filter- 
paper  or  suspending  it  over  sulphuric  acid)  or  by  dehydrating  fluids,  such  as  con- 
centrated solutions  of  neutral  alkaline  salts  (sodium  chlorid  is  said  to  stimulate 
only  the  motor  nerves  in  mammals;  sugar,  urea,  also  concentrated  glycerin  and 
solutions  of  some  metallic  salts) .  Subsequent  addition  of  water  at  times  causes 
the  contractions  and  spasm  to  disappear  and  the  nerve  may  remain  irritable.  The 
dehydration  at  first  increases  the  irritability,  but  later  it  is  diminished.  Imbi- 
bition of  water  decreases  the  irritability  of  the  nerves.  (6)  Free  alkalies,  the  min- 
eral acids  (not  phosphoric  acid),  many  organic  acids  (acetic,  oxalic,  tartaric,  lactic), 
most  salts  of  the  heavy  metals.  While  acids  generally  have  irritant  effects  only 
in  strong  concentration,  caustic  alkalies  have  such  effects  in  solutions  down  to 
0.8  per  cent,  or  even  as  low  as  o.i  per  cent.  Neutral  potassium-salts  in  concen- 
trated form  cause  rapid  destruction,  but  are  less  powerfully  irritant  than  sodium- 
combinations.  Neutral  potassium-salts,  when  used  in  dilute  solution,  at  first 
increase  the  irritability  of  the  nerves  and  then  diminish  it,  as  can  be  demonstrated 
especially  by  stimulation  with  the  opening  shock  of  an  induced  current,  (c)  The 
anesthetics  (ether,  chloroform)  and  carbon  dioxid  in  small  amounts  increase  the 
irritability  of  isolated  nerves;  in  larger  quantities  they  diminish  it.  The  haloid 
salts,  especially  the  bromids,  likewise  diminish  the  irritability.  Of  the  alkaloids 
and  narcotics  some  (opium,  cocain,  curarin,  chloral  hydrate)  diminish  the  irrita- 
bility in  part,  while  others  (morphin,  strychnin,  muscarin,  atropin)  are  indifferent 
in  action.  Other  substances,  such  as  dilute  alcohol,  bile,  salts  of  the  biliary  acids, 
and  sugar,  generally  excite  contractions  at  first,  after  which  the  nerve  rapidly 
dies.  Ammonia,  lime-water,  solutions  of  some  metallic  salts,  carbon  disulphid, 
and  the  ethereal  oils  destroy  the  nerve  without  stimulating  it  (thus  without 
inducing  contractions  in  the  frog-preparation) .  Carbolic  acid  (which  excites 
convulsions  on  direct  application  to  the  spinal  cord)  has  a  similar  action.  These 
substances  have  a  directly  irritating  effect  upon  the  muscle. 

Tannic  acid  has  no  irritating  effect  either  upon  the  nerves  or  upon  the  muscles. 
In  general,  the  irritating  substances  must  be  applied  to  the  nerves  in  more  con- 
centrated solution  than  to  the  muscles  in  order  that  contractions  may  result. 

Of  chemically  allied  substances  those  act  most  intensely  upon  motor  nerves 
that  have  a  higher  molecular  weight;  for  example  sodium  iodid  acts  more  in- 
tensely than  sodium  chlorid. 

The  Physiological  Stimulus.— The  nature  of  the  physiological  nerve-stimulus 
in  the  normal  body  is  not  known.  It  passes  either  in  a  centrifugal  direction, 
from  the  central  nervous  system,  as  motor,  secretory,  or  inhibitory  impulses,  or 
in  a  centripetal  direction,  from  the  specific  terminal  expansion  of  the  organs  of 
special  sense  and  of  the  sensory  nerves.  The  last-named  class  of  stimuli  are 
conveyed  to  the  central  nervous  organs,  where  they  are  perceived  as  sensations,  or 
they  give  rise  by  transference  within  the  center  to  effects  transmitted  in  a  centri- 
fugal direction  and  known  as  reflex  processes.  The  individual  physiological 
motor  stimulus  occupies  a  longer  time  than  the  transitory  irritation  of  an  induced 
current.  It  is  not  a  uniform  process,  causing  different  effects  in  accordance  with 
the  varying  intensity  and  the  more  or  less  frequent  repetition,  but  it  is  rather 
a  process  exhibiting  marked  variability  in  the  time  of  its  occurrence  and  attain- 
ing a  duration  as  great  as  one-eighth  of  a  second. 

Homologous  and  heterologous  irritants  and  the  law  of  specific  energy  are 
considered  on  p.  813. 

Electrical  Stimuli. — The  electrical  current  exerts  its  strongest  irritant  effects 
upon  a  nerve  at  the  time  of  its  entrance  into  the  nerve,  and  at  the  time  of 


632  IRRITABILITY    OF    NERVES. 

its  disappearance.  In  like  manner  any  rapid  increase  or  decrease  of  the  current 
passing  through  a  nerve  has  a  strong  irritant  effect.  If,  on  the  other  hand,  the 
current  be  allowed  to  pass  gradually  into  the  nerve-trunk,  or  to  disappear  gradu- 
ally, or  if  the  current  passing  through  the  nerve  be  gradually  increased  or  dimin- 
ished, the  visible  signs  of  nerve-irritation  are  much  less  marked.  In  general,  the 
stimulation  is  most  pronounced  the  more  rapid  the  current-variation  within  the 
nerve,  that  is,  the  more  suddenly  the  strength  of  the  current  passing  through  the 
nerve  is  increased  or  diminished. 

This  law  applies,  however,  only  to  the  rapidly  moving  muscles  and  their 
nerves  (frog,  warm-blooded  animals) .  For  muscles  that  move  slowly  (toad) ,  the 
unstriated  muscles  and  those  of  some  invertebrates,  slowly  acting  and  slowly  in- 
creasing electrical  stimuli  are  the  most  effective. 

If  linear  variation  in  the  current  (v.  Fleischl's  orthorheonome,  v.  Kries' 
spring  rheonome)  be  employed  as  the  stimulus,  the  intensity  of  the  current  must 
be  the  greater  in  order  to  obtain  the  same  irritant  effect  the  more  slowly  such 
linear  variation  takes  place. 

The  electrical  current  must  have  a  definite  strength  before  it  becomes  active 
(threshold- value) .  With  uniform  increase  in  the  strength  of  the  current  the  size  of 
the  muscular  contractions  first  increases  rapidly  and  then  more  slowly.  An 
electrical  current  must  continue  at  least  for  0.0015  second  in  order  to  stimulate  the 
nerve;  a  current  of  shorter  duration  will  have  no  effect.  If  the  duration  of  the 
current  be  somewhat  longer  the  stimulation  on  opening  is  wanting.  The  duration 
of  closure  of  a  constant  current  that  continues  for  a  time  just  short  enough  to 
be  inactive  need  be  prolonged  only  from  1.3  times  to  twice  as  long  in  order  to 
attain  the  most  complete  effects. 

The  electrical  current,  further,  is  most  effective  when  it  is  passed  through  the 
long  axis  of  a  nerve.  It  is  ineffective  when  applied  at  right  angles  to  the  axis 
of  the  nerve.  The  muscle  also  is  less  responsive  to  electrical  currents  that  pass 
transversely  through  its  fibers  than  to  such  as  pass  longitudinally.  The  greater, 
further,  the  length  of  nerve  through  which  the  current  passes  the  smaller  need 
the  electrical  stimulus  be. 

When  the  constant  current  is  applied  to  a  motor  nerve  it  exerts  its  most 
pronounced  stimulating  effect  on  closing  and  on  opening.  The  stimulation, 
however,  does  not  completely  cease  during  the  period  the  current  is  closed,  for  if 
the  current  be  of  moderate  strength  the  muscle  supplied  by  it  remains  in  a  con- 
dition of  tetanus — galvanotonus  or  closing  tetanus.  The  analogous  reaction  of 
the  muscle  on  direct  application  of  the  constant  current  is  considered  on  p.  563. 
When  strong  currents  are  employed  this  tetanus,  it  is  true,  subsides,  but  it  does 
so  because  as  a  result  of  the  action  of  the  current  in  the  nerve  through  diminution 
of  its  irritability  resistances  are  developed  that  prevent  the  stimulation  from 
reaching  the  muscle.  According  to  Hermann,  a  descending  current  excites  this 
tetanus  more  readily  if  the  current  is  passed  through  the  nerve  at  some  distance 
from  the  muscle ;  while  an  ascending  current  excites  the  tetanus  more  readily  when 
applied  in  the  neighborhood  of  the  muscle.  The  constant  current  manifests  its 
stimulating  influence  upon  sensory  nerves  in  most  marked  degree  at  the  moment 
of  closing  and  opening.  During  the  period  of  closure  feeble  stimulation  is  per- 
ceptible, but  strong  currents  may  under  such  circumstances  give  rise  to  un- 
bearable sensations.  Closing,  opening,  and  the  passage  of  the  current  stimulate 
all  centripetal  fibers,  and  also  the  vasodilators  of  the  skin.  The  constant  current 
has  no  effect  upon  vasoconstrictor  and  secretory  fibers. 

The  following  observation  of  Wedenskij  is  noteworthy:  If  the  sciatic  nerve  of 
a  frog  be  irritated  by  means  of  strong  and  frequent  currents  the  tetanus  induced 
soon  disappears  on  account  of  exhaustion  of  the  portion  of  nerve  concerned,  but 
begins  again  if  the  stimulus  is  either  weakened  or  made  less  frequent.  If  the 
muscle  is  relaxed  after  the  strong  irritation,  it  contracts  again  if  stimulated  directly 
by  a  current  of  moderate  intensity  after  the  nerve-stimulation  has  been  re- 
moved. The  fact  appears  noteworthy  that  if  two  tetanizing  stimuli  are  ap- 
plied to  the  nerve  of  a  frog-preparation,  the  two  stimulations  may  counteract  each 
other.  If,  for  example,  sodium  chlorid  be  applied  to  the  portion  of  nerve  near 
the  leg  until  the  muscles  are  thrown  into  a  tetanic  contraction,  this  will  cease 
if  at  the  same  time  a  portion  of  the  nerve  higher  up  is  irritated.  Both  stimulating 
effects  may,  however,  act  together. 

The  phenomenon  of  deficiency  is  discussed  on  p.  664. 

If  the  individual  short  current-shock  occurs  in  rapid  succession  the  related 
muscle  is  thrown  into  a  state  of  tetanus. 


DIMINISHED  IRRITABILITY;  DEATH  OF  THE  NERVE.  633 

The  motor  nerve  possesses  a  greater  specific  irritability  to  electrical  stimuli 
than  the  muscle-substance.  This  can  be  recognized  from  the  circumstance  that 
contractions  take  place  on  feebler  stimulation  if  the  nerve  rather  than  the  curarized 
muscle  is  stimulated. 

Mention  should  yet  be  made  of  the  remarkable  fact  that  on  irritation  of  a 
motor  nerve  the  stimulating  effect  (contraction)  is  under  certain  circumstances 
the  greater  the  nearer  the  point  of  stimulation  to  the  central  nervous  system. 
According  to  v.  Fleischl,  however,  the  nerves  are  equally  responsive  to  chemical 
stimuli  at  all  points  in  their  course.  For  electrical  stimuli  they  are  more  responsive 
in  their  proximal  portions  only  when  the  stimulating  current  is  of  the  descending 
type.  The  reverse  is  said  to  be  the  case  when  the  current  is  of  the  ascending 
type.  Rutherford  and  Hallsten  found  that  the  reflex  contractions  induced  by  the 
irritation  of  a  sensory  nerve  are  the  greater  the  more  proximally  the  irritation  is 
applied. 

Nerve-fibers  of  like  function  in  the  same  trunk  do  not  always  have  the  same 
degree  of  irritability.  Thus,  for  example,  feeble  stimulation  of  the  sciatic  nerve 
of  the  frog  causes  contractions  only  of  the  flexors,  while  stronger  stimulation  is 
required  to  induce  contraction  also  of  the  extensors.  The  effects  of  stimulation 
with  long  or  with  short  intervals  are  analogous.  According  to  Ritter,  the  nerves 
for  the  flexors  also  degenerate  first.  In  a  similar  manner  feeble  stimulation  of 
the  hypoglossal  nerve  causes  retraction  of  the  tongue,  while  strong  stimulation 
causes  protrusion.  In  the  facial  nerve  the  fibers  for  the  eyelids  are  more  irritable 
than  those  for  the  mouth  or  the  ear. 

Also  on  direct  irritation  of  the  muscles  (of  curarized  animals)  the  flexors 
contract  in  response  to  a  weaker  current  than  the  extensors,  but  at  the  same  time 
the  former  are  more  readily  exhausted.  Poisons  generally  injure  the  flexors 
earlier  than  the  extensors.  Treatment  of  a  frog-preparation  with  ether  causes 
flexion  to  occur  on  strong  stimulation  of  the  sciatic  nerve.  Increase  of  the  stimu- 
lation, however,  finally  causes  extension.  Likewise,  strong  stimulation  of  the 
recurrent,  laryngeal  nerve  during  deep  ether-narcosis  causes  dilatation,  during 
slight  intoxication  constriction,  of  the  glottis.  Dilatation  of  the  glottis  has  been 
induced  by  feeble  stimulation.  The  adductor  muscle  of  the  crab's  claw  relaxes 
on  feeble  stimulation,  while  it  undergoes  contraction  on  strong  stimulation. 

Stimuli  may  be  applied  also  by  means  of  a  single  electrode  of  the  induction  - 
apparatus — unipolar  induced  effect.  The  cause  resides  in  a  movement  of  the 
electrical  fluid  to  and  from  the  free  extremities  of  the  open  induced  circuit  at  the 
moment  of  induction. 

Upon  muscles  the  action  of  electrical  irritants  is  entirely  similar  to  that  upon 
nerves.  The  following,  however,  is  noteworthy:  currents  of  short  duration  have 
no  effect  upon  muscles  whose  nerves  are  paralyzed  by  curare,  as  well  as  .upon 
muscles  enfeebled  by  intense  exhaustion,  degeneration,  or  pathological  paralytic 
conditions. 

A  remarkable  reaction  designated  galvanotropism  is  exhibited  by  entire  animals 
when  a  current  is  passed  through  them.  Feeble  currents  cause  the  animal  to 
be  thrown  into  a  position  with  its  long  axis  corresponding  to  the  direction  of  the 
current,  while  strong  currents  have  the  opposite  effect. 


DIMINISHED  IRRITABILITY;   DEATH  OF  THE  NERVE. 
NERVE-DEGENERATION  AND  NERVE-REGENERATION. 

The  persistence  of  normal  irritability  in  a  nerve  within  the  intact 
body  depends  first  upon  normal  nutritive  processes  and  the  blood-supply 
of  the  nerve.  In  this  relation  it  should  be  especially  mentioned  that 
insufficient  nutrition  is  generally  followed  at  first  by  an  increase  in  the 
irritability.  Only  after  advanced  disturbance  does  the  irritability 
diminish. 

The  physician  should  constantly  bear  in  mind  that  whenever  he  encounters 
evidences  of  increased  irritability  of  nerves  under  the  influence  of  defective  or 
disturbed  nutrition,  as  may  be  manifested  in  various  ways-,  such  as  general  ner- 
vousness and  irritable  weakness,  etc.,  the  condition  is  the  beginning  stage  of  a 
diminution  of  nerve-energy.  Under  such  circumstances  the  nutrition  should  be 


634 


NERVE-DEGENERATION    AND    NERVE-REGENERATION. 


improved  by  restorative  remedies.  Only  the  ignorant,  misled  by  the  signs  of 
increased  irritability  of  the  nervous  system,  would  employ  depressing  measures. 
In  case  of  total  obstruction  of  the  blood-supply  to  the  nerve-trunk,  its  irritability 
may  persist  for  from  five  to  ten  hours. 

If  the  terminal  nerve-apparatus  is  exposed  to  a  temporary  disturbance  of  its 


B 


FIG.  223. — Degeneration  and  Regeneration  of  Nerves:  A,  Early, 
gross  breaking  up  of  the  myelin.  B,  Further  breaking  up  of 
the  myelin  (osmic-acid  stain).  C,  Disintegration  of  the  axis- 
cylinder,  surrounded  by  (bright)  fragments  of  myelin.  D. 
Accumulation  of  nuclei  with  remains  of  myelin  (bright)  in 
the  swollen  spindle-shaped  fiber.  E,  The  new  fiber  passing  in 
a  tortuous  course  through  the  old  sheath.  F,  The  new  com- 
pleted fiber,  with  the  new  sheath  of  Schwann  (s«)  within  the 
old  sheath  of  Schwann  (sa)  (after  Cossy  and  Dejerine). 


normal  nutrition,  it  responds  to  the  restoration  of  normal  nutritive  processes  by 
the  development  of  a  more  or  less  intense  irritative  process.  The  effective  dis- 
turbance of  nutrition  need  exist  a  shorter  time  the  more  sensitive  the  nervous 
end-apparatus  in  question  is  to  the  nutritive  disturbance,  such  as  cutting  off  of 
the  arterial  blood-supply  or  interference  with  respiration. 

Long-continued  excessive  irritation  of  a  nerve  without  suitable  in- 
tervals of  rest  for  purposes  of  recuperation  soon  causes  fatigue  of  the  nerve 


NERVE-DEGENERATION    AND    NERVE-REGENERATION.  635 

and  later  on  diminution  of  irritability  through  exhaustion.  Neverthe- 
less the  nerve  exhibits  extraordinary  resistance  to  various  stimuli.  It 
may  not  be  exhausted  even  after  irritation  continued  for  hours. 

The  enfeeblement  and  finally  the  cessation  of  muscular  contraction  after 
long-continued  stimulation  of  the  motor  nerve  connected  with  the  muscle  are  due 
to  exhaustion  of  the  muscle  and  not  of  the  nerve.  If  while  a  nerve  is  being  stimu- 
lated the  muscle  is  prevented  from  contracting,  by  rendering  the  nerve  incapable 
of  conducting  at  a  point  distal  to  the  site  of  stimulation  (by  anelectrotonus  or 
curare) ,  it  will  be  found  that  even  after  twelve  hours  of  constant  irritation  of  the 
nerve,  the  muscle  can  again  be  made  to  contract  if  this  obstruction  (blocking  of 
the  nerve)  be  removed.  Also  the  observation  that  the  negative  variation  in  the 
nerve-current  in  an  irritated  nerve  continues  for  a  long  time  is  interpreted  in  the 
same  way. 

The  recovery  of  nerves  takes  place  at  first  slowly,  then  somewhat 
more  quickly,  and  finally  again  more  slowly.  Should  recovery  not  take 
place  in  the  first  half -hour  in  the  frog,  after  long,  intense  irritation,  the 
nerve  does  not  recover  at  all. 

Long-continued  inactivity  diminishes  the  irritability  to  the  point 
of  complete  abolition. 

The  characteristic  example  of  this  is  furnished  by  the  degeneration  of  nerves 
after  amputation  of  an  extremity.  Not  only  the  sensory  nerves  to  the  cutaneous 
area,  etc.,  removed,  but  also  the  motor  nerves  to  the  muscles  removed,  undergo 
atrophy,  and  also  their  continuations  in  the  spinal  cord  exhibit  atrophic  changes. 
The  degeneration  of  the  optic  nerve  after  extirpation  of  the  eye  and  of  the  auditory 
nerve  after  that  of  the  internal  ear  is  considered  on  pp.  679  and  699. 

Excised  nerves  preserve  for  a  time,  as  does  muscle,  their  func- 
tional activity.  At  first  the  end-apparatus  of  the  nerve  degenerates ; 
then,  in  the  case  of  motor  nerves,  the  muscle;  and  finally  the  nerve 
itself. 

Nerve-fibers  are  capable  of  maintaining  their  normal  nutrition  only 
when  they  are  in  uninterrupted  connection  with  their  trophic  center, 
which  controls  the  nutritive  processes.  If,  however,  the  nerve  within 
the  otherwise  normal  body  is  separated  from  its  nutritional  center,  as 
by  section  or  crushing,  it  loses  its  irritability  in  a  short  time  and  the  per- 
ipheral end  undergoes  fatty  degeneration,  which  begins  in  warm-blooded 
animals  in  the  course  of  from  tour  to  six  days,  in  cold-blooded  animals 
after  a  longer  interval. 

The  irritability  of  the  nerve  under  these  conditions — the  so-called  reaction  of 
degeneration — is  discussed  on  p.  672.  The  degeneration  after  section  of  the  roots 
of  the  spinal  nerves  is  described  on  p.  716. 

In  the  otherwise  intact  body  both  extremities  at  the  point  of  division 
undergo  traumatic  degeneration  in  from  one  to  two  days  in  frogs,  as 
a  result  of  which  the  white  substance  of  Schwann  and  the  axis-cylinder 
can  no  longer  be  distinctly  differentiated.  This  degeneration  extends, 
however,  only  to  the  next  node  of  Ranvier.  Later,  so-called  fatty 
degeneration  takes  place  simultaneously  in  the  entire  peripheral  portion. 

Fatty  degeneration  of  nerves  begins  by  a  breaking  up  of  the  myelin  (Fig. 
223,  .4),  which  later  becomes  transformed  into  drop-like  masses  (B).  The  axis- 
cylinder  also  swells  up  and  disintegrates  (seventh  day)  (Q.  The  nuclei  in  the 
sheath  of  Schwann  become  swollen  and  proliferate  by  mitosis  (up  to  the  tenth 
day)  (D).  According  to  Ranvier,  it  is  this  nuclear  proliferation  and  that  of  the 
protoplasm  or  neuroplasm  lining  the  sheath  of  Schwann  that  first  cause  disinte- 
gration of  the  myelin  and  the  axis-cylinder  and  that  subsequently  increase  to  such 


636  NERVE-DEGENERATION    AND    NERVE-REGENERATION. 

a  degree  as  to  convert  the  entire  peripheral  portion  of  the  nerve  into  a  connective- 
tissue  strand,  the  fragments  formed  at  the  same  time  undergoing  absorption.  In 
the  motor  end-plates  degeneration  likewise  takes  place,  at  first  in  the  non-medul- 
lated  fibers,  then  in  the  terminal  filaments  and  lastly  in  the  nerve-trunk. 

If  regeneration  takes  place,  the  extremities  of  the  divided  nerve  must 
have  united,  and  for  this  purpose  in  the  human  being  nerve-suture  has 
been  employed. 

In  the  middle  of  the  fourth  week  small,  bright  bands,  developed  from  the 
proliferated  protoplasm,  appear  within  the  sheath  of  Schwann,  and  these  penetrate 
between  the  nuclei  and  the  remains  of  the  myelin  (E).  They  are  the  new  axis- 
cylinders,  which  thus  develop  in  an  endogenous  manner  within  the  old  sheath  of 
Schwann.  Soon  they  become  thicker,  and  receive  myelin,  with  Lantermann's 
clefts,  Ranvier's  nodes  and  sheaths  of  Schwann  (from  the  26.  to  the  3d  month) 
(F).  According  to  Ziegler  the  new  axis-cylinder,  which  develops  independently, 
becomes  only  later  connected  with  the  central  stump.  The  formation  of  the 
myelin  takes  place  continuously.  A  portion  of  the  nuclei  disappear;  the  outer, 
with  their  protoplasmic  portion,  give  rise  to  the  sheaths  of  Schwann.  Exactly  the 
same  process  takes  place  in  nerves  ligated  in  continuity.  It  is  a  remarkable  fact 
that  several  new  fibers  may  develop  within  an  old  fiber.  From  the  central  ex- 
tremity of  the  divided  nerve-fiber  the  axis-cylinder  after  the  fourteenth  day  grows 
toward  that  of  the  newly  formed  fiber  and  unites  with  it.  The  central  extremity 
of  a  divided  motor  nerve  may  unite  with  the  peripheral  extremity  of  another 
nerve  and  still  functionate.  Langley  united  the  central  extremity  of  the  vagus 
with  the  peripheral  extremity  of  the  sympathetic,  and  found  after  union  took 
place  that  the  vagus  had  acquired  control  of  all  structures  supplied  by  the  cervical 
sympathetic.  According  to  Gessler  restoration  of  the  end-plate  occurs  first  in 
the  process  of  regeneration;  In  the  case  of  non-medullated  fibers  the  contents 
only  and  not  the  sheaths  degenerate  from  the  third  day  on.  After  two  days 
perceptible  regeneration  begins. 

The  regeneration  of  nerves  is  under  the  influence  of  the  nerve-centers 
acting  as  nutritive  centers.  If  nerves  be  completely  and  permanently 
separated  from  these  centers  regeneration  will  not  take  place. 

In  the  regeneration  of  mixed  nerves  sensation  returns  first,  then  vol- 
untary muscular  movement,  and  finally  movement  on  irritation  of  the 
motor  branches. 

As  the  fatty  degeneration  involves  the  peripheral  extremity  of  the  nerve  the 
observation  of  this  process  in  a  divided  nerve  affords  a  means  of  determining 
the  central  origin  of  fibers  in  a  complex  arrangement  of  nerves.  The  division  of 
motor  nerves  results  also  in  fatty  degeneration  of  the  related  muscles  in  case 
restitution  does  not  take  place. 

After  division  of  the  axis-cylinder  the  nerve-cell  from  which  it  origi- 
nates undergoes  alteration,  the  Nissl  bodies  swelling  and  disintegrating, 
though  later  being  restored.  In  the  process  of  degeneration  the  cell  in- 
creases in  volume  and  the  nucleus  assumes  a  peripheral  position.  This 
period  covers  from  one  and  three-fourths  to  twenty  days.  Restitution 
occupies  about  ninety-two  days.  These  changes  are  indications  not  of 
paralysis  of  the  cells,  but  only  of  a  certain  impairment  of  their  func- 
tion. If  the  degeneration  is  permanent  the  cell  disintegrates. 

Under  the  influence  of  various  procedures,  such  as  crushing  of  the 
nerve-fiber,  the  remarkable  observation  has  been  made  that  voluntary 
impulses  or  irritating  influences  originating  above  the  site  of  compression 
are  conducted  through  the  nerve  to  the  muscle  and  give  rise  to  con- 
traction, while  the  irritability  to  stimuli  below  the  site  of  compression 
is  greatly  diminished.  Nevertheless  Erb  did  not  observe  this  difference 
with  respect  to  mechanical  stimulation.  In  an  analogous  way  it  will 


NERVE-DEGENERATION    AND    NERVE-REGENERATION.  637 

be  found  that  the  nerves  of  animals  poisoned  with  carbon  dioxid,  alcohol, 
cocain,  curare,  or  coniin,  occasionally  also  the  nerves  in  paralyzed  parts 
of  the  body  in  man,  are  no  longer  responsive  to  local  stimuli,  although 
they  still  conduct  impulses  from  the  central  areas.  The  injured  seg- 
ment of  nerve  thus  loses  its  irritability  earlier  than  its  conductivity. 
The  analogous  phenomenon  in  muscle-fibers  is  discussed  on  p.  114. 

After  the  administration  of  certain  poisons  to  living  animals,  especi- 
ally veratrin,  the  irritability  of  the  nerves  is  at  first  increased,  then 
diminished  to  the  point  of  complete  abolition,  as  indicated  by  the  extent 
of  the  contractions  in  the  muscle  supplied  by  the  affected  motor  nerve. 
In  the  case  of  other  poisons  the  abolition  of  irritability  takes  place  rapidly, 
as,  for  example,  that  induced  by  curare.  Coniin,  cynoglossum,  methyl- 
strychnin  iodid,  and  ethyl-strychnin  iodid. 

If  a  frog-preparation  consisting  of  nerve  and  muscle  be  placed  in  a  poisonous 
solution  results  are  occasionally  manifested  which  are  different  from  those  pro- 
duced if  the  poison  is  administered  internally  to  the  living  animal.  Atropin, 
for  example,  gives  rise  to  a  reduction  in  the  irritability  of  the  preparation,  with- 
out preceding  increase.  Alcohol,  ether,  and  chloroform,  first  increase  and  then 
diminish  the  irritability. 

If  the  nerve  is  separated  mechanically  from  its  connection  with  its 
centers,  as  by  section,  or  if  the  center  has  undergone  degeneration,  the 
nerve  is  first  thrown  into  a  state  of  increased  irritability  beginning  in  its 
central  extremity  and  extending  toward  the  periphery ;  then  the  irrita- 
bility diminishes  to  the  point  of  complete  abolition.  This  process  takes 
place  more  rapidly  within  the  portions  of  the  nerve  nearer  the  center 
than  in  the  more  distal  portions.  This  phenomenon  is  known  as  the 
Ritter-Valli  law. 

The  rapidity  of  conduction  of  stimuli  in  nerves  is  increased  in  the  stage  of 
increased  irritability  and  diminished  in  that  of  lowered  irritability.  In  the  latter 
stage  the  current,  on  electrical  stimulation,  must  be  continued  for  a  longer  time 
in  order  to  be  effective,  therefore  the  rapidly  successive  shocks  of  the  induced 
current  are  generally  ineffective.  Also  the  law  of  muscular  contraction  is  modified 
in  the  various  stages  of  the  alteration  in  irritability  during  the  process  of  de- 
generation. 

Finally,  attention  should  be  called  to  the  fact  that  some  nerves 
possess  a  greater  irritability  at  certain  points,  and  that  they  retain  this 
slightly  longer  at  such  points. 

Thus,  for  example,  the  sciatic  nerve  of  the  frog  in  its  upper  third  is  more 
irritable  to  various  stimuli,  in  both  its  sensory  and  its  motor  fibers,  than  at  a  more 
distal  portion.  Such  inequalities  in  the  irritability  are  due  alone  to  accidental 
injuries  inflicted  in  the  course  of  preparation.  A  branch  is  given  off  from  the 
upper  third  of  the  sciatic.  According  to  Beck,  in  an  uninjured  nerve  the  more 
central  portions  require  stronger  stimuli  than  the  more  peripheral  to  induce  the 
first  minimal  effect. 

After  section  or  crushing  of  a  nerve  all  of  the  electrical  currents  employed 
for  the  stimulation  of  the  nerve  that  pass  in  the  nerve  from  the  site  of  the  lesion 
exert  a  much  more  active  influence  than  those  in  an  opposite  direction.  The  cause 
for  this  resides  in  the  fact  that  the  current  developing  in  the  nerve  after  the  injury 
is  added  to  the  electrical  stimulating  current.  Also  in  an  uninjured  nerve,  for 
example  the  sciatic  of  the  frog,  there  are  points  at  the  central  or  peripheral  ter- 
mination of  the  nerve,  or  where  large  branches  are  given  off,  that  react  in  a  manner 
similar  to  the  sites  of  lesion  previously  mentioned. 

The  dead  nerve  has  lost  its  irritability  completely.  Death  advances 
in  accordance  with  the  Ritter-Valli  law  from  the  central  organs  of  the 
nervous  system  gradually  to  the  peripheral  paths.  An  acid  reaction, 


638  ELECTRO-PHYSIOLOGY. 

which  is  present  in  dead  muscles,  can  be  demonstrated,  though  not  con- 
stantly, in  dead  nerves. 

The  functions  of  the  brain  cease  immediately  after  the  onset  of  death,  as 
indicated  by  loss  of  consciousness  and  cessation  of  perceptive  activity;  so  that 
reports  of  brain-activity  after  decapitation  are  to  be  relegated  to  the  realms  of 
fable.  The  vital  functions  of  the  spinal  cord,  however,  persist  for  a  somewhat 
longer  time,  particularly  those  of  the  white  substance.  Death  occurs  next  in  the 
large  nerve-trunks ;  then  in  the  nerves  for  the  extensors  and  in  those  for  the  flexors 
(in  three  or  four  hours) .  The  sympathetic  fibers  retain  their  irritability  longest  (up 
to  ten  hours  in  the  intestine).  The  irritability  of  the  nerves  of  frogs  can  be  pre- 
served for  several  days  in  the  dead  body  if  kept  in  the  cold. 

The  irritability  of  the  peripheral  stumps  of  divided  nerves  is  lost  in  pigeons 
and  rodents  in  from  two  to  three  days;  in  hoofed  animals  in  from  eight  to  ten 
days;  in  other  warm-blooded  animals  in  four  days.  In  mixed  nerves  death  of 
the  fibers  takes  place  at  different  intervals;  for  example,  in  the  vagus,  of  the 
inhibitory  fibers  first,  later  of  the  accelerator  fibers  for  the  heart.  The  stumps  of 
the  cerebral  nerves  retain  their  irritability  for  a  longer  time  than  do  those  of 
the  spinal  nerves. 


ELECTRO-PHYSIOLOGY. 

The  discussion  of  electrical  phenomena  will  be  preceded  by  a  concise  summary 
of  the  necessary  preliminary  physical  considerations,  without  which  a  comprehen- 
sion of  the  subject  is  impossible.  This  presentation  will  be  made  in  a  connected 
manner,  the  apparatus  and  methods  devised  for  electro-physiological  and  electro- 
therapeutic  purposes  being  described  in  their  proper  place.  The  student  should 
familiarize  himself  thoroughly  with  this  preliminary  knowledge  of  physics. 

PRELIMINARY   PHYSICAL   CONSIDERATIONS.     THE   GALVANIC 

CURRENT. 

ELECTROMOTORS.     CONDUCTION-RESISTANCE.     OHM'S    LAW.     CONDUC- 
TION THROUGH  ANIMAL  TISSUES.     THE  RHEOCORD. 

If  two  of  the  bodies  named  later  on  are  brought  into  direct  contact  with 
each  other,  positive  electricity  will  be  appreciable  in  the  one  and  negative  electricity 
in  the  other.  The  cause  of  this  phenomenon  is  the  electromotive  force,  which 
causes  positive  electricity  to  pass  into  the  one  body  and  negative  electricity  into 
the  other.  In  accordance  with  the  relations  of  the  bodies  to  be  discussed  later 
on  these  are  divided  into  conductors  and  non-conductors,  and  the  conductors  again 
into  those  of  the  first  and  those  of  the  second  class. 

Conductors  of  the  first  class,  chiefly  the  metals,  can  be  arranged  in  such  a 
series  (tension-series)  that,  on  contact  of  the  first  mentioned  with  one  of  the 
succeeding  members  of  the  series,  the  first  body  becomes  electrically  negative  and 
the  last  positive.  This  tension-series  is:  Manganese,  carbon,  platinum,  gold,  silver, 
copper,  iron,  tin,  lead,  zinc.  The  intensity  of  the  electrical  excitation  resulting 
from  the  contact  of  two  of  these  bodies  is  the  greater  the  farther  the  bodies  are 
separated  from  each  other  in  this  tension-series.  The  contact  of  the  bodies  may 
take  place  indifferently  at  one  or  at  several  points.  If  several  of  the  bodies  in 
the  tension-series  are  placed  one  upon  the  other,  the  electrical  tension  thus  induced 
is  the  same  as  if  the  two  terminal  bodies  alone  were  brought  in  contact,  with  omis- 
sion of  the  intervening  bodies. 

If,  on  the  other  hand,  conductors  of  the  first  and  the  second  class  are  brought 
in  contact,  the  result  is  different.  Zinc  in  contact  with  water  is  strongly  negative, 
the  fluid  positive.  Zinc  in  contact  with  diluted  acids  is  likewise  negative,  while 
other  metals,  such  as  copper  and  platinum,  are  less  actively  negative  or  even 
positive. 

Experience  has  shown  that  those  metals  in  contact  with  a  fluid  become  in 
strongest  degree  electrically  negative  that  are  chemically  most  strongly  acted  upon 
by  the  fluid.  Every  combination,  however,  exhibits  a  constant  difference  in  ten- 
sion or  potential.  The  density  of  the  amounts  of  electricity  set  free  from  both 


ELECTRO-PHYSIOLOGY,    PHYSICAL    CONSIDERATIONS.  639 

bodies  is  dependent  upon  the  size  of  the  surfaces  in  contact.  The  fluids,  for 
example  the  solutions  of  acids,  alkalies  or  salts,  are  designated  exciters  of  electricity  of 
the  second  class.  They  form  no  definite  tension-series  among  themselves.  Immersed 
in  most  of  the  fluids  named,  the  metals  nearer  the  positive  side  of  the  tension- 
series,  particularly  zinc,  prove  in  greatest  degree  electrically  negative,  while  those 
situated  nearer  the  negative  side  are  so  in  less  degree. 

If  two  different  substances  of  the  first  class  be  immersed  in  a  fluid,  with- 
out coming  in  direct  contact,  for  example  zinc,  and  copper,  free  negative  electricity 
will  appear  at  the  projecting  extremity  of  the  (positive)  zinc,  and  free  positive 
electricity  at  the  projecting  extremity  of  the  (negative)  copper.  Such  a  combina- 
tion of  two  electromotors  of  the  first  class  with  an  electromotor  of  the  second 
class  is  designated  a  galvanic  circuit.  As  long  as  the  two  metals  remain  separated 
in  the  fluid,  the  circuit  is  said  to  be  open;  as  soon,  however,  as  the  projecting 
extremities  are  connected,  for  example  by  a  wire  arc,  the  circuit  is  closed  and 
a  galvanic  current  results.  Both  forms  of  electricity  flow  mutually  into  and  neutral- 
ize each  other,  although  in  accordance  with  the  degree  in  which  the  tensions 
neutralize  each  other  new  electricity  is  constantly  generated  in  the  circuit. 

The  galvanic  current  encounters  resistances  in  its  course  that  are  designated 
conduction-resistance  (W).  This  is  (i)  directly  proportional  to  the  length  (1) 
of  the  circuit;  (2)  inversely  proportional  to  the  transverse  section  of  the  circuit 
(q) ,  the  length  being  the  same;  and  (3)  dependent  upon  the  molecular  peculiarities 
of  the  materials  (specific  conduction-resistances}.  Therefore,  the  conduction  resist- 
ance W  =  (s,  1)  -i-  q. 

The  conduction-resistance  increases  in  the  case  of  metals  and  diminishes  in 
the  case  of  fluids  with  increase  in  temperature. 

The  strength  of  the  galvanic  current  (S),  or  the  quantity  of  electricity  passing 
through  the  closed  circuit,  is  thus  proportional  to  the  electromotive  force  (E),  or 
the  electrical  tension,  but  inversely  proportional  to  the  total  conduction-resist- 
ance (L).  Therefore,  S  =  E  -H  L  (Ohm's  law). 

The  total  conduction-resistance  in  the  closed  circuit,  however,  is  made  up 
(i)  of  the  resistance  in  the  closing  arc,  external  resistance,  and  (2)  of  the 
resistance  within  the  battery  itself,  internal  resistance.  The  specific  conduction- 
resistance  of  the  different  substances  is  thus  variable.  In  the  case  of  metals  it 
is  relatively  slight,  in  that  of  fluids,  however,  quite  marked.  The  specific  con- 
duction-resistance or  rather  the  specific  conductivity  is  at  present  generally  indi- 
cated with  reference  to  mercury  as  the  unit.  Accordingly,  the  conductivity  of 
copper  is  55,  that  of  iron  from  6  to  10,  that  of  German  silver  from  3  to  6.  In 
the  case  of  fluids  the  resistance  is  exceedingly  slight — for  concentrated  salt-solution 
0.00002,  for  concentrated  solution  of  copper  sulphate  0.000004. 

Conduction  in  Animal  Tissues. — In  animal  tissues  the  conduction-resistance 
is  exceedingly  great,  generally  some  millions  of  times  as  much  as  in  metals.  A 
constant  current  passing  from  the  skin  through  the  animal  body  encounters 
progressively  diminishing  resistance,  on  account  of  the  galvanic  conductivity  of 
the  water  in  the  epidermis  and  the  increased  fulness  of  the  vessels  in  consequence 
of  the  cutaneous  irritation.  Nevertheless,  different  portions  of  the  surface  of  the 
body  react  differently,  the  least  resistance  being  offered  by  the  palms  of  the  hands 
and  the  soles  of  the  feet.  The  seat  of  the  resistance  is  the  epidermis,  after  removal 
of  which,  as  by  a  cantharidal  blister,  the  resistance  is  greatly  reduced.  The 
resistance  is  diminished,  however,  by  increased  superficies  of  the  electrodes,  and  by 
increased  moisture,  heat,  and  intensity  of  their  saturation.  It  is  greatest  in  the 
extremities,  least  in  the  face.  Dead  tissue  is  usually  a  poorer  conductor  than 
living  tissue.  If  the  current  is  passed  transversely  through  a  muscle,  it  encounters 
nine  times  as  much  resistance  as  if  it  were  passed  longitudinally  through  the 
fibers  of  the  muscle.  In  the  longitudinal  direction  the  resistance  of  the  muscle 
is  two  and  a  half  million  times  greater  than  that  of  mercury.  Tetanus  and  cadaveric 
rigidity  diminish  the  resistance  in  the  muscles.  If  the  conduction-resistance  be 
tested  with  alternating  currents  much  lower  figures  are  obtained  than  if  the 
constant  current  be  employed,  because  the  occurrence  of  polarization,  especially 
internal  polarization,  can  largely  be  omitted  from  consideration. 

The  resistance  of  the  body  varies  between  260  and  1,250,000  ohms.  It  is 
high  in  cases  of  hysteria  and  melancholia,  and  low  in  cases  of  tetanus  and  ex- 
ophthalmic goiter.  Alt  and  Schmidt  make  the  following  statements  as  to  the 
degree  of  conduction-resistance  in  various  tissues:  Nerve  0.17,  muscle  i,  blood  i, 
skin  1.25.  brain  1.57,  tendon  3.25,  fat  3.92,  muscle-sheath  4.41,  bone  14.1. 

From  Ohm's  law  two  laws  of  great  importance  in  electro-physiology  may  be 


640  ELECTRICAL    UNITS.       THE    RHEOCORD. 

deduced:  I.  If  there  is  great  resistance  in  the  circuit  in  the  arc  of  closure,  as  is 
the  case  when  a  nerve  or  a  muscle  is  intercalated  in  a  closing  arc,  the  strength 
of  the  current  may  be  increased  only  by  increasing  the  number  of  electromotive 
elements.  II.  If  the  conduction-resistance  in  the  arc  of  closure,  in  comparison 
with  that  in  the  battery,  is  exceedingly  small,  an  increase  in  the  strength  of  the 
current  cannot  be  brought  about  by  increasing  the  number  of  elements,  but  only 
by  an  increase  in  the  surface  of  the  plates  in  the  element. 

It  is  important  to  differentiate  exactly  the  terms  electromotive  force  and  current- 
strength.  The  electrical  current  may  be  compared  with  a  current  of  water.  The 
cause  of  the  current  in  the  water  is  the  hydraulic  pressure,  that  of  the  electrical 
current  the  electromotive  force.  The  current-strength  is  the  amount  of  water,  or 
the  amount  of  electricity,  that  passes  in  one  second  through  the  transverse  section 
of  the  conductor.  The  pump  that  drives  the  water  to  the  top  of  a  high  vessel, 
and  thus  generates  the  hydraulic  pressure,  corresponds  to  the  electrical  element. 
In  the  current  of  water  a  mass  is  set  in  motion,  in  the  electrical  current  a  force. 

Since  1881  the  electrical  values,  especially  current-strength,  electromotive 
force  and  resistance,  have  been  indicated  with  reference  to  units  that  have  a  simple 
relation  to  the  so-called  absolute  units.  Those  units  are  designated  absolute  that 
refer  to  the  unit  of  length  (cm.),  the  unit  of  time  (sec.)  and  unit  of  weight  (gr.). 
The  unit  of  resistance  is  the  ohm  (=  io9  absolute  units).  It  is  equal  to  the  re- 
sistance of  a  column  of  mercury  at  a  temperature  of  o°  C.,  having  a  transverse 
section  of  i  square  meter  and  a  length  of  1.026  meters.  The  ohm  is,  therefore, 
only  a  little  larger  than  the  earlier  unit  of  Siemens  (i  m.  long  and  i  square  meter 
in  transverse  section) . 

The  unit  of  electromotive  force  is  the  volt  (=  io8  absolute  units).  A  Daniell's 
cell  has  an  electromotive  force  of  i.i  volts. 

The  unit  of  current-strength  is  the  ampere,  that  is  the  current  that  generates 
an  electromotor  force  of  i  volt  in  a  circuit  having  a  resistance  of  i  ohm  (therefore 
o.i  absolute  unit).  An  ampere  generates  0.174  cu.  cm.  of  exploding  gas  in  one 
second  at  a  temperature  of  o°  and  an  atmospheric  pressure  of  760  mm. 

An  electrical  current  in  passing  through  a  wire  generates  heat,  the  amount 
of  which  is  proportional  to  the  product  of  the  resistance  multiplied  by  the  square 
of  the  current-strength,  or,  according  to  the  law  of  Ohm,  of  the  current-strength 
multiplied  by^the  electromotive  force.  The  product  of  this  from  volt  and  ampere 
is  equal  to  io7  work-units  and  is  designated  a  watt. 

According  to  the  technical  designation,  i  watt  equals  0.00136  horse-power 
(i  horse-power  equals  75  kilogrammeters) . 

As,  in  absolute  measure,  the  mechanical  heat-equivalent  of  the  gram-calory 
equals  42,000,000  work-units,  ^§  or  0.24  gram-calory  is  generated  in  a  circuit 
with  an  electromotive  force  of  i  volt  and  a  current-strength  of  i  ampere  in  a  second. 

The  density  of  the  current  must  further  be  especially  distinguished  from  the 
current-strength.  As  the  same  amount  of  electricity  must  always  pass  through 
any  given  transverse  section  of  the  circuit,  the  electricity  must  obviously  be 
denser  at  the  constricted  portions  and  less  dense  at  the  wider  portions  if  the 
transverse  section  varies  in  size.  If  S  indicate  the  current-strength  and  q  the 
transverse  section  of  the  part  in  question,  the  density  (d)  at  this  point  will  be 
d  =  S  -f-  q. 

If  the  arc  of  closure  of  the  galvanic  circuit  be  divided  at  the  one  pole  into 
two  or  several  circuits,  which  are  reunited  at  the  other  pole,  the  total  of  the  current- 
strengths  is  equal  to  the  strength  of  the  undivided  current.  If,  further,  the  dif- 
ferent circuits  vary  with  respect  to  length,  transverse  section,  and  material,  the 
current-strengths  passing  through  the  wires  are  inversely  proportional  to  the 
conduction-resistances. 

According  to  this  principle,  that  of  the  derived  circuit,  the  rheocordof  du  Bois- 
Reymond  is  constructed.  With  the  aid  of  this  instrument  it  is  possible  to  pass 
from  a  galvanic  current  a  derived  current  of  any  determined  strength  for  the 
stimulation  of  a  nerve  or  a  muscle. 

From  each  of  the  poles  (Fig.  224,  a  b)  of  a  galvanic  battery  are  given  off  two 
wires,  of  which  the  one  pair  (ac  and  bd)  pass  to  the  nerve  of  the  frog-preparation 
The  intercalated  segment  of  nerve  (c  d)  offers  a  high  degree  of  resistance 
to  this  branch  of  the  current  (a  c  d  b) .  The  second  branch  of  the  current  conducted 
from  a  and  b  (a  A,  b  B)  passes  through  a  thick  brass  plate  (AB),  which  is  made 
up  of  seven  pieces  lying  side  by  side  (1-7)  and  united  through  the  brass 
plugs  (from  S,  to  S5)  placed  in  the  intervals,  except  between  i  and  2,  so  as 
to  form  an  uninterrupted  circuit.  It  will  at  once  be  clear  that  by  means  of 


THE    MULTIPLICATOR. 


641 


Si 


this  arrangement,  as  depicted  in  Fig.  224,  only  a  minimal  current  passes  through 
the  segment  of  nerve  (c  d),  which  offers  great  resistance,  while  by  far  the  greater 
portion  of  the  galvanic  current  passes  through 
the  well-conducting  brass  plate  (A  -  B) .  If  in- 
creased resistance  be  introduced  into  this  latter 
circuit,  the  branch  current  ac  d  b  must  naturally 
be  increased  correspondingly.  These  resistances 
can  be  interposed  by  means  of  the  portions  of 
fine  wire  indicated  by  the  letters  la,  I  b,  I  c,  II, 
V,  X.  If  it  be  supposed  that  all  of  the  brass 
plugs  (from  St  to  S5)  are  withdrawn,  the  branch 
current  entering  at  A  must  pass  through  the  en- 
tire system  of  fine  wire.  In  this  way  a  high  de- 
gree of  resistance  is  interposed  and  the  branch 
current  in  the  nerve  must  be  increased  corre- 
spondingly. If  but  one  plug  is  withdrawn,  the 
current  passes  only  through  the  respective  length 
of  wire.  The  resistances  offered  by  the  various 
lengths  of  wire  (from  I  a  to  X)  are  so  related 
that  la,  Ib,  and  Ic  each  represents  a  unit  of  con- 
duction-resistance, II  twice  as  much,  V  five  times 
as  much,  and  X  ten  times  as  much  resistance. 
The  distance  I  a  may  finally  be  lessened  by  the 
bridge  (L),  which  can  be  moved  upward,  the 
scale  (x  y)  indicating  the  length  of  the  resistance- 
distance.  It  will  be  readily  perceived  that  in 
accordance  with  the  manner  of  applying  the 
plugs  and  the  bridge,  the  apparatus  permits  of  a 
varied  gradation  in  the  branch  current  to  be 
sent  through  the  nerve.  If  the  bridge  L  is 
pushed  up  close  to  i,  2,  the  current  passes 
directly  from  A  to  B,  and  not  through  the 
length  of  thin  wire  I  a. 

Other  forms  of  apparatus  intended  for  intro- 
duction into  the  closing  arc  of  a  circuit,  in  order 
to  increase  the  conduction-resistance  at  will,  are      FlG'0f2thT 
designated  rheostats.  mond6 


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\U  J 

THE   ACTION   OF   THE   GALVANIC    CURRENT   UPON   THE   MAGNETIC 
NEEDLE.     THE  MULTIPLICATOR. 

If  a  galvanic  current  be  passed  (for  example  through  a  wire)  parallel  to  a 
magnetic  needle,  the  latter  will  be  deflected  from  its  position  pointing  to  the 
north.  If  it  be  conceived  that  one  is  swimming  in  the  positive  current,  the  head 
in  front  and  the  abdominal  surface  directed  toward  the  needle,  the  north  pole 
of  the  magnetic  needle  will  always  be  deflected  toward  the  left  (Ampere's  rule). 
The  deflecting  force  exerted  by  the  galvanic  current  upon  the  needle  always 
operates  at  right  angles  to  the  so-called  electromagnetic  plane,  that  is  the  plane 
passing  through  the  north  pole  of  the  needle  and  two  points  in  the  conducting 
wire  (passing  in  a  straight  direction  parallel  to  the  needle).  If,  for  example, 
the  conducting  wire  passes  just  above  and  parallel  with  the  magnetic  needle, 
whose  plane  of  oscillation  is  formed  by  the  horizontal  surface,  the  electromagnetic 
plane  will  be  vertical  to  the  horizontal  plane,  and  it  will  pass  through  the  north 
pole  of  the  needle  and  the  conducting  wire.  The  strength  of  the  galvanic  current 
that  causes  the  deflection  of  the  magnetic  needle  is  proportional  to  the  sine  of 
the  angle  between  the  electromagnetic  plane  and  the  plane  of  oscillation  of  the 
needle. 

This  deflecting  power  of  the  galvanic  current  can  be  increased  if  the  con- 
ducting wire  is  passed,  instead  of  once,  several  times  in  the  same  direction  in 
front  of  the  magnetic  needle.  An  apparatus  constructed  according  to  this  princi- 
ple is  designated  a  multiplicator.  In  this  the  conducting  wire  passes  in  numerous 
turns  at  right  angles  to  the  horizontal  plane  around  the  magnetic  needle  sus- 
pended in  the  middle  and  swinging  in  the  horizontal  plane.  The  larger  the  number 
of  turns  the  greater  will  be  the  angle  of  deflection  of  the  needle,  although  not 
exactly  in  direct  proportion,  as  the  individual  turns  are  at  varying  distances 


642 


THE    MULTIPLICATOR. 


m 


and  occupy  different  positions  with  reference  to  the  needle.  The  multiplicator 
is  thus  an  apparatus  by  means  of  which  a  feeble  current  can  readily  be  detected. 
Experience  has  taught  further  that  if  the  feeble  galvanic  current  to  be  ex- 
amined encounters  great  resistance  in  the  closed  circuit,  such  as  in  animal  tissues 
through  which  the  current  is  passed,  then  many  turns  of  a  thin  wire  are  to  be 
made  about  the  needle.  If,  however,  the  conduction-resistance  in  the  circuit  is 
but  slight,  as  is  the  case,  for  example,  in  the  application  of  the  thermoelectric 
apparatus,  only  a  few  turns  of  a  thick  conducting  wire  are  made  about  the  mag- 
netic needle. 

In  order  to  render  the  multiplicator  more  sensitive  in  another  manner  the 
magnetic  power  of  direction  of  the  needle,  by  means  of  which  it  tends  to  turn 
toward  the  north,  can  be  enfeebled.  The  extent  to  which  this  has  been  attained 
in  the  thermoelectrogalvanometer  for  the  examination  of  feeble  currents  has 
been  described  and  illustrated  in  connection  with  the  study  of  feeble  thermic 
currents  (p.  333).  It  should  be  especially  mentioned  at  this  point  that  for  the 
demonstration  of  electrical  currents  in  animal  tissues  a  coil  consisting  of  a  large 
number  of  turns  of  thin  wire  is  to  be  attached  to  that  instrument. 

In  the  multiplicator  of  Schweig- 
ger,  employed  for  physiological  pur- 
poses, the  tendency  of  the  needle  to 
point  toward  the  north  has  been 
materially  enfeebled  by  the  employ- 
ment of  the  astatic  pair  of  needles, 
as  suggested  by  Nobili.  Two  identi- 
cal magnetic  needles  are  attached 
parallel  one  above  the  other  by 
means  of  a  fixed  middle  piece  of 
horn,  but  in  such  a  manner  that  the 
north  poles  point  in  opposite  direc- 
tions. As  it  is  impossible  to  impart 
to  each  needle  a  magnetic  strength 
of  absolutely  equal  degree,  one  of 
the  needles  will  thus  be  always  some- 
what stronger  than  the  other.  This 
difference  in  strength  should,  how- 
ever, not  be  so  great  that  the  stronger 
needle  is  directed  toward  the  north, 
but  it  should  be  sufficient  only  to 
cause  the  freely  suspended  pair  of 
needles  to  assume  a  certain  angle  to 
the  magnetic  meridian,  to  which  posi- 
tion it  always  returns  after  having 
been  deflected  therefrom,  with  the 
execution  of  a  number  of  progres- 
sively diminishing  oscillations.  The 
angle  assumed  by  the  astatic  pair  of 
needles  to  the  magnetic  meridian  is 
designated  the  jree  de-flection.  The 
greater  the  degree  of  astasia  attained, 
the  more  nearly  will  the  angle  formed 
by  the  direction  of  the  free  deflection  with  the  magnetic  meridian  approximate  a  right 
angle.  The  greater  the  degree  of  astasia,  the  fewer  will  be  the  number  of  oscillations 
made  by  the  pair  of  needles  in  a  given  time,  when  they  attempt,  after  deflection, 
to  resume  their  original  position.  The  duration  of  each  of  these  periodic  oscilla- 
tions will  then  be  quite  long. 

The  multiplicator  is  so  constructed  that  the  direction  of  the  needles  is  the  same 
as  that  of  the  coils  of  wire.  The  upper  needle  oscillates  above  a  scale  graduated 
in  degrees  on  which  the  extent  of  the  deflection  of  the  needle  can  be  read.  Even 
the  purest  copper  wire  in  the  coil  always  contains  a  certain  admixture  of  iron, 
which  exerts  an  attraction  upon  the  magnetic  needle.  Therefore,  a  small  fixed 
magnetic  rod,  designated  a  correcting  rod  or  compensatory  magnet  (r),  is  attached 
to  the  multiplicator.  This  is  directed  toward  the  one  pole  of  the  upper  needle  and 
diminishes  the  strength  of  the  astatic  needles  to  such  a  degree  that  the  attracting 
force  in  the  coils  of  wire  (in  consequence  of  the  iron  present)  is  rendered  ineffective 
with  respect  to  the  force  of  the  earth's  magnetism. 


ffl 


FIG.  225. — I,  Diagrammatic  representation  of  the  multipli- 
cator adjusted  for  the  investigation  of  a  muscle-current; 
N  NI,  a  static  pair  of  needles  suspended  from  a  silk 
thread  G;  P  P,  the  conducting  vessels  with  the  muscle 
M;  II  and  III,  other  adjustments  of  the  muscle;  IV, 
non-polarizable  electrodes. 


ELECTROLYSIS.       POLARIZATION.       CONSTANT    BATTERIES.  643 


ELECTROLYSIS.      TRANSITION-RESISTANCE.      GALVANIC    POLARIZATION. 

CONSTANT  BATTERIES  AND  UNPOLARIZABLE  ELECTRODES. 

INTERNAL  POLARIZATION  OF  MOIST  CONDUCTORS. 

CATAPHORIC    ACTION    OF    THE    GALVANIC 

CURRENT.     SECONDARY  RESISTANCE. 

Every  galvanic  current  that  is  passed  through  a  fluid  conductor  causes  de- 
composition of  the  fluid  {electrolysis).  The  products  of  decomposition,  designated 
ions,  are  deposited  at  the  poles  immersed  in  the  fluid,  the  electrodes  (of  which  the 
positive  is  designated  the  anode  and  the  negative  the  kathode} ,  anions  collecting 
at  the  anode  and  kations  at  the  kathode.  If  the  products  of  decomposition  are 
deposited  upon  the  electrodes,  they  may  mechanically,  through  their  adhesion, 
either  increase  or  diminish  the  difficulty  of  conduction  through  the  electric  fluid. 
This  is  designated  transition-resistance.  If  by  this  means  the  conduction-resistance 
already  present  in  the  battery  is  increased,  the  transitional  resistance  is  designated 
positive,  while  if  it  diminishes  the  conduction-resistance  in  the  battery,  it  is  desig- 
nated negative  transition-resistance. 

The  ions  that  collect  at  the  electrodes  may,  however,  modify  the  strength  of 
the  current  also  by  the  development  between  the  anions  and  the  kations  (as 
between  two  different  bodies  connected  by  a  conducting  fluid)  of  a  new  galvanic 
current.  This  phenomenon  is  designated  galvanic  polarization.  Thus,  for  ex- 
ample, water  is  decomposed  by  immersed  platinum  electrodes  in  such  a  manner 
that  the  negative  oxygen  collects  at  the  positive  pole,  and  the  positive  hydrogen 
at  the  negative  pole.  The  polarization-current  thus  generated  usually  has  a 
direction  opposite  to  that  of  the  original  current,  and,  accordingly,  is  designated 
negative  polarization.  In  rare  cases,  however,  the  polarization-current  has  the 
same  direction  as  that  induced  by  the  decomposition  and  then  the  phenomenon 
is  known  as  positive  polarization. 

Naturally,  in  the  process  of  electrolysis  both  factors  may  be  operative, 
namely  transition-resistance,  as  well  as  polarization. 

Polarization,  when  present,  may  be  so  slight  as  not  to  be  recognizable  with 
the  naked  eye,  but  it  may  then  be  demonstrated  in  the  following  manner:  After 
the  lapse  of  a  short  time  the  primary  source  of  the  current,  for  example  the  element 
with  which  the  electrodes  were  connected,  is  excluded,  and  the  extremities  of 
the  electrodes  projecting  out  of  the  fluid  are  placed  in  communication  with  a 
multiplicator,  which  at  once  indicates  even  slight  polarization  by  deflection  of  the 
needle. 

The  ions  set  free  in  the  process  of  electrolysis  cause,  at  times,  at  the  moment 
of  their  development,  further  secondary  decomposition.  If,  for  example,  platinum 
electrodes  are  immersed  in  sodium-cmorid  solution,  chlorin  accumulates  at  the 
anode,  and  sodium  at  the  kathode.  The  chlorin,  however,  immediately  exerts  a 
decomposing  influence  upon  the  water,  the  oxygen  of  which  it  takes  up  for  oxida- 
tion, while  the  hydrogen  is  deposited  secondarily  at  the  kathode. 

The  degree  of  polarization  increases  (although  in  slighter  measure)  with 
the  current-strength,  while  it  diminishes  almost  proportionately  with  elevation 
of  temperature.  The  endeavor  to  overcome  the  polarization,  which,  as  can  be 
seen,  would  soon  modify  the  strength  of  the  galvanic  current  present,  has  led 
to  the  invention  of  two  important  devices,  namely,  constant  galvanic  batteries  and 
the  so-called  unpolarizable  electrodes. 

The  constant  batteries  yield  a  constant  current,  that  is  a  current  of  the  same 
intensity,  because  the  ions  generated  upon  the  electrodes  are  removed  at  the 
moment  of  their  development,  so  that  they  are  thus  unable  to  give  rise  to  a  polari- 
zation-current. For  this  purpose  the  two  bodies  used  for  the  tension-series  are 
each  immersed  in  a  separate  fluid,  separated  by  a  porous  septum  (porcelain 
cylinder).  In  the  zinc-platinum  cell  of  Grove  the  zinc  is  immersed  in  dilute 
sulphuric  acid,  the  platinum  in  nitric  acid.  The  oxygen  deposited  in  the  process 
of  electrolysis  at  the  positive  zinc  forms  zinc  oxid,  which  is  at  once  dissolved  in 
the  dilute  sulphuric  acid.  The  hydrogen  attracted  to  the  platinum  unites  at  once 
with  the  nitric  acid  to  form  water,  the  acid  giving  off  oxygen  and  being  converted 
into  nitrous  acid.  The  zinc-carbon  cell  of  Bunsen  acts  in  the  same  way,  the  nega- 
tive carbon  being  immersed  in  nitric  acid,  the  positive  zinc  in  dilute  sulphuric 
acid.  In  the  cell  of  Daniell  the  positive  zinc  is  immersed  in  dilute  sulphuric 
acid  and  the  negative  copper  in  a  concentrated  solution  of  copper  sulphate.  The 
zinc  undergoes  the  same  change  as  in  the  Grove  cell.  The  negative  copper,  how- 


644  UNPOLARIZABLE    ELECTRODES.       SECONDARY    RESISTANCE. 

ever,  attracts  hydrogen,  but  the  latter  at  once  in  the  nascent  state  reduces 
the  copper  from  its  combination  to  metallic  copper,  which  accumulates  on  the 
copper  plate  as  a  bright  deposit.  The  electromotor  force  of  a  Daniell  cell 
varies,  in  accordance  with  the  degree  of  amalgamation  of  the  zinc  and  the  con- 
centration of  the  fluid,  between  0.909  and  1.35  volts,  the  internal  resistance 
being  2.8  ohms. 

If  the  electrodes  of  a  constant  element  be  conveyed  to  a  moist  animal  tissue, 
for  example  nerve  or  muscle,  electrolysis  and,  as  a  result,  polarization  must, 
naturally,  at  once  take  place.  In  order  to  avoid  this,  unpolarizable  electrodes  have 
been  constructed  (Fig.  225,  IV).  As  a  result  of  the  studies  of  Regnauld,  Matteucci, 
and  du  Bois-Reymond,  it  has  been  determined  that  such  electrodes  can  be  con- 
structed if  the  conducting  wire  coming  from  each  element  be  first  connected 
with  an  amalgamated  plate  of  zinc  (z,  z),  the  latter  being  secured  (k,  k)  in  a  tube 
filled  with  a  solution  of  zinc  sulphate  (a  a),  whose  lower  extremity  is  closed 
by  means  of  an  inverted  cone  of  clay  (t,  t)  moistened  with  0.6  solution  of  sodium 
chlorid.  If  these  clay  points  are  applied  to  the  tissues,  no  polarization  takes  place 
or  at  most  only  a  very  slight  amount. 

Exactly  the  same  device  is  employed  for  examining  the  currents  in  muscles 
and  nerves  (Fig.  225,  I).  As  these  tissues  when  in  direct  connection  with  metals 
generate  currents,  a  similar  non-polarizable  device  is  employed,  but  under  such 
circumstances  it  has  a  somewhat  different  form.  It  consists  of  cups  of  zinc  (P,  P) 
filled  with  concentrated  acid-free  zinc-sulphate  solution  (s,  s).  In  each  cup  is 
immersed  a  pad  of  blotting  paper  (b,  b),  which  is  saturated  by  the  zinc-solution. 
Finally,  this  is  covered  with  a  thin  layer  of  plastic  clay  (t,  t)  moistened  with  0.6 
percent,  sodium-chlorid  solution,  which  protects  the  tissues  from  the  direct  caustic 
effects  of  the  dissolved  zinc  salt. 

Nerve-fibers  and  muscle-fibers,  as  well  as  moist  vegetable  tissues,  fibrin,  and 
similar  bodies,  which  have  a  porous  structure  filled  with  fluid,  likewise  exhibit 
the  phenomena  of  polarization  on  the  application  of  currents  of  considerable 
strength,  and  this  has  been  designated  internal  polarization  of  moist  conductors. 
It  is  believed  that  the  better-conducting  solid  particles  in  the  interior  of  these 
bodies  exert  an  electrolytic  effect  upon  the  particles  of  fluid  in  contact  with  them, 
as  do  metallic  electrodes  in  contact  with  fluid.  The  ions  resulting  from  the  dis- 
integration of  the  particles  of  the  internal  fluid  would  then  give  rise  to  the  internal 
polarization  in  consequence  of  the  tension  existing  between  them.  The  con- 
duction-resistance of  muscle  and  nerve  depends,  according  to  Hermann,  in  part 
upon  polarization.  He  considers  the  marked  polarization  of  animal  tissues  (only 
comparable  with  that  of  the  metals)  as  a  specific  vital  property  of  protoplasm. 

If  the  two  electrodes  of  the  cell  are  introduced  into  the  divisions  of  a 
fluid  separated  into  two  halves  by  a  porous  partition,  it  will  be  observed  that 
particles  of  fluid  are  conveyed  in  the  direction  of  the  galvanic  current,  from  the 
positive  to  the  negative  pole,  so  that  after  the  lapse  of  some  time  the  amount 
of  fluid  in  one  half  of  the  vessel  has  diminished,  while  that  in  the  other  half 
has  increased.  This  phenomenon  of  direct  transference  has  been  designated  the 
cataphoric  effect.  Upon  it  depends  the  galvanic  transference  of  soluble  sub- 
stances through  the  external  integument.  Upon  this  depends,  apparently,  also 
the  phenomenon  of  so-called  secondary  external  resistance.  If  the  copper  electrodes 
of  a  strong  constant  cell  are  each  introduced  into  a  vessel  filled  with  copper- 
sulphate  solution,  from  which  projects  a  pad  saturated  with  this  fluid,  and  if 
further  over  this  pad  is  placed  a  bit  of  muscle,  cartilage,  vegetable  tissue  or  a 
prismatic  strip  of  coagulated  albumin,  it  will  be  seen  that  after  closure  of  the 
circuit  the  current  undergoes  considerable  enfeeblement.  If  the  current  be  now 
reversed,  its  strength  is  at  first  increased,  but  later  it  declines  from  the  maximum. 
Thus,  a  constant  alternating  reversal  of  the  current  gives  rise  to  similar  alternation 
in  the  variation  of  the  current.  If  a  prismatic  bit  of  albumin  has  been  used  in 
the  experiment,  it  will  be  observed  that  simultaneously  with  the  enfeeblement  of 
the  current  the  albumin  has  become  deficient  in  water  and  presents  a  shrunken 
appearance  in  the  vicinity  of  the  positive  pole,  while,  conversely,  the  albumin 
applied  to  the  negative  pole  (probably  through  cataphoric  action)  is  swollen  and 
contains  more  water.  If  the  direction  of  the  current  be  altered  the  same  phe- 
nomena is  observed,  but  at  the  opposite  poles.  The  contraction  and  loss  of  water 
in  the  albumin  at  the  positive  pole  described  must  be  the  cause  of  the  resistance 
in  the  circuit  that  explains  the  enfeeblement  of  the  galvanic  current.  This  phe- 
nomenon is  designated  that  of  secondary  external  resistance. 


SELF-INDUCTION.       VOLTAIC    INDUCTION.  645 


INDUCTION.     THE  EXTRA  CURRENT.     MAGNETIZATION  OF   IRON  BY 

THE  GALVANIC  CURRENT.     VOLTAIC  INDUCTION.     UNIPOLAR 

INDUCTION-EFFECTS.     MAGNETO-INDUCTION. 

If  a  galvanic  element  be  closed  by  means  of  a  short  curved  wire  a  feeble  spark 
will  be  observed  at  the  moment  when  the  circuit  is  again  opened.  If,  however, 
the  closure  is  effected  by  means  of  a  long  wire  wound  into  a  coil  a  strong  spark 
is  observed  on  opening  the  circuit.  If  two  handles  are  attached  to  the  closing 
wire  and  held  in  the  hands  so  that  the  current  (through  interruption  of  the  wire- 
conduction  between  the  two  handles)  at  the  moment  of  opening  is  conducted 
only  by  the  body,  a  severe  shock  is  felt  at  the  moment  of  opening.  This  phe- 
nomenon is  due  to  a  current  induced  in  the  long,  coiled  spiral,  which  Faraday 
designated  the  extra  current.  The  cause  for  its  development  is  as  follows:  If 
the  circuit  is  closed  through  the  spiral  wire,  the  galvanic  current  passing  through 
the  latter  induces  an  electrical  current  in  the  adjacent  turns  of  the  same  spiral. 
This  induction-current  is,  at  the  moment  of  closure  in  the  spiral,  opposite  in 
direction  to  the  galvanic  current  in  the  circuit.  Therefore,  its  effect  is  limited 
and  it  likewise  causes  no  shock.  At  the  moment  of  opening,  this  induction-current 
has,  however,  the  same  direction  as  the  current  in  the  circuit  and,  therefore,  its 
effect  is  intensified. 

Electrical  apparatus,  which,  therefore,  is  so  constructed  that  the  irritation  to 
which  it  gives  rise  results  from  interruption  of  the  circuit  in  a  spiral  conductor 
is  designated  extra-current  apparatus. 

If  a  soft-iron  rod  be  introduced  into  the  cavity  of  a  coiled  wire  spiral,  it  becomes 
magnetic  so  long  as  an  electrical  (galvanic)  current  passes  through  the  spiral.  If 
one  extremity  of  the  iron  rod  is  turned  toward  the  observer,  and  the  other  in 
the  opposite  direction,  and  if  further  the  positive  current  passes  through  the 
spiral  in  the  direction  of  the  hands  of  a  clock,  the  extremity  of  the  rod  turned 
toward  the  observer  is  the  negative  pole  of  the  magnet.  The  strength  of  a  magnet 
thus  produced  depends  upon  the  strength  of  the  galvanic  current,  the  number 
of  spiral  turns  and  the  thickness  of  the  iron  rod.  As  soon  as  the  current  is  opened 
the  magnetism  in  the  iron  bar  disappears. 

If  a  spiral  roll  be  made  of  a  long  insulated  wire,  which  may  be  designated 
the  secondary  spiral;  if,  further,  a  similar  wire  spiral  designated  the  primary 
spiral  be  placed  in  the  vicinity  of  the  first,  and  the  ends  of  the  primary  spiral  are 
connected  with  the  poles  of  a  galvanic  element,  an  electrical  current  is  generated 
in  the  secondary  spiral  when  the  primary  current  is  closed,  or  when  opened  after 
having  been  closed.  A  current,  likewise,  appears  in  the  secondary  spiral  if  this 
is  brought  closer  to  or  removed  further  from  a  closed  primary  spiral  (through 
which  a  current  is  constantly  passing).  The  current  appearing  in  the  secondary 
spiral  is  designated  the  induced  or  faradic  current.  The  process  of  this  induc- 
tion has  been  designated  voltaic  induction  or  electrodynamic  distribution.  The 
current  developed  in  the  secondary  spiral  on  closure  of  the  primary  current 
or  on  approximation  of  the  two  coils  to  each  other  passes  in  the  direction  oppo- 
site to  that  of  the  primary  current.  On  the  other  hand  the  current  induced 
on  opening  the  primary  current  or  on  separation  of  the  two  spirals  from  each 
other  has  the  same  direction  as  the  primary  current.  While  the  primary  current 
is  closed  or  when  the  distance  between  the  two  spirals  remains  unchanged  no 
current  is  demonstrable  in  the  secondary  spiral. 

The  currents  developed  in  the  secondary  spiral  on  opening  and  closing  the 
circuit  differ  from  each  other  in  the  following  particulars.  Although  the  amount 
of  electricity  neutralized  on  opening  and  closing  the  current  is  the  same,  so  that 
the  same  effect  from  both  can  be  demonstrated  by  means  of  electrolysis,  as  also 
by  means  of  a  galvanometer,  the  electricity  at  once  attains  its  maximum  intensity 
and  continues  for  a  short  time  with  the  opening  current,  while  the  electricity  in- 
creases but  gradually,  does  not  reach  an  equally  high  maximum  and  flows  for 
a  much  longer  time  with  the  closing  current.  The  reason  for  this  important 
difference  is  as  follows:  With  the  closure  of  the  primary  circuit,  there  develops  in 
the  primary  spiral  the  extra  current,  which  passes  in  a  direction  opposite  to  that  of 
the  primary  current.  It,  therefore,  offers  resistance  to  the  more  rapid  development 
of  the  primary  current  to  its  full  strength.  The  current  induced  in  the  secondary 
spiral  therefore  develops  slowly.  As,  however,  on  opening  the  primary  spiral  the 
extra  current  in  the  latter  passes  in  the  same  direction  as  the  primary  current, 
the  disturbing  influence  mentioned  disappears.  The  more  rapid  and  profound 


646  MAGNETO-INDUCTION.       INDUCTION    APPARATUS. 

action  of  the  opening  current  is  of  great  significance  with  relation  to  the  physi- 
ological employment  of  induction-currents. 

It  may  naturally  be  desirable  under  some  circumstances  to  remove  this  ine- 
quality in  the  closing  and  opening  shocks.  This  end  can  be  attained  by  greatly 
weakening  the  extra  current.  This  is  accomplished  simply  by  giving  the  primary 
spiral  only  a  few  turns,  v.  Helmholtz  has  attained  the  same  object  by  introducing 
a  secondary  circuit  in  the  primary  circuit.  By  this  means  the  current  never  dis- 
appears entirely  in  the  primary  spiral,  but  it  is  alternately  weakened  and  strength- 
ened by  the  alternate  closing  and  opening  of  this  secondary  circuit  of  much  less 
resistance. 

If  a  current  is  made  to  appear  or  disappear  in  the  primary  coil  with  great 
rapidity,  the  induction-current  develops  in  the  secondary  spiral  not  alone  when 
the  free  extremities  of  the  spiral  wire,  which  may  be  connected  with  some  part 
of  an  animal,  are  closed,  but  also  when  only  one  extremity  of  the  wire  is  made 
to  divert  the  current  by  the  contact.  There  occur,  therefore,  on  contact  with  only 
one  extremity  of  the  secondary  spiral  contractions  in  the  frog-preparation  that 
are  designated  unipolar  induced  contractions.  Generally  they  appear  only  on 
opening  the  primary  circuit.  The  occurrence  of  these  contractions  is  favored  by 
connecting  the  other  extremity  of  the  spiral  in  diverting  contact  with  the  earth, 
and  also  if  the  frog-preparation  is  not  completely  insulated. 

Brief  consideration  may  now  be  given  to  so-called  magneto-induction.  Ac- 
cording to  Ampere  one  may  conceive  of  a  magnetic  bar  as  surrounded  perma- 
nently by  electrical  currents  in  such  a  manner  that  if  the  south  pole  be  directed 
toward  the  observer  the  currents  pass  around  each  transverse  section  of  the  bar 
like  the  hands  of  a  clock.  On  this  assumption  it  will  be  readily  understood  that 
a  magnet  will  develop  a  current  in  a  wire  coil  near  by  as  soon  as  the  two  are  ap- 
proximated, and  also  if  a  piece  of  soft  iron  is  suddenly  rendered  magnetic  or 
suddenly  loses  its  magnetism.  The  direction  of  the  currents  thus  induced  in  the 
coil  is  the  same  as  that  of  those  induced  on  voltaic  induction :  that  is  the  develop- 
ment of  magnetism  or  the  approximation  of  a  coil  of  wire  to  a  magnet  gives  rise 
to  an  induced  current  in  a  direction  opposite  to  that  of  the  current  assumed  to 
be  present  in  the  magnet;  conversely,  the  disappearance  of  the  magnetism  or  the 
separation  of  the  coil  from  the  magnet  gives  rise  to  a  current  in  the  same  direction. 

Approximation  and  separation  of  a  magnet  and  a  coiled  wire  may  be  effected 
in  rapid  succession  if  a  magnetic  bar  that  is  fastened  at  one  extremity  is  permitted 
to  vibrate  freely  in  the  vicinity  of  the  coil.  The  pitch  of  the  note  of  such  a  rod 
will  then  naturally  indicate  the  rapidity  of  the  movement  and  thereby  at  the  same 
time  the  number  of  induced  shocks — Grossmann's  acoustic  current-shocks  and  the 
resulting  acoustic  tetanus  in  the  frog-preparation. 


DU  BOIS-REYMOND'S  SLIDING  INDUCTION-APPARATUS. 
PIXII-SAXTON'S   MAGNETO-INDUCTION   MACHINE. 

The  sliding  apparatus  is  an  improved  modification  of  the  magneto-electro- 
motor of  Neef  for  physiological  purposes.  The  apparatus  is  readily  comprehensible 
from  the  accompanying  sketch  (Fig.  226).  A  wire  passes  from  one  pole  (a)  of  the 
galvanic  battery  (D)  to  the  metallic  column  (S),  from  the  upper  extremity  of 
which  an  easily  vibrating  metallic  spring  (F)  projects  in  a  horizontal  direction 
and  is  provided  at  its  free  extremity  with  a  rectangular  strip  of  iron  (e).  An 
adjustable  screw  (b)  is  approximated  to  the  middle  of  the  spring  from  above 
so  that  contact  between  the  two  takes  place.  From  the  screw  (b)  passes  an 
insulated  copper  wire  (c)  to  a  hollow  spiral  (x  x) ,  within  which  are  placed  a  number 
of  rods  of  soft  iron  (i  i)  insulated  by  a  coating  of  varnish.  From  the  spiral  the 
wire  (d)  passes  on  to  a  horseshoe  of  soft  iron  (H),  which  it  surrounds  in  spiral 
turns,  passing  finally  from  this  back  again  (at  f)  to  the  battery  (g) . 

While  the  current  is  closed  in  this  manner,  it  must  effect  the  following  results  : 
t  renders  the  horseshoe  (H)  magnetic  and  it  in  consequence  at  once  attracts 
the  movable  strip  of  iron  (e,  Neef's  hammer).  By  this  means  the  contact  of 
the  spring  (F)  with  the  screw  (b)  is  broken.  The  current  is  thus  interrupted, 
the  horseshoe  accordingly  loses  its  magnetism,  and  it  releases  e,  which  is  drawn 
upward  by  the  spring,  so  that  contact  takes  place  again  at  b.  This  new  contact 
causes  renewed  magnetization  of  H  and  attraction  and  release  are  thus 
repeated^in  rapid  succession,  in  consequence  of  which  the  primary  current  between 
b  and  b  is  alternately  opened  and  closed  with  equal  frequency. 


MAGNETO-INDUCTION    APPARATUS. 


647 


A  coil  (K  K),  designated  the  secondary  spiral,  hollow  within,  and  consisting 
of  numerous  turns  of  thin  insulated  wire,  passes  in  the  same  direction  as  the  spiral 


FIG.  226. — I,  Diagrammatic  representation  of  the  sliding  electromotor  of  du  Bois-Reymond.     II,  Key  for  tetani- 
zation.     Ill,  Electrodes  with  mechanism  for  interruption. 


(x  x)  of  the  primary  current.  This  is  mounted  upon  a  long  board  or  slide^(p  p), 
provided  with  a  scale  upon  which  it  may  be  moved  over  the  primary  spiral, 
which  it  then  receives  into  its  concavity 
(the  induced  current  being  then  strongest) , 
or  it  may  be  removed  any  desired  distance 
from  the  primary  spiral  (the  current  then 
being  feeblest) .  The  degree  of  separation 
of  the  coils  is  thus  an  index  of  the  strength 
of  the  stimulus.  The  measurement  of  the 
current-strength  may  naturally  be  made 
more  accurately  by  means  of  graduated  in- 
struments. According  to  the  laws  of  voltaic 
induction  there  develops  in  the  secondary 
spiral  (K  K)  on  closing  the  primary  current 
an  induced  current  opposite  in  direction  to 
that  of  the  primary  current,  and  on  closing 
the  primary  current  an  induced  current  in 
the  same  direction.  Moreover,  according  to 
the  laws  of  magneto-induction  the  magneti- 
zation of  the  iron  bar  (i  i)  within  the  pri- 
mary spiral  (x  x)  through  closure  of  the  pri- 
mary current  causes  the  development  of  a 
current  in  the  secondary  coil  (K  K)  in  the 
opposite  direction,  and  the  demagnetization 
of  the  bar,  by  opening  the  primary  circuit, 
an  induced  current  in  the  same  direction. 
These  facts,  explain  the  more  powerful 
effect  of  induced  opening  currents,  as  com- 
pared to  closing  currents.  The  removal  of 
the  inequality  in  the  two  currents  has  been 
discussed  on 'p.  646. 

The  magneto-induction  (or  rotation) 
apparatus  (Fig.  227),  devised  by  Pixii,  and 
improved  by  Saxton,  and  provided  by 
Stohrer  with  a  commutator,  consists  of  a 

powerful  horseshoe  steel  magnet,  opposite  to  whose  two  poles  (N  andS)  is  placed 
a  horseshoe  of  soft  iron  (H) ,  which  can  be  rotated  about  a  horizontal  axis  (a  b) . 


FIG. 


227. — Magneto-induction    Apparatus 
Stohrer's  Commutator. 


with 


648  CURRENTS    OF    INJURY    IN    MUSCLE    AND    NERVE. 

The  extremities  of  the  horseshoe  are  surmounted  by  wooden  spools  (c  d) ,  around 
which  an  isolated  wire  is  wrapped  in  numerous  spirals.  If  the  horseshoe  is  in  a 
position  of  rest,  as  indicated  in  the  figure,  it  is  exposed  to  the  influence  of  the 
large  steel  magnet,  and  it  becomes  magnetized  itself.  It  turns  to  the  poles  of  the 
steel  magnet  the  opposite  poles  s  and  n.  In  the  wire  of  the  two  wooden  spools 
c  and  d  an  electrical  current  is  developed  whenever  the  horseshoe  loses  its  mag- 
netism or  again  acquires  it.  If  half  a  rotation  of  the  axis  a  b  is  made,  so  that 
the  spool  c  is  apposed  to  the  poles,  the  magnetism  in  the  horseshoe  naturally  changes 
its  polarity,  as  the  poles  of  the  steel  magnet  N  and  S  must  always  be  in  relation 
to  the  opposite  poles  of  the  horseshoe.  This  alternation  in  the  poles  of  the  horse- 
shoe can  naturally  be  brought  about  only  when  the  original  magnetism  present 
disappears  and  the  new  magnetism  of  opposite  polarity  develops.  The  disappear- 
ance of  the  magnetism  in  the  horseshoe  and  the  development  of  the  opposite 
kind  gives  rise  in  the  spiral  to  currents  in  the  same  direction.  With  the  second 
half-rotation  the  poles  are  restored  to  their  original  position.  There  must,  therefore, 
be  induced  in  the  spiral  a  current  of  opposite  direction  from  that  of  the  current 
resulting  with  the  first  half-rotation.  Each  complete  rotation  of  the  horseshoe 
thus  gives  rise  to  two  currents  passing  through  the  spiral  in  opposite  directions, 
so  that  the  conducting  wires  o  and  p  are  alternately  positive  and  negative. 

Stohrer  has  by  the  application  of  his  commutator  succeeded  in  causing  the 
two  currents  mentioned  to  pass  in  the  same  direction.  For  this  purpose  two 
metallic  collars  (m  and  n)  well  insulated  from  each  other  are  placed  upon  the 
axis  (a  b)  one  over  the  other.  Each  collar  is  provided  at  both  its  upper  and  its 
lower  extremity  with  a  hollow  metallic  half-ring:  thus,  the  collar  n  with  the  half- 
rings  3  and  4,  and  the  collar  m  with  the  half-rings  i  and  2.  The  half-rings  are 
arranged  alternately  in  pairs.  Of  the  two  polar  wires  of  the  spiral  one  (o)  is 
connected  with  the  inner  collar  (m)  and  the  other  (p)  with  the  outer  collar  (n). 
The  divided  metallic  plates  Y  and  Z  are  prolongations  of  the  poles  and  act  as 
conductors  to  the  electrodes.  It  can  be  readily  seen  that  in  this  position  p  passes 
to  3  of  the  outer  collar  and  thence  to  Z.  After  a  half  turn,  however,  o  is  con- 
nected by  2  of  the  inner  collar  with  Z.  An  analogous  change  in  position  takes 
place  at  Y.  If,  now,  as  has  already  been  pointed  out,  o  and  p  change  their  polarity 
with  each  half-turn,  so  that  after  every  half-rotation  first  o  and  then  p  becomes 
positive,  by  means  of  the  commutator  Z  remains  constantly  connected  with  the 
positive  and,  accordingly,  Y  constantly  with  the  negative  pole.  The  half-rings 
i  and  4,  as  well  as  3  and  2,  project  somewhat  beyond  each  other  at  their  extremi- 
ties. By  this  means  it  results  that,  in  a  certain  position,  o  and  p  are  closed  for 
a  short  time  above  and  below  by  Z  and  Y.  At  this  moment  no  current  passes 
through  the  electrodes.  The  apparatus  is  most  efficient  and  it  is  also  available 
for  electrolytic  purposes. 

The  key  (Fig.  226,  II)  is  an  adjunct  to  this  apparatus.  It  consists  of  a  device 
by  means  of  which  the  current  is  made  to  pass  through  a  wide  metallic  bridge 
(y,  r,  z)  until  it  is  sent  through  the  parts  to  be  stimulated.  The  latter  takes 
place  at  the  moment  when  the  connecting  metallic  plate  (r)  is  introduced  between 
the  two  blocks  y  and  z.  The  key-electrode  (III)  can  be  employed  in  the  same 
manner  for  physiological  purposes.  This  conveys  the  current  to  the  tissues  as 
soon  as  the  spring  connecting  plate  (e)  is  raised  by  pressure  upon  k.  This  instru- 
ment can  be  controlled  with  a  single  hand:  a  b  are  the  polar  wires,  r  r  the  insulated 
electrodes  connected  with  the  parts  to  be  stimulated,  and  G  the  handle  of  the  in- 
strument. 


ELECTRICAL   CURRENTS   IN    RESTING   MUSCLE  AND   NERVE. 
CUTANEOUS   CURRENTS.      GLANDULAR   CURRENTS. 

Method. — To  test  the  law  governing  the  muscular  current  there  is  required 
a  muscle  made  up  of  parallel  fibers  and  of  simple  structure,  thus  representing  a 
prism  or  a  cylinder  (Fig.  228,  /  and  //).     The  sartorius  muscle  of  the  frog  may 
ibserve  this  purpose.     In  such  a  muscle  a  distinction  is  made  between  its  surface 
the  natural  longitudinal  section,  its  tendinous  extremities  or  the  natural  trans- 
verse sections,  and,  if  the  latter  are  divided  at  right  angles  to  the  longitudinal 
xis.the  artificial  transverse  sections;  finally  the  designation  equator  (a  b— m  n)  is 
applied  to  an  imaginary  line  that  exactly  bisects  the  length  of  the  muscle-fibers. 
As  the  currents  present  are'exceedingly  feeble,  a  multiplicator  (Fig.  225,  I)  is 


CURRENTS    OF    INJURY    IN    MUSCLE    AND    NERVE. 


649 


required  for  their  demonstration  or  a  tangent  mirror-galvanometer,  for  example 
the  electrogalvanometer  (p.  384),  with  a  damped  periodic  magnet.  If  the  wires 
of  the  multiplicator  were  placed  in  direct  communication  with  the  moist  animal 
tissue,  they  would  give  rise  to  a  current  by  reason  of  their  inequality,  and,  besides, 
polarization  would  develop  on  the  surface  of  the  wires  on  the  passage  of  a  current. 
Therefore  unpolarizable  electrodes,  upon  which  the  tissues  may  rest  (Fig.  225,  I, 
P,  P) ,  are  always  used  in  conjunction  with  the  conducting  wires. 

The  capillary  electrometer  of  Lippmann  (Fig.  229)  has  been  advantageously 
employed  for  the  demonstration  of  muscular  currents.  In  this  a  thin  column- 
of  mercury  in  a  capillary  tube  lying  in  contact  with  a  conducting  fluid  (dilute 
sulphuric  acid)  is  displaced  by  the  galvanic  current,  the  constant  of  capillarity 
of  the  mercury  undergoing  alteration  in  consequence  of  the  polarization  at  the 
surface  of  contact.  The  displacement,  which  the  observer  (B}  recognizes  with 
the  microscope  (M),  takes  place  in  the  direction  of  the  positive  current.  The 
image  of  the  capillary  tube  can  be  projected  upon  a  screen  and  the  oscillations 


III. 


FIG.  228. 


FIG.  229. — Diagrammatic  Representation  of  the  Capil- 
lary Electrometer. 


of  the  mercury  may  be  photographed.  In  Fig.  229,  representing  such  an  ap- 
paratus diagrammatically,  R  is  a  glass  tube  drawn  out  below  to  capillary  fine- 
ness, and  filled  from  above  with  mercury  and  from  c  downward  with  dilute 
sulphuric  acid.  The  capillary  tube  extends  downward  into  a  wide  glass  tube,  which 
has  a  platinum  wire  fused  into  it  below  and  is  filled  with  mercury  (<?)  and  dilute 
sulphuric  acid  (\).  The  conducting  wires  are  connected  with  unpolarizable 
electrodes,  which  are  applied  to  the  transverse  section  and  the  surface  of  a  muscle. 
On  closing  the  current  the  column  of  mercury  is  displaced  downward  from  c  in 
the  direction  of  the  arrow.  The  electromotive  force  can  be  measured  with  the  aid 
of  the  capillary  electrometer  from  the  extent  of  the  displacement  of  mercury. 
On  the  other  hand,  when  the  electrical  processes  take  place  rapidly  the  movement 
of  mercury  cannot  follow  rapidly  enough  on  account  of  the  resistance. 

The  strength  of  the  currents  in  animal  organs  is  best  measured  by  permitting 
another  current  of  graduated  and  known  strength  to  pass  through  the  electrom- 
eter circuit  in  an  opposite  direction,  so  that  the  tissue-current  present  is  reduced 
to  zero — compensatory  method  of  Poggendorf. 


650  CURRENTS    OF    INJURY    IN    MUSCLE    AND    NERVE. 

1.  Perfectly  fresh,  uninjured  muscles  exhibit  no  current  at  all,  nor  do 
wholly  dead  muscles. 

2.  Strong  electrical  currents  are  observed  if,  as  in  Fig.  225,  I  M,  the 
transverse  section  of  the  muscle  is  connected  with  one  unpolarizable 
electrode,  while  the  surface,  or  longitudinal  section,  is  connected  with 
the  other.     The  direction  of  the  current  in  the  connecting  wire  is  from 
the  positive,  longitudinal  section  to  the  negative,  transverse  section, 
therefore  in  the  muscle  itself  from  the  transverse  to  the  longitudinal 
section   (Fig.    225,  I,  and    Fig.   228,  I).     This   current   is  the  stronger 
the  more  one  electrode  is  approximated  to  the  equator  and  the  other 
to  the  center  of  the  transverse  section.     The  strength  diminishes  the 
more  the  electrode  applied  to  the  surface  approaches  the  extremity 
and  the  more  the  electrode  applied  to  the  transverse  section  approaches 
the  margin  of  the  section.     The  demonstration  of  the  strong  current 
may  even  be  made  on  a  single,  isolated  muscle-fiber.    Unstriated  muscles 
also  exhibit  similar  currents  between  transverse  section  and  surface. 

3.  Feeble   electrical   currents    are    obtained:     (a)  If  the  electrodes 
are  applied  at  two  points  on  the  surface  unequally  distant  from  the 
equator.     The  current  then  passes  from  the  positive  point  nearer  the 
equator  to  the  farther  removed  negative  point,  in  the  muscle  naturally 
in  the  reversed  direction  (Fig.  228,  II,  k  e  and  1  e).     (b)  Equally  feeble 
currents  develop  on  applying  the  electrodes  to  points  on  the  transverse 
section  unequally  distant  from  the  center,  the  current  passing  from 
the  point  nearer  the  margin  of  the  section  to  that  nearer  the  center 
of  the  section,  in  the  muscle  itself  in  the  opposite  direction  (Fig.  228, 
II,  i  c). 

4.  If  the  application  be  made  to  two  points  on  the  surface  equidis- 
tant from  the  equator  (I,  x,  y;  v,  z;  II,  r,  e)  or  to  two  equidistant  from 
the  center  of  the  transverse  section  (I,  c)  no  current  appears. 

5.  If  the  transverse  sections  of  a  muscle  are  made  obliquely  (III), 
so  that  the  form  of  the  section  is  rhombic,  the  conditions  present  will 
be.  the  same  as  those  described  in  paragraph  3.     A  point  close  to  the 
obtuse  angle  of  the  transverse  section  or  of  the  surface  is  positive  with 
relation  to  one  equally  near  the  acute  angle.     The  equator  passes  ob- 
liquely (a,  c).     These  divergent   currents   are    designated   inclination- 
currents  and  their  course  is  indicated  by  the  lines  1,2,  and  3,  III. 

The  electromotive  force  of  a  strong  muscle-current,  in  the  frog,  is  equal  to 
from  0.035  to  0.075  of  a  Daniell  cell,  and  in  the  case  of  the  strongest  inclination- 
currents  even  up  as  much  as  o.i.  The  muscles  and  nerves  of  a  curarized  animal 
exhibit  at  first  stronger  currents.  Exhaustion  of  the  muscle  diminishes  the  strength 
of  the  current,  and  it  disappears  entirely  on  the  death  of  the  muscle.  Elevation 
of  the  temperature  of  a  muscle  increases  the  current,  but  a  temperature  above  40° 
C.  again  enfeebles  it.  Reduction  of  the  temperature  lessens  the  electromotive 
force.  A  current  that  has  become  feebler  in  the  course  of  a  short  time  can  be 
made  stronger  by  application  of  the  electrodes  to  a  new  transverse  section. 
Heated  living  muscular  tissue  and  nerve-tissue  are  positive  to  cooler  tissues  of  the 
same  kind. 

6.  The  resting  nerve  exhibits  with  reference  to  the  conditions  de- 
scribed in  paragraphs  1,2,  and  3  effects  analogous  to  those  of  the  muscle. 

The  electromotive  force  of  the  strong  nerve-currents,  conducted  from  trans- 
verse section  and  surface,  equals  0.02  of  a  Daniell  cell.  Heating  the  nerve  to 
between  15°  and  25°  C.  increases  the  strength  of  the  nerve-current,  while  higher 
temperatures  enfeeble  it.  In  the  development  of  a  strong  nerve-current  the  nega- 
tivity of  the  transverse  section  rapidly  diminishes  with  the  death  of  the  nerve. 


CURRENTS    OF    INJURY    IN    MUSCLE    AND    NERVE.  651 

This  takes  place  only  up  to  the  next  annular  constriction,  and  after  it  has  been 
completed,  the  nerve  under  such  conditions  is  devoid  of  current.  A  new  trans- 
verse section  permits  again  of  the  development  of  a  strong  nerve-current. 

7.  If  the  electrodes  are  applied  to  the  two  transverse  sections  of  an 
excised  nerve  or  to  two  points  on  the  surface  equidistant  from  the 
equator,  a  feeble  current  appears  and  passes  in  a  direction  opposite 
to  that  caused  by  the  physiological  activity  of  the  nerve-fiber  (axial 
current);  therefore  in  the  case  of  centrifugal  nerves  in  a  centripetal 
direction  and  in  that  of  centripetal  nerves  in  a  centrifugal  direction. 
Perhaps  this  current  depends  upon  differences  in  the  time  of  death  at 
the  two  extremities  of  the  nerve. 

The  electromotive  force  of  such  a  current  increases  with  the  length  of  the 
nerve-segment  and  with  the  size  of  the  transverse  section.  It  is  enfeebled  by  ex- 
haustion (by  tetanization) ,  especially  in  the  case  of  motor  nerves  and  less  in  that 
of  centripetal  nerves. 

The  muscle-current  can  be  demonstrated  also  without  the  aid  of  a  multiplicator: 
i.  By  a  sensitive  frog-preparation,  designated  the  physiological  rheoscope.  A  moist 
conductor  is  applied  to  the  transverse  section  and  the  surface  of  the  gastrocnemius 
muscle  from  a  frog.  When  the  sciatic  nerve  of  a  frog-preparation  connected  with 
the  leg  is  stretched  over  the  muscle  contraction  takes  place  at  once ;  likewise  when 
the  nerve  is  again  removed.  If  at  the  lower  extremity  of  the  frog-preparation  a 
transverse  section  is  made  through  the  gastrocnemius  muscle,  and  the  sciatic 
nerve  (whose  distribution  in  the  muscle  is  connected  with  the  surface  of  all  of 
the  fibers)  is  placed  on  this  transverse  section,  the  leg  twitches  as  the  muscular 
current,  from  the  surface  to  the  transverse  section,  enters  the  nerve.  This  obser- 
vation was  familiar  to  Galvani  as  contraction  without  metals. 

2 .  An  isolated  muscle  can  be  stimulated  directly  and  made  to  contract  by  means 
of  its  own  muscle-current.     If  unpolarizable  electrodes  are  applied  to  the  transverse 
section  and  the  surface  of  a  curarized  frog-muscle  and  the  circuit  is  closed  by 
mercury  the  muscle  contracts.     In  an  analogous  manner  the  nerve  also  may  be 
stimulated  by  its  own  nerve-current.     If  the  lower  extremity  of  a  muscle  with  a 
transverse  section  be  immersed  in  a  0.6  per  cent,  solution  of  sodium  chlorid,  which 
itself  is  entirely  indifferent,  a  secondary  circuit  is  established  through  this  fluid 
between  the  transverse  section  and  the  adjacent  surface  of   the    muscle.      In 
consequence,  the  muscle  contracts.      Other  indifferent  conductors  used  to  com- 
plete the  circuit  have  a  similar  effect. 

3.  If  the  muscle-current  be  passed  through  potassium-iodid  paste  it  causes  by 
electrolysis  a  separation  of  iodin  at  the  positive  pole,  as  a  result  of  which  the  starch- 
paste  becomes  blue. 

The  total  current  in  the  body  should  be  the  resultant  of  the  electrical  currents  of 
the  individual  muscles  and  nerves,  and,  in  the  frog  deprived  of  skin,  it  passes  from  the 
extremity  of  the  limbs  to  the  trunk  and  in  the  trunk  from  the  anus  to  the  head. 
This  is  the  "corrente  propria  della  rana"  of  Leopoldo  Nobili,  or  the  "frog-current." 
In  mammals  the  corresponding  current  passes  in  an  opposite  direction. 

If  muscles  or  nerves  have  lost  their  irritability  in  the  state  of  narcosis 
induced  by  ether  or  chloroform,  the  muscle-current  may  persist  and  even  be  in- 
creased. After  death,  the  currents  disappear  earlier  than  the  irritability.  They 
persist  longer  in  the  muscle  than  in  the  nerve,  in  which  they  are  abolished  earlier 
in  the  more  central  portions.  Also  a  motor  nerve  wholly  paralyzed  by  curare 
still  exhibits  the  current  (spark) ,  as  did  also  a  nerve  in  process  of  degeneration 
that  had  lost  its  irritability  entirely  for  two  weeks.  In  the  divided  nerves  of  a 
living  animal  the  current-strength  is  at  first  increased  after  one  or  two  days,  while 
later  it  diminishes.  Muscles  that  have  become  rigid  at  times  exhibit  currents  in 
opposite  directions  in  consequence  of  inequalities  developed  in  the  process  of  decom- 
position. The  nerve-current  is  reversed  by  boiling  water  or  by  desiccation. 

Of  other  tissues  that  exhibit  electrical  currents  there  may  be  mentioned  the 
skin  (frog),  whose  surface  is  positive,  while  its  inner  aspect  is  negative.  The 
mucous  membrane  of  the  digestive  tract  exhibits  the  same  relation,  as  does  also 
the  cornea,  as  well  as  the  aglandular  skin  of  fish  and  snails.  Currents  have  been 
observed  also  in  glands,  principally  in  the  unicellular  and  multicellular  mucous 
glands  of  lower  vertebrates  (frog,  eel) . 


652  CURRENTS    OF    STIMULATED    MUSCLES    AND    NERVES. 


CURRENTS   OF   STIMULATED   MUSCLES    AND    NERVES    AND    OF 
SECRETORY  ORGANS. 

1.  If  a  muscle  that  exhibits  a  strong  electrical  current  is  thrown 
into  tetanic  contraction,  best  by  means  of  tetanization  of  its  nerve,  its 
current  is  enfeebled,  at  times  even  to  the  point  of  complete  return  of  the 
magnetic  needle  to  zero      This  phenomenon  is  the  negative  variation. 
It   is  directly  proportional  to  the  primary  deflection  of  the  magnetic 
needle  and  to  the  energy  of  the  contraction  of  the  muscle. 

After  the  tetanus  the  muscle-current  is  feebler  than  before.  If  the  muscle 
be  placed  upon  the  electrodes  in  such  a  manner  that  the  current  is  a  feeble  one, 
a  diminution  of  this  feeble  current  appears  during  tetanus  in  an  analogous  manner. 
In  the  ineffective  arrangement  the  contraction  of  the  muscle  has  no  influence 
upon  the  magnetic  needle.  If  the  contraction  of  the  muscle  is  prevented  by 
making  it  tense,  a  somewhat  slighter  negative  variation  is  observed.  Therefore, 
it  is  also  smaller  in  the  isometric  than  in  the  isotonic  act.  If  a  contracted  muscle 
be  stretched,  the  negative  variation  present  decreases.  If,  however,  a  resting 
muscle  be  stretched  the  resting  current  is  diminished. 

2.  Excised  frog-muscles  thrown  into  a  state  of  tetanus  through  their 
nerves  exhibit  electromotive  force,  action-current.     A  descending  current 
is  present,  for  example,  in  the  tetanized  gastrocnemius  of  the  frog  and 
a  similar  current  in  the  entire  hind  leg.     In  wholly  intact  muscles  of 
man,  however,  thrown  into  tetanic  contraction  through  their  nerves,  such 
a  current  is  wanting.     Also  wholly  intact  frog's  muscles  directly  thrown 
into  tetanus  exhibit  no  current. 

3.  If  a  muscle  is  momentarily  irritated  directly  at  one  extremity, 
so  that  the  contraction-wave  rapidly  traverses  the  entire  length  of  the 
muscle-fibers,  every  part  of  the  muscle  is   successively  negative   elec- 
trically shortly  before  it  undergoes  contraction.     A  wave  of  negativity 
thus  precedes  the  wave  of  contraction.     The  former  therefore  occurs 
during  the  period  of  latent  irritation.     Waves  of  negativity  and  con- 
traction have  the  same  velocity  of  about  3  meters  in  a  second.     The 
negativity,  which  at  first  increases  and  then  diminishes,  continues  at 
each  point  for  only  about  0.003  second. 

4.  Also  a  single  contraction  indicates  the  development  of  an  elec- 
trical current  in  the  muscle.     The  pulsating  frog's  heart  serves  as  an 
appropriate  illustration,  the  observation  being  made  with  the  aid  of  the 
electrogalvanometer.     Each  pulsation  causes  a  deflection  of  the  needle  of 
the  instrument,  and  this  takes  place  earlier  than  the  contraction  of  the 
heart-muscle  itself.    The  electrical  process  in  the  muscle  causing  the  nega- 
tive variation  precedes  in  general  the  contraction,  and  occurs,  therefore, 
in  the  stage  of  latency.     In  the  contraction  of  the  wholly  intact  gastroc- 
nemius muscle  of  the  frog  stimulated  through  its  nerve  there  is  at  first 
a  descending  and  then  an  ascending  current. 

Careful  investigations  of  the  electrical  processes  in  the  pulsating  heart  have 
shown  that,  with  the  cardiac  pulsation,  first  the  base  and  then  the  apex  of  the 
ventricle  becomes  negative.  A  brief  latent  period  occurs  in  advance.  If  the 
heart-muscle  is  placed  in  a  condition  of  relaxation  by  irritation  of  the  vagus,  a 
positive  variation  is  naturally  observed  in  the  muscle-current.  On  the  other 
hand,  irritation  of  the  accelerator  nerve  in  the  condition  of  arrest  due  to  muscarin, 
even  when  the  pulsation  of  the  heart  is  not  stimulated  anew,  gives  rise  to  negative 
variation. 

Also  in  man  an  electrocardiogram  can  be  obtained  if  the  two  hands  are  con- 
nected with  the  capillary  electrometer.  The  right  arm  exhibits  the  electrical 


CURRENTS    OF    STIMULATED    MUSCLES    AND    NERVES.  653 

tension  of  the  base  of  the  heart,  the  left  arm  that  of  the  apex.  In  correspondence 
with  the  different  individual  phases  of  a  cycle  of  the  heart  the  electrocardio- 
gram is  complicated.  Five  variations  appear  in  the  course  of  the  contraction: 
The  first,  third,  and  fifth  indicate  negativity  of  the  base  of  the  heart,  the  second 
and  fourth  negativity  of  the  apex.  Also  the  two  muscles  of  the  iris  exhibit  nega- 
tive variation  in  their  contraction.  Naturally,  the  descending  contraction-wave 
in  the  esophagus  observed  in  the  act  of  swallowing  is  attended  with  correspond- 
ing electrical  phenomena. 

The  electrical  processes  in  muscle  on  simple  contraction  are  exhibited  also 
by  the  frog-preparation.  If  a  segment  of  the  nerve  of  such  a  preparation  be 
placed  upon  a  muscle  the  frog-preparation  twitches  whenever  the  muscle  is  made 
to  contract.  If  the  nerve  of  a  frog-preparation  is  placed  upon  a  pulsating  mam- 
malian heart,  a  contraction  takes  place  in  the  leg  with  every  pulsation.  Thus, 
after  division  of  the  phrenic  nerve,  particularly  on  the  left  side,  the  diaphragm 
contracts  synchronously  with  the  heart-beat.  This  contraction  is  designated  the 
secondary  contraction.  The  moving  muscle  thus  stimulates  another  muscle  applied 
to  it.  This  phenomenon  occurs  readily  if  the  muscles  employed  are  in  a  state  of 
beginning  desiccation. 

A  muscle  in  a  state  of  tetanic  contraction  from  the  action  of  an  induced 
current  causes  secondary  tetanus  in  a  frog-preparation  in  contact  with  the  muscle. 
The  latter  is  considered  an  evidence  that  in  the  process  of  negative  variation  in 
the  muscle  many  current-variations  occurring  in  rapid  succession  must  have  teen 
present,  as  only  rapid  variations  of  this  kind  have  a  tetanizing  effect  upon  the 
nerve,  and  not  long-continued  current-variations. 

Also  when  the  muscle  is  in  a  state  of  tetanic  contraction  (toad)  as  a  result  of 
voluntary  innervation,  or  of  chemical  irritation,  or  of  strychnin-poisoning,  second- 
ary tetanus  generally  does  not  take  place  in  an  applied  frog-preparation,  although 
Loven  has  observed  secondary  strychnin-tetanus,  comprised  of  from  6  to  9  con- 
tractions in  a  second.  Lippmann's  sensitive  capillary  electrometer  (Fig.  229) 
also  shows  that  both  strychnin-spasm,  as  well  as  the  voluntary  contraction,  are 
discontinuous  processes.  The  slight  activity  of  chemical  irritants  is  explained  by 
the  fact  that  they  do  not  cause  the  muscle-fibers  to  enter  promptly  into  a  state  of 
uniform  contraction.  In  case  of  voluntary  tetanus  and  strychnin-tetanus  the 
electrical  process  takes  place  perhaps  with  insufficient  variation  in  the  current. 
For  this  reason  also  muscles  in  a  state  of  tetanic  contraction  in  the  normal  bcdy 
do  not  stimulate  adjacent  nerves  or  muscles. 

Biedermann  made  the  remarkable  observation  that  striated  muscle  under 
the  influence  of  ether-vapor  is  thrown  into  a  state  in  which  on  irritation  it 
exhibits  no  appreciable  alteration  of  form  or  movement,  while,  on  the  other 
hand,  changes  demonstrable  with  the  aid  of  the  galvanometer  appear  at  the  point 
of  irritation  in  the  same  degree  as  prior  to  the  action  of  the  ether,  as  an  expression 
of  the  irritation,  but  in  consequence  of  the  abolished  power  of  conduction  they 
are  capable  of  manifesting  themselves  only  locally. 

5.  If  a  nerve  resting  with  its  transverse  section  and  surface  upon  the 
electrodes  be  irritated  electrically,  chemically,  or  mechanically  (or 
also,  if  this  be  possible,  reflexly),  its  current  diminishes.  This 
negative  variation,  which  may  be  propagated  in  both  directions  in 
the  nerve,  is  made  up  of  periodic  interruptions  of  the  original  current 
occurring  in  rapid  succession,  as  in  the  contracted  muscle.  Hering 
was  able  by  this  means,  as  in  the  muscle,  to  induce  secondary  contrac- 
tion or  secondary  tetanus.  The  extent  of  the  negative  variation  is  de- 
pendent upon  the  extent  of  the  primary  deflection,  upon  the  degree  of 
irritability  of  the  nerve  and  upon  the  strength  of  the  irritant  applied. 
The  negative  variation  is  demonstrable  both  on  tetanizing  with  indi- 
vidual waves  of  irritation.  The  negative  variation  has  not  yet  been 
observed  in  wholly  intact  nerves. 

Hering  found  that  the  negative  variation  of  the  nerve-current  induced  by 
electrical  tetanization  is  followed  in  general  by  a  positive  variation.  It  increases 
to  a  certain  degree  with  the  duration  of  the  irritation,  with  the  strength  of  the 
stimulating  currents  with  commencing  desiccation  of  the  nerves,  and  if  the  point 


654  CURRENTS    OF    STIMULATED    MUSCLES    AND    NERVES. 

on  the  longitudinal  section  to  which  the  electrode  is  applied  recedes  from  the 
transverse  section.  The  negative  variation  after  chemical  or  mechanical  irrita- 
tion is  observed  especially  in  winter-frogs  exposed  to  cold,  also  on  application 
of  peripheral  pressure-irritation  to  the  skin,  as  well  as  in  the  fresh  electrical  nerve  of 
the  torpedo.  Non-medullated  nerves  exhibit  negative  variation,  just  as  they 
exhibit  in  general  all  electrophysiological  phenomena  in  the  same  manner  as 
medullated  nerves. 

The  action  of  certain  substances  upon  the  isolated  nerve  of  the  frog  gives  rise 
to  changes  in  the  appearance  of  the  electrical  phenomena.  If  the  isolated  nerve 
is  exposed  to  carbon  dioxid,  the  negative  variation  remains  in  abeyance  for  a  few 
minutes,  after  which  it  occurs  with  increased  intensity.  Chloroform  and  ether 
increase  the  electrical  activity  at  first,  later  having  an  inhibiting  effect.  Potassium 
bromid  has  an  inhibiting  effect.  The  influence  of  electrotonus  upon  negative 
variation  is  discussed  on  p.  662. 

The  galvanic  relation  of  the  still  irritable  spinal  cord  is  in  general  the  same 
as  that  of  the  nerves.  If  longitudinal  and  transverse  currents  are  established  in 
the  upper  portion  of  the  medulla  oblongata,  spontaneous  intermittent  variations, 
perhaps  due  to  the  intermittent  stimulation  of  the  centers  situated  in  this  locality, 
and  particularly  of  the  respiratory  center,  are  observed.  Similar  variations  occur 
also  reflexly  in  response  to  individual  electrical  shocks  applied  to  the  sciatic  nerve, 
while  strong  irritation  by  means  of  sodium  chlorid  or  induced  currents  inhibits 
them.  Also  the  surface  of  the  cerebrum  exhibits  the  development  of  currents,  if  the 
centers  situated  within  it,  for  example  the  psychosensorial,  are  irritated  by  stimu- 
lation through  the  organs  of  special  sense. 

6.  The  same  phenomenon  that  is  exhibited  by  the  muscle,  as  de- 
scribed in  paragraph  3,  is  exhibited  also  by  the  nerve.  The  wave  of 
negativity  can  be  best  followed  if  its  rapidity  of  propagation  is  dimin- 
ished by  the  action  of  severe  cold.  In  its  progress  the  wave  of  negativity 
does  not  decrease  in  extent,  while  it  does  so  in  the  excised  muscle. 

The  process  of  negative  variation  is  propagated  through  the  nerve-fiber  with 
measurable  rapidity,  which  is  greatest  at  a  temperature  between  15°  and  25°  C. 
This  is  the  same  as  that  of  the  propagation  of  the  stimulus  itself,  and  in  the  normal 
average  is  from  27  to  28  meters  a  second.  This  rapidity  exhibits  the  same 
variations  as  the  rapidity  of  propagation  of  the  nerve-stimulus.  The  duration 
of  an  individual  variation,  of  many  of  which  the  process  of  negative  variation  is 
constituted,  is  only  from  0.0005  to  0.0008  second.  The  length  of  the  waves  in 
the  nerve  is  estimated  at  18  mm. 

J.  Bernstein  has  by  means  of  the  differential  rheotome  found  in  the  following 
manner  the  time  required  by  the  negative  current-variation  in  the  nerve  to  pro- 
pagate itself  from  the  point  of  irritation  throughout  the  course  of  the  nerve.  A 
long  nerve  (Fig.  230,  Nil)  is  so  arranged  that  at  one  of  its  extremities  (N)  trans- 
verse section  and  surface  are  connected  with  the .  electrodes  of  a  galvanometer 
(£).  At  the  other  extremity  (n)  are  the  electrodes  of  an  induction-coil  (J).  A 
disc  (B),  rapidly  rotated  about  its  vertical  axis  (A)  by  means  of  a  pulley  (5),  is 
provided  at  one  point  of  its  periphery  with  a  device  (C)  by  means  of  which  the 
current  of  the  primary  circuit  (E)  is  rapidly  closed  and  again  opened  with  each 
revolution.  In  this  way  a  stimulating  closing  and  opening  induction-shock  is  applied 
to  the  extremity  of  the  nerve  with  each  revolution  of  the  disc.  At  the  diametric- 
ally opposite  side  (r  r)  of  the  periphery  of  the  disc  is  an  arrangement  (c)  by  means 
of  which  the  galvanometer-circuit  is  closed  and  opened  with  each  revolution. 
There  thus  take  place  at  the  same  moment  the  stimulation  and  the  closing  of  the 
galvanometer-circuit.  When  the  disc  is  rapidly  rotated,  the  galvanometer  indi- 
cates the  presence  of  a  strong  nerve-current,  the  magnetic  needle  being  deflected 
to  the  point  y.  At  the  moment  when  stimulation  takes  place,  the  negative  varia- 
tion has  not  yet  advanced  to  the  other  extremity  of  the  nerve.  If,  however,  the 
device  that  closes  the  galvanometer-circuit  is  so  displaced  at  the  periphery  of  the 
disc  (for  example  to  o)  that  the  galvanometer-circuit  is  closed  somewhat  later  than 
the  nerve  is  stimulated,  the  current  appears  to  be  enfeebled  by  the  negative  varia- 
tion, the  needle  being  deflected  only  to  x.  If  the  rapidity  with  which  the  disc 
revolves  is  known  it  will  be  readily  found  that  the  time  corresponding  to  the  dis- 
placement of  the  closing  must  be  equal  to  the  rapidity  with  which  the  stimulus 
causing  the  negative  variation  is  propagated  from  the  one  extremity  of  the  nerve 
(n)  to  the  other  (N). 


CURRENTS    OF    STIMULATED    MUSCLES    AND    NERVES. 


655 


The  negative  current-variation  in  the  nerve  is  wanting  in  degenerated  nerves 
as  soon  as  its  irritability  is  abolished. 

If  light  is  permitted  to  fall  upon  a  freshly  extirpated  eye  the  current  from  the 
positive  cornea  to  the  negative  transverse  section  of  the  optic  nerve  exhibits  at 
rirst  an  increase. 

Yellow  light  has  the  most  marked  effect,  while  other  colors  have  less  marked 
effect.  The  inner  surface  of  the  resting  retina  is  positive  with  relation  to  the  pos- 
terior surface.  On  illumination  of  the  inner  surface  a  double  variation  occurs, 
namely,  after  a  brief  latent  period,  a  negative  preceded  by  a  positive.  On  dis- 
appearance of  the  light  a  simple  positive  variation  occurs.  Retinas  with  the  visual 
red  bleached  by  light  exhibit  smaller  variations.  According  to  Beauregard  and 
Dupuy  the  auditory  nerve  also  exhibits  similar  manifestations  of  negative  varia- 
tion. One  electrode  is  applied  to  the  transverse  section  of  the  nerve,  the  other 
to  the  tympanic  membrane,  and  a  loud  sound  serves  as  the  irritant. 

Irritation  of  the  secretory  nerves  of  membranes  containing  glands  gives  rise 
to  changes  in  the  resting  currents,  with  the  formation  of  secretion.  This  secretory 
current  in  the  skin  of  the  frog  and  of  warm-blooded  animals  has  the  same  direction 
as  the  resting  current.  In  the  frog  it  is  sometimes  preceded  by  a  current  in  the 


G 


FIG.  230. — Diagrammatic  Representation  of  Bernstein's  Differential  Rheotome. 


opposite  direction.     Also,  denuded  portions  of  skin  in  cats  exhibit  analogous  phe- 
nomena. 

If  in  the  cat  a  current  is  passed  uniformly  from  the  skin  of  both  hind  legs,  and 
if  one  sciatic  nerve  is  now  irritated,  a  penetrating  secretory  current  is  set  up,  with 
secretion  of  sweat.  If,  in  an  analogous  manner,  the  electrodes  are  applied  uni- 
formly to  two  points  on  the  skin  of  the  extremities  in  man,  and  the  muscles  of 
one  extremity  are  contracted,  a  penetrating  current  is  likewise  set  up.  Tarchanoff 
observed  in  the  skin  of  man  feeble  currents  after  irritation  as  by  cold,  tickling,  and 
pain,  and  after  other  nervous  stimuli,  such  as  mental  exertion  and  bright 
light.  Destruction  of  the  gland  abolishes  both  the  secretion  and  the  secretory 
current,  as  does  also  atropin.  Portions  of  the 'skin  covered  by  hair,  but  without 
sweat-glands,  have  no  secretory  current.  The  current  of  the  gastric  mucous 
membrane  during  rest,  which,  as  a  rule,  is  penetrating,  exhibits  on  irritation  of  the 
vagus,  which  exerts  an  influence  upon  the  secretion  in  rabbits,  a  negative  variation 
preceded  by  a  slight  positive  variation.  In  the  dog  the  external  surface  of  the 
salivary  glands  is  negative  as  related  to  the  hilus.  In  case  of  abundant  watery 
secretion,  as  from  irritation  of  the  chorda  tympani,  the  surface  exhibits  a  first 
phase  of  negative  potential  with  respect  to  the  hilus,  which  is  at  times  followed  by 
a  second  phase  of  feebler  difference  of  potential  in  the  opposite  direction.  In  the 


656 


ELECTROTONIC    CURRENTS    IN    NERVES    AND    IN    MUSCLES. 


presence  of  abundant  watery  secretion,  the  first  phase  preponderates,  while  when 
the  secretion  is  less  abundant  and  more  viscid  the  second  phase  preponderates. 


CURRENTS   IN   NERVES   AND   IN   MUSCLES   IN   THE 
ELECTROTONIC    STATE. 

If  a  nerve  be  connected  with  non-polarizable  electrodes  in  such  a  manner  that 
its  transverse  section  is  applied  to  the  one  and  its  surface  to  the  other  (Fig.  231, 
I),  the  multiplicator  will  indicate  the  presence  of  a  strong  nerve-current.  If  a 
constant  electrical  current,  designated  the  polarizing  current,  be  now  passed 
through  the  length  of  the  extremity  of  the  nerve  projecting  beyond  the  electrode, 
in  a  direction  which  coincides  with  that  of  the  current  in  the  nerve,  the 
magnetic  needle  exhibits  a  still  more  marked  deflection,  as  a  sign  of  increase  in 
the  nerve-current — positive  phase  of  electrotonus.  This  is  directly  proportional 

to  the  length  of  nerve  traversed  and  the  strength 
of  the  galvanic  current,  and  inversely  to  the  dis- 
tance between  the  portion  traversed  and  the  por- 
tions of  the  nerve  applied  to  the  pads. 

If,  with  the  nerve  in  the  same  position,  the 
constant  electrical  current  is  passed  in  a  direction 
opposite  to  that  of  the  nerve-current  (II) ,  there  is 
a  diminution  in  the  electromotive  force  of  the 
latter — negative  phase  of  electrotonus. 

If  the  electrodes  are  applied  to  two  points  on 
the  surface  of  the  nerve  almost  equidistant  from 
the  equator  (1 1 1),  the  galvanometer  at  first  ex- 
hibits no  deflection  with  this  ineffective  arrange- 
ment. If,  now,  a  constant  current  be  passed 
through  the  free,  projecting  extremity  of  the 
nerve,  the  magnetic  needle  exhibits  electro- 
motive activity  in  the  same  direction  as  the 
constant  current. 


ffl 


FIG.  231. 


The  foregoing  experiments  demonstrate 
that  a  nerve  traversed  by  a  constant  elec- 
trical current  undergoes,  not  alone  within 
the    directly   traversed   portion,   but   also 
beyond  this,   an   alteration   in  its  electro- 
motive activity  that  is  designated  electro- 
tonus.    This  alteration  is  attended  with  a  change  in  the  irritability  of 
the  nerve-segment  in  question. 

The  electrotonic  current  is  strongest  near  the  electrodes.  It  may  be  25  times 
stronger  than  the  resting  nerve-current.  Its  strength  increases  with  the  strength 
of  the  constant,  polarizing  current,  likewise  with  the  length  of  the  segment  tra- 
versed. It  is  larger  upon  the  side  of  the  anode  than  upon  that  of  the  kathode. 
It  appears  with  the  closing  of  the  constant  current,  while  it  reaches  its  maximum 
earlier  at  the  kathode.  It  gradually  increases  at  the  anode  and  decreases  at 
the  kathode.  On  tetanization  it  undergoes  negative  variation  like  the  resting 
nerve-current,  while  the  polarizing  current  appears  to  be  stronger.  On  the  other 
hand,  no  noteworthy  electrotonic  increase  in  current  between  the  electrodes  can 
be  observed  beyond  the  polarizing  current  itself.  Cold  has  a  marked  inhibiting 
influence  upon  the  production  of  the  electrotonic  current. 

The  phenomena  described  occur  only  so  long  as  the  nerve  is  irritable.  Ligation 
of  the  extremity  of  the  nerve  projecting  beyond  the  galvanometer-circuit  abolishes 
the  phenomena  in  the  segment  so  shut  off.  The  galvanic  electrotonic  alterations 
in  the  extrapolar  segments  described — and  due  to  a  peculiar  diffusion  by  physical 
means  of  the  polarizing  current — are  wanting  in  the  case  of  non-medullated  nerves, 
which  on  the  other  hand  exhibit  physiological  electrotonus.  By  treating 
medullated  nerves  with  ether  the  physiological  electrotonus  may  be  abolished, 
while  the  physical  phenomena  referred  to  persist. 

The  negative  variation  appears  more  rapidly  than  the  electrotonic  increase 


THEORIES    OF    CURRENTS    IN    MUSCLES    AND    NERVES.  657 

in  current,  so  that  the  former  will  have  disappeared  before  the  electrotonic  in- 
crease in  current  is  observed;  for  the  rapidity  of  the  electrotonic  alterations  in 
current  is  less  than  the  propagation-velocity  of  the  impulse  in  the  nerve, 
namely  only  from  8  to  10  meters  a  second. 

Upon  the  electrotonic  process  depends  the  secondary  contraction  from  the 
nerve.  If  the  sciatic  nerve  of  a  frog-preparation  be  applied  to  a  divided  nerve  and 
then  a  constant  current  is  sent  through  the  free  extremity  of  the  latter  (non- 
electrical nerve-stimuli  are  ineffective) ,  contraction  takes  place  in  the  frog-prepara- 
tion. This  occurs  because  the  electrotonizing  current  in  the  excised  nerve  irritates 
the  adjacent  nerve.  On  rapidly  closing  and  opening  the  current  secondary 
tetanus  results.  The  same  conditions  are  observed  in  connection  with  the  para- 
doxical contraction.  If  the  current  is  directed  to  one  of  the  two  branches  into 
which  the  severed  sciatic  nerve  of  the  frog  divides,  the  muscles  supplied  by  both 
nerves  contract. 

If  the  constant  current  is  opened,  after-currents  appear,  which  according  to 
du  Bois-Reymond  are  due  to  internal  polarization.  In  living  nerve,  muscle,  and 
electrical  organ  this  internal  polarization-current  is  always  positive,  that  is  it  has 
the  same  direction  as  the  primary  current,  when  a  strong  primary  current  of 
short  duration  is  employed.  If  the  primary  current  be  of  greater  duration,  nega- 
tive polarization  eventually  results.  Between  the  two  there  is  a  stage  in  which 
the  preparation  exhibits  no  polarization  at  all.  Positive  polarization  appears  par- 
ticularly strong  in  the  nerve  when  the  primary  current  has  the  same  direction  as 
the  course  of  the  impulse  in  the  nerve,  in  the  muscle  when  the  primary  current 
passes  from  the  point  of  entrance  of  the  nerve  to  the  extremity  of  the  muscle. 
An  analogous  condition  is  observed  in  the  electrical  organ. 

The  muscle  likewise  exhibits  the  electrotonizing  effect  of  the  con- 
stant polarizing  current.  A  constant  current  in  the  same  direction 
intensifies  the  muscle-current,  while  a  current  in  the  opposite  direc- 
tion enfeebles  the  muscle-current.  The  effect  is,  however,  relatively 
feeble. 


THEORIES  OF  CURRENTS  IN  MUSCLES  AND  NERVES. 

In  explanation  of  the  currents  in  muscles  and  nerves  du  Bois-Reymond  pro- 
posed the  so-called  molecular  theory.  According  to  this,  nerve-fibers  and 
muscle-fibers  contain  minute  molecules,  of  electromotive  activity,  arranged  suc- 
cessively in  series,  and  surrounded  by  a  conducting  indifferent  fluid.  The  mole- 
cules are  in  a  peripolar  electrical  state,  namely,  provided  with  a  positive  equatorial 
zone,  directed  toward  the  surface,  and  two'  negative  polar  surfaces,  facing  the 
transverse  section.  Each  newly  prepared  transverse  section  exposes  new  negative 
surfaces,  and  each  artificial  longitudinal  section  new  positive  areas. 

This  arrangement  explains  the  strong  currents,  for  if  the  positive  circuit  be 
connected  by  means  of  a  closing  arc  with  the  negative  transverse  section,  a  current 
must  pass  through  this  from  the  surface  to  the  transverse  section.  On  the  other 
hand,  the  theory  does  not  explain  the  feeble  currents.  To  comprehend  these  it 
must  be  assumed  that  the  electromotive  activity  of  the  molecules  is  enfeebled 
with  varying  rapidity  on  the  one  hand  at  unequal  distances  from  the  equator,  on 
the  other  hand  at  unequal  distances  from  the  center  of  the  transverse  section. 
Then  naturally  differences  in  electric  potential  will  develop  between  the  molecules 
of  greater  activity  and  those  that  are  already  enfeebled.  The  muscles,  however, 
show  that  their  natural  transverse  section,  that  is  the  extremity  of  the  tendon, 
does  not  become  negative  electrically,  like  an  artificial  section,  but  positive  in 
greater  or  lesser  degree.  In  explanation  of  this  anomalous  phenomenon  du  Bois- 
Reymond  believes  that  a  layer  of  electropositive  muscular  substance  is  still  present 
at  the  extremity  of  the  tendon.  To  facilitate  comprehension  he  considers  the 
peripolar  elements  of  the  muscle  as  consisting  each  of  two  bipolar  elements,  a 
layer  of  the  half-element  being  so  applied  to  the  extremity  of  the  tendon  that 
its  positive  side  is  directed  toward  the  free  surface  of  the  tendon.  This  layer 
he  designates  the  parelectronomic  layer.  It  is  never  entirely  wanting.  The  better 
it  is  developed  the  greater  is  the  absence  of  current  on  conduction  from  the  sur- 
face and  the  tendon.  If  parelectronomy  be  well  developed,  the  extremity  of  the 
42 


658  THEORIES    OF    CURRENTS    IN    MUSCLES    AND    NERVES. 

tendon  may  even  become  positive  with  respect  to  the  surface.  The  parelectro- 
nomic  layer  is  destroyed  by  cauterization. 

The  negative  variation  in  current  is  explained  by  assuming  that  during  the 
activity  of  muscle  and  nerve  the  electromotive  force  of  all  of  the  molecules  is  di- 
minished. On  partial  contraction  of  the  muscle  the  contracted  portion  assumes 
rather  the  character  of  an  indifferent  conductor,  which  is  in  simple  conducting 
connection  with  the  negative  zones  of  the  resting  contents  of  the  muscular  fibers. 
The  electrotonic  currents  beyond  the  poles,  particularly  in  the  nerve-fibers,  require 
a  special  explanation,  while  the  electrotonic  state  of  the  muscles  extends  princi- 
pally to  the  intrapolar  portion.  In  explanation  of  the  electrotonic  currents,  it 
is  assumed  that  the  bipolar  molecules  have  the  property  of  rotation.  The  polar- 
izing current,  however,  exerts  a  directive  influence  upon  the  molecules  so  that 
these  turn  their  negative  surface  toward  the  anode  and  their  positive  surface 
toward  the  kathode.  In  consequence  the  molecules  of  the  intrapolar  segment  are 
arranged  like  the  voltaic  pile.  In  the  portions  of  the  nerve  lying  beyond  the 
pole  the  molecules  are  the  less  accurately  arranged  the  farther  removed  they  are. 
Therefore,  the  deflections  of  the  needle  become  correspondingly  feebler  in  the 
extra-polar  portions. 

The  differential  theory  proposed  by  Hermann,  which  has  recently  been  de- 
veloped by  Hering,  explains  the  phenomena  in  a  satisfactory  manner.  Any  proto- 
plasmic structure,  such  as  muscle,  nerve,  or  cell,  develops  no  current  that  can 
be  conducted  outward  so  long  as  its  metabolism,  that  is  the  internal  chemical 
processes,  remains  the  same  in  all  parts.  Every  disturbance  of  this  equilibrium  in 
one  part  of  the  protoplasmic  structure  causes  the  development  of  currents  that 
can  be  conducted  away.  Therefore,  (i)  the  protoplasm  at  the  point  where  death 
occurs,  whether  from  injury  of  any  kind  or  from  degeneration,  becomes  electrically 
negative  with  respect  to  living  and  irritable  protoplasm.  (2)  The  protoplasm  is 
negative  at  points  that  are  irritated  with  respect  to  those  that  remain  in  an  un- 
irritated  resting  state.  (3)  The  protoplasm  becomes  electrically  positive  in 
warmed  situations,  negative  in  cooled  situations.  In  addition  it  may  be  stated 
(4)  that  protoplasm  is  strongly  polarizable  on  its  surface  (nerve,  muscle).  The 
constant  of  polarity  is  diminished  by  irritation  (and  death) . 

In  detail  the  following  statements  may  yet  be  made  in  this  connection.  It 
has  been  shown  that  resting,  uninjured  and  absolutely  fresh  muscles  are  entirely 
without  current,  as  also  are  wholly  intact  nerves.  The  heart  likewise  is  free  from 
current,  and  also  the  muscles  of  fish  still  covered  by  skin.  As  the  skin  of  the 
frog  possesses  currents  of  its  own,  it  is  possible,  with  special  precautions,  after 
destruction  of  the  cutaneous  currents  through  cauterants,  to  demonstrate  also 
here  the  freedom  from  current  on  the  part  of  the  frog's  muscles.  Furthermore, 
L.  Hermann  found  that  the  muscle-current  always  develops  only  after  the  lapse  of 
a  certain,  though  short,  time  after  making  a  transverse  section. 

All  injuries  of  muscles  and  nerves  give  rise  at  the  site  of  injury  (the  demarca- 
tion-surface) to  negative,  dying  tissue  with  relation  to  the  positive,  intact  tissue. 
In  this  way  is  to  be  explained  the  negativity  of  the  transverse  section  with  relation 
to  the  surface.  The  current  thus  developed  is  designated  by  Hermann  the  de- 
marcation-current. If  potassium-salts  or  muscle-juice  be  applied  to  certain  parts 
of  a  muscle  these  become  electrically  negative.  If  these  substances  are  again 
removed  the  negativity  of  these  parts  disappears. 

It  appears  to  be  a  phenomenon  peculiar  to  all  living  protoplasmic  substances 
that  after  injury  at  one  point  this  becomes  negative  on  dying,  while  the  remaining 
intact  portion  is  electrically  positive.  Thus,  all  transverse  sections  of  living 
vegetable  structures  are  negative  with  relation  to  their  surface.  The  same  con- 
dition is  observed  in  animal  structures,  for  example  glands  and  bones.  The 
electrical  organ  of  fish  is  discussed  on  p.  675. 

Engelmann  has  made  a  remarkable  observation.  He  found  that  the  heart 
and  the  unstriated  muscle-fibers  again  lose  the  negativity  of  their  transverse 
section  if  the  divided  muscle-cells  have  died  completely  as  far  as  the  adjacent 
cement-substance  of  the  neighboring  cells ;  while  nerves  lose  their  negativity  when 
the  divided  segments,  each  corresponding  to  a  single  cell,  have  died  to  the  nearest 
annular  constriction  of  Ranvier.  Under  such  circumstances,  all  of  these  organs 
are  entirely  without  current,  for  the  entirely  dead  substance  reacts  essentially  as 
an  indifferent  moist  conductor.  Also  muscles  divided  subcutaneously  likewise  no 
longer  exhibit  negative  cut  surfaces  after  union  of  the  wound-surfaces. 

Notwithstanding  all  of  the  foregoing  observations  the  preexistence  of  currents 
in  resting  living  tissues  cannot  be  assumed. 


THEORIES    OF    CURRENTS    IN    MUSCLES    AND    NERVES.  659 

An  alteration  of  the  chemical  processes  in  a  part  of  the  protoplasmic  structure 
may,  according  to  Hering,  have  such  an  effect  that  the  portion  that  is  decom- 
posed (dissimilated)  is  negative  with  respect  to  the  unaltered  portion,  but  also 
that  the  portion  that  is  replaced  (assimilated)  is  positive  to  the  remaining 
portion.  Hering  thus  distinguishes  negative  and  positive  alterations,  which  must 
give  rise  to  corresponding  currents. 

According  to  Griinhagen  and  others  the  electrotonic  currents  are  due  to 
internal  polarization  in  the  nerve-fibers  between  the  conducting  tissue  of  the 
nerve  and  that  of  the  sheath.  Matteucci  had  already  found  that  if  a  wire  be 
covered  with  a  moist  sheath  and  the  latter  be  connected  with  the  electrodes  of 
a  constant  circuit,  currents  due  to  polarization  appear,  resembling  the  electrotonic 
currents  in  nerves.  If  either  the  wire  or  the  moist  covering  be  interrupted  at  a 
given  point,  the  polarization-currents  do  not  pass  beyond  the  point  of  discon- 
tinuity. The  polarization  developed  at  the  surface  of  the  wire  causes,  through 
its  transitional  resistance,  the  conducted  current  to  pass  far  beyond  the  electrodes. 

Muscles  and  nerves  consist  in  a  similar  manner  of  fibers  surrounded  by  in- 
different conductors.  As  soon  as  a  constant  current  is  closed  on  the  surface, 
internal  polarization  develops  between  the  two,  and  this  gives  rise  to  the  electro- 
tonic  diffusion  of  the  current.  The  polarization  disappears  on  opening  the  current. 
It  can  be  recognized  from  the  fact  that  in  the  living  nerve  the  galvanic  resistance 
transversely  through  the  fibers  is  five  times  as  great  and  in  muscles  seven  times 
as  great  as  through  their  length.  Recently  also  Boruttau  states  that  all  electrical 
phenomena  of  the  nerve  can  be  explained  if  it  be  considered  in  its  capacity  as  a 
conductor. 

With  reference  to  the  currents  developed  during  the  activity  of  the  muscles, 
the  currents  of  action,  Bernstein  established  the  doctrine  that  when  a  single  wave 
of  irritation  (contraction)  passes  longitudinally  through  muscle-fibers  that  are 
connected  at  two  points  with  the  galvanometer,  that  point  below  which  the  wave 
passes  is  negative  with  reference  to  the  other.  Occasionally  local  points  of  con- 
traction are  present  in  muscle-preparations  in  certain  situations  and  these  are 
negative  with  relation  to  other  resting  points  of  the  same  muscle.  In  order  to 
explain  the  currents  that  appear  in  connection  with  tetanus  of  frog's  muscles  it 
must  be  assumed  that  the  extremity  of  the  fibers  takes  part  in  lesser  degree  in 
the  process  causing  the  negativity  than  the  middle  of  the  fibers.  This  is, 
however,  the  case  only  in  exhausted  muscles  or  in  those  in  process  of  dying. 

As  will  be  pointed  out  on  p.  663  the  contraction  occurring  on  direct  application 
of  a  constant  current  to  the  muscle  takes  place  on  closure  of  the  current  at  the 
kathode,  on  opening  the  current  at  the  anode.  It  will,  thus,  be  clear  that  with 
the  closing  contraction  the  muscle  exhibits  negativity  at  the  kathode,  but  with 
the  opening  contraction  at  the  anode.  These  facts  according  to  Hering  and 
Biedermann  explain  the  after-currents  considered  on  p.  657. 

If  a  muscle  is  made  to  contract  by  stimulation  of  its  nerve,  the  wave  of  ex- 
citation passes  from  the  point  of  entrance  of  the  nerve  in  both  directions  and 
it  is  likewise  negative  to  the  resting  muscle.  In  accordance  with  the  situation  of 
the  entrance  of  the  nerve  into  the  muscle  the  ascending  or  the  descending  wave  of 
excitation  will  reach  the  extremity  (origin  or  attachment)  of  the  muscle  earlier. 
If,  therefore,  such  a  muscle  be  introduced  by  its  upper  and  lower  extremities 
into  the  circuit  of  the  galvanometer,  that  extremity  will  at  first  be  negative  that 
is  nearest  the  point  of  entrance  of  the  nerve,  for  example  in  the  gastrocnemius 
the  upper,  and  later  the  lower.  There  thus  appear  in  rapid  succession  first  a 
descending,  then  an  ascending  current  in  the  galvanometer-circuit,  in  the  muscle 
naturally  in  the  reverse  order. 

The  same  conditions  are  observed  also  in  the  forearm-muscles  of  man.  If 
these  are  thrown  into  contraction  from  the  nerve,  the  point  of  entrance  of  the 
nerve,  10  cm.  below  the  elbow,  is  first  negative,  then  the  muscle-extremities  if 
the  wave  of  contraction  has  reached  these  points  with  a  velocity  of  from  10  to 
13  meters  in  one  second.  In  this  experiment  the  brachial  plexus  is  stimulated 
in  the  axillary  cavity.  The  conduction  in  the  forearm  (in  the  upper  portion  and 
above  the  wrist-joint)  is  established  by  surrounding  the  skin  with  strips  of 
material  saturated  with  zinc  sulphate.  The  strips  themselves  come  in  contact 
with  the  paper  pads  of  the  non-polarizable  electrodes. 

If  a  wholly  intact  muscle  free  from  current  is  made  to  contract  entirely,  no 
current  is  set  up  either  with  the  individual  contraction  or  in  the  state  of  tetanus, 
because  at  the  same  moment  the  entire  muscular  structure  passes  into  a  state  of 
irritation  and  into  a  firmer  condition.  With  respect  to  the  nerves  also  it  has  in 


660  IRRITABILITY    OF    NERVE    AND    MUSCLE    IN    ELECTROTONUS. 

like    manner  been   determined  that  everywhere  dying   and  active  contents  are 
negative  to  resting  normal  contents. 

Attention  may  yet  be  called  to  the  following  facts.  If  water  passes  through 
a  capillary  space  an  electrical  movement  takes  place  in  the  same  direction.  So 
also  the  advance  of  water  in  the  capillary  interstices  of  inanimate  structures 
(pores  of  a  porcelain  plate)  is  attended  with  an  electrical  movement  in  the  same 
direction  as  the  stream  of  water.  Exactly  the  same  conditions  prevail  in  the 
movement  of  water  that  causes  the  swelling  of  a  body.  Landois  has  pointed 
out  that  imbibition  and  swelling  take  place  at  the  demarcation-surface  of  an 
injured  muscle  or  nerve;  further  that  swelling  occurs  also  at  the  contracted  por- 
tion of  a  muscle  in  consequence  of  the  absorption  of  fluid,  and  that  in  the  process 
of  secretion  movement  of  fluid  takes  place  from  the  blood  into  the  glandular 
cells  and  from  these  to  the  excretory  ducts.  Mention  should  finally  be  made  of 
the  fact,  as  H.  Munk  found,  that,  at  the  moment  of  closing  the  current  at  the 
anode  and  beyond,  loss  of  water  and  increase  in  resistance  take  place  in  the  nerve; 
and  at  other  situations  and  beyond  the  kathode  the  reverse.  The  total  resistance 
of  the  distance  traversed  diminishes  at  first,  then  increases  with  accelerated  rapid- 
ity. On  opening  the  current  neutralization  of  this  difference  rapidly  takes  place. 
In  plants  electrical  phenomena  are  observed  both  on  passive  bending  of  portions 
of  plants,  as  of  the  leaves  or  the  stems,  and  also  in  active  movements  associated 
with  bending  of  parts  of  the  plants,  for  example  in  the  movements  of  the  mimosa, 
the  dionea,  and  others.  These  electromotor  effects  are  also  to  be  explained  in 
all  probability  by  the  movement  of  water  in  the  parts  of  the  plant,  which  must 
take  place  in  their  interior  on  movement.  The  tip  of  the  root  of  germinating 
plants  is  negative  with  respect  to  the  seed-covering,  the  cotyledons  positive  with 
relation  to  all  other  portions  of  the  seedling.  In  the  incubated  bird's  egg  the 
embryo  is  positive,  the  yolk  negative. 


ALTERED  IRRITABILITY  OF  NERVE  AND  MUSCLE  IN  ELECTRO- 
TONUS. 

If  a  living  nerve  is  traversed  throughout  a  definite  length  by  a 
constant  electrical  (polarizing)  current  it  passes  into  the  condition  of 
altered  irritability  that  is  designated  the  electrotonic  state  or  simply 
electrotonus.  The  condition  of  altered  irritability  extends  not  alone 
over  the  traversed  (intrapolar)  distance,  but  is  communicated  to  the 
entire  nerve. 

Pfluger  has  discovered  the  following  law  of  electrotonus.  At  the 
positive  pole  or  anode  (Fig.  232,  A)  the  irritability  is  diminished  and 
anelectrotonus  prevails.  At  the  negative  pole  or  kathode  (K)  it 
is  increased,  and  the  increase  in  irritability  prevailing  here  is  desig- 
nated katelectrotonus.  These  alterations  in  irritability  are  most 
pronounced  near  the  poles. 

In  the  intrapolar  segment  there  must  naturally  be  a  point  where 
anelectrotonus  and  katelectrotonus  coincide  and  where  therefore  the 
irritability  is  unaltered.  This  point  is  designated  the  indifferent  point. 
It  is  situated  in  the  case  of  feeble  currents  near  the  anode  (i),  in  that 
of  strong  currents,  however,  near  the  kathode  (i^}\  therefore  in  the 
first  instance  almost  the  entire  intrapolar  segment  is  more  irritable  and 
in  the  latter  less  irritable.  Exceedingly  strong  currents  greatly  dimin- 
ish the  conducting  power  at  the  anode  and  they  may  even  render  the 
nerve  wholly  incapable  of  conducting. 

Also  at  the  kathode,  but  only  after  the  current  has  been  for  some  time  flowing 
through  the  nerve,  the  irritability  is  diminished  and  the  nerve  becomes  incapable 
of  conducting. 

Beyond  the  electrodes  (extrapolar)  the  area  of  altered  irritability 
is  the  more  extensive  the  stronger  the  current.  Further,  the  extent  of 


IRRITABILITY    OF    NERVE    AND    MUSCLE    IN    ELECTROTONUS.          66l 

extrapolar  anelectrotonus  is  greater  with  the  feeblest  currents  than 
that  of  extrapolar  katelectrotonus.  In  the  case  of  strong  currents,  this 
relation  is  reversed. 

Fig.  232  exhibits  diagrammatically  the  relations  of  irritability  of  a  nerve 
(.V  ri)  that  is  traversed  by  a  constant  current  in  the  direction  of  the  arrow.  The 
curves  are  so  constructed  that  the  degrees  of  increased  irritability  in  the  vicinity 
of  the  kathode  (K)  are  represented  as  elevations  above  the  line  representing  the 
nerve,  and  those  of  lowered  irritability  at  the  anode  (A)  as  depressions.  The 
curve  m  o  i  i,  p  r  represents  the  irritability  of  the  nerve  with  strong  currents, 
the  curve  e  f  it  h  k  that  with  currents  of  moderate  strength  and  finally  a  b  i  c  d 
that  with  feeble  currents. 

The  electrotonic  effects  increase  with  the  length  of  nerve  traversed.  The 
alteration  of  irritability  in  katelectrotonus  appears  at  the  moment  of  closure  of 
the  circuit.  Anelectrotonus  develops  and  extends  slowly.  Electrotonus  is 
diminished  by  cold,  and  by  heat  up  to  40°.  At  30°  katelectrotonus  is  increased 
and  anelectrotonus  diminished.  Also  with  induced  currents  the  anode  diminishes 
the  irritability. 

If  the  polarizing  current  is  opened  there  is  at  first  a  reversal  of  the 
conditions  of  irritability.  There  then  follows  a  transition  to  the  normal 


d       1c 


K 


n 


FIG.  232. — Diagrammatic  Representation  of  the  Electrotonic  Relations  of  Irritability. 

state  of  irritability  of  the  resting  nerve.     At  the  initial  moment  of  closure 
Wundt  observed  that  the  irritability  of  the  entire  nerve  was  augmented. 

Testing  Electrotonus  in  Motor  Nerves. — In  order  to  demonstrate  the  laws  of 
electrotonus  in  motor  nerves  the  frog  nerve-muscle  preparation  (Fig.  233),  con- 
sisting of  the  leg  and  the  sciatic  nerve,  is  employed.  By  means  of  unpolarizable 
electrodes  (Fig.  225,  IV)  the  current  of  a  constant  circuit  is  conveyed  to  the  nerve 
throughout  a  limited  distance.  An  irritant,  such  as  an  electrical  shock,  or  chemi- 
cal irritation  by  the  application  of  sodium  chlorid,  or  mechanical  irritation,  is 
now  applied  to  the  nerve  at  either  the  anode  or  the  kathode,  and  note  is  made 
whether  the  contractions  following  upon  the  irritation  vary  in  size  when  the 
polarizing  circuit  is  opened  or  when  it  is  closed.  The  contractions  themselves 
may  be  recorded  from  the  gastrocnemius  muscle  with  the  aid  of  the  myograph. 
The  following  examples  may  be  considered:  (a)  Descending  extrapolar  anelectro- 
tonus, that  is  with  a  descending  current  the  irritability  at  the  anode  within  the 
extrapolar  section  is  to  be  tested.  If  in  such  a  case  (A)  the  irritant,  sodium 
chlorid,  which  is  applied  at  R  while  the  circuit  is  still  open,  gives  rise  to  moder- 
ately large  contractions  in  the  leg,  these  become  feebler,  or  are  abolished,  as 
soon  as  the  constant  current  is  passed  through  the  nerve.  After  opening  the 
current,  the  contractions  appear  again  in  their  original  strength,  (b}  Descending 
extrapolar  katelectrotonus  (A).  The  irritating  salt  is  placed  at  R,.  The  contrac- 
tions induced  increase  immediately  on  closure  of  the  polarizing  circuit.  On  open- 
ing the  circuit  the  contractions'  resume  their  previous  activity,  (c)  Ascending 
extrapolar  anelectrotonus  (B).  The  salt  is  applied  at  r^  The  contractions  of 
moderate  intensity  present  before  closure  of  the  circuit  become  feebler  after 


662 


IRRITABILITY    OF    NERVE    AND    MUSCLE    IN    ELECTROTONUS. 


closure,  (d)  Ascending  extrapolar  katelectrotonus  (B).  The  salt  is  placed  at  r. 
In  this  case  a  distinction  must  be  made  in  accordance  with  the  strength  of  the 
polarizing  current:  (i)  If  the  current  is  extremely  weak,  and  it  can  be  appro- 
priately regulated  with  the  aid  of  the  rheocord  (Fig.  224),  increase  of  the 
contractions  is  observed  after  closure  of  the  polarizing  circuit.  (2)  If,  however, 
the  current  is  stronger,  the  contractions  become  smaller,  or  they  are  even 
wholly  abolished.  The  reason  for  this  latter  apparently 
abnormal  relation  lies  in  the  fact  that  under  the  in- 
fluence of  stronger  currents  the  conducting  power  at 
the  anode  is  diminished  or  even  abolished.  Although 
in  this  case  the  salt  acts  upon  an  irritable  segment  of 
nerve  the  effect  does  not  appear  in  the  muscle,  as  the 
conduction  of  the  stimulus  to  the  latter  is  prevented. 

The  laws  of  electrotonus  can  be  demonstrated  also 
in  an  entirely  isolated  nerve.  One  extremity  of  the 
nerve  is  applied  to  the  electrodes  of  a  galvanometer 
for  the  production  of  a  strong  current.  The  polarizing 
circuit  is  applied  to  the  nerve  at  some  distance.  If, 
now,  the  nerve  with  the  circuit  closed  is  irritated  in 
the  anelectrotonic  segment,  as,  for  example,  by  induc- 
tion-shocks, the  negative  current-variation  is  feebler 
than  if  the  polarizing  circuit  were  open.  Conversely, 
the  variation  is  stronger  if  the  irritation  be  applied  to 
the  katelectrotonic  segment.  Also  the  extrapolar  cur- 
rents appearing  in  electrotonus  exhibit  the  negative  va- 
riation when  the  nerve  is  irritated.  Katelectrotonus  is 
intensified  by  the  action  locally  of  elevation  of  temper- 
ature, of  acids  and  by  tetanization,  while  anelectro- 
tonus  is  diminished  by  the  same  influences. 
The  law  of  electrotonus  has  been  demonstrated  also  in  living  human  beings.  If 
it  be  desired  to  test  electrotonus  in  living  human  beings  the  conditions  of  the 
distribution  of  the  current  in  the  part  of  the  body  are  especially  to  be  considered. 
If,  for  example,  the  two  electrodes  are  placed  in  the  course  of  the  ulnar  nerve 
(Fig.  234),  it  will  be  seen  that  the  currents  appearing  in  the  nerve  at  the  anode 
(+  ad)  must  diminish  the  irritability,  although  above  and  below  the  anode  (at 
c  c)  the  positive  current  emerges  in  part  from  the  nerve  and  naturally  causes 
katelectrotonus  in  these  situations.  In  an  analogous  manner  increased  irritability 


FIG.  233. — Testing  the  Irritability 
in  Electrotonus. 


Ul 


FIG.  234. — Diagrammatic  Representation  of  the  Distribution  of  the  Electric  Current  in  the  Arm  on  Galvanization 

of  the  Ulnar  Nerve. 

prevails  immediately  at  the  point  of  application  of  the  kathode  (at  —  c  c} ,  but  in 
the  portions  of  the  nerve  above  and  below,  where  (at  a  a)  the  positive  current 
(from  + )  enters  the  nerve-path,  the  irritability  is  diminished— anelectrotonus.  If, 
thus  it  be  desired  to  apply  irritation  in  the  vicinity  of  an  electrode,  the  application 
would  not  be  made  to  a  portion  of  the  nerve  whose  irritability  is  influenced  by 
that  electrode.  In  order,  therefore,  to  apply  the  irritation  directly  to  the  situation 
occupied  by  the  electrode,  it  is  necessary  at  the  same  time  to  apply  the  irritation 
igh  the  electrode  itself,  for  example  mechanically,  or  by  electrical  irritation, 


DEVELOPMENT    AND    DISAPPEARANCE    OF    ELECTROTONUS.  663 

passing  the  irritating  current  simultaneously  through  the  path  of  the  polarizing 
current. 

Testing  Electrotonus  in  Inhibitory  Nerves. — In  order  to  ascertain  the  action 
of  the  cardioinhibitory  vagus  fibers  in  electrotonus  Landois  proceeded  as  follows: 
If  dyspnea  be  excited  in  rabbits,  the  number  of  heart-beats  diminishes  because  the 
dyspneic  state  of  the  blood  irritates  the  cardioinhibitory  center  in  the  medulla 
oblongata.  If,  under  such  conditions,  a  constant  descending  current  applied  to 
the  vagus  is  closed,  the  nerve  of  the  opposite  side  having  been  previously  divided, 
the  number  of  pulse-beats  again  increases — descending  extrapolar  anelectrotonus. 
If,  on  the  other  hand,  the  current  is  sent  through  the  nerve  in  an  ascending  direc- 
tion, the  number  of  heart-beats  diminishes  still  further  with  feeble  currents,  while 
with  strong  currents  the  number  increases — ascending  extrapolar  katelectrotonus. 
From  the  foregoing  it  appears  that  the  action  of  the  inhibitory  nerves  in  electro- 
tonus is  exactly  the  opposite  of  that  of  the  motor  nerves. 

Testing  Electrotonus  in  Sensory  Nerves. — In  a  decapitated  frog  the  sciatic 
nerve  on  one  side  is  dissected  free  and  isolated.  If  the  nerve  be  irritated  at  one 
point  with  sodium  chlorid  reflex  contractions  take  place  in  the  other  leg  through 
the  intact  spinal  cord.  These  disappear  as  soon  as  a  constant  current  is  closed 
on  the  nerve  in  such  a  manner  that  the  salt  is  situated  in  the  anelectrotonic 
segment. 

Testing  Electrotonus  in  Nerves  of  Special  Sense. — Katelectrotonus  at  the 
central  extremity  increases  the  irritability  in  all  nerves  of  special  sense, 
in  greatest  degree  in  the  eye  for  the  shortest  light -waves,  on  the  tongue  for  acid 
taste.  Anelectrotonus  at  the  central  extremity  diminishes  the  electrical  irrita- 
bility, in  the  eye  in  least  degree  for  the  longest  waves;  at  the  tip  of  the  tongue 
there  develops  a  salty  taste,  on  the  posterior  portion  a  bitter  taste.  At  the 
moment  of  closure  or  of  opening  there  occur  alone  in  the  eye  and  the  ear  so- 
called  flashes.  These  result,  however,  only  when  muscular  contractions  take 
place  at  the  same  time.  They  are,  therefore,  caused  in  the  eye  solely  by  sudden 
movement  of  the  eyeball,  and  in  the  ear  by  that  of  the  muscles  of  the  auditory 
ossicles,  which  are  suddenly  contracted  strongly. 

In  the  muscle  the  intrapolar  segment  is  in  a  state  of  altered  irritability 
during  electrotonus.  Also  the  delay  in  conduction  extends  only  to  this 
area. 

To  the  question  as  to  the  real  nature  of  the  galvanic  effects  Loeb 
replies  that  probably  all  electrical  effects  upon  living  tissues  are  only 
indirect,  that  those  effects  that 'are  designated  electrical  are  in  reality 
only  the  chemical  and  molecular  effects  of  the  ions  or  the  combinations 
formed  by  them. 


THE  DEVELOPMENT  AND  THE  DISAPPEARANCE  OF  ELECTRO- 
TONUS. 

THE   LAW   OF   CONTRACTION.     THE   LAW  OF  POLAR   STIMULATION. 

Both  at  the  moment  of  development  and  at  that  of  disappearance 
of  electrotonus,  therefore  on  closing  and  on  opening  the  circuit,  the 
nerve  undergoes  irritation,  i.  On  closing  the  circuit,  this  stimulation 
occurs  only  at  the  kathode,  at  the  moment  when  katelectrotonus  de- 
velops. 2.  On  opening  the  current,  the  stimulation  takes  place  only  at 
the  anode,  at  the  moment  when  anelectrotonus  disappears.  3.  Of 
these  two  stimuli  that  attending  the  development  of  katelectrotonus 
is  stronger  than  that  caused  by  the  disappearance  of  anelectrotonus. 

That  the  stimulation  on  opening  the  current  occurs  at  the  anode  was  dem- 
onstrated by  Pniiger  in  the  following  manner  with  the  aid  of  Ritter's  opening- 
tetanus.  The  latter  consists  in  the  development  of  tetanus  of  some  duration 
after  the  opening  when  a  strong  constant  current  is  passed  through  a  nerve- 
segment  of  considerable  length.  If  the  current  is  a  descending  one,  this  tetanus 
ceases  immediately  on  division  of  the  intrapolar  nerve-segment,  an  evidence  that 


664  DEVELOPMENT    AND    DISAPPEARANCE    OF    ELECTROTONUS. 

the  (tetanic)  irritation  emanates  from  the  (now  separated)  anode.  If  the  current 
is  an  ascending  one  the  same  operation  fails  to  cause  disappearance  of  the  tetanus. 
Pfliiger  and  v.  Bezold  found  further  evidence  in  favor  of  the  view  that  the 
closing  contraction  is  due  to  irritation  at  the  kathode  and  the  opening  con- 
traction from  the  anode  in  the  fact  that  they  observed  with  the  descending 
current  the  closing  contraction  take  place  earlier  after  the  moment  of  closure 
and  the  opening  contraction  later  after  the  moment  of  opening  in  the  muscle; 
and  conversely,  with  the  ascending  current  the  closing  contraction  later,  the 
opening  contraction  earlier.  The  difference  in  time  observed  corresponds  to  the 
time  required  for  the  propagation  of  the  stimulus  through  the  intrapolar  segment. 
If  a  large  portion  of  the  intrapolar  segment  of  the  nerve  of  a  frog-preparation 
be  made  inirritable  by  application  of  ammonia,  only  the  electrode  directed  toward 
the  muscle  will  have  a  stimulating  influence,  therefore  with  a  descending  current 
closure  and  with  an  ascending  current  opening. 

The  law  of  stimulation  is  applicable  to  all  kinds  of  nerves. 

The  Law  of  Contraction. — The  contractions  occurring  on  closing  and  opening 
the  circuit  exhibit  differences  in  accordance  with  the  direction  and  the  strength  of 
the  current. 

Exceedingly  feeble  currents  cause,  in  accordance  with  the  third  of  the  fore- 
going propositions,  and  whether  descending  or  ascending,  only  closing  contraction. 
The  disappearance  of  anelectrotonus  is  such  a  feeble  stimulus  that  the  nerve 
does  not  react. 

Currents  of  moderate  strength,  whether  ascending  or  descending,  cause  con- 
traction both  on  closing  and  on  opening. 

Exceedingly  strong  descending  currents  cause  contraction  only  on  closing. 
Contraction  on  opening  is  wanting  because  in  the  state  of  electrotonus  with  ex- 
ceedingly strong  currents  almost  the  entire  intrapolar  segment  has  become 
incapable  of  conduction.  Ascending  currents  cause  contraction  only  on  opening 
for  the  same  reason.  The  rnuscle  remains  in  contraction  (closing  tetanus)  during 
the  period  of  closure  with  currents  of  a  definite  strength. 

Polar  effects  may  be  observed  also  in  connection  with  rapid  variations  brought 
about  by  the  induced  current.  These  cause  irritation  to  a  certain  degree  only  at  the 
kathode  in  their  development.  At  the  anode  the  irritation  is  feebler  on  opening 
and  the  irritability  of  the  nerve  is  diminished  in  this  situation.  From  this  point 
of  view  the  phenomena  of  so-called  hypermaximal  contractions  and  deficiency  are 
to  be  explained.  If  the  nerve  of  a  frog-preparation  is  stimulated  by  a  descending 
current,  which  is  gradually  increased,  the  contractions  at  first  increase  in  extent 
with  increase  in  the  intensity  of  the  irritation.  On  further  increase,  however,  the 
extent  of  the  contractions  no  longer  increases.  If,  now,  the  increase  be  continued 
still  further  the  height  of  contraction  again  increases — hypermaximal  contraction. 
It  is  only  with  this  last  intensity  of  action  that  the  anodal  opening  stimulation 
manifests  itself,  and  this  is  added  to  the  kathodal  closing  stimulation,  which  at 
first  is  alone  effective.  If  in  an  analogous  manner  the  irritation  be  applied  by 
means  of  an  ascending  current,  the  contractions  will  be  observed  to  increase 
at  first  with  increase  in  the  strength  of  the  current;  then  with  further  increase 
the  contractions  become  smaller  and  they  may  for  a  time  be  entirely  wanting — 
deficiency.  This  omission  is  explained  by  the  action  of  anelectrotonus  in  rendering 
conduction  difficult.  If  the  increase  be  made  still  greater,  the  contractions  appear 
again  and  they  become  still  greater — hypermaximal  contractions.  This  last  phe- 
nomenon is  explicable  by  the  effects  of  anodal  opening  stimulation. 

The  nerve  in  process  of  dying,  with  change  in  irritability  according  to  the 
law  of  Ritter-Valli,  also  exhibits  a  modified  contraction-law.  In  the  stage  of 
increased  irritability,  feeble  currents  in  both  directions  cause  only  closing  con- 
traction. In  the  succeeding  stage  of  commencing  diminution  in  irritability,  feeble 
currents  in  both  directions  give  rise  to  contraction  on  closing  and  on  opening. 
Finally,  in  the  stage  of  greatly  diminished  irritability  the  descending  current 
causes  contraction  only  on  closing;  the  ascending,  contraction  only  on  opening. 

As  the  various  stages  of  irritability  advance  through  the  nerves  centrifugally, 
the  different  stages  may  often  be  observed  simultaneously  in  different  segments 
of  the  nerve.  According  to  Valentin,  A.  Fick,  Cl.  Bernard,  Schiff,  and  others, 
the  living,  wholly  intact  nerve  exhibits  only  closing  contractions  with  the  current 
in  either  direction,  but  also  opening  contractions  with  currents  of  considerable 
strength. 

Eckhard  observed  in  living  rabbits,  with  currents  of  moderate  strength,  passing 


DEVELOPMENT    AND    DISAPPEARANCE    OF    ELECTROTONUS.  665 

through  the  hypoglossal  nerve,  twitching  of  one-half  of  the  tongue  (instead  of 
contraction)  on  opening  the  circuit  of  an  ascending  current  and  a  similar  mani- 
festation on  closing  the  circuit  of  a  descending  current. 

Pfliiger  has  represented  the  contraction-law  diagrammatic  ally.  According  to 
him  the  molecules  of  the  resting  nerve  are  in  a  state  of  a  certain  moderate  degree 
of  mobility.  In  katelectrotonus  the  mobility  of  the  molecules  is  increased,  while 
in  anelectrotonus  it  is  diminished.  Accordingly,  stimulation  is  produced  if  the 
nerve-molecules  pass  from  the  state  of  moderate  mobility  into  that  of  free  mobility, 
or  if  they  pass  from  a  state  of  difficult  mobility  into  one  of  moderate  mobility 
(of  rest) . 

Analogous  phenomena,  such  as  are  yielded  by  the  contraction-law  for  the 
motor  nerves,  can  also  be  established  for  the  inhibitory  nerves.  Moleschott, 
v.  Bezold,  and  Bonders  have  examined  the  cardiac  branches  of  the  vagus  in  this 
connection.  The  results  correspond  entirely  with  those  obtained  with  motor 
nerves,  except  naturally  that  inhibition  of  the  heart's  action  occurs  in  this  in- 
stance, instead  of  the  contraction  that  takes  place  on  stimulation  of  a  motor  nerve. 

The  sensory  nerves  likewise  react  in  a  similar  manner,  although  it  must  be 
borne  in  mind  that  the  reacting  organ  in  this  instance  is  situated  at  the  central 
extremity  of  the  nerve-tract,  while  in  the  case  of  the  motor  nerve  it  is  situated 
at  the  peripheral  extremity,  in  the  muscle.  Pfliiger  studied  the  influence 
of  closure  and  opening  on  sensory  nerves  by  observing  the  resulting  reflex  con- 
traction. Feeble  currents  caused  contraction  only  on  closure;  currents  of  mod- 
erate strength  contraction  on  both  closure  and  opening;  strong  descending  currents 
contraction  only  on  opening,  and  ascending  currents  contraction  only  on  closing. 
Applied  to  the  skin  of  man  feeble  currents  give  rise  to  sensation  only  on  closing 
with  the  current  passing  in  either  direction;  while  strong  descending  currents 
give  rise  to  sensation  only  on  opening,  and  strong  ascending  currents  only  on 
closure.  During  the  closure  of  the  circuit  there  is  a  prickling,  burning  sensation, 
which  increases  with  the  strength  of  the  current.  The  phenomena  (sensations 
of  light  and  of  sound)  observed  in  the  nerves  of  special  sense,  are  analogous  to 
the  foregoing. 

In  the  muscles  the  contraction-law  is  tested  by  keeping  one  extremity  stretched, 
so  that  it  cannot  shorten,  and  closing  and  opening  the  circuit  in  this  situation. 
The  movable  extremity  then  exhibits  the  same  law  of  contraction  as  if  the  motor 
nerve  were  stimulated.  On  closing  the  contraction  begins  at  the  kathode,  on 
opening  at  the  anode. 

E.  Hering  and  Biedermann  demonstrated  more  thoroughly  in  this  connection 
that  contractions  on  closing  and  opening  are  purely  polar  effects.  They  found 
that  when  a  feeble  current  is  passed  through  the  muscle,  the  first  result  that  ap- 
pears is  a  small  contraction  confined  to  the  kathodal  half  of  the  muscle. 
Increase  in  the  strength  of  the  current  causes  greater  contraction,  which  extends 
to  the  anode,  but  is  feebler  at  this  point  than  at  the  kathode.  At  the  same  time 
the  muscle  remains  in  a  state  of  permanent  contraction  during  the  period  of 
closure.  On  opening,  the  contraction  takes  place  from  the  situation  of  the  anode. 
Also  after  opening  the  muscle  may  remain  for  some  time  in  a  state  of  contrac- 
tion, which  ceases  on  closing  the  current  passing  in  the  same  direction.  The 
law  of  polar  effects  manifests  itself  also  in  the  unstriated  muscle  of  the  ex- 
cised uterus  and  intestine  kept  warm;  also  in  the  isolated  ventricle  of  the  frog, 
as  well  as  in  the  musculocutaneous  tube  of  worms  and  holothurians. 

In  some  animals  apparent  deviations  from  the  foregoing  law  of  Pfluger  occur, 
but  these  are  only  apparent.  They  are  caused  by  the  actions  of  ions  induced 
in  part  by  the  internal  and  in  part  by  the  external  polarization.  In  the  proto- 
plasmic current  in  chars  Hermann  observed  with  each  stimulation — attended  with 
a  wave  of  negativity — sudden  arrest  of  the  movement  analogous  to  a  muscular 
contraction.  In  this  instance  there  is  thus  a  law  of  arrest  instead  of  a  law  of 
contraction. 

Destruction  of  the  extremity  of  a  muscle  by  various  procedures  gives  rise  to 
diminution  of  irritability  in  the  neighborhood  of  the  portion  destroyed.  There- 
fore, the  polar  effects  in  such  a  situation  are  but  feeble.  Also  moistening  such  a 
point  with  meat-infusion,  potassium  hydroxid,  or  alcohol  diminishes  the  polar 
effects  locally,  while  sodium-salts  and  veratrin  increase  them. 

Under  certain  circumstances  not  only  permanent  irritation,  but  also  contrac- 
tion, may  appear  at  both  extremities  of  a  muscle  on  passing  a  current  longi- 
tudinally through  it,  for  example  after  destruction  of  one  of  its  extremities,  or  in 
case  of  peripheral  muscular  paralysis  in  man,  during  closure  as  well  as  after  open- 
ing of  a  galvanic  current. 


666  DEVELOPMENT    AND    DISAPPEARANCE    OF    ELECTROTONUS. 

The  persistent  moderate  shortening  of  the  muscle — continued  closing  contrac- 
tion (Fig.  194,  IV) — at  times  observed  during  the  period  of  closure  of  the  circuit, 
is  due  to  the  abnormal  persistence  of  the  kathodal  closing  excitation  (with  strong 
stimuli  in  dying  muscles,  or  in  the  muscles  of  cooled  winter-frogs).  Also  opening 
at  times  gives  rise  to  a  similar  contraction  originating  at  the  anode.  Treatment  of 
the  muscle  with  2  per  cent,  sodium-chlorid  solution  containing  sodium  carbonate 
increases  the  permanent  contraction  considerably,  and  it  appears  occasionally  as 
rhythmic  shortening. 

If  the  entire  muscle  is  introduced  into  the  circuit  the  closing  contraction 
predominates  when  the  current  passes  in  either  direction.  During  the  period  of 
closure  a  permanent  contraction  is  most  marked  with  the  ascending  current. 

It  is  a  remarkable  fact  that  the  constant  current  has  an  effect  upon  a  muscle 
in  the  state  of  permanent  contraction  entirely  opposite  to  that  upon  a  relaxed 
muscle.  If  a  constant  current  be  passed,  by  means  of  unpolarizable  electrodes, 
longitudinally  through  a  muscle  in  a  state  of  permanent  contraction,  for  example 
as  a  result  of  poisoning  with  veratrin,  or  through  the  contracted  ventricle,  relaxa- 
tion begins  on  closure  at  the  anode  and  extends  thence.  On  opening  the  current 
in  the  permanently  contracted  muscle  the  relaxation  takes  place  from  the  kathode. 

In  correspondence  with  these  remarkable  phenomena,  the  currents  in  the 
muscular  substance  appear  in  accordance  with  the  law  that  every  contracted 
portion  is  negative  with  relation  to  every  resting  portion  of  a  muscle.  Perhaps 
the  experiments  of  Pawlow  throw  light  upon  these  observations.  This  observer 
found  that  the  sphincters  of  mussels  contain  nerve-fibers,  irritation  of  which 
causes  the  production  in  the  muscle  of  a  state  of  relaxation. 

If  a  nerve  or  muscle  has  been  traversed  for  a  considerable  time  by 
a  constant  current,  permanent  tetanus  often  appears  after  the  opening — 
so-called  Ritter's  opening  tetanus.  This  is  abolished  by  closing  a 
current  passing  in  the  original  direction,  while  the  closing  of  a  current 
in  the  opposite  direction  increases  it — Volta's  alternative.  The  per- 
sistent passage  of  the  current  increases  the  irritability  for  the  opening 
of  a  current  in  the  same  direction  and  for  the  closing  of  a  current  in  the 
opposite  direction;  while,  conversely,  it  diminishes  the  irritability  for 
the  closing  of  a  current  in  the  same  direction  and  the  opening  of  a  current 
in  the  opposite  direction. 

According  to  Grutzner,  Tigerstedt,  and  others,  the  cause  for  the  opening 
contraction  resides  in  part  in  the  development  of  polarizing  after-currents.  The 
irritating  effect  of  the  kathode  is  dependent  upon  the  escape  of  water  at  this 
point.  Engelmann  and  Grunhagen  explained  the  opening  and  closing  tetanus  in 
a  different  manner,  namely  as  due  to  latent  stimulation  of  the  prepared 
nerve,  as  a  result  of  drying  and  fluctuations  in  temperature,  the  stimuli  being 
in  themselves  too  feeble  to  cause  tetanus,  but  becoming  effective  when  increased 
irritability  of  the  nerve  is  set  up  in  the  vicinity  of  the  kathode  after  closing,  in 
that  of  the  anode  after  opening. 

Biedermann  showed  that  under  certain  circumstances  two  opening  contrac- 
tions could  be  observed  in  succession  in  the  frog-nerve-preparation,  of  which  the 
second  or  later  corresponds  to  Ritter's  tetanus.  The  first  of  these  contractions  is 
caused  by  the  disappearance  of  anelectrotonus  in  the  sense  of  Pniiger.  The 
second  is  to  be  explained  like  Ritter's  opening  tetanus  in  the  sense  of  Engelmann 
and  Grunhagen. 

Pathological. — The  observation  is  rarely  made  in  morbid  conditions  o£  the 
nervous  system  (hysteria)  that  after  interruption  of  an  electrical  current  through 
a  nerve,  tetanic  contractions  persist,  and  this  has  been  appropriately  designated 
the  neurotonic  reaction. 

Simultaneous  Action  of  the  Constant  Current  and  the  Inherent  Current. — The 
Action  of  Two  Currents. — In  the  frog-preparation  arranged  for  testing  the  con- 
traction-law, a  demarcation-current  naturally  occurs  in  the  nerve.  If  a  feeble, 
artificial,  stimulating  current  be  applied  to  such  a  nerve  interference-phenomena 
may  occur  between  these  two  currents.  The  closing  of  an  exceedingly  feeble 
constant  current  causes  a  contraction  that  is  really  no  closing  contraction,  but 
is  due  to  opening  (conduction)  of  a  branch  of  the  demarcation-current.  Con- 
versely, the  opening  of  an  exceedingly  feeble  constant  current  may  cause  a  con- 


RAPIDITY    OF    CONDUCTION    OF    THE    STIMULUS    IN    NERVES.  667 

traction  that  is  due  really  to  closing  of  the  nerve-current  branch  previously  di- 
verted in  consequence  of  secondary  closure  (through  the  electrodes) . 

If  a  motor  nerve  is  acted  on  simultaneously  by  two  induced  currents  the 
following  two  results  are  possible.  One  induced  current  may  be  so  feeble 
that  the  nerve  is  not  irritated  by  it  to  the  point  of  contraction,  while  the  other 
induces  only  a  feeble  contraction.  In  this  event  the  inframinimal  current  plays 
the  part  of  a  feeble  constant  current,  and  the  size  of  the  contraction  depends  only 
upon  whether  the  effective  irritating  current  is  applied  near  the  anode  or  the 
kathode  of  the  inframinimal  current.  If,  however,  two  stimulating  currents  of 
unequal  strength,  separated  by  a  considerable  distance  from  each  other,  in  order 
to  exclude  electrotonic  effects,  are  applied  to  a  nerve,  and  each  of  them  alone 
is  effective,  the  same  result  occurs  as  if  the  stronger  stimulus  alone  were  applied. 
The  feebler  wave  of  stimulus  is  lost  entirely  in  the  stronger. 

If  in  man  a  nerve  is  compressed  and  the  affected  portion  of  the  body  is  ren- 
dered anemic  by  compression  of  its  arteries,  the  opening  contractions  soon  pre- 
dominate greatly  and  kathodal  opening  contraction  in  greater  degree  than  anodal 
opening  contraction — compression-reaction  of  R.  Geigl. 

RAPIDITY  OF  CONDUCTION  OF  THE  STIMULUS  IN  NERVES. 

If  a  motor  nerve  is  stimulated  at  its  central  extremity  the  impulse 
is  propagated  like  a  wave-movement  through  the  course  of  the  nerve  to 
the  muscle  with  great  rapidity,  which  in  the  case  of  the  sciatic  nerve 
of  the  frog  is  equal  to  27.25  meters  in  a  second,  for  the  motor  nerves, 
and  in  that  of  man,  33.9  meters. 

The  rapidity  of  conduction  is  apparently  less  in  the  visceral  nerves;  for  ex- 
ample, 8.2  meters  in  the  pharyngeal  fibers  of  the  vagus.  Fredericq  and  van  de 
Velde  found  the  rate  in  the  motor  nerves  of  the  lobster  to  be  6  meters. 

The  propagation-rapidity  of  the  wave  of  excitation  is  susceptible  to  various 
influences.  It  is  retarded  by  cold  and  also  by  considerable  heat  applied  to  the 
nerve,  by  curare,  and  by  anelectrotonus,  while  it  is  increased  by  katelectrotonus 
in  the  freely  exposed  nerve.  It  varies  with  the  length  of  the  conducting  portion 
of  nerve,  but  it  increases  with  the  strength  of  the  stimulus,  though  not  at  first. 
The  power  of  conduction  is  diminished  in  the  anelectrotonic  portion. 

Method. — v.  Helmholtz  determined  the  velocity  of  propagation  of  the 
impulse  for  the  motor  nerves  of  the  frog  according  to  the  method  of  Pouillet, 
which  is  based  on  the  fact  that  the  needle  of  the  galvanometer  is  deflected  by  a 
constant  current  of  short  duration.  The  degree  of  deflection  is  proportional  to 
the  duration  and  the  strength  of  the  current,  which  is  known  in  this  instance. 
The  method  itself  is  so  applied  that  the  time-measuring  current  is  closed  at  the 
moment  that  the  nerve  is  irritated,  and  it  is  again  opened  when  the  muscle 
contracts.  If,  now,  the  nerve  is  irritated  first  at  the  central  extremity  and 
then  close  to  its  entrance  into  the  muscle,  the  time  between  the  beginning  of 
the  stimulation  and  the  contraction  will  in  the  latter  event  be  shorter,  and 
therefore  the  deflection  of  the  galvanometer  will  be  less,  than  in  the  first  case, 
as  the  stimulus  must  pass  through  the  entire  nerve  to  the  muscle.  The  difference 
between  the  two  periods  of  time  is  the  propagation-time  for  the  stimulus  in  the 
portion  of  nerve  examined. 

Fig.  235  is  a  diagrammatic  representation  of  the  arrangement  of  the  experi- 
ment. The  galvanometer  G  is  introduced  into  the  (still  open)  circuit  a,  b,  c,  d, 
e,  f,  g,  h,  yielding  the  time-measuring  current.  Closure  is  effected  by  depressing 
the  lever  S,  the  platinum  plate  c  of  the  pivoted  arrangement  W  being  tilted  down 
by  d.  At  once,  with  the  occurrence  of  closure  the  magnetic  needle  is  deflected 
and  the  extent  of  the  deflection  is  noted.  At  the  same  moment  that  the  current 
between  c  and  d  is  closed  the  primary  circuit  of  the  induction-apparatus,  k,  i,  p, 
O.  m,  1,  is  opened  by  raising  the  extremity  of  the  pivoted  arrangement  at  i.  By 
this  means  an  opening  current  is  induced  in  the  induction-spiral  R,  which  stimu- 
lates the  nerve  of  the  suspended  frog's  leg  at  n.  The  impulse  is  propagated 
through  the  nerve  to  the  muscle  (M) ;  the  latter  contracts  as  soon  as  the  impulse 
reaches  it,  and,  by  raising  the  lever  H,  which  can  be  rotated  about  x,  opens  the 
time-measuring  current  by  means  of  the  double  contact  e  and  f.  At  the  moment 
of  opening,  the  further  deflection  of  the  magnetic  needle  ceases.  The  contact  at 
f  consists  of  a  mercurial  dome  drawn  out  to  a  thread.  If,  after  the  contraction 


668  RAPIDITY    OF    CONDUCTION    OF    THE    STIMULUS    IN    NERVES. 


of  the  muscle,  the  lever  H  falls  so  that  the  point  e  rests  upon  the  underlying  fixed 
plate  y,  the  contact  at  f  nevertheless  remains  open,  and,  therefore,  also  the  galva- 
nometer-circuit. Another  method  is  described  on  p.  654. 

In  man  v.  Helmholtz  and  Baxt  determined  the  propagation- velocity  of  the 
impulse  in  the  median  nerve  by  having  the  musculature  of  the  thenar  eminence 
record  its  contraction  by  means  of  a  lever  upon  a  rapidly  rotating  cylinder.  The 
irritation  of  the  nerve  was  practised  on  one  occasion  in  the  axillary  cavity  and 
on  the  second  at  the  wrist-joint.  The  contraction-curves,  naturally,  exhibited 
differences  as  to  the  moment  of  beginning.  The  difference  in  the  time-value  for 
these  two  gives  the  time  for  the  conduction  in  the  intervening  nerve-segment.  In 
the  experiment  the  entire  arm  is  enclosed  in  a  plaster  bandage  in  order  to  secure 
rest  of  the  muscles  of  the  arm. 

According  to    Bernstein,  the   time   necessary  for   the    stimulus  that  passes 

from  the  motor  nerve  to  the 
muscle  to  excite  the  motor 
nerve-endings  is  on  the 
average  0.0032  second  in 
the  frog  and  0.0015  second 
in  warm-blooded  animals. 

In  the  sensory  nerves 
of  man  the  impulse  is 
probably  propagated 
with  the  same  rapidity 
as  in  the  motor  nerves. 
The  figures  obtained 
vary,  it  is  true,  between 
the  wide  limits  of  94  and 
30  meters  in  a  second. 

Method  of  Examination. 

— In  the  person  under  ob- 
servation two  points  at  as 
widely  unequal  distances 
from  the  brain  as  possible 
are  irritated  for  a  moment 
in  succession,  for  example 
the  lobule  of  the  ear  and  the 
great  toe,  as  by  an  open- 
ing induced  current.  The 
moment  of  irritation  is 

noted,  for  example  by  beginning  the  vibrations  of  a  tuning-fork  plate,  the  removal 
of  the  clamp  from  the  tuning-fork  at  the  same  time  opening  the  primary  current. 
The  person  examined  should  in  each  instance  indicate  by  an  appropriate  sign  upon 
the  registering  surface  the  time  when  irritation  is  perceived.  The  reaction-time  to 
be  taken  into  consideration  in  this  connection  is  discussed  on  p.  777. 

A  needle-prick  of  the  skin  causes  at  first  the  sensation  of  pricking.  There 
then  follows  an  interval  free  from  sensation  and  finally  again  a  pricking  sensation, 
apparently  originating  from  within. 

Pathological. — In  the  presence  of  disease  of  the  spinal  cord  the  remarkable 
observation  has  occasionally  been  made  of  a  striking  retardation  of  conduction 
in  the  sensory  nerves  of  the  skin.  The  sensation  itself  may,  under  such  circum- 
stances, be  unaltered.  Occasionally  only  the  conduction  of  painful  sensations 
was  found  to  be  retarded,  so  that  a  painful  impression  upon  the  skin  was  first 
perceived  only  as  a  tactile  sensation  and  then  as  pain,  or  conversely.  If  the 
interval  of  time  between  these  two  impressions  is  considerable,  there  may  be 
well-defined  double  sensation. 

In  the  sphere  of  the  motor  nerves  retarded  conduction  for  voluntary  movement 
is  observed,  for  example  in  cases  of  senile  paralysis  agitans.  The  observation  has 
been  made,  further,  in  rare  cases  that  with  otherwise  well-developed  musculature, 
voluntary  movements  were  executed  much  more  slowly,  as  the  interval  between 
the  impulse  of  the  will  and  the  contraction  was  prolonged,  and,  besides,  the  muscles 
occupied  a  longer  time  in  contracting,  a  sort  of  tonic  contraction  thus  resulting. 
In  nerves  exhibiting  degenerative  reactions  the  retardation  of  conduction  in 


W 


FIG.  235. — v.  Helmholtz's  Method  for  Determining  the  Propagation- 
velocity  of  the  Nerve-stimulus. 


DOUBLE    CONDUCTION    IN    NERVES.  669 

electrotonus  was  marked.     In  tabetic  patients  reflex  movements  have  also  been 
observed  to  be  retarded,  in  the  case  of  irritation  by  heat  more  than  in  that  by  cold. 


DOUBLE  CONDUCTION  IN  NERVES. 

The  property  of  living  nerve  by  means  of  which  it  transmits  an 
impulse  throughout  its  course  is  designated  conductivity.  All  pro- 
cedures that  injure  the  nerve  in  its  continuity,  such  as  division,  ligation, 
crushing,  chemical  destruction,  or  that  destroy  its  irritability  at  any 
point,  such  as  absolute  deficiency  of  blood,  certain  poisons,  for  example 
curare  for  the  motor  nerves,  also  marked  anelectrotonus,  abolish  the 
conductivity.  The  conduction  takes  place  only  through  fibers  directly 
in  communication,  and  it  can  never  be  transferred  to  an  adjacent  fiber— 
law  of  isolated  conduction.  By  double  conduction  is  understood  the 
ability  of  the  nerve  to  transmit  in  both  directions  a  stimulus  applied 
in  its  course.  Naturally,  as  a  result  of  the  anatomical  conditions  in 
the  intact  body  the  motor  nerves  are  capable  of  conducting  only  in  a 
centrifugal  direction  and  the  sensory  nerves  only  in  a  centripetal  direc- 
tion, but  under  suitable  conditions  it  can  be  shown  that  each  nerve  is 
capable,  in  the  same  way  as  an  inanimate  conductor,  of  conducting 
in  both  directions. 

The  evidence  brought  forward  in  support  of  the  presence  of  double  conduction 
is  as  follows:  If  a  nerve  be  irritated,  alterations  in  its  electrical  properties  appear 
both  in  an  upward  and  in  a  downward  direction.  If  the  posterior  free  extremity 
of  the  electrical  centrifugal  nerve-fibers  of  the  malapterurus  be  irritated,  the 
branches  arising  at  a  higher  level  are  also  set  in  irritation,  so  that  the  entire  elec- 
trical organ  is  discharged.  If  the  lower  third  of  the  sartorius  muscle  in  the  frog 
be  divided  longitudinally  and  one  division  be  irritated  mechanically,  the  irrita- 
tion passes  in  the  nerve-fibers  thus  separated  at  first  upward  to  the  point  of 
division  and  thence  centrifugally  in  the  unirritated  muscular  extremity  whose 
individual  fibers  now  contract.  The  gracilis  muscle  is  divided  by  a  tendinous 
line  into  two  halves.  The  nerves  to  both  are  derived  from  a  bifurcation  of  the 
individual  fibers  in  the  nerve-trunk.  Every  irritation  of  the  nerve  for  one  por- 
tion of  the  muscle  causes  contraction  in  both  halves  of  the  muscle. 

All  of  the  earlier  evidence  in  support  of  double  conduction  of  nerves  derived 
from  experiments  on  division  and  reunion  will  not  bear  rigid  scrutiny. 

The  intercentral  association-fibers  in  the  cerebrum  must  normally  be 
assumed  to  conduct  in  both  directions. 


EMPLOYMENT    OF    ELECTRICITY    FOR    THERAPEUTIC    PUR- 
POSES. 

DEGENERATIVE  REACTIONS  OF  MUSCLE  AND   NERVE. 

Electricity  is  much  employed  in  medicine  for  therapeutic  purposes.  It  may 
be  used  in  the  form  of  the  rapidly  interrupted  current  of  the  induction-apparatus 
(faradic  current),  or  of  the  magneto-electrical  machine,  or  of  the  extra-current 
apparatus,  or  in  the  form  of  the  constant  current.  The  employment  of  electricity 
is  based  upon  its  physical  and  physiological  properties. 

In  cases  of  paralysis  the  faradic  current  is  applied  by  means  of  suitable  wet 
electrodes  covered  with  sponge  either  to  the  muscle  itself  or  to  the  point  of  entrance 
of  the  motor  nerve  (Figs.  236,  237,  238,  239).  The  motor  points  on  the  face  are 
shown  in  Fig.  245,  those  of  the  neck  in  Fig.  244.  In  employing  the  faradic  cur- 
rent the  object  is,  by  means  of  artificially  induced  movements,  to  protect  the 
paralyzed  muscle  from  secondary  degeneration,  which  it  would  undergo  as  a 
result  of  long-continued  inactivity.  If  in  addition  to  its  motor  nerves  also  the 
trophic  nerves  of  the  paralyzed  muscle  are  inactive,  even  long-continued  faradiza- 


DEGENERATIVE    REACTIONS    OF    MUSCLE    AND    NERVE. 


tion  will  have  no  noteworthy  effect,  as  the  muscle  will  nevertheless  undergo 
atrophy.  The  application  of  the  induced  current  may,  however,  have  a  good 
effect  upon  the  paralyzed  muscle  by  increasing  the  amount  of  blood  sent  to  it  and 


N.  radialis. 

M.  brachi  il.  intern.     / 
Al.  supiiiator  long.      // 
M.  radial,  ext.  long.      '    " 


M.  radia\  ext  bre'v 
M.  extenB.  digit,  communis. 

M.  extens.  digit,  min. 
M.  extens.  indicia. 


M.  triceps  (caput  ext.) 

M.  triceps 
)  (caput  long ) 
M.  deltoideus 
,  (post,  lialf). 

<N.  axiliaris). 


M.  abduct,  pollic.  long. 

M.  extens.  pollic.  brev. 
M.  extens.  poll.  long.  v 


AI.  abduct,  digit,  min.  (N.  ulnaris.) 


Mm.  inteross.  dorsal.  I,  II,  III,  et  IV. 
(N.  ulnaris.) 

FIG.  236. — Motor  Points  of  the  Radial  Nerve  and  of  the  Muscles  supplied  by  it.     Dorsal  aspect  of  the  upper 

extremity  (after  Eichhorst). 


M.  deltoideus  <ant.  half)  N.  axiliaris. 
N.  musculo-cutaneus. 
,       M.  biceps  brachii. 


M.  abductor  poIHc.  brer. 
M  opponens  pollicis. 
M.  flex.  poll.  brev. 

ictor  pollic.  brer. 
Mm.  lumbrica.es 
1  et  II. 


M.  pronator  teres. 

K.  flex,  digitor.  cornmu 
11.  flex,  carpi  radialis. 

M.  flex,  digitor.  publim. 
M.  flex  dig  subl. 
(dig.  ind.  et  min.] 
M.  flex  poll, 
longus. 
.  medi 
anus. 


N.  ulnaris. 


M.  flexor  carpi  ulnaris. 


Mm-  luinbri- 
calesIIIetlV. 
M.  opponens  digit,  lain. 
'      M.  flexor  digit,  min. 
M.  abductor  digit  mia. 
M.  i  almaris  br«v. 


N.  ulnaris. 

FIG.  237.— Motor  Points  of  the  Median  and  Ulnar  Nerves,  as  well  as  of  the  Muscles  supplied  by  them.     Palmar 
aspect  of  the  upper  extremity  (after  Eichhorst). 


reflexly  influencing  its  metabolism.      Feeble  induction-currents    are  further  cap- 
able of  reviving  the  irritability  of  enfeebled  nerves. 

The  constant  current  deserves  consideration  in  cases  of  paralysis  not  only  as 


DEGENERATIVE  REACTIONS  OF  MUSCLE  AND  NERVE. 


67I 


a  stimulus  for  exciting  contraction,  on  closing,  opening,  reversing,  increasing, 
and  diminishing  the  current,  but  rather  through  its  so-called  polar  effects.  On 
closing  the  circuit  the  nerve  is  thrown  into  irritation  at  the  kathode,  and  on 
opening  the  circuit  at  the  anode.  Then,  during  the  period  of  closure  of  the  circuit 
through  the  nerve  the  irritability  is  increased  at  the  kathode  and  by  this  means 
a  remedial  influence  may  be  exerted  upon  the  nerve.  In  man,  however,  the  special 
conditions  described  on  p.  662  should  be  kept  in  mind  in  the  employment  of 
percutaneous  galvanization.  In  the  vicinity  of  the  anode  there  is  also  increased 
irritability.  This  is  observed  chiefly  on  repeated  reversal  of  the  current,  but  also 
after  closing  and  opening,  or  even  on  the  uniform  passage  of  the  current.  If  the 
increase  in  irritability  obtained  by  means  of  the  current  be  tested,  it  will  be  found 
that  as  a  result  of  the  application  of  the  current  the  irritability  for  the  closing  of  a 


Gluteus  maximus  rr. 


Biceps  femoris  (cap.  long.)  m, 
(Sciatic  n.) 


Biceps  femoris  (cap.  brev.)  m, 
(Sciatic  n.) 


Peroneal  n. 


Sciatic  n. 

Adductor  magnus  m. 

(Obturator  n.) 

Semitendinosus  m.  (Sciatic  n.) 
Semimembranosus  m. 
(Sciatic  n.) 


Tibial  n. 

Gastrocnemius  m.  (ext.  cap.) 
Gastrocnemius  m.  (ext.  int.) 

Soleus  m. 


Flex.  dig.  com.  long.  m. 
Flex,  hallucis  long.  m. 
Tibial  n. 


FIG.  238. — Motor  Points  of  the  Sciatic  Nerve  and  its  Branches,  the  Peroneal  and  Tibial  Nerves  (after  Eichhorst). 


current  in  the  opposite  direction  and  for.  the  opening  of  a  current  in  the  same 
direction  is  increased. 

Furthermore,  in  the  employment  of  the  constant  current  its  restorative  effect 
should  be  taken  into  account,  chiefly  the  ascending  current,  as  R.  Heidenhain 
has  found  that  exhausted  and  enfeebled  muscles  can  be  refreshed  by  the  passage 
of  a  constant  current.  Finally,  the  constant  current  must  be  conceded  a  thera- 
peutic influence  by  reason  of  its  catalytic  or  cataphoric  effects,  in  consequence 
of  which  it  exerts  a  solvent,  decomposing,  or  dispersing  action  upon  possible 
accumulated  products  of  inflammation  or  stagnation  in  nerve  or  muscle.  The 
current  may,  besides,  exert  a  direct  or  reflex  stimulating  influence  upon  the  nerves 
of  the  blood-vessels  and  lymphatics. 

If  the  cause  of  the  paralysis  reside  in  the  muscle  itself,  it  is  customary  to 
apply  the  induced  current  by  means  of  sponge-electrodes  directly  to  the  muscle. 
In  case  of  primary  lesions  of  the  motor  nerves  the  electrodes  are  applied  to  the 


672 


DEGENERATIVE  REACTIONS  OF  MUSCLE  AND  NERVE. 


latter.  The  currents  used  under  such  circumstances  must  be  only  of  moderate 
strength.  Strong  tetanic  contractions  are  to  be  avoided  as  injurious  and  likewise 
unduly  prolonged  action. 

The  galvanic  current  may  likewise  be  applied  either  to  the  muscle  alone  or 
to  the  motor  nerve  or  even  to  its  center,  or  to  both  nerve  and  muscle  at  the  same 
time.  As  a  rule,  under  such  circumstances,  the  kathode  should  be  applied  to  the 
point  whose  irritability  is  lowered,  as  under  its  influence  the  irritability  is  in- 
creased. The  anode  is  placed  at  some  indifferent  point,  for  example  upon  the 
sternum.  Stroking  along  the  nerve  with  the  kathode,  as  well  as  variation  in  the 


N.  obturator. 
M.  pectineus. 

M.  adductor  magnus. 
M.  adductor  longus. 


N.  peroneus. 

M.  tibial.  antic. 

M.  exten.  dig.  com.  long. 

M.  peroneus  longus. 

M.  peroneus  brevis. 

M.  exten.  hallucis.  long. 


M.  exten.  digit,  comm.  brevis. 


N.  cruralis. 

M.  tensor  fasciae  latae  (Nn.  glut, 
sup.) 


M.  quadriceps  femoris  (general 
center). 

M.  rectus  femoris. 

M.  cruralis. 

M.  vastus  externus. 

M.  vastus  internus. 
M.  gastrocnem.  extern. 
M.  soleus. 


M.  flexor  hallucis  long. 
M.  abductor  digiti  min. 


Mm.  interossei  dorsales. 


FIG.  239.— Motor  Points  of  the  Peroneal  and  Tibial  Nerves  on  the  Anterior  Aspect  of  the  Leg  and  Thigh. 
Peroneal  nerve  on  the  left,  tibial  nerve  on  the  right  (after  Eichhorst). 

strength  of  the  current,  is  believed  to  increase  the  favorable  effect.  When  the 
seat  of  the  lesion  is  in  the  central  organs,  galvanization  may  be  applied  along 
the  vertebral. column,  or  to  the  vertebral  column  and  the  course  of  the  nerve 
at  the  same  time,  or  to  the  head  (with  care),  or  when  possible  at  the  suspected 
seat  of  the  disease,  for  example  the  speech-center  or  the  central  convolutions. 
Care  should  be  taken  to  avoid  currents  of  undue  strength  and  applications  of  pro- 
longed duration. 

The  varied  reaction  of  the  paralyzed  nerves  and  muscles  to  the  induced  con- 
stant current  is  especially  noteworthy.  This  relation  has  been  well  designated 
the  reaction  of  degeneration.  In  the  hrst  place,  the  physiological  fact  should  be 


DEGENERATIVE    REACTIONS    OF    MUSCLE    AND    NERVE.  673 

noted  that  the  muscles  supplied  by  dying  nerves  and  also  the  muscles  of  a  curarized 
animal  respond  less  readily  to  a  rapidly  interrupted  faradic  current  than  fresh 
non-curarized  muscles.  According  to  Neumann,  it  is  the  longer  duration  of  the 
constant  current,  as  contrasted  with  the  momentary  closing  and  opening  of  the 
induced  current,  that  permits  the  possibility  of  contraction.  If  the  constant 
current  be  interrupted  with  the  same  rapidity  as  the  faradic,  it  also  will  be 
ineffective.  On  the  other  hand,  the  induced  current  can  be  made  effective 
if  it  be  permitted  to  continue  in  action  for  a  longer  time.  This  can  be  accom- 
plished in  the  sliding  apparatus  by  keeping  the  primary  circuit  closed,  and 
raising  and  depressing  the  induction-coil  upon  the  slide.  By  this  means  slowly 
increasing  and  diminishing  induced  currents  are  generated  that  act  energetically 
in  causing  contraction  of  curarized  muscles.  Therefore,  in  the  stimulation  of 
muscle  and  nerve,  not  alone  the  strength,  but  also  the  duration,  of  the  current 
must  be  taken  into  consideration,  just  as  the  deflection  of  the  magnetic  needle 
is  dependent  upon  both  factors.  According  to  E.  Remak,  however,  the  muscle 
reacts,  nevertheless,  to  individual  induced  shocks,  when  the  reaction  of  degenera- 
tion is  present,  and  with  a  contraction  of  slower  evolution,  but  this  reaction  is 
no  longer  demonstrable  after  the  lapse  of  a  short  time.  The  muscle  is,  therefore, 
not  inirritable  to  the  faradic  current,  but  only  exhausted  with  extreme  readiness. 
It  must  constantly  recuperate  after  its  exhaustion. 

The  typical  reaction  of  degeneration  is  characterized  essentially  by  the  following 
points.  For  the  muscle  there  is,  on  direct  irritation,  diminution  to  the  point  of 
abolition  of  faradic  irritability,  with  increase  of  galvanic  irritability  (from  the 
third  to  the  fifty-eighth  day),  the  latter  diminishing,  although  with  considerable 
variations,  from  the  seventy-second  to  the  eightieth  day.  There  is  also  a  prepon- 
derance of  anodal  closing  contraction  as  compared  with  kathodal  closing  con- 
traction. The  contraction  in  the  affected  muscle  takes  place  slowly;  it  is  pseri- 
taltic  and  limited  locally,  in  contradistinction  to  the  lightning-like  contraction 
of  normal  muscles.  In  the  stage  of  diminished  galvanic  irritability  the  latent 
period  is  prolonged  fourfold,  the  duration  of  contraction  twofold.  For  the  nerve 
there  is  diminution  to  the  point  of  abolition  of  faradic  and  galvanic  irritability. 
If  the  reaction  of  the  nerve  is  normal,  while  the  muscle  on  direct  stimulation  with 
the  constant  current  exhibits  the  reaction  of  degeneration,  the  condition  is  de- 
scribed as  partial  reaction  of  degeneration,  which  is  constant  in  cases  of  progressive 
muscular  atrophy.  In  the  presence  of  deranged  sensibility  in  cases  of  tabes,  the 
sensory  nerves  have  been  observed  to  react  in  a  manner  analogous  to  the  motor 
nerves  in  connection  with  the  reaction  of  degeneration. 

In  rare  cases  the  contraction  of  the  muscle  from  the  nerve  on  application  of 
the  induced  current  exhibits  also  a  sluggish  vermicular  course — faradic  reaction  of 
degeneration.  In  the  case  of  paralyzed  and  degenerated  muscles  the  motor  points 
may  be  found  displaced  further  toward  the  periphery.  The  lessened  thickness  of 
the  muscle  and  the  resulting  increase  in  density  of  the  current  may  be  the  cause 
for  this. 

Nerve-degeneration  and  nerve-regeneration  are  considered  on  p.  663. 

In  the  different  forms  of  spasm,  contracture  or  electrical  spasm,  the  constant 
current  especially  has  been  found  useful.  Under  such  circumstances  patho- 
logically increased  irritability  of  the  nerves  or  muscles  is  diminished  through  the 
effects  of  anelectrotonus.  Therefore,  the  anode  should  be  applied  to  the  nerve 
or  the  muscle,  or  in  case  of  reflex  spasm  upon  those  points  that  are  discovered  to 
be  the  actual  source  of  the  pathological  irritation.  Uniform,  feeble  currents  are 
especially  effective  under  such  circumstances.  Also  the  relaxing  (inhibiting  polar) 
action  is  to  be  considered.  The  constant  current  may,  however,  exert  a  beneficial 
influence  also  through  its  catalytic  action,  by  means  of  which  it  removes  irritants 
at  the  seat  of  disease.  Finally,  it  has  often  been  observed,  since  the  time  of  Remak, 
that  with  the  application  of  the  constant  current,  voluntary  control  of  the  affected 
motor  apparatus  is  increased.  In  cases  of  spasm  of  central  origin  the  constant 
current  may  be  applied  even  to  the  central  organ. 

Faradization  may  be  employed  in  cases  of  spasm  to  strengthen  possibly 
enfeebled  antagonists.  Under  such  circumstances  faradized  muscles  in  a  state 
of  contracture  are  said  to  acquire  increased  extensibility,  as  the  muscle  is  more 
extensible  in  a  state  of  active  physiological  contraction. 

In  the  treatment  of  cutaneous  anesthesia,  stimulation  should  be  applied  first 
to  the  skin  itself,  the  induced  current  being  often  applied  by  means  of  wire-brush 
electrodes.  In  the  employment  of  the  constant  current  the  kathode  should  be 
applied  to  the  insensitive  area.  It  is  even  possible  with  strong  currents  to  cause 
vesication  of  the  skin.  When  the  lesion  has  possibly  a  central  situation  only  the 
43 


6/4  DEGENERATIVE    REACTIONS    OF    MUSCLE    AND    NERVE. 

constant  current  should  be  employed.  The  question  should  be  raised  as  to  the 
extent  to  which  the  suppression  of  sensation  could  be  aided  by  the  establishment 
of  katelectrotonus  in  the  central  focus. 

In  cases  of  hyperesthesia  and  neuralgia,  faradic  currents  are  applied  with  the 
object  of  obtunding  to  a  certain  extent  irritated  areas  of  skin  by  hyperirritation 
by  means  of  active  applications.  For  this  purpose  strong  currents  passed  through 
a  wire  brush  cause  a  sort  of  flagellation,  and  the  brush  on  long-continued  application 
may  act  as  an  electrical  moxa.  In  addition  to  this  local  effect,  feeble  currents 
excite,  reflexly,  acceleration  of  the  circulation,  with  increased  action  of  the  heart 
and  contraction  of  the  vessels,  while  strong  currents  have  the  opposite  effect. 
Both  may,  under  certain  circumstances,  be  of  therapeutic  value. 

The  employment  of  the  constant  current  in  cases  of  neviralgia  is  intended  in 
the  first  place  to  induce  diminution  in  the  irritability  of  the  morbidly  irritated 
portion  of  the  nerve  by  causing  anelectrotonus.  In  accordance  with  the  character 
of  the  case,  the  anode  may  be  applied  to  the  nerve-trunk  or  even  to  the  center, 
and  the  kathode  to  an  indifferent  portion  of  the  body.  The  catalytic  and  cata- 
phoric effects  should  be  taken  into  consideration,  as  through  them,  especially  in 
cases  of  recent  rheumatic  neuralgia,  irritating  inflammatory  products  may  be 
dissolved  and  dispersed.  Descending  currents  kept  closed  permanently  in  the 
course  of  the  nerve  are  especially  recommended,  and  often  prove  surprisingly 
effective,  especially  in  recent  cases.  Finally,  the  constant  current,  acting  as 
a  cutaneous  irritant,  may,  like  the  faradic  current,  exert  a  reflex  influence  upon 
the  activity  of  the  heart  and  the  vessels. 

To  determine  definitely  whether  the  irritability  from  the  nerve  or  the  muscle 
is  normal,  it  is  necessary  to  have  an  absolute  current-meter,  preferably  Edel- 
mann's  unit-galvanometer,  with  an  electrode  having  a  section  of  3  sq.  cm. — -unit- 
electrode.  On  application  of  this,  the  normal  irritability  in  the  same  individual 
exhibits  a  galvanic  variation  of  2.3  milliamperes.  The  differences  in  irritability 
between  different  healthy  persons  in  the  same  nerve  are  smaller  (1.2  m.  a.)  than 
between  the  different  nerves  of  the  same  individual  (2.3  m.  a.).  Kathodal  closing 
contraction  usually  occurs  earlier  than  anodal  opening  contraction.  Stronger  cur- 
rents are  required  in  the  new-born  to  cause  contraction  on  irritation  of  nerves  and 
muscles  than  in  adults. 

v.  Ziemssen  and  Edelmann  have  established  an  accurate  dosage  for  the 
induced  current  in  the  treatment  of  diseases  of  the  nervous  system. 

Recently  sparks  from  the  electrical  machine  or  charges  from  the  same  source 
have  been  employed  successfully  by  Charcot  and  Ballet  in  the  treatment  of  anes- 
thesia, facial  paralysis,  paralysis  agitans.  According  to  the  former,  isolated  con- 
traction of  muscles  can  be  induced  in  cases  of  spinal  paralysis  by  the  spark,  even 
if  they  no  longer  react  to  the  faradic  current. 

Mention  should  finally  be  made  here  of  the  fact  that  electricity  is  also  em- 
ployed for  the  production  of  thermic  effects  in  various  forms  of  the  cautery — 
Mitteldorpf's  galvanocautery. 

The  electrolytic  properties  of  the  electrical  current  have  been  employed  for 
the  purpose  of  causing  coagulation  in  aneurysms  or  varices  (arterial  and  venous 
tumors  filled  with  blood) — galvanopuncture. 

Under  the  influence  of  currents  of  high  tension  and  extraordinary  frequency, 
d'Arsonval  observed  increased  respiratory  activity,  increased  elimination  of 
urine,  increased  combustion  in  the  body,  an  influence  upon  the  vascular  nerves 
and  the  skin,  and  also  effects  upon  the  protoplasm  of  the  cells,  attenuation  of 
toxins,  and  immunization,  through  which  perhaps  an  enlarged  view  is  opened  into 
the  treatment  especially  of  disorders  of  metabolism. 

ELECTRICAL    CHARGING    OF    THE    ENTIRE    BODY   AND    OF    INDIVIDUAL 

PORTIONS. 

The  elder  Saussure  investigated  by  means  of  the  electroscope  the  charge 
in  many  persons  placed  upon  an  insulated  stool.  He  attributed  the  irregular 
phenomena  observed  by  him  to  the  electricity  generated  through  the  friction 
of  the  clothing  upon  the  skin.  Later  Gardini  and  others  contended  that  the 
presence  of  a  positive  charge  in  the  body  is  normal,  while  Sjosten  and  others 
held  that  the  charge  is  negative.  It  is,  however,  probable  that  all  of  these  charges, 
as  well  as  those  observed  by  Meissner,  are  purely  due  to  friction-phenomena, 
modification  in  the  effects  of  the  distribution  of  the  air,  and  to  the  contact  of  hetero- 
geneous conductors. 

Strong  charges,  to  the  point  of  causing  a  spark,   have  frequently  been  de- 


COMPARATIVE.       HISTORICAL.  675 

scribed.  The  earliest  statement  that  Landois  could  find  is  made  by  Cardanus 
(1553),  who  makes  mention  of  the  appearance  of  sparks  from  the  hair  of  the 
scalp.  According  to  Hosford  (1837)  a  nervous  woman  of  Oxford  exhibited  sparks 
more  than  4  cm.  long  at  the  fingers  while  standing  on  insulated  carpet.  Sparks, 
on  combing  the  hair  or  on  stroking  cats,  horses,  etc.,  are  often  observed  when 
the  air  is  dry. 

Of  the  various  constituents  of  the  body,  recently  voided  urine  has  been  found 
to  be  electrically  negative;  likewise  the  freshly  drawn  threads  of  spiders'  webs; 
while  the  blood  has  been  found  to  be  positive.  Also  feathers  and  hairs  become 
charged  with  electricity  if  rubbed. 

COMPARATIVE.     HISTORICAL. 

Among  the  most  interesting  phenomena  in  the  domain  of  animal  electricity 
are  exhibited  by  the  electrical  fish,  of  which  about  fifty  varieties  are  known.  The 
electrical  eel,  gymnotus  electricus,  is  found  in  the  fresn  waters  of  the  Orinoco  dis- 
trict, and  attains  a  length  of  2.5  meters.  The  electrical  rays  include  torpedo  mar- 
morata,  from  30  to  70  cm.  long;  torpedo  ocellata;  nascinae,  found  in  the  Mediter- 
ranean Sea;  and  a  number  of  related  species.  The  electrical  catfish,  malapterurus 
electricus,  is  found  in  the  Nile.  Finally  there  is  mormyrus,  or  Nile-pike.  By 
means  of  a  special  electrical  organ  these  animals  are  able,  in  part  voluntarily 
(eel,  catfish),  in  part  on  reflex  stimulation  (ray),  to  give  severe  electrical  shocks. 
The  electrical  organ  consists  of  variously  formed  compartments  bounded  by  con- 
nective tissue  and  filled  with  a  mucoid,  gelatinous  substance  designated  torpedo- 
mucin  by  Weyl,  to  one  surface  of  which  the  nerves  pass  and  form  a  plexus.  The 
latter  gives  rise  finally  to  a  cellular  plate  representing  the  terminations  of  the 
telodendrites  and  designated  the  electrical  plate.  By  stimulation  of  the  afferent 
electrical  nerves  the  shock-like  discharge  of  the  organ  takes  place. 

In  the  gymnoti  the  organ,  which  is  comparable  to  a  Voltaic  pile  arranged 
longitudinally  in  a  series  of  rows,  extends  on  each  side  of  the  vertebral  column 
downward  to  the  tail  beneath  the  skin  and  receives  from  the  anterior  aspect 
several  branches  from  the  intercostal  nerves.  In  addition  to  the  larger  organ, 
there  is  situated  above  the  anal  fins  on  each  side  a  smaller  one.  The  plates 
in  this  situation  are  vertical,  and  the  direction  of  the  electrical '  current  is,  in  the 
fish,  an  ascending  one,  and  in  the  conducting  arc  of  closure,  therefore,  in  the  sur- 
rounding water,  a  descending  one. 

In  the  electrical  catfish  the  organ,  which  surrounds  the  body  of  the  fish  like 
a  mantle,  is  similarly  situated,  and  contains  a  single  nerve-fiber  whose  axis-cylinder 
arises  in  the  vicinity  of  the  medulla  oblongata  from  a  huge  giant-cell,  and  is  con- 
stituted of  dendritic  processes.  The  plates  in  this  animal  also  are  vertical  and 
receive  the  nerves  from  the  posterior  aspect.  The  direction  of  the  current  when 
the  shock  is  given  is  descending  in  the  fish. 

In  the  ray  the  organ  is  situated  just  beneath  the  skin  to  one  side  of  the  head, 
extending  to  the  thoracic  fins.  It  receives  several  nerves,  which  arise  from  the 
special  portion  of  the  brain,  the  electrical  lobe,  situated  between  the  quadrigeminate 
bodies  and  the  medulla  oblongata.  The  plates,  which  do  not  increase  in  number 
with  the  growth  of  the  animal,  occupy  a  horizontal  position.  The  nerve-filaments 
pass  from  these  plates  from  the  ventral  aspect.  The  current  passes  in  the  fish 
from  the  ventral  to  the  dorsal  aspect.  Torpedo  occidentalis,  of  the  eastern  coast 
of  America,  may  attain  a  length  of  1.5  meters  and  is  capable  of  throwing  down 
a  robust  man  by  its  discharge. 

It  is  believed  that  the  electrical  organs  are  modified  muscles,  in  which  histo- 
logically  the  nerve-endings  are  highly  developed,  while  the  contractile  substance 
has  disappeared,  and  in  whose  physiological  activity  the  chemical  potential  is 
transformed  into  electricity.  In  favor  of  this  view  is  the  circumstance  that  in 
the  process  of  development  the  organs  are  preformed  in  a  manner  analogous  to 
the  muscles;  further,  that  the  organs  in  the  resting  state  are  neutral  and  in  the 
active  or  degenerated  state  are  acid  in  reaction;  finally,  that  they  contain  an 
albuminous  substance  related  to  myosin,  and  that  both  after  death  exhibit  signs 
of  rigidity.  Stimulated  organs,  as  well  as  muscles,  exhibit  an  increase  in  phos- 
phoric acid,  resulting  from  decomposition  of  lecithin  or  nuclein.  Both  further 
become  exhausted,  and  moreover  in  both  a  period  of  latent  irritation,  lasting 
o.o 1 6  second,  follows  actual  irritation  of  the  nerve,  while  a  shock  of  the  organ, 
which  thus  resembles  the  current  in  an  active  muscle,  lasts  0.07  second.  About 
25  such  shocks  together  constitute  a  discharge,  which  lasts  about  0.23  second. 


676  COMPARATIVE.       HISTORICAL. 

The  discharge  is  thus,  like  tetanus,  a  discontinuous  process.  However,  isolated 
individual  discharges  also  take  place,  in  the  torpedo  0.006  second  in  duration,  which 
thus  would  correspond  to  single  muscular  contractions.  Veratrin  causes  marked 
discharges,  comparable  to  the  veratrin  muscular  tracings  (p.  263).  Mechanical, 
thermal,  chemical,  and  tetanic-electrical  stimuli  give  rise  to  discharge-shocks. 
During  the  occurrence  of  the  electrical  shock  in  the  fish,  a  number  of  currents  pass 
also  through  the  muscles  of  the  animal.  In  the  ray  the  muscles  are  thrown  into 
contraction,  while  in  the  eel  and  the  catfish  they  remain  at  rest.  An  electrical 
ray  may  give  fifty  shocks  in  a  minute;  it  then  becomes  fatigued  and  must  re- 
cuperate; it  is  capable  also  of  discharging  the  organ  but  partially.  The  activity 
of  the  organ  is  enfeebled  by  cooling  and  increased  by  heating  it  to  about  22  . 
The  organ  is  thrown  into  a  state  of  tetanus  by  strychnin  and  it  is  paralyzed  by 
curare.  Irritation  of  the  electrical  lobe  of  the  ray  causes  discharge;  cold  retards 
the  discharge.  Division  of  the  electrical  nerve  paralyzes  the  organ.  The  electrical 
fish  are  themselves  only  slightly  sensitive  to  strong  faradic  currents  passed  into 
the  water  surrounding  them. 

The  substance  of  the  electrical  organ  is  simply  refracting;  excised  portions 
•exhibit  a  resting  current  that  has  the  same  direction  as  the  shock  and  is  increased 
by  heat.  Tetanus  of  the  organ  enfeebles  the  current.  Mormyrus,  raja,  and  gym- 
narchus  are  among  the  "feebly  electrical  fish,"  whose  discharge  is  incomparably 
feebler,  but  which  possess  an  organ,  formerly  improperly  designated  "pseudo- 
electrical,"  analogous  in  construction  to  that  of  the  "strongly  electrical  fish" 
previously  mentioned. 

Historical. — The  ancients  were  familiar  with  the  shocks  of  the  electrical  fish 
-of  the  Mediterranean  Sea.  Richer  (1672)  made  the  first  reports  upon  the  elec- 
trical eel.  Walsh  (1772)  investigated  experimentally  the  discharge  and  the  power 
of  the  rays  to  give  shocks.  J.  Davy  was  able  to  magnetize  bits  of  steel  by  means 
of  the  shocks,  to  deflect  the  magnetic  needle,  and  to  induce  electrolysis.  In  addi- 
tion to  the  investigators  named,  Becquerel,  Brechet,  and  Matteucci  studied  the 
direction  of  the  discharging  current,  from  which  the  last  named  and  Linari  ob- 
tained from  8  to  10  sparks.  Al.  v.  Humboldt  described  the  mode  of  life  and  the 
action  of  the  gymnoti  ("trembladores")  of  South  America,  which  are  able  to 
throw  down  even  horses  by  their  shock. 

Hausen  (1743)  and  de  Sauvages  (1744)  assumed  the  active  force  in  the  nerves 
to  be  electricity.  '  The  actual  investigations  into  animal  electricity  begin — after 
Caldini  (1756)  had  first  observed  that  the  muscles  of  the  frog  move  on  applying 
an  electrical  current — with  Luigi  Galvani  (1789-92),  who  observed  contractions 
in  the  frog's  thigh  as  a  result  of  the  return  stroke  on  discharge  of  the  electrical 
machine  and  likewise  when  the  muscle  was  placed  in  contact  with  two  different 
metals.  He  believed  that  the  nerves  and  the  muscles  possess  the  power  of  gen- 
erating electricity  independently.  Alessandro  Volta,  on  the  other  hand,  attributed 
the  contraction  in  the  second  experiment  to  an  electrical  current,  whose  source 
is  situated  outside  of  the  frog-preparation  at  the  point  of  contact  of  the  hetero- 
geneous metals.  The  contraction  without  metals  of  Galvani  and  Aldini  (1794) 
appeared  at  first  to  contradict  this  view.  Then,  the  latter  showed  that  the  animal 
parts  themselves  must  contain  sources  of  electricity.  Pfaff  (1793)  was  the  first 
to  observe  the  influence  of  the  direction  of  the  current  upon  the  contraction  of 
the  frog's  leg  stimulated  from  the  nerve.  Bunzen  prepared  an  effective  pile  from 
muscles  of  the  frog.  The  subject  entered  upon  a  new  phase  as  a  result  of  the 
•discovery  of  the  galvanometer  and  of  the  classical  methods  introduced  by  du  Bois- 
Reymond  in  1843. 


PHYSIOLOGY  OF  THE  PERIPHERAL 

NERVES. 


CLASSIFICATION  OF  NERVE-FIBERS   ACCORDING  TO 

FUNCTION. 

As  the  nerve-fibers  when  stimulated  possess  the  property  of  con- 
ducting impulses  in  both  directions,  their  physiological  activity  is  es- 
sentially dependent  upon  their  relation  to  their  peripheral  end-organ 
and  to  their  central  connection.  In  this  way  the  individual  nerve  is 
distributed  to  a  definite  area,  within  which,  under  normal  conditions, 
its  function  is  exercised  in  the  uninjured  body.  This  activity  of  the  in- 
dividual nerve,  due  to  its  anatomical  arrangement  and  connections,  is 
designated  its  specific  energy. 

I.   CENTRIFUGAL  NERVES. 

(a)  Motor. — The  center  consists  of  central  or  peripheral  ganglia;  the  end- 
organ  is  a  muscle. 

1.  Motor  fibers  of  transversely  striated  muscles. 

2.  The  motor  nerves  of  the  heart. 

3.  The  motor  nerves  of  unstriated  muscle-fibers,  for  example  of  the  intestine. 
The  peculiarities  of  the  movement  induced  by  these  nerves  has  been  discussed 
in  the  section  on  the  Physiology  of  the  Movement  of  the  Digestive  Apparatus 
(pp.  280  and  547).     The  vasomotor  nerves  are  deserving  of  especial  consideration 
in  this  group. 

(6)  Secretory. — The  center  is  a  central  or  peripheral  ganglion,  the  end-organ 
the  glandular  cell. 

Examples  are  furnished  by  the  salivary  secretion,  the  secretion  of  sweat,  etc. 

(c)  Trophic. — The  as  yet  unknown  end-organ  is  situated  in  the  tissues  them- 
selves, whose  normal  metabolism,  growth,  and  uninterrupted  intact  existence  they 
control. 

In  some  tissues  a  direct  connection  with  nerves  is  known  to  exist  that  is 
capable  of  influencing  their  nutritive  processes.  Anatomically  or  physiologically, 
the  connection  of  the  nerves  with  corneal  cells,  with  the  pigment-cells  of  the 
frog's  skin,  the  connective-tissue  corpuscles  of  the  serous  coat  of  the  frog's  stomach, 
with  the  cells  that  surround  the  stomata  of  the  lymph-spaces,  is  known. 

The  statements  which  are  to  follow  with  reference  to  the  trophic  functions  of 
certain  nerves  should  be  consulted,  particularly  the  influence  of  the  trigeminus  upon 
the  eye,  upon  the  mucous  membrane  of  the  mouth  and  the  nose,  upon  the  face; 
of  the  vagus  upon  the  lungs ;  of  the  motor  nerves  upon  the  muscles ;  of  the  nerve- 
centers  upon  the  conservation  of  nerve-fibers,  and  of  certain  central  organs  upon 
individual  viscera. 

Furthermore,  a- description  will  be  given  here  of  the  influence  of  the  division 
of  nerves  upon  the  growth  of  bone.  H.  Nasse  found  that  the  bones  after  such 
an  operation  exhibited  a  diminution  in  the  absolute  amount  of  all  their  individual 
constituents,  but,  on  the  other  hand,  an  increase  of  fat.  After  division  of  the 
spermatic  nerve,  degeneration  of  the  testicle  has  been  observed;  after  destruction 
of  the  secretory  nerve,  degeneration  of  the  submaxillary  gland;  after  division  of 
the  related  nerve,  interference  with  the  nutrition  of  the  cock's  comb;  after  division 
of  the  second  cervical  nerve  (in  cats  and  rabbits),  loss  of  hair  from  the  ear;  changes 
in  the  skin  of  the  frog  after  injury  of  the  spinal  ganglia;  after  division  of  the 
cervical  sympathetic  (which  is  attended  with  hyperemia  of  the  corresponding  half 

677 


678  THE  CEREBRAL  NERVES. 

of  the  head) ,  enlargement  of  the  ear  and  increased  rapidity  in  the  growth  of  the 
hair  were  observed,  together  with  hypertrophy  of  the  muscular  coat  of  the  veins, 
of  the  cartilage,  and  of  the  horny  skin,  with  atrophy  of  the  epidermis;  further, 
diminution  in  the  size  of  the  cerebral  hemisphere  of  the  corresponding  side,  perhaps 
in  consequence  of  the  pressure  exerted  by  the  dilated  vessels.  Lewaschew  ob- 
served hypertrophy  of  the  leg  and  foot  in  the  sequence  of  long-maintained  chemical 
irritation  of  the  sciatic  nerve  in  dogs,  and  also  the  development  of  aneurysmal 
dilatation  of  the  vessels. 

In  man,  irritation  or  paralysis  of  the  nerves  or  degeneration  of  the  gray  matter 
of  the  spinal  cord  is  not  rarely  attended  with  alterations  in  the  pigment  of  the 
skin,  and  of  the  nails  and  hair  and  in  their  growth,  as  well  as  cutaneous  eruptions, 
for  example  herpes  zoster  after  inflammation  of  the  spinal  ganglia  or  nerves. 
and  a  tendency  to  bed-sores;  further,  rare  affections  and  degenerations  of  the 
joints  (in  cases  of  tabes).  Local  diseases  of  the  brain  have  been  observed  to 
be  attended,  with  unilateral  derangement  in  the  growth  of  the  hair  and  the  nails. 

(d)  Inhibitory  nerves,  which  suppress  or  diminish  a  movement  or  secretion 
already  present. 

Examples  are  found  in  the  vagus  as  the  inhibitory  nerve  of  the  movement 
of  the  heart,  the  splanchnic  as  that  of  the  movements  of  the  intestine,  the  vaso- 
dilators as  inhibitory  nerves  of  the  unstriated  muscle  of  the  vessels. 

II.  CENTRIPETAL  NERVES. 

(a)  Sensory  nerves,  which  convey  sensory  impressions  to  the  central  organ 
by  means  of  special  end-apparatus. 

(6)  Nerves  of  special  sense. 

(c)  Reflex  or  excito-motor  nerves,  which,  when  stimulated  at  the  periphery, 
conduct  the  irritation  to  the  center,  within  which  this  excitation  is  transmitted 
to  the  centrifugal  fibers  (I,  a,  b,  c,  d} ,  so  that  the  activity  of  the  latter  is  manifested 
as  reflex  movement,  reflex  secretion  or  reflex  inhibition. 

III.    INTERCENTRAL  NERVES. 

These  connect  ganglionic  centers  one  with  another  for  the  communication  of 
the  excitation  among  them,  for  example  in  the  coordinated  movements,  for  in- 
stance of  the  eyes  and  of  widespread  reflexes. 


THE  CEREBRAL  NERVES. 

All  cranial  motor  nerves  arise  from  their  cerebral  nuclei  of  origin  as 
neurites  of  ganglion-cells  in  the  same  way  as  the  fibers  of  the  anterior 
roots  of  the  spinal  cord  arise  from  the  ganglia  of  the  anterior  horns. 
The  sensory  cerebral  nerves  have  their  actual  origin  in  the  bipolar  cells 
of  the  peripheral  ganglia  of  the  sensory  nerves.  Into  each  of  these  eel's 
a  cellulipetal  dendrite  enters  from  the  region  endowed  with  sensation, 
while  a  cellulifugal  neurite  passes  from  the  cell  to  the  brain,  where  it 
comes  into  contact  with  the  terminal  ramifications  of  the  sensory  nucleus 
of  origin 

I.    OLFACTORY  TRACT  AND   BULB. 

The  strand-like  triangular-prismatic  olfactory  tract,  situated  upon  the  inferior 
surface  of  the  frontal  lobe,  becomes  enlarged  on  the  cribriform  plate  of  the  ethmoid 
bone  to  form  the  olfactory  bulb,  which  is  the  analogue  of  a  special  portion  of  the 
brain  that  exists  in  different  vertebrates  with  a  well-marked  power  of  smell. 
From  the  bulb  there  pass  through  the  cribriform  plate  between  15  and  20  olfactory 
filaments,  which  continue  first  between  the  mucous  membrane  and  the  periosteum 
and  into  the  mucous  membrane  itself  only  in  the  lower  third  of  the  olfactory 
region.  The  structure  of  the  bulb,  as  well  as  the  relations  of  the  olfactory  nerves, 
are  discussed  on  p.  914. 

The  origin  of  the  olfactory  fibers  may  be  traced  as  follows:    (i)   To  the  forni- 


OPTIC    NERVE    AND    TRACT.  679 

cate  gyrus,  median  root  (Fig.  262) .  (2)  The  lateral  root  passes  through  the  anterior 
perforated  plate  to  the  internal  capsule  (sensory  path  of  the  cerebrum) ,  and  further 
through  the  uncinate  gyrus  (sensory  cortical  center) ,  where  its  fibers  enter  into 
contact  with  the  ganglion-cells  by  means  of  telodendrites.  Possibly  the  fibers  of 
origin  decussate  within  the  cerebrum.  (3)  Fibers  may  be  traced  also  in  the  head 
of  the  caudate  nucleus  and  thence  into  the  anterior  commissure,  in  which  there 
is  a  communication  between  the  two  olfactory  bulbs. 

The  olfactory  nerve  is  the  nerve  of  smell,  the  physiological  excita- 
tion of  which  takes  place  only  through  volatile  odorous  substances. 
Congenital  deficiency  or  division  of  both  nerves  destroys  the  sense  of 
smell. 

Pathological. — The  designation  hyperosmia  is  applied  to  a  condition  in  which 
the  acuity  of  the  sense  of  smell  is  abnormally  exaggerated,  for  example  in  hysterical 
individuals.  Purely  subjective  impressions  of  the  sense  of  smell,  olfactory  hal- 
lucinations, for  example  in  the  insane,  probably  depend  upon  abnormal  excitation 
of  the  cortical  center.  In  some  persons  the  ingestion  of  antifebrin,  which  is 
odorless  and  tasteless,  excites  a  subjective  sense  of  smell  even  when  the  existence 
of  marked  coryza  renders  the  nose  incapable  of  smelling.  Hyposmia  and  anosmia, 
diminution  and  abolition  of  the  sense  of  smell,  occur  as  the  result  of  catarrhal 
conditions  of  adjacent  cavities,  through  the  action  of  injurious  gases  or  fluids, 
as  one  of  the  phenomena  of  general  intoxication  or  disease,  and  in  consequence  of 
absence  of  the  pigment  in  the  olfactory  region.  Strychnin  increases  and  morphin 
occasionally  diminishes  the  sense  of  smell. 

II.    OPTIC  NERVE  AND  TRACT. 

The  optic  tract  arises  from  the  anterior  quadrigeminal  body,  from  the  lateral 
geniculate  body,  from  the  pulvinar  and  the  zonal  stratum  of  the  optic  thalamus 
(Fig.  242)  and  from  the  tuber  cinereum.      By  means  of  a  broad  bundle  of  fibers 
(visual  fibers  of  Gratiolet) ,  which  pass  directly 
outward   from   the  posterior  horn,  the  origin 
in   the    parts  named   is   connected   with  the 
cortical  psycho-visual  center  in  the  occipital 
lobe  of  the  same  side.     Fibers  pass  from  the 
cerebellum  through  the  crura. 

The  two  tracts  unite  to  form  the  chiasm, 
from  which  on  each  side  arises  the  optic  nerve, 
the  fibers  of  which  are  medullated  but  without 
neurilemma. 

In  the  chiasm  a  semidecussation  of  the 
fibers  takes  place  as  a  rule  (Fig.  240),  so  that 
the  left  tract  sends  fibers  into  the  left  half 

of  each  retina  and  the  right  tract  fibers  into 

.1  Q    .jrrU*.  i,0if  FIG.    240. — Diagrammatic    Representation   of 

the  right  half.  the  |emidecuisation  of  the  Optic  Nerves. 

It  can  thus  be  understood  that  in  man 
destruction  of  one  tract  causes  so-called 

homonymous  hemiopia,  that  is  blindness  of  the  two  corresponding  retinal  halves 
in  the  sense  described.  As  the  left  half  of  each  retina  receives  impressions  from 
the  right  half  of  the  visual  field,  and  conversely,  all  fibers  intended  for  seeing 
objects  in  the  right  half  of  the  visual  field  are  situated  in  the  left  tract,  and  vice 
versa.  The  same  effect  is  produced  by  destruction  of  its  origins,  as  by  de- 
struction of  the  optic  tract,  according  to' Bechterew  also  by  that  of  the  external 
geniculate  body  and  the  anterior  brachium  alone.  Sagittal  division  of  the  chiasm 
has  caused  in  man  in  one  case  blindness  of  the  nasal  half  of  each  retina.  In  ex- 
ceedingly rare  cases  the  decussation  has  been  wholly  wanting  in  man. 

Among  animals  partial  decussation  occurs  in  the  following  :  Ape,  cat,  dog; 
complete  decussation  in  the  rabbit,  mouse,  guinea-pig,  pigeon,  owl.  In  the  bony 
fish  both  optic  nerves  cross  separately;  in  the  cyclostomata  there  is  no  decussation 
at  all.  Two  commissures  lying  upon  the  optic  chiasm,  that  of  Meynert  and  that 
of  Gudden,  have  really  nothing  whatever  to  do  with  the  optic  nerve. 

After  extirpation  of  an  eye  in  man  there  degenerate  centripetally  the  fibers 
that  enter  the  optic  nerve  from  the  organ,  therefore  in  man  half  of  the  fibers 
in  each  tract.  The  degeneration  extends  to  the  origins  in  the  quadrigeminal 


68O  OCULOMOTOR    NERVE. 

bodies,  the  geniculate  bodies  and  the  pulvinar,  but  not  into  the  conducting  path 
to  the  psycho-visual  center.  The  secondary  degenerations  following  destruction 
of  the  cortical  visual  center  are  discussed  on  p.  787. 

The  optic  nerve  is  the  nerve  of  vision  the  physiological  stimulation 
of  which  occurs  only  through  conveyance  of  the  vibrations  of  the 
luminiferous  ether  to  the  rods  and  cones  of  the  retina.  Every  other 
form  of  irritation  of  the  nerve,  either  in  its  course  or  at  its  center, 
causes  a  sensation  of  light.  Division  or  degeneration  of  the  nerve  gives 
rise  to  blindness.  Irritation  of  the  optic  nerve  causes  also  reflex  con- 
traction of  the  pupils  through  the  oculomotor  nerve,  and  marked  irri- 
tation, also  closure  of  the  lids  and  flow  of  tears. 

As  the  optic  nerve  has  separate  connections  both  with  the  psycho-visual  center 
and  with  the  pupil-contracting  center  it  will  be  readily  understood  that  under 
pathological  conditions,  on  the  one  hand,  blindness  with  preservation  of  the  iris- 
reaction,  and,  on  the  other  hand,  loss  of  the  movement  of  the  iris,  with  preservation 
of  vision,  have  been  observed. 

Gudden,  in  1882,  found  two  different  kinds  of  fibers  in  the  optic  nerve,  namely 
fine  or  visual  fibers,  whose  center  is  situated  in  the  quadri geminate  body,  and 
coarse  or  pupillary  fibers,  whose  origin  can  be  traced  to  the  external  geniculate 
body.  Destruction- of  the  visual  fibers  causes  blindness,  that  of  the  pupillary  fibers 
gives  rise  to  marked  dilatation  of  the  pupils. 

Pathological. — Irritation  in  the  range  of  the  entire  nervous  apparatus  may 
cause  excessive  sensitiveness  of  the  visual  organs  (optic  hyperesthesia} ,  and  also 
visual  sensations  of  varied  kind  (photopsia,  chromopsid) ,  which,  in  case  the  irrita- 
tion extends  to  the  psycho-visual  center,  may  even  become  actual  visual  hallu- 
cinations. Material  alterations  and  inflammatory  processes  in  the  nervous  appa- 
ratus are  often  followed  by  nervous  impairment  of  vision  (amblyopia)  or  even  by 
blindness  (amaurosis).  Nevertheless,  both  conditions  may  occur  as  the  signs  of 
disorder  in  other  organs,  so-called  sympathetic  symptoms,  being  often  probably 
due  to  alterations  in  the  circulation  of  the  blood  through  irritation  of  the  vaso- 
motor  nerves,  and  readily  undergoing  retrogression.  Remarkable  intermittent 
forms  of  amaurosis  are  the  day-blindness  (hemeralopia,  for  example  in  connection 
with  diseases  of  the  liver)  and  the  night-blindness  (nyctalopia} .  Disorders  of  the 
cortical  visual  center  are  considered  on  p.  787. 

III.    OCULOMOTOR  NERVE. 

The  fibers  of  the  oculomotor  nerve  arise  as  neurites  of  the  ganglion  cells  of 
the  oculomotor  nucleus  situated  in  the  gray  matter  beneath  the  aqueduct  of 
Sylvius.  Several  groups  of  cells  can  be  distinguished  in  this  nucleus:  (ij  The  lat- 
eral chief  nucleus,  consisting  principally  of  large  ganglion  cells  and  passing  below 
the  aqueduct  of  Sylvius  on  each  side  close  to  the  middle  line.  (2)  Between  the  two 
lateral  nuclei  lies  the  single,  smaller,  large-celled  central  nucleus,  and  (3)  in  front 
of  this  on  each  side,  a  smaller,  small-celled  nucleus.  The  fibers  from  the  posterior 
portions  of  the  lateral  and  central  nuclei  decussate.  In  apes  the  nerves  for  the 
external  ocular  muscles  arise  from  the  chief  nucleus  of  the  same  and  the  opposite 
side,  those  for  the  internal  muscles  from  the  accessory  nuclei. 

Frbm  the  angular  gyrus  of  the  cerebral  cortex,  the  psychomotor  center  for 
the  voluntary  movements  of  the  eyes,  and  probably  also  from  the  visual  sphere 
(for  the  involuntary  adjustment  of  the  eyes  for  direct  vision),  fibers  that  undergo 
partial  decussation  in  the  raphe  of  the  tegmentum  pass  to  the  oculomotor  nucleus, 
with  whose  cells  they  come  in  contact  by  means  of  terminal  branches.  Not  far 
from  the  pons  the  nerve  appears  in  the  midst  of  the  inner  bundle  of  fibers  of  the 
peduncle  as  a  median  and  a  posterior  lateral  group  of  fibers. 

The  oculomotor  nerve  contains :  i .  The  voluntary  motor  fibers  for  all 
of  the  external  ocular  muscles,  with  the  exception  of  the  external  rectus 
and  the  superior  oblique,  and  for  the  elevator  of  the  upper  lid.  The 
coordinated  movement  of  both  eye-balls  is,  however,  independent  of  the 
will.  2.  The  fibers  for  the  sphincter  muscle  of  the  pupil  that  are  active 
through  reflex  stimulation  from  the  retina.  3.  The  fibers  for  the  muscle 


OCULOMOTOR    NERVE. 


68l 


of  accommodation.  The  fibers  mentioned  under  2  and  3  are  given  off 
from  the  branch  for  the  inferior  oblique  muscle  as  the  short  root  of  the 
ciliary  ganglion  (Fig.  343,  3)  and  pass  from  the  latter  through  the  short 
ciliary  nerves  into  the  bulb.  v.  Trauwetter,  Adamuk,  Hensen,  and 
Volckers  observed  on  irritation  of  the  nerve  that  the  eye  underwent 
change  as  in  near  vision,  and  the  pupil  diminished  in  size.  Details  as  to 
the  origin  of  the  individual  portions  of  the  nerve  are  given  on  p.  833 


Pulvinar. 


Corpus  f  anticum. 

quadri-K 

gemina.  (.posticum. 


Locus  coeruleus. 


Eminentia  teres. 

Crus  cerebelli 
ad  pontem. 


Conarium  or  pineal  gland. 
Brachium  conjunctivum 
anticum. 


Brachium  conjuncti- 
vum posticum. 

Corpus  geniculatum 
mediale. 


Pedunculus  cerebri. 


ad  corpora 
quadri- 
gemina. 

ad  medul- 
lam  ob- 
longatam. 


Crura 
cere- 
belli. 


Ala  cinerea. 
Accessorius  nucleus. 


Funiculus  cuneatus. 

Funiculus  gracilis 


FIG.  241. — Medulla  Oblongata  and  Quadrigeminate  Bodies,  Magnified:  The  figures  from  IV  to  XII  indicate 
the  superficial  origin  of  the  cerebral  nerves;  the  figures  from  3  to  12  indicate  the  position  of  their  nuclei  of 
origin;  t,  funiculus  teres. 

The  center  for  reflex  stimulation  of  the  fibers  of  the  pupillary  sphinc- 
ter by  light  is  situated  in  the  quadrigeminate  bodies  near  the  aqueduct 
of  Sylvius.  A  detailed  description  is  given  on  p.  842.  The  contraction  of 
the  pupil  that  occurs  in  conjunction  with  the  act  of  accommodation  is 
to  be  looked  upon  as  an  associated  movement. 

In  man,  the  nerve  anastomoses  at  the  cavernous  sinus  with  the  first  branch 
of  the  trigeminus,  in  this  way  receiving  muscle-sense  fibers;  further  with  the 


682  TROCHLEAR    NERVE. 

sympathetic  through  the  carotid  plexus  and  indirectly  through  the  abducens, 
in  this  way  receiving  vasomotor  fibers.  The  rare  cases  in  which  fibers  for  the 
sphincter  have  been  found  in  the  abducens  or  even  in  the  trigeminus  must  be 
considered  as  examples  of  variations  in  the  course  of  the  pupillary  fibers. 

The  intraocular  fibers  of  the  oculomotor  nerve  are  paralyzed  by 
atropin  and  stimulated  by  physostigmin  (or  the  sympathetic  is  para- 
lyzed, or  both). 

Contraction  of  the  pupils  on  irritation  of  the  nerve  can  be  best  demonstrated 
in  the  severed  and  opened  head  of  a  bird.  Asphyxia,  sudden  cerebral  anemia 
(from  ligature  of  the  carotid  arteries  or  beheading) ,  and  likewise  sudden  venous 
stasis,  cause  dilatation  of  the  pupils,  as  in  death,  through  paralysis  of  the  oculo- 
motor nerve. 

Pathological. — Complete  paralysis  of  the  oculomotor  nerve  gives  rise:  (i)  To 
drooping  of  the  upper  lid  (paralytic  ptosis) .  (2)  To  immobility  of  the  eyeball. 
(3)  To  rotation  of  the  eye  outward  and  downward  (strabismus'],  and  as  a  result 
to  diplopia.  (4)  To  slight  protrusion  of  the  bulb,  because  the  superior  oblique, 
which  draws  the  eye  forward,  is  unopposed  by  the  action  of  its  antagonists,  the 
three  paralyzed  rectus  muscles,  which  draw  the  eye  backward.  In  animals,  which 
have  a  retractor  muscle  of  the  bulb,  this  symptom  is  more  conspicuous.  (5)  To 
moderate  dilatation  of  the  pupil  (paralytic  mydriasis) .  (6)  To  inability  on  the 
part  of  the  pupil  to  contract  upon  stimulation  by  light.  (7)  To  loss  of  the  power 
of  accommodation  of  the  eye  for  near  vision.  The  paralysis  naturally  may  be 
confined  to  individual  portions  or  be  incomplete.  Destruction  of  the  posterior 
portion  of  the  oculomotor  nucleus  causes  only  paralysis  of  the  external  ocular 
muscles  (external  ophthalmoplegia) . 

Irritation  of  the  branch  for  the  elevator  of  the  lid  causes  spastic  lagophthalmos 
in  man;  of  the  other  muscular  branches,  corresponding  spastic  strabismus.  These 
latter  irritations  may  be  induced  also  reflexly,  as,  for  example,  during  dentition 
and  in  association  with  the  diarrheas  of  childhood.  Clonic  contractions  manifest 
themselves  bilaterally  as  involuntary  oscillation  of  the  eyes  (nystagmus)  in  conse- 
quence of  irritation  of  the  quadrigeminate  bodies.  Tonic  spasm  of  the  sphincter 
of  the  pupil  is  designated  spastic  myosis,  clonic  spasm  hippus.  Spasm  of  accom- 
modation is  also  observed,  and  in  conjunction  with  it  not  rarely  macropia  in  con- 
sequence of  imperfect  estimation  of  distance. 

IV.    TROCHLEAR  NERVE. 

The  trochlear  nerve  arises  by  means  of  neurites  from  the  ganglion-cells  of 
the  trochlear  nucleus,  which  is  situated  immediately  behind  the  lateral  chief 
nucleus  of  the  oculomotor  nerve,  and  really  forms  a  continuation  of  the  anterior 
horn  (constituted  of  two  sections  joined  together),  below  the  gray  matter 
surrounding  the  aqueduct  of  Sylvius.  It  then  passes  to  the  lower  border  of  the 
posterior  quadrigeminate  body,  and  further  on  into  the  superior  medullary  velum, 
and  decussates  with  the  root  of  the  opposite  side  in  the  velum  and  then  appears 
free  (Fig.  241).  Like  the  third  and  sixth  cerebral  nerves  it  is  probably  connected 
by  fibers  with  the  cortical  motor  center  for  the  ocular  muscles. 

The  trochlear  is  the  voluntary  motor  nerve  of  the  superior  ob'.ique 
muscle.  Its  coordinated  innervation,  however,  is  involuntary. 

Its  connections  with  the  carotid  plexus  of  the  sympathetic  and  the  first  branch 
of  the  trigeminus  have  the  same  significance  as  the  analogous  connections  of  the 
oculomotor  nerve. 

Pathological.—  Paralysis  of  the  trochlear  nerve  causes  only  slight  loss  of  the 
mobility  of  the  eyeball  outward  and  downward,  with  the  development  of  slight 
rotation  inward  and  upward  and  diploplia.  The  images  are  placed  obliquely 
one  above  the  other,  approach  each  other  when  the  head  is  turned  toward 
the  unaffected  side,  and  are  separated  when  the  head  is  turned  toward  the  affected 
side.  The  patient  at  first  inclines  the  head  forward,  but  subsequently  rotates  it 
about  the  vertical  axis  towaid  the  unaffected  side.  When  the  head  is  rotated, 
the  healthy  eye  retaining  the  primary  position,  the  eye  makes  a  similar  movement. 
Spasm  of  the  trochlear  nerve  causes  rotation  of  the  eye  outward  and  downward. 


TRIGEMINAL    NERVE. 


683 


V.    TRIGEMINAL  NERVE. 

The  trigeminal  nerve  (Fig..  242)  arises,  like  a  spinal  nerve,  by  two  roots  (Fig. 
241).  The  smaller,  anterior,  motor  root  originates  as  a  bundle  of  neurites  from 
the  motor  nucleus  of  the  trigeminus  (nucleus  masticatorius  and  locus  coeruleus, 
Fig.  241,  5),  rich  in  large  cells,  on  the  floor  of  the  fourth  ventricle  close  to  the 
middle  line,  some  of  the  fibers  coming  from  the  opposite  side.  'From  the  cortical 
motor  center  of  the  cerebrum  fibers  from  the  opposite  side  pass  through  the  cerebral 
peduncle  to  this  nucleus.  In  addition,  the  descending  root  furnishes  motor  fibers. 
This  root  (5,,,)  extends 
from  the  anterior  quad- 
rigeminate  body  later- 
ally along  the  aqueduct 
of  Sylvius  downward  to 
the  point  of  exit  of  the 
nerve.  The  large  sen-  I-  olf. 

sory,  posterior  root  re- 
ceives fibers  (i)  from 
the  gray  matter  of  the 
sensory  nucleus  of  the 
trigeminus  (5t) ,  situ- 


IV.  trocJi. 
V.  try. 

VI.  aid. 

VII.  fac. 

VIII.  acust. 

IX.  glossph. 

X.  vag. 


XL  access.  — 
XII.  hypgl. 


II.  opt. 

01;  >  °^LI-  ///.  ocm. 
ated  to  the  side  of  the 
motor  nucleus,  and  the 
analogue  of  the  poste- 
rior horn.  (2)  From  the 
gray  matter  of  the  pos- 
terior horn  of  the  spinal 
cord  down  to  the  sec- 
ond cervical  vertebra. 
These  fibers  give  off 
collaterals  to  the  ori- 
gins particularly  of  the 
hypoglossal  and  facial 
nerves,  participate  in 
the  reticular  formation 
and  enter  the  white 
posterior  column  and 
then,  as  the  spinal  or 
ascending  root,  the  sen- 
sory branches  of  the 
trigeminus.  (3)  From 
the  cerebellum  (unde- 
cussated)  fibers  passing 
through  the  crus  were 
described  by  Meynert. 

The  origins  of  the 
sensory  root  are  con- 
nected with  the  motor 
nuclei  of  all  of  the 
nerves  arising  in  the 
medulla  oblongata,  with 
the  exception  of  the 
abducens.  This  fact  explains  the  various  reflex  effects. 

The  thick  trunk  appears  laterally  between  the  fibers  of  the  pons;  then  its 
posterior  root  forms  the  Gasserian  ganglion  (Figs.  242  and  243)  at  the  apex  of  the 
petrous  bone.  In  the  ganglion  the  bipolar  ganglion-cells  are  actually  the  seats  of 
origin  of  the  sensory  root.  Filaments  of  the  sympathetic  from  the  cavernous  plexus 
pass  to  the  Gasserian  ganglion.  Then  the  nerve  divides  into  its  three  large  branches. 

The  first,  or  ophthalmic,  division  (Fig.  243,  d)  receives  sympathetic 
(vasomotor)  fibers  from  the  cavernous  plexus,  then  passes  through  the 
sphenoidal  fissure  into  the  orbit.  Its  branches  are: 

i.  The  small  recurrent  nerve,  which  gives  off  sensory  branches  to  the 
tentorium  cerebelli.  To  it  are  added  fibers  from  the  carotid  plexus  of  the 
sympathetic  as  vasomotdrs  for  the  dura  mater. 


CV  1 


FIG. 


242. — The  Cerebral  Nerves,  /  to  XII  (according  to  Schwalbe):  JR. 
island  of  Reil;  h,  hypophysis;  th,  optic  thalamus;  c,  c,  corpora  albicantia; 
gm,  gl,  mesial  and  lateral  geniculate  bodies;  py,  pyramid;  ov,  olivary 
body;  CTi,  first  cervical  nerve. 


684  TRIGEMINA.L    NERVE. 

2.  The  lacrimal  nerve  gives  off  (a)  sensory  branches  to  the  conjunc- 
tiva, the  tipper  lid,  the  adjacent  skin  of  the  temple  (Fig.  243,  a) ;  (6)  true 
secretory  fibers  to  the  lacrimal  gland.     Accordingly,  irritation  of  the 
nerve  excites  the  secretion  of  tears,  while  division  causes  paralytic  flow 
of  tears.     The  secretion  can  be  excited  reflexly  by  the  irritation  of  strong 
light  and  by  irritation  of  the  first  and  second  branches  of  the  trigeminus, 
and  even  of  all  of  the  sensory  cerebral  nerves  and  some  of  the  nerves  of 
the  trunk.     The  reflex  center  for  the  secretion  of  tears  is  situated  in 
the  optic  thalamus. 

3.  The  frontal  nerve  (f)  gives  off,  through  its  supratrochlear  branch, 
sensory  fibers  to  the  upper  lid,  the  brow,  the  glabella,  and  fibers  reflexly 
stimulating  the  secretion  of  tears;  and,  through  its  supraorbital  branch, 
analogous  fibers  to  the  upper  lid,  and  the  skin  of  the  forehead  and  of  the 
adjacent  temple  to  the  vertex. 

4.  The  nasociliary  nerve  (n  c),  through  its   infratrochlear    branch, 
supplies  fibers  analogous  to  those  just  mentioned  to  the  conjunctiva,  the 
lacrimal  caruncle  and  sac,  the  upper  lid,  the  brow,  the  root  of  the  nose. 
Its    ethmoid    branch    supplies   the  tip  and  the  alae  of   the  nose  exter- 
nally and  internally  with  sensory  fibers  and  also  the  anterior  portion  of 
the  septum  and  the  lower  turbinates  with  tactile  fibers  (which  also  in 
part  excite  reflexly  the  flow  of  tears)  and  perhaps  also  with  vasomotor 
fibers,  which  may  possibly  arise  through    anastomosis   with  the  sym- 
pathetic.    From  the  naso-ciliary  branch  arise  also  the  long  roots  (Fig. 
243)  of  the  ciliary  ganglion  (c)  and  the  first,  second,  and  third  long  ciliary 
nerves. 

$  The  ciliary  ganglion  (Fig.  243,  c),  which  really  belongs  rather  to  the 
third  than  to  the  fifth  nerve,  has  three  roots:  (a)  the  short  root,  from  the 
oculomotor  (3),  (b)  the  long  root  (1)  from  the  nasociliary,  and  (c)  the 
sympathetic  root  (s)  from  the  carotid  plexus,  occasionally  united  with 
b.  From  the  ganglion  there  arise  between  six  and  ten  short  ciliary  nerves 
(t),  which,  together  with  the  long  ciliary  nerves,  penetrate  the  sclera  near 
the  entrance  of  the  optic  nerve  and  pass  forward  between  this  and  the 
choroid.  They  contain: 

1.  The   motor  fibers  for  the  sphincter  muscle  of  the  pupil  and  the 
tensor  of  the  choroid  from  the  oculomotor  root. 

The  oculomotor  root  is  connected  in  the  ciliary  ganglion  by  terminal  ramifica- 
tions with  dendrites  of  the  ganglion-cells  (not  the  sympathetic  and  those  of  the 
trigeminus).  After  division  of  the  oculomotor  nerve,  degeneration  of  its  libers 
takes  place  only  into  the  ciliary  ganglion,  but  not  further  in  a  peripheral  direction. 
Small  doses  of  nicotin  paralyze  the  oculomotor  nerve  from  its  origin  to  the  ciliary 
ganglion  and  this  portion  rapidly  loses  its  function  after  death,  while  the  ciliary 
nerves  that  cause  contraction  of  the  pupil  retain  their  irritability  for  a  considerable 
time. 

2.  Sensory  fibers  for  the  cornea,  which  are  distributed  by  means  of 
most  delicate  filaments  throughout  the  epithelium ;  and  for  the  bulbar  con- 
junctiva,  which   penetrate   the   sclera.     These   stimulate   also   reflexly 
the  flow  of  tears  (lacrimal  nerve)  and  closure  of  the  eyelids  (facial  nerve). 
The  iris,  which  is  the   seat  of  pain  in  the  presence  of  inflammatory 
processes  and  as  a  result  of  operation;  the  choroid,  which  is  the  seat  of 
painful  tension  on  contraction  of  the   tensor  of  the   choroid;  and  the 
sclera  also  receive  sensory  fibers. 

^3.  Vasomotor  nerves  for  the  vessels  of  the  iris,  the  choroid,  and  the 
retina.  These,  however,  are  derived  in  part  only  from  the  sympathetic 


TRIGEMINAL    NERVE.  685 

root  and  the  connection  of  the  sympathetic  with  the  first  division.  The 
iris  and  the  retina  probably  receive  the  larger  number  of  vasomotor 
fibers  from  the  trigemimis  itself,  and  a  small  number  from  the  sym- 
pathetic. According  to  Klein  and  Svetlin,  the  retinal  vessels  are  not  at 
all  influenced  through  the  sympathetic. 

4.  Motor  fibers  for  the  dilator  muscle  of  the  pupil,  which  are  derived 
in  largest  part  from  the  sympathetic,  particularly  the  sympathetic  root 
of  the  ganglion,  and  from  the  anastomosis  of  the  sympathetic  with  the 
trigeminus.     The    first    division    itself,    however,    also    contains    pupil- 
dilating  fibers,  passing  directly  from  the  medulla  oblongata  into  the 
first  branch. 

After  division  of  the  trigeminus  the  pupil  in  the  rabbit  and  the  frog, 
therefore,  contracts  after  a  brief  antecedent  period  of  dilatation ;  and  after 
destruction  of  the  superior  cervical  ganglion  of  the  sympathetic  the  power 
of  the  pupil  to  dilate  is  not  wholly  abolished.  The  contraction  that 
disappears  in  the  course  of  half  an  hour  in  the  rabbit  can  be  looked  upon 
as  caused  by  reflex  stimulation  of  the  oculomotor  fibers  of  the  sphincter, 
in  consequence  of  the  painful  irritation  attending  division  of  the  tri- 
geminus. 

Whether  dilator-branches  pass  in  man  through  the  sympathetic  root  of  the 
ciliary  ganglion  and  further  on  through  the  ciliary  nerves  has  not  been  demon- 
strated with  certainty.  In  the  dog  and  in  the  cat  at  least,  these  fibers  do  not 
pass  through  the  ciliary  ganglion,  but  directly  along  the  optic  nerve  to  the  eye, 
all  passing  through  the  Gasserian  ganglion,  the  first  division  and  finally  through 
the  long  ciliary  nerves.  The  center  for  the  motor  fibers  of  the  dilator  of  the  pupil 
is  described  on  p.  749. 

The  phenomena  brought  about  by  irritation  or  paralysis  of  the  cervical  sym- 
pathetic or  its  path  upward  to  the  eye  may  be  discussed  now.  Irritation  causes, 
in  addition  to  dilatation  of  the  pupil,  also  an  effect  upon  the  unstriated  muscle 
in  the  orbit  and  the  eyelids.  The  orbital  membrane,  which  separates  the  orbit 
from  the  temporal  fossa  in  animals,  contains  numerous  unstriated  muscle-fibers 
(orbital  muscle).  The  corresponding  membrane  of  the  spheno-maxillary  fis- 
sure in  man  is  also  provided  with  a  muscular  layer  i  mm.  thick,  generally  passing  in 
a  longitudinal  direction  through  the  fissure.  Further,  both  eyelids  contain  un- 
striated muscle-fibers,  which  cause  narrowing  of  the  palpebral  fissure.  In  the 
upper  lid  they  continue  as  a  prolongation  of  the  elevator  of  the  upper  lid,  in  the 
lower  they  lie  just  beneath  the  conjunctiva.  Also  the  capsule  of  Tenon  contains 
unstriated  muscle-fibers.  All  of  these  muscles  are  innervated  by  the  sympathetic 
(the  orbital  muscle  in  part  from  the  spheno-palatine  ganglion),  as  is  also  the  re- 
tractor of  the  third  eyelid  at  the  inner  canthus  of  the  eye  in  some  animals.  Irritation 
of  the  sympathetic  therefore  causes  dilatation  of  the  pupil,  enlargement  of  the 
palpebral  fissure,  and  protrusion  of  the  eyeball.  This  irritation  may  also  be  in- 
duced reflexly  by  intense  stimulation  of  sensory  nerves.  Also  active  stimulation  of 
the  nerves  of  the  sexual  organs  gives  rise  to  the  signs 'mentioned  in  the  eye  in 
moderate  degree  as  an  accompanying  manifestation.  Perhaps  the  dilatation  of 
the  pupils  in  small  children  in  connection  with  the  presence  of  intestinal  irritation 
from  worms  also  belongs  in  this  category.  Also  irritation  of  the  spinal  cord 
(sympathetic  origin)  in  cases  of  tetanus  causes  dilatation  of  the  pupils.  Division 
of  the  sympathetic  causes  narrowing  of  the  palpebral  fissure  and  permits  retraction 
of  the  eyeball  (and  projection  of  the  relaxed  third  eyelid  in  animals) .  The  division 
causes  in  dogs  internal  strabismus  because  the  external  rectus  muscle  receives 
in  part  motor  fibers  from  the  sympathetic.  The  origin  of  these  fibers  from  the 
cilio-spinal  region  is  described  on  p.  734. 

5.  It  is  as  yet  undetermined  whether  trophic  fibers  also  arise  from 
the  trigeminus  through  the  ciliary  nerves.     If  the  trigeminus  be  divided 
in  the  cranial  cavity,  there  result  in  the   course  of  from  six  to  eight 
days  inflammation,  necrosis  of  the  cornea,  and  finally  destruction  of  the 
eveball. 


686  TRIGEMINAL    NERVE. 

The  results  described  take  place,  however,  only  when  the  nerve  is  divided  in 
the  Gasserian  ganglion  or  peripherally  (but  not  centrally)  from  it.  The  cause  of 
the  nutritive  disturbances  is  dependent  upon  the  ganglion-cells.  In  an  estimation 
of  the  views  as  to  the  trophic  libers  the  following  points  must  be  taken  into  con- 
sideration: (i)  Division  of  the  trigeminus  renders  the  entire  eye  anesthetic.  The 
animal,  therefore,  is  not  conscious  of  direct  injury  and  makes  no  effort  to  escape 
it.  Also,  adherent  dust  and  mucus  are  no  longer  removed  reflexly  by  closure  of 
the  eyelids.  In  general,  in  consequence  of  absence  of  the  reflex,  the  palpebral 
fissure  is  wider  and  the  eye  is  thus  exposed  to  many  injurious  influences  and  to 
desiccation.  Reflex  secretion  of  tears  also  is  wanting.  When  Snellen  attached  in 
front  of  the  eye  the  sensitive  auricle  of  the  rabbit,  through  whose  sensibility  it 
avoided  injury,  the  inflammation  of  the  eye  occurred  much  later.  On  placing  a 
perfectly  secure  protecting  capsule  in  front  of  the  eye  the  inflammation  was  entirely 
prevented.  The  same  result  was  observed  when  Gudden  sutured  the  freshened 
margins  of  the  lids  in  rabbits  anql  permitted  them  to  grow  together.  The  cornea 
can  be  kept  intact  also  by  scrupulous  cleanliness.  There  can,  therefore,  be  no 
doubt  that  the  loss  of  the  sensibility  of  the  eye  favors  the  occurrence  of  inflamma- 
tion. Efforts  were  made,  further,  to  discover  the  trophic  nerves  and  to  divide 
them  separately.  As  Meissner,  Biittner,  and  Schiff  observed  the  eye  to  become 
the  seat  of  inflammation  after  dividing  only  the  trophic  (innermost)  fibers  of  the 
trigeminus,  the  eye  retaining  its  sensibility,  the  existence  of  trophic  fibers  might 
be  considered  as  demonstrated;  but  Cohnheim  and  Senftleben  contradict  these 
facts.  Conversely,  the  sensibility  of  the  eye  may  be  lost  in  consequence  of  partial 
injury  of  the  nerve,  and  the  eyeball  does  not  become  inflamed.  Ranvier,  wTho 
denied  the  existence  of  trophic  nerves,  incised  the  cornea  in  a  circular  manner 
through  its  superficial  layers,  at  the  same  time  dividing  the  nerves,  all  of  which 
are  present  in  this  situation.  There  resulted  anesthesia,  but  never  keratitis. 
Further,  in  men  and  animals  in  which  inability  to  close  the  eyes  exists,  redness 
with  flow  of  tears  or  slight  desiccation  and  cloudiness  of  the  surface  of  the  eyeball 
(xerosis)  set  in,  but  never  such  a  destructive  inflammation  as  that  described. 

(2)  The  following  factors,  to  which  hitherto  little  reference  has  been  made, 
should  further  be  taken  into  consideration :   Division  of  the  trigeminus  paralyzes  the 
vasomotors  in  the  interior  of  the  eyeball,  and  in  consequence  derangements  in  the 
circulation  of  the  blood  must  take  place.      According  to  Jessner  and  Griinhagen 
the  trigeminus  also  transmits  vasodilator  fibers  to  the  eye,  irritation  of  which 
causes  increased  flow  of  blood  to  the  eye,  with  consecutive  elimination  of  fibrin- 
factors  and  increase  in  the  amount  of  albumin  in  the  aqueous  humor. 

(3)  After  division  of  the  nerve  the  tension  of  the  eyeball  is  diminished.      Con- 
versely, irritation  is  followed  by  considerable  increase  in  the  intraocular  pressure. 
The  reduction  in  intraocular  pressure  must,  naturally,  alter  the  normal  relation 
between  the  fulness  of  the  blood-vessels  and  the  lymphatic  channels  and  the  move- 
ment of  the  fluids  within  them,  upon  which  the  normal  nutrition  in  large  measure 
depends. 

(4)  W.  Kiihne    observed   movement    of   the  corneal  corpuscles   on   irritation 
of  the  corneal  nerves.       It  does  not  appear  impossible  that    the    movement    of 
these  corpuscles  has    an    influence  upon    the    normal    movement  of   the  fluid    in 
the  canalicular  system  of  the  cornea.      If,  however,  it  were  dependent  upon  the 
nervous  system  destruction  of  the  latter  would  be  followed  also  by  nutritive  dis- 
turbances.    As  a  matter  of  fact,  Gaule  observed  after  division  of  the  nerve  that 
the  corneal  corpuscles  were  partly  shrunken,  partly  enlarged,  and  that  the  epithe- 
lium of  the  cornea  was  partly  necrotic,  partly  in  a  condition  of  proliferation. 

Pathological. — In  man,  inflammation  of  the  conjunctiva,  ulceration  and  per- 
foration of  the  cornea  and  finally  panophthalmitis.  which  is  designated  neuro- 
paralytic  ophthalmia,  have  been  observed  after  trigeminal  anesthesia  and  less  com- 
monly in  association  with  profound  irritative  states  of  the  fifth  nerve.  Samuel 
was  able  to  induce  the  same  effects  in  animals  by  electrical  stimulation  of  the  Gas- 
serian ganglion. 

The  affections  of  the  eye  due  to  disorders  of  the  vasomotor  nerves  are 
entirely  different  than  those  described,  as  they  never  give  rise  to  degenerative 
processes,  as  does  division  of  the  trigeminus.  In  this  category  belongs  intermit- 
tent ophthalmia,  a  condition  of  unilateral,  intermittent  marked  injection  of  the 
ocular  vessels,  due  to  malarial  influences,  associated  with  flow  of  tears,  photo- 
phobia, often  also  with  iritis  and  suppuration  in  the  chambers  of  the  eye,  which 
was  first  considered  by  Eulenburg  and  Landois  as  a  vasoneurotic  disorder  of 
the  ocular  vessels.  Pathological  observations,  as  well  as  experiments  on  animals, 


TRIGEMINAL    NERVE.  687 

have  demonstrated  that  an  intimate  physiological  connection  exists  between '  the 
vascular  distribution  in  the  two  eyes,  so  that  affections  in  the  vascular  distribu- 
tion of  one  eye  readily  excite  analogous  affections  in  the  other  eye.  This  fact 
explains  why  inflammatory  processes  chiefly  in  the  interior  of  one  eyeball  give 
rise  to  so-called  sympathetic  ophthalmia  in  the  other  eyeball.  Thus,  irritants 
affecting  the  ciliary  nerves  or  the  fifth  nerve  upon  one  side  cause  at  the  same 
time  dilatation  of  the  vessels  in  the  other  eye,  together  with  its  sequelae.  The 
pathological  excessive  tension  of  the  eye,  with  its  sequelae  (simple  glaucoma),  is 
worthy  of  mention  and  has  been  attributed  by  Bonders  to  irritation  of  the  trigem- 
inus.  Unilateral  flow  of  tears  has  been  observed  repeatedly  in  conjunction  with 
irritative  states  of  the  first  division  of  the  trigeminus  and  unilateral  suppression 
of  tears,  but  rarely  in  association  with  paralytic  states. 

The  second,  or  superior  maxillary,  division  (Fig.  243,  e)  gives  off: 

1.  The  slender  recurrent  nerve,  a  sensory  branch  to  the  dura  mater, 
which  in  the  distribution  of  the  middle  meningeal  artery  accompanies 
the  vasomotor  nerves  of  this  vessel  derived  from  the  superior  cervical 
ganglion  of  the  sympathetic.     Irritation  of  this  nerve  causes  also  reflex 
closure  of  the  lids  in  the  frog. 

2.  The  subcutaneus  mal<z,  or  orbital  nerve  (c),  supplies  with  its  two 
branches,  the  temporal  and  the  orbital,  the  external  canthus  of  the  eye 
and  the  adjacent  cutaneous  area  of  the  temple  and  the  cheek,  with  sensory 
fibers.     Some  of  the  filaments  of  the  nerve  are  said  to  be  true  secretory 
nerves  for  the  tears. 

3.  The  posterior  and  median  superior  alveolar  nerves,  and  with  them 
the  anterior  from  the  infraorbital  nerve,  give  off  sensory  fibers  to  the 
teeth  of  the  upper  jaw,  the  gums,  the  periosteum  and  the  maxillary 
ant  rum.    The  vasomotor  nerves  for  all  of  these  parts  are  supplied  by  the 
superior  cervical  ganglion  of  the  sympathetic. 

4.  The  infraorbital  nerve  (R),  which,  after  its  exit  from  the  infraorbi- 
tal foramen,  distributes  sensory  fibers  to  the  lower  eyelid,  the  bridge  and 
alae  of  the  nose  and  the  upper  lip  to  the  angle  of  the  mouth.     The  ac- 
companying arteries  receive  vasomotor  fibers  from  the  superior  cervical 
ganglion  of  the  sympathetic.     The  sweat-fibers  in  swine  are  described 
on  p.  537. 

The  sphenopalatine,  or  basal  ganglion  (n),  is  connected  with  the  sec- 
ond branch  of  the  trigeminus.  It  contains  cells  arranged  like  those  of  the 
sympathetic  ganglia.  To  it  pass,  first,  with  one  or  several  filaments, 
short  sensory  root -fibers  from  the  second  branch  itself,  which  are  desig- 
nated sphenopalatine  nerves.  Motor  fibers  pass  from  behind  into  the 
ganglion  through  the  greater  superficial  petrosal  nerve  from  the  facial 
(j)  and  finally  gray  vasomotor  fibers  from  the  sympathetic  plexus  of  the 
carotid  (greater  deep  petrosal  nerve).  The  motor  and  vasomotor  fibers 
form  the  Vidian  nerve,  which  passes  through  the  Vidian  canal  to  the 
ganglion.  The  ganglion  gives  off  the  following  fibers: 

i.  The  sensory  fibers  (N)  supply  the  roof,  the  lateral  walls,  and  the 
septum  of  the  cavity  of  the  nose  (posterior  superior  nasal  nerves).  The 
nasopalatine  nerve  passes  through  the  incisor  canal  with  its  terminal 
filaments  to  the  hard  palate  behind  the  incisor  teeth.  The  sensory  pos- 
terior inferior  nasal  nerves  for  the  lower  and  middle  turbinates  and  the 
two  lower  nasal  passages  are  derived  from  the  anterior  palatine  nerve  of 
the  ganglion,  which  descends  in  the  pterygopalatine  canal.  Finally,  the 
sensory  branches  for  the  hard  (p),  and  the  soft  palate  (pt)  and  the  tonsil 
are  derived  from  the  descending  posterior  palatine  nerve.  Irritation  of 
any  of  the  sensory  fibers  of  the  nose  causes  reflex  sneezing,  which  is 


688  TR1GEMINAL    NERVE. 

always  preceded  by  a  sense  of  tickling  in  the  nose.  The  same  result  may 
be  brought  about,  in  addition  to  direct  irritation,  also  by  dilatation  of  the 
vessels  of  the  nose.  The  latter  occurs  readily  from  the  action  of  cold 
upon  the  external  integument.  The  vascular  dilatation  is  later  on  as- 
sociated with  increased  secretion  from  the  nasal  mucous  membrane. 
Irritation  of  the  nasal  nerve  excites  also  flow  of  tears  reflexly.  Irrita- 
tion of  the  nasal  branches  causes  finally  also  expiratory  cessation  of  the 
respiratory  movements.  2.  The  vasodilators  of  the  nose  pass  with  the 
sensory  fibers  of  the  ganglion;  they  are  derived  principally  from  the 
sympathetic  root.  3.  The  motor  branches  descend,  through  the  pos- 
terior palatine  nerve  in  the  pterygopalatine  canal  and  give  off  motor 
fibers  (h)  to  the  elevator  of  the  veil  of  the  palate  and  the  azygos  uvulae. 
The  muscle-sense  fibers  are  supplied  by  the  trigeminus.  Spasmodic  con- 
ditions in  these  muscles  are  said  to  cause  paroxysmally  crackling  sounds 
in  the  ear.  4.  Filaments  representing  gustatory  fibers  pass  also  from  the 
intermediate  portion  of  the  facial  nerve  to  the  gums.  5.  The  vaso- 
motors  of  this  entire  area  are  derived  from  the  sympathetic  root,  there- 
fore from  the  cervical  sympathetic.  6.  The  trigeminus-root  furnishes 
the  secretory  nerves  for  the  mucous  glands  of  the  nasal  mucous  mem- 
brane. Irritation  excites  secretion,  while  resection  of  the  trigeminus 
diminishes  secretion  and  causes  at  the  same  time  atrophic  degeneration 
of  the  mucous  membrane.  Accordingly  trophic  functions  for  the  mucosa 
have  also  been  attributed  to  the  trigeminus. 

Feeble  electric  irritation  of  the  exposed  ganglion  causes  abundant  secretion 
of  mucus  and  elevation  of  temperature  in  the  nose,  together  with  dilatation  of 
the  vessels.  After  division  of  the  trigeminus,  redness  of  the  nasal  mucous  mem- 
brane on  the  same  side  occurs.  This  is  probably  due  to  the  fact  that  penetrating 
dust  or  secreted  nasal  mucus  is  not  removed  from  the  nose  through  reflex  influences, 
but  remains  and  causes  irritation  and  inflammation. 

The  third,  or  inferior  maxillary,  division  (g)  unites  all  of  the  motor 
filaments  of  the  fifth  nerve,  with  a  number  that  are  sensory,  into  a 
plexus,  from  which  are  given  off: 

1 .  The  recurrent  nerve,  which  arises  from  the  sensory  root  and  enters 
the  skull  through  the  spinous  foramen  and  further  on  with  the  recurrent 
nerve  of  the  second  division  supplies  the  dura  with  sensory  filaments. 
From  it  pass  also  filaments  through  the  petrososquamous  fissure  to  the 
mucous  membrane  of  the  mastoid  cells. 

2.  Motor  branches  for  the  muscles  of   mastication;    the  masseteric 
nerve,  the  two  deep  temporal  nerves,  the  external  and  internal  ptery- 
goid  nerves.     The  muscle-sense  fibers  are  probably  derived  from  the 
sensory  fibers. 

3.  The  buccinator  is  a  sensory  nerve  for  the  mucous  membrane  of 
the  cheek  and  the  angle  of  the  mouth  as  far  as  the  lips. 

According  to  Jolyet  and  Laffont  it  contains  besides,  probably  in  the  last 
instance  derived  from  the  sympathetic,  vasomotors  for  the  mucous  membrane  of 
the  cheek  and  the  lower  lip,  and  their  mucous  glands. 

As  after  division  of  the  trigeminus  this  region  of  the  mucous  membrane 
becomes  ulcerated,  it  has  been  thought  that  the  buccinator  contains  also  trophic 
fibers.  Rollet,  however,  called  attention  to  the  fact  that  section  of  the  third 
division  causes  paralysis  of  the  muscles  of  mastication  on  the  same  side,  and  as 
a  result  the  teeth  do  not  come  in  vertical  apposition,  but  are  pushed  against  the 
cheek.  In  addition,  in  consequence  of  the  anesthesia  in  the  mouth,  remnants  of 
food,  often  insufficiently  comminuted,  remain  in  contact  with  the  cheeks,  and 
irritate  the  mucous  membrane  both  mechanically  and,  as  a  result  of  decomposi- 


TRIGEMINAL    NERVE.  689 

tion,  also  chemically.  Subsequently,  by  reason  of  the  abnormal  attrition  of  the 
teeth,  ulcers  form  also  on  the  healthy  side.  The  assumption  of  trophic  fibers  is, 
therefore,  not  justified. 

4.  The  lingual  nerve  (k)  receives  at  an  acute  angle  the  chorda  tym- 
pani  (i  i),  a  branch  of  the  facial  nerve,  after  its  exit  from  the  tympanic 
cavity.     The  lingual  contains  no  motor  fibers ;  it  is  the  sensory  and  tactile 
nerve  of  the  tongue,  the  anterior  palatine  arch,  the  tonsil,  and  the  floor 
of  the  mouth.     Irritation  of  this  nerve,  as  well  as  of  all  of  the  remaining 
sensory  fibers  of  the  cavity  of  the  mouth,  excites  reflex  secretion  of  saliva. 
In  addition,  the  lingual  is  the  gustatory  nerve  for  the  tip  and  margins 
of  the  tongue  (which  are  not  supplied  by  the  glossopharyngeal  nerve), 
for  after  division  of  the  lingual  nerve  in  man,  Busch,  Inzani,  Lussana,  and 
others  observed  abolition  of  tactile  sensation  upon  the  entire  half  of  the 
tongue  and  of  the  sense  of  taste  upon  the  anterior  portion  of  the  tongue . 
These  fibers,  however,  are,  as  a  rule,  derived  from  the  chorda  tympana, 
as  has  been  pointed  out  in  the  description  of  the  facial  nerve. 

According  to  Schiff,  the  lingual  nerve  itself  contains  gustatory  fibers,  and 
this  view  is  supported  by  cases  of  Erb,  Senator,  Ziehl,  Schreier,  and  others.  These 
are  probably  exceptional  cases.  A.  Schmidt  believes  that  the  gustatory  fibers 
reach  the  brain  through  the  trunk  of  the  fifth  nerve  in  the  following  manner 
(Fig.  243):  chorda,  facial  trunk,  connection  with  the  lesser  superficial  petrosal 
nerve  (B),  otic  ganglion,  third  division,  trunk  of  the  fifth  nerve.  In  the  interior 
of  the  tongue  the  lingual  filaments  are  supplied  with  small  ganglia.  The  lingual 
appears  to  receive  vasodilators  for  the  tongue  and  the  gums  from  the  chorda. 
After  division  of  the  trigeminus  animals  often  bite  the  tongue,  whose  position 
and  movement  in  the  mouth  they  are  unable  to  feel,  and  in  consequence  injuries 
and  inflammations  often  result. 

5.  The  inferior  alveolar  nerve  is  the  tactile  nerve  of  the  tongue  and 
the  gums;  the  vasomotors  pass  through  the  superior  cervical  ganglion. 
Before  entering  the  alveolar  canal,  it  gives  off  the  mylohyoid  nerve, 
which  supplies  the  motor  fibers  for  the  mylohyoid  muscle  and  the  ante- 
rior belly  of  the  digastric,  and  likewise  filaments  for  the   triangularis 
menti  and  the  platysma;  muscle-sense  fibers  also  probably  are  contained 
in  these  filaments.     The  mental  nerve,  which  makes  its  exit  from  the 
mental  foramen,  is  only  the  tactile  branch  for  the  chin,  the  lower  lip, 
and  the  skin  at  the  margin  of  the  jaw. 

6.  The   auriculotemporal   nerve  (A)  sends  sensory  fibers  to  the  an- 
terior wall  of  the  external  auditory  canal,  the  tympanic  membrane,  the 
anterior  portion  of  the  ear,  the  adjacent  temporal  region,  and   to  the 
inferior  maxillary  articulation. 

In  Fig.  244  the  area  of  distribution  of  the  trigeminal  branches  to  the  head, 
as  well  as  that  of  the  cervical  nerves,  is  indicated,  and  from  this  the  nerves  in- 
volved can  be  determined  in  the  presence  of  morbid  affections  (neuralgia,  anes- 
thesia) involving  the  parts  mentioned. 

The  otic  ganglion  is  situated  beneath  the  oval  foramen  upon  the 
inner  aspect  of  the  third  division.  There  enter  into  it  as  roots:  i. 
Motor  filaments  from  the  third  division  itself.  2.  Vasomotor  fibers 
from  the  plexus  of  the  middle  meningeal  artery  (therefore  passing 
through  the  superior  cervical  ganglion  of  the  sympathetic).  3.  From 
the  tympanic  branch  of  the  glossopharyngeal  nerve  filaments  pass  to  the 
tympanic  plexus  (Fig.  243,  /),  thence  through  the  petrosal  canal  in  the 
lesser  superficial  petrosal  nerve  into  the  cranial  cavity,  then  through  the 
sphenoidal  fissure  into  the  otic  ganglion  (m).  Through  the  chorda 
tympani  the  facial  nerve  is  in  constant  connection  with  the  ganglion, 
just  below  which  it  passes  (Fig.  243,  m,  i). 

44 


690 


TRIGEMINAL    NERVE. 


FIG.  243. — Semidiagrammatic  Representation  of  the  Ocular  Nerves,  the  Connections  of  the  Trigeminus  and  Its 
Ganglia  and  Those  of  the  Facial  and  Glossopharyngeal  Nerves:  3,  branch  to  the  inferior  oblique  muscle 
(Oi)  from  the  oculomotor  nerve,  with  the  thick,  short  root  to  the  ciliary  ganglion  (c);  t,  ciliary  nerves;  1,  long 
root  to  the  ganglion  from  the  nasociliary  nerve  (nc);  s,  sympathetic  root  from  the  plexus  of  the  sympathetic 
(Sy)  surrounding  the  internal  carotid  artery  (G);  d,  first  division  of  the  trigeminus  (5),  with  the  nasociliary 
nerve  (nc)  and  the  terminal  branches  of  the  lacrimal  (a),  supraorbital  (b)  and  frontal  (f);  e,  second  division 
of  the  trigeminus;  R,  infraorbital  nerve;  n,  sphenopalatine  ganglion,  with  the  roots  (j)  from  the  facial,  and 
(v)  from  the  sympathetic;  N,  the  nasal  branches  p  p,  the  palatal  branches  of  the  ganglia;  g,  third  division 
of  the  trigeminus,  k  lingual  nerve;  i  i,  chorda  tympani;  m,  otic  ganglion  wth  the  moots  from  the  tympanic 
plexus,  the  carotid  plexus,  and  from  the  third  division,  and  with  its  branches  to  the  auriculotemporal  (A) 
and  the  chorda  (i  i);  L,  submaxillary  ganglion,  with  the  roots  from  the  tympanicplingual  and  the  sympathetic 
plexus  of  the  external  maxillary  artery  (q).  7,  Facial  nerve — j,  its  greater  superficial  petrosal  nerve;  a,  genicu- 
late  ganglion;  /3,  branch  to  the  tympanic  plexus;  y.  stapedius  branch;  8,  anastomoses  with  the  auricular 
branch  of  the  vagus,  s,  Stylomastoid  foramen.  9,  Glossopharyngeal  nerve— -A.,  its  tympanic  branch;  TT  and 
e,  connections  with  the  facial;  U,  termination  of  the  gustatory  fibers  of  the  ninth  nerve  in  the  circumvallate 
papillae.  Sy,  Sympathetic,  with  (Cg  S)  the  superior  cervical  ganglion.  I,  II,  III,  IV,  the  four  upper  cervical 
nerves.  P,  Parotid  gland;  M,  submaxillary  gland. 


TRIGEMINAL    NERVE. 


691 


The  otic  ganglion  gives  off  (as  a  continuation  of  i):  i.  Motor 
branches  for  the  tensor  tympani  muscle  and  the  tensor  of  the  veil  of  the 
palate  (with  which  muscle-sense  fibers  probably  are  also  admixed).  2. 
One  or  several  connecting  branches  of  the  ganglion  to  the  auriculotem- 
poral  nerve  are  probably  conveyed  through  the  root -fibers  (2  and  3) 
from  the  sympathetic  and  the  glossopharyngeal  nerve,  which  the 
nerve  in  question  (Fig.  243,  A)  gives  off  to  the  parotid  gland  (P)  in  its 
passage  through  it.  These  branches  control  the  salivary  secretion  of  the 
parotid,  as  has  been  pointed  out  on  p.  259. 


Mure,  temporal!*. 


Muse,  masseter 


N.  hypoglossus. 


Platysma  myoide  . 
Muse,  sternohyoideus. 

Muse,  steruothyi  eoide 

Muse,  oniohyoideus. 


N'n.  thoraciei  anterlores. 


Mnsc.  gplenius. 


Muse,  steruocleidomastoideus. 

accessorius 
Muse,  levator  anguli  scapulae. 

Muse,  cucullaris  or  trapeziua. 
N.  dorsalis  scapulae. 


K.  axillaris. 


N.  thoracic^  Icngn^ 


N.  phrenicus. 


FIG.  244.— Distribution  of  the  Sensory  Nerves  of  the  Head,  together  with  the  Situation  of  the  Motor  Points  on 

the  neck. 

SO,  Distribution  of  the  supraorbital  nerve;  ST,  supratrochlear  nerve;  IT,  infratrochlear  nerve;  L,  lacrimal  nerve; 
N,  ethmoid  nerve;  IO,  infraorbital  nerve;  B,  buccinator  nerve;  SM,  subcutaneous  malar  nerve;  AT, 
auriculotemporal  nerve;  AM,  great  auricular  nerve;  OMj,  greater  occipital  nerve;  OMi,  lesser  occipital  nerve; 
C-A,  third  cervical  nerve;  CS,  cutaneous  branches  of  the  cervical  nerves;  CW,  situation  of  the  central  convo- 
lutions of  the  cerebral  hemisphere;  SC,  situation  of  the  speech-center  (third  frontal  convolution). 


Division  of  the  trigeminus  causes  inflammatory  changes  in  the  mucous  mem- 
brane of  the  tympanum  in  all  possible  degrees  (in  the  rabbit).  Lesions  of  the 
sympathetic  or  the  glossopharyngeal  are  ineffective. 

The  submaxillary  or  lingual  ganglion  (Fig.  243,  L)  lies  upon  the  con- 
vex arch  of  the  united  tympanicolingual  nerve  and  the  excretory  duct 
of  the  submaxillary  gland  (M),  and  receives  as  root -fibers:  i.  Branches 
of  the  chorda  tympani  (i  i).  These  are  related  to  the  salivary  secretion 


6g2  TRIGEMINAL    NERVE. 

of  the  submaxillary  and  sublingual  glands,  inasmuch  as  they  contain  se- 
cretory nerves,  yielding  a  limpid  saliva,  and  vasodilators.  In  addition, 
they  give  branches  to  the  unstriated  muscular  fibers  of  Wharton's  duct. 
Not  all  of  the  fibers  of  the  chorda,  however,  pass  to  the  gland;  some  are 
distributed  to  the  tongue.  2.  The  sympathetic  root  of  the  ganglion 
arises  from  the  plexus  of  the  submental  branch  of  the  external  maxillary 
artery  (q),  thus  from  the  carotid  plexus  of  the  sympathetic.  It  passes 
to  the  glands  and  is  the  secretory  nerve  yielding  concentrated  saliva. 
It,  further,  transmits  the  vasoconstrictors  to  the  vessels  of  the  glands. 
3.  Sensory  root -fibers  derived  from  the  lingual  nerve  in  part  send  fila- 
ments to  the  glands  and  their  excretory  ducts,  and  in  part,  again  entering 
the  tympanicolingual  from  the  ganglion,  pass  peripherally  to  the  tongue. 

Pathological. — Spasm  of  the  muscles  of  mastication  occurs  as  a  pathological 
manifestation  in  the  distribution  of  the  third  division.  It  is,  as  a  rule,  bilateral, 
and  it  may  be  either  clonic  (chattering  of  the  teeth)  or  tonic  (trismus).  The 
spasm  is  generally  one  of  the  manifestations  of  widespread  convulsions;  rarely  it 
is  isolated  as  a  symptom  of  cerebral  focal  disease  of  the  medulla  oblongata,  the  pons, 
or  the  cortex  in  the  situation  of  the  motor  center  of  the  trigeminus.  The  spasm 
may,  naturally,  be  also  reflex  in  origin,  principally  in  consequence  of  irritation 
of  sensory  nerves  of  the  head. 

Degeneration  of  the  motor  nucleus  or  affections  of  the  root  in  the  skull  cause 
paralysis  of  the  muscles  of  mastication,  which  is  rarely  bilateral.  Paralysis  of  the 
tensor  tympani  muscle  is  said  to  have  caused  impairment  of  hearing  or  roaring 
in  the  ears.  In  this  connection,  as  well  as  with  respect  to  paralysis  of  the  tensor 
of  the  veil  of  the  palate,  further  observations  are  desirable. 

With  reference  to  all  of  the  branches  of  the  trigeminus,  mention  must  be 
made  first  of  neuralgia,  which  is  attended  paroxysmally  with  intense  radiating 
pain  in  the  peripheral  distribution  of  the  nerve.  Generally  unilateral,  the  dis- 
order usually  involves  only  a  few  branches  or  even  fibers.  Points  of  radiation 
for  the  pain  are  often  constituted  by  the  bony  canals  from  which  the  branches 
make  their  exit.  Rarely  the  ear,  thie  dura  mater,  and  the  tongue  are  involved. 
Occasionally  twitching  occurs  in  the  corresponding  group  of  facial  muscles  in 
conjunction  with  the  attack,  either  being  excited  reflexly  or  developing  directly 
as  a  result  of  peripheral  irritation  of  the  facial  fibers  connected  with  the  terminal 
fibers  of  the  trigeminus.  The  reflex  contractions  if  marked  may  extend  even  to 
the  muscles  of  the  arms  and  the  trunk. 

Marked  redness  of  the  affected  area  occurs  as  an  accompanying  manifestation 
of  pain  in  the  face,  and  in  some  cases  increased  or  diminished  secretion  from  the 
conjunctiva  and  the  nasal  and  buccal  mucous  membrane.  The  condition  is  cer- 
tainly a  reflex  phenomenon  of  sympathetic  origin.  The  derangement  in  cerebral 
activity  often  observed  in  consequence  of  the  altered  distribution  of  blood  is  proba- 
bly due  to  reflex  vasomotor  stimulation.  C.  Ludwig  and  Dittmar  found  that 
irritation  of  sensory  nerves  causes  contraction  of  the  arterial  blood-stream  and 
increased  pressure  in  the  cerebral  vessels.  Thus,  melancholia  and  hypochondriasis 
are  often  found  in  marked  degree.  Landois  had  cognizance  of  a  case  in  which 
during  the  severe  attacks,  involving  the  third  division,  marked  visual  hallucina- 
tions appeared.  Disorders  of  the  fifth  nerve  are  capable,  in  general,  of  causing 
varied  reflex  affections. 

The  trophic  disorders  that  occur  in  association  with  affections  of  the  trigeminus 
are  of  great  interest.  Among  these  are  brittleness  and  splitting  of  the  hairs, 
graying  and  falling  out  of  the  hair,  circumscribed  inflammation  of  the  skin  and 
vesicular  eruptions  on  the  face  (zoster)  and  also  the  cornea  (neuralgic  herpes  of 
the  cornea). 

Finally,  there  should  be  mentioned  progressive  facial  atrophy,  which  is  almost 
always  unilateral,  but  may  also  be  bilateral.  It  is  probably  due  to  derangement 
in  the  trophic  activity  (of  the  descending  root?)  of  the  trigeminus,  although  the 
vasomotor  activity  of  the  sympathetic  may  also  be  invoked  reflexly.  Landois 
found  on  sphygmographic  examination  of  the  famous  case  of  Romberg  (in  a  man 
named  Schwahn)  that  the  pulse-tracing  from  the  carotid  on  the  atrophic  side  was 
distinctly  smaller  than  that  from  the  vessel  on  the  unaffected  side.  Intracranial 
division  of  the  sensory  root  of  the  fifth  nerve  causes  in  dogs  a  similar  trophic  dis- 
turbance. The  antithesis  of  this  obscure  disorder,  which  is  dependent  upon  the 


ABDUCENS    NERVE.  693 

trophic  relations  of  the  nerves  to  the  tissues,  is  the  rare  condition  of  unilateral 
hypertrophy  of  the  face,  which  bears  some  resemblance  to  the  analogous  manifesta- 
tions of  so-called  partial  giant-growth  (acromegaly) . 

Reference  should  be  made  here  also  to  the  extremely  remarkable  observation 
of  Urbantschitsch,  who  found  that  irritation  of  branches  of  the  trigeminus,  and 
principally  those  that  pass  to  the  ear,  causes  increase  in  the  light-sense  of  the 
individual  in  question.  Blowing  on  the  cheek  or  the  nasal  mucous  membrane, 
electrical  irritation,  the  snuffing  of  tobacco,  the  smelling  of  strong  odors  may  tem- 
porarily increase  the  sensibility  to  light.  Also  the  gustatory  and  the  olfactory 
sense,  as  well  as  the  sensibility  of  certain  cutaneous  areas,  may  be  thus  increased 
reflexly  through  slight  irritation  of  the  trigeminus.  In  the  presence  of  severe 
affections  of  the  ear,  in  consequence  of  which  fibers  of  the  trigeminus  may  be 
seriously  involved,  the  sense-functions  mentioned  may  be  impaired.  Local  im- 
provement in  the  aural  disorder  is  then  attended  with  an  increase  in  the  activity 
of  the  special  senses  mentioned. 

After  extirpation  of  the  Gasserian  ganglion,  together  with  its  roots,  in  man 
the  entire  distribution  of  the  trigeminus  has  been  found  completely  and  irremedi- 
ably anesthetic.  All  parts  remained  intact  so  far  as  their  trophic  state  was  con- 
cerned, but  the  anesthetic  eye  was  less  resistant  to  influences  exciting  inflamma- 
tion, and  Keen  and  Laguaite  observed  keratitis  after  extirpation  of  the  ganglion, 
and  Seheier  ulceration  of  the  cornea  and  the  mucous  membrane  of  the  mouth 
and  the  nose  after  injury  to  the  nerve.  The  secretion  of  tears  was  in  some  in- 
stances diminished,  in  others  abolished.  The  skin  of  the  cheek  and  of  the  eyebrow 
exhibited  slight  trophic  change.  Immediately  after  the  operation  the  skin  ex- 
hibited signs  of  abnormal  distribution  of  the  blood  and  later  a  sense  of  heat  on 
the  forehead  and  in  the  eye.  The  sense  of  taste  was  impaired  in  the  distribution 
of  the  lingual  nerve  and  likewise  that  of  smell  in  the  corresponding  nasal  cavity. 
The  muscles  of  mastication  are  paralyzed,  and  the  delicacy  of  movement  in  the 
muscles  of  the  face  was  impaired  in  consequence  of  absence  of  the  muscle-sense. 
In  the  course  of  time  the  anesthetic  area  becomes  smaller,  as  branches  from  adja- 
cent nerves  grow  into  it. 

VI.    ABDUCENS  NERVE. 

The  abducens  nerve  arises  from  the  abducens  nucleus  with  neurites  from 
large  cells  that  correspond  to  those  of  the  anterior  horns  of  the  spinal  cord.  The 
nucleus  lies  below  the  eminentia  teres  on  the  floor  of  the  fourth  ventricle  (Fig.  241) 
and  below  the  knee-shaped  flexure  of  the  facial  nerve.  Probably  some  oculo- 
motor fibers  arise  from  the  abducens  nucleus,  and  from  the  left  those  fibers  of 
the  right  oculomotor  that  rotate  the  right  eye  inward  (this  explains  the  synergistic 
action  of  the  two  eyes  in  lateral  movement).  Physiologically,  connecting  fibers 
should  pass  between  the  nucleus  of  origin  and  the  contralateral  cortical  center  in 
the  cerebrum  for  the  ocular  movements.  The  nerve  makes  its  appearance  at  the 
posterior  margin  of  the  pons  (Fig.  242). 

The  abducens  is  the  voluntary  nerve  of  the  external  rectus  muscle, 
although  in  the  coordinated  movements  of  the  eye  it  is  stimulated  in- 
voluntarily. 

Branches  of  considerable  size  pass  from  the  sympathetic  in  the  cavernous 
sinus  to  the  abducens  nerve  (Fig.  243,  6);  smaller  branches  from  the  trigeminus, 
whose  significance  is  the  same  as  that  of  analogous  branches  of  the  trochlear  and 
oculomotor. 

Pathological. — Complete  paralysis  causes  internal  strabismus,  and  as  a  result 
diplopia.  In  dogs,  division  of  the  cervical  sympathetic  causes  slight  rotation 
of  the  eyeball  inward.  This  must  be  due  to  the  fact  that  the  abducens  receives 
motor  muscle-nerves  from  the  cervical  sympathetic.  Spasm  of  the  abducens 
causes  external  strabismus. 

With  reference  to  strabismus,  it  should  be  mentioned  that  it  may  be  caused, 
in  addition  to  irritation  or  paralysis  of  the  nerves,  also  by  primary  muscular 
affections,  such  as  congenital  shortness,  contractures,  injuries.  Finally,  strabis- 
mus occurs  in  connection  with  cloudiness  of  the  transparent  media  of  the  eye, 
the  individual  involuntarily  rotating  the  eye  so  that  the  visual  rays,  so  far  as 
possible,  pass  through  the  portions  of  the  media  that  are  still  clear.  Lesions  of 
the  retina  at  the  yellow  spot  give  rise  to  similar  results.  The  affected  eye,  further, 


694  FACIAL    NERVE. 

may  be  rotated  involuntarily,  in  order  that  it  may  not  interfere  with  the  vision 
of  the  unaffected  eye,  the  patient  thus  unconsciously  placing  himself  in  the  position 
of  a  person  with  but  one  eye. 

VII.    FACIAL  NERVE. 

The  facial  nerve  arises  with  centrifugal  fibers  from  the  ganglion-cells  of  two 
nuclei  on  the  floor  of  the  fourth  ventricle.  The  anterior,  smaller  nucleus,  which 
is  situated  immediately  behind  the  most  posterior  cells  of  the  oculomotor  nucleus, 
is  the  origin  for  the  muscular  nerves  of  the  eyelids  and  the  structures  about  the 
orbit.  The  posterior,  larger  nucleus  is  situated  in  the  most  ventral  portion  of 
the  tegmentum  to  the  inner  side  of  the  ascending  root  of  the  fifth  nerve.  The 
fibers  that  arise  here  surround  the  nucleus  of  the  abducens  and  contain  the  nerve 
for  the  muscles  of  the  mouth  and  of  the  remainder  of  the  face.  In  their  passage 
from  the  facial  center  in  the  cerebral  cortex  to  the  nuclei  the  fibers  for  the  mouth 
decussate,  while  the  fibers  for  the  eyes  in  part  do  not  decussate. 

The  nerve  makes  its  appearance  at  the  posterior  margin  of  the  pons  to  the 
inner  side  of  the  auditory  nerve.  Between  the  two  arises  the  thin  intermediate 
portion  of  Wrisberg,  which  sends  most  of  its  fibers  to  the  facial  nerve  and  the 
remainder  to  the  auditory.  The  filaments  of  origin  of  the  intermediate  portion 
arise  from  the  glossopharyngeal  nucleus.  The  gustatory  and  the  tactile  fibers 
possessed  by  the  chorda  tympani  appear  to  enter  the  facial  through  these  filaments. 
These  fibers  have  ganglion-cells  in  the  geniculate  ganglion.  The  intermediate  por- 
tion would  thus  be  a  separate  division  of  the  gustatory  nerve,  which  unites  with 
the  facial  and  passes  through  the  tongue  with  the  chorda.  With  the  auditory 
nerve  the  facial  first  enters  the  internal  auditory  canal  and  at  the  bottom  of  this, 
separated  from  the  former,  it  enters  the  facial  or  Fallopian  canal.  At  first  it  has  a 
transverse  direction  as  far  as  the  hiatus  of  this  canal.  It  then  turns  at  a  right 
angle  at  the  geniculate  ganglion  (Fig.  243,  a),  containing  ganglion-cells,  passing 
over  the  tympanic  cavity,  to  descend  into  the  bone  on  the  posterior  aspect  of 
this  cavity.  Finally,  it  makes  its  exit  at  the  stylomastoid  foramen,  penetrates 
the  parotid  gland,  and  divides  into  its  terminal  branches,  to  be  distributed  in  a 
fan-shaped  manner  (pes  anserinus  major). 

The  branches  of  the  facial  nerve  (Fig.  243)  are : 

1.  The  motor  greater  superficial  petrosal  nerve  (j).     It  passes  from 
the  geniculate  ganglion  through  the  hiatus  out  of  the  facial  canal  into  the 
cranial  cavity,  then  downward  upon  the  anterior  surface  of  the  petrous 
bone,  next  through  the  sphenoidal  fissure  to  the  inferior  surface  of  the 
base  of  the  skull,  and  finally  through  the  Vidian  canal  to  the  spheno- 
palatine  ganglion.     It  is  also  possible  that  the  nerve  transmits  sensory 
fibers  to  the  facial  from  the  second  division  of  the  trigeminus. 

2.  From  the  geniculate  to  the  otic  ganglion  connecting  fibers  (ft)  whose 
course  and  function  are  described  on  p.  689. 

3.  The  motor  branch  to  the  stapedius  muscle  0). 

4.  The  chorda  tympani  nerve  (i  i)  arises  before  the  exit  of  the  facial 
from  the  stylomastoid  foramen  (s),  passes  through  the  tympanic  cavity, 
above  the  tendon  of  the  tensor  tympani,  between  the  handle  of  the  mal- 
leus and  the  long  process  of  the  incus,  then  through  the  petrotympanic 
fissure  externally  to  the  base  of  the  skull  and  downward  at  an  acute 
angle  into  the  lingual  nerve.     In  advance  of  this  union  an  exchange  of 
fibers  takes  place  between  the  chorda  and  the  otic  ganglion  (m).     Both 
these,  as  well  as  the  connection  of  the  chorda  with  the  lingual  nerve,  may 
transmit  sensory  fibers  to  the  chorda  and  later  on  to  the  facial  nerve. 
The  chorda  contains  sensory  fibers,  for  irritation  of  the  nerve,  which  is  pos- 
sible in  man  when  the  tympanic  membrane  is  destroyed,  causes  a  stick- 
ing and  prickling  sensation  in  the  anterior  lateral  portion  and  at  the  tip 
of  the  tongue.     After  division  of  the  chorda  O.  Wolf  found  sensibility 
for  tactile  and  thermic  irritations  abolished  in  man  in  the  same  distri- 
bution, and  also  gustatory  sensation. 


FACIAL    NERVE.  695 

The  chorda  contains  secretory  fibers  for  the  sublingual  and  sub- 
maxillary  glands  and  vasodilators  for  these  and  the  tongue.  From 
the  observations  of  numerous  investigators  it  has,  further,  been  estab- 
lished that  the  chorda  tympani  contains  also  gustatory  fibers  for  the 
margin  and  the  tip  of  the  tongue,  which,  further  on,  it  gives  off  to  the 
tongue  in  the  course  of  the  lingual.  Urbantschitsch  observed  a  man 
whose  chorda  was  exposed  and  in  whom  irritation  of  the  nerve  in  the 
tympanic  cavity  caused  gustatory  sensations,  together  with  sensory  im- 
pressions. 

It  must,  therefore,  be  accepted  as  established  that  the  gustatory 
fibers  of  the  chorda  originate  in  the  glossopharyngeal  nerve.  They  may 
enter  the  chorda :  i .  Through  the  intermediary  portion  of  Wrisberg,  and 
this  view  has  recently  received  general  acceptance.  2.  A  further  pos- 
sible means  of  communication  is  afforded  beyond  the  stylomastoid  fora- 
men, namely,  through  the  communicating  branch  with  the  glossopharyn- 
geal nerve  (Fig.  243,  e),  which  passes  from  the  nerve  last  mentioned  into 
that  branch  of  the  facial  that  at  the  same  time  contains  the  motor  fibers 
for  the  stylohyoid  muscle  and  the  posterior  belly  of  the  digastric  (Henle's 
styloid  nerve).  This  nerve  gives  off  also,  perhaps,  muscle-sense  fibers  for 
the  stylohyoid  muscle  and  the  posterior  belly  of  the  digastric.  In  addi- 
tion, it  is  assumed  that  by  means  of  this  anastomosis  motor  fibers  from  the 
facial  are  brought  to  the  glossopharyngeal.  A  third  point  of  union  be- 
tween the  ninth  and  seventh  nerves  is  situated  in  the  tympanic  cavity : 
the  tympanic  branch  of  the  glossopharyngeal  (/)  that  enters  the  tympanic 
cavity  is  connected  in  the  tympanic  plexus  with  the  lesser  superficial 
petrosal  nerve  (ft),  which  is  derived  from  the  geniculate  ganglion  of  the 
facial.  The  lesser  superficial  petrosal  nerve  may  thus  transmit  gustatory 
fibers  to  the  geniculate  ganglion  of  the  facial.  It  may,  however,  convey 
the  gustatory  fibers  first  to  the  otic  ganglion,  which  is  constantly  con- 
nected with  the  chorda  tympani.  Finally,  a  fourth  connection  has  been 
described  as  taking  place  through  a  filament  (~)  from  the  petrous  gan- 
glion of  the  ninth  nerve  directly  to  the  facial  trunk  in  the  Fallopian 
canal. 

The  chorda  contains  vasodilators  for  the  anterior  two-thirds  of  the 
tongue. 

Mention  should  be  made  here  of  the  remarkable  fact  that  from  i  to  3 
weeks  after  division  of  the  hypoglossal  nerve,  irritation  of  the  chorda 
causes  movements  in  the  paralyzed  tongue.  These  movements  are 
feeble  and  tardy,  in  comparison  with  those  resulting  from  hypoglossal 
stimulation.  The  phenomenon  is  explained  on  p.  559.  It  depends  essen- 
tially upon  an  increased  supply  of  blood,  in  conjunction  with  an  aug- 
mented secretion  of  lymph,  as  a  result  of  which  the  corresponding  half 
of  the  tongue  becomes  edematous.  Heidenhain  designates  this  action 
pseudomotor . 

With  respect  to  Heidenhain 's  interpretation  it  should  be  recalled  that  mus- 
cular contraction  depends  on  swelling  through  the  taking  up  of  fluid.  The  pseudo- 
motor  contraction  has  a  latent  stage  ten  times  as  long  as  that  of  hypoglossal 
irritation.  A  single  moderate  induction-shock  is  ineffective,  as  is  also  chemical 
irritation;  nevertheless  reflex  stimulation  may  occur  through  various  sensory 
nerves.  Nicotin  first  stimulates,  then  paralyzes,  movement  excited  through  the 
chorda.  The  chorda  transmits  motor  impulses  even  for  a  short  time  after  sup- 
pression of  the  circulation.  The  pseudomotor  contraction  gives  rise  to  no  muscular 
sound. 

5.  Even  before  the  chorda  is  given  off  the  trunk  of  the  facial  enters 


696 


FACIAL    NERVE. 


into  direct  relations  with  the  auricular  branch  of  the  vagus  (<5),  which 
crosses  its  path  in  the  mastoid  canal  and  from  which  it  may  receive  sen- 
sory fibers. 

6.  After  making  its  exit  from  the  canal  the  facial  nerve  gives  off  only 
motor  branches  to  the  stylohyoid  muscle  and  the  posterior  belly  of  the 
digastric,  to  the  occipital  muscle,  as  well  as  to  all  of  the  muscles  of  the 
external  ear  and  of  the  face,  to  the  buccinator  and  to  the  platysma.  It 
contains  also  sweat -fibers  for  the  face. 

Although  the  facial  nerve,  in  most  of  its  branches  on  the  face,  is  under  the 
control  of  the  will,  most  persons  are  unable  to  move  voluntarily  the  muscles 
of  the  nose  and  the  auricle.  Landois  was  able  to  contract  the  transverse  and 
oblique  muscles  of  the  auricle,  a  rumbling  sound  being  at  the  same  time  audible  in 


Frontal  muscle. 

Corrugator  supercilii. 
Orbicularis  palpebrarum. 


Uppermost  facial  branch, 
Facial  trunk, 

Mm .  retrahens  et  attolens  auriculae . 

Occipital  muscle. 

Middle  facial  branch. 

Stylohyoid  muscle. 

Digastric  muscle. 


Lower  facial  branch 


Compressor  nasi  et  pyramidalis. 
Levator  labii  sup.  alaeque  nasi. 
Levator  labii  superioris  propriis. 
Zygomaticus  minor. 
Dilatator  narium. 
Zygomaticus  major. 

Orbicularis  orus. 


Levator  menti. 

Quadratus  menti. 

—  Triangularis  menti. 


FIG.  245. — Motor  Points  of  the  Facial  Nerve  and  of  the  Muscles  Supplied  by  It  (after  Eichhorst). 


the  corresponding  ear  from  the  flexion  of  the  cartilage  of  the  external  ear.  He  was 
able  also  to  contract  one-half  of  the  Orbicularis  oris  of  the  lower  lip.  According 
to  Mendel  the  fibers  of  the  facial  for  the  orbicularis  take  their  origin  from  the 
posterior  extremity  of  the  oculomotor  nucleus. 

On  the  face  the  facial  branches  unite  regularly  with  those  of  the  tri- 
geminus.  In  this  way  the  latter  furnish  also  muscle-sense  fibers  to  the 
muscles.  The  peripheral  anastomoses  of  the  sensory  branches  of  the 
auricular  nerve  of  the  vagus  and  the  great  auricular  nerve  have  the  same 
significance  for  the  muscles  of  the  ear,  as  well,  finally,  as  the  anastomoses 
of  the  sensory  filaments  from  the  third  cervical  nerve  for  the  facial 
fibers  of  the  platysma.  Division  of  the  facial  at  the  stylomastoid 


FACIAL    NERVE.  697 

foramen  is  painful,  but  still  more  painful  is  that  of  the  peripheral  facial 
branches,  as  will  be  obvious  from  what  has  been  stated. 

The  foregoing  illustration  shows  accurately  the  course  of  the  trunk  of  the 
facial  nerve  and  its  superior,  middle  and  inferior  branches  on  the  face,  as  well 
as  the  points  where  the  individual  motor  fibers  pass  into  their  muscles.  By  the 
application  of  one  electrode  at  these  points,  the  other  being  applied  to  any  in- 
different part  of  the  body,  the  individual  muscles  can  be  made  to  contract  elec- 
trically. The  electrodes  are  applied  in  the  same  way  in  employing  electricity  for 
therapeutic  purposes. 

Pathological. — In  connection  with  paralysis  of  the  facial  nerve  it  is  above  all 
important  to  determine  whether  the  seat  of  the  affection  is  a  peripheral  one,  in 
the  neighborhood  of  the  stylomastoid  foramen,  or  in  the  course  of  the  long 
Fallopian  canal,  or,  finally,  central  (cerebral).  A  careful  analysis  of  the  symp- 
toms will  lead  to  a  conclusion  in  this  respect.  A  frequent  cause  for  paralysis  at  the 
stylomastoid  foramen  is  designated  rheumatic  and  probably  depends  upon  exuda- 
tion paralyzing  the  nerve  by  compression  (perhaps  at  the  situation  of  the  lymph- 
space  discovered  by  Rtidinger  at  the  inner  side  of  the  Fallopian  canal  between 
the  periosteum  and  the  nerve,  an  evagination  of  the  arachnoid  sac).  Other  causes 
are  inflammation  of  the  parotid,  direct  traumatism,  pressure  of  the  obstetric 
forceps  in  the  new-born.  In  the  course  of  the  canal  fractures  of  the  petrous  bone, 
effusions  of  blood  into  the  canal,  syphilitic  deposits,  caries  of  the  petrous  bone, 
principally  in  connection  with  inflammation  of  the  middle  ear,  are  to  be  mentioned 
as  causes  of  the  paralysis.  Among  intracranial  causes  there  should  finally  be 
mentioned  affections  of  the  cerebral  membranes  and  the  base  of  the  skull  in  the 
vicinity  of  the  nerve,  disease  of  the  facial  nucleus,  and  finally  of  the  cortical  center 
for  the  nerve  and  the  connections  between  this  and  the  nucleus. 

The  symptoms  of  unilateral  facial  palsy  are  as  follows:  i.  Paralysis  of  the 
muscles  of  the  face:  the  forehead  is  smooth,  free  from  furrows;  the  palpebral 
fissure  is  open  (paralytic  lagophthalmos) ,  with  the  external  canthus  at  a  lower 
level.  The  anterior  surface  of  the  eye  readily  becomes  dry,  and  the  cornea  appears 
dull,  chiefly  because  the  distribution  of  tears  is  interfered  with  by  absence  of 
winking,  and,  in  consequence  of  the  dryness,  slight  inflammatory  irritation  may 
result  (xerotic  keratitis) .  According  to  some  observers  the  facial  nerve  is  believed 
to  be  the  secretory  nerve  for  the  lacrimal  gland  (so  that  the  secretion  of  tears  is 
interfered  with  when  the  nerve  is  paralyzed)  and  the  vasomotor  nerve  for  the 
conjunctiva.  Its  course  is  believed  to  be  as  follows:  facial,  greater  superficial 
petrosal  nerve,  sphenopalatine  ganglion,  second  division  of  the  trigeminus,  orbital 
nerve.  In  order  to  protect  the  eye  from  exposure  to  light,  the  patient  generally 
rotates  the  globe  upward  and  outward  beneath  the  upper  eyelid,  and  relaxes  the 
elevator  of  the  upper  eyelid,  so  that  the  lid  droops  somewhat.  The  nose  cannot 
be  moved,  and  the  nasolabial  fold  is  obliterated.  In  consequence,  the  sense  of 
smell  may  be  impaired,  because  the  nasal  orifice  can  no  longer  be  dilated.  The 
derangement  of  smell,  however,  is  due  principally  to  the  defective  distribution  of 
tears  (in  consequence  of  paralysis  of  winking  and  of  the  muscle  of  Horner) ,  which 
leaves  the  corresponding  side  of  the  nasal  cavity  dryer  than  normal.  Horses, 
which  in  breathing  visibly  dilate  the  nostrils,  are  said  either  to  die  after  bilateral 
division  of  the  facial  nerve  from  interference  with  respiration  or  at  least  to  suffer 
from  marked  respiratory  difficulty.  The  entire  face  is  drawn  toward  the  unaf- 
fected side,  so  that  the  nose,  the  mouth,  and  the  chin  generally  occupy  an  oblique 
position.  In  consequence  of  paralysis  of  the  stylohyoid  muscle  and  the  posterior 
belly  of  the  digastric,  the  base  of  the  tongue  on  the  paralyzed  side  may  occupy 
a  lower  level,  and  on  forced  movement  of  the  base  of  the  tongue  this  organ 
may  undergo  a  deviation  toward  the  unaffected  side.  Paralysis  of  the  buccinator 
interferes  with  the  normal  formation  of  the  bolus  of  food,  which  collects  in  the 
concavity  of  the  relaxed  cheeks  from  which  the  patient  must  eventually 
remove  it  with  the  fingers.  Saliva  and  fluid  readily  escape  from  the  angle  of  the 
mouth.  In  strong  expiration  the  cheek  is  distended  like  a  sail.  Speech  may  be 
interfered  with  in  consequence  of  difficulty  in  forming  the  labial  consonants 
(particularly  when  the  paralysis  is  bilateral)  and  also  the  vowels  o  u  6.  Speech 
becomes  nasal  in  the  presence  of  (bilateral)  paralysis  of  the  branches  to  the  muscles 
of  the  palate.  Whistling,  suckling,  blowing,  expectoration  are  interfered  with. 
Bilateral  paralysis  causes  many  of  these  symptoms  in  exaggerated  degree.  Others, 
such  as  the  oblique  position  of  the  face,  naturally  are  wanting.  The  face  is  com- 
pletely relaxed,  without  any  play  of  expression,  and  the  patients  cry  and  laugh 


698  FACIAL    NERVE. 

"as  behind  a  mask."  2.  In  the  presence  of  paralysis  of  the  palate,  the  uvula 
is  deflected  toward  the  unaffected  side,  and  the  paralyzed  half  of  the  palate  is 
depressed  and  relaxed  and  cannot  be  elevated  (greater  superficial  petrosal  nerve). 
It  has  not  as  yet  been  determined  whether  and  to  what  extent  it  affects  the  move- 
ments of  swallowing  and  the  formation  of  consonants.  3.  Impairment  of  the 
sense  of  taste  (either  absence"  upon  the  anterior  two-thirds  of  the  tongue  or  delay 
and  alteration  in  the  sensation)  results  in  accordance  with  what  has  been  stated 
concerning  the  chorda  tympani.  4.  Diminution  in  the  secretion  of  saliva  upon 
the  paralyzed  side  was  first  described  by  Arnold,  although  it  will  have  to  be 
determined  to  what  extent  any  impairment  of  taste  that  may  be  present  at  the 
same  time  may  give  rise  to  interference  with  the  reflex  secretion  of  saliva,  or 
whether,  possibly,  increased  evaporation  of  saliva  from  the  separated  lips  and  the 
angle  of  the  mouth  may  result  in  greater  dryness  of  the  affected  side  of  the  mouth. 
5.  Since  the  time  of  Roux  increased  attention  has  been  called  to  acuity  of  hearing 
(oxyakoia  or  hyperacusis  of  Willis).  The  paralysis  of  the  stapedius  muscle 
causes  oscillation  of  the  stapes  in  the  oval  window,  so  that  impulses  from  the 
tympanic  membrane  are  strongly  transmitted  to  this  bone,  which  in  turn  gives 
rise  to  marked  oscillations  in  the  labyrinthine  fluid.  Less  commonly,  in  conse- 
quence of  paralysis  of  the  stapedius  muscle,  it  is  observed  that  deeper  notes  are 
heard  at  a  greater  distance  than  upon  the  unaffected  side.  6.  As  the  facial 
nerve  in  man  appears  to  contain  sweat-fibers,  it  is  clear  that  with  the  occurrence 
of  atrophy  of  this  nerve  loss  of  sweating  in  the  face  must  result.  7.  Derangement 
of  sensibility  naturally  cannot  occur  in  connection  with  pure  central  affections  of 
the  facial  nerve.  As,  however,  numerous  sensory  fibers  enter  the  peripheral  por- 
tion of  the  nerve,  peripheral  paralysis  will  be  attended  with  a  certain  limited 
impairment  of  sensibility  (principally  affecting  the  muscle-sense)  in  the  face. 

Division  of  the  facial  nerve  in  young  animals  causes  atrophy  of  the  related 
muscles.  Therefore,  the  bones  of  the  face  are  retarded  in  their  growth.  They 
remain  smaller  and  the  bones  of  the  opposite  side  finally  extend  beyond  the 
middle  line  toward  the  affected  side.  Also  the  salivary  glands  remain  smaller. 

Irritation  of  the  facial  nerve  gives  rise  to  circumscribed  or  diffuse,  direct  or 
reflex,  tonic  or  clonic  spasm.  The  diffuse  form  of  spasm  is  designated  mimetic 
facial  spasm.  Among  the  forms  of  circumscribed  spasm  tonic  spasm  of  the  eyelids, 
blepharospasm,  is  the  most  frequent,  being  caused  by  stimulation  of  the  sensory 
nerve  of  the  eye,  principally  in  connection  with  scrofulous  inflammation  of  the 
eye  or  in  consequence  of  excessive  irritability  of  the  retina  (photophobia) .  Less 
commonly  the  irritation  is  transmitted  from  a  remote  point,  for  example  in  one 
case  in  consequence  of  inflammatory  irritation  of  the  anterior  palatine  arch. 
The  center  for  reflex  stimulation  is  the  facial  nucleus.  The  clonic  form  of  spasm, 
abnormal  winking  (spasmus  nictitans) ,  is  generally  of  reflex  origin  through  irrita- 
tion of  the  eyes,  the  dental  nerves  or  even  remotely  situated  nerves.  In  marked 
cases  the  disorder  is  bilateral,  and  the  spasm  may  extend  to  the  muscles  of  the 
neck,  the  trunk  and  the  upper  extremities.  Twitching  of  the  muscles  of  the  lips 
is  caused  in  part  by  emotional  influences,  in  part  by  reflex  influences.  Fibrillary 
twitching  appears  also  in  the  sequence  of  paralysis  of  the  facial  nerve  as  a  de- 
generative phenomenon.  In  dogs  Schiff  observed  for  years  fascicular  twitching 
in  the  paralyzed  facial  area,  which  in  contradistinction  to  fibrillary  twitchings, 
could  be  excited  reflexly,  and  to  which  Schiff  attributes  the  oblique  position  of 
the  face  in  man.  Intracranial  irritation  of  the  most  varied  form,  affecting  the 
cortical  center  or  the  nucleus  of  the  nerve,  may  likewise  cause  spasm.  Finally, 
facial  spasm  may  occur  as  part  of  general  convulsions,  such  as  attend  epilepsy, 
eclampsia,  chorea,  hysteria,  and  tetanus.  Aretasus  (81  A.  D.)  made  the  interesting 
observation  that  the  muscles  of  the  auricle  take  part  in  the  convulsions  of  tetanus. 
With  respect  to  the  influence  of  irritation  of  the  facial  nerve  upon  the  sense  of 
taste  information  must  be  derived  from  future  careful  investigations.  Rarely, 
spasmodic  elevation  of  the  palate  and  increased  salivation  have  been  described 
in  connection  with  irritation  of  the  facial  nerve.  Moos  observed  profuse  secretion 
of  saliva  on  irritation  of  the  chorda  in  consequence  of  an  operation  in  the  tympanic 
cavity.  Aristotle  had  already  observed  transitory  impairment  of  hearing  during 
the  act  of  yawning  and  this  has  been  attributed  by  Landois  to  spasm  of  the  stape- 
dius. This  is  the  antithesis  of  the  hyperacusis  of  Willis.  In  conjunction  with 
this  there  occurs  a  feeble  droning  sound,  due  to  the  vibrations  of  the  labyrinth 
induced  by  the  contraction  of  the  muscle  named.  Gottstein  observed  in  one  case 
this  stapedius  droning  to  occur  paroxysmally  in  addition  to  blepharospasm. 


AUDITORY    NERVE.  699 

VIII,    AUDITORY  NERVE. 

Two  roots  serve  for  the  origin  of  the  auditory  nerve,  an  anterior  median  root 
with  coarse  fibers,  and  a  posterior  lateral  root  with  fine  fibers.  The  vestibular 
nerve  arises  from  the  former,  the  cochlear  nerve  from  the  latter.  The  two  are 
entirely  distinct  in  the  sheep  and  the  horse.  Each  vestibular  and  cochlear  nerve 
arises  from  a  peripheral  ganglion  (the  vestibular  ganglion  in  the  internal  auditory 
canal  and  the  spiral  ganglion  in  the  cochlea),  constituted  like  the  spinal  ganglia, 
and  at  the  same  time  the  trophic  center  for  the  fibers.  Into  each  gan- 
glion-cell there  enters  a  cellulipetal  dendrite  passing  from  the  sensory  epithelium 
in  the  labyrinth,  while  on  the  other  hand  each  cell  sends  to  the  medulla  oblongata 
a  cellulipetal  neurite  to  the  nuclei  of  origin  of  the  auditory  nerve,  with  whose 
cells  it  comes  in  contact  by  means  of  terminal  filaments  and  collaterals.  The 
vestibular  nerve  is  essentially  connected  with  gray  matter  that  is  in  relation  with 
the  cerebellum  and  probably  subserves  the  purpose  of  maintaining  the  equilibrium. 
From  the  origin  of  the  cochlear  fibers  the  main  portion  passes  on  the  opposite 
side  to  the  posterior  quadrigeminate  body  and  the  internal  geniculate  body  and 
further  (particularly  through  the  lower  fillet,  the  upper  olive  and  the  trapezoid 
body)  to  the  temporal  lobe  of  the  cerebrum,  in  which  the  psycho-auditory  cortical 
center  is  situated.  After  extirpation  of  the  temporal  lobe  its  fibers  through  the 
corona  radiata  atrophy  into  the  internal  capsule,  as  well  as  fibers  in  the  posterior 
quadrigeminate  body  and  the  internal  geniculate  body.  The  striae  acusticas  rep- 
resent a  central  path  for  the  lateral  auditory  root.  They  form  a  secondary  pro- 
jection-system of  the  auditory  nerve,  decussating  somewhat  like  a  chiasm.  The 
nuclei  of  origin  of  both  auditory  nerves  are  connected  in  the  brain  by  commissural 
fibers.  In  the  internal  auditory  canal  root-fibers  pass  from  the  intermediate 
portion  into  the  auditory  nerve. 

The  auditory  nerve  has  a  double  function :  in  the  first  place  it  is  the 
nerve  of  hearing.  Every  irritation  at  its  origin,  in  its  course  or  in  its 
terminal  distribution  causes  auditory  impressions ;  every  injury,  in  accord- 
ance with  its  intensity,  impairment  of  hearing  to  the  point  of  deafness; 
also  destruction  of  the  labyrinths,  the  end-organs  of  the  auditory 
nerves,  causes  complete  deafness. 

As  animals  after  removal  of  both  cochleae  still  react  to  coarse  sounds,  the 
ampullas  must  serve  for  the  perception  of  the  sounds,  and  the  cochlea  for  the 
appreciation  of  the  remaining  auditory  qualities.  After  extirpation  of  the  laby- 
rinth the  auditory  nerve  undergoes  atrophy  in  an  upward  direction. 

Entirely  distinct  from  the  auditory  is  the  function  of  the  nerve  that 
is  localized  exclusively  in  the  semicircular  canals,  namely  that  govering 
the  necessary  movements  for  the  maintenance  of  the  bodily  equilibrium, 
through  stimulation  of  the  peripheral  distribution  in  the  ampullae. 

Of  especial  importance  is  the  behavior  of  the  auditory  nerve  in  response  to 
the  galvanic  current.  If  an  electrode  is  placed  in  a  healthy  person  upon  the 
tragus  on  each  side,  it  will  be  found  that  upon  the  anodal  side  with  closure  of 
the  current  silence  occurs,  on  opening  the  current  a  sense  of  sound,  while  the 
opposite  takes  place  upon  the  kathodal  side  (Brenner's  normal  formula).  If  one 
electrode  is  placed  on  the  tragus  and  the  other  is  held  in  the  hand,  the  same  result 
is  observed,  except  that  the  sound  upon  the  unarmed  ear  is  much  feebler.  The 
sound  agrees  exactly  with  the  resonance  fundamental  tone  of  the  sound-conducting 
apparatus  of  the  ear  itself. 

The  appearance  of  this  sound  is  to  be  explained  in  the  following  manner:  In 
the  middle  ear  there  exists  a  permanent  blood-murmur,  to  which  the  system  of 
cavities  of  the  middle  ear  resonates  with  its  fundamental  tone.  In  consequence 
of  habituation  this  tone  is,  as  a  rule,  not  noted,  but  it  appears  at  once  if  the  auditory 
nerve  is  placed  in  a  condition  of  increased  irritation,  namely  (in  the  sense  of 
electrotonus)  on  kathodal  closure  and  anodal  opening. 

According  to  Gradenigo,  Pollak,  and  Gartner,  the  auditory  nerve  in  healthy 
persons  does  not  react  at  all  to  currents  of  moderate  strength.  Only  in  the  pres- 
ence of  hyperemic  and  irritative  states  of  the  auditory  apparatus  does  a  reaction 


yoo 


AUDITORY    NERVE. 


take  place,  and  then  in  both  ears  even  when  only  one  side  is  affected.  The  reac- 
tion-formula resulting  under  such  circumstances  conforms  entirely  with  Pniiger's 
law,  namely  kathodal  closure  causes  ringing  in  the  ears  and  anodal  opening  deeper 
roaring.  While  the  current  is  closed,  a  permanent  reaction  exists  even  when  the 
strength  of  the  current  is  slight.  Even  in  the  presence  of  complete  deafness  this 
typical  reaction  may  persist. 

Pathological. — Increased  irritability  of  the  auditory  nerve  at  any  point  in  its 
course,  its  centers,  or  its  terminal  distribution  causes  nervous  acuity  of  hearing 
(hyperacusis) ,  which  is  generally  a  symptom  of  widespread  increase  in  nervous 
irritability,  for  example  in  hysterical  persons.  If  present  in  particularly  marked 
degree  it  may  give  rise  to  a  distinctly  painful  sensitiveness,  which  may  be  designated 
acoustic  hyperalgia.  Irritation  of  the  area  named  causes  auditory  perceptions, 
among  which  nervous  roaring  or  ringing  in  the  ears  (tinnitus}  is  due  to  the  fact 
that  either  the  vascular  noises  in  the  ear  are  abnormally  loud  or  the  auditory 
nerve  is  hyperesthetic.  In  this  way  is  explained  the  tinnitus  following  large  doses 
of  quinin  or  salicylates  in  consequence  of  vasomotor  influences  upon  the  laby- 
rinthine vessels,  which  may  increase  to  the  degree  of  causing  rupture  of  a  vessel. 
Frequently,  in  the  presence  of  roaring  in  the  ears,  the  reaction  is  increased  upon 
applying  the  galvanic  current.  Less  commonly  there  is  a  so-called  paradoxical 
reaction,  that  is,  upon  applying  the  galvanic  current  to  one  ear  there  appears, 
in  addition  to  the  reaction  in  this  ear,  the  opposite  in  the  ear  through  which  the 
current  is  not  passed.  This  phenomenon  can  be  explained  in  the  sense  of  trans- 
ference. In  other  cases  of  lesions  of  the  auditory  nerve  noises  rather  than  musical 
notes  can  be  excited  by  the  current.  In  addition,  various  deviations  from  the 
formula  of  Brenner  have  been  observed,  and  even  complete  reversal  of  this  formula. 
Excitation,  particularly  of  the  cortical  center  of  the  auditory  nerve,  especially  in 
the  insane,  may  cause  auditory  hallucinations.  If  the  irritability  of  the  auditory 
nerve  is  diminished  or  even  destroyed,  nervous  impairment  of  hearing  (hypac^^sis) 
and  nervous  deafness  (anacusis)  develop.  Often  disease  of  one  ear  is  attended 
by  a  compensatory  relation  to  the  other. 

The  Semicircular  Canals  of  the  Labyrinth. — After  division  of  the  canals,  espe- 
cially if  bilateral,  marked  disorders  of  equilibrium  appear.  The  oscillating 
movement  of  the  head  in  the  direction  of  the  plane  of  the  injured  canal  is  charac- 
teristic. If  the  horizontal  canal  is  divided  the  head  (of  the  pigeon)  is  rotated 
alternately  to  the  right  and  the  left.  The  rotation  appears  chiefly  when  the 
animal  attempts  to  make  movements;  during  rest,  the  movements  cease.  The 
phenomenon  may  persist  for  months.  Injury  to  the  posterior  vertical  canal 
causes  marked  upward  and  downward  nodding  movements,  in  connection  with 
which  the  animal  occasionally  falls  forward  or  backward.  Injury,  finally,  of  the 
upper  vertical  canal  causes  likewise  oscillatory  vertical  movements  of  the  head, 
frequently  with  falling  forward.  Destruction  of  all  of  the  canals  is  frequently 
followed  by  various  oscillatory  movements  of  the  head  that  often  render  standing 
impossible.  Breuer  observed  on  mechanical,  thermic  and  electrical  irritation  of 
the  canals  analogous  rotation  of  the  head.  On  applying  salt-solution  with  a 
brush  to  the  exposed  canals  Landois  likewise  observed  the  oscillatory  movements 
described,  which  occasionally  disappeared  after  having  persisted  for  some  time. 
The  instillation  of  a  25  per  cent,  solution  of  chloral  into  a  rabbit's  ear  will  in 
the  course  of  fifteen  minutes  have  an  effect  similar  to  that  due  to  destruction  of  the 
canals.  Division  of  the  auditory  nerves  in  the  skull  has  the  same  effect. 

Goltz  considers  the  canals  as  the  sensory  mechanism  for  maintaining  the 
equilibrium  of  the  head.  Mach  considered  them  as  a  mechanism  for  appreciating 
the  movements  of  the  head.  According  to  Goltz,  the  endolymph,  with  every 
position  of  the  head,  exercises  a  maximum  degree  of  pressure  upon  a  given  portion 
of  the  semicircular  canals,  and  in  this  way  stimulates  the  nerve-terminations  in  the 
ampullae  in  varying  degree.  According  to  Breuer  there  ocdur  in  the  semicircular 
canals  on  rotation  of  the  head  currents  in  the  endolymph  that  stand  in  fixed  rela- 
tions to  the  direction  and  extent  of  the  movement  of  the  head,  and  which,  there- 
fore, if  perceived  constitute  a  delicate  means  for  estimating  the  movement  of  the 
head.  The  nervous  end-organs  of  the  ampullae  are  adapted  to  execute  this  per- 
ception. If,  therefore,  the  semicircular  canals  act  as  a  mechanism,  in  a  measure 
as  a  static  sense-organ,  for  the  sense  of  equilibrium,  the  appreciation  of  the 
position  or  of  the  movements  of  the  head,  their  destruction  or  irritation  will 
modify  these  perceptions  and  thus  give  rise  to  abnormal  oscillations  of  the  head. 
Breuer,  as  a  result  of  his  experiments,  reaches  the  conclusion  that  the  labyrinth 
is  intended  as  a  means  of  orientation  in  space,  and,  particularly,  that  the  semi- 


AUDITORY    NERVE.  701 

circular  canals  bring  rotatory  and  angular  movements  to  perception,  while  the 
nerve-terminations  in  the  saccule,  with  the  otoliths,  do  the  same  for  the  position 
of  the  head  with  relation  to  the  vertical  and  the  existence  of  straight  translational 
movements.  Vertigo  (with  nystagmus)  cannot  be  induced  in  deaf-mutes  and 
animals  whose  labyrinths  have  been  destroyed,  nor  in  a  labyrinthine  inverte- 
brates, and  young  tadpoles,  which  are  as  yet  unprovided  with  semicircular 
canals. 

The  feeling  of  vertigo,  of  deception  as  to  spatial  relations  of  the  surroundings, 
and  at  the  same  time  of  oscillation  of  the  body,  occurs  particularly  in  connection 
with  acquired  alterations  in  the  normal  movements  of  the  eyes,  whether  these 
consist  either  in  involuntary  lateral  movements  of  the  eyeballs  (nystagmus),  or 
in  paralysis  of  these  movements.  On  active  or  passive  movement  of  the  head 
or  of  the  body,  synchronous  movements  of  the  eyeballs  take  place  normally,  and 
these  are  definite  for  each  position  of  the  body.  The  general  characteristic  of 
these  bilateral  ocular  movements,  wrhich  may  be  designated  as  compensatory, 
consists  in  the  fact  that  through  them  both  eyes  in  the  various  changes  in  the 
position  of  the  head  and  of  the  body  tend  to  retain  their  primary  position  of 
rest.  Division  of  the  aqueduct  of  Sylvius  at  the  level  of  the  anterior  quadri- 
geminate  bodies,  the  cerebral  portion  on  the  floor  of  the  fourth  ventricle,  the 
auditory  nuclei,  both  auditory  nerves,  as  well  as  destruction  of  the  membranous 
labyrinth  on  each  side,  cause  loss  of  these  movements.  Irritation  of  the  same 
parts,  conversely,  causes  bilateral  associated  ocular  movements.  It  thus  appears 
that  compensatory  ocular  movements  are  under  normal  conditions  excited  re- 
flexly  from  the  membranous  labyrinth.  Both  labyrinths  are  connected  with  both 
eyes  by  means  of  reflex  nerve-paths,  nerve-fibers  passing  to  each  eye  from  both 
labyrinths.  These  pass  through  the  auditory  nerve  to  the  center  (which  extends 
from  the  interbrain  to  the  commencement  of  the  spinal  cord)  and  from  the  center 
centrifugal  fibers  pass  to  the  ocular  muscles.  Destruction  of  the  semicircular 
canals  thus  causes  change  in  the  normal  compensatory  ocular  movements  and  in 
this  way  gives  rise  to  vertigo. 

Chloroform  and  other  poisons  exhaust  the  compensatory  ocular  movements. 
Nicotin  and  others,  as  well  as  asphyxia,  suppress  them  through  an  action  upon 
the  center.  Cyon  found  that  irritation  of  the  horizontal  semicircular  canal  causes 
horizontal  nystagmus,  irritation  of  the  posterior  canal  vertical  nystagmus  and 
irritation  of  the  anterior  canal  oblique  nystagmus.  Irritation  of  one  auditory 
nerve  causes  rotatory  nystagmus  and  axial  rotation  of  the  animal  toward  the  irri- 
tated side. 

The  thought  suggests  itself  that  the  disorders  of  equilibrium,  attacks  of  vertigo 
and  the  feeling  of  apparent  movement  of  external  objects  that  are  observed  on 
the  passage  of  a  galvanic  current  through  the  head  between  the  ears  or  between 
the  two  mastoid  processes  are  due  to  influences  acting  on  the  semicircular  canals 
of  the  labyrinth.  Under  such  circumstances  also  oscillation  of  the  eyes  takes 
place,  as  well  as  a  movement  of  the  head  on  closure  of  the  circuit  at  the  anode. 

Pathological. — The  attacks  of  vertigo  of  sudden  onset  occurring  in  the  course 
of  disorders  of  the  labyrinth  and  of  so-called  Meniere's  disease,  the  latter  not 
rarely  being  attended  with  roaring  in  the  ears,  vomiting,  staggering  gait  and 
marked  impairment  of  hearing,  must  be  referred  to  an  affection  of  the  ampullar 
nerves  or  their  central  organs  or  of  the  semicircular  canals.  The  labyrinthine 
nerves  may  be  affected  also  reflexly,  or  in  the  form  of  a  pure  neurosis.  Even 
irritative  phenomena  upon  one  side  may  cause  vertigo.  Forcible  injections  into 
the  ears  of  rabbits  also  cause  attacks  of  vertigo,  with  nystagmus  and  rotation 
of  the  head  toward  the  side  treated.  Also  in  workmen  exposed  to  greatly 
increased  atmospheric  pressure,  analogous  phenomena  appear.  In  the  presence 
of  deficiencies  in  the  tympanic  membrane  in  man  Lucae  observed,  on  application 
of  the  air-douche  to  the  auditory  canal,  rotation  of  the  eyes  and  vertigo.  Inflam- 
mation of  the  middle  ear  in  man  may  likewise  cause  nystagmus  with  vertigo. 
In  this  way  is  explained  the  vertigo  observed  in  connection  with  spasm  of  the 
tensor  tympani,  as  a  result  of  which  excessive  pressure  is  exerted  upon  the  laby- 
rinth. Urbantschitsch  found  that  even  certain  tones  are  capable  of  causing  in 
persons  occupying  the  vertical  position  disturbance  of  equilibrium  and  apparent 
movement.  Also  transitory  derangement  of  the  circulation  in  the  nuclei  for  the 
nerves  to  the  ocular  muscles  is,  according  to  Mendel,  often  a  cause  of  vertigo. 
Strabismus,  paralysis  of  ocular  muscles,  pupillary  changes  are  rare  as  reflex 
phenomena  from  the  ear.  It  is  a  remarkable  fact 'that  occasionally  a  tendency 
to  attacks  of  vertigo  occurs  in  association  with  chronic  disease  of  the  stomach 


FIG.  246. 


702 


GLOSSOPHARYNGEAL    NERVE.  703 

(Trousseau's  gastric  vertigo).  This  condition  may  result  from  irritation  of  the 
vasomotor  nerves  of  the  labyrinth  secondary  to  that  of  the  gastric  nerves,  pro- 
ducing an  influence  upon  the  pressure-relations  of  the  endolymph.  Intestinal 
vertigo,  laryngeal  vertigo  and  urethral  vertigo  have  been-  described  as  occurring  in 
an  analogous  manner. 

IX.    GLOSSOPHARYNGEAL  NERVE. 

The  glossopharyngeal  nerve  arises  from  three  nuclei  : 
i.  The  sensory,  gustatory  nucleus,  constituted  of  small  cells,  is  situated  near 
the  ala  cinerea  to  the  side  of  the  hypoglossal  nucleus  just  beneath  the  floor  of 
the  fourth  ventricle.  The  fibers  related  to  this  nucleus  arise  actually  from  periph- 
eral ganglion -cells  (ganglionic  plexus  of  the  lingual  branch) .  From  these  peripheral 
ganglion-cells  the  cellulifugal  neurites  enter  into  contact  in  the  gustatory  nucleus ; 
the  cellulipetal  dendrites  are  derived  from  the  neighborhood  of  the  sense-cells  of 
the  tongue.  2.  The  motor  nucleus  is  constituted  of  larger  cells  and  is  more 
deeply  situated.  It  passes  without  sharp  limitation  into  the  motor  nucleus  of  the 
vagus  and  sends  as  neurites  motor  fibers  to  the  ninth  and  also  to  the  tenth  nerve. 
3.  The  sensory,  descending  root  is  situated  at  the  side  of  the  solitary  bundle, 
and  with  it  also  filaments  from  the  vagus  are  associated.  The  cells  of  the 
jugular  and  petrosal  ganglia  serve  for  its  origin ;  from  them  neurites  pass  into  the 
medullary  nucleus,  while  the  dendrites  are  derived  from  the  mucous  membrane  of 
the  pharynx.  The  most  anterior  portion  of  the  sensory  nucleus  of  origin  is  con- 
sidered as  the  root  of  the  portio  intermedia  of  Wrisberg. 

The  filaments  unite  to  form  two  nerves,  which  subsequently  coalesce,  and 
leave  the  medulla  in  front  of  the  vagus  (Fig.  241).  Close  to  the  point  of  exit 
it  forms  the  jugular  ganglion,  then  in  the  petrosal  fossa  the  petrous  ganglion 
(Fig.  246).  In  the  jugular  ganglion  the  nerve  anastomoses  with  the  trigeminus, 
the  facial  (Fig.  243,  t-  and  TT),  the  vagus  (Fig.  246)  and  the  carotid  plexus. 
From  this  ganglion  there  ascends  vertically  the  tympanic  nerve  (Fig.  243,  /) 
into  the  tympanic  cavity  to  unite  with  the  tympanic  plexus.  This  branch  gives 
sensory  branches  also  to  the  tympanic  cavity  and  the  Eustachian  tube.  Further, 
through  the  lesser  superficial  petrosal  nerve  it  transmits  fibers  for  the  salivary 
secretion  of  the  parotid  gland  (in  the  dog) . 

Functionally,  the  glossopharyngeal  is:  i.  The  gustatory  nerve  for 
the  posterior  third  of  the  tongue,  the  lateral. portion  of  the  soft  palate  and 
the  glossopalatine  arch. 

The  gustatory  activity  of  the  anterior  two-thirds  of  the  tongue  has  been 
discussed  in  connection  with  the  consideration  of  the  lingual  nerve  and  of  the 
chorda  tympani.  The  lingual  branches  are  provided  with  ganglia,  principally  at 
the  plexuslike  points  of  division  and  at  the  base  of  the  vallate  papillae.  The 
terminal  branches  can  be  traced  to  the  circumvallate  papillae  (Fig.  243,  U),  whose 
taste-buds  they  surround  as  telodendrites. 

2.  The  glossopharyngeal  is  the  motor  nerve  for  the  stylopharyngeus 
muscle.  Nevertheless,  the  motor  fibers  of  origin  later  pass  also  through 
the  pharyngeal  branches  of  the  vagus. 

FIG.  246,  p.  702. 

I.  Diagrammatic  Representation  of  the  Distribution  of  the  Vagus  and  Accessory  Nerves :  10,  exit  of  the  left  trunk 
of  the  vagus  from  the  cranial  cavity.  (101,  right  vagus.)  9,  Glossopharyngeal  nerve.  7,  Facial  nerve,  i, 
Deep  posterior  auricular  branch  of  the  facial.  2,  Pharyngeal  branch  of  the  vagus.  6,  Pharyngeal  branch  of 
the  glossopharyngeal  3,  Superior  laryngeal  nerve,  with  its  anastomoses  (/)  with  the  sympathetic  and  its 
division  (4)  into  the  internal  branch  (v)  and  the  external  branch  (e).  5,  Inferior  or  recurrent  laryngeal.  au, 
Auricular  branch  of  the  vagus.  Cardiac  nerves:  g,  cardiac  branches  from  the  trunk  of  the  vagus  and  from 
the  superior  laryngeal;  i,  h,  the  three  cardiac  branches  from  the  superior  (8),  middle  (x),  and  inferior  (y) 
cervical  ganglia  of  the  sympathetic,  k,  Ansa  Vieussenii.  /,  Cardiac  branch  from  the  recurrent  nerve  L, 
Lung  with  the  anterior  and  posterior  pulmonary  plexuses,  r,  Esophageal  plexus,  o,  o,  Gastric  branches  of 
the  left  vagus,  together  with  the  hepatic  branches  («).  m,  Celiac  plexus,  k,  The  splanchnic  nerve,  n, 
Accessory  nerve  of  Willis,  which  sends  its  inner  branch  into  the  gangliform  plexus  of  the  vagus;  its  outer  branch 
supplies  with  fibers  (ac)  the  sternocleidomastoid  muscle  (Si)  and  (ac\)  the  trapezius  (Cc).  O,  External  auditory 
canal.  Oh,  Hyoid  bone.  K,  Thyroid  cartilage.  T,  Trachea.  H,  Heart.  P,  Pulmonary  artery.  A,  A, 
Aorta,  c,  Right  carotid.  c\,  Left  carotid.  5,  Right  subdavian.  s,  Left  subclavian.  Z,  Z,  Diaphragm. 
N,  Kidney.  Nn,  Adrenal  body.  M ,  Stomach,  m,  Spleen.  LI,  Lung  and  liver.  (The  viscera  are  reduced 
in  size.) 

II.  Diagrammatic  Representation  of  the  Course  of  the  Depressor  Nerve  (Its  origin  from  the  Vagus  is  situated 
at  a  higher  level),  as  well  as  of  the  Accelerator  Branch  of  the  Sympathetic  Nerve  (of  the  cat). 


704  VAGUS    NERVE. 

3.  The  glossopharyngeal  is  the  sensory  nerve  for  the  posterior  third 
of  the  tongue,  the  anterior  aspect  of  the  epiglottis,  the  tonsils,  the  an- 
terior palatine  arches,  the  soft  palate  and  a  portion  of  the  pharynx. 
These  nerves  exert  an  inhibitory  influence  upon  the  act  of  deglutition 
and  that  of  respiration.     They  cause,  as  do  likewise  the  gustatory  fibers, 
reflex  secretion  of  saliva. 

4.  The  salivary  fibers  are  described  on  p.  259. 

5.  A  branch  accompanies  the  lingual  artery.     This  is  vasodilator  for 
the  posterior  third  of  the  tongue. 

Definite  pathological  observations  in  man  referable  to  pure  and  isolated 
affections  of  the  ninth  nerve  are  wanting. 

X.    VAGUS  NERVE. 

The  origin  of  the  vagus  in  connection  with  that  of  the  ninth  and  eleventh 
nerves  consists  of:  i.  A  sensory  nucleus,  constituted  of  small  cells,  situated  to 
the  dorsal  aspect  of  the  hypoglossal  nucleus  (Fig.  241).  2.  Other  fibers  of  origin 
arise  from  a  solitary  bundle  of  longitudinal  fibers  (Lenhossek's  bundle,  W.  Krause's 
respiratory  bundle)  situated  on  the  outer  side  of  the  nucleus  and  extending  down- 
ward into  the  cervical  enlargement  of  the  spinal  cord.  3.  Finally,  a  motor  nucleus 
(nucleus  ambiguus),  situated  further  inward  and  a  continuation  of  the  anterior 
horn  of  the  spinal  cord,  gives  off  fibers  from  either  side. 

The  vagus  leaves  the  medulla  oblongata  behind  the  ninth  nerve  (Fig.  242) 
by  means  of  from  10  to  15  filaments  between  the  pyramidal  and  lateral  columns 
and  forms  at  the  jugular  foramen  the  jugular  ganglion,  which,  together  with  the 
gangliform  plexus,  behaves  like  a  spinal  ganglion  with  reference  to  the  fibers  of 
origin.  Its  branches  contain  fibers  of  varied  function. 

The  sensory  meningeal  branch  (from  the  jugular  ganglion),  in  as- 
sociation with  vasomotor  fibers  from  the  sympathetic,  follows  the  pos- 
terior branch  of  the  middle  meningeal  artery,  and  also  sends  branches 
to  the  occipital  and  transverse  sinuses. 

In  cases  of  marked  cerebral  congestion  and  inflammation  of  the  dura  mater 
irritation  of  this  branch  may  cause  vomiting. 

The  auricular  branch  (Fig.  246,  au),  from  the  jugular  ganglion,  re- 
ceives a  communication  from  the  petrous  ganglion  of  the  ninth  nerve ; 
then,  passing  through  the  mastoid  canal,  it  crosses  the  path  of  the  facial 
(7),  which  it  is  supposed  to  supply  with  sensory  fibers.  In  its  further 
course,  it  gives  sensory  fibers  to  the  posterior  portion  of  the  auditory  canal 
and  the  adjacent  portion  of  the  auricle.  A  branch  passes  with  the  posterior 
auricular  nerve  of  the  facial,  to  which  it  gives  muscle-sense  fibers  for  the 
muscles. 

Irritation  of  this  branch,  as  by  inflammation  or  from  the  presence  of 
foreign  bodies  in  the  external  auditory  canal,  may  cause  vomiting.  Irritation  in 
the  depth  of  the  external  auditory  canal  in  the  area  of  innervation  of  the  auricular 
branch  also  excites  reflex  cough,  less  commonly  symptoms  of  cardiac  inhibition. 
Finally  irritation  of  the  auricular  nerve  causes  reflex  contraction  of  the  vessels 
of  the  ear. 

The  anastomotic  branches  of  the  vagus  are  as  follows :  i .  A  branch 
that  connects  the  petrous  ganglion  of  the  ninth  directly  with  the  jugular 
ganglion  of  the  tenth  nerve.  Its  function  is  unknown.  2.  Just  above 
the  gangliform  plexus  of  the  vagus,  the  entire  inner  half  of  the  accessory 
nerve  enters  the  trunk  of  the  vagus.  This  transmits  to  the  latter  motor 
fibers  for  the  larynx  (through  the  recurrent  branch  of  the  vagus),  for 
the  pharynx  (?)  and  the  cervical  portion  of  the  esophagus  and  the 
stomach  (?),  as  well  as  the  cardiac  inhibitory  fibers.  3.  In  the  gangli- 


VAGUS    NERVE.  705 

form  plexus,  nbers  of  unknown  function  from  the  hypoglossal,  the 
superior  cervical  ganglion  of  the  sympathetic  and  the  cervical  plexus 
unite  with  the  vagus. 

According  to  Grossmann  the  fibers  for  the  cricothyroid  arise  in  rabbits  from 
the  glossopharyngeal,  as  do  also  the  Hering-Breuer  pulmonary  fibers.  According 
to  Grabower,  the  fibers  for  the  muscles  of  the  larynx  come  from  the  vagus  itself. 
According  to  Kreidl,  the  fibers  for  the  esophagus  are  situated  in  the  glossopharyn- 
geal in  the  rabbit,  but  enter  the  trunk  of  the  vagus. 

To  the  pharyngeal  plexus  the  vagus  (2)  sends  from  the  upper 
portion  of  the  gangliforrn  plexus  one  or  two  branches  that  at  the  level 
of  the  middle  constrictor  of  the  pharynx,  together  with  the  pharyngeal 
branches  of  the  ninth  nerve  and  the  superior  cervical  ganglion  of  the 
sympathetic,  form  the  pharyngeal  plexus  at  the  side  of  the  ascending 
pharyngeal  artery.  The  posterior  portion  of  the  trunk  of  the  vagus 
itself  supplies  through  this  plexus  the  three  constrictors  of  the  pharynx, 
as  well  as  the  palatoglossus  and  palatopharyngeus  muscles  (according 
to  observations  on  the  ape)  .with  motor  fibers.  Filaments  from  the 
middle  of  the  anterior  accessory  root  innervate  the  elevator  of  the  veil 
of  the  palate.  Sensory  fibers  from  the  vagus  to  the  pharyngeal  plexus 
supply  the  pharynx  from  a  point  below  the  level  of  the  veil  of  the  palate 
downward.  These  fibers  stimulate  reflexly  the  constrictors  of  the 
pharynx  in  the  act  of  deglutition.  In  case  of  considerable  abnormal 
irritation  they  are  also  capable  of  inducing  vomiting.  The  sympathetic 
fibers  of  the  pharyngeal  plexus  give  vasomotor  fibers  to  the  vessels  of 
the  pharynx.  The  pharyngeal  branches  of  the  ninth  nerve  are  described 
on  p.  703. 

The  vagus  sends  two  branches  to  the  larynx:  (a)  The  superior 
laryngeal  nerve  (3),  which  after  receiving  a  vasomotor  filament  from  the 
superior  cervical  ganglion  of  the  sympathetic  divides  into  an  external 
and  an  internal  branch,  (i)  The  external  branch  receives  from  the  same 
source  vasomotor  fibers  (which  later  on  accompany  the  superior  thyroid 
artery)  and  it  supplies  the  cricothyroid  muscle  with  motor  fibers  (which 
in  the  ape  are  derived  from  the  posterior  fibers  of  the  trunk  of  the 
vagus)  and  the  inferior  lateral  portion  of  the  laryngeal  mucous  mem- 
brane with  sensory  fibers.  (2)  The  internal  branch  gives  off  only  sensory 
fibers:  to  the  glottoepiglottic  fold  and  the  adjacent  lateral  portion  of 
the  root  of  the  tongue,  to  the  aryepiglottic  fold  and  to  the  entire  interior 
of  the  larynx  (in  so  far  as  it  is  not  supplied  by  the  external  branch). 
Irritation  of  these  sensory  branches  causes  reflex  cough,  although  irrita- 
tion of  the  vocal  bands  does  not,  but  only  that  in  the  vicinity  of  the 
respiratory  glottis.  The  same  effect  is  brought  about  through  the  sen- 
sory branches  of  the  vagus  to  the  trachea,  particularly  at  the  point  of 
bifurcation,  also  through  those  of  the  bronchial  mucous  membrane,  as 
well  as  those  of  the  pulmonary  tissue  and  of  the  pleura  when  altered 
by  disease  (inflammation).  The  cough-center  is  supposed  to  be  situ- 
ated on  either  side  of  the  raphe  in  the  neighborhood  of  the  ala  cinerea. 
Severe  attacks  of  coughing  may  be  attended  with  vomiting  in  conse- 
quence of  irritation  of  the  pharynx  or  as  an  associated  movement. 
Hedon  found  in  the  superior  laryngeal  nerve  vasodilator  and  secretory 
fibers  for  the  mucous  membrane  of  the  larynx  and  Kokin  in  both  laryn- 
geal nerves  secretory  fibers  for  the  mucous  glands  of  the  larynx  and  the 
trachea. 
45 


yo6 


VAGUS    NERVE. 


It  is  a  noteworthy  fact  that  in  some  persons  coughing  can  be  induced  by 
irritation  of  even  remotely  situated  sensory  nerves,  for  example  of  the  external 
auditory  canal  (auricular  branch  of  the  vagus) ,  the  nasal  mucous  membrane 
(trigeminal  cough  of  Schadewald),  the  liver,  the  spleen,  the  stomach  and  intestine, 
the  uterus,  the  mammary  glands,  the  ovaries,  and  even  some  portions  of  the  skin. 
Whether  under  such  circumstances  the  perhaps  abnormally  irritable  cough-center 
is  directly  stimulated  centripetally  through  the  irritated  nerve,  or  whether  in 
consequence  of  the  nerve-irritation  the  vascularization  and  the  secretion  of  the 
respiratory  organs  are  first  affected,  and  in  turn  cause  the  cough-reflex, 
must  be  submitted  to  future  investigation,  although  to  the  writer  the  latter 
appeared  the  more  probable. 

The  cough  induced  through  irritation  of  the  trachea  and  the  bronchi  (dog, 
cat)  occurs  immediately  and  persists  as  long  as  the  irritation  continues.  On 
irritation  of  the  larynx  there  occurs  first  inhibition  of  breathing,  with  accompany- 
ing movements  of  deglutition,  cough  occurring  only  on  cessation  of  the  irritation. 

The  superior  laryngeal  contains  further  centripetal  fibers,  irritation  of  which 
causes  arrest  of  breathing,  with  closure  of  the  glottis;  and  also  fibers  that  excite 
movements  of  swallowing;  and,  finally,  centripetal  fibers,  irritation  of  which 
stimulates  the  vasomotor  center  to  increased  activity,  therefore  designated  pressor 
fibers. 

(6)  The  inferior  laryngeal  or  recurrent  nerve  passes  on  the  left  around 
the  arch  of  the  aorta,  on  the  right  around  the  subclavian  artery,  and, 
ascending  in  the  interval  between  the  trachea  and  the  esophagus,  gives 
off  motor  fibers  to  these  structures  and  the  inferior  constrictor  of  the 
pharynx,  and  then  passes  to  the  larynx,  to  whose  muscles  it  distributes 
motor  fibers  (with  the  exception  of  the  cricothyroid  muscle).  In  apes 
these  fibers  are  derived  from  the  most  posterior  fibers  of  the  internal 
branch  of  the  accessory  nerve.  The  muscles  of  the  epiglottis  (aryepi- 
glottic  and  thyroepiglottic)  are  innervated  at  times  by  the  superior  and 
at  other  times  by  the  inferior  laryngeal  nerve.  Irritation  of  the  latter 
nerve  also  exerts  an  inhibitory  effect  upon  the  respiratory  center. 

The  fibers  of  the  nerves  that  subserve  the  respiratory  functions  pass  isolated 
from  those  that  control  the  phonetic  activity  of  the  muscles,  from  the  origin  to 
the  muscle.  From  the  superior  laryngeal  nerve  an  anastomotic  branch  passes  to 
the  inferior  laryngeal  (the  so-called  anastomosis  of  Galen) ,  and  it  gives  off  sensory 
branches  to  the  upper  half  of  the  trachea,  to  the  larynx,  perhaps  also  to  the  eso- 
phagus, and  the  muscle-sense  fibers  (?)  for  the  laryngeal  muscles  supplied  by  the 
recurrent  nerve. 

Exner  describes  a  middle  laryngeal  nerve,  derived  from  the  pharyngeal  nerve 
of  the  vagus  and  its  anastomoses  in  the  pharyngeal  plexus,  which  takes  part 
in  the  innervation  of  the  cricothyroid  muscle  (present  only  in  rabbits)  and  the 
anterior  and  inferior  portions  of  the  laryngeal  mucous  membrane.  According  to 
Onodi  fibers  from  the  inferior  cervical  and  the  superior  thoracic  ganglion  of  the 
sympathetic  take  part  in  the  innervation  of  the  laryngeal  muscles.  On  the  other 
hand,  the  accessory  is  not  believed  to  participate  in  this. 

Irritation  of  the  superior  laryngeal  nerves  is  painful  and  causes  movement  of 
the  cricothyroid  muscles,  as  well  as,  reflexly,  of  the  remaining  laryngeal  muscles. 
Division  of  these  nerves  is  said  to  cause  slight  slowing  of  the  respiration  in  conse- 
quence of  the  paralysis  of  the  cricothyroids.  At  the  same  time  the  voice  in  the 
dog  becomes  deeper  and  rough  in  consequence  of  deficient  tension  of  the  vocal 
bands.  Further,  the  larynx  is  anesthetic,  so  that  fluid  from  the  mouth  and 
particles  of  food  (without  causing  reflex  closure  of  the  larynx  or  coughing)  gain 
entrance  into  the  trachea  and  the  lungs,  in  consequence  of  which  so-called  deglu- 
tition-pneumonia results,  with  a  fatal  termination. 

Irritation  of  the  recurrent  nerves  causes  spasm  of  the  glottis.  Division 
paralyzes  the  laryngeal  muscles  supplied  by  these  nerves  and  the  voice  becomes 
toneless  and  rough  (in  the  pig,  in  man,  the  dog,  the  cat,  while  rabbits  retain  their 
clear,  shrill  voice).  The  glottis  is  small.  With  each  inspiration  the  vocal  bands 
approach  each  other  considerably  in  their  anterior  portions.  In  expiration  they 
are  blown  apart.  Therefore,  inspiration  (particularly  in  young  individuals  having 
a  narrow  respiratory  glottis)  is  labored  and  noisy,  while  expiration  takes  place 


VAGUS    NERVE.  707 

with  perfect  ease.  In  the  course  of  a  few  days  the  animal  (carnivora)  becomes 
quieter,  breathes  less  laboriously  and  the  passive,  flabby  movement  of  the  vocal 
bands  disappears.  If,  however,  in  the  further  course  of  events,  even  after  a 
considerable  time,  the  animal  is  actively  stimulated,  there  occurs  in  the  presence 
of  the  marked  need  for  air  an  attack  of  extreme  dyspnea,  which  subsides  only 
when  the  animal  (dog)  gradually  becomes  quieter.  In  consequence  of  the  paralysis 
of  the  larynx,  foreign  bodies  may  gain  entrance  into  the  trachea,  particularly  as 
the  paralysis  of  the  uppermost  portion  of  the  esophagus  renders  swallowing  diffi- 
cult. In  this  way  bronchopneumonia  may  develop. 

The  depressor  nerve,  which  in  rabbits  arises  from  the  trunk  of  the 
superior  laryngeal  and  occasionally,  with  a  second  root  from  the  trunk 
of  the  vagus  itself,  passes  with  the  sympathetic  downward  in  the  neck, 
descends  into  the  stellate  ganglion  and  enters  thence  into  the  cardiac 
plexus.  It  is  a  centripetal  nerve,  irritation  of  which,  and  also  of  its 
central  stump,  diminishes  the  energy  of  the  vasomotor  center,  so  that 
the  blood-pressure  falls.  At  the  same  time  this  irritation  is  conveyed 
to  the  cardiac  inhibitory  center,  so  that  the  number  of  pulsations  of  the 
heart  diminishes. 

The  depressor  nerve  is  present  also  in  the  cat  (Fig.  246,  77),  the  hedgehog, 
the  rat,  and  the  mouse.  In  the  horse  and  in  man  fibers  analogous  to  the  de- 
pressor nerve  pass  back  again  into  the  trunk  of  the  vagus.  Also  in  the  rabbit 
fibers  having  a  depressing  effect  may  pass  in  the  trunk  of  the  vagus  itself.  The 
depressor  fibers  of  the  rabbit  enter  the  oblongata  through  the  upper  root-filaments 
of  the  vagus.  The  inhibitory  reflex  for  the  heart  is  effective  only  upon  the  same 
side. 

The  branches  of  the  vagus  for  the  cardiac  plexus  (g,  /),  as  well  as 
the  latter  itself,  have  already  been  described.  They  contain  the  in- 
hibitory fibers  for  the  movement  of  the  heart  (they  are  derived  from 
the  most  anterior  root-filaments  of  the  inner  branch  of  the  accessory 
nerve),  also  sensory  fibers  for  the  heart  (in  the  frog  and  in  part  in 
mammals).  Finally,  the  heart  receives  also  through  the  vagus  a 
portion  of  its  accelerator  fibers ;  feeble  irritation  of  the  vagus  causes  at 
times  acceleration  of  the  heart-beat.  In  cases  of  poisoning  with  atropin 
and  nicotin,  which  paralyzes  the  inhibitory  fibers,  irritation  of  the  vagus 
causes  acceleration  of  the  heart -beat.  The  following  experiment  tends 
to  support  the  existence  of  vasomotor  fibers  in  the  cardiac  branches : 
Persistent  irritation  of  the  peripheral  stump  of  the  vagus  causes  ex- 
travasation of  blood  into  the  endocardium  (long-continued  poisoning 
with  digitalin  or  strychnin  has  a  similar  effect),  in  consequence  of  spas- 
modic contraction  of  the  endocardial  vessels,  with  secondary  paralytic 
relaxation  and  rupture. 

The  pulmonary  branches  of  the  vagus  are  grouped  together  in  the 
anterior  and  posterior  pu  monary  plexuses.  The  former  supplies 
sensory  and  motor  branches  to  the  trachea  and  passes  then  on  the 
anterior  surface  of  the  bronchial  ramifications  into  the  lungs  (L).  The 
posterior  plexus,  formed  of  from  three  to  five  large  branches  derived 
from  the  trunk  of  the  vagus  at  the  side  of  the  bifurcation,  anastomoses 
with  branches  from  the  inferior  cervical  ganglion  of  the  sympathetic  and 
with  fibers  of  the  cardiac  plexus,  and,  after  fibers  from  each  side  have 
interchanged  by  decussation,  passes  with  the  branches  of  the  bronchial 
tree  into  the  lungs.  The  pulmonary  branches  are  supplied  with  gan- 
glion-cells, as  are  also  the  larynx,  the  trachea,  and  the  bronchi.  From 
the  pulmonary  plexus  filaments  pass  to  the  pericardium  and  the  superior 
vena  cava. 


708  VAGUS    NERVE. 

The  function  of  the  pulmonary  branches  of  the  vagus  is  a  varied 
one :  ( i )  They  supply  the  motor  branches  for  the  unstriated  muscles  of 
the  entire  bronchial  tree.  (2)  They  supply  the  sensory  fibers  (exciting 
cough)  to  the  entire  bronchial  tree  and  the  lungs.  (3)  They  supply, 
in  smaller  part,  vasomotor  nerves  to  the  pulmonary  vessels,  although 
these  are  in  largest  part,  if  not  wholly,  derived  from  the  anastomosis 
with  the  sympathetic  (in  animals  from  the  superior  thoracic  ganglion). 
(4)  They  contain,  in  the  ape  situated  in  the  posterior  portion  of  the 
trunk  of  the  vagus  itself,  centripetal  fibers  passing  from  the  parenchyma 
of  the  lungs  to  the  medulla  oblongata,  irritation  of  which  stimulates 
the  respiratory  center.  Division  of  both  vagi  is,  accordingly,  followed 
by  marked  reduction  in  the  number  of  respirations,  which  at  the  same 
time  are  deepened,  so  that  the  animals  for  a  time  exchange  the  normal 
volume  of  air  containing  normal  amounts  of  oxygen  and  carbon  dioxid. 
Irritation  of  the  central  stumps  of  the  vagi  causes  acceleration 
of  respiration.  This  labored  and  embarrassed  breathing  is  explained 
as  due  to  elimination  of  these  reflex-stimulating  fibers,  which  main- 
tain the  normal  easy  play  of  reflex  breathing.  After  division  of 
the  nerves,  the  stimulation  of  the  respiratory  movements  must  take 
place  in  the  medulla  oblongata  itself.  (5)  They  contain  centripetal 
fibers,  irritation  of  which  has  a  depressant  effect  upon  the  vasomotor 
center,  as  shown  by  fall  of  the  blood-pressure  on  forced  expiratory 
pressure.  (6)  Also  fibers,  irritation  of  which  has  an  inhibitory  influence 
upon  the  cardiac  inhibitory  fibers  of  the  vagus,  thus  accelerating 
the  pulse.  Simultaneous  irritation  of  the  last  two  sets  of  fibers  men- 
tioned is  capable  of  altering  the  rhythm  of  the  pulse. 

Carbon  dioxid,  as  well  as  the  vapors  of  ammonia  and  chloroform,  introduced 
into  the  air-passages,  cause  (from  the  mucous  membrane  of  the  large  bronchi) 
inspiration,  while,  acting  upon  the  entrance  to  the  respiratory  tract  situated  above 
the  trachea,  they  cause  reflex  expiration. 

Pneumonia  after  section  of  both  vagi  has  attracted  the  interest  of  investigators 
since  the  time  of  Valsalva  (died  1723),  Morgagni  (1740)  and  Legallois  (1812). 
In  explanation  of  this  condition  the  following  facts  are  to  be  taken  into  con- 
sideration: (a)  In  the  first  place,  section  of  both  vagi  is  attended  by  loss  of 
the  motility  of  the  larynx,  as  well  as  of  the  sensibility  of  the  larynx  (if  the  section 
has  been  made  above  the  origin  of  the  superior  laryngeal  nerve),  the  trachea, 
the  bronchi,  and  the  lungs.  Therefore,  the  larynx  fails  to  close  during  the  act  of 
swallowing,  and  reflex  closure  of  the  larynx  when  foreign  bodies  threaten  to  enter 
(fluids  in  the  mouth,  particles  of  food,  irritating  gases)  does  not  take  place,  and 
reflex  cough  for  the  expulsion  of  substances  that  have  entered  is  suppressed. 
Thus,  foreign  bodies  enter  the  lung  without  hindrance,  and  all  the  more  readily 
as  the  associated  paralysis  of  the  esophagus  permits  the  food  to  remain  lodged 
in  this  tube  for  a  time,  and  thus  readily  enter  the  larynx.  That  herein  resides  an 
essential  exciting  factor  for  the  inflammatory  process  Traube  was  able  to  show  by 
demonstrating  that  the  inflammation  could  be  prevented  by  permitting  the  ani- 
mals to  breathe  through  a  tracheal  cannula  introduced  through  an  external  wound 
in  the  neck.  If,  however,  only  the  motor  filaments  of  the  recurrent  nerves  were 
divided,  and  the  esophagus  was  ligated,  so  that  foreign  bodies  necessarily  entered  the 
air-passages,  so-called  foreign-body  pneumonia  resulted  in  an  analogous  manner, 
with  a  fatal  termination.  (6)  A  second  factor  resides  in  the  fact  that  in  conse- 
quence of  the  extensive  and  labored  snoring  and  noisy  breathing,  the  lungs  must 
become  hyperemic,  as  during  the  protracted  and  marked  dilatation  of  the  chest 
the  pressure  of  the  air  in  the  lungs  must  be  abnormally  low.  As  a  result,  serous 
transudates  (pulmonary  edema)  result,  or  even  extravasation  of  blood  and  dilata- 
tion of  the  pulmonary  vesicles  at  the  margins  of  the  lungs.  Through  this  influence 
the  entrance  of  foreign  bodies,  particularly  of  fluid,  into  the  glottis  is  facilitated. 
A  tracheal  cannula  introduced  from  without  will  likewise  prevent  the  inflammation 
under  these  circumstances,  (c)  Perhaps  partial  paralysis  of  the  pulmonary 


VAGUS    NERVE.  709 

vasomotors  takes  some  part  in  the  inflammation,  as  the  hyperemia  thus  induced 
affords  an  inviting  field  for  the  complication,  (d)  Finally,  it  is  still  to  be  determined 
whether  trophic  fibers  in  the  vagus  subserve  the  normal  preservation  of  the  lung- 
tissue.  According  to  Michaelson  the  pneumonia  developing  immediately  after 
section  of  the  vagus  is  seated  principally  in  the  middle  and  lower  lobes,  while  the 
catarrhal  inflammation  that  develops  more  slowly  after  section  of  the  recurrent 
nerves  is  situated  usually  in  the  upper  lobes.  Rabbits  die  amid  symptoms  of  pneu- 
monia as  a  rule  within  twenty-four  hours;  when  the  precautions  mentioned  are 
taken,  in  the  course  of  several  days.  Dogs  may  survive  for  a  considerable  time.  It 
is  doubtful  whether  the  paralysis  of  the  intra-abdominal  fibers  of  the  vagus  favors 
the  occurrence  of  death.  In  rabbits,  extirpation  of  the  ninth,  tenth,  and  twelfth 
nerves  on  one  side  causes  death  from  pneumonia.  After  section  of  both  vagi  in 
rabbits  acute  fatty  degeneration  of  the  heart  and  abnormal  friability  of  the  smaller 
coronary  vessels  develop  in  consequence  of  loss  of  the  trophic  functions  of  the 
vagus.  In  birds  the  lungs  remain  free  from  inflammation  after  section  of  both 
vagi,  because  the  upper  portion  of  the  larynx  retains  its  faculty  of  reflex  closure. 
Nevertheless,  death  results  in  a  week  from  inanition  in  consequence  of  paralysis 
of  the  crop,  in  which  the  food  undergoes  putrefaction.  At  the  same  time  the 
heart  is  in  a  state  of  fatty  degeneration,  as  are  also  the  liver,  the  stomach,  and 
the  muscles.  According  to  Wassilieff  the  heart  exhibits  parenchymatous  swelling 
and  slight  waxy  degeneration.  In  ruminants  considerable  tympanitic  distention 
of  the  stomach  results,  because  eructation  is  impossible.  Frogs,  which  with  each 
inspiration  open  the  glottis,  which  is  closed  during  rest,  die  of  asphyxia  after  section 
of  the  trunks  of  the  vagi.  Section  of  the  pulmonary  branches  is  unattended  with 
injurious  effect.  If  the  vagi  are  divided  below  the  origin  of  the  recurrent  nerves 
the  lungs  remain  healthy  in  the  dog,  although  disorders  of  secretion  and  of  the 
movements  of  the  stomach  set  in.  As  a  result  putrefactive  decomposition  occurs 
in  the  stomach,  in  consequence  of  which  death  takes  place. 

The  esophageal  plexus  (r)  is  formed  by  branches  above  from  the 
inferior  laryngeal,  then  from  the  pulmonary  plexus,  and  below  from  the 
trunk  of  the  vagus  itself  (being  derived  from  the  posterior  root-fibers 
of  the  trunk).  The  plexus  endows  the  esophagus  with  motility  and  with 
indistinct  sensibility  (also  that  of  muscular  contraction)  only  in  its 
upper  portion  and  it  supplies  it  with  reflex  fibers. 

The  gastric  plexus  (o  o)  consists  of  the  anterior  (left)  extremity 
of  the  vagus,  which  also  sends  fibers  to  the  esophagus  and  passes  along 
the  lesser  curvature  and  in  part  sends  fibers  through  the  transverse 
fissure  to  the  liver.  The  posterior  (right)  vagus,  after  giving  off 
a  few  fibers  to  the  esophagus,  takes  part  in  the  formation  of  the  gastric 
plexus,  which  receives  sympathetic  fibers  at  the  pylorus.  The  vagi 
supply  the  stomach  with  motor  fibers,  derived  from  its  root  (not  from 
the  accessory  nerve) ,  and  also  inhibitory  or  relaxing  fibers  for  the  cardia. 
Further,  the  vagus  supplies  the  secretory  fibers  for  the  gastric  mucous 
membrane.  These  contain  vasomotor  fibers.,  for  division  of  the  trunks 
of  the  vagi  causes  hyperemia  of  the  mucous  membrane  of  the  stomach. 
The  gastric  fibers,  however,  receive  the  centripetal  filaments,  through 
which  the  secretion  of  saliva  is  stimulated.  Whether  also  vomiting  can 
be  excited  through  them  is  still  doubtful. 

After  section  of  both  vagi  below  the  diaphragm  death  results,  at  the  latest 
after  an  interval  of  three  months,  preceded  by  emaciation,  inflammatory  altera- 
tions in  the  mucous  membrane  of  the  stomach  and  perivascular  hyperplasia  in  the 
liver  and  in  the  kidneys. 

About  two-thirds  of  the  right  vagus,  however,  passes  at  the 
stomach  into  the  celiac  plexus  (m)  and  thence,  accompanying  the 
arteries,  to  the  liver,  the  spleen,  the  pancreas,  the  small  intestines,  the 
kidneys,  and  the  adrenal  glands.  The  influence  of  the  vagus  upon 
the  movements  of  the  intestine  has  been  discussed  in  the  considera- 


7io 


VAGUS    NERVE. 


tion  of  the  intestinal  nerves.  According  to  some  observers,  irritation 
of  the  vagus  causes  movements  in  the  small  as  well  as  in  the  large 
intestine.  Irritation  of  the  peripheral  stump  of  the  vagus  causes  in  the 
spleen  contraction  of  the  unstriped  muscular  fibers  in  the  capsule  and 
in  the  trabeculae  (in  the  dog  and  the  rabbit).  With  respect  to  the  kid- 
neys, irritation  of  the  vagus  at  the  cardia  causes  increased  secretion  of 
urine,  with  dilatation  of  the  renal  vessels  and  redness  of  the  blood  in 
the  renal  veins.  In  dogs  and  rabbits  a  number  of  vasomotor  fibers  are 
said  to  be  supplied  to  the  abdominal  viscera  by  the  vagus,  while  the 
overwhelming  majority  are  derived  from  the  splanchnic. 

The  trunk  and  the  branches  of  the  vagus  contain  also  fibers  (in 
part  already  mentioned),  irritation  of  which  acts  in  a  centripetal  direction 
upon  certain  nervous  stuctures: 

(a)  The  vasomotor  center  is  affected  through  (n)  pressor  fibers  (especially 
in  the  two  laryngeal  nerves) ,  irritation  of  which  causes  reflex  contraction  of  -the 
arteries  and  thus  increase  in  blood-pressure ;  (/?)  depressor  fibers  (in  the  depressor 
nerve  or  in  the  vagus  itself),  which  exert  a  contrary  effect.  This  subject  is  dis- 
cussed in  connection  with  the  vasomotor  center. 

(6)  The  respiratory  center  is  affected  through  (<•/)  accelerator  fibers  (pulmonary 
branches),  irritation  of  which  accelerates  the  respiration;  and  (/?)  inhibitory 
fibers  (in  the  two  laryngeal  branches),  irritation  of  which  inhibits  respiration. 
This  subject  is  discussed  in  connection  with  the  respiratory  center. 

(c)  The  cardio-inhibitory  system  is  influenced  through  fibers  in  the  trunk  of 
the  vagus,  irritation  of  which  acts  on  the  center  in  a  centripetal  direction  and 
places  the  heart  in  a  condition  of  diastolic  rest.     Irritation  of  the  central  stump 
of  the  vagus,  therefore,  causes  arrest  of  the  heart.      In  conformity  with  these  facts 
is  the  observation  of  Mayer  and  Pribram  that  sudden  dilatation  of  the  stomach 
causes  slowing  and  even  arrest  of  the  heart,  the  arteries  of  the  medulla  oblongata 
contracting  at  the  same  time  with  increase  in  blood-pressure. 

(d)  The  vomiting  center  is  excited  by  irritation  of  the  central  stump  of  the 
vagus  and  of  a  number  of  centripetal  fibers  of  the  vagus. 

(e)  The  secretion  of  the  pancreas  is  influenced  by  irritation  of  the  central  stump 
of  the  vagus,  the  secretion  being  arrested  in  this  way;   therefore,  probably  through 
the  intermediation  of  certain  pancreatic  nerves. 

(/)  According  to  Claude  Bernard  the  pulmonary  branches  contain  fibers, 
irritation  of  which  causes  reflex  increase  in  the  formation  of  sugar  in  the  liver, 
perhaps  through  the  intermediation  of  the  hepatic  branches  of  the  vagus;  for 
after  section  of  both  vagi  the  formation  of  glycogen  in  the  liver  ceases.  Con- 
versely, irritation  of  the  peripheral  stump  of  the  vagus  causes  an  increase  in  the 
formation  of  sugar  in  the  liver. 

The  various  branches  and  paths  of  the  vagus  possess  an  unequal  degree  of 
irritability.  If  irritation,  at  first  feeble,  be  applied  in  a  centrifugal  direction,  the 
muscles  of  the  larynx  move  first,  then  the  heart-beat  is  slowed.  If  the  central 
stump  is  stimulated  the  excito-respiratory  fibers  become  exhausted,  even  on  feeble 
irritation,  and  only  later  the  inhibito-respiratory  fibers.  According  to  Steiner, 
the  various  fibers  are  so  arranged  in  the  vagus  of  the  rabbit  that  the  centripetal 
are  situated  in  the  outer  and  the  centrifugal  in  the  inner  half  of  the  cervical  trunk. 

Pathological. — Irritation  or  paralysis  in  the  distribution  of  the  vagus  will 
present  a  varying  clinical  picture  accordingly  as  the  lesion  involves  the  entire 
trunk  or  only  individual  branches,  and  accordingly,  also,  as  the  affection  is  unilateral 
or  bilateral.  Paralysis  of  the  pharynx  and  the  esophagus,  which  is  generally  of 
central  or  at  least  intracranial  origin,  renders  difficult  or  abolishes  movements  of 
deglutition,  so  that  stagnation  in  the  esophagus,  entrance  of  foreign  bodies  into 
the  larynx,  dyspnea,  and  the  passage  of  food  into  the  nares  are  observed.  In  drink- 
ing, a  rumbling  murmur  is  at  times  audible  in  the  relaxed  tube  (deglutatio  sonora) . 
When  the  paralysis  is  incomplete,  the  act  of  swallowing  is  only  delayed  and  ren- 
dered difficult,  and  large  masses  of  food  are  most  -readily  swallowed.  Increased 
contraction,  even  spasmodic  constriction,  is  observed  in  association  with  the  symp- 
toms of  general  nervous  irritability. 

Spasm  of  the  muscles  of  the  larynx  causes  especially  spasmodic  closure  of  the 
glottis,  so-called  spasm  of  the  glottis.  The  latter  is  peculiar  to  childhood,  and 
occurs  paroxysmally  with  dyspnea,  tight,  whistling  inspiration,  with  which  twitch- 
ing of  the  muscles  of  the  eyes,  the  jaw,  the  fingers,  the  toes,  etc.,  may  be  associated. 


VAGUS    NERVE.  yil 

The  condition  is  probably  one  of  reflex  spasm  that  can  be  excited  from  the  sensory 
nerves  of  various  areas  (such  as  the  teeth,  the  intestine,  the  skin)  in  the  medulla 
oblongata.  Spasm  of  the  dilators  of  the  glottis  and  of  other  laryngeal  muscles 
also  occurs. 

Irritation  of  the  sensory  nerves  of  the  larynx,  as  is  well  known,  causes  cough. 
If  the  irritation  is  intense,  for  example  in  cases  of  whooping-cough,  the  Lbers  in 
the  laryngeal  nerves,  having  an  inhibitory  influence  upon  the  respiratory  center, 
may  also  be  irritated;  there  occurs  diminution  in  the  respiratory  frequency  and 
finally  arrest  of  respiration  with  relaxation  of  the  diaphragm;  in  the  presence 
of  the  most  intense  irritation,  spasmodic  arrest  in  expiration  occurs,  with  closure 
of  the  glottis,  even  for  as  long  as  fifteen  seconds.  The  condition  is  an  inhibitory 
neurosis  of  the  respiratory  apparatus.  Paralysis  of  the  laryngeal  nerves  causing 
alterations  in  the  voice  has  already  been  considered.  Paralysis  of  both  recurrent 
nerves,  due,  for  example,  to  stretching  in  consequence  of  dilatation  of  the  aorta 
and  the  innominate  artery,  is  attended  with  great  waste  of  air  as  a  result  of  the 
fruitless  efforts  at  phonation;  expectoration  is  rendered  difficult,  and  forcible 
'cough  impossible.  In  addition  severe  attacks  of  dyspnea  may  occur  on  exertion, 
entirely  like  those  that  can  be  induced  experimentally  in  animals.  The  increased 
irritability  of  hysterical  persons  is  associated  with  hyperesthesia  and  anesthesia 
of  the  larynx,  the  upper  air-passages,  aphonia,  a  tendency  to  vomiting,  a  slow 
and  irregular  heart-beat  as  signs  of  a  neurosis  of  the  vagus.  Attacks  of  extreme 
dyspnea  lasting  for  from  one-quarter  of  an  hour  to  several  hours  have  been  referred 
to  irritation  of  the  pulmonary  plexus,  which  is  supposed  to  cause  spasm  of  the 
bronchial  muscles,  bronchial  asthma.  Physical  examination  of  the  lungs  discloses 
in  addition  to  rhonchi,  no  indication  as  to  the  cause  of  the  severe  attack.  If  the 
condition  is  really  one  of  spasm,  this  is  probably  in  most  instances  of  reflex  origin, 
the  centripetal  nerves  of  the  respiratory  passages,  or  of  the  skin  (cold),  or  of  the 
genitalia  (sexual  asthma)  being  involved.  Landois,  however,  was  of  the  opinion 
that  in  many  cases  considered  as  instances  of  asthma,  the  condition  is  one  of 
transitory  paresis  of  the  pulmonary  nerves,  exerting  a  stimulating  effect  upon  the 
respiratory  center.  The  attack  would,  then,  be  a  reproduction  of  the  labored 
breathing  following  section  of  both  vagi.  Whether  the  acute  pulmonary  emphy- 
sema constantly  observed  in  connection  with  this  disease  is  due  to  irritation  or  to 
paralysis  of  the  muscular  fibers  in  the  lungs  is  as  yet  a  matter  of  doubt.  Ac- 
cording to  Biermer  this  is  due  to  slight  obstructions  to  expiration  in  the  small 
bronchi  that  are  more  readily  overcome  in  inspiration  than  in  expiration.  Such 
obstructions  comprise  catarrhal  swelling  of  the  mucous  membrane,  accumulation 
of  mucus  or  of  blood,  or  spasm  of  the  bronchi. 

Irritation  in  the  distribution  of  the  cardiac  branches  of  the  vagus  may,  by 
direct  excitation,  cause  attacks  of  diminished  or  even  temporarily  suspended  con- 
traction of  the  heart,  together  with  a  feeling  of  extreme  prostration  and  of  abolition 
of  the  functions  of  life,  occasionally  also  with  pain  in  the  precordium.  Such 
attacks  may  likewise  be  induced  reflexly  through  irritation  of  the  abdominal 
viscera,  in  conformity  with  the  percussion-experiment  of  Goltz.  Landois  first 
analyzed  these  symptoms  in  1865  on  the  lines  of  a  physiological  experiment  and 
designated  them  pneumogastric  or  reflex  angina  pectoris.  Extirpation  of  the 
larynx  is  occasionally  followed  by  circulatory  disturbances  that  may  eventually 
prove  fatal.  These  are  due  to  a  persistent  state  of  irritation  of  the  laryngeal 
nerves,  eventually  with  extension  to  the  vagus  itself.  Hennoch  and  Silbermann 
observed  slowing  of  the  heart  in  children  presenting  irritative  phenomena  referable 
to  the  stomach,  and  Landois,  intermission  of  the  heart-beat  even  in  adults.  Through 
the  same  reflex  action  a  derangement  in  the  respiratory  functions  of  the  vagus 
that  Hennoch  has  designated  dyspeptic  asthma  may  be  brought  about.  A  similar 
condition  may  be  brought  about  reflexly  also  through  other  sensory  nerves  (uterine 
asthma) .  Rarely,  intermittent  paralysis  of  the  cardiac  branches  of  the  vagus  is 
attended  with  marked  acceleration  of  the  heart-beat,  up  to  between  160  and  240 
beats,  the  rhythm^and  the  strength  at  times  exhibiting  great  irregularity,  and  dysp- 
nea in  part  setting  in  at  the  same  time.  Under  such  circumstances  a  careful 
analysis  is  necessary  in  each  case  in  order  to  determine  to  what  extent  irritation 
of  the  heart-muscle,  the  heart-centers  or  the  accelerator  cardiac  fibers  are  con- 
cerned. Little  of  a  trustworthy  nature  is  known  with  regard  to  abnormal  affec- 
tions of  the  intra-abdominal  fibers  of  the  vagus.  If  the  trunks  of  the  vagi  or  their 
centers  are  paralyzed,  the  most  conspicuous  symptom  is  labored,  deep,  slow  breath- 
ing, exactly  as  occurs  after  section  of  both  vagi. 


712 


ACCESSORY    NERVE    OF    WILLIS. 


XI.     ACCESSORY  NERVE  OF  WILLIS. 


The  single  elongated  nucleus  of  origin  (Fig.  241)  comprises  the  dorsolateral 
group  of  cells  of  the  anterior  horn  of  the  cervical  cord,  which  begins  below  at  the 
level  of  the  seventh  cervical  nerve  and  extends  upward  without  interruption  in  the 
medulla  oblongata  to  the  upper  extremity  of  the  pyramidal  decussation.  The 
nucleus  of  origin  approaches  at  its  highest  point  the  hypoglossal  nucleus,  then 
is  situated  above  the  first  cervical  nerve  in  the  middle  of  the  anterior  horn, 
next  passes  laterally,  and  between  the  second  and  fourth  nerves  is  situated  at 
the  lateral  margin  of  the  anterior  horn.  Still  further  downward,  to  below  the 
sixth  cervical  nerve,  it  is  situated  at  the  base  of  the  lateral  horn.  All  fibers 
arise  from  the  ganglia  as  neurites.  From  the  cortical  center  on  the  opposite  side 
there  must  pass  to  the  nucleus  fibers  through  which  voluntary  stimulation  of  the 
motor  fibers  is  effected. 

The  fibers  pass  upward  in  the  lateral  column  of  the  spinal  cord  and  leave  the 
latter  in  several  bundles  between  the  anterior  and  posterior  cervical  nerve-roots. 
Then  the  root-fibers  that  ascend  through  the  great  occipital  foramen  come  together 
without  uniting  in  the  neighborhood  of  the  jugular  foramen  and  form  the  two 
branches  of  the  nerve.  Of  the  latter  the  inner  enters  wholly  into  the  gangliform 
plexus  (Fig.  246)  and  supplies  the  vagus  with  most  of  its  motor  fibers  and  also 
its  cardiac  inhibitory  fibers.  In  man,  accordingly,  total  paralysis  of  the  accessory 
nerve  is  attended  with  immobility  of  the  corresponding  half  of  the  larynx  and 
soft  palate. 

According  to  Kreidl  the  inhibitory  fibers  for  the  heart  are  situated  in  the 
most  anterior  root-bundles  of  the  inner  branch  of  the  accessory  nerve.  If  these 
roots  are  divided,  the  cardiac  inhibitory  fibers  undergo  degeneration.  If  the 
trunk  of  the  vagus  in  the  neck  is  irritated  four  or  five  days  after  the  operation  the 
cardiac  inhibitory  action  is  no  longer  exhibited. 

The  external  branch  of  the  accessory  nerve  is  derived  from  the  spinal 
portion  of  the  nucleus.  This  anastomoses  with  sensory  filaments  from 
the  posterior  root  of  the  first,  less  commonly  also  of  the  second  cervical 
nerve,  which  supply  muscle-sense  fibers  to  it.  It  then  passes  backward 
over  the  transverse  process  of  the  atlas  and  terminates  as  a  motor  nerve 
in  the  sternocleidomastoid  and  trapezius  muscles  (Fig.  246).  The  latter 
large  muscle  receives,  however,  motor  filaments  for  its  acromial  portion 
from  the  cervical  plexus. 

The  external  branch  anastomoses  also  with  several  cervical  nerves.  Either 
these  fibers  take  part  in  the  innervation  of  the  muscles  named,  or  the  accessory 
nerve  returns  to  them,  in  part,  the  sensory  filaments  received  from  the  posterior 
roots  of  the  two  uppermost  cervical  nerves,  which  then  constitute  the  cuta- 
neous branches  of  these  cervical  nerves. 

Pathological. — Irritation  of  the  external  branch  causes  clonic  and  tonic  spasm 
of  the  muscles  named,  usually  upon  one  side.  If  the  branch  for  the  sternocleido- 
mastoid is  alone  affected,  the  head  responds  to  the  traction  of  this  muscle  in 
the  presence  of  clonic  spasm.  If  the  disorder  is  bilateral,  the  traction  is  usually 
alternating;  much  less  commonly  the  action  is  bilateral;  so  that  the  head  executes 
a  nodding  movement.  In  the  presence  of  clonic  spasm  of  the  trapezius,  the  head 
is  drawn  backward  and  to  the  side;  the  scapula  generally  follows  the  traction  of 
the  bundle  of  this  great  muscle  that  is  most  severely  involved.  Tonic  spasm  of 
the  sternomastoid  causes  the  characteristic  position  of  caput  obstipum  (spasticum) 
—-spasmodic  wry-neck.  Similar  spasm  of  the  trapezius  usually  involves  only  indi- 
vidual portions  of  the  muscle,  which  then  naturally  cause  special  positions  of  the 
head  or  of  the  scapula.  Irritation  of  the  root  causes  at  the  same  time  spas- 
modic movements  of  the  muscles  of  the  larynx  and  of  the  uvula.  f 

Paralysis  of  one  sternomastoid  causes  the  head  to  be  turned  toward  the  opposite 
side  by  the  preponderant  action  of  the  muscle  of  that  side  (paralytic  torticollis} . 
Paralysis  of  the  trapezius  is  usually  confined  to  individual  portions  of  the  muscle. 
Paralysis  of  the  entire  accessory  trunk,  principally  in  consequence  of  central  pro- 
cesses, gives  rise,  in  addition  to  paralysis  of  the  sternocleidomastoid  and  the  tra- 
pezius, also  to  paralysis  of  the  motor  branches  of  the  vagus  previously  mentioned. 
Bilateral  paralysis  is  extremely  rare  and  is  said  to  be  attended  with  acceleration 
of  the  heart-beat. 


HYPOGLOSSAL    NERVE.       THE    SPINAL    NERVES.  713 

XII.   HYPOGLOSSAL  NERVE. 

The  elongated  nucleus  of  origin  of  the  hypoglossal  nerve  consists  of  large 
cells,  and  is  a  continuation  of  the  anterior  horn  of  the  spinal  cord.  It  is  situated 
in  the  depth  of  the  lowermost  portion  of  the  floor  of  the  fourth  ventricle.  It 
receives  anastomotic  fibers  from  the  cerebral  cortex  of  the  opposite  side.  The 
nuclei  of  both  sides  are  connected  by  a  commissure. 

The  nerve  arises  as  a  bundle  of  neurites  of  from  ten  to  fifteen  filaments,  and 
makes  its  exit  in  a  direction  parallel  with  that  of  the  anterior  roots  of  the  spinal 
nerves  (Fig.  242).  In  its  development  the  hypoglossal  shows  itself  to  be  in  part 
a  spinal  nerve. 

Purely  motor  at  its  root,  the  hypoglossal  is  the  motor  nerve  of  all 
of  the  muscles  of  the  tongue,  including  the  geniohyoid  and  thyrohyoid. 
The  trunk  of  the  hypoglossal  nerve  anastomoses  with :  i .  The  superior 
cervical  ganglion  of  the  sympathetic,  through  which  it  receives  vaso- 
motor  fibers,  for  division  of  the  hypoglossal  (together  with  that  of  the 
lingual)  is  followed  by  redness  of  the  corresponding  half  of  the  tongue. 
2.  Muscle-sense  fibers  enter  the  hypoglossal  from  the  gangliform  plexus 
and  from  the  small  lingual  branch  of  the  vagus,  also  from  anastomoses 
with  the  cervical  nerves  and  through  those  with  the  lingual  beneath  the 
tongue.  After  division  of  the  lingual  nerve  the  tongue  still  possesses 
dull  sensibility.  3.  The  loop  of  the  hypoglossal  nerves  anastomoses 
with  the  two  upper  cervical  nerves.  These  anastomoses  pass  further 
through  the  descending  branch  (through  which  also  muscle-sense  fibers 
from  the  lingual  descend)  as  motor  branches  for  the  sternohyoid,  omo- 
hyoid  and  sternothyroid.  Irritation  of  the  roots  of  the  hypoglossal 
affects  the  muscles  named  only  rarely  and  in  slight  degree. 

Division  of  both  hypoglossal  nerves  paralyzes  the  tongue.  Dogs  are  no  longer 
able  to  drink  and  they  bite  the  flabby,  pendulous  tongue.  Frogs,  which  catch 
their  prey  with  the  tongue,  must  starve;  in  hanging  out  of  the  mouth  the  tongue 
prevents  closure  of  this  cavity  and  as  a  result  the  animals  die  from  asphyxia, 
because  they  are  able  to  pump  air  into  the  lungs  only  when  the  mouth  is  closed. 

Pathological. — Paralysis  of  the  hypoglossal  nerve  (glossoplegid)  is  generally 
of  central  origin,  and  it  causes  derangement  of  speech.  The  deviation  of  the 
tongue  in  case  of  unilateral  paralysis  is  described  on  p.  276.  Paralysis  of  the 
tongue  renders  chewing  difficult,  prevents  formation  of  the  bolus  and  swallowing 
in  the  mouth.  In  consequence  of  deficiency  in  the  friction-movement  of  the 
tongue,  the  sense  of  taste  is  impaired.  The  singing  of  high  notes  and  of  falsetto 
notes,  in  the  production  of  which  special  positions  of  the  tongue  appear  to  be 
necessary,  is  interfered  with. 

Spasm  of  the  tongue,  causing  aphthongia,  is  generally  of  reflex  origin,  and.  in 
any  event,  is  extremely  rare.  Cases  of  idiopathic  spasm  of  the  tongue  have  also 
been  described,  the  tongue  being  moved  with  great  violence.  The  seat  of  irritation 
has  been  either  in  the  cerebral  cortex  or  in  the  medulla  oblongata. 

THE  SPINAL  NERVES. 

The  thirty-one  spinal  nerves  are  connected  with  the  spinal  cord  by  means  of 
two  roots:  The  anterior  roots  arise  as  neurites  of  the  ganglia  of  the  anterior  horns; 
the  posterior  roots  have  in  reality  grown  into  the  spinal  cord  from  without.  They 
arise  from  the  pear-shaped  bipolar  cells  of  the  ganglia  of  the  posterior  roots,  one 
fiber  of  which  enters  the  gray  matter  of  the  spinal  cord  as  a  neurite  and  here 
enters  into  contact  with  ganglion-cells  (Fig.  251);  and  the  other  fiber  of  which 
passes  to  the  ganglion  as  a  dendrite  from  peripheral  areas  endowed  with  sensi- 
bility. The  posterior  roots  make  their  exit  from  the  sulcus  between  the  posterior 
and  lateral  columns  of  the  spinal  cord;  the  anterior  roots,  from  the  groove 
between  the  lateral  and  anterior  columns.  The  posterior  forms  the  spindle- 
shaped  spinal  ganglion.  Then  the  two  roots  enter  into  intimate  union  and  form, 
still  within  the  vertebral  canal,  a  mixed  trunk.  The  two  branches  originating 


7*4 


THE     SPINAL    NERVES. 


from  the  trunk  always  contain  fibers  of  both  roots.      Each  spinal  nerve  is  derived 
from  two  or  three  or  even  several  spinal  segments. 

The  roots  growing  from  the  spinal  ganglion  into  the  spinal  cord  not  only  enter 
the  spinal  segment  corresponding  to  them,  but  grow  into  other  segments  of  the 
spinal  cord  and  thus  are  connected  with  many  segments.  The  motor  roots  are 
localized  exclusively  in  their  spinal  segments.  Toward  the  periphery  the  spinal 
nerves  (motor  and  sensory)  likewise  not  only  pass  to  the  segments  of  the  body 
corresponding  to  them,  but  extend  beyond  these  limits  into  the  areas  of  other 
segments.  This  is  observed  particularly  in  the  extremities,  less  commonly  on  the 
trunk,  especially  on  the  skin,  and  in  more  marked  degree  in  the  fibers  that  pass 
to  the  sympathetic  ganglia. 

A  B 


10  me 
FIG.  247.— Distribution  of  the  Cutaneous  Nerves  of  the  Upper  Extremity  (after  Henle). 

A.  Dorsal  aspect  of  the  upper  extremity:  i  sc, 
supraclavicular  nerves;  2  ax,  axillary  nerve; 
3  cps,  posterior  superior  cutaneous  nerve 
(radial);  4  cmd,  middle  or  internal  cutaneous 
nerve;  5  cpi,  posterior  inferior  cutaneous 
nerve  (radial);  6  cm,  middle  cutaneous 
or  greater  internal  cutaneous  nerve;  7  cl,  lat- 
eral or  external  cutaneous  nerve;  8  u,  ulnar 
nerve;  gra,  radial  nerve;  lome,  median  nerve. 


B.  Ventral  aspect  of  the  upper  extremity:    i  sc, 
supraclavicular  neryes;    2  ax,  axillary  nerve; 

3  cmd.   middle  or  internal  cutaneous  nerve; 

4  cl,  lateral  or  external  cutaneous  nerve;  5  cm, 
middle  or  greater  internal  cutaneous  nerve; 
6  me,  median  nerve;   7  u,  ulnar  nerve. 


Charles  Bell,  in  1811,  discovered  the  law  named  after  him,  namely, 
that  the  anterior  roots  contain  the  motor,  and  the  posterior  roots  the 
sensory  fibers. 

Magendie,  in  1822,  noted  the  remarkable  fact  that  the  anterior  roots  of  warm- 

Dlooded  animals,  but  not  of  the  frog,   likewise  contain   sensory  fibers,   so  that 

irritation  of  them  causes  pain.     This,  however,  is  due  to  the  fact  that  fibers  from 

the  sensory  root  pass  in  a  centripetal  direction  in  the  anterior  root  after  the  junction 

the    two.     This    phenomenon   is    designated    recurrent    sensibility    (sensibilite" 


THE    SPINAL    NERVES. 


715 


recurrente).  The  sensibility  of  the  anterior  root,  therefore,  ceases  at  once  as  soon 
as  the  posterior  root  is  divided.  In  conjunction  with  the  loss  of  sensibility  of 
the  anterior  roots  thus  brought  about,  that  of  the  surface  of  the  spinal  cord  in 
the  vicinity  of  the  root  is  also  abolished.  A  considerable  time  after  division  of  the 
anterior  root  (if  degeneration  has  already  taken  place),  a  number  of  fibers  that 
are  not  degenerated  are  found  in  its  peripheral  extremity,  while  a  number  of 
degenerated  (sensory)  fibers  are  present  in  its  central  stump.  In  cases  in  which 

A  B 


\lk  A 


*j 


FIG.  248. — Distribution  of  the  Cutan?ous 
A.  Anterior  aspect:  i,  crural  nerve;  2,  external 
or  lateral  cutaneous  nerve  of  the  femur, 
Henle;  3,  ilioinguinal  nerve;  4,  lumboin- 
guinal  nerve;  5,  external  spermatic  nerve; 
6,  posterior  cutaneous  nerve;  7,  obturator 
nerve;  8  greater  saphenous  crural  nerve;  9, 
communicating  peroneal  or  fibular  nerve;  10, 
superficial  peroneal  nerve;  u,  deep  peroneal 
nerve;  12,  communicating  tibial  or  sural 
nerve. 


Nerve  of  the  Lower  Extremity  (after  Henle). 

B.  Posterior  aspect:  i,  posterior  cutaneous  nerve; 
2,  external  or  lateral  cutaneous  nerve  of  the 
femur,  Henle;  3,  obturator  nerve;  4,  poste- 
rior median  cutaneous  nerve  of  the  femur 
(peroneal  nerve);  5,  communicating  peroneal 
or  fibular  nerve;  6,  greater  saphenous  nerve 
(crural  nerve);  7,  communicating  tibial  or 
sural  nerve;-  8,  proper  plantar  cutaneous  nerve 
(tibial  nerve);  9,  middle  plantar  nerve  (tibial 
nerve);  10,  lateral  plantar  nerve  (tibial  nerve). 


the  motor  fibers  were  degenerated,  Schiff  found  unaltered  fibers  in  the  anterior 
root,  and  these  passed  over  to  the  spinal  meninges.  In  rare  cases  the  anterior  root 
receives  its  sensibility,  besides,  from  other  sources  than  from  its  corresponding 
posterior  root.  The  passage  of  sensory  fibers  into  the  motor  root  takes  place 
either  at  the  point  of  junction  between  the  two  roots,  or  in  the  plexus,  or  in  the 
vicinity  of  the  peripheral  terminal  distribution.  Thus,  sensory  fibers  passing  in  a 
centripetal  direction  also  enter  from  the  periphery  into  several  motor  branches 


716  THE    SPINAL    NERVES. 

of  the  cranial  nerves.  Even  sensory  branches  of  other  sensory  nerves  may  enter 
also  into  the  trunks  of  sensory  nerves.  This  fact  explains  the  remarkable  ob- 
servation that,  after  division  of  a  nerve-trunk,  for  example  the  median,  its  peripheral 
extremities  remain  sensitive.  Landois  offers  the  simple  explanation  for  the  condi- 
tions described  that  the  tissue  of  the  motor  and  sensory  nerves  contains  (as  do 
most  of  the  tissues  of  the  body)  sensory  fibers. 

As  a  result  of  carefully  observed  experiments  with  division  of  the  roots,  as 
well  as  after  discovery  of  the  reflex  relations  of  the  sensory  roots  to  irritation 
of  the  anterior  root  (reflex  movement)  by  Johannes  Miiller  and  Marshall  Hall,  the 
following  deductions  may  be  readily  made  from  the  general  law  of  Bell:  (i)  At 
the  moment  of  division  of  the  anterior  root  a  contraction  (mechanical  irritation 
of  the  motor  fibers)  occurs  in  the  muscles  supplied  from  this  root.  (2)  A  sensation 
of  pain,  however,  also  results  (recurrent  sensibility).  (3)  After  the  section  the 
related  muscles  are  paralyzed.  (4)  Irritation  of  the  peripheral  stump  of  the 
anterior  root  causes  (in  the  first  period  after  the  operation)  contraction  of  the 
muscles,  eventually  also  a  sensation  of  pain  in  consequence  of  the  recurrent 
sensibility.  (5)  Irritation  of  the  central  stump  is  entirely  without  effect.  (6) 
Sensation  is  completely  preserved  in  the  paralyzed  parts  of  the  body.  (7)  Severe 
pain  occurs  at  the  moment  of  division  of  a  posterior  root.  (8)  A  reflex  movement 
occurs  at  the  same  time.  (9)  After  the  section,  all  regions  supplied  by  the  divided 
root  are  anesthetic.  (10)  Irritation  of  the  peripheral  stump  of  the  divided  root 
is  without  any  effect,  (n)  Irritation  of  the  central  stump  causes  pain  and  reflex 
movement.  (12)  Motility  is  entirely  preserved  in  the  anesthetic  parts,  for  ex- 
ample the  extremities. 

According  to  Waller,  the  peripheral  portion  always  undergoes  degeneration 
after  division  of  the  anterior  root.  Division  of  the  posterior  root  in  advance  of 
or  behind  the  ganglion  leaves  unaltered  the  peripheral  fibers  that  have  retained 
their  connection  with  the  ganglion.  Those  that  are  severed  degenerate.  There- 
fore, according  to  Waller,  the  spinal  cord  is  the  nutritional  center  for  the  anterior 
roots,  and  the  spinal  ganglion,  on  the  other  hand,  for  the  posterior. 

After  division  of  the  posterior  roots,  for  example  of  the  nerves  for  the  posterior 
extremities,  the  muscles  retain  their  motility,  but,  nevertheless,  characteristic  dis- 
turbances can  be  recognized  in  them.  These  consist  in  an  apparent  awkwardness 
with  which  the  animal  executes  the  movements  (jumping  about  in  an  uncertain 
manner,  holding  the  legs  far  apart  in  walking,  etc.) ,  which  detracts  from  the  normal 
harmony  and  elegance — centripetal  ataxia.  Landois  observed  that  dogs  in  which 
the  posterior  roots  for  the  posterior  extremities  were  divided  on  both  sides  ex- 
hibited, after  complete  recovery  in  other  respects,  difficulty  in  balancing  the 
posterior  part  of  the  body,  which  often  fell  over  in  running  or  in  wagging  the 
tail.  The  phenomena  are  due  to  the  fact  that  in  consequence  of  the  anesthesia 
of  the  muscles  and  the  skin,  the  animal  is  unconscious  of  the  resistances  opposed 
to  its  movements.  Therefore,  the  measure  of  muscular  force  to  be  employed 
cannot  be  properly  estimated.  All  aids  excited  through  reflex  influences  are  also 
naturally  excluded.  Animals  with  abolition  of  sensibility  in  individual  extremities 
often  hold  these  in  abnormal  positions,  from  which  the  animal  with  preserved 
sensibility  would  at  once  remove  them.  Analogous  ataxic  disorders  of  movement 
have  been  observed  also  in  human  beings  with  degenerated  peripheral  extremities 
of  the  cutaneous  nerves. 

Under  some  circumstances  division  of  the  sensory  nerves  in  certain  regions 
may  indeed  be  attended  with  abolition  of  movement.  In  whole-hoofed  animals, 
immobility  of  the  upper  lip  was  observed  after  resection  of  the  infraorbital  nerve, 
immobility  of  the  corresponding  side  of  the  larynx  after  division  of  the  superior 
laryngeal  nerve,  also  loss  of  motility  of  the  esophagus  after  paralysis  of  its  sensory 
nerve.  The  motility  is  thus,  in  large  measure,  dependent  upon  preservation  of 
the  sensory  nerves  (sensomobility) . 

Harless,  Ludwig  and  Cyon  have  made  the  observation,  which,  however,  has 
been  disputed  by  v.  Bezold,  Uspensky,  Griinhagen,  and  G.  Heidenhain,  that  the 
anterior  roots  possess  a  greater  degree  of  irritability  so  long  as  the  posterior  remain 
intact  and  irritable,  that,  however,  they  exhibit  signs  of  lessened  irritability  as 
soon  as  the  posterior  roots  are  divided.  In  explanation  of  this  phenomenon  it 
must  be  assumed  that  in  the  intact  body  a  series  of  slight  irritations  pass  succes- 
sively through  the  posterior  roots  (from  contact,  position,  the  influence  of  tem- 
perature upon  the  parts  of  the  body,  and  the  like),  and  are  transmitted 
renexly  through  the  spinal  cord  to  the  motor  roots,  so  that,  as  a  result,  a 
slighter  additional  irritation  is  required  in  order  to  excite  the  anterior  roots  than 


THE    SPINAL    NERVES.  717 

if  this  reflex  impulse  from  the  posterior  roots  for  the  increase  of  the  irritability 
were  removed.  Obviously,  the  irritation  required  for  the  excitation  of  an  already 
slightly  irritated  nerve-fiber  need  be  less  than  for  a  similar  fiber  that  is  not  irri- 
tated, as,  in  the  first  instance,  the  existing  irritation  is  added  to  that  which  is 
in  constant  action. 

The  anterior  roots  of  the  spinal  nerve  supply  with  centrifugal  fibers  : 

1 .  All  striated  muscles  of  the  trunk  and  of  the  extremities  under  the 
control  of  the  will.     Every  muscle  receives  its  motor  fibers  from  several 
anterior  roots,  and  not  from  a  single  root;  while  every  root  distributes 
fibers  to  a  related  group  of  muscles. 

The  experiments  made  by  Ferrier  and  Yeo  on  the  anterior  roots  in  apes  have 
shown,  accordingly,  that  irritation  of  each  root  (in  the  brachial  and  lumbosacral 
plexuses)  induces  a  synergistic  coordinated  movement.  Division  of  one  root 
failed  also  to  cause  complete  paralysis  of  the  muscles  taking  part  in  the  combined 
movement,  but  these  had  suffered  only  loss  in  strength.  These  experiments  con- 
firm pathological  observations  made  on  man.  The  fibers  for  functionally  related 
groups  of  muscles,  for  example  flexors  and  extensors,  arise  from  special  circum- 
scribed regions  of  the  spinal  cord.  Thus  the  cervical  and  lumbar  swellings  of  the 
cord  represent  centers  for  highly  coordinated  muscular  movements. 

2.  The  anterior  roots  supply,  also,  motor  fibers  to  a  number  of  organs 
provided  with  unstriated  muscle-fibers,  such  as  the  urinary  bladder,  the 
vasa  deferent ia,  the  uterus,  the  skin. 

3.  Motor  fibers  for  the  unstriated  muscles  of  the  vessels,  the  vaso- 
motors. 

4.  Inhibitory   fibers   for   the   contraction   of  the   vascular   muscles 
(known  only  in  part) :   vasodilators. 

5.  Secretory  fibers  for  the  sweat. 

6.  Trophic  fibers  for  the  tissues. 

The  posterior  roots  contain  the  sensory  nerves  for  the  skin  and  the  in- 
ternal tissues,  with  the  exception  of  the  anterior  part  of  the  head,  the 
face  and  the  inner  portions  of  the  head.  They  contain  also  the  tactile 
nerves  for  the  cutaneous  surfaces  indicated.  Irritations,  exciting  re- 
flex action,  are  also  conveyed  to  the  spinal  cord  through  the  posterior 
roots. 

Every  sensory  root  gives  fibers  to  different  peripheral  nerves.  Every 
posterior  root  corresponds  to  a  circumscribed  area  of  the  skin,  although 
adjacent  cutaneous  areas  overlap  in  part,  so  that  probably  every  portion 
of  skin  is  innervated  from  at  least  two  roots.  Thus,  for  example,  the 
nipple  is  supplied  with  sensory  fibers  from  the  fourth  and  from  the  third 
and  fifth  sensory  thoracic  roots.  The  areas  even  extend  somewhat  be- 
yond the  middle  line  of  the  abdomen  and  the  back  and  into  one  another. 
The  innervational  areas  of  the  sensory  nerve  descend  lower  than  those  of 
the  nerve-fibers  arising  from  the  corresponding  anterior  roots. 

Fig.  247  and  Fig.  248  illustrate  the  areas  of  distribution  of  the  sensory  nerves 
of  the  extremities,  Fig.  244  those  of  the  sensory  spinal  branches  on  the  head. 
In  cases  of  neuralgia  and  anesthesia  the  nerves  involved  can  be  readily  determined 
by  comparison  with  these  illustrations. 

There  receive  sensory  nerves  as  follows:  Heart  and  lungs  from  the  vagus  and 
the  upper  thoracic  nerves;  stomach,  small  intestine,  liver,  spleen  and  pancreas 
from  the  vagus  and  the  middle  inferior  thoracic  and  upper  lumbar  nerves;  adrenals, 
kidneys,  testicles,  ovaries,  uterus  from  the  middle  and  lower  thoracic  and  upper 
lumbar  nerves;  rectum,  prostate,  penis,  uterus,  vagina  from  the  sacral  nerves  and 
the  hypogastric  plexus  (from  the  lower  dorsal  and  upper  lumbar  cord) . 

In  the  hen  it  is  a  remarkable  fact  that  a  few  motor  fibers  pass  out  through  the 
posterior  roots;  also  in  some  fish;  with  extreme  rarity  also  in  the  frog;  further  in 
the  dog  and  the  cat  vasodilators  (for  the  hind  leg) ;  in  the  frog  motor  nerves  for 
the  unstriated  muscles  of  the  digestive  tract  and  the  urinary  bladder. 


7i8 


SYMPATHETIC    NERVOUS    SYSTEM. 


SYMPATHETIC  NERVOUS  SYSTEM. 

Connected  with  the  cerebrospinal  system,  the  sympathetic  occupies  a  special 
position  in  consequence  of  the  peculiarity  of  arrangement  of  its  tracts,  as  well 
as  on  account  of  the  presence  of  non-medullated,  gray  fibers  and  characteristically 
constructed  ganglion-cells.  The  anterior  branch  of  each  spinal  nerve  gives  off  a 
visceral  branch  (formerly  designated  communicating  branch  of  the  sympathetic) , 
which  is  derived  either  from  the  anterior  or  the  posterior  root  of  the  spinal  nerve, 
and  this  naturally  (in  the  sense  of  Bell's  law)  indicates  the  function  of  the  nerve. 
All  of  the  visceral  branches  collect  on  each  side  of  the  vertebral  column  to  form  the 
sympathetic  chain,  in  the  course  of  which  ganglionic  nodes  are  interpolated. 
From  the  first  dorsal  nerve  downward  there  is  a  ganglion  at  the  point  where  each 
visceral  branch  enters  the  sympathetic.  In  the  cervical  portion  a  contraction 
and  partial  coalescence  of  the  ganglia  has  occurred,  and  the  eighth  and  the 
seventh  and  also  the  sixth  and  the  fifth  nerves  are  represented  by  single  ganglia, 
and  the  four  upper  cervical  nerves  together  by  the  superior  cervical  ganglion. 
Sympathetic  filaments  also  pass  through  the  path  of  individual  visceral  branches 
from  the  sympathetic  into  the  cerebrospinal  nervous  system. 

From  the  sympathetic  system  fibers  pass  to  the  various  viscera  of  the  head, 
the  chest  and  the  abdomen,  where  again  they  form  ganglionic  plexuses,  from 
which  finally  fibers  endowed  with  varied  functions  pass  to  the  different  organs. 

Visceral  branches  pass  also  from  the 
cerebral  nerves  (although  demonstrable 
with  greater  difficulty)  and  are  con- 
nected with  ganglia.  The  ciliary  gan- 
glion belongs  to  the  third  nerve  as  a  part 
of  the  sympathetic  system  The 
sphenopalatine  nerves  pass  from  the 
second  division  of  the  trigeminus  as 
visceral  branches  into  the  sphenopala- 
tine ganglion.  The  greater  superficial 
petrosal  nerve  also  is  to  be  considered 
as  a  second  visceral  branch  of  this 
ganglion.  The  otic  ganglion  is  to  be 
looked  upon  as  a  sympathetic  ganglion 
of  the  third  division;  likewise  the  sub- 
maxillary  ganglion,  the  chorda  tympani 
being  the  visceral  branch.  It  appears 
that  the  glossopharyngeal,  the  vagus 
and  the  hypoglossal  have  their  visceral 
branches  in  part  in  anastomotic  fila- 
ments that  they  send  to  the  superior 
cervical  ganglion,  which,  therefore, 
gives  off  these  cerebral  nerves,  together 
with  the  four  upper  cervical  nerves,  to 
the  common  ganglion. 
The  sympathetic  consists:  (i)  Of  medullated  fibers  supplied  to  it  as  visceral 
branches  by  cerebral  and  spinal  nerves,  and  (2)  of  fibers  of  Remak,  which  arise 
from  sympathetic  ganglia.  The  medullated  fibers  are  (a)  sensory,  (6)  motor,  for 
vessels  (vasomotors)  and  viscera,  the  latter  entering  into  sympathetic  ganglia, 
whence  Remak's  fibers,  as  well  as  medullated  fibers,  pass  from  the  ganglion-cells 
to  the  innervated  areas;  (c)  inhibitory  fibers  and  vasodilators,  in  the  course  of 
which  no  sympathetic  ganglia  are  intercalated.  The  fibers  of  Remak  are  all 
motor  and  they  innervate  directly  or  indirectly  (that  is  entering  again  into  ganglia) 
the  unstriated  musculature  of  the  vessels,  the  viscera,  the  skin,  and  the  muscles 
of  the  heart. 

The  conduction  of  the  sympathetic  nerve-fibers  is  in  part  direct  and  uninter- 
rupted by  means  of  sensory,  inhibitory  and  vasodilator  fibers.  The  medullated 
motor  fibers  from  the  visceral  branches  conduct  indirectly,  that  is  they  pass  at 
first  in  sympathetic  ganglia,  where  they  surround  the  cells,  whose  neurites  then 
continue  the  conduction.  The  sympathetic  contains  further  secretory  fibers  and 
fibers  that  control  chemical  processes,  as  in  the  thyroid  gland  and  the  adrenals. 
According  to  Langley  all  motor  and  sensory  tracts  derived  from  the  spinal  cord 
and  situated  in  the  sympathetic  make  their  exit  from  the  cord  between  the  first 
dorsal  and  the  second  lumbar  nerve. 


FIG.  249. — Diagrammatic  Representation  of  the  Course 
of  a  Thoracic  Branch  of  the  Sympathetic:  i,  spinal 
cord;  2,  ventral  root;  3,  dorsal  root  with  spinal 
ganglion;  4,  intercostal  nerve;  5,  dorsal  branch; 
6,  visceral  branch;  7,  ganglion  of  the  sympathetic 
cord;  8,  lateral  cutaneous  branch  (pectoral  and 
abdominal);  a,  posterior  branch;  b,  anterior 
branch;  9,  anterior  cutaneous  branch  (pectoral 
and  abdominal). 


DIVISIONS    OF    THE     SYMPATHETIC.  719 

Light  is  thrown  upon  the  significance  of  the  ganglia  in  the  sympa- 
thetic system  by  poisoning  with  nicotin.  In  an  animal  thus  poisoned 
the  ganglion-cells  are  paralyzed,  for  irritation  of  the  ganglia  is  without 
effect,  as  is  also  irritation  of  the  nerves  passing  to  the  ganglion.  On  the 
other  hand,  irritation  of  the  nerve-fibers  that  pass  peripherally  from  the 
ganglion  is  still  attended  with  results. 

As  to  the  functions  of  the  sympathetic  only  a  general  summary  will  be 
given  here. 

I.  Independent    junctions  of    the  sympathetic  are  those  of  certain 
plexuses  that  persist  after  all  the  nervous  connections  with  the  cerebro- 
spinal  axis  are  severed.     These  include: 

1.  The  automatic  ganglia  of  the  heart. 

2.  The  myenteric  plexus  of  the  intestine. 

3.  The  plexuses  of  the  uterus,  the  oviducts,  the  vasa  deferentia,  and 
also  of  the  blood-vessels  and  the  lymphatics.     The  activity  of  these 
plexuses  may  be  in  part  stimulated,  in  part  inhibited,  through  centrifugal 
nerves  from  the  cerebrospinal  axis. 

II.  Dependent  F~  unctions. — The  sympathetic  contains  also  fibers  that, 
like  the  peripheral  nerves,  functionate  only  in  connection  with  the  cen- 
tral nervous  system,  for  example  the  sensory  fibers  in  the  splanchnic 
nerve.     Other  fibers  convey  to  ganglia  impulses  received  from  the  cen- 
tral nervous  system,  the  ganglia  in  turn  conducting  the  stimuli  further 
on  in  the  form  of  inhibition  or  motion  to  the  respective  organs. 

A.    CEREBRAL    AND    CERVICAL    DIVISION    OF    THE    SYMPATHETIC. 

1.  Pupil-dilating  Fibers. — According  to  Budge,  these  arise  from  the  spinal 
cord,  and  they  pass,  according  to  Langley,  through  the  three  or  four  uppermost 
dorsal  nerves  in  the  sympathetic  cord  and  ascend  to  the  head  (in  the  cat) .      Division 
of  the  sympathetic  cord  or  its  communicating  branches  causes,  therefore,  con- 
traction of  the  pupil.     The  central  origin  of  these  fibers  is  discussed  on  pp.  734 
and  749. 

2.  The  motor  fibers  for  the  unstriated  muscles  of  H.  Mtiller  in  the  orbit  and 
the  lids  and  for  the  external  rectus  pass  in  part  through  the  dorsal  nerves  from 
the  first  to  the  fifth  (in  the  cat).     According  to  Frl.  Klumpke  and Oppenheim  the 
communicating  branch  of  the  first  dorsal  nerve  in  man  is  the  path  for  i   and  2. 

3.  Vasomotor  fibers  for  the  vessels  of  the  external  ear  and  the  side  of  the 
face,  the  tympanic  cavity,  the  conjunctiva,  the  iris,  the  choroid,  the  retina  (only 
in  part),  the  pharynx,  the  larynx,  the  thyroid  gland,  the  brain  and  its  mem- 
branes, derived  from  the  thoracic  nerves  from  the  first  to  the  fifth. 

4.  The  cervical  sympathetic  cord  contains  centripetal  fibers  that  stimulate 
the  vasomotor  center  in  the  medulla  oblongata. 

5.  Secretory,  trophic,  and  vasomotor  fibers  for   the    salivary  glands,  appearing 
in  the  thoracic  nerves  between  the  first  and  the  fifth. 

6.  The  sweat-fibers  are  described  on  p.  537. 

7.  Also  the  lacrimal  glands  receive  sympathetic  secretory  fibers. 

B.    THORACIC    AND    ABDOMINAL    DIVISION    OF    THE    SYMPATHETIC. 

1.  This  division  includes  first  the  sympathetic  portion  of  the  cardiac  plexus, 
which  sends  to  the  heart   accelerator  fibers  from  the  inferior  cervical  and    the 
superior  thoracic   ganglion  arising  (in  the   cat)   from   the   upper  cervical   nerves 
between  the  first  and  the  sixth. 

2.  The  vasomotors  for  the  extremities,  the  skin  of  the  trunk,  the  lungs   (in 
part  from  the  vagus),  passing  through  the  sympathetic  are  described  on  p.  763, 
the  vasodilators  on  p.  772. 

3.  The  pilomotor  fibers  arise  from  the  nerves  between  the  fourth  thoracic  and 
the  third  lumbar.       They  pass  to  the  sympathetic  cord,  where  a  ganglion-cell  is 


720  DIVISIONS    OF    THE    SYMPATHETIC. 

intercalated  in  each  fiber.  The  sympathetic  fibers  have  the  same  peripheral 
area  of  distribution  as  do  the  sensory  fibers  of  the  roots  of  the  same  spinal 
nerve. 

4.  The  cervical  sympathetic  cord  and  the  splanchnic  nerves  are  believed  to 
contain  fibers  irritation  of  which  excites  in  a  centripetal  direction  the  cardiac  in- 
hibitory system  in  the  medulla  oblongata. 


767, 

vical  to 

from  the  solar  ganglion. 

6.  The  significance  of  the  celiac  and  mesenteric  plexuses  is  discussed  on  pp.  328 
and  359.     After  extirpation  of  the  celiac  ganglion  Lamansky  observed  transitory 
derangement  of  digestion,  in  consequence  of  which  undigested  food  was  discharged 
from  the  anus. 

7.  Sweat-fibers  are  discussed  on  p.  536. 

8.  Finally,  the  abdominal  division  of  the  sympathetic  contains  motor  and 
vasomotor  fibers  for  the  spleen,  the  large  intestine   (to  which  they  pass  with  the 
arterial  trunks),  the  bladder,  the  ureters  (to  which  they  pass  in  the  hypogastric 
plexus),  the  vasa  deferentia  and  the  seminal  vesicles.     Irritation  of  any  of  these 
nerve-tracts  causes  increased  movement  of  the  organs  in  question,  the  diminished 
supply  of  blood  also  acting  as  an  exciting  factor.     Section  causes  vascular  dilata- 
tion, with  secondary  derangement  of  the  circulation,  and  finally  of  the  nutrition. 
The  relations  of  the  adrenal  bodies  to  the  sympathetic  have  been  discussed  on 
p.  107.     The  renal  plexus  is  described  on  p.  515,  and  the  cavernous  plexus  in  con- 
nection with  erection  on  p.  955. 

From  the  lumbosacral  portion  of  the  spinal  cord  there  issue  as  sympathetic 
filaments  almost  exclusively  medullated  fibers  that  pass  in  the  sympathetic  cord 
and  thence  partly  to  the  inferior  mesenteric  ganglion  and  thence  to  the  hypo- 
gastric  and  inferior  mesenteric  nerves,  and  partly  through  the  sacral  sympathetic 
ganglia  to  the  sacral  nerves  to  the  skin. 

The  lumbar  branches  contain  inhibitory  fibers  for  the  musculature  of  the 
descending  colon  and  the  rectum.  Inhibitory  and  motor  fibers  pass  to  the  internal 
sphincter  ani.  Irritation  of  the  branches  causes  also  contraction  of  the  unstriated 
muscle-fibers  of  the  skin  surrounding  the  anus  and 'pallor  of  the  anal  mucous 
membrane. 

The  sacral  branches  send  motor  fibers  to  the  rectum  and  the  colon,  in  addition 
inhibitory  fibers  to  the  internal  sphincter  ani,  the  adjacent  musculature  of  the  skin 
and  vasodilators  to  the  mucous  membrane  of  the  rectum  and  the  external  geni- 
talia.  The  inferior  mesenteric  ganglion  acting  as  a  reflex  center  may  transmit 
motor  impulses  to  the  bladder  in  response  to  irritation  of  sensory  nerves  of  this 
viscus. 

Pathological. — In  accordance  with  the  varied  ramifications  of  the  sympathetic 
it  offers  a  wide  field  for  pathological  disturbances.  It  should  be  stated  that 
affections  of  all  of  the  fibers  related  to  the  vascular  system  are  discussed  elsewhere 
(P-  77°). 

The  cervical  sympathetic  is  most  frequently  paralyzed  or  irritated  by  direct 
traumatic  influences.  Gunshot-wounds  or  punctured  wounds,  tumors,  enlarged 
lymphatic  glands,  aneurysms,  inflammations  of  the  apices  of  the  lungs  and  the 
adjacent  pleura,  exostoses  of  the  vertebral  column  may  exert  in  part  an  irritant, 
in  part  a  paralyzant  effect.  The  resulting  symptoms  have  been  in  part  analyzed 
in  the  discussion  of  the  ciliary  ganglion  (p.  684).  Irritation  of  the  cervical  sympa- 
thetic causes  in  man  dilatation  of  the  pupil  (spastic  mydriasis) ,  together  with  pallor 
of  the  face  and  occasionally  hyperidrosis ;  disorders  in  near  vision,  the  pupil  being 
unable  to  contract,  so  that  spherical  aberration  must  have  a  disturbing  effect; 
protrusion  of  the  eyeball,  with  widening  of  the  palpebral  fissure.  Paralysis  causes 
an  increased  supply  of  blood  to  the  affected  side  of  the  head,  occasionally  in 
association  with  anidrosis.  The  reddening  may  increase  to  a  pathological  degree. 
Later  on,  paralysis  of  the  cervical  sympathetic  is  attended  with  dilatation  of  the 
pupil  (paralytic  myosis),  which  in  the  act  of  accommodation  undergoes  change 
in  diameter,  but  not  on  stimulation  by  light;  it  is  slightly  dilated  by  atropin. 
At  the  same  time  the  palpebral  fissure  is  narrowed,  the  eyeball  retracted,  the 
cornea  somewhat  flattened,  and  the  tension  of  the  eyeball  diminished.  Irrita- 
tion of  the  sympathetic  has  been  attended  with  increased  secretion  of  saliva 
Among  the  symptoms  of  irritation  of  the  cervical  sympathetic  described,  unil 


COMPARATIVE.        HISTORICAL.  7  21 

lateral  facial  atrophy  has  been  observed.  Irritative  phenomena  in  the  distribution 
of  the  splanchnic  nerve,  especially  as  a  result  of  lead-poisoning,  are  attended 
with  severe  pain  (saturnine  colic) ,  inhibition  of  the  movements  of  the  intestine 
(and,  therefore,  obstinate  constipation),  reflex  inhibition  of  the  action  of  the  heart 
(in  the  sense  of  the  percussion-experiment  of  Goltz) .  Among  the  forms  of  irritation 
in  the  distribution  of  the  sensory  nerves  of  the  sympathetic  are  the  painful  affection 
in  the  hypogastrium  and  sacral  regions  designated  hypogastric  neuralgia,  hysteral- 
gia,  neuralgia  of  the  testicle,  which  are  localized  in  the  respective  plexuses  of  the 
sympathetic.  In  connection  with  affections  of  the  abdominal  sympathetic  obsti- 
nate constipation  is  at  times  observed,  and,  in  addition  to  irritation  of  the  splanch- 
nic, there  may  be  deficient  secretion  on  the  part  of  the  intestinal  glands;  at  other 
times  increased  secretion  from  the  intestinal  mucous  membrane.  With  respect  to 
all  of  these  subjects,  however,  there  is  as  yet  considerable  obscurity. 

COMPARATIVE.     HISTORICAL. 

Some  of  the  cerebral  nerves  behave  like  the  anterior,  and  others  like  the 
posterior  roots  of  the  spinal  nerves.  In  selachians  the  nerve-branches  arising  as 
posterior  roots  supply  upon  the  head  the  muscles  of  the  visceral  skeleton.  In  the 
vertebrates  some  of  the  cerebral  nerves  may  be  entirely  wanting;  others  may  be 
abortive  or  become  branches  of  other  nerves.  Cetaceans  possess  no  olfactory  nerve. 
The  facial  nerve,  which  in  man  is  the  mimetic  and  the  respiratory  nerve  of  the 
face,  grows  smaller  and  smaller  in  the  lower  classes  of  vertebrates,  in  conjunction 
with  reduction  in  the  size  of  the  facial  muscles.  In  birds  and  reptiles  it  innervates 
the  muscles  attached  to  the  hyoid  bone  or  the  superficial  muscles  of  the  neck 
and  the  nucha.  In  amphibia  (frog) ,  the  facial  is  no  longer  present  as  a  separate 
nerve.  The  branch  equivalent  to  it  is  derived  from  the  ganglion  of  the  trigeminus. 
In  fish  the  fifth  and  seventh  nerves  form  a  common  complex.  The  portion  cor- 
responding to  the  facial  (also  designated  opercular  branch  of  the  trigeminus)  is 
especially  the  motor  nerve  of  the  muscles  of  the  gill-cover  and,  therefore,  proves 
itself  to  be  a  respiratory  nerve.  The  cyclostomata  (lamprey)  possess  an  inde- 
pendent facial  nerve.  The  vagus  is  present  in  all  vertebrates.  In  fish  and  tad- 
poles the  great  lateral  nerve  of  the  abdomen  is  derived  -from  it,  passing  in  the 
middle  line  of  the  body  along  the  lateral  canal.  Its  diminutive  analogue  in  man 
is  the  auricular  branch.  In  the  frog,  the  ninth,  tenth  and  eleventh,  and  also  the 
seventh  and  eighth  nerves  arise  from  a  common  trunk.  In  fish  and  amphibia  the 
hypoglossus  is  the  first  spinal  nerve.  In  the  amphioxus  cerebral  and  spinal  nerves 
are  not  to  be  distinguished  from  each  other.  In  them  also  the  posterior  roots 
supply  the  muscles  of  the  viscera.  In  other  respects  the  spinal  nerves  in  all 
classes  of  vertebrates  exhibit  marked  uniformity.  The  sympathetic  is  wanting  in 
cyclostomata,  being  replaced  by  the  vagus.  In  the  remaining  fish  its  course  is 
along  the  vertebral  column,  where  it  receives  the  communicating  branches  of  the 
spinal  nerves.  In  the  region  of  the  head  its  anastomoses  with  the  fifth  and  tenth 
nerve,  are  especially  conspicuous  in  fish.  In  frogs,  and  in  still  greater  degree  in 
birds,  these  anastomoses  with  the  cerebral  nerves  are  more  extensive. 

The  vagus  and  the  sympathetic  were  already  known  to  the  school  of  Hip- 
pocrates. Herophilus  (307  B.  C.)  was  the  first  to  distinguish  the  nerves  from 
the  tendons,  which  Aristotle  still  confounded.  He  was  aware  of  the  decussation 
of  the  optic  nerves.  According  to  Erasistratus  all  nerves  originate  from  the  brain 
and  the  spinal  cord.  He  distinguished  motor  and  sensory  nerves.  Marinus 
(80  A.  D.)  was  the  first  to  describe  seven  pairs  of  cerebral  nerves.  Galen  already 
possessed  a  comprehensive  knowledge  of  the  functions  of  the  nerves.  He,  as  well 
as  Rufus  of  Ephesus  (97  A.  D.),  was  familiar  with  the  embarrassed  breathing 
following  section  of  both  vagi.  He  observed  aphonia  after  ligation  of  the  recur- 
rent nerve.  He  was  familiar  with  the  accessory  nerve  and  also  with  the  ganglia 
connected  with  the  abdominal  nerves.  He  did  not  place  the  olfactory  nerve  in 
the  same  category  as  the  other  cerebral  nerves.  Achillini  (died  1525)  discovered 
the  true  olfactory  filaments.  Fallopius  placed  the  glossopharyngeus  in  an  inde- 
pendent position.  The  cauda  equina  is  mentioned  in  the  Talmud.  Goiter  (1573) 
described  accurately  the  anterior  and  posterior  roots  of  the  spinal  nerves.  Van 
Helmpnt  (died  1644)  announced  that  the  peripheral  motor  nerves  are  also  sensitive 
to  pain;  and  Caesalpinus  (1571)  stated  that  interruption  of  the  circulation  in  a 
part  renders  it  insensitive.  Thomas  Willis  described  the  portion  of  the  accessory 
nerve  derived  from  the  spinal  cord,  as  well  as  the  principal  ganglia  (1664).  The 
46 


722  COMPARATIVE.         HISTORICAL. 

first  reference  to  reflex  movements  was  made  by  Des  Cartes  (1670) .  Stephen  Hales 
and  Robert  Whytt  showed  that  the  spinal  cord  was  necessary  for  their  occurrence. 
Prochaska  first  demonstrated  the  reflex  path.  Duverney  (1761)  discovered  the 
ciliary  ganglion;  Varolius  (1573)  the  chorda  tympani.  Gall  traced  more  accu- 
rately the  third  and  the  sixth  nerves,  as  well  as  the  spinal  nerves,  into  the  gray 
matter.  Up  to  this  time  only  nine  cerebral  nerves  were  described.  Sommering 
(1791)  differentiated  the  facial  and  the  auditory;  Andersch  (1797)  the  ninth, 
tenth  and  eleventh  nerves. 


PHYSIOLOGY  OF  THE  NERVOUS 
CENTERS. 


GENERAL  CONSIDERATIONS. 

The  central  nervous  organs  are  in  general  characterized  by  the  follow- 
ing properties  : 

1.  They  contain  nerve-cells,  which,  arranged  in  groups,  are  situated 
either  within  the  central  organs  of  the  nervous  system  or  peripherally 
in  the  course  of  the  nerves. 

2.  The  nervous  centers  are  capable  of  discharging  reflexes,  as,  for 
example,  reflex  movements,  reflex  secretion,  reflex  inhibition. 

3.  The    centers    may   be    capable    of    automatic    activity,  that    is, 
apparently  without  external  stimulation,  they  may  give  rise  to  impulses 
that  are  conveyed  to  peripheral  organs.     This  automatic  stimulation 
may  be  either  continuous,  that  is  persisting  without  interruption  (tonic 
automatism   or    tonus),  or   intermittent,  pursuing    a    certain    rhythm 
(rhythmic  automatism). 

The  central  organs  are  the  trophic  centers  for  the  nerves  passing  out 
from  them.  They  may  also  act  as  centers  for  the  nutrition  of  the  tissues 
innervated  by  them.  Psychic  activity  is  dependent  on  an  intact  con- 
dition of  the  ganglionic  central  organs. 

The  foregoing  functions  are  related  to  different  centers,  none  of  which 
is  capable  of  representing  several  activities. 


THE  SPINAL  CORD. 

THE  STRUCTURE  OF  THE  SPINAL  CORD. 

The  spinal  cord  (Fig.  250)  contains  within  its  structure  the  gray  matter,  which 
on  section  is  H-shaped,  and  exhibits  the  anterior  horns  (co.d),  the  posterior 
horns  (co.p)  and  the  central  connecting  segment  constituted  of  the  anterior  and 
the  posterior  gray  commissures.  In  the  middle  of  the  last-named  structure,  from 
the  calamus  scriptorius  downward,  passes  the  central  canal,  which  is  the  remains 
of  the  embryonal  medullary  tube  and  is  lined  by  two  or  three  layers  of  cylindrical 
epithelial  cells. 

The  white  matter  surrounds  the  gray  and  it  is  divided  into  several  columns. 
In  the  median  line,  anteriorly,  a  deep  fissure  (s.a)  extends  into  the  cord,  but 
not  quite  to  the  gray  matter,  leaving  at  its  bottom  the  white  commissure  (c.d) 
intact.  The  anterior  column  (f.a)  is  situated  between  the  anterior  longitudinal 
fissure  and  the  groove  for  the  exit  of  the  anterior  roots.  The  lateral  portion  of 
the  white  matter  between  the  anterior  and  posterior  roots  is  known  as  the  lateral 
column  (/./).  Finally,  the  area  between  the  line  of  exit  of  the  posterior  roots 
and  the  posterior  longitudinal  fissure  is  designated  the  posterior  column  (f.p). 
The  posterior  longitudinal  fissure  (s.p)  penetrates  more  deeply  than  the  anterior 
into  the  cord,  up  to  the  gray  matter. 

The  white  substance  consists  of  medullated  nerve-fibers  provided  with  horny 
sheaths,  and  arranged  longitudinally  in  the  columns.  The  incoming  roots,  as  well 

723 


724 


THE    STRUCTURE    OF    THE    SPINAL    CORD. 


as  the  longitudinal  fibers  entering  the  columns  from  the  gray  matter,  have  in  part 
a  transverse  and  in  part  an  oblique  course.  In  the  anterior  white  commissure, 
fibers  passing  in  a  transverse  direction  decussate. 

The  gray  matter  exhibits  in  cross-section  the  anterior  horns  (co.a),  from 
which,  on  each  side,  the  anterior  roots  of  the  spinal  nerves  arise;  also  the  pos- 
terior horns  (co.p),  with  the  incoming  posterior  roots  (r.p);  and  in  addition  the 
smaller  lateral  horns  (co.l).  In  the  anterior  horn  the  following  groups  of 
cells  can  be  distinguished:  (i)  The  large  root-cells  (a)  situated  anteriorly  and 
laterally,  from  whose  neurites  the  anterior  roots  arise  directly.  The  dendrites 
of  these  cells  pass  into  the  anterior  and  lateral  columns,  and  in  part  also  into 
the  anterior  white  commissure.  (2)  The  commissural  cells  (6),  principally  ante- 
rior and  median  in  situation,  but  in  part  also  in  the  gray  matter,  which  send 
their  neurites  through  the  anterior  white  commissure  to  the  opposite  side,  where 
they  divide  into  an  ascending  and  a  descending  branch. 


-fa. 


co.a. 


FIG.  250.— Transverse  Section  of  the  Spinal  Cord  at  the  Level  of  the  Eighth  Dorsal  Nerve,  X   10  (after  Schwalbe). 
s.a,  Anterior  longitudinal  fissure;    s.p,  posterior  septum,  occupying  the  posterior  longitudinal  fissure;    c.a, 
anterior  commissure;    s.g.c.  central  gelatinous  substance;    c.c,  central  canal;    c.p,  posterior  commissure;    v, 
vein;  co .a,  anterior  horn;  co.l,  lateral  horn,  and  behind  it  the  reticular  process;  co.p,  posterior  horn;  a,  antero- 
f  c  nr  anterior  median  group  of  ganglion-cells;   c,  cells  of  the  lateral  horn;   d,  cells  of  the  columns 

oi  bulling  and  Clarke;  e,  solitary  cells  of  the  posterior  horn;  r.a,  anterior  root;  r.p,  posterior  root;  /,  its 
posterior-horn  bundle;  /',  posterior-column  bundle;  /",  longitudinal  fibers  of  the  posterior  horn;  s.g.R,  gelat- 
inous substance  of  Rolando;  /.a,  anterior  column;  /./,  lateral  column;  f.p,  posterior  column. 

The  lateral  horns  contain  the  so-called  column-cells  (co.l),  that  is  small  ganglia 

whose  neurites  form  short  connecting  tracts  between  groups  of  cells  at  different 

levels  of  the  cord.     These  connecting  tracts  are  situated  in  the  anterior,  posterior 

and  lateral  white  columns  (Fig.  252,  b,  f,  d),  and  they  serve  for  the  conduction  of 

extensive  coordinated  reflexes.     Internal  to  the   origin  of  the  posterior  horns, 

adjacent  to  the  posterior  commissure,  is  situated  a  group  of  cells  forming  the  column 

:  btillmg  and  Clarke  (d) .     This  group  of  cells  is  plainly  visible  from  the  lower 

extremity  of  the  cervical  to  the  beginning  of  the  lumbar  enlargement,  and  its 

leuntes   pass  partly  in   the   direct   cerebellar  tract,    and  partly  to  the  anterior 

white  commissure. 

In  addition  there  are  in  the  anterior  portion  of  the  gray  matter  ganglia  with 
Hart  neurites  whose  complex  ramifications  terminate  in  the  immediate  vicinity 


THE    STRUCTURE    OF    THE    SPINAL    CORD. 


725 


of  the  ganglia — further  pluricordonal  ganglia,  whose  neurites  repeatedly  send 
divided  fibers  into  the  white  columns  of  the  same  side  (or  after  passing  through 
the  commissure)  of  the  opposite  of  the  cord. 

The  posterior  horn  contains  in  addition  to  the  gelatinous  substance  of  Rolando 
(s.g.R.):  (i)  The  exceedingly  small,  spindle-shaped  ganglion-cells,  whose  neurites 
pass  into  the  posterior  column,  and  whose  intricately  branched  dendrites  penetrate 
the  base  of  the  posterior  horn;  (2)  the  rather  superficial  limiting  cells  situated 
near  the  apex  of  the  posterior  horn,  whose  neurites  pass  through  the  gelatinous 
substance  into  the  lateral  column;  (3)  star-shaped  cells,  whose  dendrites  in  part 
enter  the  column  of  Burdach,  in  part  the  gelatinous  substance. 

The  gray  matter  contains,  in 
addition  to  the  ganglion-cells,  an 
exceedingly  fine  network  of  most 
delicate  nerve-fibers.  This  is  formed 
in  part  of  intricately  divided  fine 
fibers,  the  dendrites  of  the  ganglion- 
cells,  but  also  of  numerous  fibrils 
given  off  by  the  longitudinal  axis- 
cylinders  present  in  all  of  the  white 
columns  of  the  spinal  cord.  These 
have  been  designated  collaterals  by 
Santiago  Ramon  y  Cajal.  The  ante- 
rior columns  send  a  rich  network  of 
collaterals  to  the  anterior  horns;  the 
lateral  columns  to  the  region  of  the 
columns  of  Clarke  and  the  central 
canal,  and,  in  conjunction  with  the 
collaterals  from  all  three  columns, 
they  form  the  posterior  gray  commis- 
sure. The  fibers  of  the  posterior 
columns  send  collaterals  to  the  poste- 
rior horn,  the  anterior  horn,  and  the 
columns  of  Clarke. 

The  motor  fibers  passing  through 
the  white  columns  of  the  spinal  cord 
give  off  numerous  collaterals  to  the 
gray  matter  throughout  the  entire 
length  from  above  downward  to  the 
level  at  which  the  motor  conduct- 
ing tract  reaches  the  motor  cells  of 
the  anterior  horn  by  contact  (Fig. 
251,  m.c). 

The  neurites  that  form  the  ante- 
rior roots  give  off  collaterals  to  the 
gray  matter  before  they  leave  it. 

If  a  posterior  root-fiber  be 
followed  into  the  spinal  cord,  it 
will  be  found  to  divide  into  an 
ascending  and  a  descending  branch 
in  the  posterior  column.  From  both 
of  these  branches,  as  well  as  from 
the  root-fiber  itself,  collaterals  are 
given  off  that  enter  the  gray  matter 

and  terminate  in  arborescent  rami-  FIG.  251. 

fications  (Fig.   251,    s,  c).      The   ex- 
tremity of  the  descending  branch  forms   a  collateral   in  the  gray  matter  of  the 
cord,  that  of  the  ascending  branch  a  collateral  in  the  medulla  oblongata. 

The  White  Matter. — All  of  the  longitudinal  nerve-fibers  composing  the  white 
matter  of  the  columns  of  the  spinal  cord  are  arranged  systematically,  according 
to  their  function,  into  separate  bundles. 

Tiirck  observed  that  after  disease  of  certain  portions  of  the  brain  the  definite 
tracts  of  fibers  in  the  spinal  cord  were  secondarily  degenerated.  P.  Schieferdecker 
confirmed  this  observation  by  animal  experimentation.  Finally,  Flechsig  dem- 
onstrated that  the  fiber-systems  in  the  spinal  cord  receive  their  myelin-sheaths 
at  different  times  in  the  process  of  development,  and  that  those  "fibers  whose 


726  THE    STRUCTURE    OF    THE    SPINAL    CORD. 

course  is  the  longest  receive  them  latest.      In  this  way  he  established  the  fol- 
lowing systems  of  longitudinal  tracts  (Fig.  252) : 

(i)  The  anterior  column  contains  adjacent  to  the  anterior  median  fissure  (a) 
the  direct  pyramidal  tract;  externally  to  this  (b)  the  anterior  ground-bundle. 
(a)  The  posterior  column  contains  (c)  the  column  of  Goll  or  slender  column, 
and  (d)  the  column  of  Burdach  or  wedge-shaped  column.  (3)  The  lateral  col- 
umn contains  (e)  the  antero-lateral  tract  of  Gowers,  (f)  the  lateral  ground-bundle, 
(g)  the  crossed  pyramidal  tract,  and  (h)  the  direct  cerebellar  tract. 

Of  these,  the  pyramidal  tracts,  direct  (a)  and  crossed  (g),  contain  all  the  con- 
nections that  pass  from  «he  central  convolutions  of  the  cerebral  cortex  as  the 
path  for  voluntary  motor  impulses.  The  direct  cerebellar  tract  (k)  connects  in 
an  ascending  direction  the  superior  vermis  of  the  cerebellum  on  both  sides  through 
the  restiform  body  with  the  columns  of  Stilling  and  Clarke.  As  posterior  roots 
of  the  same  side  enter  the  columns  of  Clarke,  the  direct  cerebellar  tract  connects 
the  cerebellum  with  the  posterior  roots  of  the  trunk  (not  of  the  extremities). 
Gowers'  tract  (e)  also  terminates  in  the  superior  vermis  almost  entirely  upon  the 
same  side  (b,  f),  and  a  portion  of  d  arises  from  the  columnar  cells  of  the  gray 
matter  and  represents  the  short  tracts  connecting  the  reflex  centers  in  the  gray 

matter  of  the  cord  and  in  the  medulla 
oblongata.  Sensory  conduction-paths  are 

,T         h  present  also  in  b,  e,  and  f.     Finally,  the 

columns  of  Goll  (c)  connect  the  posterior 
roots  with  the  gray  nuclei  of  the  funiculi 
graciles  of  the  medulla  oblongata.  The 
column  of  Burdach  (d)  contains  paths 
connecting  the  entering  posterior  roots 
with  the  nucleus  funiculi  fcuneiformis 
and  also  tracts  from  the  posterior  roots 
through  the  restiform  body  to  the  vermis 
of  the  cerebellum. 

The    direction    of    conduction    in   the 
posterior    columns    (the    continuations  of 
the  posterior  roots)  is  undoubtedly  ascend- 
ing,   as    they    degenerate     upward     after 
<]  /  destruction  of  the  posterior  roots. 

The  following  additional    points  have 

— System  of  Conducting  Tracts  .in  been    established    with    regard    to    these 

tracts:    The   pyramidal   tracts    (Fig.   a«. 
black  central  portion  of  the  figure  is  the  i  and   2),  the  direct  cerebellar  tracts  (3), 

gray  matter;    v,  anterior   root;    hw,  pos-  an(i    the  columns    of    Goll    (O  exhibit  pro- 

^dtind^^Er  c'oKS''  I  Strive  diminution  in  size  in  cross  section 

column  of  Goll;  d,  column  of  Burdach;  from    above    downward.        1  hey    connect 

e  and  f,  mixed  tracts  of  the  lateral  column;  intracranial  central  parts  with  the  groups 

h,  direct  cerebellar  tract.  Qf  ganglia  distributed  throughout  the  gray 

matter  of  the  spinal  cord.     The  columns  of 

Burdach  and  the  anterior  ground-bundle,  together  with  the  bundle  of  Gowers  and 
the  ground-bundle  of  the  lateral  tract  (6)  show  marked  variations  in  the  area 
of  section  at  different  levels  of  the  spinal  cord  in  proportion  to  the  size  of  the 
incoming  nerve-roots.  It  can,  therefore,  be  concluded  that  these  tracts  contain 
fibers  that  connect  the  gray  matter  at  the  different  levels  of  the  spinal  cord  and 
finally  also  in  the  medulla,  without,  however,  penetrating  into  the  higher  parts 
of  the  brain  itself. 

The  trophic  center  for  the  pyramidal  tracts  is  situated  in  the  cerebrum;  that 
for  the  anterior  roots  of  the  spinal  cord  in  the  ganglia  of  the  gray  matter  of  the 
cord.  After  division  of  the  spinal  cord  the  columns  of  Goll  and  the  direct  cere- 
bellar tracts  degenerate  in  an  ascending  direction.  The  trophic  center  for  the 
former  is  situated  in  the  cells  of  the  spinal  ganglia  of  the  posterior  roots,  that  for 
the  latter  in  those  of  the  columns  of  Clarke.  Those  fibers  of  the  white  substance, 
finally,  that  do  not  degenerate  at  all  after  section  of  the  cord  (and  of  which  there 
are  many  in  the  anterior  and  lateral  columns)  are  probably  commissural  fibers 
of  the  cord,  which  pass  from  ganglion  to  ganglion  (columnar-cell  fibers)  and 
have  their  trophic  centers  in  the  ganglion  at  either  extremity. 

Flechsig  makes  the  following  statements  with  reference  to  the  time  of  forma- 
tion of  the  different  systems :  The  first  to  form  are  the  paths  between  the  periphery 
and  the  central  gray  matter  of  the  cord,  especially,  therefore,  the  nerve-roots. 


THE    STRUCTURE    OF    THE     SPINAL    CORD. 


727 


Level  of 

I  he  first 

cervical  nerv< 


III.  Cervical  nerve. 


VI.  Cervical  nerve. 


Then  there  develop  fibers  that  connect  the  different  centers  in  the  gray  matter 

of  the  cord.     Next  there  appear  fibers  that  connect  the  gray  matter  of  the  cord 

with  the  cerebellum,  and  also  the 

former   with  the    tegmentum    of 

the  cerebral   peduncle.      Finally, 

there    develop    the    fiber-systems 

that  connect  the   ganglia  of   the 

pes  of  the  cerebral  peduncle  and 

perhaps  also  the  gray  matter  of 

the  cerebral  cortex  with  the  gray 

matter   of  the  spinal  cord.     The  s'^^mar  •  /'W--\      ^Xi^    ^   7, 

pyramidal    tracts  at  the  time  of  2     /^£ /  Hi   S^T^*  '' s^ 

birth  are  still  non-medullated.    In  g    ^/~J^p — «j  ^^ 

cases  of  congenital  absence  of  the 

cerebrum,    neither  the  pyramids 

nor  the  pyramidal  tracts  develop. 

Even  prior  to  birth    myelinated 

fibers  develop  in  the  brain  in  the 

paracentral    lobule,    the    central 

gyri,  the  occipital  lobe,  the  island 

of  Reil,  and  latest  in  the  frontal 

lobes. 

The  connective  tissue  of  the 
spinal  cord  is  derived  in  part  from 
the  pia  mater  and  penetrates  with 
the  vessels  only  into  the  white 
matter,  to  separate  the  nerve- 
fibers  into  separate  bundles.  From 
it  the  neuroglia  must  be  distin- 
guished -. —  the  true  supporting 
tissue.  This  is  not  a  connective 
tissue,  being  derived  from  the 
ectoderm.  It  consists  of  a  homo- 
geneous, structureless,  semisolid 
ground-substance,  together  with 
spider-shaped,  star-shaped,  or 
tree-shaped  glia-cells,  intricately 
interwoven,  and  nucleated  or  non- 
nucleated  fibers  composed  of 
keratin.  The  function  of  the 
neuroglia  is  to  afford  a  support- 
ing framework  for  the  nerve- 
tissues,  to  protect  them  from 
pressure  and  to  isolate  them.  In 
addition  it  forms  channels  for  the 
fluids,  or  lymphatic  passages, 
without  endothelial  lining,  for 
the  lymph  so  abundantly  given 
off  by  the  nervous  elements, 
especially  the  ganglia,  as  a  result 
of  their  activity,  to  eventually 
reach  the  perivascular  spaces  or 
the  subpial  space  directly.  This 
supporting  tissue  is  much  denser 
around  the  central  spinal  canal 
than  the  so-called  central  epen- 
dyma- fibers;  further,  it  is  more 
abundant  at  the  apex  and  the 
margins  of  the  posterior  horns, 
where  it  is  known  as  the  gelatin- 
ous substance  of  Rolando.  The 

npurno-lia     ic    -nrpc^nt     liV^Turicp.    in     FlG-    253.— Diagrammatic  Representation  of  the  Principal  Tracts 
neuroglia    IS    present     likewise   in  Of  the  Spinal  Cord:  1^5,  Anterior  pyramidal  tracts  (direct); 

the      cerebrum.         I  he      ganglion-  (2)  apsb,  lateral  pyramidal  tracts  (crossed);  (3)  3ksb,  direct 

Cells      are      surrounded      bv     CUp-  cerebellar  tracts;   (4)4dks,  external  column  of  Burdach;  (5) 

cl-ia-n<=>rl  KrmT->Vi  c-na/-«e>c  ^5<  internal  column  of  Goll;   (6)  6vsr,  combined  anterior 

ground-bundles.  Gowers'  column,  and  lateral  ground-bundles. 


Ill.  Dorsal  nerve. 


VI.  Dorsal  ner 


XII.  Dorsal  nerve. 


IV.  Lumbar  nerve.   - — 


728  THE    SPINAL    REFLEXES. 

THE  SPINAL  REFLEXES. 

By  reflex  movements  are  understood  such  as  are  induced  by  irritation 
of  a  centripetal  (sensory)  nerve.  The  latter  takes  up  the  irritation,  and 
conveys  it  to  the  spinal  cord,  the  cellular  gray  matter  of  which  acts  as 
the  reflex  center.  Here  the  impulse  is  transferred  to  the  motor  centrif- 
ugal path.  Three  factors  are  thus  concerned  in  a  reflex  movement 
and  together  constitute  the  so-called  reflex  arc:  the  centripetal  fiber, 
the  transferring  center  in  the  gray  matter,  and  the  centrifugal  fiber  (Fig. 
251,  s  h  v  m).  The  activity  of  the  will  is  excluded  in  the  occurrence  of 
a  reflex  movement. 

Three  varieties  of  reflex  movement  are  distinguished:  i.  The 
simple  or  partial  reflex,  which  is  characterized  by  contraction  of  a  single 
muscle  or  at  most  of  a  small  group  of  muscles  as  a  result  of  stimulation  of 
a  sensory  nerve.  Examples  of  this  type  of  reflex  movement  are  the 
contraction  of  the  quadriceps  femoris  muscle  following  a  tap  on  the  knee ; 
and  the  closure  of  the  lids  as  a  result  of  irritation  of  the  cerebral  nerves 
on  the  eye.  2.  The  widespread  Uncoordinated  reflex,  or  reflex  spasm. 
This  occurs  in  the  form  of  tonic  or  clonic  contractions  involving  entire 
groups  of  muscles,  or  even  all  of  the  muscles  of  the  body.  The  reflex 
spasm  is  due  to  a  double  cause :  (a)  the,  gray  matter  of  the  spinal  cord 
may  be  in  a  condition  of  excessive  irritability,  so  that  the  conveyed  stim- 
ulus can  be  readily  transferred  from  its  point  of  entrance  to  the  readily 
irritated  adjacent  central  areas.  Such  excessive  irritability  is  caused 
"by  certain  poisons,  particularly  strychnin,  and  also  brucin,  caffein,  atro- 
pin,  nicotin,  carbolic  acid,  etc.  The  slightest  touch  of  an  individual  pois- 
oned by  strychnin  is  sufficient  at  once  to  throw  all  of  the  muscles  of  the 
body  into  spasm.  Reducing  the  temperature  of  the  body  to  23°  C.  like- 
wise gives  rise  in  the  dog  to  marked  reflex  irritability.  Also  certain 
pathological  and  morbid  conditions  may  bring  about  a  similar  result.  An 
illustration  is  the  excessive  irritability  in  cases  of  hydrophobia  and  teta- 
nus. Conversely,  the  central  organs  may  be  placed  in  a  condition  in 
which  extensive  reflex  convulsions  cannot  occur.  Thus,  in  the  state 
of  apnea  the  convulsions  usually  attending  strychnin-poisoning  do  not 
occur,  in  consequence  of  the  passive  artificial  respiratory  movements, 
which  cause  stretching  of  the  cutaneous  nerves  of  the  abdomen  and  chest. 
Also  the  practice  of  other  periodic  passive  movements  of  portions  of  the 
body  gives  rise  to  a  similar  condition ;  and  considerable  reduction  in  the 
temperature  of  the  spine  inhibits  reflex  convulsions,  (b)  Extensive  reflex 
convulsions  may,  however,  occur  when  the  reflex  stimulation  is  severe. 
Examples  of  this  kind  are  observed  in  man,  as  in  the  widespread  con- 
vulsions attending  intense  neuralgias. 

The  general  convulsion  is  extensor  in  type  (involving  the  spinal  column: 
opisthotonus) ,  because  the  strength  of  the  extensors  is  greater  than  that  of 
the  flexors.  Nerves  arising  from  the  medulla  oblongata  may  be  excited  reflexly 
also  by  stimulation  of  remotely  situated  central  nerves,  without  the  occurrence 
of  general  convulsions. 

Strychnin,  the  most  powerful  of  the  poisons  exciting  reflex  convulsions,  acts 
directly  upon  the  ganglia  of  the  gray  matter  of  the  spinal  cord.  Therefore,  the 
same  reflex  convulsions  occur  when  the  poison  (in  the  frog,  after  ligation  of  the 
heart)  is  applied  directly  to  the  exposed  spinal  cord.  The  spasms  occur  after 
mechanical,  thermal,  or  electrical  stimulation,  but  not  after  chemical  stimulation. 
During  the  spasm  the  heart  stops  in  diastole  from  irritation  of  the  vagus,  and 
the  pressure  in  the  arteries  undergoes  a  marked  rise  as  a  result  of  irritation  of 


THE    SPINAL    REFLEXES.  729 

the  vasomotor  centers  in  the  medulla  and  spinal  cord.     Mammals  may  die  from 
asphyxia  during  the  attack;    although  after  large  doses  death  results  from  spinal 

Earalysis   when  the   convulsions   subside  early.     Fowl  are  as  a  rule  immune  to 
lirly  large  doses. 

Elicitation  of  the  Reflexes.  Feeble  stimuli  that,  applied  once,  are  in- 
capable of  exciting  a  reflex  may  do  so  after  repeated  application.  Under 
such  circumstances  a  summation  of  the  individual  stimuli  takes  place 
in  the  spinal  cord. 

In  order  to  obtain  such  a  result  three  feeble  stimuli  in  a  second  suffice;  the 
best  results  are  obtained  from  sixteen  in  a  second,  and  beyond  this  no  increase 
in  the  intensity  of  the  effects  is  possible.  Nevertheless,  stimuli  (induction-shocks) 
within  other  limits,  namely  an  interval  of  from  0.05  to  0.04  second,  have  been 
found  effective.  W.  Stirling  has  shown  that  the  reflexes  are  probably  due  to 
repetition  of  the  impulses  sent  to  the  nervous  centers. 

Diffusion  of  Reflexes.  Pfliiger  has  established  the  law  according  to  which 
the  diffusion  of  reflexes  takes  place:  (i)  The  reflex  movement  takes  place  first  on 
the  same  side  as  that  on  which  the  sensory  nerve  is  stimulated,  and  only  those 
muscles  are  thrown  into  action  whose  nerves  arise  from  the  same  level  of  the  cord. 
(2)  If  the  reflex  extends  to  the  other  side,  it  always  occurs,  as  an  asso- 
ciated movement  only  in  the  muscles  that  are  already  contracted  on  the  primary 
side.  (3)  If  the  intensity  of  the  spasm  is  different  on  the  two  sides,  the  move- 
ments are  stronger  on  the  primary  side.  (4)  On  diffusion  of  the  reflex  irritation 
to  adjacent  motor  nerves  those  are  involved  always  that  are  situated  in  the  direc- 
tion toward  the  medulla  oblongata.  Sherrington,  however,  has  observed  also 
diffusion  of  reflexes  in  a  caudal  direction.  (5)  Finally,  all  of  the  muscles  become 
involved  in  the  spasm. 

In  exceptional  cases,  however,  deviations  from  these  rules  occur.  If,  for 
example,  the  region  of  the  eye  in  a  frog,  after  extirpation  of  the  cerebrum,  be 
stroked,  a  reflex  in  the  hind  leg  of  the  opposite  side  often  occurs.  Tickling  the 
foreleg  of  decerebrated  tritons,  lizards,  turtles,  and  deeply  narcotized  dogs  and 
cats,  often  causes  a  movement  of  the  hind  leg  on  the  opposite  side.  These  mani- 
festations have  been  called  crossed  reflexes.  If  in  animals  a  section  be  made 
throughout  the  length  of  the  spinal  cord  in  the  median  line  the  reflexes  will  natur- 
ally remain  unilateral. 

Every  sensory  root  has,  in  its  individual  spinal  segment,  a  motor  reflex  path, 
which  offers  the  least  resistance  to  the  discharge  (simple  reflex).  There  are,  how- 
ever, also  reflex  paths  into  adjacent  and  remote  segments;  there  is  a  functional 
relation  between  certain  motor-cell  groups  and  certain  muscle-groups  that  act 
synergistically.  The  long  association-paths  in  the  spinal  cord  are  primarily  un- 
decussated;  crossed  conduction  appears,  however,  to  exist  between  segments  not 
widely  separated.  The  crossed  reflex  path  can  be  traversed  with  varying  ease 
at  different  levels  in  the  cord.  The  reflex  readily  passes  in  a  crossed  direction 
from  the  anterior  to  the  posterior  extremity;  on  the  other  hand,  from  the  pos- 
terior extremity  more  readily  to  that  of  the  opposite  side. 

The  reflex  can  be  conveyed  within  various  levels  of  the  cord.  On  applying 
feeble  stimuli  to  the  leg  of  a  decerebrated  frog,  the  reflex  transference  takes  place 
at  the  junction  of  the  cervical  cord  and  the  medulla;  on  applying  stronger  stimuli 
transference  takes  place  at  the  lower  portion  of  the  spinal  cord,  which  can  be 
stimulated  reflexly  with  greater  difficulty.  If  alternating  hemisections  of  the  cord 
be  made,  the  reflex  irritation  may  nevertheless  be  propagated  upward,  passing 
through  both  sides  of  the  cord  in  a  serpentine  manner.  The  greater  the  number 
of  sections,  the  stronger  must  be  the  irritation  of  the  sensory  nerves. 

3 .  The  widespread  coordinated  reflex  is  characterized  by  the  occurrence 
in  entire  and  even  different  groups  of  muscles  of  complex  movements 
having  a  purposive  character  or  resembling  voluntary  movements  and 
following  irritation  of  a  sensory  nerve. 

The  observations  are  made  either  on  cold-blooded  animals  (such  as  decapitated 
frogs,  lizards,  or  eels)  or  on  mammals,  the  four  arteries  passing  to  the  brain  being 
ligated  (artificial  respiration  being  maintained),  so  that  the  brain  is  rendered  incap- 
able of  functionating.  Reflexes  involving  the  lower  portion  of  the  spinal  cord  may 
be  studied  also  in  animals  (or  man)  after  transverse  section  of  the  spinal  cord  in 


730  THE    SPINAL    REFLEXES. 

the  upper  dorsal  region,  but  some  time  must  have  elapsed  after  the  section  so 
that  the  primary  irritation  of  the  lesion   (so-called  shock),  which  at  first  has  a 
reflex-inhibiting  effect,  may  subside.     Young  mammals  exhibit  reflex  activity  for 
some  time  even  after  decapitation.* 
The  coordinated  reflexes  include: 

1.  Protective  movements  and  movements  of  escape  are  observed  in  decere- 
brated  or  decapitated  frogs  and  turtles,  as  well  as  the  removal  of  acids  when 
applied  to  the  skin,  resistance  to  fixation-instruments,   etc.     All  of  these  move- 
ments  are   executed   apparently  with  deliberation  and  with  the  employment  of 
the  most  serviceable  groups  of  muscle,  so  that  Pfliiger  was  led  to  attribute  them 
to  a  spinal  consciousness.     Even  excised  portions  of  eel  turn  away  from  an  intense 
irritant  such  as  a  flame.     Also  the  tail  of  a  decapitated  triton,  lizard,  salamander, 
eel,  or  adder  submits  to  gentle  stroking,  but  turns  away  from  intense  irritation. 

2.  Goltz's  croaking  experiment,  which  consists  in  the  croaking  of  a  decere- 
brated  frog  when  the  skin  of  the  back  is  stroked. 

3.  Goltz's  embracing  experiment:  The  portion  of  the  trunk  of  a  young  male 
frog  between  the  skull  and  the  fourth  vertebra,  particularly  during  the  breeding 
season,  embraces  every  solid  body  that  comes  in  contact  with  the  skin  of  the  chest 
and  exerts  a  slightly  stimulating  effect. 

In  the  intact  animal  the  stimulating  irritant  consists  in  the  degree  of  fulness 
of  the  male  seminal  organs.  The  reflex  immediately  ceases  after  slight  irritation 
of  the  optic  thalamus. 

4.  In  warm-blooded  animals  (dogs)  the  following  are  among  the  coordinated 
reflexes  related  to  the  posterior  divided  extremity  of  the  cord:  Scratching  of  tickled 
portions  of  the  skin  with  the  hind-paw,  as  in  normal  animals;     the  movements 
necessary  for  the  evacuation  of  the  bladder   and  the   rectum,  for  erection   and 
the  act  of  parturition,  the  coordinated  movements  of  the  feet  and  the  tail  in 
decapitated  ducks  and  pigeons.     Coordinated  reflexes   simultaneously  in  widely 
separated  segments  of  the  cord  appear  as  a  rule  no  longer  .to  occur  after  removal 
of  the  medulla  oblongata.     For  this  reason  it  is  believed  that  the  medulla  may 
contain  a  complex  organ  of  higher  order  connecting  the  different  reflex  areas  in 
the  spinal  cord  (by  white  fibers) . 

5.  In  man  coordinated  reflexes  occur  also  during  sleep,  as  well  as  in  comatose 
states. 

By  far  the  majority  of  the  movements  executed  unconsciously  during  the 
waking  state,  or  when  the  mental  activities  are  otherwise  intently  engaged,  must 
be  included  among  the  coordinated  reflexes.  Many  complicated  movements  must 
first  be  learned  before  they  can  again  unconsciously  be  executed  harmoniously 
as  coordinated  reflexes,  such  as  dancing,  skating,  and  riding.  Coughing,  sneezing, 
and  vomiting  are  among  the  coordinated  reflexes  emanating  from  the  spinal  cord 
and  the  medulla  oblongata. 

With  reference  to  the  peculiarities  of  the  reflexes  the  following  points 
are  noteworthy: 

1.  The  reflexes  can  be  elicited  more  readily  and  in  more  complete 
degree  when  the  stimulus  is  applied  to  the  specific  end-organ  of  the  cen- 
tripetal nerve,  rather  than  to  the  trunk  of  the  nerve  itself  . 

2.  For  the  production  of  a  reflex  movement  a  stronger  stimulus  is 
required  than  for  direct  stimulation  of  the  motor  nerve.     The  reflex 
movement  induced  by  a  stimulus  of  adequate  intensity  appears  at  once 
as  a  moderately  strong  contraction,  which  does  not  increase  in  intensity 
with  increase  in  the  intensity  of  the  stimulus. 

3.  A  reflex  movement  is  of  shorter  duration  than  the  same  movement 
executed   voluntarily.     Further,  its    occurrence    after   the   moment    of 
irritation  is  distinctly  delayed,  the  interval  until  the  appearance  of  the 
muscular  contraction  (in  the  frog)  being  twelve  times  as  long  as  that 
required  for  conduction  through  the  sensory  and  motor  nerves.     The 
spinal  cord  thus  interposes  resistance  to  the  rapid  passage  of  the  impulse. 

The  reflex  time  (that  is   the  time  required  for  the  transference  of  the  impulse 

within  the  ganglion-cells  of  the  spinal  cord)  is  in  the  case  of  closure  of  the  eyelids 

man  0.042   second,  in  the  frog  on  an  average  in  various  muscles  from  0.008 


INHIBITION    OF     REFLEXES.  731 

to  0.015  second.  This  time  is  increased  by  about  a  third  if  the  impulse  passes 
to  the  opposite  side  or  through  the  length  of  the  cord  (from  the  sensory  root  of 
the  anterior  extremity  to  the  motor  root  of  the  posterior  extremity).  Heat 
diminishes  the  reflex  time  and  increases  the 'reflex  activity.  Lowering  of  the 
temperature  (winter- frogs) ,  likewise  the  poisons  previously  mentioned  that  in- 
crease reflex  activity,  increase  the  reflex  time,  while  at  the  same  time  increasing 
reflex  irritability.  Conversely,  the  reflex  time  diminishes  with  increase  in  the 
intensity  of  the  stimulus  and  it  may  thus  even  be  of  minimal  duration.  It  would 
appear  as  if  the  reflex  resulting  from  the  action  of  a  strong  stimulus  tra- 
verses a  shorter  path  (spinal  cord  in  the  frog)  than  that  resulting  from  the  action 
of  a  feeble  stimulus,  in  which  case  the  impulse  must  ascend  to  the  portion  of  the 
cord  below  the  calamus  scriptorius,  where  the  transfer  takes  place.  There  are, 
thus,  two  reflex  paths,  one  for  strong  stimuli,  the  other  for  feeble  stimuli,  the 
latter  being  generally  the  normal. 

The  reflex  time  can  be  measured  by  noting  the  time  of  irritation  of  the  sensory 
fiber  and  that  of  contraction.  From  the  result  thus  obtained  there  must  be 
deducted  the  time  required  for  conduction  through  the  two  nerve-tracts,  as  well 
as  the  duration  of  the  latent  stimulation. 

In  accordance  with  their  location  Jendrassik  divides  the  reflexes  as  follows: 

I.  Spinal  reflexes   (tendinous,  muscular,  periosteal,  bony,  articular,   genital- 
muscle  reflexes.     The  pathological  spinal  reflex  occurs  only  in  case  of  total  or  almost 
total  transverse  section  of  the  spinal  cord  and  is  manifested  as  flexor,  less  com- 
monly as  extensor,  movement  of  the  lower  extremities. 

II.  Cerebral  cortical  reflexes,  elicitable  especially  by  tickling  the  skin:  scapular, 
abdominal,  cremasteric,  scrotal,  gluteal,  plantar,  auricular,  palpebral,  palatal,  con- 
junctival,  anal  reflexes. 

III.  Complex  reflexes,   for   which  a  spinal  and  a  cerebral   reflex  center  are 
necessary:    sneezing,  vomiting,  swallowing,  coughing,  evacuation  of  bladder  and 
rectum,  ejaculation,  all  of  which  belong  to  the  vegetative  functions. 

INHIBITION  OF  REFLEXES. 

There  exist  in  the  body  mechanisms,  by  means  of  which  the  pro- 
duction of  reflexes  can  be  suppressed,  and  which  accordingly  have  been 
designated  reflex-inhibiting  mechanisms  : 

1 .  Through  the  action  of  the  will  reflexes  both  in  the  cerebral  and  in 
the  spinal  distribution  can  be  voluntarily  inhibited;  for  example,  keeping 
the  eyes  open  when  the  bulb  is  touched ;  suppression  of  movement  on  tick- 
ling the  skin.    It  should,  however,  be  observed  in  this  connection  that  the 
inhibition  of  the  reflexes  is  possible  only  to  a  certain  point.     If  the  stimu- 
lus be  strong  and  frequently  repeated  the  reflex  action  finally  predomi- 
nates over  the  volitional  inhibitory  impulses.     Moreover,  such  reflex 
movements  as  cannot  under  any  circumstances  be  executed  voluntarily, 
cannot  be  inhibited.    Thus,  erection,  ejaculation,  the  act  of  parturition, 
and  the  movements  of  the   iris   can   neither  be  executed  voluntarily, 
nor  if  excited  reflexly  can  they  be  inhibited  by  the  will. 

2.  Setschenow' s  inhibitory  center  is  the  designation  given  to  another 
cerebral  apparatus,  located  in  the  frog  on  both  sides  in  the  optic  thalamus 
and  the  quadrigeminate  bodies.     Separation  of  these  parts  by  section 
increases  reflex  irritability,  while  irritation  of  the  lower  cut  surface  (by 
sodium  chlorid  or  blood)  suppresses  reflex  movements.     This  result  can 
be  observed  also  on  one  side.     It  is  believed  that  analogous  organs  exist 
in  the  higher  vertebrates  in  the  quadrigeminate  bodies  and  in  the  medulla 
oblongata.     From  what  has  been  said,  it  is  clear,that  reflexes  occur  more 
regularly  and  are  more  readily  elicited  after  exclusion  of  the  brain. 

3.  Strong  irritation  of  a  sensory  nerve  suppresses  reflex  movement. 
The  reflex  does  not  appear  even  when  the  centripetal  nerve  involved  is 
strongly  irritated;  for  example,  inhibition  of  sneezing  by  friction  of  the 


732  INHIBITION    OF     REFLEXES. 

nose;  inhibition  of  the  movements  usually  elicited  by  tickling,  by  biting 
the  tongue.  Especially  strong  irritation  may  even  suppress  the  reflexes 
coordinated  for  voluntary  movement.  Intense  pain  in  the  abdominal 
organs  (intestine,  uterus,  kidneys,  liver,  bladder)  renders  impossible  the 
act  of  walking  or  of  standing.  In  the  same  category  belongs  the  falling 
down  which  follows  injury  to  viscera  richly  supplied  with  nerves,  and 
which,  either  by  involvement  of  motor  nerves  or  by  loss  of  blood,  would 
of  itself  be  insufficient  to  account  for  the  inability  to  maintain  the 
erect  posture.  Stimulation  of  the  central  organs  through  other  centri- 
petal paths  (such  as  the  organs  of  special  sense,  the  sexual  nerves,  etc.) 
diminishes  the  reflexes  in  other  paths. 

4.  During  the  discharge  of  an  energetic  reflex,  such  as  ejaculation, 
the  production  of  less  active  reflexes,  such  as  coughing,  is  suspended. 

5.  Attention  should  also  be  called  to  the  fact  that  inhibition  of  re- 
flexes, whether  through   the  will,  or   through  the  irritation  of  sensory 
nerves,  therefore  by  reflex  action,  is  often  attended  with  the  excitation 
of  antagonistic  movements.      In   some  cases,  further,  it  appears  to  be 
sufficient  to  inhibit  a  reflex  to  concentrate  the  attention  on  the  execu- 
tion of   such  a  complicated  reflex  movement  in  order  to  prevent  it. 
Some  persons,  for  example,  are  unable  to  sneeze  if  they  think  intently 
of  the  motor  processes  concerned;  as  the  will,  in  a  measure  prematurely, 
begins  to  control  the  reflex  center  by  the  thought,  the  normal  course 
of  the  reflex  excitation  for  the  stimulus  from  the  periphery  is  interfered 
with. 

6.  Certain  poisons,  such  as  chloroform,  picrotoxin,  morphin,  quinin, 
potassium  bromid,   and   others,   diminish   reflex  irritability,   probably 
after  a  transitory  increase.     A  constant  current  passed  longitudinally 
through  the  spinal  cord  enfeebles  the  reflexes,  particularly  a  descending 
current.     If  a  frog  be  paralyzed  by  asphyxia  in  air  free  from  oxygen, 
the  brain  and  the  spinal  cord  are  wrholly  unirritable  and  are,  therefore. 
incapable  of  reflex  excitation.     The   motor  nerves   and  the  muscles, 
however,  suffer  little  impairment  of  irritability,  even  after  the  lapse  of 
several  days. 

According  to  the  method  of  Turck  the  degree  of  reflex  irritability  in  decapi- 
tated frogs  is  tested  by  estimating  the  time  that  elapses  between  immersion  of 
the  foot  in  dilute  sulphuric  acid  and  withdrawal  of  the  part.  After  application  of 
blood  to  the  optic  lobes  or  after  irritation  of  a  sensory  nerve,  the  time  is  in- 
creased. 

Setschenow  differentiates  the  reflexes  into  tactile,  or  those  that  are  elicited 
by  irritation  of  tactile  nerves,  and  pathic,  or  those  resulting  from  irritation  of 
sensory  (pain-transmitting)  fibers.  He  believes,  with  Paschutin,  that  the  tactile 
reflexes  are  inhibited  by  the  will,  and  the  pathic  by  the  center  described  by  him. 

Theory  of  Reflexes. — The  following  theory  has  been  proposed  to  explain  the 

phenomena  observed  in  connection  with  reflex  movements.     It  is  believed  that 

the   centripetal   fiber,   in    the   transmission    of    the   impulse    conveyed   through 

it   encounters  considerable  resistance  within  the  gray  matter,  with  the  ganglion - 

;lls  of  which  it  is  contact  on  all  sides  through  the  fibrous  network  of  the  gray 

matter.     The  least  resistance  is  in  the  direction  of  those  motor  nerves  that  make 

their  exit  at  the  same  spinal  level  on  the  same  side.     In  this  way  the  weakest 

irritation  gives  rise  to  the  simple  reflex,  which  in  general  can  be  recognized  as  a 

simple  protective  or  defensive  movement  with  respect  to  the  seat  of    sensory 

timulation.     In  the  direction  of  other  motor  ganglion-cells  the  conduction  of 

the  impulse  encounters  still  greater  resistance.     In  order  for  the  reflex  to  be  trans- 

:d  also  along  these  paths,  either  the  stimulus  must  be  considerably  increased 

increasing  strength  and  duration  of  the  stimulation  the  reflex' movement 

may  increase  in  extent) ,  or  the  resistance  in  the  course  of  the  conduction  between 


INHIBITION    OF     REFLEXES.  733 

the  cells  of  the  gray  matter  must  be  diminished.  The  latter  may  be  brought 
about  by  the  action  of  the  poisons  mentioned,  as  well  as  under  the  influence  of 
general  increase  in  nervous  irritability,  such  as  is  observed  in  cases  of  hysteria 
and  neurasthenia.  Thus,  extensive  reflex  convulsions  may  occur  as  a  result  of 
increase  in  the  intensity  of  the  stimulus  or  of  a  diminution  in  the  conduction- 
resistance  in  the  spinal  cord.  Of  those  measures  that  have  been  shown  by  experi- 
ence to  diminish  or  prevent  reflex  manifestations,  the  conclusion  is  justified  that 
they  interpose  increased  resistance  in  the  conducting  paths  of  the  reflex  arc.  The 
action  of  influences  inhibiting  reflexes  must)  be  interpreted  in  a  similar  manner. 
As,  obviously,  the  fibers  of  the  reflex  arc  must  be  connected  with  the  reflex-in- 
hibiting conducting  tracts,  it  is  believed  that,  through  the  reflex-inhibiting  stimu- 
lation, resistance  is  at  the  same  time  interposed  in  the  reflex  arc.  Difficulty  is 
encountered  in  explaining  the  widespread,  coordinated  reflexes  according  to  the 
view  discussed.  It  has  been  assumed  that  from  long  use  and  also  through  hereditv 
those  groups  of  ganglion-cells  that  first  receive  the  impulses  are  placed  in  com- 
munication, under  conditions  most  favorable  to  conduction,  with  others  that  trans- 
mit the  impulse  to  those  groups  of  muscles  whose  activity  best  removes  the  body 
or  the  respective  member  from  possible  injurious  effects  of  the  stimulus  by  a 
coordinated,  purposive  movement.  Thus,  a  stimulus  always  excites  a  group  of 
ganglion-cells  coordinated  by  practice  and  responding  to  the  stimulus  as  an  har- 
monious, coordinated  motor  mechanism. 

Pathological. — Abnormalities  in  the  reflex  activity  afford  the  physician  a 
large  and  important  field  in  the  investigation  of  diseases  of  the  nervous  system. 
Enfeeblement  or  even  abolition  -of  reflex  activity  may  occur  (i)  as  a  result  of 
impairment  or  loss  of  irritability  in  the  centripetal  fibers;  (2)  as  a  result  of  analo- 
gous disorders  in  the  central  organs;  (3)  or,  finally,  in  the  centrifugal  fibers.  The 
reflexes  are  enfeebled  or  abolished  when  the  entire  nervous  system  is  greatly 
depressed,  as  after  concussion,  compression,  inflammation  of  the  central  organs, 
during  asphyxia  and  deep  coma,  and  in  consequence  of  various  intoxications. 
After  division  of  the  upper  portion  of  the  spinal  cord  in  man,  and  in  apes,  abolition 
of  the  reflexes  is  often  observed  in  the  parts  below  the  level  of  division.  It 
appears  that  the  upper  portions  of  the  cord  contain  the  region  where  normally 
the  reflexes  are  readily  transferred,  and  after  division  of  which  the  reflexes  are  in 
abeyance.  Dogs  and  cats,  like  the  frog,  exhibit  active  reflexes  after  division  of 
the  spinal  cord. 

Under  abnormal  conditions  special  attention  has  been  given  to  the  behavior 
of  certain  reflexes,  for  example  the  so-called  tendon-reflexes,  which  consist  in 
reflex  contraction  of  a  muscle  when  a  blow  is  struck  on  its  tendon,  for  example 
the  quadriceps  extensor  of  the  thigh,  the  tendo  Achillis.  etc.  Thus,  Westphal, 
Erb.  and  others  have  found  that  the  tendon-reflexes,  particularly  the  patellar- 
tendon  reflex,  also  known  as  knee-phenomenon  or  knee-jerk,  is  almost  constantly 
wanting  in  cases  of  ataxic  tabes  dorsalis,  but  is  abnormally  increased  and  extensive 
in  cases  of  spastic  spinal  paralysis,  which  is  characterized^  by  a  lesion  of  the  pyra- 
midal tracts.  Division  of  the  muscle-nerves  abolishes  the  patellar  phenomenon 
in  rabbits,  as  does  also  division  of  the  spinal  cord  between  the  fifth  and  sixth 
lumbar  vertebra1.  In  Landois  the  contraction  of  the  quadriceps  occurred  0.040 
second  after  the  blow  upon  the  patellar  ligament;  according  to  Jendrassik  0.039 
second  after  the  blow.  A  stronger  blow  has  no  effect  upon  the  reflex  time.  Ac- 
cording to  Westphal  these  phenomena  are  not  simple  reflex  processes,  but  com- 
plicated phenomena  related  to  muscle-tone,  so  that,  for  example,  diminution  in 
the  tone  of  the  quadriceps  fcmoris  may  abolish  the  phenomenon.  The  intact 
existence  of  the  external  segments  of  the  posterior  columns  of  the  spinal  cord 
is  necessary  for  the  preservation  of  the  phenomenon.  It  is  enfeebled  by  ph; 
or  mental  fatigue  and  increased  by  transitory  stimuli  that  involve  the  attention. 
Jendrassik  found  it  especially  marked  when  muscles  of  the  body  were  contracted 
voluntarily,  for  example  the  muscles  of  the  arm.  It  is  enfeebled  by  strong  and 
prolonged  contraction  and  extreme  tension. 

Another  reflex  of  diagnostic  importance  is  the  abdominal  reflex,  which  consists 
in  contraction  of  the  abdominal  muscles  on  stroking  the  skin  of  the  abdomen  with 
the  handle  of  a  percussion-hammer.  Thus  absence  of  this  reflex  on  both  sides  is 
indicative  of  diffuse  disease  of  the  brain  in  the  presence  of  a  cerebral  disorder. 
Absence  on  one  side  is  indicative  of  a  local  disorder  in  the  opposite  half  of  the  cere- 
brum. The  hypochondriac,  anal,  cremasteric,  conjunctival.  mammillary,  pupil- 
lary, nasal  reflexes  and  others  may  also  be  made  objects  of  investigation.  Cerebral 
lesions  attended  with  hemiplegia  always  exhibit  diminution  of  the  reflexes  upon 


734  CENTERS    IN    THE    SPINAL    CORD. 

the  paralyzed  side,  although  not  rarely  the  patellar  reflex  is  increased.  In  case 
of  extensive  cerebral  disease,  the  reflexes  are  wanting  on  both  sides  if  coma  is 
present  at  the  same  time,  naturally  also  those  of  the  anus  and  the  bladder. 

In  going  to  sleep  there  is  transitory  increase  of  the  reflexes.  In  early  sleep 
the  reflexes  are  enfeebled,  the  pupils  small.  During  sound  sleep  the  abdominal, 
cremasteric,  and  patellar  reflexes  are  wanting;  tickling  of  the  soles  of  the  feet 
and  of  the  nose  is  effective  only  when  of  a  certain  degree  of  intensity.  During 
narcosis,  as,  for  example,  that  induced  by  chloroform  or  morphin,  the  abdominal 
reflex  disappears  first,  then  the  conjunctival  and  the  patellar  reflex,  and  finally 
the  pupils  become  contracted. 

Abnormal  increase  in  reflex  activity  is  generally  indicative  of  an  increase  in 
the  irritability  of  the  reflex  center.  Abnormal  irritability  of  the  centripetal 
nerves  may  also  be  the  cause,  while  injury  is  a  cause  of  inhibition.  As  the  har- 
monious execution  of  voluntary  movements  is  largely  controlled  and  regulated  by 
reflex  activities,  it  will  be  readily  understood  that  various  derangements  in  those 
movements  are  observed  in  the  presence  of  disease  of  the  spinal  cord,  as  for  ex- 
ample the  characteristic  disorder  of  gait  and  of  the  movements  of  the  hands  in 
cases  of  tabes  dorsalis. 

CENTERS  IN  THE  SPINAL  CORD. 

The  spinal  cord  contains,  in  various  situations,  centers  that  on  reflex 
stimulation  permit  the  evolution  of  certain  coordinated  motor  mechan- 
isms. These  centers  are  capable  of  preserving  their  activity  even  when 
the  spinal  cord  is  separated  from  the  medulla  oblongata.  Further,  the 
centers  situated  in  the  lower  portion  of  the  cord  may  remain  active  after 
division  of  the  upper  portion,  but  in  the  normal  body  these  spinal  centers 
are  subordinate  in  their  activity  to  other  higher  reflex  centers  in  the 
medulla  oblongata.  The  centers  may,  therefore,  be  designated  also 
subordinate  spinal  centers.  Further,  the  cerebrum  may,  partly  through 
the  formation  of  conceptions,  partly  as  the  organ  of  the  will,  exert  an 
influence  upon  certain  of  the  subordinate  spinal  centers  by  excitation  or 
inhibition  of  the  reflexes.  The  following  particulars  are  deserving  of 
mention : 

The  center  for  dilatation  of  the  pupil  is  situated  in  the  lower  cervical 
portion,  extending  downward  to  the  level  of  the  first,  second,  and  third 
thoracic  vertebras — Budge's  ciliospinal  center.  It  is  stimulated  by 
darkness.  In  man  both  pupils  react  simultaneously  if  the  retina  on  one 
side  is  darkened.  Extirpation  of  this  portion  of  the  spinal  cord  on  one 
side  is  followed  by  contraction  of  the  pupil  on  the  same  side.  The  motor 
fibers,  which  have  their  trophic  center  in  the  same  situation,  pass  through 
the  anterior  roots  of  the  upper  three  thoracic  nerves,  in  the  cat,  into  the 
cervical  sympathetic. 

In  goats  and  cats  this  center,  separated  from  the  medulla  oblongata,  may 
be  stimulated  directly  by  a  state  of  the  blood  causing  dyspnea,  and  likewise  by 
reflex  stimulation  of  sensory  nerves,  for  example  the  median,  especially  if  the 
irritability  of  the  spinal  cord  has  been  increased  by  strychnin  or  atropin.  After 
total  division  of  the  upper  portion  of  the  cervical  cord,  subsequent  section  of  the 
sympathetic  is  followed  by  contraction  of  the  pupils.  The  superior  dilator  center 
situated  in  the  medulla  oblongata  is  described  on  p.  749. 

The  center  for  defecation — Budge's  anospinal  center.  The  centripetal 
nerves  are  contained  in  the  hemorrhoidal  and  inferior  mesenteric  plex- 
uses. The  center  is  situated  at  the  level  of  the  fifth  (in  the  dog)  or  sixth 
and  seventh  (in  the  rabbit)  lumbar  vertebrae.  The  centrifugal  fibers 
are  derived  from  the  pudendal  plexus  and  pass  to  the  sphincter  muscle. 
I  he  excitation  of  this  center  and  its  domination  by  the  cerebrum  are  dis- 
cussed on  p.  285. 


CENTERS    IX    THE    SPINAL    CORD.  735 

After  division  of  the  spinal  cord  Goltz  observed  that  the  anal  sphincter  con- 
tracted rhythmically  about  a  finger  introduced  into  the  rectum.  The  coordinated 
activity  of  the  center  is,  therefore,  possible  only  through  connection  with  the 
cerebrum.  After  extirpation  of  the  lumbar  cord,  the  anal  sphincter  at  first  loses 
its  tone,  although  this  is  partially  restored  later.  The  muscle  does  not  degenerate; 
perhaps  its  trophic  center  is  situated  in  the  mesenteric  ganglion. 

The  center  for  micturition.  Budge's  vesicospinal  center,  for  the  sphinc- 
ter muscle  is  situated  at  the  level  of  the  fifth  (dog)  or  the  seventh  (rabbit) 
lumbar  vertebra,  for  the  muscular  wall  of  the  bladder  at  a  somewhat 
higher  level.  It  functionates  in  a  coordinated  manner  only  when  con- 
nected with  the  cerebrum  (see  p.  522). 

The  center  for  erection  is  situated  in  the  lumbar  portion  of  the  cord. 
The  centripetal  fibers  are  the  sensory  nerves  of  the  penis.  The  centrif- 
ugal fibers  are,  for  the  deep  artery  of  the  penis,  the  vasodilator  nerves 
from  the  first,  second  and  third  sacral  nerves  (Eckhard's  erector  nerves), 
for  the  ischiocavernosus  and  the  deep  transverse  perineal  muscle  the 
motor  fibers  from  the  third  and  fourth  sacral  nerves.  The  latter  may 
be  stimulated  also  voluntarily,  the  former  also  in  part  from  the  cerebrum 
by  directing  attention  to  sexual  activity.  Eckhard  observed  erection 
also  after  stimulation  of  higher  portions  of  the  spinal  cord  (Landois 
likewise  in  man),  as  well  as  of  the  pons  and  the  cerebral  peduncles. 

In  accordance  with  clinical  observations  the  centers  for  the  bladder  and  the 
rectum  and  for  erection  are  situated  at  the  point  of  exit  of  the  first,  second,  third 
and  fourth  sacral  nerves. 

The  center  for  ejaculation.  The  sensory  (dorsal  nerve  of  the  penis) 
are  the  exciting  nerves.  The  center  (Budge's  genitospinal  center)  is 
situated  at  the  level  of  the  fourth  lumbar  vertebra,  in  rabbits.  The 
motor  fibers  of  the  vasa  deferentia  are  derived  from  the  fourth  and  fifth 
lumbar  nerves,  which  enter  the  sympathetic  and  finally  pass  thence  to 
the  vasa  deferentia.  The  motor  fibers  for  the  bulbocavernous  muscle, 
the  ejaculator  of  the  seminal  fluid  from  the  bulb  of  the  urethra,  are 
contained  in  the  third  and  fourth  sacral  nerves  (perineal  nerves).  Ejac- 
ulation may  be  induced  by  mechanical  stimulation  of  the  lumbar  cord, 
in  guinea-pigs. 

The  center  for  the  act  of  parturition  is  situated  at  the  level  of  the  first 
and  second  lumbar  vertebrae.  The  centripetal  fibers  are  derived  from 
the  uterine  plexus,  into  which  also  the  motor  fibers  from  the  spinal  cord 
again  enter.  Goltz  and  Freusberg  observed  impregnation  and  delivery 
in  a  bitch  with  the  spinal  cord  divided  at  the  level  of  the  first  lumbar 
vertebra.  Similar  results  have  been  observed  in  women  with  the  spinal 
cord  divided.  Normal  birth  occurred  with  subsequent  involution  of  the 
uterus  and  secretion  of  milk. 

Centers  for  the  vascular  nerves,  both  vasomotor  and  vasodilator,  are 
distributed  throughout  the  entire  spinal  axis.  Among  these  is  to  be 
included  also  the  center  for  the  spleen,  which  is  situated  between  the 
first  and  fourth  cervical  vertebrae,  in  the  dog.  They  can  be  excited 
reflexly,  although  they  are  subordinated  to  the  dominating  centers  in 
the  medulla  oblongata.  They  may  be  influenced  also  by  psychic  stimu- 
lation, from  the  cerebrum. 

Centers  for  the  secretion  of  sweat  have  perhaps  a  distribution  analogous 
to  that  of  the  centers  for  the  vascular  nerves. 

The  movements  excited  from  the  centers  named  are,  in  accordance  with  what 
has  been  stated,  to  be  designated  coordinated  reflexes  and  fundamentally  to  be 


736  IRRITABILITY    OF    THE    SPINAL    CORD. 

included  with  the  coordinated  reflexes  of  the  musculature  of  the  trunk  and  the 
extremities. 

Muscular  Tone. — Automatic  functions  also  were  formerly  credited  to  the  spinal 
cord,  one  of  which  was  a  certain  moderate  degree  of  active  tension  of  the  muscles 
that  is  designated  tone.  It  was  thought  that  the  tone  of  the  transversely  striated 
fibers  was  demonstrated  by  the  retraction  of  the  extremities  of  a  divided  muscle, 
but  this  is  due  simply  to  the  circumstance  that  all  of  the  muscles  are  somewhat 
stretched  beyond  their  normal  length,  and  for  this  reason  also  paralyzed  muscles, 
which  must  have  lost  their  nervous  tone,  exhibit  exactly  the  same  phenomenon. 
Also  the  increased  contraction  of  certain  muscles  after  paralysis  of  their  antagonists, 
and  the  distortion  of  the  face  toward  the  healthy  side  after  unilateral  facial  paraly- 
sis, have  been  cited  as  examples  of  tone.  These,  however,  are  due  to  the  fact  that 
after  activity  of  the  intact  muscle  strength  is  wanting  to  restore  the  parts  affected 
to  the  normal  median  position  of  rest.  The  following  experiment  of  Auerbach 
and  Heidenhain  is  opposed  to  the  assumption  of  a  tonic  contraction.  If  the 
muscles  of  a  decapitated  frog's  leg  be  made  tense,  they  do  not  elongate  after 
division  of  the  sciatic  nerve,  or  after  paralysis  of  jthis  nerve  by  application  of 
ammonia  or  carbolic  acid.  If,  however,  a  decapitated  frog  is  suspended  in  an 
abnormal  position,  it  will  be  observed  that  if  the  sciatic  nerve  on  one  side  or  the 
posterior  roots  of  the  nerves  of  this  extremity  have  been  divided,  then  the  member 
upon  this  side  hangs  in  a  relaxed  manner,  while  the  member  upon  the  intact 
side  is  slightly  retracted.  The  sensory  nerves  of  the  latter  are  by  the  weight  of 
the  member  thrown  permanently  into  a  state  of  gentle  stimulation,  so  that  by 
this  means  a  slight  reflex  retraction  upward  of  the  member  is  brought  about, 
which  fails  to  occur  as  soon  as  the  sensory  nerve-fibers  of  the  member  are  paralyzed. 
If  the  slight  retraction  mentioned  is  to  be  considered  as  tone,  then  it  is  to  be 
characterized  as  reflex  tone.  With  this  experiment  that  of  Harless,  C.  Ludwig 
and  Cyon  should  be  compared  (p.  716). 

IRRITABILITY  OF  THE  SPINAL  CORD. 

At  the  present  time  there  is  no  unanimity  of  opinion  as  to  whether 
the  spinal  cord,  like  a  peripheral  nerve,  is  irritable,  or  whether  it  is  char- 
acterized by  the  remarkable  peculiarity  that  most  of  its  conducting 
paths  and  ganglia  are  without  reaction  to  direct  electrical  and  mechani- 
cal stimuli. 

An  outline  of  the  views  of  the  opposing  investigators  is  as  follows:  If  stimuli 
are  carefully  applied  to  the  exposed  white  or  gray  matter,  neither  movement  nor 
sensory  perception  results.  In  making  this  observation,  however,  the  greatest 
care  must  be  taken  to  avoid  irritation  of  the  roots  of  the  spinal  nerves,  as  these 
naturally  react  to  stimuli  and  thus  excite  sensations,  as  well  as  reflex  movements, 
on  the  one  hand,  and  also  directly  excited  movements  on  the  other  hand.  As 
the  spinal  cord  thus  conveys  to  the  brain  the  impulses  brought  to  it  through 
the  stimulated  posterior  roots,  but  is  incapable  of  reacting  even  to  stimuli  exciting 
sensory _  impressions  Schiff  has  designated  it  as  esthesodic,  that  is  transmitting 
perceptions.  Moreover,  as  the  cord  is  capable,  in  like  manner,  of  conducting  both 
voluntary  and  reflex  motor  impulses,  without,  however,  being  itself  receptive  for 
motor  impulses  applied  directly,  it  is  kinesodic,  that  is  movement-conducting. 

According  to  Schiff,  therefore,  all  of  the  results  that  follow  stimulation  of 
the  uninjured  spinal  cord,  such  as  spasm  and  contracture,  are  caused  by  simul- 
taneous stimulation  of  anterior  roots,  or  they  are  reflexes  from  the  posterior 
columns  alone  or  from  the  posterior  columns  and  the  posterior  roots  at  the  same 
time.  Diseases  involving  only  the  anterior  and  lateral  columns  never  cause 
irritative,  but  only  paralytic  symptoms.  In  the  state  of  complete  anesthesia  and 
in  that  of  apnea,  all  stimulation  is  without  effect.  According  to  Schiff' s  view  all 
of  the  centers,  both  spinal  and  cerebral,  cannot  be  stimulated  by  artificial  means. 
The  situation  of  a  center  can  for  this  reason  be  determined  onlv  bv  the  paralvtic 
method. 

Schiff  concludes,  therefore,  that  in  the  posterior  columns  the  sensory 
root -fibers  produce  pain  on  stimulation,  but  not  the  actual  paths  for  the 
posterior  columns  themselves.  Schiff,  however,  observed  as  a  sign  that 
stimulation  of  the  actual  paths  caused  tactile  sensations,  dilatation  of 


IRRITABILITY    OF    THE    SPINAL    CORD.  737 

the  pupils  with  each  stimulation.  Removal  of  the  posterior  columns 
causes  anesthesia,  loss  of  touch.  Algesia,  pain-sensation,  is  preserved, 
and  at  first  there  is  even  hyperalgesia. 

The'  anterior  columns  cannot  be  stimulated  so  as  to  affect  either 
transversely  striated  or  unstriated  muscles,  if  only  the  actual  tracts  are 
stimulated.  Movements  may  occur,  however,  either  if  the  motor  root- 
fibers  are  stimulated  or  if  the  current  reaches  the  posterior  columns,  in 
which  it  stimulates  the  sensory  root -fibers  and  thus  causes  reflex  move- 
ments. 

Numerous  investigators  are  opposed  to  these  views  and  express  themselves 
in  favor  of  the  possibility  of  direct  stimulation  of  the  spinal  cord.  Pick  maintains 
that  he  is  able  to  induce  movements  of  the  hind  legs  by  irritating  directly  the 
anterior  columns  isolated  for  a  considerable  distance  in  order  to  eliminate  diffusion 
of  the  current.  Biedermann  reaches  the  conclusion  that  the  motor  nerve  is  most 
irritable  on  its  transverse  section.  Also  on  transverse  section  of  the  spinal  cord, 
in  the  frog,  feeble  stimuli,  such  as  descending  opening  shocks,  are  effective,  but 
not  further  downward.  This  observation  is  in  favor  of  analogous  sensibility  to 
stimuli  on  the  part  of  both.  According  to  Schiff's  investigations  in  this  con- 
nection, however,  the  anterior  column  of  the  spinal  cord  of  the  frog  contains, 
in  addition  to  the  longitudinal  fibers  controlling  movement,  also  sensory  fibers, 
stimulation  of  which  may  cause  reflexes.  Therefore,  all  of  the  observations  made 
on  the  anterior  columns  of  the  frogs  are  not  available  as  evidence  in  favor  of  the 
direct  irritability  of  the  motor  paths  in  the  anterior  columns.  The  sensory  fibers  in 
question  are  believed  to  rise  from  the  gray  matter  and  to  pass  within  the  spinal  cord 
to  the  anterior  columns,  without  first  making  their  exit  through  the  posterior 
roots — intracentral  nerves. 

The  vasoconstrictors  passing  downward  from  the  vasomotor  center 
through  the  spinal  cord  can  be  irritated  within  the  cord  by  all  stimuli. 
Direct  stimulation  of  any  transverse  section  of  the  spinal  cord  causes 
contraction  of  all  of  the  vessels  innervated  below  that  level.  In  a  similar 
manner  the  fibers  ascending  in  the  spinal  cord  and  exerting  a  pressor 
effect  upon  the  vasomotor  center  can  be  irritated.  Their  stimulation 
causes  no  sensation.  According  to  Schiff,  the  results  obtained  in  these 
observations  are,  however,  likewise  not  due  to  direct  irritation 

The  spinal  cord  appears  to  be  insensitive  to  chemical  stimuli,  such 
as  moistening  the  cut  surfaces  with  blood. 

The  motor  centers  can  be  irritated  directly  by  blood  at  a  temperature 
above  40°  C.  and  by  blood  from  an  asphyxiated  person  or  by  sudden  and 
total  anemia  in  consequence  of  ligation  of  the  aorta ;  likewise  by  certain 
poisons,  such  as  picrotoxin,  nicotin,  barium-compounds: 

In  experiments  of  this  character  the  spinal  cord,  for  example  at  the  level  of 
the  last  thoracic  vertebra,  must  have  been  divided  some  twenty  hours  previously, 
in  order  that  it  shall  have  recovered  from  shock.  The  posterior  roots  in  the 
lower  portion  should  also  have  been  divided  previously,  in  order  to  eliminate 
any  possible  reflex  influences.  If  dyspnea  be  induced  in  cats  thus  prepared,  or 
if  their  blood  be  overheated,  extensor  spasm,  vascular  contraction,  secretion  of 
sweat,  evacuation  of  the  bladder  and  the  rectum,  as  well  as  contraction  of  the 
uterus  or  the  vasa  deferentia,  occur  in  the  distribution  of  the  nerves  from  the 
lower  portion  of  the  cord.  The  administration  of  certain  poisons,  such  as  picro- 
toxin, has  a  similar  effect.  In  animals  with  the  medulla  oblongata  divided, 
rhythmic  respiratory  movements  can  even  be  induced  in  this  way,  if  the  spinal 
cord  has  been  previously  rendered  highly  irritable  by  the  administration  of  strych- 
nin or  the  action  of  heat. 

Also  mechanical  stimuli  are  capable  of  irritating  the  ganglion-cells 
of  the  anterior  horns,  and,  according  to  Biedermann,  the  gray  matter 
responds  to  electrical  stimulation. 
47 


738  CONDUCTING    PATHS    IN    THE    SPINAL    CORD. 

The  remarkable  fact  is  worthy  of  mention  that  after  unilateral  division  of 
the  spinal  cord,  or,  in  the  rabbit,  of  the  posterior  and  the  innermost  portion  of  the 
lateral  column,  hyperesthesia  below  the  level  of  the  section  appears  upon  the 
same  side,  so  that  rabbits  cry  aloud  on  slight  pressure  being  made  upon  the  toes. 
The  phenomenon  may  persist  for  some  three  weeks,  and  it  may  be  replaced  by 
normal  or  subnormal  sensibility.  The  healthy  side  exhibits  permanent  impair- 
ment of  sensibility.  Similar  results  have  been  observed  in  human  beings  with 
like  lesions.  An  analogous  phenomenon  occurs  after  division  of  the  anterior 
columns,  that  is,  a  marked  tendency  to  contractions  in  the  muscles  below  the 
level  of  the  section — hyperkinesis. 

In  the  intact  body  the  normal  irritability  of  the  spinal  cord  is 
dependent  upon  the  continuance  of  the  normal  circulation.  Ligation 
of  the  abdominal  aorta  gives  rise  rapidly  to  paralysis  and  anesthesia  in 
the  lower  portions  of  the  body. 

Sudden  total  anemia,  as  from  occlusion  of  the  aorta,  in  dogs,  causes  at  first 
convulsions,  lasting  for  twenty  seconds;  then  paralysis,  lasting  for  one  minute; 
next  sensory  excitation,  lasting  for  two  minutes;  and  finally  anesthesia,  lasting 
for  three  minutes.  Incipient  degenerative  processes  appear  in  the  ganglion-cells 
in  the  course  of  a  few  hours. 

After  prolonged  ligation  the  anterior  roots  of  the  spinal  cord  and  the 
entire  gray  matter  of  the  lower  portion  of  the  cord  that  has  been  rendered 
anemic  undergo  degeneration.  Motility  and  sensibility  a^e  permanently 
lost  in  the  posterior  extremities. 

CONDUCTING  PATHS  IN  THE  SPINAL  CORD. 

Method. — The  conducting  paths  in  the  spinal  cord  can  be  demonstrated  by 
means  of  histological  examination;  of  no  less  importance  is  a  study  of  the  func- 
tional disturbances  exhibited  by  persons  suffering  from  injury  or  degeneration 
in  circumscribed  areas.  Animal  experimentation  is  capable  of  affording  confirma- 
tion in  an  analogous  manner,  although  certain  differences  in  the  relations  of  the 
conditions  are  observed  as  compared  with  those  present  in  human  beings. 

Flatau  established  the  general  law  that  the  short  paths  in  the  spinal 
cords  are  situated  nearer  the  gray  matter,  and  the  long  paths  nearer 
the  surface. 

Localized  tactile  impressions — pressure-sense,  sensation  of  cold,  muscle- 
sense — are  conveyed  upward  through  the  posterior  columns  on  the  same 
side.  The  conduction  of  the  sensation  of  heat  is  said  to  take  place 
throughout  the  entire  gray  matter.  Interruption  of  the  posterior  col- 
umns abolishes  the  sense  of  cold,  the  pressure-sense,  and  the  muscular 
sense.  The  course  in  the  brain  is  described  on  p.  745. 

The  columns  of  Goll  in  the  cervical  cord  contain  continuations  of  the  pos- 
terior dorsolumbar  and  lower  dorsal  roots.  The  path  for  the  muscle-sense  is 
through  the  column  of  Burdach;  where  it  approaches  the  medulla  oblongata  is 
situated  the  path  for  the  muscle-sense  in  the  arms. 

In  the  rabbit  the  path  for  localized  tactile  sensation  is  situated  in  the  lateral 
column  in  the  lower  portion  of  the  dorsal  cord.  Division  of  certain  portions  of 
the  lateral  column,  in  the  rabbit,  abolishes  this  sensation  for  certain  related 
cutaneous  areas.  Total  division  upon  one  side  has  the  same  effect  for  the  entire 
half  of  the  body  below  the  level  of  the  section.  The  condition  of  abolished  tactile 
and  muscular  sense  is  designated  anesthesia. 

The  impulses  for  localized  voluntary  movements  are  conducted  in  man 
through  the  anterior  and  lateral  columns  of  the  same  side,  through 
the  pyramidal  tracts.  At  the  corresponding  level  of  the  spinal  cord  the 
fibers  enter  first  into  contact  with  the  ganglion-cells  of  the  anterior  horns 
and  thence  the  impulses  pass  into  the  appropriate  anterior  root  (Fig. 
355-  M). 


CONDUCTING    PATHS    IN    THE    SPINAL    CORD.  739 

The  exact  division-experiments  of  C.  Ludwig  and  Woroschiloff,  Ott  and 
Meade  Smith  demonstrated  in  the  rabbit  that  in  the  lower  dorsal  portion  of  the 
cord  the  course  of  the  fibers  is  exclusively  in  the  lateral  column.  Partial  division 
of  the  lateral  column  abolishes  voluntary  movement  in  individual  related  muscles 
below  the  level  of  the  section.  From  what  has  already  been  stated  it  will  be 
clear  that  the  lateral  columns  increase  progressively  in  size  and  in  the  number 
of  fibers  they  contain  from  below  upward.  In  the  anterior  horn  every  motor 
fiber  enters  into  relation  with  one  ganglion-cell,  as  has  been  demonstrated  in  the 
frog. 

The  fibers  that  intermediate  the  tactile,  widespread,  coordinated  re  flexes 
enter  through  the  posterior  roots  and  then  pass  to  the  columnar  cells. 
At  the  various  levels  of  the  cord,  the  groups  of  ganglion-cells  that  con- 
trol the  coordinated  reflexes  are  further  connected  by  fibers  that  for  the 
extremities  pass  within  the  anterior  mixed  tracts  of  the  lateral  column 
(the  ground-bundle  of  the  anterior  column  ?)  and  for  the  trunk  in  the 
posterior  column.  From  the  motor  ganglion-cells  the  fibers  for  the 
stimulated  muscles  pass  through  the  anterior  roots. 

Ataxic  tabes  dorsalis,  in  which,  principally  on  a  syphilitic  basis,  degeneration 
of  the  posterior  columns  is  encountered,  is  noteworthy  on  account  of  its  charac- 
teristic motor  disturbances.  Voluntary  movements  can,  it  is  true,  be  executed 
with  full  strength,  but  they  lack  the  fine  harmonious  gradation  with  reference  to 
intensity  and  extent.  This  function  is  in  part  subserved  by  the  normal  existence 
of  tactile  sensations  and  of  the  muscular  and  articular  sense,  the  paths  for  which 
are  situated  in  the  posterior  columns.  After  degeneration  of  the  latter,  not  only 
anesthesia,  but  also  derangement  in  the  execution  of  the  tactile  reflexes,  occurs, 
as  the  centripetal  segment  of  the  arc  is  interrupted.  Also  the  tone  of  the  muscles, 
which  depends  essentially  upon  reflex  stimulation,  is  considerably  lowered,  and  in 
consequence  the  muscles  exhibit  an  excessive  degree  of  passive  extensibility.  An 
associated  lesion  of  the  simply  sensory  nerves,  however,  may  in  an  analogous 
manner,  as  a  result  of  anesthesia  and  loss  of  the  pathic  reflexes,  give  rise  also  to 
disturbances  in  coordination  of  movement.  As  the  fibers  of  the  posterior  roots 
pass  through  the  white  matter  of  the  posterior  columns,  it  will  thus  be  clear  that 
disorders  in  the  sensory  sphere  occur  as  a  result  of  degeneration  of  these  parts. 

The  view  also  is  maintained  by  some  that  tabes  represents  a  disease  of  the 
posterior  roots  extending  to  the  spinal  cord,  for  the  roots  also  are  found  involved 
in  the  degenerative  process,  and  their  involvement  may  be  responsible  for  the 
derangement  in  the  sensory  sphere.  The  latter  consists  in  part  in  an  abnormal 
increase  of  tactile  or  pain  impressions,  associated  with  lancinating  pains,  while 
in  part  it  may  be  increased  to  the  point  of  anesthesia  or  analgesia.  At  the  same 
time  tactile  sensibility  is  altered,  in  consequence  of  irritation  of  the  posterior 
columns,  as  indicated  by  sensations  of  numbness,  softness,  formication,  or  con- 
striction. Often  sensory  conduction  is  delayed.  The  sensibility  of  the  muscles, 
joints  and  internal  parts  is  altered.  If,  finally,  the  posterior  columns  really 
contain  fibers  for  the  conduction  of  widespread  coordinated  reflexes,  the  ataxia 
can  be  explained  in  part  by  an  interruption  of  these  paths.  The  exceedingly  rare 
cases  of  tabes  without  sensory  derangement  are  to  be  interpreted  only  by  assuming 
that  either  the  conducting  paths  of  the  coordinated  reflexes  or  the  ganglion-cells 
are  injured. 

Inhibition  of  the  tactile  reflex  takes  place  through  the  tracts  of  the 
anterior  columns.  At  the  proper  level  the  conducting  fibers  pass  from 
the  anterior  column  into  the  gray  matter,  in  order  to  enter  into  contact 
with  the  fibers  of  the  reflex  apparatus. 

The  transmission  of  pain  impressions  takes  place  through  the  pos- 
terior roots  and  thence  through  the  entire  gray  matter.  Loss  of  pain  or 
of  thermal  sensibility  occurs  in  man  as  a  result  of  disease  of  the  spinal 
cord  in  or  near  the  posterior  horn.  In  part  decussation  of  the  fibers 
that  pass  from  one  side  to  the  other  takes  place  in  the  cord.  Their 
further  course  to  the  brain  is  described  on  p.  745. 


74-O  CONDUCTING    PATHS    IN    THE    SPINAL    CORD. 

If  the  gray  matter  is  divided  except  for  a  small  connecting  band,  this  alone 
will  suffice  to  convey  pain  impressions  upward.  According  to  Schiff,  however, 
the  transmission  under  such  circumstances  is  delayed.  Only  after  the  gray 
matter  has  been  wholly  divided  does  the  conduction  of  all  pain  sensation  from 
the  portions  of  the  body  below  the  level  of  the  section  cease.  In  this  way  the 
condition  of  analgesia  is  brought  about,  while  tactile  sensibility  persists  if  the 
posterior  columns  are  intact.  A  similar  condition  is  not  rarely  observed  in  human 
beings  during  incomplete  chloroform-narcosis,  and  particularly  during  the  narcosis 
induced  by  the  combined  administration  of  chloroform  and  morphin.  As  these 
poisons  benumb  the  nerves  transmitting  pain  sensations  earlier  than  the  tactile 
nerves,  those  operated  on  maintain  that  they  appreciate  the  operation  as  a  tactile 
impression,  as  pressure,  etc.,  but  not  as  pain.  As  the  conduction  of  pain  takes 
place  everywhere  through  the  gray  matter,  and  as,  further,  the  excitation  of  pain 
extends  the  more  widely  throughout  the  gray  matter  the  more  intense  the  painful 
manipulation,  the  so-called  irradiation  of  the  pain  impressions  can  be  under- 
stood. In  the  presence  of  severe  pain,  the  pain  appears  to  radiate  widely  from 
its  seat  of  origin.  Thus,  for  example,  in  case  of  severe  toothache  beginning  in  a 
given  tooth  the  pain  soon  radiates  to  the  entire  maxillary  region  and  even  to  the 
entire  half  of  the  head.  In  contradiction  of  this  statement  Bechterew  maintains 
that  the  path  for  pain  impressions  is  situated  in  the  lateral  columns,  in  the 
rabbit,  hen  and  dog. 

The  impulses  for  spasmodic,  involuntary,  Uncoordinated  movements 
are  transmitted  through  the  gray  matter  and  from  the  latter  through 
the  anterior  roots. 

Such  transmission  occurs,  for  example,  in  cases  of  epilepsy  and  as  a  result 
of  certain  intoxications,  for  instance  with  strychnin,  in  cases  of  uremic  intoxica- 
tion and  of  tetanus.  Also  the  convulsions  associated  with  anemia  and  dyspnea  are 
transmitted  downward  from  the  medulla  oblongata  through  the  entire  gray 
matter. 

The  impulses  for  widespread  reflex  convulsions  are  transmitted  from 
the  posterior  roots  to  the  ganglion-cells  of  the  gray  matter,  further 
through  the  anterior  horns  and  finally  into  the  anterior  roots,  and  under 
conditions  that  have  been  described  in  the  discussion  of  this  variety  of 
reflex  convulsions. 

Inhibition  of  the  pathic  reflexes  is  effected  through  the  anterior  column 
downward  and  then  in  the  gray  matter  to  the  connecting  tracts  of  the 
reflex  organs,  into  which  resistance  is  introduced. 

The  vasomotors  pass  through  the  lateral  columns  and,  after  having 
entered  the  ganglion-cells  of  the  gray  matter  at  a  given  level,  leave  the 
spinal  cord  through  the  anterior  roots.  Later  on,  they  approach  vessels 
provided  with  a  muscular  coat,  either  simply  through  the  path  for  the 
spinal  nerves,  or,  more  frequently,  they  pass  through  the  communicating 
branches  into  the  sympathetic  and  from  this  to  the  vascular  plexuses. 

Division  of  the  spinal  cord  paralyzes  all  of  the  vasomotors  below  the  level 
of  the  section.  Stimulation  of  the  peripheral  stump  of  the  cord  conversely  causes 
contraction  of  all  of  the  vessels. 

Fibers  having  a  pressor  action  enter  the  cord  through  the  posterior 
roots,  then  pass  upward  in  the  lateral  column  and  undergo  incomplete 
decussation. 

Their  final  goal  is  the  dominating  vasomotor  center  in  the  medulla  oblongata, 
which  thus  they  stimulate  reflexly.  Analogous  depressor  fibers  must  pass  through 
the  spinal  cord,  although  nothing  concerning  them  is  known. 

From  the  respiratory  center  in  the  medulla  oblongata  there  pass 
downward  in  the  lateral  column  on  the  same  side  the  respiratory  nerves, 
which,  after  reaching  the  ganglion-cells  of  the  gray  matter,  pass  through 
the  anterior  roots  into  the  motor  nerves  to  the  muscles  of  respiration. 


COURSE    OF    THE    MOTOR    AND    SENSORY    TRACTS.  741 

Unilateral  or  total  division  of  the  spinal  cord  at  progressively  higher  levels 
paralyzes,  accordingly,  respiratory  nerves  arising  at  successively  higher  levels  on 
the  same  side  or  on  both  sides. 

Pathological. — In  case  of  degeneration  or  direct  injury  of  the  spinal  cord  or 
of  individual  portions  of  the  cord,  it  should  be  especially  noted  that  occasionally 
in  recent  cases  irritative  and  paralytic  phenomena  occur  side  by  side  in  closely 
adjacent  portions  of  the  cord,  and  as  a  result  an  analysis  of  the  clinical  picture 
is  rendered  difficult. 

Degeneration  of  the  posterior  columns,  without  involvement  of  the  afferent 
posterior  roots,  causes  loss  of  tactile  sensibility  as  the  most  conspicuous  symptom, 
while  thermal  sensibility  is  preserved.  Degeneration  of  the  ganglion-cells  in  the 
anterior  horns,  for  example  in  cases  of  spinal  paralysis  of  infants,  gives  rise  to 
paralysis  in  the  distribution  of  the  efferent  motor  nerves.  At  the  same  time  the 
muscles  supplied  by  these  nerves  undergo  rapid  atrophy.  The  ganglion-cells  are 
the  trophic  centers  for  the  nerves  and  the  muscles.  The  results,  under  such  cir- 
cumstances, are  the  same  as  those  that  follow  permanent  division  of  a  peripheral 
motor  nerve.  As  some  fibers  pass  from  above  downward  through  the  anterior 
horn  to  the  opposite  side,  also  some  fibers  on  the  contralateral  side  degenerate. 
Degeneration  of  the  posterior  gray  horns  gives  rise  to  impairment  of  cutaneous 
sensibility  and  to  trophic  disorders  in  the  skin.  Degeneration  of  the  central  por- 
tion of  the  gray  matter  causes,  in  addition  to  trophic  disorders  in  the  skin,  loss 
of  thermal  sensibility. 

It  is  a  highly  interesting  fact  that  temporary  occlusion  of  the  abdominal  aorta, 
in  rabbits,  causes  permanent  sensory  and  motor  paralysis  in  the  entire  area  con- 
trolled by  the  portion  of  the  spinal  cord  whose  circulation  is  cut  off.  Ganglion- 
cells  and  nerve-fibers  of  the  anterior  horns  undergo  degeneration.  Then  secondary 
degeneration  of  the  anterior  roots  follows  (with  the  exception  of  the  contained 
vasomotor  fibers),  and  of  the  white  matter  adjacent  to  the  anterior  horns.  Sub- 
sequently the  posterior  horns  also  undergo  reduction  in  size.  All  of  the  tracts 
passing  into  the  cord  remain  intact,  namely  the  posterior  roots,  the  spinal  ganglion- 
cells,  the  posterior  columns  and  the  extreme  periphery  of  the  anterolateral  tract. 

Destruction  of  the  lower  portion  of  the  spinal  cord,  in  the  dog,  up  to  the 
cervical  cord  gives  rise,  in  addition  to  loss  of  sensation  and  of  motion,  to  reduction 
in  the  temperature  of  the  lower  portion  of  the  body,  but,  if  great  care  be  taken, 
to  no  trophic  disorder,  except  that  the  bones  appear  to  be  brittle.  The  anus  is 
dilated  only  at  first,  but  later  the  sphincter  regains  its  normal  tone  and  sponta- 
neously contracts  rhythmically  (perhaps  it  contains  its  innervational  center  within 
itself),  while  all  the  other  paralyzed  muscles  of  the  body  undergo  degeneration. 
The  digestive  processes,  the  intestinal  movements,  the  act  of  parturition,  the  act 
of  nursing  are  performed  normally;  but  the  temperature  of  the  body  can  be 
regulated  only  within  certain  limits.  The  paralysis  of  the  bladder  present  at 
first  improves;  the  tone  of  the  blood-vessels  is  restored  in  the  course  of  a  few 
days.  A  series  of  important  vital  processes  are,  therefore,  not  directly  dependent 
upon  the  existence  of  the  spinal  cord,  but  they  are  rather  decentralized. 


THE  BRAIN. 

GENERAL  OUTLINE  OF  THE  STRUCTURE  OF  THE  BRAIN. 

COURSE  OF  THE  MOTOR  AND   SENSORY  TRACTS. 

With  respect  to  an  organ  exhibiting  such  a  high  degree  of  complexity  of 
structure  as  the  brain,  it  is  of  the  greatest  importance  to  be  acquainted  with  its 
general  arrangement,  even  if  only  from  a  brief  description.  It  is  to  the  credit 
of  Meynert  that  he  devised  a  practical  system  of  this  character  based  on  extensive 
investigations.  This  will  be  used  in  the  discussion  of  the  subject  that  follows, 
although  consideration  will  be  given  also  to  the  results  of  more  recent  investi- 
gation. , 

The  weight  of  the  brain  in  man  is  on  the  average  in  the  male  1372  grams, 
in  the  female  1231  grams.  The  uppermost  and  outermost  layer  of  the  cortex 
consists  of  a  layer  of  glia  containing  nerve-fibers.  Beneath  this  is  the  layer  of 
small  ganglion-cells,  and  next  to  this  the  layer  of  large  pyramidal  cells,  which 


742          COURSE  OF  THE  MOTOR  AND  SENSORY  TRACTS. 

in  turn  covers  the  layer  of  irregularly  formed  ganglion-cells.  Each  ganglion-cell 
possesses  a  neurite  and  numerous  dendrites.  Between  the  cells  everywhere  lie 
large  numbers  of  bundles  of  medullated  nerve-fibers. 

The  cortex  of  the  brain  consists  of  peripheral  gray  matter  with  numerous 
convolutions  and  sulci  (Fig.  254,  C).  This  can  be  recognized  as  the  central  organ 
of  the  nervous  system  from  the  presence  of  large  numbers  of  ganglion-cells.  From 
it  pass  all  of  the  motor  fibers  that  can  be  stimulated  by  the  mind  (will,  conception) , 
and  to  it  pass  all  of  the  fibers  derived  from  the  organs  of  special  sense  and  the 
sensory  organs  that  intermediate  the  psychical  perception  of  external  impressions. 

All  of  these  tracts  together,  in  part  corticopetal,  in  part  corticofugal,  pursue 
in  general  a  convergent  course  toward  the  central  part  of  each  cerebral  hemisphere, 
where  the  large  central  ganglia  of  the  brain  are  situated,  corpus  striatum  (C.  s.), 
lenticular  nucleus  (N.  1.),  optic  thalamus  (T.  o.)  and  quadrigeminate  bodies  (v). 
Some  fibers  merely  pass  by  these  structures  (5,  5),  but  many  enter  the  central 
gray  matter.  The  fiber-system  mentioned,  which  has  a  radiating  arrangement 
within  the  cerebral  hemisphere,  is  known  as  the  corona  radiata,  or  the  projection- 
system  of  the  first  order.  In  addition  to  this,  the  white  matter  contains  two  other 
groups  of  fibers,  namely  (a)  the  commissural  fibers — corpus  callosum  and  anterior 
commissure  (c  c) ,  which  connect  the  two  hemispheres ;  and  (6)  the  association- 
fibers,  by  means  of  which  different  areas  of  the  cortex  of  the  same  side  are  con- 
nected (a  a) . 

The  large,  cellular,  gray  masses  of  the  central  cerebral  ganglia  form  the  first 
stage  in  the  course  of  a  large  number  of  fibers  of  the  projection-system  of  the 
first  order.  On  entering  these  central  masses  the  fibers  undergo  an  interruption 
in  their  course,  while  a  reduction  in  the  number  of  fibers  of  the  corona  radiata 
takes  place.  In  detail  the  relation  of  the  fibers  of  the  corona  radiata  to  the  great 
central  ganglia  according  to  Meynert  is  as  follows:  The  entire  mass  of  fibers  of 
the  system  of  the  corona  radiata  breaks  up  in  general  into  as  many  bundles  as 
there  are  ganglia  on  each  side.  There  are  thus  systems  for  the  striate  body  (i,  i), 
the  lenticular  nucleus  (2,  2),  the  optic  thalamus  (3,  3)  and  the  quadrigeminate 
bodies  (4,  4). 

According  to  Flechsig  the  convolutions  of  the  brain  can  be  divided 
into  two  groups:  The  first  group  contains  only  association  and  com- 
missural fibers,  by  means  of  which  the  convolutions  are  connected  with 
other  cortical  areas.  The  other  group  contains  in  addition  bundles 
which  pass  to  the  optic  thalamus  in  the  corona-radiata.  These  Flechsig 
designates  sense-centers,  of  which'  each  possesses  its  own  motor  ap- 
paratus. 

The  central  convolutions,  the  seat  of  the  cutaneous  and  the  muscular  sense, 
serve  as  the  principal  source  of  origin  for  the  association-tracts.  Then  the  auditory 
area,  and  in  lesser  degree  the  visual  area,  play  an  important  role  as  the  source 
of  origin  of  the  association- tracts. 

From   the   large   central   ganglia   there    develops,    later   passing   downward, 

the  projection-system  of  the  second  order,  whose  longitudinal   fibers  reach  their 

temporary  termination  in  the  so-called  gray  matter  of   the  central  cavity.     This 

is  the  cellular  gray  matter  that  extends  from  the  third  ventricle  through  the 

aqueduct  of  Sylvius,  the  floor  of  the  fourth  ventricle,  to   the  lowermost  portion 

the    gray   matter   of   the  spinal  cord,  occupying  the  interior  of  the  medul- 

A  ry  tli-  6*          represents  likewise  the  second  stage  in  the  course  of  the  fibers. 

Accordingly,  the  projection-system  of  the  second  order  extends  from  the  large 

tral    ganglia  of  the  cerebrum  downward  to  the  gray  matter  of  the  central 

cavity.     The  fibers  of  this  system  must  obviously  be  of  widely  varying  length, 

some  terminating  in  the  gray  matter  of  the  central  cavity  above  the  medulla 

ongata  (oculomotor  origin) ,  while  others  extend  to  the  level  of  the  last  spinal 

'TIT6'  * J       gra^  matter  of  the  central  cavity  forms  a  mass  for  the  interruption 

the  fibers,  and  an  increase  in  the  number  of  fibers  takes  place  in  it,  for  many 

lore  fibers  pass  out  from  the  gray  matter  of  the  medulla  oblongata  and  the  spinal 

cord  to  the  periphery  than  were  sent  to  it  from  above  from  the  central  ganglia 

of  the  cerebrum.  » 

With  reference  especially  to  the  arrangement  of  the  fibers  of  this  projection - 

the  second  order,  it  is  assumed  that  the  fibers  descending  from  the 

:icular  nucleus  and  the  striate  body  (8,  8)  unite  to  form  a  special  tract  passing 


COURSE  OF  THE  MOTOR  AND  SENSORY  TRACTS. 


745. 


through  the  upper  portion  of  the  crusta  of  the  cerebral  peduncle  downward  into 
the  medulla  oblongata,  or  only  to  the  pons  according  to  Flechsig.  In  a  similar 
manner  a  bundle  passes  from  the  optic  thalamus  (7)  and  from  the  quadrigeminate 
bodies  (6,  6)  that  descends  through  the  tegmentum  (H)  of  the  cerebral  peduncle. 
Both  groups  of  fibers,  those  in  the  crusta  as  well  as  those  in  the  tegmentum, 
unite  below  in  the  spinal  cord.  £'_,  •  s  v 


h.W. 


FIG.  254. — I.  Diagrammatic  Representation  of  the  Structure  of  the  Brain:  C,  C,  cerebral  cortex;  C.  s,  striate 
body;  N.I,  lenticular  nucleus;  T.o,  optic  thalamus;  V,  quadrigeminate  bodies;  P,  cerebral  peduncle;  H, 
tegmentum;  p,  crusta;  i,  i,  fibers  of  the  corona  radiata  to  the  striate  body;  2,  2,  to  the  lenticular  nucleus; 
3,  3,  to  the  optic  thalamus;  4,  4,  to  the  quadrigeminate  bodies;  5.  direct  fibers  to  the  cerebral  cortex;  6,  6, 
fibers  from  the  quadrigeminate  bodies  to  the  tegmentum;  7,  fibers  from  the  optic  thalamus  to  the  tegmentum; 
m,  their  further  course;  8,  8,  fibers  from  the  striate  body  and  the  lenticular  nucleus  to  the  crusta  of  the  cere- 
bral peduncle;  M,  their  further  course;  S,  S,  course  of  the  sensory  fibers;  R,  transverse  section  of  the  spinal 
cord;  v.W,  anterior  and,  h.W,  posterior  root;  a,  a,  association-fibers;  c,  c,  commissural  fibers.  II.  Trans- 
verse Section  through  the  Posterior  Pair  of  the  Quadrigeminate  Bodies  and  the  Cerebral  Peduncles  of  Man 
(after  Meynert):  p,  Crusta  of  the  peduncle;  s,  substantia  nigra;  v,  the  quadrigeminate  bodies  with  the  trans- 
verse section  of  the  aqueduct.  III.  A  Like  Section  from  the  Dog.  IV.  From  the  Ape.  V.  From  the  Guinea-pig. 

According  to  Wernicke  the  lenticular  and  caudate  nuclei  are  not  parts  of  the 
cerebrum  into  which  fibers  of  the  corona  radiata  from  the  cortex  enter,  but  they 
are  independent  structures  analogous  to  the  cortex,  from  which  fibers  originate. 
These  fibers  later  on  reach  the  tegmentum,  where  they  lie  side  by  side  with  the 
fibers  derived  from  the  optic  thalami  and  the  quadrigeminate  bodies. 


744      COURSE  OF  THE  TRACTS  FOR  VOLUNTARY  MOVEMENTS. 

The  fibers  that  pass  from  the  thalamus  and  the  quadrigeminate  bodies  through 
the  tegmentum  of  the  cerebral  peduncle  (6,  6,  7)  represent,  according  to  Meynert, 
reflex  paths.  Accordingly,  the  cerebral  masses  mentioned  would  be  the  centers 
for  certain  extensive  coordinated  reflexes.  This  is  indicated  by  the  fact  that  after 
destruction  of  the  paths  for  the  conduction  of  voluntary  impulses  in  animals  the 
technical  perfection  of  the  movements,  in  so  far  as  these  are  induced  by  reflex 
activity,  remains  intact.  The  fibers  named  pass  in  the  spinal  cord  at  first  down- 
ward upon  the  same  side  (m) ,  but  they  probably  cross  below  in  the  spinal  cord 
itself. 

Finally  there  passes  out  of  the  entire  gray  matter  of  the  central  cavity  a 
group  of  fibers  that  constitute  the  projection-system  of  the  third  order.  These  are 
the  peripheral  nerves,  sensory  and  motor.  They  exhibit  in  their  totality  an  in- 
crease of  fibers  as  compared  with  the  number  of  fibers  in  the  projection-system 
of  the  second  order. 

The  cerebellum  represents  a  separate  central  organ  of  special  character  con- 
taining gray  matter  in  part  as  a  cortical  layer  and  in  part  as  central  accumulations. 
It  is  connected  with  the  cerebrum  (i)  through  the  superior  cerebellar  peduncles, 
formed  of  fibers  from  the  system  of  the  corona  radiata,  passing  then  into  the 
tegmentum,  and  reaching  the  cerebellum  after  total  decussation;  and  (2)  through 
the  middle  cerebellar  peduncles  to  the  pons  and  from  the  pons  through  the  cerebral 
peduncles  to  the  hemispheres.  The  cerebellum  is  connected  also  with  the  spinal 
cord,  namely  (i)  with  the  posterior  column  (cuneate  and  gracile  columns)  and  (2) 
with  the  anterior  column  (restiform  body).  The  two  hemispheres  are  connected 
by  the  transverse  commissural  fibers  of  the  pons. 

The  distribution  of  the  cerebral  vessels  is  deserving  of  consideration  from  the 
practical  standpoint.  The  artery  of  the  fossa  of  Sylvius  supplies  the  motor  areas 
of  the  cortex  in  animals — in  man  the  paracentral  lobule  is  supplied  by  the  anterior 
cerebral  artery.  The  region  of  the  third  frontal  convolution,  which  is  of  such 
importance  for  the  function  of  speech,  is  supplied  by  a  special  branch  of 
the  Sylvian  artery.  Those  portions  of  the  frontal  lobe,  injury  of  which,  according 
to  Ferrier,  causes  derangement  of  intelligence,  are  supplied  by  the  anterior  cerebral 
artery.  The  middle  cerebral  artery  supplies  the  internal  capsule,  with  the  excep- 
tion of  its  most  posterior  portion,  which,  together  with  the  uncinate  gyrus,  is 
supplied  by  the  anterior  choroid  artery.  Those  portions  of  the  cortex,  lesions  of 
which,  according  to  Ferrier,  give  rise  to  hemianesthesia,  are  supplied  by  the  pos- 
terior cerebral  artery.  Isolated  anemia  of  this  area  is  believed  to  have  some 
connection  with  melancholic  states  in  human  beings. 

Course  of  the  Tracts  for  Voluntary  Movements:  Psychomotor  or 
Corticomuscular  Paths  (Fig.  255).— From  the  motor  regions  of  the  cere- 
bral cortex,  from  which  impulses  are  sent  for  voluntary  movements  in 
the  distribution  of  the  cerebral  and  spinal  motor  nerves,  the  fibers  that 
constitute  the  pyramidal  tracts  (Fig.  255,  a,  6,  c)  pass  through  the 
anterior  two-thirds  of  the  posterior  limb  of  the  internal  capsule  (Fig.  255, 
G.i;  Figs.  263,  264),  and  then  through  the  crusta  of  the  cerebral  peduncle 
(Fig-  254,  middle  portion  of  the  lower  free  circumference  of  the  crusta), 
through  the  pons  on  the  same  side  (P)  into  the  pyramid  (Py)  of 
the  medulla  oblongata.  At  this  point  the  majority  of  the  fibers  cross 
through  the  pyramidal  decussation  to  the  opposite  side  and  pass  down- 
ward in  the  lateral  column  (lateral  pyramidal  tract,  a)  to  the  level  of  the 
spinal  cord  (Fig.  25 5),  from  which  the  anterior  root  for  the  transmission 
of  the  voluntary  impulse  in  question  makes  its  exit.  Before  entering  the 
anterior  root  the  fibers  enter  into  communication  with  the  ganglion-cells 
of  the  anterior  horn  (surrounding  them  by  delicate  arborizations). 
From  each  ganglion-cell  there  passes  as  a  neurite  a  motor  filament  into 
the  nerve-fiber  of  the  anterior  root.  The  largest  number  of  decussated 
fibers  in  the  pyramids  pass  to  the  motor  nerves  of  the  extremities.  A 
smaller  number  of  fibers  (Fig.  255,  b),  however,  do  not  decussate  in 
the  pyramid,  but  pass  on  the  same  side  in  the  anterior  column 
of  the  spinal  cord  (anterior  pyramidal  tract,  b,  z)  and  remain 


COURSE    OF    THE    TRACTS    FOR    CONSCIOUS    SENSATION. 


745 


upon  the  same  side.  These,  however,  in  their  further  course  through 
the  spinal  cord  likewise  cross  over  to  the  opposite  side  through  the  an- 
terior white  commissure.  A  portion  of  these  fibers,  at  first  undecus- 
sated,  appear,  however,  to  remain  upon  the  same  side.  It  is  perhaps 
their  function  to  innervate  those  muscles  of  the  trunk  that,  like  the 
respiratory,  the  abdominal  and  the 
perineal  muscles,  are  generally  made 
to  contract  together  on  both  sides. 

With  reference  to  the  relations  of  the 
crossed  and  uncrossed  fibers  individual  varia- 
tions occur.  In  isolated  cases  the  con- 
ditions are  reversed,  and  in  rare  instances 
the  pyramidal  tracts  remain  upon  the 
same  side  from  the  brain  downward.  In 
this  way  are  to  be  explained  the  exceedingly 
rare  cases  in  which  paralysis  of  voluntary 
movement  has  been  observed  on  the  same 
side  as  the  lesion  of  the  cerebral  cortex. 
Cases  are  uncommon  also  in  which  the 
muscles  of  the  trunk  and  the  lower 
extremities  are  moved  bilaterally  on  volun- 
tary efforts  at  unilateral  movement.  Finally, 
it  should  be  mentioned  that  Unverricht 
occasionally  observed  in  the  dog  a  double 
decussation  of  the  tracts:  once  in  the  pyra- 
mids and  again  in  the  spinal  cord.  Pyram- 
idal tracts  are  present  only  in  mammals. 

The  cerebral  motor  nerves  naturally 
have  their  center  for  voluntary  stimu- 
lation in  the  cortex  of  the  cerebral 
hemisphere.  From  this  point  the  fibers 
that  transmit  voluntary  impulses  pass 
through  the  internal  capsule  and  the 
crusta  of  the  cerebral  peduncle,  where 
they  lie  in  front  of  and  internal  to  the 
pyramidal  tracts.  Then  their  course 
is  directed  to  their  nuclei  of  origin. 
In  Fig.  255,  c  represents  the  course  of 
the  facial  nerve  to  its  nucleus  of  origin. 
The  hypoglossal  nerve  passes  with  the 
pyramidal  tract  and  behaves  like  the 
anterior  root  of  a  spinal  nerve. 

Course  of  the  Tracts  for  Conscious 
Sensation. — From  the  cortical  area  in 
which  is  situated  the  center  for  sensi- 
bility, which  is  designated  the  sensory 
sphere  and  is  fully  described  on  p.  785, 
the  conducting  tracts  pass  through 

the  posterior  third  of  the  posterior  limb  of  the  internal  capsule  (Figs. 
263,  264).  The  fibers  for  the  transmission  of  the  muscle-sense  pass 
through  the  middle,  those  for  the  sensations  of  pressure,  temperature, 
and  pain  through  the  inner  half  of  the  posterior  third  of  the  internal 
capsule.  The  tracts  then  pass  through  the  tegmentum  of  the  cerebral 
peduncle  and  their  continuation  through  the  pons  and  further  to 
the  medulla  oblongata.  The  fibers  for  the  transmission  of  cutaneous 


A  R 


FIG.  255. — Course  of  the  Paths  for  Voluntary 
.  Movement:  a,  b,  Paths  for  the  cerebral 
motor  nerves;  c,  path  for  the  facial  nerve; 
5,  corpus  callosum;  N.c,  caudate  nucleus; 
G.i,  internal  capsule;  N.I,  lenticular  nu- 
cleus; P,  pons;  A".  /,  nucleus  of  origin 
of  the  facial  nerve;  Py,  pyramid,  with 
decussation;  O.I,  olivary  body;  G.r, 
restiform  body;  P.R,  posterior  root; 
A.R,  anterior  root;  x,  lateral  pyramidal 
tract;  z,  anterior  pyramidal  tract. 


746 


COURSE    OF    THE    TRACTS    FOR    CONSCIOUS    SENSATION. 


sensibility  pass  through  the  fillet  and  the  ventral  portion  of  the  reticular 
formation. 

The  connections  of  the  posterior  roots  of  the  nerves  of  the  spinal  cord, 
through  which  sensibility  is  transmitted,  are,  according  to  recent  inves- 
tigators, as  follows: 

The  posterior  columns  transmit  impulses  from  the  afferent  poste- 
rior roots  upward.  A  lateral  and  a  median  bundle  can  be  recognized 
in  the  posterior  root.  The  median  bundle  of  each  afferent  root  in  its 
course  upward  in  the  posterior  column  is  generally  situated  to  the  outer 
side  close  to  the  posterior  horn  (Fig.  257,  2).  Each  root  as  it  enters  at  a 
higher  level  (i)  displaces  further  and  further  inward  the  fibers  derived 
from  the  roots  situated  at  a  lower  level.  Therefore,  the  sensory  fibers  com- 
ing from  the  lower  extremities  are,  in  the  cervical  cord,  situated  princi- 
pally in  the  columns  of 
Goll,  while  the  columns 
of  Burdach  still  contain 
many  fibers  from  the 
upper  extremities.  As- 
cending, the  fibers  of 
the  posterior  columns 
terminate  above  in  the 
medulla  oblongata,  in 
the  formations  (nuclei  of 
the  gracile  and  cuneate 
columns)  known  as  the 
nuclei  of  the  posterior 
columns.  From  these 
nuclei  many  fibers  pass 
into  the  fillet  (L)  of  the 
opposite  side.  Other 
fibers  pass  to  the  cere- 
bellum. The  lateral 
fibers,  coarse  and  fine,  of 
the  posterior  root  (3,  4) 
enter  the  delicate  plexus 
of  the  posterior  horn,  in 
which  the  ganglion-cells 
of  the  posterior  horn  are 
lodged.  From  the  plexus 
of  the  posterior  horns 
there  arise  numerous 

fibers  that  pass  forward  through  the  gray  matter,  undergo  decussa- 
tion,  and  then  continue  toward  the  cerebrum  in  the  anterior  and  lateral 
columns.  At  a  higher  level  these  fibers,  with  their  original  accom- 
paniments, reunite  (at  L),  so  that  almost  all  of  the  posterior  root-fibers 
(decussated)  again  lie  together  in  the  fillet  or  the  intermediary  layer  of  the 
The  further  course  of  these  fibers  to  the  cerebral  cortex  is  dis- 


FIG.  256.— Course  of  the  Motor  and  Sensory  Paths  through  a  Trans- 
verse Section  of  the  Spinal  Cord:  i,  Anterior  pyramidal  tract; 
3,  lateral  pyramidal  tract;  4  and  5,  decussating  sensory  paths  in 
the  spinal  cord;  6,  ascending  sensory  paths  not  decussating  in  the 
spinal  cord;  7,  sensory  path  to  the  columns  of  Stilling  and  Clarke, 
and  thence  undecussated  upward  through  the  lateral  cerebellar 
tracts;  2,  origin  of  a  motor  fiber  as  a  neurite  from  a  ganglion-cell 
of  the  anterior  horn. 


olive. 


cussed  on  p.  80 1.  A  portion  (5)  of  the  fibers  of  the  posterior  roots,  which 
are  not  connected  with  the  cells  of  the  spinal  ganglia,  terminate  in  the 
cells  of  the  column  of  Stilling  and  Clarke,  which  are  at  the  same  time 
the  trophic  centers  for  those  fibers.  The  fibers  turn  outward  from  the 
.s  and  ascend  in  the  lateral  cerebellar  tract.  Their  further  course  is 
upward  to  the  restiform  body,  and  thence  to  the  cerebellum.  These 


COURSE   OF    THE    TRACTS    FOR    CONSCIOUS    SENSATION. 


747 


fibers  are  concerned  in  the  regulation  of  equilibrium,  and  their  superior 
path  of  conduction  is  situated  in  the  cerebellum.  In  cases  of  tabes  these 
tracts  and  the  columns  of  Stilling  and  Clarke  are  often  degenerated. 

In  the  human  brain  the  sensory  conducting  path  for  the  tactile  and  the  mus- 
cular sense  (continuation  of  the  posterior  roots  and  the  direct  cerebellar  tract) 
develops  first.  This  passes  from  the  nuclei  of  the  posterior  columns  (Fig.  257) 
through  the  thalamus  and  the  lenticular  nucleus  to  the  central  convolutions, 
especially  the  posterior. 

The  circumstance  that  a  portion  of  the  sensory  cutaneous  nerves 
cross  in  the  spinal  cord  to  the  opposite  side  explains  the  fact  that  uni- 
lateral division  of  the  spinal  cord  in  man,  and  in  apes,  abolishes  cutaneous 
sensation  upon  the  opposite  side  of  the 
body  below  the  level  of  the  lesion,  while 
the  muscular  sense  is  preserved.     Upon 
the  side  of  the  injury  hyperesthesia  is 
present  below  the  level  of  the  section. 

From  experiments  on  mammals  Brown- 
Se"quard  concluded  that  the  decussating 
sensory  nerve-fibers  cross  in  the  spinal  cord 
to  the  opposite  side  at  various  levels — the 
fibers  that  transmit  tactile  sensibility  at  the 
lowest  level,  then  those  that  transmit  sensa- 
tions of  tickling  and  pain,  and  at  the  highest 
level  those  that  transmit  thermal  impressions. 

All  of  the  fibers  that,  pursuing  a 
longitudinal  course,  connect  the  spinal 
cord  with  the  medullary  mass  of  the 
cerebrum,  thus,  as  a  rule,  undergo  com- 
plete decussation  in  their  course.  There- 
fore, in  man  the  result  of  a  destructive 
lesion  of  one  cerebral  hemisphere  is  gen- 
erally complete  paralysis  and  abolition 
of  sensation  upon  the  opposite  side  of 
the  body.  Also  the  fibers  arising  from 
the  nuclei  of  origin  of  the  cerebral 
nerves  decussate  within  the  brain. 


tffunic. 
grac. 


G.S. 


A.R. 


FIG.  257. — Course  of  the  Sensory  Fibers 
from  the  Posterior  Roots  through  the 
Spinal  Cord  upward  to  the  Cerebrum. 
The  explanation  of  the  fibers  will  be 
clear  from  the  description  in  the  text, 
and  with  it  also  Fig.  256  should  be 
compared:  A,R,  anterior  root;  P.R, 
posterior  roof,  V.G,  ground-bundle  of 
the  anterior  column;  Py.V,  anterior 
pyramidal  tract;  Py.S,  lateral  pyram- 
idal tract;  G.S,  ground-bundle  of 
the  lateral  column;  Kl.S,  cerebellar 
tract  of  the  lateral  column;  G,  column 
of  Golj;  B,  column  of  Burdach;  Py, 
pyramid;  O/,  olive;  L,  fillet  or  inter- 
mediary layer  of  the  olive;  £ 


fibre 

arcuatae;  restiform  body;  nucleus  of 
the  slender  column  and  nucleus  of  the 
cuneate  column  of  the  medulla  ob- 
longata. 


Only  in  those  cases,  not  rare  it  is  true,  in 
which  the  lesion,  as  from  pressure,  inflamma- 
tion, etc.,  involves  the  cerebral  nerves  situated 
at  the  base,  are  paralysis  and  anesthesia  ob- 
served on  the  same  side  of  the  head. 

Particulars  as  to  the  site  of  decussation 
have  already  been  stated.  Decussation  takes 
place  (i)  in  the  spinal  cord,  (2)  in  the  medulla 
oblongata,  and  finally  (3)  in  the  pons.  Decus- 
sation is  already  complete  in  the  peduncles.  Gubler  observed,  in  cases  of 
unilateral  injury  of  the  pons,  paralysis  of  the  facial  nerve  on  the  same  side,  but 
paralysis  of  the  body  on  the  opposite  side.  From  this  he  concluded  that  the 
nerves  from  the  trunk  must  undergo  decussation  below  the  pons,  the  facial 
fibers  within  the  pons.  Such  rare  instances  are  designated  alternating  hemiplegia. 
The  conditions  are  made  clear  in  Fig.  255. 

Exceptions  to  decussation  are  formed  by  the  olfactory  nerves,  which  do  not 
decussate  at  all  (?),  and  the  optic  nerves,  which  decussate  only  partially  in  the 
chiasm. 


748  THE    MEDULLA    OBLONGATA. 

THE  MEDULLA  OBLONGATA. 

The  medulla  oblongata,  which  connects  the  spinal  cord  with  the  brain, 
resembles  the  cord  in  many  respects,  particularly  from  the  fact  that  it 
contains  centers,  which,  like  those  in  the  spinal  cord,  convey  simple 
reflexes  (for  example  that  of  closure  of  the  eyelids).  Further,  it  contains 
centers,  however,  that  occupy  a  controlling  relation  to  centers  of  analo- 
gous function  in  the  spinal  cord;  for  example  the  centers  controlling 
the  vasomotor  nerves,  the  secretion  of  sweat,  dilatation  of  the  pupils,  the 
reflex  movements  of  the  body.  With  reference  to  the  irritation,  some 
of  the  centers  are  reflex,  others  automatic. 

The  normal  function  of  the  centers  is  related  to  the  gaseous  inter- 
change maintained  by  the  normal  circulation  in  the  medulla.  If  this 
is  interrupted  by  asphyxia  or  sudden  anemia  or  venous  stasis,  the  centers 
are,  at  first,  thrown  into  a  state  of  increased  irritation,  being  later  par- 
alyzed by  overstimulation.  Overheating  also  acts  as  an  irritant  to  the 
centers.  Not  all  of  the  centers  are  active  at  the  same  time  and  they  do 
not  all  exhibit  the  same  degree  of  irritability.  In  the  normal  body  the 
respiratory  and  vasomotor  centers  are  in  constant  rhythmic  activity. 
The  cardiac  inhibitory  center  is  in  some  animals  not  continuously  irri- 
tated ;  in  others  slight  stimulation  occurs  normally  only  with  inspiration 
(in  conjunction  with  stimulation  of  the  respiratory  center).  The  spasm- 
center  is  not  irritated  at  all  under  normal  conditions,  and  the  respiratory 
center  not  during  intrauterine  life.  The  medulla  oblongata  is,  as  the 
seat  of  many  centers  of  importance  with  reference  to  the  maintenance  of 
life,  as  well  as  for  the  transmission  of  various  nerve-paths,  of  the  greatest 
significance.  The  details  are  considered  in  what  follows.  The  reflex 
centers  will  be  considered  first  and  then  the  automatic  centers. 

REFLEX  CENTERS  IN  THE  MEDULLA  OBLONGATA. 

The  medulla  oblongata  contains  a  number  of  reflex  centers  that 
permit  the  execution  of  coordinated  movements. 

The  center  for  closure  of  the  eyelids.  The  sensory  fibers  of  the  trigem- 
inus  to  the  cornea  and  the  conjunctiva,  as  well  as  the  skin  in  the  vicinity 
of  the  eye,  conduct  centripetally  the  impressions  received  to  the  medulla 
oblongata,  where  they  are  transferred  to  the  motor  path  of  the  facial 
branch  that  innervates  the  orbicular  muscle  of  the  lids.  The  center 
extends  from  about  the  middle  of  the  ala  cinerea  upward  to  the  posterior 
margin  of  the  pons. 

Intense  illumination  of  the  eye  also  causes  closure  of  the  eyelids 
through  the  intermediation  of  the  optic  nerve.  The  stimulation  passes 
through  the  quadrigeminate  bodies  to  the  center. 

Reflex  closure  of  the  eyelids  takes  place  in  man  always  on  both  sides,  but 
voluntarily  the  eyelids  can  be  closed  on  one  side.  On  intense  irritation  the  cor- 
ugator  and  the  muscle-group  that  elevates  the  nose  and  the  cheek  toward  the 
lower  margin  of  the  orbit  also  contract  in  order  to  secure  more  perfect  protection 
and  closure  of  the  eye.  The  duration  of  voluntary  and  reflex  closure  of  the  eye- 
lids is  from  0.3  to  0.45  second. 

The  center  for  sneezing.  The  centripetal  path  is  through  the  inner 
nasal  branches  of  the  trigeminus  and  probably  also  through  the  olfactory 
nerve  (for  strong  odors).  The  motor  path  leads  to  the  expiratory  mus- 
cles. Sneezing  cannot  be  practised  voluntarily. 


REFLEX    CENTERS    IN    THE    MEDULLA    OBLONGATA.  749 

The  center  for  coughing,  according  to  Kohts,  is  situated  above  the 
inspiratory  center  and  is  excited  centripetally  through  the  sensory 
branches  of  the  vagus.  The  centrifugal  fibers  are  the  expiratory  nerves, 
including  the  constrictors  of  the  glottis. 

The  phonation-center.  The  center  for  the  control  of  the  voice-mech- 
anism is  situated  from  the  origin  of  the  vagus  upward  to  the  quadri- 
geminate  bodies.  New-born  animals  from  which  the  brain  was  removed, 
with  preservation  of  this  portion  of  the  brain,  are  still  able  to  cry. 

The  center  for  the  movements  of  sucking,  as  well  as  of  chewing.  The 
centripetal  nerves  are  the  sensory  fibers  of  the  mouth,  including  those  of 
the  lips  (second  and  third  divisions  of  the  trigeminus  and  the  glosso- 
pharyngeal).  The  motor  nerves  for  the  movements  of  sucking  are  the 
facial  (the  lips),  the  hypoglossal  (the  tongue),  the  third  division  of  the 
trigeminus  (elevator  of  the  lower  jaw  and  the  branches  of  the  depressor 
of  the  lower  jaw).  After  transitory  (by  cocain)  or  permanent  paralysis 
of  the  trigeminus  the  sucking-reflex  ceases.  The  same  motor  nerves  take 
part  in  the  act  of  chewing,  but  the  action  especially  of  the  hypoglossal 
for  the  movement  of  the  tongue  and  of  the  facial  for  that  of  the  buc- 
cinator is  necessary  to  keep  the  food  between  the  teeth. 

The  center  for  the  secretion  of  saliva  is  situated  on  the  floor  of  the 
fourth  ventricle,  and  can  be  stimulated  reflexly.  Irritation  of  the 
medulla  oblongata,  when  the  chorda  tympani  and  the  glossopharyngeal 
nerve  are  preserved,  causes  active  secretion  of  saliva;  a  lesser  amount  of 
secretion  when  these  nerves  are  divided;  and,  finally,  none  at  all  when 
the  cervical  sympathetic  also  is  destroyed. 

The  center  for  the  act  of  deglutition  is  situated  on  the  floor  ot  the 
fourth  ventricle  above  the  respiratory  center  and  is  stimulated  through 
the  sensory  nerves  of  the  palate  and  the  pharynx  (second  and  third  divi- 
sions of  the  trigeminus  and  the  vagus).  The  centrifugal  path  is  through 
the  motor  branches  of  the  pharyngeal  plexus.  Irritation  of  the  glosso- 
pharyngeal does  not  cause  swallowing,  but  rather  inhibition  of  the  act 
of  deglutition.  On  the  other  hand,  every  act  of  swallowing  excited  by 
irritation  of  the  palatine  nerves  or  the  superior  laryngeal  nerve  causes 
rapid,  abortive  contraction  of  the  diaphragm  (deglutitional  breathing). 

The  center  for  vomiting  is  discussed  on  p.  282.  The  relations  be- 
tween certain  branches  of  the  vagus  and  the  act  of  vomiting  have  been 
pointed  out  on  p.  710.  The  center  may  be  set  into  activity  by  direct 
application  of  apomorphin  or  emetin. 

The  upper  center  for  the  dilator  muscle  of  the  pupil  and  the  unstriated 
muscles  of  the  orbit  and  the  eyelids  is  situated  in  the  medulla  oblongata. 
The  pupillary  fibers  passing  through  the  trigeminus  arise  from  the  origin 
of  this  nerve  and  downward  as  far  as  the  second  cervical  nerve  (in 
the  rabbit).  Anastomotic  fibers  pass  from  this  point  downward  through 
the  lateral  columns  of  the  spinal  cord  to  the  ciliospinal  region,  and  thence 
through  the  three  or  four  uppermost  thoracic  nerves  into  the  cervical 
sympathetic.  The  center  is  normally  stimulated  reflexly  by  cutting 
off  the  light  from  the  retina.  It  is  irritated  directly  by  states  of  the 
blood  causing  dyspnea  or  by  occlusion  of  the  carotids. 

The  center  may  be  irritated  reflexly  also  by  stimulation  of  sensory 
nerves  of  the  trunk  (sciatic).  These  fibers  pass  (from  the  sciatic) 
through  the  two  lateral  columns  up  to  the  center. 

Finally,  there   is   situated   in  the   medulla   a   higher  center,  which 


750  THE    RESPIRATORY    CENTER    AND    NERVES. 

establishes  a  connection  among  the  various  centers  for  the  reflexes,  in  the 
spinal  cord.  When  Owsjannikow  divided  the  medulla  6  mm.  above  the 
calamus  scriptorius  (in  rabbits) ,  the  general  reflexes  of  the  body,  in  which 
the  anterior  and  the  posterior  extremities  took  part,  persisted.  When 
the  section  was  made  i  mm.  lower,  only  partial,  local  reflexes  usually 
appeared.  The  center  extends  upward  to  a  little  above  the  lower  third 
of  the  medulla. 

In  the  frog  the  medulla  contains  the  sole  center  for  movement  from 
place  to  place.  Division  of  this  abolishes  such  movement  in  response  to 
external  irritation  and  only  simple  reflexes  remain,  but  no  reflex  move- 
ment, such  as  jumping,  crawling,  swimming. 

Pathological. — The  medulla  oblongata  *may  be  the  seat  of  a  typical  disease 
designated  bulbar  paralysis,  or  glossopharyngolabial  paralysis,  attended  with 
progressive  paralysis  of  the  bulbar  (bulbus  rhachiticus,  medulla  oblongata)  nuclei 
of  various  cerebral  nerves,  which  often  represent  the  motor  segments  of  important 
reflex  mechanisms.  From  the  latter  point  of  view  the  clinical  picture  deserves 
consideration.  Generally,  the  disorder  begins  with  paralysis  of  the  tongue,  at- 
tended with  fibrillary  twitching,  in  consequence  of  which  speech,  the  formation 
of  the  bolus,  and  swallowing  in  the  mouth  are  rendered  difficult.  The  secretion  of 
an  extremely  viscous  saliva  indicates  an  inability  to  secrete  a  watery  saliva  by 
reason  of  paralysis  of  the  facial  nerve.  Further,  swallowing  is  rendered  difficult 
or  even  impossible  in  consequence  of  paralysis  of  the  pharynx  and  the  palate. 
As  a  result  of  the  latter  the  formation  of  consonants  between  the  tongue  and 
the  soft  palate  is  interfered  with;  speech,  further,  becomes  nasal;  and  often 
especially  fluid  articles  of  food  enter  the  nares  on  efforts  at  swallowing.  Then,  the 
facial  branches  for  the  lips  become  paralyzed.  The  mimetic  expression  of  the 
mouth  is  extremely  characteristic,  "as  if  frozen  stiff,"  and,  at  the  same  time, 
in  consequence  of  horizontal  enlargement  of  the  opening  of  the  mouth  (as  the 
orbicularis  oris  especially  is  paralyzed),  marked  by  a  lacrimose  appearance. 
Later  on,  speech  becomes  more  greatly  interfered  with.  When  the  disorder  is 
marked,  all  of  the  muscles  of  the  face  are  paralyzed.  Under  such  circumstances, 
the  laryngeal  muscles  are  not  rarely  paralyzed,  so  that  phonation  is  abolished, 
and  the  ready  entrance  of  fluids  into  the  larynx  is  favored.  The  enormous  re- 
tardation of  the  pulse-beat  often  present  indicates  irritation  of  the  cardiac  in- 
hibitory fibers,  derived  from  the  accessory  nerve.  If,  later  on,  attacks  of  dyspnea 
occur,  such  as  have  been  observed  after  paralysis  of  the  recurrent  nerve,  or  such 
as  are  constant  after  section  of  the  pulmonary  branches  of  the  vagi,  death  may 
take  place  suddenly  amid  signs  of  asphyxia  if  the  attacks  become  more  severe 
and  more  frequent.  Rarely,  the  clinical  picture  is  complicated  by  paralysis  of 
the  muscles  of  mastication  (in  consequence  of  paralysis  of  the  motor  portion  of 
the  fifth  nerve),  contraction  of  the  pupils  (in  consequence  of  paralysis  of  the 
dilator-center)  and  paralysis  of  the  abducens  nerve. 

THE  RESPIRATORY  CENTER  AND  THE  INNERVATION  OF  THE 
RESPIRATORY  APPARATUS. 

Flourens  determined  the  position  of  the  respiratory  center  in  the 
medulla  oblongata,  behind  the  point  of  exit  of  the  vagi,  on  either  side 
of  the  posterior  extremity  of  the  floor  of  the  fourth  ventricle,  between 
the  nuclei  of  the  vagus  and  accessory  nerves.  He  designated  this  the 
vital  point  OT  n&ud  vital,  because  its  destruction  is  followed  at  once  by 
arrest  of  respiration  and  therefore  by  death.  The  center  occupies  ex- 
actly the  same  situation  in  man,  as  Kehrer  has  demonstrated  in  a  per- 
forated new-born  child.  The  center  is  bilateral,  and  it  can  be  divided 
by  a  median  section,  the  respiratory  movements  continuing  symmet- 
rically upon  both  sides.  If  one  vagus  is  divided  the  respiration  be- 
comes slowed  upon  the  corresponding  side.  If,  however,  both  vagi  are 
divided,  the  breathing  is  unequal  in  frequency  and  vigor  on  the  two 
sides  of  the  body.  Irritation  of  the  central  stump  of  one  of  the  two 


THE    RESPIRATORY    CENTER    AND    NERVES.  751 

divided  vagi  causes  arrest  of  respiration  only  upon  the  corresponding 
side,  while  respiration  continues  upon  the  other  side.  The  same  result 
is  brought  about  if  the  trigeminal  nerve  upon  one  side  is  irritated.  On 
unilateral  transverse  division  of  the  center  the  respiratory  movement 
ceases  upon  the  side  of  the  injury. 

According  to  Schiff  the  respiratory  center  is  situated  near  the  lateral  margin 
of  the  gray  matter  forming  the  floor  of  the  fourth  ventricle,  extending  posteriorly 
not  so  far  as  the  ala  cinerea.  According  to  Gierke  and  Heidenhain  and  others 
that  portion  of  the  medulla,  destruction  of  which  is  followed  by  cessation  of  respira- 
tory movement  is  a  single  or  double  nerve-like  strand,  passing  downward  in  the 
substance  of  the  medulla,  within  which,  however,  gray  matter  with  small  ganglia 
is  found.  This  is  said  to  be  constituted  in  part  of  the  roots  of  the  vagus,  'tri- 
geminus,  accessory  and  glossopharyngeal,  connected  with  those  of  the  oppo- 
site side  by  means  of  fibers  and  extending  downward  into  the  cervical  enlarge- 
ment of  the  spinal  cord.  The  strand  thus  connects  as  an  intercentral  bundle 
the  spinal  cord  (the  seat  of  origin  for  the  motor  respiratory  nerves)  with  the  nuclei 
of  origin  of  the  cerebral  nerves  named,  the  relations  of  which  to  the  respiratory 
movements  are  in  part  demonstrated. 

It  is  most  probable  that  the  dominating  center  that  controls  the  rhythm 
and  the  symmetry  of  the  respiratory  movements  is  situated  in  the  medulla  ob- 
longata,  but  that  in  addition  other  centers  of  subordinate  importance  are  situated 
in  the  spinal  cord  and  are  controlled  by  the  center  in  the  medulla,  receiving  their 
impulse  to  activity  from  that  center.  If  in  new-born  animals  the  cord  is  divided 
below  the  medulla  by  means  of  an  exceedingly  sharp  instrument  respiratory  move- 
ments of  the  chest  will  occasionally  persist,  from  stimulation  of  the  spinal  cen- 
ters, an  observation  that  Landois  was  able  to  confirm  in  young  dogs  and  cats. 

The  spinal  respiratory  centers  are,  moreover,  susceptible  even  to  reflex  in- 
fluences (excitation  or  inhibition).  Nitschmann  divided  the  spinal  center 
situated  in  the  upper  cervical  cord  by  means  of  a  longitudinal  section  into  two 
equal  parts,  both  of  which  then  had  an  excito-respiratory  influence  upon  the 
diaphragm  upon  each  side,  even  though  the  medulla  just  below  the  calamus 
scriptorius  had  been  divided  upon  one  side.'  Accordingly,  the  spinal  centers  of 
both  sides  must  be  connected  in  the  spinal  cord.  Irritation  originating  in  one- 
half  of  the  center  in  the  medulla  may  thus  affect  the  spinal  centers  on  both  sides, 
for  example  the  origins  of  both  phrenic  nerves.  The  spinal  center  for  the  phrenic 
nerve  is  situated  between  the  third  and  seventh  segments. 

In  addition  to  the  spinal  cord,  the  brain  also  contains  subordinate  cerebral 
respiratory  centers.  In  the  tissue  between  the  striate  body  and  the  optic  thalamus 
I.  Ott  found  a  center,  irritation  of  which  markedly  increased  the  number  of  respira- 
tions. On  destruction  of  this  center  the  dyspneic  respiratory  acceleration  (lieat- 
dyspnea)  induced  by  heat  ceases. 

In  the  optic  thalamus,  on  the  floor  of  the  third  ventricle,  Christiani  found 
further  a  special  inspiratory  center,  which  through  stimulation  of  the  optic  and 
auditory  nerves,  also  after  previous  extirpation  of  the  cerebrum  and  the  striate 
bodies,  or  also  through  direct  irritation,  causes  deepening  of  inspiration  and  accel- 
eration of  respiration,  and  even  arrest  in  inspiration.  This  inspiratory  center  can 
be  extirpated  and  it  can  then  be  demonstrated  that  a  center  controlling  expiration 
is  situated  in  the  substance  of  the  anterior  quadrigeminate  body  not  far  from 
the  aqueduct  of  Sylvius.  Finally,  the  posterior  quadrigeminate  body  contains  a 
second  cerebral  inspiratory  center  and  also  an  inspiratory  inhibiting  center.  Ob- 
viously all  of  these  centers  are  connected  with  the  center  in  the  medulla. 

According  to  Marckwald,  the  regular  rhythm  of  the  respiratory  movements 
is  maintained,  in  addition  to  the  posterior  quadrigeminate  bodies,  also  by  the. 
sensory  nucleus  of  the  trigeminus. 

The  respiratory  center  consists  of  two  central  areas  engaged  in  alter- 
nate activity;  the  inspiratory  and  expiratory  centers,  of  which  each 
forms  the  motor  central  point  for  the  well-known  group  of  inspiratory 
and  expiratory  muscles.  The  center  is  an  automatic  one,  for,  even  after 
division  of  all  of  the  sensory  nerves  that  may  exert  a  reflex  influence  upon 
it,  it  preserves  its  activity.  The  irritability  and  the  stimulation  of  the 
center  are  dependent  upon  the  state  of  the  blood,  particularly  the  amount 


7^2  THE    RESPIRATORY    CENTER. 

of  oxygen  and  carbon  dioxid  present.     In  this  connection  the  following 
distinctions  are  to  be  recognized : 

1.  Apnea,  that  is  the    cessation  of  the   respiratory  movements  in 
consequence  of  deficient  need  therefor.     It  occurs  when  the  blood  is 
saturated  with  oxygen  and  is  deficient  in  carbon  dioxid.    Blood  in.  such  a 
state   fails  to   stimulate  the  center,  and,  therefore,  the   muscles  con- 
trolled by  it  remain  at  rest.     The  fetus  is  in  this  condition;  likewise 
some  animals  in  the  state  of  hibernation.     If,  further,  an  abundance  of 
air  is  made  to  pass  into  the  lungs  of  animals  by  means  of  artificial 
respiratory  apparatus,  they  cease  to  breathe  because  the  marked  arte- 
rialization  of  their  blood  does  not  permit   of  stimulation   of  the   res- 
piratory center.     If,  further,  a  similar  state  of  the  blood  is  induced  by 
rapid  and  deep  respirations  apneic  pauses  of  considerable  duration  occur. 

A.  Ewald  found  the  blood  in  the  arteries  of  apneic  animals  almost  completely 
saturated  with  oxygen,  while  the  amount  of  carbon  dioxid  was  diminished.  The 
venous  blood  contained  less  oxygen  than  under  normal  conditions.  The  latter 
fact  is  probably  due  to  the  circumstance  that  the  apneic  state  of  the  blood  greatly 
reduces  the  blood-pressure,  and  in  consequence  .the  circulation  is  slowed.  There- 
fore, the  oxygen  can  be  taken  from  the  capillary  blood  in  much  larger  amount. 
In  general,  however,  the  consumption  of  oxygen  during  the  state  of  apnea  is 
not  increased.  Gad  calls  attention  to  the  fact  that  on  forced  artificial  respiration 
the  pulmonary  alveoli  are  greatly  filled  with  atmospheric  air,  and  in  consequence 
they  are  capable  of  arterializing  for  a  considerable  time  the  blood  entering  the 
lungs,  so  that  the  necessity  for  respiration  must  be  diminished.  According  to 
Gad  and  Knoll  the  respiratory  center  during  apnea  is  in  a  state  of  diminished 
irritability,  which  can  be  induced  reflexly  through  the  forcible  stretching  of  the 
terminal  pulmonary  branches  of  the  vagi  in  connection  with  the  artificial  respira- 
tory movements.  This  is  shown  also  by  the  fact  that  the  respiratory  movements 
commence  again  only  after  the  blood  has  already  become  dark,  when,  in  conse- 
quence of  this  venous  state  of  the  blood,  signs  of  irritation  through  the  venosity 
of  the  blood  appear  in  the  heart,  the  vascular  system  and  the  intestine.  Apnea 
cannot  be  induced  in  young  mammals. 

2.  The  normal  stimulus  for  the  respiratory  centers  for  quiet  breath- 
ing, eupnea,  is  furnished  by  a  state  of  the  blood  in  which  the  amount  of 
oxygen  and  carbon  dioxid  does  not  exceed  the  normal  limits. 

3.  All  factors  that  diminish  the  normal  amount  of  oxygen  and  in- 
crease the  amount  of  carbon  dioxid  in  the  blood  circulating  through  the 
centers  cause  acceleration  and  deepening  of  the  respiration,  which  finally 
may  increase  to  the  point  of  strained  and  laborious  activity  of  all  of  the 
respiratory  muscles.     This  condition  is  designated  dyspnea. 

In  case  of  normal  breathing  and  beginning  air-hunger  the  gases  in  the  blood, 
according  to  Gad,  irritate  only  the  inspiratory  center.  Expiration  takes  place 
reflexly  through  irritation  of  the  pulmonary  branches  of  the  vagus  stimulated  by 
the  distention  of  the  lungs.  Gad  believes  that  the  normal  respiratory  movements 
are  excited  by  the  carbon  dioxid.  If  dyspneic  blood  be  passed  through  the 
vessels  of  the  brain  of  a  normal  animal,  the  latter  becomes  dyspneic.  In  case  of 
dyspnea  in  consequence  of  excessive  physical  activity,  an  as  yet  unknown  body, 
formed  as  a  result  of  the  muscular  activity,  acts,  in  addition  to  the  change  in 
the  gases  of  the  blood  mentioned,  as  an  irritant  for  the  center,  perhaps  as  an 
acid.  The  alterations  in  the  dyspneic  respiratory  rhythm  are  described  on 
p.  211. 

4.  If  the  abnormal  conditions  of  the  blood  mentioned  contiriue  to 
exert  an  irritant  effect,  or  if  they  are  further  intensified,  there  finally 
results  a  state  of  exhaustion  in  consequence  of  overstimulation  of  the 
respiratory  centers ;  the  respiration  is  again  diminished  with  respect  to 
the  number  and  the  depth  of  the  movements,  and  later  on  only  a  few 


THE    RESPIRATORY    CENTER.  753 

gasping  respirations  occur.  Then  the  exhausted  muscles  cease  con- 
tracting entirely,  and  soon  the  movement  of  the  heart  also  ceases.  This 
condition  is  designated  asphyxia  and  it  may  terminate  fatally  in  suf- 
focation. If,  however,  the  causative  factors  can  be  removed,  the 
asphyxia  can  be  dissipated  under  favorable  conditions  by  means  of  ar- 
tificial stimulation  of  the  respiratory  muscles  and  of  the  cardiac  activity, 
so  that  following  the  state  of  dyspnea  that  of  eupnea  may  be  again 
obtained.  If  the  state  of  the  blood  becomes  only  gradually  more 
and  more  venous,  asphyxia  may  result  without  the  signs  of  previous 
dyspnea,  death  taking  place  quietly  and  gradually.  The  condition  here 
is  in  a  certain  measure  one  of  insidiousness  of  the  irritation. 

Convulsions  are  associated  with  the  dyspnea  of  acute  onset.  Extirpation  of 
the  cerebral  hemispheres,  likewise  deep  narcosis  by  means  of  chloroform,  renders 
these  slight  or  abolishes  them.  After  removal  of  the  optic  thalami  general 
convulsions  appear  not  to  take  place. 

Among  the  causes  of  dyspnea  there  should  be  mentioned: 

i.  Direct  limitation  of  the  activity  of  the  respiratory  organs:  Diminution  in 
the  respiratory  surface  in  consequence  of  inflammation,  acute  edema  or  collapse 
of  the  alveoli,  occlusion  of  the  alveolar  capillaries,  compression  or  collapse  of  the 
lungs  in  consequence  of  the  entrance  of  air  into  the  pleural  cavities  and  stenosis 
of  the  air-passages.  2.  Exclusion  of  the  normal  respiratory  air  through  stran- 
gulation, enclosure  in  narrow  spaces,  drowning.  3.  Failure  of  the  circulation,  in 
consequence  of  which  a  sufficient  amount  of  blood  is  not  sent  to  the  medulla  and 
as  a  result  the  necessary  ventilation  does  not  take  place,  as  in  connection  with 
degenerations  of  the  heart,  valvular  lesions,  artificially  through  ligature  of  the 
carotid  arteries,  also  obstruction  to  the  escape  of  the  venous  blood  from  the  cranial 
cavity,  finally  through  the  injection  of  large  quantities  of  air  or  of  indifferent 
bodies  into  the  right  heart.  4.  Direct  loss  of  blood,  which  may  be  effective 
likewise  through  interference  with  the  gaseous  interchange  in  the  medulla.  In 
this  category  belongs  also  the  dyspneic  gasping  for  air  of  the  decapitated  head, 
particularly  of  young  animals. 

If  the  rapidity  with  which  these  factors  influence  the  respiratory  activity  be 
observed  it  will  be  noted  that  there  occurs  first  accelerated  and  deepened  breathing; 
there  then  follows,  after  the  general  convulsions  and  the  associated  expiratory 
spasm,  a  stage  of  complete  respiratory  rest,  in  relaxation,  asphyctic  respiratory 
pause.  Finally,  there  occur  only  a  few  gasping  inspirations  before  death  takes 
place. 

Generally  the  deficiency  of  oxygen  and  the  excess  of  carbon  dioxid  tend  at 
the  same  time  to  excite  the  dyspnea,  although  in  the  variations  of  the  inspired 
air  from  the  normal,  the  increase  of  carbon  dioxid  has  an  irritating  effect  earlier 
and  in  more  marked  degree  than  the  diminution  of  oxygen,  i.  Dyspnea  from 
deficiency  of  oxygen  occurs  on  breathing  in  closed  space  of  moderate  size,  in  a 
space  the  air  of  which  is  rarefied,  as  well  as  on  breathing  indifferent  gases  free 
from  oxygen.  On  intense  ventilation  of  the  blood  with  nitrogen  or  hydrogen, 
the  amount  of  carbon  dioxid  contained  may  even  be  diminished,  and  death  takes 
place,  nevertheless,  amid  the  signs  of  asphyxia.  2.  Dyspnea  from  excess  of 
carbon  dioxid  occurs  on  breathing  mixtures  of  gas  rich  in  carbon  dioxid  (which 
form  also  on  breathing  for  a  long  time  in  a  closed  space  of  considerable  size  or 
in  an  atmosphere  of  pure  oxygen) .  Gaseous  mixtures  rich  in  carbon  dioxid  cause 
dyspnea  even  when  the  amount  of  oxygen  contained  is  greater  than  that  of  the 
atmosphere.  Even  the  blood  itself  may  be  found  to  contain  more  oxygen  than 
normal. 

Elevation  of  temperature  also  may  stimulate  the  respiratory  center  to  increased 
activity.  This  takes  place  even  when  the  brain  alone  receives  warmer  blood,  as 
was  observed  by  A.  Fick  and  Goldstein  when  they  imbedded  the  exposed  carotid 
arteries  in  heated  tubes.  In  this  experiment  the  heated  blood  obviously  affects 
directly  the  medulla  and  the  cerebral  respiratory  centers.  Direct  lowering  of  the 
temperature  diminishes  the  irritability.  When  the  temperature  is  elevated,  apnea 
cannot  be  induced  by  means  of  forced  artificial  respiration  and  the  resulting 
arterialization  of  the  blood.  Emetics  act  in  the  same  manner. 

Kronecker  and  Marckwald  found  electrical  irritation  of  the  center  also  effective. 
Irritation  of  the  medulla  oblongata  separated  from  the  brain  excited  respiratory 
48 


754  THE    RESPIRATORY    CENTER. 

movements  or  increased  these  if  already  present.  Langendorf  observed  in  con- 
sequence of  electrical,  mechanical  or  chemical  irritation  (with  salt)  generally  an 
expiratory  effect;  on  the  other  hand,  after  irritation  of  the  cervical  cord  (sub- 
ordinate center),  an  inspiratory  effect.  According  to  Laborde,  a  superficial  lesion 
in  the  neighborhood  of  the  apex  of  the  calamus  scriptorius  causes  arrest  of  the 
respiratory  movements  of  a  few  minutes'  duration. 

If  arrest  of  the  heart  is  caused  by  irritation  of  the  peripheral  stump  of  the 
divided  vagus,  arrest  of  respiration  for  a  few  seconds  ensues  at  the  same  time. 
In  consequence  of  the  arrest  of  the  heart,  transitory  anemia  occurs,  as  a  result 
of  which  the  irritability  of  the  respiratory  center  is  diminished,  so  that  respiration 
ceases  for  a  time.  The  observations  of  Ahlfeld  are  most  remarkable,  in  which  in 
spite  of  abolition  of  the  action  of  the  heart  in  the  new-born  the  respiratory  move- 
ments still  persisted,  as  in  dogs  after  poisoning  with  antiar. 

Reference  has  already  been  made  to  the  great  correspondence  in  the  regula- 
tion of  the  respiratory  and  the  intestinal  nervous  systems  (p.  288). 

In  addition  to  direct  irritation  of  the  respiratory  center  locally,  it 
may  be  influenced  also  by  the  will  and  reflexly  through  a  number  of  cen- 
tripetal nerves. 

Through  the  will  it  is  possible  to  suppress  the  breathing  for  only 
a  short  time,  that  is  until  the  increased  venosity  of  the  blood  excites  the 
respiratory  center  to  renewed  activity.  The  number  and  the  depth  of 
the  movements  can  be  increased  for  a  considerable  time ;  in  addition  the 
will  has  an  influence  upon  the  rhythm.  The  influence  of  the  cerebral 
cortex  upon  the  respiration  is  considered  on  p.  790. 

The  respiratory  center  can  be  influenced  reflexly,  and  there  are 
both  excitor  and  inhibitory  nerves.  The  nerves  through  which  the 
respiratory  center  is  stimulated  reflexly  are  contained  in  the  pulmonary 
branches  of  the  vagus,  also  in  the  sensory  nerves  of  the  eye,  the  ear,  and 
the  skin.  Under  normal  conditions  their  action  preponderates  over  that 
of  the  inhibitory  nerves.  Thus,  for  example,  a  cold  bath  makes  the 
respirations  deeper  and  thus  causes  moderate  acceleration  of  pulmonary 
ventilation. 

Influence  of  the  Vagus. — Division  of  the  vagus  on  both  sides  causes,  in  con- 
sequence of  removal  of  the  influence  of  these  stimulating  fibers,  slowing  of  the 
respiratory  movements.  Under  such  circumstances,  the  entire  amount  of  air  ex- 
changed remains  for  a  time  unchanged,  but  respiration  is  deepened  and  takes 
place  with  excessive  and  inadequate  inspiratory  effort.  In  agreement  with  experi- 
mental section,  subsequent  feeble  tetanizing  irritation  of  the  central  stump  of  the 
vagus  is  again  followed  by  acceleration  of  the  respiratory  movements.  More 
marked  irritation  causes  arrest  of  breathing  in  inspiration  or  (particularly  when 
the  nerve  is  exhausted)  in  expiration.  Irritation  of  the  sensory  nerves  of  the 
thoracic  and  abdominal  wall  causes  retardation  of  breathing  when  both  vagi  are 
divided. 

According  to  Lewandowsky  slight  irritation  of  the  central  stump  of  the  vagus 
by  means  of  induced  currents  causes  diminished  depth  of  inspiration.  Then,  as 
the  strength  of  the  current  is  increased,  respiration  becomes  accelerated.  A  still 
stronger  irritation  causes  the  thorax  to  assume  the  inspiratory  position,  then 
arrest  in  inspiration  and  finally  irregular  restlessness  of  the  respiratory  move- 
ments i  the  constant  current  be  employed,  closure  of  an  ascending  current  or 
(in  chloral-narcosis)  an  uninterrupted  ascending  current  applied  to  the  central 
stump  of  the  vagus  causes  arrest  of  breathing  in  expiration  or  slowing  of  the 
respiratory  rhythm  (inhibitory  effect);  while  an  interrupted  descending  current, 
as  well  as  closure  of  descending  current,  cause  arrest  of  breathing  in  inspiration, 
or  acceleration  of  breathing  (stimulating  effect) . 

^       Chemical  irritation  of  the  central  stump  of  the  vagus  by  means  of  sodium 
»did  or  potassium   chlorid  causes   expiratory  arrest  of  breathing.     Momentary 

;ant  influences  cause  inspiratory,  continued  irritation,  expiratory  effects.  The 
active  fibers  are  situated  in  the  uppermost  root-bundles  of  the  centers  of  the 
ninth,  tenth  and  eleventh  nerves  in  the  rabbit 


THE    RESPIRATORY    CENTER.  755 

If  one  lung  is  atelectatic  (devoid  of  air),  the  pulmonary  fibers  of  the  vagus 
of  the  same  side  are  inirritable.  Section  of  the  vagus  upon  the  side  of  the  healthy 
lung  acts,  therefore,  in  the  same  way  as  section  of  both  vagi. 

The  inhibitory  -fibers  which  act  upon  the  center  for  the  respiratory 
movements  pass  in  the  superior  and  inferior  laryngeal  nerves  to  the  res- 
piratory center.  The  recurrent  fibers  are  inactive  in  deep  narcosis. 

Even  direct  electrical,  mechanical  or  chemical  irritation  of  the  center  itself 
may  inhibit  respiration,  perhaps  because  the  irritation  affects  the  central  ex- 
tremities of  the  inhibitory  fibers  at  their  point  of  entrance  into  the  ganglia. 

Irritation  of  the  inhibitory  fibers  or  their  central  stumps  causes, 
therefore,  slowing  and  even  cessation  of  breathing  in  expiration.  Ir- 
ritation also  of  the  nasal  branches  of  the  trigeminus,  and  the  orbital 
branches,  as  well  as  the  olfactory  and  the  glossopharyngeal,  causes 
arrest  of  breathing  in  expiration,  as  does  also  irritation  of  the  pulmonary 
fibers  of  the  vagus  by  the  introduction  of  certain  irritant  gases  into 
the  lungs.  Chemical  irritation  of  the  trunk  of  the  vagus,  by  means  of 
weak  solutions  of  sodium  carbonate,  induces  especially  expiratory  inhibi- 
tion of  breathing;  mechanical  irritation  (rubbing  with  a  glass  rod),  in- 
spiratory  inhibition.  Also  the  irritation  of  sensory  cutaneous  nerves, 
particularly  of  the  chest  and  the  abdomen,  for  example  by  a  sudden  cold 
douche,  and  also  of  the  splanchnic  nerve,  causes  arrest  in  expiration,  the 
former  often  after  preceding  clonic  spasm  of  the  respiratory  muscles. 
The  influence  of  irritation  of  sensory  nerves  upon  respiration  is  in 
general  widely  distributed,  thus,  for  example,  that  of  the  sensory  fibers 
of  the  phrenic  nerve,  the  heart,  the  aorta,  the  abdominal  viscera.  The 
slowing  of  the  respiration  in  conjunction  with  pressure  upon  the  brain 
is  particularly  noteworthy,  the  breathing  not  rarely  becoming  labored 
and  stertorous. 

In  man  irritation  of  the  nasal  mucous  membrane  in  inspiration  causes  at 
first  inhibition  of  breathing  in  the  phase  present  at  the  time ;  then  follows  inspira- 
tion. During  the  period  of  reflex  slowing  of  respiration  the  amount  of  work 
performed  by  the  respiratory  muscles  is  altered,  and  particularly  the  work  in  the 
slow  respirations  is  increased  through  fruitless  efforts  at  inspiration.  On  the 
other  hand,  it  has  been  found  that  the  volume  of  gases  interchanged  in  the  lungs 
remains  the  same  during  corresponding  periods,  and  that,  also,  the  respiratory 
interchange  of  gases  is  at  first  not  altered  directly. 

Under  normal  conditions  the  pulmonary  branches  of  the  vagus  appear 
to  affect  the  respiratory  centers  through  a  mechanism  of  self-regulation 
in  such  a  manner  that  the  inspiratory  dilatation  of  the  lungs,  and  the 
associated  rarefaction  of  the  contained  air,  exerts  a  mechanical  irri- 
tation upon  the  nerve-fibers  stimulating  the  expiratory  center  reflexly. 
Conversely,  the  expiratory  diminution  in  the  size  of  the  lungs,  and  the 
resulting  increase  in  intrapulmonary  air-pressure,  causes  irritation  of  the 
nerve-fibers  passing  to  the  inspiratory  center.  These  fibers  are  situated 
in  the  posterior  portion  of  the  true  trunk  of  the  vagus. 

According  to  Lewandowsky  there  is  a  special  expiratory  center,  although  in 
normal  breathing  the  inspiratory  center  alone  is  active,  rhythmically  stimulating 
the  inspiratory  muscles  and  then  permitting  them  to  relax. 

Deglutitional  breathing,  that  is,  a  slight  contraction  of  the  dia- 
phragm after  each  act  of  swallowing,  occurs  as  an  irradiation  from  the 
irritation  of  the  swallowing-center  to  the  respiratory  center. 

The  Excitation  of  the  First  Respiratory  Movements. — The  fetus  im- 
mediately after  birth  is  in  a  state  of  apnea,  as  oxygen  is  abundantly 


756  ARTIFICIAL    RESPIRATION. 

supplied  to  it  through  the  placenta.  All  factors  that  interfere  with  this 
supply,  therefore  especially  compression  of  the  umbilical  vessels  and  per- 
sistent uterine  contractions,  cause  reduction  of  oxygen  and  increase  of 
carbon  dioxid  in  the  blood,  and  in  consequence  a  state  of  the  blood 
results  that  stimulates  the  respiratory  center,  and  with  this  the  im- 
pulse for  the  respiratory  movement  itself.  Thus  the  fetus  within 
the  unopened  membranes  may  be  stimulated  to  respiratory  move- 
ments. If  the  factors  interrupting  the  gaseous  interchange  persist, 
the  stimulated  respiration  becomes  dyspneic,  and  finally  death  occurs 
from  asphyxia.  If  the  venosity  of  the  fetal  blood  develops  gradually, 
as,  for  example,  in  case  of  slow,  quiet  death  of  the  mother,  the  medulla 
oblongata  of  the  fetus  may  die  gradually  without  the  development  of 
respiratory  movement,  without,  therefore,  the  interruption  of  fetal 
apnea.  This  is  a  paralysis  due  to  slowly  insidious  irritation. 

Accordingly,  the  respiratory  movement  is  excited  in  the  medulla  directly  by 
the  dyspneic  state  of  the  blood.  Asphyxia  of  the  mother  may  have  the  same 
effect  as  compression  of  the  umbilical  vessels.  In  such  an  event  the  maternal 
blood  rapidly  becomes  venous  and  abstracts  the  oxygen  from  the  blood  of  the 
fetus,  in  consequence  of  which  the  death  of  the  latter  is  accelerated.  If  the  mother 
has  been  rapidly  asphyxiated  by  carbon  monoxid  the  life  of  the  fetus  may  be 
prolonged,  as  the  carbon-monoxid  hemoglobin  of  the  maternal  blood  naturally 
can  remove  no  oxygen  from  the  fetal  blood.  When  the  poisoning  takes  place 
slowly  carbon  monoxid  also  passes  over  into  the  fetal  blood. 

In  many  instances,  especially  when,  after  persistent  uterine  contrac- 
tions, the  irritability  of  the  respiratory  center  is  already  greatly  en- 
feebled, the  dyspneic  state  of  the  blood,  which  becomes  even  more 
marked  after  birth,  is  not  in  itself  sufficient  to  stimulate  the  respiratory 
movements  in  rhythmic  and  typical  form.  For  this  purpose  there  is 
required  in  addition  irritation  of  the  external  integument,  for  example 
through  lowering  of  the  temperature  on  evaporation  of  the  amnial  liquor 
in  the  air.  If,  also,  in  consequence  of  the  first  movements  that  follow, 
air  has  entered  the  respiratory  passages,  the  air  may  exert  a  stimulating 
influence  upon  the  pulmonary  branches  of  the  vagus. 

According  to  the  observations  of  v.  Preuschen  the  stimulation  of  the  respira- 
tory center  through  the  nerves  of  the  external  integument  is  more  effective  than 
that  through  the  branches  of  the  vagus  to  the  respiratory  organ.  Also  in  animals 
that  have  been  made  apneic  by  means  of  vigorous  artificial  respiration,  this  ob- 
server noted  active  respiratory  movements  setting  in  after  application  of  cutaneous 
irritants,  such  as  a  douche  of  cold  water.  Mechanical  cutaneous  irritants,  such  as 
friction  or  slapping,  support  advantageously  the  stimulation  of  the  respiratory 
center,  as  does  also  douching  with  cold  water  or  irritation  with  the  electric  brush. 
the  placental  circulation  is  completely  intact,  cutaneous  irritation,  however, 
alone  induces  no  respiratory  movements. 

Artificial  Respiratory  Movements  in  the  Asphyxiated. — In  man,  it  is  customary, 
for  purposes  of  resuscitation  in  the  presence  of  asphyxia,  to  practise  artificial 
respiratory  movements.  The  subjects  under  such  circumstances  have  usually 
been  suffocated,  strangulated  or  drowned,  or  are  children  born  in  a  state  of  as- 
phyxia (intrauterine  suffocation).  The  first  duty  in  the  presence  of  such  a  con- 
lition  is  the  removal  from  the  air-passages  of  foreign  matters,  such  as  mucus 

lematous  fluid  in  the  newborn  or  the  asphyxiated,  water  in  the  case  of  the 

drowned    by,  lowering  the  head;  in  desperate  cases,  even  after  tracheotomy,  by 

suction  through  an  elastic  catheter  introduced  into  the  opening.     Next,  artificial 

respiration  must  be  undertaken  at  once.     Various  devices  and  methods  have  been 

Ascribed  for  this  purpose,  but  these  cannot  be  considered  in  detail  here.     Alternate 

dilatation  and  contraction  of  the  chest,  and  thereby  gaseous  interchange,  can  be 

ed  by  rhythmic  compression  of  the  thorax  by  application  of  the  flat  hand. 

I  he  asphyxiated  individual  is  placed  in  the  dorsal  decubitus,  the  vertebral  column 

>emg  flexed  backward  (with  the  aid  of  suitable  support)  as  far  as  possible      The 


ARTIFICIAL    RESPIRATION.  757 

mouth  is  held  open  and  the  tongue  (which  would  depress  the  epiglottis  by  falling 
backward)  is  drawn  forward.  Artificial  dilatation  of  the  thorax  can  be  effected 
by  stimulating  the  phrenic  nerves  at  suitable  intervals  by  means  of  sponge- 
electrodes  connected  with  an  induction-apparatus.  The  electrodes  are  placed  in 
the  situation  of  the  anterior  surface  of  the  scalene  muscle,  irritation  of  which 
will  augment  the  inspiration.  In  desperate  cases  air  may  be  blown  directly  into 
the  opened  trachea  through  an  elastic  tube  by  means  of  a  bellows  or  with  the 
mouth.  Care,  however,  is  required  in  this  connection,  in  order  to  avoid  injury  to 
the  lungs.  Artificial  respiration  has  a  vivifying  effect  through  both  the  supply 
of  oxygen  to,  and  the  removal  of  carbon  dioxid  from,  the  blood  ;  therefore  par- 
ticularly favoring  the  movement  of  the  blood  in  the  heart  and  in  the  large  vessels 
of  the  thorax,  and  thus  stimulating  the  circulation.  If  the  action  of  the  heart 
has  already  ceased,  resuscitation  cannot  be  hoped  for.  In  the  case  of  asphyxiated 
newborn  children  efforts  at  resuscitation  should  not  be  abandoned  too  early,  that 
is  before  cessation  of  the  heart -beat,  even  if  at  first  they  appear  hopeless,  as  the 
medulla  retains  for  a  long  time  some  measure  of  irritability.  Pfluger  and  Zuntz 
observed  the  reflex  irritability  and  the  heart-beat  persist  in  the  fetus  for  several 
hours  after  death  of  the  mother.  In  the  case  of  resuscitated  newborn  children  the 
resuscitating  measures  should  be  suspended  only  after  loud  crying  has  taken  place. 

Reference  should  be  made  here  to  the  remarkable  experiments  of  Bohm,  who 
succeeded  by  means  of  rhythmic  compression  of  the  heart  in  conjunction  with 
artificial  respiration  in  resuscitating  animals  (cats)  whose  respiration  and  heart- 
beat had  ceased  entirely  for  forty  minutes  in  consequence  of  asphyxia  or  poisoning 
with  potassium-salts  or  chloroform  and  in  which  the  carotid  pressure  had  fallen. 
The  compression  of  the  heart  causes  a  slight  movement  of  blood  (much  like  a 
feeble  systole) ;  at  the  same  time  the  compression  acts  as  a  rhythmic  stimulus 
for  the  heart.  The  heart-beat  returns  first,  then  also  the  respiration.  The  resus- 
citated heart-beat  itself  causes  interchange  of  air.  After  restoration  of  breathing 
reflex  irritability  also  returns  and  gradually  likewise  voluntary  movements.  The 
animals  are  blind  for  a  few  days,  the  brain  torpid  in  function,  the  urine  rich  in 
sugar.  The  experiments  show  the  great  importance,  in  the  resuscitation  of 
asphyxiated  individuals,  of  simultaneous  action  upon  the  heart. 

For  physiological  purposes  artificial  respiration  is  practised  by  blowing  air  by 
means  of  a  bellows  into  a  tracheal  cannula  provided  with  a  small  lateral  opening 
for  the  escape  of  the  expired  air.  If  the  animal  is  at  the  same  time  paralyzed  by 
curare  it  cannot  be  thrown  into  a  state  of  disturbing  restlessness  in  consequence 
of  independent  and  reflex  movements  of  the  musculature  of  the  body. 

Pathological. — If  the  lung  is  distended  with  air,  it  cannot  be  deprived  of  this 
by  direct  compression,  probably  because  in  consequence  of  the  direct  pressure 
affecting  the  lung  the  small  bronchi  are  compressed  before  air  can  escape  from 
the  pulmonary  alveoli.  If,  however,  a  lung  be  filled  with  carbon  dioxid  instead 
of  air  and  if  it  be  suspended  under  water,  the  carbon  dioxid  will  be  absorbed  by 
the  water  and  the  lung  may  thus  become  entirely  airless  (atelectatic).  The 
occurrence  of  atelectasis  in  certain  portions  of  the  lung  in  connection  with  disease 
of  this  organ  can  be  explained  in  this  manner.  If  bronchi  are  occluded  by  mucus 
or  exudate,  marked  accumulation  of  carbon  dioxid  takes  place  in  the  related 
pulmonary  vesicles.  This  becomes  the  greater  the  more  richly  the  blood  in  the 
lungs  (in  consequence  of  the  existing  disease  of  the  lung)  is  itself  impregnated 
with  carbon  dioxid.  If,  finally,  the  carbon  dioxid  is  absorbed  from  the  capillary 
blood  of  the  alveoli,  or  from  the  lymph,  the  affected  pulmonary  area  may  become 
atelectatic. 

Among  the  pathological  phenomena  that  are  caused  by  abnormal  (direct  or 
usually  reflex)  irritation  of  the  respiratory  center  are  spasm  of  the  respiratory 
muscles,  inspiratory,  expiratory  or  complex  spasm;  also  attacks  of  diminished 
respiratory  frequency  (spanipnea)  or  increased  respiratory  frequency  (pyknopnea) 
observed  in  neurotic  individuals,  together  with  dyspnea  and  a  sense  of  fear. 

As  the  brain  has  relations  to  the  respiratory  movements  the  modification  in 
these  movements  in  connection  with  cerebral  disorders  are  readily  explained.  The 
paralytic  affections  are,  as  a  rule,  upon  the  same  side  as  the  paralysis.  Also 
Cheyne-Stokes  breathing  is  observed. 


758  THE    CARDIAC    INHIBITORY    CENTER. 

THE  CENTER  FOR  THE  INHIBITORY  NERVES   (DIMINISHING 
THE  FREQUENCY  AND  THE  STRENGTH)  OF  THE  HEART 
AND  THE   FIBERS  PASSING  TO  THE  VAGUS. 

The  fibers  of  the  vagus  nerve,  moderate  irritation  of  which  diminishes 
the  activity  of  the  heart,  strong  irritation  causing  arrest  of  the  heart, 
and  which  are  conveyed  to  the  vagus  through  the  accessory  nerve,  have 
their  center  in  the  medulla  oblongata  far  to  the  side  of  the  floor  of  the 
fourth  ventricle  near  the  restiform  body.  The  center  sends  to  all  por- 
tions of  the  heart,  including  the  muscles  of  the  superior  vena  cava,  fibers 
that  diminish  the  number  of  beats  and  others  that  diminish  the  vigor 
of  the  contractions.  Slight  irritation  of  the  vagus  occasionally 
exerts  an  inhibitory  effect  only  upon  the  auricles.  The  force-diminishing 
fibers  at  the  same  time  also  prolong  the  diastole.  If  the  diastole  is 
rendered  difficult  by  increased  pressure  within  the  pericardium,  irritation 
of  the  vagus  is  believed  to  cause  a  prolongation  of  the  diastolic  distention. 

This  center  can  be  stimulated  both  directly  and  reflexly  from  centri- 
petal nerves. 

Many  investigators  assume  that  this  center  is  in  a  state  of  tonic  innervatipn, 
that  is  that  impulses  pass  out  from  it  uninterruptedly  through  the  vagus  '"exerting 
a  regulatory  and  inhibitory  influence  upon  the  heart-beat.  According  to  Bern- 
stein this  tonic  irritation  is  induced  reflexly  through  the  abdominal  and  cervical 
cords  of  the  sympathetic.  Landois  did  not  accept  this  view,  but  maintained  that 
under  normal  conditions  of  the  respiration  and  the  state  of  the  blood,  the  center 
is  not  irritated,  but  that  it  is  placed  in  a  state  of  irritation  only  under  special 
conditions. 

Direct  Irritation  of  the  Center. — The  center  can  be  irritated  locally 
by  the  same  influences  that  affect  the  respiratory  center,  i.  Sudden 
anemia  of  the  medulla  oblongata  (through  ligation  of  both  carotid  and 
both  subclavian  arteries,  or  through  decapitation  of  a  rabbit,  with  preser- 
vation of  the  vagi  alone)  causes  slowing  and  even  temporary  arrest  of 
the  heart -beat.  2.  Sudden  venous  hyperemia,  which  can  be  brought 
about  by  ligation  of  the  veins  passing  from  the  head,  has  a  similar  effect. 
3.  Also  increased  venosity  of  the  blood,  either  through  direct  interruption 
of  breathing  (in  the  rabbit),  or  through  insufflation  into  the  lungs  of  a 
gaseous  mixture  containing  much  carbon  dioxid,  acts  in  a  similar  way. 
As,  with  marked  uterine  contractions,  the  circulation  in  the  placenta,  the 
actual  lung  of  the  fetus,  is  interfered  with,  the  constant  enfeeblement  of 
the  heart's  action  in  association  with  severe  uterine  contractions  is  to  be 
looked  upon  as  a  dyspneic,  central  irritation  of  the  vagus.  4.  At  the 
moment  when  inspiration  takes  place  as  a  result  of  irritation  of  the 
respiratory  center  there  is  a  fluctuation  in  the  irritation  of  the  cardiac 
inhibitory  center.  5.  Also  increased  blood-pressure  in  the  cerebral  arte- 
ries stimulates  the  cardiac  inhibitory  center. 

That  the  center  (in  rabbits)  is  under  normal  conditions  not  in  a  state  of  tonic 
innervation  was  demonstrated  in  1863  by  Landois  by  the  fact  that  when,  after 
exposure  of  the  vagi,  care  was  taken,  by  means  of  artificial  respiration,  that  the 
number  of  heart-beats  remained  exactly  the  same  as  in  the  intact  rabbit,  section 
of  both  vagi  failed  to  cause  increase  in  pulse-frequency.  These  observations  were 
confirmed  by  Schiff .  It  is  true  that  in  dogs  after  division  of  the  vagi  (in  adult 
dogs  and  never  in  the  newborn)  sudden  increase  in  pulse-frequency  and  in 
blood-pressure  has  been  observed  occasionally,  but  by  no  means  constantly. 
The  frequency  of  the  pulse  of  the  previously  resting  animal  under  observation 
should,  however,  be  carefully  determined  first;  and  it  should  also  be  noted  whether 
the  preparations  for  the  experiment  did  not  cause  slowing  of  the  pulse.  Then, 


THE    CARDIAC    INHIBITORY    CENTER.  759 

the  section  itself  may  cause  irritation  the  accelerator  fibers  in  the  vagi  or  the 
pressor  fibers,  which  likewise  accelerate  the  heart -beat.  In  the  dog  whose  vagi 
are  paralyzed  after  injection  of  curare  into  the  veins,  with  maintenance  of  artificial 
respiration,  the  heart -beat  is  not  accelerated,  and  in  the  frog  section  of  both  vagi 
is  invariably  unattended  with  acceleration  of  pulse.  Also,  the  increase  in  blood- 
pressure  after  division  of  both  vagi  is  not  solely  dependent  upon  the  associated 
increase  in  the  pulse-rate  that  occurs. 

The  cardiac  inhibitory  center  can  be  stimulated  reflexly:  i. 
Through  the  irritation  of  sensory  nerves.  2.  Through  irritation  of  the  vagus 
itself,  as  by  irritation  of  the  central  stump  of  one  vagus,  with  preserva- 
tion of  the  other.  3.  Irritation  of  the  sensory  nerves  of  the  ab- 
dominal viscera,  by  percussion  of  the  abdomen  of  the  frog  (Goltz's 
percussion-experiment),  has  a  cardiac  inhibitory  effect;  as  does  also 
irritation  of  the  splanchnic  directly  or  of  the  abdominal  and  cervical 
cords  of  the  sympathetic.  Severe  irritation  of  sensory  nerves,  however, 
inhibits  the  reflexes  affecting  the  vagus  described,  and  has  a  reflex 
inhibiting  effect  generally. 

The  experiment  of  Goltz  succeeds  at  once  if  the  irritation  is  permitted  to 
act  upon  the  exposed  intestines  (of  the  frog) ,  which  become  inflamed  on  protracted 
exposure  to  the  air.  Also  in  dogs  irritation  of  the  stomach  causes  slowing  of  the 
pulse. 

The  irritation  of  the  cardiac  inhibitory  center  can  be  diminished 
reflexly,  according  to  Hering,  by  vigorous  distention  of  the  lungs  with 
atmospheric  air.  Under  such  circumstances  there  is  marked  reduction 
in  blood-pressure. 

In  man  forcible  expiratory  effort  causes  acceleration  of  the  heart-beat  in  conse- 
quence of  the  increased  intrapulmonary  pressure,  and  this  has  been  attributed  by 
Sommerbrodt  to  reduction  in  the  activity  of  the  cardiac  branches  of  the  vagi, 
which  are  in  a  state  of  tonic  innervation.  At  the  same  time  a  depressant  effect 
is  exerted  upon  the  vasomotor  center. 

In  the  entire  course  from  the  center  downward  through  the  trunk  of  the 
vagus  and  further  on  through  its  cardiac  branches,  irritation  causes  slowing  and 
enfeeblement  and  finally  cessation  of  the  activity  of  the  heart.  In  the  frog  this 
result  can  be  brought  about  even  by  irritation  of  the  fibers  of  the  vagus  at  the 
venous  sinus  of  the  heart.  Feeble  irritants  slow  the  heart-beat,  while  stronger 
irritants  cause  diastolic  arrest.  If  irritants  of  considerable  intensity  affect  either 
the  center  or  the  course  of  the  nerve  for  a  considerable  period  of  time,  the  irritated 
area  becomes  exhausted  and  the  heart  again  pulsates  more  rapidly  in  spite  of 
the  persistent  irritation.  If,  however,  the  site  of  irritation  is  displaced  nearer  to 
the  heart,  renewed  inhibition  takes  place,  as  the  irritation  now  affects  a  new 
nerve  segment. 

With  reference  to  the  irritation  of  the  inhibitory  fibers  the  following  points 
are  wrorthy  of  note:  i.  It  is  probable  that  the  fibers  diminish  the  number  of 
heart-beats  and  those  diminishing  the  strength  of  the  heart  are  distinct,  both 
with  reference  to  their  anatomic  arrangement,  as  well  as  with  respect  to  their 
susceptibility  to  various  poisons.  The  experiments  of  Heidenhain  on  frogs,  con- 
firmed by  Lowit,  have  shown  that  electrical  and  chemical  stimulation  of  the  vagus 
have  varying  results  with  reference  to  the  size  and  the  number  of  the  heart -beats. 
Either  the  contractions  become  only  smaller,  or  they  become  only  less  frequent, 
or  they  become  smaller  and  at  the  same  time  less  frequent.  Those  branches  of 
the  vagus  that  in  the  frog  are  situated  in  the  nerves  of  the  septum  exert  an  influ- 
ence alone  upon  the  strength  and  the  tone.  Those  fibers,  however,  that  enter 
the  frog's  heart  outside  of  the  nerves  of  the  septum  have  an  influence  alone  upon 
the  number  of  heart-beats.  In  the  turtle  also,  both  sets  of  fibers  are  anatomically 
distinct.  2.  To  obtain  the  inhibitory  effect  persistent  irritation  is  not  necessary, 
but  a  moderately  rapid  rhythmic,  interrupted  irritation  will  suffice :  from  eighteen 
to  twenty  irritations  in  a  second  in  warm-blooded  and  two  or  three  in  cold-blooded 
animals.  3.  Bonders  observed  in  association  with  Prahl  and  Nuel  that  the  inhi- 
bition manifested  itself  not  immediately  at  the  moment  of  irritation,  but  that 
from  one-sixth  to  two-fifths  of  a  second  elapsed  before  the  onset  of  the  action. 


760  THE    CARDIAC    AUGMENTOR    CENTER. 

After  removal  of  the  irritation,  the  heart  still  remains  for  a  short  time  in  a 
state  of  rest.  Irritation  of  the  vagus  has  thus  an  inhibitory  after-effect.  4.  Also 
chemical  irritation  of  the  center  is  effective:  a  crystal  of  sodium  chlorid  placed 
upon  the  medulla  of  the  frog  inhibits  the  heart-beat.  5.  If  the  heart  has 
been  arrested  by  irritation  of  the  vagus,  it  makes  a  single  coordinated  contraction 
on  direct  irritation  (for  example  by  a  needle-prick) ,  although  the  contractions  of 
the  heart  in  vagus-arrest,  both  after  irritation,  as  well  as  those  that  arise  secondarily 
in  a  portion  of  the  heart  in  consequence  of  irritation  of  another  portion,  take 
place  with  greater  difficulty,  especially  in  the  auricles  6.  In  the  water-turtle 
the  inhibitory  fibers  are,  according  to  A.  B.  Mayer,  contained  only  in  the  right 
vagus.  Landois  found  this  by  no  means  constant  in  rabbits.  7.  The  nerve  can 
occasionally  be  successfully  stimulated  mechanically  also  in  human  beings  by 
digital  compression  against  the  cervical  portion  of  the  vertebral  column ;  although 
alarming  attacks  of  syncope  have  been  observed  to  follow^  this  procedure  and  for 
this  reason  its  practice  is  to  be  cautioned  against.  8.  The  behavior  of  the  vagus 
ne.rve  in  the  electrotonic  state  has  been  considered  on  p.  663  and  the  contraction- 
law  for  the  same  nerve  on  p.  665.  9.  Schiff  found  that  irritation  of  the  vagus 
in  the  frog  caused  acceleration  of  the  pulse  (through  an  action  upon  the  accelerator 
fibers  contained  in  the  vagus),  after  he  had  displaced  the  blood  in  the  heart  by 
a  solution  of  sodium  chlorid.  If,  subsequently,  blood-serum  is  again  introduced 
into  the  heart,  the  inhibitory  action  of  the  vagus  is  restored.  10.  Many  sodium- 
salts,  naturally  in  suitable  concentration,  are  capable  of  abolishing  the  inhibitory 
action  of  the  vagi;  while,  conversely,  potassium-salts  possess  the  property  of 
restoring  the  inhibitory  function  of  the  vagi  suspended  by  the  action  of  sodium- 
salts.  Both  sodium-salts  and  potassium-salts,  however,  can,  after  protracted 
action,  induce  a  state  in  which  the  restitution  of  the  suspended  inhibitory  function 
of  the  vagi  is  no  longer  possible.  Under  such  circumstances  the  heart-beat  is 
generally  arrhythmic,  n.  If  the  pulsations  of  the  heart  are  greatly  accelerated 
in  consequence  of  high  intracardiac  pressure  the  activity  of  the  cardiac  branches 
of  the  vagus  is  correspondingly  diminished.  This  is  the  case  also  in  connection 
with  the  simultaneous  action  of  direct  cardiac  irritants.  The  lessened  activity  of 
the  vagus  in  conjunction  with  high  internal  pressure  within  the  heart  occurs  only 
if  the  auricles  and  the  venous  sinus  (in  the  frog)  are  at  the  same  time  greatly 
distended.  12.  In  the  frog  reduction  in  temperature  impairs  the  inhibitory  in- 
fluence of  the  vagus,  while  elevation  of  temperature  increases  it.  In  the  newborn 
and  in  the  state  of  hibernation  the  irritation  is  ineffective. 

Among  poisons  muscarin  irritates  the  terminations  of  the  vagus  in  the  heart, 
and  it  may  even  cause  diastolic  arrest,  which  may  then  be  neutralized  by  atropin. 
Digitalin  reduces  the  frequency  of  the  heart-beat  by  irritation  of  the  vagus-center. 
Doses  of  considerable  size  diminish  the  irritability  of  the  vagus-center  and  at  the 
same  time  increase  that  of  the  accelerator  ganglia  of  the  heart,  so  that  the  fre- 
quency of  the  heart-beat  is  increased.  In  small  doses  digitalin  also  increases  the 
blood-pressure  by  irritation  of  the  vasomotor  center  and  the  structures  of  the 
vessel-walls.  Nicotin  first  stimulates  the  vagus  (and  the  resulting  arrest  can  be 
neutralized  by  curare  or  atropin)  and  then  paralyzes  it;  as  does  also  hydrocyanic 
acid.  Atropin  and  curare  paralyze  the  vagi,  as  do  marked  reduction  in  tempera- 
ture and  high  fever. 

THE   CENTER   FOR  THE  ACCELERATOR  AND  AUGMENTING 

CARDIAC   NERVES  AND  THE   FIBERS  TO  WHICH  IT 

GIVES   RISE. 

It  is  more  than  probable  that  the  medulla  oblongata  contains  a  center 
that,  on  the  one  hand,  sends  to  the  heart  accelerating  fibers,  increasing 
the  number  of  heart -beats,  and,  on  the  other  hand,  fibers  that  increase 
its  systolic  force.  These  pass  from  the  medulla,  in  which  the  exact  situa- 
tion of  their  origin  has  not  yet  been  determined,  downward  in  the  spinal 
cord  and  enter  through  the  communicating  branches  of  the  inferior  cervi- 
cal and  the  six  upper  thoracic  nerves  into  the  sympathetic.  Thence,  a 
main  branch  of  these  fibers  passes  principally  through  the  first  thoracic 
ganglion  of  the  sympathetic  and  the  loop  of  Vieussens,  and  hence  to  the 
cardiac  plexus.  This  nerve  is  designated  the  accelerator  nerve  of  the 


THE    CARDIAC    AUGMENTOR    CENTER.  761 

heart.  Accordingly,  irritation  of  the  medulla,  of  the  lower  extremity 
of  the  divided  cervical  cord,  of  the  inferior  cervical  ganglion  (stellate 
ganglion),  or  of  the  superior  dorsal  node,  is  attended  with  acceleration  of 
the  heart-beat  and  increase  of  its  strength  (in  the  dog  and  the  rabbit) ; 
or,  if  the  heart's  action  has  already  ceased,  with  renewal  of  its  beat, 
without  change  in  blood-pressure. 

It  is  probable  that  the  accelerator  nerves  and  those  increasing  the  strength  of 
the  heart  are  distinct,  both  with  respect  to  their  anatomical  arrangement,  and 
with  regard  to  their  susceptibility  to  various  poisons. 

When  the  medulla  oblongata  or  the  cervical  cord  is  irritated,  the  vasomotor 
nerves  situated  in  them  are  also  irritated.  In  consequence,  the  vessels  that 
derive  their  motor  fibers  from  the  irritated  area  contract,  and  the  blood-pressure 
is  markedly  increased.  As,  however,  the  increase  in  blood-pressure  alone  causes 
acceleration  of  the  heart-beat,  the  irritation  described  does  not  directly  demon- 
strate the  existence  of  accelerator  fibers  in  these  central  structures.  The  ex- 
periment would  be  convincing  only  if  before  the  irritation  is  applied  the  blood- 
pressure  were  enormously  lowered  by  destruction  of  the  splanchnic  nerves,  so  that 
the  former  could  no  longer  exert  an  accelerating  influence.  Indirectly  it  can  be 
demonstrated  also  that,  if  all  of  the  nerves  of  the  cardiac  plexus,  therefore  also 
the  accelerator  fibers,  are  extirpated,  after  irritation  of  the  medulla  or  the  cervical 
cord  the  pulse-frequency  does  not  rise  (in  consequence  of  increase  in  blood-pressure) 
in  the  same  degree  as  before  the  extirpation. 

The  center  is  in  any  event  not  in  a  state  of  tonic  irritation,  for  section 
of  the  nerve  does  not  cause  slowing  of  the  heart.  Destruction  of  the 
medulla  or  of  the  cervical  cord  itself  likewise  has  a  negative  effect. 
Nevertheless,  in  this  instance  also,  the  splanchnic  nerve  must  be  pre- 
viously destroyed,  to  bring  about  marked  lowering  of  the  blood-pressure, 
in  order  that  the  reduction  in  the  number  of  heart -beats  that  occurs  in 
consequence  of  the  lowered  blood-pressure  after  destruction  of  the 
cord  shall  not  be  incorrectly  interpreted  as  being  due  to  destruction  of  the 
accelerator  center. 

Cardiac  accelerator  fibers  pass,  according  to  the  statements  of  earlier 
investigators  and  of  v.  Bezold,  in  part  into  the  cervical  sympathetic, 
in  part  through  the  vagus  to  the  heart,  and  irritation  accelerates  the 
heart -beat  or  strengthens  the  cardiac  contractions,  or  both.  The  inhib- 
itory fibers  of  the  vagus  lose  their  irritability  more  readily  than  the  accel- 
erator fibers,  but  they  are  more  irritable  than  the  latter. 

The  fibers  of  the  vagus  that  influence  the  force  of  the  contractions  are  situated 
in  the  frog  in  the  nerves  of  the  septum.  The  acceleration  of  pulse  attending 
increased  muscular  activity  is  attributable  to  irritation  of  the  accelerator  fibers, 
occurring  in  conjunction  with  stimulation  of  the  motor  nerves,  while  the  irritation 
of  the  inhibitory  nerves  is  diminished.  The  acceleration  appears  especially  in  de- 
bilitated convalescents.  The  heart,  after  a  period  of  increased  activity,  later 
resumes  its  normal  action.  Practice  in  the  form  of  activity  favors  such  resumption. 

The  cases  described  by  Tarchanoff  and  van  de  Velde  are  most  striking.  In 
these,  human  beings  were  able,  solely  through  the  influence  of  the  will  (at  rest 
and  without  alteration  of  respiration) ,  to  increase  the  number  of  pulse-beats  even 
to  twice  the  normal. 

Direct  irritation  of  the  accelerator  nerve  gives  rise  to  slowly  developing  effects, 
which  disappear  gradually  after  cessation  of  the  irritation.  If  the  vagus  and  the 
accelerator  are  irritated  simultaneously,  only  the  inhibitory  action  of  the  vagus 
makes  its  appearance.  According  to  Hunt,  in  the  case  of  this  simultaneous 
irritation,  the  action  of  that  nerve  appears  which  is  most  strongly  irritated.  If 
during  the  activity  of  the  accelerator  nerve,  the  vagus  is  suddenly  irritated, 
prompt  reduction  in  the  number  of  heart-beats  occurs,  and  if  the  irritation  of 
the  vagus  ceases  the  acceleration  soon  begins  again.  The  activity  of  the  accel- 
erator nerves  (in  the  frog)  is  enfeebled  by  cold  and  increased  by  heat. 


762  THE    VASOMOTOR    CENTER    AND    NERVES. 

According  to  experiments  of  Strieker  and  Wagner  section  of  both  vagi  in 
the  dog  causes  reduction  in  the  number  of  heart-beats  when  the  accelerator 
fibers  on  both  sides  are  divided.  This  circumstance  would  indicate  a  state  of 
tonic  innervation  of  the  latter. 

The  center  can  be  stimulated  reflexly  through  irritation  of  the  central  stumps 
of  many  sensory  nerves. 

THE   VASOMOTOR  CENTER  AND  NERVES. 

The  dominating  center,  which  supplies  all  of  the  muscles  of  the  arterial 
system  with  motor  fibers  (vasomotors,  vasoconstrictors),  is  situated  in 
the  medulla  oblongata  at  a  point  in  part  rich  in  large  ganglia.  It  is  3 
mm.  long  and  i^  mm.  wide  in  the  rabbit  and  extends  from  the  region 
of  the  upper  portion  of  the  floor  of  the  fourth  ventricle  to  about  4  or  5  mm. 
above  the  calamus  scriptorius.  Each  half  of  the  body  has  as  its  own 
center,  which  is  situated  2$  mm.  from  the  middle  line  in  that  portion 
of  the  medulla  on  each  side  that  represents  the  prolongation  of  the  lateral 
columns  of  the  spinal  cord  (lower  portion  of  the  superior  olive).  Irri- 
tation of  this  central  point  causes  contraction  of  all  of  the  arteries  and  in 
consequence  increase  in  arterial  blood-pressure,  the  veins  and  the  heart 
becoming  distended.  Paralysis  of  the  center  causes  relaxation  and 
dilatation  of  all  of  the  arteries,  with  enormous  reduction  in  blood-pres- 
sure. Under  normal  conditions  the  vasomotor  center  is  in  a  state  of 
moderate  tonic  excitation.  Like  the  cardiac  inhibitory  and  the  res- 
piratory center,  the  vasomotor  center  can  be  stimulated  directly  and 
reflexly. 

Direct  Stimulation  of  the  Center. — In  this  connection  the  amount  of 
gases  contained  in  the  blood  circulating  in  the  medulla  oblongata  is  of 
paramount  importance.  In  the  state  of  apnea  the  center  appears  to  be 
in  a  condition  of  slightest  excitation,  as  the  blood-pressure  is  exceedingly 
low.  With  the  state  of  the  blood  present  under  normal  conditions  the 
center  is  in  a  condition  of  moderate  excitation.  Fluctuations  in  the 
irritation  of  the  center  accompany  the  respiratory  movements  (Traube- 
Hering  fluctuations),  as  can  be  seen  from  the  simultaneous  increase  in 
blood-pressure.  When  the  blood  presents  marked  venosity,  in  conse- 
quence of  asphyxia  or  insufflation  of  air  rich  in  carbon  dioxid,  the  center 
is  more  actively  stimulated,  so  that  all  of  the  arteries  contract,  with 
marked  increase  in  blood-pressure,  and  the  venous  system  and  the  heart 
are  greatly  distended  with  blood.  Under  such  circumstances  the  veloc- 
ity of  the  blood-current  is  increased.  The  same  effect  is  produced  by 
sudden  anemia  of  the  medulla  through  ligation  of  both  carotid  and  sub- 
clavian  arteries,  and  likewise  by  sudden  stagnation  of  the  blood  in  the 
presence  of  venous  hyperemia. 

The  venosity  of  the  blood  that  always  develops  after  death  causes  quite  con- 
stantly active  stimulation  of  the  vasomotor  center,  as  a  result  of  which  the  arteries 
are  strongly  contracted.  As,  in  consequence  of  this,  the  blood  is  driven  to  the 
capillaries  and  the  veins,  the  state  of  emptiness  of  the  arteries  after  death,  which 
was  familiar  to  the  ancients,  is  explained. 

Upon  this  circumstance  is  dependent  also  the  fact,  as  Landois  has  found,  that 
hemorrhage  from  large  wounds  takes  place  much  more  freely  when  the  vasomotor 
center  is  preserved  than  when  it  has  previously  been  destroyed  (in  the  frog). 
As  emotional  disturbances  have  a  corresponding  influence  upon  the  vasomotor 
center,  their  influence  upon  the  control  of  hemorrhage  is  obvious  Thus  it  has 
been  observed  in  hysterical  individuals  that  a  wound  yields  only  one-third  as 
much  blood  as  the  same  condition  in  a  normal  individual.  If  the  hemorrhage  is 
considerable,  the  anemic  irritation  of  the  medulla  may  finally  exert  a  constricting 


THE    VASOMOTOR    CENTER    AND    NERVES.  763 

influence  upon  the  bleeding  artery.  In  this  way  is  to  be  explained  the  phenomenon 
familiar  to  surgeons  that  dangerous  hemorrhage  often  ceases  as  soon  as  anemic 
syncope  occurs.  In  the  frog,  after  ligation  of  the  heart,  all  of  the  blood  is  finally 
driven  into  the  veins,  likewise  as  a  result  of  anemic  irritation  of  the  medulla. 
In  mammals  the  equalization  of  the  blood-pressure  in  the  arterial  and  the  venous 
system  that  follows  exclusion  of  the  heart  takes  place  more  slowly  after  destruction 
than  after  preservation  of  the  medulla. 

Among  poisons,  strychnin  stimulates  the  center  directly,  even  in  curarized 
dogs;  and  nicotin  and  calabar  bean  have  the  same  effect. 

In  animals  in  which  the  center  is  irritated  electrically,  it  has  been  found  that 
single  induction-shocks  of  moderate  strength  are  effective  only  when  two  or  three 
shocks  occur  in  a  second.  There  is  thus  a  summation  of  the  effects  of  the  indi- 
vidual stimuli.  The  maximum  vasoconstrictor  effect,  which  can  be  recognized 
from  the  maximum  blood-pressure,  is  observed  as  a  result  of  from  ten  to  twelve 
strong  or  from  twenty  to  twenty-five  moderately  strong  shocks  in  one  second. 

The  course  of  the  vasomotor  nerves  is  such  that  in  part  medullated  and  in  part 
non-medullated  nerve-fibers,  partly  mixed  with  ganglion-cells,  pass  to  the  muscular 
coats  of  the  vessels.  They  pass  from  their  center  in  part  directly  through  the 
tract  of  some  of  the  cerebral  nerves  to  their  distribution;  through  the  trigeminus 
in  part  to  the  interior  of  the  eye,  through  the  hypoglossus  to  the  tongue,  through 
fibers  of  the  vagus  to  the  heart  and  in  limited  number  to  the  lungs  and  to  the 
intestines.  All  other  vasomotor  nerves  descend  in  the  lateral  column  of  the  spinal 
cord  (so  that  irritation  of  the  lower  extremity  of  the  divided  cord  causes  con- 
striction of  the  vessels  supplied  from  a  lower  level),  and  are  connected  within 
the  gray  matter  with  centers  of  subordinate  significance  by  means  of  contact. 
They  make  their  exit  through  the  anterior  roots  of  the  spinal  nerves,  then  pass 
through  the  visceral  branches  into  the  ganglia  of  the  sympathetic  cord,  where 
the  ganglion-cells  are  intercalated  in  the  course  of  the  individual  fibers.  In  the 
sympathetic  cord  they  pass  upward  or  downward  and  finally  hence  either  to  the 
vascular  plexuses  or  through  other  visceral  branches  again  into  the  trunks  of 
spinal  or  cerebral  nerves  and  from  these  to  the  respective  vessels. 

In  detail,  the  distribution  in  the  cerebral  region  is  as  follows:  The  cervical 
division  of  the  sympathetic  supplies  in  largest  measure  the  head.  In  its  area  of 
innervation  the  great  auricular  nerve  in  some  animals  also  supplies  a  number  of 
vasomotors,  which,  in  the  rabbit,  however,  are  derived  from  the  inferior  cervical 
ganglion  of  the  sympathetic.  The  cerebral  vessels  are  supplied  principally  by  the 
sympathetic,  irritation  of  which  slows  the  blood-current  in  the  small  cerebral 
arteries  and  increases  the  resistance  in  them;  on  the  other  hand  dyspnea,  as  well 
as  administration  of  chloroform  and  amyl  nitrite,  causes  acceleration  of  the  blood- 
current.  The  nerves  reach  the  cerebral  vessels  not  only  through  the  cervical 
sympathetic,  but  also  through  other  tracts.  The  superior  ganglion  of  the  cervical 
sympathetic  supplies  the  thyroid  gland. 

The  upper  extremities  receive  their  vasomotor  nerves  through  the  anterior 
roots  of  the  dorsal  nerves  from  the  fourth  to  the  tenth  and  thence  through  the 
sympathetic  cord  to  the  first  thoracic  ganglion  and  from  this  through  visceral 
branches  to  the  brachial  plexus.  The  vasomotors  for  the  skin  of  the  trunk  are 
derived  from  the  dorsal  and  lumbar  nerves.  The  last  three  dorsal  and  the  three 
uppermost  lumbar  nerves  contain  the  fibers  for  the  lower  extremity  (in  the  dog) , 
which  first  pass  through  the  sixth  and  seventh  lumbar  and  the  first  and  second 
sacral  ganglia  and  then  enter  the  trunks  of  the  lumbar  and  sacral  plexuses. 

The  lungs  are  supplied  (in  addition  to  a  number  of  fibers  in  the  vagus)  by 
the  first  thoracic  ganglion.  According  to  Fr.  Franck  the  sympathetic  supplies 
vasoconstrictors  to  the  lesser  circulation,  arising  from  the  second  and  third  dorsal 
nerves.  They  are  stimulated  reflexly  through  irritation  of  sensory  nerves.  The 
activity  of  the  vasomotors  of  the  lesser  circulation  is  relatively  slight.  In  the  frog 
the  vagus  supplies  the  vasomotors  of  the  lungs. 

The  splanchnic  is  the  most  important  of  all  of  the  vasomotor  nerves,  supplying 
the  abdominal  viscera.  Its  vasoconstrictor  fibers  arise  from  the  fifth  dorsal  nerve 
and  below.  Irritation  of  the  communicating  branches  between  the  eleventh  dorsal 
and  the  second  lumbar  nerve  causes  marked  dilatation  after  primary  contraction 
of  the  vessels.  Dilatation  is  caused  also  by  irritation  of  the  vagus.  Asphyxia 
causes  contraction  of  all  of  the  vessels  of  the  entire  intestine,  the  liver,  and  the 
pancreas.  Irritation  of  sensory  nerves,  for  example  the  crural,  causes  reflex  con- 
traction of  the  vessels  of  the  small  intestine,  the  kidney,  the  spleen,  the  pancreas, 
and  dilatation  of  the  vessels  of  the  large  intestine.  Irritation  of  the  centripetal 


764  THE    VASOMOTOR    CENTER    AND    NERVES. 

fibers  of  the  vagus  causes  dilatation  of  the  vessels  of  the  intestine,  the  pancreas 
and  the  kidney.  The  vasomotors  of  the  liver  are  discussed  on  p.  313,  those  of 
the  kidneys  on  p.  514,  and  those  of  the  spleen  on  p.  195.  The  vasomotors  are 
all  medullated  from  their  origin  to  the  sympathetic  cord. 

In  general  the  vessels  of  the  skin  of  the  trunk  and  the  extremities  are  inner- 
vated by  those  nerves  that  supply  the  same  parts  also  with  other,  for  example 
sensory,  fibers. 

The  various  vascular  areas  respond  differently  with  respect  to  the  intensity 
of  the  action  of  the  vasomotors.  These  affect  in  greatest  degree  the  vessels  of  the 
peripheral  portions  of  the  body,  for  example  the  toes,  the  fingers,  the  ears,  less 
markedly  the  central  areas,  for  example  the  lesser  circulation. 

Reflex  Stimulation  of  the  Center. — The  most  varied  centripetal  nerves 
contain  fibers,  irritation  of  which  has  an  influence  on  the  vasomotor 
center.  Irritation  of  some  of  these  nerves  causes  stimulation  of  the 
center  and,  thus,  increased  contraction  of  the  arteries,  together  with 
increased  blood-pressure.  These  are  designated  press  or  fibers.  On 
the  other  hand,  there  are  fibers  irritation  of  which  causes  reflex  dimi- 
nution in  the  irritability  of  the  vasomotor  center.  The  result  is,  there- 
fore, the  opposite  of  the  former.  The  nerves  act  really  as  inhibitory 
nerves  of  the  center  and  are  designated  depressor  fibers. 

Pressor  fibers  have  already  been  pointed  out  as  present  in  the  superior 
and  inferior  laryngeal  nerves,  also  in  the  trigeminus,  the  direct  irritation 
of  which  has  a  pressor  effect,  which  occurs  also  as  a  result  of  insufflation 
of  irritating  vapors  into  the  nose.  Aubert  and  Roever  discovered  pressor 
fibers  in  the  cervical  sympathetic.  S.  Mayer  and  Pribram  observed 
that  mechanical  irritation  of  the  stomach,  particularly  of  the  serosa,  has 
a  pressor  effect.  Irritation  of  any  sensory  nerve  is  said  to  cause  first 
a  pressor  effect. 

Thus  O.  Naumann  observed  after  feeble  electrical  irritation  of  the  skin  at 
first  a  pressor  effect,  namely  contraction  of  the  mesenteric  vessels,  the  lungs  and 
the  web,  with  simultaneous  excitation  of  the  heart's  action  and  acceleration  of 
the  circulation  (in  the  frog).  Strong  irritation,  however,  had  the  opposite  or 
depressor  effect,  with  simultaneous  reduction  in  the  heart's  action.  Griitzner  and 
Heidenhain  observed  a  pressor  effect  from  contact  with  the  skin,  while  manipu- 
lations causing  severe  pain  were  ineffective.  Reflex  alteration  in  the  lumen  of  the 
vessels  and  in  the  activity  of  the  heart  can  be  induced  also  through  the  cutaneous 
application  of  heat  and  cold.  Schuller  observed  contractions  of  the  vessels  of  the 
pia  (in  rabbits)  after  pinching  of  the  skin,  likewise  after  warm  baths  or  the  ap- 
plication of  warm  compresses,  while  cold  baths  or  compresses  caused  dilatation 
of  the  vessels.  Schuller  interprets  these  phenomena  in  part  as  pressor  and  de- 
pressor effects,  although  he  considers  the  principal  cause  to  consist  in  the  con- 
traction of  the  cutaneous  vessels  in  consequence  of  the  cold,  resulting  in  increase 
of  the  blood-pressure  and  therefore  in  dilatation  of  the  vessels  of  the  pia.  Heat 
naturally  has  the  opposite  effect. 

In  man  most  forms  of  irritation  of  the  sensory  nerves,  such  as  slight  cutaneous 
irritation,  tickling  (also  disagreeable  odors,  a  bitter  or  a  sour  taste,  optical  or 
auditory  irritation),  cause  reduction  of  temperature  at  the  point  of  application, 
and  diminution  in  the  volume  of  the  affected  extremity,  at  times  also  increase 
in  the  general  blood-pressure  and  alteration  in  the  action  of  the  heart.  The  opposite 
effects  are  induced  by  painful  impressions,  as  well  as  by  the  action  of  heat  (also 
agreeable  odors  and  a  sweet  taste) .  The  forms  of  irritation  first  mentioned  cause 
at  the  same  time  dilatation  of  the  cerebral  vessels  and  increase  in  the  amount 
of  blood  in  the  skull,  while  the  latter  bring  about  the  opposite  results.  The  time 
for  the  reflex  is  between  three  and  five  seconds. 

Depressor  fibers,  irritation  of  which  lowers  the  activity  of  the  vaso- 
motor center,  are  present  in  many  nerves.  The  depressor  nerve  of  the 
vagus  has  already  received  special  mention.  The  trunk  of  the  vagus 
below  the  latter  contains  depressor  fibers,  and  so  also  do  its  pulmonary 


THE    VASOMOTOR    CENTER    AND    NERVES.  765 

branches  (in  the  dog).  The  latter  have  a  depressant  effect  also  in  con- 
nection with  marked  expiratory  pressure.  In  accordance  with  this  fact 
Hering  showed  that  marked  distention  of  the  lungs  (at  a  pressure  of  50 
mm.  of  mercury)  caused  lowering  of  the  blood-pressure  and  acceleration 
of  the  heart -beat.  Irritation  of  sensory  nerves,  particularly  if  intense 
and  long  continued,  causes  dilatation  of  the  vessels  in  the  areas  innervated 
by  them.  Also  irritation  of  the  muscle-nerves  by  pressure  has  a  de- 
pressant effect.  According  to  Latschenberger  and  Deahna  all  sensory 
nerves  contain  both  pressor  and  depressor  fibers. 

Schiff  observed  after  irritation  of  sensory  nerves  the  periodic  contractions  in 
the  ear  of  the  rabbit,  normally  occurring  from  three  to  five  times  in  a  minute, 
give  way  to  dilatation,  after  a  preceding  contraction  of  short  duration.  Direct 
pressure  upon  an  artery  within  its  distribution  has  a  depressor  effect,  as  can  be 
seen,  for  example,  from  the  fact  that  after  long-continued  pressure  of  the  sphygmo- 
graph  the  pulse-tracing  becomes  larger  and  exhibits  signs  of  lessened  arterial 
tension. 

In  the  intact  body  slowly  alternating  contraction  and  dilatation, 
without  uniform  rhythm,  are  observed  in  the  arterial  branches  (arteries 
of  the  rabbit's  ear,  in  the  membrane  of  the  bat's  wing,  the  web  of  the 
frog's  foot).  This  movement,  discovered  by  Schiff,  is  for  the  purpose 
of  supplying  the  organ  in  question  at  times  with  a  larger,  at  other  times 
with  a  smaller,  supply  of  blood,  accordingly  as  its  nutrition  or  external 
influences  demand.  This  phenomenon  can  appropriately  be  designated 
periodic-regulatory  vascular  movement.  It  is  probably  responsible,  in 
case  of  occlusion  of  the  vessels,  for  example  after  ligature,  for  the  prompt 
establishment  of  the  collateral  circulation.  This  occurs  with  distinctly 
greater  difficulty  after  division  of  the  nerve. 

According  to  Bier  the  final  cause  resides  in  the  cellular  activity  in  the  tissues 
that  have  become  anemic.  After  transitory  anemia  the  small  vessels  of  the  skin 
open  widely  for  the  reception  of  the  arterial  blood-current,  while  they  close  to 
the  venous  current,  and,  moreover,  independently  of  the  central  nervous  system. 
Nothnagel  agrees  with  v.  Recklinghausen  that  the  increased  velocity  with  which 
the  blood  flows  through  the  collateral  branches  of  the  obstructed  vessel  is  the 
factor  that  causes  hypertrophy  of  the  walls  of  the  vessel  and  dilatation  of  the 
lumen  of  the  collateral  branches. 

Perhaps  the  arteries  are  capable  of  another  form  of  movement,  namely  the 
pulsatory,  which  consists  in  active  contraction  after  each  pulsatory  dilatation 
of  the  vessel.  It  would,  therefore,  correspond  with  the  registration  of  the  de- 
scending limb  in  the  tracing.  From  what  has  been  said  as  to  the  propagation- 
velocity  of  the  pulse-wave,  this  contraction  must  be  propagated  centrifugally  in 
a  peristaltic  manner  with  the  same  velocity  as  the  pulse-waves.  It  should,  how- 
ever, be  stated  that,  as  yet,  this  form  of  movement  has  not  been  demonstrated 
with  certainty. 

The  lumen  of  the  vessel  can  be  influenced  directly  by  local  applica- 
tion, cold  and  moderate  electrical  stimulation  causing  contraction,  and, 
conversely,  heat  and  strong  mechanical  or  electrical  stimulation,  causing 
dilatation,  the  latter  two  probably  after  transitory  preceding  contrac- 
tion. 

Elevation  of  the  temperature  of  the  arm  to  43°  C.  causes  relaxation  of  the  vessels, 
reduction  to  between  10°  and  20°  C.  contraction.  Abrupt  alterations  in  tempera- 
ture always  cause  transitory  contraction  of  the  vessels  (also  those  of  the  opposite 
arm).  Irritation  by  heat  and  cold  is  capable,  in  addition  to  its  influence  upon 
the  vessels  themselves  locally  at  the  seat  of  irritation,  also  of  affecting  the  lumen 
of  the  vessels  through  reflex  stimulation.  Thus  cold,  for  example,  may  cause 
dilatation  of  the  vessels.  Electrical  stimuli  likewise  exert  their  effects  principally 


766  THE    VASOMOTOR    CENTER    AND    NERVES. 

in  a  reflex  way.  Among  poisons,  almost  all  of  the  members  of  the  digitalis- 
group  cause  constriction.  Quinin  and  salicin  cause  constriction  of  the  vessels  of 
the  spleen.  The  remaining  febrifuges  cause  dilatation  of  the  vessels,  as  does  also 
Witte's  peptone. 

The  influence  of  the  vasomotor  nerves  upon  the  temperature,  both  of 
limited  portions  of  the  body  as  well  as  of  the  entire  body,  is  of  great 
significance. 

Local  effects.  Division  of  a  peripheral  vasomotor  nerve,  for  ex- 
ample the  cervical  sympathetic,  causes  dilatation  of  the  vascular  area 
supplied  by  it,  as  the  paralyzed  vessels  are  readily  distended  by  the 
intra-arterial  pressure.  In  consequence,  a  larger  amount  of  arterial 
blood  at  once  enters  this  area,  and  as  a  result  injection-redness  develops, 
and,  at  the  same  time,  also  in  parts  that  readily  become  cool,  such  as 
the  ear  and  the  skin  of  the  face — elevation  of  temperature.  Increased 
transudation  takes  place  through  the  walls  of  the  relaxed  capillaries. 
Within  the  dilated  vessels  the  velocity  of  the  blood-current  is,  naturally, 
diminished,  while  the  blood-pressure  is  increased.  Further,  the  pulse 
is  more  readily  palpated  in  such  situations,  because  the  lumen  of  the 
vessel  is  increased.  With  the  increased  size  of  the  blood-current  the 
blood  may  be  bright  red  as  it  enters  the  veins  and  the  pulse  may  even  be 
followed  into  the  veins.  Every  irritation  of  a  peripheral  vasomotor  nerve 
gives  rise  to  the  opposite  phenomena,  namely  pallor,  diminished  trans- 
udation and  reduction  in  temperature  in  the  external  integument. 
Smaller  arteries  become  contracted  to  the  point  of  complete  disappear- 
ance of  their  lumen.  Long-continued  irritation  causes  finally  exhaus- 
tion of  the  nerve  and  gives  rise  at  the  same  time  to  symptoms  of  paralysis 
of  the  vessel-wall. 

The  phenomena  described  as  following  paralysis  of  vasomotor  nerves  do  not, 
however,  remain  unchanged.  The  paralysis  of  the  muscular  coat  of  the  vessels 
must  obviously  give  rise  to  stagnation  in  the  circulation  of  the  blood,  as  the 
muscular  coat  constitutes  an  important  factor  in  the  normal  distribution  of  the 
blood  in  the  vessels.  The  slower  blood-movement  is  responsible  for  the  fact  that 
parts  exposed  to  the  air  become  more  readily  cooled.  Thus,  the  primary  stage 
of  elevation  of  temperature  after  division  of  the  vasomotor  nerves  may  be  followed 
by  a  second  stage  of  reduction  in  temperature.  As  a  result  of  numerous  experi- 
ments Landois  was  able  to  confirm  the  observation  of  Schiff  that  in  rabbits  from 
which  the  cervical  sympathetic  had  been  removed  some  weeks  previously,  the 
ear  upon  the  intact  side  was  always  warmer,  and  particularly  if  the  animals 
were  actively  stimulated,  in  consequence  of  which  the  circulation  in  the  intact 
vessels  was  accelerated.  If,  as,  for  example,  in  the  paralyzed  extremities  of 
human  beings,  the  muscle-nerves  are  paralyzed  in  addition  to  the  vasomotors, 
the  extremity  will  become  cooler  in  the  course  of  time,  because  the  paralyzed 
muscles  are  no  longer  capable  of  generating  heat  by  their  contraction,  and, 
further,  because  the  dilatation  of  the  muscle- vessels,  which  occurs  with  each  con- 
traction of  the  muscles,  is  lost.  If,  finally,  the  paralyzed  muscles  undergo  atrophy 
the  vessels  contained  in  them  also  become  reduced  in  size.  There  is  thus  afforded 
an  explanation  for  the  fact  that  paralyzed  extremities  in  human  beings  are  as 
a  rule  cold  in  the  further  course  of  the  case,  although  primarily  the  temperature 
is  elevated. 

If  in  consequence  of  the  same  procedure  the  vasomotor  nerves  of 
extensive  areas  of  the  skin  are  paralyzed,  as,  for  example,  in  the  lower 
half  of  the  body  after  section  of  the  dorsal  cord,  so  much  heat  is  given 
off  by  the  dilated  vessels  that  either  an  elevation  of  the  temperature  of 
the  skin  is  observed  for  only  a  short  time  and  in  slight  degree  or  reduction 
in  temperature  takes  place  at  once.  Thus,  some  observers  have  noted 
elevation  of  temperature  after  division  of  the  cervical  cord,  although 
Riegel  did  not. 


THE    VASOMOTOR    CENTER    AND    NERVES.  767 

Pfluger  found  that  a  rabbit  with  division  of  the  cervical  cord  pro- 
duced more  carbon  dioxid  when  the  surrounding  temperature  was  ele- 
vated and  less  when  the  temperature  was  lowered.  The  human  being 
injured  in  a  similar  manner  exhibits  analogous  conditions,  being  more 
readily  cooled  when  the  surrounding  temperature  is  low-and  more  readily 
overheated  when  the  surrounding  temperature  is  high. 

Influence  upon  the  Temperature  of  the  Entire  Body. — Irritation  or 
paralysis  of  vasomotor  nerves  within  small  areas  has  practically  no 
influence  upon  the  temperature  of  the  entire  body.  If,  however,  the 
vessels  in  an  extensive  area  of  the  skin  are  suddenly  dilated  by  paralysis 
of  their  vasomotor  nerves,  the  temperature  of  the  entire  body  falls,  be- 
cause much  more  heat  is  given  off  from  the  dilated  vessels  than  under 
normal  conditions.  This  is  the  case,  for  example,  after  high  division  of 
the  spinal  cord.  Inhalation  of  two  or  three  drops  of  amyl  nitrite  is  also 
attended  with  reduction  in  the  bodily  temperature  in  man  in  consequence 
of  the  resulting  dilatation  of  the  vessels  of  the  skin.  Under  opposite 
conditions  of  irritation  of  extensive  areas  the  temperature  of  the  body  is 
elevated  because  the  constricted  vessels  give  off  less  heat.  This  fact 
explains  in  part  febrile  elevations  in  temperature. 

Also  the  cardiac  activity,  that  is  the  number  and  the  energy  of  the 
contractions  of  the  heart,  is  greatly  influenced  by  the  state  of  irritability 
of  the  vasomotor  nerves.  If  these  nerves  are  paralyzed  throughout 
considerable  areas,  the  vessels  whose  walls  contain  muscle-fibers  dilate, 
and  the  blood  itself  does  not  reach  the  heart  with  its  usual  rapidity  and 
abundance,  as  the  pressure  under  which  it  flows  has  become  considerably 
•essened.  The  consequence  is  that  the  heart  makes  extremely  small, 
slow  and  labored  contractions,  somewhat  like  a  damaged  pump,  to  which 
sufficient  material  is  not  sent  for  propulsion  onward.  Strieker  even 
observed  arrest  of  the  heart  in  the  dog  on  extirpation  of  the  spinal  cord 
between  the  first  cervical  and  the  eighth  dorsal  vertebra.  Conversely, 
it  is  known  that  on  irritation  of  the  vasomotor  nerves,  in  consequence  of 
the  resulting  contraction  of  the  vessels  with  a  muscular  coat,  the  blood- 
pressure  rises  considerably.  As  the  arterial  pressure  is  effective  up  to 
the  left  ventricle,  it  causes,  as  a  mechanical  irritant  to  the  wall  of  the 
, heart,  an  increase  in  the  activity  of  the  heart,  with  respect  both  to  the 
number  of  beats  and  to  their  vigor,  in  the  course  of  a  short  while.  As 
a  result,  the  circulation,  already  accelerated  by  the  increase  in  pressure 
in  the  arterial  system  in  consequence  of  the  arterial  contraction,  is  further 
accelerated. 

By  far  the  most  extensive  area  of  the  circulation  is  controlled  by  the  splanchnic 
nerve,  as  it  innervates  the  large  branches  of  all  of  the  arteries  of  the  abdomen. 
Irritation  of  this  nerve  is,  therefore,  followed  by  marked  increase  in  the  blood- 
pressure.  Conversely,  paralysis  of  the  nerve  is  attended  with  such  marked  stag- 
nation of  blood  in  the  dilated  abdominal  vessels  that  all  the  remaining  portions 
of  the  body  become  anemic,  and  death  may  even  result,  in  a  measure  in  conse- 
quence of  intravascular  hemorrhage.  For  the  same  reason  animals  die  of  anemia 
after  ligation  of  the  portal  vein. 

The  capacity  of  the  interior  of  the  vascular  system,  by  reason  of  its  dependence 
upon  the  vasomotor  nerves,  has  obviously  also  an  influence  upon  the  bodily  weight, 
especially  in  consequence  of  variations  in  the  amount  of  fluid  taken  up  into  or 
given  off  from  the  blood.  Strong  irritation  of  the  vasomotor  apparatus  may  cause 
a  fall  in  bodily  weight  through  rapid  loss  of  water.  In  this  category  belongs 
probably  the  loss  of  weight  observed  by  some  after  epileptic  convulsions,  in 
consequence  of  polyuria,  increased  sweating,  secretion  of  tears  or  of  saliva.  Con- 
versely, paralysis  or  paresis  of  the  vasomotor  nerves  causes  dilatation  of  the 


768  THE    VASOMOTOR    CENTER    AND    NERVES. 

blood-stream,  with  increase  in  the  weight  of  the  body.  Such  a  result  is  brought 
about  by  a  number  of  poisons,  for  example  alcohol  in  large  doses.  After  disappear- 
ance of  the  intoxication  the  normal  weight  is  restored  after  copious  urination. 

The  trophic  disorders  that  accompany  affections  of  the  vasomotor  nerves  are 
deserving  of  especial  consideration.  Paralysis  of  the  vasomotors  gives  rise,  in 
addition  to  vascular  dilatation  and  local  increase  in  the  blood-pressure,  also  to 
increased  transudation  from  the  capillaries.  In  consequence  of  the  loss  of  the 
muscular  activity  in  the  vessels  the  blood-stream  becomes  slowed,  and  stagnates; 
as  a  result,  the  capillaries  are  dilated  and  the  slowly  moving  blood  in  them  becomes 
markedly  venous,  so  that  the  skin  acquires  a  livid  color.  Further,  normal  trans- 
piration is  interfered  with,  so  that  dryness  of  the  epidermis  results,  and  often 
also  desquamation  and  fissuration.  Passive  hyperemia,  a  tendency  to  occlusion 
of  the  capillaries  and  to  the  formation  of  thrombi  in  the  veins,  together  with 
passive  transudates  and  edematous  swelling,  are  not  rare.  Also  the  normal  growth 
of  the  hair  and  the  nails  is  readily  interfered  with,  the  skin  exhibits  increased 
vulnerability  and  the  nutrition  of  all  of  the  remaining  tissues  may  suffer.  In 
consequence  of  long-continued  irritation  of  vasomotor  nerves  the  amount  of 
blood  passing  through  the  affected  vessels  becomes  diminished,  and  it  may  be 
conceived  that,  as  a  result,  nutritive  disturbances  occur  in  the  parts  to  be  sup- 
plied. Tangl  found  on  long-continued  faradic  stimulation  of  the  spinal  cord  a 
reduction  in  oxidation-processes  in  the  tissues,  as  a  result  of  which  gaseous  inter- 
change, and  finally  also  the  bodily  temperature,  fall  markedly. 

In  addition  to  the  dominating  vasomotor  center  in  the  medulla  ob- 
longata,  the  vessels  are  tinder  the  control  of  subordinate  centers  in  the 
gray  matter  of  the  spinal  cord.  This  can  be  recognized  from  the  following 
observation :  If  the  spinal  cord  be  divided  in  an  animal,  all  of  the  vessels 
supplied  by  nerves  arising  below  this  level  soon  undergo  paralytic  dila- 
tation, in  consequence  of  section  of  the  vasomotors  from  the  medulla. 
If  the  animal  survive,  the  vessels  regain  their  previous  caliber  in  the 
course  of  a  few  days,  and  the  rhythmic  movements  of  their  muscular 
coat  are  now  controlled  by  the  subordinate  vasomotor  centers  in  the 
lower  extremity  of  the  spinal  cord. 

The  subordinate  spinal  centers  can  be  stimulated  directly  through  a  dyspneic 
state  of  the  blood.  Reflex  stimulation  also  is  possible;  after  destruction  of  the 
medulla  oblongata  the  arteries  of  the  web  of  the  frog's  foot  contract  on  irritation 
of  the  sensory  nerves  of  the  opposite  hind  leg.  In  the  dog  a  spinal  vasomotor 
center  susceptible  of  reflex  irritation  is  situated  between  the  third  and  sixth 
dorsal  nerves  (origin  of  the  splanchnic),  and  a  similar  center  is  present  in  the 
lower  portion  of  the  spinal  cord.  According  to  Spina  the  cerebral  vessels  have 
such  a  center  extending  to  the  third  cervical  vertebra. 

If,  after  the  section,  the  lower  extremity  of  the  spinal  cord  is  crushed, 
the  vessels  again  undergo  paralytic  dilatation,  in  consequence  of  de- 
struction of  the  subordinate  centers.  Even  now,  however,  in  surviving 
animals  the  dilatation  is  gradually  replaced  by  normal  contraction  and 
rhythmic  movement,  and  henceforth  this  movement  of  the  vessel-wall 
is  controlled  by  the  ganglia  everywhere  distributed  throughout  it.  The 
latter  are  thus  capable  of  acting  independently  and  of  maintaining  the 
movement  of  the  vessel-wall.  Increased  tension  in  the  vessel  causes 
contraction  of  the  muscular  coat.  Even  the  vessels  of  excised  surviving 
kidneys,  through  which  blood  is  passed,  exhibit  these  periodic  fluctua- 
tions in  caliber.  The  observation  is  further  worthy  of  mention  that 
the  vessel-walls  contract  as  soon  as  the  state  of  the  blood  becomes  in 
marked  degree  venous.  The  vessels  oppose  a  greater  resistance  to  the 
flow  of  venous  blood  than  to  that  of  arterial  blood.  Perhaps  the  general 
disturbance  of  nutrition  exhibited  by  individuals  suffering  from  dyspneic 
states  of  long  standing  is  to  be  explained  in  this  way.  In  any  event  the 


THE    VASOMOTOR    CENTER    AND    NERVES.  769 

vessel-walls,  however,  appear  after  the  series  of  procedures  described 
not  to  attain  again  the  complete  mobility  and  reactivity  that  they  pos- 
sess under  normal  conditions. 

Through  the  intermediation  of  these  peripheral  vessel-ganglia  the  movements 
of  the  vessels  also  appear  to  take  place  that  are  observed  to  occur  on  application 
of  direct  mechanical,  chemical  or  electrical  irritation  to  the  vessels.  The  arteries 
contract  often  to  the  point  of  obliteration  of  their  lumen.  Amyl  nitrite  and 
digitalis  have  an  effect  upon  the  lumen.  The  pulsating  veins  in  the  bat's  wing 
continue  their  movement  after  division  of  all  of  the  nerves,  and  this  is  indica- 
tive of  the  local  innervation  through  peripheral  nerve-centers. 

Finally,  the  cerebrum  undoubtedly  has  an  influence  upon  the  vaso- 
motor  center,  as  is  shown  by  the  sudden  pallor  of  the  external  integument 
in  conjunction  with  emotional  disturbances,  such  as  fright,  fear.  This 
observation  has  received  a  satisfactory  explanation  in  the  discovery 
made  by  Eulenburg  and  Landois  that  the  gray  cortex  of  the  cerebrum 
contains  a  circumscribed  area  (in  the  cruciate  sulcus  in  the  dog),  irri- 
tation of  which  gives  rise  to  reduction  of  temperature  and  destruction 
to  elevation  of  temperature  in  the  contralateral  extremities.  From  this 
area  fibers  therefore  probably  pass  to  the  center  in  the  medulla,  which 
they  stimulate  to  either  increased  or  diminished  activity.  In  this  way 
is  to  be  explained  the  fact,  as  observed  by  Landois  together  with  Budge, 
that  irritation  of  both  cerebral  peduncles  causes  contraction  of  all  of  the 
vessels.  Heidenhain  noted,  accordingly,  that  irritation  in  the  further 
course,  at  the  junction  between  the  pons  and  the  medulla  oblongata, 
caused  rapid  rise  in  the  bodily  temperature. 

Emotional  influences  generally  increase  the  tone  of  the  vessels  (as  observed 
in  the  arm),  while  fatigue  and  joy  diminish  it. 

Although  the  medulla  contains  a  dominating  vasomotor  center  for 
all  of  the  vessels  in  common,  it  is  to  be  assumed  that  this  is  divisible 
into  a  number  of  central  points  lying  close  together  and  controlling 
definite  vascular  areas.  In  this  connection  there  have  been  isolated 
the  centers  for  the  vessels  of  the  liver  and  for  those  of  the  kidneys. 

Finally,  it  should  be  mentioned  that  certain  poisons  especially  stimulate  the 
vasomotor  apparatus,  such  as  ergotin,  tannic  acid,  balsam  of  copaiba  and  cubebs; 
while  others  at  first  stimulate  and  then  paralyze,  such  as  chloral  hydrate,  morphin, 
laudanosin,  digitalin,  veratrin,  physostigma.  alcohol;  while  still  others  rapidly 
paralyze,  such  as  amyl  nitrite,  carbon  monoxid,  atropin  and  muscarin.  The 
paralyzant  action  of  poisons  is  recognized  from  the  fact  that  after  division  or 
paralysis  of  the  cardiac  fibers  of  the  vagus  and  of  the  accelerator  nerve  irritation 
of  either  the  pressor  or  the  depressor  nerves  is  unattended  with  any  effect.  Cer- 
tain agents  having  a  pathological  effect  have  an  influence  upon  the  vasomotor 
nerves.  In  surviving  organs,  narcotics  and  antipyretics  cause  dilatation  and 
members  of  the  digitalis-group  contraction. 

The  veins  are  controlled  by  vasomotor  nerves,  for  example,  the  ear- 
veins  of  the  rabbit  through  the  cervical  sympathetic,  the  portal  vein 
through  the  splanchnic,  the  veins  of  the  hind  leg  through  the  sciatic. 
On  the  whole,  the  venomotors  pursue  the  same  course  as  the  arterio- 
motors  and  the  sweat-fibers. 

Little  is  known  with  regard  to  the  dependence  of  the  lymphatics  upon 
the  nerves.  Camus  and  Gley  observed  on  irritation  of  the  peripheral 
extremity  of  the  splanchnic  nerve  that  the  receptacle  for  the  chyle  gener- 
ally dilated.  Irritation  of  other  sympathetic  fibers  caused  contraction 

49 


770. 


THE    VASOMOTOR    CENTER    AND    NERVES. 


of  the  thoracic  duct  and  the  receptacle,  as  did  also  suspension  of  breath- 
ing. Irritation  of  the  thoracic  cord  of  the  sympathetic  is  followed  by 
dilatation  or  contraction  of  the  thoracic  duct.  The  constrictor  fibers, 
however,  are  more  readily  exhausted. 

Pathological. — Disorders  in  the  function  of  the  vasomotor  nerves  (angioneu- 
roses)  may  occur  in  different  forms.  The  points  of  attack  for  the  abnormal 
irritations  of  the  vasomotor  nerves  may  be  the  ganglia  in  the  vessels  themselves 
or  the  spinal  centers,  together  with  the  dominating  center  in  the  medulla,  or, 
finally,  the  cortical  vasomotor  centers  in  the  cerebrum.  The  action  may  be  either 
direct  or  reflex.  In  conformity  with  the  phenomena  of  physiological  experimen- 
tation, irritation  of  the  vasomotor  nerves  will  give  rise  to  contraction  of  the  blood- 
stream, pallor  and  reduction  of  temperature  in  the  external  integument  and 
diminished  diffusion  in  the  tissues.  Conversely,  paralysis  must  give  rise,  in  addi- 
tion to  dilatation  of  the  vessels,  to  elevation  of  temperature  and  redness  of  the 
integument,  as  well  as  increased  transudation  in  the  tissues. 

In  the  skin,  affections  of  the  vasomotor  nerves  give  rise,  first  of  all,  to  diffuse 
redness  or  pallor,  which  may  be  unilateral.  There  may,  however,  also  be  cir- 
cumscribed disorders,  such  as  the  local  cutaneous  arterial  spasm  induced  by 
irritation  of  individual  vasomotor  nerves.  Later  on,  various  forms  of  paralytic 
phenomena  involving  the  cutaneous  vasomotor  nerves  appear  upon  the  skin,  in 
the  sequence  of  a  number  of  acute  febrile  diseases,  after  preceding  initial  severe 
irritation  of  the  vasomotors,  especially  in  the  stage  of  chill  in  the  course  of 
various  fevers.  These  may  appear  as  simple  circumscribed  areas  of  redness  or 
as  increased  transudation  from  the  paralyzed  vessels,  with  the  formation  of 
wheals,  or  even  escape  of  red-  and  white  blood-corpuscles  from  the  paralyzed, 
greatly  dilated  vascular  areas,  or  edema,  eruptions  or  even  partial  gangrene. 
In  individuals  suffering  from  epilepsy  or  other  severe  nervous  affections,  pe- 
culiar, red  angioparalytic  areas  of  geographical  outline  have  occasionally  been 
observed  (Trousseau's  taches  cerebrales).  Weir  Mitchell,  in  1872,  designated  as 
erythromelalgia  an  angioneurosis  in  which  paroxysmal  redness  and  swelling  of  the 
skin  appear  at  the  periphery  of  the  extremities  usually  in  association  with  pain. 
As  occasionally  trophic  and  secretory  disorders  also  appear,  the  condition  is  not 
exclusively  a  vasomotor  but  a  combined  neurosis.  Long-continued,  strong  irrita- 
tion of  the  vasomotor  nerves  may  cause  interruption  of  the  circulation,  in  conse- 
quence of  which  the  affected  parts  may  undergo  gangrene,  which  may  involve 
deeper  parts,  as  well  as  the  skin.  Inflammations  in  cutaneous  areas  whose  vaso- 
motors are  paralyzed  are  aggravated  in  the  course  of  time. 

Among  the  angioneuroses  of  circumscribed  distribution  is  the  unilateral  spasm 
of  the  branches  of  the  carotid  on  the  head,  which  is  attended  with  severe  head- 
ache', so-called  sympatheticotonic  hemicrania.  Under  such  circumstances  the  cer- 
vical sympathetic  is  greatly  irritated;  and  pallor,  relaxation  and  coolness  of  one- 
half  of  the  face,  cord-like  contraction  of  the  temporal  artery,  dilatation  of  the 
pupil  and  discharge  of  viscid  saliva  are  unequivocal  signs  of  this  affection.  Eulen- 
burg  has  described  as  the  converse  of  this  disorder  a  sympathetico  paralytic  hemi- 
crania, in  which  at  the  height  of  the  attack  the  opposite  symptoms  appear,  in 
conjunction  with  paralysis  of  the  sympathetic.  This  form  may  succeed  immedi- 
ately upon  the  first,  as  paralysis  in  the  sequence  of  intense  irritation.  Berger  even 
observed  both  forms  in  alternation. 

Exophthalmic  goiter  is  a  remarkable  affection  of  the  sympathetic,  in  which  the 
vasomotor  nerves  are  involved.  It  occurs  in  individuals  of  a  neurotic  disposition, 
and  there  develop  consecutively  palpitation  of  the  heart  (from  90  to  120  or  200 
beats  in  a  minute) ,  enlargement  of  the  thyroid  gland  (struma)  and  protrusion  of 
the  eyeballs  (exophthalmos) ,  with  defective  associated  movement  of  the  upper 
eyelid  in  elevating  and  depressing  the  plane  of  vision.  It  is  believed  that  per- 
verted function  of  the  thyroid  gland  results  in  the  formation  of  materials  that 
act  like  a  poison  on  the  nerves  affected.  As  a  matter  of  fact  exophthalmos  is 
wanting  in  one-half  and  goiter  in  one-fifth  of  the  cases.  It  is  possible  that  this 
obscure  disease  depends  upon  simultaneous  irritation  of  the  accelerator  nerve  of 
the  heart,  of  the  motor  filaments  for  the  muscles  of  M  tiller  in  the  orbits  and  the 
eyelids,  and  perhaps  also  of  the  filaments  for  the  unstriated  muscles  discovered 
by  Sappey  in  the  orbital  aponeurosis,  as  well  as  of  the  dilators  of  the  thyroid 
vessels.  The  disorder  might  arise  as  result  of  direct  irritation  of  the  sympathetic 
paths  named  or  of  their  final  areas  of  origin,  or  finally  it  might  be  the  result  of 


THE    VASODILATOR    CENTER    AND    NERVES.  771 

reflex  irritation.  On  the  other  hand,  the  clinical  picture  has  been  explained  by 
assuming  that  the  exophthalmos  and  the  goiter  are  results  of  paralysis  of  the 
vasomotors,  which  gives  rise  to  distention  of  the  vessels.  The  increased  action 
of  the  heart  is  looked  upon  as  a  sign  of  diminished  or  abolished  action  of  the  cardiac 
inhibitory  fibers  of  the  vagi.  All  of  these  phenomena,  it  is  said,  can  be  induced  by 
injury  of  the  upper  portion  of  the  restiform  body  on  each  side  in  rabbits,  and 
according  to  Durdufi  below  the  auditory  tubercle. 

Landois  was  the  first,  in  1866,  to  describe  and  designate  as  vasomotor  angina 
pectoris  an  affection  of  paroxysmal  occurrence  involving  either  all  or  at  least 
a  large  number  of  the  vasomotor  nerves.  In  consequence  of  intense  irritation 
the  vessels  undergo  contraction;  the  arteries  are  hard  and  small,  the  skin,  espe- 
cially of  the  hands  and  the  feet,  pallid  and  cold,  and  at  the  same  time  the  seat 
of  formication  and  prickling  at  the  tips  of  the  fingers.  The  increase  in  blood- 
pressure  brought  about  by  the  vascular  contraction  causes  enormous  acceleration 
of  pulse,  together  with  a  feeling  of  oppression,  of  vertigo,  of  fear,  of  abolition  of 
the  vital  functions  and  even  painful  palpitation  of  the  heart. 

The  appearance  of  sudden  hyperemia,  with  transudation  and  ecchymoses  in 
individual  thoracic  or  abdominal  viscera  must  likewise  be  referred  to  an  angio- 
neurotic  origin.  In  this  connection  it  should  be  recalled  that  Schiff,  Brown- 
S6quard  and  others  observed  hyperemia  and  extravasations  of  blood  in  the  lungs, 
the  pleurae,  the  intestines  and  the  kidneys,  after  injury  of  the  pons,  the  striate 
body  and  the  optic  thalamus.  Crushing  or  section  of  one-half  of  the  pons  causes, 
according  to  Brown-Sequard,  especially  extravasations  of  blood  into  the  lung  of 
the  opposed  side.  The  same  observer  noted  also  extravasations  of  blood  into 
the  capsules  of  the  kidneys  after  injury  to  the  lumbar  cord.  The  pulmonary  vessels 
may  be  relaxed  through  the  intermediation  of  the  nerves,  and  attacks  of  asthma 
may  thus  be  induced.  Rarely,  the  vasomotor  distribution  upon  an  entire  side  of 
the  body  has  been  observed  to  be  irritated  or  paretic. 

The  dependence  of  glycosuria  upon  vasomotor  influences  has  been  pointed  out 
on  p.  313,  the  influence  of  the  vasomotors  upon  the  urinary  secretion  on  p.  514. 
The  effect  of  fever  upon  the  vasomotor  nerves  in  the  form  of  irritation  is  shown 
by  the  pale  skin  in  the  stage  of  chill  attending  some  fevers,  followed  by  redness 
in  consequence  of  consecutive  paralysis.  Sudden  elevation  of  temperature  of 
paroxysmal  occurrence  has  been  considered  as  a  sign  of  irritation  of  the  vasomotor 
center  in  the  medulla. 

Little  is  known  concerning  affections  in  the  distribution  in  the  veins  dependent 
upon  the  nerves.  Moltschanoff  observed  that  in  the  sequence  of  inflammation 
of  the  ulnar  and  median  nerves,  with  anesthesia,  venous  dilatation  occurred  in 
the  distribution  of  the  basilic  vein. 

It  should,  finally,  be  pointed  out  that  sensory  nerves  in  the  form  of  delicate 
networks  have  been  found  on  the  blood-vessels.  Pathological  manifestations  of 
pain  in  the  course  of  the  vessels,  in  association  with  arterial  spasm,  aneurysm, 
arteriosclerosis,  and  thrombosis,  are  probably  indicative  of  morbid  states  of  irrita- 
tion of  the  nerves. 


THE  VASODILATOR  CENTER  AND  NERVES. 

Although  a  center  for  vasodilator  or  vessel-relaxing  nerves  has  not 
yet  been  demonstrated,  the  existence  of  such  a  center  in  the  medulla 
may  nevertheless  be  suspected.  It  would,  thus,  be  the  antagonist  of  the 
vasomotor  center.  The  center  is,  in  any  event,  not  in  a  state  of  per- 
manent (tonic)  irritation.  The  vasodilator  nerves  are  analogous  in 
function  to  the  cardiac  branches  of  the  vagus,  as  irritation  of  both  causes 
relaxation  in  the  state  of  rest.  The  nerves  may,  therefore,  be  designated 
vaso  inhibitory  nerves.  A  dyspneic  state  of  the  blood  irritates  the  center 
(as  it  does  also  that  for  the  vasomotors),  and,  as  a  result,  especially  the 
cutaneous  vessels  are  dilated,  while  at  the  same  time  the  vessels  of  the 
internal  organs  become  anemic  in  consequence  of  simultaneous  irri- 
tation of  the  vasoconstrictors.  Chloral  hydrate  in  small  doses  is  a  stimu- 
lant to  the  vasodilators.  Irritation  of  the  depressor  nerve  also  excites 
them  reflexlv. 


772  THE    COURSE    OF    THE     VASODILATOR    NERVES. 

The  Course  of  the  Vasodilator  Nerves. — The  vasodilators  pass  to  some  organs 
as  special  nerves,  while  to  other  parts  of  the  body  they  are  distributed,  in  asso- 
ciation with  vasoconstrictor  and  other  nerves.  The  buccofacial  region  receives 
dilators  in  part  from  the  medulla  oblongata  directly  through  the  trigeminus,  and 
in  part  from  the  spinal  cord.  The  latter,  according  to  Dastre  and  Morat,  make 
their  exit  with  the  first,  second  and  third  dorsal  nerves  (in  the  dog)  and  pass 
through  the  visceral  branches  (limb  of  the  loop  of  Vieussens)  into  the  sympa- 
thetic cord,  then  to  the  superior  cervical  ganglion  and,  finally,  thence  through  the 
carotid  plexus  to  the  Gasserian  ganglion  of  the  trigeminus.  The  retina  receives 
vasodilator  nerves  through  the  sympathetic  and  the  trigeminus;  the  ear  from  the 
first  dorsal  and  the  inferior  cervical  ganglion;  the  brain  from  the  sympathetic; 
the  heart  through  the  sympathetic  and  less  through  the  vagus;  the  upper  ex- 
tremity from  the  thoracic  sympathetic;  the  lower  extremity  from  the  posterior 
roots  ,of  the  origin  of  the  sciatic.  The  vasodilators  for  the  submaxillary  and 
sub  lingual  glands  pass  in  the  chorda  tympani,  as  do  also  those  for  the  anterior  por- 
tion of  the  tongue.  Those  for  the  posterior  portion  of  the  tongue  are  contained 
in  the  glossopharyngeus,  those  for  the  thyroid  gland  in  the  laryngeal  branches  of 
the  vagus,  those  for  the  liver  in  the  splanchnic,  those  for  the  pancreas  in  the 
vagus,  those  for  the  small  intestine  in  the  splanchnic,  those  for  the  kidney  in 
the  vagus.  The  lungs  (in  the  rabbit)  receive  dilators  from  the  cervical  sympa- 
thetic; according  to  Henriques  (in  dogs  and  rabbits)  from  the  vagus.  Irritation 
of  the  nervi  erigentes  arising  from  the  sacral  plexus  causes  erection  through  dilata- 
tion of  the  arteries  of  the  penis.  The  muscles  receive  the  dilator  fibers  for  their 
vessels  through  the  trunks  of  the  motor  nerves.  If  the  muscle-nerves  or  the 
spinal  cord  be  irritated,  the  lumen  of  the  vessels  undergoes  dilatation  during  the 
contraction  of  the  muscle-fibers.  The  latter  phenomenon  appears  even  when  the 
contraction  of  the  muscles  is  prevented.  The  vasodilators  remain  medullated 
out  to  the  terminal  ganglia. 

The  vasodilators  have  subordinate  centers  in  the  spinal  cord,  as  do  the  vaso- 
motors;  for  example  the  fibers  of  the  buccolabial  region  at  the  level  of  the  first, 
second  and  third  dorsal  vertebras.  These  can  be  influenced  reflexly  through 
the  pulmonary  fibers  of  the  vagus,  but  also  through  the  sciatic  nerve.  According 
to  Goltz,  a  similar  center  is  situated  in  the  lower  portion  of  the  spinal  cord,  reflex 
irritation  of  which  can  be  induced  through  the  visceral  nerves.  The  portion  of 
the  cerebral  cortex  having  vasodilator  functions  is  described  on  p.  789. 

Goltz  showed,  in  1874,  that  vasomotors  and  vasodilators  are  situated  side  by 
side  in  the  trunks  of  the  extremities,  for  example  in  the  sciatic  (through  the  inter- 
mediation of  the  sympathetic) .  If  the  peripheral  stump  of  this  nerve  is  irritated 
immediately  after  division  the  action  of  the  vasomotors  predominates.  If,  how- 
ever, the  peripheral  stump  is  irritated  in  the  course  of  from  four  to  six  days, 
during  which  time  the  vasoconstrictors  will  have  lost  their  irritability,  the  ves- 
sels become  dilated  in  consequence  of  the  action  of  the  vasodilators.  Irritants 
affecting  the  nerves  at  long  intervals  stimulate  especially  the  vasodilators.  Tetan- 
izing  irritants,  however,  stimulate  the  vasoconstrictors.  The  latent  period  of  the 
vasodilators  is  longer  and  they  are  also  more  readily  exhausted  than  the  vaso- 
constrictors. Reduction  in  temperature  lowers  the  irritability  of  the  vasodilators 
in  lesser  degree  than  that  of  the  vasomotors.  Exposure  of  the  nerves  directly  to 
high  degrees  of  temperature  (up  to  50°  C.)  causes  irritation  of  the  vasodilators 
for  a  long  time,  as  do  also  closing  and  opening,  as  well  as  permanent  continued 
passage,  of  the  constant  current.  The  phenomena  described  (which  have  been 
observed  by  Goltz,  Heidenhain  and  Ostroumoff,  Putzeys  and  Tarchanoff  and 
others)  can  be  explained  by  assuming  that  the  ganglia  situated  in  the  vessels,  in 
analogy  with  the  automatic  ganglia  of  the  heart,  are  influenced  through  both 
sorts  of  vascular  nerves,  the  vasoconstrictors  causing  excitation,  the  vasodilators 
inhibition  of  the  activity  of  these  ganglia. 

Certain  nerve-trunks  contain  fibers  through  which  reflex  dilatation  of  vessels 
can  be  induced,  and,  in  addition,  others  through  which  reflex  vasoconstriction  can 
be  brought  about.  The  former  are  less  sensitive  to  cold,  are  more  irritable  and 
regenerate  more  quickly  after  injury. 

Irritation  of  the  loop  of  Vieussens  gives  rise  to  pseudomotor  contractions  in 
the  muscles  of  the  face  paralyzed  in  consequence  of  destruction  of  the  facial  nerve, 
in  the  same  way  as  does  irritation  of  the  chorda  tympani  in  the  tongue  paralyzed 
in  consequence  of  section  of  the  hypoglossus. 

In  an  analysis  of  the  phenomena  related  to  the  vessels,  inquiry  should  be 
directed  especially  to  determine  whether  such  dilatations  as  may  be  present  and 


THE    SPASM-CENTER.       THE    SWEATING    CENTER.  773 

due  to  nervous  influences  are  a  result  of  irritation  of  the  vasodilators  or  of  paralysis 
of  the  vasoconstrictors.  This  is  of  great  significance  with  respect  to  the  interpreta- 
tion of  pathological  phenomena.  Emotional  influences  may  also  affect  the  vaso- 
dilator center.  Thus,  the  blush  of  shame,  which  may  not  only  involve  the  face, 
but  may  also  extend  to  the  entire  skin,  is  probably  due  to  irritation  of  the  vaso- 
dilator center. 

The  vasodilator  nerves  obviously  have  a  marked  influence  upon  the  bodily 
temperature  and  upon  that  of  individual  portions  of  the  body,  as  may  be  inferred 
from  what  has  been  said  with  reference  to  the  influence  of  the  vasoconstrictors. 

It  cannot  be  denied  that  both  vascular  nerve-centers  represent  important 
regulators  for  the  dissipation  of  heat  through  the  vessels  of  the  skin.  Probably 
they  are  maintained  in  activity  by  reflex  influences  through  sensory  nerves. 
Derangement  in  the  function  of  these  centers  may  result  in  abnormal  accumu- 
lation of  heat  (as  in  the  presence  of  fever)  or  in  abnormal  reduction  of  tempera- 
ture. 

THE  SPASM-CENTER.     THE  SWEATING  CENTER. 

The  medulla  oblongata  at  its  junction  with  the  pons  contains  a  center 
irritation  of  which  causes  general  convulsions.  This  can  be  excited 
through  sudden  venosity  of  the  blood  (aspkyxial  convulsions],  also 
through  sudden  anemia  of  the  medulla  oblongata  either  in  consequence 
of  rapid  hemorrhage  or  after  momentary  ligation  of  both  carotid  and 
subclavian  arteries  (kemorrkagic  or  anemic  convulsions] ;  finally,  also 
through  the  action  of  sudden  venous  stasis  as  a  result  of  constriction  of 
the  veins  passing  from  the  head.  Under  all  these  conditions  the  irritation 
of  the  center  must  be  looked  for  in  the  sudden  interruption  of  the  normal 
gaseous  interchange  If  these  influences  operate  gradually,  death  may 
take  place  without  the  occurrence  of  convulsions,  as  the  uninterrupted 
gaseous  interchange  always  associated  with  the  onset  of  quiet  death 
shows.  Also  direct  irritation  by  means  of  the  application  of  chemical 
substances,  such  as  ammonium  carbonate,  potassium-salts,  sodium- 
salts,  and  others,  is  capable  of  rapidly  exciting  severe  general  convulsions. 
Finally,  it  has  long  been  known  that  intense  direct  mechanical  irritation 
of  the  medulla  oblongata,  as,  for  example,  by  sudden  crushing,  causes 
general  convulsions. 

As  the  convulsions  occur  only  when  the  cerebrum  is  preserved,  Bechterew 
adopts  the  view  that  this  portion  of  the  nervous  system  contains  only  a  motor 
center,  but  no  spasm-center,  as  with  its  destruction  the  power  of  locomotion 
ceases.  Convulsions  occur  on  irritation  of  the  area  after  the  irritation  is  con- 
veyed first  to  the  cerebral  cortex. 

According  to  Nothnagel  the  spasm-center  in  the  rabbit  extends  above  the  ala 
cinerea  upward  to  the  quadri geminate  bodies.  It  is  bounded  laterally  by  the 
locus  coeruleus,  together  with  the  auditory  tubercle,  and  internally  by  the  eminen- 
tia  teres.  The  center  is  generally  irritated  in  connection  with  extensive  reflex 
spasm. 

Numerous  poisons,  most  heart-poisons,  nicotin,  picrotoxin,  the  salts  of  am- 
monia and  the  compounds  of  barium  cause  death  preceded  by  convulsions,  as 
they  irritate  the  spasm-center. 

Pathological. — Schroder  van  der  Kolk  pointed  out  that  in  cases  of  general 
convulsions  in  epileptics  the  seat  of  irritation  is  situated  within  the  medulla  ob- 
longata, the  vessels  of  which  he  found  repeatedly  dilated  and  increased  in 
number.  Under  such  conditions  the  medulla  would  be  in  a  state  of  increased  irrita- 
bility. Now,  it  has  been  shown,  in  the  discussion  of  the  vasomotor  centers,  that 
irritation  of  sensory  nerves  may  cause  both  sudden  contraction  as  well  as  dilatation 
of  the  cerebral  vessels.  If  this  takes  place  in  the  vessels  of  the  medulla,  sudden 
anemia  or  transitory  hyperemia  will  develop  in  that  structure.  Both  conditions 
are  capable,  however,  of  irritating  the  medulla  in  such  a  manner  that  epileptiform 
convulsions  result.  It  is  often  the  case  in  connection  with  general  epileptic  con- 
vulsions that  the  nerve  can-  be  distinctly  demonstrated,  irritation  of  which  gives 


774  PSYCHIC    FUNCTIONS    OF    THE    CEREBRUM. 

rise  to  the  vascular  change.  The  peculiar  sensation,  aura,  that  occurs  in  the 
course  of  such  a  nerve  before  the  outbreak  of  the  convulsions  has  long  been  known. 
Naturally,  the  convulsions  may  be  induced  by  direct  irritation  of  the  medulla  of 
different  character. 

Brown-Sequard  observed  that  guinea-pigs  became  epileptic  after  injuries  of 
the  central  and  peripheral  nervous  system — spinal  cord,  medulla,  cerebral  peduncle, 
quadrigeminate  bodies,  sciatic  nerve;  and  the  disease  thus  induced  was  even 
inherited.  Irritation  of  the  cheek  and  the  anterior  aspect  of  the  neck— epilep- 
togenous  zone — excites  the  attack,  and  in  the  presence  of  unilateral  injuries  of  the 
spinal  cord  and  the  sciatic,  if  the  same  side  be  irritated;  in  the  presence  of  injuries 
of  the  peduncle,  if  the  contralateral  region  is  irritated.  Westphal  made  guinea- 
pigs  epileptic  by  repeated  gentle  blows  upon  the  skull.  There  developed  a  perfect 
epileptic  condition,  which  likewise  was  inheritable.  As  the  cause  he  found  ex- 
travasation of  blood  into  the  medulla  oblongata  and  the  upper  portion  of  the 
cervical  cord. 

Epileptic  convulsions  after  intense  irritation  of  the  motor  cortical  region  of 
the  cerebrum  are  discussed  on  p.  783. 

A  dominating  center  for  the  secretion  of  sweat  for  the  entire  surface  of 
the  body,  to  which  the  local  centers  in  the  spinal  cord  are  subordinate, 
is  situated  in  the  medulla  oblongata.  It  is  bilateral  and  unequally  irri- 
table in  the  rare  cases  of  unilateral  sweating. 

Physostigma,  nicotin,  picrotoxin,  camphor,  ammonium  acetate,  stimulate  the 
secretion  of  sweat  by  a  direct  action  upon  the  sweating  center.  Muscarin  causes 
local  irritation  of  the  peripheral  sweat-fibers;  it  therefore  causes  sweating  of  the 
hind  paw  even  after  section  of  the  sciatic  nerve.  Atropin  neutralizes  the  effects 
of  muscarin. 

PSYCHIC  FUNCTIONS  OF  THE  CEREBRUM. 

The  cerebral  hemispheres  in  man  are  the  seat  of  all  psychic  activities. 
Only  when  the  former  are  intact  are  the  processes  of  thinking,  feeling  and 
volition  possible.  After  destruction  of  the  hemisphere  the  organism  is 
reduced  to  the  level  of  a  complex  machine,  the  entire  activity  of  which 
can  be  considered  only  as  the  expression  of  internal  and  external 
stimuli  acting  upon  it.  The  psychic  activities  appear  to  be  localized  in 
both  hemispheres  and  in  such  a  manner  that  after  extensive  injury  of 
one  hemisphere  the  other,  or  after  injury  upon  both  sides,  the  remaining 
cerebral  tissue,  is  capable  of  assuming  vicariously  the  functions  of  that 
which  has  been  destroyed. 

Cases  in  which  after  extensive  unilateral  destruction  of  one  hemisphere  the 
psychic  activities  apparently  had  not  suffered  are  not  rare.  Even  when  both 
hemispheres  are  destroyed  in  moderate  degree  the  intelligence  may  be  apparently 
intact.  The  statement  that  the  psychic  faculties  have  remained  intact  under 
such  circumstances  should,  however,  be  received  with  caution,  as  it  is  obviously 
infinitely  difficult  to  determine  to  what  extent  these  had  been  developed  in  various 
directions  prior  to  the  accident.  Exceedingly  rare  cases  are  known  in  which 
alternately  one  or  the  other,  and  then  both  hemispheres  together,  took  part  in 
the  mental  processes.  Recently  a  certain  violence  of  manner,  maliciousness  and 
indifference  have  been  observed  repeatedly  after  injuries  of  the  frontal  portion 
of  the  brain  in  man — changes  that  Ferrier  attributes  to  loss  of  the  conceptions 
acquired  by  education  and  association  with  others,  and  which  agree  with  the 
analogous  changes  in  animals  described  by  Goltz. 

Developmental  Defects  of  the  Brain. — Microcephalus  and  hydrocephalus  cause 
loss  or  impairment  of  mental  functions  to  the  degree  of  most  profound  idiocy.  Ex- 
tensive inflammation,  degeneration,  pressure,  anemia  of  the  cerebral  vessels,  as 
well  as  the  influence  of  narcotic  drugs,  abolish  these  functions  altogether.  The 
extent  to  which  the  hemispheres  are  concerned  in  these  processes  is,  as  yet,  a 
matter  of  doubt.  Flourens  believed  that  the  hemispheres  take  part  in  every 
psychic  act  throughout  their  entire  extent.  Therefore,  even  a  small  remnant  of 
healthy  hemisphere  is  sufficient  for  the  maintenance  of  all  its  functions.  To  the 


PSYCHIC    FUNCTIONS    OF    THE    CEREBRUM.  775 

degree  in  which  the  hemispheres  are  removed,  all  of  the  functions  of  the  brain 
are. impaired.  If  the  latter  is  entirely  eliminated,  all  of  the  faculties  are  lost. 
Therefore,  neither  the  different  functions  nor  the  different  impressions  are  localized 
in  special  situations.  Goltz  agrees  with  Flourens  in  the  view  that  an  uninjured 
remnant  of  the  same  kind  of  cerebral  tissue  is  capable  to  a  certain  degree  of  assum- 
ing the  functions  of  a  destroyed  portion.  This  capability  on  the  part  of  portions 
of  the  brain  to  act  vicariously  for  portions  that  have  been  lost  is  designated  by 
Vulpian  as  "loi  de  suppleance" — law  of  functional  substitution. 

As  opposed  to  the  opinion  of  Flourens  the  phrenological  teachings  of  Goll  (died 
1828)  may  be  recalled.  According  to  this  observer  the  various  mental  functions 
are  localized  in  definite  situations  in  the  brain.  A  conspicuous  faculty  always 
corresponds  with  a  voluminous  development  of  the  respective  portion  of  the  cere- 
bral cortex,  which  may  even  be  recognized  externally  from  the  configuration  of 
the  skull — cranioscopy.  Thus,  the  different  mental  functions  are  to  be  referred 
to  certain  portions  of  the  cerebral  cortex.  Spurzheim,  who  elaborated  the  system 
of  his  friend,  set  up  the  following  categories:  The  first  class  comprises  the  sensa- 
tions, including  the  instincts  and  the  feelings.  The  second  comprises  the  faculty 
of  comprehension,  including  the  power  of  recognition  and  that  of  thought.  Al- 
though the  detailed  application  of  this  system  exhibits  a  certain  inflexibility, 
obvious  deficiencies  and  undeniable  error,  nevertheless  the  question  is  worthy  of 
serious  consideration  whether  the  fundamental  thought  of  the  system  is  entirely 
to  be  rejected.  The  discovery  of  the  localization  of  movements  under  the  control 
of  the  will  and  of  conscious  impressions  and  their  association  in  the  cerebrum 
justify  renewed  examination  of  the  phrenological  system,  although  in  quite  another 
manner  than  that  pursued  by  the  originator. 

After  removal  of  both  cerebral  hemispheres  in  animals  all  voluntary 
and  consciously  performed  movement  ceases,  as  well  as  every  conscious 
sensation  and  sensory  impression.  On  the  other  hand  the  entire  mechan- 
ism, the  harmony  and  the  equilibrium  of  the  movements  persist,  as  well 
as  those  functions  that,  independent  of  the  memory,  have  been  desig- 
nated as  lower  or  instinctive.  The  latter  functions  are  localized  in  the 
midbrain  and  are  controlled  through  important  reflex  paths. 

Sudden  arrest  of  the  circulation  in  the  brain,  for  example  through  decapita- 
tion, is  attended  with  immediate  cessation  of  the  mental  processes.  On  permitting 
arterial  blood  from  a  living  horse  to  pass  immediately  through  the  carotids  of  the 
decapitated  head  of  a  dog,  Hayem  and  Barrier  observed  signs  of  maintained  corv 
sciousness  and  of  volition  in  the  head  for  more  than  ten  seconds,  but  not  later. 

The  midbrain  is  connected  not  only  with  the  gray  matter  of  the 
spinal  cord  and  the  medulla  oblongata,  the  seat  of  the  most  extensive 
coordinated  reflexes,  but  it  contains  also  sensory  elements,  as  well  as 
fibers,  derived  from  the  higher  sense-organs,  which  may  likewise  have  a 
reflex  effect  upon  motility.  Finally,  the  midbrain  contains  inhibitory 
apparatus  for  reflexes.  The  associated  action  of  all  of  these  parts  makes 
the  midbrain  a  controlling  organ  for  the  harmonious  execution  of  move- 
ments, and  in  a  higher  degree  than  the  medulla  oblongata.  This  is  seen 
especially  from  the  fact  that  animals  with  the  midbrain  preserved  are 
capable  under  varied  conditions  of  maintaining  the  equilibrium  of  their 
body,  which  is  lost  at  once  if  the  midbrain  is  destroyed.  Christiani 
determined  the  situation  of  the  coordinating  center  for  locomotion 
and  the  maintenance  of  equilibrium  in  mammals  to  be  in  front  of  the 
inspiratory  center  of  the  third  ventricle. 

The  significance  of  the  cooperation  between  cutaneous  sensibility  and  sense- 
impressions  for  the  maintenance  of  equilibrium  will  be  made  clear  from  the 
following  considerations:  The  frog  deprived  of  its  brain  at  once  loses  its  power 
of  equilibration  as  soon  as  the  skin  is  removed  from  the  hind  legs.  The  influence 
of  visual  impressions  is  recognized  from  the  inability  to  maintain  the  equilibrium 
that  is  observed  in  connection  with  nystagmus,  and  from  the  vertigo  that  often 


776 


PSYCHIC    FUNCTIONS    OF    THE    CEREBRUM. 


accompanies  paralysis  of  the  external  ocular  muscles.  In  human  beings  with 
impaired  cutaneous  sensibility,  the  eyes  constitute  the  main  dependence  for  the 
maintenance  of  the  equilibrium.  Such  individuals  fall  on  closing  the  eyes. 

The  frog  with  its  cerebrum  extirpated  maintains  the  harmonious  equilibrium 
of  its  body.  Placed  upon  its  back,  it  at  once  rolls  over;  irritated,  it  makes  one 
or  two  jumps;  thrown  into  the  water,  it  swims  to  the  margin  of  the  reservoir, 
climbs  upon  this  and  remains  quietly  seated.  Under  the  most  complex  inciting 
conditions  it  exhibits  complete  control,  harmony  and  uniformity  of  its  move- 
ments. Without  external  irritation,  however,  it  makes,  at  least  at  first,  no  inde- 
pendent voluntary,  purposeful  movement.  On  the  contrary,'  it  sits  constantly 
in  the  same  place  as  if  asleep,  it  takes  no  food,  it  has  no  conscious  sense  of  hun- 
ger or  thirst,  it  exhibits  no  fear  and,  finally,  it  dries  into  a  mummy. 

The  pigeon  behaves  in  the  same  way  when  its  cerebral  hemispheres  are  re- 
moved. Unirritated,  it  remains  seated  as  if  in  sleep,  although  if  stimulated  it 
exhibits  complete  coordination  in  all  movements  in  walking,  flying,  perching, 
and  balancing  of  the  body.  In  the  course  of  several  days  it  changes  its  position 
apparently  without  external  excitation.  The  sensory  nerves  and  those  of  special 
sense,  it  is  true,  still  conduct  impulses  to  the  brain,  but  these  are  capable  of  ex- 
citing only  reflex  movements,  and  are  no  longer  capable  of  exciting  conscious 
sensations.  Therefore,  the  bird  starts  when  a  firearm  is  discharged  in  its  vicinity, 
its  eyes  blink  when  a  flame  is  brought  near- them  and  the  pupils  contract,  it  turns 
its  head  when  the  vapor  of  ammonia  is  applied  to  its  nose.  All  of  these  stimuli, 
however,  are  not  appreciated  consciously  as  such.  Conception,  will,  memory  are 
lost,  and  the  animal  spontaneously  takes  neither  food  nor  drink.  If  these  are 
placed  in  the  pharynx  the  animal  swallows,  and  in  such  a  manner  its  life  may 
be  preserved  for  months. 

Fish  behave  somewhat  differently.  A  carp  whose  cerebrum  has  been  extir- 
pated is  capable  of  seeing  and  even  of  selecting  its  food  and  of  moving  voluntarily. 
Under  these  circumstances  the  psychic  function  must  be  located  also  in  the  optic 
thalamus.  According  to  Schrader  the  frog  is  said  in  the  further  course  of  ob- 
servation to  behave  in  a  similar  manner.  Reptiles  also  are  able  later  to  move 
spontaneously,  although  they  exhibit  neither  fear  nor  anger.  Birds  also  are  said 
later  on  to  exhibit  spontaneous  movement.  Their  organs  of  special  sense  func- 
tionate, but  they  are  mind-blind,  mind-deaf,  etc. 

Mammals.  Goltz  was  able  to  remove  the  cerebrum  from  dogs  and  to  keep 
the  animals  alive  for  a  long  time.  Subsequently  they  exhibited  good  powers  of 
locomotion  and  the  ability  to  take  food,  as  well  as  taste,  tactile  sensibility,  hearing 
and  muscular  sensibility.  They  were  sensitive  to  bright  light,  without,  how- 
ever, being  actually  able  to  see.  In  other  respects  the  dogs  were  in  a  state  of 
most  profound  dementia.  Feeding  alone  affected  them  agreeably  and  they  showed 
also  a  sense  of  satiety.  In  other  respects  the  loss  was  evident  of  all  those  mani- 
festations from  which  conclusions  are  formed  as  to  the  existence  of  intelligence, 
memory  and  judgment. 

Observations  on  somnambulists  show  that  also  in  man  complete 
coordination  of  all  movements  may  be  present  without  the  aid  of  con- 
scious volition  or  conscious  sensation  and  perception.  Most  ordinary 
movements  in  the  waking  state,  however,  take  place  without  the  aid  of 
consciousness,  being  controlled  from  the  midbrain. 

The  degree  of  development  of  the  mental  activities  in  the  animal  kingdom  varies 
in  accordance  with  the  size  of  the  cerebral  hemispheres  in  proportion  to  the  re- 
maining portions  of  the  central  nervous  system.  If,  however,  the  brain  alone 
is  taken  into  consideration  it  will  be  found  that  those  animals  possess  the  higher 
grade  of  intelligence  in  which  the  cerebral  hemispheres  greatly  preponderate  over 
the  midbrain.  The  latter  is  represented  in  the  lower  vertebrates  by  the  optic 
lobes,  in  the  higher  by  the  quadrigeminate  bodies.  In  Fig.  258,  VI  represents 
the  brain  of  the  carp,  V  that  of  the  frog,  IV  that  of  the  pigeon.  In  all  of  these 
figures  the  hemispheres  are  indicated  by  the  numeral  i,  the  optic  lobes  by  the 
numeral  2,  the  cerebellum  by  the  numeral  3  and  the  medulla  oblongata  by  the 
numeral  4.  In  carps  the  cerebrum  is  even  smaller  than  the  optic  thalami,  while 
in  frogs  it  is  already  larger  than  the  latter.  In  pigeons  the  cerebrum  extends 
downward  to  the  cerebellum.  In  correspondence  with  these  variations  in  size  is  the 
degree  of  intelligence  present  in  the  animals  named.  In  the  dog's  brain  (Fig.  2  58,  II) 


PSYCHIC    FUNCTIONS    OF    THE    CEREBRUM.  777 

the  hemispheres  cover  the  quadri geminate  bodies  entirely,  but  the  cerebellum 
still  lies  behind  the  cerebrum.  Only  in  man  do  the  occipital  lobes  of  the  cere- 
brum entirely  cover  the  cerebellum. 

According  to  Meynert  these  relations  can  be  made  clear  in  another  manner. 
It  is  well  known  that  fibers  pass  downward  from  the  cerebral  hemispheres  through 
the  cerebral  peduncles,  particularly  their  lower  portion,  which  is  known  as  the 
crusta  of  the  peduncle.  This  is  separated  by  the  substantia  nigra  from  the  upper 
portion,  which  is  designated  the  tegmentum  and  is  connected  with  the  quadri  - 
geminate  bodies  and  the  optic  thalami.  The  larger,  therefore,  the  cerebral  hemi- 
spheres the  more  numerous  are  the  fibers  passing  to  the  crusta.  In  Fig.  254  at  II 
is  shown  a  vertical  section  through  the  posterior  quadri  geminate  bodies,  including 
the  aqueduct  of  Sylvius,  and  the  two  cerebral  peduncles  from  an  adult  man: 
p  p  is  the  crusta  of  each  peduncle,  over  which  is  the  substantia  nigra  (s).  Fig.  IV 
exhibits  the  same  relations  in  the  ape,  Fig.  Ill  in  the  dog  and  finally  Fig.  V  in 
the  guinea-pig.  It  will  at  once  be  seen  that  the  size  of  the  crusta  diminishes  in 
the  order  named.  In  correspondence  with  this  there  is  an  analogous  diminution 
in  the  size  of  the  cerebral  hemispheres  and  at  the  same  time  of  the  intelligence 
of  the  respective  animals. 

Finally  >  the  degree  of  intelligence  is  dependent  upon  the  complexity  of  the 
fissures  in  the  hemispheres.  While  the  fissures  are  yet  wholly  wanting  in  the 
lower  animals  (fish,  frog,  bird,  Fig.  258,  IV,  V,  VI)  two  shallow  fissures  are  present 
on  each  side  in  the  rabbit  (III).  The  brain  of  the  dog  already  exhibits  numerous 
convolutions  (I,  II).  The  complexity  of  the  convolutions  in  the  elephant,  the 
most  intelligent  of  animals,  is  striking.  Even  in  evertebrates,  as,  for  example,  a 
number  of  insects  endowed  with  delicate  instincts,  convolutions  have  been  ob- 
served in  the  cerebrum.  Naturally,  it  cannot  be  denied  that  even  some  animals 
of  low  intelligence,  such  as  the  cow,  possess  hemispheres  with  complex  convolu- 
tions. A  similar  condition  has  often  been  found  in  man  in  association  with 
marked  mental  development,  although  brains  rich  in  convolutions  have  been  ob- 
served also  in  incompetent  persons.  In  the  male  sex  the  average  absolute  weight 
of  the  brain  of  the  first  two  decades  is  greater  than  in  females.  The  absolute 
weight  of  the  brain  cannot  be  taken  as  an  index  of  the  degree  of  intelligence. 
The  elephant  has  the  absolutely  heaviest,  man  the  relatively  heaviest  brain. 

The  cerebrum  consists  in  all  vertebrates  of  three  divisions:  the  olfactory  lobe, 
the  striate  body  and  the  cortex.  The  olfactory  apparatus  is  situated  at  the  base 
and  is  well  developed  in  fish,  although  it  varies  greatly  in  size  in  verte- 
brates. It  is  large  in  reptiles  and  small  in  birds.  The  striate  body  is  pretty  uni- 
formly developed  and  serves  as  a  means  of  connection  between  the  optic  thalamus 
and  the  forebrain;  from  birds  and  mammals  onward  connections  between  the 
thalamus  and  the  cerebral  cortex  appear.  The  cerebral  cortex  is  the  most  important 
portion  of  the  brain  with  respect  to  mental  development.  In  the  bony  fish  and 
the  ganoids  it  is  represented  by  merely  a  thin  epithelial  plate.  In  reptiles  a 
cerebral  cortex  related  to  psychic  activity  first  appears,  but  at  the  beginning  there 
is  only  an  olfactory  sphere.  These  animals  are,  therefore,  the  earliest  that  are 
able  to  retain  olfactory  impressions  in  memory  and  to  utilize  them  psychically. 
In  birds  the  visual  sphere  and  the  optic  radiation  appear  first  and  these  animals 
are  therefore  the  lowest  that  appreciate  visual  impressions  psychically.  In  mam- 
mals the  other  spheres  are  added.  In  mammals  the  relations  between  the  sensory 
and  the  sensorial  nerve-paths  to  the  cerebral  cortex  increase  progressively.  The 
brain  of  the  mammal,  however,  is  characterized  particularly  by  the  remarkable 
development  of  association-paths. 

Time-relations  of  Mental  Processes. — For  the  occurrence  of  mental  processes 
it  is  necessary  for  a  certain  time  to  elapse  between  the  application  of  the  stimulus 
and  the  conscious  reaction.  This  reaction-time,  which  is  much  longer  than  the 
simple  reflex  time,  can  be  measured  by  noting  the  moment  of  irritation,  and  then 
having  the  individual  under  examination  make  a  signal  indicating  the  resulting 
correct  conception.  The  reaction-time  will  then  consist:  (i)  Of  the  duration  of 
perception  (entrance  into  consciousness) ;  (2)  of  the  duration  of  apperception 
(consciousness  of  the  special  qualities  of  the  sensation,  such  as  form,  pitch,  color, 
etc.),  (3)  of  the  duration  of  the  voluntary  impulse  (for  the  making  of  the  signal). 
In  addition  there  is  to  be  taken  into  account  (4)  the  time  required  in  the  propa- 
gation through  the  centripetal  nervous  apparatus  and  (5)  through  the  motor 
nerve.  If  the  signal  is,  as  usual,  given  with  the  hand,  the  reaction-time  for  im- 
pressions of  sound  is  from  0.136  to  0.167  second,  of  light  from  0.15  to  0.224 
second,  of  taste  from  0.15  to  0.23  second,  of  touch  from  0.133  to  0.201  second. 


778  PSYCHIC    FUNCTIONS    OF    THE    CEREBRUM. 

Heat  is  appreciated  later  than  cold,  pressure  earlier  than  heat.  The  reaction-time 
for  the  perception  of  odor,  which  naturally  is  dependent  upon  many  circum- 
stances, such  as  respiratory  phases,  draft,  is  from  0.2  to  0.5  second. 

Irritation  of  considerable  intensity,  increased  attentiveness,  practice,  anticipa- 
tion of  familiar  impressions  shorten  the  time.  According  to  Lange  in  the  case  of 
the  sensorial  reaction  after  prepared  attentiveness,  the  apperception  coincides 
with  the  perception.  The  muscular  reaction,  on  giving  the  signal,  may  finally, 
however,  be  converted  also  into  a  simple  reflex.  In  the  case  of  tactile  impressions 
those  are  most  rapidly  perceived  that  affect  situations  endowed  with  the  greatest 
acuity  of  the  spatial  sense.  The  time  may  be  prolonged  in  the  case  of  strong 
irritants  and  in  that  of  complex  objects  to  be  distinguished.  The  duration  of 
apperception  for  a  number  of  from  one  to  three  figures  was  in  observations  of 
Tigerstedt  and  Bergquist  from  0.015  to  0.035  second.  Alcohol  and  anesthetics 
alter  the  time,  occasionally  shortening  it,  or  they  prolong  it,  in  accordance  with 
the  intensity  of  their  effects.  If  two  different  impressions  are  to  be  recognized 
psychically  in  rapid  succession  a  certain  interval  of  time  is  necessary,  which  for 
the  ear  is  0.002  to  0.007  second,  for  the  eye  from  0.044  to  0.047  second,  for  the 
tactile.organ  of  the  finger  0.0277  second  (for  two  electrical  cutaneous  stimuli  from 
0.022  to  0.056  second). 

During  sleeping  and  waking  the  periodicity  of  the  active  and  resting  state  of 
the  mind  can  be  recognized.  During  sleep  there  is  diminished  irritability  of  the 
entire  nervous  system,  which  is  explicable  only  in  part  through  fatigue  of  the 
centripetal  nerves,  but  is  especially  attributable  in  a  peculiar  manner  to  the 
central  nervous  system.  During  sleep  stronger  irritation  is  required  in  order  to 
excite  reflexes.  During  deepest  sleep  the  psychic  activities  appear  to  be  wholly 
at  rest,  so  that  the  sleeping  person  may  be  compared  to  a  being  with  extirpated 
cerebral  hemispheres.  Toward  the  time  for  awaking,  however,  psychic  activities 
may  appear  in  the  form  of  dreams,  but  in  a  manner  differing  from  normal  psychic 
processes.  They  comprise  either  sensations  of  which  the  objective  cause  is  want- 
ing (therefore  hallucinations),  or  volitional  impulses  or  conceptions  that  usually 
are  not  executed  and  that  are  for  the  most  part  absent  in  the  healthy  logic  of  the 
thinking  process  during  the  waking  state.  Often,  especially  toward  the  time  of 
awaking,  actual  stimuli  are  interwoven  with  the  dream-images  and  they  may  affect 
various  organs  of  special  sense.  Reduction  in  the  activity  of  the  heart,  of  the 
blood-pressure  in  the  arteries,  of  the  amount  of  blood  in  the  brain,  of  the  irritability 
of  the  motor  cortical  centers,  of  the  activity  of  respiration,  of  gastric  and  intestinal 
movement,  in  the  .generation  of  heat,  in  the  secretions  indicates  a  lessening  in 
the  activities  of  the  respective  nerve-centers,  and  the  diminished  reflex  activity  a 
lessening  in  the  activities  of  the  spinal  cord.  The  pupils  during  sleep  are  the 
smaller  the  deeper  the  sleep,  so  that  in  deepest  sleep  they  cannot  be  made  to 
contract  on  exposure  to  light.  They  dilate  in  response  to  sensory  or  auditory 
stimulation  and  in  greater  degree  the  less  deep  the  sleep.  They  attain  their 
greatest  size  at  the  moment  of  awaking.  It  appears  that  during  sleep  a  state  of 
•ritation  ot  the  central  organ  exists  through  which  increased  activity  of  certain 
sphincter-muscles,  such  as  the  sphincter  of  the  iris  and  that  for  closure  of  the 
eyelids  is  brought  about.  The  soundness  of  sleep  can  be  determined  from  the 
intensity  of  the  sound  that  is  required  to  cause  awaking.  Thus,  Kohlschutter 
found  that  sleep  at  first  rapidly,  then  more  slowly  deepens,  and  after  an  hour, 
according  to  Monninghoff  and  Priesbergen  after  if  hours,  is  most  profound;  then, 
at  first  rapidly  and  later  more  slowly  it  becomes  again  shallow  and  finally  several 
hours  before  awaking  continues  in  almost  uniform  shallow  depth.  External 
or  internal  irritation  is  capable  suddenly  of  diminishing  the  depth,  although 
renewed  deepening  follows.  The  deeper  the  sleep  the  longer  it  lasts 

ihe  cause  of  sleep  is  the  consumption  of  potential  energy  in  the  nerves  princi- 
pally in  the  central  organs,  which  renders  restitution  necessary.  Perhaps  accumu- 
lations of  decomposition-products  in  the  body  (?  lactates)  induce  sleep.  The  ad- 
vent of  sleep  is  favored  by  the  removal  as  far  as  possible  of  all  sense-irritations, 
bleep  cannot  voluntarily  be  postponed  indefinitely,  or  be  interrupted  The  hypnotic 
>t  many  narcotics  is  remarkable.  Absolute  sleeolessness  causes  death  (in 
the  dog  after  one  hundred  and  twenty  hours),  with  reduction  of  temperature, 
diminished  reflex  activity  and  changes  in  the  brain 

HtyplJ?tism'— In  connection  with  the  subject  of  sleep  reference  should  be  made 

to  the  most  important  results  of  investigations  into  hypnotism  or  animal 

SJ!"  ES  ^lscl°sed  b^  th?  studies  of  Weinhold,  Heidenhain,  Griitzner,  Berger 
and  others.  As  the  cause  of  this  condition  Heidenhain  considers  an  inhibition 


PSYCHIC    FUNCTIONS    OF    THE    CEREBRUM.  779 

of  the  activity  of  the  ganglion-cells  of  the  cerebral  cortex,  induced  by  slight  per- 
sistent irritation  of  the  face  (by  means  of  gentle  stroking,  feeble  electrical  cur- 
rents) ,  or  of  the  optic  nerve  (staring  at  a  bright  button) ,  or  of  the  auditory  nerves 
(uniform  sounds).  Intense  and  sudden  irritation  of  the  same  nerves  rapidly 
abolishes  the  state,  particularly  blowing  on  the  face.  Berger  attaches  especial 
significance  to  the  psychological  influence  of  the  artificially  excited  conception  and 
attention  and  their  concentration  upon  certain  portions  of  the  body.  Schneider 
believes  that  the  abnormal  exclusive  concentration  of  consciousness  upon  the 
act  of  hypnotization  furnishes  the  cause  for  the  phenomenon.  The  first  hyp- 
notization  of  an  individual  is  effected  with  greatest  difficulty,  and  long  fixation 
of  a  brilliant  object,  which  Braid  recommended  as  early  as  1841  for  the  develop- 
ment of  an  anesthetic  state,  appears  in  this  connection  to  be  of  special  significance; 
although  the  ability  to  be  hypnotized  varies  greatly  in  different  individuals.  On 
repeated  hypnotization  the  condition  can  often  be  induced  with  extreme  ease, 
for  example  by  means  of  simple  pressure  upon  the  brow  or  by  placing  the  subject 
passively  in  a  definite  position  or  by  stroking.  In  some  individuals  the  mere 
conception  of  the  approach  of  the  condition  is  sufficient  to  induce  it,  as  Cardanus 
observed  in  himself  in  1553. 

The  hypnotized  individual  is  first  incapable  of  opening  the  closed  eyelids. 
There  is  then  spasm  of  the  accommodative  apparatus  of  the  eye,  the  range  of 
accommodation  being  diminished,  and  abnormal  positions  of  the  eye  are  observed. 
Next  there  appear  irritative  phenomena  in  the  distribution  of  sympathetic  nerves 
arising  from  the  medulla  oblongata,  such  as  widening  of  the  palpebral  fissure, 
dilatation  of  the  pupils,  exophthalmos,  acceleration  of  respiration  and  of  pulse. 
At  a  certain  stage  a  marked  increase  in  the  acuity  of  the  special  senses  can  at 
times  be  demonstrated,  and  also  of  muscular  sensibility.  Later  on,  analgesia  may 
appear,  with  preservation  of  tactile  sensibility  and  loss  of  the  sense  of  taste. 
The  temperature-sense  disappears  with  greater  difficulty,  and  still  later  the  senses 
of  sight,  smell  and  hearing  become  affected.  The  stimuli  affecting  the  organs  of 
special  sense  cause  no  conscious  sensory  impressions  on  account  of  the  suspension 
of  consciousness.  At  the  same  time,  however,  the  irritation  of  the  organs  of 
special  sense  may  induce  movements  on  the  part  of  the  hypnotized  individual; 
such  as  unconscious  acts  that  appear  to  be  voluntarily  executed  in  imitation  of 
others.  In  this  way  is  to  be  explained  the  fact  that  the  hypnotized  individual 
appears  to  perform  even  foolish  acts  on  command,  while  he  imitates  movements 
first  made  by  the  experimenter,  without  consciousness  of  the  significance  of 'his 
acts.  In  individuals  with  greatly  increased  reflex  irritability  voluntary  move- 
ments may  excite  reflex  spasm,  for  example  inability  to  make  coordinated  speech- 
movements. 

According  to  Griitzner  there  are  several  fundamental  types  of  hypnotism:  (i) 
Quiet  sleep,  words  being  still  understood,  and  occurring  especially  in  girls.  (2) 
In  consequence  of  increased  reflex  irritability  of  the  transversely  striated  muscles, 
which  may  persist  for  days,  groups  of  muscles  become  contracted,  especially  in 
strong  persons.  At  the  same  time,  there  may  be  ataxia,  and  the  muscles  may 
fail  to  perform  their  function.  Hypnotized  individuals  can  be  placed  in  positions 
of  varied  kind — artificial  catalepsy.  In  the  stage  of  hysterical  lethargy  the 
tendon-reflexes  are  at  times  increased.  At  the  same  time  the  muscles  become 
firmly  contracted  as  soon  as  they  or  their  nerves  are  pressed  upon.  Nerve  and 
muscle  in  the  cataleptic  state  exhibit  increased  irritability  to  the  constant  current 
and  diminished  irritability  to  the  faradic  current.  In  the  condition  of  hysterical 
catalepsy  the  tendon-reflexes  are  often  entirely  absent.  (3)  Command-autonomy, 
in  which  the  hypnotized  individuals  are  obedient  in  shallow  sleep,  at  first  with 
still  preserved  consciousness.  When  grasped  by  the  hand  or  stroked  upon  the 
head  they  perform  involuntary  movements,  such  as  running  about,  dancing, 
riding  upon  a  chair  and  the  like.  The  effects  of  so-called  suggestion  are  peculiar, 
that  is  conceptions  can  be  aroused  in  the  hypnotized  subject  by  suggestion  and 
these  may  dominate  the  impulses  and  sensations  of  the  individual  for  a  consider- 
able time.  (4)  Hallucinations  occur,  and  only  in  certain  individuals,  on  gradual 
awakening  from  deep  sleep.  The  hallucinations,  generally  of  phenomena  related 
to  fire  and  olfactory  impressions,  are  usually  quite  profound,  both  the  agreeable 
as  well  as  the  frightful  ones,  and  they  often  recur  in  dreams.  (5)  Imitation  is  rare. 
Gross  movements,  such  as  walking,  are  readily  imitated;  more  delicate  or  even 
the  most  delicate,  principally  in  the  uneducated,  occur  less  commonly.  Echo- 
speech  can  be  induced  by  pressure  upon  the  neck  and  speaking  into  the  pharynx, 
against  the  epigastrium  and  against  the  nape  of  the  neck.  Pressure  upon  the 


780        THE  MOTOR  CORTICAL  CENTERS  OF  THE  CEREBRUM. 

right  eyebrow  often  inhibits  speech.  Color-perception  is  abolished  or  disturbed 
by  applying  the  warm  hands  upon  the  eye  or  by  stroking  the  opposite  side  of  the 
head.  Stroking  in  a  direction  opposite  to  that  in  which  stroking  had  previously 
been  practised  gradually  abolishes  the  rigidity  of  the  members  in  sleep ;  blowing 
does  this  immediately.  Insane  persons  are  susceptible  to  hypnotism  equally 
with  healthy  persons.  Disagreeable  complications  arise  only  if  the  practice  be 
overdone;  if,  for  example,  it  be  repeated  daily  for  one  or  two  weeks  with  the  same 
person,  who  then  readily  falls  spontaneously  into  a  state  of  hypnotism  and  cata- 
lepsy. 

Hypnotic  states  can  be  induced  also  in  animals.  Hens  (also  after  removal  of 
the  cerebrum)  assume  a  rigid  position  if  an  object  be  suddenly  placed  in  front 
of  the  eye,  or  a  straw  be  placed  over  the  beak,  or  a  chalk  line  be  drawn 
in  front  of  the  head  pressed  upon  the  ground  (Kircher's  miraculous  experiment, 
1644).  Birds,  rabbits,  frogs  remain  irresponsive  when  held  for  a  time  by  gentle 
pressure  in  a  fixed  position  upon  the  back;  crabs  stand  upon  the  top  of  the  head, 
as  well  as  the  tips  of  their  claws. 

Hypnotism  may  be  employed  therapeutically  in  cases  of  color-blindness,  in- 
somnia, hysterical  convulsions  and  emotional  disturbances.  Also  the  influence  of 
suggestion  may  be  important,  but  great  care  is  necessary  in  its  employment. 

THE  MOTOR  CORTICAL  CENTERS  OF  THE  CEREBRUM. 

Fritsch  and  Hitzig,  in  1870,  discovered  upon  the  surface  of  the  con- 
volutions of  the  cerebrum  a  number  of  circumscribed  areas,  electrical 
stimulation  of  which  causes  movement  in  definite  groups  of  muscles 
on  the  opposite  side  of  the  body  (Fig.  258,  I,  II). 

Method. — To  the  exposed  gyri  of  the  cerebrum  (dog,  ape)  two  blunt  unpolar- 
izable  electrodes  are  applied  close  together,  and  stimulation  is  practised  by  means 
of  closure,  opening  or  alternation  of  a  constant  current,  the  strength  of  which 
causes  a  distinct  sensation  at  the  tip  of  the  tongue;  or  the  induced  current  is 
employed,  the  strength  of  which  causes  a  readily  tolerated  irritation  at  the  tip 
of  the  tongue.  Luciani  observed  movements  appear  in  consequence  of  mechanical 
stimulation  by  scraping.  The  cerebrum  is  wholly  insensitive  to  painful  ma- 
nipulations. 

The  regions  of  the  cerebral  cortex,  stimulation  of  which  causes  char- 
acteristic movements,  must  be  considered  as  true  centers,  as  is  evident 
from  the  fact  that  the  latent  period  after  irritation  of  the  centers  and  the 
duration  of  the  muscular  contraction  are  longer  than  if  the  subcortical 
fibers  passing  from  the  centers  into  the  depth  are  irritated.  In  favor 
of  this  view,  further,  is  the  circumstance  that  the  irritability  of  the  areas 
in  question  can  be  modified  by  stimulation  of  centripetal  nerves.  Prob- 
ably it  is  these  centers  upon  which  the  will  operates  in  the  execution  of 
intended  movements,  and  for  this  reason  they  are  designated  psycho- 
motor  centers  by  Landois.  The  motor  zone  of  the  brain  is  shown  to  be 
a  center  also  from  the  presence  of  special,  large  pyramidal  cells. 

There  are  animals  that  come  into  the  world  with  completely  developed  motor 
and  sensory  functions.     In  these  the  motor  cortical  centers  of  the  new-born  are 
already  irritable.     In  such  animals,  however,  that  are  born  with  incomplete  motor 
and  sensory  functions  either  the  irritability  of  the  cortex  is  still  wanting  entirely, 
so  that  only  the  deeper  fibers  of  the  corona  radiata  are  irritable,  or  movements  can- 
not yet  be  induced  separately,  and  they  are  at  the  same  time  slower  and  more 
sluggish,  with  a  longer  latent  period.     Man  may  exhibit  an  analogous  condition. 
Deep  narcosis,  as  well  as  apnea  and  asphyxia,  abolish  the  irritability  of  the 
:rs,  while  the  subcortical  conducting  fibers  retain  their  irritability.     Inter- 
ference with  the  blood-supply  to  the  head  gives  rise  to  loss  of  irritability  of  the 
cortical  centers  and  of  the  conducting  fibers  passing  from  them.     After  restoration 
ot  the  circulation  in  the  brain  the  irritability  returns.     Small  doses  of  narcotic 
poisons    of  atropm,  moderate  loss  of  blood,  increased  blood-pressure  in  the  brain 
and  slight  inflammation  increase  the  irritability,  while  more  profound  influences 
the  same  kind  abolish  it,  as  does  also  direct  application  of  cold  or  of  cocain. 


THE  MOTOR  CORTICAL  CENTERS  OF  THE  CEREBRUM.       781 

If  the  cerebral  cortex  is  removed  from  an  animal,  the  irritability  of  the  fibers 
of  the  corona  radiata  disappears  completely  at  about  the  fourth  day,  exactly  as 
does  that  of  a  peripheral  nerve  separated  from  its  center. 

As  the  fibers  (of  the  corona  radiata  or  projection-system  of  the  first  order) 
pass  from  the  cerebral  cortex  toward  the  center  of  the  hemispheres,  it  can  be 
understood  that  after  removal  of  the  cortex,  inasmuch  as  the  course  of  the  nerve- 
fibers  in  the  depth  of  the  hemispheres  is  followed,  the  same  motor  effect  can  be 
obtained  by  irritation  of  those  fibers.  If  the  stimulation  be  thus  continued  pro- 
gressively to  the  internal  capsule,  where  the  conducting  fibers  lie  close  together, 
general  contractions  of  the  contralateral  muscles  will  be  observed.  The  motor 
fibers  are  irritable  also  within  the  cms  cerebri. 

Time-relations  of  the  Irritation. — According  to  Franck  and  Pitres  0.045  second 
elapses  between  the  moment  of  stimulation  of  the  cerebral  cortex  and  the  move- 
ment, after  subtraction  of  the  muscular  latent  period  and  the  time  for  con- 
duction through  the  spinal  cord  and  the  nerve  of  the  extremity.  Bubnoff  and 
Heidenhain  found  that  in  morphin-narcosis  of  moderate  degree  the  contraction 
became  greater  and  the  reaction-time  shorter  with  increasing  strength  of  the 
stimulating  current.  After  removal  of  the  cortex  the  total  delay  in  the  onset 
of  contraction,  after  beginning  stimulation  of  the  white  medullary  tissue,  is  dimin- 
ished from  one-quarter  to  one-third.  The  form  of  the  muscular  contraction  (con- 
traction-curve) is  longer  and  more  extended  if  the  cortex  is  stimulated  than  if  the 
subcortical  conducting  path  is  stimulated.  If  the  animal  (dog)  is  in  a  state  of 
marked  reflex  irritability,  these  differences  do  not  appear.  In  either  event  the 
contraction  takes  place  rapidly.  In  case  of  strong  irritation,  the  muscles  of  the 
same  side  also  contract,  though  somewhat  later  than  those  of  the  opposite  side. 
If  the  motor  point  for  the  foreleg  and  that  for  the  hind  leg  are  stimulated  at  the 
same  time,  the  latter  contracts  the  later.  If  the  stimulus  is  applied  to  a  motor 
point  forty  times  in  a  second  the  muscles  in  question  make  forty  individual  con- 
tractions. With  forty-six  separate  stimuli  in  a  second  persistent  contraction  re- 
sults. In  the  same  animal  the  same  number  of  stimuli  are  necessary  for  the 
production  of  sustained  contraction,  whether  the  cortical  center  or  the  motor 
nerve  or  even  the  muscle  is  irritated. 

In  the  case  of  exceedingly  feeble  stimulation  the  phenomenon  of  summation 
of  stimuli  is  observed,  the  muscular  contractions  commencing  only  after  several 
at  first  ineffective  stimuli.  The  time  required  for  the  voluntary  inhibition  of  a 
movement  already  present  is  about  equal  to  the  time  for  the  voluntarily  induced 
movement. 

The  situation  of  the  motor  centers  in  the  brain  of  the  dog  can  be  seen  in  Fig. 
258,  I  and  II.  For  purposes  of  orientation  it  should  be  stated  that  the  surface 
of  the  brain  in  the  dog  exhibits  two  primary  fissures,  the  cruciate  sulcus  (S)  which 
intersects  the  longitudinal  sulcus,  dividing  the  hemisphere  in  its  anterior  third, 
almost  at  a  right  angle.  The  second  primary  fissure  is  the  fossa  of  Sylvius  (F). 
Four  primordial  convolutions  are  arranged  in  a  definite  relation  to  these  primary 
fissures.  The  first  primitive  convolution  (I)  surrounds  with  marked  flexion  the 
sharply  defined  fossa  of  Sylvius  (F).  The  second  primitive  convolution  (II) 
passes  almost  parallel  to  the  first.  The  fourth  primitive  convolution  is  bounded 
in  the  middle  line  by  the  convolution  of  the  opposite  side.  It  surrounds  the 
cruciate  sulcus  (S)  anteriorly,  so  that  the  portion  lying  in  front  of  this  can  be 
readily  differentiated  as  the  precruciate  gyrus  from  the  postcruciate  gyrus  lying 
behind  it.  The  third  primitive  convolution  (III)  is  in  general  parallel  with  the 
fourth. 

In  Fig.  258,  I  and  II,  the  situations  of  the  motor  centers  are  indicated  by 
dots,  although  their  position  varies  somewhat  and  may  even  be  different  upon  the 
two  sides  of  the  brain.  It  should,  however,  be  stated  that  the  individual  centers 
do  not  have  merely  a  punctate  extent,  but  that  in  accordance  with  the  size  of 
the  animal  they  represent  areas  the  size  of  a  pea  and  larger,  whose  central  points 
are  indicated  by  the  dots  in  the  illustration. 

Fritsch  and  Hitzig  isolated  the  following  motor  centers:  (i)  For  the  mus- 
cles of  the  nape  of  the  neck:  a  second  center  was  found  by  Werner  below  7. 
(2)  For  the  extensors  and  abductors  of  the  foreleg.  (3)  For  flexion  and  rotation 
of  the  foreleg.  (4)  For  the  movements  of  the  hind  leg,  which  Luciana  and  Tam- 
burini  were  able  to  separate  into  two  centers  with  antagonistic  effects.  (5)  For 
the  muscles  of  the  face,  or  the  center  for  the  facial  nerve  (according  to  these 
investigators  often  more  than  0.5  cm.  in  diameter).  Ferrier  has  discovered  the 
following  additional  centers:  (6) 'For  the  lateral  wagging  movements  of  the  tail. 


782  THE    MOTOR    CORTICAL    CENTERS    OF    THE    CEREBRUM. 

(7)  For  retraction  and  abduction  of  the  foreleg.  (8)  For  elevation  of  the  shoulder 
and  extension  of  the  foreleg  (walking  movement).  The  area  9  9  o  controls  the 
movements  of  the  orbicular  muscle  of  the  eyelids,  the  zygomatic  (closure  of  the 


F 


FIG.  258. — I,  Cerebrum  of  the  dog,  viewed  from  above;  II,  from  the  side.  I,  II,  III,  IV,  the  four  primitive 
convolutions;  S,  the  cruciate  sulcus;  F,  the  fossa  of  Sylvius;  o,  olfactory  bulb;  p,  optic  nerve;  i,  motor 
point  for  the  muscles  of  the  nape  of  the  neck;  2,  for  the  extensors  and  abductors  of  the  foreleg;  3, 
for  the  flexors  and  rotators  of  the  foreleg;  4,  for  the  muscles  of  the  hind  leg;  5,  for  the  facial  nerve;  6,  for 
lateral  wagging  movements  of  the  tail;  7,  for  retraction  and  abduction  of  the  foreleg;  8,  for  elevation  of  the 
shoulder  and  extension  of  the  foreleg  (walking  movement);  9,  9,  for  the  orbicular  muscle  of  the  eyelids,  the 
zygomatic,  closure  of  the  eyelids.  II,  a,  a,  for  retraction  and  elevation  of  the  angle  of  the  mouth;  b,  for  open- 
ing the  mouth  and  for  the  movements  of  the  tongue  (mouth-center);  c,  c,  for  the  platysma;  d,  for  opening  the 
eye.  I  t,  The  thermic  center,  according  to  Eulenburg  and  Landois.  Ill,  The  cerebrum  of  the  rabbit,  viewed 
from  above.  IV,  The  brain  of  the  pigeon,  viewed  from  above.  V,  The  brain  of  the  frog,  viewed  from  above. 
VI,  The  brain  of  the  carp,  viewed  from  above.  (In  all  of  these  illustrations  o  is  the  olfactory  bulb,  i  the  cere- 
brum, 2  the  optic  lobe,  3  the  cerebellum,  4  the  medulla  oblongata.) 

eyelids,  together  with  upward  rotation  of  the  eyeball  and  contraction  of  the  pupil). 
In  the  anterior  9  is  the  point  for  the  movements  of  the  tongue,  between  the  ante- 
rior and  the  middle  9  that  for  closure  of  the  jaw.  Stimulation  of  the  points  a  a  (II) 


THE  MOTOR  CORTICAL  CENTERS  OF  THE  CEREBRUM.       783 

caused  retraction  and  elevation  of  the  angle  of  the  mouth,  with  partial  opening 
of  the  mouth.  On  stimulation  of  b  Ferrier  observed  opening  of  the  mouth,  with 
protrusion  and  retraction  of  the  tongue  (bilateral  action !) ,  the  dog  not  rarely 
making  barking  sounds.  He  designates  this  area  the  mouth-center.  Stimulation 
of  c  c  causes  retraction  of  the  angle  of  the  mouth  by  the  platysma,  stimulation 
of  c'  elevation  of  the  angle  of  the  mouth  and  of  the  side  of  the  face  to  the  point 
of  closing  the  eye  (the  same  as  at  9).  On  stimulation  of  the  middle  e  opening 
of  the  eye  and  dilatation  of  the  pupil  result,  the  eyes  and  the  head  being  rotated 
toward  the  opposite  side.  Stimulation  of  the  postcruciate  gyrus  causes  contraction 
of  the  perineal  muscles.  Stimulation  of  the  anterior  declivous  surface  of  the 
precruciate  gyrus  causes  movements  of  the  pharynx  and  the  larynx.  Stimulation 
of  a  definite  point  in  the  anterior  half  of  the  foot  of  the  ascending  frontal  convo- 
lution (in  the  ape)  gives  rise  to  contraction  of  the  glottis,  as  in  phonation.  Stimu- 
lation anteriorly  and  exteriorly  to  the  center  for  the  extremities  (in  the  rabbit) 
causes  movements  of  mastication  and  deglutition. 

Observations  on  the  ape  showed  likewise  a  strict  localization  of  the  centers. 
The  movement  caused  by  stimulation  with  induction-currents  proved  similar  to 
those  executed  voluntarily.  Rarely  a  single  muscle  contracted;  generally  a  co- 
ordinated group.  The  antagonists  are  at  times  thrown  into  activity,  in  so  far  as 
the  primary  movement  may  be  followed  by  that  of  the  antagonists.  The  contrac- 
tion exhibits  an  oscillatory  rhythm  of  from  ten  to  fifteen  movements  in  one  second. 

On  more  marked  irritation,  in  addition  to  the  muscles  of  the  opposite 
side,  those  of  the  same  side  may  be  made  to  contract,  the  irritation 
extending  to  the  other  side.  Muscles  such  as  those  of  the  eyes,  the  peri- 
neum, the  larynx,  the  pharynx,  the  muscles  of  mastication,  that  are 
moved  on  both  sides  at  the  same  time,  appear  to  have  a  center  not  only 
in  the  opposite  hemisphere,  but  also  in  that  on  the  same  side.  The 
question  is  of  great  practical  significance  from  a  diagnostic  standpoint 
whether  movements  cannot  be  excited  by  irritation  due  to  local  disease, 
such  as  inflammation,  tumor,  degenerative  processes,  and  the  like,  in- 
volving the  motor  areas  in  the  brain  of  man.  Hughlings-Jackson  answers 
this  question  in  the  affirmative,  and  explains  in  this  manner  the  occur- 
rence of  unilateral,  localized  epileptiform  convulsions,  which  Ferrier 
and  Landois  observed  as  a  result  of  inflammatory  irritation.  By  means 
of  marked  irritation  of  the  motor  areas  a  complete  general  convulsive 
epileptic  attack  can  be  induced  in  dogs. 

This  begins  with  twitchings  in  the  specially  related  group  of  muscles,  passes 
then  to  the  corresponding  member  of  the  opposite  side  and  involves  the  entire 
musculature  of  the  body,  at  first  in  clonic,  then  in  tonic,  and  finally  again  in  clonic 
spasms.  Above  the  internal  capsule  feeble  irritation  is  often  sufficient  to  excite 
this  form  of  epilepsy.  The  opposite  side  of  the  body  has  also  been  observed  to 
be  involved  in  convulsions,  and  from  below  upward,  after  the  movements  had 
been  present  in  all  parts  on  the  side  first  affected.  The  spasmodic  irritation 
passes  from  center  to  center,  and  intervening  motor  areas  are  never  skipped. 
After  a  primary  attack  of  such  character,  the  slightest  irritation  is  often  sufficient 
for  the  excitation  of  other  epileptic  attacks.  During  the  attack  the  circulation 
in  the  brain  is  accelerated  and  the  vessels  of  the  pia  are  dilated.  As,  at  the  same 
time,  also  the  intracranial  pressure  is  greatly  increased,  Kocher  has  suggested 
the  making  of  a  trephine-opening  in  the  skull  in  epileptics  and  covering  it  only 
with  soft  parts,  in  order  in  this  way  to  provide  to  a  certain  degree  a  safety-valve. 
With  the  object  of  preventing  the  variations  in  the  fulness  of  the  blood-vessels 
that  are  observed  in  epileptic  attacks  the  suggestion  to  extirpate  the  cervical 
sympathetic  in  epileptics  would  appear  justifiable.  Perhaps  it  would  be  advisable 
to  ligate  the  cerebral  carotid  at  the  same  time. 

The  irritation  of  the  centers  appears  to  be  followed  by  a  brief  state  of  lessened 
irritability,  the  refractory  period.  Also  irritation  of  the  subcortical  white  matter 
causes  general  convulsions,  which,  however,  begin  in  the  muscles  of  the  same 
side. 

If  certain  motor  points  are  extirpated,  the  convulsions  may  be  wanting  in 
the  epileptic  attack  in  the  muscles  controlled  from  these  points.  Severance  of 


784       THE  MOTOR  CORTICAL  CENTERS  OF  THE  CEREBRUM. 

the  motor  cortical  points  by  means  of  a  horizontal  incision  during  an  attack 
causes  cessation  of  the  attack.  If  an  epileptic  attack  is  of  short  duration,  it  is 
not  rarely  possible,  by  extirpation  of  the  cortical  center  for  one  extremity,  to 
exclude  this  alone,  while  the  remainder  of  the  body  continues  to  be  agitated  by 
the  convulsions. 

Long-continued  administration  of  potassium  bromid  prevents  the  possibility 
of  causing  epilepsy  by  irritation  of  the  cortex. 

Chemical  irritation  is  further  of  particular  interest.  When  in  1887 
Landois  applied  to  the  motor  regions  a  number  of  substances  that  occur 
in  urine,  for  example  kreatin,  kreatinin,  acid  potassium  phosphate, 
uratic  sediment  from  human  urine,  and  others,  he  observed  the  occur- 
rence of  marked  eclamptic  (clonic-tonic)  convulsions,  which  were  re- 
peated spontaneously  for  a  considerable  time  and  were  followed  by  pro- 
found coma  (in  the  dog).  Landois  does  not  insist  that  the  uremic  con- 
vulsions in  human  beings,  as  well  as  epileptic  convulsions  induced 
through  autointoxication,  are  to  be  compared  with  the  phenomena 
observed  in  his  experiments.  The  sensorial  centers  are  also  affected  in 
the  same  way,  the  sense  of  vision  suffering  especially. 

Certain  poisons  are  capable  of  exciting  convulsions  by  irritation  of  the  cor- 
tical centers.  Among  these  are  santonin,  physostigmin,  carbolic  acid,  acetone 
(in  cases  of  diabetes),  also  tannic  acid  on  direct  application.  Under  such  cir- 
cumstances convulsions  upon  both  sides  of  the  body  may  be  excited  by  irritation 
of  one  hemisphere.  The  convulsions  no  longer  occurred  after  the  cortical  centers 
were  removed  on  both  sides.  Birds  and  lower  vertebrates  exhibit  no  convul- 
sions. 

Extirpation  of  the  motor  centers  gives  rise  to  characteristic  derangement 
of  movement  in  the  affected  contralateral  muscles.  Landois,  together 
with  other  investigators,  observed  in  the  dog  after  destruction  of  the 
motor  points  for  the  extremities  feeble  and  awkward  movements  of  the 
latter,  such  as  improper  placing  of  the  foot,  slipping,  yielding,  dragging. 
While  some  investigators  consider  these  phenomena  as  transitory  only, 
Landois  was  able  to  observe  them  for  months.  In  dogs,  particularly 
the  paws  remain  paralyzed  with  respect  to  all  of  those  movements  in 
which  the  paws  are  employed  to  a  certain  degree  as  hands,  and  which 
thus  are  acquired  through  education.  In  the  course  of  time  the 
pyramidal  tracts  degenerate  downward  and  the  related  muscles  undergo 
atrophy. 

The  higher  the  development  of  the  intelligence  in  the  animals  and  the  more 
they  are  required  to  learn  their  movements  and  gradually  to  subordinate  them 
to  the  control  of  the  will,  the  more  profound  and  persistent  are  the  disturbances 
of  movement  after  destruction  of  the  cortical  psychomotor  centers.  While,  in 
the  lower  vertebrates,  including  birds,  extirpation  of  the  entire  hemispheres  does 
not  appreciably  affect  the  movements,  the  coordinated  reflexes  sufficing  com- 
pletely for  the  latter,  in  the  dog  extirpation  of  individual  motor  centers  is  attended 
at  times  with  appreciable  permanent  derangement  of  motility,  which  in  apes  and 
human  beings  becomes  intense  and  long  continued. 

Hitzig  attributes  the  disturbances  of  movement  following  removal  of  the  motor 
centers  to  the  loss  of  muscular  consciousness.  According  to  Schiff ,  tactile  sensa- 
tion alone  is  lost  in  consequence  of  destruction  of  the  motor  cortical  centers, 
and  it  never  returns. 

In  a  dog  in  which  the  motor  centers  for  the  extremities  were  destroyed 
on  both  sides  Landois,  in  1876,  observed  derangement  of  voluntary  movement, 
which  he  was  first  to  designate  cerebral  ataxia;  that  is  the  animal  was  unable  to 
execute  coordinated  movements  for  the  purpose  of  walking,  standing,  etc.  He 
therefore  believed,  even  at  that  time,  that  the  cortical  centers  are  the  direct 
motor  points  for  the  operation  of  the  will  and  also  that  conscious  sensation  of 
muscular  contractions  is  localized  in  them. 


THE    MOTOR    CORTICAL    CENTERS    OF    THE    CEREBRUM.  785 

The  irritability  of  the  motor  centers  may  be  considerably  influenced 
in  various  ways.  Thus,  it  is  impaired  by  stimulation  of  sensory  nerves, 
as  this  lowers  the  contraction-curve  of  the  muscles  and  extends  and  pro- 
longs the  reaction-time.  The  irritability  of  the  cortical  centers  appears 
to  be  increased  only  when  active  reflex  muscular  contractions  occur  in 
connection  with  severe  sensory  irritation.  It  is  an  especially  remarkable 
fact  that  in  a  certain  stage  of  morphin-narcosis  a  stimulus  that  is  too 
feeble  to  induce  a  contraction  becomes  at  once  active  if,  shortly  before  its 
application  to  the  cortical  centers,  the  skin  in  certain  portions  of  the 
body  is  exposed  to  even  slight  tactile  irritation.  The  contractions  ac- 
quire a  tonic  character  on  strong  pressure  upon  the  paw,  so  that  all  stimuli 
that  in  the  normal 'state  cause  in  the  centers  only  transitory  excitation 
now  exert  a  permanent  stimulating  effect.  If,  during  the  tonic  con- 
traction, the  skin  on  the  dorsum  of  the  paw  is  gently  stroked,  or  the  face 
is  blown  upon,  or  the  nose  is  gently  struck,  or  the  animal  is  called,  or  the 
sciatic  is  irritated,  relaxation  of  the  muscles  suddenly  takes  place.  These 
phenomena  are  suggestive  of  the  analogous  observations  on  hypnotized 
individuals. 

It  is  a  further  remarkable  fact  that  if  contracture  of  the  muscles  in 
question  is  induced  by  reflex  irritation  or  strong  electrical  stimulation  of 
the  cortical  center,  feeble  stimulation  of  the  same  center,  and  also  of  any 
other  cortical  region,  suppresses  the  movement.  There  is  thus  afforded 
the  peculiar  phenomenon  that  irritation  of  the  same  cortical  region,  in 
accordance  with  the  intensity  of  the  current  employed,  excites  irritation 
of  the  motor  apparatus  or  inhibits  an  irritation  already  present.  H.  E. 
Hering  and  Sherrington  observed  on  irritation  of  the  motor  centers  of  the 
ape,  relaxation  of  the  antagonistic  muscles,  which  occurred  even  when 
the  stimulus  for  the  excitation  of  the  movement  in  the  muscles  related 
to  the  center  was  still  too  weak.  With  currents  of  a  certain  strength 
they  obtained  such  simultaneous  contraction  and  relaxation  not  from 
the  same  cortical  area,  but  from  widely  separated  areas.  Further,  in 
addition  to  this  reciprocal  innervation  of  the  true  antagonists,  there  was 
a  complicated  relation  between  various  groups  of  muscles.  Thus,  for 
example,  on  closure  of  the  fist,  dorsal  flexion  occurs  at  the  wrist-joint. 
The  relaxation  of  the  antagonists  takes  place  somewhat  in  advance  of  the 
contraction  of  the  irritated  muscle. 

Sherrington  stimulated  the  central  stump  of  the  flexor  nerves  of  the 
leg  containing  the  muscle-sense  nerves,  and  observed  at  once  loss  of 
tone  in  the  extensor  muscles  stimulated  from  the  cerebrum. 

According  to  the  investigations  of  Fano  and  Libertini  and  others  there  is  in 
the  pref rental  region  of  the  dog  an  inhibitory  center  for  movements,  therefore 
a  psycho  inhibitory  center  for  the  opposite  side  of  the  body.  Irritation  of  the 
contralateral  cerebral  hemisphere,  for  example  by  application  of  a  crystal  of 
sodium  chlorid  (in  the  frog),  causes  inhibition  of  the  irritability  of  the  motor 
nerves.  Also  irritation  of  the  contralateral  basal  portion  of  the  midbrain  or  a 
transverse  section  of  the  spinal  cord  may  have  a  similar  effect. 

THE   SENSORIAL  CORTICAL  CENTERS. 

The  investigations  of  Ferrier  and  H.  Munk  have  shown  that  areas 
are  present  in  definite  portions  of  the  cerebral  cortex  in  which  the  act 
of  conscious  sense-perception  takes  place.  These  areas  are  connected 
by  means  of  fibers  with  the  nerves  of  special  sense.  They  are  designated 
also  sensorial  cortical  centers,  sense-centers,  or,  according  to  the  suggestion 

50 


786  THE    SENSORIAL    CORTICAL    CENTERS. 

of  Landois,  psyckosensorial  centers.  Total  destruction  of  such  a  center 
abolishes  conscious  perception  on  the  part  of  the  organ  of  special  sense 
in  question.  On  partial  destruction  of  such  a  center,  the  mechanism 
of  sense-activity  may  remain  intact,  but  the  mental  connection  is  want- 
ing. A  dog  with  such  injured  centers,  it  is  true,  sees,  hears,  and  smells, 
but  he  no  longer  recognizes  what  he  sees,  hears,  and  smells.  The  centers 
are  to  a  certain  degree  the  repositories  for  experiences  gained  through 
the  special  senses.  Irritation  of  these  areas  may  give  rise  to  movements 
such  as  occur  when  sudden,  intense  sense-impressions  are  produced; 
these  movements  are,  therefore,  reflex.  In  this  group  belongs  also  dila- 
tation of  the  pupil  and  of  the  palpebral  fissure,  as  well  as  lateral  move- 
ment of  the  eyeball.  It  appears,  however,  that,  in  addition,  each  cen- 
ter possesses  its  own  motor  apparatus,  by  means  of  which  the  movements 
of  the  related  organ  of  special  sense  are  executed. 


FIG.  259.— The  Psycho-optic  and  Psycho-auditory  Centers  and  the  Sensory  Sphere  of  the  Dog's  Brain 

(after  H.  Munk). 

The  psycho-optic  center  or  the  visual  sphere  comprises,  according  to  Munk, 
the  portion  of  the  occipital  lobe  in  the  dog  marked  "  Seeing  "  (Fig.  259).  If  this 
region  is  completely  destroyed,  the  dog  becomes  permanently  almost  totally 
blind  in  the  opposite  eye — cortical  blindness.  If,  however,  only  the  more  cen- 
trally situated  portion  (with  circular  outline)  is  destroyed,  there  will  be  loss 
of  conscious  sensation  of  vision  on  the  opposite  side,  and  this  may  be  desig- 
nated mind-blindness  or  optic  amnesia.  Tt  is  a  remarkable  fact  that  destruction 
of  this  area  on  one  side  is  soon  followed  by  compensation.  It  appears  that  other 
adjacent  cortical  areas  of  the  visual  sphere  are  capable  of  assuming  the  function  of 
the  injured  portion.  Under  these  circumstances  it  will  be  found  that  the  animals 
with  the  affected  eye  must  to  a  certain  extent  again  learn  to  see  as  in  earliest 
youth.  Destruction  of  the  entire  center  on  each  side  causes  total  blindness  on 
both  sides,  while  that  of  the  central  (shaded)  portions  alone  in  the  dog  causes 
mind-blindness  on  both  sides. 

A  psycho-optic  center  is  observed  first  in  birds,  the  optic  nerve  terminating 
m  the  midbrain  in  the  lower  vertebrates.  In  accordance  with  the  extent  of  the 
decussation  of  the  optic  nerves  in  different  animals  the  psycho-optic  center  is 
related  to  the  retinas. 

Munk  determined  in  the  dog,  further,  that  both  retinas  are  connected  with 
each  psycho-optic  cortical  center,  and  in  such  a  manner  that  each  retina  receives 


THE  SENSORIAL  CORTICAL  CENTERS.  787 

the  largest  number  of  fibers  from  the  opposite  cortical  center,  and  fibers  only 
for  the  outermost  lateral  marginal  portion  from  the  center  of  the  same  side.  If 
the  surface  of  one  retina  be  conceived  as  projected  upon  the  centers,  the  outer- 
most margin  of  the  former  will  be  connected  with  the  center  of  the  same  side, 
the  inner  margin  of  the  retina  with  the  inner  portion  of  the  opposite  center,  the 
upper  marginal  portion  with  the  anterior  portion,  and  the  inferior  marginal 
portion  of  the  retina  with  the  posterior  portion  of  the  opposite  center.  The 
(shaded)  middle  of  the  center  corresponds  to  the  point  of  direct  vision  of  the 
retina  of  the  opposite  side. 

Irritation  of  the  visual  center  causes  in  the  dog  movements  of  both  eyes 
toward  the  opposite  side,  at  times  with  movements  of  the  head  of  like  character 
and  contraction  of  the  pupils.  If  an  eye  is  excised  from  a  new-born  dog  the  contra- 
lateral  psycho-optic  center  will  after  an  interval  of  months  be  found  to  be  less 
well  developed.  After  extirpation  of  the  visual  sphere  in  young  animals  the 
external  geniculate  body,  the  pulvinar  (Fig.  263),  the  anterior  quadrigeminate 
body  (of  the  same  side  and  in  part  also  of  the  opposite  side),  undergo  atrophy, 
together  with  degeneration  of  the  sensory  sphere  for  the  eye  (Fig.  259),  and  at 
a  later  period  also  the  optic  tract  and  nerve  undergo  atrophy.  A  similar  condi- 
tion has  been  observed  after  degeneration  of  the  visual  sphere  in  man. 

The  situation  of  the  visual  center  has  been  outlined  in  a  different  manner  by 
different  investigators.  According  to  Ferrier  it  is  located  in  the  dog  in  the  region 
of  the  occipital  portion  of  the  third  primitive  convolution  indicated  by  e  e  e  (Fig. 
258) ,  and  according  to  more  recent  statements  in  the  occipital  lobe  and  the  angular 
gyrus. 

According  to  Luciani,  the  visual  field  includes,  in  addition  to  the  occipital, 
also  the  parietal  lobe  (in  the  dog  and  the  ape) .  He  also  dissents  from  the  precise 
projection  of  the  retinas  upon  the  cerebral  cortex.  He  believes  that  both  optic 
nerves  are  connected  with  all  portions  of  the  occipitoparietal  region.  Moreover, 
he  is  of  the  opinion  that  the  visual  images  are  only  transformed  in  the  cortex 
psychically,  but  that  they  arise  in  the  quadrigeminate  body,  as  he  admits,  even 
after  most  extensive  destruction  of  the  occipitoparietal  region  on  both  sides, 
the  development  only  of  mind-blindness,  but  not  permanent  actual  blindness. 
Even  previously  Christiani  had  maintained  that  rabbits  deprived  of  their  cere- 
brum still  avoided  obstructions  in  running,  because  they  were  able  to  appreciate 
them  with  their  eyes.  In  such  animals,  therefore,  optic  impressions  must  be 
advantageously  utilized,  and  in  such  a  manner  that  the  optical  impressions  so 
affect  the  chief  reflex  and  the  coordination-center  in  the  optic  thalamus  that  the 
animals  make  appropriate  reflex  movements.  Conscious  vision  is  thus  lost,  while 
the  coordinated  reflex  activities  excited  from  the  visual  apparatus  are  still  pre- 
served. 

In  apes  the  center  is  situated  at  the  apex  of  the  occipital  lobe.  Destruction 
of  the  center  on  one  side  causes  blindness  for  the  halves  of  both  retinas  upon  the 
side  of  the  injury.  In  birds  the  visual  sphere  is  situated  in  the  portion  of  the 
cerebral  cortex  extending  from  the  peduncle  upward  and  forward  and  covering 
the  ventricle.  The  retina  of  the  opposite  eye  is  supplied  from  one  hemisphere, 
with  the  exception  of  its  most  posterior  portion,  which  is  supplied  from  the  hemi- 
sphere of  the  same  side.  In  the  frog  the  visual  center  is  situated  in  the  optic 
lobe;  frogs  and  fish  thus  see  without  a  cerebrum. 

The  psycho-auditory  center  or  the  auditory  sphere  is  situated  in  the  dog  in 
the  region  of  the  second  primitive  convolution  indicated  by  the  letters  f  f  f  (Fig. 
258,  II)  .according  to  Munk  in  that  portion  of  the  temporal  lobe  marked  "  Hearing  " 
(Fig.  259).  Destruction  of  the  entire  region  causes  deafness  in  the  contralateral 
ear;  destruction  of  the  middle  shaded  portion  alone  causes  mind-deafness  or  audi- 
tory amnesia,  that  is  the  animal  has  lost  the  memory-images  of  auditory  impres- 
sions. Irritation  of  the  center  is  followed  by  a  reaction  that  corresponds  to  the 
abrupt  start  induced  by  a  sudden  and  unexpected  loud  noise.  Irritation  of  the 
center  on  one  side  causes  movement  of  the  ear  on  the  opposite  side.  Under  these 
circumstances  also,  the  disturbances  attending  injury  of  the  middle  portion 
on  one  side  disappear  in  the  course  of  a  few  weeks  (as  in  the  case  of  the  psycho- 
optic  center) ,  so  that  the  animal  must  again  learn  to  hear.  Destruction  of  the 
middle  portion  on  both  sides  causes  mind-deafness  on  both  sides.  Dogs  thus 
injured  no  longer  prick  their  ears  in  response  to  auditory  impressions  and  they 
gradually  lose  the  faculty  of  barking.  The  anterior  portions  of  the  auditory 
sphere  appear  to  subserve  the  perception  of  high  notes  and  the  posterior  portions 
the  perception  of  deeper  notes.  Munk  observed  after  destruction  of  one  ear  in 


788  THE    SENSORIAL    CORTICAL    CENTERS. 

the  new-born  dog  that  the  contralateral  center  was  less  well  developed.  Destruc- 
tion of  the  entire  region  on  both  sides  causes  deafness  (with  mutism).  Ferrier 
demonstrated  the  center  in  apes,  rabbits,  jackals,  and  cats. 

According  to  Luciani  the  auditory  center  extends  from  the  temporal  lobe  to 
the  parietal  and  frontal  lobes,  the  hippocampal  gyrus  and  the  cornu  Ammonis. 
Each  ear  is  in  connection  with  both  centers,  although  most  intimately  with  that 
of  the  opposite  side.  After  total  extirpation  of  the  auditory  center  on  both 
sides  mind-deafness  alone  develops. 

Munk  and  Ferrier  locate  the  olfactory  center  in  the  dog  in  the  hippocampal 
gyrus.  After  destruction  of  the  center  on  each  side  in  the  ape  the  sense  of  smell 
and  that  of  taste  were  abolished.  The  psycho-osmic  and  psychogeusic  centers 
located  in  this  situation  have  as  yet  not  been  differentiated.  According  to  Luciani 
the  hippocampal  gyrus  and  the  cornu  Ammonis  constitute  the  olfactory  center. 
Partial  decussation  is  to  be  assumed  also  in  this  case,  but  the  non-decussating 
bundle  is  the  larger. 

On  irritation  of  this  area  Luciani  observed  in  apes,  dogs,  cats,  and  rabbits 
distortion  of  the  lips  and  partial  closure  of  the  nasal  orifice  on  the  same  side. 
According  to  Zuckerkandl,  who  bases  his  conclusions  upon  comparative  anatomical 
observations,  the  cortical  portion  of  the  olfactory  center  is  constituted  of  the 
central  extremity  and  the  frontal  extremity  of  the  lobe  of  the  corpus  callosum, 
of  the  hippocampal  lobe  together  with  the  uncus,  of  the  cornu  Ammonis  including 
the  marginal  convolution  (particularly  the  dentate  fascia),  of  the  cortex  of  the 
olfactory  peduncle,  of  the  cortex  of  the  anterior  perforated  lamina  and  of  the 
olfactory  bulb. 

A  cortical  olfactory  center  is  present  among  vertebrates  first  in  reptiles, 
and  this  is  at  the  same  time  the  earliest  psychosensorial  organ  that  appears.  It 
may  be  concluded  from  this  fact  that,  phylogenetically,  the  first  psychic,  activity 
in  the  animal  kingdom  is  concerned  with  the  perception  of  odors. 

Munk  believes  that  the  surface  of  the  brain  in  the  region  of  the  motor 
centers  is  at  the  same  time  the  sensory  sphere,  that  is  that  it  serves  also  for 
the  reception  of  tactile,  muscular,  and  innervational  impressions  from  the  oppo- 
site side.  The  boundaries  of  the  areas  for  the  individual  portions  of  the  body 
in  the  dog  are  indicated  in  Fig.  259.  After  injury  of  this  region  the  function 
mentioned  is  lost.  The  sensory  sphere  in  apes  is  situated  in  the  parietal  lobe  and 
each  individual  area  is  related  to  a  definite  portion  of  the  body.  After  total 
extirpation  of  the  arm-area  and  the  leg-area,  tactile  sensibility  is  lost  perma- 
nently, while  after  partial  extirpation  return  of  sensibility  takes  place  later. 

Luciani,  however,  rejects  such  precise  limitation  for  the  individual  regions  of 
the  body.  According  to  Bechterew  the  centers  in  the  dog  for  the  perception  of 
tactile  impressions,  the  muscle-sense  and  sensations  of  pain  are  situated  in  the 
neighborhood  of  the  motor  zone,  the  first  immediately  behind  and  external  to 
the  motor  area,  the  others  in  the  region  just  above  the  beginning  of  the  fossa  of 
Sylvius.  According  to  Schafer  extirpation  of  the  gyrus  fornicatus  is  followed 
by  permanent  impairment  of  sensibility  in  apes. 

THE  CORTICAL  THERMIC   CENTER. 

DIVERGENT  VIEWS   AS   TO    THE   LOCALIZATION   IN    THE   CORTEX. 
OTHER   CORTICAL  FUNCTIONS. 

A.  Eulenburg  and  Landois  succeeded  in  discovering  on  the  surface 
of  the  cerebrum  of  the  dog  an  area  from  which  an  undoubted  influence 
is  exerted  upon  the  temperature  and  the  size  of  the  vessels  in  the  con- 
tralateral extremities.  This  area  (Fig.  258  I,  t)  comprises  in  general 
the  region  in  which  at  the  same  time  the  motor  centers  for  the  flexors 
and  the  rotators  of  the  foreleg  (3)  and  for  the  muscles  of  the  hind  ex- 
tremity (4)  are  situated.  The  effective  areas  for  the  anterior  and  pos- 
terior extremities  are  widely  separated  from  each  other.  That  for  the 
foreleg  is  situated  somewhat  further  forward,  close  to  the  lateral  ex- 
tremity of  the  cruciate  sulcus.  Destruction  of  this  region  is  followed  by 
elevation  of  the  temperature  in  the  contralateral  extremities,  and  this 
may  be  variable  in  degree — from  1.5°  to  2°  or  even  as  much  as  13°  C. 


THE  CORTICAL  THERMIC  CENTER.  789 

This  observation  has  been  confirmed  by  Hitzig,  Bechterew,  Wood,  and 
others.  The  elevation  of  temperature  bears  no  relation  to  muscular 
disturbances  that  may  be  present  in  the  affected  extremities.  It  is  in 
almost  all  cases  marked  for  a  considerable  time  after  the  injury,  although 
attended  with  considerable  fluctuations.  It  has  been  observed  to  per- 
sist for  as  long  as  three  months,  while  in  other  cases  gradual  return  to 
normal  sets  in  on  the  second  or  third  day.  In  marked  cases  there  is 
a  reduction  in  the  resistance  of  the  wall  of  the  femoral  artery  to  pressure 
and  a  lowering  of  the  pulse-tracings. 

Localized  electrical  irritation  of  the  areas  causes  slight  transitory 
reduction  in  the  temperature  of  the  contralateral  extremities.  In  dogs 
the  same  result  may  be  brought  about  even  by  percutaneous  irritation. 
The  center  can  be  irritated  also  by  application  of  sodium  chlorid,  al- 
though under  such  circumstances  the  phenomenon  of  destruction  soon 
follows.  Irritation  of  the  cortical  center  causes  also  in  curarized  animals 
marked  elevation  of  blood-pressure  in  consequence  of  vascular  contrac- 
tion. The  demonstration  of  a  thermic  center  for  the  half  of  the  head  has 
not  as  yet  been  made.  In  cerebral-epileptic  attacks  the  bodily  tempera- 
ture rises,  in  part  in  consequence  of  increased  production  of  heat  by  the 
muscles,  in  part  in  consequence  of  lessened  heat-dissipation  through  the 
vessels  of  the  skin  as  the  result  of  irritation  of  the  cortical  thermic  centers. 

According  to  Wood /destruction  of  this  central  area  in  the  dog  causes  at  the 
same  time  an  increase  in  heat-production  demonstrable  calorimetrically,  while 
irritation  causes  lessened  heat-production.  In  dogs  in  which  the  internal 
capsule  was  divided  by  means  of  a  small  knife  (which  was  made  to  close  sud- 
denly in  the  depth  of  the  wound  by  traction  on  a  cord) ,  Landois  observed  likewise 
elevation  of  temperature,  and  he  concluded,  therefore,  that  the  fibers  controlling 
thermic  influences  traverse  the  internal  capsule.  Furthermore,  injury  of  the 
cerebral  peduncle  is  followed  by  obvious  elevation  of  temperature.  In  rabbits 
destruction  of  the  anterior  portion  of  the  cortex  has  no  obvious  influence,  although 
that  of  the  posterior  portion  has. 

The  experiments  described  explain  the  fact  that  psychic  stimu- 
lation of  the  cerebrum  may  have  an  influence  upon  the  size  of  the 
vessels  and  upon  the  temperature,  as  indicated  by  momentary  pallor  and 
blushing,  v.  Bechterew  and  Mislawski  locate  a  vasodilator  center  in  the 
external  and  middle  portions  of  the  anterior  segment  of  the  cruciate 
gyms  and  in  portions  of  the  parietal  region. 

In  opposition  to  the  outlined  doctrine  of  localization  in  the  cerebrum  the 
views  of  Goltz  must  be  discussed  in  an  unprejudiced  manner.  Goltz  has  de- 
scribed in  detail  the  phenomena  that  appear  in  dogs  subjected  to  extensive  de- 
struction of  the  cerebral  cortex.  He  distinguishes  on  the  one  hand  inhibitory 
phenomena,  which  are  transitory  and  are  referable  to  temporary  suppression  of 
the  functions  of  nervous  structures  that  are  not  injured  anatomically.  These 
are  to  be  explained  in  the  same  way  as  the  inhibition  of  the  reflexes  by  strong 
irritation  of  sensory  nerves.  Opposed  to  these  are  the  permanent  phenomena  of 
deficiency,  which  are  due  to  the  loss  of  function  of  the  nerve -structures  destroyed 
by  the  operative  procedure.  Such  a  dog  with  extensive  loss  of  cortex  may  be 
looked  upon  as  an  eating,  complex  reflex  machine.  It  behaves  like  a  profoundly 
demented  animal,  walks  slowly  in  an  awkward  manner,  with  head  depressed,  and 
exhibits  impairment  of  cutaneous  sensibility  in  all  of  its  qualities.  It  is  less 
sensitive  to  pressure  upon  the  skin,  pays  less  attention  to  variations  in  tempera- 
ture and  does  not  know  how  to  touch  objects.  It  is  scarcely  able  to  adjust  itself 
with  relation  to  the  outer  world  or  to  its  own  body.  This  is  noted  especially  in 
looking  for  and  taking  up  its  food.  On  the  other  hand  there  is  no  paralysis  of 
its  muscles.  It  is  true  the  dog  still  sees,  but  without  conscious  appreciation  of 
what  is  seen.  It  sees  like  a  somnambulist,  who  avoids  obstructions,  without 
being  perfectly  conscious  of  their  character.  It  is  true,  the  animal  hears,  for  it 


THE  CORTICAL  THERMIC  CENTER. 

can  be  awakened  from  sleep  by  loud  shouting,  but  it  hears  much  like  a  hu- 
man being  who  has  just  been  aroused  from  deep  sleep  by  being  called,  without 
at  once  comprehending  the  call  with  clear  consciousness.  The  disturbance  of 
the  other  senses  is  analogous  in  character.  The  animal  howls  when  hungry, 
then  eats  until  its  stomach  is  entirely  filled.  It  is  absolutely  indifferent  and 
without  sexual  instinct. 

With  reference  to  the  localization  in  the  cerebrum  Goltz  holds  dissenting 
views.  He  believes  that  every  portion  of  the  cerebrum  takes  part  in  the  func- 
tions upon  which  volition,  sensation,  imagination,  and  thought  are  based.  Every 
portion,  independently  of  the  others,  is  connected  by  conducting  paths  with  all 
of  the  voluntary  muscles,  and  on  the  other  hand,  with  all  of  the  sensory  nerves  of 
the  body. 

After  removal  of  an  anterior  lobe,  including  the  motor  zone,  there  develop 
first  unilateral  motor  and  sensory  paralysis  and  unilateral  visual  disturbance. 
Of  these  only  the  loss  of  muscle-sense  is  left  after  the  lapse  of  months.  Removal 
of  the  anterior  lobe  on  both  sides  gives  rise  to  these  phenomena  in  more  marked 
degree,  and  in  addition  there  occur  innumerable  involuntary  associated  move- 
ments and  increased  reflex  irritability.  Goltz  observed  repeatedly  general  hyper- 
esthesia,  a  remarkable  motor  propensity  and  an  irritable  aggressive  character  in 
the  dog.  Marked  permanent  disorders  in  the  utilization  of  the  senses  of  sight, 
hearing,  smell,  and  taste  are  not  necessarily  present,  even  in  connection  with  pro- 
found and  extensive  destruction  of  the  forebrain. 

Removal  of  the  occipital  lobes  disturbs  the  utilization  of  the  sense-perceptions 
in  consequence  of  the  defect  of  intelligence  present.  The  sense  of  sight  is  injured 
most.  Removal  of  the  occipital  lobe  on  both  sides  causes  marked  disturbance 
of  vision,  but  not  total  blindness.  In  character  the  dogs  become  good-natured 
and  considerate.  There  are  never  disorders  of  movement  and  of  the  muscular 
sense. 

According  to  Loeb,  a  pupil  of  Goltz,  the  disorders  of  vision,  of  sensibility, 
and  of  motility  that  develop  after  partial  injury  of  the  cortex  can  be  summarized 
as  follows:  On  the  opposite  side  stimulation  of  the  retina  and  the  sensory  nerves 
causes  less  marked  effects  that  appear  more  slowly.  Likewise  the  stimulation 
of  the  muscles  in  connection  with  intended  movements  of  the  body  is  less  marked 
upon  the  opposite  side  of  the  body. 

Injuries  of  the  cerebrum  give  rise  also  to  inhibitory  phenomena,  including 
motor  disturbances;  and  Goltz  considers  the  complete  hemiplegia  that  is 
not  rarely  observed  after  coarse  unilateral  injuries  of  the  cortex  as  an  inhibitory 
phenomenon.  The  injury  exerts  an  inhibitomotor  influence  upon  other  (infra- 
cortical)  organs,  which  resume  their  movement  as  soon  as  the  inhibitory  influence 
is  removed. 

Other  Cerebral  Functions. — Some  investigators  have  observed  variations  in 
blood-pressure  and  change  in  the  heart-beat  after  irritation  of  the  cerebral  cortex ; 
thus,  for  example,  Bochefontaine  after  electrical  irritation  of  the  motor  area  for 
the  extremities.  After  irritation  of  the  cortical  center  for  the  facial  nerve  (Fig. 
258,  5)  R.  Danilewsky  observed  increase  in  the  blood-pressure,  the  pulse  being  at 
first  accelerated  and  later  slowed  (and  also  upon  irritation  of  the  caudate  nucleus 
and  the  adjacent  white  matter).  At  the  same  time,  he  observed,  under 
such  conditions,  slowing  and  at  times  interruption  of  the  respiration.  Balogh 
observed  acceleration  of  the  pulse  after  irritation  of  various  portions  of  the  cortex 
in  the  dog  and  slowing  of  the  pulse  after  irritation  of  one  point.  Eckhard  irri- 
tated the  surface  of  the  cerebrum  in  rabbits  and  found,  as  a  rule,  that  so  long  as 
only  a  few  contralateral  movements  take  place  in  the  anterior  extremities,  no 
influence  upon  the  heart  is  observed,  but  that  cardiac  symptoms  appear  only  in 
association  with  the  occurrence  of  other  movements.  They  consist  in  slower, 
stronger  pulse-beats,  intermixed  with  feebler  beats,  together  with  slight  increase 
in  the  blood -pressure.  If  the  vagus  on  each  side  be  first  divided  the  influence 
upon  the  pulse-beat  is  not  exhibited,  but  the  elevation  of  the  blood -pressure 
persists.  All  of  these  experiments  fail  to  afford  a  satisfactory  explanation  of 
the  relations  of  the  cerebrum  to  the  action  of  the  heart.  That  such  a  relation 
exists  is  indicated  indubitably  by  the  effect  of  psychic  influences  upon  the  heart- 
beat, as  Homer  and  Chrysippus  knew. 

Irritation  of  the  cortex  laterally  from  the  base  of  the  olfactory  tract  exerts 
a  slowing  or  inhibitory  influence  upon  respiration,  while  irritation  in  the 
motor  regions  has  an  accelerating  influence,  and  irritation  of  the  uncinate  gyrus 
causes  sniffing.  Unverricht  observed  arrest  of  respiration  in  the  dog  on  irritation 


THE  CORTICAL  THERMIC  CENTER.  7QI 

of  a  point  in  the  third  primitive  convolution  external  to  the  center  for  the 
orbicularis  of  the  eyelids.  Preobraschensky  observed  inspiratory  spasm  of  the 
diaphragm  in  the  cat  after  irritation  of  a  point  behind  this  center.  The  increased 
secretion  of  saliva  observed  by  Landois  has  been  referred  to  on  page  262. 

According  to  v.  Bechterew  and  Ostankow  a  point  irritation  of  which  causes 
swallowing  movements  is  situated  externally  to  the  cruciate  sulcus.  Bochefon- 
taine  and  L6pine  observed  further,  particularly  after  irritation  in  the  neighbor- 
hood of  the  cruciate  sulcus  in  dogs,  slowing  of  the  movements  of  the  stomach, 
peristalsis  of  the  intestines,  contraction  of  the  spleen,  the  uterus,  and  the  bladder, 
and  increased  respiratory  frequency.  Bufalini  observed  the  occurrence  of  secre- 
tion of  the  gastric  juice  with  elevation  of  the  temperature  in  the  stomach  after 
irritation  of  the  same  cortical  area  whose  irritation  in  rabbits  caused  movements 
of  the  jaw.  The  relations  of  the  region  about  the  cruciate  sulcus  in  the  dog  to 
the  cardia  are  considered  on  page  281.  According  to  Bechterew  and  Mislawski 
irritation  of  various  points  in  this  region  causes  in  part  movements  at  the  pylorus, 
and  in  part  inhibition  of  such  movements;  occasionally  the  cardia  is  set  in  motion. 
From  the  same  point  and  from  the  third  primitive  convolution  situated  poste- 
riorly and  externally  contraction  and  relaxation  of  the  muscles  of  the  perineum  can 
be  induced,  and  also  from  the  optic  thalami.  The  conducting  paths  are  contained 
in  part  in  the  vagi,  in  part  in  the  spinal  cord.  From  the  latter  the  fibers  for  the 
small  intestine  pass  through  the  eight  lower  dorsal  and  the  uppermost  lumbar 
nerves  in  the  dog  to  the  sympathetic  plexus,  those  for  the  large  intestine  through 
the  last  two  lumbar  and  the  upper  three  sacral  nerves.  The  foregoing  statements 
afford  an  explanation  of  the  fact  that  in  epileptic  attacks  induced  by  irritation 
of  the  cortex  contraction  of  the  stomach,  the  intestine,  and  the  bladder  have  also 
been  observed. 

Electrical  stimulation  of  the  inner  portion  of  the  sigmoid  gyrus  in  the  dog 
causes  dilatation  of  the  pupils  (as  does  also  chemical  irritation  of  the  parietal 
region  in  the  rabbit) ;  secretion  of  tears,  protrusion  of  the  eyeballs,  and 
retraction  of  the  third  eyelid  in  the  dog.  Increased  contractions  of  the  vagina 
in  rabbits  could  be  induced  by  irritation  of  the  anterior  portion  of  the  hemisphere, 
in  dogs  by  irritation  of  the  sigmoid  gyrus.  By  irritation  in  the  neighborhood, 
or  by  increased  irritation,  an  inhibitory  effect  could  be  induced.  Irritation  of 
the  optic  thalamus  or  of  the  central  stump  of  the  vagus  likewise  gave  rise  to  in- 
crease in  the  movements,  while  irritation  of  the  peripheral  stump  of  the  vagus 
caused  relaxation  of  the  vagina. 

Attention  should  finally  be  directed  to  a  number  of  observations  of  pathological 
significance  made  after  injuries  to  the  brain.  Thus,  Schiff,  Ebstein,  Klosterhalfen, 
and  v.  Preuschen  observed,  after  injuries  to  the  pons,  the  striate  body,  the  optic 
thalamus,  the  cerebral  peduncle,  the  quadri geminate  bodies,  the  middle  cere- 
bellar  peduncle,  and  the  medulla  oblongata,  often  hyperemia  and  extravasations  of 
blood  into  the  lungs,  the  pleurae,  the  stomach,  the  intestines,  and  the  kidneys. 
In  this  manner  is  to  be  explained  the  occurrence  of  hemorrhage  into  the  stomach 
in  new-born  infants  with  injury  to  brain  (melasna  neonatorum) ;  perhaps  also  the 
occurrence  of  gastric  ulcer  in  adults  in  association  with  cerebral  disease,  v.  Preu- 
schen observed  gastric  and  intestinal  hemorrhage  in  rabbits  also  after  injury  of 
the  cornu  Ammonis,  the  floor  of  the  anterior  horn,  the  frontal  lobe,  and  the  upper 
portion  of  the  spinal  cord.  Analogous  phenomena  have  been  observed  in  man 
after  cerebral  hemorrhage  or  softening.  Brown-Sequard  and  Nothnagel  induced 
hemorrhage  into  the  lungs  by  irritation  of  basal  portions  or  of  a  point  on  the 
surface  of  the  brain. 

The  cerebral  unilateral  acute  decubitus  described  by  Charcot  is  particularly 
noteworthy,  occurring  always  upon  the  paralyzed  side,  therefore  on  that  opposite 
to  the  cerebral  focal  lesion.  It  may  begin  as  early  as  the  second  or  the  third  day 
and  rapidly  progress  to  a  fatal  termination,  with  profound  destruction  (but- 
tock, lower  extremity).  The  decubitus  that  appears  in  connection  with  disease 
of  the  spinal  cord  generally  begins  in  the  middle  line  of  the  buttocks  and  spreads 
thence  symmetrically  toward  either  side.  In  cases  of  injury  of  one  side  of  the 
spinal  cord  this  destruction  takes  place  on  the  corresponding  side  of  the  sacrum. 

PHYSIOLOGICAL  TOPOGRAPHY  OF  THE  SURFACE   OF  THE 
CEREBRUM  IN  MAN. 

In  the  brain  of  man  the  physiologically  analogous  systems  of  fibers  receive 
medullary  sheaths  approximately  at  the  same  time,  the  olfactory  tract  among 


792  PHYSIOLOGICAL    TOPOGRAPHY    OF    SURFACE    OF    CEREBRUM. 

the  first.  According  to  Flechsig  the  cortex  is  developmentally  divisible  into  forty 
different  fields.  These  can  be  arranged  in  three  groups:  (a)  The  primordial 
areas,  which  are  formed  even  before  mature  birth;  (6)  intermediary  areas,  which 
begin  to  be  surrounded  with  medullary  tissue  up  to  one  month  after  birth;  (c] 
the  terminal  areas,  which  are  formed  later  than  one  month  (from  four  to  four  and 
a  half  months)  after  birth'.  The  primordial  areas  coincide  with  the  sense-centers 
in  their  rudimentary  form;  the  terminal  areas  comprise  association-areas;  and 
the  intermediary  areas,  amplifications  in  part  of  the  sense-centers  and  in  part  of 
the  association-centers.  The  human  brain  is  distinguished  from  that  of  the 
anthropoids  principally  through  the  terminal  areas.  They  vary  in  size  in  different 
individuals  and  they  contribute  in  large  measure  to  the  shape  of  the  human 
skull,  under  the  eminences  of  which  they  are  situated.  Thus,  for  example,  the 
anthropoids  are  unprovided  with  the  area  destruction  of  which  causes  pure  alexia. 
For  this  reason  alone  apes  cannot  acquire  the  faculty  of  speech. 

The  motor  areas  comprise  the  anterior  (Fig.  246,  A)  and  posterior 
(B)  central  convolutions,  and  the  paracentral  lobule,  and  extend  pos- 
teriorly into  the  precuneus  (Fig.  262).  They  contain  large  ganglion  - 
cells,  which,  however,  are  not  present  before  the  age  of  one  and  one-half 
months.  Degeneration  of  the  entire  area  causes  paralysis  of  the  opposite 
side  of  the  body.  This  at  first  is  total,  but  gradually  passes  into  a  con- 
dition in  which  especially  all  of  the  delicate  movements  under  the  control 
of  the  will  and  acquired  by  education  and  exercise  are  abolished,  while 
associated  and  bilateral  movements  (which,  for  example,  are  present  in 
animals  that  after  birth  are  at  once  capable  of  executing  various  complex 
movements)  are  preserved  more  or  less  intact.  Therefore,  the  hand  is 
paralyzed  in  man  in  greater  degree  than  the  arm,  and  this  in  turn  in 
greater  degree  than  the  leg,  the  lower  branches  of  the  facial  nerve  in 
greater  degree  than  the  upper,  and  the  nerves  of  the  trunk  finally  almost 
not  at  all. 

In  hemiplegic  individuals  the  strength  of  the  unparalyzed  side  of  the  body 
is  also  impaired.  This  is  not  fully  explained  by  the  fact  that  some 
fibers  of  the  pyramidal  tracts  remain  upon  the  same  side  of  the  body.  Among 
the  movements  in  human  beings  there  are  some  that  have  to  be  learned  with  great 
effort,  and  therefore  gradually  become  subordinated  to  the  varying  impulses  of 
the  will,  such,  for  example,  as  the  delicate  movements  of  the  hands.  These 
movements  are  restored  but  slowly  and  incompletely  or  not  at  all  after  lesions 
of  the  psychomotor  centers.  Those  movements,  however,  that  are  at  once  at 
the  command  of  the  body,  such  as  the  associated  movements  of  the  eyes,  the 
face,  in  part  also  of  the  lower  extremities,  either  recover  rapidly  after  the  lesions 
described,  or  they  appear  to  suffer  but  little  at  all.  Thus,  the  facial  muscles 
appear  never  to  be  so  completely  paralyzed  after  a  cortical  lesion  as  after  a  lesion 
of  the  trunk  of  the  facial  nerve;  for  example  the  eye  can  yet  be  closed  fairly 
well.  Sucking  movements  have  been  observed  even  in  hemicephalic  new-born 
children. 

From  the  motor  cortical  centers  the  path  for  the  fibers  of  the  facial 
and  hypoglossal  nerves  passes  through  the  genu,  that  for  the  muscles  of 
the  extremities  through  the  middle  third  of  the  posterior  limb  of  the 
internal  capsule  (Fig.  263).  Irritation  of  these  paths  causes  movement 
in  the  muscles  on  the  opposite  side.  After  destruction  of  the  cortical 
areas  degeneration  takes  place  in  these  corticomotor  paths,  which  pass 
downward  and  whose  continuation  is  designated  the  pyramidal  tracts. 
This  degeneration  has  been  found  within  the  white  matter  below  the 
cortex,  in  the  genu,  and  in  the  anterior  two-thirds  of  the  posterior  divi- 
sion of  the  internal  capsule,  in  the  cerebral  peduncle  (middle  portion  of 
the  lower  free  circumference  of  the  crusta,  where  the  tracts  for  the  ex- 
tremities and  the  nerves  of  the  trunk-muscles  lie  externally  and  those  for 
the  motor  nerves  of  the  head  internally),  in  the  pons,  in  the  pyramids 


PHYSIOLOGICAL  TOPOGRAPHY  OF  SURFACE  OF  CEREBRUM. 


793 


of  the  medulla  (Fig.  261),  and  thence  in  the  pyramidal  tracts  of  the 
spinal  cord.  It  is  obvious  that  lesions  of  these  tracts  at  any  point  in 
their  course  must  have  the  same  effect,  namely  hemiplegia.  In  the 
progress  of  the  degenerative  process  the  paralyzed  muscles  may  exhibit  a 
certain  degree  of  spastic  rigidity  and  an  increase  of  irritability  to  mechan- 
ical stimulation  (tendon-reflexes),  which  must  be  considered  as  an  irrita- 
tive degeneration  phenomenon.  Later  on,  degenerative  changes  are  ob- 
served in  the  ganglion-cells  of  the  anterior  horn  and  in  consequence  of 
these,  atrophy  and  disappearance  of  the  related  muscles. 


cm 


02 


FIG.  260. — The  Cerebrum  with  the  Principal  Convolutions  and  Sulci  (after  A.  Ecker)  in  its  Longitudinal  Rela- 
tion to  the  Skull:  S,  the  Sylvian  fissure,  with  its  vertical  ascending  short  anterior  limb  and  its  horizontal  pos- 
terior longer  limb;  C,  the  central  fissure  or  sulcus,  or  fissure  of  Rolando;  A  anterior,  B  posterior  central 
convolution ;  Fj  superior,  F2  middle,  F3  inferior  frontal  convolution;  f i  superior,  f2  middle,  f3  vertical 
frontal  fissure  (precentral  sulcus);  P,,  superior  parietal  lobule;  P2,  inferior  parietal  lobule,  with  P2  indicating 
the  supramarginal  gyrus  and  P..,1  angular  gyrus;  ip,  interparietal"  sulcus;  cm,  extremity  of  the  callosomargi- 
nal  sulcus;  Ot  first,  O2  second,  O3  third  occipital  convolution;  po,  parieto-occipital  fissure;  o,  transverse 
occipital  sulcus;  o2,  inferior  longitudinal  sulcus;  T,  first,  T2  second,  T3  third  temporal  convolution;  tt  first, 
t2  second  temporal  fissure;  Klf  K2,  Ks,  points  in  the  sagittal  suture;  L,,  L2,  points  in  the  lambdoid  suture. 

The  muscular  atrophy  is  not  always  proportionate  to  the  intensity  of  the 
paralysis.  Perhaps  special  trophic  fibers,  separated  from  the  motor  fibers,  and 
situated  nearer  the  sensory  fibers,  pass  from  the  cerebrum  downward  through 
the  internal  capsule.  The  tract  for  the  seventh,  eleventh,  and  twelfth  cerebral 
nerves  is  situated  in  the  genu  of  the  internal  capsule.  The  tracts  for  the  rotation 
of  the  eyes,  the  muscles  of  the  trunk  and  the  nape  of  the  neck  are  situated  on  either 
side  in  the  internal  capsule  for  both  sides  of  the  body. 

According  to  observations  of  Flechsig  and  Hoesel  it  appears  that  the  motor 
area  is  at  the  same  time  the  sensory  center  for  the  muscle-sense  and  innervational 


794     PHYSIOLOGICAL  TOPOGRAPHY  OF  SURFACE  OF  CEREBRUM. 

impressions.  Therefore,  the  larger  portion  of  the  ascending  fibers  in  the  posterior 
columns  of  the  medulla  must  pass  to  the  central  convolutions.  By  others  the 
superior  parietal  lobule  (Pt)  is  considered  as  the  seat  for  impressions  of  position 
and  movement.  The  conducting  tracts  are  believed  to  be  situated  immediately 
behind  the  motor  tracts  in  the  internal  capsule.  It  is  a  noteworthy  fact  that, 
in  man,  on  the  one  hand  exclusive  loss  of  muscle-sense  or  of  conception  of  position 
has  been  observed,  and  on  the  other  hand  also  pure  motor  paralysis  without  a 
lesion  of  the  former. 

The  psychomotor  centers  may  also,  at  times,  be  stimulated  to  activity  through 
psychic  influences  (grimace,  pantomime,  gesture),  at  times  be  inhibited  through 
psychic  shock  ("paralyzed  by  fright,"  "  spell-bound  with  fear,"  "speechless  from 
grief,"  etc.).  On  stimulation  of  voluntary  movements  within  certain  muscles 
an  inhibitory  mechanism  in  the  cortex  at  the  same  time  becomes  effective  and 
renders  the  adjacent  cortical  centers  inactive.  If  this  inhibition  is  enfeebled,  un- 
intentional associated  movements  take  place.  Thus,  in  children,  for  instance, 
associated  movements  of  the  mouth  are  observed  during  writing  exercises. 

Pathological. — Irritation  of  the  psychomotor  areas  from  internal  pathological 
causes  may  give  rise  to  maniacal  motor  activity,  for  example  in  the  state  of  so- 
called  "possession."  Involuntary  twitchings  in  individual  muscles  due  to  irri- 
tation of  the  motor  centers  occur  in  the  condition  of  paramyoclonus  multiplex. 
Deficient  activity  of  the  previously  referred  to  inhibition  of  the  psychomotor 
centers  is  capable  of  causing  cerebral  chorea.  In  analogy  with  the  ataxic  motor 
states  in  animals  first  described  by  Landois  there  occurs  also  in  human  beings 
a  condition  of  cerebral  ataxia.  The  cerebral  paralysis  of  childhood  is  due  to 
degenerative  inflammatory  processes  in  the  motor  areas.  In  acephalous  fetuses 
marked  deficiency  in  the  development  of  the  pyramidal  tracts  has  been  observed. 

In  man  the  entire  system  of  the  pyramidal  tracts  may  undergo  degeneration 
also  from  internal  causes.  Paralysis,  spastic  contractures,  and  atrophy  of  the 
muscles  of  the  body  (on  one  side  or  upon  both  sides)  are  characteristic,  as  observed 
in  the  amyotrophic  lateral  sclerosis  of  the  spinal  cord  of  Charcot.  In  childhood 
the  normal  development  of  the  pyramidal-tract  system  may  fail  to  take  place 
and  cerebrospinal  paralysis  thus  result. 

Well-observed  clinical  cases  aid  in  the  localization  of  the  individual  motor 
subcenters.  (i)  The  center  for  the  movement  of  the  leg  is  situated  in  the 
vicinity  of  the  upper  extremity  of  the  fissure  of  Rolando  (Fig.  260,  C),  and  in  the 
paracentral  lobule  (Fig.  262,  A  B}.  (2)  The  center  for  the  upper  extremity  is 
situated  in  the  middle  third  of  the  anterior  central  convolution  or  somewhat 
lower  (Fig.  260).  The  center  for  the  thumbs  and  the  fingers  is  situated  in  the 
posterior  central  convolution  below  the  center  for  the  upper  extremity.  (3)  The 
center  for  the  facial  nerve  is  situated  at  the  lower  extremity  of  the  anterior  central 
convolution  (center  for  the  mouth  and  the  lower  portion  of  the  face) .  The  lower 
third  of  the  anterior  central  convolution  on  the  left  and  the  adjacent  foot  of 
the  second  and  third  frontal  convolutions  contains,  on  each  side,  the  center  for 
the  trigeminus  (movement  of  mastication).  The  anterior  portion  of  the  ante- 
rior central  convolution  is  connected  with  the  hypoglossal  nerve.  The  most 
anterior  and  inferior  portion  of  the  anterior  central  gyrus  appears  to  be  the  seat 
controlling  the  action  of  the  tensors  of  the  vocal  bands.  The  island  of  Reil  con- 
trols the  movements  of  the  vocal  bands.  (4)  The  portion  of  the  frontal  lobe 
lying  in  front  of  the  middle  third  of  the  anterior  central  convolution  controls 
the  muscles  of  the  nape  of  the  neck.  The  centers  for  the  muscles  of  the  trunk 
are  situated  upon  the  surface  of  the  anterior  central  convolution  above  the  centers 
for  the  upper  extremity.  (5)  The  external  ocular  muscles  appear  to  have  their 
cortical  center  in  the  angular  gyrus  (Fig.  260,  P2l).  The  centers  for  the  lateral 
movement  of  the  head  and  the  eyes  are  situated  in  the  posterior  portion  of  the 
second  frontal  convolution. 

The  motor  centers  may  be  paralyzed  either  individually  or  collectively,  and 
accordingly  cortical  oculomotor  monoplegia,  crural  (rare),  brachial,  brachiocrural, 
linguofacial,  and  finally  faciobrachial  forms  of  monoplegia  have  been  distinguished. 

If  the  motor  centers  are  irritated  by  morbid  processes — particularly 
hyperemia  and  inflammation  of  syphilitic  origin,  rarely  tubercle,  tumors, 
cysts,  cicatrices,  splinters  of  bone — convulsive  movements  take  place  in 
the  related  groups  of  muscles.  Those  muscles  that  are  usually  moved 
upon  both  sides  appear  thus  to  be  stimulated  from  one  center. 


PHYSIOLOGICAL    TOPOGRAPHY    OF    SURFACE    OF    CEREBRUM. 


795 


In  accordance  with  their  seat  these  convulsive  movements  are  designated 
facial,  brachial,  crural  monospasm,  and  the  like.  Such  movements  naturally 
may  also  involve  several  centers  at  the  same  time.  In  men  with  the  surface  of 
the  hemisphere  freely  exposed,  the  region  of  the  motor  centers  has  been  success- 
fully stimulated  by  electricity  by  Bartholow,  Sciamanna,  and  others. 

If  intense  irritation  be  applied  upon  one  side  bilateral  convulsive 
movements  with  suspension  of  consciousness  may  occur  (properly  desig- 
nated Jacksonian  or  cerebral  epilepsy). 

The  following  observations  have  been  made  bearing  upon  the  center  for 
voluntary  combined  movements  of  the  eyes  in  the  cortex  in  man :  Both  eyeballs 
are  controlled  from  each  hemisphere.  In  the  presence  of  paralyzing  lesions  of 
the  cortex  or  of  the  tracts  that  pass  off  from  it  both  eyeballs  are  occasionally 
found  in  a  state  of  lateral  deviation.  If  the  paralyzing  lesion  be  situated 
in  a  cerebral  hemisphere  con- 
jugate deviation  of  the  eye- 
balls takes  place  toward  the 
unaffected  side.  If,  how- 
ever, it  be  seated  in  the 
conducting  tracts,  where  de- 
cussation  has  already  taken 
place,  namely  in  the  pons,  the 
deviation  of  the  eyes  takes 
place  toward  the  paralyzed 
side.  If  the  seat  of  the  lesion 
is  in  a  state  of  irritation  caus- 
ing contractions  on  one  side 
of  the  body,  the  deviation  of 
the  eyes  is  naturally  in  a  direc- 
tion opposite  to  that  in  which 
it  would  be  in  association  with 
paralysis.  In  cases  of  cere- 
bral paralysis  there  is  occa- 
sionally, instead  of  the  marked 
lateral  deviation  of  the  eye- 
balls, only  a  paresis  of  the 
lateral  rotators  of  the  eyeballs, 
so  that  though  during  rest  the 
eyes  are  not  rotated  toward 
the  unaffected  side,  they  can- 
not be  adequately  rotated  to- 
ward the  affected  side.  Also 
the  elevator  of  the  upper  eye- 
lid appears  to  have  its  center  in  the  angular  gyrus;  but  according  to  some 
observers  this  is  situated  in  the  posterior  limb  of  the  second  frontal  convolution, 
extending  into  the  first  frontal  convolution. 

The  motor  speech-center,  which  controls  the  voluntary  movements 
of  the  tongue  (hypoglossal  nerve)  and  the  mouth  (facial  nerve),  including 
the  lower  jaw  (third  division  of  the  fifth  nerve),  is  situated  in  most  per- 
sons in  the  left  third  frontal  convolution  (Fig.  260,  F3).  The  fact 
that  most  persons  are  right-handed  also  indicates  a  more  refined  develop- 
ment of  the  motor  apparatus  for  the  upper  extremity  in  the  left  hemi- 
sphere. Human  beings  with  well-developed  right-handedness  are  ob- 
viously left -brained.  Perhaps  this  arrangement  is  dependent  upon  an 
embryological  basis.  By  far  the  majority  of  persons  are  thus  left- 
brained  speakers,  although  there  are  exceptions.  As  a  matter  of  fact, 
left-handed  persons  have  been  observed  to  lose  the  faculty  of  speech 
after  lesions  of  the  right  hemisphere. 

Studies  of  the  brains  from  distinguished  men  have  shown  that  in 
them  the  third  frontal  convolution  attains  a  greater  size  and  a  less  simple 


FIG.  261. — Secondary  Degeneration  of  the  Motor  Tracts  in  the 
Cerebral  Peduncle,  the  Pons  and  the  Pyramid.  The  shaded 
areas  (*)  are  degenerated  (after  Charcot). 


796          PHYSIOLOGICAL    TOPOGRAPHY    OF    SURFACE    OF    CEREBRUM. 

form  than  in  the  brains  from  persons  of  lower  grade  of  intelligence.  In 
deaf-mutes  this  convolution  is  exceedingly  simple  and  in  microcephalic 
fetuses  and  in  apes  it  is  merely  rudimentary. 

Injuries  of  this  speech-center,  as  well  as  transitory  functional  dis- 
orders, for  example  in  consequence  of  copious  hemorrhage,  are  followed 
either  by  loss  or  at  least  by  more  or  less  considerable  derangement  of 
the  faculty  of  speech.  The  loss  of  the  faculty  of  speech  is  designated 
aphasia.  Stimulation  of  this  region  causes  sensations  of  speech-movement, 
which  occur  rarely,  the  sensations  often  being  referred  by  the  patients, 
for  example  paralytics,  to  other  parts  of  the  body. 


FIG.  262. — View  of  the  Median  Surface  of  the  Human  Brain:  CC,  the  divided  corpus  callosum;  F',  first  frontal 
convolution  continuous  at  a  with  the  anterior  central  convolution  04);  B,  posterior  central  convolution; 
between  A  and  B  is  the  median  extremity  of  the  fissure  of  Rolando  (AB  designated  paracentral  lobule);  Gf, 
gyrus  fornicatus,  bounded  by  the  callosomarginal  fissure  (cm}  from  the  first  frontal  and  the  central  convolu- 
tions. The  callosomarginal  fissure  (cm  in  Fig.  260)  passes  upward  between  B  and  P  (the  superior  parietal 
lobule);  po,  the  parieto-occipito  fissure  (po  in  Fig.  260)  separates  the  occipital  lobe  (O)  from  the  parietal 
lobe  (P);  Q,  quadrate  lobe  (precuneus);  Cu,  cuneus;  cc,  calcarine  fissure;  Lg,  lingual  lobe  (median  occipito- 
temporal  gyrus);  Fs,  fusiform  lobule  (lateral  occipito-temporal  gyrus);  H,  hippocampal  gyrus;  U,  uncinate 
gyrus;  h,  hippocampal  sulcus;  F,  frontal,  P,  parietal,  O,  occipital  lobe. 


The  motor  .tract  for  speech  passes  from  the  third  frontal  convolution  first  along 
the  upper  margin  of  the  island  of  Reil,  then  in  the  depth  of  the  hemisphere  in- 
ternally to  the  posterior  margin  of  the  lenticular  nucleus,  and  then  through  the 
crusta  of  the  left  cerebral  peduncle  and  the  left  half  of  the  pons  to  the  medulla 
oblongata,  the  seat  of  the  nuclei  of  all  the  motor  nerves  concerned  in  the  act  of 
speaking — trigeminus,  facial,  hypoglossus,  vagus,  respiratory  nerves.  Total 
destruction  of  this  motor  tract  causes,  therefore,  total  aphasia.  Partial  lesions 
cause  more  or  less  coarse  derangement  of  the  mechanism  of  articulation,  which 
has  been  designated  anarthria. 

Three  types  of  activity  are  necessary  for  the  function  of  speech :  i . 
The  normal  movement  of  the  speech-apparatus — tongue,  lips,  mouth, 
respiratory  apparatus.  2.  A  knowledge  of  the  symbols  for  objects  and 
ideas — speech,  writing,  and  gesture.  3.  The  correct  association  of  the 
two.  Therefore,  the  following  essentially  different  forms  of  aphasia 
must  be  distinguished: 


PHYSIOLOGICAL    TOPOGRAPHY    OF    SURFACE    OF    CEREBRUM.  797 

1.  Ataxic  aphasia,  or  psychomotor  aphasia,    is  loss   of  the  power  of  speech 
in  consequence  of  inability  to  execute  in   a  coordinate  manner  the  movements 
necessary  for  speech.     Under  such  circumstances,  the  ability  has  been  lost  to 
form  a  conception  of  the  movements  for  speech,  as  well  as  the  power  also  of  recog- 
nizing the  position  of  the  organs  of  speech.     The  intention  to  speak  causes  in- 
coordinate  grimaces  and  the  utterance  of  inarticulate  sounds.     Therefore,  the 
patients  are  unable  to  repeat  what  is  spoken  to  them.     At  the  same  time,  the 
mental  processes  necessary  for  the  faculty  of  speech  are  wholly  preserved,  and  all 
words  are  probably  retained  in  memory,  so  that  some  are  still  able  to  express 
themselves  in  writing.     If,  however,  the  delicate  movements  acquired  by  edu- 
cation that  are  necessary  for  writing  are  lost  in  consequence  of  a  lesion  of  possibly 
a  special  center  at  the  extremity  of  the  second  frontal  convolution  there  results 
at  the  same  time  ataxic  agraphia,  that  is  an  inability  to  perform  the  movements 
necessary  for  writing.     The  intention  to  record  thought  on  paper  results  only 
in  an  illegible  scrawl.     At  times  even  pantomime-speech  may  be  interfered  with 
under  such  circumstances — am-im-ia.     There  may  be  also  a  purely  functional  hys- 
terical aphasia. 

2.  Amnesic   aphasia   or   psycho  sensor ial   aphasia,   a   condition   in   which   the 
memory  of  words  is  lost.     Occasionally,  only  certain  groups  of  words  are  lost, 
or  even  only  portions  of  certain  words,  so  that  these  may  be  produced  in  a  de- 
formed  or  partial   manner.     The   movements   necessary   for  speech   are  intact. 
Therefore,  the  patient  is  capable  of  repeating  at  once  all  that  is  spoken  to  him 
or  of  writing  on  dictation.     In  polyglot  individuals  all  forms  of  language  are  lost 
and  not  only  one.     Amnesic  aphasia  has  been  observed  in  connection  with  de- 
struction of  the  first  temporal  convolution  on  the  left.     There  is  also  a  combined 
form  of  ataxo-amnesic  aphasia.     In    another  variety  of  amnesic    aphasia  while 
the  words  are  still  retained  in  memory,  they  cannot  be  expressed  fluently,  that 
is  the   association  of  word  and  conception  is  inhibited.     The  failure  to  recall 
persons  and  the  names  of  objects  is,  particularly  in  advanced  age,  a  phenomenon 
observed  within  physiological  limits,  but  which  eventually  may  terminate  in  senile 
amnesia.     Kussmaul  has,  further,  included  among  the  cerebral  derangements  of 
speech  the  following  special  varieties: 

3.  Paraphasia,  or  the  inability  to  associate  correctly  the  word-images  with 
their  conceptions,  so  that,  instead  of  intelligent  word-pictures,  reversed  or  wholly 
incomprehensible  word-pictures  are  aroused.     There  occurs  to  a  certain  degree 
permanent  confusion  of  speech. 

4.  Agrammatism  and  acataphasia,  or  the  inability  correctly  to  form  words 
grammatically  and  to  arrange  them  syntaxically  in  sentences.     In  addition  there 
may  be: 

5.  Abnormal  slowness  of  speech,  bradyphasia,  or  abnormal  acceleration  of  speech 
(tumultus  sermonis),  a  lisping  or  abnormally  slow  speech,  which  likewise  are  de- 
pendent upon  cortical  disorders.     Derangements  of  speech  that  are  'dependent 
upon  affections  of  the  peripheral  nerve  or  the  muscles  of  the  organs  of  voice  and 
speech  have  been  described  on  pages  617,  697  and  713. 

The  faculty  of  musical  expression  may  be  preserved  or  lost  in  connection  with 
aphasia — amusia,  note-blindness,  sound-deafness;  it  is  perhaps  represented  by 
a  special  cortical  center,  possibly  situated  in  the  posterior  portion  of  the  first 
and  second  temporal  convolutions. 

The  cortical  thermic  center  for  the  extremities  discovered  by  Eulen- 
burg  and  Landois  is  at  the  same  time,  related  to  the  localization  of  the 
motor  points.  There  are  observations  on  record  of  injury  or  degenera- 
tion in  these  areas,  with  inequality  in  the  temperature  on  the  two  sides 
of  the  body.  After  the  existence  of  paralysis  for  a  considerable  length 
of  time  the  temperature  of  the  affected  members,  which  at  first  is  higher, 
may  become  lower  than  that  of  the  unaffected  side.  Stimulation  of  this 
area  gives  rise  also  to  increase  in  the  blood-pressure,  as,  for  example,  in 
connection  with  epileptic  convulsions.  Wounds  made  for  the  exposure 
of  the  brain  therefore  usually  bleed  more  freely  during  such  an  attack. 
According  to  Schiiller  the  center  for  the  entire  contralateral  half  of  the 
body  is  situated  just  in  front  of  the  precentral  gyrus  in  the  second  tem- 
poral convolution. 


798  PHYSIOLOGICAL    TOPOGRAPHY    OF    SURFACE    OF    CEREBRUM. 

In  cases  of  progressive  paralysis  of  the  insane,  attended  with  inflammation 
of  the  cerebral  cortex,  the  temperature  in  the  axilla  is  usually  higher  upon  the 
side  on  which  the  paralytic  phenomena  are  situated.  Conversely,  in  the  case  of 
convulsions  caused  by  inflammatory  irritation  of  the  cortical  centers,  the  tem- 
perature upon  the  contralateral  side  is  several  tenths  of  a  degree  lower  during 
their  continuance.  If  extensive  vascular  areas  are  paralyzed,  the  temperature 
of  the  body  may  fall,  for  example  in  paralytics  to  as  low  as  25°  C. 

Degeneration  of  the  internal  capsule  gives  rise  to  vasomotor  disorders  and 
from  this  fact  it  is  to  be  concluded  that  the  tracts  for  the  thermic  fibers  pass 
through  this  structure.  The  morbidly  increased  flushing  from  psychic  influences, 
particularly  from  fear  preceding  the  onset  of  the  flushing  (erythrophobia) ,  has 
been  attributed  by  v.  Bechterew  and  Mislawski  to  irritation  of  the  area  discovered 
by  them  to  have  vasodilator  effects  as  a  result  of  experiments  on  dogs. 

The  sensorial  areas  or  the  sense-centers  are  the  situations  in  which 
conscious  perception  of  sense-impressions  takes  place.  In  addition, 
they  constitute  also  the  substratum  of  sensory  conceptions  and  of  sensory 
memory.  The  sense-centers  are,  according  to  Flechsig,  developmentally 
primordial,  that  is  in  so  far  as  they  are  indicated  up  to  the  time  of  birth, 
and,  secondary,  in  so  far  as  they  attain  complete  development  with  their 
connections  at  a  later  period. 

The  psycho-optic  center,  visual  center,  visual  sphere,  comprises  in  its 
primordial  rudiment  up  to  the  time  of  birth  the  lips  of  the  calcarine 
fissure  (Fig.  262)  and  the  first  occipital  convolution.  In  its  secondary 
development  it  comprises  further  the  entire  median  surface  of  the  oc- 
cipital lobe,  on  the  convexity  only  a  small  zone  within  the  first  occipital 
convolution  and  the  occipital  pole,  but  not  the  external  occipital  gyri 
and  the  angular  gyms. 

According  to  clinical  observation  the  first  occipital  convolution  (Fig. 
246,  O1),  including  the  cuneus,  contains  the  optical  perception-field.  Ac- 
cordingly, destruction  of  this  region  on  one  side  cause  homonymous 
hemiopia.  To  the  patient  the  half  of  the  visual  field  of  the  same  side 
appears  not  as  black,  but  only  as  if  not  present  (deficiency  of  visual 
perception).  In  an  analogous  manner  irritative  conditions  on  one  side 
give  rise  to  photopsias  in  the  homonymous  halves  of  the  visual  fields. 
Hemiopia,  occasionally  associated  with  hallucinations  within  the  blind 
halves,  has  been  observed.  Injury  of  the  region  named  on  both  sides 
(also  the  effects  of  poisons,  such  as  alcohol  or  lead)  causes  total  blindness. 
Irritation  of  both  centers  gives  rise  to  manifestations  of  light  or  color,  or 
to  visual  hallucinations  in  the  entire  visual  field.  Cases,  further,  of 
cerebral  lesions  in  which  the  spatial  sense  and  the  light-sense  are  wholly 
intact,  while  the  color-sense  alone  is  destroyed,  indicate  that  the  center 
for  the  color-sense  must  be  especially  located  within  the  visual  center, 
perhaps  in  the  most  posterior  portion  of  the  fusiform  and  lingual  lobules 
(Fig.  262).  Color-hemiopia  has  even  been  observed. 

The  clinical  observations  of  hemiopia  teach  that  the  visual  field  of  each  eye 
can  be  divided  into  a  larger  external  and  a  smaller  internal  portion,  the  two  being 
separated  by  a  vertical  line  passing  through  the  yellow  spot.  The  right  or  left 
halves  of  both  visual  fields  are  controlled  from  one  hemisphere.  The  left  halves 
must  be  projected  upon  the  right  occipital  lobe  and  the  right  upon  the  left  occip- 
ital lobe.  Thus,  every  image,  on  binocular  vision,  if  not  too  small,  must  be  seen 
in  two  halves,  the  left  half  from  the  right  and  the  right  half  from  the  left  cerebral 
hemisphere.  The  yellow  spot  is  in  direct  connection  only  with  the  external 
geniculate  body,  and  the  connecting  fibers  terminate  in  the  wall  of  the  calcarine 
fissure.  It  is  a  remarkable  fact  that  in  case  of  bilateral  hemiopia  a  small  central 
field  of  visual  activity  is  preserved.  In  cases  of  hemiopia  also  the  action  of  the 
pupils  is  impaired. 


PHYSIOLOGICAL  TOPOGRAPHY  OF  SURFACE  OF  CEREBRUM.     799 

Exclusive  irritation  of  the  color-center  gives  rise  to  the  appearance  of  color- 
hallucinations,  as  observed  in  the  colored  aura  in  cases  of  epilepsy.  Colored 
vision  occurs  also  in  conjunction  with  other  cerebral  affections,  for  example  as 
erythropia.  Rarely,  the  subject  has  observed  everything  as  yellow,  or  blue,  or 
violet.  Some  poisons  give  rise  to  the  same  result  through  an  influence  upon  the 
cerebral  color-center:  yellow  vision  due  to  santonin,  red  vision  due  to  henbane, 
violet  vision  due  to  hashish.  Lesions  of  the  color-center  have  been  found  as  the 
result  of  cerebral  concussion  and  after  the  action  of  various  poisons,  permanent 
or  transitory,  total  or  partial  color-blindness  resulting. 

The  remaining  portion  of  the  center  contains  the  optical  memory- 
field,  destruction  of  which  gives  rise  to  mind-blindness,  in  case  of  a  lesion 
on  one  side  especially  upon  the  contralateral  side.  A  special  form  of 
this  condition  is  known  as  word-blindness,  the  individual  no  longer  recog- 
nizing the  symbols  of  writing — alexia.  The  area  comprises,  according 
to  Flechsig,  the  supramarginal  gyms  and  the  parietal  lobule.  Figures 
and  letters  appear  to  have  special  central  memory-fields. 

An  interesting  case  of  mind-blindness  may  be  cited.  After  severe  emotional 
disturbance  loss  of  the  memory  of  visual  perceptions  developed  suddenly  in  an 
intelligent  man.  Everything  with  which  he  had  been  familiar — persons,  streets, 
houses — appeared  entirely  strange  to  him  and  he  even  no  longer  recognized  his 
image  in  the  mirror.  On  attempting  to  read  or  figure  he  was  compelled  to  speak 
the  words  and  figures  aloud.  In  his  dreams  visual  images  were  entirely  wanting. 

In  consequence  of  morbid  irritation  of  the  visual  center,  pronounced  visual 
hallucination  may  develop  in  man,  principally  in  the  insane.  Famous  instances 
of  visual  hallucination  are  furnished  by  Jeanne  dArc,  Cardanus,  Swedenborg, 
Nicolai,  Justinus  Kerner,  Holderlin.  "The  spirit  and  the  demons  of  all  time, 
the  divine  vision  of  the  ascetics" — inanition-hallucinations  in  fasting  persons — 
"the  spiritual  representation  of  the  magician,  the  dream-object  and  the  hallu- 
cination of  the  febrile  and  insane  patient  are  one  and  the  same  phenomenon" 
(Johannes  Muller).  Cases  have  also  been  observed  in  which  hallucinations  were 
present  only  in  one  eye.  Occasionally,  these  are  seen,  for  example,  in  cases  of 
delirium  tremens,  principally  without  color,  therefore  gray. 

After  degeneration  of  the  cortical  center,  in  the  first  and  second  occipital 
convolutions,  cuneus  and  lingual  lobe,  the  fibers  degenerate  that  connect  the 
occipital  lobe  with  the  external  geniculate  body,  the  anterior  quadrigeminate 
body  and  the  pulvinar  of  the  optic  thalamus;  further,  these  structures  themselves 
and  later  on  the  origin  of  the  optic  tract  of  the  same  side. 

The  lower  in  the  animal  kingdom  one  descends  the  less  is  the  significance  of 
the  cortical  center,  and  of  the  external  geniculate  body  and  the  pulvinar, 
which  together  subserve  the  function  of  psychic  vision  in  the  higher  vertebrates, 
with  respect  to  the  act  of  vision,  while  at  the  same  time  the  anterior  quadrigeminate 
body  increases  in  size,  until,  finally,  in  fishes  it  constitutes  the  sole  visual  center. 

In  the  new-born  the  optic  radiation  to  the  cortex  is  yet  wanting,  developing 
only  in  the  course  of  weeks.  The  infant  is  also  up  to  this  time  without  psychic 
utilization  of  what  is  seen,  that  is  it  is  for  the  time  being  still  mind-blind.  The 
deeper  centers  alone  are  at  first  active  and  excite  only  reflex  action.  With  the 
development  of  the  cortical  center,  the  activity  of  the  deeper  centers  later  on 
diminishes  to  such  a  degree  that,  as  soon  as  consciousness  has  developed,  blind- 
ness occurs  after  destruction  of  the  psycho-optic  centers.  In  certain  varieties  of 
hysterical  impairment  of  vision  it  appears  that  while  the  cortical  center  is  still 
functionally  active  the  mind  of  the  patient  does  not  appreciate  what  is  seen. 

The  psycho-auditory  center  or  auditory  sphere  is  situated  on  each  side 
(crossed)  in  the  temporal  convolutions,  particularly  in  the  root  and  the 
posterior  portion  of  the  first  and  concealed  in  the  wall  of  the  fossa  of 
Sylvius.  Total  destruction  of  this  center  causes  deafness;  partial  injury 
on  the  left  side  may  give  rise  to  mind-deafness.  Among  the  phenomena 
of  the  latter  is  verbal  deafness,  which  has  been  observed  alone  and  also 
in  association  with  verbal  blindness.  Wernicke  found  in  cases  of  word- 
deafness  softening  in  the  posterior  third  of  the  first  temporal  convolution 
(T1)  on  the  left  (!),  and  Naunyn  designated  the  third  and  fourth  fifths 


800  PHYSIOLOGICAL    TOPOGRAPHY    OF    SURFACE    OF    CEREBRUM. 

as  the  active  areas.  Complete  deafness  occurs  only  on  destruction  of 
the  latter  areas  on  both  sides.  Word-deafness  is  followed  by  secondary 
atrophy  of  the  motor  speech-center. 

Verbal  blindness  and  deafness  may  be  included  clinically  in  the  group  of 
aphasic  disorders,  in  so  far  as  they  resemble  the  amnesic  variety.  The  word-deaf 
or  the  word-blind  patient  resembles  an  individual  who  in  early  youth  had  learned 
a  foreign  language,  which  in  later  life  he  has  completely  forgotten.  He 
hears,  therefore,  or  he  reads  well  the  words  and  the  symbols  of  writing  and  he  is 
able  also  to  repeat  the  words  spoken  to  him  and  to  write  them  on  dictation,  but 
he  has  entirely  lost  comprehension  of  the  signs.  While,  therefore,  the  amnesic 
aphasic  has  lost  only  the  key  of  the  door  to  his  speech-mechanism,  the  word-deaf 
or  word-blind  patient  has  lost  this  mechanism  itself.  From  a  case  in  which 
recovery  took  place  it  is  known  that  the  word  sounds  to  the  patient  like  a  confused 
murmur.  In  left-handed  persons  destruction  of  the  left  temporal  lobe  is  not 
followed  by  word-deafness,  as  in  them  the  center  is  probably  situated  on  the  right 
side.  The  hallucinations  of  hearing  induced  by  irritation  of  the  psycho-auditory 
center  appear  usually  in  the  right  ear,  although  they  may  appear  in  both.  Occa- 
sionally they  are  at  the  same  time  different  in  content  and  character  in  both  ears. 
Huguenin  observed  atrophy  of  the  temporal  lobe  after  deafness  of  long  standing. 

Agra'phia  also  may  be  due  to  word-blindness,  the  patient  being  unable  to 
write  from  copy,  although  he  can  write  spontaneously  or  on  dictation;  and  like- 
wise to  word-deafness,  the  patient  being  unable  to  write  on  dictation,  although 
he  can  write  spontaneously  or  from  copy. 

According  to  Flechsig  the  psycho-osmic  center  or  the  olfactory  sphere 
comprises  the  entire  posterior  margin  of  the  base  of  the  frontal  lobe  and 
the  basal  portion  of  the  fornicate  gyrus,  the  uncinate  gyrus,  and  a  portion 
of  the  adjacent  inner  pole  of  the  temporal  lobe.  The  psychogeusic 
center  or  the  gustatory  sphere  is  supposed  by  Flechsig  to  be  situated  within 
or  at  the  margin  of  the  center  for  bodily  sensations  or  the  olfactory  sphere. 

Subjective  sensations  of  taste  or  smell  in  the  insane  and  in  epileptics  are  due 
to  abnormal  irritation  in  these  regions,  destruction  of  which  will  cause  loss 
of  the  corresponding  functions.  In  the  new-born  the  olfactory  center  appears 
to  be  one  of  the  earliest  to  enter  upon  functional  activity.  It  degenerates  after 
destruction  of  the  olfactory  tract. 

The  sphere  for  bodily  sensation,  psycho-esthetic  and  psycho-algic  center, 
comprises  the  area  between  the  fossa  of  Sylvius  and  the  corpus  callosum, 
including  the  central  convolutions,  the  foot  of  all  of  the  frontal  convolu- 
tions, the  paracentral  lobule,  and  the  gyrus  fornicatus,  especially  in  its 
middle  third.  The  superficial  tactile  impressions  and  the  sensations  of 
movement  are  impaired  after  destruction  of  the  central  convolutions, 
while  painful,  thermic,  and  pressure  sensations  are  preserved.  After 
destruction  of  the  fornicate  gyrus  and  the  hippocampal  gyrus,  tactile 
and  thermic  and  common  sensibility  are  partially  lost.  Destruction  of 
certain  regions  (marginal  gyrus)  cause  failure  to  recognize  objects  through 
the  sense  of  touch. 

On  electric  stimulation  in  a  trephined  human  being  sensory  impres- 
sions (creeping)  were  observed  in  peripheral  portions  of  the  skin.  All 
sensory  impulses  that  rise  from  the  posterior  spinal  roots  pass  through 
the  lateral  nucleus  of  the  optic  thalamus  and  from  here  they  reach  the 
central  convolutions,  which  therefore  are  connected  with  the  sensory 
nuclei  of  the  posterior  and  lateral  columns  of  the  spinal  cord. 

Irritative  disorders  of  sensibility  occur  in  consequence  of  cortical  irritation, 
including  hallucinations  of  tactile,  motor,  and  visceral  sensations,  the  sensation 
of  itching,  prickling,  and  burning,  which  may  reach  a  painful  degree,  as  in  epileptics 
and  hysterics.  Some  cases  of  migraine,  especially  those  associated  with  epilepsy, 
may  be  due  to  cortical  irritation. 


PHYSIOLOGICAL  TOPOGRAPHY  OF  SURFACE  OF  CEREBRUM.     8oi 

In  cases  of  epilepsy  marked  excitation  of  the  sensorial  centers,  mani- 
fested by  excessive  subjective  impressions,  often  in  association  with 
psychic  irritative  disorders,  for  example  the  appearance  of  definite 
thoughts,  has  been  observed  as  an  irritative  accompaniment  of  the  con- 
vulsive seizure.  Such  excitation  may  appear  even  without  accompany- 
ing convulsions  as  so-called  sensory  epilepsy,  which  may  be  partial, 
that  is  unilateral  and  confined  to  individual  impressions,  in  the  latter 
event  without  loss  of  consciousness.  In  cases  of  congenital  inactivity 
of  a  psychosensorial  center  hallucinations  in  this  region  never  develop. 

Epileptoid  hallucinations  of  the  character  described  occur  without  convul- 
sions but  accompanied  only  by  brief  derangement  of  consciousness  (absence). 
Under  such  circumstances  amaurosis  has  also  been  observed,  gradually  disappear- 
ing later  and  being  replaced  by  a  concentric  contraction  of  the  visual  field.  Occa- 
sionally only  the  psychic  cortical  centers  are  affected,  preepileptic  and  postepi- 
leptic  insanity,  loss  of  memory  for  certain  periods  of  time,  derangement  of  con- 
sciousness resulting.  Cases  are  extremely  rare  in  which  epilepsy  occurs  with 
loss  of  consciousness  but  without  convulsions,  and  so  also  are  cases  in  which  the 
convulsions  occur  without  derangement  of  consciousness. 

The  nerve-fibers  passing  from  the  sensorial  and  sensory  organs  to  the 
psychosensorial  cortical  centers  traverse  the  posterior  third  of  the  pos- 
terior limb  of  the  internal  capsule  (Fig.  263).  Destruction  at  this  point 
causes,  therefore,  anesthesia  on  the  contralateral  half  of  the  body.  Only 
the  viscera  retain  their  sensibility.  Also  contralateral  loss  of  hearing, 
of  smell,  and  of  taste,  as  well  as  hemiopia,  appear.  Whether  the  visceral 
sensations,  sensations  of  internal  processes  associated  with  pleasure  or 
displeasure,  are  localized  in  the  cerebral  cortex  or  in  the  midbrain  is 
undetermined. 

Pathological. — In  human  beings  with  more  or  less  complete  injury  or  degenera- 
tion of  this  tract,  more  or  less  well-marked  loss  of  the  pressure-sense  and  the  temper- 
ature-sense, of  cutaneous  and  of  muscular  sensibility,  of  taste,  smell,  and  hearing  is 
accordingly  found.  The  eye  is  rarely  entirely  blind,  but  visual  acuity  is  greatly 
impaired,  the  visual  field  is  contracted  and  the  color-sense  may  be  partially  or 
totally  abolished.  The  eye  upon  the  same  side  may  suffer  alone  in  lesser  degree. 
In  addition  to  material  lesions  of  the  brain,  sensory  anesthesia  is  observed  also 
as  a  functional  disorder  in  association  with  hysteria,  neuroses,  and  psychoses. 
With  reference  to  the  mutual  relations  of  the  individual  conducting  paths  within 
the  internal  capsule  Redlich  maintains  that  behind  the  pyramidal  tracts  there 
pass  first  the  fibers  for  muscular  sense,  then  those  for  cutaneous  sensibility, 
and  finally  the  visual  fibers. 

Cases  of  injury  in  the  anterior  frontal  region  without  motor  and  sen- 
sory disorders  have  been  collected  in  large  number  by  Charcot,  Pitres, 
Ferrier,  and  others.  On  the  other  hand,  enfeeblement  of  intelligence 
and  idiocy  have  been  observed  in  connection  with  acquired  or  congenital 
deficiencies  of  the  frontal  region.  According  to  Flechsig,  there  is  no 
doubt,  in  accordance  with  clinical  observation,  that  the  frontal  lobe  and 
the  temporo-occipital  zone  bear  an  intimate  relation  to  mental  processes, 
particularly  those  of  a  higher  order,  which  disappear  largely  in  the  old 
and  in  epileptics. 

The  anterior  portions  of  the  first  and  second  frontal  convolutions,  portions 
of  the  third  and  of  the  gyrus  rectus  in  the  frontal  lobe,  the  island  of  Reil,  the 
first  and  second  parietal  convolutions,  the  second  and  third  temporal  convolu- 
tions, the  occipitotemporal  gyrus,  and  the  precuneus  are  association-centers. 
They  connect  the  various  sense-spheres  and  they  have  the  function  of  associating 
irritative  states  of  various  sense-spheres. 

Situation  of  the  Cerebral  .Regions  in  the  Skull. — In  order  to  indicate  the  posi- 
tion of  the  principal  fissures  and  convolutions  in  the  uninjured  head  various 


802  THE  BASAL  GANGLIA  OF  THE  CEREBRUM. 


points  suggested  by  Broca  have  been  marked  in  Fig.  260,  which  shows  the  different 
parts  of  the  brain  according  to  A.  Ecker.  Kt  K2  K3  are  points  in  the  coronal 
suture  that  can  be  felt  through  the  scalp.  Kt  is  placed,  in  order  to  avoid  the 
longitudinal  sinus,  15  mm.  to  one  side  of  the  median  line.  K2  is  the  point  of 
intersection  of  the  coronal  suture  and  the  temporal  line.  At  K3  the  coronal 
suture  intersects  the  upper  margin  of  the  great  wing  of  the  sphenoid  bone.  Lj 
and  L2  are  situated  in  the  lambdoid  suture,  the  former  15  mm.  to  one  side  of  the 
highest  point,  and  the  latter  in  the  middle  of  the  posterior  border  of  the  parietal 
bone.  M  corresponds  to  the  highest  point  of  the  arch  of  the  squamous  suture. 
If  horizontal  lines  be  drawn  backward  from  the  points  Kj  K2  K3,  the  central  fissure 
C,  which  is  so  important  in  localization,  is  situated,  in  the  adult,  at  its  upper 
extremity  about  45  mm.  and  at  its  lower  extremity  about  30  mm.  behind  the 
coronal  suture.  According  to  Merkel  the  lower  extremity  is  almost  5  cm.  verti- 
cally above  the  inferior  maxillary  articulation.  The  bifurcation  of  the  large 
fossa  of  Sylvius  is  4  or  5  mm.  behind  K3  or,  according  to  Merkel,  from  4  to  4.5  cm. 
above  the  middle  of  the  malar  arch.  Its  anterior  branch  is  parallel  with  the 
coronal  suture,  and  its  posterior  branch  passes  through  the  point  M.  The  parieto- 
occipital  fissure  (po)  is  situated  almost  exactly  in  the  lambdoid  suture  or,  meas- 
ured -with  compasses,  6  cm.  above  the  external  occipital  protuberance.  The 
frontal  eminence  forms  the  boundary  between  the  first  and  second  temporal  con- 
volutions. The  parietal  eminence  covers  the  supramarginal  gyrus. 

The  corpus  callosum  contains  commissural  fibers  from  both  hemispheres 
(according  to  Mott  and  Schafer  between  the  two  corticomotor  centers) ,  the  angular 
gyri  and  the  occipital  and  temporal  lobes.  Division  of  this  structure  in  the  dog 
causes  no  appreciable  disturbance.  In  accordance  with  this  fact  almost  total 
destruction  has  been  observed  in  man  without  the  development  of  noteworthy 
derangement  of  motility,  coordination,  sensibility,  reflex  activity,  the  special 
senses,  speech,  or  considerable  impairment  of  intelligence.  The  posterior  portion 
of  the  anterior  commissure  serves  for  the  connection  of  the  two  lingual  gyri. 

THE    BASAL   GANGLIA   OF   THE    CEREBRUM.     THE    MIDBRAIN. 
FORCED    MOVEMENTS.     OTHER  CEREBRAL  FUNCTIONS. 

The  striate  body  and  the  lenticular  nucleus  (Figs.  263,  264)  have  no 
direct  connection  with  the  cerebral  cortex,  although  fibers  pass  from 
their  connections  to  the  cerebral  peduncle  and  the  medulla  oblongata. 
Their  development  in  the  animal  kingdom  keeps  pace  with  that  of  the 
cerebral  cortex.  The  general  muscular  contractions  on  the  opposite  side 
of  the  body  observed  on  electrical  stimulation  are  probably  due  to  asso- 
ciated irritation  of  adjacent  cortico -muscular  tracts. 

Gliky  observed  no  movement  on  irritation  of  the  striate  body  in  the  rabbit. 
It,  therefore,  appears  that  the  motor  tracts  in  this  animal  do  not  traverse  the 
portion  of  the  brain  named,  but  pass  by  it. 

Destruction  of  the  lenticular  nucleus  or  the  striate  body  gives  rise, 
according  to  earlier  statements,  to  loss  of  voluntary  movements  on  the 
opposite  side  of  the  body,  with  or  without  preservation  of  sensibility; 
although  under  such  circumstances  there  is  also  associated  injury  of  the 
cortico -muscular  tracts.  Recently,  after  injuries  transitory  weakness  of 
the  contralateral  extremities  (loss  of  muscular  sense)  has  been  observed, 
with  increased  general  irritability  and  fear,  as  well  as  rapid  (transitory) 
elevation  of  temperature.  Irritation  of  the  striate  body  is  unattended 
with  pain. 

Pathological. — In  man  every  lesion  in  the  anterior  portion  of  the  striate  body 
that  is  not  too  small  causes  contralateral  paralysis,  which  is  permanent  if  the 
internal  capsule  is  affected,  but  which  may  gradually  disappear  if  the  lenticular 
and  caudate  nuclei  are  affected.  Occasionally  vascular  dilatation  occurs  in  con- 
sequence of  vasomotor  paralysis  if  the  posterior  portion  is  affected,  and  is  attended 
with  redness  and  slight  elevation  of  temperature  in  the  paralyzed  extremities 
(at  least  for  a  time) ,  swelling  (edema) ,  sweating,  alterations  in  pulse  demonstrable 


THE  BASAL  GANGLIA  OF  THE  CEREBRUM. 


803 


with  the  aid  of  the  sphygmograph,  acute  decubitus  on  the  paralyzed  side,  abnor- 
malities of  the  nails,  the  hair,  the  skin,  acute  inflammation  of  the  joints,  par- 
ticularly the  shoulder- joint.  Subsequently,  contractures  occur  in  the  paralyzed 
muscles.  In  individual  cases  there  may  be,  besides,  cutaneous  anesthesia,  occa- 


Gyrus  fornicatus 
Corpus  callosum. 


Septum  lucidum. 

Columnae  fornicis.-^, 

Corpus  striatum. 

Stria  terminalis. 
Thalamus  opticus. 
Pulvinar. 


Brachium  cpnjunc 

tivum  posticum. 

Pedunculus  cerebri. 

(ad  corpora 
quadrige- 
mina. 
..    .- ad  medullam 
cerebelh          oblongatam 


\ad  pontem. 


Cornu  anticum. 


Caput  nuclei  caudati. 

Capsula  interna 
(anterior  limb). 

Capsula  externa. 
Island  of  Reil. 
Nucleus  lentiformis. 
Claustrum. 


Capsula  interna 
(posterior  limb). 
Thalamus  opticus. 

Corpus  genicula- 
tum  mediale. 

Cauda  nuclei 
caudati. 


Hippocampus. 


~  Calcar  avis. 


Ala  cinereae. 


Obex 


Funiculus  gracilis. 


FIG.  263.  —  Cerebrum  of  Man.     On  the  right  the  hemisphere  is  removed  by  a  horizontal  section.     4,  Trochlear 
nerve;    8,  auditory  nerve;    6,  origin  of  the  abducens  nerve. 

sionally  also  impairment  of  sense-activity  on  the  paralyzed  side;  both  if  the  pos- 
terior segment  of  the  internal  capsule  is  affected.  Generally  hemiplegia  and 
hemianesthesia  exist  together. 

The    optic   thalamus    is    connected    with    all    of    the   sense-centers. 
As  it  is  connected  with  the  cerebral  cortex  by  fibers,  principally  as  a 


804  THE  BASAL  GANGLIA  OF  THE  CEREBRUM. 

partial  origin  of  the  optic  nerve,  it  probably  bears  some  relation  to  the 
sensation  of  vision.  In  man  injury  of  the  posterior  third  may  give  rise 
to  visual  disturbances.  Removal  of  the  optic  thalamus  or  destruction 
of  the  parts  in  the  neighborhood  of  the  inspiratory  center  in  the  wall  of 
the  third  ventricle  impairs  coordinated  movement  in  rabbits.  Also  in 
man,  contralateral  disorders  of  coordination,  choreiform  twitchings  or 
ataxia  have  been  observed  to  follow  degeneration  of  the  optic  thalamus. 
Destruction  of  the  optic  thalamus  gives  rise  in  man  to  loss  of  mimetic 
expression  on  the  opposite  side  of  the  face  in  response  to  emotional 
influences,  although  the  muscles  can  be  moved  voluntarily. 

Bechterew  concludes  as  a  result  of  experiments  and  of  pathological  observa- 
tions that  the  optic  thalami  play  an  important  part  with  respect  to  the  expression 
of  varied  perceptions,  sensations,  and  emotional  activities.  They  are  motor 
centers  through  the  intermediation  of  which  principally  the  congenital  movements 
of  expression  (such  as  laughing  or  crying)  are  executed,  and  which  are  excited 
under  the  influence  of  involuntary  psychical  impulses,  such  as  emotions,  or  they 
can  be  stimulated  reflexly  through  tactile  stimulation  and  irritation  of  other 
sensory  organs.  The  thalamus  and  the  anterior  quadri geminate  body  contain 
the  centers  for  complex  reflexes.  Both  receive  connections  from  the  posterior 
nerve-roots  of  the  spinal  cord  and  from  the  sensory  cerebral  nerves,  and  the 
thalamus,  in  addition,  from  the  olfactory  and  optic  tracts.  The  anterior  quadri- 
geminate  body  contains  a  common  optico-auditory  reflex  path.  The  optic  thal- 
amus contains  also  the  reflex  center  for  the  secretion  of  tears  and  from  this  situa- 
tion the  sensory  irritation  is  conveyed  to  the  path  for  the  secretory  branches  of 
the  trigeminus  and  the  facial,  as  well  as  of  the  sympathetic. 

After  injury  of  one  thalamus  paresis  or  paralysis  of  the  contralateral  muscles, 
together  with  circular  movements,  have  been  reported  in  some  cases,  and  contra- 
lateral  hemianesthesia  with  or  without  involvement  of  the  motor  sphere  in  other 
cases.  Fibers  pass  from  the  thalamus  to  the  cortex  of  all  of  the  cerebral  lobes, 
also  to  the  cornu  Ammonis  and  the  tegmentum  of  the  cerebral  peduncle, 
Extirpation  of  certain  portions  of  the  cerebral  cortex  in  the  rabbit  is  followed  by 
atrophy  of  certain  portions  of  the  thalamus.  The  relations  of  the  optic  thalamus 
to  reflex  inhibition  are  discussed  on  page  731,  to  the  movements  of  the  stomach 
on  page  288,  to  those  of  the  intestines  on  page  791.  The  heat-center  supposed  to  be 
situated  in  the  thalamus  is  described  on  page  395. 

Injury  of  the  cerebral  peduncles  gives  rise,  first  of  all,  to  severe  pains 
and  spasms  on  the  opposite  side  of  the  body,  where  the  salivary  glands 
secrete.  These  irritative  phenomena  are  followed,  as  paralytic  symp- 
toms, in  man  by  contralateral  anesthesia  and  loss  of  voluntary  control 
of  the  muscles  as  well  as  paralysis  of  the  vasomotors.  In  case  of  lesions 
of  the  peduncles  in  man  the  oculomotor  nerve  should  be  observed,  as  it 
is  often  paralyzed  on  the  same  side. 

The  middle  third  of  the  cerebral  peduncle  comprises  the  well-known  conduct- 
ing path  of  the  pyramidal  tracts.  The  fibers  of  the  inner  third  connect  the  frontal 
lobe  through  the  superior  cerebellar  peduncle  with  the  cerebellum.  The  outer 
third  contains  fibers  that  connect  the  pons  with  the  temporal  and  occipital  lobes 
of  the  cerebrum.  The  fibers  passing  from  the  tegmentum  into  the  corona  radiata 
serve  for  sensory  conduction. 

According  to  Goltz  section  of  the  cerebral  peduncle  in  the  dog  is  followed 
by  a  tendency  to  fall  to  the  same  side;  the  movements  of  the  contralateral  ex- 
tremities appear  larger  and  cutaneous  sensibility  is  impaired  on  the  entire  contra- 
lateral  side.  The  animal  sees  especially  only  objects  that  make  an  impression 
upon  the  right  half  of  each  retina.  Therefore,  each  peduncle,  according  to  Goltz, 
contains  motor  and  sensory  fibers  for  the  entire  body. 

Irritation  or  section  of  the  pons  gives  rise  to  pain  and  spasm.  After 
section  of  the  contained  conducting  fibers — sensory,  motor,  and  vasomotor 
— paralyses  appear,  together  with  forced  movements.  An  explanation  is 


THE    BASAL    GANGLIA    OF    THE    CEREBRUM. 


805 


wanting  as  to  the  significance  of  the  ganglia  present  in  the  pons.  For 
diagnostic  purposes  in  man  attention  should  be  directed  to  the  presence 
of  possible  alternate  hemiplegia. 

The  quadrigeminate  bodies  or  the  midbrain.  Destruction  of  the  quad- 
rigeminate  bodies  on  one  side  in  mammals,  or  of  the  optic  lobe  in  birds, 
amphibia,  and  fish,  is  followed  by  blindness,  which  may  be  situated  upon 
the  same  or  upon  the  opposite  side  in  accordance  with  the  conditions  of 
decussation  in  the  optic  chiasm.  Total  destruction  of  the  bodies  on  both 
sides  causes  blindness  in  both  eyes.  As  a  result  the  reflex  between  irri- 
tation of  the  retina  and  the  oculomotor  nerve  is  abolished,  that  is,  the 
pupils  no  longer  contract  after  illumination  of  the  retina.  If  the  cere- 
bral hemispheres  alone  are  removed,  the  pupils  still  contract  on  light- 
stimulation,  as  well  as  after  mechanical  irritation  of  the  optic  nerve. 
Extirpation  of  the  eye- 
ball is  followed  by 
atrophy  of  the  contra- 
lateral  anterior  quad- 
rigeminate body. 

According  to  Bech- 
terew  the  fibers  of  one 
optic  tract  pass  through 
the  brachium  conjuncti- 
vum  anterius  (Fig.  241) 
into  the  external  per- 
iphery of  the  anterior 
quadrigeminate  body. 
The  fibers  that  decussate 
in  the  chiasm  (Fig.  240) 
pass  into  the  posterior 
quadrigeminate  body.  In 
accordance  with  this  dis- 
tribution are  the  symp- 
toms of  partial  blindness 
after  destruction  of  an 
anterior  or  posterior  quad- 
rigeminate body.  Fibers 
pass  onward  to  the  cortex 
in  the  internal  periphery 
of  the  anterior  quadrigem- 
inate body. 

In  animals  deafness 
has  been  observed  to 
develop  after  destruc- 
tion of  the  posterior 

quadrigeminate  body.  Animals  exhibit  under  such  conditions  diffi- 
culty in  phonation  even  to  the  point  of  loss.  In  man  a  paralyzing 
lesion  of  the  tegmentum  or  of  the  internal  capsule  is  present  in  all 
cases  of  midbrain  deafness.  Destruction  of  the  quadrigeminate  bodies 
is  followed  further  by  disturbance  in  the  perfect  harmony  of  movement; 
disorders  of  equilibration  and  incoordination  of  movement  also  occur. 

The  cochlear  nerve  undergoes  partial  decussation  in  the  posterior  quadri- 
geminate body  and  in  the  pons.  The  quadrigeminate  bodies  react  to  electrical, 
chemical,  and  mechanical  stimulation.  The  reports  are  contradictory,  however, 
as  to  the  results  of  irritation.  According  to  some  observers  dilatation  of  the  pupil 
on  the  same  side  takes  place ;  according  to  Ferrier  the  contralateral  pupil  dilates 
first  and  later  also  the  pupil  on  the  same  side.  The  irritation  extends  from  the 


FIG.  264. — Frontal  Section  through  the  Cerebrum:  i  ic,  internal  capsule; 
2  Ik,  nucleus  lentiformis;  3  nc,  caudate  nucleus;  4  tho,  optic  thala- 
mus;  5  cc,  corpus  callosum;  6  aec,  external  capsule;  7  cl,  claustrum; 
8  i,  island. 


806  FORCED    MOVEMENTS. 

quadri geminate  bodies  to  the  medulla  oblongata  and  further  on  to  the  origin 
of  the  sympathetic,  for  after  section  of  the  cervical  sympathetic  the  dilatation 
no  longer  takes  place.  According  to  Knoll  contraction  of  the  pupil,  such  as  was 
observed  by  earlier  investigators,  takes  place  only  when  the  adjacent  optic-nerve 
tract  is  irritated.  In  addition,  irritation  of  the  right  anterior  quadri  geminate 
body  causes  rotation  of  both  eyes  to  the  left,  and  conversely.  If  the  irritation 
be  continued  the  head  also  is  rotated  toward  the  same  side.  Vertical  section  of 
the  quadrigeminate  bodies  in  the  median  line  is  followed,  on  unilateral  irritation, 
by  this  result  only  upon  the  same  side.  Ferrier  observed,  further,  signs  of  pain 
on  irritation  of  the  quadrigeminate  bodies  in  mammals.  Danilewsky,  Ferrier, 
and  Lauder  Brunton  observed,  finally,  increase  in  blood-pressure  and  slowing  of 
the  heart-beat,  together  with  deep  respirations. 

Bechterew  attributes  all  of  the  phenomena  that  occur  after  injury  or  irritation 
of  the  quadrigeminate  bodies,  except  those  referable  to  vision  itself,  to  lesions 
of  more  deeply  situated  parts.  Therefore,  according  to  him,  the  quadrigeminate 
bodies  themselves  contain  neither  the  center  for  the  movements  of  the  pupils  nor 
that  for  the  combined  movements  of  the  eyes,  nor  do  they  contain  that  for  main- 
taining the  equilibrium  of  the  body.  Irritation  of  the  quadrigeminate  body  causes 
the  animals  to  start  back  markedly  as  a  reflex  phenomenon.  Nystagmus,  forced 
movements,  and  uncertainty  in  walking  occur  also  only  in  association  with 
injuries  of  more  deeply  situated  parts. 

Pathological. — Lesions  of  the  anterior  quadrigeminate  bodies  in  man  give  rise, 
in  accordance  with  their  extent,  to  visual  disturbances,  immobility  of  the  pupils  and 
even  blindness.  In  addition  profound  injury  may  be  attended  with  paralysis  of 
the  oculomotor  nerves  on  both  sides,  in  consequence  of  which  the  affected  ocular 
muscles  are  not  involved  with  entire  symmetry  and  not  in  equal  degree.  An  un- 
certain staggering  gait,  especially  if  it  appears  as  the  first  symptom,  is  likewise 
characteristic. 

Destruction  of  the  posterior  commissure  in  rabbits  has  the  same  effect  as 
section  of  both  oculomotor  nerves;  a  lesion  causes  only  diminution  in  the  irrita- 
bility of  these  nerves.  An  incomplete  asymmetrical  lesion  causes  asymmetrical 
diminution  in  the  irritability  of  the  two  nerves,  the  nerve  upon  the  side  of  the 
lesion  being  less  irritable  than  that  upon  the  opposite  side. 

Forced  Movements. — The  significance  of  the  midbrain  in  relation  to 
the  harmonious  execution  of  movements  makes  it  clear  that  unilateral 
injuries  of  such  parts  as  are  connected  with  it  by  means  of  conducting 
fibers  cause  peculiar  unilateral  disturbances  of  equilibrium  and  devia- 
tions from  the  symmetrical  movements  of  both  sides  of  the  body  that 
have  been  designated  forced  movements.  In  this  category  belong  the 
circular  movement  (mouvement  de  manege),  in  which  the  animal,  with 
the  intention  of  running  onward,  moves  constantly  in  a  circle;  the  index- 
movement,  in  which  the  fore  part  of  the  body  is  moved  about  the  station- 
ary posterior  part,  like  an  indicator  about  its  axis;  the  rolling  movement, 
by  means  of  which  the  body  is  revolved  about  its  longitudinal  axis.  All 
of  these  forms  of  movement  may  pass  into  one  another,  and  they  rep- 
resent only  gradual  variations  in  the  same  disorder.  The  parts  injury 
of  which  causes  these  forced  movements  are  the  striate  body,  the  optic 
thalamus,  the  cerebral  peduncle,  the  pons,  the  middle  cerebellar  pedun- 
cle, certain  portions  of  the  medulla;  and  even  after  injury  of  the  surface 
of  the  cerebrum  Eulenburg  and  Landois  observed  index-movements  in 
rabbits,  and  Bechterew  in  dogs.  Also  in  man  forced  movements  have  been 
observed,  especially  in  association  with  lesions  of  the  parietal  convolu- 
tions. Forced  movements,  together  with  nystagmus  and  rotation  of  the 
eyes,  are  caused  also  by  injury  to  the  olive. 

On  pathological  degeneration  of  one  olive  of  the  medulla  oblongata  pronounced 
rotatory  movements  toward  the  same  side  have  been  observed  in  man. 

Statements  differ  as  to  the  direction  and  the  character  of  the  movements 
after  the  individual  injuries.  The  following  observations  have  been  made:  Sec- 
tion of  the  anterior  portion  of  the  pons  and  the  cerebellar  peduncles  causes 


FORCED    MOVEMENTS.  807 

index-movement  and  rolling  movements  toward  the  opposite  (paretic?)  side;  section 
of  the  posterior  portion  of  the  same  regions  causes  rolling  movements  toward  the 
same  (paretic?)  side,  as  does  also  deeper  puncture  of  the  auditory  tubercle  or  the 
restiform  body.  Incision  of  one  cerebral  peduncle  causes  circular  movement, 
with  the  convexity  directed  toward  the  same  side.  The  closer  the  incision  is 
situated  to  the  pons  the  narrower  becomes  the  circle  of  movement.  Finally, 
index-movement  occurs.  Injury  of  one  optic  thalamus  causes  much  the  same 
phenomena  as  puncture  of  the  anterior  portion  of  the  cerebral  peduncle,  because  the 
latter  is  injured  at  the  same  time.  Injury  of  the  anterior  portion  of  one  optic 
thalamus  gives  rise  to  forced  movement  in  the  opposite  direction,  that  is  with  the 
concavity  directed  toward  the  side  of  the  injury.  Flexion  of  head  and  vertebral 
column,  with  the  convexity  toward  the  affected  side,  together  with  circular  move- 
ment, is  caused  by  injury  of  the  spinal  extremity  of  the  medulla;  the  convexit}^  is 
directed  toward  the  unaffected  side  as  a  result  of  injury  to  the  anterior  extremity 
of  the  calamus  and  above. 

Rotation  (strabismus)  and  involuntary  oscillation  (nystagmus)  of  the  eyes 
may  be  included  among  forced  movements.  Nystagmus  occurs  as  a  result  of 
unilateral  superficial  lesions  of  the  restiform  body,  as  well  as  of  the  floor  of  the 
fourth  ventricle,  and  as  a  result  of  irritation  of  the  cerebellum.  Unilateral,  deep, 
transverse  injuries  from  the  apex  of  the  calamus  downward  to  the  auditory 
tubercle  cause  strabismus  of  the  eye  of  the  same  side  downward  and  forward, 
and  of  the  opposite  eye  backward  and  upward.  Bilateral  injuries  cause  this 
strabismus  to  disappear.  It  is,  therefore,  to  be  inferred  that  the  medulla  ob- 
longata  contains  a  mechanism  controlling  the  ocular  movements,  which  can 
be  irritated  as  a  result  of  sudden  anemia  (ligature  of  the  cerebral  arteries  in  the 
rabbit) . 

In  explanation  of  the  forced  movements  it  has  been  in  part  assumed  that  they 
are  due  to  unilateral  incomplete  paralysis,  so  that  the  animal,  on  attempting  to 
move  about,  drags  the  paretic  side  somewhat  (as,  for  example,  in  the  circular 
movement  on  the  side  of  the  body  directed  toward  the  center  of  the  circle) ,  and 
therefore  the  symmetry  of  movement  is  lost.  Others  have  attempted,  in  direct 
opposition  to  this  view,  to  establish  an  irritation  through  the  act  of  injury  as  the 
cause  of  an  excessive  activity  upon  one  side  of  the  body.  Landois,  as  a  result 
of  his  own  observations,  ranged  himself  on  the  side  of  those  investigators  who 
consider  vertiginous  sensations  induced  by  the  injury  as  the  cause  of  the  move- 
ments. He  observed,  at  times,  that  immediately  after  the  injury  (stilet-puncture) , 
the  movement  took  place  in  a  direction  opposite  to  that  appearing  somewhat 
later.  He  considered  this  phenomenon  as  the  effect  of  the  irritation  and  paraly- 
sis induced  in  quick  succession  by  the  injury.  The  latter,  by  irritating  or  paralyzing 
the  apparatus  controlling  locomotor  sensations,  may  give  rise  to  a  false  impression 
as  if  the  body  of  the  animal  or  also  the  objects  of  the  external  world  moved  in 
a  definite  direction.  As  a  result  of  this  motor  deception  the  movements  described 
are  executed  as  a  reaction,  with  the  intention  of  correcting  the  abnormal  fictitious 
movements  by  means  of  suitable  counter-movements.  The  circular  movements 
after  injury  of  the  optic  thalamus  may  be  induced  by  apparent  movement  in 
consequence  of  injury  to  the  optic  nerve. 

In  this  connection  it  may  be  mentioned  that  injury  of  a  point  not  far  from 
the  posterior  extremity  of  the  cerebral  hemisphere  causes  after  the  lapse  of  some 
time  marked  forward  or  lateral  movements,  likewise  probably  as  the  result  of  a 
false  motor  impression.  The  unrestrained  running  movement  after  injury  of  an 
area  in  the  middle  of  the  striate  body  near  the  free  margin  directed  toward  the 
ventricle  is  probably  to  be  explained  in  the  same  way.  At  first  the  animal  re- 
mains quiet.  If  driven,  however,  it  runs  furiously  until  restrained  by  some  ob- 
struction. Landois  has  made  the  observation  that  every  manipulation  of  the 
central  organs  that  affects  the  equilibrium  in  considerable  degree  is  attended 
with  marked  increase  and  deepening  of  the  respirations. 

FUNCTIONS  OF  THE   CEREBELLUM. 

Injuries  of  the  cerebellum  cause  in  marked  degree  disturbances  in 
the  harmony  of  the  movements  of  the  body.  Probably  the  cerebellum 
represents  a  central  organ  for  the  more  delicate  gradation  and  the  nor- 
mal sequence  of  movements,  inasmuch  as  it  regulates  especially  con- 
tinuous and  tonic  muscular  contractions.  Thomas  designates  it  a  reflex 


808  FUNCTIONS    OF    THE    CEREBELLUM. 

center  for  maintaining  the  equilibrium.  Its  connections  with  all  of  the 
ganglionic  masses  of  the  central  organs  render  the  cerebellum  adapted  to 
this  purpose. 

Through  the  lateral  cerebellar  tracts  stimuli  are  conveyed  to  the  cerebellum 
and  these  serve  as  guides  to  the  position  of  the  trunk.  Connections  of  the  vestibu- 
lar  nerve  with  the  cerebellum  have  a  similar  effect  with  respect  to  the  equilibrium. 
The  cerebellum  may  influence  the  motor  nerves  of  the  spinal  cord  through  fibers 
that  pass  downward  through  the  restiform  body  into  the  lateral  tract  of  the 
spinal  cord.  The  cerebellum  itself  is  insensitive  to  injuries. 

The  experiments  of  Luciani  upon  the  functions  of  the  cerebellum 
prove  that  each  portion  of  this  structure  has  the  same  function  as  the 
whole.  The  functions  are  threefold :  i.  The  cerebellum  provides  volun- 
tary movements  with  sufficient  strength.  2.  It  increases  the  tone  of  the 
muscles  during  rest.  3.  It  accelerates  the  rhythm  of  the  individual 
motor  impulses  that  constitute  the  movements  and  it  fuses  the  impulses 
into  a  continuous  act.  4.  Russell  has  found,  after  extirpation  of  the 
cerebellum,  incoordination  of  movement,  rigidity  of  the  muscles,  and 
motor  weakness  as  characteristic  symptoms. 

After  almost  complete  removal  of  the  cerebellum  dogs  exhibit  paresis  and 
deficient  tone  especially  in  the  muscles  of  the  vertebral  column  and  the  hind  legs. 
The  animal  is  able  neither  to  stand  nor  to  walk  and  the  head  oscillates  to  and  fro. 
Immediately  after  the  operation  there  appear  as  irritative  phenomena:  tonic 
spasm  of  the  muscles  of  the  nape  of  the  neck,  the  back,  and  the  forelegs,  con- 
vergence of  the  eyes,  occasionally  falling  forward  of  the  body.  Intelligence  and 
sense-impressions,  including  the  muscle-sense,  remain  intact. 

Median  division  of  the  cerebellum  without  extirpation  causes  permanent 
enfeeblement  of  all  voluntary  movements,  diminution  of  the  muscular  tone  present 
during  rest,  as  well  as  tremor,  discontinuous  muscular  contractions,  incoordination 
and  uncertainty  in  voluntary  movements.  Extirpation  of  the  vermis  causes,  as 
irritative  phenomena,  tonic  contraction  of  the  muscles  of  the  nape  of  the  neck 
and  of  the  forelegs,  which  at  times  is  followed  by  paresis  especially  of  the  hind 
legs.  Complete  removal  of  one-half  of  the  cerebellum  is  followed,  as  irritative 
phenomena,  by  rolling  movements  about  the  longitudinal  axis,  as  well  as  rotation 
of  the  eyes  toward  the  unaffected  side,  curvature  of  the  vertebral  column  toward 
the  side  operated  on  and  tonic  extensor  spasm  of  the  foreleg  and  less  commonly 
of  the  hind  leg  upon  the  same  side.  These  are  followed,  as  paralytic  phenomena, 
by  relaxation  of  the  muscles  of  the  same  side  (atony),  a  somewhat  less  energetic 
contraction  (asthenia)  and  a  want  of  fusion  of  the  composite  movements,  so  that 
tremor,  swaying  and  rhythmic  oscillations  (astasia)  result.  Superficial  injury  or 
partial  removal  of  one  hemisphere  is  neutralized  by  the  assumption  of  its  function 
by  the  intact  portions  of  the  cerebellum.  Animals  deprived  of  their  equilibrium 
after  extirpation  of  the  cerebellum  can  regain  it  through  the  motor  impulses 
gradually  sent  from  the  motor  cortical  centers  of  the  cerebrum  in  standing,  walk- 
ing, and  swimming. 

Luciani  observed,  eventually,  in  animals  after  extirpation  of  the  cerebellum, 
general  marasmus,  and  he  believed,  therefore,  that  the  organ  exercises  a  trophic 
function.  In  accordance  with  this  view,  Friedeberg  observed  loss  of  weight  after 
disease  of  the  cerebellum. 

Extirpation  of  the  cerebellum  is  followed  by  secondary  degeneration  of  the 
portion  of  the  pons  surrounding  the  pyramids,  of  the  inferior  olivary  bodies,  all 
of  the  cerebellar  peduncles  and  the  direct  cerebellar  bundle  of  Flechsig,  principally 
on  the  same  side,  in  lesser  degree  on  the  opposite  side.  Degeneration  takes  place, 
also,  in  some  fibers  within  all  of  the  cerebral  nerves  and  the  anterior  roots  of  the 
spinal  nerves. 

In  frogs  an  important  organ  for  locomotion  is  situated  at  the  junction  of  the 
medulla  with  the  cerebellum.  After  its  removal  the  animal  is  no  longer  able  to 
hop  about  or  to  creep  in  a  coordinate  manner. 

Pathological. — Asymmetrical  or  unilateral  lesions  of  the  cerebellum  cause  in 
man  a  tendency  to  fall  toward  the  side  of  the  injury,  while  bilateral  injuries  cause 
a  tendency  to  fall  backward.  If  the  middle  lobe  is  affected  disorders  of  coordi- 
nation occur,  particularly  a  stumbling,  staggering  gait  and  marked  vertigo,  as 


PROTECTIVE    AND    NUTRITIVE    APPARATUS    OF    THE    BRAIN.  809 

well  as  atony,  asthenia,  and  ataxia.  Irritative  disease  of  the  middle  cerebellar 
peduncle  causes  complete  rotation  of  the  body  about  its  axis,  with  rotation  of 
the  eyes  and  the  head  in  the  same  direction. 

If  an  electrical  current  be  passed  through  the  head  of  a  man,  the  electrodes 
being  placed  in  the  mastoid  fossae  behind  each  ear,  and  in  such  a  manner  that  the 
positive  pole  is  applied  upon  the  right  and  the  negative  pole  upon  the  left,  a 
marked  feeling  of  vertigo  occurs  on  closure,  and  the  head  and  body  fall  toward 
the  positive  pole,  while  the  objects  of  the  outer  world  appear  to  move  toward 
the  left.  If  during  the  passage  of  the  current  the  eyes  are  closed,  the  apparent 
movement  is  transferred  to  the  individual  himself,  who  then  has  a  feeling  of 
rotation  toward  the  left.  At  the  moment  when  the  head  falls  toward  the  anode, 
the  eyes  also  are  rotated  in  the  same  direction  and  frequently  exhibit  nystagmus. 
The  electrical  current  under  such  circumstances  probably  exerts  an  irritative 
effect  upon  the  nerves  of  the  ampullae,  disorders  of  which  cause  vertigo. 

PROTECTIVE  AND  NUTRITIVE  APPARATUS  OF  THE  BRAIN. 

The  cerebral  dura  mater  is  intimately  united  with  the  periosteum  of  the  cranial 
cavity.  The  spinal  dura  mater  forms  about  the  spinal  cord  a  freely  suspended 
long  sac  attached  only  on  its  anterior  aspect.  The  dura  mater  is  a  fibrous  mem- 
brane consisting  of  firm  bands  of  connective  tissue,  interwoven  with  a  large  num- 
ber of  elastic  fibers  and  provided  with  flat  connective-tissue  cells  and  Waldeyer's 
glasma-cells.  The  smooth  inner  surface  is  lined  by  squamous  endothelium. 
lood-vessels  are  present  only  in  moderate  number,  though  in  somewhat  greater 
abundance  in  the  outer  layers,  while  lymphatics  are  numerous.  Nerves  with 
unknown  terminations  (Pacinian  bodies  have  been  found  on  the  petrous  bone) 
endow  the  dura  with  great  sensitiveness  to  painful  impressions  (also  in  the  dog, 
but  not  in  the  rabbit). 

Between  the  dura  and  the  arachnoid  is  situated  the  lymphatic  subdural  space. 
The  pia  mater  and  the  arachnoid  united  to  it  by  means  of  a  reticular  network 
really  form  a  common  membrane,  which  cannot  be  separated.  Between  the 
two  layers,  as  if  enclosed  in  dropsical  connective  tissue,  cerebrospinal  lymph 
is  present  in  a  space,  the  subarachnoid  space,  which  is  lined  by  endothelium.  The 
external  limiting  layer  of  this  stratum,  correctly  designated  also  arachnoid  in 
the  strict  sense,  is  thin,  poor  in  vessels,  without  nerves  and  lined  on  both  surfaces 
by  squamous  endothelium.  It  is,  however,  separated  from  the  pia  only  over  the 
spinal  cord,  so  that  between  the  two  lies  the  lymphatic  subarachnoid  space. 
Over  the  brain  the  two  are  in  large  measure  united,  except  where  they  form  bridges 
over  the  sulci.  Over  these  the  arachnoid  merely  passes,  while  the  pia  penetrates 
into  the  depth.  The  cerebral  ventricles  communicate  freely  with  the  lymphatic 
subarachnoid  space,  but  not  with  the  subdural  space.  The  subdural  and  sub- 
arachnoid  spaces  do  not  communicate  with  each  other.  The  pia,  made  up  of  deli- 
cate bundles  of  connective  tissue,  without  elastic  fibers,  exceedingly  rich'  in 
blood-vessels  and  lymphatics,  conveys  nerves  in  association  with  the  vessels 
into  the  structure  of  the  central  organs. 

The  lymphatics  of  the  brain,  apart  from  those  accompanying  the  vessels,  consist 
of  spaces  surrounding  the  ganglia  and  of  the  glia-cells  of  the  cortex  with  their  pro- 
cesses. They  all  empty  finally  into  the  subarachnoid  space.  The  cerebrospinal 
fluid  is  described  on  p.  367.  The  Pacchionian  granulations  are  connective-tissue 
villi  that  serve  for  the  flow  of  lymph  from  the  subdural  and  subarachnoid  spaces 
into  the  sinuses  of  the  dura  mater,  particularly  the  superior  longitudinal  sinus, 
into  which  they  project.  The  subarachnoid  space  communicates  also  with  the 
spongy  cavities  of  the  cranial  bones  and  with  the  veins  of  the  surface  of  the  skull 
and  of  the  face.  The  subdural  space  communicates,  further,  with  lymphatic 
spaces  of  the  dura,  and  the  latter  communicate  directly  with  the  veins  of  the 
dura.  The  two  lymphatic  intermeningeal  spaces  communicate  also  with  the 
lymphatics  of  the  nasal  mucous  membrane.  The  space  external  to  the  spinal 
dura  (epidural  space)  may  also  be  considered  as  a  lymphatic  space.  From 
it  the  pleural  and  peritoneal  cavities  may  be  readily  filled.  It  does  not,  however, 
communicate  with  the  cranial  cavity.  The  venous  plexuses,  which  perhaps 
secrete  the  cerebrospinal  fluid,  consist  of  convolutions  of  vessels  surrounded  by 
undeveloped  connective  tissue.  The  telae  choroideas  in  the  newborn  are  still 
provided  with  ciliated  epithelium. 

The  pulsations  of  the  large  blood-vessels  at  the  base  of  the  brain  impart 
pulsatory  movements  to  the  latter.  As  a  result  of  the  physical  conditions  present 


8lO  PROTECTIVE    AND    NUTRITIVE    APPARATUS    OF    THE    BRAIN. 

in  the  calvarium,  the  large  amount  of  blood  thrown  into  the  arteries  with  every 
systole  causes  the  expulsion  of  an  equal  amount  of  blood  from  the  veins.  The 
act  of  breathing  causes,  besides,  a  respiratory  movement  of  the  brain,  which  is 
elevated  on  expiration  and  falls  on  inspiration.  This  movement  is  due  in  part 
to  the  respiratory  fluctuation  in  pulse  and  in  part  to  variations  in  the  amount 
of  blood  in  the  veins  of  the  cranial  cavity.  Finally,  there  is  to  be  recognized  a 
movement  of  vascular  elevation  and  depression,  occurring  from  twice  to  six  times 
in  a  minute,  corresponding  to  the  periodic-regulatory  dilatation  and  contraction 
of  the  vessels.  This  movement  is  influenced  by  emotional  disturbances.  It  occurs 
most  regularly  during  sleep. 

The  movements  of  the  brain  are  apparent  especially  where  its  membranes 
offer  slight  resistance,  therefore,  for  example,  at  the  fontanels  in  children  and  in 
artificial  trephine-openings.  The  presence  of  the  cerebrospinal  fluid  is,  however, 
exceedingly  important  with  respect  to  this  movement,  probably  because  it  prop- 
agates the  pressure  uniformly  and,  thus,  concentrates  every  systolic  and  ex- 
piratory vascular  dilatation  upon  the  portion  on  the  calvarium  that  does  not 
offer  resistance.  If  the  fluid  is  drained  away  the  movement  becomes  small  to 
the  point  of  disappearance. 

As  the  arteries  within  the  rigid  calvarium  undergo  change  in  volume  with  the 
movement  of  the  pulse  a  pulsatory  variation  in  the  volume  of  the  veins  (sinuses) 
is  constantly  observed,  the  opposite  of  that  in  the  arteries.  Emotional  disturb- 
ances increase  the  pulsation  of  the  brain.  At  the  moment  of  awaking  the  amount 
of  blood  in  the  brain  diminishes,  while  sensorial  irritations  during  sleep,  without 
awakening  the  subject,  increase  the  amount  of  blood.  In  slight  degree  the  brain 
may  undergo  passive  movement  within  the  cranial  cavity  on  change  in  the  position 
of  the  head. 

The  vessels  of  the  pia  are  naturally  in  part  under  the  influence  of  the  vaso- 
motor  nerves  accompanying  them;  in  part  their  size  may  be  influenced  from 
remote  parts  of  the  body.  If  a  trephine-opening  be  closed  by  means  of  a  small 
glass  window,  the  effects  upon  the  lumen  of  the  vessels  can  be  observed  with  the 
aid  of  a  microscope.  Irritation  of  the  sympathetic  affects  only  the  vessels  of  the 
same  side,  but  does  not  alter  the  blood-pressure  upon  the  other  side  (through 
the  circle  of  Willis).  Paralysis  of  the  vasomotor  nerves,  also  by  means  of  nar- 
cotics, causes  dilatation  of  the  vessels.  The  vessels  contract  strongly  in  death. 
They  are  dilated  in  connection  with  cerebral  activity,  as  well  as  during  sleep. 
Transitory  anemia  of  the  cerebral  arteries  is  followed  by  their  secondary  dilata- 
tion and  hyperemia.  Irritation  of  the  vasomotor  center,  for  example  by 
asphyxia  or  strychnin  or  reflexly,  causes  the  presence  of  an  increased  amount  of 
blood  in  the  arteries  of  the  central  nervous  system  in  consequence  of  collateral 
hyperemia.  These  arteries,  therefore,  do  not  take  part  in  the  contraction  of  all 
of  the  remaining  arteries.  Excessive  elevation  of  pressure  in  the  cerebrospinal 
cavity  in  consequence  of  hyperemia  is  offset  by  the  escape  of  cerebrospinal  fluid 
into  the  lymph-sheaths  of  the  cerebrospinal  nerves.  Cerebral  irritation  that 
excites  epileptic  attacks  cause  an  increased  supply  of  blood  independently  of  the 
blood-pressure.  Sudden  ligation  of  all  of  the  cerebral  arteries  causes  immediate 
loss  of  the  sensonum,  and  later  on  marked  irritation  of  the  medulla  oblongata 
and  its  centers  and  finally  rapid  death  with  convulsions. 

As  a  result  of  the  free  anastomoses  at  the  base,  the  individual  portions  of  the 

cerebrum  are  protected  against  anemia  on  compression  or  ligature  of  one  or  another 

vessel.     Within  the  cerebrum  the  arteries  are  distributed  as  terminal  arteries, 

that  is  in  the  area  of  their  terminal  distribution  they  do  not  form  anastomoses 

with  neighboring  arterial  branches.     On  the  other  hand,  the  peripheral  arteries 

on  the  outer  surface   of  the  brain,  the    arteries  of   the  corpus  callosum,  of   the 

lossa  of   Sylvius,   and  the   deep   cerebral,  form  free   anastomoses.     The   sudden 

assumption  of  the  erect  posture  by  persons  who  have  occupied  the  recumbent 

position  for  a  long  time  and  are  at  the  same  time  anemic  is  not  rarely  attended 

ith  cerebral  anemia  from  hydrostatic  causes,  associated  with  loss  of  conscious- 

s  and  obscuration  of  the  senses.     Alterations  in  the  position  of  the  body  have 

herwise  no. effect  upon  the  pressure  in  the  cerebral  vessels.     Death  occurs  in 

some  animals  after  vertical  elevation  of  the  trephined  skull  and  even  more  quickly 

they  are  placed  upon  the  centrifuge.     Exceedingly   severe  muscular  exertion 

LS  well  as  marked  activity  on  the  part  of  other  organs  greatly  reduce  the  pressure 

in  the  carotid  arteries. 

Cerebral  Pressure.— Enclosed  within  the  unyielding  calvarium  there  is  on  the 
;  nand  the  brain  together  with  the  nutritive  fluid  (lymph)  that  permeates  it, 


PROTECTIVE    AND    NUTRITIVE    APPARATUS    OF    THE    BRAIN.  8ll 

as  well  as  the  cerebrospinal  fluid,  and,  on  the  other  hand,  the  system  of  blood- 
vessels. If  the  volume  of  the  latter  is  increased  in  consequence  of  the  presence 
of  an  increased  amount  of  blood  in  the  skull,  the  brain  becomes  poorer  in  fluid, 
like  an  expressed  sponge.  Conversely,  in  case  of  excessive  production  of  the 
fluids  mentioned  the  Wood  must  escape  from  the  vascular  system.  That  the 
latter,  however,  is  possible  must  be  concluded  from  the  circumstance  that  the 
formation  of  the  fluid  is  not,  under  all  circumstances,  dependent,  as  a  simple 
transuding  filtrate,  solely  upon  the  blood-pressure,  but  that  it  may  take  place  also 
independently  of  the  latter  as  a  result  of  the  secretory  activity  of  the  vessels. 

The  brain  and  the  fluid  surrounding  it  are  constantly  under  a  certain  mean 
pressure,  which  is  influenced  by  the  atmospheric  pressure,  so  that  the  pressure 
within  the  skull  is  altered  in  correspondence  with  fluctuations  in  the  atmospheric 
pressure.  According  to  Grashey  there  prevails  in  the  skull  of  an  adult  a  negative 
pressure  of  — 13  cm.  of  water;  at  the  foramen  magnum  it  is  zero.  In  the  dural 
sac  of  the  spinal  cord  there  is  a  positive  pressure,  below  (in  the  erect  posture) 
greater  than  above,  but  on  the  average  +60  cm.  of  water.  The  investigations 
of  Naunyn  and  Schreiber  upon  pathological  brain -pressure,  or  cerebrospinal 
pressure,  have  shown  that  this  pressure  must  reach  a  level  somewhat  below  the 
arterial  pressure  in  the  carotid  artery  before  the  distinctive  symptoms  of  cerebral 
pressure  appear.  These  consist  of  headache  of  paroxysmal  occurrence,  with 
marked  vertigo  to  the  point  of  unconsciousness,  vomiting,  slowing  of  the  pulse, 
slow  and  shallow  respiration,  convulsions,  injection  of  the  conjunctiva,  and  in- 
crease of  the  pressure  of  the  cerebrospinal  fluid.  The  cause  of  these  symptoms 
resides  in  anemia  of  the  brain,  so  that  bloodletting  is  to  be  avoided.  In  conse- 
quence of  excessive  tension  of  the  cerebrospinal  fluid  the  brain  is  expressed  like  a 
sponge.  The  blood  escapes  from  it,  and  naturally  from  the  capillaries  most 
readily,  as  these  can  be  most  readily  expressed  on  account  of  their  lower  internal 
pressure.  Acute  cerebral  anemia  is  thus  induced.  If  the  degree  of  pressure 
attains  only  a  moderate  level  the  symptoms  described  may  remain  latent.  Never- 
theless, nutritive  disorders  develop  in  the  brain,  with  consecutive  phenomena, 
such  as  persistent  slight  headache,  a  feeling  of  vertigo,  muscular  weakness,  visual 
disturbances  (in  consequence  of  neuroretinitis  with  papillitis).  The  symptoms 
may  be  relieved  by  elevation  of  the  blood-pressure,  while  reduction  of  the  pressure 
causes  more  marked  symptoms  of  cerebral  pressure. 

At  a  pressure  of  from  70  to  80  mm.  pain  appears  in  dogs  only  in  consequence 
of  mechanical  irritation  of  the  dura;  at  a  higher  pressure,  loss  of  consciousness; 
at  a  pressure  of  100  mm.,  convulsions  similar  to  those  attending  sudden  occlusion 
of  the  arteries.  A  pressure  of  from  100  to  120  mm.  gives  rise  to  slowing  of  the 
pulse  in  consequence  of  central  irritation  of  the  vagus,  while  the  respiratory 
frequency  exhibits  a  transitory  increase  and  later  a  reduction.  Marked  com- 
pression of  long  standing  terminates  fatally  sooner  or  later.  The  blood-pressure 
is  first  increased  in  consequence  of  reflex  stimulation  of  the  vasomotor  center, 
as  a  result  of  irritation  of  the  sensory  nerves  by  pressure.  Then  the  blood-pressure 
falls,  with  marked  slowing  of  the  pulse.  In  addition,  variations  in  blood-pressure 
of  irregular  occurrence  are  indicative  of  direct  central  irritation  of  the  vasomotor 
center  by  pressure. 

At  the  level  of  the  cauda  equina  the  pressure  of  the  spinal  fluid  in  the  arach- 
noid sac  is  only  between  7.5  and  12  mm.  of  mercury  in  the  dog.  After  evacuation 
of  the  cerebrospinal  fluid  restoration  takes  place  rapidly.  Artificial  increase  is 
soon  neutralized,  the  excess  of  fluid  passing  into  the  lymphatics  and  the  veins. 


COMPARATIVE.     HISTORICAL. 

Nerves  are  wanting  in  the  protozoa.  Among  the  celenterates  the  first  in- 
dications of  a  nervous  system  are  present  in  the  neuromuscular  cells  of  the  hydroids 
and  the  medusze.  In  the  latter  a  closed  nervous  chain  passes  along  the  mar- 
gin [of  the  umbrella  and,  corresponding  to  the  marginal  bodies,  exhibits  cell- 
like  thickenings  from  which  filaments  pass  to  the  sense-organs.  In  worms  a 
ring  is  often  attached  to  the  head  and  it  surrounds  the  pharynx  in  those  provided 
with  intestines  as  a  single  or  a  double  ring.  From  this  there  pass  into  the  elongated 
body  longitudinal  trunks,  frequently  two,  which  are  provided  with  ganglia  corre- 
sponding to  the  body-segments,  and  here  they  anastomose.  In  the  leech  only 
one  longitudinal  trunk  provided  with  ganglia,  the  so-called  abdominal  medulla,  is 
present.  In  echinoderms  the  mouth  is  surrounded  by  a  large  nervous  ring,  from 


812  COMPARATIVE.       HISTORICAL. 

which  thick  nerves  pass  off  corresponding  to  the  main  trunks  of  the  water-vas- 
cular system.  At  the  point  of  origin  the  nervous  ring  is  provided  with  the 
so-called  ambulacral  brains.  Arthropods  possess  above  the  pharynx  a  large  cephalic 
ganglion  from  which  the  sense-nerves  arise.  Another  ganglion  below  the  pharynx 
is  connected  on  each  side  with  the  first  by  means  of  a  commissure.  From  this 
point  the  abdominal  chain  of  ganglia  extends  through  the  thorax  and  the  abdomen. 
At  times  several  ganglia  are  fused  into  a  nervous  node  of  considerable  size;  at 
other  times  they  remain  isolated  for  the  majority  of  the  segments  of  the  body. 

In  molluscs  also  the  pharyngeal  ring  is  still  present,  although  the  ganglionic 
masses  occupy  a  varying  position  in  it.  A  number  of  remotely  situated  ganglia 
connected  with  the  pharyngeal  ring  by  means  of  filaments  represent  the  sympa- 
thetic. In  cephalopods  a  portion  of  the  pharyngeal  ring  almost  entirely  devoid 
of  commissures  is  enclosed  as  the  brain  in  a  cartilaginous  calvarium.  In  addition 
ganglia  are  found  in  the  stomach  and  the  heart.  In  vertebrates  the  nervous 
system  is  always  situated  on  the  dorsal  aspect  of  the  body.  In  the  amphioxus 
it  is  not  yet  subdivided  into  brain  and  spinal  cord.  The  divisions  of  the  brain 
of  vertebrates  have  been  discussed  on  p.  776,  the  peripheral  nerves  on  p.  721. 

Historical. — Alkmaeon  (580  B.  C.)  located  consciousness  in  the  brain,  Galen 
(131-203  A.  D.)  the  impulse  for  voluntary  movements.'  Aristotle  (384  B.  C.) 
described  the  brain  of  man  as  relatively  the  largest.  He  designated  it  as  unirri- 
table  to  stimuli  (insensitive).  He  considered  small  persons  as  mentally  superior. 
He  considered  it  a  function  of  the  brain  to  cool  the  heat  arising  from  the  heart. 
Herophilus  (300  B.  C.)  properly  considered  the  region  of  the  posterior  horn  as 
the  principal  seat  for  sensation.  He  described,  further,  the  calamus  scriptorius. 
Probably  as  a  result  of  experiment,  he  considered  the  fourth  ventricle  as  the 
most  important  for  life.  Homer  makes  repeated  references  to  the  danger  of 
injury  of  the  neck  (the  seat  of  the  medulla  oblongata).  Hippocrates,  Galen, 
Aretaeus,  and  Cassius  Felix  (97  A.  D.)  knew  that  a  lesion  of  one-half  of  the  brain 
causes  paralysis  on  the  opposite  side  of  the  body.  Galen  recognized  the  spinal 
cord  as  containing  the  conducting  tract  for  motion  and  sensation.  The  ascetics 
of  the  Middle  Ages  were  familiar  with  visual  hallucinations  (visions)  and  the  like, 
and  many  important  paintings  are  to  be  considered  as  representations  of  such 
hallucinations,  the  eye  of  the  expert  now  and  again  recognizing  in  them  photoptic 
secondary  phenomena,  for  example  scintillating  scotoma.  Vesalius  described 
(1540)  the  five  ventricles  of  the  brain.  R.  Columbo  observed  (1559)  the  move- 
ment of  the  brain  synchronous  with  the  action  of  the  heart,  while  the  respiratory 
movement  of  the  brain  was  first  described  accurately  in  1811  by  Ravinna.  Varo- 
lius  (born  1543)  described  the  pons.  Goiter  noted  (1573)  the  possibility  for  life 
to  continue  after  removal  of  the  cerebrum.  Wepfer  discovered  in  1658  the 
hemorrhagic  nature  of  apoplexy  ("sanguine  extra  vasa  effuso  ex  rupto  ramo"), 
while  Sylvius  de  le  Boe  described  the  fossa  and  the  aqueduct  named  after  him. 
Schneider  (1660)  determined  the  weight  of  the  brain  of  different  animals.  Mis- 
tichelli  (1709)  and  Petit  (1710)- described  the  decussation  of  the  fibers  of  the 
medulla  below  the  pons.  Haller  and  his  pupil  Zinn  were  familiar  with  the  cir- 
cular movements  following  injuries  of  the  brain.  Lorry  was  the  first  to  observe 
disorders  of  coordination  in  a  pigeon  after  puncture  of  the  cerebellum  (1760). 
Gall  demonstrated  the  partial  origin  of  the  optic  nerve  from  the  anterior  quad- 
rigeminate  body  and  he  gave  the  best  descriptions  of  the  fibers  and  of  the  convolu- 
tions of  the  brain  from  dissection  of  the  brain  from  below.  Luigi  Rolando  (1809) 
described  the  great  central  fissure  of  the  brain.  He  and  Bellinger  (1823)  described 
more  fully  the  form  of  the  gray  matter  of  the  spinal  cord.  Carus  described  (1814) 
the  central  canal  of  the  spinal  cord,  which  had  already  been  observed  in  the 
seventeenth  century  by  J.  Conrad  Brunner.  A  most  extensive  anatomical 
work  upon  the  brain  was  written  by  Burdach  (1819-1826). 


PHYSIOLOGY  OF  THE  ORGANS  OF 
SPECIAL  SENSE. 


INTRODUCTORY  REMARKS. 

The  function  of  the  organs  of  special  sense  is  to  transmit  to  the 
sensorium  impressions  of  the  various  phenomena  of  the  outer  world; 
they  act,  therefore,  as  the  intermediate  apparatus  of  sensory  per- 
ceptions. In  order  that  these  may  be  brought  about,  the  following 
conditions  must  be  fulfilled:  (i)  The  sense-organ,  with  its  specific  end- 
apparatus,  must  be  anatomically  intact,  and  be  capable  of  performing 
its  physiological  function.  (2)  A  "  specific  stimulus"  must  be  present 
and  act  upon  the  end-organ  in  a  normal  manner.  (3)  There  must 
be  an  uninterrupted  communication  from  the  sense-organ  through  the 
course  of  the  afferent  nerve  to  the  brain.  (4)  At  the  time  of  stimulation, 
psychic  activity  (attention)  must  be  directed  toward  the  process  of 
stimulation;  in  this  manner  the  sensation  (as,  for  instance,  of  light  or 
sound)  first  originates  through  the  sense-organ.  (5)  If,  finally,  through 
a  psychic  act,  the  sensation  is  referred  to  its  external  cause  (a  process 
that'takes  place  in  the  cerebral  cortex  of  t£e  psychosensorial  centers), 
a  conscious  sense-percept  is  formed.  Often,  however,  this  reference 
is  made  unconsciously,  inasmuch  as  it  is  deduced  only  from  experiences 
previously  made.  (6)  The  sensory  nerves  are  connected  not  only  with  the 
cerebral  cortex,  but  also  with  more  deeply  situated  central  nuclei,  where- 
by reflexes  are  produced,  which  (in  the  absence  of  a  conscious  sensory 
perception)  appear  as  movements,  for  the  purpose  of  guarding  the 
sensory  mechanisms  against  irritation,  and  protecting  them.  In  the 
lower  animals  the  instinctive  movements  for  the  material  preservation 
of  the  animal  that  take  place  on  irritation  of  the  sense-organs  are 
effectuated  in  this  way. 

Among  the  stimuli  that  affect  the  terminal  apparatus  of  the  sense- 
organs  there  are  distinguished:  (i)  Adequate  or  homologous  stimuli, 
that  is,  those  for  the  activity  of  which  the  organ  is  especially  constructed, 
for  example  the  rods  and  cones  of  the  retina  for  the  undulations  of  the 
luminiferous  ether.  Thus,  there  is  a  specific  stimulus  for  each  sensory 
nerve-ending  (Johannes  Miiller's  law  of  specific  energy).  (2)  Other  stimuli 
of  a  different  nature  (mechanical,  thermal,  chemical,  electrical,  internal 
somatic)  are  also  efficient,  as,  for  instance,  the  seeing  of  stars  in  con- 
sequence of  a  blow  upon  the  eye,  or  ringing  in  the  ears  as  a  result  of 
cerebral  hyperemia.  These  heterologous  stimuli  may  affect  the  nervous 
elements  of  the  sensory  apparatus  throughout  their  entire  course  from 
the  terminal  sense-organ  to  the  cerebral  cortex.  On  the  other  hand,  the 
adequate  stimuli  act  only  upon  the  terminal  apparatus ;  for  example 
light  thrown  upon  the  trunk  of  the  exposed  optic  nerve  has  no  effect 
whatsoever. 

813 


814  PHYSIOLOGY    OF    THE    ORGANS    OF    SPECIAL    SENSE. 

The  homologous  stimuli  are  effective  with  respect  to  the  sense-organs 
only  within  certain  limits  of  intensity.  Exceedingly  feeble  stimuli,  to 
begin  with,  are  without  any  effect.  The  degree  of  intensity  of  stimu- 
lation that  originates  the  first  trace  of  sensation  is  called  the  threshold  of 
sensation,  or  the  "threshold  value."  With  increase  in  the  intensity  of 
the  stimulus  the  sensations  increase,  and  the  sensations  increase  equally 
when  the  intensity  of  the  stimulus  increases  in  like  proportions.  For 
example,  the  same  sensation  of  equal  increase  in  brightness  is  produced 
by  the  light  of  n  candles,  instead  of  10,  or  of  no  candles  instead  of 
100  (the  ratio  of  increase  in  each  case  being  equal  to  one-tenth).  As  the 
logarithms  of  the  numbers  increase  equally,  the  law  has  been  expressed 
as  follows :  The  sensations  increase  not  as  the  absolute  intensities  of  the 
stimuli,  but  approximately  as  the  logarithms  of  the  intensities.  The 
universal  applicability  of  this  psychophysical  law  of  Fechner  has, 
however,  been  disputed  recently  by  E.  Hering.  Specific  stimuli  of 
excessive  activity  give  rise  to  peculiar  painful  sensations,  as,  for  instance, 
the  sense  of  blinding,  of  deafening  of  the  ear,  etc.  The  sense-organs 
react  to  adequate  stimuli  only  within  certain  definite  limits;  as,  for 
instance,  the  ear  responds  to  vibrations  of  sonorous  bodies  only  with- 
in the  range  of  a  definite  number  of  vibrations,  and  the  retina  only 
to  the  undulations  of  the  luminiferous  ether  between  red  and  violet, 
although  not  to  the  heat-waves  nor  to  the  chemically  active  vibrations. 

The  designation  after-sensation  is  applied  to  the  phenomenon 
that  the  sensation,  as  a  rule,  lasts  longer  than  the  stimulus;  to  these 
belong  the  after-images,  the  persistent  sensation  after  pressure  upon  the 
skin,  etc.  Subjective  sensations,  finally,  are  brought  about  by  the 
irritation  of  the  nervous  part  of  the  apparatus  by  internal,  somatic  causes. 
The  highest  order  of  these  subjective  sensations,  which  usually  depend 
upon  pathological  irritation  of  the  psychosensorial,  cortical  centers 
are  known  as  hallucinations ;  as,  for  example,  when  a  person  in  delirium 
sees  forms  or  hears  voices  that  are  not  present.  In  'contradistinction  to 
these,  the  designation  illusions  is  applied  to  the  modifications,  by  the 
mind,  of  a  sensation  actually  present ;  as,  for  example,  when  the  rolling  of  a 
wagon  is  thought  to  be  thunder.  Each  of  these  subjects  will  be  taken 
up  in  detail  under  the  individual  sense-organs. 

In  newborn  infants  the  sense  of  touch  is  strongly  developed,  the  pain-sense 
poorly;  muscular  sensations  are  doubtfully  present;  while  smell  and  taste  are 
frequently  confused.  Auditory  stimuli  are  perceived  from  the  second  day  on, 
visual  stimuli  immediately  after  birth,  but  a  peripheral  visual  field  does  not  yet 
exist.  Toward  the  fourth  or  fifth  week  movements  of  convergence  and  accom- 
modation are  observed,  while  after  four  months  colors  are  differentiated.  Dif- 
ferent stimuli  are  not  perceived  simultaneously — a  reflex  inhibitory  center  is  not 
yet  developed. 


THE    VISUAL    APPARATUS.  815 


THE  VISUAL  APPARATUS. 

PRELIMINARY    ANATOMICAL    AND    HISTOLOGICAL    OBSERVA- 
TIONS.     THE    INTRAOCULAR    PRESSURE. 

The  following  anatomical  and  histological  sketch  can  refer  only  to  the  physio- 
logically important  points;  it  presupposes,  naturally,  a  knowledge  of  the  anatomical 
structure  of  the  eye. 

I.  External  or  fibrous  tunic  of  the  bulb,  consisting  of  the  cornea  and  the  solera. 

The  cornea  is,  for  the  sake  of  simplicity,  assumed  to  have  a  uniformly 
spherical  curvature,  although  in  reality  it  deviates  from  this  form.  It  represents 
rather  the  vertical  segment  of  a  somewhat  oblate  ellipsoid,  which  must  be  conceived 
as  produced  by  the  rotation  of  an  ellipse  about  its  long  axis ;  numerous  deviations 
from  such  a  regular  figure  occur,  however.  It  is  approximately  of  the  same 
thickness  throughout;  except  that  in  the  newborn  the  central  portion  is  some- 
what thicker,  while  in  adults  it  is  rather  thinner.  The  cornea  is  composed  of 
the  following  layers:  (i)  The  anterior,  stratified,  nucleated  epithelium,  0.03  mm. 
thick  (Fig.  266,  a),  consists  of  numerous  layers  of  cells,  all  of  which  are  connected 
by  delicate  processes  of  protoplasm.  The  deepest  cells  are  rather  cone-shaped, 
are  arranged  vertically  side  by  side  and  are  known  as  supporting  cells.  The 

Corneal  corpuscles  in  the 
lymph-spaces  in  man. 


Lymph-spaces 
communicating  with  "\^^          \U'^  *>  ^     L^-f*f  ^40 ^£9  ^\    Lymph-spaces 

one  another.  ^^-j"t^  '- -     .  ;  — ~I^'   for  the  corneal 

corpuscles. 


FIG.  265. 

roundish  cells  of  the  middle  layers  are  more  arched,  and  possess  tooth-like  processes, 
which  fit  into  corresponding  depressions  in  the  adjoining  cells.  The  deeper  cells 
contain  a  diplosoma.  The  superficial  cells  are  flat,  entirely  smooth,  and  hard 
squamous  epithelium,  containing  keratin.  The  conjunctiva  contains  scattered 
goblet-cells, 'which  produce  mucus.  (2)  The  epithelial  layer  rests  on  the  anterior 
surface  of  the  rather  uneven  anterior  elastic  membrane,  or  Bowman's  membrane, 
a  structureless,  hyaloid  membrane  (6)  o.oi  mm.  thick,  under  the  action  of  re- 
agents having  a  fibrillar  appearance,  and  posteriorly  passing  gradually  in- 
to: (3)  The  true  corneal  tissue,  which  consists  of  doubly  refracting  fibers, 
constituted  of  exceedingly  delicate  connective-tissue  fibrils.  These  fibers  are 
woven  into  about  60  mat-like  lamellae  (/),  which  overlie  one  another  and  are 
cemented  together  in  layers.  Near  the  anterior  elastic  membrane  these  bundles 
bend  forward  as  supporting  fibers.  Some  fibers  pass  through  this  entire  layer  as 
"perforating"  fibers.  In  the  interstices  of  the  mesh  work  there  is  a  system  of 
intercommunicating  passages,  which  possess  a  sort  of  parietal  layer.  These 
anastomosing  canals  are  lymphatic  in  nature  and  communicate  with  the  lymph- 
vessels  of  the  conjunctiva.  The  fixed  corneal  corpuscles  (Fig.  266,  c)  lie  in  these 
spaces;  they  are  provided  with  anastomosing  processes,  and  possess  the  character 
of  protoplasmic  cells.  Kiihne  saw  these  cells  retract  upon  stimulation  of  the 
corneal  nerves;  the  anatomical  connection  of  the  nerves  with  the  cells  has  also 
been  shown.  According  to  v.  Recklinghausen  wandering  cells  may  also  penetrate 


8l6     PRELIMINARY    ANATOMICAL    AND    HISTOLOGICAL    OBSERVATIONS. 

these  channels  from  without,  and  increase  greatly  in  the  presence  of  inflammation. 
(4)  The  transparent,  structureless  posterior  elastic  membrane  (d),  0.006  mm. 
thick,  Descemet's  or  Demour's  membrane,  possesses  in  many  animals  a  striated 
appearance  indicative  of  a  lamellar  structure,  and  toward  the  corneal  periphery, 
where  it  becomes  thicker,  it  occasionally  exhibits  slight  conical  projections.  This 
membrane  is  exceedingly  tough  and*  (in  the  presence  of  inflammation,  etc.)  re- 
sistant; when  it  is  detached,  it  curls  up  toward  its  convex  side.  Its  peripheral 
portion  passes  over  into  the  fibre-elastic  network  of  the  pectinate  ligament  of  the 
iris,  the  trabeculae  of  which  are  lined  with  epithelial  cells.  (5)  The  posterior 
corneal  epithelium  is  composed  of  a  single  layer  of  flat,  delicate,  hexagonal,  nucleated 


FIG.  266.— Meridional  Section  through  the  Corneoscleral  Junction:  a,  Anterior  corneal  epithelium;  b,  Bowman's 
membrane;  c,  corneal  corpuscles  or  lymph-spaces;  I,  corneal  lamella;  the  layer  between  b  and  d  is  the  true 
tissue  of  the  cornea;  d,  Descemet's  membrane;  e,  its  epithelium;  /,  junction  of  the  cornea  and  the  sclera; 
g,  hmbus  .conjunctivas;  h,  conjunctiva;  «,  Schlemm's  canal;  k,  Leber's  venous  plexus,  considered  by  Leber 
as  belonging  to  Schlemm  s  canal;  m  m,  meshes  in  the  tissue  of  the  pectinate  ligament  of  the  iris;  n,  root 
of  the  iris;  o  longitudinal,  p  circular  (transversely  divided)  fiber-bundles  of  the  sclera;  q,  perichoroidal  space; 
s  meridional,  /  equatorial  (circular)  bundles  of  the  ciliary  muscle;  «,  section  of  a  ciliary  artery;  v,  epithelium 
»f  the  ins  (continuation  of  that  on  the  posterior  surface  of  the  cornea);  w,  stroma  of  the  iris;  x,  pigment  of 
the  iris;  z,  a  ciliary  process. 

cells  (/),  bound  together  by  fine  processes,  the  attached  portions  of  which  have 

fibrous  appearance.     These  cells  extend  from  the  edge  of   the  cornea  onto  the 

surface  of  the  ins  (v).     In  the  interspaces  between  the  individual  cells 

here  arettne  lymph-spaces  that  communicate  with  a  delicate  canal-system  beneath 

the  epithelial  layer,  and,  further,  through  Descemet's  membrane,  with  the  corneal 

lacunae. 

The  nerves  of  the  cornea  arise  from  the  large  and  short  ciliary  nerves,  and  are 

•tly  sensory  m  function.     They  enter  the  margin  of  the  cornea  as  trunks  that 

;s  medullary  sheaths.     Further  inward  the  sheaths  are  lost,  and  the  nerves 

form  a  network  on  the  surface  of  the  cornea.     The  branching,  naked  fibrillae 


PRELIMINARY    ANATOMICAL    AND    HISTOLOGICAL    OBSERVATIONS.     817 

penetrate  into  the  epithelial  layer,  again  divide,  ascending  perpendicularly,  and 
end  finally  between  the  epithelial  cells  as  minute  fibers  with  small  knobs  (visible 
on  treatment  with  gold  chlorid)  (Fig.  334).  The  trophic  fibers  of  the  cornea  are 
probably  the  deeper-lying  twigs  that  are  connected  with  the  corneal  corpuscles. 

Blood-vessels  are  present  only  in  the  outer  edge  of  the  cornea  (Fig  267,  v], 
and  extend  inward  from  the  limbus  a  distance  of  2  mm.  above,  1.5  mm.  below, 
and  i  mm.  laterally;  the  outermost  capillary  loops  bend  backward  in  an  arched 
manner.  The  cornea  is  nourished  from  its  outer  margin.  Opacities  of  the  cornea 
produce  corresponding  disturbances  of  vision;  pathologically,  blood-vessels  may 
be  formed  within  it. 

The  cornea  contains  collagen  and  mucin  (but  no  chondrin) ;  the  anterior 
epithelium  two  globulins.  The  "membranin"  of  Descemet's  membrane  stands 
between  elastin  and  mucin,  and  is  digested  by  trypsin. 

The  sclera  is  a  dense,  fibrous  tunic  composed  of  connective-tissue  bundles, 
running  in  an  equatorial  (p)  and  a  meridional  (o)  direction,  with  which  are  asso- 
ciated many  elastic  fibers.  In  its  interstices,  which  communicate  with  those 
of  the  cornea,  there  are  flat  connective-tissue  corpuscles,  some  of  which  are  color- 
less, some  pigmented,  and  also  wandering  lymph-cells.  It  is  thickest  posteriorly, 
and  thinnest  in  the  equatorial  region;  further  forward  it  becomes  thicker  at  the 
point  of  insertion  of  the  tendons  of  the  four  recti  muscles.  It  contains  only  a  few 
blood-vessels,  which  form  a  wide-meshed  capillary  network  immediately  under 
its  inner  surface.  Other  vessels  form  an  arterial  circle  around  the  optic -nerve 
entrance.  In  rare  instances  it  is  spherical,  but  usually  it  is  more  like  an  ellipsoid, 
which  must  be  conceived  as  produced  by  the  rotation  of  an  ellipse  either  about 
its  short  axis  (short  eyes),  or  about  its  long  axis  (long  eyes).  Above  and  below, 
the  sclera  overlaps  the  transparent  corneal  margin,  so  that  the  cornea  has  an 
elliptical  form  if  viewed  from  in  front,  and  a  circular  form  when  viewed  from 
behind.  Following  the  margin  of  the  cornea,  but  within  the  scleral  substance, 
runs  a  circular  canal,  the  canal  of  Schlemm  (i),  which  anastomoses  with  other 
venous  channels  (Leber's  venous  plexus)  (&) ;  Schwalbe  and  Waldeyer  regard 
Schlemm's  canal  as  a  lymph-channel.  Posteriorly  the  sclera  is  continuous  with 
the  sheath  of  the  optic  nerve  derived  from  the  dura  mater.  The  sclera  also 
possesses  nerves,  which  are  said  to  terminate  in  the  cellular  elements  within  its 
substance. 

II.  Median  or  vascular  tunic  of  the  bulb,  consisting  of  the  choroid,  the  ciliary  pro- 
cesses, and  the  iris. 

The  choroid  is  composed  of  the  following  layers:  (i)  On  its  inner  surface  there 
is  a  transparent  boundary  layer,  only  0.7  //  thick,  which  becomes  somewhat 
thicker  anteriorly.  (2)  The  extremely  vascular  capillary  network  of  the  chorio- 
capillary  layer  or  membrane  of  Ruysch,  embedded  in  a  homogeneous  layer. 
Bounding  this  is:  (3)  A  dense  network  of  elastic  fibers,  which  is  lined  on  both 
surfaces  by  endothelium.  Then  follows  (4)  the  choroid  proper,  a  layer  with 
pigmented  connective-tissue  corpuscles,  which  in  the  form  of  an  elastic  network 
contains  numerous  veins,  with  their  accompanying  lymph-sheaths,  as  well  as 
arteries,  which  are  provided  with  unstriated  muscle-fibers  in  their  connective- 
tissue  sheaths.  Finally,  there  is  (5)  the  supra-choroid  layer  or  lamina  fusca, 
which  bounds  the  large  perichoroidal  lymph-space  (q) ;  the  latter  is  lined  with 
endothelium  and  is  crossed  by  branched  and  anastomosing  trabeculae  covered  with 
endothelial  and  connective-tissue  cells.  In  newborn  infants,  who  always  have 
dark-blue  irides,  the  uveal  tissue  contains  no  pigment;  in  bruns  the  pigment 
develops  later,  while  in  blonds  the  uvea  remains  unpigmented. 

In  the  ciliary  portion  of  the  uveal  tract,  the  pigmented  connective-tissue  cells 
are  not  so  numerous.  In  this  position  lies  the  ciliary  muscle  (muscle  of  accom- 
modation or  tensor  of  the  choroid),  whose  meridional  fibers  (s)  arise  by  means 
of  a  branched,  reticulated,  connective-tissue  insertion  at  the  inner  side  of  the 
corneo-scleral  margin,  near  Schlemm's  canal,  and  extend  backward  into  the 
choroid;  the  radial  fibers  pass  inward  toward  the  interior  of  the  eyeball;  and  the 
circular  bundles  (0  are  situated  more  internally,  just  within  the  ciliary  border 
(Heinr.  Miiller's  muscle).  The  motor  nerve  of  this  unstriated  muscle  is  the  oculo- 
motor. Within  the  ciliary  processes  ganglion-cells  have  been  found,  which  prob- 
ably belong  to  the  trigeminus. 

The  iris  consists  of  the  following  layers,  from  before  backward:  The  anterior 

epithelium,  a  single  layer  of  cells  (v) ;    a  stroma  with  connective-tissue  fibers  and 

cells   (vascular  layer) ;  and.  finally,  a  posterior,  structureless  limiting  membrane 

(membrane  of  Bruch),  which  is  covered  with  the  double  layer  of  pigment-cells 

52 


818     PRELIMINARY    ANATOMICAL    AND    HISTOLOGICAL    OBSERVATIONS. 


(x).  This  pigment-layer  is  lined  by  the  exceedingly  delicate  limiting  membrane 
of  the  iris,  which  is  a  continuation  of  the  internal  limiting  membrane  of  the  retina. 
Within  the  vascular  layer  (which  contains  pigmented  connective-tissue  cells  in 
bruns)  are  the  two  unstriated  muscles:  the  sphincter  of  the  pupil  (Fig.  281), 
which  surrounds  the  pupil,  and  lies  near  the  posterior  surface  of  the  iris  (it  is 
innervated  by  the  oculomotor) ;  and  the  dilator  of  the  pupil.  The  latter  consists 

of  a  thin  layer  of  radially  arranged 
fibers,  some  of  which  pass  to  the 
pupillary  margin,  while  some  bend 
around  into  the  sphincter.  At  the 
outer  extremity  of  the  iris  the  radia- 
ting fibers  are  arranged  in  anastomo- 
sing arches  and  form  a  circular  muscle- 
bundle.  The  chief  nerve  of  the  dilator 
of  the  pupil  is  the  sympathetic. 
Ganglia  are  found  on  the  ciliary 
nerves  in  the  choroid.  Gerlach  has 
given  the  appropriate  name  of  avenu- 
lar  ligament  of  the  bulb  to  the  pris- 
matic bundle  of  fibrous  tissue  that 
bounds  the  periphery  of  the  iris,  and 
forms  the  point  of  union  of  the  ciliary 
body,  the  iris,  the  ciliary  muscle,  the 
venous  sinus  of  the  iris,  and  the  transi- 
tion from  the  cornea  to  the  sclera. 

The  course  of  the  choroidal  vessels 
is  of  great  importance  for  the  nutrition 
of  the  eye.  This  is  described  by 
Leber  as  follows :  Among  the  arteries 
are:  (i)  The  short  posterior  ciliary 
(Fig.  267,  a,  a),  about  20  in  number, 
which  penetrate  the  sclera  near  the 
optic  nerve.  They  terminate  in  the 
vascular  network  of  the  chorio-capil- 
lary  layer  (w),  which  reaches  as  far 
as  the  or  a  serrata.  (2)  The  two  long 
posterior  ciliary  arteries,  one  of  which 
lies  on  the  nasal,  the  other  on  the  tem- 
poral side.  They  pass  to  the  ciliary 
portion  of  the  choroid  (6),  where  they 
divide  dichotomously  and  enter  the 
iris,  to  help  form  the  circulus  arteriosus 
iridis  major  (p).  (3)  The  anterior 
ciliary  arteries  (c~),  which  arise  from 
the  muscular  branches,  perforate  the 
sclera  anteriorly,  and  give  off  branches 
to  the  ciliary  portion  of  the  choroid 
and  to  the  iris.  About  12  branches 
run  backward  (o)  from  them  to  the 
chorio-capillary  layer.  The  veins 
carry  off  the  blood  as  follows:  (i) 


FIG.  267.— Diagrammatic  Representation  of  the  Blood- 
vessels of  the  Eye  (after  Th.  Leber).  Horizontal 
section — veins  dark,  arteries  light,  with  a  double 
contour:  a,  short  posterior  ciliary,  b,  long  poste- 
rior ciliary  arteries;  c  c',  anterior  ciliary  artery 
and  vein;  d,  d',  conjunctival  artery  and  vein; 
e  ef,  central  artery  and  vein  of  the  retina;  /,  ves- 
sels of  the  inner,  g  of  the  outer  sheath  of  the  optic 
nerve;  h,  vorticose  veins;  i,  short  posterior  ciliary 
vein,  running  only  to  the  sclera;  k,  branch  of  the 
short  posterior  ciliary  artery  to  the  optic  nerve; 
I,  anastomosis  between  the  choroidal  vessels  and 
those  of  the  nerve;  m,  chorio-capillary  layer;  «, 
episcleral  branches;  o,  recurrent  rVmrnirlal  art*™- 


,  >,  recurrent  choroidal  artery, 
p,  circulus  arteriosus  iridis  major  (cross-section); 
q,  vessels  of  the  iris;  r,  ciliary  process;  s,  branch 
of  a  vorticose  vein  from  the  ciliary  muscle;  /, 
branch  of  the  anterior  ciliary  vein  from  the  ciliary 
muscle;  «,  circulus  venosus;  v,  marginal  network 
ol  the  corneal  limbus;  w,  anterior  conjunctival 
artery  and  vein. 


b°y  (     sthe  bi°°d 


The  anterior  ciliary  veins  (c1)  receive 
the  blood  from  the  anterior  part  of 
the  uvea;  they  pass  outward  and 
communicate  with  Schlemm's  canal 
and  Leber's  venous  plexus.  They 
do  not  collect  any  blood  from  the 
(2)  The  venous  plexus 


quitearro      even  SUr/aCe  °f  the  lens'    th    posterior  chamterfs 

b"ue  is  fnSIed^r,  rt        t5'  an<J  I"  m^ants  it;  is  nearly  obliterated.    When  Berlin 
ciUarv  veins       -Pn       rS  antenor  chamber,  it  almost  invariably  enters  the  anterior 
ary  vems,  even  m  living  animals;  the  same  is  true  of  carmfne.     It  is,  therefore, 


PRELIMINARY    ANATOMICAL   AND    HISTOLOGICAL    OBSERVATIONS.     819 

.concluded  that  there  must  be  a  direct  communication  between  the  veins  and  the 
anterior  chamber,  as  a  diffusion  of  these  substances  through  membranes  is  im- 
possible. 

'  Internally  to  the  choroid  lies  the  single  layer  of  hexagonal  epithelial  cells,  from 
0.0135  to  0.02  mm.  in  diameter,  which  are  filled  with  pigment.  This  layer  belongs 
really  to  the  retina.  In  front  of  the  ora  serrata  it  forms  a  double  layer  of  cells, 
which  extends  to  the  posterior  surface  of  the  iris  (Fig.  266,  x).  In  albinos  it  is 
free  from  pigment;  the  outer  cells  on  the  ridges  of  the  ciliary  processes  are  also 
devoid  of  pigment. 

III.  Internal  tunic  of  the  bulb,  consisting  of  the  retina  (optic  portion)  and  its  con- 
tinuations, the  ciliary  and  iridic  portions  of  the  retina. 

The  retina  is  bounded  externally  by  the  hexagonal  pigment-epithelium  (Fig. 
268,  Ft),  which  embryologically  and  functionally  belongs  to  the  retina.  The  cells 
are  not  flat,  but  send  pigmented  processes  into  the  spaces  between  the  ends  of 
the  rods.  In  some  animals  the  cells  contain  drops  of  fat  (rabbit)  and  other  sub- 
stances. At  the  ora  serrata  the  cells  are  larger  and  darker.  Of  the  true  layers 
of  the  retina:  (i)  The  visual  cells,  or  the  "rods"  (50  and  "cones,"  called  also  "neu- 
roepithelium,"  lie  most  externally.  They  are  absent  at  the  optic-nerve  entrance. 
The  outer  portions  of  the  rods  contain,  during  life,  a  red  pigment,  the  "visual 
purple,"  which  is  preserved  in  the  dark,  but  is  bleached  by  daylight,  and  is  con- 
tinually reprodticed  in  the  eye.  It  may  be  extracted  by  2.5  per  cent,  solution 
of  the  biliary  acids,  especially  from  retinas  that  have  lain  in  TO  per  cent,  solution 
of  sodium  chlorid.  The  rods  are  from  0.04  to  0.06  mm.  high,  and  from  o. 0016  to 
o.ooiS  mm.  broad,  and  exhibit  longitudinal  striation,  due  to  depressions;  in  the 
axis  runs  a  fine  fibril.  The  outer  segment  breaks  up,  occasionally,  into  numerous, 
exceedingly  fine  transverse  discs.  Krause  found  an  ellipsoid  body,  the  "rod- 
ellipsoid,"  at  the  junction  of  the  outer  and  inner  rod-segments.  The  flask-shaped 
cones  are  devoid  of  visual  purple;  the  outer  segment  exhibits  also  longitudinal 
striation,  and  breaks  up  readily  into  transverse  discs.  In  the  macula  lutea  (the 
yellow  pigment  of  which  lies  only  in  the  outer  retinal  layers,  and  not  in  the  cones) 
cones  alone  are  present;  near  the  macula  each  cone  is  surrounded  by  a  garland 
of  rods.  The  greater  the  distance  from  the  macula,  the  fewer  are  the  cones. 
Nocturnal  animals  (owl  and  bat)  possess  either  no  cones  whatever,  or  only  im- 
perfect forms.  In  birds  the  retina  has  many  cones,  in  the  lizard  cones  alone.  The 
rods  and  cones  rest  on  the  sieve-like,  fenestrated  external  limiting  membrane 
(Le) ;  both  send  processes  through  the  openings:  the  cones  to  the  larger  cone- 
granules,  and  those  lying  at  a  higher  level,  the  rods  to  the  transversely  striated 
rod-granules.  The  granules  belong  to :  (2)  The  outer  nuclear  layer  (du  K~) ;  this 
and  all  the  succeeding  layers,  are  designated  the  cerebral  layers.  There  then 
follows:  (3)  The  narrow  outer  reticular  (granular,  plexiform)  layer.  (4)  The 
inner  nuclear  layer  (inK).  The  nuclei  represent  bipolar  ganglion-cells  (ganglion 
of  the  retina)  and  are  called  rod-bipolars  or  cone-bipolar  s,  whose  course  is  shown 
in  Fig.  269,  E.  Each  bipolar  sends  out,  in  addition,  a  fine  fiber  between  the  vis- 
ual cells,  and  ends  with  a  punctate  knob  near  the  limiting  membrane.  Ganglion- 
cells  without  demonstrable  neurites,  called  amacrine  cells,  are  of  unknown  nature. 
(5)  The  inner  reticular  (granular,  plexiform)  layer  (in.gr).  (6)  Ganglion-cell  layer 
(ganglion  of  the  optic  nerve)  (Ggl).  Finally:  (7)  The  layer  of  optic-nerve  fibers 
(o) ,  which  is  next  to  the  internal  limiting  membrane  (Li) .  According  to  Salzer 
there  are  in  all  438,000;  according  to  W.  Krause,  however,  400,000  broad  and  an 
equal  number  of  the  finest  optic-nerve  fibers.  For  each  fiber  there  are  7  or  8 
cones,  about  100  rods,  and  7  pigmented  cells  (of  the  choroid).  The  fibers  are 
naked  axis-cylinders;  they  are  absent  in  the  macula  lutea,  where,  however,  the 
ganglion-cells  are  numerous. 

The  newer  investigations  have  shown  that  there  is  no  uninterrupted  fiber- 
connection  between  the  rods  and  cones  and  the  optic-nerve  fibers.  According 
to  Ram6n  y  Cajal  (Fig.  269)  the  fibers  arising  from  the  rods  (a)  end  in  the  outer 
reticular  layer  (C)  as  tiny  knobs,  after  passing  through  the  outer  nuclear  layer(d) : 
the  cone-fibers  below  the  cone-granules  (c)  like  unraveled  threads  (z) .  The  bi- 
polar processes  of  the  internal  nuclear  layer  (e  E)  break  up  into  fibrils  in  the  outer 
reticular  layer  (C)  and  in  the  inner  reticular  layer  (F) ,  which  are  only  approxi- 
mately in  contact,  on  the  one  hand  with  ganglion-cell  processes  (r),  on  the  other 
hand,  with  the  elements  in  the  outer  reticular  layer  (C).  From  each  ganglion- 
cell  (i,  k)  an  axis-cylinder  process  is  sent  off  centripetally,  while  one  or  more 
dendrites  enter  the  inner  reticular  layer.  The  optic-nerve  fibers  contain  also 
a  number  of  centrifugal  fibers  (s,  s).  The  further  course  of  the  optic  nerve  is 


820     PRELIMINARY    ANATOMICAL    AND    HISTOLOGICAL    OBSERVATIONS. 

discussed  on  p.  679.  Between  the  two  homogeneous  limiting  membranes  (Ri  and 
Le)  lies  the  supporting  tissue  of  the  retina  (not  true  connective-tissue).  It  in- 
cludes the  supporting  fibers  of  Miiller  (Fig.  268,  Rf),  which  contain  nuclei  (k) 
and  pass  through  all  the  cerebral  layers,  and  end  in  expanded  terminations  at  the 
internal  limiting  membrane  (Rk).  In  addition,  the  supporting  tissue  forms  a 
network  throughout  all  the  retinal  layers,  with  openings  for  the  penetrating  ner- 
vous elements  (Sg) .  In  the  outer  reticular  layer,  there  are  also  flattened ,  partly 
nucleated  supporting  cells,  with  long  processes,  and,  at  the  optic-nerve  entrance, 
glia-cells.  The  inner  segments  of  the  rods  and  cones  are  also  surrounded  by  a 
basket-like  supporting  tissue.  In  the  nerve-fiber  layer  there  are  flat,  stellate  cells. 
From  the  ora  serrata  forward,  the  retina  becomes  suddenly  thin,  and,  as  the 
ciliary  portion  of  the  retina,  consists  only  of  a  layer  of  cylindrical  cells,  which 
seems  to  have  arisen  from  the  coalescence  of  the  -two  nuclear  layers,  and  is 


Pi. 


FIG.  269. — Transverse  Section  of  a  Mammalian  Retina 
(after  Ramon  y  Cajal):  A,  layer  of  rods  and  cones; 
B,  visual  cells  (outer  nuclear  layer);  C,  outer 
reticular  layer;  E,  bipolars  (inner  nuclear  layer); 
F,  inner  reticular  layer;  G,  ganglion-cells;  H, 
nerve-fiber  layer;  a,  rods;  b,  cones;  e,  a  rod- 
bipolar;  f,  a  cone-bipolar;  r,  lower  ramification 
of  the  rod-bipolar;  f,  lower  ramification  of  a  cone- 
bipolar;  g,  h,  i,  j,  k,  ganglion-cells  branching  at 
various  levels  in  F;  x,  z,  contact  of  rods  and  cones 
with  the  bipolars;  t,  Miiller's  supporting  fibers;  s, 
centrifugal  nerve-fiber. 


covered  on  the  inner  side  by  the  limiting  membrane 
of  the  iris,  a  continuation  of  the  internal  limiting 
membrane  of  the  retina.  This  layer  extends  to  the 
posterior  surface  of  the  iris,  as  the  iridic  portion  of 
the  retina. 

The    blood-vessels   of    the   retina    lie  in   the  inner 
layers,   as  far    outward    as    the    inner    nuclei.     They 

communicate   with    the   choroidal   vessels   only   by   fine   branches   at  the  optic- 
•ance;     they   are    surrounded    by   perivascular   lymph-channels.      The 

TfcT*™  er  ol    the    capillaries    run  internally   to   the   inner   nuclear  layer. 

ine  lovea  centralis  has  no  vessels.       Except  in  the  mammalia,  the  eel,  and  several 

ret^aca^StlStoi.        retina  C°ntainS  n°  Vessds  at  alL     Dest™ction  of  the 


FIG.  268. — Layers  of  the  Retina. 


J6tina4  has  an  acid  reacti°n,  but  becomes  alkaline  if   kept  in  the 
-BlotalM  ™ds  and  cones  contain  albumin,  neurokeratin  ,  nuclein,  and  colored 

m  the  cones):    so-called  chromophanes. 
same  constituents  as  the  gray  matter  of  the  brain. 

than 


The  other  layers  have  the 

*  t5ansParent-  elastic  capsule,  which  is  thicker  anteriorly 
and  is  lined   on   the  inner  surface  of  its  anterior  portion  by  a 


PRELIMINARY    ANATOMICAL    AND    HISTOLOGICAL    OBSERVATIONS.     821 


Lens-fibers. 


layer  of  low,  cuboidal  cells.  Toward  the  equator  of  the  lens  these  cells  become 
elongated  into  mon enucleated  fibers,  all  of  which  bend  around  the  margin  of  the 
lens,  and  meet  on  both  sides  of  the  lens,  their  ends  forming  a  stellate  figure  (lens- 
star),  and  being  held  together  by  a  cement-substance.  The  lens-fibers  contain 
globulin,  enclosed  in  a  sort  of  sheath.  They  are  flattened  mutually  into  hex- 
agonal fibers,  those  of  the  central  layers  having  their  edges  interlocked  by  means 
of  toothed  projections. 

For  the  sake  of  simplicity,  the  lens  may  be  considered  as  a  biconvex  body, 
with  spherical  surfaces,  the  posterior  surface  having  the  greater  curvature.  The 
anterior  surface,  however,  really  represents  a  part  of  an  ellipsoid,  produced  by 
rotation  about  the  short  axis.  The  posterior  surface  resembles  the  vertical 
section  of  a  paraboloid,  that  is  it  may  be  considered  as  produced  by  the  rotation 
of  a  parabola  about  its  axis.  The  outer  layers  of  the  lens  have  a  lower  index  of 
refraction  than  the  more  internal  layers.  The  central  nucleus  is  of  greater 
density  than  the  lens  as  a  whole,  and  it  is,  at  the  same  time,  more  convex.  The 
edge  of  the  lens  is  always  separated  by  an  interspace  from  the  ciliary  process. 

The  zonule  of  Zinn,  which  arises  from  the  ora  serrata,  is  applied  to  the  ciliary 
portion  of  the  choroid  in  the  form  of  a  ruffled,  folded  membrane,  in  such  a  way 
that  the  ciliary  processes  occupy  its  folds,  and  are  attached  to  them.  It  then 
passes  to  the  edge  of  the  lens,  on  the  anterior 
portion  of  which  it  is  inserted  in  a  wavy  man- 
ner. Behind  the  zonule  of  Zinn,  reaching 
to  the  vitreous  body,  is  the  canal  of  Petit. 
The  zonule  is  a  fibrous  fenestrated  mem- 
brane; according  to  Merkel  and  H.  Virchow, 
the  canal  of  Petit  also  is  occupied  by  exceed- 
ingly fine  fibers:  it  is  consequently  not  a 
true  canal,  but  a  complicated  system  of 
communicating  spaces.  The  zonule  is  always 
stretched  and  keeps  the  lens  in  position,  so 
that  it  may  be  considered  as  the  suspensory 
ligament  of  the  lens. 

Opacities  of  the  lens  (gray  cataract)  hinder 
the  entrance  of  rays  of  light  into  the  eye. 
The  absence  of  the  lens  (aphakia) ,  following 
operations  for  cataract,  may  be  compensated 
by  the  use  of  strong  convex  glasses.  Such  an 
eye,  of  course,  possesses  no  power  of  accom- 
modation. The  lens  contains  albuminoid 
bodies,  some  of  which  are  soluble  in  water 
and  sodium  chlorid  (chiefly  globulin  and  some 
albumin)  and  some  insoluble. 

The  vitreous  body  is  invested  by  the 
transparent  hyaloid  membrane,  the  outer 

surface  of  which,  as  far  forward  as  the  ora  serrata  is  in  contact  with  the  internal 
limiting  membrane  of  the  retina.  From  this  point  forward  the  meridional  fibers 
of  the  zonule  of  Zinn  arise  between  the  two,  and  are  adherent  to  the  surface  of 
the  vitreous  and  to  the  ciliary  processes.  A  canal,  2  mm.  in  diameter,  the 
hyaloid  canal,  runs  from  the  optic  papilla  to  the  posterior  surface  of  the  lens; 
in  fetal  life  it  is  occupied  by  blood-vessels.  The  peripheral  portion  of  the  vitreous 
body  is  laminated  like  an  onion.  The  central  portion  is  homogeneous.  In  the 
former,  especially  in  newborn  infants,  there  are  spherical  (leukocytes),  spindle- 
shaped,  or  stellate,  and  also  vacuolated  cells  of  mucoid  tissue;  in  the  center 
there  are  only  disintegrated  remains  of  these  cells.  Running  between  them  are 
transparent  fibers  and  lamellae.  The  vitreous  body  is  gelatinous  in  character, 
and  contains  only  i.i  per  cent,  of  solids,  consisting  of  mucin,  with  albumin, 
and  traces  of  globulin  and  glutin. 

The  lymph-tracts  of  the  eye  include  an  anterior  and  a  posterior  set.  The 
anterior  is  composed  of  the  anterior  and  posterior  chambers,  which  communicate 
with  the  lymph-vessels  of  the  iris,  the  ciliary  processes,  the  sclera,  the  cornea  and 
the  conjunctiva.  The  posterior  chamber  communicates  with  the  canal  of  Petit. 

To  the  posterior  lymph-system  belongs,  in  the  first  place,  the  hyaloid  canal, 
and  secondly  the  large  pcrichoroidal  space  situated  between  the  sclera  and  the 
choroid.  The  latter  communicates  by  means  of  lymph-vessels,  which  surround 
the  emerging  trunks  of  the  vorticose  vessels  of  Stenon,  with  the  large  lymph -space 


Polygonal  transverse 

sections  of  lens-fibers. 


FIG.  270. 


822 


THE  INTRAOCULAR  PRESSURE. 


of  Tenon,  which  lies  between  the  sclera  and  Tenon's  capsule.  Posteriorly 
this  is  continuous  with  a  lymph-space  surrounding  the  surface  of  the  optic  nerve  in 
the  form  of  a  sheath;  anteriorly  it  is  in  direct  communication  with  the  subcon- 
junctival  lymph-spaces  of  the  eyeball.  The  optic  nerve  has  three  sheaths:  (i) 
The  dural;  (2)  the  arachnoid;  and  (3)  the  pial,  arising  from  the  corresponding 
cerebral  membranes.  Between  these  three  sheaths  there  are  two  lymph-spaces: 
•the  subdural,  between  i  and  2,  and  the  subarachnoid,  between  2  and  3  (Fig.  271). 
Both  are  lined  by  endothelial  cells:  fine  trabeculse  extending  from  one  wall  to 
the  other  are  similarly  covered  by  cells.  According  to  Axel  Key  and  Retzius 
these  lymph-spaces  communicate  anteriorly  with  the  perichoroidal  space. 

The  aqueous  humor  resembles  closely  the  cerebrospinal  fluid,  and  contains 
albumin,  some  sugar,  urea  and  sarcolactic  acid  (which  is  present  in  the  vitreous 
body).  The  albumin  increases  when  the  difference  between  the  blood-pressure 
and  the  intraocular  pressure  is  augmented.  Such  changes  of  pressure  and  like- 
wise intense  irritations  applied  to  the  eye  cause  the  production  of  fibrin  in  the 
anterior  chamber. 


MHHBVw 

7.  I     /*   /» 


FIG.  271.—  Horizontal  Section  through  the  Optic  Nerve,  at  its  Entrance  into  the  Eyeball  through  the  Coats  of  the 
Jiye:  a  inner,  b  outer  layers  of  the  retina;  c,  choroid;  d,  sclera;  e,  physiological  cup;  /,  central  artery  of  the 
retina  m  the  nerve;  g,  its  point  of  bifurcation;  h,  lamina  cribrosa;  /,  outer  (dural)  sheath;  m,  outer  (subdural) 
lymph-space;  n,  inner  (subarachnoid)  lymph-space;  r,  middle  (arachnoid)  sheath;  p,  inner  (pial)  sheath 
t,  nerve-fiber  bundles;  k,  connective-tissue  (longitudinal)  septa. 


,     .The  fluid  within  the  eye  is  under  a  definite  pressure,  the  intraocular  pressure, 

This  depends  ultimately  upon  the  pressure  in  the  arteries  in  the 

interior  of  the  eye,  and  must  rise  and  fall  with  the  latter.     It  is  determined  by 

the  resistance  or  the  yielding  of  the  eyeball  with  the  fingers.     It  may  be 

measured  more  accurately  by  an  apparatus,    the  "ophthalmotonometer."     Like 

tne  arterial  pressure,  it  is  influenced  by  many  circumstances.     It  is  increased 

with  every  pulse-beat  and  every  expiration  and  it  is  decreased  with  every  inspira- 

ie  elasticity  of  the  sclera  and  the  cornea  acts  as  a  regulator  with  every 

:rease  m  the  arterial  pressure,  causing,  like  the  air-chamber  of  a  fire  engine, 

e  venous  blood  to  be  driven  out  when  more  arterial  blood  is  pumped  into  the 

is  also  important  for  the  stability  of  the  intraocular  pressure  that  the 

aqueous  humor  is  secreted  as  rapidly  as  it  is  absorbed.     Increase  of  the  intra- 

ocular pressure  makes  the  cornea  flatter. 

The  secretion  of  the  aqueous  humor  takes  place  with  comparative  rapidity,  a  fact 
tnat  Landois  ;  proved  by  the  appearance  of  hemoglobin  in  the  anterior  chamber  of  a 
dog  nail  an  hour  after  the  introduction  of  free  hemoglobin  (transfusion  of  lamb's. 


PRELIMINARY    DIOPTRIC    CONSIDERATIONS.  823 

blood)  in  the  blood  of  the  dog.  It  takes  place  more  rapidly  if  the  aqueous  humor 
is  previously  removed  from  the  chamber  through  a  corneal  wound.  Ehrlich  used 
fluorescein  for  the  study  of  the  movements  of  the  fluids  within  the  eye.  This  is  an 
innocuous  substance  which,  when  introduced  into  the  body,  penetrates  into  the 
fluids  of  the  eye,  and  may  be  recognized  by  its  greenish  fluorescence  in  reflected 
light ,  even  in  a  solution  of  i  part  to  two  million  parts  of  water.  From  observations 
on  the  entrance  of  this  substance  into  the  aqueous  humor,  it  is  now  assumed 
that  the  ciliary  body  is  the  secreting  organ  for  the  aqueous  humor,  which  passes 
through  the  pupil  into  the  anterior  chamber. 

Section  of  the  cervical  symphathetic,  and  still  more,  that  of  the  trigeminus, 
accelerates  the  secretion  of  the  aqueous  humor,  but  decreases  its  amount. 

The  cornea  permits  the  entrance  of  fluids  into  the  anterior  chamber,  for 
example  atropin  and  fluorescein. 

The  excretion  of  the  aqueous  humor  takes  place  by  filtration  in  the  angleTof 
the  anterior  chamber;  it  passes  through  the  clefts  of  the  spaces  of  Fon tana,  which 
communicate  with  the  anterior  chamber,  and  enters  the  vessels  of  the  circular  canal 
of  Schlemm,  which  lies  directly  on  their  outer  side  (plexus  ciliaris  venosus  in 
animals).  None  passes  through  the  cornea,  although  some  is  imbibed  by  its 
posterior  layers,  which  are  thus  nourished,  and  there  are  no  special  lymph-vessels 
to  remove  it  from  the  anterior  chamber. 

Under  normal  circumstances,  the  pressure  is  the  same  in  the  vitreous  as  in 
the  aqueous,  although  atropin  seems  to  increase  the  pressure  in  the  former,  and 
to  decrease  it  in  the  latter,  while  physostigma  has  the  opposite  action.  Arrest  of 
the  outflow  of  the  venous  blood  often  increases  the  pressure  in  the  vitreous,  and 
decreases  that  in  the  aqueous.  Compression  of  the  eyeball  from  without  will 
cause  more  fluid  to  pass  out  of  the  eye  temporarily  than  enters  it.  The  decrease 
of  the  intraocular  pressure  after  section  of  the  trigeminus  is  striking;  likewise  its 
increase  upon  irritation  of  the  same  nerve — facts  often  observed  by  Landois. 
The  statements  with  regard  to  a  possible  analogous  action  of  the  sympathetic  vary. 
Interruption  of  the  outflow  of  venous  blood  raises  the  pressure;  an  insufficient 
supply,  associated  with  a  normal  outflow,  decreases  the  pressure.  The  innervation 
of  the  vessels  of  the  eyeball  is  discussed  on  p.  684. 


PRELIMINARY  DIOPTRIC    CONSIDERATIONS. 

The  eye  is  comparable  as  an  optical  apparatus  to  the  camera  obscura.  In 
both  a  diminished,  inverted  image  of  objects  of  the  outer  world  is  found  on  the 
background  (the  projection-surface).  Instead  of  the  simple  lens  of  the  camera, 
however,  the  eye  possesses  several  refractive  media,  behind  one  another:  cornea, 
aqueous  humor,  lens  (the  several  parts  of  which:  capsule,  cortex  and  nucleus,  also 
possess  different  refractive  indices) ,  and  vitreous  body.  Each  medium  is  separated 
from  the  one  next  to  it  by  a  ref acting  surface,  which  is  assumed  to  be  spherical. 
The  projection-surface  of  the  eye  is  the  retina,  which  is  colored  by  the  visual 
purple.  As  this  substance  is  bleached  chemically  by  light,  so  that  the  images 
may  even  be  fixed  temporarily  on  the  retina,  the  comparison  of  the  eye  to  the 
camera  is  still  more  striking. 

In  order  that  the  passage  of  the  light-rays  through  the  media  of  the  eye  may 
be  accurately  followed,  the  following  factors  must  be  known:  (i)  The  refractive 
indices  of  the  media;  (2)  the  shape  of  the  refracting  surfaces;  (3)  the  distance 
of  the  various  media  from  each  other  and  from  the  projection-surface. 

The  action  of  a  convex  lens  will  first  be  considered.  There  are  to  be  distin- 
guished in  such  a  lens  the  centers  of  curvature,  that  is,  the  centers  of  the 
two  spherical  surfaces  (Fig.  272  I,  m  m^.  The  line  connecting  these  points  is 
called  the  principal  axis:  the  center  of  this  line  is  the  optical  center  of  the  lens 
(O).  All  rays  that  pass  through  the  optical  center  of  the  lens  (and  which  may  be 
countless)  pass  through  unbent.  They  are  called  principal  rays,  or  secondary 
axes  (nj).  The  following  laws  governing  the  refraction  of  rays  by  convex  lenses 
must  be  remembered: 

i.  Rays  falling  on  the  lens  parallel  to  the  principal  axis  are  so  refracted  that 
they  meet  on  the  opposite  side  of  the  lens  at  a  point  that  is  known  as  the  focus 
or  principal  focus  (f).  The  distance  of  this  point  from  the  optical  center  of  the 
lens  (O)  is  called  the  focal  distance  (f  O)  of  the  lens.  The  converse  of  this  propo- 
sition is  evident:  Rays  that  diverge  from  the  principal  focus,  and  strike  the 
lens,  become  parallel  to  the  principal  axis  on  the  opposite  side,  and  do  not  meet. 


824 


PRELIMINARY    DIOPTRIC    CONSIDERATIONS. 


2.  Rays  proceeding  from  a  point  (IV,  1)  in  the  prolonged  principal  axis  beyond 
the  principal  focus  (f) ,  are  united  at  a  point  on  the  opposite  side  of  the  lens  (v) 
(conjugate  focus).     The  following  conditions  are  possible:    (a)   If  the  distance  of 
the  point  of  light  from  the  lens  is  double  the  focal  distance,  the  conjugate  focus 
is  at  an  equal  distance  on  the  opposite  side  (double  the  focal  distance).      (6)  As 
the  point  of  light  moves  nearer  the  lens,  the  conjugate  focus  moves  further  away. 
(c)   If  the  point  of  light  is  more  than  double  the  focal  distance  from  the  lens,  the 
conjugate  focus  is  correspondingly  closer  to  the  lens. 

3.  Rays  that  proceed  from  a  point  in  the  principal  axis  (III,  b)  within  the 
focal  distance  are   rendered  less  divergent,  but  do  not  meet  again;    conversely, 
rays  that  converge  on  a  convex  lens  are  united   at  a  point  within  the  principal 
focal  distance. 

4.  If  the  point  of  light   (V,  a)  lies  in  a  secondary  axis  (a  b)  the  same  laws 
hold  good,  provided  that  the  angle  made  by  the  secondary  axis  with  the  prin- 
cipal axis  is  small. 


Formation  of  Images  by  Convex  Lenses.— After  what  has  been  said  about 
e  conjugate  foci  of  rays  proceeding  from  a  point  of  light,  it  is  easy  to  construct 
ic  image  of  an  object  produced  by  a  convex  lens.     This  is  done  simply  by  pro- 
ting  the  images  of  various  points  of  the  object.      For  example  (in  V)  b  is  ob- 
viously the  image  of  the  point  a  of  the  object,  v  the  image  of  1;    the  picture  is 
or.1v  o/e  T^K-     +    Convex.lenses  form  inverted  and  real  images  (upon  a  screen) 
1      obJects  as  are  situated  beyond  the  principal  focus  of  the  lens, 
regard  to  the  size  and  distance  of  the  image  from  the  lens,  the  following 

ft  ^  t0  be  Ii°t^d:  (a)   If  the  obJect  is  d°uble  the  focal  distance  from 
its  image  is  of  the  same  size  as  the  object  and  at  an  equal  distance  from 
and  at  t'hp     *  As.the   object  approaches  the  principal  focus,  the  image  recedes 
^  H    ^f  V?16   becomes  larger,      (c)   On  the  other  hand,  if  the  object  is 
JS  double  the  focal  distance  from  the  lens,  the  image  approaches  the  lens, 
the  same  time  becomes  smaller. 


PRELIMINARY    DIOPTRIC    CONSIDERATIONS. 


825 


The  distance  of  the  image  from  the  lens  may  be  readily  calculated  by  the 
following  formula,  in  which  1  represents  the  distance  of  the  point  of  light,  b  the 
distance  of  the  image,  and  f  the  focal  distance  of  the  lens: 


Examples:    Let  1  =  24  cm.,  f  =  6  cm.    Then  JL  =  JL — JL  =  JL;  therefore 

b          6          24 
b  =  8  cm.,  that  is,  the  image  is  formed  8  cm.  behind  the  lens.     Further:    Let 

1  =  10  cm.,  f  =  5  cm.   (or  1  =  2f).      Then  JL  =  JL —  J_  =  JL;  therefore  b  =  10 

b  5          10        10 

cm.,  that  is,  the  image  is  double  the  focal  distance  from  the  lens.     Finally,  let 

1  =  oo.     Then    *  -  =  JL-      -L,  or  b  =  f ,  that  is,  the  focus  for  parallel  rays,  coming 

from  an  infinite  distance,  is  in  the  principal  focus  of  the  lens. 

Index  of  Refraction. — A  ray  of  light  passing  from  one  medium  to  another 
medium  of  different  density,  in  a  direction  perpendicular  to  the  surface,  passes 
through  the  latter  without  changing  its  direction  If,  therefore  (Fig.  273)  G  D. 
is  perpendicular  to  A  B,  then  D  D  is  also  perpendicular  to  A  B.  For  a  horizontal 
surface  A  B  the  axis  of  incidence  is  the  vertical  line  G  D,  while  for  a  spherical 


FIG.  273. 


FIG.  274. 


surface  the  axis  of  incidence  is  the  prolonged  radius.  If  the  ray  of  light  strikes 
the  surface  obliquely,  it  is  refracted,  that  is  deflected  from  its  original  direction. 
The  incident  and  refracted  rays  lie,  however,  in  the  same  plane.  If  the  oblique, 
incident  ray  passes  from  a  rarer  medium  to  a  denser  one  (for  example,  from  air 
into  water),  the  refracted  ray  is  deflected  toward  the  perpendicular.  Conversely, 
if  the  ray  passes  from  a  denser  medium  into  a  rarer  one,  it  is  deflected  away  from 
the  perpendicular.  The  angle  that  the  incident  ray  (S  D)  forms  with  the  per- 
pendicular (G  D),  (angle i)  is  called  the  angle  of  incidence.  The  angle  that  the  re- 
fracted ray  (D  Sx)  forms  with  the  prolonged  perpendicular  (D  D)  is  called  the 
angle  of  refraction  (angle  r) .  The  degree  of  the  refraction  is  expressed  by  the  index 
of  refraction  (or  exponent  of  refraction) ;  it  is  represented  for  each  substance  by 
the  relation  of  the  sine  of  the  angle  of  incidence  to  the  sine  of  the  angle  of  refrac- 
tion of  a  ray  passing  from  air  into  that  substance.  Thus,  n  =  sine  i  :  sine 
r  =  a  b  :  c  d.  In  comparing  the  indices  of  refraction  of  two  media,  it  is  assumed 
that  the  ray  of  light  passes  from  the  air  into  the  media.  In  passing  from  air  into 
water,  the  ray  of  light  is  deflected  to  such  a  degree  that  the  ratio  of  the  sine  of  the 
angle  of  incidence  to  the  sine  of  the  angle  of  refraction  is  as  4  :  3 ;  the  index  of 
refraction  is  therefore  ^  (more  exactly  =  1.336).  With  glass  the  ratio  is  3  :  2 


826 


PRELIMINARY    DIOPTRIC    CONSIDERATIONS. 


(more  exactly  the  index  of  refraction  is  1.535).  The  sines  of  the  angles  of  inci- 
dence and  refraction  are  in  the  same  ratio  as  the  velocities  with  which  the  rays 
of  light  pass  through  the  two  media. 

The  refracted  ray  is,  therefore,  easily  constructed,  if  the  indices  of  refraction 
are  known.  Example:  Let  L  (Fig.  274)  represent  the  air,  G  a  denser  medium 
(glass),  with  a  spherical  surface,  x  y,  the  center  of  which  is  at  m;  P  O  represents 
the  oblique  incident  ray;  m  Z  is  then  the  axis  of  incidence,  and  the  angle  i  the 
angle  of  incidence.  Let  the  index  of  refraction  be  |;  what  is  the  direction  of 
the  refracted  ray? 

Construction. — Draw  a  circle  of  any  radius,  with  its  center  at  O;  then  from  a 
draw  a  line  a  b  perpendicular  to  the  axis  of  incidence  m  Z ;  then  a  b  is  the  sine  of 
the  angle  of  incidence,  i.  Divide  the  line  a  b  into  3  equal  parts,  and  prolong  it  a 
distance  equal  to  two  of  these  parts,  that  is  to  P.  Now,  draw  from  P  the  line  P  n, 
parallel  to  m  Z.  Then  the  line  joining  the  two  points  O  and  n  is  the  direction  of 
the  refracted  ray.  If  the  line  n  s  is  drawn  perpendicular  to  m  Z,  n  s  =  b  P.  Further, 
ns  =  the  sine  of  the  angle  r.  According  to  the  construction,  ab  :  sn  (or  :  b  P) 
=  3  :  2,  or  sine  i  :  sine  r  =  £. 

Optical  Cardinal  Points  of  a  Simple  Collecting  System. — Two  refractive  media 
(Fig.  275,  L  and  G),  which  are  separated  from  each  other  by  a  spherical  surface 
(a  b) ,  form  a  simple  collecting  system.  From  a  knowledge  of  certain  properties 
of  such  a  system,  it  is  easy  to  construct  an  incident  ray  from  the  first  medium  (L) 
striking  the  separating  surface  obliquely,  and  also  its  direction  in  the  second 


FIG.  275. 

medium  G,  as  well  as  to  determine,  from  the  position  of  a  luminous  point  in  the 
first  medium,  the  position  of  its  image  in  the  second  medium.  The  requisite  proper- 
ties and  points  of  such  a  simple  collecting  system  are  as  follows: 

L  (Fig.  275)  is  the  first,  and  Gthe  second  medium;  a  b  is  the  spherical  surface 
separating  them,  and  m  its  center  of  curvature.  All  radii  drawn  from  m  to  ab 
(m  x,  m  n)  are,  of  course,  normal  to  the  surface,  so  that  all  rays  of  light  coming  in 
the  direction  of  the  radii,  must  pass  through  m  without  deviation.  All  such  rays 
are  called  axial  rays;  and  m,  their  point  of  intersection,  is  the  nodal  point.  The 
line  that  connects  m  with  the  vertex  of  the  spherical  surface  (x)  and  is  prolonged 
in  both  directions  is  called  the  optical  axis  (O  Q) .  A  plane  (E  F)  erected  perpen- 
dicular to  O  Q  at  x  is  the  principal  plane,  and  x  is  its  principal  point.  The  follow- 
ing facts  have  been  determined: 

(i)  All  rays  (from  a  to  a5)  that  fall  upon  a  b  and  are  parallel  to  each  other  and 

the  optic  axis  in  the  first   medium  will  be  so  deflected  by  the  second  medium 

that  they  are  united  at  one  point  (Pl)  in  the  latter.     This  point  is  called  the  second 

principal  focus.     A  plane  erected  at  this  point  perpendicular  to  O  Q  is  called  the 

second  focal  plane  (C  D).      (2)  All  rays  (from  c  to  c2)  that  are  parallel  to  each 

rtner  in  the  first  medium,  but  not  parallel  to  O  Q,  are  reunited  at  a  point  in  the 

second  focal  plane  (r)  at  the  intersection  of  the  undeflected  axial  ray  (c^m  r)  with 

us  plane  (the  angle,  however,  that  the  rays  from  c  to  c2  make  with  O  Q  must  be 

i  he  converse  of  propositions  i  and  2  is  also  true:    the  rays  diverging 

trom  Pl,  and  directed  toward  a  b,  continue  through  the  first  medium  parallel  to 


PRELIMINARY    DIOPTRIC    CONSIDERATIONS. 


827 


each  other  and  to  the  axis  O  Q  (from  a  to  a5) ;  and  the  rays  coming  from  r  run 
parallel  to  each  other  in  the  first  medium,  but  not  parallel  to  the  axis  O  Q  (from 
c  to  c2).  (3)  All  rays  in  the  second  medium  that  are  parallel  to  each  other  (from 
b  to  bg)  and  to  the  axis  O  Q  are  united  at  a  point  in  the  first  medium  (p) ,  the 
first  principal  focus  (the  converse  of  this  proposition  is  also  true) .  A  plane  erected 
at  this  point  perpendicular  to  O  Q  is  known  as  the  first  focal  plane  (A  B).  The 
radius  (m  x)  of  the  refracting  surface  is  equal  to  the  difference  between  the  dis- 
tances of  the  principal  focal  points  (p  and  pt)  from  the  principal  point  (x) ;  hence 
mx  =  pi  x  —  p  x. 


FIG.  276. 

1.  From  a  knowledge  of  these  simple  relations  the  direction  of  the  refracted 
ray  may  be  constructed.     Let  A  (Fig.  276)  be  the  first,  B  the   second  medium; 
c  d  the  spherical  surface  between  them;  a  b  the  optical  axis,  k  the  nodal  point,  p 
the  first  and  pj  the  second  principal  focus;  C  D  the  second  focal  plane.     If,  now, 
x  y  is  the  direction  of  the  incident  ray,  what  is  the  direction  of  the  refracted  ray 
in  the  second  medium  ? 

Construction:    Draw  the  undeviated  axial  ray  P  k  Q  parallel  to  x  y.     Then  the 
line  y  Q  must  be  the  direction  of  the  refracted  ray  (according  to  proposition  2) . 

2.  Construction  of  the  Image  of  a  Given  Point  in  an  Object. — [The  letters  A,  B, 
c  d,  a  b,  k,  p  and  plf  C  D,in  Fig.  277  have   the  same  designations  as  before.]     If 
now  a  point  of  light  be  given  at  o,  where  will  be  its  image  in  the  second  medium? 

Construction:   Draw  the  undeflected  axial  ray  o  k  P.    Then  draw  the  ray  o  x  par- 
allel to  the  axis  a  b.     The  parallel  rays  a  e  and  o  x  are  united  at  pt  (according  to 


FIG.  277. 


proposition  i).  If  x  pt  is  prolonged  until  it  intersects  the  ray  o  P,  P  is  the  image 
of  the  point  o,  for  the  image  will  be  situated  at  the  intersection  of  the  rays  o  x  and 
o  k  in  the  second  medium,  consequently  at  P. 

Construction  of  the  Refracted  Ray  and  of  the  Image  when  Several  Refractive 
Media  are  Present. — If  several  refractive  media  are  placed  behind  one  another, 
the  construction  must  be  made  from  medium  to  medium  in  the  manner  already 
described.  This,  however,  would  be  a  troublesome  procedure,  especially  in 
dealing  with  small  objects.  In  1840  Gauss  calculated  (by  methods  that  cannot 
be  explained  in  an  elementary  treatise)  that  in  all  such  cases  the  method  of  con- 
struction may  be  greatly  simplified.  If  the  media  are  "centered,"  that  is  if  all 


828 


PRELIMINARY    DIOPTRIC    CONSIDERATIONS. 


have  the  same  optical  axis,  such  a  system  may  be  represented  by  two  surfaces 
having  equal  indices  of  refraction,  separated  by  a  definite  distance.  The  rays 
that  fall  on  the  first  surface  are  not  refracted  by  it,  but  are  only  displaced  laterally 
and  run  parallel  to  their  original  direction  as  far  as  the  second  surface.  The 
refraction  takes  place  at  this  point,  and  in  the  same  way  as  previously  constructed: 
that  is  as  if  only  one  refracting  surface  were  present.  For  this  calculation  the 
indices  of  refraction  of  the  media,  the  radii  of  the  refracting  surfaces,  and  finally 
the  distance  between  these  surfaces  must  be  known :  but  this  subject  cannot  be 
discussed  in  any  further  detail  here.  The  refracted  ray  is  constructed  in  the 
following  manner:  Let  a  b  (Fig.  278,  I)  represent  the  optic  axis,  H  the  first 
principal  focus  determined  by  calculation,  h  h  the  first  principal  plane,  Ht 
the  second  focal  point,  hj  hj  the  second  principal  plane,  k  the  first  nodal  point, 
kx  the  second  nodal  point,  F  the  second  principal  focus,  and  Ft  Fx  the  second 
focal  plane.  Let  m  n  be  the  direction  of  the  incident  ray;  what  is  the  direction 
of  the  refracted  ray? 


FIG  278. 

Construction:  Displace  the  ray  m  n  parallel  with  itself  as  m,  n,,  to  the  second 
principal  plane.  Now,  draw  the  line  p  klf  parallel  to  mx  n.  According  to  rule 
2,  pki  and  m,  n  must  intersect  at  a  point  of  the  plane  F  F,.  As  p  k,  passes 
through  unrefracted,  the  ray  from  nx  must  likewise  pass  through  r;  and  n,  r  is 
therefore  the  direction  of  the  refracted  ray. 

Construction  of  the  Image  of  a  Point.— Let  o  (Fig.  278,  II)  represent  a  point 
31  light;  where  is  the  image  of  this  point  in  the  last  medium?  Draw  from  o  the 
axial  ray  o  k,  and  make  o  x  parallel  to  a  b.  Displace  both  rays  parallel  to  them- 
selves to  the  second  principal  plane:  then  draw  mk,  parallel  to  o  k,  and  prolong 
?J  +U^  ™  my  parallrel  to  a  b  Passes  through  F;  m  klf  as  the  axial  ray,  is  not 
The  image  of  the  point  n  will  be  found  at  the  point  of  intersection 
of  the  prolonged  rays  n  F  and  m  ka  (at  O) . 

These  constructions  are  not  applicable  to  objects  that  are  at  some  distance 
the  optical  axis.     For  such   a  condition  the   eye  is  more   advantageously 
ructed  than  a  camera  obscura  (being  periscopic),  because  its  surface  of  pro- 
is  a  hemisphere,  and  consequently  the  images  are  sharper  in  its  lateral 
portions  than  would  be  possible  on  a  flat  surface. 


DIOPTRIC    LAWS.        CONSTRUCTION    OF    RETINAL    IMAGE. 


829 


APPLICATION  OF  DIOPTRIC   LAWS   TO    THE  EYE.       CONSTRUC- 
TION OF    THE  RETINAL  IMAGE.     THE   OPHTHALMOMETER. 

ERECT    IMAGES. 

The  eyeball  represents  a  centered  system,  composed  of  several 
refracting  media  separated  by  spherical  surfaces,  the  anterior  surface 
of  the  cornea  being  in  contact  with  the  air.  In  order  to  determine  the 
course  of  the  rays  through  these  media,  it  is  necessary  to  know  the  posi- 
tion of  both  principal  foci.  Following  the  simplified  solution  of  Gauss 
previously  discussed,  Listing  and  v.  Helmholtz  in  particular  have 
estimated  the  position  of  those  points.  In  order  to  make  this  calcula- 
tion, a  knowledge  of  the  indices  of  refraction  of  the  ocular  media,  the 
radii  of  the  refracting  surfaces,  and  the  distance  between  them  is  neces- 
sary. These  will  be  taken  up  later.  According  to  this  calculation : 
(i)  The  first  principal  point  lies  2.1746  mm.,  and  (2)  the  second  principal 
point  2.5724  mm.,  behind  the  anterior  surface  of  the  cornea;  (3)  the 
first  nodal  point  is  0.7580  mm.,  and  (4)  the  second  nodal  point  0.3602 
mm.  in  front  of  the  posterior  surface  of  the  lens;  (5)  the  second 


FIG.  279. 


principal  focus  is  14.6470  mm.  behind  the  posterior  surface  of  the  lens, 
and  (6)  the  first  principal  focus  is  12.8326  mm.  in  front  of  the  anterior 
surface  of  the  cornea. 

As  the  distance  between  the  two  principal  points  and  between  the 
two  nodal  points  is  so  small  (only  0.4  mm.),  a  point  in  the  middle  of 
each  pair  may  be  adopted  instead  of  the  two  separate  points,  without 
committing  much  error  in  the  construction.  In  this  way  there  is 
only  one  refracting  surface  for  all  the  media,  and  only  one  nodal  point, 
through  which  all  of  the  axial  rays  coming  from  without  must  pass  un- 
refracted.  Such  a  simplified  eye  is  known  as  the  "reduced  eye"  of 
Listing. 

The  construction  of  the  image  on  the  back  of  the  eye  is  now  simple. 
The  inverted  image  is  formed  on  the  retina  with  distinct  vision.  Let 
A  B  (Fig.  279)  represent  an  object  standing  perpendicularly  before  the 
eye.  From  A  a  pencil  of  rays  enters  the  eye;  the  axial  ray  A  d  passes 
through  the  nodal  point  k  without  being  refracted.  As  the  image  of  A 
must  lie  on  the  retina,  all  the  rays  from  A  must  come  to  a  focus  at  d. 
The  same  is  true  for  the  rays  from  B,  and  of  course  for  the  rays  coming 


830  OPHTHALMOMETER.   ERECT  IMAGES. 

from  -any  point  of  the  object  A  B.  As  all  the  axial  rays  must  pass 
through  the  common  nodal  point  k,  this  is  also  called  the  '  'point  of  in- 
tersection of  the  visual  rays." 

In  the  enucleated  eye  of  an  albino,  or  in  any  eye  in  which  a  piece  of  the  sclera 
and  choroid  has  been  replaced  by  a  piece  of  glass,  the  inverted  image  may  be  readily 
seen.  In  fact,  the  inverted  image  of  a  candle  held  in  front  of  the  eye  may  be 
seen  through  the  sclera,  if  the  eye  is  turned  strongly  to  one  side,  and  if  it  contains 
but  little  pigment. 

By  means  of  the  construction  of  the  retinal  image  the  size  of  this  image  may 
be  easily  calculated,  if  the  size  of  the  object  and  its  distance  from  the  cornea  are 
known.  As  the  two  triangles  A  B  k,  and  cdkare  similar,  obviously  A  B  :c  d  = 
f  k  :  k  g.  Therefore,  c  d  =  (A  B  X  k  g)  :  f  k.  All  of  these  values  are  known: 
namely  kg  =  15.16  mm. ;  further  fk=ak  +  af,  of  which  a  f  may  be  measured 
directly  and  a  k  =7.44  mm.  The  size  of  A  B  is  obtained  by  measurement. 

The  angle  A  k  B  is  designated  the  visual  angle;  the  angle  c  k  d  is,  of 
course,  equal  to  it.  It  may  be  readily  seen  that  the  objects  x  y  and  r  s, 
situated  nearer  the  eye,  must  have  the  same  visual  angle.  For  this 
reason  all  three  objects  A  B,  x  y,  and  rs  have  a  retinal  image  of  the 
same  i'size.  Objects  whose  peripheral  points,  when  united  with  the 
nodal  point,  subtend  a  visual  angle  of  the  same  size,  and  which  conse- 
quently have  retinal  images  of  the  same  size  are  said  to  have  the  same 
"apparent  size." 


FIG.  280.— Ophthalmometer  (after  v.  Helmholtz). 


For  the  determination  of  the  optical  cardinal  points  by  the  method 
of  Gauss  a  knowledge  of  the  following  relations  is  necessary : 

1.  The  indices  of  refraction  are :  for  the  cornea  1.3739,  f°r  the  aqueous 
humor  and   the  vitreous  humor   1.377,  f°r  the  lens  1.4545  (the  mean 
value  of  the  different  layers),  air  being  taken  as  i,  and  water  as  1.33 

2.  The  radii  of  the  spherical  refracting  surfaces  are:  for  the  cornea 
7.7  mm. ;  for  the  anterior  surface  of  the  lens  10.3  ;  for  the  posterior  surface 
of  the  lens  6.1  mm. 

3.  The  distances  between  the  refracting  surfaces  are :  from  the  anterior 
surface  of  the  cornea  to  the  anterior  surface  of  the  lens  3.4  mm. ;  from 
the  latter  to  the  posterior  surface  of  the  lens  (axis  of  the  lens)  4  mm. ; 
the  diameter  of  the  vitreous  body  is  14.6  mm.     The  total  length  of  the 
optical  axis  is  therefore  22.0  mm. 

As  it  is  impossible  to  measure  the  normal  curvatures  of  the  eye  after  death 
curately,  on  account  of  the  rapid  collapse  of  the  eye,  the  calculation  of  the 
the  refracting  surfaces  is  made  according  to  Kohlrausch's  method,  from 
ne  size  01  the  reflected  images  in  the  living  eye.     The  size  of  a  luminous  object  is 
the  reflected  image  as  the  distance  of  each  to  half  the  radius  of  the 
The  size  of  the  reflected  image  must,  therefore,  be  determined, 
rement  is  made  by  the  ophthalmometer  of  v.  Helmholtz.     The  ap- 
:ted  on  the  following  principle:    If  an  object  is  seen  through  an 
glass  plate,  it  appears  to  be  displaced  laterally.     This  displacement 


ACCOMMODATION    OF    THE    EYE.  831 

is  the  greater  the  more  obliquely  the  plate  is  set.  Hence,  if  the  observer  A  looks 
through  the  telescope  F,  in  front  of  whose  objective  (in  its  upper  half)  the  oblique 
plate  G'  is  placed,  and  sees  the  corneal  image  ab  of  the  eye  B,  the  latter  appears 
to  be  displaced  laterally,  that  is  to  a'  br.  If  a  second  plate  G  is  placed  before  the 
lower  half  of  the  eye-piece  of  the  telescope,  and  is  inclined  in  an  opposite  direction 
(so  that  both  plates  meet  at  an  angle,  in  the  horizontal  diameter  of  the  objective) 
the  observer  sees  the  corneal  image  a  b  displaced  laterally  to  a"  b".  As  the  two 
glass  plates  may  be  rotated  on  each  other  (at  their  points  of  intersection)  they  are 
so  placed  that  the  two  reflected  images  have  their  inner  edges  exactly  in  contact 
(so  that  b'  touches  a").  From  the  size  of  the  angle  that  the  two  plates  make, 
the  size  of  the  image  may  be  calculated  (but  the  thickness  of  the  glass  plates,  and 
the  refractive  index  of  the  glass  must  be  taken  into  consideration).  In  this 
way  the  size  of  the  reflected  image  of  the  cornea  and  also  of  the  lens  can  be  deter- 
mined, both  in  the  state  of  rest,  and  in  that  of  accommodation  for  near  vision. 

All  of  the  ocular  media,  including  the  retina,  have  a  certain  amount  of  fluores- 
cence, the  lens  most,  the  vitreous  least. 

As  the  retinal  image  is  inverted,  the  perception  of  the  object  as  an 
erect  one  is  yet  to  be  explained.  By  a  psychical  act  the  impulses  from 
each  point  of  the  retina  are  projected  outward:  thus  the  stimulation  of 
the  point  d  (Fig.  279)  to  A,  that  of  c  to  B.  This  projection  outward 
is  so  accomplished  that  all  the  points  appear  to  lie  in  a  surface  suspended 
before  the  eye,  which  is  called  the  "field  of  vision."  This  field  of 
vision  is  therefore  the  surface  of  the  retina  projected  outward  and  in- 
verted; consequently  the  field  of  vision  appears  erect,  as  the  inverted 
retinal  image  is  projected  outward  and  inverted. 

That  the  stimulation  of  each  point  is  projected  in  an  inverse  direction  through 
the  nodal  point  is  shown  by  the  simple  experiment  that  pressure  on  the  outer 
side  of  the  eyeball  is  referred  to  the  inner  aspect  of  the  visual  field.  The  entoptical 
phenomena  of  the  retina  are  likewise  projected  outward  and  inverted;  so  that, 
for  example,  the  point  of  entrance  of  the  optic  nerve  is  referred  to  the  outer  side 
of  the  yellow  spot,  and  the  like.  All  sensations  of  the  retina  are  thus  referred 
externally.  ,,Wir  sehen  die  Sonne,  die  Sterne  an  den  Himmel,  nicht  an  dem  Him- 
rnel"  (v.  Helmholtz). 

ACCOMMODATION  OF  THE  EYE. 

The  image  of  a  point  of  light,  as,  for  example,  of  a  flame,  formed  by  a  convex 
lens,  is  always  at  a  definite  distance  from  the  point  (according  to  rule  2,  page 
824).  If  a  projecti  on -surf  ace  (a  screen)  is  placed  in  this  position,  a  real  and 
inverted  image  is  formed  upon  it.  If,  however,  the  screen  is  placed  close  to  the 
lens  (Fig.  272,  IV,  ab)  or  farther  awray  from  it  (cd),  the  image  is  not  distinct,  and 
diffusion-circles  are  formed:  in  the  first  instance,  because  the  rays  have  not  yet 
united;  in  the  second,  because  the  rays  have  already  crossed  and  are  again 
diverging.  When  the  point  of  light  is  alternately  approached  to  and  withdrawn 
from  the  lens,  the  screen  must  be  correspondingly  moved  closer  to  the  lens  or 
farther  away  from  it,  if  the  sharpness  of  the  image  is  to  be  preserved.  If  the 
screen  is  fixed,  while  the  distance  of  the  point  of  light  from  the  lens  varies,  a  sharp 
image  could  be  formed  only  by  increasing  the  curvature  of  the  lens,  and  thus 
increasing  its  refractive  power  when  the  point  of  light  is  approached  to  the  lens, 
or  by  diminishing  its  curvature,  and  thus  making  it  less  refractive,  when  the 
point  of  light  is  withdrawn. 

As  the  eye  has  its  surface  of  projection  (retina)  fixed  at  an  unchanging  position, 
and  as  the  eye  possesses  the  ability  to  form  on  the  retina  sharp  images  of  both 
far  and  near  objects,  it  must  possess  the  power  of  altering  its  refractive  strength 
(the  form  of  the  lens)  to  correspond  in  every  case  to  the  distance  of  the  object. 

By  accommodation  is  meant  the  power  of  the  eye  to  form  sharp 
images  of  both  distant  and  near  objects  upon  the  retina.  This  depends 
upon  its  ability  to  make  the  lens  more  or  less  convex  (thicker  or  thinner), 
according  to  the  distance  of  the  object.  If  the  lens  is  absent,  accom- 
modation is  impossible. 


832 


ACCOMMODATION    OF   THE    EYE. 


When  the  eye  is  at  rest,  it  is  accommodated  for  the  greatest  distance; 
that  is,  sharp  images  are  formed  on  the  retina  of  objects  at  an  infinite 
distance  (as,  for  example,  the  moon).  In  other  words,  parallel  rays  (ap- 
proximately) that  enter  the  eye  are  united  on  the  retina  of  the  normal- 
sighted  eye  at  rest;  the  principal  focus  is  therefore  in  the  retina. 
Distant  vision  is  thus  accomplished  without  the  aid  of  any  muscular 
action. 

That  no  muscular  activity  is  actually  required  for  distant  vision  is  proved  by 
the  following  facts:  (i)  Normal-sighted  persons  see  sharply  and  distinctly  at  a 
distance  without  the  slightest  feeling  of  exertion.  On  opening  the  eyelids  after 
a  considerable  period  of  rest,  distant  objects  are  at  once  seen  with  sharp  outlines. 


FIG.  281.— Anterior  Quadrant  of  a  Horizontal  Section  of  the  Eyeball.  Cornea  and  lens  cut  in  the  middle  of  their 
vertical  diameter:  a,  substantia  propria  of  the  cornea;  b,  Bowman's  membrane;  c,  anterior  corneal  epithelium; 
tf,  Descemet  s  membrane;  e,  its  epithelium;  /,  conjunctiva;  g,  sclera;  h,  iris;  i,  sphincter  muscle  of  the  iris; 
7,  pectinate  ligament  of  the  iris  with  the  adjacent  fenestrated  tissue;  k,  canal  of  Schlemm;  /.  longitudinal, 
m,  circular  fibers  of  the  ciliary  muscle;  n,  ciliary  process;  o,  ciliary  portion  of  the  retina;  q,  canal  of  Petit, 
with  the  zonule  of  Zmn  (Z)  in  front  of  it,  the  posterior  leaflet  of  the  hyaloid  membrane  (p)  behind  it;  r, 
anterior,  s,  posterior,  capsule  of  the  lens;  /,  choroid;  «,  perichoroidal  space;  T,  pigment  epithelium  of  the 
ins;  x,  margin  (equator)  of  the  lens. 

(2)  If  the  eye  has  lost  its  power  of  accommodation  in  consequence  of  paralysis  of 
the  oculomotor  nerve,  sharp  images  of  distant  objects  are  still  found  on  the  retina. 
Paralysis  of  the  accommodation-apparatus  is  always  associated  with  disturbance 
f  near  vision,  never  of  distant  vision.  Temporary  paralysis,  with  the  same 
result,  is  produced  by  the  instillation  of  atropin  or  duboisin  (and  by  taking  toxic 
doses  internally). 

When  the  eye  is  accommodated  for  near  objects,  the  lens  becomes 
thicker  and  its  anterior  surface  is  more  curved  and  protrudes  further  into 
the  anterior  chamber.  The  mechanism  producing  this  change  is  as 
follows:  While  at  rest  the  lens  is  kept  flat  against  the  vitreous  by  the 
traction  of  the  stretched  zonule  of  Zinn  (Fig.  281,  Z),  which  is  attached 
to  its  margin.  When  the  ciliary  muscle  (1,  m)  contracts  to  focus  for 


ACCOMMODATION    OF    THE    EYE. 


833 


near  objects,  it  draws  the  margin  of  the  choroid  forward,  and  the  zon- 
ule,  which  is  in  intimate  relation  with  it,  is  relaxed.  As  a  result,  the 
lens  assumes  a  more  curved  form,  by  virtue  of  its  elasticity,  so  that  it 
becomes  more  convex  as  soon  as  the  flattening  tension  of  the  zonule 
relaxes.  As  the  posterior  surface  of  the  lens  rests  in  the  saucer-shaped, 
unyielding  depression  of  the  vitreous,  the  anterior  surface,  in  becoming 
more  convex,  must  protrude  further  forward. 

Hensen  and  Volckers  discovered  the  origin  of  the  nerve  of  accommodation 
in  the  most  anterior  portion  of  the  oculomotor  nucleus.  Irritation  of  the  posterior 
part  of  the  floor  of  the  third  ventricle  produces  accommodation;  if  the  irritation 
is  applied  a  little  further  back,  the  pupil  contracts.  The  fibers  for  the  sphincter 
of  the  iris  and  for  the  ciliary  muscle  are  derived  from  the  upper  oculomotor 
nucleus;  close  by  this  is  the  center  for  the  elevator  of  the  eyelid.  If  the  boundary 
between  the  third  ventricle  and  the  aqueduct  of  Sylvius  is  irritated,  the  internal 
rectus  muscle  contracts;  irritation  of  the  posterior  part  of  the  aqueduct  causes 
contraction  of  the  superior  rectus,  the  inferior  rectus  and  the  inferior  oblique. 

The  movement  during  accommodation  may  be  recognized  by  means  of  the  fol- 
lowing phenomena: 


as.' 


FIG.  282. — Diagrammatic  Representation  of  Accommodation  for  Near  and  Far  Objects.  On  the  right  the  con- 
dition during  accommodation  is  shown;  on  the  left  the  condition  during  rest.  On  both  sides  one-half  of 
the  contour  of  the  lens  is  drawn  as  a  continuous  line,  the  other  half  as  a  dotted  line.  The  letters  appearing; 
twice — both  on  the  right  and  left  sides — have  the  same  significance;  those  on  the  right  side  are  primed.  A  left, 
B  right  half  of  the  lens;  C,  cornea;  S,  sclera;  C.S..  canal  of  Schlemm;  V.K.,  anterior  chamber;  /,  iris;  P, 
pupillary  margin;  V  anterior,  H  posterior  surface  of  the  lens;  R,  equator  of  the  lens;  F,  edge  9f  the  ciliary 
processes;  a  and  b,  interval  between  them.  The  line  Z  X  shows  the  thickness  of  the  lens  in  the  act  of 
accommodation  for  a  near  object;  Z  Y,  the  thickness  of  the  lens  when  the  eye  is  at  rest. 

i.  The  images  of  Purkinje-Sanson.  If  the  light  of  a  candle  is  allowed  to 
fall  on  the  human  eye  a  little  from  the  side,  or,  better  still,  if  the  light  comes 
through  two  small  triangular  openings  in  a  piece  of  cardboard,  placed  one 
above  the  other,  the  observer  sees  three  pairs  of  reflected  images  in  the  eye.  The 
brightest  and  most  distinct  pair  (virtual)  are  formed  by  the  anterior  surface 
of  the  cornea  (Fig.  283,  a).  The  second  pair  (likewise  virtual)  are  the  largest, 
but  at  the  same  time  the  faintest;  they  are  reflected  from  the  anterior  surface 
of  the  lens  (b)  and  lie  8  mm.  behind  the  plane  of  the  pupil.  (The  images 
produced  by  convex  mirrors  are  the  larger  the  longer  the  radius  of  curvature.) 
The  third  pair  are  the  smallest  and  stand  midway  in  intensity;  they  are  inverted, 
and  lie  about  in  the  plane  of  the  pupil  (c).  These  images  are  also  virtual,  because 
they  do  not  lie  in  the  second  medium,  which  is  represented  here  by  the  air.  The 
posterior  capsule  of  the  lens,  which  reflects  these  last  images  acts  as  a  concave 
mirror.  (If  a  luminous  object  is  placed  at  a  distance  from  a  concave  mirror,  an 
inverted,  real  image,  reduced  in  size,  is  formed  near  the  focal  point  of  the  mirror, 
on  the  same  side  as  the  object.)  While  the  observer  watches  these  images,  with 
the  eye  of  the  person  at  rest,  the  latter  is  requested  to  accommodate  suddenly 
for  a  near  object.  Changes  in  the  images  are  at  once  recognized.  The  middle  pair 
(from  the  anterior  surface  of  the  lens)  become  smaller,  and  brighter,  and  approach 
each  other  (b),  because  the  anterior  surface  of  the  lens  becomes  more  convex. 
At  the  same  time  they  approach  the  corneal  images,  because  the  anterior  surface 
53 


834  ACCOMMODATION    OF    THE    EYE. 

of  the  lens  is  nearer  to  the  cornea.  Neither  of  the  other  pairs  (a,  and  c,)  change 
either  in  size  or  in  position.  By  means  of  the  ophthalmometer,  the  diminution 
of  the  radius  of  curvature  of  the  anterior  surface  of  the  lens  during  accommoda- 
tion for  near  vision  can  be  determined. 

2.  As  a  result  of  the  increased  curvature  of  the  lens  during  accommodation 
for  near  vision,  the  refractive  conditions  within  the  eye  must  be  changed.     Ac- 
cording to  v.  Helmholtz  the  measurements  for  the  resting  eye,  and  for  the  eye 
accommodated  for  near  vision  are  as  follows  (the  first  number  is  for  the  resting, 
the  second  for   the    accommodated  eye):    Radius  of  the  cornea  8  mm.,  8  mm. 
Radius  of  the  anterior  surface  of  the  lens  10  mm.,  6  mm.       Radius  of  the  posterior 
surface  of  the  lens  6  mm.,  5.5  mm.       Distance  of  the  vertex  of  the  anterior  sur- 
face of  the  lens  from  the  vertex  of  the  anterior  surface  01  the  cornea  3.6  mm., 
3.2  mm.;    of  the  vertex  of  the  posterior  surface  of  the  lens  7.2  mm.,  7.2   mm.; 
of  the  anterior  focal  point  12.91  mm.,  11.24  mm.;    of  the  first  principal  point 
1.94  mm.,  2.03  mm.;    of  the  second  principal  point  2.35  mm.,  2.49  mm.;    of  the 
first  nodal  point  6.96  mm.,    6.51  mm.,    of  the  posterior  focal  point  22.23  mm., 
20.25  mm.,  behind  the  anterior  corneal  surface. 

3.  If  the  resting  eye  is  viewed  from  the  side,  the  pupil  appears  as  a  narrow 
black  streak.     This  becomes  broader  as  soon  as  the  eye  is  accommodated  for 
near  vision,  as  the  entire  pupil  moves  forward. 

4.  If  light  is  thrown  obliquely  into  the  anterior  chamber,  the  focal  line  formed 
by  the  concave  surface  of  the  cornea  falls  upon  the  iris.     If  the  experiment  is  made 
with  an  eye  arranged  for  distant  vision,  so  that  the  focal  line  lies  near  the  pupillary 
margin  of  the  iris,  the  line  will  recede  immediately  toward  the  scleral  margin 

of  the  iris,  as  soon  as  the  eye  is  accom- 
modated for  near  vision,  because  the 
iris  is  placed  more  obliquely,  as  its 
pupillary  margin  moves  forward. 

5.  In  accommodation  for  near  vision 
the  pupil  contracts;  in  distant  vision 
it  dilates.  The  contraction  takes  place, 
however,  somewhat  later  than  the 
accommodation.  This  phenomenon  may 
be  interpreted  as  an  associated  move- 
ment, as  both  the  ciliary  muscle  and  the 
FIG.  283.-The  Images  of  Purkinje-Sanson:  a  b  c,  sphincter  of  the  pupil  are  innervated  by 

in  the  eye  at  rest;  a\  hi  c\,  in  the  eye  accommo-  the  Oculomotor  nerve.      Examination  of 

dated  for  near  vision.  Pig     2gl    will    ghow  that    the    sphincter 

may  assist  the  muscle  of  accommodation 
directly;  for  if  the  inner  margin  of  the 

ins  moves  inward  (toward  r),  this  movement  will  be  transmitted  to  the  ciliary 
margin  of  the  choroid,  which  must  likewise  follow  inward  to  some  extent.  The 
movement  of  the  choroid  is,  it  is  true,  effected  principally  by  the  tensor  of  the 
choroid.  Accommodation  is,  however,  still  possible  even  when  the  iris  is  absent 
or  when  its  fibers  are  split. 

6.  On  rotation  of  the  eyeball  inward,  the  eye  is  accommodated  involuntarily 
for  near  vision.     As  both  eyes  rotate  inward  when  the  optic  axes  are  directed 
toward  near  objects,  it  is  evident  that  the  eye  must  be  involuntarily  accommo- 
dated at  the  same  time  for  near  vision. 

7.  The  accommodation  from  a  near  to  a  far  object  (simple  relaxation  of  the 
tensor  of  the   choroid)   takes    place  more  quickly  than  the  reverse  movement, 
trom  far  to  near.     The  process  of  accommodation  requires  a  longer  time  the 
nearer  the  object  is  brought  to  the  eye.     The  time  required  for  the  image  formed 
oy  the  anterior  surface  of  the  lens  to  complete  its  change  of  position  is  less  than 
that  required  for  subjective  accommodation. 

8.  When  the  eye  is  accommodated  for  a  certain  distance,  it  obtains  a  sharp 
image  not  only  of  one  point,  but  of  a  whole  series  of  points  behind  one  another. 
I  he  line  in  which  these  points  are  situated  is  called  the  line  of  accommodation. 
1  he  farther  away  the  point  is  for  which  the  eye  is  accommodated  the  longer  this 
Jine  becomes;   beyond  a  distance  of  from  60  to  70  meters  from  the  eye  all  objects, 

the  most  remote,  appear  equally  distinct.     The  shorter  the  distance,  the 
>rter  the  line  becomes;  that  is,  during  the  highest  degree  of  accommodation  for 
Sltuated  a  short  distance  behind  the  fixed  point  will  appear 


9-  The  question  whether  it  is  possible  for  the  lens  to  change  its  form  partially, 


ACCOMMODATION    OF    THE    EYE. 


835 


that  is  in  one  or  another  meridian,  and  therefore  for  one  section  of  the  ciliary 
muscle  to  contract  independently,  is  answered  in  the  affirmative  by  Dobrowolsky, 
E.  Fick,  Michel  and  others,  and  in  the  negative  by  Hess. 

10.  In  strong  accommodative  effort,  the  lens  sinks  downward  from  gravity, 
whatever  the  position  of  the  head,  on  account  of  the  relaxation  of  the  zonula. 
Eserin  causes  strong  contraction  of  the  ciliary  muscle. 

The  refractive  action  of  the  lens  in  accommodation  for  both  distant  and  near 
vision  is  illustrated  with  especial  clearness  by  Schemer's  experiment.  A  piece  of 
cardboard  (Fig.  284,  K  K,)  containing  two  small  openings  (S,  d)  separated  by  a  dis- 
tance less  than  the  diameter  of  the  pupil  is  held  before  the  eye,  and  the  observer 
looks  at  two  needles  (p  and  r)  placed  behind  each  other;  if  the  first  needle  (p) 
is  fixed  by  the  observer,  the  second  one 
(r)  appears  double;  and  conversely. 

If  the  near  needle  (p)  is  fixed  and  the  _  B 

eye  is  accommodated  for  it,  the  rays 
passing  from  it  are  naturally  focussed 
at  the  image  on  the  retina  (p,) ;  the 
rays,  however,  from  the  distant  needle 
(r)  have  already  come  to  a  focus 
within  the  vitreous,  and,  diverging, 
form  two  images  (r,  r,,)  on  the 
retina.  If  the  right  hole  in  the  card 
(d)  be  closed,  the  left  image  of  the 
distant  needle  (r,,)  disappears.  The 
result  is  analogous  if  the  eye  is  accom- 
modated for  the  distant  needle  (R). 
Then  the  near  needle  (P)  forms  a  double 
image  (P,  P,,)  because  the  rays  passing 
from  it  have  not  yet  come  to  a  focus. 
Closure  of  the  right  hole  (d,)  makes  the 
right  image  (P,)  disappear.  It  must  be 
noted  especially  (with  regard  to  the  pro- 
jection of  the  retinal  image  outward 
into  the  field  of  vision)  that  when  the 
observing  eye  is  accommodated  for  the 
near  needle,  and  one  of  the  holes  is 
closed,  the  homonymous  double  image 
of  the  distant  needle  disappears.  If, 
however,  the  distant  needle  is  fixed, 
and  the  opening  is  closed,  the  crossed 
image  of  the  near  needle  disappears. 

Statements  have  been  made  recently 
that  in  animals  and  even  in  man  the 
sympathetic  takes  part  in  accommoda- 
tion for  distant  vision.  Irritation  of  the 
sympathetic  is  said  to  cause  the  lens  to  become  flatter.  This  is  shown  by  the  fact 
that  the  pupillary  sphincter  cannot  act  as  an  auxiliary  muscle  of  accommodation 
when  the  pupil  is  widely  dilated. 

Mammalia,  birds,  and  reptiles  exhibit  the  same  mechanism  for  accommoda- 
tion. In  cephaloppds  and  osseous  fishes,  whose  eyes  when  at  rest  are  accom- 
modated for  near  vision,  active  accommodation  for  distant  vision  is  effected  by  ap- 
proximation of  the  lens  to  the  retina,  in  fishes  by  the  activity  of  a  retractor  muscle 
of  the  lens.  In  some  amphibia  and  snakes  active  accommodation  of  the  eye 
for  near  vision  takes  place  through  the  separation  of  the  lens  from  the  retina  in 
consequence  of  changes  in  the  intraocular  pressure.  Some  nocturnal  animals 
and  some  sensitive  to  light  have  no  power  of  accommodation  whatever. 


FIG.  284. — Schemer's  Experiment. 


REFRACTIVE  POWER  OF  THE  NORMAL  EYE. 
OF  REFRACTION. 


ANOMALIES 


The  limits  of  distinct  vision  vary  greatly  for  different  eyes.  A 
distinction  is  made  between  the  far  point  (or  resting  point)  and  the  near 
point.  The  far  point  is  the  greatest  distance  from  the  eye  to  which  an 
object  may  be  removed  and  still  be  seen  distinctly;  the  near  point  is  the 


836 


REFRACTIVE    POWER    OF    THE    NORMAL    EYE. 


FIG.  285  and  FIG.  286. — Refractive  Condition  of  the  Normal 
Eye,  at  Rest  and  in  Accommodation. 


shortest  distance  at  which  an  object  can  still  be  seen  distinctly  The 
distance  between  these  two  points  is  called  the  range  of  accommodation. 
Three  types  of  eyes  are  distinguished: 

The  normal  (emmetropic)  eye  is  so  constructed  that,  when  it  is  at 

rest,  parallel  rays  (Fig. 
2 8 5,  rr)  from  objects  at  an 
infinite  distance  come  to  a 
focus  (rt)  on  the  retina. 
The  far  point  therefore 
equals  oo.  On  the  strong- 
est effort  of  accommoda- 
tion for  near  vision,  during 
which  the  lens  increases 
its  convexity  (Fig.  286,  a), 
rays  come  to  a  focus  upon 
the  retina  (px)  that  are 
emitted  by  a  point  of 
light  (p)  5  inches  from  the 
eye,  that  is  the  near  point 
is  5  inches  ( i  inch  equals  2  7 
mm. ) .  The  range  of  accom- 
modation is,  therefore,  oo. 

2.  The  short-sighted  (myopic,  hypometric,  long)  eye  (Fig.  287)  is 
unable,  when  at  rest,  to  focus  parallel  rays  on  the  retina.  Such  rays 
cross  within  the  vitreous  (at  o),  and  then  diverge  and  form  a  circle  of 
diffusion  on  the  retina. 
The  objects  must  be 
at  a  distance  of  from 
60  to  120  inches  (at  /) 
from  the  resting  eye 
in  order  that  the  rays 
may  be  united  on  the 
retina.  The  resting 
short-sighted  eye  is, 
therefore,  capable  of 
bringing  only  diverg- 
ent rays  to  a  focus 
upon  the  retina.  The 
far  point,  therefore, 
lies  abnormally  near. 
By  the  most  power- 
ful effort  of  accom- 
modation, objects 
may  be  distinctly 
seen  at  distances  of 
from  4  to  2  inches,  or 
even  less.  The  near 
point  also  is  abnor- 
mally close;  the  range  of  accommodation  is  diminished. 


....- — r-.~'f*^!f 


FIG.  287  and    FIG.  288. — Refractive  Condition  of    the  Short-sighted' and 
the  Far-sighted  Eye. 


Myopia  is  usually  dependent  upon  an  elongation  of  the  eyeball,  which  is 
congenital  and  often  inherited.  The  correction  of  this  anomaly'  of  refraction  is 
effected  by  the  use  of  a  concave  glass,  which  causes  parallel  rays  from  a  great 


MEASURE    OF    THE    POWER    OF    ACCOMMODATION.  837 

distance  to  diverge,  so  that  they  can  be  brought  to  a  focus  upon  the  retina.  It 
is  remarkable  that  most  infants  are  myopic  at  'birth.  This  myopia,  how- 
ever, depends  upon  excessive  curvature  of  the  cornea  and  lens,  and  on  ex- 
cessive proximity  of  the  lens  to  the  cornea.  As  the  eye  grows  this  myopia  dis- 
appears. Either  the  too  constant  activity  of  the  tensor  of  the  choroid  (in  reading, 
writing,  etc.),  or  the  continuous  convergence  of  the  eyeballs,  whereby  the  external 
pressure  on  the  eyeballs  is  increased,  is  considered  as  the  cause  of  the  myopia 
arising  or  increasing  during  school-life. 

3.  The  far-sighted  (hyperopic,  hypermetropic,  presbyopic,  over- 
sighted,  flat)  eye  (Fig.  288)  is  capable,  when  at  rest,  of  focusing  only 
convergent  rays  on  the  retina  (c).  Distinct  images  can,  therefore,  be 
formed  only  when  the  rays  from  objects  are  made  convergent  by  a 
convex  lens,  because  parallel  rays  would  come  to  a  focus  behind  the 
retina  (at  /).  All  rays  coming  from  natural  objects  are  either  di- 
vergent, or  at  most  approximately  parallel,  never  convergent.  There- 
fore, no  hyperope  can  see  distinctly  when  the  eye  is  at  rest,  without  a 
convex  glass.  When  the  ciliary  muscle  contracts,  slightly  convergent, 
parallel  and  finally  even  somewhat  divergent  rays  may  be  brought  to  a 
focus,  by  increasing  efforts  of  accommodation.  The  far  point  is  conse- 
quently negative,  the  near  point  abnormally  remote  (more  than  8  or 
10  inches),  while  the  range  of  accommodation  is  infinitely  great. 

The  cause  of  this  defect  is  abnormal  shortness  of  the  eye,  which  is  generally 
the  result  of  imperfect  development  in  all  directions.  In  addition  the  lens 
becomes  flattened  in  old  age.  The  error  is  corrected  by  means  of  a  convex  lens. 

The  far  point  of  an  eye  is  determined  by  bringing  toward  it  objects  that 
subtend  a  visual  angle  of  only  5  minutes  (for  example,  Snellen's  small  letters,  or 
the  medium  type — from  4  to  8 — of  Jaeger)  and  finding  the  point  at  which  they 
first  become  distinctly  visible.  The  distance  from  the  eye  indicates  the  far  point. 
In  obtaining  the  far  point  of  a  myope,  the  same  objects  (subtending  a  visual 
angle  of  5  minutes)  are  placed  at  a  distance  of  20  inches  from  the  eye,  and  the 
weakest  concave  glass  is  selected  that  will  enable  him  to  see  the  objects  distinctly. 
The  near  point  is  found  by  bringing  minute  objects  (for  example  fine  print)  closer 
and  closer  to  the  eye,  until  it  becomes  indistinct.  The  shortest  distance  at  which 
distinct  vision  is  possible  is  designated  the  near  point. 

The  optometer  may  also  be  employed  to  determine  the  far  and  near  points. 
A  small  object,  such  as  a  pin,  is  moved  to  and  fro  over  a  scale,  along  which  the 
eye  sights,  as  along  a  gun-barrel.  The  object  is  brought  as  close  as  possible  and 
is  then  removed  as  far  as  possible,  so  as  to  permit  of  distinct  vision.  The  scale 
shows  directly  the  near  and  far  points  and  also  the  range  of  accommodation. 

Other  optometers  are  based  on  Schemer's  experiment.  By  an  arrangement 
similar  to  that  described  the  object  is  viewed  through  two  small  openings  in  a 
card.  When  the  object  is  within  the  near  point,  it  appears  double;  and  similarly 
when  it  is  beyond  the  far  point.  This  may  be  readily  understood  from  a  con- 
sideration of  Schemer's  experiments.  The  instruments  of  Porterfield  and  Stampfer 
are  constructed  on  this  principle.  In  the  latter  a  narrow,  luminous  slit,  which 
can  be  moved  in  a  dark  tube,  is  used  as  the  fixing  object.  The  optometer  of 
Th.  Young  and  Lehot  consists  of  a  white  thread  stretched  over  a  black  scale. 
The  thread  is  observed  through  two  small  openings,  and  appears  single  and  dis- 
tinct when  within  the  range  of  accommodation;  within  the  near  point,  and  beyond 
the  far  point,  however,  it  appears  broken  up  into  diverging  lines. 


MEASURE   OF  THE  POWER  OF  ACCOMMODATION. 

The  range  of  accommodation,  which  is  easily  determined  by  in- 
vestigation, does  not  of  itself  indicate  the  degree  of  force  or  the  power 
of  accommodation.  The  measure  of  this  is  the  mechanical  work  done 
by  the  ciliary  muscle.  It  cannot,  of  course,  be  determined  directly  in 
the  eve  itself.  It  is,  therefore,  necessarv  to  take  as  its  measure  the 


838  MEASURE    OF    THE    POWER    OF    ACCOMMODATION. 

optical  effect  produced  by  the  change  in  the  form  of  the  lens  that  is 
brought  about  by  the  muscular  activity. 

These  relations  may  first  be  considered  in  the  emmetropic  eye.  In 
the  condition  of  rest,  those  (dotted)  rays  that  pass  in  a  parallel  direction 
from  an  infinite  distance  on  the  retina  are  united  (Fig.  289,  f).  In 
order  to  focus  rays  that  come  from  the  near  point  at  a  distance  of  5 
inches  (p),  the  muscle  of  accommodation  must  exercise  its  full  strength, 
so  that  the  lens  may  be  made  sufficiently  convex.  The  power  of  ac- 
commodation, therefore,  produces  an  optical  effect  by  increasing  the 
convexity  of  the  previously  passive  flat  lens  (A)  to  an  amount  equal  to 
B;  or  in  other  words,  it  is  as  though  a  new  convex  lens  B,  had  been 
added  to  the  original  lens  A.  What,  therefore,  must  be  the  focal  dis- 
tance of  the  lens  B,  in  order  that  rays  coming  from  the  near  point  (5 
inches)  may  be  focused  on  the  retina?  Manifestly  the  lens  B  must 
render  the  divergent  rays  parallel ;  then  A  can  focus  them  at  f .  Convex 
lenses  render  parallel  rays  that  come  from  their  principal  focus.  In 
the  instance  cited  the  lens  consequently  must  have  a  focus  of  5  inches. 
Therefore,  the  normal  eye,  with  a  far  point  of  infinity,  and  a  near  point  of 

5  inches,  has  a  power  of 
accommodation  equiva- 
lent to  a  lens  of  5  inches 
focus.  If,  now,  the  lens 
is  made  more  refractive 
by  its  power  of  accom- 
modation, the  increase 
may  be  readily  elimi- 
nated by  placing  before 

FIG  2gg  the  eye  a  concave  lens 

that  has  an  optical  effect 
exactly  the  opposite  of 

that  due  to  the  increase  of  accommodation  (B).  Hence,  it  is  possible 
to  use  a  lens  of  definite  focus  as  the  measure  of  the  power  of  accom- 
modation of  the  eye,  that  is  for  the  optical  effect  produced  by  the 
latter.  According  to  Bonders  the  measure  of  the  power  of  accom- 
modation of  an  eye  is  the  reciprocal  value  of  the  focal  distance  of  a 
concave  lens  that,  when  placed  before  the  accommodated  eye,  so 
refracts  a  bundle  of  rays  coming  from  the  near  point  (p)  that  it 
appears  to  come  from  the  far  point  (resting  point  of  the  eye). 

In  accordance  with  the  foregoing  considerations,  the  power  of  accommodation, 
then,  is  calculated  by  the  following  formula:  -  —•  that  is,  the  power 

of  accommodation  (expressed  by  the  dioptric  value  of  a  lens  of  x  inches  focus)  is 

equal  to  the  difference  between  the  reciprocals  of  the  distances  of  the  near  (p) 

1  far  points  (r)  from  the  eye.     Examples:  In  the  emmetropic  eye,  as  already 

mentioned,  p  =  5;  r  =  oo.  Its  power  of  accommodation  is  therefore  —  =  ± ] 

x  ^° 

therefore  x  =  5;    that  is,  it  is  equal  to  a  lens  of  5  inches  focus.     In  a  myopic  eye, 

p  =  4,   r  =  12;    so  that  —  •.=  %  — fa    and  x  =  6.     Another  myopic  eye  with 

p  =  4,  and  r  =20,  has  x  =  5,  in  other  words,  normal  accommodative  power. 

Iwo  eyes  with  different  ranges  of  accommodation  may  have  the  same  power  of 

:ommodation.     Example:    One  eye  may  have  p  =  4,  r  =   oo;    the  other  p  =3, 

r  -  4.     For  each  eye  —   =  £,  or  the  power  of  accommodation  of  each  is  equal 


SPECTACLES.  839 

to  the  dioptric  value  of  a  lens  of  4  inches  focus.  Conversely,  two  eyes  may  have 
the  same  range  of  accommodation,  and  yet  have  unequal  power  of  accommoda- 
tion. Example:  One  eye  may  have  p  =  3,  r  =  6,  the  other  p  =  6,  r  =9  (both 
have  a  range  of  accommodation  of  3  in.).  The  power  of  accommodation  for  the 

first  is    ]-  =  £  —  \\  orx  =6;   for  the  second  — —  =£ — £;  or  x  =  18.    The  general 

x  x 

law  for  these  relations  is  as  follows:  If  the  ranges  of  accommodation  of  two  eyes 
are  equal,  their  powers  of  accommodation  are  equal,  provided  their  near  points 
are  the  same.  If,  however,  the  range  of  accommodation  is  the  same  for  each 
eye,  but  the  near  points  are  unequal,  then  the  powers  of  accommodation  are 
unequal;  and  that  eye  has  the  greatest  power  of  accommodation  that  has  the 
shortest  near  point.  The  reason  for  this  is  "that  every  difference  in  distance  near  a 
lens  has  a  much  greater  influence  on  the  image  than  the  same  difference  in  distance 
far  from  the  lens.  The  normal  eye  can,  in  fact,  see  distinctly  all  objects  at  a 
distance  between  60  or  70  meters  and  infinity  without  any  accommodation. 

While  p  and  r  can  be  directly  determined  for  the  emmetropic  and  the  myopic 
eye,  this  is  not  possible  for  the  far-sighted  eye.  The  resting  point  (far  point) 
in  the  latter  is  negative;  in  fact  in  cases  of  hyperopia  of  high  grade  even  the 
near  point  may  be  negative.  The  far  point,  however,  may  be  determined  by 
means  of  the  convex  lens  that  renders  the  far-sighted  eye  emmetropic.  The 
relative  near  point  is  then  determined  by  means  of  the  lens. 

From  the  fifteenth  year  on  the  power  of  accommodation  for  near  vision  com- 
mences to  diminish,  perhaps  because  the  lens  gradually  loses  its  elasticity. 

SPECTACLES. 

Older  Measurement  in  Inches  (i  Inch  =  27  Mm.). — The  focal  length  of  both 
concave  (diverging)  and  convex  (converging)  glasses  depends,  of  course,  upon 
the  refractive  index  of  the  glass  (usually  3:2),  and  upon  the  length  of  the  radius 
of  curvature.  If  the  curvature  of  both  sides  of  the  lens  is  the  same  (biconcave 
or  biconvex) ,  then  with  the  ordinary  refractive  index  of  glass  the  focal  length  is 
equal  to  the  radius  of  curvature.  If  one  side  of  the  lens  is  plane,  the  focal  length 
is  twice  the  radius  of  curvature  of  the  spherical  surface.  The  glasses  may  be 
designated  either  in  accordance  with  their  focal  lengths  in  inches,  none  shorter 
than  i  inch  being  usually  taken;  or  in  accordance  with  their  refractive  power. 
By  this  method  the  unit  chosen  is  the  refractive  power  of  a  lens  with  a  focal  dis- 
tance of  i  inch.  A  lens  with  a  focal  distance  of  2  inches,  refracts  the  light  only 
one-half  as  much  as  a  lens  with  a  focal  distance  of  i  inch ;  a  lens  of  3  inches  focus  has 
a  refractive  power  only  one-third  as  great,  etc.  This  is  true  for  both  convex  and 
concave  lenses,  the  latter  of  course  having  negative  focal  distances.  For  example, 
the  designation  "convex  £"  would  indicate  a  convex  lens  with  a  refractive  power 
only  one-fifth  as  great  as  a  lens  with  a  focal  distance  of  i  inch;  or  "concave  £" 
would  indicate  a  concave  lens  that  caused  the  rays  of  light  to  diverge  only  one- 
eighth  as  much  as  the  concave  lens  (negative)  with  a  focal  distance  of  i  inch. 

If  the  far  point  (always  too  close)  of  a  myopic  eye  is  determined,  a  concave 
lens  of  the  same  focal  distance  as  the  far  point  will  be  required  in  order  to  make 
the  divergent  rays  coming  from  the  far  point  parallel.  The  emmetropic  eye 
has  a  far  point  of  infinity.  If,  for  example,  a  myopic  eye  has  a  far  point  of  6 
inches,  it  needs  a  concave  lens  with  a  focus  of  6  inches  in  order  to  see  distinctly 
at  an  infinite  distance.  Therefore  in  a  myopic  eye,  the  readily  determined  dis- 
tance of  the  far  point  from  the  eye  is  directly  equal  to  the  focus  of  the  (weakest) 
concave  lens  that  enables  the  eye  to  see  distant  objects  distinctly;  this  lens 
is  usually  the  number  of  the  glass  to  be  chosen.  Example:  A  myopic  eye  with 
a  far  point  of  8  inches  needs,  therefore,  a  concave  lens  with  a  focus  of  8  inches, 
that  is  the  concave  glass  No.  8.  For  the  hyperopic  eye  the  focal  distance  of  the 
strongest  convex  lens  that  still  allows  the  eye  to  see  distant  objects  clearly  is 
at  the  same  time  the  distance  of  the  far  point  from  the  eye.  Example:  A  hyper- 
opic eye  that  sees  objects  at  a  distance  clearly  through  a  convex  lens  with  a  focus 
of  12  inches  has  a  far  point  of  12;  the  proper  glass  is  likewise  No.  12. 

Newer  Measurement  in  Diopters. — Instead  of  the  older  designation  of  the 
strength  of  lenses  in  inches,  the  meter  has  been  adopted  as  a  unit,  following  the 
suggestion  of  Bonders,  Nagel,  Zehender,  and  others.  By  this  system  the  lenses 
are  designated  according  to  their  refractive  power.  The  unit  is  a  lens  of  small 
refractive  power  (large  focus),  that  is  one  with  a  focus  of  i  meter — 40  inches. 
This  unit  is  called  a  diopter  (abbreviated,  D).  The  refractive  power  of  D  is 


840  CHROMATIC    AND    SPHERICAL    ABERRATION. 

j  meter.  No.  2  is  a  lens  of  twice  this  strength,  namely,  2  D;  that  is  its  refractive 
power  =  f  meter,  and  its  focus  =  \  meter.  No.  3  has  three  times  the  strength  =  3  D, 
that  is,  its  refractive  power  =  f  meter,  and  its  focus  =  \  meter.  No.  4  is  four 
times  as  strong  =  4  D:  its  refractive  power  =  f  meter,  and  its  focus  =  \  meter. 
No.  5  is  5  times  as  strong  =  50,  etc.  Weaker  glasses  than  i  D  have  been  chosen: 
of  0.75  D,  with  a  focus  of  1.33  meter;  further,  of  0.50  D,  with  a  focus  of  2  meters; 
and  0.25  D,  with  a  focus  of  4  meters.  Between  the  whole  numbers  of  diopters  \ 
and  \  diopter  may,  of  course,  be  introduced. 

In  cases  of  recognized  myopia  or  hyperopia,  glasses  should  by  all  means  be 
worn  for  the  preservation  of  the  eye.  If  the  far  point  in  a  case  of  myopia  is 
beyond  5  inches,  the  glass  may  be  worn  constantly,  but  generally  the  distance 
for  ordinary  near  work,  such  as  reading,  writing,  and  handwork,  should  always 
be  about  12  inches.  If  the  work  is  so  fine  (embroidering,  dissection,  drawing, 
etc.)  that  the  object  must  be  held  closer  to  the  eye  in  order  to  obtain  a  larger 
retinal  image,  the  glass  may  be  removed  or  a  weaker  one  be  substituted.  The 
)erope  may  use  his  glass  for  near  vision,  and  especially  in  a  poor  light,  because  the 


diffusion-circles  are  then  unusually  large  on  account  of  the  dilatation  of  the  pupil. 
It  is  advisable  to  choose  rather  excessively  strong  convex  glasses  at  first.  Cylin- 
drical glasses  will  be  discussed  under  Astigmatism.  Smoked  or  blue  glasses  are 
worn  to  protect  the  eye  from  unduly  intense  illumination  when  the  retina  is 
sensitive.  Stenopaic  glasses  consist  of  narrow  diaphragms  placed  in  front  of 
the  eye,  which  compel  the  eye  to  look  in  a  definite  direction,  namely  through 
the  opening  in  the  diaphragm.  Contact-glasses  are  discussed  on  p.  841. 

CHROMATIC  AND  SPHERICAL  ABERRATION. 

DEFECTIVE      CENTERING     OF     THE     REFRACTING      SURFACES.       ASTIG- 
MATISM. 

Chromatic  Aberration  in  the  Eye. — All  rays  of  white  light  that  undergo  refrac- 
tion are  at  the  same  time  decomposed  into  the  prismatic  colors  of  which  white 
light  is  composed,  because  these  colors  possess  different  degrees  of  refrangibility. 
The  violet  rays  are  refracted  the  most,  the  red  rays  the  least.  A  white  point 
on  a  black  ground  does  not  form  a  sharp,  simple  image  on  the  retina;  many 
colored  points  are  formed  instead,  one  behind  the  other.  If  the  eye  is  accom- 
modated to  focus  the  violet  rays,  the  succeeding  colors  must  yield  concentric 
diffusion-circles,  those  near  the  red  being  the  largest.  In  the  center  of  the  circles, 
where  all  the  colors  are  superposed,  a  white  point  is  formed  by  their  union,  while 
around  it  are  the  colored  circles.  The  distance  of  the  focus  of  the  red  rays  from 
that  of  the  violet  rays  in  the  eye  is  from  0.58  to  6.62  mm.  v.  Helmholtz  calculated 
the  focus  for  red  in  the  reduced  eye  as  20.524  mm.,  that  for  violet  as  20.140  mm. 
Therefore,  both  the  near  and  far  points  for  violet  light  are  closer  to  the  eye  than 
those  for  red.  Hence  white  objects  beyond  the  far  point  seem  to  have  a  reddish 
tinge;  those  within  the  near  point  a  violet  shade.  The  eye  must  also  accom- 
modate more  strongly  for  red  rays  than  for  violet ;  so  that  red  objects  are  thought 
to  be  closer  at  hand  than  equally  distant  violet  objects.  This  fact  should  be 
taken  into  account  by  artists. 

Monochromatic  or  Spherical  Aberration. — Apart  from  the  decomposition  of 
white  light  into  its  components,  the  rays  from  a  point  of  simple  light  are  prevented 
from  coming  to  a  single  focus  by  the  fact  that  the  edges  of  refracting  (even  though 
only  approximately)  spherical  surfaces  refract  the  rays  much  more  strongly 
than  do  the  middle  portions.  Many  images  are,  therefore,  formed,  instead  of 
one.  In  the  eye  this  defect  is  naturally  corrected  by  the  iris,  which  cuts  off  the 
marginal  rays  (Fig.  289),  especially  when  the  lens  is  strongly  curved,  and  at  the 
same  time  the  pupil  is  most  contracted.  The  marginal  part  of  the  lens,  in  addition, 
has  less  refractive  power  than  the  central  nucleus.  Finally,  the  marginal  portions 
of  the  refracting  surfaces  in  the  eye  are  less  curved  than  those  lying  nearer  the 
optic  axis,  as  will  be  seen  by  comparing  the  form  of  the  cornea  (p.  815)  and  that 
ot  the  lens-surfaces  (p.  821). 

Defective  Centering  of  the  Refracting  Surfaces.— The  absence  of  exact  center- 
ing ot  the  refracting  surfaces  in  the  eye  disturbs  somewhat  the  sharp  projection 
t  the  image.  The  vertex  of  the  cornea  does  not  lie  exactly  at  the  end  of  the 
optic  axis.  The  same  is  true  of  the  vertices  of  the  lens  and  also  of  the  various 
layers  ot  the  lens.  The  deviations  and  the  visual  disturbances  produced  by  them 
are,  it  is  true,  usually  but  slight. 


THE    IRIS. 


841 


Regular  Astigmatism.— When  the  curvature  of  the  refracting  surfaces  of  the 
eye  is  unequally  great  in  its  different  meridians,  rays  of  light  cannot  be  united 
at  a  single  point.  Under  such  circumstances  the  cornea  usually  has  the  greatest 
curvature  in  the  vertical  meridian  and  the  smallest  in  the  horizontal  meridian,  as 
is  shown  by  ophthalmometric  measurement  (p.  830).  The  rays  that  pass  through 
the  vertical  meridian  naturally  come  together  first,  and  in  a  horizontal  focal  line; 
while  the  rays  passing  through  the  horizontal  meridian  are  brought  together  further 
back  in  a  vertical  line.  Such  an  eye,  therefore,  does  not  possess  a  common  focus  for 
light-rays:  hence  the  name  "astigmatism."  The  lens  also  exhibits  some  inequal- 
ity of  curvature  in  the  various  meridians,  but  just  reversed.  As  a  result,  a  part 
of  the  inequality  of  curvature  of  the  cornea  is  thus  compensated,  and  only  part 
of  it  has  any  dioptric  effect.  The  emmetropic  eye  possesses  an  exceedingly 
slight  degree  of  this  inequality  (normal  astigmatism) .  If  two  fine  lines  are  drawn 
at  right  angles  to  each  other  on  a  piece  of  white  paper,  it  will  be  found  that  the 
paper  must  be  held  closer  to  the  eye,  in  order  to  see  the 
horizontal  line  distinctly,  than  to  see  the  vertical  line;  the 
normal  eye  is,  thus,  somewhat  more  short-sighted  for 
horizontal  than  for  vertical  objects.  If  the  inequality  of 
curvature  is  more  considerable,  sharp  vision  naturally  is 
altogether  impossible.  For  the  correction  of  this  error,  a 
glass  is  used  that  is  ground  in  the  form  of  a  cylinder;  that 
is  in  one  direction  it  has  no  curvature,  while  in  the  other 
direction,  perpendicular  to  the  former,  it  is  curved.  The 
glass  is  so  placed  before  the  eye  that  the  direction  of  its 
curvature  corresponds  to  the  direction  of  lesser  curvature 

of    the    eye.       For  example,   the   section   C  a  b  c  d    of    the 
glass  cylinder  (Fig.  290)  represents  a  plano-convex  cylindri- 

a  concavo-convex    cylindrical 


FIG.  290.  —  Cylindrical 
Glasses  for  Astigma- 
tism. 


cal   glass;   the   section 
glass. 

Irregular  Astigmatism. — As  a  result  rof  the  stellate 
arrangement  of  the  fibers  in  the  center  of  the  crystalline 
lens,  and  of  the  unequal  course  of  the  fibers  within  different 
portions  of  one  and  the  same  lens-meridian,  all  of  the 
rays  passing  through  one  meridian  cannot  be  focused  at 
the  same  point.  For  this  reason  sharp  images  of  distant  points  of  light  (stars 
or  lamps)  are  not  obtained,  but  rather  stellate,  jagged  figures,  with  projecting 
rays.  The  same  thing  may  be  seen  by  holding  a  card  with  a  fine  perforation 
toward  the  light,  at  a  somewhat  greater  distance  from  the  eye  than  the  far  point. 
Slight  degrees  of  this  irregular  astigmatism  are  normal,  but  if  developed  to  a  high 
degree  the  condition  disturbs  the  visual  acuity  greatly,  by  producing  several 
images  of  each  point  of  an  object,  instead  of  one  image  (monocular  polyopia). 
This  condition  cannot,  of  course,  be  present  in  eyes  deprived  of  their  lens. 
Irregular  curvatures  of  the  cornea  act  in  a  similar  way.  A.  E.  Fick  has  elimin- 
ated these  by  the  use  of  a  lens  in  the  form  of  a  watch  glass,  placed  in  contact 
with  the  cornea  (contact-spectacles);  Lohnstein,  by  placing  before  the  eye  a 
chamber  closed  in  front  by  a  spherical  glass,  and  filling  the  interspace  (between 
the  cornea  and  the  spherical  glass)  with  0.85  per  cent,  solution  of  common  salt 
(hydrodiascope). 


THE  IRIS. 

i .  The  iris  acts  like  a  diaphragm  in  an  optical  apparatus  by  cutting  off 
the  marginal  rays  (Fig.  279),  the  entrance  of  which  would  produce  a 
decided  spherical  aberration,  and  as  a  result,  indistinct  vision.  2.  As 
the  pupil  contracts  strongly  in  bright  illumination,  it  regulates  the 
amount  of  light  that  enters  the  eye ;  in  this  way  fewer  rays  of  light  enter 
the  eye  when  the  light  is  strong  than  when  it  is  feeble.  3.  The  iris 
acts,  further,  as  an  auxiliary  to  the  muscle  of  accommodation. 

As  the  retina  can  adapt  itself  to  a  comparatively  wide  range  of  illumination, 
the  pupil  (after  the  first  reaction)  can  resume  its  size  (from  3i  to  4  mm.)  if  the 
limits  of  illumination  are  between  100  and  uoo  meter-candles. 


842 


THE    IRIS. 


The  size  of  the  pupil  increases  from  the  first  month  of  life  up  to  from  the 
third  to  the  sixth  year;  and  with  it  also  the  amplitude  of  reaction  decreases, 
though  more  slowly. 

With  regard  to  the  size  of  both  pupils  it  may  be  remarked  that  when 
there  is  semidecussation  of  the  optic  nerves,  the  pupils  are  always  of  the 
same  size,  and  they  react  symmetrically  (man,  cat).  In  animals  in 
which  the  decussation  is  total  (horse,  owl),  and  in  those  that  have  only  a 
few  uncrossed  fibers  in  the  optic  tract  (rabbit),  the  pupillary  reflex  is 
confined  to  the  eye  tested. 

The  iris  has  two  muscles:  the  sphincter,  which  surrounds  the  pupil 
and  is  supplied  by  the  oculomotor  nerve;  and  the  dilator  of  the 
pupil,  supplied  chiefly  by  the  cervical  sympathetic  and  the  trigeminus. 
The  two  muscles  are  antagonistic;  the  pupil  dilates,  therefore,  after 
paralysis  of  the  oculomotor,  by  the  predominance  of  the  sympathetic; 
conversely,  it  contracts  after  excision  of  the  sympathetic.  Simultane- 
ous irritation  of  both  nerves  causes  the  pupil  to  contract;  the  excita- 
bility of  the  oculomotor  is  consequently  the  greater. 

According  to  Arnstein  and  A.  Mayer  all  the  nerve-fibers  lose  their  myelin- 
sheaths  after  a  short  course.  Most  of  the  motor  fibers  near  the  sphincter  consist 
of  naked  bundles  of  fibers.  Under  the  anterior  epithelium  there  is  a  network 
of  exceedingly  fine  sensory  nerves.  Numerous  fibers  pass  to  the  capillaries 
and  arteries  as  vasomotor  nerves. 

The  movements   of  the  iris    take  place  under  the  following  conditions : 

1.  Irritation  of  the  retina  by  light  causes  a  contraction  of    the  pupil  corre- 
sponding to  the  intensity  and  extent  of  the  irritation.      Irritation  of  the  optic 
nerve  itself  has  the  same  effect.     This  movement  is  a  reflex  action  transferred 
to    the   path  of  the  oculomotor  nerve      The  center    is  situated  in  the  anterior 
pair   of   quadrigeminate    bodies  near  the    aqueduct    of    Sylvius.      After    section 
of  the    optic  nerve   the  pupil  dilates  and  subsequent  section  of  the  oculomotor 
causes  no    further  dilatation.     In  the   dark  the   pupil  dilates,  at  first  rapidly, 
later   more    slowly.       Immediately  after   the    darkening    an   illumination   must 
have  considerable  strength  to  cause  pupillary  contraction.      After  the  eye  has 
become  accustomed  to  the  darkness,  a  weaker  light  is    sufficient.      A    flash   of 
lightning  following  a  long  period  of    darkness   produces   strong   and   prolonged 
contraction.     A  slow  increase  in  illumination  is  almost  without  effect. 

2.  The  center  for  the  dilator  fibers  of  the  pupil  is  irritated  by  a  state  of  the 
blood  causing  dyspnea.     If  the  dyspnea  passes  into  asphyxia,  the  dilatation  of 
the  pupil  diminishes.     Previous  section  of  the  peripheral   dilator  fibers   makes 
these  reactions  impossible.     Sudden  anemia  also  has  a  stimulating  action. 

_  3.  The  center,  as  well  as  the  ciliospinal  region  of  the  cord  subordinated  to 
it,  is  also  susceptible  to  reflex  irritation.  Painful  excitation  of  the  sensory  nerves 
produces  dilatation  of  the  pupils  and  protrusion  of  the  eyeballs,  as  was  demon- 
strated by  the  ancient  acts  of  torture.  Labor-pains,  loud  noises  in  the  ear,  irrita- 
tions of  the  nerves  of  the  sexual  organs,  and  even  slight  tactile,  sensations  have 
the  same  effect.  According  to  Bechterew,  these  results  are  due  to  an  inhibition 
of  the  light-reflex,  in  the  sense  expressed  on  p.  731. 

4.  The  condition  of  the  blood-vessels  of  the  iris  has  an  important  influence 
on  the  size  of  the  pupil.  Everything  that  increases  their  injection  contracts 
the  pupil,  while  everything  that  diminishes  the  amount  of  blood  dilates  the  pupil. 
The  pupil  is  contracted,  therefore,  by  forced  expiration,  which  prevents  the 
return  of  blood  from  the  head;  momentarily  by  each  pulsation  of  the  heart  (by 
diastolic  filling  of  the  arteries);  by  decrease  of  intraocular  pressure,  for  example 
after  puncture  of  the  anterior  chamber,  because  more  blood  can  enter  the  vessels 
of  the  iris,  owing  to  the  diminished  intraocular  pressure;  further,  by  paralysis 
of  the  vasomotor  fibers  of  the  iris.  Conversely,  the  pupil  is  dilated  by  conditions 
the  reverse  of  those  already  mentioned,  and  also  by  strong  muscular  exertion, 
during  which  blood  rushes  into  the  dilated  muscular  branches,  and  further,  when 
death  takes  place.  The  influence  of  the  amount  of  blood  accounts  also  for  the 
fact  that  the  pupil  when  dilated  by  atropin  becomes  narrower  as  soon  as  the 
superior  cervical  sympathetic  ganglion,  which  supplies  a  part  of  the  vasomotors 


THE    IRIS.  843 

of  the  iris,  is  excised;  and,  further,  that,  after  excision  of  this  ganglion,  atropin 
has  less  effect  upon  the  pupil  of  the  same  side.  The  increased  dilatation  of  the 
pupil  by  irritation  of  the  sympathetic  after  instillation  of  atropin  is  probably 
also  the  result  of  diminished  injection  of  the  vessels  of  the  iris.  If  an  animal 
whose  pupil  is  dilated  by  atropin  be  bled  to  death  quickly,  the  pupil  contracts 
on  account  of  the  irritation  of  the  oculomotor  center  by  the  anemia.  The  dila- 
tation of  the  pupil  in  cases  of  trigeminal  neuralgia  must  be  referred  partly  to 
irritation  of  the  dilator  fibers,  and  partly  to  irritation  of  the  vasomotor  fibers 
of  the  iris. 

5.  Contraction  of  the  pupil  occurs  as  an  associated  movement  during  accom- 
modation for  near  vision,  further,  as  a  result  of  strong  effort  to  close  the  lids, 
and  in  rotation  of  the  eyeball  inward,,  which  is  the  case  during  sleep.  Conversely, 
intense  movement  of  the  iris,  caused  by  variations  in  the  brightness  of  dazzling 
lights,  for  example  of  electric  light,  produces  disturbing  associated  movements 
of  the  ciliary  muscles.  In  connection  with  certain  movements  excited  in  the 
medulla  oblongata  (forced  breathing,  chewing,  swallowing,  vomiting)  dilatation 
of  the  pupil  occurs  as  a  kind  of  associated  movement. 

Direct  stimulation  of  the  corneal  limbus  causes  dilatation  of  the  pupil.  In 
fact  partial  dilatation  may  be  produced  by  direct  irritation  of  a  circumscribed 
portion  of  the  margin  of  the  iris,  by  contraction  of  the  dilator  fibers,  although 
also  the  sphincter  contracts  at  the  same  time. 

If  a  flame  be  placed  in  a  dark  room  on  one  side  of  an  eye  directed  straight 
ahead,  and  attention  is  suddenly  directed  to  the  flame,  without  changing  the 
direction  of  vision,  the  pupil  contracts.  This  movement  is  known  as  the  "cortical 
reflex."  Other  things  being  equal,  an  analogous  dilatation  of  the  pupil  also 
takes  place;  one  may  observe  variations  in  the  size  of  the  pupil  from  the  mere 
conception  of  light  or  darkness,  even  in  the  blind.  Bechterew  saw  a  case  of  uni- 
lateral voluntary  dilatation  of  the  pupil. 

As  to  the  action  of  poisons  on  the  iris  ignorance  still  prevails.  The  mydriatics 
cause  dilatation:  Atropin,  homatropin,  duboisin,  scopolamin,  daturin,  hyoscyamin, 
hyoscin,  probably  through  paralysis  of  the  oculomotor  chiefly.  They  must  also 
stimulate  the  dilating  fibers  at  the  same  time,  for  in  the  presence  of  complete 
oculomotor  palsy  the  moderately  dilated  pupil  is  still  further  dilated  by  atropin. 
Minimal  doses  of  atropin  cause  contraction  of  the  pupil  by  stimulation  of  the 
pupil-contracting  fibers.  Excessive  doses  cause  moderate  dilatation  as  the 
result  of  paralysis  of  both  the  dilating  and  contracting  fibers.  Atropin  acts 
even  after  destruction  of  the  cijiary  ganglion,  in  fact  on  the  enucleated  eye. 

For  the  action  of  the  constrictors,  or  myotics:  physostigmin  (or  eserin,  the 
alkaloid  of  physostigma) ,  nicotin,  pilocarpin,  muscarin,  and  morphin,  some 
investigators  assume  a  stimulation  of  the  oculomotor,  others  a  paralysis  of  the 
sympathetic.  As  these  drugs  cause  contraction  of  the  ciliary  muscle  Griinhagen 
supposes  an  analogous  action  upon  the  sphincter.  In  all  probability  they  para- 
lyze the  dilator  fibers,  and  stimulate  the  oculomotor  fibers  at  the  same  time. 

Intravenous  injection  of  suprarenal  extract  causes  all  signs  of  irritation  of 
the  cervical  sympathetic  in  the  eye. 

If  one  pupil  is  contracted  or  dilated  by  these  drugs,  the  other  pupil  is  con- 
versely dilated  or  contracted  on  account  of  the  variation  in  the  amount  of  light 
that  enters  the  eye  into  which  the  drug  has  been  introduced. 

The  Anesthetics. — Chloroform,  in  the  excitation-stage  of  narcosis  (beginning 
of  unconsciousness),  stimulates  the  center  for  the  dilatation  of  the  pupil.  Later, 
this  center  is  paralyzed  (so  that  no  dilatation  occurs  on  the  application  of  external 
stimuli).  Then,  the  contracting  center  is  'stimulated  (the  pupil  becoming  reduced 
to  the  size  of  a  pinhead) ,  and  finally  (with  danger  of  death)  this  center  becomes 
paralyzed,  and  the  pupil  dilates. 

The  movements  of  the  iris  are  always  accompanied  by  variations  in  the  intra- 
ocular pressure.  Dilatation  of  the  pupil  increases,  contraction  of  the  pupil 
diminishes  the  intraocular  pressure.  Irritation  of  the  sympathetic  increases, 
section  diminishes,  the  pressure.  Instillation  of  atropin,  after  a  short  temporary 
lowering  of  the  pressure,  produces  an  increase.  Eserin,  after  a  primary  increase, 
causes  diminution  of  the  pressure. 

According  to  Hocker,  atropin  decreases  the  pressure ;  eserin  increases  it  pri- 
marily and  then  decreases  it  on  the  appearance  of  myosis. 

Reflex  dilatation  of  the  iris  occurs  slightly  later  than  reflex  contraction: 
respectively  0.5  and  0.3  second  after  the  light-stimulus.  A  certain  period  of 
time  always  elapses  before  the  size  of  the  pupil  adapts  itself  to  the  amount  of 


844  ENTOPTIC    PHENOMENA. 

illumination  that  stimulates  the  retina.  In  birds,  irritation  of  the  oculomotor 
produces  exceedingly  rapid  contraction ;  in  rabbits  dilatation  of  the  pupil  does  not 
appear  until  0.89  second  after  irritation  of  the  sympathetic. 

In  the  enucleated  eyes  of  amphibians  and  fishes,  stimulation  by  light  causes 
contraction  of  the  pupil.  In  fact  the  iris  of  the  eel,  when  removed  from  the 
eye  and  laid  in  salt-solution,  contracts  on  stimulation  by  light,  the  green  and 
blue  rays  being  the  most  active.  In  these  animals  the  cells  of  the  sphincter 
muscle  are  pigmented;  the  contractile  action  of  the  light-rays  seems  to  take 
place  through  the  intermediation  of  the  pigment. 

Increase  of  temperature  produces  mydriasis  of  the  enucleated  eye  of  the  frog 
or  eel,  while  decrease  of  temperature  causes  myosis. 

Grunhagen  has  disputed  the  existence  of  the  dilator  muscle.  He  explains 
the  dilating  action  of  the  sympathetic  by  the  contraction  of  the  vessels  of  the 
iris,  while  Gaskell  ascribes  it  to  an  inhibitory  action  on  the  sphincter.  However, 
the  dilatation  of  the  pupil  is  not  synchronous  with  the  vascular  contraction. 
Irritation  near  the  center  of  the  cornea  causes  contraction  of  the  pupil. 

Pathological. — Imperfect  contraction  of  the  pupil  on  illumination  of  the 
eyes  may  be  caused:  (i)  By  a  lowered  sensibility  of  the  retina  (loss  of  sensory 
reflex),  or  (2)  by  paralysis  of  the  pupillary  oculomotor  fibers  (loss  of  motor  reflex), 
or  (3)  both  may  be  combined.  Such  conditions  have  also  been  designated  by 
the  badly  chosen  term  reflex  immobility  of  the  pupil.  The  remarkable  cases  of 
so-called  paradoxical  light-reaction  exhibit  dilatation  of  the  pupil  upon  stimula- 
tion by  light,  perhaps  as  the  result  of  profound  exhaustion  of  the  oculomotor,  which 
is  soon  paralyzed  by  the  light-stimulation. 


ENTOPTIC    PHENOMENA. 

SUBJECTIVE  OPTICAL  MANIFESTATIONS. 

The  designation  entoptic  phenomena  is  applied  to  those  that  depend 
on  the  perception  of  objects  that  are  present  in  the  eye  itself  Subjective 
visual  sensations  are  those  that  are  not  produced  by  the  normal,  homol- 
ogous stimulation  of  the  retina  by  light,  but  by  internal,  heterologous 
(mechanical,  electrical,  somatic)  stimuli,  which  act  upon  the  eye,  the 
optic  nerve,  or  parts  of  the  central  organs 

Among  entoptic  phenomena  are: 

i.  Shadows  of  various  opaque  bodies  thrown  on  the  retina.  They  may  be 
recognized  by  the  following  method :  the  small  image  of  a  light  is  thrown  upon  a 
pasteboard  screen  by  means  of  a  convex  lens ;  a  fine  hole  is  pricked  through  the 
image  of  the  flame  and  the  eye  is  placed  on  the  other  side  of  the  screen,  so  that  the 

.uminated  point  coincides  with  the  anterior  focal  point  of  the  eye   (about    13 
mm    from  the  cornea).     As  the  rays  from  this  point  pass  parallel  through  the 

cular  media,  a  diffusely  illuminated  field  is  formed,  which  is  surrounded  by  the 
dark  outlines  of  the  pupillary  margin.  All  dark  objects  that  intercept  these 
rays  throw  shadows  on  the  retina  and  appear  as  spots  (Fig.  291).  Several  varieties 
of  these  shadows  can  be  distinguished:  (a)  The  muco-lacrimal  spectrum,  especi- 
\l  -u°n  •  lld-margms>  arising  from  particles  of  mucus,  fat-globules  from  the 
Meibomian  glands,  dust  mixed  with  tears.  These  give  rise  to  striated,  nebulous 
or  drop-like  shadows,  which  are  dissipated  by  winking.  (6)  Pressure  on  the 
cornea  with  the  finger  produces  wrinkled  shadows,  due  to  temporary  corneal 
pressure-folds,  (c)  Bead-like  or  dark  specks,  light  and  dark  stellate  figures, 
ormer  arising  from  deposits  on  and  within  the  lens,  the  latter  from  the  stellate 
structure  of  the  lens,  (d)  The  mouches  volantes  (muscae  volitantes) ,  like  strings  of 
beads,  circles,  groups  of  tiny  balls,  or  pale  threads,  are  images  of  small,  opaque  par- 
ticj*f  m  the  V1treous  cells,  broken-down  cells,  granular  fibers.  They  move  about  on 
sudden  movement  of  the  eye.  Listing  showed  that  it  is  possible  to  determine  the 
approximate  position  of  these  objects.  If  the  source  of  light  (the  illuminated  open- 
u1  •  t!S  £aised  and  lowered,  those  shadows  that  retain  their  relative  position  in  the 
bright  field  of  vision  are  due  to  objects  at  the  plane  of  the  pupillary  orifice  (2) ; 
that  move  apparently  in  the  same  direction  as  the  light  are  due  to  bodies  in 
the  pupillary  plane  (i) ;  those,  however,  that  move  in  the  opposite  direc- 


ENTOPTIC    PHENOMENA.  845 

tion  are  due  to  bodies  behind  the  pupillary  plane  (3).  It  should  be  noted  in 
this  connection  that  the  impressions  of  the  stimulated  portions  of  the  retina  are 
projected  outward  in  the  opposite  direction. 

"  2.  Purkinje's  figure  depends  upon  shadows  thrown  by  the  blood-vessels  within 
the  retina  upon  the  posterior  percipient  layer,  the  layer  of  rods  and  cones.  In 
ordinary  vision  they  cannot  be  perceived.  According  to  v.  Helmholtz  this  is 
probably  because  the  sensitiveness  of  these  shaded  portions  of  the  retina  is  greater 
than  that  of  the  remainder  of  the  retina,  and  their  irritability  is  less  exhausted. 
As  soon  as  the  position  of  the  vessel-shadow  is  changed,  so  that  it  is  thrown  to 
one  side,  instead  of  directly  backward,  on  places,  therefore,  that  ordinarily  do 
not  receive  shadows  from  the  vessels,  the  Purkinje  figure  at  once  appears.  The 
light  must  enter  the  eye  as  obliquely  as  possible.  The  experiment  may  be  made 
in  several  ways:  (i)  A  small  bright  image  of  a  light  may  be  thrown  upon  the 
sclera.  As  it  moves  up  and  down  the  vessel-figure  moves  with  it.  (2)  Looking 
directly  upward  at  the  sky,  the  depressed  upper  lid  is  blinked,  so  that  momen- 
tarily, in  correspondence  with  the  blinking  movement,  oblique  rays  of  light 
enter  the  lowest  part  of  the  pupil  from  above  downward.  (3)  One  may  look 
through  a  small  opening  toward  the  sky,  and  move  the  opening  quickly  to  and  fro, 
so  that  shadows  fall  rapidly  from  both  sides  of  the  vessels  on  the  neighboring 
rods;  or  (4)  one  may  look  straight  ahead  in  a  dark  room,  and  move  a  light  to 
and  fro  below  the  eye.  Occasionally  in  this  experiment  the  macula  lutea  is  seen 
— like  a  non vascular  shaded  depression,  appearing  (on  account  of  the  inversion 
of  objects)  on  the  inner  side  of  the  optic-nerve  entrance. 

3.  Recognition  of  the  Movement  of  the  Blood-corpuscles  in  the  Retinal  Capilla- 
ries.— -On  looking  (without  accommodation)  at  a  large  bright  surface,  or  at  the  sun 


FIG.  291. — The  Entoptic  Shadows. 

through  a  dark-blue  glass,  brilliant  points  like  tiny  sparks  are  seen  to  move  in 
various  tortuous  paths  over  larger  or  smaller  spaces.  The  movement  appeared 
to  Landois  to  resemble  most  that  of  a  Gyrinus  swarm  (small  water-beetles) 
on  the  surface  of  the  water.  The  particles  can  often  be  seen  to  follow  each  other 
in  definite,  outlined  paths.  According  to  some  observers,  the  phenomenon  is 
due  to  the  fact  that  the  red  blood-corpuscles — in  the  capillaries  outside  of  the 
external  nuclear  layer — act  as  small  concave  discs,  concentrating  the  light  falling 
on  them  upon  the  rods  of  the  retina.  Each  corpuscle  must  be  in  a  suitable  posi- 
tion; if  it  turn  over,  the  light-phenomenon  disappears.  Vierordt,  who  projected 
the  movement  upon  a  screen,  calculated,  from  its  rapidity,  that  the  velocity  of  the 
blood-current  in  the  retinal  capillaries  is  from  0.5  to  0.75  mm.  per  second,  and 
this,  in  fact,  corresponds  to  the  direct  observations  of  E.  H.  Weber  and  Volkmann 
on  the  blood-current  in  other  capillaries.  Compression  of  the  carotid  artery 
retards  the  movement,  release  of  the  vessel,  as  well  as  short  expiratory  pressure, 
accelerate  it.  As  Landois  occasionally  observed  the  points  as  dark  spots  on  a  light 
ground,  and  as  bright  ones  on  a  dark  surface,  the  phenomenon  is  probably  better 
explained  as  a  pressure-phosphene  (according  to  5) ,  from  the  friction  of  the  blood- 
corpuscles  in  the  capillaries  against  the  rods. 

4.  The   yellow   spot   appears    also   occasionally,   when   viewed   with    uniform 
blue  illumination,  as  a  dark  circle.      In  stronger  light  the  position  of  the  yellow 
spot  may  be  seen  surrounded  by  a  bright  area,  having  a  diameter  about  thrice 
as  large  (Lowe's  ring). 

5.  Pressure-phosphenes,    that    is    those    phenomena   that    appear   under   the 
influence  of  pressure  on  the  eyeball,      (a)    Partial  pressure  on  the  eyeball  induces 


846  ENTOPTIC    PHENOMENA. 

the  so-called  luminous  pressure-picture  or  phosphene,  which  was  known  to 
Aristotle.  By  the  projection  of  this  retinal  stimulation  outward,  the  phos- 
phene is  perceived  on  the  side  of  the  visual  field  opposite  to  that  where  the  pressure 
was  made  upon  the  retina.  For  example,  pressure  on  the  outer  side  of  the  eye- 
ball causes  the  light-phenomenon  to  appear  on  the  inner  side.  If  the  retina  is 
darkened,  the  phosphene  appears  bright;  if  the  retina  is  illuminated,  the  phos- 
phene appears  as  a  dark  spot  within  which  the  visual  sensation  is  momentarily 
abolished.  (6)  If  uniform  pressure  from  before  backward  be  made  for  some  time 
on  the  eyeball,  there  appear  in  the  field  of  vision  after  a  time,  as  Purkinje  pointed 
out,  bright,  changing  figures  which  produce  a  strange  phantastic  play,  often  similar 
to  the  most  brilliant  kaleidoscopic  pictures — probably  comparable  to  the  feeling 
of  formication  produced  by  pressure  upon  the  sensory  nerves  (limbs  "going  to 
sleep"),  (c)  By  applying  equable  and  continued  pressure,  Steinbach  and  Purkinje 
saw  appear  a  vascular  network  of  a  bluish-silvery  color,  with  streaming  contents, 
which  seemed  to  correspond  to  the  retinal  veins.  Vierordt  and  Laiblin  recognized 
in  addition  the  ramifications  of  the  choroidal  vessels,  red  on  a  dark  background, 
as  a  network  with  the  forms  characteristic  of  these  capillaries,  (d)  According 
to  Houdin  it  is  possible  also  to  recognize  the  position  of  the  yellow  spot  by  pres- 
sure on  the  eyeball. 

6.  The  entoptic  pulse-phenomenon  belongs  to  the  pressure-phosphenes,  and 
depends  upon  the  mechanical  stimulation  of  the  optic-nerve  fibers  by  the  pulsating 
retinal  vessels. 

7.  The  point  of  entrance  of  the  optic  nerve  may  be  perceived  on  rapid,  jerking 
movements  of  the  eye,  especially  inward,  as  a  fiery  circle  or  semicircle,  slightly 
larger  than  a  pea.     Probably  the  retina  around  the  nerve-entrance  is  irritated 
mechanically  by  the  bending  of  the  nerve.     Landois  saw  this  ring,  as  did  Purkinje, 
remain  persistent  when  the  eye  was  turned  strongly  inward.    If  the  retina  is  strongly 
illuminated,  the  ring  appears  dark,  and  when  the  visual  field  is  colored,  the  ring 
has  a  different  hue.     If  Purkinje's  figure  be  produced  at  the  same  time,  the  blood- 
vessels appear  to  spring  from  this  ring — a  proof  that  the  ring  corresponds  to  the 
optic-nerve  entrance. 

8.  Accommodation-spot. — If  the  eye  is  accommodated  as  strongly  as  possible 
for  a  white  surface,  a  small  bright,  vibrating  shimmer  appears,  in  the  middle 
of  which  a  brownish  spot  the  size  of  a  pea  may  shortly  be  observed.     If  pressure 
be  made  on  the  eyeball  at  the  same  time,  this  spot  becomes  more  distinct.     When 
this  phenomenon  is  once  recognized,  a  brighter  spot  may  be  seen  in  the  middle 
of  the  visual  field  when  lateral  pressure  is  made  upon  the  open  eye,  another  proof 
that  the  intraocular  pressure  rises  during    accommodation.     By  producing   the 
preceding  phenomenon   (No.  7)   it  is  demonstrated  that  the  phenomenon  takes 
place  at  the  optic-nerve  entrance. 

9.  The  accommodation-phosphene  consists  in  the  appearance  of  a  fiery  ring 
at  the  periphery  of  the  visual  field  when  the  eyes  are  .suddenly  allowed  to  come 
to  rest  after  prolonged,  intense  accommodation  for  near  vision  in  the  dark.     The 
sudden  tension  of  the  zonule  of  Zinn  resulting  from  the  relaxation  produces  a  me- 
chanical stretching  of  the  edge  of  the  retina,  or  more  probably  of  the  retina  just 
beyond.     Purkinje  saw  the  phenomenon  also  after  sudden  cessation  of  pressure 
upon  the  eye. 

10.  Mechanical  Irritation  of  the  Optic  Nerve. — When  the  optic  nerve  is  severed 
in  man,  in  the  course  of  an  operation,  a  bright  flash  appears  at  the  moment  of 
section.     The  incision  through  the  optic-nerve  fibers  is  painless ;    only  the  sheaths 
are  sensitive. 

1 1 .  Electrical  Phenomena. — With  variations  in  an  electric  current  (one  pole 
on  the  upper  lid,  the  other  on  the  neck)  bright  flashes  of  light  shoot  over  the  entire 
visual  field.     The  closing  flash  is  stronger  with  an  ascending  current,  the  opening 
flash  stronger  with  a  descending  current.     A  uniform,  constant,  ascending  cur- 
rent applied  to  the  closed  eye  reveals  the  optic-nerve  papilla  as  a  dark  disc  in  a 
whitish-violet  field.     At  the  same  time  sensibility  for  white  is  increased,  that 
for  black  diminished.     With  a  descending  current,  on  the  other  hand,  the  visual 
field  appears  greenish-yellow,  and  darkened,  and  in  its  midst  the  position  of  the 
nerve  appears  light  blue.      If  external  colors  are  observed  at  the  same  time,  these 
tones  blend  to  form  violet  or  yellow  with  the  colors  looked  at.     Under  the  in- 
fluence of  an  ascending  current  external  objects  are  said  to  be  seen  less  distinctly 
and  diminished  in  size  when  the  eyes  are  open;  while  a  descending  current  makes 
them  more   distinct   and  larger.      During  anelectrotonus  of  the  retina    (in  con- 
formity with  the  laws  of    electrotonus)   the  sensibility  for  the    electrical  light- 


ILLUMINATION    OF    THE    EYE,    AND    THE    OPHTHALMOSCOPE. 


847 


phenomena  and  also  that  for  objective  light  are  diminished.  At  times  the  macula 
lutea  appears  as  a  dark  spot  on  a  light  ground,  at  other  times  as  a  light  spot  on 
a  dark  ground,  according  to  the  direction  of  the  current.  If  the  current  is  broken, 
the  phenomena  are  reversed  and  the  eye  soon  returns  to  rest. 

When  the  eye  is  directed  toward  a  source  of  polarized  light,  Haidinger's 
polarization  brushes  appear  at  the  point  of  fixation.  They  may  be  seen  if  a  bright 
cloud  is  looked  at  through  a  Nicol's  prism.  They  appear  as  bright,  bluish  spots 
on  a  white  ground,  bounded  by  two  similar  hyperbolas;  the  dark  bundle  sepa- 
rating them  is  narrowest  in  the  center,  and  has  a  yellowish  color.  Blue  alone 
of  the  various  colors  of  homogenous  light  exhibits  the  brushes.  According 
to  v.  Helmholtz  the  seat  of  the  phenomenon  is  the  yellow  spot,  and  it  depends 
upon  the  fact  that  the  yellow-colored  elements  of  this  spot  are  slightly  birefringent, 
and  they  absorb  more  of  the  rays  in  one  place  than  in  others. 

Finally,  there  should  be  mentioned  the  sensations  of  light  produced  by  in- 
ternal causes,  by  congestion  of  the  retina  (as  from  violent  spells  of  coughing), 
increased  intraocular  pressure  and  the  like,  or  by  congestion  of  the  central  cerebral 
organs.  Irritation  of  the  psychooptical  centers  may  induce  distinct  phantasms, 
which  Cardanus,  Goethe,  Johannes  Miiller,  Nageli.and  others  could  in  fact  excite 
in  themselves .  voluntarily.  "Video  quae  volo,  nee  omnino  semper  cum  volo. 
Moventur  autem  perpetuo  quae  videntur.  Itaque  video  lucos,  animalia,  orbes 
ac  quaecunque  cupio"  (Cardanus).  In  men  suffering  from  delirium  tremens 
something  similar  at  times  takes  place :  they  are  able  to  call  forth  hallucinations 
even  in  daytime,  as  soon  as  they  think  of  certain  things — voluntary  hallucinations. 

ILLUMINATION  OF  THE  EYE,  AND  THE  OPHTHALMOSCOPE. 

The  light  that  enters  the  eye  is  partly  absorbed  by  the  black  uveal 
pigment,  and  partly  reflected  again  from  the  eye,  and  always  in  the  same 


FIG.  292. — Apparatus  for  Illuminating  the  Back  of  the  Eye  B. 

direction  from  which  it  has  entered.  If  a  person  place  himself  directly 
before  the  eye  of  another,  the  head  of  the  former,  as  an  opaque  body, 
naturally  cuts  off  a  considerable  number  of  rays.  As  no  rays  can  fall 
upon  the  eye  from  the  direction  of  the  head  of  the  first  person,  none  can  be 
reflected  from  the  eye  of  the  other,  which,  therefore,  appears  black  to  the 
former,  for  the  reason  that  he  cuts  off  all  those  rays  that  could  be  re- 
flected toward  his  eye.  As  soon,  however,  as  it  is  possible  to  throw 
light  into  the  eye  of  the  second  person  in  the  same  direction  in  which 
the  first  looks  into  the  eye  of  the  other,  the  eyeground  at  once  appears 
brightly  illuminated. 


848 


ILLUMINATION    OF    THE    EYE,    AND    THE    OPHTHALMOSCOPE. 


The  simple  apparatus  shown  in  Fig.  292  is  sufficient  to  corroborate  what 
has  been  said:  Let  B  represent  the  eye  to  be  examined,  and  A  the  eye  of  the 
observer.  If  a  flame  be  placed  at  x,  its  rays  will  be  thrown  upon  the  glass  plate 
5  5,  which  reflects  them  in  the  direction  of  the  dotted  lines  into  the  eye  B.  The 
eyeground  appears  in  this  position  brightly  illuminated  around  b  in  diffusion- 
circles.  As  the  observer  A  can  see  through  the  glass  plate  5  5  without  difficulty, 
and  in  the  same  direction  as  the  reflected  ray  x  y,  he  will  see  the  retina  brightly 
illuminated  at  b. 


FIG. 


FIG.  294. 


FIG.  295. 

It  is  important  for  practical  purposes  to  be  able  to  recognize  the 
etails  of  the  eye-ground :  the  blood-vessels,  the  macula  lutea,  the  optic- 
nerve  entrance,  abnormalities  of  the  retina,  of  the  choroidal  pigment, 
and  the  like.  How  this  is  to  be  done  will  be  understood  from  the 
following  considerations:  As  has  been  seen  (and  as  Fig  279  p  829 
shows)  a  small,  inverted  image  is  formed  on  the  retina  (c  d]  of  an  object 
(A  &)  tor  which  the  eye  is  accommodated.  Conversely,  according  to  the 


ILLUMINATION    OF    THE    EYE,    AND    THE    OPHTHALMOSCOPE. 


849 


same  dioptric  law,  an  enlarged,  inverted  real  image  (c  d)  must  be  formed 
outside  of  the  eye  (at  A  B)  of  any  illuminated,  circumscribed  portion  of 
the  retina  (when  the  eye  is  accommodated  for  a  certain  distance).  If 
the  eyeground  is  sufficiently  illuminated,  this  image  formed  in  the  air 
will  possess  a  corresponding  degree  of  brightness. 

In  order  to  examine  more  carefully  the  individual  portions  of  this 
image  of  the  retina,  the  observer  must  accommodate  for  the  situation 
of  the  image.  His  eye  is  then  separated  from  the  retina  of  the  eye  under 
observation  a  distance  equal  to  the  sum  of  the  focal  distances  of  his  own 
and  the  other  eye.  At  this  distance  the  finer  details  of  the  eyeground 
cannot  be  recognized.  Moreover,  as  the  pupil  of  the  eye  examined  is 
narrow,  only  a  small  portion  of  the  eyeground  can  be  seen,  and  only 
under  a  low  visual  angle;  aside  from  this,  it  is  often  impossible  to 
accommodate  for  the  image. 

It  is  necessary,  therefore,  to  bring  the  eye  of  the  observer  closer 
to  the  eye  under  examina- 
tion. This  may  be  done  in 
two  ways,  (i)  By  placing 
before  the  eye  under  exam- 
ination a  strong  convex  lens 
with  a  focus  of  i  inch  (Fig. 

293,  C).     As  the  image  of  the 
retina  is  thus  brought  closer 
to  the  eye  (at  B),  as  the  result 
of  the  refraction  of  the  rays 
by  the  lens,  the  observer  M 
can    approach    much    nearer 
and    can    still   accommodate 
for   the   image.      (2)    Or   by 
placing  a  concave  lens  (Fig. 

294,  o)  before  the  eye  exam- 
ined.      The    rays    emerging 
from  this  eye  are  either  made 
parallel  by  the  concave  lens 
o,   and  are   then   focused  on 
the  retina  of  the  emmetropic 
observer   A;   or,   if   the   lens 
make     the     rays     divergent 
(Fig.  295),  an  upright,  virtual 
image    of    the    eyeground   is 

formed  in  the  distance,  behind  the  investigated  eye  (at  R).  Under 
such  circumstances  also  the  observer  can  approach  much  nearer, 

The  illuminating  apparatus,  together  with  one  of  these  lenses  forms 
the  ophthalmoscope  of  v.  Helmholtz,  the  basis  of  modern  ophthalmo- 
scopy,  by  means  of  which  all  the  details  of  the  eyeground  can  be 
examined. 

For  the  illumination,  v.  Helmholtz  used  several  plates  of  glass  placed  behind 
one  another  (for  better  reflection),  in  the  same  position  as  55  in  Fig.  292.  A 
plane  mirror  or  a  concave  mirror,  with  a  focus  of  7  inches,  through  the  center  of 
which  a  hole  is  bored  (Fig.  293,  Si,  52)  may  also  be  employed.  Fig.  296  shows 
the  ophthalmoscopic  appearance  of  the  optic-nerve  entrance,  and  its  vicinity, 
in  a  normal  eye.  The  letters  indicate  the  details.  In  albinos  the  fundus  appears 
light  red,  because  light  passes  into  the  eye  through  the  nonpigmented  sclera 

54 


FIG.  296. — The  Optic-nerve  Entrance,  with  the  Surrounding 
Structures,  of  a  Normal  Eyeground  (after  Ed.  Jaeger): 
A,  Optic  disc  (papilla);  a,  connective  tissue  ring  ;  b,  cho- 
roidal  ring;  c,  arteries;  d,  veins;  g,  point  of  division  of  the 
central  artery;  h,  of  the  central  vein;  L,  lamina  cribrosa; 
/,  temporal  (outer)  side;  n,  nasal  (inner)  side. 


8S° 


THE    FUNCTION    OF    THE    RETINA    IN    VISION. 


and  uvea.  If  a  diaphragm  be  placed  in  front  of  the  eye,  so  that  only  the  pupil 
is  free,  the  eyeground  appears  dark.  In  many  animals  the  eyes  have  a  bright- 
green  luster.  These  possess  a  special  layer,  the  tapetum,  or  the  membrana  versi- 
color  of  Fielding,  which  in  the  carnivora  is  composed  of  cells,  in  the  herbivora  of 

fibers;  it  lies  between  the  chorio- 
capillary  layer  and  the  stroma  of  the 
uvea,  yielding  interference-colors,  and 
reflecting  a  considerable  amount  of 
light,  so  that  the  eyes  have  a  colored 
luster. 

For  examination  of  the  anterior 
chamber  oblique  illumination  is  em- 
ployed. A  bright  beam  of  light,  con- 
densed by  a  convex  lens,  is  thrown 
obliquely  into  the  eye,  upon  the  point 
to  be  examined,  which  appears  clear 
and  distinct.  The  point  thus  illumin- 
ated, for  example  a  part  of  the  iris, 
can  then  be  magnified  and  examined 
with  the  help  of  a  lens,  or  even  of  a 
microscope. 

Czermak  constructed  the  ortho- 
scope  (Fig.  297),  by  means  of  which 
the  eye  is  placed  under  water.  A 
small  glass  trough,  one  side  of  which 
is  removed,  is  filled  with  water  and 
pressed  against  the  face,  so  that  the 
eye  and  the  face  form  the  sixth  side  of 
the  trough,  and  the  cornea  is  covered 
with  water.  As  the  index  of  refraction 
of  the  water  is  the  same  as  that  of  the 
media  of  the  eye,  the  rays  pass  out  of 
the  eye  unrefracted.  Hence,  objects 
in  the  anterior  chamber  can  be  seen 
directly,  and  appear  as  though  outside 
of  the  eye.  A  further  advantage  lies 
in  the  fact  that  the  objects  are  brought 
closer  to  the  observer's  eye.  The  rays 
from  the  point  a  of  the  eyeground  would  leave  the  eye  parallel  as  b  c,  b  c, 
if  the  eye  were  surrounded  by  air.  Seen  under  water,  however,  these  rays  a  b,  a  b 
continue  in  the  same  direction  as  far  as  d,  d,  where  they  are  deflected  from  the 
perpendicular  on  emerging  from  the  water,  that  is  toward  d  e,  d  e.  The  ob- 
server's eye,  looking  in  the  direction  e  d,  sees  the  point  a  closer,  that  is  in  the 
direction  e  d  af ',  consequently  situated  at  of '. 


FIG.  297. — Mechanism  of  the  Orthoscope. 


THE  FUNCTION  OF  THE  RETINA  IN  VISION. 

The  rods  and  cones  are  the  only  parts  of  the  retina  sensitive  to 
light;  they  alone  are  stimulated  by  the  vibrations  of  the  luminiferous 
ether.  This  is  confirmed  by  Mariotte's  experiment,  which  shows  that 
the  optic-nerve  entrance,  where  rods  and  cones  are  absent,  has  no  light- 
perception.  This  is,  therefore,  called  the  blind  spot. 

If  the  letter  f  (Fig.  279,  p.  829)  of  the  two  black  letters  B  and  f  is  fixated  with 
one  eye  (the  other  being  closed),  so  that  its  image  falls  on  the  fovea  centralis 
(n),  and  the  image  of  B  falls  on  the  optic-nerve  entrance  (N),  the  letter  B  dis- 
appears immediately.  If  three  points,  A  f  B,  are  drawn,  and  the  eye  fixes  the 
middle  point  f,  B  disappears,  but  the  points  A  and  f  are  visible. 

The  optic-nerve  entrance  lies  about  3.5  mm.  to  the  inner  side  of  the  visual 
axis  in  the  retina.  It  has  a  diameter  of  i  .8  mm.  In  the  field  of  vision  the  horizon- 
tal diameter  of  the  blind  spot  measures  apparently  6°  56';  it  lies  from  12°  8 1' 
to  1 8  55  external  to  the  point  of  fixation.  This  diameter  would  cover  n  full 
moons,  placed  side  by  side,  and  would  conceal  a  human  face  at  a  distance  of  more 
than  2  meters. 


THE    FUNCTION    OF    THE    RETINA    IN    VISION.  851 

The  proof  that  it  is  really  the  optic-nerve  entrance  that  is  not  sensitive  is 
furnished  by  the  following  observations:  (i)  Donders,  by  means  of  a  mirror, 
threw  a  small  image  of  a  flame  directly  on  the  optic-nerve  entrance  of  another 
person,  who  had  no  sensation  of  light.  This  appeared,  however,  as  soon  as  the 
image  was  displaced  to  the  neighboring  portions  of  the  retina.  (2)  If  Mariotte's 
experiment  be  combined  with  the  experiments  that  yield  entoptic  phenomena  at 
the  optic-nerve  entrance,  the  latter  coincide  with  the  blind  spot. 

In  order  to  determine  the  form  and  apparent  size  of  the  blind  spot  in  one's 
own  eye,  the  head  should  be  placed  at  a  distance  of  about  25  cm.  from  a  piece 
of  white  paper.  Then  a  small  point  should  be  fixed  with  the  eye,  and  the  position 
of  the  blind  spot  on  the  paper  determined  by  moving  a  white  feather  about  in 
various  directions,  making  a  mark  wherever  its  point  first  becomes  visible.  In 
this  way  the  blind  spot  may  be  mapped  out,  and  it 
will  be  found  to  have  an  irregularly  elliptical  form, 

from  which  processes  extend,  representing  the  insensi-       o  V~\  (^ 

tive  origins  of  the  large  central  vessels  of  the  retina.       CL  t<J  l^s 

Mariotte  concluded,  from  his  experiment,  that  the 
choroid,  which  is  perforated  by  the  optic  nerve,  is  the 
light-perceiving  membrane,  as  the  nerve-fibers  are  p]  / r\\ 

nowhere  absent  from  the  retina.  ^  \^ / 

The  blind  spot  in  the  eye  causes  no  appreciable 
defect   in  the  visual   field.     As  the  area  is  not  excited 

by  light,  a  black  spot  cannot  appear  in  the  visual  field,       Q.  L-*  j 

for  the  sensation   of  black  presupposes  the  presence      £5  »  1  1 

of  retinal  elements,  which,  however,  are  absent  at  the 
blind  spot.  The  circumstance  that,  despite  the  in- 
sensitive spot,  no  unoccupied  spot  in  the  visual  field  is  perceived  is  due  to  psy- 
chical action.  The  unoccupied  part  of  the  field,  corresponding  to  the  blind 
spot,  is  probably  filled  out  by  a  psychical  process.  Hence,  when  a  white  point 
on  a  black  surface  disappears,  the  entire  surface  appears  black.  A  white  surface 
of  which  a  black  point  falls  upon  the  blind  spot  appears  entirely  white,  a  printed 
page  grayish  throughout,  etc.  In  the  same  way,  parts  of  a  circle,  the  middle  parts 
of  a  long  line,  the  middle  portion  of  a  cross  are  probably  supplied.  Such  images, 
though,  that  cannot  be  reconstructed  on  a  basis  of  probability  are  not  completed, 
for  example  the  end  of  a  line,  or  a  human  countenance.  Under  other  conditions 
a  phenomenon  contributes  to  the  filling  out  of  the  empty  space  that  has  been 
designated  the  "contraction  of  the  visual  field."  This  becomes  clear  if  the  letter 
e  is  made  to  disappear  from  among  the  nine  adjoining  letters;  the  three  letters  of 
each  side  are  no  longer  seen  in  a  straight  line,  but  b,  f,  h,  d  are  drawn  in  toward 
e.  The  surrounding  portions  of  the  field  seem  to  stretch  out  over  the  position 
of  the  blind  spot  and  help  to  replace  it. 

The  outer  segments  of  the  rods  and  cones  possess  rounded  con- 
tours ;  they  are  placed  close  together,  but  there  must  be  spaces  between 
them  (corresponding  to  the  interspaces  between  circles  placed  in  con- 
tact). These  spaces  are  insensitive  to  light,  so  that  the  retinal  image 
is  constructed  like  a  mosaic  of  small  round  stones.  The  diameter  of  a 
cone  in  the  yellow  spot  measures  from  2  to  2.5  //.  If  two  closely  sit- 
uated points  form  images  on  the  retina,  they  will  be  perceived  as  isolated 
points,  provided  that  the  images  fall  upon  two  different  cones.  A  dis- 
tance of  from  3  or  4  to  5 .4  //  between  the  images  on  the  retina  is  sufficient 
to  enable  them  to  be  seen  separately,  as  they  will  then  fall  on  two  neigh- 
boring cones.  If  the  distance  is  so  diminished  that  both  images  fall 
on  one  cone,  or  one  on  a  cone,  and  the  other  on  an  interspace,  only  one 
point  will  be  perceived.  In  the  peripheral  portions  of  the  retina,  the 
images  must  be  still  further  apart  in  order  to  be  perceived  separately. 

As  the  rounded  ends  of  the  cones  are  not  placed  in  exactly  straight  lines, 
but  so  that  a  row  of  circles  is  adapted  to  the  interstices  of  the  succeeding  row, 
exceedingly  fine  dark  lines,  drawn  parallel,  appear  to  have  alternating  twists, 
as  their  images  must  fall  on  the  cones  alternately  to  right  and  to  left.  In  the  same 
way  every  straight  edge  of  an  object  appears  wavy  when  its  retinal  image  is  moved 
across  the  retina  with  moderate  rapidity. 


852 


THE    FUNCTION    OF    THE    RETINA    IN    VISION. 


The  sharpest  vision  is  obtained  at  the  fovea  centralis,  where  cones 
alone  are  found,  placed  closely  together.  In  the  peripheral  portions  of 
the  retina  the  cones  are  placed  less  closely  together,  and  here  vision  is 
less  acute.  From  this  it  may  be  concluded  that  the  cones  are  more 
important  for  vision  than  the  rods.  In  order  to  see  an  object  as  dis- 
tinctly as  possible,  the  eyes  are  therefore  turned  involuntarily  so  that 
the  retinal  images  fall  on  the  fovea  centralis.  This  adjustment  is  known 


FIG.  298.— Horizontal  Section  of  the  Right  Eye:   a,  Cornea;   6,  conjunctiva-    c,  sclera'    d 
taming  the  aqueous  humor;    e,  iris;   /,  /',  pupil;    g,  posterior  chamber;    I,  canal 'of  I 
k,  corneo-scleral  junction;   »,  canal  of  Schlemm;   m,  choroid;   n,  retina;    o,  vitreous  t 


anterior  chamber,  con- 
Petit;   /,  ciliary  muscle; 

g,  nerve-sheaths;  p,  nerve-fibers;  Ic,  lamina  cribrosa'.  "  The  Hne'^  *O  islhe'op'dc  axis,  S  r  the  visual  axis,  r  the 
position  of  the  fovea. 


as  -fixation;  the  visual  ray  drawn  from  the  fovea  to  a  point  in  the  object 
is  called  the  visual  axis  (Fig.  298,  5  r).  This  forms  with  the  optic  axis  of 
the  eye  (0  A),  which  unites  the  centers  of  the  spherical  surfaces  of  the 
refracting  media,  an  angle  of  only  from  3.5°  to  7°.  The  point  of  inter- 
section lies,  of  course,  in  the  nodal  point  (k  n)  of  the  lens  (Figs.  279,  298). 
Vision  with  the  optic  axes  directed  upon  the  object  is  known  as  direct 
vision. 


THE    FUNCTION    OF    THE    RETINA    IN    VISION.  853 

Faintly  illuminated  objects  are  not  appreciated  with  the  same  degree  of 
accuracy  by  the  fovea  centralis  as  by  the  surrounding  retina. 

If  light  be  allowed  to  fall  on  the  fovea  centralis  through  a  screen  perforated 
like  a  sieve,  it  appears  as  a  continuous  bright  surface,  if  one  point  of  light  falls  on 
each  cone.  For  this  it  is  necessary  that  from  140  to  149  points  of  light  fall  on 
o.oi  sq.  mm.  of  the  fovea  centralis.  According  to  Salzer  there  are  138  cones 
in  this  area.  If  the  points  of  light  in  the  screen  are  to  be  appreciated  separately, 
each  illuminated  cone  must  be  surrounded  by  a  circle  of  nonilluminated  cones. 
In  this  case  72  points  of  light  must  fall  on  o.oi  sq.  mm.  of  the  fovea. 

To  test  the  visual  acuity  in  direct  vision,  two  fine  parallel  lines  drawn  close 
together,  are  gradually  removed  further  from  the  eye,  until  they  appear  to  fuse 
almost  into  one.  From  the  distance  between  the  two  lines,  and  the  separation 
of  the  drawing  from  the  eye,  the  size  of  the  retinal  image  is  determined,  and  also 
that  of  the  corresponding  visual  angle,  which  is  ordinarily  between  60  and  90 
seconds — the  lowest  limit  has  been  found  to  be  between  50  and  27  seconds. 

Indirect  vision  occurs  when  the  rays  of  light  from  an  object  fall  upon 
the  peripheral  portions  of  the  retina.  Indirect  vision  is  much  less  sharp 
than  the  direct,  but  the  periphery  of  the  retina  has  a  well-developed 
power  of  recognizing  movements,  changes  or  intermissions  in  visual 
impressions. 

Perimetry. — For  the  determination  of  indirect  vision  the  perimeter  of  Aubert 
and  Forster  is  used.  The  eye  is  placed  opposite  a  fixation -point,  from  which 
extends  a  semicircle,  so  that  the  eye  lies  at  its  center.  As  the  semicircle  can  be 
revolved  about  the  fixation-point,  the  surface  of  a  hemisphere  is  formed  by  this 
rotation,  in  the  center  of  which  the  eye  is  placed.  An  object  is  now  pushed  outward 
from  the  fixation-point  along  the  semicircle  toward  the  periphery  of  the  visual 
field,  until  it  becomes  indistinct  and  finally  disappears.  This  test  is  made  along 
the  various  meridians  by  moving  the  arc  into  corresponding  positions.  The 
further  away  from  the  fixation-point  two  closely  placed  points  are  carried,  the 
further  they  must  be  separated,  to  prevent  their  being  fused.  The  power  of 
distinguishing  colors  diminishes  more  rapidly  in  the  periphery  than  does  that  for 
distinguishing  differences  in  brightness.  The  decrease  is,  moreover,  more  marked  in 
the  vertical  meridian  of  the  eye  than  in  the  horizontal,  and  decreases  with  the 
distance  from  the  fixation-point.  Aubert  and  Forster  discovered  the  remark- 
able fact  that  in  accommodation  for  a  distant  object  the  decrease  of  the  differentiat- 
ing power  in  the  periphery  occurs  more  rapidly  than  in  accommodation  for  near 
vision.  The  sensibility  of  the  retina  for  colors  and  for  brightness  is  greater  at 
points  on  the  temporal  side  of  the  fovea  than  at  equidistant  points  on  the  nasal 
side. 

If  the  arc  of  the  perimeter  be  divided  into  90  degrees,  commencing  at  the 
fixation-point  (Fig.  299)  and  proceeding  to  L  and  M,  and  if  a  series  of  concentric 
circles  be  drawn  about  the  fixation-point,  a  topographical  chart  of  the  visual  power 
can  be  mapped  out  for  the  normal  and  the  diseased  eye.  Fig.  299  will  serve  as 
an  example.  The  thick  lines  refer  to  a  diseased  eye;  the  corresponding  fine  lines 
to  a  normal  one.  The  continuous  line  represents  the  limit  for  the  perception  of 
white;  the  interrupted  line,  that  for  blue;  the  dotted  and  interrupted  line  that  for 
red  (m  is  the  blind  spot,  according  to  Hirschberg).  The  limits  for  the  normal 
eye  are  as  follows: 

FOR  WHITE.  BLUE.  RED.  GREEN. 

Outward, 70-88°  65°  60°  40° 

Inward 50-60°  60°  50°  40° 

Upward 45-55°  45°  40°  3°-35° 

Downward,    65-70°  60°  50°  35* 

The  rods  and  cones  alone  possess  the  specific  energy  of  being  thrown 
by  the  vibrations  of  the  luminiferous  ether  into  the  activity  that  is 
designated  sight.  Nevertheless,  mechanical  and  electrical  stimuli 
applied  to  any  portion  of  the  course  of  the  nervous  apparatus  can  also 
produce  sensations  of  light.  The  mechanical  stimulation  is  more 
intense  than  that  produced  by  light-rays,  as  is  shown  by  the  fact  that, 


854 


THE    FUNCTION    OF    THE    RETINA    IN    VISION. 


when  the  dark  figure  is  produced  by  pressure  on  the  open  eye  in  con- 
sequence of  which  the  circulation  of  the  retina  is  disturbed,  external 
objects  are  not  perceived  by  the  retina. 

When  the  eye  is  well  rested,  it  has  a  diminished  sensitiveness  for  colors  in  a 
poor  light,  and  the  green  portion  of  the  spectrum  seems  to  possess  the  greatest 
degree  of  brightness,  v.  Kries  believes  that  under  such  circumstances  the  rods 
are  active,  while  with  vision  in  strong  illumination  the  cones  functionate.  As 
color-blind  individuals  perceive  the  brightness  in  the  spectrum  in  the  same  way 
as  does  the  well-rested  eye  in  a  poor  light,  perhaps  in  their  case  only  the  rods 
take  part  in  vision. 

The  duration  of  the  retinal  stimulation  need  be  but  brief.  The 
stimulation  by  light  does  not  reach  its  full  strength  at  once,  but  it  increases 
gradually,  so  that  a  weak  light  that  persists  for  some  time  may  appear 


FIG.  299. — Perimetric  Chart  of  a  Healthy  and  of  a  Diseased  Eye. 

just  as  bright  as  a  strong  light  that  persists  for  but  a  short  time.  In 
general,  the  larger  and  the  brighter  the  objects  the  less  the  time  necessary 
for  their  perception.  If  light  and  darkness  are  quickly  alternated,  the 
same  degree  of  illumination  is  produced  as  if  the  action  of  the  light 
were  divided  uniformly  over  the  entire  time  of  the  observation.  A 
light-stimulus  having  17  or  1 8  alternations  in  a  second,  produces  the 
strongest  sensation.  In  order  that  two  flashes  of  light  shall  be  per- 
ceived separately,  0.027  second  must  elapse  between  them.  Further 
an  increase  or  decrease  of  o.oi  part  of  the  light-intensity  will  be  recog- 
nized. A  shorter  time  is  required  for  the  perception  of  yellow  than  for 
that  of  red  and  violet.  Long  exposure  to  darkness,  as  during  the  night 
makes  the  retina  more  sensitive  to  light.  When  the  light-stimulus  is 


THE    FUNCTION    OF    THE    RETINA    IN    VISION.  855 

of  long  duration  and  great  intensity,  retinal  fatigue  sets  in,  beginning 
earlier  in  the  center  than  at  the  periphery.  It  progresses  more  quickly 
at  first  than  later,  and  is  most  striking  in  the  morning. 

During  direct  vision,  objects  must  have  an  angular  velocity  of  from 
one  to  two  minutes  in  a  second  in  order  to  appear  to  be  in  motion. 

The  manner  in  which  light  acts  upon  the  terminal  apparatus  of  the 
retina  has  already  been  discussed  in  connection  with  the  visual  purple 
(p.  819).  Kiihne  showed  that  by  illuminating  the  retina,  actual, 
permanent  pictures  could  be  produced  on  the  retina,  for  instance  the 
picture  of  a  window,  but  these  gradually  disappear.  The  retina  acts 
in  some  respects  like  the  sensitive  plate  of  a  photographic  apparatus, 
and  the  light  is  conceived  as  having  a  chemical  action,  especially  as  non- 
illuminated  retinas  have  a  more  acid  reaction  than  illuminated  ones. 

The  visual  purple  is  given  off  by  the  pigmented  epithelium  of  the  retina,  as 
a  sort  of  secretion,  to  the  rods  alone,  and  not  to  the  cones.  A  bleached  retina 
can  take  up  the  purple  again  if  placed  in  contact  with  living  pigmented  epithelium. 
There  are  two  modifications  of  the  purple  in  the  animal  kingdom.  The  mammalian 
retina  is  bleached  about  sixty  times  more  quickly  than  the  frog's.  In  fixed 
rabbits'  eyes,  under  atropin-mydriasis  Ewald  and  Kiihne  obtained  sharp  opto- 
grams  of  bright  objects  at  a  distance  of  24  cm.,  in  from  i£  to  i£  minutes;  the 
picture  is  fixed  by  4  per  cent,  solution  of  alum.  The  visual  purple  is  preserved 
when  dissolved  in  bile  and  when  saturated  with  sodium  chlorid.  It  resists  all 
oxidizing  agents;  zinc  chlorid,  acetic  acid,  and  mercuric  chlorid  transform  it  into 
a  yellow  substance.  It  becomes  white  only  through  the  action  of  light;  the 
nonluminous  heat  rays  have  no  effect;  it  is  decomposed  by  temperatures  above  52°. 

Kuhne  found  that  in  the  illuminated  frog's  eye  the  pigment-granules  of  the 
pigmented  epithelium  extend  further  between  the  outer  segments  of  ^the  rods 
and  cones,  and  in  darkness  withdraw  again  into  the  outer  part  of  the  pigmented 
epithelial  cells.  In  the  eye  of  the  fish  exposure  to  light  produces  also  decrease  of 
the  chromatin  in  the  granules  and  ganglia. 

A  further  important  fact  should  be  mentioned,  namely,  that  the 
inner  segments  of  the  cones  become  shorter  under  the  influence  of  light, 
and  elongate  in  the  dark.  The  action  is  always  bilateral,  even  when 
only  one  eye  is  exposed  to  light;  but  after  destruction  of  the  brain,  the 
effect  is  confined  to  one  side;  strychnin-tetanus,  thermal,  chemical,  or 
electrical  irritations  act  in  the  same  way  as  light.  The  optic  nerve,  there- 
fore, must  contain  motor  (retinomotor)  fibers,  in  addition  to  the  light- 
perceiving  fibers.  Motor  phenomena  are  observed  also  in  the  ganglion- 
cells,  and  in  the  outer  and  inner  segments  of  the  rods ,  the  cells  of  the  external 
nuclear  layer  changing  their  form  at  the  same  time.  In  fact  these 
movements  cause  electrical  phenomena  in  the  eye.  Isolated  inner 
cone-segments  and  granules  likewise  exhibit  changes  of  form  when 
exposed  to  light. 

According  to  v.  Kries  the  rods  are  entirely  color-blind,  and  their 
chief  function  is  related  to  vision  in  weak  light ;  the  cones  are  for  the  per- 
ception of  colors. 

In  changing  from  a  light  to  a  dark  room,  or  the  reverse,  the  eye 
must  adapt  itself  first  to  the  action  of  the  light.  The  eye  adapted  to 
light  has  been  found  superior  in  visual  activity  to  the  eye  adapted  to 
darkness. 

Destruction  of  the  rods  or  cones  of  the  retina  causes  corresponding 
dark  spots  in  the  visual  field. 

Strong  visual  impressions  render  the  retina  insensitive  to  light,  and 
permanent  injury  and  blindness  may  result  from  necrosis  of  the  ret- 
inal elements  with  edema. 


856  PERCEPTION    OF    COLORS. 


PERCEPTION  OF  COLORS. 

Physical  Considerations. — The  undulations  of  the  hmriniferous  ether  are 
perceived  by  the  retina  only  within  definite  limits.  If  a  beam  of  white  light, 
for  example  from  the  sun,  be  allowed  to  pass  through  a  prism,  its  rays  are  refracted, 
and  are  decomposed  into  the  prismatic  spectrum  (Fig.  12) .  The  white  light  contains 
rays  of  widely  different  wave-length,  or  number  of  vibrations.  The  dull  heat- 
rays  are  the  least  refracted;  their  wave-length  measures  0.00194  mm.;  they  do 
not  affect  the  retina,  and  are,  therefore,  invisible,  although  as  is  well  known  they 
affect  the  sensory  nerves.  About  90  per  cent,  of  these  rays  are  absorbed  by  the 
ocular  media.  Commencing  at  Fraunhofer's  line  A  (Fig.  15)  the  oscillations 
of  the  ether  excite  the  retina,  and  the  colors  appear  in  the  following  order:  red, 
with  481  billions  of  vibrations  in  a  second;  orange,  with  532;  yellow,  with  563; 
green,  with  607  ;  blue,  with  653 ;  indigo,  with  676 ;  and  violet,  with  764  billions  in  a 
second.  The  perception  of  color  depends,  therefore,  upon  the  number  of  vibra- 
tions of  the  ether,  just  as  the  pitch  of  a  note  depends  upon  the  number  of  vibra- 
tions of  the  sounding  body.  The  heat-rays  that  lie  in  the  colored  spectrum  are 
transmitted  by  the  ocular  media  in  about  the  same  way  as  by  water.  Beyond 
the  violet  rays  lie  the  chemically  active  or  actinic  rays.  The  ultra-violet  rays  are 
largely  absorbed  by  the  ocular  media,  especially  by  the  lens.  On  shutting  off 
the  entire  spectrum,  including  the  violet  rays,  the  ultra-violet  rays  may  yet  be 
recognized  from  their  pale,  grayish-blue  color.  The  ultra-violet  rays  can  be  most 
easily  demonstrated  by  the  phenomenon  of  fluorescence:  on  illuminating  a  solution 
of  quinin  sulphate  with  ultra-violet  v.  Helmholtz  saw  a  bluish-white  light  arise 
from  all  parts  of  the  solution  that  were  reached  by  ultra-violet  rays.  As  the 
ocular  media  themselves  exhibit  fluorescence,  they  must  increase  the  power  of 
the  retina  to  distinguish  these  rays. 

In  order  that  color  may  be  recognized,  it  is  necessary  for  a  certain 
amount  of  light  to  fall  upon  the  retina.  The  lowest  degree  of  brightness 
by  which  blue  may  be  recognized  as  a  color  is  1 6  times  less  than  that 
required  by  red.  If,  therefore,  in  a  bright  illumination,  a  red  and  a  blue 
object  appear  equally  bright,  the  blue  will  appear  brighter  as  soon  as  the 
illumination  is  decreased:  Purkinje's  phenomenon.  The  retina  is 
least  readily  stimulated  by  red,  and  the  variations  in  intensity  of  red 
are  recognized  with  the  greatest  difficulty.  Therefore,  according  to 
Briicke,  intermittent  white  light  is  perceived  as  greenish,  because  the  red 
component  in  white  light  acts  upon  the  retina  with  greater  difficulty. 
Yellow,  on  the  contrary,  acts  more  powerfully,  and  then  follows  blue. 
In  weak  illumination  green  possesses  the  greatest  brightness ;  then  come 
yellow,  blue,  red.  In  strong  illumination  the  analogous  succession  of 
colors  is:  yellow,  red,  green,  blue. 

While,  therefore,  light  of  varying  rapidity  of  vibration  produces  in  the  eye  the 
sensation  of  different  colors,  the  amplitude  of  vibration  (height  of  the  waves)  deter- 
mines the  intensity  of  the  visual  impression,  just  as  the  loudness  of  a  note  depends 
upon  the  amplitude  of  the  vibrations  of  the  sounding  body.  All  of  the  colors  are 
united  in  sunlight,  and  their  simultaneous  action  on  the  retina  produces  the 
sensation  that  is  designated  as  the  sensation  of  white.  If  the  colors  of  the 
spectrum  obtained  by  means  of  a  prism  are  again  united,  white  light  is  once 
more  produced.  If  the  retina  is  not  influenced  by  vibrations  of  the  luminiferous 
ether,  all  sensation  of  light  and  of  color  is  absent ;  but  this  cannot  be  designated 
black  It  is  rather  the  absence  of  sensation,  as  is  the  case  also  when  a  ray  of 
light  falls  on  the  skin  of  the  back.  The  skin  perceives  neither  black  nor  any 
light-sensation  whatever. 

When  a  colored  object  is  illuminated  by  a  monochromatic  light,  it  gives  no 
impression  of  color.  If  a  colored  object  is  illuminated  by  two  lights  of  different 
color,  the  color-impression  appears  best  if  one  of  the  lights  contains  those  rays 
that  would  be  most  strongly  reflected  by  the  color  of  the  object,  and  the  other 
light,  on  the  contrary,  contains  such  rays  as  stand  closer  to  the  color  in  the  solar 
spectrum  than  does  the  complementary  color. 


PERCEPTION    OF    COLORS. 


857 


The  recognition  of  the  impression  of  light  requires  lesser  intensity 
of  action  than  does  that  of  a  color.  If  the  colored  object  is  exceedingly 
small,  if  it  is  poorly  illuminated,  or  if  it  is  seen  for  only  a  short  time, 
it  appears  colorless.  The  different  colors  show  different  gradations  of 
activity  in  this  respect,  red  furnishing  the  most  unfavorable  conditions. 
Simple  colors,  for  example  those  of  the  spectrum,  are  produced  by 
the  action  of  a  definite  number  of  oscillations  upon  the  retina.  Mixed 
colors  are  produced  when  the  retina  is  stimulated  by  two  or  more  simple 
colors,  either  simultaneously  or  in  rapid  alternation.  The  most  com- 
plex mixed  color  is  white,  which  is  composed  of  all  of  the  simple  colors 
of  the  spectrum.  Complementary  colors  comprise  any  two  whose  ad- 
mixture produces  white.  For  the  sake  of  completeness  contrast-colors 
must  be  mentioned,  as  they  are  closely  related  to  the  complemen- 
tary colors.  They  comprise  any  two  colors  that  when  mixed  produce 
the  tone  of  the  general  illumination  that  prevails  at  the  time.  In  the 
blue  light  of  the  sky,  the  two  contrast-colors  must  yield  bluish  white, 
in  bright  gaslight,  yellowish  white.  In  pure  white  illumination  the 
contrast-colors  are,  naturally,  the  same  as  the  complementary  colors. 

Methods  of  Mixing  Colors. — (i)  Two  solar  spectra  are  projected  upon  a  screen, 
and  the  colors  to  be  mixed  are  superposed.  (2)  The  observer  looks  obliquely 
through  a  vertical  glass  plate  at  a  color  lying  behind  it.  A  second  color  is  placed 
in  front  of  the  plate,  so  that  its  image  is  reflected  by  the  glass  into  the  eye  of 
the  observer.  In  this  way  transmitted  light  from  one  color  and  reflected 
light  from  the  other  enter  the  eye  at  the  same  time.  (3)  By  means  of  the 
"color-top"  small  sectors  of  various  colors  are  rotated  rapidly  on  a  disc. 
By  rapid  rotation  the  impressions  produced  by  the  individual  colors  are  united 
to  produce  a  mixed  color.  If  the  rotating  disc  which  yields  for  example,  a  white 
color  from  the  mixture  of  the  prismatic  colors,  is  viewed  in  a  rapidly  rotating  mir- 
ror, the  individual  components  of  the  white  reappear.  (4)  Two  different  colored 
glasses  are  placed  before  the  little  holes  in  the  cardboard  used  in  Scheiner's  ex- 
periment (p.  835,  Fig.  284).  The  colored  rays  of  light  passing  through  the  holes 
are  united  on  the  retina  for  the  production  of  the  mixed  color. 

Investigation  has  shown  that  the  following  colors  of  the  spectrum  are  com- 
plementary, that  is  two  together  produce  white:  red  +  greenish  blue;  orange 
+  cyan  blue;  yellow  +  indigo  blue;  greenish  yellow  +  violet.  Green  has 
the  compound  complementary  color  purple.  All  of  the  mixed  colors  may  be 
determined  from  the  following  table.  At  the  head  of  the  vertical  and  horizontal 
columns  are  placed  the  simple  colors;  the  mixed  color  is  found  at  the  intersection 
of  the  respective  horizontal  and  vertical  columns: 


VIOLET. 

INDIGO. 

CYAN  BLUK. 

BLUISH 
GREEN. 

GREEN. 

GREENISH 
YELLOW. 

YELLOW. 

Red,  

Purple. 

Dark  rose. 

Whitish 

White. 

Whitish 

Golden 

Orange. 

Orange,  

Dark  rose. 

Whitish 

rose. 
White. 

Whitish 

yellow. 
Yellow. 

yellow. 
Yellow. 

Yellow,  

Whitish 

rose. 
White. 

Whitish 

yellow. 
Whitish 

Greenish 

Greenish  yellow,  .  .  . 
Green 

rose. 
White. 

Whitish 

Whitish 
green. 
Watery 

green. 
Whitish 
green. 
Bluish 

green. 
Green. 

yellow. 

Bluish  green,  
Cyan  blue,  

blue. 
Watery 
blue. 
Indigo. 

blue. 
Watery 
blue. 

green. 

Observations  upon  the  mixing  of  colors  have  yielded  the  following 
results:  (i)  When  two  simple,  but  not  complementary  colors  are  mixed, 
they  produce  a  color-sensation  that  may  be  represented  by  a  color  situated 
between  them  in  the  spectrum,  to  which  a  certain  amount  of  white  is 


858 


PERCEPTION    OF    COLORS. 


added.  Therefore,  any  color-mixture  may  be  produced  by  a  color  of  the 
spectrum  plus  white.  (2)  The  less  white  the  colors  contain,  the  more 
saturated  they  are  said  to  be;  the  more  white  they  contain,  the  less 
saturated  do  they  appear.  The  degree  of  saturation  of  a  color  dimin- 
ishes with  the  intensity  of  the  illumination.  In  a  steadily  increasing 
illumination,  the  colors  become  more  nearly  white,  and  at  the  same  time 
they  lose  more  and  more  their  specific  character;  for  example,  in  a  bright 
light,  yellow  readily  passes  into  white. 

As  the  pigment  of  the  macula  lutea  partly  absorbs  certain  colored  lights, 
an  explanation  is  afforded  for  the  fact  that  colors  seen  by  the  macula  alone  have 
a  different  appearance  from  those  seen  by  other  portions  of  the  retina. 

Since  the  time  of  Newton,  attempts  have  been  made  to  construct  a  so-called 
geometric  color-chart,  on  which  any  mixed  color  can  be  found,  according  to  the 
principle  of  construction  of  the  center  of  gravity.  The  accompanying  figure 
shows  such  a  color-chart:  white  is  placed  in  the  middle,  and  different  colors  are 
represented  at  points  in  the  curve  surrounding  it.  From  the  center  (white) 
to  each  of  these  points  of  the  curve,  lines  may  be  drawn  and  each  color  may  be 
conceived  as  applied  to  the  line  in  such  a  manner  that,  commencing  at  white, 
there  is  the  lightest  tint,  and  then  gradually  more  saturated  ones,  until,  finally, 
at  the  point  of  the  curve  designated  by  the  name  of  the  color  the  latter  appears 

in  a  pure  saturated  form.  Be- 
tween violet  and  red,  their  mixed 
color,  purple,  is  indicated.  In 
order  to  determine  from  this 
chart  the  mixed  color  produced 
by  any  two  colors  of  the  spectrum, 
the  points  of  these  colors  should 
be  connected  by  a  straight  line; 
in  each  point  weights  may  be 
conceived  as  placed  correspond- 
ing to  the  units  of  intensity  of 
these  colors.  Then  the  position 
of  the  center  of  gravity  of  the 
two  in  the  connecting  line  indi- 
cates the  situation  of  the  mixed 
color  in  the  color-chart.  The 
mixed  color  of  two  spectral  colors 
lies  in  the  straight  line  that  con- 
nects the  two  color-points  on  the 
color-chart.  It  is  easily  seen, 
FIG.  300.— Geometric  Color-chart.  further,  that  the  impression  of 

the   mixed   color   corresponds  to 
an    intermediate    spectral    color 

mixed  with  white.  The  complementary  color  of  any  spectral  color  is  found  by 
drawing  a  line  from  the  point  of  this  color  through  white,  until  it  intersects  the  op- 
posite edge  of  the  color-chart.  The  point  of  intersection  gives  the  complemen- 
tary color.  If  pure  white  is  to  be  made  from  a  mixture  of  two  complementary 
>rs,  the  color  lying  nearest  white  on  the  connecting  line  must  be  especially 
strong,  for  then  only  would  the  center  of  gravity  of  the  connecting  line  be 
situated  in  the  point  white. 

The  color-chart  permits,  further,   of  the  determination  of  the  mixed  color 
produced  by  three  or  more  colors.     For  example,  the  colors  designated  by  the 
nts  a  (pale  yellow),  b   (comparatively  saturated  greenish  blue)    and  c   (com- 
paratively saturated  blue)  are  chosen  for  mixing.     In  the  three  points  are  placed 
weights  that  represent  the  intensities  of  the  colors,  and    the    center  of    gravity 
riangle  a  b  c  is  determined;  this  will  lie  at  p.     It  is  obvious,  however,  that 
s  mixed  impression,  whitish-greenish-blue  can  be  produced  also  by  the  color 
greenish-blue  +  white  (according  to  rule  i),  for  p  can  just  as  well  be  the  center 
of  gravity  of  two  weights  that  lie  on  the  line  connecting  greenish-blue  and  white. 
Around  the  color-chart  a  triangle  V  Gr  R  may  be  drawn,  enclosing  the  figure 
The  three  primary  or  fundamental  colors,  red,  green  and  violet, 
lie  in  the  angles  of  the  triangle.     It  is  evident  that  every  colored  impression, 
that  is  any  point  of  the  color-chart,  may  be  determined  by  placing  at  the  angles 


Violet 


Cyan  blue 


Indigo 


Orange 


PERCEPTION    OF    COLORS. 


859 


of  the  triangle  weights  corresponding  to  the  intensities  of  the  primary  colors,  so 
that  the  point  of  the  color-chart,  consequently  the  mixed  color  sought,  is  the 
center  of  gravity  of  the  triangle,  with  its  angles  thus  weighted.  In  the  production 
of  the  mixed  color,  the  intensity  of  the  three  primary  colors  must  be  represented 
in  the  same  proportion  as  the  weights. 

Various  theories  have  been  suggested  to  explain  color-perception: 

1.  According  to  one  theory,  the  elements  of  the  retina,  while  uniform  in  type, 
are  affected  in  different  ways  by  the  variously  colored  lights  (vibrations  of  the 
ether  of  different  wave-length,  rapidity  of  vibration,  and  refractive  exponent). 

2.  The  theory  of  Thomas  Young  and  Hermann  v.  Helmholtz  assumes  the 
existence  of  three   different  terminal  elements  in  the  retina,   corresponding  to 
the  primary  colors:    Stimulation  of  the  first  kind  produces  the  sensation  of  red, 
of    the  second  green,  and  of  the  third  violet.     The  red-perceiving  elements  are 
affected  most  strongly  by  the  light  of  greatest  wave-length  (red  rays) ,  the  green- 
perceiving  by  the  light  of  medium  wave-length  (green  rays) ,  the  violet-perceiving 
by  the  light  of  shortest  wave-length  (violet  rays).     For  the  explanation  of  many 
phenomena  it  must  be  assumed  that  each  spectral  color  excites  all  forms  of  fibers, 
some  slightly,  and  others  strongly.     If  it  be  conceived  that  the  spectral  colors 
placed   in  their  natural  order  in  a  horizontal  direction  in  Fig.  301   (from  red  to 
violet),  then  the  three  curves  shown  may  represent  the  amount  of  excitation  of 
the   three    kinds   of   retinal   elements:    the  continuous   curved   line   that  of  the 
red-perceiving,  the  dotted  line  that  of  the  green-perceiving,  and  the  interrupted 


FIG.  301. — Diagrammatic  Representation  of  the  Young-Helmholtz  Color  Theory. 

line  that  of  the  violet-perceiving.  Pure  red  excites  the  red-perceiving  elements 
strongly,  but  the  other  two  forms  slightly  (expressed  by  the  heights  of  the  ordinates 
erected  at  R),  and  the  sensation  of  red  results.  Pure  yellow  excites  the  red- 
perceiving  and  the  green-perceiving  elements  with  moderate  activity,  the 
violet  elements  less  actively,  and  the  sensation  of  yellow  results.  Pure"  green 
excites  the  green-perceiving  elements  strongly,  much  less  so  the  two  other  forms, 
and  the  sensation  of  green  results.  Pure  blue  excites  the  green  and  violet  ele- 
ments with  moderate  activity,  the  red  element  slightly,  and  the  sensation  of  blue 
results.  Violet  excites  the  corresponding  elements  strongly,  the  others  slightly, 
and  the  sensation  of  violet  results.  Stimulation  of  any  two  elements  produces 
the  impression  of  a  mixed  color;  while  an  equal  stimulation  of  all  gives  rise  to 
the  sensation  of  white.  This  hypothesis  of  the  Young-Helmholtz  theory,  affords, 
in  fact,  a  simple  and  clear  survey  and  explanation  of  the  phenomena  of  the  physio- 
logical doctrine  of  color.  The  theory  is  a  development  of  the  doctrine  of  Joh. 
Miiller  as  to  the  specific  energy  of  the  nerve-fibers.  The  findings  in  the  structure 
of  the  retina,  moreover,  have  been  adapted  to  the  theory.  Accordingly,  the 
cones  alone  are  supposed  to  be  the  terminal  apparatus  tor  color-perception.  In 
cases  of  congenital  color-blindness  the  cones  appear  to  be  absent  in  the  peripheral 
portions  of  the  retina.  The  presence  of  longitudinal  striations  in  their  outer 
segments  is  regarded  as  proving  that  they  represent  multiple  terminal  end-organs. 
The  degree  of  sensitiveness  of  any  part  of  the  retina  to  color  is  proportionate  to 
the  number  of  cones.  It  is  most  developed  in  the  macula  lutea,  which  has  only 
cones;  much  less  so  further  away  from  the  macula,  being  lost,  finally,  in  the 
periphery.  The  rods  are  supposed  to  be  concerned  only  with  the  power  of  dis- 
tinguishing between  quantitative  sensations  of  light.  According  to  v.  Kries, 
they  are  especially  adapted  for  vision  in  poor  illumination. 

3.  In  explanation  of  visual  perception,  Ewald  Hering  proceeds  upon  the 
proposition  that  what  reaches  consciousness  as  a  visual  perception  is  the  psychic 
expression  of  the  metabolic  change  in  the  visual  substance,  that  is  in  those  nervous 
elements  that  are  concerned  in  the  act  of  vision.  This  substance,  like  every 
other  organic  substance,  undergoes  decomposition  or  dissimilation  during  the 


86o  COLOR-BLINDNESS:  ITS  PRACTICAL  IMPORTANCE. 

process  of  metabolic  change;  while  during  rest  it  must  be  renewed,  or  undergo 
assimilation.  For  the  perception  of  white  (light)  and  black  (dark)  Hering  assumes 
two  different  chemical  processes  in  the  visual  substance,  namely  that  the  sensation 
of  white  or  light  corresponds  with  dissimilation  (decomposition) ,  that  of  black 
(dark)  with  assimilation  (reconstruction)  of  the  visual  substance.  Accordingly, 
the  different  degrees  of  distinctness  or  intensity  with  which  these  two  sensations 
appear  in  the  various  transitional  shades  from  pure  white  to  deepest  black,  or, 
in  other  words,  the  proportions  in  which  they  appear  to  be  mixed  (gray) ,  corre- 
spond to  the  relative  intensity  of  these  two  psychophysical  processes.  Conse- 
quently the  consumption  and  the  restoration  of  the  visual  substance  are  the 
primary  processes  in  the  perception  of  white  and  black.  The  consumption  of 
the  visual  substance  in  the  perception  of  white  is  the  result  of  the  stimulation 
of  the  vibrating  ether- waves,  and  the  degree  of  the  perception  of  brightness  is 
proportional  to  the  amount  of  material  consumed.  The  restoration  of  the  material 
produces  the  sensation  of  black;  the  more  intensely  this  takes  place  the  deeper 
is  the  sensation.  The  consumption  of  the  visual  substance  in  one  place  evokes 
greater  reproduction  in  the  neighborhood.  Each  process  influences  the  other 
simultaneously  and  conjointly.  In  this  way  a  physiological  explanation  is  pro- 
vided for  the  phenomenon  of  contrast  (see  p.  864),  for  which  the  older  view  could 
offer  only  a  psychical  interpretation. 

In  an  entirely  analogous  manner,  color-sensation  is  regarded  as  a  sensation 
of  decomposition  (dissimilation)  and  of  reconstruction  (assimilation) .  In  addition 
to  white,  red  and  yellow  are  the  expression  of  decomposition;  green  and  blue, 
on  the  other  hand,  represent  the  sensation  of  reconstruction.  The  visual  substance 
is,  thus,  subject  to  three  different  forms  of  chemical  change,  or  metabolism. 
The  colored  contrast-phenomena  or  after-images  are  thus  explained.  The  black- 
white  sensation  may,  further,  be  combined  with  all  of  the  colors.  It  gives  a  dark 
or  a  light  tone  to  each  color-sensation,  so  that  there  are  no  absolutely  pure  colors. 
There  are,  thus,  three  different  constituents  of  the  visual  substance:  that  which 
is  sensitive  to  black-white  (colorless),  that  sensitive  to  blue-yellow,  and  that 
sensitive  to  red-green.  All  rays  of  the  visible  spectrum  decompose  the  black- 
white  substance,  but  the  different  rays  do  so  in  different  degrees.  Only  certain 
rays,  on  the  contrary,  decompose  the  blue-yellow,  or  the  red-green  substance; 
others  reproduce  them;  and  still  others  have  no  effect  whatever.  Mixed  light 
appears  colorless  when  it  causes  an  equally  strong  dissimilation  and  assimilation 
in  the  blue-yellow  and  the  red-green  substances,  so  that  the  two  processes  neutralize 
each  other,  and  the  action  upon  the  black- white  substance  alone  appears.  Two 
objective  kinds  of  light,  which  together  yield  white,  are  consequently  not  to  be 
considered  as  complementary,  but  as  antagonistic,  for  they  do  not  combine  to 
form  white,  but,  as  antagonists,  allow  it  to  appear  of  itself  because  each  neutralizes 
the  effect  of  the  other. 

The  weakness  of  the  Young-Helmholtz  color-theory  lies  in  the  fact  that  it 
assumes  the  existence  of  only  one  kind  of  irritability,  stimulation  and  exhaustion 
(corresponding  to  Hering's  dissimilation),  and  that  it  ignores  the  antagonistic 
relations  of  certain  light-rays  to  the  eye.  Therefore,  it  does  not  recognize  that 
white  is  produced  from  complementary  colors  by  the  neutralization  of  their 
action  in  the  colored  visual  substances,  but  by  their  supplementing  each  other. 
,  . .  *n.  Applying  Hering's  theory  to  color-blindness,  it  must  be  assumed  that  the  red- 
blind  individual  has  no  red-green  visual  substance.  His  solar  spectrum  con- 
tains only  two  partial  spectra:  the  black- white  and  the  yellow-blue.  The  green 
part  appears  colorless  to  him;  the  rays  from  the  red  portion  are  visible  to  the 
extent  that  the  yellow  and  the  white  sensations  that  they  arouse  are  strong  enough 
to  stimulate  the  retina  .sufficiently.  He  divides  his  spectrum  into  a  yellow 
and  a  blue  half.  The  violet-blind  individual  has  no  yellow-blue  visual  substance. 
His  spectrum  contains  only  two  partial  spectra:  the  black- white  and  the  red- 
green.  In  cases  of  complete  color-blindness  both  the  yellow-blue  and  the  red- 
green  visual  substances  are  absent,  and  the  individual  has  only  the  sensation  of 
Lgnt  and  dark.  The  sensibility  to  light  and  the  length  of  the  spectrum  are 
preserved;  the  brightest  area  is  in  the  yellow,  just  as  in  the  normal  eye. 

COLOR-BLINDNESS:   ITS  PRACTICAL   IMPORTANCE. 

By  color-blindness  (dyschromatopsid)  is  understood  a  pathological  condition. 

as  the  result  of  which  the  affected  individuals  are  unable  to  recognize  certain 

t  was  recognized  by  Tuberville  in  1684,  and  by  Huddart  in  1777,  but 


COLOR-BLINDNESS:  ITS  PRACTICAL  IMPORTANCE.  861 

it  was  first  accurately  described  in  1794  by  the  physicist  Dalton,  who  was  him- 
self red-blind.  The  designation  color-blindness  was  given  the  condition  by 
Brewster. 

The  adherents  of  the  Young-Helmholtz  theory  assume  the  following  varieties 
of  color-blindness,  corresponding  to  paralysis  of  the  three  color-perceiving  ele- 
ments  of    the    retina:      (i)   Red-blindness;     (2)   green-blindness;     (3)  violet-blind- 
ness.    In  addition  there  is  the  most  pronounced  form — total  color-blindness. 
The  adherents  of  E.  Bering's  color-theory  distinguish  the  following  varieties: 

1.  Complete  Color-blindness   (Achromatopsia). — The  spectrum  appears  achro- 
matic, the  green-yellow  portion  is  the  brightest,  and  the  adjacent  parts  on  either 
side  are  darker.     A  colored  painting  appears  like  a  photograph  or  an  engraving. 
Occasionally  the  different  degrees  of  light-intensity  are  recognized  as  one  shade 
of  color  (for  instance  yellow) ,  which  cannot   be  compared  with  any  other  color. 
O.  Becker  and  v.  Hippel  observed  cases  of  unilateral,  congenital  complete  color- 
blindness, in  which  the  other  eye  had  normal  color-perception. 

2.  Blue-yellow  Blindness. — The  spectrum  is  dichromatic,  consisting  only  of 
red  and  green;    the  blue-violet  end  of  the  spectrum  usually  is  greatly  shortened. 
In  pure  cases,  only  the  spectral  red  and  green  are  recognized  correctly  (Mauthner's 
erythrochloropia) ,  not  however  the  other  colors.     This   has    been  observed  also 
unilaterally. 

3.  Red-green  Blindness. — The  spectrum  is  dichromatic;    yellow  and  blue  are 
recognized  correctly,  while  violet  and  blue  are  both  seen  as  blue.     The  perception 
of  red  and  green  is  absent.     In  this  category  the  following  types  are  further 
distinguished:     (a)   Green-blindness    or    red-green    blindness    without    shortening 
of  the  spectrum   (Mauthner's    xanthocyanopia) ,   in  which  light  green   and  dark 
red  are  confounded.     In  the  spectrum  yellow  passes  directly  into  blue,  or  at  most 
a  band  of  gray  lies  between  the  two.     The  maximum  of  brightness  lies  in  the 
yellow.     This  defect  may  be  unilateral;    it  is  often  hereditary.      (b)  Red-blind- 
ness  (or  red-green  blindness  with  shortening  of  the  spectrum;    also  designated 
Daltonism},  in  which  light  red  is  confused  with  dark  green.     The  spectrum  con- 
sists of  yellow  and  blue,  but  the  yellow  lies  in  the  orange,  and  the  red  end  of  the 
spectrum  is  colorless  or  even  dark.     The  greatest  illumination,  as  well  as  the 
boundary  between  yellow  and  blue,  lies  more  to  the  right.     Between  these  two 
forms  there  are  transitions.     According  to  Hering  the  cause  of  the   difference 
resides  in  a  variation  in  the  amount  of  absorption  by  the  macula  lutea  of  the  rays 
of  short  wave-length. 

4.  Incomplete    color-blindness,  or    diminished    color-sense,   is    that    condition 
in  which  the  acuteness  of  color-perception  is  lowered,  so  that  colors  are  recog- 
nized, for  example,  only  in  objects  of  considerable  size  or  only  at  near  range; 
also,  on  addition  of  white  they  are  no  longer  perceived  as  such.     A  certain  degree 
of  this  form  is  frequent,  in  so  far  as  many  are  unable  to  distinguish  between 
greenish  blue  and  bluish  green. 

Acquired  color-blindness  occurs  also  in  connection  with  diseases  of  the  retina, 
and  inflammation  and  atrophy  of  the  optic  nerve,  with  beginning  tabes,  with 
cerebral  diseases  and  with  intoxications  (tobacco,  alcohol,  etc.).  Green-blindness 
appears  first,  and  is  followed  shortly  by  red-blindness.  The  peripheral  zone  of 
the  retina  suffers  before  the  central  portion.  In  cases  of  hysteria  and  of  epilepsy 
there  may  be  intermittent  attacks  of  color-blindness;  and  also  in  hypnotized 
individuals. 

The  retina  may  be  made  temporarily  color-blind  for  a  given  color  by  intense 
action  of  the  color.  Prolonged  gazing  into  the  dark-red,  setting  sun  causes 
scarlet  to  appear  black. 

Finally,  the  remarkable  observation  of  H.  Cohn  must  be  mentioned;  he  found 
that  color-blindness  in  several  individuals  disappeared  temporarily  on  heating 
the  eyeball.  Holmgren  found  that  2.7  per  cent,  of  persons  examined  were  color- 
blind, most  of  them  being  red-blind  and  green-blind;  only  a  few  were  violet-blind. 

The  examination  of  the  power  of  color-perception  in  the  normal  retina,  best 
made  with  the  Aubert-Forster  perimeter,  has  revealed  the  surprising  fact  that 
complete  color-perception  is  present  only  in  the  center  of  the  visual  field.  Around 
this  lies  a  middle  zone,  in  which  only  blue  and  yellow  are  perceived,  and  in  which 
there  is,  therefore,  red-blindness.  Beyond  this  zone  there  is,  finally,  a  peripheral 
girdle,  in  which  there  is  complete  color-blindness.  The  red-blind  individual 
is  distinguished,  therefore,  from  the  normal  by  an  absence  of  the  central  area 
of  the  normal  visual  field,  which  is  included  in  the  middle  zone.  The  visual 
field  of  the  green-blind  individual  is  distinguished  from  that  of  the  normal  by 


862  TIME-RELATIONS    OF    RETINAL    STIMULATION. 

the  fact  that  its  peripheral  zone  corresponds  to  the  intermediate  and  peripheral 
zones  of  the  normal  eye.  In  the  violet-blind,  on  the  contrary,  the  normal  periph- 
eral zone  is  absent.  Incomplete  color-blindness  of  these  two  types  is  character- 
ized by  a  uniformly  contracted  central  field. 

In  the  presence  of  hyperesthesia  of  the  optic  nerve  resulting  from  cerebral 
conditions,  there  is,  curiously,  a  widening  of  the  normal  color-limits  toward  the 
periphery. 

When  colored  objects  are  exceedingly  small,  and  illuminated  for  only  a  short 
time,  the  normal  eye  first  fails  to  perceive  red.  It  appears,  therefore,  that  a 
comparatively  strong  stimulus  is  required  for  the  perception  of  red.  The  obser- 
vation of  Briicke's,  that  rapidly  intermittent  white  light  appears  green,  is  also 
in  favor  of  this  view,  because  the  short  duration  of  the  stimulus  is  not  capable 
of  exciting  the  red-perceiving  elements  of  the  retina. 

To  Holmgren  belongs  the  credit  of  having  shown  the  necessity  for  examining 
all  railroad-officials  and  all  pilots  as  to  the  trustworthiness  of  their  color-sense, 
as  the  correct  recognition  of  red  and  green  signal-lights  is  impossible  for  a  color- 
blind person. 

Method  of  Examination. — Holmgren,  in  conjunction  with  Seebeck,  chooses 
embroidery-wool  as  the  simplest  material,  in  skeins  of  at  least  five  shades  each 
of  red,  orange,  yellow,  greenish-yellow,  green,  greenish-blue,  blue,  violet,  purple, 
rose,  brown,  gray;  it  is  best  to  have  several  different  shades  of  the  various 
colors.  In  the  examination ,  one  strand  of  this  yarn  (for  example  light  green  or  rose) 
should  be  selected  and  put  to  one  side.  That  color  is  chosen  for  which  the  indi- 
vidual is  to  be  especially  tested ;  and  he  is  then  requested  to  pick  out  the  strands 
whose  colors  resemble  most  closely  that  of  the  sample,  and  place  them  by  its 
side.  According  to  the  way  in  which  he  performs  this  task  a  judgment  is 
reached  as  to  his  color-sense.  A  more  accurate  determination  is  made  by 
means  of  the  spectrum. 

Mace"  and  Nacati  have  measured  the  visual  acuity  for  a  small  object  when 
illuminated  by  different  portions  of  the  spectrum.  They  compared  with  the 
results  of  their  investigation  the  observations  on  red-blind  and  green-blind 
individuals.  It  was  shown  that  red-blind  persons  find  green  light  much  brighter 
than  do  normal  persons.  In  the  green-blind  there  is  an  excessive  sensitiveness 
to  red  and  violet.  It  seems,  therefore,  that  what  color-blind  individuals  lack  in 
perception-power  for  one  color,  they  gain  for  other  colors.  They  possess  also  a 
greater  power  of  distinguishing  variations  in  brightness. 

TIME-RELATIONS  OF  RETINAL  STIMULATION. 

POSITIVE      AND      NEGATIVE      AFTER-IMAGES.        IRRADIATION.        CON- 
TRAST. 

As  with  irritation  of  every  other  nervous  apparatus,  a  definite, 
though  short  time  elapses  after  the  entrance  of  the  rays  into  the  eye, 
before  the  visual  effect  is  manifest,  whether  in  the  form  of  conscious 
perception,  or  a  reflex  effect  on  the  iris.  The  intensity  of  the  impres- 
sion, here  also,  will  depend  essentially  upon  the  irritability  of  the  retina' 
and  the  other  nervous  structures.  If  the  visual  impression  continues  for 
some  time  with  the  same  intensity,  the  stimulation,  after  having  reached 
its  culminating  point,  soon  diminishes,  at  first  rapidly,  then  more  slowly. 
If  the  light-stimulation  of  the  retina  is  suddenly  removed  after  it  has 
continued  for  some  time,  the  retina  remains  for  a  time  in  an  excited 
condition,  which  is  the  more  intense  and  persistent  the  stronger  and 
longer  the  light-stimulation,  and  the  more  sensitive  the  retina.  After 
every  visual  perception,  therefore,  especially  when  it  has  been  quite 
bright  and  sharp,  a  so-called  after-image  persists.  There  is  recognized, 
in  the  first  place,  the  positive  after-image,  which  persists  with  similar 
brilliancy  and  color. 

A  light-stimulus  of  short  duration  excites  first  a  sensation  of  light,  which 
lasts  longer  than  the  stimulus;  thereupon  a  negative  after-image  appears  (in 


TIME-RELATIONS    OF    RETINAL    STIMULATION.  863 

the  complementary  color)  and  lasts  £  of  a  second,  being  the  more  distinct  the 
shorter  the  light-stimulation.  Then  follows  the  positive  after-image,  whose 
duration  increases  with  the  intensity  of  the  illumination. 

"That  the  impression  of  any  image  in  the  eye  persists  for  some  time  we  know 
as  a  physiological  phenomenon;  excessive  duration  of  such  an  impression,  how- 
ever, may  be  considered  pathological.  The  weaker  the  eye  the  longer  does  the 
image  remain  in  it.  The  retina  does  not  recover  so  quickly,  and  the  effect  may 
be  looked  upon  as  a  sort  of  paralysis.  This  is  not  to  be  wondered  at  in  the  case 
of  dazzling  images.  If  one  looks  directly  at  the  sun,  he  may  carry  the  image 
about  for  several  days.  The  same  is  also  relatively  true  of  images  that  are  not 
dazzling.  Biisch  relates  of  himself  that  an  engraving  remained  before  his  eye, 
completely  with  all  its  details,  for  seventeen  minutes"  (Goethe). 

Experiments  and  Apparatus  for  Demonstrating  After-images. — (i)  The  ap- 
pearance of  a  ring  of  fire  on  rapid  rotation  of  a  coal.  (2)  The  thaumatrope  of 
Paris:  a  pasteboard  card  contains,  for  example,  on  one  side  the  picture  of  a  torso- 
statue,  on  the  other  side  the  picture  of  the  remaining  portions  drawn  in  ap- 
propriate positions.  If  the  card  be  rotated  so  that  the  two  surfaces  in  al- 
ternation are  rapidly  turned  toward  the  observer,  the  statue  appears  complete. 
(3)  The  phanakistoscope  or  the  stroboscopic  discs.  Objects  are  drawn  on  a 
disc  or  cylinder  in  succession,  so  that  the  drawings  represent  successive  details 
of  a  continuous  movement.  On  rapid  rotation  of  the  disc,  the  observer,  looking 
through  a  small  opening,  sees  the  moving  images  pass  before  the  eye,  each  phase 
rapidly  replacing  the  preceding.  As  the  impression  of  each  image  remains  until  the 
following  one  takes  its  place,  one  and  the  same  figure  seems  to  go  through  the  succes- 
sive movements  continuously.  The  apparatus,  at  present  popularized  by  Anschutz 
in  the  form  of  the  zoetrope  (perfected  by  Edison  as  the  kinematograph  or  kineto- 
scope) ,  was  not  discovered  by  the  two  investigators  mentioned ,  in  1 83  2 ,  as  is  generally 
supposed;  but  it  was  described  by  Cardanus  as  early  as  1550.  It  may  be  used  also 
scientifically  for  the  representation  of  certain  movements:  as,  for  example,  of 
spermatozoids  and  ciliated  epithelial  cells;  likewise  the  movements  of  the  heart 
and  of  walking  may  be  instructively  shown  and  analyzed.  (4)  The  color-top 
contains  in  the  sectors  on  its.  surf  ace  the  colors  that  are  to  be  mixed.  As  the 
color  of  each  sector  causes  a  stimulation  of  the  retina,  lasting  throughout  the 
revolution  of  the  top,  all  of  the  colors  must  be  seen  simultaneously,  and  be  per- 
ceived as  a  mixed  color. 

Occasionally,  especially  if  the  retinal  excitation  is  of  considerable 
duration  and  intensity,  a  negative  after-image  appears,  instead  of  the  posi- 
tive. The  former  is  characterized  by  the  fact  that  bright  portions  of  the 
object  appear  dark,  and  the  colored  portions  in  corresponding  contrast- 
colors. 

Examples  of  Negative  After-images. — After  gazing  for  a  long  time  at  a  brightly 
illuminated  white  window,  and  then  closing  the  eyes,  there  results  the  impression 
of  a  window  with  bright  cross  lines,  and  dark  panes.  Colored  negative  after- 
images are  shown  beautifully  by  Norrenberg's  apparatus:  the  eye  is  fixed  for 
some  time  on  a  colored  surface,  such  as  a  yellow  card,  in  the  center  of  which 
is  pasted  a  small  blue  square.  Suddenly  a  white  screen  is  dropped  in  front  of 
the  card,  and  the  white  surface  then  appears  bluish,  with  a  yellow  square  in 
the  center. 

The  usual  explanation  of  the  dark  negative  after-images  is  that  the  retinal 
elements  are  so  fatigued  by  the  light  that  they  become  less  irritable  for  a  time,  so 
that  in  these  portions  of  the  retina  the  light  can  be  only  faintly  perceived,  and 
darkness,  therefore,  must  prevail.  Bering  explains  the  dark  after-images  as 
resulting  from  the  process  of  assimilation  of  the  black-white  visual  substance. 

For  the  explanation  of  colored  after-images  the  Young-Helmholtz  theory 
assumes  that  by  the  action  of  the  color,  for  example  red,  the  retinal  elements 
for  this  particular  color  are  paralyzed.  If,  now,  the  eye  looks  at  a  white  surface, 
this  mixture  of  all  colors  appears  as  white  minus  red,  that  is  green  (the  contrast- 
color,  which  in  bright  daylight  lies  close  to  the  complementary  color).  Accord- 
ing to  Hering,  this  contrast-colored  after-image  is  the  result  of  the  assimilation 
of  the  corresponding  colored  visual  substance,  in  the  case  cited,  of  the  "red-green." 
From  the  beginning  of  a  momentary  illumination  until  the  appearance  of  an 
after-image  0.344  second  elapses. 


864  TIME-RELATIONS    OF    RETINAL    STIMULATION. 

Not  infrequently,  after  intense  stimulation  of  the  retina,  positive 
and  negative  after-images  alternate,  until  they  gradually  fuse.  Thus, 
after  gazing  at  the  dark-red,  setting  sun,  one  sees  alternately  discs  of 
red  and  green.  In  the  peripheral  portions  of  the  retina,  the  contrast- 
phenomena  undergo  some  modification  on  account  of  the  partial  color- 
blindness that  exists  in  these  areas. 

Irradiation  is  the  term  applied  to  certain  phenomena  that  are  the 
result  of  false  estimates  of  visual  sensations  due  to  inexact  accommo- 
dation. If,  for  example,  the  edges  of  objects  are  thrown  upon  the 
retina  in  diffusion- circles,  the  mind  has  a  tendency  to  add  the  blurred 
edge  to  that  part  of  the  image  which  is  the  most  prominent.  Bright 
things  appear  larger  and  more  prominent  than  dark  ones,  and  an  object 
itself,  without  reference  to  brightness  or  color,  appears  more  prominent 
than  the  background.  In  the  exercise  of  sharp  accommodation  the 
phenomenon  of  irradiation  is  not  present. 

"A  dark  object  appears  smaller  than  a  bright  one  of  the  same  size.  If  one 
look  at  the  same  time  at  a  white  circle  on  a  black  background,  and  a  black  circle 
on  a  white  background,  both  of  the  same  diameter,  at  some  distance  from  the  eye, 
the  latter  will  appear  to  be  one-fifth  smaller  than  the  former.  If  the  black  circle 
be  made  that  much  larger,  both  will  appear  of  the  same  size.  Tycho  de  Brahe 
observed  that  the  moon  appeared  one-fifth  smaller  when  in  conjunction  (dark) 
than  when  in  opposition  (full  moon).  The  first  quarter  of  the  moon  appears  to 
belong  to  a  larger  disc  than  the  dark  part  adjoining  it  which  can  often  be 
distinguished  at  the  time  of  the  new  moon.  Dark  clothing  makes  persons  appear 
much  thinner  than  light  clothing.  Lights  seen  behind  an  edge  make  an  apparent 
indentation  therein.  A  ruler  held  before  a  candle-light  seems  to  be  notched. 
The  rising  and  setting  sun  appears  to  make  a  depression  in  the  horizon"  (Goethe}. 

By  simultaneous  contrast  is  understood,  in  the  first  place,  the  phe- 
nomenon that  when  light  and  dark  parts  are  present  in  an  image  at  the 
same  time  the  light  (white)  parts  always  appear  the  more  intense  the 
greater  the  absence  of  light  from  the  immediate  vicinity,  consequently 
the  darker  the  latter;  and  conversely  the  light  parts  appear  the  less 
bright  the  greater  the  degree  in  which  white  tones  are  present  around 
them.  The  analogous  phenomenon  in  connection  with  colored  pictures 
belongs  in  the  same  category :  a  color  in  a  picture  appears  the  more  intense 
the  more  completely  this  color  is  absent  from  the  immediate  neighbor- 
hood, that  is  the  more  the  neighborhood  contains  the  tones  of  the 
contrast-color.  The  simultaneous  contrast  arises  thus  from  two  im- 
pressions simultaneously  existing  side  by  side  and  affecting  two  different 
but  adjoining  portions  of  the  retina. 

Examples  of  the  contrast  for  light  and  dark:  (i)  If  a  white  grating  be  viewed 
upon  a  black  background,  the  points  of  intersection  of  the  white  lines  appear 
darker,  because  the  least  amount  of  black  is  present  in  their  vicinity.  (2)  If 
a  point  in  a  narrow  strip  of  dark-gray  paper  be  viewed  against  a  dark  background 
and  a  large  piece  of  white  paper  is  then  inserted  between  the  two,  the  strip  appears 
much  darker  than  before ;  if  the  white  paper  be  removed,  the  strip  immediately 
appears  brighter.  (3)  The  following  is  also  a  most  instructive  experiment: 
If,  first,  a  grayish-white  surface — for  example,  the  ceiling  of  a  room — be  looked  at 
with  both  eyes,  and  then,  after  a  time,  a  paper  tube  blackened  on  the  inside,  about 
as  long  as  the  hand,  and  a  finger's  breadth  in  diameter,  be  brought  before  one  eye: 
the  part  of  the  ceiling  seen  through  the  tube  appears  as  a  round,  bright  spot. 

Examples  of  contrast  for  colors:  (i)  If  a  piece  of  gray  paper  be  placed  on  a  red, 
yellow  or  blue  background,  it  appears  immediately  in  the  contrast-color,  respec- 
tively green,  blue  or  yellow.  The  appearance  is  still  more  distinct,  if  the  whole 
is  covered  quickly  with  transparent  tracing  paper.  Under  similar  conditions 
printed  characters  on  a  colored  background  appear  in  the  complementary  color. 
(2)  An  air-bubble  in  the  deeply  stained  field  of  a  thick  microscopical  preparation 


TIME-RELATIONS    OF    RETINAL    STIMULATION.  865 

appears  in  an  intense  contrast-color.  (3)  On  a  rotating  white  disc  are  pasted 
four  green  sectors,  each  of  which  is  interrupted  in  its  center  by  a  narrow  band  of 
black,  concentric  with  the  disc.  On  rotation  of  the  disc,  this  ring  appears  red,  and 
not  gray.  (4)  If  a  grayish-white  surface  be  looked  at  with  both  eyes  and  a  tube  about 
the  length  and  diameter  of  a  finger,  made  of  transparent,  colored  oiled  paper,  through 
the  wralls  of  which  light  can  pass,  be  placed  in  front  of  one  eye,  the  part  of  the 
white  surface  seen  through  the  tube  appears  in  the  contrast-color.  The  experiment 
also  shows  beautifully  the  contrast  in  the  intensity  of  illumination.  (5)  A  piece 
of  white  paper,  with  a  round,  black  spot  in  the  middle,  when  seen  through  a  blue 
glass,  appears  blue  with  a  black  spot.  If  a  white  spot  of  the  same  size  on  a  black 
background  be  placed  in  front  of  the  glass,  so  that  its  reflected  image  covers 
exactly  the  black  spot,  it  appears  in  the  contrast-color,  yellow.  (6)  The  colored 
shadows  also  belong  to  the  simultaneous  contrasts.  "Two  conditions  are  neces- 
sary for  the  production  of  colored  shadows — first,  that  the  light  casting  the 
shadow  shall  in  some  manner  color  the  white  surface;  and  second  that  a  second 
light  shall  illuminate  the  shado\v  to  a  certain  degree.  A  short  burning  candle 
is  placed  on  a  white  paper,  in  the  twilight;  between  them  and  the  diminishing 
daylight  a  lead-pencil  is  placed  vertically  so  that  the  shadow  thrown  by  the 
candle  is  illuminated  but  not  extinguished  by  the  feeble  daylight;  the  shadow 
will  appear  of  a  beautiful  blue.  That  this  shadow-  is  blue  will  be  observed  at 
once :  but  it  is  only  by  close  observation  that  one  can  convince  himself  that  the  wrhite 
paper  acts  as  a  reddish-yellow  surface,  through  the  luster  of  which  the  blue  color 
is  conveyed  to  the  eye.  One  of  the  prettiest  instances  of  colored  shadows  may  be 
seen  during  the  full  moon.  The  light  of  a  candle  and  that  of  the  moon  can  be  exactly 
equalized.  Both  shadows  can  be  made  of  equal  strength  and  distinctness,  so 
that  the  two  colors  completely  balance.  A  board  is  exposed  to  the  light  of  the 
full  moon,  with  the  candle  a  little  to  one  side,  and  an  opaque  body  is  held  at  a 
suitable  distance  in  front  of  the  board.  A  double  shadow  results,  that  thrown 
by  the  moon  and  illuminated  by  the  candle-light  appearing  of  an  intense  reddish- 
yellow  color,  while  that  thrown  by  the  candle  and  illuminated  by  the  moon  appear- 
ing of  a  beautiful  blue.  Where  the  two  shadows  coincide  and  unite  to  form  one 
a  black  shadow  results  (Goethe).  (7)  The  colored  reflections  are  the  reverse  of 
the  colored  shadows.  If  a  piece  of  silverware  be  placed  near  a  window,  in  the 
twilight,  and  the  light  from  a  candle  be  allowed  to  fall  on  it  at  the  same  time,  the 
reflected  image  of  the  flame  appears  yellowish,  that  of  the  lessening  daylight 
decidedly  blue.  (8)  A  piece  of  white  paper  is  placed  on  the  table  and  above  it, 
separated  by  a  horizontal  line,  a  piece  of  black  paper.  Now  a  vertical,  black 
strip  is  pasted  on  the  white  paper  and  on  the  black  paper  a  white  strip.  If  these 
strips  are  seen  through  a  birefringent  spar-prism,  each  will  be  doubled,  and  possess 
a  gray  color,  because  the  strip  is  composed  of  white  and  black  mixed.  The  strips 
on  the  dark  background,  however,  appear  brighter,  and  those  on  the  white  ground 
darker.  Likewise,  in  an  analogous  way,  with  colored  strips  on  a  differently  col- 
ored background  the  experiment  shows  the  contrast-colors  beautifully.  Landois 
has  found  this  excellent  experiment  especially  convincing  if  the  objects  are  cov- 
ered with  translucent  tracing  paper. 

Some  have  tried  to  explain  these  phenomena  as  errors  of  judgment ;  in  other 
words,  when  different  impressions  act  simultaneously,  the  judgment  is  so  de- 
ceived that  if  the  action  takes  place  in  one  position,  it  will  have  an  extremely 
slight  effect  in  the  neighborhood.  Thus,  if  light  affects  one  portion  of  the  retina, 
judgment  wrongly  assumes  a  slight  illumination  of  the  neighboring  parts  of  the 
retina.  The  same  would  be  true  of  colors.  The  phenomena  are,  however, 
much  more  correctly  explained  by  Hering  as  true,  physiological  processes. 
Partial  stimulation  by  light  affects  not  only  the  parts  so  acted  upon  but  also  the 
surrounding  retina;  the  directly  stimulated  portion  by  increased  dissimilation, 
the  (indirectly  stimulated)  vicinity  by  increased  assimilation,  in  such  a  way, 
that  the  latter  increase  is  most  pronounced  in  the  immediate  vicinity  of  the 
illuminated  spot,  and  decreases  rapidly  with  the  distance  from  it.  As  a  result 
of  the  increase  in  assimilation  at  the  part  not  occupied  by  the  image  of  the  object, 
the  diffused  light  is  ordinarily  not  perceived.  As  the  increase  in  assimilation  is 
greatest  in  the  immediate  neighborhood  of  the  illuminated  spot,  the  perception 
of  this  relatively  strong  diffused  light  is  largely  made  impossible. 

On  looking  for  a  long  time  at  a  dark  or  a  bright  object,  or  at  a  colored  one 
(for  example  red) ,  and  then  allowing  the  contrast-effects  to  appear  on  the  retina, 
respectively  bright  or  dark,  or  the  contrast-color  (green),  these  appear  especially 
intense.  This  phenomenon  has  been  designated  successive  contrast.  In  this 
connection  the  negative  after-images  obviously  take  part  at  the  same  time. 

55 


866  OCULAR    MOVEMENTS    AND    OCULAR    MUSCLES. 

OCULAR  MOVEMENTS  AND  OCULAR  MUSCLES. 

The  spherical  eyeball  is  capable  of  extensive  and  free  movement  in  the 
correspondingly  excavated  cushion  of  fat  in  the  orbit,  like  the  head  of  a 
bone  in  the  corresponding  socket  of  a  freely  movable  arthrodial  joint. 
The  motion  is  limited,  in  the  first  place,  by  the  attachment  of  the  muscles 
and  in  such  a  manner  that  in  the  action  of  one  muscle  its  antagonist, 
acting  like  a  rein,  serves  to  limit  the  movement;  and  secondly  by  the 
insertion  of  the  optic  nerve.  The  soft  elastic  orbital  pad  on  which  the 
eyeball  rests  may  itself  be  moved  backward  and  forward,  so  that  the 
eyeball  must  follow  these  movements. 

Protrusion  of  the  eyeball  takes  place:  (i)  As  a  result  of  marked  distention 
of  the  blood-vessels,  especially  of  the  orbital  veins,  when  there  is  an  obstruction 
to  the  outflow  of  venous  blood  (for  example  in  the  head  after  execution  by  hang- 
ing). (2)  As  a  result  of  contraction  of  the  unstriated  muscle-fibers  in  Tenon's 
capsule,  in  the  sphenomaxillary  fissure,  and  in  the  eyelids,  which  are  innervated 
by  the  cervical  sympathetic.  (3)  As  a  result  of  voluntary,  forcible  opening  of 
the  palpebral  fissure,  because  the  pressure  of  the  lids  from  before  backward  is 
diminished.  (4)  As  a  result  of  the  action  of  the  oblique  muscles,  which  pull  the 
eye  inward  and  forward.  If  the  superior  oblique  is  made  to  contract,  while  the 
palpebral  fissure  is  forcibly  widened  the  eyeball  may  protrude  about  i  mm.  Patho- 
logical protrusion  of  the  eyeball  (especially  caused  by  2  and  i)  is  called  exophthal- 
mos. 

Conversely,  retraction  of  the  eyeball  is  caused:  (i)  By  forcible  closure  of  the 
palpebral  fissure.  (2)  By  an  empty  condition  of  the  retrobulbar  blood-vessels, 
diminished  succulence  or  disappearance  of  the  orbital  tissue.  (3)  In  dogs,  section 
•of  the  cervical  sympathetic  causes  recession  of  the  eyeball.  The  smooth  muscula- 
ture of  Tenon's  capsule  probably  prevents  the  four  rectus  muscles  from  pulling 
the  eye  backward  unduly.  Many  animals  possess  a  special  retractor  muscle 
of  the  eyeball,  for  example  amphibians,  reptiles,  and  many  mammals;  the  rumi- 
nants have,  in  fact,  four  of  them. 

The  ocular  movements  are  almost  always  accompanied  by  similar 
movements  of  the  head,  especially  in  looking  upward,  less  in  looking 
laterally  and  least  in  looking  downward. 

Difficult  investigations  into  the  ocular  movements  have  been  carried  out 
especially  by  Listing,  Meissner,  v.  Helmholtz,  Donders,  A.  Pick,  E.  Hering  and 
others. 

Orchansky  placed  a  closely  fitting  hemisphere  against  the  eyeball,  inside 
of  the  conjunctival  sac  (with  an  opening  cut  for  the  pupil),  and  in  this  way 
could  observe  the  simple  and  combined  movements,  and  also  register  them  graphic- 
ally by  means  of  a  writing  lever. 

All  movements  of  the  eyeball  take  place  about  its  center  of  rotation  (Fig 
302,  O),  which  lies  1.77  mm.  behind  the  center  of  the  visual  axis,  or  10.957  mm- 
from  the  vertex  of  the  cornea.  In  order  to  study  the  movements  more  exactly, 
certain  fixed  data  must  be  determined.  Three  axes,  intersecting  at  right  angles 
in  .the  center  of  rotation,  are  conceived  to  be  erected,  namely:  (i)  The  visual 
axis  (S  Si)  or  sagittal  axis  of  the  eyeball,  which  connects  the  center  of  rotation 
with  the  fovea  centralis,  and  is  prolonged  forward  in  a  straight  line  to  the  vertex 
of  the  cornea.  (2)  The  transverse  or  horizontal  axis  (Q  QJ,  being  the  direct  pro- 
longation outward  of  the  line  connecting  the  centers  of  rotation  of  the  two  eyes 
(naturally  at  a  right  angle  with  i).  (3)  The  vertical  axis,  erected  perpendicularly 
to  i  and  2  at  the  center  of  rotation.  These  three  axes  form  a  physical  system  of 
coordinates.  Further,  a  similar,  but  always  fixed  system  of  axes  may  be  con- 
ceived to  be  erected  in  the  orbital  cavity,  the  center  of  which  coincides  with  the 
center  of  rotation  of  the  eyeball.  In  the  position  of  rest  (primary  position)  of 
i  eye,  the  three  axes  of  the  eye  coincide  exactly  with  the  axes  of  the  orbital 
system.  11  however,  the  eyeball  is  moved,  two  or  three  of  the  axes  cease  to 
coincide  and  must  form  angles  with  the  fixed  orbital  system  of  axes. 

For  further  study,  partly  also  for  further  determinations,  three  planes  may 
be  imagined  as  passing  through  the  eye,  each  of  whose  positions  is  determined 


OCULAR    MOVEMENTS    AND    OCULAR    MUSCLES.  867 

by  two  of  the  axes,  (i)  The  horizontal  plane  of  division  cuts  the  eyeball  into 
an  upper  and  a  lower  half;  it  is  determined  by  the  visual  axis  and  the  transverse 
axis.  In  its  passage  through  the  retina,  it  forms  the  horizontal  line  of  division 
of  this  membrane,  and  it  cuts  the  tunics  of  the  eye  in  the  horizontal  meridian. 
(2)  The  vertical  plane  of  division  cuts  the  eye  into  an  inner  and  an  outer  half; 
it  is  determined  by  the  visual  and  vertical  axes.  It  intersects  the  retina  in  its 
vertical  line  of  division,  and  the  periphery  of  the  eyeball  in  the  vertical  meridian 
of  the  eyeball.  (3)  The  equatorial  plane  divides  the  eye  into  an  anterior  and  a 
posterior  half.  Its  position  is  determined  by  the  vertical  and  transverse  axes. 
It  cuts  the  sclera  in  the  equator  of  the  eyeball.  The  horizontal  and  vertical  lines 
of  division  of  the  retina  intersect  in  the  fovea  centralis,  and  divide  the  retina 
into  four  quadrants. 

v.  Helmholtz  has  further,  introduced  the  following  terms  for  designating  the 
positions  of  the  eyes:  the  line  of  fixation  is  the  straight  line  connecting  the  center 
of  rotation  with  the  fixed  point  in  the  external  world.  A  plane  passed  through 
the  lines  of  fixation  of  both  eyes  is  called  the  plane  of  fixation.  The  base  line  of 
this  plane  is  the  line  joining  the  two  centers  of  rotation  (consequently  the  transverse 
axis).  A  sagittal  plane  may  further  be  imagined  as  passing  through  the  head 
and  divides  it  into  a  right  and  a  left  half.  This  plane  will  bisect  the  base  line  of 
the  plane  of  fixation,  and  if  prolonged  anteriorly  will  intersect  the  plane  of  vision 
in  its  median  line.  The  fixation-point  of  the  eye  may  (i)  be  raised  or  lowered. 
The  field  that  it  traverses  is  called  the  field  of  fixation.  '  It  is  part  of  a  hemisphere, 
the  center  of  which  is  the  center  of  rotation  of  the  eye.  Starting  from  the  primary 
position  of  both  eyes,  which  is  characterized  by  the  fact  that  the  two  lines  of  fixa- 
tion are  parallel  and  horizontal,  the  elevation  of  the  plane  of  fixation  may  be 
determined  by  the  angle  that  it  makes  with  the  plane  of  the  primary  position. 
This  angle  is  called  the  angle  of  elevation  of  fixation.  It  is  termed  positive  when 
the  plane  of  fixation  is  raised  (toward  the  forehead) ,  and  negative  when  the  plane 
is  lowered  (toward  the  chin).  (2)  The  line  of  fixation  may  be  turned  also  from 
the  primary  position  in  a  lateral  direction  in  the  plane  of  fixation,  that  is  toward 
the  median  line,  or  away  from  it.  The  amount  of  this  lateral  movement  is 
measured  by  the  angle  of  lateral  rotation,  that  is  the  angle  that  the  line  of  fixation 
makes  with  the  median  line  of  the  plane  of  fixation.  The  angle  is  called  positive 
when  the  posterior  extremity  of  the  line  of  fixation  moves  toward  the  right,  and 
negative  when  the  extremity  moves  toward  the  left. 

In  accordance  with  the  foregoing  preliminary  considerations 
the  eyes  may  assume  the  following  positions  as  the  result  of  their 
movements : 

i.  Primary  position,  in  which  both  lines  of  fixation  are  parallel,  and 
the  plane  of  fixation  is  horizontal.  In  this  case  the  three  axes  of  the 
eye  coincide  with  the  three  fixed  axes  erected  in  the  orbital  cavity. 
2.  Secondary  positions  result  from  simple  movements  of  the  eyes  from 
the  primary  position.  There  are  two  different  kinds  of  secondary 
positions,  namely:  (a)  The  lines  of  fixation  are  parallel,  but  are  directed 
upward  or  downward.  The  transverse  axis  of  each  eye  remains  the 
same  as  in  the  primary  position.  The  deviation  of  the  other  two  axes 
is  expressed  on  the  line  of  fixation  by  the  size  of  the  angle  of  elevation 
(as  has  already  been  mentioned),  (b)  The  second  kind  of  secondary 
position  is  produced  by  convergence  or  divergence  of  the  lines  of  fixation. 
Here  the  vertical  axes  about  which  the  lateral  rotation  is  effected  remain 
the  same  as  in  the  primary  position.  The  other  axes  form  angles.  The 
amount  of  the  deviation  (as  already  noted)  is  expressed  by  the  angle  of 
lateral  rotation.  The  eye  can  be  turned  from  the  primary  position  out- 
ward 42°,  inward  45°,  upward  54°,  and  downward  57°.  3.  A  tertiary 
position  is  one  assumed  by  the  eye  when  the  lines  of  fixation  are  con- 
vergent, and  at  the  same  time  are  inclined  upward  or  downward.  None 
of  the  three  axes  coincides  now  with  its  situation  in  the  primary  position. 
The  exact  direction  of  the  lines  of  fixation  is  determined  by  the  size  of 
the  angles  of  elevation  and  lateral  rotation.  In  connection  with  tertiary 


868  OCULAR    MOVEMENTS    AND    OCULAR    MUSCLES. 

positions  another  important  point  comes  into  consideration,  namely 
that  the  eyeball  rotates  at  the  same  time  about  its  line  of  fixation  and  its 
axis.  As  the  iris  rotates  about  the  line  of  fixation  as  a  wheel  around  its 
axle,  these  movements  of  rotation,  which  are  always  associated  with 
the  tertiary  positions,  are  termed  wheel-movements.  Every  oblique 
movement  can  be  considered  as  composed  of  a  rotation  (i)  about  the 
vertical  axis,  and  (2)  about  the  transverse  axis;  or  it  may  be  conceived 
as  a  rotation  about  a  single,  constant  axis,  lying  between  these  two 
axes,  and  passing  through  the  center  of  rotation  of  the  eye,  perpendicu- 
lar to  the  primary  and  the  secondary  direction  of  the  visual  axis  (line  of 
fixation).  The  amount  of  the  wheel-movement  (circular  rotation) 
is  measured  by  the  angle  that  the  horizontal  line  of  division  of  the 
retina  forms  with  the  horizontal  line  of  division  of  the  retina  when  the 
eyes  are  in  the  primary  position.  This  angle  is  positive  when  the  eye 
has  turned  in  the  same  direction  as  the  hand  of  a  clock  that  it  observes, 
that  is,  when  the  upper  end  of  the  vertical  line  of  division  of  the  retina 
deviates  toward  the  right. 

According  to  Bonders  the  angle  of  rotation  increases  with  the  angles  of  ele- 
vation and  lateral  rotation;  it  may  increase  to  more  than  10°.  With  equally 
great  elevation  or  depression  of  the  plane  of  fixation,  the  rotation  is  stronger  the 
greater  the  elevation  or  depression  of  the  line  of  fixation. 

In  looking  upward  in  the  tertiary  position,  the  upper  ends  of  the  vertical 
lines  of  division  of  the  retina  diverge;  in  looking  downward  they  converge.  If 
the  plane  of  fixation  is  raised,  the  circular  rotation  is  toward  the  left  when  the 
eye  turns  laterally  toward  the  right;  and,  conversely,  the  circular  rotation  is 
toward  the  right  when  the  eye  turns  laterally  toward  the  left.  If  the  plane  of 
fixation  is  lowered,  however,  the  eye  rotates  in  the  same  direction,  to  the  right 
or  the  left,  when  it  turns  laterally  respectively  toward  the  right  or  the  left.  Ex- 
pressed otherwise :  if  the  angles  of  elevation  and  of  lateral  movement  have  the 
same  signs  (+  or  — ),  the  rotation  of  the  eyeball  is  negative,  but  if  they  have  dis- 
similar signs,  the  rotation  is  positive.  In  order  to  make  the  wheel-movement 
visible  in  one's  own  eye,  a  surface  divided  by  vertical  and  horizontal  lines  is  fixed 
with  one  eye,  a  positive  after-image  is  excited,  and  then  the  eye  is  rapidly  placed 
in  a  tertiary  position.  The  lines  of  the  after-image  then  form  angles  with  the  lines 
of  the  background.  As  the  position  of  the  vertical  meridian  of  the  eye  is  important 
from  a  medical  point  of  view,  it  may  be  again  particularly  pointed  out  that  in 
the  primary  and  secondary  positions  of  the  eyes  the  vertical  meridian  retains 
its  vertical  position.  In  looking  upward  and  to  the  left,  and  downward  and  to 
the  right,  the  vertical  meridians  of  both  eyes  are  inclined  to  the  left;  conversely 
they  are  inclined  to  the  right  in  looking  downward  and  to  the  left,  or  upward 
and  to  the  right. 

In  the  secondary  positions  of  the  eye  rotations  never  take  place.  Exceedingly 
slight  rotation  of  the  eyes  occurs,  however,  when  the  head  is  inclined  toward 
the  shoulder,  and  in  the  opposite  direction  from  the  inclination.  It  amounts  to  i° 
for  every  10°  of  inclination  of  the  head. 

Ocular  Muscles. — The  movements  of  the  eyeball  are  effected  by  the 
four  straight  and  the  two  oblique  ocular  muscles.  In  order  to  determine 
the  action  of  each  of  these  muscles,  a  knowledge  of  the  plane  of  traction 
of  the  muscle  and  of  the  axis  about  which  it  rotates  the  eye  is  necessary. 
The  plane  of  traction  is  found  by  constructing  a  plane  through  the 
middle  of  the  points  of  origin  and  insertion  of  the  muscle  and  through 
the  center  .of  rotation  of  the  eye.  The  axis  of  rotation  is  always-  per- 
pendicular to  the  plane  of  traction,  and  passes  through  the  center  of 
rotation. 

Measurement  has  yielded  the  following  data:  i.  The  internal 
rectus  (Fig.  302,  I)  turns  the  eye  almost  exactly  inward,  and  the  external 
rectus  (E)  outward.  The  plane  of  traction  lies,  therefore,  in  the  plane 


OCULAR    MOVEMENTS    AND    OCULAR    MUSCLES. 


869 


of  the  paper:  Q  E  is  the  direction  in  which  the  external  rectus  acts, 
Qx  I  that  in  which  the  internal  rectus  acts.  The  axis  of  rotation  is 
perpendicular  to  the  plane  of  the  paper  at  the  center  of  rotation  O,  and 
thus  coincides  with  the  vertical  axis  of  the  eyeball.  2.  The  axis  of 
rotation  of  the  superior  and  inferior  recti  (the  dotted  line  R.  sup. — 
R.  inf.)  lies  in  the  horizontal  plane  of  division  of  the  eye,  but  it  forms 
an  angle  of  about  20°  with  the  transverse  axis  (Q  Qx).  The  line  of 
action  for  both  muscles  is  indicated  by  the  line  s  i.  It  will  be  seen  at 
once  that  by  the  action  of  the  superior  rectus  the  cornea  must  move 
upward  and  somewhat  inward;  or  downward  and  inward  by  the  action 


v«t 


E  i          I 

FIG.  302. — Lines  of  Traction  and  Axes  of  Rotation  of  the  Ocular  Muscles. 


of  the  inferior  rectus.  3.  The  axis  of  rotation  of  the  two  oblique  muscles 
(the  dotted  line  Obi.  sup. — Obi.  inf.)  lies  also  in  the  horizontal  plane 
of  division  of  the  eyeball,  but  it  forms  an  angle  of  60°  with  the  transverse 
axis.  The  line  of  action  of  the  inferior  oblique  is  shown  by  the  line  a  b, 
that  of  the  superior  oblique  by  the  line  c  d.  The  action  of  these  muscles 
causes  the  cornea  to  move  respectively  outward  and  upward,  or  out- 
ward and  downward.  These  actions  of  the  muscles  are  effective  only 
when  the  eye  is  in  the  primary  position;  in  every  other  position  the 
axis  of  rotation  of  each  muscle  changes. 

When  the  eye  is  at  rest,  the  muscles  are  in  equilibrium.     Because  of 


870  BINOCULAR    VISION. 

the  greater  strength  of  the  internal  recti,  the  visual  axes  converge  some- 
what, and  if  prolonged,  would  intersect  40  cm.  in  front  of  the  eye.  In 
the  movements  of  the  eye,  only  one,  or  two  or  even  three  muscles  may 
be  involved.  One  muscle  acts  alone  in  rotation  of  the  eye  directly  out- 
ward and  directly  inward,  namely  the  external  rectus  and  the  internal 
rectus  respectively.  Two  muscles  act  in  rotating  the  eye  directly  upward 
(superior  rectus  and  inferior  oblique)  or  directly  downward  (inferior 
rectus  and  superior  oblique).  Three  muscles  are  employed  in  the  diag- 
onal directions,  namely  for  inward  and  upward  movement  the  internal 
rectus,  the  superior  rectus,  and  the  inferior  oblique;  for  inward  and 
downward  movement,  the  internal  rectus,  the  inferior  rectus,  and  the 
superior  oblique ;  for  outward  and  downward  movement,  the  external 
rectus,  the  inferior  rectus,  and  the  superior  oblique;  for  outward  and 
upward  movement,  the  external  rectus,  the  superior  rectus,  and  the 
inferior  oblique. 

Ruete  has  imitated  the  movements  of  the  eyes  by  means  of  a  special  model 
of  the  eyeballs  and  their  muscles,  and  which  he  called  the  ophthalmotrope. 

The  extent  of  movement  of  the  eyeball  decreases  with  age,  likewise  the  length 
of  the  eye.  The  mobility  is  less  in  the  vertical  direction  than  in  the  lateral; 
and  less  upward  than  downward.  The  emmetrope  and  the  myope  can  move 
the  eye  further  outward,  the  hyperope  further  inward.  The  external  and 
internal  recti  act  most  vigorously  in  rotation  of  the  eye  outward;  the  oblique 
in  rotation  inward.  One  eye  can  be  turned  more  strongly  inward,  if  at  the  same 
time  the  other  is  turned  outward,  than  if  this  eye  also  is  turned  inward.  In 
near  vision  the  right  eye  can  be  turned  less  toward  the  right,  and  the  left  eye  less 
toward  the  left  than  in  distant  vision. 

Both  eyes  are  always  moved  simultaneously,  even  when  one  is  totally 
blind;  indeed,  the  ocular  muscles  move  even  after  the  eyeball  has  been 
extirpated.  When  the  head  is  held  erect,  the  movements  proceed  in 
such  a  manner  that  both  lines  of  fixation  (visual  axes)  lie  in  the  same 
plane.  The  visual  axes  can  diverge  anteriorly  to  only  a  slight  degree, 
but  they  can  converge  to  a  considerable  extent.  When  single  muscles 
are  paralyzed,  the  position  of  the  visual  axes  in  the  same  plane  is  often 
disturbed  (squinting).  The  individual  can  no  longer  direct  both  visual 
axes  to  one  point  at  the  same  time,  though  each  eye  can  be  so  directed 
singly  in  succession.  Nystagmus  also  occurs  in  both  eyes  simultane- 
ously, and  in  the  same  manner.  The  congenital,  simultaneous  move- 
ment of  both  eyes  is  termed  an  associated  movement.  E.  Hering  showed 
that  all  ocular  movements  are  attended  with  a  uniformity  of  innervation. 
Even  with  such  movements  in  which  one  is  apparently  at  rest,  a  move- 
ment takes  place,  nevertheless,  of  two  antagonists,  as  may  be  recognized 
from  slight  to-and-fro  movements. 

The  nerves  of  the  ocular  muscles  are  the  oculomotor,  the  trochlear,  and  the 
abducens.  The  center  is  situated  in  the  corpora  quadrigemina,  the  cortical 
center  in  the  angular  gyrus. 

BINOCULAR  VISION. 

The  conjoint  action  of  both  eyes  in  the  visual  act  has  the  following 
advantages :  ( i )  The  visual  field  of  the  two  eyes  is  much  larger  than  that 
of  either  one.  (2)  The  conception  of  depth  is  facilitated,  as  the  retinal 
images  are  obtained  from  two  different  standpoints.  (3)  A  more 
accurate  estimation  of  the  distance  and  the  size  of  objects  is  rendered 
possible,  as  a  result  of  the  estimation  of  the  degree  of  convergence  of  the 
two  eyes.  (4)  Certain  errors  in  one  eye  may  be  corrected  by  the  other. 


SINGLE    VISION.       IDENTICAL    RETINAL    POINTS.  871 

If  the  head  is  fixed,  an  idea  of  the  form  of  the  common  field  of  vision  can  be 
obtained  by  alternately  closing  one  eye,  and  turning  the  other  inward.  It  will 
then  be  seen  that  the  field  is  pear-shaped,  broad  above,  narrow  below,  and  that 
the  profile  of  the  nose  cuts  out  a  portion  corresponding  to  its  size,  between  the 
upper  broader  portion  and  the  lower  narrow  part.  If  a  pasteboard  card  be  held 
upright  close  to  the  face,  the  outline  of  the  common  field  may  be  traced  upon  it 
with  a  pen. 

SINGLE  VISION.     IDENTICAL  RETINAL  POINTS. 

HOROPTER.     SUPPRESSION  OF  DOUBLE  IMAGES. 

If  the  retinas  of  both  eyes  be  considered  as  a  pair  of  concave  saucers 
placed  one  within  the  other,  so  that  the  two  yellow  spots,  and  the  corre- 
sponding quadrants  of  the  retinas  coincide,  all  those  points  that  corre- 
spond are  called  identical  or  corresponding  points.  The  two  meridians 
that  separate  the  corresponding  quadrants  are  known  as  lines  of  separa- 
tion. The  identical  points  are  characterized  physiologically  by  the  fact 
that  when  light  acts  upon  them  at  the  same  time,  the  stimulation  is 
referred  by  a  psychical  act  to  one  and  the  same  place  in  the  visual  field 
(in  a  direction  through  the  nodal  point  of  each  eye).  The  stimulation 
of  the  two  identical  points  of  the  retina  produces,  therefore,  only  one 
image  in  the  field.  Hence,  all  of  those  objects  of  the  external  world, 
the  rays  from  which  pass  through  the  nodal  points  to  identical  points 
of  the  retina,  are  seen  singly,  because  their  images  are  referred  to  the 
same  part  of  the  visual  field,  so  that  they  coincide.  Double  images  are 
produced  by  all  other  objects,  whose  images  do  not  fall  on  identical 
portions  of  the  retina. 

The  proof  for  what  has  been  said  is  readily  provided.  If  a  linear  object  with 
the  points  1,2,3  (Fig-  303)  be  looked  at  with  both  eyes,  the  corresponding  points 
of  the  retinal  images  will  be  i,  2,  3  and  3,  2,  i,  which  are  obviously  identical 
(corresponding)  points  on  the  two  retinas.  If  there  is,  at  the  same  time,  a  point 
(A)  closer  to  the  eye,  or  another  point  (B)  farther  from  the  eye,  and  the  eyes  are 
directed  toward  the  object  i,  2,  3,  the  visual  rays  from  neither  A  (A  a,  A  a)  nor 
B  (B  b,  B  b)  will  fall  upon  identical  retinal  points:  therefore  double  images  of 
A  and  B  appear. 

The  following  simple  experiment  also  is  instructive.  If  a  point  of  ink  (for 
example  2)  upon  white  paper  be  looked  at,  the  image  will  fall  in  both  foveas  (2,  2), 
which  are  of  course  identical  points.  By  pressing  laterally  on  one  eye,  so  that  it  is 
somewhat  displaced,  two  points  immediately  appear,  because  the  image  of  the 
point  no  longer  falls  on  the  fovea  of  the  displaced  eye,  but  on  an  adjoining,  not 
identical,  point.  Similarly  in  intentional  squinting  all  objects  appear  to  be  double. 

The  vertical  lines  of  division  of  the  retinas  do  not  coincide  exactly  with  the 
vertical  meridians;  but  exhibit  a  slight  divergence  above  (from  0.5°  to  3°),  which 
varies  in  amount  in  different  individuals,  and  even  in  the  same  individual 
at  different  times,  while  the  horizontal  lines  of  division  coincide.  Images  that 
fall  upon  the  vertical  lines  of  division  appear  to  be  perpendicular  to  those  on  the 
horizontal,  although  they  are  in  reality  not  so.  Therefore,  the  vertical  lines  of 
division  are  the  pseudovertical  meridians. 

Some  investigators  consider  the  identical  points  of  the  retina  a  congenital 
arrangement,  while  others  think  that  they  are  acquired  by  ordinary  use.  In- 
dividuals who  squint  from  birth  have,  however,  single  vision;  under  such  cir- 
cumstances the  identical  points  must  be  arranged  differently. 

Horopter  is  the  term  used  to  indicate  the  aggregate  of  all  those  points  in 
space,  from  which  rays,  entering  both  eyes,  held  in  any  given  position,  meet  at 
identical  points  of  the  retinas.  It  varies  for  the  different  positions  of  the  eyes. 

i.  In  the  primary  position  of  both  eyes,  when  the  visual  axes  are  parallel, 
rays  drawn  from  two  identical  points  of  the  two  retinas  are  also  parallel  and 
intersect  only  at  an  infinite  distance.  The  horopter  for  the  primary  position  is, 
therefore,  a  vertical  plane  at  an  infinite  distance. 


872  SINGLE    VISION.       IDENTICAL    RETINAL    POINTS. 

2.  In  the  secondary  position  of  the  eyes,  with  convergent  visual  axes,  the 
horopter  for  the  transverse  lines  of  division  is  a  circle  passing  through  the  nodal 
points  of  both  eyes  (Fig.  304,  KKj)  and  through  the  point  fixed  (I,  II,  III).     The 
horopter  of  the  vertical  lines  of  division  is  in  this  position  perpendicular  to  the 
plane  of  fixation. 

3.  In  the   (symmetrical)   tertiary  positions,  in  which  horizontal  and  vertical 
lines  of  division  form  angles,  the  horopter  for  the  vertical  lines  of  division  is  a 
straight  line  inclined  toward  the  horizon.     For  identical  points  of  the  horizontal 
lines  of  division  there  is  no  horopter  for  these  positions,  as  the  rays  from  these 
points  do  not  meet  at  a  distance. 

4.  In   the  unsymmetrical   tertiary  positions    (with   rotation),   in  which  the 
point  fixed  is  at  an  unequal  distance  from  the  two  nodal  points,  the  horopter 
is  a  curve  of  complicated  form. 

It  will  not  be  possible  to  enter  into  a  more  complete  description  of  the  diffi- 
cult details  of  the  horopter.  For  the  determination  of  the  horopter,  v.  Helmholtz 
constructs,  in  the  primary  position,  similar  meridians  and  parallel  circles  over 
both  retinas;  the  identical  points  lie  then  as  if  on  two  globes  of  equal  length  and 
breadth.  Hering  draws  two  systems  of  planes  through  the  eyeballs  in  the  primary 
position:  those  of  one  system  (the  transverse)  intersect  in  the  transverse  axis 

fi 


FIG.  303. — Diagrammatic  Representation  of  Identical  FIG.  304. — Horopter  for  the  Secondary  Posi- 

and  Nonidentical  Retinal  Points.  tion,  with  Convergence  of  the  Visual  Axes. 

connecting  the  nodal  points  of  the  eyeballs.  Those  of  the  second  system  inter- 
sect in  a  perpendicular  drawn  through  the  nodal  point  of  each  eye.  The  identical 
points  he  at  the  intersections  of  the  similar  perpendicular  and  transverse  planes 
of  the  retinas. 

All  objects  whose  rays  fall  on  nonidentical  (disparate)  points  of  the 
retinas  appear  in  double  images.  A  distinction  is  made  between  homony- 
mous  and  crossed  (heteronymous)  double  images,  according  as  the  rays 
from  the  disparate  retinal  points  intersect  in  front  of  or  behind  the 
fixed  point. 

In  illustration,  two  fingers  are  held,  one  behind  the  other,  in  front  of  the  eyes, 
it  the  tar  finger  is  looked  at,  the  other  appears  double,  while  if  the  near  one  is 
fixed,  the  far  one  appears  double.  If,  while  looking  at  the  far  finger,  the  right 
eye  is  closed  the  left  (crossed)  image  of  the  first  finger  disappears.  If  the  near 
finger  is  fixed  and  the  right  eye  is  closed,  the  right  (homonymous)  image  of  the 
second  finger  disappears. 

The  double  images,  like  the  single  images,  are  referred  to  the  proper  distance 
by  the  eyes. 


STEREOSCOPIC    VISION.       JUDGMENT    OF    SOLIDITY.  873 

In  spite  of  the  large  number  of  double  images  that  are  constantly  formed, 
they  are  not  a  source  of  disturbance.  They  are  usually  suppressed,  and  to  such 
an  extent,  in  fact,  that  the  attention  must  be  directed  to  them,  in  order  that 
they  may  be  seen.  The  suppression  of  the  double  images  is  favored  by  the  follow- 
ing factors:  (i)  Attention  is  always  directed  to  that  point  of  the  visual  field 
which  for  the  time  being  is  fixed.  This  throws  its  image  on  the  two  yellow  spots, 
which  are  identical  points.  (2)  Form  and  color  are  less  sharply  seen  by  the  lateral 
portions  of  the  retina.  (3)  The  eyes  are  always  accommodated  for  those  points 
that  are  fixed.  Therefore,  only  indistinct  images  arise  from  the  objects  that 
produce  double  images  (in  diffusion-circles),  and  these  can  be  more  easily  sup- 
pressed. (4)  Many  double  images  lie  so  close  together  that  when  they  are  large, 
the  greater  portions  of  them  overlap.  (5)  Images  that,  strictly  speaking,  do  not 
coincide  are  often  united  by  a  psychical  habit. 

STEREOSCOPIC  VISION.     JUDGMENT  OF  SOLIDITY. 

The  images  formed  by  the  two  eyes  in  looking  at  solid  objects  are  not 
exactly  alike,  but  differ  somewhat,  because  the  eyes  look  at  the  ob- 
ject from  two  different  points  of  view.  The  right  eye  can  see  more  of 
the  side  opposite  to  it,  and  the  same  is  true  of  the  left  eye.  Despite  this 
dissimilarity,  the  two  images  are  united. 

The  question  as  to  how  the  impression  of  solidity  is  obtained  by  the 
combination  of  such  different  images  may  be  best  solved  by  analyzing 
two  corresponding  stereoscopic  pictures. 

In  Fig.  305,  III,  L  and  R  are  two  such  pictures  that,  when  seen  with  a  stereo- 
scope, form  a  truncated  pyramid,  projecting  toward  the  eye  of  the  observer,  and 
the  similarly  designated  points  coincide.  If  the  distances  between  the  corre- 
sponding points  in  the  two  figures  be  measured,  it  will  be  found  that  the  distances 
A  a,  B  b,  C  c,  D  d  are  equal,  and  are  at  the  same  time  the  greatest  between  any 
of  the  points  of  the  two  figures;  further,  the  distances  E  e,  F  f,  G  g,  H  h  are  equal, 
but  are  smaller  than  the  first  set.  Considering,  finally,  the  lines  A  E,  a  e,  and 
B  F,  b  f,  which  coincide,  it  may  easily  be  seen  that  all  points  of  these  lines  that 
lie  nearer  A  a  and  B  b  are  further  apart  than  those  that  lie  nearer  E  e  and  F  f. 

From  a  consideration  of  these  relations  in  comparison  with  the 
stereoscopic  images  the  following  principles  for  stereoscopic  vision 
appear:  (i)  All  those  points  of  two  stereoscopic  images  (and  naturally 
of  two  retinal  images  of  solid  objects)  that  are  at  equal  distances  from 
each  other  in  the  two  images  appear  in  the  same  plane.  (2)  All  points 
that  are  closer  together  (than  the  others)  project  toward  the  observer. 
(3)  Conversely,  the  points  that  are  further  apart  recede  perspectively 
into  the  background. 

The  reason  for  this  phenomenon  resides  simply  in  the  following 
principle:  "In  binocular  vision  we  constantly  refer  the  position  of  the 
individual  points  of  the  image  in  the  direction  of  the  visual  axes  where 
they  intersect." 

The  following  stereoscopic  experiment  proves  this.  In  Fig.  305  I,  two  pairs 
of  points  are  taken  as  the  two  images  (a  b  and  «  ft}  that  are  at  unequal  distances 
from  each  other  on  the  surface  of  the  paper.  If  they  are  made  to  coincide,  by 
means  of  a  stereoscope,  the  point  (A),  formed  by  the  union  of  a  and  a,  appears  in 
the  plane  of  the  paper,  while  the  other  (B)  formed  by  the  points  b  and  p,  which 
are  closer,  seems  to  float  in  the  air  in  front  of  A.  Fig.  305,  I,  shows  the  construc- 
tion clearly.  The  following  experiment  also  illustrates  the  same  condition.  Two 
sets  of  lines,  similar  to  B  A,  A  E  and  b  a,  a  e  in  Fig.  305,  III,  are  drawn  as  the 
figures  to  be  superposed.  In  the  lines  B  A  and  b  a  all  the  points  to  be  superposed 
lie  equally  distant  from  each  other;  on  the  contrary,  all  points  in  A  E  and  a  e, 
which  lie  nearer  to  E  and  e,  are  successively  closer  to  each  other.  Looked  at 
with  a  stereoscope,  the  superposed  perpendicular  line  A  B  and  a  b  lies  in  the  plane 
of  the  paper,  while  the  oblique  line  formed  by  A  E  and  a  e  projects  obliquely 


874 


STEREOSCOPIC    VISION.       JUDGMENT    OF    SOLIDITY. 


outward  from  the  plane  of  the  paper  toward  the  observer.  From  these  two 
fundamental  experiments  all  stereoscopic  pairs  of  pictures  may  be  easily  analyzed; 
particularly,  it  will  be  seen  also  that  if  in  Fig.  305,  III,  the  two  pictures  be  ex- 
changed, so  that  R  lies  in  the  place  of  L,  the  impression  of  a  truncated  pyramidal 
hollow  vessel  must  result. 

_  Two  stereoscopic  pictures,  which  are  so  constructed  that  one  contains  an 
object  taken  from  in  front  and  above,  the  other  the  object  taken  from  in  front 
and  below  (for  example,  if  the  figures  in  Fig.  305,  III,  had  the  lines  A  B  and 
a'b  as  base  line),  are  never  united  by  means  of  the  stereoscope.  If  these  two 
figures  be  turned  so  that  they  have  an  oblique  position  (so  that  the  corners  Ct  c 


II 


a, 

III 

j 

C     a                c 

\JE    G/ 

V      9/ 

z*  ^ 

/f       h\ 

D     b 


FIG.  305.— I,  Diagrammatic  Representation  of  Brewster's  stereoscope;  II,  that  of  Wheatstone;  III,  two  stereo- 
scopic drawings;    IV,  v.  Helmholtz's  telestereoscope. 

deviate  toward  the  right  and  downward) ,  the  impression  of  solidity  will  be  more 
and  more  interfered  with;  but  Landois  was  able  to  preserve  the  stereoscopic 
appearance  up  to  a  similar  rotation  of  30°. 

The  process  of  stereoscopic  vision  has  been  explained  also  in  another 
way      In  the  figure  R  and  L  (Fig.  305,  III)  only  A  B  C  D  and  a  b  c  d  fall 
on  identical  points  of  the  retinas,  and,  therefore,  these  alpne  can  coin- 
cide (or  in  another  convergence  of  the  visual  axes  only  E  F  G  H  and 
f  g  h  coincide,  for  the  same  reason).     If  it  be  supposed  that  the  quad- 
bases  of  the  figures  coincided  first,  it  has  been  further  assumed 
that  both  eyes  then  make  a  quick  "groping"  motion  toward  the  apex 


STEREOSCOPIC    VISION.       JUDGMENT    OF    SOLIDITY. 


875 


of  the  pyramid;  and  as  the  axes  of  the  eyes  would  have  to  converge 
more  and  more  in  doing  this,  the  apex  of  the  pyramid  appears  to  project ; 
for  all  points  appear  closer  when  the  eyes  must  be  converged  in  order  to 
see  them.  In  this  way,  all  corresponding  parts  of  both  figures  would  be 
brought  successively  on  identical  points  by  the  movements  of  the  eyes 
toward  each  other. 

To  this  the  objection  has  been  urged  that  the  duration  of  the  electric 
spark  is  sufficient  for  stereoscopic  vision ;  a  length  of  time  that  is  entirely 
too  short  for  the  ocular  movements.  Although  this  is  true  for  many 
figures,  this  movement  of  the  visual  axes  is  not  precluded  for  the  correct 
combination  of  complex  or  unusual  figures,  and  it  is  in  fact  of  con- 
siderable advantage,  especially  for  certain  individuals. 

It  appears  that  not  merely  the  movements  that  actually  take  place, 
but  rather  the  sense  of  innervation  of  the  muscles  necessary  to  the  move- 
ment is  sufficient  to  produce  the  impression  of  solidity.  Consequently, 


FIG.  306. — Wheatstone's  Prism-pseudoscope. 


FIG.  307. — Ewald's  Mirror  Pseudoscope. 


stereoscopic  vision  may  depend  in  part  on  a  muscle-sensation :  the  feeling 
that  a  greater  convergence  of  the  visual  axes  is  necessary  for  the  super- 
position of  two  points  in  the  stereoscopic  figures  produces  the  impression 
that  the  points  are  nearer;  conversely,  the  feeling  that  to  secure  the 
congruence  of  two  points  a  greater  divergence  of  the  visual  axes  is 
necessary  produces  the  impression  of  greater  distance. 

If,  now,  in  the  momentary  superposition  of  two  figures  making  a  solid  image, 
a  movement  of  the  eyes  does  not  take  place,  many  points  in  the  stereoscopic 
figures  are  apparently  united  that,  strictly  speaking,  do  not  fall  on  identical 
retinal  points.  The  latter  therefore  cannot  be  designated  with  mathematical 
accuracy  as  corresponding  points  of  the  retinas,  but,  from  a  physiological  view- 
point, all  points  must  be  designated  as  identical,  the  simultaneous  stimulation 
of  which  produces  as  a  rule  a  single  image.  In  this  coalescence  the  mind  plays 
a  part:  there  is  a  certain  psychical  tendency  to  fuse  the  double  impressions  of 
both  retinas  into  one,  as  experience  has  taught  that  they  belong  to  one  single 


876  STEREOSCOPIC    VISION.       JUDGMENT    OF    SOLIDITY. 

image.  If,  however,  the  differences  between  the  two  stereoscopic  figures  are  ex- 
cessive, so  that  too  widely  separated  retinal  points  are  affected,  or  if  new  lines 
are  introduced  into  a  figure  that  do  not  harmonize  with  the  solid  figure,  or  would 
disturb  the  coalescence,  the  stereoscopic  fusion  ceases. 

The  stereoscope  is  an  instrument  by  means  of  which  two  similar  pictures, 
drawn  in  perspective,  may  be  superposed,  so  that  they  appear  single,  and  give 
the  impression  of  solidity.  Wheatstone  accomplished  this  by  means  of  two  mirrors 
placed  at  an  angle  (Fig.  305,  II),  Brewster  by  means  of  two  prisms  (Fig.  305,  I). 
The  construction  and  mode  of  action  are  shown  by  the  figures. 

Even  without  a  stereoscope  some  persons  are  able  to  unite  two  such  pictures 
by  directing  the  visual  axis  of  each  eye  to  the  picture  opposite  to  it. 

Two  exactly  similar  pictures,  that  is,  those  in  which  all  corresponding  points 
are  at  an  equal  distance  from  each  other  (for  example  the  identical  pages  of  two 
copies  of  a  book),  appear  exactly  on  the  same  level  under  the  stereoscope; 
but  just  as  soon  as  one  point  in  one  or  the  other  is  closer  to,  or  farther  from, 
the  corresponding  point  than  the  others,  it  appears  immediately  to  project 
in  front  of  or  behind  the  plane.  In  this  way  Dove  taught  how  to  distinguish 
false  banknotes  from  good  ones,  by  their  failure  to  yield  perfectly  flat  images. 

Solid  objects  seen  from  a  great  distance,  such  as  the  remote  parts  of  a  land- 
scape, appear  flat,  as  in  a  picture,  and  do  not  stand  out,  because  the  difference 
in  the  position  of  the  eyes  is  too  small  relatively  to  be  taken  into  consideration. 
In  order  to  obtain  a  stereoscopic  view  of  such  objects,  v.  Helmholtz  constructed 
the  telestereoscope  (Fig.  305,  IV) ,  an  instrument  that,  by  means  of  parallel  mirrors, 
moves  the  points  of  view  of  both  eyes  to  some  extent  farther  apart.  The  mirrors 
L  and  R  throw  their  images  respectively  on  the  mirrors  1  and  r,  toward  which 
the  eyes  O  o  are  directed.-  According  to  the  distance  of  L  and  R,  both  eyes  may 
be  apparently  separated  several  feet  (to  Oj  Oj) .  The  distant  landscape  thus  ha's 
a  distinct  appearance  of  solidity.  In  order  to  see  the  distant  objects  more  distinctly 
and  at  closer  range,  a  telescope  (field-glass)  can  be  placed  before  each  eye.  In- 
struments of  this  sort,  re  lief -telescopes,  have  been  constructed  in  great  perfection 
recently  by  Zeiss;  instead  of  mirrors  they  contain  similarly  acting  prisms. 

If  in  two  stereoscopic  pictures  the  corresponding  surfaces  are  made  black 
in  the  one  and  white  in  the  other  (for  example,  if  two  truncated  pyramids  are 
drawn,  as  in  Fig.  305,  III,  and  one  figure  is  drawn  exactly  like  L,  that  is  with 
white  surfaces  and  black  lines,  while  the  other  is  drawn  with  black  surfaces  and 
white  lines),  the  body  appears  to  shine  in  the  stereoscope.  The  explanation  of 
luster  is  that  the  shining  object,  in  a  certain  position,  reflects  bright  light 
into  one  eye,  and  not  into  the  other;  because  at  a  given  angle  the  reflected  ray 
cannot  enter  both  eyes  at  the  same  time. 

An  interesting  experiment  for  illustrating  stereoscopic  vision  is  furnished 
by  Wheatstpne's  pseudoscope.  This  consists  of  two  right-angled  prisms  enclosed 
in  tubes  (Fig.  306,  A  and  B),  through  which  the  observer  looks  in  a  direction 
parallel  to  their  oblique  surfaces.  If  a  spherical  surface  is  seen  through  this 
instrument,  the  images  falling  in  the  eyes  will  be  reversed  laterally.  The  right 
eye  thus  obtains  a  view  usually  received  by  the  left  eye,  and  conversely;  the 
shadow  projected  is  also  reversed.  The  result  of  this  is  that  the  ball  appears 
hollow.  R.  Ewald  constructed  the  apparatus  with  four  mirrors,  and  its  action  will 
be  readily  understood  from  Fig.  307. 

The  stereoscope  can  also  be  used  to  explain  the  "rivalry  of  the  visual  fields." 
In  other  words,  both  eyes  are  almost  never  simultaneously  and  equally  active  in 
binocular  vision,  but  they  rather  relieve  each  other  more  or  less  completely,  so 
that  at  one  time  the  image  of  one  retina,  at  another  time  that  of  the  other  prevails. 
For  example,  if  two  differently  colored  surfaces  are  placed  in  the  stereoscope, 
they  will  alternate  in  the  common  field  of  vision,  especially  if  they  are  brightly 
illuminated,  accordingly  as  one  or  the  other  eye  is  especially  active.  If  two  sur- 
faces are  used,  on  which  lines  are  so  drawn  that  they  would  cross  if  the  surfaces 
were  superposed,  the  lines  first  of  one  system  and  then  of  the  other  appear  more 
prominently.  The  rivalry  of  the  visual  fields  is  similarly  shown  in  looking 
through  differently  colored  glasses  at  a  landscape. 


ESTIMATION    OF    SIZE    AND    OF    DISTANCE.  877 

ESTIMATION  OF  SIZE  AND   OF  DISTANCE. 

FALSE  ESTIMATES  OF   SIZE  AND   DIRECTION. 

The  judgment  as  to  the  size  of  an  object  depends,  apart  from  all  other 
factors,  upon  the  size  of  the  retinal  image;  thus  the  moon  is  estimated 
to  be  larger  than  a  star.  If,  while  looking  at  a  distant  landscape,  a 
fly  suddenly  crosses  the  field  of  vision,  close  to  the  eye,  its  image  may 
give  the  impression  of  a  large  bird,  because  of  the  relatively  great  size  of 
the  retinal  image.  If  the  image  is  seen  in  diffusion-circles, 'on  account  of 
a  lack  of  accommodation,  it  may  appear  even  larger.  As,  however, 
objects  widely  unequal  in  size  yield  equally  large  retinal  images,  especi- 
ally when  their  distance  is  such  that  they  subtend  the  same  visual  angle 
(Fig.  279),  the  estimate  of  the  distance  is  of  the  greatest  importance  in 
estimating  the  actual  size  of  an  object,  as  opposed  to  the  apparent  size, 
which  is  determined  by  the  visual  angle  alone. 

An  estimate  of  the  distance  of  an  object  is  formed  from  the  feeling  of 
accommodation,  as  a  greater  effort  of  accommodation  is  required  for 
accurate  vision  of  a  near  object  than  for  seeing  distant  objects.  As, 
however,  of  two  unequally  distant  objects  forming  retinal  images  of  the 
same  size  the  one  that  is  nearer  is  found  from  experience  to  be  the 
smaller,  the  object  for  which  greater  accommodation  is  made  is  esti- 
mated to  be  the  smaller. 

This  fact  explains  the  following  observation:  beginners  in  microscopy  usually 
make  a  strong  accommodative  effort,  while  trained  observers  work  without  exer- 
cising their  accommodation.  Hence,  beginners  estimate  all  microscopical  images 
as  too  small,  and  in  drawing  them,  make  them  much  too  small.  The  following 
experiment  is  a  further  proof.  An  after-image  appears  smaller  if  the  eye  accom- 
modates for  near  vision,  and  much  larger  when  the  eye  comes  to  rest.  If  a  small 
object  is  held  as  close  as  possible  to  the  eye,  an  object  behind  it,  which  is  seen  indi- 
rectly, appears  to  be  smaller. 

A  much  more  important  means  of  estimating  the  size  of  an  object, 
by  judging  the  distance,  is  given  by  the  degree  of  convergence  of  the 
visual  axes.  The  position  of  an  object  that  is  seen  binocularly  is  re- 
ferred to  the  point  where  these  axes  cross.  The  angle  that  is  formed  by 
the  visual  axes  at  their  point  of  intersection  is  called  the  angle  of  con- 
vergence of  the  visual  axes.  The  larger,  therefore,  this  angle  of  conver- 
gence (with  equal  retinal  images),  the  nearer  the  object  is  judged  to  be. 
The  nearer,  however,  the  object,  the  smaller  it  may  be  in  order  to  subtend 
the  same  visual  angle  as  a  larger,  more  distant  object.  From  this  it  may 
be  concluded  that  when  objects  have  the  same  apparent  size  (equal 
visual  angles,  or  equal  retinal  images)  that  object  is  judged  to  be  the 
smallest  that  requires  the  greatest  convergence  of  the  visual  axes  during 
binocular  vision.  The  muscular  sense  of  the  ocular  muscles  gives  the 
information  as  to  the  amount  of  muscular  effort  that  is  necessary. 

The  following  experiments  afford  the  proofs  for  this  statement:  i.  The 
tapestry- phenomenon  described  by  Herm.  Meyer.  If  a  background  with  a  reg- 
ular, chessboard-pattern  (tapestry  or  wickerwork)  be  looked  at  the  squares  appear 
of  a  certain  size  when  the  visual  axes  are  parallel.  If  now  the  eyes  are  converged 
on  an  object  closer  to  the  eyes,  so  that  the  visual  axes  cross,  the  pattern  appears 
to  move  into  the  same  plane  as  the  point  fixed,  the  crossed  double  images,  dis- 
placed laterally,  coincide,  and  the  pattern  appears  smaller.  2.  Rollett  looked 
at  an  object  through  two  thick  glass  plates;  in  one  case  the  plates  were  so  placed 
(Fig.  308,  II)  that  the  apex  of  the  angle  between  the  two  plates  was  turned  toward 


ESTIMATION    OF    SIZE    AND    OF    DISTANCE. 


the  observer;  in  the  other  case  (I)  the  opening  of  the  angle  is  toward  the  observer. 
In  order  that  both  eyes  f  and  i  (in  I)  may  see  the  object  a,  the  eyes  must  converge 
more  than  if  they  were  turned  directly  toward  a,  because  the  glass  plates  displace 
the  rays  a  c  and  a  g  parallel  with  each  other  (e  f  and  h  i)  .  Therefore  the  object 
appears  nearer  and  smaller  at  a.  In  II  the  rays  b:  k  and  bj  o  from  the  smaller, 
nearer  object  bt  fall  on  the  glass  plates.  In  order  to  see  the  object  blf  the  eyes 
(n  and  q)  must  diverge  more,  and  the  object  appears  at  f  ,  enlarged  and  more  distant. 
3.  By  examination  of  Wheatstone's  stereoscope  (Fig.  305,  II),  it  will  readily  be 
seen  that  the  nearer  the  two  pictures  are  brought  to  the  observer,  the  more  the 
latter  must  converge  (because  the  angles  of  incidence  and  reflection  become 
larger).  Therefore,  the  fused  image  seems  smaller.  If  the  middle  of  the  picture 
R  is  moved  to  R1;  the  angle  Su  r  f  must  be  made  equal  to  Sj  r  R:  (likewise  naturally 
on  the  left).  4.  As,  in  using  the  telestereoscope,  the  eyes  are,  in  a  manner,  moved 
far  apart,  they  must  be  converged  more  strongly,  in  looking  at  objects  at  a  certain 
distance,  than  in  normal  vision.  Objects  in  the  landscape,  therefore,  appear  as 
in  a  small  model.  As,  however,  it  is  customary  to  consider  the  distance  great 
when  the  objects  are  so  small,  the  latter  appear  to  be  moved  at  the  same  time 
to  a  remarkable  distance. 

With  respect  to  the  judgment  of  distance  the  following  rules  may  be 
noted:  With  retinal  images  of  equal  size,  the  distance  is  estimated  to  be 

the  greater  the  less  the  effort  of  ac- 
commodation (and  conversely).  In 
binocular  vision,  with  retinal  images  of 
equal  size  that  object  is  judged  to  be 
furthest  away  that  requires  the  least 
convergence  of  the  visual  axes  (and 
conversely). 

The  estimation  of  size  and  distance, 
therefore,  go  largely  hand  in  hand,  and 
the  correct  judgment  of  distance  affords 
also  a  correct  estimate  of  the  size  of 
objects.  A  further  aid  to  the  estima- 
tion of  distance  is  furnished  by  the  ob- 
servation of  the  apparent  displacement 
of  objects  on  movement  of  the  head  or 
body.  During  such  movements  ,  ob  j  ects 
are  apparently  displaced  laterally  more 
rapidly  the  nearer  they  are.  For  this 
reason,  in  traveling  in  an  express 
train,  the  objects  change  their  position 

h  great  rapidity,  and  they  appear  nearer  and  consequently  smaller 
than  they  are. 

Finally,  those  objects  appear  nearest  that  are  most  distinct  in  the 
neld.  or  vision. 


9  w '  (b 

T         '  " 

I  I 

FIG.  308.— Rollett's  Glass  Plate  Apparatus. 


f    A  Hght  in  a  dark  landscaPe,  likewise  a  dazzling  mountain-top 
th  ™    ai  Sn°W'  ^^    exceedinSly  "ear.     Viewed    from  a  high  mountain 

level   of  ^^g1^?mg'  Wm^m1  S^reams  not  rarel>T  aPPear  to  be  lifted  above  the 
the  landscape.     On  looking  at  the  railway  embankment  from  a  train, 

fixedgfor  ^PtaSSf  mdlstmctly  b^ore  the  eyes.  If  suddenlv  a  certain  point  is 
levd  towaf™eyVe1S1°n'  *  ^^  ""^  to  project  from  the  general 

tefmlfdiafp^f8  °f  Size1and  Direction.—  i.   A   given   distance   filled  out  by 
Sre  X  ,W  ?  aPPears  lar?er  than  the  same  distance  without  them.     There- 

the  dit  of^F6^8  elllPtlca1'  mstead  of  hemispherical;  and  for  the  same  reason 
2  If  a  oirHP^  ™  1  ^naPPea^s  larger  than  when  it  is  high  in  the  heavens. 

eilir.se  I  <  ft  f^n  ed/owfeto  and  fr°  behind  a  slit'  *  aPPears  as  a  horizontal 
be  drawn  ohTn  T  rapidly,  it  appears  as  a  vertical  ellipse.  3.  If  a  fine  line 
be  drawn  obliquely  across  a  heavy,  black,  vertical  line,  the  former  appears  to 


ORGANS    FOR   THE    PROTECTION    OF    THE    EYE.  879 

deviate  from  its  original  direction  on  either  side  of  the  heavy  line.  4.  Three  hori- 
zontal parallel  lines,  i  cm.  apart,  are  drawn,  and  through  the  upper  and  lower 
ones  are  drawn  short  parallel  strokes  obliquely  from  above  and  to  the  left  down- 
ward and  to  the  right,  and  through  the  middle  line  similar  oblique  lines  from  the 
right  above  downward  and  to  the  left.  The  three  horizontal  lines  no  longer  ap- 
pear parallel.  5.  On  looking  at  a  bright,  vertical  line  in  a  dark  room,  and  in- 
clining the  head  toward  the  shoulder,  the  line  appears  to  be  rotated  in  the  oppo- 
site direction. 

ORGANS  FOR  THE  PROTECTION  OF  THE  EYE. 

The  Eyelids. — The  structure  of  the  eyelids  and  the  arrangement  of  their 
component  parts  are  shown  in  Fig.  309  and  the  accompanying  description.  The 
tarsus  is  composed  not  of  cartilage,  but  of  a  firm  connective-tissue  plate,  in  which 
the  Meibomian  glands  are  embedded.  They  are  acinous  sebaceous  glands  that 
anoint  the  lid-rriargin.  At  the  basal  margin  of  the  tarsus,  especially  the  upper, 
the  acinotubular  glands  of  Krause  have  their  opening  close  to  the  transition- 
fold  of  the  conjunctiva.  The  conjunctiva  covers  the  anterior  surface  of  the 
eyeball  as  far  as  the  corneal  margin,  the  cornea  being  covered  only  with  the  epi- 
thelium. The  conjunctiva  on  the  posterior  surface  of  the  lids  has  a  papillary 
structure  in  places,  the  furrows  of  which  have  been  considered  small  mucous 
glands  in  man  and  in  several  mammalia;  a  sharp  distinction  between  furrows  and 
glands,  however,  cannot  be  made.  The  epithelium  is  composed  of  layers  of 
columnar  cells,  with  intervening  goblet-cells.  Ruminants  possess  sweat-glands 
surrounding  the  cornea;  external  to  the  cornea,  toward  the  outer  canthus, 
the  pig  has  simple,  glandular,  blind  sacs.  Waldeyer  discovered  modified  sweat- 
glands  at  the  margin  of  the  tarsus  in  man.  Small  lymphatic  follicles  of  the  con- 
junctiva are  called  trachoma-glands.  The  lymph-vessels  of  the  conjunctiva  are 
connected  with  the  lymph-spaces  of  the  cornea  and  sclera.  Stohr  saw  leukocytes 
wander  upon  the  free  surface  of  the  conjunctiva.  Krause  found  end-bulbs  in  the 
conjunctiva  of  the  globe,  Dogiel  at  the  lid-margin.  The  secretion  of  the  conjunc- 
•tiva,  aside  from  some  mucus,  consists  of  the  lacrimal  fluid,  which  can  be  produced  in 
as  large  a  quantity  by  the  numerous  conjunctival  vessels  as  by  the  lacrimal 
glands  themselves. 

Closure  of  the  eyelids  is  effected  by  the  orbicularis  palpebrarum 
muscle  (facial  nerve),  the  upper  lid  falling  by  its  own  weight.  The 
muscle  contracts:  (i)  voluntarily,  (2)  involuntarily  in  individual  con- 
tractions (winking),  (3)  as  a  reflex  act  from  irritation  of  any  of  the 
sensory  fibers  of  the  trigeminus  distributed  to  the  eyeball  and  the 
surrounding  tissues,  likewise  from  intense  stimulation  of  the  retina  by 
light;  (4)  persistent,  involuntary  closure  occurs  during  sleep. 

Opening  of  the  lids  is  brought  about  by  passive  dropping  of  the  lower 
and  active  elevation  of  the  upper  lid  by  the  levator.  The  unstriated 
muscular  fibers  of  the  lids,  which  are  in  a  state  of  tonic  contraction,  act 
in  the  same  way  by  shortening  the  lid.  In  looking  downward  the  lower 
lid  is  drawn  down  by  bands  of  connective-tissue  fibers  running  from 
the  fascia  of  the  inferior  rectus  muscle  to  the  lower  tarsus. 

The  Lacrimal  Apparatus. — The  straight  and  freely  branching  tubules  of  the 
lacrimal  gland  have  secreting  cells,  which  are  tall  when  "loaded,"  and  contain 
a  reservoir  for  the  secretion  in  the  fine-meshed  protoplasm;  and  smaller  cells 
entirely  filled  with  secretion  in  the  form  of  large  drops.  A  dumbbell-shaped 
pair  of  rods  represents  the  nucleus  in  each  cell.  The  secretion  is  discharged  by 
contraction  of  the  protoplasm.  Intercellular  secretory  passages  penetrate  be- 
tween the  cells  to  the  level  of  the  nucleus.  A  terminal  intercellular  network 
is  formed  by  exceedingly  fine  nerve-fibers.  The  secretory  nerves  have  been 
described  on  p.  684.  Four  or  five  large,  and  from  eight  to  ten  small,  excretory 
ducts  convey  the  tears  into  the  fornix  conjunctivas,  just  above  the  outer  canthus. 
The  lacrimal  canaliculi,  with  their  open  extremities,  the  lacrimal  puncta,  dip  into 
the  lacrimal  lake.  The  ducts  are  composed  of  connective  tissue  and  elastic  fibers, 
and  are  lined  by  stratified  epithelium.  Striated  muscle-fibers  accompany  the 
ducts,  and,  by  their  contraction,  keep  them  open.  A  sphincter  surrounding  the 


88o 


ORGANS    FOR    THE    PROTECTION    OF    THE    EYE. 


punctum  was  overlooked  by  Toldt;  Gerlach  found  an  incomplete  sphincter- 
muscle.  The  canaliculi  empty  at  separate  points  into  a  dilatation  of  the  lacrimal 
sac.  The  connective-tissue  covering  of  the  sac  and  the  canal  is  united  to  the 
neighboring  periosteum.  The  thin  mucous  membrane,  rich  in  lymphoid  cells, 

has  a  double  layer  of  (ciliated  ?) 
cylindrical  epithelium,  which 
becomes  stratified  and  squa- 
mous  below.  The  opening  of 
the  canal  is  often  provided 
with  a  valve-like  fold  (Has- 
ner's  valve). 

The     tears     are     con- 
ducted   between   the   lids 
and  the  eyeball  by  capil- 
larity,   being    distributed 
evenly  by  the  movements 
of   winking.     The   Meibo- 
mian    secretion    prevents 
the  tears  from  overflowing 
the  lid-margins.     The  pas- 
sage of  the  tears  through 
the  puncta,  the  canaliculus 
and  the  canal  is  effected 
largely  by  siphonage,  but 
this  is  assisted  materially 
by      Homer's       muscle 
(known  also  to  Duvernoy 
in  1678),  which ,  with  every, 
act  of  winking,  draws  the 
posterior  wall   of  the   sac 
backward,  dilating  the  sac, 
and  thus  exerting  an  aspir- 
atory     influence     on     the 
tears.  Scimemi  has  demon- 
strated   this     experimen- 
tally   by     introducing    a 
fine  tube  through  the  wall 
into    the     lumen    of     the 
lacrimal    sac    (in    human 
beings      with      lacrimal 
fistula) :  fluid  is  aspirated 
in    this    tube   with    every 
closure  of  the  lids. 

E.  H.  Weber  and  v.  Has- 
ner  believe  that  the  tears  are 
aspirated  by  rarefaction  of 
the  air  in  the  nasal  cavities 
in  the  act  of  inspiration  and 
in  that  of  insufflation.  Arlt 
thinks  the  sac  is  compressed 
by  _  the  contraction  of  the 
orbicularis,  so  that  the  tears 


FIG. 


Lid 

corum;    B  and 


.—Vertical 

ieyer):  A,  cutis;  i,  epidermis;  .,  ^unum,  D  ana  7 
subcutaneous  connective  tissue;  C  and  7,  obicularis  muscle, 
with  its  bundles;  Z>,  loose,  submuscular  connective  tis- 
sue; E,  insertion  of  Heinrich  Miiller's  muscle-  F  tarsus' 
Cr,  C9njunctiva;  /,  inner  lid-margin;  k,  outer  lid-margin-' 
4,  Pigment-cells,  in  the  cutis;  5,  sweat-glands;  6,  hair- 
follicles  with  hairs;  8  and  23,  cross-section  of  nerves;  9, 
arteries;  10,  veins;  u,  aha;  12,  modified  sweat-glands 
^'n?  ary  ™usdS''-  J4'  orifice  of  a  Meibomian 

1,  15,  cross-section  of  its  acini;  16,  posterior  tarsal 
glands,  18  and  19,  tissue  of  the  tarsus;  20,  pretarsal  or 
submuscular  connective  tissue;  2I  and  22  conjunctiva 
with  its  epithelium;  24,  adipose  tissue;  loose-meshed 
posterior  extremity  of  the  tarsus;  26,  section  of  a  palpe- 


must  escape  toward  the  nose, 
illy,  Stellwag  believes  that 

-j -~  ^L  the  lids;   while  according 

tor  pumping  the  tears  into  the  lacrimo-nasal  canal  exists. 
lowever,  to  one  point,  namely  that  the  tissue  surrounding 


COMPARATIVE.       HISTORICAL.  88l 

the  sac  and  the  canal  contains  numerous  large  venous  radicles.  In  expiration, 
especially  in  forced  expiration,  these  radicles  swell,  and  press  the  walls  of  the 
ducts  together.  For  this  reason  air  cannot  be  driven  into  the  lacrimonasal 
canal,  even  by  forced  pressure.  If  strong  inspiratory  efforts  are  made,  as  in 
the  act  of  deep  frequent  insufflation,  the  veins  are  emptied,  and  as  the  walls  again 
retract  they  exert  an  aspiratory  influence  on  the  tears. 

The  secretion  of  tears  results  from  direct  irritation  of  the  lacrimal 
nerve,  the  subcutaneus  malae,  the  facial,  and  the  cervical  sympathetic, 
which  have  been  designated  the  secretory  nerves.  Reflex  secretion  of 
tears  may  be  brought  about  by  irritation  of  the  nasal  mucous  membrane 
on  the  same  side.  The  ordinary  secretion  in  the  waking  hours  is 
probably  a  reflex  result  of  irritation  of  the  anterior  surface  of  the  eye- 
ball (by  the  air,  by  evaporation  of  the  tears) ;  the  cornea  and  the  con- 
junctiva possess  sensibility  to  pain  and  touch,  to  cold  and  heat.  In- 
tense irritation  by  light  also  produces  a  reflex  flow  of  tears  through  the 
intermediation  of  the  optic  nerve.  In  the  rabbit  the  center  does  not 
extend  further  forward  than  the  origin  of  the  trigeminus,  but  it  extends 
downward  to  the  fifth  vertebra.  During  sleep  the  factors  mentioned 
are  absent,  and  the  tears  dry  up.  Reichel  under  the  direction  of  Heid- 
enhain  found  that  the  active  gland,  after  injection  of  pilocarpin,  con- 
tains cloudy,  granular  diminutive  cells,  with  obscure  outlines,  and  spher- 
ical nuclei,  whereas  in  the  resting  gland  the  cells  are  light  and  slightly 
granular,  with  irregularly  formed  nuclei.  The  overflow  of  tears  pro- 
duced by  emotion  is  still  unexplained,  -as  is  also  that  caused  by  hearty 
laughing.  In  coughing  or  vomiting,  the  secretion  of  tears  is  increased 
by  reflex  influences,  and  the  drainage  of  the  tears  is  impeded  by  the 
expiratory  pressure. 

The  tears  moisten  the  eyeball,  protect  it  from  desiccation,  and  carry 
off  small  particles,  with  the  assistance  of  winking.  Atropin  diminishes 
their  quantity. 

The  tears  are  alkaline  in  reaction  and  have  a  salty  taste ;  they  represent  a 
"serous"  secretion,  containing  from  98.1  to  99  per  cent,  of  water,  1.46  of  organic 
substances  (o.i  of  albumin  and  mucin,  o.i  of  epithelial  cells),  from  0.4  to  0.8 
of  salts  (principally  sodium  chlorid). 

Pathologically,  bacteria  arc  present;  in  the  secretion  within  the  lacrimal 
canal,  streptothrix. 

COMPARATIVE.     HISTORICAL. 

Comparative. — The  simplest  form  of  visual  apparatus  consists  of  deposits 
of  pigment  in  the  external  covering  of  the  body  connected  with  the  terminations 
of  afferent  nerves.  The  pigment  absorbs  the  light-rays  and  undergoes  a  chemical 
change  as  "visual  substance,"  and,  as  a  result  of  the  action  of  the  luminiferotts 
ether,  it  discharges  kinetic  energy,  which  stimulates  the  terminations  of  the  nervous 
end-apparatus.  Deposits  of  pigment  with  efferent  nerves,  and  in  addition  a  bright, 
refractive  body,  are  found  in  the  margins  of  the  swimming-bells  of  the  higher 
medusae,  while  the  lower  forms  have  spots  of  pigment  only  at  the  base  of  the 
tentacles.  In  many  of  the  lower  worms  there  are  spots  of  pigment  near  the 
brain.  In  the  earthworm  the  head  is  sensitive  to  light  because  of  the  presence 
of  light-cells,  the  caudal  end  less  so.  In  others  the  pigment  surrounds  the  nerve- 
endings,  which  are  represented  by  the  so-called  crystalline  rods,  or  crystalline 
balls  (for  example  the  rotifera,  or  wheel-animalcules).  In  leeches  the  eyes. 
which  are  usually  situated  in  the  head,  are  not  typically  developed.  Many  of 
the  lower  worms,  and  especially  the  parasites,  possess  no  visual  apparatus  whatever. 
In  starfishes  the  eyes  are  in  the  ends  of  the  arms,  and  consist  of  spherical  crystal- 
line organs,  surrounded  by  pigment,  and  supplied  with  nerves.  In  all  the  other 
echinodcrms,  only  deposits  of  pigment  are  present.  Among  the  articulates 
eyes  in  different  stages  of  devejopment  are  met  with:  i.  Eyes  without  cornea  that 
56 


882 


COMPARATIVE.       HISTORICAL. 


may  consist  of  single  crystalline  cones,  surrounded  by  pigment  (nervous  end- 
organ),  are  found  in  the  neighborhood  of  the  brain  (the  larvae  of  some  crabs), 
or  there  may  be  several  crystalline  rods  in  the  compound  eye  (lower  crabs).  2. 
Eyes  with  cornea,  which  consists  of  a  lenticular  shaped,  chitinous  formation  of 
the  outer  external  integument,  are  found  to  be  either  simple,  consisting  of  a  single 
crystalline  rod,  or  compound.  The  latter  have  either  only  one  large  lens-shaped 
cornea,  common  to  all  the  crystalline  rods,  as  in  spiders  (Fig.  310);  or  each 
crystalline  rod  possesses,  for  itself  a  special  lens-shaped  cornea.  The  numerous 
rods,  surrounded  by  pigment,  are  placed  close  together,  and  form  a  curved  sur- 
face. The  chitinous  covering  of  the  head  is  faceted,  and  forms  a  cornea-lens 
on  the  surface  of  each  rod  (Fig.  311).  There  are  two  theories  as  to  the  way  in 
which  the  image  is  produced  by  this  compound  eye  of  the  arthropods.  According 


rz 


k 


FIG.  310. — Eye  of  the  Cross-spider,  according  to 
Grenacher;  decolorized:  cl,  cornea-lens; 
hz,  hypodermal  cells;  b,  basal  membrane; 
gkz,  vitreous  cells;  rz,  retinal  cells;  k,  nuclei 
of  the  retinal  cells;  s,  rods;  n,  nerve. 

to  one,  each  facet,  with  the  lens  and  crystal  sphere, 
is  a  separate  eye:  while  man  has  two  eyes,  the  in- 
sect is  supposed  to  have  many  hundreds  of  eyes. 
Each  eye  sees  the  image  of  the  outer  world  as  a 
whole.  The  following  experiment  of  Ant.  Leeuwen- 
hoeck  seems  to  indicate  this:  If  the  cornea  is  cut 
off,  each  of  its  facets  forms  a  separate  image  of 
objects.  If,  for  example,  a  cross  is  placed  on  the 
mirror  of  a  microscope,  while  a  piece  of  faceted 
cornea  is  plated  as  an  object  on  the  stage,  an  image 
of  the  cross  can  be  seen  in  each  facet.  Consequently 
a  separate  image  would  be  formed  for  each  rod 
(crystal-sphere).  This  takes  place,  however,  only 
when  the  crystal-sphere  is  removed.  In  combina- 
tion with  the  latter,  each  corneal  facet  forms  only 
a  part  of  the  (upright)  image  of  the  external 
world,  so  that  the  image  must  be  conceived  to  be 
composed  like  a  mosaic  (mosaic  vision).  The 
Rontgen  rays  appear  to  be  visible  to  insects  (flics) . 
Among  molluscs  the  fixed  brachiopods  have  two 
pigment-spots  near  the  brain,  but  only  in  their  free 
larval  condition.  Similarly,  the  larvae  of  mussels 

have  pigment-spots  with  refractive  bodies.  Adult  mussels,  however,  have  pigment- 
spots  only  at  the  margin  of  the  mantle,  but  some  of  them  have  pedunculated, 
emerald-lustrous  highly  developed  eyes.  Among  the  snails  several  of  the  lower 
forms  possess  no  eyes  at  all,  others  have  a  pair  of  pigment-spots  on  the  head,  and 
a  number  have  eyes  in  various  stages  of  development  (Figs.  312,  313).  The 
garden-snail  has  its  eyes  on  a  special  pedicle,  and  they  are  provided  with  a  cornea, 
optic  nerve,  retina,  and  finally,  even  lens  and  vitreous.  Of  the  ccphalopods 
the  nautilus  has  no  cornea  or  lens,  and  the  seawater  flows  freely  into  the  ocular 
cavity.  Others  possess  a  lens,  but  the  cornea  is  absent,  while  still  others  have  an 


FIG  .311 . — Individual  Eye  of  a  Libel- 
lula  Larva  (Dragon-fly),  diagram- 
matic and  simplified,  according  to 
Carriere:  a,  longitudinal  section; 
b,  cross-section;  cl,  cornea-lens; 
kz,  crystal  sphere  (cells);  hz,  hy- 
podermis  cells;  p,  pigment-cells; 
rz,  retinal  cells,  surrounding  rh  , 
the  retinal  rod. 


COMPARATIVE.       HISTORICAL.  883 

opening  in  the  cornea  (sepia,  octopus,  loligo) ;  all  other  parts  of  the  eyes  are  well 
developed.  The  eye  of  the  vertebrates  needs  no  detailed  description.  The 
amphioxus  is  without  eyes,  which  are  undeveloped  in  proteus,  and  in  the  mammal 
spalax,  whose  life  in  the  dark  has  caused  the  visual  organ  to  atrophy.  In  many  fishes, 
amphibians  and  reptiles  the  eye  is  covered  by  skin,  which  has  become  transparent. 
Several  varieties  of  sharks,  crocodiles,  and  birds  have  eyelids,  and,  in  addition, 
a  nictitating  membrane  in  the  inner  angle  of  the  eye.  Connected  with  it  is  the 
Harderian  gland.  In  mammals  the  nictitating  membrane  is  reduced  to  the  plica 
semilunaris.  There  is  no  lacrimal  apparatus  in  fishes.  The  tears  of  reptiles 
remain  under  the  watchglass-shaped  cuticular  covering  that  extends  over  the 
eye.  The  sclera  of  the  osseous  fishes  has  two  bands  of  cartilage,  which  are  often 
ossified;  from  the  middle  of  the  choroid,  a  muscular  organ  (falciform  process) 
proceeds  forward,  and  its  anterior  enlarged  extremity,  which  is  called  the  campanula 
H alien,  is  inserted  into  the  outer  margin  of  the  lens.  The  campanula,  called 
by  Beer  the  retractor  muscle  of  the  lens,  pulls  the  lens  nearer  to  the  retina,  and 
in  this  way  produces  an  accommodation  for  distance  (the  eye  being  accommodated 
for  near  vision,  when  at  rest) .  In  birds  the  similar  muscular  structure,  the  pecten, 
often  reaches  nearly  to  the  lens-capsule.  The  cornea  of  birds  is  surrounded  by  a 


FIG.  312.— Eye  of  a  Sea-snail  (Patella 
coerulea),  diagrammatic  and  sim- 
plified, according  to  Fraisse;  the 
Nerve  according  to  Hilger:  e, 
body-epithelium;  r,  retinal  cells; 
n,  nerve. 

bony  ring.  In  the  birds  of  prey  the  cornea 
changes  with  the  lens.  The  whale  has  a  tremen- 
dously thick  sclera.  The  lens  in  the  aquatic 

animals  is  strongly  convex.     The  muscles  of  the  FIG.  313. — Eye  of  a  Sea-snail 

iris  and  the  choroid  are  striated  transversely  in  tuberculata),  diagrammatic  and  sim- 

reptiles  and  in  birds.     It  should  yet  be  especially  ^SSTSg,  %£S$S?&S& 

mentioned    that    the    retinal   rods  of    vertebrates  body  inside;    r,  retina;    n,  branched 

(most     reptiles     have     no    rods    in    the    retina  nerve, 

and  no  visual  purple)  are  directed  from  before 

backward,  while  the  analogous  elements  in  invertebrates  (crystalline  rods,  and 
spheres)  are  directed  from  behind  forward.  In  the  prehistoric  salamanders, 
the  existence  of  a  third  eye  is  assumed  in  the  parietal  region  (parietal  eye) .  The 
pineal  gland  of  vertebrates  appears  to  be  the  atrophic  remnant  of  the  parietal 
eye.  In  lizards  the  parietal  eye  is  present  beneath  the  skin,  which  is  transparent 
in  the  iguana,  so  that  it  serves  here  probably  in  small  measure  as  a  visual  ap- 
paratus. 

The  investigations  of  Loeb  have  shown  that  (as  in  plants)  the  direction  of 
the  visual  rays  has  an  influence  on  the  direction  of  movement  of  many  animals — 
heliotropism.  In  fact  many  animals  without  eyes  exhibit  heliotropism.  Some 
turn  toward  the  light,  others  away  from  it.  By  increasing  the  temperature  or 
the  concentration  of  the  surrounding  sea-water,  Loeb  was  able  to  reverse  this 
action. 

Historical. — The  Platonics  and  Stoics  considered  the  visual  act  as  material. 
Rays  of  light  were  supposed  to  proceed  from  the  eye  and  from  the  objects,  and 
to  meet,  and  the  rays  from  the  eye  to  return  to  it  with  the  feeling  of  the  object 
The  Epicureans  believed  that  small  corporeal  images  proceeded  directly  from 
the  objects;  the  Peripatetics  that  the  images  were  noncorporeal.  According 
to  Aristotle  the  eye  does  not  take  from  the  object  any  of  its  substance,  but  only 
its  semblance,  as  the  wax  takes  the  impression  of  the  seal.  The  Greeks  were 


884  COMPARATIVE.       HISTORICAL. 

familiar  with  the  ideas  of  fixation-point,  field  of  vision,  binocular  single  and  double 
vision.  Descartes  originated  the  hypothesis  of  the  vibrations  of  the  ether,  which 
were  supposed  to  exist  also  in  the  eye,  and  to  stimulate  the  nerve.  The  following 
may  be  mentioned  with  regard  to  the  different  parts  of  the  eye,  and  their  functions: 
The  school  of  Hippocrates  knew  of  the  optic  nerve  and  the  lens.  Aristotle  (384 
B.  C.)  records  the  fact  that  division  of  the  optic  nerve  as  a  result  of  injury  causes 
blindness.  He  was  familiar  with  after-images,  mentions  hyperopia  and  myopia, 
states  that  blue  eyes  exhibit  more  vigorous  iris-reactions  on  exposure  to  light 
than  dark  eyes,  and  that  man  alone  has  cilia  on  both  eyelids.  He  mentions  a 
man  who  was  able  to  see  visions,  as  Quinctilian  relates  of  the  painter  Theon  von 
Lamos.  Herophilus  (307  B.  C.)  discovered  the  retina;  the  ciliary  body  was  first 
recognized  in  his  school.  Galen  (131-203  A.  D.)  described  the  six  ocular  muscles, 
the  lacrimal  puncta,  and  the  tear-ducts.  According  to  him,  the  retina  receives  the 
impressions  of  light:  he  refers  the  origin  of  the  optic  nerve  to  the  thalamus. 
Berengar  (1521)  was  aware  of  the  oily  condition  of  the  lid-margins;  Stephanus 
(1545)  and  Casseri  (1609)  mentioned  the  Meibomian  glands,  which  were  named 
after  Meibomius  (1666).  Aranzi  described  (1586)  the  muscles  of  the  lid.  Fallopia 
designated  the  hyaloid  membrane  and  the  ciliary  ligament.  Plater  emphasized 
the  greater  curvature  of  the  posterior  surface  of  the  lens  (1583).  Aldrovardi 
saw  vestiges  of  the  pupillary  membrane  (1599). 

Even  in  the  time  of  Vesalius  (1540)  the  refractive  power  of  the  lens  was 
discussed:  Porta  (1560)  compared  the  eye  to  the  camera  obscura,  and  Maurolykos 
the  action  of  the  lens  to  that  of  a  lens  of  glass,  but  Kepler  (1611)  was  the  first  to 
show  the  true  refractive  indices  of  the  eye,  and  the  formation  of  the  retinal  image; 
he  believed,  however,  that  accommodation  was  effected  by  the  movement  of  the 
retina  backward  and  forward.  The  Jesuit  father  Scheiner  (1619)  proved,  how- 
ever, that  the  lens  was  made  more  convex  by  the  ciliary  processes,  and  he  assumed 
the  existence  of  muscle-fibers  in  the  uvea.  At  the  same  time  he  recognized  the  si- 
multaneous contraction  of  the  pupil  in  accommodation  for  near  vision.  He  believed 
myopia  and  hyperopia  to  be  due  to  the  curvature  of  the  lens,  and  he  first  showed 
the  inverted  image  on  the  retina  of  an  enucleated  eye.  Briggs'  remark  (1676), 
"  Ligamentum  ciliare  e  fibris  motricibus  constans,"  likewise  the  analogous  one  of 
Ruysch  (1743) ,  led  Morgagni  to  the  correct  interpretation  of  the  process  of  accom- 
modation. Edm.  Mariotte  recognized  that  the  reflex  from  the  pupil  arose  from 
reflected  light  (1668).  As  to  the  use  of  glasses,  there  is  a  note  as  early  as  Pliny. 
At  the  beginning  of  the  fourteenth  century,  the  Florentine,  Sal  vino  d'Armato 
degli  Armati  di  Fir  (died  1317),  is  said  to  have  invented  them;  likewise  the  Pisan 
monk  Alessandro  de  Spina  (died  1313).  Kepler  in  1611,  and  Descartes  in  1637 
were  the  first  to  explain  their  action  correctly.  Huyghens  made  an  apparatus 
in  imitation  of  the  eye,  and  showed  upon  it  the  action  of  glasses  (1695).  Tne 
struggle  of  the  visual  fields  is  ascribed  to  Gassendus  (1658).  Agulonius  (1613) 
occupied  himself  with  the  horopter.  Briggs  (1676)  surmised  that  single  vision 
occurred  when  the  object  formed  an  image  on  homologous  fibers  of  the  retina: 
de  Peiresc  described  positive  and  negative  after-images  (1634) ;  v.  Muschenbroeck 
knew  of  the  color-top  (1762).  Leonardo  da  Vinci  (died  1519)  was  well  acquainted 
with  contrast-phenomena,  Otto  v.  Gericke  (1672)  with  the  colored  shadows, 
Kepler  (1611)  with  irradiation.  The  last  named  explained  correctly  upright 
vision,  the  perception  of  depth,  and  the  estimation  of  distance.  Nuck  analyzed  the 
aqueous  humor  (1688) ,  Chrouet  the  lens  (1688).  De  la  Hire  (the  younger)  ascribed 
to  the  aqueous  and  the  vitreous  the  same  refractive  power,  and  tested  that  of  the 
lens  and  the  cornea  (1707).  Maitre-Jean  referred  the  movement  of  the  iris  to  its 
circular  and  radial  fibers  (1707).  Knowledge  of  the  eye  was  greatly  advanced 
by  Zinn  (1755).  Ruysch  described  the  muscular  fibers  of  the  iris,  Monro  (1794) 
later  the  sphincter  of  the  pupil  more  fully.  Berzelius  demonstrated  chemically  the 
presence  of  muscle-tissue  in  the  iris.  Jacob  discovered  the  layer  of  rods  of  the 
retina.  Sommering  (1791)  first  described  the  yellow  spot.  Ant.  Leeuwenhoeck 
knew  of  the  lens-fibers.  Reil  noted  the  star-shaped  fissility  of  the  lens.  Berzelius 
examined  chemically  the  lens,  the  aqueous,  the  vitreous,  the  pigment,  and  the 
tears.  Young  first  observed  astigmatism  (1801).  Brewster  and  Chossat  (1819) 
tested  the  refractive  power  of  the  ocular  media.  Purkinje  studied  subjective 
vision  thoroughly  (1819).  Helmholtz'  "Physiological  Optics"  summed  up  the 
entire  science  in  a  classical  work  (1856-66). 


THE    AUDITORY    APPARATUS.  885 

THE  AUDITORY  APPARATUS. 

PLAN  OF  THE  STRUCTURE   OF  THE  EAR. 

The  auditory  nerve  is  excited  normally  by  waves  of  sound, 
which  are  supposed  to  set  in  vibration  the  end-organs  of  the  auditory 
nerve.  These  lie  in  the  endolymph  of  the  labyrinth  of  the  inner  ear,  on 
membranous  expansions  of  the  cochlea,  the  saccule  and  utricle,  and  the 
semicircular  canals.  The  waves  of  sound  are  first  communicated  to  the 
labyrinthine  fluid,  producing  wave-motions  that  set  up  similar  vibrations 
in  the  nerve-endings.  The  stimulation  of  the  auditory  nerve  is  brought 
about,  therefore,  by  the  mechanical  irritation  produced  by  the  un- 
dulations of  the  labyrinthine  fluid. 

The  labyrinthine  fluid  is  enclosed  in  the  extraordinarily  dense  and 
hard  mass  constituting  the  petrous  portion  of  the  temporal  bone  (Fig. 
314).  At  one  situation  in  the  shape  of  a  small,  rounded  triangle  (fenes- 
tra  rotunda),  the  boundary  is  formed  of  a  delicate,  yielding  membrane, 
the  opposite  side  of  which  is  in  contact  with  the  air  in  the  tympanum 
(P).  Not  far  from  the  fenestra  rotunda  is  the  fenestra  ovalis  (o),  into 
which  the  basal  plate  of  the  stapes  (s)  is  fixed  by  means  of  a  yielding 
membranous  ring.  The  outer  surface  of  this  also  is  in  contact  with  the 
air  in  the  tympanum.  As  the  labyrinthine  fluid  is  enclosed  at  these  two 
places  by  flexible  boundaries,  it  is  evident  that  it  is  capable  of  an  undu- 
latory  movement,  as  yielding  limiting  membranes  are  able  to  follow  these 
undulations. 

If  it  be  asked  further,  in  what  ways  the  waves  of  sound  can  set  the 
labyrinthine  fluid  in  movement,  three  different  methods  suggest  them- 
selves: 

i.  Conduction  through  the  bones  of  the  skull.  This  takes  place 
especially  when  solid,  sounding  bodies  are  placed  directly  on  the  head 
(for  example,  a  tuning-fork;  the  sound  is  then  propagated  most  strongly 
in  the  direction  of  the  prolonged  handle  of  the  tuning-fork),  also  when 
the  sound  is  transmitted  to  the  head  through  fluids  (for  example,  water 
under  which  the  head  is  submerged).  If  the  external  auditory  canal 
is  stopped  up,  the  vibrations  of  the  tuning-fork  are  more  strongly  heard. 
From  this  it  has  been  concluded  that  the  vibrations  in  the  bone  set  the 
air  in  the  middle  ear  and  the  auditory  canal  in  vibration,  and  that  this 
is  communicated  to  the  tympanic  membrane,  so  that  the  stimulation 
arises  from  this,  as  under  normal  circumstances — craniotym panic  stimu- 
lation. Waves  of  sound  in  the  air  are  practically  not  transmitted  to  the 
bones  of  the  skull,  as  is  shown  by  the  inability  to  hear  when  the  ears 
are  closed. 

Of  the  soft  parts  belonging  to  the  head,  only  those  that  are  directly  in  contact 
with  the  bones  conduct  sound  well;  of  the  detached  portions,  the  cartilaginous 
part  of  the  external  ear  is  the  best  conductor.  Even  under  the  most  favorable 
circumstances,  conduction  through  the  bones  of  the  skull  affords  less  favorable 
conditions  for  excitation  of  the  auditory  nerves  than  conduction  of  the  sound 
through  the  auditory  canal.  For  example,  if  a  vibrating  tuning-fork  be  held 
between  the  teeth  until  its  sound  is  no  longer  heard,  its  tone  may  be  still  distinctly 
heard  if  it  is  brought  quickly  in  front  of  the  ear.  Sounds  are  also  better  con- 
ducted through  the  bones  of  the  skull  if  the  oscillations  arc-  not  freely  transmitted 
by  the  bones  to  the  tympanic  membrane,  and  by  this  to  the  air  of  the  auditory 
canal.  Therefore,  sounds  are  heard  better  if  the  ears  are  closed  at  the  same  time, 


886 


PRELIMINARY    PHYSICAL    CONSIDERATIONS. 


as  the  transmission  is  thus  restricted.  If  in  persons  hard  of  hearing  conduction 
and  hearing  through  the  bones  of  the  skull  are  still  normal,  the  cause  of  the  deaf- 
ness is  not  in  the  nervous  parts  of  the  ear,  but  in  the  external  sound-conducting 
part  of  the  apparatus. 

2.   Normal   conduction,   in   ordinary   hearing  through   the   external 
auditory  canal,  takes  place  as  follows:  the  vibrations  of  the  air  first  set 

the  tympanic  mem- 
brane (Fig.  314,  T) 
into  vibration ;  this 
in  turn  moves  the 
malleus  (h),  the 
incus  (a),  and  the 
stapes  (s),  the  last 


of  which  transmits 
the  vibrations  of 
its  base  to  the  fluid 
of  the  labyrinth. 

3.  In  individ- 
uals, in  whom  as 
a  result  of  destruc- 
tive disease  of  the 
middle  ear,  the 
tympanic  mem- 
brane and  the 
ossicles  are  de- 
stroyed, stimula- 
tion of  the  auditory 
apparatus  can  take 
place  (to  be  sure, 
only  in  an  impaired 
degree)  also  by  a 
transmission  of  the 


FIG.  314. — Diagrammatic  Representation  of  the  Auditory  Apparatus:  AG, 
external  auditory  canal',  T,  tympanic  membrane,  K,  malleus,  with  its 
head  (h),  short  process  (kf)  and  manubrium  (m);  a,  incus,  with  its 
short  process  (x)  and  long  process,  which  is  united  with  the  stapes  (s) 
by  the  os  orbiculare  (ossicle  of  Sylvius);  P,  tympanic  cavity,  o,  oval 
window;  r,  round  window,  X,  beginning  of  the  lamina  spiralis  of  the 
cochlea;  pt,  the  scala  tympani,  and  vt,  the  scala  vestibuli;  V,  vesti- 
bule; S,  saccule;  U,  utricle;  H,  semicircular  canals;  TE,  Eustachian 
tube.  The  long  arrow  indicates  the  direction  of  action  of  the  tensor 
tympani  muscle,  the  short  curved  arrow  that  of  the  stapedius  muscle. 


atmospheric  vibra- 

tions directly  to  the  membrane  covering  the  fenestra  rotunda  (r)  and  the 
structure  closing  the  fenestra  ovalis  (o).  The  membrane  of  the  fenes- 
tra rotunda  can,  in  fact,  be  set  in  vibration  alone,  even  if  the  parts  clos- 
ing the  fenestra  ovalis  have  become  unyielding. 


PRELIMINARY  PHYSICAL  CONSIDERATIONS. 

Sound  is  produced  by  the  oscillations  of  elastic  bodies  capable  of  vibration. 
These  oscillations  cause  alternate  condensations  and  rarefactions  of  the  surround- 
ing air;  or  in  other  words  waves,  in  which  the  particles  vibrate  longitudinally, 
that  is  in  the  direction  of  transmission  of  the  sound.  These  condensations  and 
rarefactions  form  concentric  hollow  spheres  around  the  point  of  origin  of  the 
sound,  which  propagate  the  sound-vibrations  to  the  ear.  The  vibrations  of 
sonorous  bodies  are  called  stationary  vibrations,  that  is  all  of  their  particles  are 
always  in  the  same  phase  of  movement,  as  they  begin  to  move  simultaneously, 
reach  the  maximum  of  vibration  at  the  same  time,  and  begin  the  return  motion 
at  the  same  time  as,  for  example,  the  particles  of  a  sounding,  vibrating  metallic 
rod.  Sound  is  produced,  therefore,  by  the  stationary  vibrations  of  elastic  bodies, 
and  it  is  propagated  by  advancing  wave-motions  of  elastic  media  (ordinarily  of 
the  air).  The  wave-length  of  a  tone,  that  is  the  distance  between  one  maximum 
of  condensation  and  the  succeeding  one  in  the  air  (or  between  two  condensation- 
spheres  of  the  air)  is  proportional  to  the  time  of  oscillation  of  the  body  whose 
vibrations  produce  the  sound-waves. 


AURICLE.       EXTERNAL    AUDITORY    CANAL.  887 

If  /  is  the  wave-length  of  a  tone,  t  the  time  in  seconds  of  an  oscillation 
of  the  body  producing  the  wave,  then  /  =  nt,  in  which  n  =  340.88  meters 
the  velocity  in  each  second  of  sound- transmission  through  the  air.  The  ve- 
locity of  sound-transmission  in  water  has  been  found  to  be  1435  meters 
in  each  second — or  about  four  times  as  great  as  in  air,  In  solid  sonorous  bodies, 
it  is  from  7  to  18  times  greater  than  in  air.  Sound  is  conducted  best  when  it 
remains  in  one  medium;  if  it  passes  through  different  media,  it  is  always  weakened. 

Reflection  of  sound-waves  occurs  when  they  strike  a  solid  obstacle,  in  which 
case  the  angle  of  reflection  is  always  equal  to  the  angle  of  incidence. 

At  this  place  some  additional  facts  relating  to  wave-movements  may  be  stated. 
Two  varieties  of  wave-movements  are  distinguished: 

I.  Progressive  Wave-movements. — These  can  appear  in  two  different  forms: 
As    longitudinal    waves,   in    which    the    individual    particles    of    the    oscillating 
body  vibrate  about  their  center  of  gravity  in  the  direction  of  the  propagation 
of  the  wave.     To  these  belong  the  waves  in  water  and  in  air.     In  this  form  of 
motion,  the  particles  are,  of  necessity,  heaped  up  in  certain  places,  for  example, 
on  the  crests  of  water-waves,  while  in  other  places  they  are  diminished  in  number. 
This  form  of  wave  is,  therefore,  called  a  wave  of  condensation  and  rarefaction. 
If,  however,  each  particle  in  the  advancing  wave  moves  only  up  and  down  ver- 
tically, that  is  transversely  to  the  direction  of  propagation  of  the  wave,  then 
there  result  simple  transverse  waves  or  progressive  flexion-waves,  in  which  there 
is  no  condensation  or  rarefaction  in  the  direction  of  propagation,  as  the  particles 
are  merely  displaced  laterally.     An  example  of  this  wave-motion  is  afforded  by 
the  progressive  waves  in  a  rope. 

II.  Stationary   Flexion-waves. — If   all   the   particles   of   an   elastic   vibrating 
body  oscillate  in  such  a  manner  that  they  are  always  in  the  same  phase  of  move- 
ment, like  the  two  prongs  of  a  sounding  tuning-fork,  or  a  twanged  cord,  the  resulting 
movements  are  designated  stationary  flexion-waves.     As  bodies  of  little  extent  in 
the  direction  of  oscillation  vibrate  to  and  fro  in  stationary  flexion -waves,  it  is 
evident  that  the  small  parts  of  the  auditory  apparatus  also  (tympanic  membrane, 
auditory   ossicles,   endolymph)    oscillate  in   stationary  flexion -waves.     Stretched 
strings,  interrupted  by  nodal  points,  can  also  execute  stationary  flexion-waves  in 
individual  segments. 


AURICLE.     EXTERNAL  AUDITORY  CANAL. 

When  the  cartilaginous  (elastic)  auricle  is  absent,  the  acuteness  of  hearing 
is  but  little  altered.  Consequently  the  auricle  is  physiologically  of  minor  im- 
portance. It  has  been  supposed  that  the  elevations  and  depressions  of  the  auricle 
have  a  favorable  action  in  reflecting  the  sound-waves.  Many  of  the  latter  are 
manifestly  reflected  outward  again,  and  those  that  reach  the  deep  part  of  the 
concha  are  supposed  to  be  thrown  against  the  tragus,  to  be  reflected  from  this  into 
the  external  auditory  canal.  It  has  also  been  suggested  that  the  auricle  intensi- 
fies the  sound  by  oscillating  in  unison  with  it.  By  filling  the  depressions  of  the 
auricle  with  wax,  up  to  the  meatus,  Schneider  claims  to  have  reduced  the  acute- 
ness  of  hearing,  but  Harless  and  Esser  found  it  unchanged.  Against  the  assump- 
tion that  there  is  an  effective  reflection  of  the  sound-waves  both  from  the  parts 
of  the  auricle  and  from  the  walls  of  the  canal,  Mach  with  justice  raises  the  objection 
that  the  dimensions  of  these  parts  are  too  small  in  comparison  to  the  wave-lengths 
of  sounds.  Finally,  it  has  been  assumed  that  the  auricle,  as  an  independent, 
elastic  plate,  takes  up  the  sound-waves,  and  conducts  them  to  the  cranial  bones; 
so  that,  in  this  way,  the  stimulation  of  the  auditory  nerves  is  strengthened.  As, 
however,  the  conduction  of  sound  through  the  bones  of  the  skull,  from  the  air,  is 
exceedingly  slight,  no  serious  consideration  can  be  given  to  such  a  theory. 

According  to  Kessel  there  are  in  the  auricle  five  situations  from  which  the 
sound  is  conducted  to  the  ear,  in  varying  degree,  when  the  head  is  held  still; 
or  if  the  head  is  moved,  variations  in  intensity  will  occur.  If  the  posterior  surface 
of  the  auricle  is  covered  with  rubber,  the  acuity  of  hearing  and  the  ability  to  local- 
ize sound-impressions  coming  from  behind  are  decreased. 

Muscles  of  the  External  I'.ar. —  (i)  The  entire  auricle  is  moved  by  the  retrahens, 
attrahens,  and  attolens.  (2)  The  form  of  the  auricle  may  be  altered  by  the 
tragicus,  an titragicus,  helicis  major  and  minor  internally;  and  by  the  transversus 
and  obliquus  auriculae  externally.  Individuals  who  can  move  their  ears  observe 
no  alteration  in  hearing  during  the  movement.  The  helicis  major  and  minor 


888 


THE    TYMPANIC    MEMBRANE 


FIG.  315. — The  External  Auditory  Canal,  and 
the  Tympanum:  M,  cavities  in  the  tem- 
poral bone;  PC,  cartilaginous  portion  of 
the  canal;  Po,  osseous  portion  of  the  canal; 
L,  membranous  portion  between  them; 
F,  glenoid  cavity  for  the  condyle  of  the 
lower  jaw  (Urbantschitsch). 


are  elevators  of  the  helix;    the  transverse  and  oblique  muscles  of  the  auricle  are 

dilators  of  the  depressions  in  the  auricle;  the  tragicus  and  antitragicus  are  con- 
strictors of  the  canal;  they  correspond 
to  analogous  muscles  in  animals.  In 
animals,  however,  the  auricle  and  its 
muscular  activity  have  a  decided  in- 
fluence upon  hearing.  The  muscles,  in 
the  first  place,  direct  the  openings  of 
the  auricles  toward  or  away  from  the 
source  of  the  sound  (pricking  up  the 
ears).  The  internal  muscles,  moreover, 
contract  or  dilate  the  cavity  of  the 
auricle.  In  many  diving  animals,  valve- 
like  appendages  close  the  canal.  The 
human  auricle  may  be  most  appropriately 
considered  as  a  perfectly  formed  but 
functionally  degenerate  organ. 

The  external  auditory  canal  measures 
from  3  to  3.25  cm.  in  length,  from  8 
to  9  mm.  in  height,  and  from  6  to  8 
mm.  in  breadth  at  the  meatus;  it  is 
the  conductor  of  the  sound-waves  to 
the  tympanic  membrane.  As  it  has 
a  slightly  spiral  curve  (in  order  to 
look  into  the  canal,  the  auricle  should 
be  drawn  upward),  almost  all  of  the 
sound-waves  strike  first  against  its  wall, 
and  are  reflected  thence  to  the  tympanic 
membrane.  Occlusion  of  the  auditory 
canal,  especially  by  masses  of  inspissated 

cerumen    (secreted    by    the    ceruminous    glands,  which    are    similar    to    swreat- 

glands) ,  interferes,  naturally,  with  the  hearing. 

THE  TYMPANIC  MEMBRANE. 

The  tympanic  membrane  (Fig.  316)  is  an  unyielding,  and  almost  inexpansible, 
elastic  membrane,  with  a  thickened  border,  set  in  a  special  bony  groove,  and 
stretched  rather  loosely.  It  is  about  o.i  mm.  thick,  50  sq.  mm.  in  area  (in  small 
animals  not  much  smaller),  elliptical  in  shape  (its  larger  diameter  is  from  9^5 
to  10  mm.,  its  smaller  8  mm.),  and  it  is  placed  obliquely  at  the  inner  extrem- 
ity of  the  external  auditory  canal  at  an  angle  of  40°  from  above  down- 
ward and  inward.  Both  membranes  converge  anteriorly  so  that,  if  prolonged, 
they  would  meet  at  an  angle  of  from  130°  to  135°.  The  oblique  position  allows 
the  membrane  to  present  a  greater  surface  than  if  it  were  placed  vertically,  and 
thus  many  more  waves  of  sound  can  fall  vertically  upon  it.  The  membrane  is 
not  evenly  stretched,  but  is  drawn  inward  just  below  the  center  (umbo)  by  the 
handle  of  the  malleus,  which  is  attached  to  it;  while  the  short  process  of  the  mal- 
leus projects  forward  somewhat  at  the  upper  edge  of  the  membrane  (Figs.  314 
and  315). 

The  tympanic  membrane  consists  of  three  layers:  (i)  The  membrana  propria 
is  a  fibrous  membrane,  composed  of  radial  fibers  on  its  outer  surface,  and  of  circular 
fibers  on  its  inner  surface.  (2)  The  surface  facing  the  external  auditory  canal 
has  a  thin  covering  of  cuticle.  (3)  The  side  facing  the  tympanic  cavity  has  a 
delicate  mucosa  with  a  single  layer  of  squamous  epithelium.  Numerous  nerves 
and  lymph- vessels,  as  well  as  internal  and  external  blood-vessels  are  found  in 
the  membrane. 

The  tympanic  membrane  takes  up  the  sound-waves  that  enter  the 
auditory  canal,  and  is  set  into  vibration  by  them,  in  correspondence  with 
the  number  and  amplitude  of  the  movements  of  the  sound-waves  in  the 
air.  Politzer  connected  the  ossicles  attached  to  the  tympanic  mem- 
brane of  a  duck  with  a  recording  apparatus,  and  was  able  to  register  the 
vibrations  of  the  membrane  produced  by  sounding  any  tone.  On 
account  of  its  small  dimensions  the  tympanic  membrane  moves  to  and 


THE    TYMPANIC    MEMBRANE. 


889 


fro  as  a  whole  in  accordance  with  the  condensations  and  rarefactions  of 
the  undulating  air  (in  the  direction  of  the  sound-waves).  The  mem- 
brane, therefore,  makes  transverse  vibrations,  for  which  it  is  especially 
adapted,  owing  to  the  relatively  slight  resistance. 

Stretched  cords  and  membranes  are  set  into  decided  sympathetic  vibration 
only  when  they  are  affected  by  tones  that  correspond  with  their  own  fundamental 
tone,  or  whose  rate  of  vibration  is  some  multiple  of  their  own  rate  (octave,  duo- 
decime,  etc.)-  If  they  are  affected  by  other  tones,  their  associated  movement 
will  be  only  inconsiderable.  This  may  be  illustrated  by  a  simple  example:  if 
a  membrane  be  stretched  over  a  cylinder  or  a  funnel,  and  a  piece  of  sealing-wax 
be^  suspended  by  a  silkwTorm-thread,  so  that  it  just  touches  the  middle  of  the 
membrane,  it  will  remain  comparatively  quiet  when  musical  tones  are  struck 
in  its  vicinity.  As  soon,  however,  as  the  fundamental  tone  of  the  apparatus 
is  sounded,  the  piece  of  wax  will  be  greatly  agitated  by  the  marked  vibrations 
of  the  membrane. 


FIG.  .516. — Tympanic  Membrane  and  Auditory  Ossicles  (left) 
viewed  from  within  (from  the  tympanic  cavity):  M, 
manubrium  of  the  malleus;  T,  insertion  of  the  tensor 
tympani;  h,  head  of  the  malleus;  1  F,  long  process  of  the 
malleus;  a,  incus,  with  its  short  (K)  and  its  long  (1)  process; 
S,  plate  of  the  stapes.  A  x,  A  x  is  the  common  axis  of  ro- 
tation of  the  ossicles.  S  the  rachet-like  arrangement  be- 
tween the  malleus  and  the  incus. 


FIG.  317. — Tympanic  Membrane  of  a 
Newborn  Infant,  viewed  from  the 
Outside,  with  the  Handle  of  the 
Malleus  shining  through:  At,  tym- 
panic ring,  with  its  anterior  (tO  and 
posterior  (h)  end. 


FIG.  318. — Tympanic  Membrane  and 
Ossicles  (left)  viewed  from  within: 
Ci,  Cm,  C/i,  chorda  tympani;  T, 
pocketlike  depression  (Urbant- 
schitsch). 


If  these  conditions  be  transferred  to  the  tympanic  membrane,  this 
would  also  be  set  into  marked  vibration  when  its  fundamental  tone  is 
sounded,  but  only  into  slight  vibration  when  other  tones  are  produced. 
Such  a  state  of  affairs  would  be  attended  with  an  enormous  inequality 
in  the  act  of  hearing,  and  provision  is,  therefore,  made  in  the  tympanic 
membrane  for  the  neutralization  of  this  inequality.  This  end  is  attained : 
(i)  Through  the  great  resistance  to  the  vibrations  of  the  membrane 
that  the  chain  of  attached  ossicles  offers.  They  act  as  a  damping 
apparatus,  which  (as  in  the  case  of  any  damped  membrane)  prevents  the 
tympanic  membrane  from  vibrating  excessively  when  its  fundamental 
tone  is  struck.  The  damping  reduces  the  amplitude  of  vibration  of  the 
membrane  for  all  other  tones  also.  In  this  way  all  of  the  vibrations  of 
the  tympanic  membrane  are  moderated,  but  especially  the  excessive 


890  THE    AUDITORY    OSSICLES    AND    THEIR    MUSCLES. 

vibration  on  the  sounding  of  its  fundamental  tone  is  diminished.  There- 
fore, the  membrane  is  better  adapted  to  respond  to  the  vibrations  of 
different  wave-lengths,  although  to  a  lessened  degree.  The  damping 
also  prevents  effectually  disturbing  after- vibrations.  (2)  The  sym- 
pathetic vibrations  of  the  membrane  must  be  small,  in  accordance  with 
its  diminutive  size.  Further,  these  slight  elongations  are  quite  sufficient 
to  transfer  the  sound-movement  to  the  extremely  delicate  end-organs  of 
the  auditory  nerves.  In  fact  in  the  description  of  the  auditory  ossicles 
it  will  be  seen  that  there  exist  other  arrangements  that  still  further 
diminish  the  oscillations  of  the  tympanic  membrane. 

As  v.  Helmholtz  has  pointed  out,  the  increased  associated  vibration  of  the 
tympanic  membrane  when  its  own  note  is  sounded  is  not  completely  equalized 
by  the  damping  arrangement  described.  He  calls  attention  to  the  fact  that  to  most 
men  the  tones  of  the  sixth  octave  e  and  g  are  especially  piercing  and  shrill  (for 
example  the  shrill  tones  of  the  cricket),  and  he  supposes,  therefore,  that  the 
individual  note  of  the  auditory  apparatus,  including  the  tympanic  membrane, 
lies  in  this  region,  so  that  the  membrane  vibrates  strongly  in  unison  when  these 
tones  are  sounded.  In  general  the  sounds  that  are  designated  as  piercing  seem 
especially  to  cause  the  fundamental  vibrations  of  the  auditory  apparatus. 

According  to  Kessel,  the  individual  portions  of  the  tympanic  membrane 
have  an  independent  relation  to  sounds:  the  shortest  radial  fibers  in  the  upper 
portion  of  the  anterior  segment  and  in  the  upper  segment  vibrate  with  the  highest 
tones,  while  the  longest  fibers  on  the  posterior  segment  vibrate  with  the  deepest 
tones.  Noises  are  supposed  to  be  transmitted  by  the  upper  portion  of  the  posterior 
segment;  therefore,  deep  tones  are  readily  disturbed  and  extinguished  by  noises. 

According  to  Fick  the  tympanic  membrane  possesses,  in  addition  to  the  prop- 
erty of  taking  up  all  vibrations  almost  equally  well,  also  that  of  a  resonance- 
apparatus,  that  is,  it  admits  of  an  accumulation  of  the  energy  of  successive  vibra- 
tions. It  owes  this  property  to  its  funnel-shaped  retracted  form,  as  well  as  to 
the  radially  placed,  rigid  handle  of  the  malleus,  as  artificially  constructed  models 
have  shown. 

Pathological.— Thickening  and  inflexibility  of  the  tympanic  membrane 
diminish  the  acuity  of  hearing,  in  consequence  of  the  lessened  vibrating  ability 
of  the  membrane.  Perforations  and  loss  of  substance  have  the  same  effect.  In 
cases  of  extensive  destruction,  artificial  eardrums  have  been  inserted  into  the 
canal,  the  vibrations  of  which  replace  to  a  certain  extent  those  of  the  lost  mem- 
brane. 

THE  AUDITORY  OSSICLES  AND   THEIR  MUSCLES. 

The  auditory  ossicles  have  a  double  function:  (i)  They  transmit 
the  vibrations  of  the  tympanic  membrane  to  the  endolymph  of  the 
labyrinth  by  means  of  the  chain  that  they  form.  (2)  They  afford 
points  of  attachment  for  the  muscles  of  the  middle  ear,  which  through 
the  bones  alter  the  tension  of  the  tympanic  membrane  and  the  pressure 
on  the  fluid  of  the  labyrinth. 

Figs.  319  and  320  show  the  form  and  position  of  the  ossicles,  which  constitute 
an  articulated  chain  connecting  the  tympanic  membrane  (M)  with  the  labyrin- 
thine fluid  through  the  malleus  (h) ,  the  incus  (a) ,  and  the  stapes  (S) .  The  manner 
in  which  the  ossicles  move  deserves  especial  attention.  The  handle  of  the  malleus 
Fig.  320,  »)  is  firmly  attached  to  the  fibers  of  the  tympanic  membrane.  In 
addition,  the  malleus  is  fixed  by  ligaments  that  regulate  the  direction  of  its  move- 
ments. Two  of  them,  the  anterior  ligament  of  the  malleus,  arising  from  the 
processus  Fohanus,  and  the  posterior  ligament,  arising  from  a  small  crest  on  the 
neck  of  the  malleus,  form  together  a  common  axial  band,  which  crosses  the  tym- 
panic cavity  from  behind  forward,  consequently  parallel  to  the  surface  of  the 
tympanic  membrane.  The  neck  of  the  malleus  lies  between  the  insertions  of 
the  two  ligaments.  The  united  ligament  determines  the  axis  of  rotation  for  the 
movement  of  the  malleus.  When  the  handle  of  the  malleus  is  drawn  inward, 
its  head  must  naturally  make  the  opposite  outward  movement.  The  incus 


THE    AUDITORY    OSSICLES    AND    THEIR    MUSCLES.  891 

(a)  is  only  partially  fixed  in  its  position  by  a  ligament  that  secures  its  short 
process  to  the  wall  of  the  tympanic  cavity,  in  front  of  the  entrance  to  the  mastoid 
cells  (K).  It  is  materially  supported  by  the  rather  loose  articulation  with  the 
head  of  the  malleus  (h) ,  the  saddle-shaped  articulating  surface  of  which  is  inserted 
into  a  depression  in  the  incus.  Special  attention  must  be  directed  to  the  ratchet- 
like  lower  border  of  the  incus  (Fig.  316,  S).  When  the  handle  of  the  malleus 
moves  inward,  this  arrangement  causes  the  long  process  of  the  incus  (1),  which 
is  parallel  to  the  manubrium  of  the  malleus,  and  is  attached  to  the  stapes  (S) 
almost  at  right  angles  through  the  sesamoid  bone  of  Sylvius  (s) ,  to  move  inward 
at  the  same  time.  If,  however,  the  tympanic  membrane,  together  with  the  handle 
of  the  malleus,  is  moved  outward,  as  by  condensation  of  the  air  in  the  tympanic 
cavity,  the  long  process  of  the  incus  does  not  make  the  same  movement,  as  the 
malleus  alone  moves  away  from  the  ratchetlike  edge  of  the  incus.  There  is, 
consequently,  no  pull  on  the  stapes,  and,  therefore,  no  disturbing  agitation  of  the 
endolymph.  As  Ed.  Weber  has  well  shown,  the  malleus  and  the  incus  represent 
a  rectangular  lever,  whose  movement  occurs  about  a  common  axis  (Fig.  316,  and 
Fig.  320  Ax,  Ax) .  In  the  movement  inward,  the  incus  follows  the  malleus  as  if  the 
two  were  one  piece.  The  common  axis  (Fig.  316)  is  not,  however,  the  axial  liga- 
ment of  the  malleus,  but  it  is  formed  anteriorly  by  the  processus  Folianus  (IF), 
which  is  directed  forward,  and  posteriorly  by  the  short  process  of  the  incus  (K), 
which  is  directed  backward.  The  rotation  of  the  two  ossicles  about  this  axis 
takes  place  in  a  plane  perpendicular  to 
the  plane  of  the  tympanic  membrane. 
During  the  rotation,  the  parts  above 
this  axis  (head  of  the  malleus  and  upper 
part  of  the  incus)  move  in  a  direction 
opposite  to  that  in  which  move  those 
lying  beneath  it  (manubrium  of  the 
malleus  and  long  process  of  the  incus) , 
as  is  indicated  in  Fig.  320  by  the 
direction  of  the  arrow.  The  movement 
of  the  manubrium  must  always  follow 
that  of  the  tympanic  membrane,  and 

the  reverse,  while  the  excursion  of  the  \\  O.S 

stapes   is  necessarily  the  same  as  that 
of  the  long  process  of  the  incus.  Atten- 
tion   must    be    called    to  One  more    im-        FIG.  319-— The  Auditory  Ossicles  (right):   C.w,  head; 
•nnrfant  -nrn'rif  Ac  +1^   Irmrr  i~>i-™-oce  nf  C,  neck;  Pbr,  short  process;  Prl,  long  process;   A/, 

portant  point.         As  the   long  process  Of  manubrium  of  the  malleus;  O',body;  G.articulat- 

the     incus    IS    only    two-thirds    as    long  ing  surface;    k  short  and  v  long  process  of  the 

as  the  manubrium   (Figs.    316,  317,  320)  incus;    O.S,  lenticular  bone;  C.s,  head;  a  ante- 

the  excursion  of  the  apex  of  the  former,  rior  and  p  P°sterior  hmb'  p<  base  of  the  s^^s- 

and  with  it   that  of  the  stapes,  must 

be  correspondingly  less  than  that  of  the  apex  of  the  manubrium.  On  the  other 
hand,  the  force  of  the  movement,  corresponding  to  the  diminution  of  the  excursion, 
will  be  increased. 

Movements  of  the  tympanic  membrane  inward  thus  cause  less  ex- 
tensive, but  more  powerful,  movements  of  the  base  of  the  stapes  against 
the  fluid  of  the  labyrinth,  which  v.  Helmholtz  and  Politzer  estimated 
to  be  about  0.07  mm.  in  amplitude. 

The  way  in  which  the  vibrations  of  the  tympanic  membrane  are 
transmitted  to  the  endolymph  through  the  chain  of  ossicles  is  exactly 
analogous  to  the  method  of  movement  of  these  parts,  as  already  ex- 
plained. For  the  study  of  this  movement,  long  delicate  glass  threads 
have  been  attached  to  the  various  portions  of  the  ossicles,  and  the 
movements,  when  sounds  were  conveyed  to  the  auditory  apparatus, 
have  been  thus  recorded  on  smoked  paper.  Bright  particles  have  also 
been  pasted  on  the  individual  parts,  whose  oscillating  movements  appear 
as  lines  of  light,  which  have  been  followed  and  measured  with  the  aid  of 
the  microscope.  All  experiments  have  proved  that  the  transmission 
of  the  sound-vibrations  takes  place  through  the  mechanism  of  the 
rectangular  lever  formed  by  the  ossicles,  as  has  been  described. 


892 


THE    AUDITORY    OSSICLES    AND    THEIR    MUSCLES. 


Although  the  vibrations  of  the  tympanic  membrane  are  transmitted 
through  the  malleus  to  the  incus,  there  is,  however,  a  loss  of  about  one- 
fourth  of  their  original  amplitude. 

As  the  excursions  of  the  ossicles  caused  by  the  sound-vibrations  are 
extremely  small,  the  articulations  do  not  change  position  with  every 
vibration.  Such  a  change  occurs  probably  only  when  larger  movements 
are  produced  by  the  muscles,  as  will  now  be  explained. 

The  muscles  of  the  auditory  ossicles  affect  the  position  of  the  latter  and 
also  the  tension  of  the  tympanic  membrane,  as  well  as  the  pressure  in 
the  endolymph.  The  tensor  tympani  muscle  is  situated  in  an  osseous 
groove  above  the  Eustachian  tube;  its  tendon  is  deflected  over  a  bony 
process  of  this  prolonged  groove  in  a  direction  outward  almost  at  right 

angles,  and  is  inserted  on 
the  malleus  just  below  its 
axis  of  rotation  (Fig.  321, 
M).  When  the  muscle 
contracts  (in  the  direction 
of  the  arrow  t,  Fig.  320) 
the  handle  of  the  malleus 
(n)  pulls  the  tympanic 
membrane  (M)  inward  and 
makes  it  tense.  The  incus 
and  stapes  are  moved  at 
the  same  time,  and  the 
stapes  (S)  is  pressed  more 
deeply  into  the  fenestra 
ovalis,  as  has  been  already 
fully  described.  When  the 
muscle  relaxes,  the  original 
position  is  again  assumed 
as  a  result  of  the  elasticity 
of  the  rotated  axial  liga- 
ment and  the  tense  tym- 
panic membrane.  The 
motor  nerve  of  the  muscle 
comes  from  the  trigeminus 
and  passes  through  the 
otic  ganglion.  C.  Ludwig 
and  Politzer  observed  the 
motion  described  follow 
irritation  of  the  fifth  nerve 
in  the  cranial  cavity. 

Ihe  stretching  of  the  tympanic  membrane  effected  by  the  tensor 
has  a  double  purpose:  (i)  The  tense  membrane  offers  greater  resistance 
to  sympathetic  vibration  when  the  sounds  are  loud,  as  tense  membranes 
are  always  the  more  difficult  to  set  in  sympathetic  vibration  the  more 
they  are  stretched.  In  this  connection  the  tensor  acts  as  a  protection 
for  the  ear,  by  preventing  the  transmission  of  excessively  strong  impulses 
through  the  tympanic  membrane  to  the  nerve-endings.  (2)  The  tension 
of  the  tympanic  membrane  must  vary  according  to  the  degree  of  con- 
traction. In  this  way  the  membrane'has  a  different  fundamental  tone 
according  to  the  tension,  and  is  therefore  enabled  alwavs  to  vibrate  more 


FIG.  320. — Tympanic  Membrane  and  Auditory  Ossicles  (left),  en- 
larged: A.G.  External  auditory  canal;  M,  tympanic  membrane 
with  which  the  handle  of  the  malleus  (n)  and  its  short  process 
(p)  are  in  contact;  h.  head  of  the  malleus;  a,  incus;  K,  its  short 
process  with  its  fixation-ligament;  1,  its  long  process;  s, 
ossicle  of  Sylvius;  S,  stapes.  A  x,  A  x,  the  axis  of  rotation  of  the 
ossicles  (it  is  drawn  in  perspective  and  must  be  conceived  as 
stuck  through  the  surface  of  the  paper);  t,  direction  of  action 
of  the  tensor  tympani  muscle.  The  other  arrows  indicate 
the  movement  of  the  ossicles  when  the  tensor  tympani  contracts. 


THE    AUDITORY    OSSICLES    AND    THEIR    MUSCLES.  893 

strongly  in  sympathy  with  the  especial  tone  for  which  it  is,  as  it  were, 
adjusted.  By  this  means  the  perception  of  feeble  tones  is  facili- 
tated. 

In  this  respect  the  tympanic  membrane  has  been  well  compared  with  the  iris. 
Both  membranes,  by  contracting — narrowing  of  the  pupil  and  stretching  of  the 
tympanic  membrane — prevent  the  excessive  action  of  the  specific  stimulus  from 
causing  excessive  irritation,  and  both  adapt  the  sensory  apparatus  to  the  action 
of  moderate  or  weak  stimuli.  The  movement  in  both  membranes  is  the  result 
of  a  reflex  action:  for  the  ear  through  the  auditory  nerve,  which  constitutes  the 
path  for  reflex  stimulation  of  the  motor  fibers  of  the  tensor. 

That  increased  tension  of  the  tympanic  membrane  makes  it  less  sensitive 
to  sound-vibrations  can  be  readily  shown  by  closing  the  mouth  and  nostrils,  and 
either  making  a  forcible  expiration,  so  that  air  is  forced  through  the  Eustachian 
tube  into  the  tympanic  cavity,  and  the  tympanic  membrane  is  bulged  outward, 
or  by  making  a  strong  inspiration,  so  that  the  tympanic  membrane  is  drawn 
inward  as  a  result  of  rarefaction  of  the  air  in  the  tympanic  cavity.  In  both  cases 
hearing  is  interfered  with  as  long  as  the  increased  tension  persists,  as  may  be  dis- 
tinctly observed  on  listening  for  a  note  to  die  out. 

If  air  is  blown  into  the  external  auditory  canal  of  a  normal  individual,  by 
means  of  a  rubber  bag,  both  tensors  of  the  tympanum  contract,  and  in  consequence 
the  ear  not  blown  into  becomes  momentarily  hard  of  hearing.  Johannes  Miiller 
made  the  same  action  clear  by  means  of  the  following  experiment:  If  a  funnel, 
with  a  small  lateral  opening,  be  placed  in 
the  auditory  canal,  and  the  wide  end  be 
covered  with  a  tense  membrane,  hearing  is 
less  acute  as  soon  as  the  membrane  is  made 
more  tense  by  means  of  a  traction-apparatus. 
In  other  words,  the  membrane  of  the  funnel 
represents  a  second  tympanic  membrane, 
which  is  placed  in  front  of  the  ear. 

The  normal  mode  of  stimulation  of 
the  tensor  tympani  is,  as  has  been  said, 
reflex.  The  muscle  is  not  directly  and 
solely  under  the  influence  of  the  will. 
L.  Fick  explains  the  following  phenomenon 
as  an  associated  movement  of  the  tensor : 
When  he  pressed  his  jaws  firmly  together, 
he  heard  in  his  ear  a  high  peeping-singing  . 
tone,  and  in  a  capillary  tube,  placed  air- 
tight in  the  auditory  canal,  he  saw  a  drop  move  FIG.  321. — Tensor  Tympani  Muscle;  the 
quickly  inward.  During  this  experiment  an  Eustachian  Tube  (Left), 

individual  with  normal  acuteness  of  hearing 
perceives  a  reinforcement  of  all  musical  tones, 

but  a  weakening  of  all  high,  nonmusical  tones.  In  yawning,  with  great  stretch- 
ing of  the  muscles  of  the  face  and  jaws,  v.  Helmholtz  and  Politzer  found  an  im- 
pairment of  hearing  for  certain  tones,  which  Landois  also  was  able  distinctly  to 
perceive  in  himself,  and  which  he  was  more  inclined  to  ascribe  to  an  increased 
activity  of  the  stapedius. 

Hensen  found  that  the  tensor  tympani  muscle  takes  part  in  the  act  of  hearing 
by  sudden  movements,  and  not  by  tonic  contraction.  At  the  commencement 
of  the  act  a  contraction  occurs  that  facilitates  the  perception  because  the  mem- 
brane, when  set  in  motion  by  the  muscle,  vibrates  more  readily  in  sympathy 
with  the  higher  tones  than  when  at  rest.  On  exposing  the  tympanum  in  dogs 
and  cats,  he  showed  that  the  contraction  takes  place  only  at  the  commencement 
of  the  sound,  and  that  it  then  quickly  ceases,  although  the  sound  may  continue. 

The  stapedius  muscle,  which  is  situated  within  the  pyramidal 
eminence,  and  is  inserted  from  behind  forward  on  the  head  of  the  stapes 
and  the  sesamoid  bone  of  Sylvius,  has  the  following  action:  by  pulling 
on  the  head  of  the  stapes  (indicated  in  Fig.  314  by  the  small  curved 
arrow)  it  places  the  bone  in  an  oblique  position,  so  that  the  posterior 
extremity  of  the  base  of  the  stapes  is  pressed  more  deeply  into  the  fenes- 
tra  ovalis,  and  the  anterior  extremity  is  displaced  outward.  The  stapes  is, 


894  EUSTACHIAN    TUBE.       TYMPANIC    CAVITY. 

in  this  way,  more  firmly  fixed,  as  through  the  oblique  position  mentioned 
the  ligamentous  mass  inserted  around  the  edge  of  the  base  must  be 
more  strongly  stretched.  Hence,  the  action  of  the  muscle  prevents 
unduly  strong  impulses  communicated  by  the  incus  from  being  trans- 
mitted in  their  full  strength  to  the  endolymph.  The  nerve  is  derived 
from  the  facial. 

In  some-  persons  the  stapedius  nerve  is  innervated  through  associated  move- 
ment by  forcible  closure  of  the  eyelids,  a  rumbling  noise  being  heard  at  the  same 
time.  Landois  was  able  to  excite  such  innervation  through  reflex  influences 
by  scratching  with  the  fingernail  directly  in  front  of  the  auditory  meatus;  Henle 
accomplished  the  same  thing  by  gently  stroking  the  outer  margin  of  the  orbit. 
The  nerve  seems  to  be  susceptible  to  reflex  irritation  also  in  many  ear-patients 
by  syringing  the  tympanic  cavity.  Under  fhese  circumstances  Voltolini  and 
Politzer  observed  contractions  of  the  auricle  as  associated  movements  and  Ziem, 
blepharospasm . 

Opinions  are  still  much  divided  as  to  the  action  of  the  stapedius.  In  the 
oblique  position  of  the  stapes,  the  head  of  the  bone  forces  the  long  process  of 
the  incus,  and  with  it  the  malleus  and  tympanic  membrane,  outward.  Conse- 
quently the  stapedius  has  been  designated  also  the  antagonist  of  the  tensor  t}'m- 
pani.  Politzer  observed  a  decrease  of  the  pressure  in  the  labyrinth  on  irritation 
of  the  muscle.  According  to  Toynbee  the  stapedius  is  supposed  to  raise  the  stapes 
out  of  the  fenestra  ovalis,  and  make  it  more  movable,  so  that 
it  will  vibrate  more  readily.  The  stapedius  would,  there- 
fore, be  the  true  listening  muscle  of  the  ear.  Henle  believed 
that  the  stapedius  is  more  concerned  in  fixing  the  stapes 
than  in  making  it  movable,  and  that  it  acts  only  when 
there  is  danger  of  a  violent  motion  being  transmitted  to 
the  stapes  from  the  malleus  through  the  incus.  Landois 
agreed  with  this  view,  and  considered  the  orbicularis 
palpebrarum  and  the  stapedius  as  muscles  for  the  protec- 
tion of  important  sense-apparattis.  Both  are  innervated 
FIG.  322. — Stapedius  by  the  facial  nerve,  and  both  can  be  stimulated  reflexly  by 

Muscle  (Right).  irritation    of    the    sensory   nerves   in    the    vicinity   of    the 

sense-organ.  Strong  contraction  of  the  orbicularis  induces 
associated  movement  of  the  stapedius.  Lucae,  who  demon- 
strated an  associated  movement  of  the  stapedius  with  powerful  movements  of  the 
facial  muscles,  for  example  with  closure  of  the  lids  (in  association  with  which  a 
deep  entotic  sound  is  heard) ,  believes  that  the  muscle  effects  an  accommodation 
of  the  tympanic  membrane  for  the.  highest,  nonmusical  tones  (just  as  the  tensor 
does  for  musical  tones).  These  highest  tones  sound  louder,  therefore,  in  this 
experiment. 

Pathological. — Immobility  of  the  ossicles  in  consequence  of  cicatricial  adhe- 
sions of  their  joints  or  of  ankyloses  causes  impairment  of  hearing  in  accordance 
with  the  degree  of  immobility.  Firm  adhesions  of  the  stapes  within  the  fenestra 
ovalis  have  the  same  effect.  In  the  presence  of  contractures  of  the  tensor 
tympani,  the  tendon  of  this  muscle  has  occasionally  been  cut.  Paralysis  of  the 
tensor  is  discussed  in  connection  with  the  otic  ganglion  (p.  691)  that  of  the  sta- 
pedius on  p.  698. 

EUSTACHIAN  TUBE.     TYMPANIC  CAVITY. 

The  Eustachian  tube,  which  is  4  cm.  long,  is  the  ventilating  tube  for 
the  tympanic  cavity.  It  keeps  the  air  in  the  interior  of  the  cavity  of  the 
same  density  as  the  outer  air  by  means  of  the  communication  that  is 
established  between  the  two  in  the  pharynx  (Figs.  314,  321).  The 
normal  vibration  of  the  tympanic  membrane  is  possible  only  under  this 
condition.  The  tube  is  ordinarily  closed.  In  swallowing,  however, 
the  canal  is  dilated  by  the  traction  of  the  fibers  of  the  tensor  of  the 
veil  of  the  palate  (sphenosalpingostaphylinus  or  abductor  tubse,  or  dila- 
tator tubse)  upon  its  membranocartilaginous  portion,  into  which  they 
are  inserted  (Fig.  323).  As  the  tube  is  closed,  the  vibrations  of  the 


EUSTACHIAX    TUBE.       TYMPANIC    CAVITY.  895 

tympanic  membrane  can  be  transmitted  with  less  impairment  to  the 
ossicles  than  if  the  tube  were  open  and  the  air  allowed  to  escape  through 
it  during  the  vibrations.  If,  however,  the  tympanum  were  permanently 
closed,  the  air  within  it  would  soon  be  so  rarefied,  that  the  tympanic 
membrane  would  be  drawn  inward,  under  abnormal  tension,  and  hard- 
ness of  hearing  would  result.  The  tube  serves,  moreover,  as  a  drainage- 
canal  for  the  secretion  of  the  tympanic  cavity  by  means  of  the  ciliated 
epithelium. 

If,  after  destruction  of  the  tympanic  cavity,  gas  is  allowed  to  stream  into 
the  ear  of  a  narcotized  dog,  through  the  external  canal,  it  passes  through  the 
tube  into  the  throat  only  when  the  tensor  tympani  contracts. 

The  tube  opens  its  valvelike  mechanism  more  easily  in  the  direction  of  the 
pharynx  than  in  the  opposite  direction.  The  valve  is  placed  behind  the  orifice 
of  the  tube ;  after  each  opening  of  the  mouth  of  the  tube  the  valve  is  again  closed 
through  the  elasticity  of  the  tube-walls. 

A  tuning-fork  held  before  the  nostrils  is  heard  more  strongly  during  a  swallow- 
ing movement,  because  the  tube  is  opened.     One's  own  voice  seems  deafening 
at  the  moment  that  the  tube  is  opened  by  an  influx  of  air,  and  the  voice  seems 
to  sound  as  if  within  the  ear.     Patulousness  of  the  tube  as  a  result  of  pathological 
conditions  may  produce  a  similar  result — autophony.     The 
pulsation  of  the  vessels  and  the  respiratory  sounds  are  then 
also  abnormally  distinct. 

If  the  act  of  swallowing  is  performed  slowly  in  the 
pharynx,  while  the  tensors  of  the  palate  are  stretched,  a 
sharp  hissing,  or  loud  crackling  noise,  is  heard  distinctly. 
This  sounds  much  like  the  noise  produced  by  forcing 
saliva  between  the  incisor  teeth  by  pushing  the  tongue  for- 
ward when  the  mouth  is  closed,  and  it  results  from  the 
separation  of  the  moistened  walls  of  the  tube  from  each 
other.  Another  person  can  hear  this  noise  by  applying  his 
ear,  or  by  using  a  stethoscope.  It  was  formerly  thought  to 
be  a  cracking  of  the  joints  of  the  ossicles  through  the 
action  of  the  tensor  tympani. 

In  Valsalva's  experiment  air  enters  the  tube  as  soon  as  FIG.  323.  —  Section 
the  air-pressure  equals  betwreen  TO  and  40  mm.  of  mercury.  ^ruug)r>-  Eustac*\la.n 

TT    j  i_  j/i.  Tj-1  j    .c  .LI  •  lube  (Diagrammatic): 

Under  such  conditions  Landois  heard  first  the  same  noise,         m,   median   plate;    /, 
and  then  he   felt   suddenly  the    increased    tension    of    the         lateral  plate;   *,  mar- 
tympanic  membrane   due   to   the   entrance  of   air  into  the         SoRC"/tSSioc«f  flS 
tympanic    cavity.        During    forced  inspiration,    while    the         paiate;  L,  lumen° 
mouth  and  nostrils  are  held  closed,  air  is  sucked  out,  and 
finally  the  tympanic  membrane  is  drawn  inward. 

The  elevator  of  the  veil  of  the  palate  forms  in  this  situation  the  levator- 
cushion  as  it  passes  under  the  floor  of  the  pharyngeal  orifice  of  the  tube  (Fig.  330). 
Consequently,  when  this  muscle  contracts,  and  its  belly  thickens  (in  the  com- 
mencement of  the  act  of  swallowing),  and  also  with  every  elevation  of  the  soft 
palate  during  inspiration,  the  lower  wall  of  the  pharyngeal  opening  is  forced 
upward,  and  the  opening  is  narrowed.  The  subsequent  contraction  of  the  tensor 
of  the  veil  of  the  palate,  in  the  further  course  of  the  act  of  swallowing,  then  dilates 
the  tube.  (The  subject  is  further  discussed  with  the  act  of  swallowing.)  The 
result  is  that  by  this  action  of  the  levator  the  tension  of  the  air  in  the  tympanum 
is  at  first  increased;  it  is  then  diminished  by  the  action  of  the  tensor,  as  may 
be  recognized  under  favorable  conditions  from  corresponding  movements  of  the 
tympanic  membrane. 

The  tympanic  cavity  forms  a  protective  chamber  for  the  auditory 
ossicles  and  their  muscles.  Its  air-capacity,  amplified  by  the  communi- 
cations with  the  mastoid  cells,  permits  free  oscillations  of  the  tympanic 
membrane. 

The  assumption  that  the  tympanum  strengthens  by  resonance  the  sound- 
vibrations  that  strike  the  ear,  for  the  purpose  of  delicate  hearing,  must  be  con- 
sidered erroneous.  That,  further,  the  air  of  the  tympanum  can  transmit  vibra- 
tions to  the  membrane  of  the  iVm-stru  rotunda  must  be  admitted,  but  with  normal 


896  SOUND-CONDUCTION    IN    THE    LABYRINTH. 

hearing  this  slight  conduction  is  of  but  little  significance  in  comparison  with  that 
of  the  ossicles. 

The  Eustachian  tube  and  the  tympanum  have  a  common  mucous  membrane ; 
the  parts  within  the  tympanum  are  lined  by  the  mucosa.  The  epithelium  is 
composed  of  ciliated  columnar  cells ;  it  is  not  ciliated  on  the  surface  of  the  ossicles 
and  the  promontory.  Troltsch  and  Wendt  found  racemose  mucous  glands  in 
the  mucous  membrane. 

Pathological. — Among  the  diseases  of  the  Eustachian  tube,  obstruction 
attending  chronic  catarrhal  conditions,  and  narrowing  from  scars,  hypertrophy 
of  the  mucous  membrane  or  pressure  by  tumors  may  be  mentioned.  The  im- 
pairment of  hearing  thus  produced  can  often  be  corrected  by  catheterizing  the 
tube  through  the  nares.  Effusions  and  collections  of  pus  in  the  tympanum  must, 
of  course,  disturb  the  normal  function  of  all  the  sound-conducting  parts  within 
the  tympanum.  Inflammatory  processes  often  have  also  injurious  effects  upon 
the  tympanic  plexus.  Moreover,  progressive  destruction  of  the  temporal  bone 
by  caries,  commencing  in  the  tympanic  cavity  may  finally  cause  fatal  inflam- 
mation of  the  neighboring  portions  of  the  brain. 

SOUND-CONDUCTION  IN  THE  LABYRINTH. 

The  oscillations  of  the  basal  plate  of  the  stapes  in  the  fenestra  ovalis 
of  the  vestibule  produce  waves  in  the  fluid  of  the  labyrinth,  so-called 
flexion- waves,  that  is  the  labyrinthine  fluid  moves  as  a  whole  before  each 
impulse  of  the  stapes.      This  yielding  of  the  fluid  is 
possible  only  because  in   one   place  a  flexible  mem- 
brane, the  membrane  of  the  fenestra  rotunda  (of  the 
cochlea)   or  secondary   tympanum,   which,   when   at 
rest,  projects  into  the  scala  tympani,  can  be  forced 
outward  toward  the  tympanic  cavity  by  the  move- 
ment of  the  stapes  (Fig.  314,  r).     These  waves  must 
correspond    in   number   and  intensity   to  the  move- 
Lab-     ments  of  the  auditory  ossicles,  and  must  also  excite 
dowthieadine  True/the     the  terminati°ns  of  the  auditory  nerve,  which  float 
vestibule, ' the  'codiiea!     free  in  the  fluid  of  the  labyrinth. 
ri£8<JFS5  horiz'cSal  As  both  the  cochlea  anteriorly  and  the  semicircular 

(J)  semicircular  canal  canals  posteriorly  communicate  with  the  saccules  of 
the  vestibule,  the  fluid  of  which  first  receives  the  im- 
pulse of  the  vibrations,  the  movement  of  the  fluid  must 
be  propagated  through  these  canals.  In  the  cochlea  the  movement  passes 
upward  from  the  sacculus  (hemisphaericus)  through  the  scala  vestibuli 
to  the  apex  of  the  cochlea,  here  through  the  helicotrema  into  the  scala 
tympani,  at  the  extremity  of  which  the  membrane  of  the  fenestra  rotunda 
moves  outward.  In  a  similiar  manner  the  wave-motion  commencing 
in  the  utricle  (sacculus  hemiellipticus)  passes  along  through  the  semi- 
circular canals.  Thus,  Politzer  saw  the  fluid  of  the  labyrinth  mount 
upward  into  the  superior  canal  (which  was  exposed)  when  he  caused 
contraction  of  the  tensor  tympani  by  stimulating  the  trigeminus, 
which  must  force  the  base  of  the  stapes  against  the  labyrinthine  fluid, 
with  each  sound-vibration  of  the  tympanic  membrane. 

Hensen  showed  that  a  membrane  that  is  set  in  motion  by  water  exercises 
a  strong  attraction.  This  attraction  may  be  noticed  also  on  the  oval  membrane 
of  the  labyrinth,  which  is  weighted  by  the  base  of  the  stapes;  the  fluid  must, 
consequently,  move  toward  the  stapes,  and  then  away  from  it.  Otoliths  are 
probably  also  under  the  influence  of  this  attraction,  and  their  mechanical  action 
upon  the  endings  of  the  auditory  nerve  is  thus  clearly  explained. 


STRUCTURE    OF    THE    LABYRINTH. 


897 


STRUCTURE  OF  THE  LABYRINTH  AND  THE  TERMINATIONS 
OF  THE  AUDITORY  NERVE. 

The  vestibule  of  the  labyrinth  (Fig.  325,  III)  possesses  two  separate  sacs: 
one,  the  saccule  (sacculus,  or  S.  hemisphcericus,  S)  communicates  with  the  cochlear 
duct  (Cc)  of  the  cochlea;  the  other,  the  utricle  (utriculus  or  sacculus  hemiellipticus, 
U)  communicates  with  the  semicircular  canals  (Cs,  Cs) .  The  interior  of  the  cochlea, 
which  consists  of  2^  spiral  turns,  is  divided  into  two  compartments  by  a  horizontal 
septum  (lamina  spiralis  ossea  et  membranacea) ,  which  is  bony  internally  and 
membranous  externally  (Fig.  325,  I).  The  lower  compartment  is  the  scala 
tympani ;  it  is  separated  from  the  tympanic  cavity  by  the  membrane  of  the  fenestra 
rotunda.  The  upper  compartment  is  the  scala  vestibuli,  which  leads  into  the 
vestibule  of  the  labyrinth  (Fig.  314).  These  two  passages  are  in  direct  com- 
munication with  each  other  through  a  small  opening  (helicotrema)  at  the  apex 
of  the  cochlea.  A  smaller  space  is  separated  from  the  upper  passage  by  the 
obliquely  placed  membrane  of  Reissner  (Fig.  325,  I),  which  bridges  over  the  lower 
outer  angle.  This  space  (ductus  or  canalis  cochlearis,  Cc)  is  bounded  below 
chiefly  by  the  lamina  spiralis  membranacea,  on  which  the  organ  of  Corti,  the 
end-organ  of  the  cochlear  nerve,  is  placed.  The  lower  end  of  the  cochlear  canal 
(III)  is  blind  and  faces  the  saccule,  with  which  it  is  united  by  the  fine  canalis 
reuniens  (Cr).  The  three  semicircular  canals  (Cs,  Cs)  communicate  with  the 


FIG.  325. — I,  Cross-section  of  the  cochlea;  II,  A,  ampulla  with  the  crista  acustica;  a  p,  a  hair-cell  and  its  bristle; 
T,  otoliths;  III,  diagrammatic  representation  of  the  human  labyrinth;  IV,  diagrammatic  representation  of 
the  labyrinth  of  a  bird;  V,  diagrammatic  representation  of  the  labyrinth  of  a  fish. 

utricle  (Fig.  325,  III,  U) .  Each  begins  in  an  ampulla,  within  which  lie  the  termina- 
tions of  the  ampullar  nerves;  while  at  the  other  extremity  they  have  only  two 
openings,  as  the  posterior  and  superior  canals  unite  so  as  to  form  one  common 
canal.  A  membranous  lining  continues  from  the  utricle  through  the  semicircular 
canals.  The  limpid  perilymph,  which  is  present  also  in  both  cochlear  passages, 
and  the  viscid  endolymph  fill  the  entire  cavity  of  the  labyrinth.  All  of  these 
compartments  are  lined  by  low,  cylindrical  epithelium. 

Only  those  portions  of  the  system  of  cavities  that  are  filled  with  endolymph 
contain  the  nervous  end-organs.  The  cochlea,  the  semicircular  canals,  and  the 
ampullae  belong  to  the  organs  of  hearing.  After  extirpation  of  the  cochlea 
on  each  side  there  is  still  a  distinct  reaction  to  coarse  sounds.  The  cavities  of  the 
labyrinth  are  all  in  communication  with  each  other,  the  semicircular  canals  directly 
with  the  utricle,  the  cochlear  duct  with  the  saccule  through  the  canalis  reuniens. 
Finally,  the  saccule  and  the  utricle  communicate  through  the  endolymphatic  duct, 
which  arises  as  an  isolated  branch  from  each  sac.  The  canal  thus  formed  passes 
through  the  osseous  aqueduct  of  the  vestibule,  to  end  beneath  the  dura  in  an 
endolymphatic  sac  on  the  posterior  aspect  of  the  petrous  portion  of  the  temporal 

57 


STRUCTURE    OF    THE    LABYRINTH. 


bone  (Fig.  325,  III,  R).  Another  small  canal,  the  aqueduct  of  the  cochlea,  is  a 
narrow  passage  that  begins  in  the  scala  tympani,  just  in  front  of  the  round 
window  and  emerges  near  the  jugular  fossa.  It  forms  a  communication  be- 
tween the  perilymph  of  the  cochlea  and  the  subarachnoid  space. 

Semicircular  Canals  and  Saccules. — The  membranous  semicircular  canals 
do  not  fill  the  corresponding  osseous  cavities  completely,  but  are  separated  from 
the  walls  by  a  rather  wide  space,  which  is  filled  with  the  perilymph.  On  the 
concave  margin  alone  they  are  more  closely  attached  to  the  bone  by  connective 
tissue.  The  ampullag,  however,  fill  the  bony  cavities  completely.  Semicircular 
canals  and  saccules  consist  of  an  outer  vascular  connective-tissue  layer,  upon 
which  lies  a  hyaloid  membrane,  bearing  a  single  layer  of  squamous  epithelium. 
The  vestibular  branch  of  the  auditory  nerve  sends  a  twig  to  each  ampulla  and  to 
the  saccule  and  the  utricle.  In  the  ampullae  (Fig.  325,  II,  A)  the  nerve-ending 
(c)  lies  on  a  yellowish,  equatorial  ledge,  which  projects  into  the  interior  (crista 
acustica).  The  medullated  nerve-fibers  (n),  passing  through  ganglia,  form  a 
plexus  in  the  connective-tissue  layer,  then  lose  their  sheaths  near  the  basement 
membrane  and  end  by  means  of  telodendrites  by  contact  in  the  characteristic 
cells,  each  of  which  is  provided  with  an  immovable,  rigid  bristle  (o,  p),  90  « 


FIG.  326. — Organ  of  Corti. 


long,  and  which  are  situated  on  the  crista;  between  them  are  indifferent  cylin- 
drical cells  (hair-cells,  a),  which  often  contain  yellowish  pigment-granules.  The 
bristles  or  auditory  hairs  are  composed  of  many  fine  fibers.  An  exceedingly 
delicate  membrane  (membrana  tectoria)  covers  the  hairs.  The  nerve-ending's 
in  the  maculae  acusticse  of  the  saccule  and  utricle  are  exactly  the  same  as  in  the 
ampullae,  except  that  the  free  surface  of  the  membrana  tectoria  is  covered  with 
small  chalky-white  otoliths  (II,  T)  composed  of  calcium  carbonate.  These  are 
partly  amorphous,  and  partly  in  the  form  of  arragonite,  with  a  minute  central 
nucleus,  and  they  lie  fixed  in  the  homogeneous  membrane  of  the  otoliths.  Here 
also  the  nonmedullated  axis-cylinders  of  the  saccular  nerves  come  into  contact 
with  the  hair-cells,  through  the  medium  of  telodendrites. 

Cochlea. — Only  that  portion  of  the  cochlear  canal  or  duct  (Fig.  325,  I,  C.c, 
and  III,  Cc,  and  Fig.  326)  that  is  covered  by  the  membrane  of  Reissner,  and 
whose  endolymph  surrounds  the  organ  of  Corti,  contains  in  the  latter  the  end- 
organs  of  the  cochlear  nerve.  The  organ  of  Corti  lies  on  the  fibrous  lamina  spiralis 
membranacea  (membrana  basilaris)  and  consists  of  a  supporting  structure  com- 
posed of  the  so-called  arches  of  Corti,  each  of  which  consists  of  two  rods  of  Corti 


QUALITY    OF    AUDITORY    PERCEPTIONS.  899 

(z  y),  which  are  inclined  toward  each  other  and  meet  above  like  the  beams  in 
the  roof  of  a  house;  but  every  two  rods  do  not  form  an  arch,  as  there  are  always 
three  inner  to  two  outer  rods.  There  are  about  4500  outer  rods. 

The  cochlear  duct  becomes  larger  toward  the  apex  of  the  cochlea,  and  the  rods 
also  become  longer.  The  inner  ones  are  30  fj.  long  in  the  first,  and  34  n  in  the 
upper  turns;  the  outer  rods  respectively  47  //  and  69  //.  Likewise,  the  width  of 
the  arches  increases.  The  cylindrical  hair-cells  (cells  of  Corti),  observed  by 
Corti,  of  which  there  are  from  16,400  to  20,000,  serve  as  the  actual  end- 
organs  of  the  cochlear  nerve.  There  is  one  row  of  inner  cells  (i)  which  rest  on 
a  layer  of  small  granular  cells  (k) ;  the  outer  cells  (a  a)  number  12,000  in  man, 
and  rest  upon  the  basement  membrane,  in  three  or  even  in  four  rows.  The 
cells  are  directly  connected  by  fibrous  processes  with  the  fibers  of  the  basilar 
membrane,  so  that  each  cell  is  connected  with  two  or  three  fibers,  and  must, 
therefore,  vibrate  in  unison  with  the  latter.  Between  the  outer  hair-cells  there 
are  other  cellular  structures,  which  are  regarded  either  as  special  cells  (Deiter's 
cells) ,  or  merely  as  processes  of  the  hair-cells.  Following  the  outer  cells  of  Deiter 
come  the  cylindrical  cells  of  Henle,  which  gradually  pass  into  the  ordinary  epi- 
thelium of  the  cochlear  duct. 

The  fibers  of  the  cochlear  nerve  (N)  emerge  from  the  bony  spiral  lamina, 
and,  after  passing  through  the  intercalated  ganglion-cells,  (Fig.  325,  I,  G)  end 
by  fine  varicose  fibrils  on  the  hair-cells,  with  which  their  telodendrites  are  in 
contact  (Fig.  326).  The  bristles  of  the  hair-cells  consist  in  vertebrates  of  closely 
massed  fine  fibrils. 

The  arches  of  Corti  and  the  hair-cells  are  covered  by  a  special  membrane 
(o,  reticular  membrane),  through  openings  in  which  project  the  upper  extremities 
of  the  hair-cells  with  the  hairs.  This  membrane  consists  of  cement-substance 
holding  these  parts  together.  Mention  should  be  made  finally  of  the  soft  mem- 
brane of  Corti,  which  is  comparatively  thick,  and  extends  from  above  outward 
over  the  organ  of  Corti.  Waldeyer  regards  this  as  a  damping  apparatus  for  the 
organ  of  Corti. 

The  fluid  within  the  labyrinth  also  is  under  a  constant  pressure — the 
intralabyrin thine  pressure.  Every  diminution  in  the  pressure  of  the 
air  in  the  middle  ear  is  accompanied  by  a  temporary  diminution  in  the 
intralabyrin  thine  pressure,  while,  conversely,  every  increase  in  air- 
pressure  is  accompanied  by  an  increase  in  the  intralabyrin  thine  pressure. 

The  perilymph  of  the  internal  ear  flows  chiefly  through  the  aqueduct 
of  the  cochlea  within  the  jugular  foramen  into  the  peripheral  lymphatic 
system,  which  also  takes  up  the  cerebrospinal  fluid  of  the  subarachnoid 
space,  while  a  small  portion  passes  through  the  internal  auditory  meatus 
to  the  subdural  space. 

QUALITY  OF  AUDITORY  PERCEPTIONS. 
PERCEPTION  OF  THE  PITCH  AND  INTENSITY  OF  TONES. 

Every  normal  ear  is  able  to  recognize  musical  tones  and  noises  as 
such,  and  to  distinguish  between  them.  Physical  experiments  have 
proved  that  musical  tones  are  produced  when  a  vibrating,  elastic  body 
executes  a  periodic  movement,  that  is  a  movement  that  is  exactly 
reproduced  at  equal  intervals  of  time,  as  in  the  vibration  of  a  twanged 
cord.  A  noise  is  produced  when  the  vibrating  object  executes  nonperi- 
odic  movements,  that  is,  when  unequal  movements  occur  at  equal  time- 
intervals.  This  is  readily  proved  by  means  of  the  siren.  If  there  be 
on  the  circular  disc  of  this  instrument  a  number  of  holes,  for  example 
forty,  arranged  in  a  circle  and  placed  exactly  the  same  distance  from 
each  other,  and  if,  on  rotating  the  disc,  a  current  of  air  is  blown  against 
it,  the  air  will  be  alternately  rarefied  and  compressed  exactly  40  times 
with  every  revolution,  and  every  two  rarefactions  and  condensations 
will  be  separated  from  each  other  by  an  equal  interval  of  time.  This 


900  QUALITY    OF    AUDITORY    PERCEPTIONS. 

arrangement  produces  a  characteristic  musical  tone.  If,  however, 
holes  are  made  in  another  circle  of  the  same  disc  perforated  at  unequal 
distances  apart,  the  current  of  air  directed  against  the  disc  gives  rise 
to  a  whirring,  rushing  nonmusical  noise,  because  the  movements  of  the 
sounding  body,  the  condensations  and  rarefactions  of  the  air,  are  non- 
periodic. 

Every  sound  must  last  a  certain  length  of  time  in  order  to  be  heard  by 
the  ear  (the  feeblest  sound  at  least  two  seconds) ;  on  the  other  hand,  after 
a  sound  is  once  heard,  the  stimulation  of  the  ear  persists  for  some  time. 
Hence,  when  sounds  recur  at  short  intervals,  no  intermission  can  be 
detected. 

The  normal  ear  distinguishes  in  every  tone  three  distinct  qualities: 

1.  The  Intensity  of  the  Tone. — This  depends  upon  the  amplitude  of 
the  vibrations  of  the  sounding  body.     It  is  well  known  that  a  gradually 
weaker   and  weaker   sounding   string   exhibits  correspondingly  smaller 
amplitude  of  vibration.     The  intensity  of  a  sound  corresponds  to  the 
degree  of  illumination  or  brightness  in  vision. 

2.  The  Pitch  of  the  Tone. — This  depends  upon  the  number  of  vibra- 
tions that  occur  in  a  given  unit  of  time.      This  also  is  demonstrated  by 
means  of  the  siren.     If  the  rotating  disc  have  a  series  of  40  holes,  and 
another  of   80  holes,  at  equal  intervals,  on    blowing   a  current   of  air 
against  the  rotating  disc,  two   sounds  of  unequal  pitch  will  be  heard, 
one  being  an  octave    above  the  other.     The    perception  of  pitch  cor- 
responds to  the  sensation  of  color  in  vision. 

3.  The  quality  or   timbre  of  the  tone,  which  is  peculiar  to  different 
sonorous  bodies.     As  will  appear  later,  this  depends  upon  the  peculiar 
form  of  the  vibration  of  the  sonorous  body.     There  is  no  analogous 
sensation  in  the  case  of  light. 

Perception  of  Pitch. — Through  the  sense  of  hearing,  it  is  learned  that  different 
tones  have  a  different  pitch.  In  this  connection  the  established  difference  in 
the  pitch  of  the  notes  of  the  so-called  musical  scale  or  gamut  is  characteristically 
distinct  to  the  normal  ear.  In  addition,  there  are  four  tones  in  the  scale  that, 
when  sounded  together,  cause,  in  the  normal  ear,  the  sensation  of  pleasing  sound; 
and  that,  when  once  recognized,  may  be  easily  reproduced  always  with  charac- 
teristic difference  in  pitch.  These  are  the  tones  of  the  so-called  accord  or  major 
chord,  consisting  of  the  first,  third,  and  fifth  tones  of  the  scale,  to  which  the  eighth 
tone  or  octave  is  added.  It  is  necessary  to  determine  first  the  pitch  of  the  tones 
of  the  accord,  and  then  that  of  the  other  tones  of  the  scale.  The  siren  serves  for 
the  determination  of  the  first,  and  from  this  the  others  can  easily  be  calculated. 
Four  concentric  circles  are  drawn  upon  the  disc  of  the  siren,  the  inner  one  contain- 
ing 40  holes,  the  second  50,  the  third  60,  and  the  outer  one  80,  all  of  the  holes 
being  at  an  equal  distance  from  one  another.  If  the  disc  be  rotated,  and  a  current 
of  air  be  forced  against  each  series  of  holes  in  turn,  there  will  be  heard  successively 
the  four  tones  of  the  accord  (major  chord) .  When  the  entire  four  series  are  blown 
upon  simultaneously,  the  major  chord  is  produced  in  complete  purity.  The 
relative  number  of  the  holes  in  the  four  series  indicates,  in  the  simplest  manner, 
the  relative  pitch  of  the  tones  of  the  major  chord.  While  40  condensations  and 
rarefactions  of  the  air  in  each  revolution  are  necessary  to  produce  the  fundamental 
tone,  double  this  number  in  the  same  time  (one  revolution)  are  required  to  pro- 
duce the  octave.  Hence,  the  relation  of  the  number  of  vibrations  of  the  funda- 
mental tone  or  keynote  to  the  octave  next  above  it  is  i  :  2 .  In  the  second  series 
there  are  50  holes,  which  produce  the  pitch  of  the  third.  Therefore,  the  relation  of 
the  fundamental  tone  to  the  third  in  this  case  is  40  :  50  or  i  :  i£  =  f ;  that  is  for 
every  vibration  of  the  fundamental  tone  there  are  f  vibration  in  the  third.  In 
the  third  series  there  are  60  holes,  which,  when  blown  upon  produce  the  fifth. 
Hence,  the  ratio  of  the  fundamental  tone  to  the  fifth  in  the  disc  is  40  :  60,  or 
i  :  ij  —  f.  In  this  way  the  pitch  of  the  four  tones  of  the  major  chord  is  deter- 
mined experimentally;  it  is  found  that  the  number  of  vibrations  of  the  first,  third, 
fifth,  and  octave  are  to  each  other  as  i  :  ;  ?, ;  :  2. 


QUALITY    OF    AUDITORY    PERCEPTIONS.  QOI 

The  minor  chord  is  just  as  agreeable  to  the  normal  ear  as  the  major, 
from  which  it  differs  in  the  fact  that  its  third  is  a  half-tone  lower.  It  may  be 
readily  shown  by  the  siren  that  the  minor  third  is  produced  by  a  number  of  vibra- 
tions that  have  the  relation  of  6  :  5  to  the  fundamental  tone;  that  is  if  5  vibra- 
tions occur  in  a  given  time  in  the  fundamental  tone,  then  6  occur  in  the  minor 
third;  and  its  vibration  number  is,  therefore,  f. 

From  these  relations  of  the  major  and  minor  chords,  the  relations  of  other 
agreeable  tones  in  the  scale  may  readily  be  calculated,  and  it  must  be  remembered 
that  the  octave  of  a  tone  always  yields  the  fullest  and  most  complete  harmony. 
It  is  evident  that  if  the  major  third,  the  minor  third,  and  the  iifth  harmonize 
with  the  fundamental  tone,  or  keynote,  they  must  also  harmonize  with  its  octave. 
Hence,  from  the  major  third,  with  the  vibration-ratio  f,  there  is  obtained  the 
minor  sixth  =  |;  from  the  minor  third,  with  f,  the  major  sixth  =  (fa  =)  |; 
from  the  fifth,  with  f ,  the  fourth  =  f .  This  process  is  known  as  the  inversion 
of  the  intervals.  These  tone-relations  are,  collectively,  the  consonant  intervals 
of  the  scale. 

The  dissonant  intervals  of  the  scale  may  be  estimated  from  these  consonant 
relations  as  follows:  There  are  known  the  fundamental  tone  C,  with  the  vibra- 
tion-number i,  the  third  E  =  f ,  the  fifth  G  =  f,  the  octave  C1  =  2.  From 
the  fifth,  or  dominant,  G  there  is  constructed  a  major  chord ;  this  is  G,  B ,  D l .  The 
vibration-ratio  of  these  three  tones  is  evidently  the  same  as  in  the  major  chord 
C,  E,  G.  Hence,  the  number  of  vibrations  of  G  :  B,  is  as  that  of  C  :  E.  Substitut- 
ing the  values  in  this  equation,  we  have  f :  B  =  i  :  f ;  so  that  B  =  -1/-.  Further, 
D1  :  B  =  G  :  E;  therefore,  D  :  -\*  =  f  :  f,  or  D1  =  V,  °r  E)  an  octave  lower 
=  f.  If  a  major  chord  is  constructed  upon  F  (subdominant),  that  is  F,  A,  C1, 
the  relation  of  A  :  C1  =  E  :  G;  or  A  :  2  =  f  :  f,  and  A  =  f .  Finally,  F  :  A 
=  C  :  E;  or  F  :  f  =  i  :  f ,  and  F  =  f.  Consequently,  all  the  tones  of  the  scale 
have  the  following  vibration-ratios:  I.  C  =  i;  II.  D  =  f;  III.  E  =  f ;  IV. 
F  =  f ;  V.  G  =  |;  VI.  A  =  $;  VII.  B  =  V;  VIII.  C1  =  2. 

Since  1885  it  has  been  agreed  to  call  a  tone  of  435  vibrations  per  second 
a.  The  previous  agreement  was  440  vibrations  for  a.  From  this  the  absolute 
number  of  vibrations  for  the  tones  of  the  scale  is  estimated,  using  the  foregoing 
vibration-ratios:  C  =  33  vibrations;  D  =37. 125;  £=41.25;  F=44; 
G  =  49-5J  A  =  55;  B  =  61.875.  The  number  of  vibrations  of  the  tones  of  the 
octave  above  are  found  by  multiplying  these  figures  by  2. 

The  lowest  notes  used  in  music  are:  double-bass  E,  with  41.25  vibrations; 
piano  C  with  33;  grand  piano  A1  with  27.5,  and  organ  C1  with  16.5.  The  highest 
notes  in  music  are  the  piano  cv,  with  4224  vibrations,  and  dv  on  the  piccolo-flute, 
with  4752  vibrations  in  the  second. 

The  limits  of  audible  sounds  lie  between  16  and  23  vibrations  per 
second,  on  the  one  hand,  and  20,480 — evn — (at  the  most  avn)  on  the 
other;  they  embrace  about  ioj  octaves.  These  boundaries,  however, 
depend  a  good  deal  upon  the  intensity  of  the  tone.  Fewer  vibrations  than 
1 6  in  the  second  (organ-tones)  are  not  heard  as  tones,  but  as  separate, 
rumbling  impulses.  Beyond  the  highest  tones,  produced  by  stroking 
small  tuning-forks,  or  by  metallic  rods,  harmonica-tongues,  or  small 
whistles,  the  ear  likewise  no  longer  appreciates  the  vibrations  as  tones, 
but  these  cause  instead  a  piercing,  painful  impression  upon  the  ear. 
The  highest  tones,  which  the  ear  is  no  longer  capable  of  appreciating, 
still  affect  the  sensitive  flame. 

The  power  of  hearing  high  notes  decreases  with  advancing  age  about  £  an 
octave.  In  rare  cases  tones  of  35,000  vibrations  can  be  perceived.  During 
contraction  of  the  tensor  tympani,  tones  of  from  3000  to  5000  vibrations  higher 
may  be  heard,  but  rarely  more.  According  to  Lucae  there  are  among  normal 
individuals,  and  especially  among  those  hard  of  hearing,  some  whose  ears  are 
better  adapted  for  hearing  deep  tones,  others  for  hearing  high  tones.  He  calls 
them  deep-hearing  or  high-hearing  persons  respectively.  Both  conditions  are 
disadvantageous  for  the  normal  perception  of  speech.  The  deep-hearing  individ- 
uals hear  the  high  consonants  imperfectly,  for  example  ch  in  "Kirche";  while 
the  high-hearing  individuals  hear  the  deep  consonants  indistinctly,  for  example 
ch  in  "Auch."  Diminished  tension  of  the  sound-conducting  apparatus  decreases 


pO2  QUALITY    OF    AUDITORY    PERCEPTIONS. 

the  perception  for  high  tones.  Abnormal  power  of  hearing  low  tones  is  present 
also  in  cases  of  rheumatic  facial  paralysis,  that  for  hearing  high  tones  in  cases  of 
absence  of  the  tympanic  membrane,  the  malleus  and  the  incus.  The  stapedius 
is  said  to  possess  the  power  of  making  the  highest  high  tones  (even  up  to  80,000 
vibrations)  perceptible  at  the  expense  of  the  low  ones.  Pathologically,  an 
increased  perception  for  high  tones  is  found  in  conjunction  with  any  condition 
producing  increased  tension  of  the  sound-conducting  apparatus. 

If  the  eye  be  compared  with  the  ear,  it  is  evident  that  the  ear  greatly  exceeds 
the  eye  in  its  range  of  perception.  As  the  red  of  the  spectrum  makes  about  456 
billions  of  vibrations  in  the  second,  and  the  visible  violet  only  667  billions,  the  eye 
can  take  cognizance  only  of  vibrations  of  the  other  that  are  less  than  i  octave 
from  each  other  (double  number  of  vibrations). 

How  many  vibrations  must  follow  successively  for  the  ear  to  receive 
the  impression  of  a  tone  ?  Two  are  sufficient  in  the  case  of  low  tones  up 
to  3168  vibrations,  5  for  a  tone  of  6000,  10  for  one  of  7040  per  second, 
20  for  all  tones.  When  tones  follow  one  another  in  rapid  succession, 
they  are  heard  as  separate  tones  if  there  is  an  interval  of  at  least  o.i 
second  between  them;  if  the  interval  is  less,  tones  become  fused,  al- 
though for  many  musical  tones  a  shorter  interval  is  sufficient. 

A  person  is  said  to  have  an  "accurate  ear'7  who  is  able  to  distinguish  a 
difference  in  the  pitcji  of  two  tones  of  nearly  the  same  number  of  vibra- 
tions. This  power^an  be  greatly  increased  by  practice,  so  that  musi- 
cians can  distinguish  tones  that  have  only  a  difference  of  pitch  of  -^-g- 
or  even  T^IRT  °f  their  number  of  vibrations.  It  is  easier  to  determine 
differences  in  pitch'  from  the  purity  of  musical  intervals  than  when 
tones  are  almost  in  unison. 

With  reference  to  the  time-sense  of  the  ear,  it  should  be  remarked 
that  time  is  appreciated  with  greater  precision  by  the  ear  than  by  any 
other  sense-organ. 

Pathological. — Many  normal  persons  are  said  to  hear  the  same  tone  higher 
with  one  ear  than  with  the  other;  v.  Wittich  found  that,  during  an  attack  of  in- 
flammation of  the  ear;  he  heard  a  tone  a  half-note  higher  with  one  ear  than  with 
the  other,  Spalding  even  a  minor  third  higher.  In  a  case  seen  by  Moos,  the  deep 
tones  were  heard  one-third  of  a  tone  too  high,  the  high  ones  too  low.  Perhaps  the 
cause  of  the  unilateral  heightening  of  tone-perception  associated  with  this  condition, 
which  has  been  designated  binaural  diplacusis,  consists  in  an  abnormal  change 
in  those  portions  of  the  labyrinth  that  are  set  in  sympathetic  vibration.  The 
condition  designated  monaural  diplacusis,  in  which  a  note  sounded  in  one  ear 
is  perceived  as  two  notes,  is  rare.  It  is  due  to  the  irritation  of  the  elements 
producing  the  second  tone  in  addition  to  those  producing  the  first  tone.  In 
rare  cases,  sudden  loss  of  the  perception  of  certain  tones  has  been  observed,  for 
example  bass-deafness;  in  a  case  described  by  Magnus,  the  tones  from  d1  to  h1 
were  not  heard. 

Perception  of  Intensity. — With  respect  to  the  intensity  of  the  tone  it  has 
been  established  that  it  is  dependent  upon  the  amplitude  of  the  vibrations  of 
the  sounding  body.  The  intensity  of  the  tone  is  proportional  to  the  square  of 
the  amplitude  of  the  vibrations;  consequently,  with  an  amplitude  multiplied 
2,  3,  01-4  times,  the  intensity  of  the  tone  is  4,  9,  1 6  times  as  great.  As  the  sound- 
vibrations  are  transmitted  to  the  ear  by  the  wave-movements  of  the  air,  it  is  evi- 
dent that,  just  as  the  waves  in  water  become  progressively  smaller  and  smaller 
with  the  distance  from  their  point  of  origin,  until  they  finally  disappear,  so  also 
the  intensity  of  the  sound  diminishes  with  the  distance  of  the  sounding  body 
from  the  ear,  and  finally  it  must  become  zero.  The  sound-intensities,  however, 
are  not  exactly  as  the  inverse  ratios  of  the  squares  of  the  distances  from  the  ear 
to  the  source  of  the  sound,  but  the  intensity  diminishes  slowly  near  the  source 
of  the  sound,  and  more  rapidly  as  the  distance  increases.  The  ear  is  little  sen- 
sitive to  differences  in  intensity;  differences  can  be  distinguished,  if  the  intensities 
are  in  the  proportion  of  72  MOO. 

For  the  determination  of  the  sound-intensity  that  is  necessary  to  stimulate 
the  ear  the  following  methods  may  be  pursued:  (i)  A  feeble  source  of  sound, 


PERCEPTION    OF    TIMBRE.       ANALYSIS    OF    VOWELS.  903 

such  as  a  ticking  watch,  is  placed  horizontally  at  a  distance  from  the  ear,  and, 
by  bringing  it  closer  and  removing  it  further  away,  the  most  remote  point  is 
determined  at  which  the  ticking  can  be  heard.  The  distance  is  determined  by 
measurement.  (2)  Itard  uses  a  small  hammer,  suspended  like  a  pendulum, 
which  strikes  on  a  hard  surface  when  allowed  to  fall.  The  sound  is  increased 
4-fold,  g-fold,  and  i6-fold  when  the  angle  of  elevation  is  2,  3,  or  4  times  as  great, 
although  this  is  true  only  when  the  elevation  does  not  exceed  60.  (3)  In  a  similar 
manner,  balls  of  different  weight  may  be  dropped  from  different  heights  on  a 
sounding-plate.  In  this  case  the  sound-intensities  are  proportional  to  the  pro- 
duct of  the  weight  of  the  ball  by  the  height  of  the  fall.  (4)  If  a  tuning-fork  is 
permitted  to  sound  before  the  ear,  always  with  the  same  amplitude  of  vibra- 
tion, a  normal  ear  hears  the  note  longer  than  a  diseased  ear. 

It  has  been  determined  with  respect  to  the  limits  of  barely  appreciable  tone- 
intensities  that  a  cork  sphere,  weighing  i  milligram,  falling  from  a  height  of  i 
mm.  on  a  glass  plate,  may  be  heard  at  a  distance  of  5  cm.  There  are,  however, 
individual  variations,  and  also  differences  in  acuity  between  the  two  ears  of  the 
same  person.  Topler  and  Boltzmann  estimate  the  amplitude  of  vibration  of 
the  air-particles  that  are  capable  of  setting  the  tympanic  membrane  in  vibration 
so  that  an  auditory  sensation  results  as  equal  to  only  0.00004  mm.;  Rayleigh 
estimates  it  as  only  o.oooooi  mm.  Direct  observation  of  movements  so  minute 
would  exceed  the  limits  of  the  best  microscope,  through  which  it  is  possible  to 
recognize  objects  not  smaller  than  0.000217  mm.  in  diameter.  The  author's 
brother  made  the  discovery  that  animals  make  sounds  that,  on  account  of  their 
weakness,  cannot  be  heard  by  human  ears.  Thus,  some  Capricorn  beetles  (Cer- 
ambyx)  produce  shrill  tones  by  rubbing  a  grooved  plate  on  the  neck  against  the 
sharp  edge  of  the  chest.  For  example,  Gracilia  pygmacea  produces  the  tone 
f111,  with  1413  vibrations,  which  cannot  be  heard  because  of  its  weakness. 
[The  number  of  vibrations  (s)  of  the  tone  is  estimated  from  the  length  (1)  of  the 
rubbing  plate  of  the  insect  in  mm.,  the  number  of  grooves  (a)  to  each  mm.,  and 
the  time  of  the  rubbing  motion;  s  =  (1 .  n)  :  t.]  Larger  Capricorn  beetles  produce 
sounds  that  can  be  heard. 

PERCEPTION  OF  TIMBRE.     ANALYSIS  OF  VOWELS. 

By  tone-quality  or  timbre  is  meant  a  special  property  of  tones,  by  means  of 
which  they  may  be  distinguished  independently  of  their  pitch  and  intensity. 
For  example,  a  flute,  a  horn,  a  violin,  and  a  human  voice  may  produce  the  same 
note  with  equal  intensity,  and  yet  each  is  immediately  recognized  by  its  quality 
or  timbre.  What  constitutes  the  quality?  Investigations,  especially  those 
of  v.  Helmholtz,  have  shown  that  of  all  the  sound-producing  instruments,  only 
the  metal  rod  fastened  at  one  end  and  swinging  to  and  fro  like  a  pendulum,  and 
the  tuning-fork,  produce  simple  oscillatory  and  continuous  vibrations.  This 
may  be  shown  by  fastening  a  fine  point  to  one  branch  of  a  tuning-fork,  and 
registering  its  movements  on  a  moving  strip  of  smoked  paper,  on  which  there  will 
appear  then  perfectly  uniform  wave-lines,  with  equal  elevations  and  depressions. 
Only  those  sounds  that  are  produced  by  such  simple  oscillatory  vibrations  are 
called  "tones." 

Further  investigations  have  shown  that  the  tones  of  all  musical  instruments 
and  of  the  human  voice,  all  of  which  have  a  characteristic  quality,  are  composed 
of  many  individual  simple  tones.  Of  these,  there  is  one  that  is  especially  con- 
spicuous by  reason  of  its  intensity,  and  which  at  the  same  time  determines  the 
pitch  of  the  whole  composite  "tone-picture."  This  is  known  as  the  fundamental 
tone  or  keynote.  The  other,  weaker  tones,  which  are  added  to  this  fundamental 
tone  or  keynote  vary  in  number  and  intensity  for  the  different  instruments. 
They  are  called  overtones.  Their  rate  of  vibration  is  always  2,  3,  4,  or  5  times  that 
of  the  fundamental  tone.  In  general,  it  may  be  said  that  all  those  musical  tones 
that  possess  numerous  strong  overtones,  especially  high  ones,  have  a  sharp,  cut- 
ting, rough  quality  (for  example  trumpet,  clarionet),  and,  on  the  contrary,  tones 
with  few  and  weak,  and  especially  deep  overtones  are  peculiarly  soft  and  mild 
(for  example  flute).  Only  a  trained,  musical  ear  is  able,  without  assistance,  to 
detect  the  overtones  present  in  a  given  note,  in  addition  to  the  fundamental 
tone.  This  is  easily  done,  however,  with  the  aid  of  so-called  resonators.  These 
are  funnel-shaped  hollow  receivers  connected  with  the  external  auditory  canal 
by  means  of  a  short  tube.  They  are  so  attuned  that  each  succeeding  resonator 
possesses  as  its  fundamental  tone  that  of  the  next  following  multiple  of  the  first. 


9°4 


PERCEPTION    OF    TIMBRE.       ANALYSIS    OF    VOWELS. 


If,  for  example,  the  first  resonator  has  B  as  its  fundamental  tone  (which  is  easily 
heard  by  blowing  upon  it) ,  then  the  tone  of  the  second  resonator  is  b  (of  the  fol- 
lowing octave),  that  of  the  third  is  f1  (three  times  the  rate),  that  of  the  fourth 
b1  (the  second  higher  octave),  that  of  the  fifth  d11  (five  times  the  rate).  Then 
come  fn,  as11,  b11,  etc. 

If  such  a  resonator  be  applied  to  the  ear,  it  is  easy  to  distinguish  the  weakest 
overtone  of  the  same  rate  of  vibration  in  the  sound  of  a  musical  instrument 
and  v  Helmholtz  found  that  each  instrument  possesses  a  definite  number  of 
overtones,  differing  in  pitch  and  intensity.  The  tuning-fork,  and  the  simple 
swinging  metal  bar,  however,  have  no  overtones,  but  yield  only  the  single  funda- 
mental tone.  Following  v.  Helmholtz,  only  the  simple  oscillatory  sound-vibra- 
tions are  designated  simple  tones,  while  sound-vibrations  consisting  of  funda- 
mental tone  and  overtones  are  designated  musical  tones  (Klange) . 

If  it  be  borne  in  mind  that  each  musical  tone  possesses  a  fundamental  tone, 
and  a  number  of  overtones  of  definite  intensity,  which*  determine  its  quality, 
it  becomes  possible  to  construct  geometrically  the  vibration-curve  of  the  tone  by 
a  combination  of  the  vibrations  of  the  fundamental  tone  and  those  of  the  overtones. 
In  Fig.  327  the  continuous  curved  line  A  represents  the  vibration-curve  of 
the  keynote,  and  B  that  of  the  first,  moderately  weak  overtone.  The  combination 
of  these  two  curves  is  made  by  putting  together  the  heights  of  the  ordinates, 

whereby  the  ordinates  lying  above  the 
horizontal  are  added  to  those  of  the 
keynote,  and  those  below  the  hori- 
zontal are  subtracted.  In  this  way 
the  curve  C  is  obtained,  which  does  not 
correspond  to  a  simple  oscillation,  but 
to  an  unsteady  movement.  To  the 
curve  C  a  new  curve  of  the  second 
overtone,  with  three  times  the  rate  of 
vibration,  can  be  added,  etc.  The  final 
result  of  all  such  combinations  is  that 
the  vibration-curves  corresponding  to 
compound  musical  tones  are  irregular, 
periodic  curves.  All  of  these  curves 
must,  naturally,  differ  according  to  the 
number  and  the  height  of  the  combined 
overtone-curves.  Hence,  if  the  number 
and  the  intensity  of  the  overtones  in 
the  sound  of  an  instrument  have  been 
analyzed  by  the  resonators,  the  geomet- 
rical vibration-curve  of  the  sound  can  be 
constructed  therefrom. 

The  form  of  vibration  of  the  same 
tone  may  vary  considerably,  if  in  com- 
bining the  curves  A  and  B  the  curve  B  is  displaced  laterally.  If  B  is  displaced  to  such 
an  extent  that  the  depression  r  falls  under  A,  the  addition  of  the  two  curves 
yields  the  curve  r  r  r  with  narrow  summits  and  broad  valleys.  If  B  is  displaced 
still  further,  until  the  summit  h  coincides  with  A,  still  another  form  is  produced. 
Hence,  by  displacing  the  phases  of  the  wave-movements  of  the  simple  oscillatory 
vibrations  that  are  to  be  combined,  there  arise  numerous  different  forms  of 
the  same  musical  tone,  but  this  displacement  of  the  phases  has  no  influence  what- 
ever upon  the  ear. 

The  simple  tones,  produced  by  simple  oscillations,  have  a  uniform  increase 
and  decrease  in  the  oscillations,  while  the  musical  tones,  according  to  the  number 
and  the  strength  of  their  overtones,  have  a  characteristic  form  of  elevation  and 
depression  of  the  vibration-curve. 

Just  as  the  irregular  curve  of  vibration  of  a  musical  tone  may  be  constructed 
from  several  simple  oscillating  tones,  so  every  such  curve  may  be  analyzed.  In 
fact,  Fourier  has  shown  that  each  complicated,  irregular  curve  of  vibration  may 
be  resolved  into  a  sum  of  simple  oscillatory  vibrations,  whose  number  has  a  ratio  of 
1:2:3:4  .  .  ..  .  There  can  be  only  one  set  of  simple  tones  in  such  an  analysis. 
On  the  other  hand,  every  complicated  irregular  movement  may  be  resolved  in 
many  ways  into  movements  that  are  likewise  irregular.  The  result  of  this  deduc- 
tion is  that  the  quality  of  a  musical  tone  depends  upon  the  characteristic  form  of 
the  vibratory  movement. 


FIG.  327. 


PERCEPTION    OF    TIMBRE.       ANALYSIS    OF    VOWELS.  905 

Analysis  of  the  Vowels. — The  human  larynx  represents  a  wind-instru- 
ment, with  vibrating,  elastic  reeds  (vocal  bands).  In  producing  the 
various  vowels,  the  mouth  assumes  a  characteristic  form,  so  that  its 
cavity  sustains  a  definite  fundamental  tone,  which  is  produced  when 
the  air  passes  into  it  from  the  larynx.  In  this  manner  certain  over- 
tones are  added  to  the  fundamental  tone  produced  by  the  larynx,  and 
they  give  to  the  voice  the  vocal  quality.  The  vowel-sound,  therefore, 
is  the  timbre  of  a  musical  sound  produced  by  the  larynx.  The  timbre 
depends  upon  the  number,  strength  and  pitch  of  the  overtones,  and  \  the 
latter  depend  upon  the  configuration  of  the  vocal-cavity  in  producing 
the  various  vowels. 

If  the  different  vowels  are  sung  one  after  the  other  in  a  definite  pitch,  for  ex- 
ample b,  it  can  be  determined  with  the  aid  of  the  resonators  what  overtones  are 
added  to  the  fundamental  tone,  and  in  what  strength.  According  to  v.  Helm- 
holtz,  if  the  note  b  is  sung,  there  is  one  characteristic  overtone  of  definite,  absolute 
pitch  for  three  vowels,  namely  b11  for  A;  b1  for  O,  and  f  for  U.  The  other  vowels 
(and,  in  German,  the  modified  vowels)  have  each  two  especially  characteristic 
overtones,  because  the  oral  cavity  is  so  shaped,  while  producing  them,  that  there 
is  a  fundamental  tone  both  for  the  posterior,  more  capacious  portion,  and  for  the 
anterior,  narrow  portion  (I  and  E,  p.  612).  According  to  v.  Helmholtz  these 
two  overtones  are  for  E,  bm  and  f1  ;  for  I  div  andf;  for  A  gm  and  d11:  for  6, 
cis111,  and  f1;  for  U  gin  and  f.  These  are,  however,  only  the  especially  character- 
istic overtones.  Fundamentally  there  exist  for  the  vowels  almost  generally  many 
others,  which,  however,  are  considerably  less  conspicuous. 

Thus  the  partial  tones  present  in  the  same  absolute  pitch  are  always  charac- 
teristic of  the  vowels;  according  to  v.  Helmholtz,  Hensen,  Pipping  and  others, 
they  are  harmonic  overtones  of  the  note  of  the  vocal  bands  strengthened  by 
resonance.  According  to  Hermann  the  overtone  is  an  independent  note  produced 
in  the  oral  cavity,  and  it  need  have  no  harmonic  relation  with  the  sound  produced 
by  the  larynx. 

Just  as  it  is  possible  to  resolve  a  vowel  into  its  fundamental  tone  and  overtones 
by  means  of  resonators,  so  the  vowel  can  be  reproduced  by  sounding  together 
the  strong  fundamental  tone  and  the  weaker  overtones.  This  may  be  done  in 
the  following  ways:  (i)  Most  simply  by  singing  loudly  a  vowel,  for  example  A, 
at  a  certain  pitch,  into  an  open  piano  against  the  free  strings,  while  the  damper 
is  at  the  same  time  raised  by  the  pedal.  If  the  voice  suddenly  ceases,  the  vowel 
is  sounded  by  the  strings  of  the  piano.  In  other  words,  all  those  strings  are  set 
into  sympathetic  vibration  whose  overtones  (apart  from  the  fundamental  tone) 
occur  in  the  vowel-sound.  They  continue  to  sound,  therefore,  for  some  time 
after  the  voice  has  been  interrupted.  This  experiment  may  be  modified  by  raising 
the  damper  from  those  notes  only  that  occur  as  overtones  (by  holding  down  the 
keys).  In  this  way  it  is  possible  to  combine  the  vowel-sound,  note  for  note. 

(2)  The  vowel-apparatus  of  v.  Helmholtz  consists  of   a  number  of  tuning-forks, 
which  are  kept  in  constant  vibration  by  electromagnets.     The  lowest  fork  yields 
the  fundamental  tone  B,  the  others  in  succession  the  overtones.     In  front  of  each 
fork  there  is  placed  a  resonance-tube,  which  can  be  opened  and  closed  by  a  lid. 
When  the  tube  is  closed,  the  tone  of  the  corresponding  tuning-fork  cannot  be 
heard,  but  when  one  or  more  of  the  tubes  are  opened  their  notes  are  heard  dis- 
tinctly with  an  intensity  proportional  to  the  size  of  the  opening.     In  this  way 
different  combinations  of  the  fundamental  tone  with  one  or  more  harmonic  over- 
tones, in  various  degrees  of  intensity,  can  be  made,  and  musical  tones  of  varying 
quality    (the  vowels)   produced,     v.   Helmholtz  made  the   following  vowel-com- 
binations:   U  =  B,  together  with  faint  b  and  f1;    O  =  subdued  B,  and  strong  b1 
and  weaker  b,  f1,  d";    A  =  b   (as  fundamental  tone),  with  moderately  loud  b1 
and  f11,  and  strong  b11  and  dm;     Ae  =  b  as  fundamental  tone,  with  b1  and  f11, 
somewhat  stronger  than  for  A,  d11  strong,    b11  weaker,  din  and  fm  as  strong  as 
possible;  E  =  b  as  fundamental  tone,  rather  strong,  with  b1  moderate,  f1  likewise, 
and  fni,  as111  flat,  and  b111  as  strong,  as  possible;   I  cannot  be  produced  in  this  way. 

(3)  G.   Appunn  has  constructed  a  vowel-apparatus  of  organ-pipes.     There  are 
20  open,  loud-sounding  pipes  from  the  fundamental  tone  to  the   19  succeeding 
overtones,  and  20  stopped,  weakly  sounding  pipes,  placed  in  two  rows  on  a  special 
air-chest.     Each  pipe  can  be  opened  and  closed  by  a  valve.     A  large  valve,  at 


PERCEPTION    OF    TIMBRE.       ANALYSIS    OF    VOWELS. 


E 


the  entrance  of  the  air-chest  allows  all  the  opened  pipes  to  sound  together.  The 
two  rows  of  pipes  make  possible  three  degrees  of  tone-intensity,  namely  loud  tones, 
when  both  rows  sound;  moderately  loud,  when  the  open  pipes  sound;  and  weak, 
when  the  stopped  pipes  alone  sound.  The  formation  of  the  vowels  by  this  ap- 
paratus is  not  so  satisfactory  as  that  by  the  tuning-forks,  because  the  pipes  do 
not  yield  simple  tones,  but  contain  several  weak  (especially  the  uneven)  overtones. 
Moreover,  the  graduation  of  tone-intensity  cannot  be  made  as  fine  as  with  the 

resonators  of  the  tuning-forks. 
However,  several  of  the  vowels 
can  be  beautifully  reproduced. 
They  always  sound  the  best 
when  they  are  quite  short.  Thus, 
a  good  A  is  produced  by  b  and  b1 
weak,  fn  moderately  strong,  b11 
strong,  din  weak  and  fni  moderately 
strong.  U  is  produced  by  B  strong, 
and  b  moderately  strong.  Deep 
O  =  B  and  b  moderately  strong,  f1 
and  b1  strong,  with  f11  weak.  A  high 
O  is  produced  by  b1  weak,  d11  mod- 
erately strong,  fn  and  b11  strong,  din 
and  f111  weak.  The  other  vowel- 
sounds  are  produced  imperfectly: 
E  =  d11  weak,  with  b11,  d111,  a111  strong. 
A  =  b1,  f11,  b11  weak,  d111,  f"1  moder- 
ately strong,  a111  flat  strong  and 
a111  moderately  strong.  O  =  b1  weak, 
f11,  b11  strong,  fm  weak,  bm,  civ,  div 
moderately  strong.  U  =  f1,  f11  'weak, 
f ni,  civ  strong.  I  cannot  be  produced. 
The  highest  pipe  div  yields  approxi- 
mately the  character  of  I.  Similarly 
the  stopped  pipe  B  yields  an  obscure 
U  and  the  open  B  a  rather  clearer  U. 
According  to  the  foregoing  con- 
siderations, the  vowels,  being  com- 
posed of  a  fundamental  tone  and 
overtones,  must  have  definite  vibra- 
tion-curves. These  may  be  demon- 
strated in  various  ways.  If  a  vowel 
be  spoken  against  a  delicate  glass 
membrane  closing  the  extremity  of 
a  hollow  cylinder,  at  whose  center 
is  a  fine  curved  style,  applied  to  a 
cylinder  covered  with  a  layer  of 
paraffin-wax  and  capable  of  revolv- 
ing uniformly  and  of  being  displaced 
laterally,  the  style  will  trace  the 
vowel-curve  on  the  layer  of  wax. 
If,  now,  a  small  point  connected 
with  the  membrane  is  allowed  to 
run  in  the  groove  traced  by  the 
style,  the  resulting  vibrations  of  the 
membrane  will  reproduce  the  sound 
(Edison's  phonograph).  Enlarged 
curves  of  the  sound-impressions 
may  be  obtained  by  transmitting 

the  impressions  on  the  cylinder  to  a  suitable  apparatus.  The  vowels  yield  the 
same  sound  only  when  the  rapidity  of  revolution  of  the  cylinder  remains  the  same. 
If  on  the  other  side  of  such  a  membrane,  there  is  a  small,  closed  gas-chamber, 
from  which  a  gas-burner  passes,  a  characteristic  tracing  of  the  vibrating  flame 
can  be  obtained  in  a  rotating  mirror  when  the  vowel  is  produced  (Fig.  328). 
Nagel  and  Sawojloff  made  use  of  the  tympanic  cavity  and  the  tympanic  mem- 
brane for  this  purpose — gas  being  introduced  into  the  tympanic  cavity  of  a  fresh 


0 


U 


FIG.  328. — Flame  Pictures  and  Phonautographic  Tracings 
of  the  Vowels.  The  vowels  were  sung  in  the  key  of  C' 
(=  256  vibrations  in  the  second).  The  measure  a  b 
shows  the  height  of  the  flame  at  rest.  The  curves 
traced  below  are  registered  by  the  phonautograph. 


FUNCTION    OF    THE    LABYRINTH    IJN    THE    ACT    OF    HEARING.  907 

animal's  head,  and  this  being  connected  with  a  gas-bttrner — and  they  were  thus 
enabled  to  see  characteristic  vowel-curves  in  a  rotating  mirror. 

If  one  limb  of  a  Y-shaped  tube  be  fitted  into  the  nostrils,  while  the  second  is 
connected  with  a  gas-fixture,  and  the  third  with  a  burner,  every  time  a  vowel 
is  uttered  the  flame  is  set  into  sonorous  vibrations,  which  reproduce  exactly  the 
sound  of  the  vowel.  If  the  vowel  is  given  a  nasal  sound,  the  flame  shoots  up  high, 
because  the  air  is  forced  into  the  nasal  cavity.  Such  a  flame  also  may  be  analyzed 
in  the  rotating  mirror. 

The  movements  of  the  membrane  may  be  drawn  or  photographed  by  means 
of  a  writing  lever  placed  in  contact  with  it.  In  this  way  characteristic  curves 
are  obtained  for  each  vowel:  phonautograph  of  Hensen,  A.  Fick,  and  others, 
Fig.  328  shows  the  flame-pictures  of  the  vowels,  and  under  each  the  corresponding 
tracing  as  registered  by  the  phonautograph. 

FUNCTION  OF  THE  LABYRINTH  IN  THE  ACT  OF  HEARING. 

With  respect  to  the  part  played  by  the  ear  in  the  appreciation  of 
timbre  it  may  be  said  that,  just  as  a  musical  tone  can  be  resolved  into  its 
fundamental  tone  and  overtones  by  means  of  resonators,  so  the  ear  is 
able  to  make  such  an  analysis.  The  ear  resolves  the  complicated  wave- 
motions  into  their  components,  which  it  perceives  as  separate  tones 
harmonizing  with  one  another.  As  a  result  of  adequately  trained 
observation  the  ear  can  bring  these  components  separately  to  the  notice 
of  consciousness,  and  it  distinguishes  as  different  qualities  of  sound 
only  different  combinations  of  these  simple  tone-sensations.  This 
resolution  of  the  complicated  vibrations  into  simple  pendulum-like 
vibrations  is  a  most  striking  property  of  the  ear.  What  are  the  mechan- 
isms in  the  ear  through  which  this  resolution  is  effected?  If  with  the 
dampers  raised  the  vowel-sound  A  be  sung  loudly  in  a  certain  note 
(for  example  b)  against  the  strings  of  an  open  piano,  all  of  those  strings, 
and  only  those  strings,  are  set  into  vibration  that  are  contained  in  the 
vowel-sound.  It  must,  therefore,  be  assumed  that  a  similarly  acting 
apparatus  is  present  in  the  ear,  which  is  tuned  for  certain  pitches,  and 
is  set  into  sympathetic  vibration  when  a  note  is  sounded,  like  the  strings 
of  a  piano.  "If  we  could  connect  each  string  of  a  piano  with  a  nerve-fiber 
in  such  a  way  that  the  nerve-fiber  would  be  stimulated  and  receive  an 
impression  every  time  the  string  was  set  in  motion,  each  musical  tone 
that  strikes  the  instrument  would,  in  fact,  as  is  actually  the  case  in  the 
ear,  excite  a  series  of  sensations,  corresponding  exactly  to  the  oscillatory 
vibrations  into  which  the  original  movement  of  air  could  be  resolved; 
and  thus  the  existence  of  every  individual  overtone  would  likewise  be  per- 
ceived exactly  as  it  is  by  the  ear.  Under  these  circumstances  the  percep- 
tions of  the  various  high  tones  would  devolve  upon  different  nerve-fibers, 
and,  therefore,  would  occur  separately  and  independently  of  one 
another.  Now,  in  fact,  the  recent  discoveries  of  the  microscopists 
as  to  the  intimate  structure  of  the  ear  permit  the  assumption  that 
similar  arrangements  exist  in  the  ear,  such  as  we  have  just  considered. 
Thus,  the  end  of  each  fiber  of  the  auditory  nerves  is  connected  with 
small  elastic  particles,  of  which  we  must  assume  that  they  are  set  in 
vibration  in  sympathy  with  the  sound-waves"  (v.  Helmholtz). 

v.  Helmholtz  believed  formerly  that  the  arches  of  Corti  are  the  appa- 
ratus attuned  to  the  individual  tones,  stimulating  the  nerve  by  sym- 
pathetic vibration;  in  other  words  that  they  represent  a  sort  of  keyboard. 
As,  however,  amphibians  and  birds  have  no  arches  of  Corti,  although 
they  are  certainly  able  to  hear  musical  tones,  the  stretched  radial  fibers 


908  SIMULTANEOUS    ACTION    OF    TWO    TONES. 

of  the  basilar  membrane  (on  which  the  organ  of  Corti  rests),  which 
are  shortest  in  the  first  turn  of  the  cochlea,  and  become  longer  near  the 
apex,  must  be  considered  as  the  organ  that  takes  up  the  vibrations. 
Hence,  there  would  be  a  fiber  of  the  basal  membrane  vibrating  in  sym- 
pathy with  each  possible  simple  tone.  According  to  Hensen  the  hairs 
of  varying  length  in  the  labyrinth  may  also  subserve  the  same  purpose. 
The  foregoing  assumption  is  sufficient  also  to  explain  the  perception 
of  noises.  Many  of  these  may  be  resolved  into  a  confused  mass  of 
simple  pure  tones.  True  noise  in  the  physical  sense  must,  like  separate 
explosions,  be  perceived  by  the  saccules  and  ampullae. 

R.  Ewald  has  proposed  a  new  theory,  the  so-called  sound-picture  theory. 
He  believes  that  the  impulses  produced  by  the  sound  on  the  basilar  membrane 
give  rise  to  a  wave-picture  (sound-picture),  the  special  form  of  which  enables 
the  basal  membrane  to  form  a  link  in  the  chain  of  transmitting  mechanisms  that 
are  interposed  between  the  sound  and  its  perception. 

If  the  parts  played  by  the  cochlea  and  the  saccules  together  with  the 
ampullae  be  compared,  it  may  be  said  that  only  the  fundamental  sen- 
sation, the  general  perception  of  hearing  from  concussion  of  the  auditory 
nerves,  as  through  blows  and  noises,  is  excited  by  the  saccules  and 
ampullae;  whereas,  on  the  other  hand,  the  pitch  and  the  depth  of  the 
vibrations  and  their  musical  character  are  appreciated  by  the  cochlea. 

According  to  another  view  each  nerve-cell  of  the  cochlea  hears  every  tone; 
therefore  separate  cells  are  not  attuned  for  different  tones.  The  sharpness  of 
hearing  is  supposed  to  result  from  the  sum  of  the  sensitive  auditory  cells,  all  of 
which  hear  the  same  thing.  According  to  Held,  several  hair-cells  are  connected 
with  one  nerve-fiber;  hence  tones  of  different  pitch  can  excite  one  and  the  same 
fiber. 

The  relations  between  the  semicircular  canals  and  the  bodily  equilibrium  are 
treated  in  the  consideration  of  the  auditory  nerve  (p.  699). 

Pathological. — In  the  presence  of  varying  degrees  of  deafness,  loss  either 
of  all  or  of  only  certain  tones  in  greater  or  lesser  amount  has  been  found.  Laby- 
rinthine affections  and  those  of  the  auditory  nerve  both  cause  disturbances  of 
hearing,  but  with  the  following  differences:  In  the  presence  of  affections  of  the 
labyrinth  tones  having  from  12  to  64  vibrations  are  heard  poorly  with  air-con- 
duction; while,  in  the  presence  of  so-called  torpor  of  the  auditory  nerve,  such 
tones  are  well  heard.  Bone-conduction  is  good  in  both  cases  for  the  lowest  tones. 
In  the  presence  of  torpor  of  the  nerve  high  tones  are  well  perceived,  but  in  that 
of  affections  of  the  labyrinth,  poorly.  The  hearing  of  spoken  sounds  and  bone- 
conduction  are  much  reduced  in  both  cases.  Double  hearing  is  rarely  produced 
by  affections  both  of  the  middle  and  of  the  internal  ear. 

SIMULTANEOUS  ACTION  OF  TWO  TONES. 

HARMONY.      BEAT.      DISCORD.      DIFFERENTIAL     TONES     AND     SUMMA- 
TION-TONES. 

If  two  tones  of  different  pitch  are  heard  at  the  same  time,  they  pro- 
duce different  sensations  in  accordance  with  the  difference  in  pitch. 

If  the  number  of  vibrations  of  the  two  tones  is  in  the  ratio  of  simple 
multiples,  or  as  i :  2  :  3  : 4,  so  that,  while  the  lower  tone  makes  one  vibra- 
tion, the  higher  one  completes  2,  or  3,  or  4,  the  ear  obtains  an  impression 
of  complete  harmony  or  concord. 

If  the  number  of  vibrations  of  the  tones  is  not  in  the  ratio  of  simple 
multiples  interference  must  result  if  the  two  are  sounded  together.  The 
summits  and  valleys  of  one  wave  can  no  longer  always  coincide  with  the 
corresponding  summits  and  valleys  of  the  other,  but  in  accordance  with  the 
difference  between  the  number  of  vibrations  there  must  be  places  where 


SIMULTANEOUS    ACTION    OF    TWO    TONES.  909 

the  summits  and  valleys  come  together.  Consequently,  if  two  summits 
fall  together  there  must  be  an  increase  in  the  strength  of  the  tone,  but 
if  the  summit  of  one  wave  coincides  with  the  valley  of  another,  there 
must  be  a  diminution  in  the  strength  of  the  tones.  In  this  way  there  is 
obtained  an  impression  of  variation  in  tone-intensity  that  is  designated 
beat  or  tremor  (battements). 

The  number  of  beats  is,  naturally,  equal  to  the  difference  between  the  number 
of  vibrations  in  the  two  tones.  The  beats  are  most  clearly  perceived  when  two 
deep  tones  of  the  same  pitch,  for  example,  of  organ-pipes,  are  slightly  out  of  tune. 
If  of  two  organ-pipes,  each  of  wrhich  produces  C  with  33  vibrations  in  the  second, 
one  is  made  to  yield  34  vibrations,  one  distinct  beat  will  be  heard  every  second. 
It  is  evident,  further,  that  the  beats  are  fewer  the  less  the  difference  between 
the  two  vibration-numbers,  and  that  they  are  more  frequent  the  greater  this 
difference.  Further,  with  equal  relative  difference  in  pitch  of  two  tones,  the 
beats  are  fewer  the  deeper  the  tones,  and  they  are  the  more  frequent  the  higher 
the  tones.  If,  for  example,  the  tone  c  with  66  vibrations  is  sounded  with  a  second 
tone  with  68  vibrations  in  the  second,  two  beats  must  occur  in  every  second 
(while  in  the  preceding  example,  with  equal  relative  differences  in  pitch,  only 
one  beat  is  heard). 

The  beats  produce  widely  different  impressions  upon  the  ear,  accord- 
ing to  the  rapidity  with  which  they  follow  one  another. 

When  they  occur  at  long  intervals,  they  may  be  perceived  as  com- 
pletely isolated  reinforcements  of  the  tone,  with  subsequent  enfeeble- 
ments;  they  thus  produce  the  sensation  of  completely  isolated  beats. 

If  the  beats  follow  one  another  more  rapidly,  the  inequality  pro- 
duced causes  a  continuous,  disagreeable,  whirring  impression  that  is 
designated  a  discordant  sensation.  The  highest  degree  of  disagreeable, 
painful  discord  is  felt  when  there  are  33  beats  in  the  second. 

The  intense  unpleasantness  of  this  sensation  may  be  well  likened  to  the  dis- 
agreeable impression  produced  by  a  nickering  light  before  the  eye.  It  is  evident 
that  in  order  to  produce  this  intense  discord,  two  low  tones  must  have  a  much 
greater  difference  of  pitch  than  two  high  tones. 

If,  by  an  increase  in  the  difference  in  the  number  of  vibrations  of  the 
tones,  the  beats  follow  oftener  than  33  in  the  second,  the  sensation  of 
harsh  discord  gradually  disappears,  as  the  beats  become  more  frequent. 
Hence  the  sensation  progresses  from  moderately  inharmonious  tone- 
ratios  (which  in  music  demand  a  resolution  in  the  succeeding  chords) 
to  more  and  more  consonant,  and  finally  to  completely  harmonious 
ratios.  These  tone-ratios  are  successively  the  second,  seventh,  minor 
third,  minor  sixth,  major  third,  major  sixth,  fourth,  and  fifth. 

As  33  beats  in  the  second  produce  the  greatest  discord,  it  is  evident  that  for 
the  production  of  discord  in  tones  of  low  pitch,  the  tones  of  the  scale  must  lie 
further  apart  than  when  they  are  of  high  pitch.  In  deep  tones  the  major  third 
may  easily  be  discordant;  in  high  tones,  on  the  contrary,  even  those  lying  close 
together  sound  much  less  discordant,  because  the  number  of  beats  quickly  exceeds 
33  in  the  second,  on  account  of  the  high  number  of  vibrations.  In  general,  there- 
fore, musical  passages  that  possess  but  little  harmony  are  much  less  inharmonious 
in  high  notes  than  in  low  ones. 

The  conditions  are  exactly  the  same  for  two  musical  tones  that  are 
heard  at  the  same  time  by  the  ear  as  for  two  simple  tones.  Under  such 
circumstances,  however,  the  overtones  come  into  consideration,  as  well 
as  the  fundamental  tones  that  determine  the  pitch.  The  degree  of  dis- 
cord of  two  musical  tones  is,  therefore,  all  the  more  prominent  the  more 
the  two  fundamental  tones  and  the  overtones  (and  finally  the  differen- 


AUDITORY    PERCEPTIONS. 

tial  tones,  which  will  be  considered  presently)  produce  beats  that  number 
about  33  in  the  second. 

Finally,  two  simple  tones  or  musical  tones  sounded  together  may  give 
rise  to  new  tones  if  they  sound  simultaneously  and  in  suitable  intensity. 
In  addition  to  these  two  primary  tones  or  musical  sounds,  a  third  new 
tone  is  heard  on  listening  intently,  the  number  of  whose  vibrations  is 
equal  to  the  difference  between  the  two  primary  tones.  These  tones 
are  called  differential  tones,  or  Andreas  Sorge's  or  Tatini's  tones. 

If,  for  example,  two  tones  in  the  relation  of  the  fifth  (2  :  3)  or  of  the  fourth 
(3  :  4)  or  of  the  third  (4  15),  are  sounded,  the  fundamental  tone  =  i  is  heard  as 
a  differential  tone.  Musical  tones  that  are  rich  in  overtones  yield  differential 
tones  of  higher  order.  Thus,  if  the  third  (produced  by  two  metal  bars)  in  a  high 
register,  namely  16:20  (=4:  5)  is  sounded,  the  tone  =  4  (fundamental  tone) 
is  readily  heard  as  the  first  differential  tone.  This  tone  4  forms,  however,  with 
1 6  another  differential  tone  of  second  order,  that  isi6  —  4=12.  In  fact,  with 
the  aid  of  resonators  the  differential  tone  of  third  order  may  be  heard,  namely 
12  — 4  =8. 

Helmholtz  showed,  further,  that  new  tones  may  also  result  through 
addition  of  their  vibration-numbers  (so-called  summation- tones). 
These  are  difficult  to  hear,  though  best  when  the  two  primary  tones  be- 
long to  the  middle  and  lower  register,  and  are  rich  in  overtones. 

When  musical  tones  are  sounded  together,  the  harmony  of  the  differential 
tones  must  also  be  taken  into  account.  In  the  major  chord  these  are  consonant; 
in  the  minor  chord  there  is  dissonance  of  the  differential  tones.  Therefore,  the 
first  have  a  finished,  complete,  satisfying  character,  while  the  latter  produce  a 
feeling  of  unsatisfactoriness,  melancholy,  contention,  which  requires  a  resolution 
into  more  finished  consonant  harmonies. 

AUDITORY  PERCEPTION.     FATIGUE  OF  THE    EAR.     OBJECTIVE 

AND  SUBJECTIVE  HEARING.  ASSOCIATED  SENSATIONS. 

AUDITORY  AFTER-SENSATIONS. 

When  the  stimulations  of  the  nerve-endings  in  the  labyrinth  are 
referred,  by  a  psychical  act,  to  the  source  of  the  sound  in  the  outer 
world,  there  result  objective  auditory  perceptions.  Only  such  stimu- 
lations, however,  are  referred  outward  as  are  transmitted  to  the  tympanic 
membrane  by  vibrations  of  the  air.  This  is  proved  by  the  fact  that, 
when  the  head  is  held  under  water,  so  that  the  external  auditory 
canals  are  rilled,  all  sound-vibrations  will  be  heard  as  if  originating 
in  the  head;  the  same  is  true  of  one's  own  voice,  if  the  auditory  canals 
are  held  closed,  and  also  of  sound-waves  conducted  through  the  bones  of 
the  skull. 

As  to  the  direction  from  which  a  sound  comes  a  judgment  is  formed 
from  the  relation  of  the  auditory  canals  to  the  source  of  the  sound,  espe- 
cially if  this  direction  is  estimated  from  time  to  time  by  turning  the  head. 
The  direction  from  which  musical  tones  combined  with  noises  come  is 
more  easily  recognized  than  that  from  which  simple  tones  come.  With 
equally  strong  stimulation  of  both  ears,  the  source  of  sound  is  referred 
to  the  median  plane  in  front  as  a  single  sound ;  but  if  one  ear  is  more 
strongly  affected,  the  sound  is  referred  to  that  side.  The  position  of  the 
auricles,  which  act  as  collecting  funnels  for  the  sound-waves,  is  naturally 
important  in  judging  the  direction  from  which  these  come.  According 
to  Eduard  Weber  it  is  much  more  difficult  to  determine  the  direction 
when  the  auricles  are  held  firmly  pressed  against  the  head.  This  ob- 
server states  that  if  the  hands  are  placed  over  the  ears  in  such  a  manner 


AUDITORY    PERCEPTIONS.  911 

as  to  form  cavities  opening  backward,  a  sound  coming  from  in  front 
will  be  heard  as  though  coming  from  behind.  The  semicircular  canals 
probably  also  possess  the  function  of  determining  the  direction  of  sound, 
as  a  sound  coming  from  a  certain  direction  must  always  strike  one  canal 
(or  the  same  one  of  both  sides)  more  strongly  than  the  others.  For 
example,  the  left  horizontal  canal  is  most  strongly  excited  by  a  hori- 
zontal sound-impulse  coming  from  the  .left  side.  Other  investigators 
ascribe  to  the  tympanic  membrane  the  function  of  localizing  the  sound, 
inasmuch  as  certain  portions  of  the  membrane  are  often  affected  alone. 

As  to  the  distance  of  the  sound,  the  strength  of  the  sound-vibrations 
serves  as  a  guide,  an  estimate  of  this  having  been  formed  as  a  result  of 
experience  in  the  case  of  familiar  sounds,  but  error  in  this  connection  is 
not  rare. 

A  certain  time  always  elapses  before  a  tone  is  heard  by  the  ear, 
especially  if  the  tone  is  faint  (from  i  to  2  seconds).  Likewise,  the 
auditory  sensation  persists  for  some  time  after  the  sound  has  ceased. 

Among  subjective  auditory  sensations  there  may  be  distinguished : 

After-vibrations,  especially  of  loud  and  persistent  musical  sounds.  Roaring 
in  the  ears,  which  often  is  caused  by  abnormalities  in  the  circulation  of  the  blood 
(hyperemia  or  anemia)  in  the  ear,  depends  upon  mechanical  irritation  of  the 
auditory  nerve-fibers  (by  the  blood-current) .  Abnormal  pressure  in  the  labyrinth 
may  also  cause  subjective  noises.  There  are  also  undoubted  subjective  sensa- 
tions of  a  purely  nervous  character  in  the  entire  nervous  apparatus.  Ringing 
in  the  ears  is  ascribed  partly  to  tetanic  contraction  of  the  tensor  tympani  muscle, 
and  partly  to  circulatory  abnormalities.  Also,  many  poisons,  such  as  quinin, 
and  others,  cause  subjective  noises.  Entotic  perceptions,  which  are  due  to  processes 
within  the  ear  itself,  consist  in  hearing  the  pulse-beat  in  the  neighboring  arteries, 
and  rushing  noises  in  the  blood-current,  which  are  especially  loud  when  there 
is  increased  resonance  in  the  ear,  as  from  occlusion  of  the  external  canal  or  of  the 
tympanic  cavity,  or  a  collection  of  fluid  in  the  latter;  further,  when  the  action 
of  the  heart  is  increased,  or  in  association  with  hyperesthesia  of  the  auditory 
nerve.  Entotic  sounds  are  produced  also  by  crunching  and  crackling  noises  in 
the  articulations  of  the  lower  jaw,  by  muscular  traction  on  the  Eustachian  tube, 
and  by  the  entrance  of  air  into  the  tube  or  when  the  drum  is  moved  inward  or 
outward.  Other  instances  of  subjective  auditory  sensations  are  referred  to  on 
p.  701:  Pathological. 

The  ear  exhibits  the  phenomena  of  fatigue;  and  this  confines  itself  to  that 
tone  or  group  of  tones  to  which  the  ear  is  exposed,  while  its  sensitiveness  to 
other  tones  is  not  demonstrably  diminished.  In  the  course  of  a  few  seconds, 
however,  complete  recovery  takes  place. 

The  auditory  phenomena  resulting  from  applications  of  the  galvanic  current 
are  discussed  on  p.  701. 

The  following  auditory  after-sensations  can  be  distinguished:  (i)  Those  that 
correspond  to  positive  after-images,  and  may  be  designated  echoes  or  resonances, 
that  is  the  after-sensation  is  so  intimately  related  to  the  original  sound  that 
they  appear  to  be  continuous.  (2)  There  are  also  auditory  after-sensations 
attended  with  a  pause  between  the  end  of  the  objective  and  the  beginning  of  the 
subjective  tone.  A  splashing  sound  has  been  heard  as  a  peculiar  after-sensation 
for  a  minute  after  a  tone  has  been  listened  to  for  some  time.  (3)  A  third  variety 
of  after-sensation  may  be  compared  with  negative  after-images.  As  such  may 
be  designated  the  sense  of  striking  stillness  noted  by  Landois  after  interruption 
of  a  long-continued,  loud  sound. 

Some  persons  associate  the  perception  of  tones  with  the  appearance  of  sub- 
jective sensations  of  color  or  of  light  (colored  hearing),  for  example,  the  tone  of 
the  trumpet  with  the  sensation  of  yellow.  Photisms  of  this  kind  are  more  rarely 
observed  when  the  nerves  of  taste,  smell,  and  sensation  are  stimulated.  There 
are  persons  in  whom  every  form  of  sensory  impression  necessarily  calls  forth 
another  subjective  one.  It  is  more  frequent  to  find  a  sympathetic  irritation 
of  sensory  nerves  in  connection  with  loud,  sharp  sounds.  In  this  category  be- 
longs the  cold  chill  that  many  feel  when  they  hear  the  squeaking  of  a  slate-pencil, 
or  any  similar  shrill  tone. 


gI2  COMPARATIVE.       HISTORICAL. 

According  to  Urbantschitsch  analogous  relations  exist  between  all  of  the 
sensory  organs :  Shading  the  eyes  usually  weakens  the  hearing;  subjective  auditory 
sensations  are  usually  increased  by  light;  gustatory  sensations  are  frequently 
strengthened  by  red  and  green,  etc.  Color-blind,  individuals  exhibit  also  typical 
defects  of  musical  sense ;  those  that  are  green-blind  confuse  different  tones  that 
they  hear  or  repeat  in  a  way  that  is  different  from  those  that  are  red-blind. 

It  is  often  observed  that  the  auditory  impulse  conveyed  to  one  ear  strengthens 
the  function  of  the  other  ear,  as  a  result  of  stimulation  of  the  auditory  centers 
of  both  sides. 

The  auditory  apparatus  may  be  excited  not  only  by  sound-vibrations,  but 
also  by  other  heterologous  stimuli.  It  is  mechanically  excited  by  a  sudden  blow 
or  shock  to  the  ear.  If  the  fingers  are  placed  tightly  in  the  canal,  and  a  trembling 
motion  is  made,  a  singing,  ringing  sound  is  caused  by  the  condensation  and  rare- 
faction of  the  air  in  the  canal.  Stimulation  of  the  auditory  nerve  by  electricity 
is  discussed  on  p.  699  and  pathological  conditions  of  irritation  on  p.  700. 

COMPARATIVE.    HISTORICAL. 

The  lowest  forms  of  fishes,  the  cyclostomata  (lampreys)  possess  only  a  saccule, 
provided  with  auditory  hairs  and  otoliths,  communicating  with  two  semicircular 
canals;  the  myxinoids  have  only  one  semicircular  canal.  Most  of  the  other  fishes 
have  a  utricle,  with  three  semicircular  canals  typically  developed.  The  osseous 
fishes  have  in  the  cysticula  of  Brechet  (Fig.  325,  V,  C)  the  first  indication  of  the 
cochlear  canal  leading  from  the  saccule.  In  the  carp  and  the  shad  posterior 
prolongations  and  diverticula  of  the  labyrinth  are  connected  with  the  air-bladder 
by  means  of  a  chain  of  three  auditory  ossicles.  In  several  of  the  herrings  and 
perches,  bladder-like  processes  of  the  air-bladder  are  either  in  immediate  contact 
with  the  labyrinth,  or  in  close  proximity  to  it.  According  to  Kreidl  the  carps, 
and  according  to  Beer  the  crustaceans,  do  not  react  at  all  through  the  auditory 
apparatus  to  auditory  stimuli,  and  the  fishes  only  through  their  highly  developed 
cutaneous  sense,  which  is  set  into  activity  by  the  sound-waves.  The  organs 
of  the  "side  line"  in  fishes  are  intended  for  the  preservation  of  the  equilibrium. 
The  amphibia  are  in  general  closely  related  to  the  fishes  with  respect  to  the  con- 
struction of  the  labyrinth,  but  the  cochlea  is  not  typically  developed.  Most 
of  them,  except  the  frog,  have  no  tympanum.  The  fenestra  ovalis  alone  exists, 
and  not  the  fenestra  rotunda,  the  former  being  connected  in  frogs  with  the  exposed 
tympanic  membrane  by  means  of  three  ossicles  In  reptiles  the  saccule,  appended 
to  the  cochlear  canal,  is  quite  prominent;  in  tortoises  it  is  still  a  simple  sac,  but 
in  crocodiles  it  is  longer  and  somewhat  curved  and  dilated  at  its  extremity.  In 
all  reptiles  the  round  window  is  found  for  the  first  time;  through  it  the  cochlea 
communicates  with  the  vestibule.  The  cochlea  is  divided  into  a  scala  tym- 
pani  and  a  scala  vestibuli  in  crocodiles  and  birds.  Snakes  have  no  tym- 
panic cavity.  In  birds  the  saccule  and  the  utricle  are  fused  (Fig.  325,  IV,  US). 
The  cochlear  canal  (UC),  which  is  connected  with  the  saccule  by  means  of  a 
fine  tube  (C),  is  already  longer.  It  exhibits  indications  of  a  spiral  arrangement, 
and  it  possesses  a  flask-like,  blind  end,  the  lagena  (L),  which  is  present  likewise 
in  crocodiles.  The  auditory  ossicles  in  reptiles  and  birds  are  reduced  to  one, 
which  is  columnar  in  shape,  and  corresponds  to  the  stapes;  it  is  known  as  the 
columella.  The  lowest  mammals  (echidna  and  duck-bill)  are  still  more  like  the 
birds  in  structure ;  the  higher  mammals,  however,  exhibit  the  same  type  of  auditory 
apparatus  as  man  (Fig.  325,  III).  In  whales  the  Eustachian  tube  is  always 
open.  According  to  G.  Retzius  all  vertebrates  possess  so-called  hair-cells  as  end- 
organs  of  the  auditory  nerves. 

Among  invertebrates  the  ear  is  found  in  a  simple  form  in  several  of  the  medusas, 
annelids,  and  molluscs.  It  is  a  round  vesicle,  filled  with  fluid,  on  the  wall  of  which 
are  the  auditory  nerves  with  ganglionic  enlargements.  The  inner  wall  of  the 
vesicle  bears  cells  provided  with  cilia  (auditory  cells) ,  which  contain  either  only 
one  otolith  composed  of  concentric  layers,  or  numerous  crystalline  movable 
otoliths.  The  otoliths  consist  of  an  organic  base,  which  is  impregnated  with 
lime-salts.  In  the  medusae  the  auditory  vesicles  lie  in  the  margin  of  the  bell 
(marginal  bodies).  According  to  more  recent  views,  however,  the  otoliths  regulate 
the  equilibrium  of  the  animal,  by  pressing  harder  in  one  direction  on  the  surface 
beneath  them,  with  every  change  of  position.  Verworn  proposes,  therefore,  to 
call  them  statohths.  Extirpation  of  the  saccules  containing  the  otoliths  disturbs 
the  equilibrium  of  the  animals. 


THE    ORGAN    OF    SMELL.  913 

In  molluscs  the  ears  are  situated  on  the  side  of  the  gullet,  and  in  several 
they  are  connected  with  the  surface  of  the  body  by  a  fine  tube  (helix).  In  the 
Crustacea  there  are  otolith-saccules,  partly  closed  and  partly  open.  The  auditory 
bristles  are  supplied  with  nerves,  and  are  of  various  lengths;  they  support  the 
otoliths.  Other  auditory  bristles,  supplied  by  the  same  nerve-trunk,  are  found 
on  the  surface  of  the  body,  on  the  antennae,  and  on  the  tail.  When  a  sound  was 
conducted  into  the  water  Hensen  observed  several  bristles  to  be  set  in  vibration, 
which  were  attuned  to  various  pitches.  The  lining  membrane  of  the  auditory 
vesicle  is  lost  with  every  shedding,  and  the  animals  voluntarily  replace  their 
otoliths  by  grains  of  sand.  In  insects  the  ear  is  represented  by  a  tympanic  mem- 
brane, to  which  a  tracheal  vesicle  is  attached,  and  between  which  there  is  a  gan- 
glionic  nervous  expansion.  In  the  acridia  (cricket)  the  ear  lies  over  the  base 
of  the  third  foot,  in  grasshoppers  in  the  forefeet,  in  beetles  at  the  root  of  the 
hind  wings,  and  in  flies  at  the  bases  of  the  poisers.  There  are,  however,  also 
in  the  antennae,  bristles  connected  with  ganglionic  fibers,  and  still  other  formations 
that  are  considered  as  auditory  organs,  as,  for  instance,  the  "auditory  pencils" 
of  arthropods.  In  cephalopods  the  ear  is  connected  with  the  head-cartilage,  and 
the  first  indications  of  a  membranous  and  cartilaginous  labyrinth  are  found. 
The  nerve  passes  to  a  plate  or  ledge  of  horn,  on  which  ciliated  epithelial  cells 
represent  the  end-organs. 

Historical.  Empedocles  (473  B.  C.)  referred  auditory  impressions  to  the 
cochlea.  The  school  of  Hippocrates  was  familiar  with  the  tympanic  membrane; 
Aristotle  (384  B.  C.)  knew  of  the  Eustachian  tube.  According  to  Cassius  Felix 
(97  A.  D.)  hearing  is  dulled  during  the  act  of  yawning.  Vesalius  (1571)  described 
the  tensor  tympani  muscle,  Ingrassias  the  stapes;  the  latter  connected  the  func- 
tion of  the  tensor  with  accurate  hearing.  Cardanus  (1560)  first  mentioned  sound- 
conduction  through  the  cranial  bones.  More  exact  descriptions  of  the  finer  parts 
of  the  ear  were  made  by  Fallopius  (1561),  who  described  the  vestibule,  the  semi- 
circular canals,  the  chorda  tympani,  the  two  windows,  the  cochlea,  and  the  aque- 
duct; by  Eustachius  (died  1570),  who  described  the  modiolus,  and  the  bony 
staircase  of  the  cochlea,  the  Eustachian  tube,  and  the  muscles  of  the  auricle; 
by  Plater,  who  described  the  ampullae  (1583);  by  Casseri  (1600),  who  de- 
scribed the  spiral  lamina  of  the  membranous  cochlea.  Sylvius  de  le  Boe 
discovered  (1667)  the  ossicle  named  after  him,  Vesling  the  stapedius  muscle 
(1641).  Mersenne  (1618)  knew  of  overtones.  Gassendius  determined  the  velocity 
of  sound  (1658).  Follius  described  accurately  the  membranous  labyrinth  and  the 
process  of  the  malleus  named  after  him  (1645).  Tulpius  (1641)  considered  the 
possibility  of  air  passing  through  the  ears  (when  the  drum  is  perforated),  a  con- 
dition that,  curiously,  was  spoken  of  by  Alkmaon  (580  B.  C.)  as  normal  in  goats. 
Subsequently,  there  was  much  discussion  as  to  the  possible  existence  of  a  normal 
opening  in  the  tympanic  membrane  (foramen  Rivini).  Scarpa  made  a  masterly 
dissection  of  the  ear.  Perrault  (1666)  suggested  a  theory  similar  to  that  of  v. 
Helmholtz  .as  to  the  perception  of  pitch  by  the  cochlea.  Berzelius  investigated 
the  cerumen  chemically,  Krimer  the  labyrinthine  fluid.  According  to  Authenrieth, 
the  three  differently  placed,  semicircular  canals  are  supposed  to  aid  in  hearing 
sounds  from  the  respective  directions.  The  study  of  acoustics  was  greatly 
advanced  by  Chladni  (1802).  A  most  complete  work  on  the  ear  of  the  verte- 
brates was  written  by  G.  Retzius  (1881-84). 

THE  ORGAN   OF  SMELL. 

STRUCTURE  OF  THE  OLFACTORY  APPARATUS. 

The  entrance  to  the  nasal  cavity  is  formed  by  the  vestibular  region  or  the 
vestibule.  Its  mucous  membrane  is  covered  with  papillae  and  it  is  lined  with 
squamous  epithelium,  which  reaches  to  the  anterior  extremity  of  the  inferior 
meatus  and  the  inferior  turbinate  bone.  Near  the  opening  of  the  nostril  there 
are  hairs  (vibrissae)  with  greatly  developed  sebaceous  glands.  Mucous  glands 
are  found  toward  the  cartilages"  The  area  of  the  terminal  expansions  of  the 
olfactory  nerve,  the  olfactory  region,  measures  about  500  sq.  mm.,  and  in  man  it 
includes  only  the  tipper  part  of  the  septum,  and  the  islands  of  the  superior  tur- 
binate (Fig.  330,  Cs}\  detached  islands  or  peninsulas  are  found  in  the  vicinity 
of  this  chief  olfactory  region.  The  remainder  of  the  nasal  cavity  is  desig- 
nated the  respiratory  region.  The  differences  between  the  olfactory  and 

58 


SENSATION    OF    SMELL. 


respiratory  regions  are  as  follows:  (i)  The  olfactory  region  possesses  a  thicker 
mucous  membrane;  (2)  it  is  covered  with  a  single  layer  of  cylindrical  epithelium, 
0.06  mm.  thick  (Fig.  329,  E),  the  branched  basal  portions  of  which  often  contain 
a  yellow  or  brownish-red  pigment  (denser  in  animals),  while  the  respiratory 
region  has  a  double  layer  of  ciliated  epithelium,  mixed  with  goblet-cells;  (3) 
the  olfactory  region  is,  therefore,  distinguished  by  the  coloration  mentioned;  (4) 
it  contains  peculiar  club-shaped  tubular  glands  (the  glands  of  Bowman),  which  are 
considered  mucous  glands,  while  the  respiratory  portion  contains  principally 
acinous  glands.  According  to  A.  Heidenhain,  the  latter  are  serous,  according 
to  Stohr  (in  man)  mixed  glands.  Lymph-follicles  are  found  in  the  mucosa  be- 
neath the  epithelium,  and  from  them  numerous  leukocytes  make  their  way  on  to 
the  free  surface.  (5)  Finally,  the  olfactory  region  contains  the  end-organs  of 
the  olfactory  nerve.  The  olfactory  cells  (N)  lie  scattered  between  the  long, 
cylindrical  epithelial  cells  (E)  of  the  surface.  A  spindle-shaped  cell-body,  with  a 
nucleus  and  large  nucleolus  sends  upward,  between  the  cylindrical  cells  a  smooth 


Rip. 


P.S.JI  h 


FIG.  329.— N,   Olfactory  FIG.    330.  — Nasal     Cavity    and     Nasopharynx:     L,     levator 

cell    from     man     (the  pad;    p^p      salpingopalatine    fold;     P.s.ph.,    salpingo- 

hairs  have  fallen  off);  pharyngeal     fold;     Cs,    Cm,     Ci,    the    three    turbinates 

n'-lrTi          iir°g]       '  (Urbantschitsch). 

epithehal      cell     from 
the  olfactory  region. 

rod,  from  p. 9  to  1.8  //thick,  from  the  extremity  of  which  from  6  to  8  fine  olfactory 
hairs  project  through  the  pores  of  a  delicate,  structureless  limiting  membrane 
covering  the  surface  of  the  epithelium.  The  olfactory  cells  become  continuous 
with  fine  varicose  nerve-fibrils  in  the  depths  of  the  mucosa,  and  these  pass  into  the 
olfactory  nerve.  According  to  C.  K.  Hoffmann  and  Exner,  after  section  of  the 
olfactory  nerves  in  frogs  the  specific  end-organs  are  converted  into  a  nonciliated 
cylindrical  epithelium,  while  in  warm-blooded  animals  they  undergo  fatty  de- 
generation; but,  at  the  same  time,  the  epithelial  cells  between  them  exhibit 
signs  of  degeneration. 

The  olfactory  cell  of  the  olfactory  region  is  a  ganglion-cell  whose  neuron  is 
represented  by  a  nerve-fiber,  which  enters  the  olfactory  bulb.  The  telodendrites 
neurons  come  in  contact  within  the  spherical  glomeruli  with  dendrites  from 
ganglion-cells  of  the  bulb  Passing  through  further  layers  of  the  bulb  (gelatinous 
olffin  Ytr  °t  PyTam*d*1  C1flls'  g^nular  layer)  the  origin  of  the  fiblrs  in  the 
^factory  tract  is  reached,  the  course  of  which  is  described  on  p.  678. 

,         SENSATION  OF  SMELL. 

The  sensation  of  smell  is  brought  about  by  the  action  of  odorous 
substances  in  a  gaseous  state,  which  come  in  direct  contact  with  the 
)lfactory  cells,  especially  in  their  passage  through  the  nares  during 


SENSATION    OF    SMELL.  915 

inspiration.  In  the  act  of  inhalation,  the  air  passes  along  the  septum, 
upward  beneath  the  bridge  of  the  nose,  and  under  the  roof  of  the  nasal 
cavity,  and  it  then  curves  backward  and  downward.  But  little  air  passes 
through  the  meatuses,  especially  through  the  superior;  most  passes 
through  the  middle  meatus.  Odorous  substances  received  through 
the  mouth  and  then  expired  through  the  choanae  may  also  be  smelled, 
although  not  so  well. 

The  first  moment  of  contact  of  the  odorous  substance  with  the 
olfactory  cells  seems  to  be  the  most  effectual  for  the  sensation ;  conse- 
quently it  is  customary  to  repeat  these  inspiratory  acts  with  closed 
mouth  when  it  is  desired  to  smell  accurately:  sniffing.  By  this  means 
the  air  in  the  accessory  cavities  is  rarefied,  and  as  the  air-pressure 
gradually  becomes  equalized,  the  odorous  fumes  are  capable  of  diffusing 
over  the  entire  region.  Nothing  is  practically  known  as  to  the  nature  of 
the  action  of  odorous  substances,  but  many  odorous  vapors  have  a 
decided  power  of  absorbing  heat. 

There  is  as  yet  no  criterion  for  a  special  classification  of  odorous 
substances.  The  observation  that  certain  categories  of  olfactory  sensa- 
tions can  be  abolished,  while  others  remain  intact,  would  seem  to  indi- 
cate that  there  are  qualitatively  different  forms  of  olfactory  nerves  or 
end-organs. 

The  strength  of  the  sensation  depends:  (i)  Upon  the  extent  of 
the  surface  affected ;  hence  animals  with  great  acuteness  of  smell  (for  ex- 
ample the  seal)  are  found  often  to  have  exceedingly  complex  tur- 
binates,  which  are  covered  with  the  olfactory  membrane.  (2)  Upon 
the  frequency  with  which  the  fumes  are  conducted  to  the  olfactory  cells 
(sniffing).  (3)  Upon  the  concentration  of  the  odorous  air-mixture; 
many  substances,  however,  can  be  detected  even  in  remarkable  dilution. 
(4)  There  are  many  connections  between  smell  and  taste;  chloroform 
has  an  ethereal  odor  and  a  sweet  taste  at  the  same  time.  Moreover, 
it  excites  the  pain-producing  and  cold-perceiving  nerves.  Ether  has  a 
similar  action,  but  it  has  a  bitter  taste. 

Bromin  may  be  detected  by  its  odor  in  a  dilution  of  jo^-s',  hydrogen  sulphid 
in  a  dilution  of  15^^77  mgm.  when  contained  in  i  cu.  cm.  of  air.  The  odor  of 
T6<r<T<n><T  mgm.  of  chlorphenol,  and  of  ¥<j<j^0oo<j  mgm.  of  mercaptan  can  be 
detected. 

Odorous  substances  dissolved  in  indifferent  solutions  (for  example  0.73  per 
cent,  sodium  chlorid  solution)  and  introduced  into  the  nose  excite  a  feeble  smell. 
The  olfactory  nerve  is  exhausted  by  olfactory  sensations  that  persist  for  more 
than  a  few  minutes;  the  exhausted  nerve  may  recover,  however  in  the  course  of 
a  minute.  The  sensation  is  impaired  by  fever,  and  also  by  cocain.  Mechanical 
and  thermal  stimuli  do  not  excite  olfactory  sensations. 

Variations  of  the  olfactory  sensation  are  described  on  p.  679.  If  both  nos- 
trils are  filled  with  substances  of  different  odors,  some  individuals  do  not  ^appreciate 
a  mixture  of  the  odors,  but  at  times  one  and  at  other  times  the  other  prevails ; 
in  some,  however,  there  is  a  mixture  of  odors.  Many  odors  cause  others  to  dis- 
appear, when  they  act  upon  the  nose  at  the  same  time,  for  example  bitter  almonds 
and  musk,  caoutchouc  and  wax.  Under  such  circumstances  both  odors  may  be 
taken  either  into  both  nostrils,  or  into  one  and  the  same  nostril. 

The  extremely  sensitive  sensory  nerves  of  the  nasal  cavity  are  painfully 
irritated  by  some  pungent  fumes,  for  example  of  ammonia  and  of  acetic  acid;  the 
latter  act  upon  the  olfactory  nerves  even  in  great  dilution.  The  nose  is  important 
as  a  sentinel  to  guard  against  the  introduction  of  bad  air  an4  food.  The  sense  of 
smell  frequently  assists  the  sensations  of  taste,  and  cpnversely.  Earlier  ar.d 
recent  investigators  speak  of  a  connection  between  the  nose  and  sexual  activity. 

To  test  the  olfactory  acuity  Zwaardemaker  makes  use  of  the  olfactometer, 
that  is  a  hollow  cylinder  of  an  odorous  substance  (for  example  vulcanized  caout- 


THE    ORGAN    OF    TASTE 

chouc) ,  through  which  air  is  drawn  into  the  nostril.  A  nonodorous  tube  can  be 
introduced  into  this,  so  that  any  desired  length  of  the  odorous  surface  may  be 
covered.  The  intensity  of  the  smell  is  proportional  to  the  length  of  the  cylinder 
used. 

The  galvanic  current — one  electrode  being  placed  in  or  on  the  nose,  the  other 
(indifferent)  being  held  in  the  hand — upon  kathodal  closure  and  persistence  of  the 
current,  likewise  upon  anodal  opening,  excites  a  sensation  of  smell  that  Kiesel- 
bach  compares  to  the  smell  produced  upon  striking  flint.  Induced  currents  have 
no  effect. 

Comparative. — In  the  lowest  vertebrates  the  olfactory  apparatus  is  represented 
by  depressions  to  which  the  olfactory  nerve  passes.  Amphioxus  and  the  cyclo- 
stomes  have  only  one  olfactory  depression,  while  all  other  vertebrates  have  two. 
In  many  selacians  the  olfactory  depression  communicates  with  the  mouth  by 
means  of  a  canal.  In  frogs  the  olfactory  organs  open  into  the  mouth  through  short 
passages.  In  the  higher  vertebrates  the  nose  develops  together  with  the  palate, 
and  becomes  more  and  more  independent.  In  the  gymnophions,  a  group  of 
amphibians,  the  olfactory  apparatus  is  extraordinarily  developed  from  the  presence 
of  four  nerves,  while,  on  the  other  hand,  the  ears  and  eyes  are  stunted.  The 
cetaceans  have  no  olfactory  nerve.  In  many  mammals  there  is  in  the  anterior 
part  of  the  septum  a  hollow  cavity,  lined  with  cells  similar  to  the  olfactory  cells, 
opening  either  into  the  nasal  cavity  or  into  the  canalis  incisivus,  and  to  which  a 
branch  of  the  olfactory  nerve  runs;  it  is  known  as  Jacobson's  organ,  and  is  un- 
developed in  man.  Cephalopods  have  olfactory  depressions,  lined  with  ciliated 
olfactory  cells,  back  of  the  eyes;  the  olfactory  nerve  arises  near  the  optic  nerve. 
In  molluscs  also,  there  are  ciliated  places  that  are  considered  olfactory  organs. 
In  arthropods  the  olfactory  organs  lie  in  the  feelers  and  antennas,  in  the  first  as 
cilia  in  connection  with  a  ganglion  and  nerve.  In  crabs  they  are  situated  in  the 
outer  arms  of  the  antennula.  Ciliated,  shallow  or  flask-shaped  depressions 
supplied  with  nerves  represent  the  olfactory  apparatus  in  the  higher  worms. 
All  other  animals  appear  to  possess  no  especial  organ. 

Historical. — Theophrastus  (born  311  B.  C.)  mentions  the  short  nose  of  man; 
that  animals  enjoy  their  food  only  from  its  odor;  that  strong  perfumes  cause 
headache;  that  many  fragrant  salves  impart  an  odor  to  the  urine;  that  there 
are  many  connections  between  smell  and  taste.  Rufus  Ephesius  described  the 
passage  of  the  olfactory  nerves  through  the  cribriform  plate  of  the  ethmoid  (97 
A.D.).  According  to  Galen  the  sense  of  smell  has  its  seat  in  the  cerebral  ven- 
tricles. The  monk  Theophilus  Protospatharius  (end  of  the  eighth  century)  de- 
scribed the  olfactory  nerve  as  the  nerve  of  smell.  Rudius  (1600)  dissected  a  man 
with  congenital  anosmia,  in  whom  the  olfactory  nerves  were  absent.  Sommering 
wrote  a  masterly  description  of  the  olfactory  apparatus,  Cloquet  (1815)  of  its 
physiological  and  pathological  phenomena. 

THE  ORGAN    OF  TASTE. 

SITUATION  AND  STRUCTURE  OF  THE  ORGANS  OF  TASTE. 

There  are  still  many  contradictory  views  as  to  the  extent  of  the  region 
in  which  the  sensation  of  taste  is  developed,  and  accordingly  as  to 
whether  the  various  nerves  in  question  are  to  be  considered  as  possessing 
taste-fibers  or  not.  (i)  The  root  of  the  tongue  in  the  region  of  the 
circumvallate  papillae,  the  area  of  distribution  of  the  glossopharyngeal 
nerve,  is  undoubtedly  endowed  with  taste.  (2)  So  also  is  the  tip  of  the 
tongue  and  its  margins,  through  the  intermediation  of  most  of  the 
fungiform  papillae  (the  filiform  papillae  and  about  20  per  cent,  of  the 
fungiform  papillae  are  insensitive  to  taste),  but  with  many  individual  vari- 
ations; so  that  often  not  all  varieties  of  taste  are  appreciated.  The 
relations  of  the  nerves  to  these  situations  are  pointed  out  in  the  descrip- 
tions of  the  lingual  nerve  and  the  chorda  tympani.  (3)  The  lateral 
portion  of  the  soft  palate,  its  posterior  surface,  the  glossopalatine  arch, 
the  inner  surface  of  the  epiglottis  are  endowed  with  taste  through 


GUSTATORY    SENSATIONS. 


917 


the  glossopharyngeal  nerve.  (4)  It  is  uncertain  whether  the  hard 
palate  also  possesses  the  sense  of  taste ;  it  is  usually  said  not  to  be  present 
in  the  middle  of  the  tongue. 

The  end-organs  of  the  gustatory  nerves  are  the  taste-buds  or  taste-goblets 
discovered  by  Schwalbe  and  Loven.  These  are  found  on  the  lateral  surfaces  of 
the  circumvallate  papillae  (Fig.  331,  I)  facing  the  capillary  cleft  R  R  of  the  sur- 
rounding furrow,  more  rarely  on  the  surface  of  the  papillae,  and  on  the, opposite 
side  of  the  furrow.  They  occur  also  on  the  fungiform  papillae,  on  the  papillae 
of  the  soft  palate  and  on  the  uvula,  but  also  on  the  under  surface  of  the  epi- 
glottis, the  upper  portions  of  the  posterior  surface  of  the  larynx  and  the  inner 
aspect  of  the  arytenoid  cartilage,  and  on  the  vocal  bands.  Many  of  these  buds 
are  said  to  disappear  with  age.  The  gustatory  goblets,  81  //  high  and  33  /u  thick,  are 
bud-shaped  or  barrel-shaped  cellular  structures,  embedded  in  the  thick  squamous 
epithelium  of  the  tongue.  The  outer  portions  are  made  up  of  curved,  fusiform, 


FIG.  331.— I,  Transverse  Section  through  a  Circumvallate  Papilla:  W,  the  papilla;  \i  v},  the  wall  in  section;  R  R, 
the  ring-shaped  cleft;  K  K,  the  taste-bud  in  position;  N  N,  nerves.  II,  Isolated  taste-bud;  D,  cortical 
portion;  K,  lower  extremity;  E,  free  open  extremity,  with  projecting  tips  of  the  taste-cells.  Ill,  Isolated 
cortical  cells  (d)  and  taste-cells  (e).  k 

nucleated  investing  or  supporting  cells,  like  the  staves  of  a  barrel  (Fig.  331,  II, 
D;  isolated  III,  d).  Toward  the  free  surface  they  surround  an  opening,  the 
porus,  and  beneath  this  a  small  depression.  Surrounded  by  these  cells,  in  the 
axis  of  the  bud,  there  are  from  one  to  ten  taste-cells  (II,  E),  some  of  which  possess 
a  delicate  process  at  their  upper  extremity  (pin-cells — III,  e),  while  others  do  not 
(rod-cells).  The  gustatory  nerves  lose  their  myelin-sheaths,  and  form  plexuses, 
always  ending  free  in  the  taste-buds,  either  by  surrounding  the  buds  with 
delicate  fibrils  on  the  outer  side  like  a  basket  or  by  penetrating  their  interior. 
They  terminate,  ultimately,  free,  on  a  level  with  the  opening  of  the  taste-bud. 
After  section  of  the  glossopharyngeal  nerve,  the  taste-buds  degenerate  within 
thirty  hours,  and  the  protecting  cells  are  converted  into  ordinary  epithelial  cells  in 
the  course  of  twelve  days.  Leydig  found  in  the  skin  of  fresh-water  fishes  goblet- 
shaped  organs  similar  to  the  taste-buds. 

The  glands  of  the  tongue,  to  which  the  ninth  cranial  nerve  sends  secretory 
fibers,  are  discussed  on  p.  256;  the  follicles  likewise. 

GUSTATORY  SENSATIONS. 

There  are  four  different  qualities  of  taste:  the  sensations  of  sweet, 
bitter,  sour  and  salty.  Sour  and  salty  substances  irritate  also  the 
sensory  nerves  of  the  tongue.  In  greatest  dilution,  however,  they 
stimulate  only  the  endings  of  the  specific  nerves  of  taste.  In  all  proba- 
bility a  special  perceptive  fiber  exists  for  each  quality  of  taste  (in 
accordance  with  the  doctrine  of  the  specific  energies). 


918  GUSTATORY    SENSATIONS. 

The  proof  of  this  is  as  follows:  Oehrwall,  and  after  him  Goldscheider  and 
H.  Schmidt,  found  that  among  the  fungiform  papillae  some  reacted  to  sugar, 
but  not  to  tartaric  acid;  some  to  quinin,  but  not  to  tartaric  acid;  and  some  to 
quinin,  but  not  to  sugar.  Electrical  stimulation  of  some  papilla?  excited  a  bitter 
taste,  of  others  a  salty  taste,  and  of  still  others  a  sweet  taste.  With  the  constant 
current,  the  purest  sensation  was  at  the  anode. 

The  leaves  of  Gymnema  sylvestre,  when  applied  to  the  tongue,  destroy  the 
sensation  of  sweetness  and  bitterness. 

Continued  stimulation  of  taste  is  followed  by  phenomena  of  fatigue  for  the 
various  taste-sensations.  This  fact  may  be  readily  explained  by  the  assumption 
of  specific  end-apparatus  for  the  different  categories  of  taste,  which  are  present 
in  relatively  different  number  on  the  various  papillae. 

With  regard  to  the  character  of  the  stimulation  of  the  gustatory 
nerves,  no  real  advance  has  been  made  since  the  time  of  Democritus 
(469  B.  C.),  who  attributed  the  taste-impression  to  the  form  of  the 
tasting  atoms.  In  order  that  a  gustatory  impression  may  be  made,  a  solu- 
tion of  the  substance  in  the  fluids  of  the  mouth  is  necessary,  especially 
if  it  is  in  a  solid  or  gaseous  state.  The  intensity  of  the  gustatory  sen- 
sation depends:  (i)  Upon  the  extent  of  the  surface  affected,  as  Camerer 
especially  showed  by  placing  the  substance  upon  i,  2,  3  or  4  circum- 
vallate  papillae.  By  rubbing  the  substance  into  the  furrows  and  between 
the  papillae  (rubbing  movements  of  the  tongue  in  the  act  of  tasting) 
the  perception  is  facilitated.  (2)  The  concentration  of  the  sapid 
substance  is  of  great  importance.  Valentin  found  that  the  following 
series  of  bodies  ceased  to  be  tasted  in  the  order  stated,  as  they  were 
progressively  diluted:  sirup,  sugar,  salt,  aloes,  quinin,  sulphuric  acid. 
Quinin  can  be  diluted  20  times  more  than  salt  before  it  becomes  tasteless. 
(3)  The  time  that  elapses  between  the  application  of  the  substance 
and  the  appearance  of  the  sensation  varies  with  different  substances. 
Salt  is  most  quickly  tasted  (after  0.17  second),  then  sweet,  sour  and 
bitter  (quinin  after  0.258  second).  This  is  true  also  of  mixtures  of 
these  substances.  The  last-named  substances  produce  the  longest 
after-taste.  (4)  The  delicacy  of  taste  is  in  the  first  place  congenital 
(the  newborn  infant  is  said  to  be  able  to  distinguish  qualities  of  taste), 
but  it  can  be  greatly  improved.  Prolonged  tasting  of  the  same  substance, 
or  of  similar  or  of  strongly  tasting  substances,  quickly  impairs  correct  gus- 
tatory judgment.  (5)  The  sense  of  taste  is  greatly  assisted  by  the  sense  of 
smell,  and  the  one  is  often  confounded  with  the  other.  Thus,  musk  and 
asafetida  affect  only  the  organ  of  smell  without  stimulating  the  sense 
of  taste.  Even  the  eye  is  capable  of  assisting  the  sense  of  taste  by  the 
excitation  of  conceptions  of  familiar  tastes.  Thus,  alternate  testing 
of  red  and  white  wine,  with  the  eyes  bandaged,  soon  results  in  uncer- 
tairty'o  ^  The  m°st  suitable  temperature  for  taste  lies  between  10° 
and  35  C.;  hot  and  cold  water  abolish  taste  temporarily. 

in^i  PllCet-.°,n   the    tonSue   suppresses    temporarily    all   power  of  taste,  co- 

anH  fSy         +bltte/  taSt£'  chewinS  the   leaves  of  Gymnema  sylvestre  the  bitter 

sweet  tastes.     Two  per  cent,  sulphuric  acid  makes  water  taken  subse- 

taste^wtt     Tet-     ?ugar  dissolved  in  a  tasteless  solution  of  salt  or  quinin, 

>   sweeter  then  when   dissolved  in  water.     Children   and    the    insane  who 

n  hv  l"1^  *?mfiimes  be  ^duced  to  partake  of  substances  repugnant  to 
tnern  by  the  smell  of  an  agreeable  perfume 

at  the  no3t?v/T " ^f^'-The  constant  current  excites   an   acid  sensation 

of  the  curre/t     *«S'         u  °r  Cl°Smg  and  °n  °Pening-  **  well  as  during  the  passage 

at  the  ne^v.  nol  ^  T^6'  °r  m^  correctly  an  astringent-burning,  sensation 

negative  pole.     This  cannot  be  the  result  of  electrolysis  of  the  saliva,  for 


GUSTATORY    SENSATIONS.  919 

even  when  the  tongue  is  moistened  with  an  acid  solution,  the  alkaline  taste  per- 
sists at  the  negative  pole.  The  most  probable  explanation  is  that  electrolytes 
are  formed  in  the  interior  of  the  taste-bud  that  irritate  the  end-organ  during  the 
passage  of  the  current.  This  is  proved  by  the  fact  that  the  taste-sensation  changes 
on  the  use  of  currents  of  different  tension,  so  that  it  is  dependent  upon  the  ions 
liberated  by  the  current.  The  constant  current  as  such  irritates  the  end-organs 
of  the  gustatory  nerves  directly  only  at  the  moment  of  closure  and  of  opening. 
The  sensation  thus  produced  is  added  to  the  preceding  excitation.  If  one  electrode 
is  placed  on  the  tongue  and  the  other  (indifferent)  in  the  hand  the  following 
phenomena  appear:  Kathodal  closure  and  the  passage  of  the  current  excite  no 
taste-sensation  on  the  root  of  the  tongue ;  and  the  same  is  true  of  anodal  opening. 
If,  however,  the  anode  is  placed  on  the  tongue,  a  sour  taste  is  excited,  both  on 
closure  and  during  the  passage  of  the  current,  and  also  on  kathodal  opening. 
On  the  tip  of  the  tongue,  and  on  its  middle  portion,  a  salty  or  a  bitter  taste  is  excited 
when  the  kathode  is  placed  on  the  tongue,  upon  closure  and  while  the  current 
is  passing;  likewise  on  opening,  when  the  anode  is  placed  on  the  tongue.  No 
sensation  results  on  anodal  closure,  or  while  the  current  is  passing,  or  on  kathodal 
opening.  Rapidly  interrupted  currents  cause  no  taste-sensation.  Applications 
of  cocain  to  the  tongue  abolish  the  electrical  taste  temporarily.  The  experiments 
of  v.  Vintschgau,  whose  taste  was  imperfect  at  the  tip  of  the  tongue,  showed  that 
the  electrical  current  never  excited  a  taste-sensation  when  applied  there  (although 
a  distinct  tactile  sensation). 

In  experiments  on  Honigschmied,  who  had  normal  taste-sensation  at  the  tip 
of  the  tongue,  the  positive  pole  often  excited  a  metallic  taste  at  the  tip  but  not 
rarely  also  an  acid  taste;  while  at  the  negative  pole,  taste  was  often  absent,  and 
when  present,  it  was  almost  always  alkaline,  exceptionally  acid.  It  is  important 
to  note  that  after  interruption  of  the  current  a  metallic  after-taste  could  be  recog- 
nized with  both  directions  of  the  current. 

Pathological. — Diseases  of  the  tongue,  coating  of  the  tongue,  and  dryness 
disturb  or  destroy  the  sensation.  Subjective  tastes  are  common  among  insane 
or  nervous  patients,  probably  from  irritation  of  the  psychogeusic  center.  A 
bitter  taste  has  been  noted  after  poisoning  with  santonin,  bitter  and  acid  tastes 
after  subcutaneous  injections  of  morphin.  Gymnemic  acid  is  capable  of  de- 
stroying subjective  tastes  and  parageusis. 

The  designations  hypergeusis,  hypogeusis  and  ageusis  are  applied  respectively 
to  increase,  decrease  and  abolition  of  taste-sensations.  Many  forms  of  tactile 
sensation  on  the  tongue  are  confused  with  gustatory  sensations,  for  example 
so-called  biting,  cooling,  pricking,  sandy,  mealy,  pasty,  astringent,  bitter  tastes. 

Comparative. — In  cattle  there  are  as  many  as  1760  taste-buds  to  a  circum- 
vallate  papilla.  A  large  taste-organ,  with  numerous  folds  is  described  as  the 
foliate  papilla  in  the  lateral  posterior  portion  of  the  tongue  in  rabbits.  This 
has  an  analog  in  man  in  the  form  of  parallel  furrows  on  the  posterolateral  edge 
of  the  tongue,  the  fimbrise  linguae.  Reptiles  and  birds  have  no  taste-buds, 
which  are  numerous  in  the  gill-slits  of  the  tadpole,  although  the  tongue  of  the 
adult  frog  is  lined  only  with  an  epithelium  suggestive  of  taste-cells.  The  goblet- 
shaped  organs  in  the  epidermis  of  fishes  and  tadpoles  are  similar  in  structure  to 
the  taste-buds,  and  probably  have  the  same  function.  Taste-buds  are  present 
on  the  palate  of  the  carp,  and  in  the  mouth  of  the  shark  and  ray.  In  aquatic 
amphibians  and  in  fish,  the  end-organ  of  the  olfactory  nerve  is  probably  stimu- 
lated like  the  taste-buds,  that  is  the  stimulation  takes  place  through  the  action  of 
substances  dissolved  in  the  water. 

The  tongue  of  the  cyclostomes  serves  as  a  suction-apparatus,  while  in  other 
fish  it  has  no  muscular  tissue.  Salamanders  and  most  of  the  batrachians  can 
extrude  the  tongue  from  the  mouth  and  again  withdraw  it.  In  many  of  the  lower 
vertebrates  the  entoglossal  bone  serves  as  a  support  for  the  tongue,  while  in  the 
higher  forms  it  is  replaced  by  the  cartilage  or  the  septum  of  the  tongue.  The 
nerve-endings  in  the  proboscis  (flies),  jaw  and  tongue  (ants),  palate  and  epi- 
pharynx  are  the  seat  of  the  taste-organs  in  insects.  Taste-organs  have  been 
found  also  in  snails. 

Historical. — Bellini  considered  the  papilla?  of  the  root  of  the  tongue  as  the 
gustatory  organs  (1665).  Sulzer  reported  in  1760  as  to  electrical  taste-sensations. 
Baur  was  the  first  to  describe  accurately  the  course  and  the  division  of  the  muscles 
in  the  tongue;  and  Rudolphi  the  course  of  the  nerves.  Elsasser  (1834)  showed 
that  the  sensation  of  taste  was  most  intense  for  all  substances  on  the  vallate 
papillae,  and  on  the  posterior  portion  of  the  lateral  margin  of  the  tongue. 


920 


TOUCH. 


Richerand,  Fodera,  and  Mayo  considered  the  lingual  nerve  alone  to  be  the  gustatory 
nerve.  Magendie  showed,  however,  that  after  section  of  this  nerve,  the  posterior 
part  of  the  tongue  retained  its  taste-sensation.  Panizza  (1834)  designated  the 
glossopharyngeal  as  the  gustatory,  the  lingual  as  the  tactile,  and  the  hypoglossal 
as  the  motor  nerve  of  the  tongue. 


TOUCH. 


TERMINATIONS  OF  THE  SENSORY  NERVES. 

The  tactile  corpuscles,  discovered  by  Meissner  in  1852,  are  ellipsoidal  in  form, 
from  40  to  200  ,«  long,  and  from  60  to  70  fj.  wide,  and  they  lie  in  the  papillae  of  the 
corium.  They  are  abundant  in  the  palm  of  the  hand,  and  on  the  sole  of  the  foot, 
likewise  on  the  fingers  and  toes  (21  to  each  sq.  mm.  of  skin,  or-io8  for  each  400 
vascular  papillae).  They  are  less  abundant  on  the  back  of  the  hand  and  foot,  on 

the  mammilla,  the  lips, 
and  the  tip  of  the 
tongue;  rare  on  the 
glans  clitoridis,  isolated 
on  the  volar  aspect  of 
the  forearm  (also  in 
anthropoid  apes  and  the 
raccoon) . 

The  tactile  corpus- 
cles have  in  their  in- 
terior an  ellipsoidal 
inner  bulb  composed  of 
nucleated  epithelial  cells. 
The  supplying  nerve- 
fiber  loses  the  sheaths 
of  Henle  and  of  Schwann 
at  the  base  of  the  inner 
bulb,  and  these  in  turn 
surround  and  enclose  the 
bulb.  The  nerve-fiber, 
at  first  medullated,  then 
nonmedullated,  makes 
spiral  turns  around  the 
inner  bulb,  after  which 
it  breaks  up  into  fibrils 
and  penetrates  the  bulb. 
Here  the  isolated  nerve- 
fibrils  terminate  with 
nodular  enlargements 
between  the  cells  of  the 
bulb. 

Arth.  Kollmarm  dis- 

--   *--— — -o  --  —"•  ••«•*-"«-  wji^/uo^ic,    c,   lin-me  corpuscle;    /,  nerve- 
deck?)  transversely;  g,  cells  of  the  Malpighian  layer  (Biesia- 


FIG.  332  r_r _t ^ 

fiber  passing ( to  the  tactile  "corp"usde;    e,  tactile  corpuscle;    /,' nerve- 


,  Vascular  papilla;   b,  touch-papilla;   c,  blood-vessel;   d,  n 


tinguishes  especially  on 
the  hand  three  princi- 
pal tactile  areas:  (i) 

th™i  v  SorPusc!esf°J.each  10  mm.  of  length;    (2)  t£fhree^iiinTnc2 

the  palm  behind  the  mterdigital  spaces,  where  there  are  from  5.4  to  2.7 
™ptir0rpUS? ?  I?  GVery  X?  mm-  °f  len^h;  (3)  the  thenar  and  hypothenar 
The  fi«J tx  6  there.  ^  1fr°m  3-*  to  3-5  tactile  corpuscles  for  each  mm. 

vvo  areas  contain  also  numerous  corpuscles  of  Vater,  the  third  onlv  a 

lesl' numerous          mmg  ^       ^  hand  the  nervous  end-organs   are   much 

in  tLC«3!U8?eS  °f  \ater  and  Padni  (FiS'  333)  are  from  i  to  2  mm.  long,  and 

fiLTrs  and  to?,  r?eOUS^lSS1fe'  esPe,cially  on  the  nerves  of  the  flexor  aspect  of  the 

SVfaLS^nte    !°0         M00  '  m  the  mammillary  region,  in  the  neighbor- 

the  tendons    on  th       I5'  On  ^ inteJ°sseous  membrane,  on  the  perimysium,  on 

>ns,  on  the  plexuses  of  the  abdominal  sympathetic,  at  the  side  of  the 


TOUCH. 


921 


abdominal  aorta  and  of  the  coccygeal  gland,  in  the  pancreas,  on  the  pericardium, 
at  the  side  of  the  knee  of  the  facial  nerve,  on  the  back  of  the  penis  and  of  the 
clitoris,  as  well  as  in  the  mesocolon  of  the  cat.  Numerous  connective-tissue 
capsules,  separated  from  one  another  by  fluid,  like  the  layers  of  an  onion,  surround 
the  homogeneous  central  bulb,  which  is  filled  with  neuroplasm  and  is  lined 
by  flat  epithelial  cells.  The  lamellae  of  the  corpuscle  are  formed  by  hypertrophy 


— Bulbous  swelling  of  the  axis- cylinder. 


Axis-cylinder. 


Concentric  layer.-- 


Medullated  nerve-fibe 


FIG.  333. — Vater-Pacinian  Corpuscle. 

of  Henle's  layer  of  the  nerve-fiber,  and  are  composed  of  nucleated,  flat  cells. 
The  medullated  nerve-fiber,  which  enters  the  pedicle,  loses  its  myelin-sheath, 
and  its  sheath  of  Schwann,  and  terminates  as  an  axis-cylinder  either  in  a  single 
or  in  a  bifurcated  extremity,  with  a  slight  terminal  enlargement,  the  end-bulb, 
within  which  each  nerve-fibril  ends  in  a  most  delicate  terminal  nodule. 

Krause's  longitudinal  end-bulbs   (Fig.   335)   are  found  in  the  conjunctiva  of 


Cells  from  which  thr 
end-bulb  is  formed. 


Sheath  with  nucle 


.Centrifugal  nerve. 


FIG.  334. — Spherical  End-bulb  in  the  Human  Conjunctiva  (Longworth). 


the  eyeball,  on  the  floor  of  the  mouth,  at  the  margin  of  the 
lips,  in  the  nasal  mucous  membrane,  on  the  epiglottis,  on 
the  fungiform  and  circumvallate  papillae,  on  the  glans 
penis  and  clitoridis,  in  the  tendilemma,  in  the  tendons, 
on  the  sole  of  the  foot  in  man,  on  the  plantar  surfaces  of 
the  toes  (porpoise),  on  the  ear  and  trunk  (mouse)  and  in 
the  wing  of  the  bat.  They  are  from  0.075  to  °-I4  mm-  lon§ 
and  are  probably  present  in  all  mammals  in  the  cutis  and  the 

mucous  membranes  as  the  regular  form  of  nerve-ending.  The  adventitia  of  the 
double-contoured  fiber  passes  over  into  the  connective-tissue  covering  of  the  bulb, 
the  sheath  of  Schwann  becomes  thickened  and  it  develops  into  the  inner  bulb,  con- 
sisting of  cells  of  the  longitudinal  bulb.  The  spheroidal  end-bulbs  in  man  (nasal 
mucous  membrane,  conjunctiva,  mouth,  epiglottis,  folds  of  the  rectal  mucous 
membrane)  consist,  according  to  Longworth  and  Waldeyer,  in  the  interior  of  a 


FIG.  335. — Longitudinal 
End-bulb:  a,  the  nu- 
cleated sheath. 


SENSORY  AND  TACTILE  SENSATIONS. 


FIG.  336.— Grandry-Merkel  Corpuscles: 
A  consisting  of  3  cells;  B  of  2  cells; 
n,  nerve  (tongue  of  the  duck). 


spherical  connective-tissue  sheath  of  numerous  closely  grouped  cells,  between 
which  the  terminal  fibrils  of  the  nerves  end  (Fig.  334).  Waldeyer  compares  these 
cells  with  those  of  the  Grandry-Merkel  corpuscles.  These  structures  evidently 
are  closely  allied  to  the  genital  and  articular  corpuscles.  The  first  appear  to  be 
end-bulbs  fused  together  in  varying  degree  in  the  skin  of  the  glans  penis  and 

clitoridis.  The  joint-corpuscles  are  found 
in  the  synovial  membrane  of  the  finger- 
joints;  they  are  larger  than  the  end-bulbs, 
and  exhibit  on  the  outer  surface  numerous 
oval  nuclei ;  as  many  as  four  nerves  pene- 
trate their  interior. 

The  Grandry-Merkel  corpuscles  occur 
in  the  so-called  waxy  covering  of  the 
bill,  and  in  the  tongue  of  ducks  and 
geese.  They  are  large  cells  with  spherical 
nuclei  and  nucleoli,  surrounded  by  a 
fibrous  sheath,  and  between  them  a  naked 
nerve-fiber  is  interposed  by  means  of  a 
protoplasmic  disc — tactile  disc.  Two  or 
more  cells  are  often  found  on  top  of  one 
another,  with  a  nerve-end  disc  between 

them.  When  a  number  of  such  cells  are  placed  upon  one  another  and  side  by 
side  larger  structures  are  produced  that  appear  to  be  transitional  forms  to  the 
tactile  corpuscles.  In  animals  there  are  many  other  kinds  of  terminal  corpuscles 
on  the  sensory  nerves:  The  corpuscles  of  Hefbst  in  birds,  resembling  small  cor- 
puscles of  Vater,  with  longitudinal  striation  in  the  periphery  and  transverse 
striation  within,  but  without  a  distinct  capsule;  the  tactile  cones  in  the  snout 
of  the  mole  and  allied  animals;  the  end-capsules  on  the  penis  of  the  hedgehog, 
and  on  the  tongue  of  the  elephant;  the  tactile  bulbs  on  the  beak  and  the  tongue 
of  several  birds ;  the  nerve-rings 
in  the  auricles  of  the  mouse. 
Terminal  ganglion-cells,  con- 
nected with  cilia,  form  the 
tactile  organ  in  the  rotifera, 
crustaceans,  and  insects. 

The  termination  of  the 
nerves  by  means  of  most  deli- 
cate fibrils  with  knob-like 
ends  (terminal  nodules)  be- 
tween the  epithelial  cells  of 
the  cornea  has  already  been 
described  (p.  816).  A  similar 
arrangement  exists  also  be- 
tween the  cells  of  the  epider- 
mis and  between  the  epithelial  m 
cells  of  the  genital  organs. 

In  sensitive  situations  the 
peripheral  ends  of  the  nerve- 
fibers  form  distinct  patelliform 
tactile  discs  (tactile  menisci) 
within  the  epidermis,  and  upon 

them  the  lower  cells  of  the  Malpighian  layer  are  placed.  These  structures  are 
found  in  man  and  in  animals,  for  example  in  the  snout  of  the  pig  (Fig.  337). 

On  the  hairs,  which  are  in  many  places  connected  with  the  tactile  apparatus, 
there  is  below  the  opening  of  the  sebaceous  gland  a  nervous  end-organ  in  the 
external  root-sheath,  consisting  of  longitudinal  and  circular  fibers,  forming  a 
network.  Tactile  discs  are  present  in  the  cells  of  the  outer  root-sheaths  of  the 
tactile  cilia  in  mammals. 


FIG.  337. — Tactile  Discs  with  Nerves  from  the  Epidermis 
(snout  of  the  pig):  c,  epidermal  cells;  a,  tactile  cells; 
m,  tactile  discs;  «,  nerve. 


SENSORY  AND  TACTILE  SENSATIONS. 

The  sensory  nerve-trunks  contain  two  functionally  different  sets  of 
nerve-fibers,  namely:  (i)  Those  that  convey  painful  sensations,  and 
are  sensory  nerves  in  the  narrow  sense  of  the  word,  and  (2)  those 


SENSORY    AND    TACTILE    SENSATIONS.  923 

that  receive  tactile  impressions,  and  are  consequently  designated 
nerves  of  touch  or  tactile  fibers.  Tactile  sensations  include  the  per- 
ceptions of  temperature  and  of  pressure.  Some  observers  assume  that 
the  sensory  and  tactile  nerves  possess  separate  end-organs  and  nerve- 
fibers,  and  that  they  likewise  have  special  perception-centers  in  the  brain, 
although  little  of  a  definite  nature  is  known  in  this  connection.  This 
view  is  supported  :  ( i )  By  the  fact  that  both  sensory  and  tactile  sensations 
are  not  excited  at  the  same  time  in  all  of  the  areas  endowed  with  feeling. 
Tactile  sensations  (including  pressure  and  temperature)  are  transmitted 
only  by  the  coverings  of  the  external  integument,  the  oral  cavity,  the 
entrance  and  floor  of  the  nasal  cavity,  the  pharynx,  the  end  of  the 
rectum,  and  the  urogenital  openings;  feeble,  indistinct  sensations  of 
temperature  are  appreciated  also  in  the  esophagus.  On  the  other 
hand,  tactile  sensations  are  wanting  in  all  the  viscera,  as  experiments  on 
men  with  fistulas  of  the  stomach,  intestine,  and  bladder  teach;  in  these 
situations  pain  alone  can  be  excited.  (2)  The  paths  for  the  tactile  and 
sensory  nerves  are  far  apart  in  the  spinal  cord ;  this  renders  probable  the 
assumption  that  also  their  central  and  peripheral  extremities  are  dis- 
tinct. (3)  The  reflexes  (tactile  and  painful)  excited  by  the  two  kinds 
of  nerves  are  probably  controlled  or  inhibited  respectively  by  special 
central  organs.  (4)  Under  pathological  conditions  and  under  the  in- 
fluence of  narcot- 
ics, the  one  kind  of 
sensation  may  be 
abolished ,  while 
the  other  is  pre- 
served. 


Bier    and    Hilde- 

brandt  found  in  them-  ^^^^^^^^     ^^^^ Branches  passing  to  the 

selves  that  after  injec-  "^S^J^  epithelium. 

tl°n  /f    iC°Cain     int?  ^  Nerve-trunks, 

the    aural    cavity    of 

the     spinal     COrd,    the  FIG.  338. — Nerve-endings  in  the  Corneal  Epithelium, 

sensation  of  pain  was 
abolished,    while    the 

sensation  of  touch  persisted;  sensations  of  cold  and  heat  were  preserved,  but 
intense  heat  caused  no  pain.  According  to  another  view,  the  sensation  of  pain 
belongs  to  the  nerves  both  of  pressure-sense  and  of  common  sensation,  and  rep- 
resents only  an  increase  in  the  irritation  of  these  nerves. 

The  nerves  of  sensation  must  be  subjected  to  relatively  strong  irrita- 
tion in  order  that  pain  may  be  excited.  The  irritant  may  be  mechanical, 
electrical,  thermal,  chemical,  or  somatic,  the  last  in  connection  with 
inflammatory  processes,  nutritive  disorders,  etc.  The  nerves  are  sensitive 
to  irritations,  not  only  at  the  peripheral  extremity,  but  also  through- 
out their  entire  course ;  and  the  central  extremity  is  sensitive  to  irrita- 
tion by  pain  The  pain,  however,  is,  according  to  the  law  of  peripheral 
perception,  always  referred  to  the  periphery. 

The  tactile  nerves  can  convey  pressure-sensations  only  as  a  re- 
sult of  moderately  strong,  mechanical  irritations  causing  differences  in 
pressure,  and  temperature-sensations  as  a  result  of  thermal  stimuli;  and 
in  both  instances  only  when  the  peripheral  end-organs  are  irritated.  If 
pressure  or  cold  be  applied  in  the  course  of  a  nerve -trunk,  for  example  to 
the  ulnar  in  the  depression  in  the  inner  condyle,  sensations  of  pain- 
never  of  touch — are  excited  in  the  peripheral  distribution.  All  intense 


924 


SENSE    OF    SPACE. 


irritants   disturb   normal  tactile   sensations  by  over-stimulation,   and, 
therefore,  excite  only  pain. 

v.  Vintschgau  discovered  that  if  two  electrical  tactile  stimuli  are  applied  to 
the  middle  of  the  forehead  in  succession,  a  shorter  interval  of  time  is  usually 
required  to  perceive  them  as  separate  (0.022  sec.)  than  if  they  are  applied  to 
the  dorsal  surface  of  the  lower  arm  (0.033  sec.). 

If  rapidly  interrupted  electrical  or  mechanical  stimuli  which  can  still 
be  perceived  as  separate  irritations,  are  permitted  to  act  on  the  skin, 
and  if  the  stimuli  are  then  suddenly  withdrawn,  a  new  sensation  arises 
after  a  short  interval  of  rest.  This  secondary  sensation  appears  as  a  short 
stinging  sensation.  It  is  supposed  to  result  as  a  summation  within 
the  cells  of  the  sensory  paths  in  the  spinal  cord,  and  to  be  identical 
with  the  phenomenon  of  delayed  sensation  of  pain. 

The  law  of  specific  energies  presupposes  the  existence  among  the 
cutaneous  nerves  of  different  fibers  with  different  end-organs,  which  con- 
duct the  various  forms  of  sensation  (pressure,  temperature,  pain).  In 
fact  Blix  and  Goldscheider  have  found  such  fibers.  Electrical  stimula- 
tion causes  different  sensations  in  different  minute  punctate  areas  of  the 
skin:  in  one  place  pain  alone  is  perceived,  in  another  cold,  in  a  third 
heat,  and  in  a  fourth  the  sensation  of  pressure.  At  each  temperature- 
point  there  is  insensitiveness  to  pain  or  pressure.  The  pressure-points 
are  much  closer  together  and  usually  more  numerous  than  the  tempera- 
ture-points. There  are  also  special  pain-points  and  ticklish  points. 
These  sensory  points  are  arranged  in  linear  chains,  which  usually  radiate 
from  the  hair-papillae.  Ticklish  points  coincide  with  the  pressure-points 
and  pain-points.  The  sensations  of  tickling  and  itching  correspond  to 
the  feeblest  irritation  of  the  nerve -fiber,  that  of  pain  to  the  strongest 
irritation.  The  pain -points  may  be  shown  by  the  needle  and  by 
electricity,  especially  in  the  wrinkles  of  the  skin,  in  which  the  pressure- 
sense  is  absent. 

Goldscheider  removed  small  pieces  of  his  own  skin,  in  which  he  had  previously 
determined  the  various  points,  and  examined  the  tissues  microscopically.  At 
every  sensory  point  be  found  an  extraordinary  number  of  nerves;  at  the  pressure- 
points  there  were  no  tactile  corpuscles. 

The  best  way  of  testing  the  tactile  sense  in  general,  according  to  E.  Hering,  is 
by  means  of  numerous  rods,  wrapped  with  wire  of  different  size.    The  coarse  wire  is, 
naturally,  the  easiest  to  distinguish  on  account  of  its  unevenness,  while  fine  wire 
appears,  on  the  contrary,  almost    smooth  when   the  tactile  sense  is  not  acute. 
:erent  portions  of  skin  exhibit  varying  degrees  of  tactile  delicacy,  and  they 
my  be  arranged  in  the  following  order,  from  the  most  delicate  to  the  least  delicate : 
nger-tips,  palm  of  the  hand,  inferior  surface  of  the  toes,  back  of  the  hand,  flexor 
irlace  ol  the  forearm,  buttocks,  extensor  surface  of  the  forearm,  leg,  upper  arm, 
thigh,  scapular  region. 

SENSE  OF  SPACE. 

Man  is  able  not  only  to  distinguish  differences  in  pressure  or  in 
;emperature  and  also  pain  as  such,  by  means  of  his  nerves,  but  also 
the  sCatial  ^en  mt  ^^  ^  impression  is  made  '> this  faculty  is  designated 

dwJSS0?™!™  Testing.—(i)  Two  blunt   compass-points  are  placed   at   different 

is  d^erminS?  nt     ^P£r!l0n         skl"  tO  be  examined,  and  the  greatest  distance 

minea  at  which  the  two  points  are  still  perceived  as  one.     Instead  of  the 

^fixed    ^rltl^  ^esthesl°meter  may  be  used.     This  consists  of  two  points, 

ed,  and  the  other  movable  on  a  scale  like  a  cobbler's  measure.      (2)   With 


SENSE    OF    SPACE.  925 

the  points  fixed  at  a  distance  at  which  they  can  be  perceived  as  separate  they  are 
moved  over  other  parts  of  the  skin,  and  the  subject  is  asked  whether  the  points 
seem  to  move  closer  or  further  apart.  (3)  Two  compasses  with  their  points 
separated  unequally  are  placed  on  two  different  portions  of  the  skin,  and  the 
subject  is  asked  to  state  when  they  seem  to  be  equally  separated:  Fechner's 
method  of  equivalents.  Thus,  a  separation  of  four  lines  on  the  forehead  seems  to 
be  equal  to  a  separation  of  2.4  lines  on  the  upper  lip.  Camerer  found,  in  general, 
that  the  separation  of  the  points  applied  to  a  portion  of  the  skin  endowed  witn 
delicate  tactile  sensitiveness  is  equivalent  to  a  much  greater  separation  in  a 
less  sensitive  area.  (4)  A  portion  of  the  skin  can  be  touched  with  a  blunt  rod, 
and  the  subject  with  his  eyes  closed  be  asked  to  indicate  exactly  where  he  was 
touched. 

Investigation  has  yielded  the  following  results:  The  spatial  sense 
in  a  given  portion  of  skin  is  the  more  highly  developed : 

1 .  The  more  numerous  the  tactile  nerves  that  ter- 
minate in  the  area  in  question. 

2 .  The  greater  the  mobility  of  the  part ;  hence  it 
is  most  delicate  in  the  extremities,  toward  the  fingers 
and  toes ;  also  in  parts  of  the  body  that  are  moved 
with  great  rapidity. 

3.  In  the  extremities  the  sensitiveness  is  greater 
in  the  transverse  than  in  the  long  axis.    It  is  one-eighth 
greater  on  the  flexor  surface  of  the  upper  arm,  and  one- 
fourth  greater  on  the  extensor  surface.     Likewise,  the 
flexor  surface  is  more  sensitive  than  the  extensor — 
one-sixth  more  in  the  upper  extremity. 

4.  The  method  of  application  of  the  compass-points 
has  an  influence :  (a)  if  they  are  applied  in  succession, 
instead  of  together,  or  if  they  are  considerably  warmer 

or  colder  than  the  skin,  or  if  they  are  unequally  warm,      FIG.  339.— Compasses  for 
it  is  possible  to  distinguish  a  separation  of  shorter 
distances;  (£>)  if  the  examination  is  begun  with  the 
points  far  apart  and  the  distance  is  gradually  lessened,  it  is  possible 
to  recognize  shorter  distances  than  when  the  examination  is  begun  with 
the  points  separated  by  an  indistinguishable  distance  and  the  distance  is 
gradually  increased;  (c)  if  one  point  is  cold,  and  the  other  hot,  two  im- 
pressions are  felt  when  the  minimum  distance  is  exceeded,  but  it  is  im- 
possible to  determine  their  relative  position. 

5.  The  spatial  sense  can  be  sharpened  by  practice;  hence  its  delicacy 
in  the  blind,  and  the  improvement  is  always  bilateral. 

6.  Moistening  the  skin  with  indiffer- 
ent fluids   increases  the  delicacy  of  the 
m^i   .    .   .  rc5^  ,  spatial  sense.     If,  however,  the  skin  be- 

tnL_Jiiilinilf'iiWn|-''i'il'iilnii;__JiiiliiiiliiiiliiMhT?jfl\  .  '  '  .  , 

HI  tween  two  points  that  are  still  recognized 

FIG.  340.— Sieveking's  Esthesiometer.  as  separate  be  gently  tickled  or  be  tra- 
versed by  imperceptible  electrical  cur- 
rents, the  impressions  become  fused. 

The  spatial  sense  is  sharpened  at  the  kathode  on  applying  the  constant 
current,  likewise  by  congestion  of  the  skin  in  consequence  of  irritation, 
and  also  by  slight  stretching  of  the  skin ;  further  after  carbonated  baths 
or  warm  sodium  chlorid  baths,  and  temporarily  by  the  use  of  caffein. 
7.  Anemia  (induced  by  elevation  of  the  extremities)  and  venous 
hyperemia  (induced  by  compression  of  the  veins)  impair  the  spatial 
sense ;  likewise  too  frequent  repetition  of  the  tests  (as  a  result  of  fatigue). 


926  SENSE    OF    SPACE. 

The  same  influence  is  exerted  by  the:  application  of-  cold  to  the  skin,  by 
the  action  of  the  anode,  strong  stretching  of  the  skin,  for  example  of  the 
abdominal  walls  during  pregnancy,  likewise  previous  exertion  of  the 
muscles  situated  beneath  the  cutaneous  area ;  as  well  as  certain  poisons : 
atropin,  daturin,  morphin,  strychnin,  alcohol,  potassium  bromid, 
cannabin,  and  chloral  hydrate. 

The  shortest  distances  in  millimeters  at  which  two  compass  points  were 
recognized  as  separate  by  an  adult  are  as  follows  (the  analogous  figures  for  a 
boy  twelve  years  old  are  enclosed  in  parenthesis) :  Tip  of  the  tongue  i .  i  mm.  (i.  i)  ; 
palmar  aspect  of  the  third  phalanx  of  the  finger  2-2.3  C1-?);  red  part  of  the  lip 
4.5  (3.9);  palmar  aspect  of  the  second  phalanx  of  the  finger  4-4. 5  (3.9);  palmar 
aspect  of  the  first  phalanx  of  the  finger  5-5.5;  dorsal  aspect  of  the  third  phalanx 
of  the  finger  6.8  (4.5);  tip  of  the  nose  6.8  (4.5);  palmar  aspect  of  the  head  of  a 
metacarpal  bone  5-5.5-6.8  (4.5);  thenar  eminence  6.5-7 ;  hypothenar  eminence 
5.5-6;  middle  of  the  palm  of  the  hand  8-9;  middle  and  border  of  the  back  of  the 
tongue,  white  part  of  the  lips,  metacarpus  of  the  thumb  9  (6.8) ;  plantar  aspect  of 
the  third  phalanx  of  the  great  toe  11.3  (6.8) ;  dorsal  aspect  of  the  second  phalanx 
of  a  finger  11.3  (9);  cheek  11.3  (9);  eyelid  11.3  (9);  middle  of  the  hard  palate 
13.5  (11.3);  palmar  aspect  of  the  lower  third  of  the  forearm  15;  skin  over  the 
front  part  of  the  zygoma  15.8  (11.3);  plantar  aspect  of  the  metatarsal  bone  of 
the  toe  15.8  (9) ;  dorsal  aspect  of  the  first  phalanx  of  a  finger  15.8  (9) ;  dorsal  aspect 
of  a  metacarpal  bone  18  (13.5) ;  inner  aspect  of  lip  20.3  (13.5) ;  skin  over  the  pos- 
terior part  of  the  zygoma  22.6  (15.8) ;  lower  portion  of  the  forehead  22.6  (18) ;  pos- 
terior portion  of  the  heel,  22.6  (20.3) ;  lower  portion  of  the  occiput  27.1  (22.6) ;  back 
of  the  hand  31.6  (22.6);  submental  region  33.8  (22.6) ;  top  of  the  head  33.8  (22.6); 
patella  36.1  (31.6);  sacrum  and  gluteal  region  40.6  (33.8);  forearm  and  leg  40.6 
(36.1) ;  back  of  the  foot  near  the  toes  40.6  (36.1) ;  sternum  45.1  (33.8) ;  upper  por- 
tion of  the  neck  54.1  (36.1);  spine  (fifth  dorsal  vertebra) ,  lower  dorsal  and  lumbar 
54.1;  middle  portion  of  the  neck  67.7:  arm,  thigh,  and  middle  of  the  back  67.7 
(31.6-40.6). 

By  experimenting  according  to  method  4  (p.  925),  it  is  found  that  the  spatial 
sense  is  best  developed  in  the  face  and  in  the  furrows  of  the  finger-joints;  then 
follow:  the  palm  of  the  hand,  the  back  of  the  hand  (error  as  high  as  i£  cm.),  the 
neck,  the  arm  (error  up  to  2  cm.) ,  the  clavicular  region,  the  upper  arm,  the  abdomen 
(error  up  to  3  cm.),  the  chest,  the  back  of  the  foot,  the  leg  (error  up  to  4  cm.), 
thigh  (error  up  to  7  cm.).  The  touching  of  one  toe  is  often  confused.  Pregnant 
women  localize  poorly  upon  the  abdomen. 

Illusions  of  the  spatial  sense  are  quite  common.  The  most  striking  are:  (i) 
A  uniform  movement  over  the  surface  of  the  skin  seems  to  be  more  rapid 
on  those  parts  that  possess  the  most  delicate  spatial  sense.  (2)  If  the  skin 
be  merely  touched  by  two  compass-points,  they  seem  further  apart  than  when 
they  are  stroked  over  the  skin.  (3)  A  sphere  provided  with  short  rods  appears 
larger  than  one  with  long  rods.  (4)  When  two  fingers  are  crossed,  small  objects 
placed  between  them  seem  to  be  doubled  (Aristotle's  experiment).  (5)  If,  how- 
ever, the  terminal  phalanges  of  two  fingers  are  first  touched  in  the  normal  position 
ot  the  fingers,  and  then  "the  same  places  when  the  fingers  are  crossed,  the  two  points 
touched  seem  to  lie  in  the  same  relative  position.  (6)  If  flaps  of  skin  are  trans- 
planted, for  example  a  flap  with  a  pedicle  from  the  forehead  to  the  nose,  the  patient 
will  often  for  months  have  the  feeling  in  the  new  portion  of  the  nose  as  though  it 
were  the  forehead,  providing  the  nerves  of  the  forehead  remain  intact. 

Many  attempts  have  been  made  to  explain  the  phenomena  of  the  spatial 

.se.     &.  H.  Weber  started  from  the  assumption  that  one  and  the  same  nerve- 

iber,  passing  from  the  brain  to  the  skin  could  receive  and  transmit  only  one  kind 

)f  impression  within  the  area  supplied  by  it.     He  gave  the  name  of  sensory  circle 

each  region    of   the    skin  to  which   a  single   fiber  was    distributed.      If  two 

.mpressions  act  simultaneously  upon  the  tactile  apparatus,  they  are  recognized 

Louble  if  one  or  more  sensory  circles  lie  between  the  two  points.     This  inter- 

3n,  based  on  anatomical  considerations,  cannot  be  reconciled  with  the  fact 

the  circles  of  sensation  may  be  reduced  in  size  by  practice,  and,  further, 

that  only  one  sensation  arises  when  the  two  points  are  so  applied  that,  although 

ther  apart  than  the  diameter  of  such  a  circle,  they  at  times  lie  upon  two  ad- 

es,  and  at  other  times  upon  two  other  circles  separated  by  a  third. 


THE    PRESSURE-SENSE.  927 

Following  Lotze,  Wundt  assumes  from  a  psychophysiological  standpoint  that 
each  area  of  the  skin  sends  to  the  brain,  together  with  tactile  impressions,  informa- 
tion as  to  the  localization  of  the  sensation.  Hence,  each  area  is  able  to  give  to 
the  tactile  sensation  a  local  coloring,  which  is  made  use  of  as  a  local  sign.  Wundt 
assumes  that  this  local  coloring  varies  from  point  to  point  of  the  skin.  The 
gradation  is  abrupt  on  those  parts  of  the  skin  in  which  the  spatial  sense  is  highly 
developed,  but  gradual  in  those  where  it  is  comparatively  poor.  Separate  im- 
pressions become  fused  wherever  the  gradation  of  this  local  coloring  is  imper- 
ceptible. As  it  is  possible  by  exercise  and  attention  to  distinguish  differences 
of  sensation  that  cannot  ordinarily  be  appreciated,  the  reduction  in  the  size  of 
the  circles  of  sensation  by  practice  can  be  thus  explained.  The  circle  of  sensation 
is  an  area  of  skin  within  which  the  local  coloring  of  the  sensation  is  so  little  changed 
that  two  separate  impressions  are  fused  into  one. 

Loeb  has  made  experiments  upon  the  tactile  area  of  the  hand,  that  is  the 
total  number  of  points  that  an  individual  can  reach  with  the  tip  of  the  forefinger, 
without  change  in  the  position  of  the  body.  If,  with  closed  eyes,  the  hands  are 
moved  along  a  cord  stretched  transversely  to  the  right  and  the  left  respectively, 
an  inequality  within  the  distance  traversed  will  be  apparent :  in  right-handed  per- 
sons the  distance  to  the  right  is  generally  smaller,  and  in  left-handed  the  distance  to 
the  left.  Nervous  patients  often  exhibit  marked  deviations.  In  the  attempt 
to  make  movements  of  the  same  extent,  the  movement  executed  will  be  the  smaller 
the  more  the  muscles  are  already  contracted.  The  perception  of  the  size  and 
the  direction  of  voluntary  movements  depends  upon  the  voluntary  impulse  sent 
to  the  muscles. 


THE  PRESSURE-SENSE. 

Through  the  pressure-sense  information  is  obtained  as  to  the  amount 
of  weight  placed  upon  the  skin;  v.  Frey  considers  the  hair-nerves  and 
Meissner's  corpuscles  as  the  organs  of  the  pressure-sense.  The  pressure- 
sense  is  subserved  by  specific  nervous  end-organs  having  a  punctate 
arrangement.  These  pressure -points  possess  different  degrees  of  sen- 
sibility ;  in  many  places  (such  as  the  back 
and  the  thigh)  they  are  characterized  by 

an    especially    marked    after-sensation.  .  •'.'.. :•*.'.•       ••.  •:•  .;-.' 

The  distribution  of  the  points  corre-  J::VO  /.''/.Vv;.  :..["•';./*'.'••• 
spends  to  that  of  the  temperature-  ••:[-'::.vX'  ::.:*-V'!i  *!"."•" !:";""•"•" 
points.  The  chains  of  pressure-points  %%:V.*  • 

usually  take  a  different  direction  from  <*  b  c 

that  of  thf»  Vint    anH   r>n1H  nnintc  •    in    o-An  FlG-  34i- — Pressure  Points:  a,  from  the   mid- 

d  cold  points ,  in  gen-        dle  o{  the  ^  o{  the  foot.  bt  from  the  skin 

eral     their     density    is    greater;     but    this  of   the    zygoma;    c,   from   the  back  (after 

varies  in  different  regions.  In  places 
provided  with  hair  the  number  of  pres- 
sure-points does  not  correspond  exactly  with  the  number  of  hairs,  but 
the  points  always  lie  in  circles  around  the  hairs.  Hence,  the  hair  when 
touched  can  also  transmit  the  pressure-sensation,  as  it  presses  like  a 
lever  on  the  nerves  of  the  root-sheaths.  The  smallest  distances  at 
which  two  pressure-points  applied  simultaneously  can  be  felt  as  double 
have  been  found  to  be  as  follows:  on  the  back,  from  4  to  6  mm.;  on  the 
chest,  0.8;  on  the  abdomen,  from  1.5  to  2 ;  on  the  cheek,  from  0.4  to  0.6; 
on  the  arm,  from  0.6  to  0.8;  on  the  forearm,  from  0.5  to  i ;  on  the  back 
of  the  hand,  from  0.3  to  0.6;  on  the  palm  of  the  hand,  from  o.i  to  0.5 ; 
on  the  palmar  aspect  of  the  distal  phalanx  of  a  finger,  o.i ;  on  the  dorsal 
aspect,  from  0.3  to  0.5 ;  on  the  leg,  from  0.8  to  2 ;  on  the  back  of  the  foot, 
from  0.8  to  i ;  on  the  sole  of  the  foot,  from  0.8  to  i  mm.  In  the  parts 
of  the  body  devoid  of  hair,  the  tactile  corpuscles  are  supposed  to  transmit 
the  pressure-sensation. 


THE    PRESSURE-SENSE. 

Method  of  Examination. — (i)  Weights  of  different  amount  are  placed  suc- 
cessively on  the  parts  of  the  skin  to  be  tested,  and  the  subject  is  asked  to  form  an 
estimate  of  the  differences  in  pressure.  In  order  to  exclude,  so  far  as  possible, 
the  influence  of  temperature,  displacement  and  inequality  in  application,  the 
area  of  skin  should  be  previously  covered  by  a  plate,  which  is  allowed  to  remain 
throughout  the  experiment.  The  influence  of  the  muscular  sense  must  also  be 
eliminated.  (2)  A  projecting  arm  from  a  scale-beam  is  placed  on  the  skin, 
and  by  the  addition  or  removal  of  weights  the  differences  in  pressure  are  learned 
that  the  subject  is  capable  of  estimating.  (3)  In  order  to  avoid  the  troublesome 
changing  of  weights  A.  Eulenburg  constructed  his  baresthesiometer,  an  apparatus 
constructed  upon  the  principle  of  the  spiral-spring  balance.  It  is  provided  with 
a  small  button  directed  downward,  which  is  depressed  by  the  force  of  the  spring. 
An  indicator  marks  directly  the  pressure  in  grams,  and  this  can  at  once  be  readily 
varied.  (4)  Goltz  employed  a  pulsating,  elastic  tube,  in  which  waves  of  different 
height  could  be  produced.  He  determined  how  high  they  had  to  be  before  they 
were  perceived  as  pulse-waves  on  the  different  areas  of  skin  on  which  the  tube 
was  placed.  (5)  The  mercurial  pressure-balance  constructed  by  the  author  satis- 


fies all  requirements  completely  (Fig.  342). 
A  scale-beam  (W)  resting  on  knife-bl 


(W)  resting  on  knife-blades  (O  O)  is  supported  on  the  horizontal 
arm  (b)  of  a  heavy  stand  (T).  One  arm  of  the  scale  possesses  a  thread  (m) 
on  which  a  balancing  weight  (S)  can  be  moved  to  and  fro.  The  other  arm  (d) , 
which  passes  vertically  upward,  terminates  in  a  graduated  tube  (R).  From  the 
latter  there  projects  downward  a  pressure-button  (P) ,  to  which  weights  (G)  can 
be  added  at  will,  and  which  rests  upon  the  area  of  skin  to  be  tested  (H). 
From  a  buret  (B)  near  by,  which  is  supported  on  an  upright  (A),  mercury  can 
pass  through  the  hollow  arm  of  the  scale,  in  the  direction  of  the  arrow,  and  mount 
upward  in  the  tube  (R).  A  thin,  readily  movable  piece  of  rubber  tubing  connects 
the  arm  (O)  with  a  fixed  glass  tube,  and  the  latter  passes  subsequently  to  the 
rubber  tube  (D  D)  of  the  buret.  If  the  cock  (h)  is  closed,  the  mercury  moves 
onward  in  d  and  rises  in  R,  thus  increasing  the  pressure  of  the  button  (P)  when- 
ever pressure  is  made  on  the  tube  (D  D).  The  weight  of  the  mercury  filling  one 
division  of  the  tube  (R)  is  known.  The  apparatus  permits,  without  any  agitation 
whatever,  of  rapid  or  slow  variation  in  pressure,  with  any  selected  initial  weight 
(through  G) .  In  the  figure  a  indicates  a  screw  for  varying  the  position  of  the 
supporting  arm  (b) :  t  is  an  arrangement  with  two  screws  to  prevent  the  scale - 
arm  from  tipping  over.  The  more  extensively  pressure  is  made  upon  the  tube 
(D  D) ,  the  greater,  naturally,  will  be  each  increase  of  pressure.  By  raising  the 
buret  (B),  if  h  is  open,  the  pressure  can  also  be  increased. 

If  P  is  at  first  supported  the  mercury  can  be  allowed  to  rise  in  R  to  different 
heights  (in  order  to  produce  different  amounts  of  pressure) ,  and  after  closing  the 
cock  (h) ,  the  pressure  of  the  button  can  be  permitted  to  act  suddenly  by  quickly 
releasing  its  support.  In  general,  those  methods  are  to  be  preferred  in  which 
the  different  pressures  act  at  distinct  intervals  of  time,  instead  of  allowing  the 
original  pressure  to  increase  or  decrease  gradually,  because  in  the  latter  method 
the  cutaneous  nerves  are  gradually  fatigued.  Both  the  pressure-sense  and  the 
temperature-sense  (to  be  discussed  presently)  may  be  most  reliably  tested  by 
the  principle  of  the  least  perceptible  difference,  that  is  by  permitting  different 
pressures  (or  temperatures)  to  act  in  graduated  order,  commencing  either  with 
great  differences  or  with  the  smallest  ones,  and  seeking  the  limit  at  which  or 
within  which  a  positive  recognition  of  the  difference  takes  place. 

The  results  of  the  investigations  of  the  pressure-sense  are  as  follows  : 
i.  The  minimal  pressure  that  can  just  be  perceived  on  different 
parts  of  the  body  varies  greatly  in  accordance  with  the  locality.  The 
most  delicate  areas  are  the  forehead,  the  temple,  the  back  of  the  hand, 
and  the  forearm,  which  perceive  a  pressure  of  0.002  gm.  The  fingers 
do^  not  recognize  a  pressure  of  less  than  from  0.005  to  0.015  gm.;  the 
chin,  the  abdomen,  the  nose  a  pressure  of  less  than  from  0.04  to  0.05 
gm. ;  nor  the  finger-nails  of  less  than  i  gm.  In  order  to  test  the  pressure- 
sense  of  individual  small  points,  they  may  be  pressed  upon  with  a 
flexible,  elastic  hair.  The  most  delicate  pressure-sensations  in  these 
situations  were:  the  face,  as  low  as  0.0007  gm.,  the  arm  and  the  leg, 
as  low  as  0.012  gm.  Pressure  is  more  readily  perceived  when  applied 


THE    PRESSURE-SENSE. 


929 


suddenly  than  when  gradually  increased.     Decrease  of  pressure  is  less 
readily  perceived  than  increase. 

2.  Intermittent  variations  of  pressure  are  more  readily  recognized 
than  light  pressure,  rapid  variations  with  more  difficulty  than  those 
occurring  at  longer  intervals. 

The  greater  the  sensitiveness  of  a  portion  of  the  skin  the  more  rapidly  may 
individual  impulses  or  blows  follow  one  another  and  yet  be  perceived  as  separate: 
on  the  posterior  aspect  of  the  thigh  52,  on  the  back  of  the  hand  61,  on  the  finger- 
tips 70  impulses  in  a  second. 

3.  Differences  between  two  weights   are  perceived  by  the  finger- 
tips when  they  are  in  the  ratio  of  29:30  (by  the  forearm  when  the  ratio 
is  18.2  :  20),  provided  that  the  weights  are  not  too  light  or  too  heavy. 


FIG.  342. — Landois'  Mercurial  Pressure-balance. 

Ascending  from  light  to  heavier  weights,  the  accuracy  in  distinguishing 
between  two  weights  increases  at  first,  and  then  decreases  rapidly  for 
heavier  weights.  This  observation  is  contradictory  of  the  psycho- 
physical  law  of  Fechner. 

4.  A.  Eulenburg  found  the  following  gradations  in  the  accuracy  of 
the  pressure-sense:  the  forehead,  the  lips,  the  back  of  the  tongue,  the 
cheek,  and  the  temple  showed  differences  of  from  -£$  to  -^\  (from  200  :  205 
to  300:310  gm.).  The  dorsal  aspect  of  the  last  phalanx  of  the 
fingers,  of  the  forearm,  of  the  hand,  of  the  first  and  second  phalanges, 
the  palmar  aspect  of  the  hand,  and  of  the  forearm  and  the  arm  perceived 
59 


THE    TEMPERATURE-SENSE. 

differences  of  from  TV  to  YV  (from  200  :  220  to  200  :  210  gm.).  The  anterior 
surface  of  the  leg  and  thigh  resembled  the  forearm.  Then  followed  the 
back  of  the  foot  and  of  the  toes ;  the  sensitiveness  was  much  less  on  the 
plantar  aspect  of  the  toes,  the  sole  of  the  foot,  and  on  the  posterior  aspect 
of  the  thigh  and  leg.  Dohrn  tried  to  determine  the  smallest  increase  of 
weight  that  in  the  presence  of  a  weight  of  i  gm.  could  be  appreciated  by 
different  portions  of  the  skin.  This  was  for  the  third  phalanx  of  the 
finger  0.499  gm.,  the  back  of  the  foot  0.5  gm.,  the  second  phalanx  of 
the  finger  0.771  gm.,  the  first  phalanx  0.82  gm.,  the  leg  i  gm.,  the  back 
of  the  hand  1.156  gm.,the  palm  of  the  hand  1.018  gm,  the  patella  1.5 
gm.,  the  forearm  1.99  gm.,  the  sternum  3  gm.,  the  umbilical  region  3.5 
gm.,  the  back  3.8  gm.  The  delicate  lanugo-hairs  of  the  skin  are  espe- 
cially sensitive  to  pressure. 

5  Too  long  a  time  must  not  elapse  between  the  application  of  two 
weights,  but  as  much  as  100  seconds  may  elapse  if  the  difference  in 
weight  is  in  the  ratio  of  4  :  5. 

6.  The  after-effect  in  connection  with  the  pressure-sense  is  especially 
pronounced  when  pressure  of  considerable  amount  is  applied  for  some 
time.     Even  slight  pressures,  however,   when   applied  repeatedly  and 
successively,  must  be  separated  by  intervals  of  at  least  from  g-^-g-  to  T|-g- 
second  in  order  to  be  perceived  individually.     More  rapid  succession 
causes  confusion  of  the  impressions.     Valentin  found  that,  when  he  held 
the  finger-tip  against  a  wheel  set  with  blunt  teeth,  he  had  the  impression 
of  a  smooth  edge  if  the  teeth  struck  the  skin  at  the  intervals  mentioned ; 
when  the  revolution  was  slower,  each  tooth  excited  a  separate  pressure- 
sensation.     Vibrations   of  strings   are   recognized  .  as   such   when   they 
make  from  1506  to  1552  vibrations  in  the' second. 

7.  It  is  remarkable  that  pressure  effected  by  thoroughly  uniform 
compression  of  a  part  of  the  body,  for  example  by  immersing  an  arm 
in  mercury,  is  not  perceived  as  such;  the  ringer  dipped  in  mercury 
perceives  the  pressure  only  at  the  limit  of  the  fluid  on   the   palmar 
surface  of  the  finger. 

8.  The  points  that  are  sensitive  to  pressure  are  also  sensitive  to 
traction.     If  pressure  and  traction  are  applied  alternately  to  the  same 
area  of  the  skin,  the  distinction  is  possible  only  when  the  irritation  has 
a  certain  extent,  duration  and  intensity.     Traction  (acting  somewhat 
as  a  negative  pressure)  is  tested  by  the  application  of  small  pieces  of 
plaster,  which  can  be  drawn  upon  by  means  of  a  thread.     The  forehead 
and  the  temple  are  capable  of  recognizing  0.05  gm.  of   traction-force, 
the  finger-tips  and  the  lower  lip  0.5  gm.,  the  forearm  9  gm.,  the  leg  20 
gm. 

THE  TEMPERATURE-SENSE. 

Through  the  temperature-sense  information  is  obtained  as  to  the 
variations  of  the  temperature  of  the  surface  of  the  body.  The 
temperature-sense  is  subserved  by  specific  nerve-endings  having  a 
punctate  arrangement.  These  temperature-points  are  arranged  in  chains 
or  lines,  which  usually  are  slightly  curved.  They  radiate  from  certain 
points  of  the  skin  (chiefly  from  the  roots  of  the  hairs).  The  chains  of 
the  cold-points  do  not  coincide,  as  a  rule,  with  those  of  the  heat-points, 
although  both  have  the  same  areas  of  radiation.  These  lines  of  points 
are  frequently  not  complete,  but  are  indicated  only  by  isolated  points, 


THE    TEMPERATURE-SENSE. 


931 


between  which  points  of  another  sensation  are  frequently  interposed. 
In  this  way  mixed  punctate  chains  arise.  Near  hairs  there  are  almost 
always  temperature -points ;  in  areas  of  the  skin  with  feeble  temperature- 
sensibility,  the  temperature -points  are  present  only  near  the  hairs. 
According  to  Abrutz  the  cold-points  are  situated  more  superficially  in 
the  skin  than  the  heat-points;  according  to  v.  Frey,  Krause's  bulbs  are 
the  organs  for  the  perception  of  cold,  the  nerve -plexus  that  for  the 
perception  of  heat. 

The  heat-points  are  larger  than  the  cold-points ;  the  slightest  mechani- 
cal irritation  of  the  latter  excites  a  sensation  of  cold.  The  cold-points 
react  to  feebler  e'ectrical  stimuli  than  do  the  heat-points;  chemical 
irritants  also  are  capable  of  exciting  the  heat-points.  The  feeling  of 
cold  occurs  at  once,  that  of  heat  appears  gradually. 

A  gentle  touch  is  not  perceived  as  such  at  the  temperature -points, 
which  seem  to  be  anesthetic  for  pressure  and  pain.  In  general,  the  cold- 
points  preponderate  upon  the  entire  body,  and  they  are  denser,  while 
in  many  places  the  heat-points  are  entirely  wanting.  With  regard  to 
the  degree  of  sensibility  the  points  may  be  divided  into  those  that  are 


C.P. 


W.P. 


B 


c 


D 


FIG.  343- — A  Cold-points;  B  heat-points  on  the  palmar  aspect  of  the  distal  phalanx  of  the  index-finger  to  the  margin 
of  the  nail  (Goldscheider).  C,  Cold-points  and  D  heat-points  on  the  radial  half  of  the  dorsal  aspect  of  the 
wrist  (the  arrow  indicates  the  direction  in  which  the  hair  points  (Goldscheider). 

extremely  sensitive,  those  that  are  moderately  so,  those  that  are  slightly 
so,  and  those  not  at  all  sensitive.  It  is  possible  to  indicate  the  intensity 
of  the  temperature-stimulus  and  the  point  where  it  is  applied.  The 
heat-points  are,  on  an  average,  perceived  as  double  at  greater  distances 
than  the  cold-points.  The  minimal  distances  upon  the  forehead  are 
for  the  cold-points  0.8  mm.,  for  the  heat-points  from  4  to  5  mm.,  on  the 
chest  the  respective  values  are  2  and  from  4  to  5  mm.,  on  the  back 
from  1.5  to  2,  and  from  4  to  6,  on  the  back  of  the  hand  from  2  to  3  and 
from  3  to  5,  on  the  palm  of  the  hand  0.8  and  2,  on  the  thigh  and  leg 
from  2  to  3,  and  from  3  to  4  mm. 

For  testing  the  heat-points  and  the  cold-points  a  pencil-shaped 
metallic  rod  heated  to  from  45°  to  49°,  or  cooled  to  15°,  is  employed. 
When  the  cold-points  are  lightly  touched  only  the  cold  rod  is  felt  and 
as  cold;  and  only  heat  is  appreciated  by  the  heat -points.  Both  kinds 
of  points  are  insensitive  to  lightly  applied  objects  of  the  same  tempera- 
ture as  the  skin. 

The  determining  factor  with  respect  to  temperature-sensibility  is, 
according  to  E.  Hering,  the  temperature  of  the  thermal  end-organ  itself. 
Whenever  the  temperature  of  the  latter  in  any  part  of  the  cutaneous 
surface  is  above  its  own  zero-tempefature,  that  is,  its  normal  temperature, 


THE    TEMPERATURE-SENSE. 

there  will  be  the  sensation  of  warmth;  under  opposite  conditions,  the 
sensation  of  cold.  The  greater  the  deviation  of  the  thermal  apparatus 
from  its  zero-temperature,  the  more  distinct  or  the  more  intense  will 
be  the  sensation  of  heat  or  cold.  The  zero-point  may,  however,  be 
displaced  quite  rapidly  within  certain  limits  as  a  result  of  external 
conditions. 

Method  of  Examination. — Areas  of  the  skin  are  successively  touched  with 
objects  of  different  temperature,  of  equal  size  and  possessing  equal  heat-con- 
ducting powers,  (i)  Nothnagel  employs  for  this  purpose  small  wooden  cups, 
with  metal  bottoms,  which  are  filled  with  cold  or  warm  water,  and  are  placed  on 
the  skin;  the  temperature  of  the  water  is  indicated  by  a  thermometer.  (2)  Two 
thermometers,  which  are  heated  unequally  (if  necessary  by  electrical  means), 
can  be  applied  directly  to  the  skin  for  comparison. 

The  following  facts  have  been  ascertained  with  regard  to  the  tem- 
perature-sense : 

i.  In  general,  the  feeling  of  cold  arises  when  a  body  applied  to  the 
skin  withdraws  heat,  and,  conversely,  that  of  warmth,  when  heat  is 
communicated  to  the  skin. 

2  The  greater  the  heat-conducting  power  of  the  body  touching 
the  skin  the  more  intense  is  the  feeling  of  heat  or  of  cold. 

3.  Between  the  limits  of   15.5°  and  35°  C.  the  finger-tips  are  able 
to  distinguish  differences  of  temperature  of  from  0.20°  to  0.25°  C.     The 
temperatures  most  exactly  determined  are  those  that  lie  close  to  the 
temperature  of  the  blood  (from  33°  to  27°  C.),  differences  as  small  as  0.05° 
C.  being  recognized  (in  the  most  sensitive  situations).     Temperatures 
between  33    and  39°  C.  and  also  those  between  14°  and  27°  C.  are  less 
accurately   determined.     Temperatures  of   52.6°  C.  and  4-2.8°  C.  and 
lower  cause  in  addition  to  the  temperature-sensation,   marked  pain, 
but  in  this  respect  there  are  variations  in  different  individuals,  and  in 
different  places  between  — 11.4°  and  +36.3°  C. 

4.  The  sensitiveness  for  cold  is  in  general  greater  than  that  for 
heat,  and  greater  on  the  left  hand  than  on  the  right.     The  different 
portions  of  the  skin  differ  in  their  acuteness  of  heat-perception,  and 
in  the  following  order:    tip  of  the  tongue,  eyelids,  cheeks,  lips,  neck, 
trunk.     Nothnagel  found  the  minimum  of  differentiation  on  the  chest 
0.4°,  on  the  back  0.9°,  on  the  back  of  the  hand  0.3°,  on  the  palm  0.4°, 
on  the  arm  0.2°,  on  the  back  of  foot  0.4°,  on  the  thigh  0.5°,  on  the  leg 
0.6°,  on  the  cheek  from  0.4  to  0.2°,  on  the  temple  from  0.4  to  0.3°  C. 
Curiously,  the  skin  in  the  median  line  (for  example  of  the  nose)  has  a 
less  acute  heat-perception  than  the  lateral  portions  (alae  of  the  nose). 
According  to  Dessoir,  the  glans  penis  has  no  perception  of  heat. 

Fig-  343  shows  the  difference  in  the  topographical  arrangement  of 
the  heat-sense  and  the  cold-sense  on  the  same  portion  of  the  skin. 

Goldscheider  assumes  12  empirically  determined  grades  of  sensitiveness  for 
the  perception  of  cold,  and  8  for  that  of  heat.  Each  part  of  the  skin  has  a 
comparatively  constant  grade  of  sensitiveness.  For  example,  the  skin  of  the 
mammilla  has  the  grade  n  for  cold-perception,  the  grade  8  for  heat-perception; 
the  middle  of  the  sole  of  the  foot  respectively  7  and  2 . 

Application  of  a  10  per  cent,  solution  of  cocain  to  the  tongue  and  the  mucous 
membrane  of  the  mouth  abolishes  completely  the  sensibility  for  heat  and  cold. 
L  he  cooling  sensation  due  to  menthol  depends  upon  stimulation  of  the  nerves  for 
cold;  carbon  dioxid  irritates  the  heat-nerves  of  the  external  skin. 

5.  The  differences  in  temperature  are  best  recognized  when  different 
degrees  of  temperature  are  applied  to  one  portion  of  the  skin  in  rapid 


THE    TEMPERATURE-SENSE. 


933 


succession.  Gradual  variations  of  a  temperature  continuously  in  opera- 
tion are  the  more  imperfectly  recognized  the  more  slowly  they  take 
place  If  two  different  temperatures  are  allowed  to  act  at  the  same 
time,  near  each  other,  the  impressions  are  readily  confused,  especially 
if  the  two  positions  are  close  together. 

6.  Practice    sharpens    the    temperature-sense;     venous    congestion 
of  the  skin  blunts  it;    ischemia  increases  its  delicacy.     The  power  of 
differentiation  is  greater  when  the  application  is  made  to  a  large  cutan- 
eous surface  than  when  made  to  a  small  surface.     Rapid  variations, 
further,   cause  more  pronounced  sensations  than  gradual  changes  of 
temperature.     Fatigue  occurs  readily. 

7.  According  to  Abrutz  strong  thermal  irritants  excite  sensations 
of  cold  as  well  as  of  heat :   the  feeling  of  heat  is  supposed  to  result  from 
a  combination  of  these  two  sensations.     Direct  application  of  carbon 
dioxid  excites  a  sensation  of  warmth ;  menthol  gives  rise  to  a  sensation 
of  coldness  and  burning. 


FIG.  344. — Topography  of  the  Cold-sense  and  the  Heat-sense  on  the  Same  Part  of  the  Anterior  Surface  of  the  Thigh: 
a,  cold-sense;  b,  heat-sense.  (The  dark  areas  are  the  highly  sensitive,  the  shaded  areas  the  moderately  sensi- 
tive, the  dotted  areas  the  slightly  sensitive,  and  the  clear  areas  the  nonsensitive  points.) 


Various  illusions  may  occur  also  in  connection  with  the  temperature-sense : 

(1)  Occasionally  the  sensation  of  heat  and  cold  will  alternate  in  a  paradoxical 
manner:   for  example  if  the  skin  be  immersed  in  water  at  a  temperature  of  10°  C., 
a  sensation  of  cold  results;    if  it  then  be  immediately  transferred  to  water  at  a 
temperature  of  16°  C.,  there  is  first  a  sensation  of  heat,  but  soon  again  that  of  cold. 

(2)  The  same  temperature  will  be  estimated  as  higher  when  applied  to  a  large 
surface  of  the  skin  than  when  applied  to  a  small  surface.     Thus,  the  entire  hand 
immersed  in  water  at  a  temperature  of  29.5°  feels  warmer  than  when  the  finger 
is  dipped  into  water  at  a  temperature  of  32°  C.     Cold  weights  feel  heavier  than 
warm  ones. 

Pathological. — Sharpening  of  the  tactile  sense  (hyperpselaphesia)  occurs  but 
rarely,  although  greater  sensitiveness  for  differences  in  temperature  has  been 
observed  in  places  where  the  epidermis  is  thinned  after  the  use  of  vesicants  and 
after  vesicular  eruptions  (zoster) ;  likewise  in  tabetic  patients.  Sharpening  of 
the  spatial  sense  has  been  noted  also  under  the  two  conditions  first  named  and  in 
•cases  of  erysipelas.  Brown-Sequard  describes  as  an  abnormality  of  the  tactile 


934 


COMMON    SENSATION.       PAIN. 


sense  the  sensation  of  three  points  when  only  two  are  in  contact  with  the  skin, 
or  of  two  when  only  one  is  applied.  The  author  observed  in  himself  as  a  peculiar 
paradoxical  localization  of  sensation  that  pressure  with  the  edge  of  the  finger- 
nail over  the  junction  of  the  manubrium  with  the  body  of  the  sternum  always 
caused  a  sense  of  pricking  in  the  chin.  In  this  case  irritation  of  one  of  the  terminal 
branches  of  the  subcutaneous  nerves  of  the  neck  is  referred  to  the  periphery  of 
another  branch  of  the  same  nerve.  A  similar  phenomenon  is  observed  in  other 
nervous  territories,  especially  where  exact  localization  is  rarely  or  never  attempted. 
The  latter  is  the  case  with  the  sensory  nerves  of  the  intestines.  Hence,  it  is  not 
astonishing  that  in  the  presence  of  painful  affections  of  the  intestines,  pains 
appear  in  distant  parts  of  the  skin  supplied  by  nerves  from  the  same  level  of  the 
spinal  cord  into  which  also  the  sensory  visceral  nerve  enters.  In  the  same  category 
is  the  familiar  occurrence  of  pains  in  the  left  arm  in  connection  with  heart-disease. 
Analogous  conditions  prevail  in  the  head  and  the  neck.  A  remarkable  alteration 
of  the  spatial  sense  consists  in  the  circumstance  that,  when  the  eyes  are  closed, 
the  individual  feels  his  body  to  be  abnormally  large,  or  greatly  reduced  in  size, 
or  at  times  has  a  sensation  of  the  trunk  being  doubled.  The  author  has  observed 
the  first  condition  also  in  connection  with  moderate  morphin -intoxication.  In 
cases  of  degeneration  of  the  posterior  columns  of  the  spinal  cord  Obersteiner 
observed  that  the  patient  was  uncertain  whether  he  was  touched  on  the  right  or 
the  left  side  (allocniria) .  Brown-Sequard  observed  after  section  of  a  lateral  half 
of  the  cord  that  irritants  applied  to  the  left  side  were  felt  on  the  right  side,  and 
conversely.  Rarely  in  cases  of  brain-disease  irritation  applied  to  both  sides  of 
the  body  has  been  felt  only  on  one  side. 

Impairment  of  tactile  sensibility  to  the  point  of  abolition  (hypopselaphesia 
and  apselaphesid)  may  be  present  in  association  with  corresponding  disorders 
of  the  sensory  nerves  or  occur  independently.  Less  commonly  individual  qualities 
of  the  tactile  sensations  are  lost,  for  example  the  pressure-sense,  or  the  tempera- 
ture-sense, or  only  sensibility  for  heat  and  cold,  conditions  that  have  been  desig- 
nated partial  paralysis  of  the  tactile  sense.  Limbs  that  are  sound  asleep,  and  are 
insensitive  to  slight  pressure-irritations,  do  not  appreciate  cold;  the  function  of 
the  pressure-fibers  and  the  heat-fibers  is  not  disturbed  until  much  later. 

COMMON  SENSATION.      PAIN. 

By  common  sensations  are  understood  pleasant  or  unpleasant  sen- 
sations in  parts  of  the  body  endowed  with  feeling,  which  are  not 
referable  to  external  objects,  and  which  in  their  peculiarity  can  be 
neither  described  nor  compared  with  other  sensations.  These  include 
pain,  hunger,  thirst,  disgust,  fatigue,  horror,  vertigo,  tickling,  sensuality, 
comfort  and  discomfort,  and  the  respiratory  sensations  of  free  or  em- 
barrassed breathing. 

Pain  can  appear  wherever  sensory  nerves  are  present.  The 
organs  subserving  this  sensation  appear  to  be  the  free  interepithelial 
nerve-endings.  The  pain -points  do  not  coincide,  in  general,  with  the 
pressure -points,  and  they  are  about  1000  times  less  sensitive  than  the 
latter.  The  cause  of  the  pain  is  always  an  irritation  of  the  sensory 
nerves  exceeding  the  normal.  All  kinds  of  irritation:  mechanical, 
thermal,  chemical,  electrical,  and  somatic  (inflammatory  processes, 
disturbances  of  nutrition  and  the  like)  may  excite  pain.  Especially 
the  last  named  appear  to  be  particularly  effective,  as  some  tissues 
are  exceedingly  painful  when  inflamed  (for  example  muscles  and  bones), 
while  they  are  comparatively  insensitive  when  incised.  Pain  may 
be  excited  throughout  the  entire  course  of  a  sensory  nerve,  from  its 
center  to  the  periphery,  but  the  sensation  is  invariably  referred  to  the 
peripheral  extremity,  in  accordance  with  the  law  of  peripheral  reference. 
Inus,  it  may  happen  that  irritation  of  the  nerves,  as  in  the  scar  of  an 
amputation-stump,  may  cause  pain  that  is  referred  to  parts  that  have 
been  long  since  removed.  As  a  result  of  frequent  irritation  in  the 


COMMON    SENSATION.       PAIN.  935 

course  of  a  sensory  nerve  the  latter  may  lose  its  function  at  the  site  of  the 
affection,  so  that  peripheral  impressions  can  no  longer  be  perceived. 
If  the  painful  irritation  affects  the  central  extremity  of  the  nerve- 
tract,  it  will  still  be  referred  to  the  peripheral  extremity  of  the  nerve. 
In  this  way  there  arises  the  apparently  paradoxical  condition  of  painful 
anesthesia.  It  is  noteworthy  that  pain-sensations  cannot  be  localized 
with  precision.  The  localization  succeeds  best  when  the  irritation 
is  applied  peripherally  to  a  small  area  (for  example  a  pin -prick).  When, 
however,  the  stimulation  is  applied  in  the  course  of  the  nerve,  or  in 
the  center,  or  to  nerves  whose  peripheral  extremities  are  inaccessible 
(such  as  the  intestines),  pain  results  that  cannot  be  localized  (for  ex- 
ample belly-ache).  When  the  pains  are  severe  the  phenomenon  of 
irradiation  of  pain  is  added,  in  consequence  of  which  localization  is 
impossible  The  pain  rarely  continues  in  uniform  degree,  but  there 
occur,  as  a  rule,  exacerbations  and  remissions  in  the  intensity  and  also 
paroxysmal  exacerbations.  This  probably  is  due  to  the  fact  that  pain 
often  results  from  a  summation  of  irritations,  each  of  which  causes  no 
pain  of  itself. 

The  intensity  of  the  pain  depends  first  upon  the  irritability  of  the 
sensory  nerves.  In  this  respect  there  are  important  individual  varia- 
tions, some  nerves,  for  example  the  trigeminus  and  the  splanchnic, 
being  extremely  sensitive  as  compared  with  others.  The  greater  the 
number  of  nerve-fibers  affected  the  more  severe  is  the  pain.  Finally, 
the  duration  is  of  importance,  as  the  same  irritation,  long  continued, 
may  cause  an  intensification  of  the  pain  beyond  the  point  of  endurance. 

According  to  the  character  of  the  sensation  the  pain  is  described, 
as  stinging,  cutting,  boring,  burning,  shooting,  throbbing,  pressing, 
gnawing,  tearing,  twitching,  and  dull,  the  causes  for  the  differences 
being,  however,  entirely  unexplained.  Painful  sensations  are  abolished 
by  anesthetics  and  narcotics,  such  as  ether,  chloroform,  morphin,  etc. 

The  best  means  for  testing  cutaneous  sensibility  consists  in  the  employment 
of  constant  or  induced  electrical  currents.  The  minimum  of  sensibility  is  deter- 
mined as  that  strength  of  current  that  excites  the  first  trace  of  sensation ;  and  also 
the  minimum  of  pain,  that  is,  the  weakest  current  that  first  excites  distinct  pain. 
The  electrodes  are  metallic,  about  the  size  of  a  knitting-needle,  and  they  are  placed 
from  i  to  2  cm.  apart.  According  to  Bernhardt  the  following  distances  of  the 
cylinders  of  the  induction-apparatus  represent  the  minima  of  sensation,  and  the 
figures  in  parenthesis  the  minima  of  pain  in  a  healthy  person:  tip  of  the  tongue 
17.5  (14.1) ;  palate  16.7  (13.9) ;  tip  of  the  nose,  eyelids,  gums,  back  of  the  tongue, 
red  lips  15.7-15.1  (13-12.5);  cheek,  lips,  forehead,  14.8-14.4  (13-12.5);  acromion, 
sternum,  nape  of  the  neck  13.7-13  (11.5-12.2);  back  of  the  arm,  buttocks,  occiput, 
loin,  neck,  forearm,  vertex,  coccyx,  thigh,  back  of  the  first  phalanx,  back  of  the 
foot  12. 8-12  (12-9.2);  back  of  the  second  phalanx,  back  of  the  metacarpal  bone, 
back  of  the  hand,  leg,  distal  phalanx,  knee  11.7-11.3  (10.2-8.7);  palmar  aspect 
of  the  head  of  the  metacarpal  bone,  tip  of  the  toe,  palm  of  the  hand,  palmar 
aspect  of  the  second  phalanx,  hypothenar  eminence,  plantar  aspect  of  the  first 
metatarsal  bone,  10.9-10.2  (8-4).  Motczutkowski  found  the  pelvic  region 
the  least  sensitive  to  painful  impressions,  the  sensitiveness  increasing  from  this 
situation  in  all  directions.  The  ventral  aspect  of  the  body  is  less  sensitive  than 
the  lateral,  and  the  latter  less  so  than  the  dorsal.  Those  regions  exhibit  less 
sensitiveness  that  have  a  thick  epidermis;  those  that  are  less  exposed  to  external 
injuries  and  areas  over  joints  and  interosseous  sutures  exhibit  increased  sensitive- 
ness. 

Pathological. — When  there  is  increased  sensibility  of  the  nerves  transmitting 
painful  impressions  even  slight  contact  with  the  skin,  or  a  mere  breath  of  air 
upon  it,  may  cause  the  most  violent  pain  (cutaneous  hyperalgja),  especially  in 
the  presence  of  inflammatory  or  exanthematous  conditions  of  the  skin.  The 


936  THE    MUSCULAR    SENSE.       POWER-SENSE. 

designation  cutaneous  paralgia  may  be  applied  to  certain  unpleasant  or  painful 
abnormalities  of  sensation  that  are  frequently  localized  in  the  skin,  namely 
itching,  formication,  ^burning,  and  cold.  In  cases  of  cerebrospinal  meningitis 
a  prick  on  the  sole  of  the  foot  has  occasionally  been  observed  to  cause  a  double 
sensation  of  pain  and  a  double  reflex  contraction.  Perhaps  this  phenomenon  may 
be  explained  by  supposing  that  the  conduction  is  delayed  in  a  part  of  the  irritated 
nerve.  Neuralgia  occurs  in  the  form  of  characteristic  paroxysms  of  pain  of  great 
violence,  with  radiation  elsewhere  (for  example  neuralgia  of  the  fifth  nerve,  p. 
692).  It  is  due  to  pathological  processes  in  the  nervous  apparatus.  Frequently 
during  the  attacks  excessive  pain  is  produced  by  pressure  on  the  points  where  the 
nerve-trunks  emerge  from  the  bony  canals  or  openings  in  the  fasciae,  or  grooves 
(Valleix'  points  douloureux).  The  skin  itself  to  which  the  sensory  nerve  passes 
may,  especially  at  first,  be  the  seat  of  great  sensitiveness,  but  if  the  neuralgia  be 
of  long  duration,  the  sensibility  may  be  much  impaired,  up  to  the  point  of  analgesia. 
In  the  latter  event  there  may  be  pronounced  painful  anesthesia. 

Diminution  or  abolition  of  the  sense  of  pain  (hypalgia  and  analgia)  may  be 
due  to  affections  of  the  nerve -terminations,  or  of  the  nerve- trunks,  or  of  the  central 
insertions  of  the  nerves. 

In  hysterical  subjects,  suffering  from  hemianesthesia,  the  remarkable  ob- 
servation has  been  made  that  the  feeling  of  the  affected  side  is  restored  when  small 
metallic  plates  or  compresses  are  applied  to  the  skin  (metalloscopy) .  At  the  same 
time  that  the  affected  part  recovers  its  sensibility,  the  corresponding  part  of  the 
opposite,  healthy  side  or  limb  becomes  anesthetic.  It  has  been  thought  that 
a  transference  of  sensibility  takes  place  from  the  healthy  to  the  affected  side  of 
the  body.  The  application  of  the  metallic  plates  gives  rise  to  galvanic  currents 
whose  intensity  varies  with  the  character  of  the  metal,  but  the  resulting  phenom- 
ena cannot  be  attributed  to  these  currents.  The  explanation  of  the  fact  is  found 
in  the  circumstance  that  a  similar  result  occurs  under  entirely  normal,  physio- 
logical conditions.  In  a, "healthy  person  every  increase  in  sensibility  on  one  side 
of  the  body,  produced  by  the  application  of  warm  metallic  plates  or  compresses, 
is  followed  by  a  diminution  in  sensibility  on  the  opposite  side.  Conversely,  it 
is  found  that  when  one  side  of  the  body  is  made  less  sensitive  by  the  application 
of  cold  metallic  plates,  the  homologous  part  of  the  other  side  becomes  more  sen- 
sitive. 

THE  MUSCULAR  SENSE.      POWER-SENSE. 

The  sensory  nerves  of  the  muscles  constantly  convey  impressions 
as  to  the  inactivity  or  activity  of  the  muscles,  and  in  the  latter  event, 
as  to  the  degree  of  contraction  (power  of  distinguishing  the  weights 
of  various  objects).  They  furnish  information  also  as  to  the  amount  of 
the  contraction  to  be  employed  to  overcome  resistance  (power-sense). 
The  power  of  differentiating  the  weight  of  objects  lifted  is  based  upon 
a  comparison  of  the  degree  of  innervation  with  the  duration  of  the 
latent  period,  that  is  of  the  time  that  elapses  between  the  willing  of 
the  movement  to  raise  the  object  and  the  actual  commencement  of 
the  movement.  In  a. wider  sense  the  muscular  sense  includes  also  the 
appreciation  of  active  and  passive  movements,  the  recognition  of  posi- 
tion, and  finally  that  of  resistance  and  weight.  Obviously,  the  muscular 
sense  must  be  largely  aided  by  the  pressure-sense,  and  conversely; 
although  E.  H.  Weber  showed  that  the  muscular  sense  exceeds  the 
pressure-sense  in  delicacy,  as  by  its  aid  weights  in  the  ratio  of  39  :  40 
can  be  distinguished,  while  with  the  aid  of  the  pressure-sense  only  those 
in  the  ratio  of  29  :  30  can  be  distinguished.  In  some  cases  in  man 
perfectly  retained  muscular  sense  has  been  observed  in  conjunction 
with  total  cutaneous  insensibility.  A  parallel  condition  is  the  ability 
of  a  frog  deprived  of  the  skin  on  its  legs  to  jump  without  material 
disturbance.  The  muscular  sense  is  also  greatly  aided  by  the  sensibility 
of  the  joints,  the  bones,  the  fascias  and  the  tendons.  By  the  associated 
action  of  several  sensations,  especially  in  the  muscles  and  tendons, 


THE    MUSCULAR    SENSE.       POWER-SENSE.  937 

there  results  the  recognition  of  the  temporary  position  of  the  extremities. 
Some  muscles,  for  example  the  respiratory  muscles,  possess  only  slight 
muscular  sensibility,  which  seems  to  be  absent  normally  from  the  heart 
and  unstriated  muscles. 

Method  of  Testing. — Weights  are  wrapped  in  a  cloth  and  are  suspended  from 
the  part  to  be  tested  (for  example  the  leg)  by  a  sling.  The  subject  estimates 
the  amount  of  the  weight  by  lowering  and  raising  it;  and  also  the  difference  in 
resistance  (of  the  weights),  as  well  as  the  minimum  of  resistance  (appreciation  of 
the  smallest  weight).  The  electro-muscular  sensibility  also  may  be  tested  by 
causing  the  muscles  to  contract  by  means  of  induction-currents  and  having  the 
subject  report  as  to  the  sensation  thereby  produced.  In  this  way  also  the  mini- 
mum of  sensibility  and  of  pain  can  be  determined. 

A  healthy  person  recognizes  a  weight  of  i  gram  applied  to  his  upper  extremity ; 
likewise  an  addition  of  one  gram  when  the  original  weight  was  15  grams,  an  addi- 
tion of  two  grams  when  the  original  weight  was  50  grams;  and  an  addition  of  3 
grams  when  the  original  weight  was  100  grams.  The  power-sense  differs  in 
different  fingers.  The  lower  extremity  (with  the  weight  suspended  from  the 
knee),  recognizes  from  30  to  40  grams;  but  often  only  a  heavier  weight.  Often, 
a  difference  of  from  10  to  20  grams  can  be  detected,  or  from  30  to  70  grams.  In 
general,  the  same  differences  are  detected  whether  the  original  weights  are  light 
or  heavy.  In  blind  persons  the  muscular  sense  is  often  heightened. 

Section  of  the  sensory  nerves  causes  derangement  of  the  fine  grada- 
tions of  movements.  Meynert  supposed  that  the  motor  cortical  centers 
represented  the  cerebral  center  for  the  muscular  sense,  the  muscles  being 
connected  by  motor  and  sensory  paths  with  the  ganglion-cells  in  these 
centers.  Support  is  given  this  view  by  the  occurrence  of  complete 
ataxia  as  a  result  of  destruction  of  those  areas  in  which  the  psychomotor 
cortical  centers  of  the  extremities  are  situated. 

Illusions  occur  in  the  range  of  the  muscular  sense.  A  weight  held 
by  one  limb  appears  to  become  lighter  as  soon  as  other  muscles  of  the 
limb  are  contracted,  although  these  do  not  themselves  aid  in  supporting 
the  weight.  Under  converse  conditions  the  weight  appears  to  be 
heavier.  If  equally  heavy  objects  of  different  size  are  lifted,  the  larger 
appear  to  be  the  lighter.  A  weight  raised  with  both  hands  seems 
lighter  than  when  raised  with  one  hand.  The  following  illusion  has 
been  observed  with  respect  to  the  muscular  sense  of  the  tongue.  If 
the  tip  of  the  tongue  is  pressed  against  a  narrow  interval  between  the 
teeth,  and  is  moved  to  and  fro,  there  results  a  feeling  as  if  the  teeth 
yielded  in  movement. 

Excessive  muscular  activity  causes  the  sensation  of  fatigue,  of 
oppression  and  weight  in  the  limbs,  which  is  referable  to  the  muscular 
sense. 

Pathological. — Abnormal  heightening  of  the  muscular  sense  is  rare  (muscular 
hyperalgia  and  hyperesthesia) .  It  occurs  in  the  distressing  condition  of  unrest 
designated  anxietas  tibiarum  (fidgets),  which  is  attended  with  continual  change 
in  the  position  of  the  limbs,  and  not  rarely  may  be  a  source  of  annoyance  even 
to  healthy  persons  at  night.  Cramp  is  a  condition  attended  with  intense  pain 
as  a  result  of  irritation  of  the  sensory  nerves  of  the  muscles;  it  occurs  also  in 
association  with  inflammatory  processes.  Impairment  of  the  irritability  of  the 
nerves  of  muscular  sensibility  appears  also  in  part  to  be  responsible  for  certain 
choreic  and  ataxic  movements.  In  tabetic  patients  the  muscular  sense  in  the 
upper  extremities  may  be  normal  or  diminished;  in  the  lower  extremities  it  is 
usually  considerably  diminished.  Occasionally,  the  electromuscular  sensibility 
is  impaired  or  even  lost;  in  other  cases  the  subjective  sense  of  muscular  activity 
is  lost  (paralysis  of  muscular  consciousness).  Adequate  doses  of  cocain  or  alco- 
hol are  capable  of  heightening  the  muscular  sense,  while  amyl  nitrite  blunts  it. 


PHYSIOLOGY  OF  REPRODUCTION   AND 
DEVELOPMENT. 


VARIETIES  OF  GENERATION. 

Abiogenesis  (Spontaneous  or  Equivocal  Generation). — Even  until  modern 
times  it  was  believed  that  inanimate  substances,  derived  from  the  decomposition 
of  organized  matter,  could  under  certain  conditions  again  be  transformed  spon- 
taneously into  living  matter.  While  Aristotle  believed  that  spontaneous  genera- 
tion could  be  extended  to  include  the  insects  (vermin) ,  the  few  modern  adherents  of 
this  theory  applied  it  only  to  the  lowest  forms  of  life.  As  a  result  of  much  research 
along  this  line  it  has  been  demonstrated  conclusively  that  when  organized  matter 
is  subjected  to  a  high  temperature  (200°  C.)  within  hermetically  sealed  tubes  and 
all  bacteria  therein  are  actually  destroyed,  spontaneous  generation  cannot  take 


,( 


FIG.  345. — Ovum  from  the 
Uterus  of  a  Sexually  Ma- 
ture Proglottis  of  the 
Taenia  solium:  a,  albu- 
minous envelop;  b,  remains 
of  the  accessory  yolk;  c, 
embryonal  shell;  d,  embryo 
provided  with  embryonal 
hooklets. 


FIG.  346.— Encapsulated  Cysticerci  (from 
Taenia  solium)  in  the  Flesh  of  the  Sartorius 
Muscle  in  Man.  Natural  size. 


a 


FIG.  347. — Cysticerci  from 
Taenia  solium,  with  their  Con- 
nective-tissue Capsule  Re- 
moved: i,  natural  size;  2, 
enlarged  with  a  magnifying 
glass;  a,  embryonal  vesicle; 
b,  the  hollow  bud  produced 
by  sprouting  from  the  em- 
bryonal vesicle;  c,  suckers 
and  crown  of  hooklets  of 
the  head  of  the  tapeworm. 


place.  This  fact  sustains  the  doctrine  that  all  life  is  derived  from  previous  life 
(  pmne  vivum  ex  ovo  "  or  "  ex  vivo  ") ;  or  as  Harvey  says:  ut  omnibus  viventibus 
pnmordium  insit,  ex  quo  et  a  quo  proveniant. 

It  is  a  noteworthy  fact  that  even  some  of  the  higher  invertebrates  (gordius, 

anguilula   tardigrada,  rotatoria)  may,  when  kept  dry  for  some  time,  apparently 

e  and  lie  dormant  for  a  considerable  time,  but  when  supplied  with  moisture 

lay  be  resuscitated— anabiosis.     Rotatoria   (wheel-animalcules)   recovered  after 

oeen  kept  in  a  dry  vacuum  for   eighty-two   days,  and  immediately  after 

exposure  for  thirty  minutes  to  dry  heat  at  a  temperature  of  100°  C.     Rotatoria 

sd  gradually  in  their  natural  habitation  proliferated  when  again  moistened  after 

938 


VARIETIES    OF    GENERATION. 


939 


the  lapse  of  eleven  years,  and  the  same  is  true  of  anguilulae  after  twenty-eight 
years.  Spores  and  seeds  can  be  placed  in  a  state  in  which  metabolic  activity 
is  no  longer  demonstrable,  and  from  which,  as  has  long  been  known,  they  may 
under  suitable  conditions,  again  germinate.  According  to  Decandolle,  vegetable 
seeds  may  exhibit  this  property  after  from  sixty  to  one  ^hundred  and  fifty  years. 
Division  takes  place  in  many  protozoa  (amoebae,  infusoria),  and  in  such  a 
manner  that,  in  accordance  with  the  character  of  the  cellular  division,  the  organ- 
ism, including  its  inner  nuclear  structure,  and  the  cell-body,  divides  by  an  active 
process  into  two  organisms.  Starfish  (ophidiaster)  divide  spontaneously,  or  they 


FIG.  348. — Cysticercus  from  Tasnia 
solium  with  Everted  Hollow  Bud 
(Cephalic  Segment) :  I  a,  caudal 
vesicle  (embryonal  vesicle);  b,  the 
head  of  the  tapeworm  with  suckers 
and  ring  of  booklets  (scolex); 
cervical  portion.  .Enlarged 
magnifying  glass. 


FIG.  349. — Portion  of  an  Echino- 
coccus-cyst  with  Brood-capsule:  a, 
capsule;  b,  parenchymatous  layer; 
c,  brood-capsule  filled  with  scolices 
(Figs.  345-349  after  Sommer). 


FIG.  350. — Tsenia  mediocanellata. 
Natural  size. 


eliminate  an  arm,  which  may  develop  into  a  complete  animal.  The  artificial 
division  of  lower  forms  of  animal  life  and  the  development  of  the  fragments  into 
entire  beings  were  first  demonstrated  by  Trembley  in  the  hydra. 

Budding  or  sprouting  takes  place  in  most  marked  degree  in  polyps;  but  also 
in  infusoria  (vorticellidas)  and  others.  It  consists  in  the  sprouting  of  a  bud- 
like  structure  from  the  maternal  body,  which  it  gradually  comes  to  resemble. 
The  bud-like  formations  either  remain  attached  permanently  to  the  maternal 
organism,  so  that  gradually  a  complete  animal  of  considerable  size  is  formed 
(polypariae) ,  the  bodies  of  the  individual  remaining  directly  connected  with 


940 


VARIETIES    OF    GENERATION. 


one  another  (they  may  even  possess  a  common  "colonial"  nervous  system,  like 
the  bryozoa) ;  or  they  may  detach  themselves  and  individually  enter  upon  an 
independent  existence.  In  some  animal  forms  (siphonophores) ,  the  individual 
beings  at  times  exhibit  a  definite  differentiation  of  function,  so  that,  for  example, 
digestive,  motor  and  reproductive  activities  may  be  distinguished — physiological 
division  of  labor.  The  formation  of  buds  within  the  organism,  which  subsequently 
are  detached,  has  been  observed  in  rhizopods.  Among  animals  that  multiply 
by  division  or  by  budding,  there  has  been  observed  in  part  also  the  formation  of 
spermatozoa  and  ova  (polyps,  infusoria),  so  that  here,  together  with  asexual 
reproduction,  there  is  at  the  same  time  sexual  reproduction. 

Conjugation  or  concrescence  is  the  name  applied  to  a  variety  of  generation 
that  is  already  suggestive  of  sexual  reproduction,  for  example  that  of  unicellular 
gregarines.  In  such  a  being  the  anterior  extremity  unites  with  the  posterior 
extremity  of  another.  Both  become  encysted  into  one  round,  resting  body. 
The  two  nuclei  coalesce  and,  after  previous  spindle-formation,  a  polar  body 


351.— Sexually  Active  (Middle)  the  Proglottis  of  Taenia  mediocanellata  (after  Sommer):  d,  sexual  eminence 
with  the  genital  pore  e,— into  the  latter  the  penis  (cirrus,  /)  projects  from  above,  advancing  in  the  segment 
into  the  tortuous  vas  deferens,  which  exhibits  extensive  ramification  and  leads  to  numerous  testicular  vesicles 
(most  of  the  testicular  vesicles  are  not  yet  connected  by  excretory  ducts  with  the  vas  deferens):  g,  vagina;  h, 
/ary;  *,  albumin-gland;  k,  group  of  shell-glands;  /,  uterus;  b,  excretory  longitudinal  trunk  with  transverse 
anastomosis  c;  a,  lateral  nerve. 


is  expelled.     The  united  body-mass  is  resolved  into  a  shapeless  structure,  from 

ich  numerous  vesicles  arise.     In  each  vesicle   many  boatlike  figures    appear 

(pseudonavicellae).     These  give  rise  to  ameboid  organisms,  which  by  the  forma- 

>i  a  nucleus  and  a  protecting  envelop  are  in  turn  transformed  into  gregarines. 

Concrescence  has  been  observed  also  among  some  infusoria 

sexual  reproduction  requires  the  formation  of  the  offspring  from  the  union  of 

male  and  the  female  generative  elements  (semen  and  ovum).     These  elements 

:rived  from  two  different  individuals,  male  and  female,  or  they  may 

long  to  the   same  individual    (hermaphroditism,   for  example  in   tapeworms, 

snails,  etc.)       Sexual  reproduction  embraces  also  the  following  forms  of  generation : 

Metamorphosis  is  the  name  applied  to  that  form  of  sexual  reproduction  in 

which,  from  the  fertilized  ovum  on,  the  organism  appears  in  a  succession  of  out- 

itterent  forms  (for  example  caterpillar,  chrysalis) ,  which  possess  no  power 


VARIETIES    OF    GENERATION. 


941 


of  propagation.  Then,  finally,  there  develops  the  sexually  mature  form  (imago, 
for  example  butterfly),  which  yields,  through  the  union  of  sperm  and  ovum,  the 
fecundated  initial  form  in  the  developmental  process.  Metamorphosis  occurs 
extensively  among  insects,  either  with  many  (holometabola)  or  with  few  inter- 
mediate stages  (hemimetabola) ;  likewise  in  other  arthropods  and  in  some  worms 
(for  example  trichina).  The  sexually  mature  male  and  female  descendants  of 
the  trichina  are  set  free  in  the  intestine,  where  they  enter  into  sexual  union  and 
live  for  but  a  short  time.  They  are  known  as  intestinal  trichina.  They  produce 
many  eggs,  which  penetrate  the  muscular  tissues  of  the  host  and  constitute  the 
larva.  The  encapsulated  sexually  immature  muscle-trichinae,  which  may  remain 
quiescent  for  more  than  thirty  years,  are  the  pupce,  and  these,  when  ingested  in 
the  living  state  by  another  suitable  organism,  develop  in  the  intestine  of  the  latter 
into  sexually  mature  and  active  individuals.  Among  vertebrates,  metamorphosis 
occurs  also  in  the  amphibia  (frogs) ,  and  among  fish  in  lampreys  (petromyzon) . 
The  alternation  of  generations  (metagenesis)  exhibits  in  common  with  meta- 
morphosis the  series  of  externally  different  forms  in  the  process  of  development. 
It  differs  materially  from  metamorphosis,  however,  in  the  circumstance  that  the 
animal  can  multiply  asexually  in  one  or  the  other  of  the  stages.  The  final  stage 
alone  then  exhibits  the  sexual  reproduction.  Medically,  the  most  important 


I  12  II 

FIG.  352. — Heads  of  Taenia  solium  (I)  and  Taenia  mediocanellata  (II)  and  Mature  Proglottids  of  each  (i,  2). 

example  is  furnished  by  the  tapeworms  (teniae).  The  sexually  mature,  hermaph- 
roditic individual,  with  hundreds  of  testicles,  vasa  deferentia,  penises,  ovaries, 
yolks,  shell-glands,  vaginas  and  uteruses  (Fig.  351),  is  the  protoglottis  (tapeworm- 
segment),  which  becomes  detached  and  evacuated  with  the  feces;  it  is  motile 
and  occasionally  continues  to  grow.  From  an  ovum  (Fig.  345),  rendered  capable 
of  reproduction  by  self-impregnation,  there  results  an  elliptical  embryo,  provided 
with  six  booklets.  This  gains  entrance  with  food  into  the  intestine  of  another 
animal,  whence  it  penetrates  into  the  tissues  and  there  develops  into  the  third 
stage,  the  bladder-worm — cysticercus,  cenurus,  echinococcus.  Within  this 
vesicle  there  develops  only  one  (cysticercus,  Fig.  347)  or  several  (cenurus) 
short-pedicled  tapeworm-heads;  or  within  the  vesicle  there  develop  at  first 
numerous  daughter- vesicles,  and  within  those  many  heads  (echinococcus,  Fig. 
349).  For  further  development  the  bladder-worm  must  be  consumed  alive  by 
another  being.  Then,  the  tapeworm-heads  (scolex)  attach  themselves  to  the 
wall  of  the  intestines  by  means  of  their  hooklets  or  suckers  and  by  budding  form 
a  chain  of  numerous  segments  (Fig.  3 50),  each  developed  link  of  which  constitutes 
a  sexually  mature  offspring  of  the  tenia.  The  most  important  tapeworms  are 
as  follows:  Tasnia  solium  is  found  in  the  intestine  of  man.  Its  bladder-worm, 
cysticercus  cellulosae  (Fig.  352),  occurs  in  swine,  seldom  in  man.  Taenia  medio- 
canellata is  found  in  the  intestine  of  man  (Fig.  352);  its  bladder-worm  in  the 


942 


THE    SEMINAL    FLUID. 


cow  Tsenia  ccenunis  is  found  in  the  intestine  of  the  dog,  its  cysticercus  in  the  brain 
of  the  sheep  (coenurus  cerebralis,  the  cause  of  staggers).  Taenia  echmococcus  pos- 
sesses but  two  or  three  segments,  a  few  millimeters  long,  which  are  present  in 
innumerable  quantity  in  the  intestine  of  the  dog.  Its  encysted  form  (acephalo- 
cyst,  with  daughter-cysts)  often  attains  the  size  of  a  child's  head  in  man.  It  occurs 
in  the  liver,  but  also,  though  less  frequently,  in  all  other  tissues.  It  is  often 
dangerous  to  life  and  it  is  found  also  in  slaughter- animals.  Bothriocephalus 
latus  is  found  in  the  intestine  of  man,  its  bladder-worm  in  the  meat  of  the  pike. 

Among  lower  animals  the  medusae  also  exhibit  alternation  of  generation: 
among  insects  gall-gnats  (cecidomyia,  with  endogenous  larval  multiplication) 
and  plant-lice.  The  latter  develop  in  the  spring  from  impregnated,  hibernated 
ova  as  asexual  organisms.  These  produce  successively  in  numerous  generations 
unfertilized,  living,  likewise  asexual  offspring.  In  the  late  autumn  the  last  of  the 
young  males  and  females  are  thus  produced,  and  the  latter,  impregnated,  deposit 
the  fertilized  ova. 

Parthenogenesis  or  virgin  reproduction  is  characterized  by  the  circumstance 

that,  in  addition  to  sexual  pro- 
creation, generation  without  sexual 
connection  may  also  take  place  at 
the  same  time.  The  asexually  pro- 
duced brood  is  always  of  but  one  sex. 
The  beehive  serves  as  an  example. 
It  contains  the  queen-bee  (sexually 
mature  procreative  female)  the 
workers  (imperfect  females)  and  the 
drones  (males) .  In  swarming  (nuptial 
flight)  the  queen  is  impregnated 
by  a  drone.  The  semen  stored  for 
three  or  four  years  of  the  repro- 
ductive life  in  the  receptaculum 
seminis  can  apparently  be  added 
by  the  queen  to  the  ova  to  be 
deposited  for  purposes  of  fertilization 
or  be  withheld  from  them.  It  is 
also  possible  that  the  matter  of 
impregnation  depends  upon  me- 
chanical conditions  related  to  the 
size  of  the  comb  in  which  the  ova 
are  lodged.  Impregnated  ova  give 
rise  to  females  only,  unimpregnated 
ova  to  males  only.  If  the  queen  is 
incapacitated  for  flying  and  if  she  cannot  be  impregnated,  she  deposits  ova  that 
produce  drones  only.  Generous  feeding  of  the  larvae  of  the  impregnated  ovum, 
perhaps  also  the  size  of  its  comb  (queen-bee  cradle),  favors  the  development 
of  a  perfect  female  (queen-bee),  while  if  the  nourishment  be  insufficient,  sexually 
deficient  working  females  result.  This  description  has  recently  been  challenged, 
it  being  maintained  that  the  normally  impregnated  queen  always  deposits  only 
impregnated  ova,  whose  sexual  development  depends  upon  nutritive  influences 
on  the  part  of  the  workers. 

In  many  of  the  higher  animals  the  ova  may  pass  through  the  first  stages  of 
development  without  impregnation,  for  example  the  hen,  swine,  rabbits,  salpians, 
to  the  stage  of  division.  Unfecundated  ova  of  starfish  even  develop  to  the  larval 
form. 

Sexual  reproduction  without  intermediate  forms  occurs  in  mammals,  birds, 
reptiles  and  most  fish. 

THE  SEMINAL  FLUID. 

The  ejaculated  seminal  fluid  is  intermixed  with  the  secretion  of  the 
alveolar  glands  of  the  tubules  of  the  epididymis,  the  racemose  glands 
of  the  vas  deferens,  the  glands  of  Cowper  and  the  prostate  gland,  and 
with  the  fluid  of  the  seminal  vesicles.  It  has  a  neutral  or  alkaline 
reaction  and  it  contains  82  per  cent,  of  water,  serum-albumin,  alkali- 
albuminate  (propeptone  from  the  accessory  glands),  nuclein  (nucleinic 


FIG.  353. — Seminal  Crystals. 


THE    SEMIXAL    FLUID. 


943 


acid  -f-  protamin),  lecithin,  cholesterin,  fats,  also  fat  containing  phos- 
phorus, and  of  salts  (somewhat  more  than  2  per  cent.)  particularly 
alkaline  and  earthy  phosphates,  together  with  sulphates,  catenates  and 
chlorids. 

The  testicle  contains  besides  a  hyaline-like  albuminous  body,  leucin,  tyrosin, 
kreatin,.  xanthin -bodies,  inosite  and  glycogen  (starch-like  granules  in  birds). 

The  tenacious,  whitish-yellow  seminal  fluid,  for  the  greater  part  a  mixture 
of  the  secretions  from  the  organs  previously  mentioned,  is,  on  exposure  to  air, 
at  first  coagulated  into  a  gelatinous  mass,  then  becomes  again  diffluent,  on  addition 
of  water  gelatinous  and  separating  in  the  form  of  whitish,  translucent  flocculi. 
It  forms,  on  standing  for  some  time,  elongated  tapering,  rhombohedral  crystals 
that  consist  of  the  phosphate  of  an  organic  base,  spermin  (C5H]4N2),  which  results 
on  the  decomposition  of  nuclein. 


• 


FIG.  354. — Spermatozoa:  i,  human  (X  600),  the  head  viewed  from  the  surface;  2,  the  head  viewed  from  the  side; 
k,  head;  m,  middle  piece;  /,  tail;  e,  terminal  filament  (after  Retzius);  3,  spermatozoon  from  the  mouse; 
4,  from  bothriocephalus  latus;  5,  from  the  deer;  6,  from  the  mole;  7,  from  the  green  woodpecker;  8,  from 


the  black  swan;   Q,  from  the  bastard  of  a  goldfinch  (male)  and  a  canary  bird  (female);    10,  from  the  cobitis 
(weather-fish)  (after  A.  Ecker). 


These  crystals  (Fig.  353)  are  derived  in  part  also  from  the  prostatic  fluid  (and 
they  resemble  the  so-called  Charcot's  crystals  observed  in  sputum).  A  small 
amount  of  seminal  fluid  (also  stains  dissolved  in  water) ,  heated  with  a  concentrated 
watery  solution  of  iodin  and  potassium  iodid,  yields  a  crystalline  formation  (not 
unlike  hemin-crystals) .  The  formation  is  caused  by  a  step  in  the  disintegration 
of  lecithin.  Also  other  bodies  containing  lecithin  form,  through  putrefaction, 
neurin,  cholin  and  other  decomposition-products  and  then  yield  the  same  reaction. 

The  prostatic  fluid  is  a  thin,  milky  fluid,  amphoteric  or  of  a  feebly  acid  reaction, 
and  it  possesses  the  odor  of  the  seminal  fluid,  which  is  given  off  by  the  base  of 
Schreiner  in  solution .  The  phosphoric  acid  necessary  to  the  formation  of  the  crys- 
tals is  supplied  by  the  semen.  Perhaps  the  prostatic'secretion  furnishes  to  the  sper- 
matozoa the  motor  stimulation  essential  for  their  power  of  impregnation.  The  ovary, 
the  thyroid  gland,  the  spleen,  the  pancreas  and  the  leukocytes  likewise  contain 
spermin,  though  in  less  amount.  An  odor  similar  to  that  of  the  seminal  fluid 
is  possessed  by  Brieger's  cadaverin  (pentamethyldiamin),  a  nontoxic  cadaveric 


THE    SEMINAL    FLUID. 

alkaloid,  as  well  as  by  the  free  diamins.  It  is  these  substances  that  give  the  odor 
to  the  sawdust  of  macerated  bones,  and  occasionally  to  stale  eggs  or  pike,  and 
probably  also  to  some  plants,  such  as  rhubarb,  rhus,  berberis.  The  secretion  ot 
the  seminal  vesicles  (of  the  guinea-pig)  contains  a  considerable  amount  of  fibrin- 
ogen. 

The  seminal  thread  (spermatozoon,  spermatosoma),  50  /j.  long, 
consists  of  a  flattened  pear-shaped  head  (Fig.  354,  i  and  2  k),  a  bodkin- 
shaped  middle  segment  (m)  attached  to  the  broader  pole  of  the  head 
and  the  thread-like  elongated  cilium  (flagellum  or  tail)  (/),  through 
whose  to-and-fro  movements  the  sperm,  often  rotating  on  its  axis, 
traverses  400  times  its  own  length  in  one  minute,  or  from  0.05  to  0.15 
mm.  in  one  second.  This  activity  is  most  pronounced  directly  after 
ejaculation. 

The  head,  containing  chromatin  (mammals),  consists  of  an  anterior  and  a 
posterior  segment.  From  the  posterior  segment  a  process  projects  like  a  sphere 
into  the  interior  of  the  anterior  segment.  A  delicate  membrane  covers  the  anterior 
segment  of  the  head  like  a  hood.  The  spermatozoa  of  some  vertebrates  possess 
at  the  anterior  extremity  of  the  head  a  projection  furnished  with  barbs,  which 
corresponds  to  the  hood.  The  middle  segment  of  the  spermatozoon  sometimes 
presents  transverse  striations,  due  to  a  spiral  structure. 

G.  Retzius  describes  the  spermatozoon  as  possessing  a  special,  detached 
terminal  segment  of  the  tail,  which  represents  the  extremity  of  the  latter.  An 
axial  fiber  (Fig.  354,  i,  <?).  surrounded  by  a  protoplasmic  sheath,  passes  through 
the  middle  segment  and  the  tail.  The  sheath  is  lacking  only  at  the  extremity 
of  the  tail.  The  axial  fiber  consists  of  two  filaments,  each  of  which  in  turn  is 
made  up  of  numerous  primitive  fibrils.  Also  the  terminal  segment  may  be  re- 
solved into  four  fibrils.  Some  vertebrates  possess  a  marginal  filament  arising 
from  the  middle  segment,  also  an  accessory  filament  parallel  to  the  axial  fiber 
and  a  steering  membrane  in  advance  of  the  terminal  segment.  In  insects  and  am- 
phibia the  nonfibrillated  axial  fiber  forms  the  supporting  structure.  In  some 
organisms  the  spermatozoon  is  still  more  complicated.  Only  axial  fibers  having 
a  fibrillar  structure  exhibit  motility;  those  not  so  constructed  are  motionless. 

The  number  of  spermatozoa  in  man  reaches  60,900  in  i  cu.  mm. ;  it  is  increased 
after  sexual  excitement.  To  each  mature  human  ovule,  there  are  approximately 
850,000,000  spermatozoa. 

The  movement  of  the  spermatozoa  is  due  to  the  circular,  whip-like  oscillation 
of  the  tail,  which  at  the  same  time  causes  rotation  about  the  long  axis  and  is 
brought  about  by  the  protoplasm  of  the  middle  segment  and  the  tail.  Both 
of  these,  even  if  detached,  are  capable  of  movement.  Ciliated  cells,  whose  in- 
dividual cilia  consist  of  numerous  filaments  lying  side  by  side,  swarm-spores  in 
plants  and  ameboid  cells  show  analogous  motility,  as  transitions  between  ciliated 
and  ameboid  movement  have  been  observed,  as  in  monera. 

Human  spermatozoa  preserved  without  heat  have  exhibited  motility  after 
the  lapse  of  nine  days;  spermatozoa  from  the  guinea-pig  after  the  lapse  of  eleven 
days.  Permitted  to  rest  passively  in  the  testicle,  in  the  absence  of  any  diluting 
fluid,  the  spermatozoa  possess  no  motility.  They  remain  especially  active  in 
the  normal  secretions  of  the  female  genitalia.  They  retain  their  motility  for  a 
considerable  length  of  time  also  in  all  normal  animal  secretions,  except  saliva. 
On  addition  of  water  they  become  rolled  into  rings  and  cease  their  movement. 
Also  alcohol,  ether,  chloroform,  creosote,  gum,  dextrin  and  vegetable  mucus, 
concentrated  solution  of  grape-sugar,  as  well  as  excessively  alkaline  uterine, 
and  exceedingly  acid  vaginal  mucus,  acids  and  metallic  salts  and  excessively 
high  and  excessively  low  temperature  inhibit  the  activity  of  the  spermatozoa. 
Their  motility  is  unaffected  by  narcotics,  insofar  as  they  are  chemically  indifferent, 
and  by  solutions  of  urea,  sugar,  albumin,  common  salt,  glycerin,  amygdalin  and 
other  substances  of  moderate  strength ;  although  these  inhibit  motility  like  water 
if  greatly  diluted  and  by  abstraction  of  water  if  unduly  concentrated. 

It  is  noteworthy  that  the  rest  occurring  after  the  action  of  water,  as  well  as 
that  on  gradual  cessation  of  movement,  may  be  terminated  by  the  action  of  weak 
alkalies,  as  may  be  observed  also  in  ciliated  epithelium.  Perhaps  the  alkalies 
neutralize  an  acidity  of  the  protoplasm  induced  by  fatigue ;  although  Engelmann 
attributes  restorative  power  to  small  quantities  of  acid,  alcohol,  and  ether. 


THE    SEMINAL    FLUID. 


945 


The  spermatozoa  of  the  frog  may  be  frozen  four  times  successively  without 
injury;  they  endure  a  heat  of  43.75°  C.  and  continue  to  live  for  seventy  days 
in  the  testicle  transplanted  to  the  abdominal  cavity  of  another  frog. 

On  account  of  the  large  proportion  of  earthy  salts  they  contain,  spermatozoa  can 
be  fused  on  a  glass  slide  and  nevertheless  retain  their  form,  like  trie  cells  of  some 
plants  rich  in  ash,  for  example  the  equisetaceag.  Nitric,  sulphuric,  hydrochloric 
and  boiling  acetic  acid,  and  caustic  alkalies  do  not  destroy  the  form  of  the  sper- 
matozoa. Solutions  of  sodium  chlorid  and  potassium  nitrate,  of  from  10  to 
15  per  cent.,  transform  the  spermatozoa  into  amorphous  clumps.  The  organic 
substance  resembles  the  semisolid  albumin  of  epithelial  cells. 

In  addition  to  spermatozoa  the  seminal  fluid  contains  seminal  cells,  a  few 
epithelial  cells  from  the  vasa  deferentia  (isolated  examples  of  which  are  in  a  state 
of  colloid  degeneration) ,  numbers  of  lecithin-granules  and  occasionally  laminated 
amyloid  bodies,  granular  or  scaly  yellow  pigment,  especially  in  later  life,  leuko- 
cytes and  sperm-crystals. 

The  development  of  the  spermatozoon  (Fig.  _  3  55)  has  been  made  clear  only 
in  recent  times  after  considerable  research,  especially  by  v.  Ebner,  whose  results 
were  obtained  simultaneously  and  independently  by  the  author.  From  the  nuclear 
protoplasmic  layer  (Fig.  355,  /,  b  and  IV,  h}  lining  the  inner  surface  of  the  wall 
of  the  seminal  tubules  (/,  a  and  IV,  n),  which  is  composed  of  several  layers  of 
interlacing  elastic  fibers  (interspersed  with  flat  cells),  large  columnar  processes, 


a 


FIG.  355. — Spermatogenesis  (Semidiagrammatic) :  /,  Transverse  section  of  a  seminal  tubule;  a,  its  sheath;  b,  its 
protoplasmic  internal  layer;  c,  spermatoblast;  s,  seminal  cells.  //,  Immature  sperm atoblast;  /,  its  rounded 
upper  lobules;  p,  seminal  cells.  ///,  Spermatoblast  with  released  spermatozoon;  /,  spermatozoon;  p, 
seminal  cell.  IV,  Spermatoblast  with  mature  heads  (£)  and  cilia  (r);  n,  wall  of  the  seminal  tubule;  h,  pro- 
toplasmic layer  of  the  tubule;  p,  seminal  cell. 


0.053  mm-  l°ng  (I,  c  and  //,  ///,  IV),  project  into  the  lumen.  These  break  up 
at  their  free  extremities  into  several  oval  lobules  (//)  like  ears  of  corn  and  are 
known  as  spermatoblasts  or  seminal  ears.  These  formations  were  first  dis- 
covered by  Sertoli,  who  considered  and  designated  them  "supporting  cells." 
They  consist  of  soft,  finely  granular  protoplasm  and  contain  an  oval  nucleus 
usually  in  their  lower  portion.  In  the  course  of  development  each  lobule  of  the 
spermatoblast  is  prolonged  into  a  long  cilium,  like  the  grains  of  an  ear  of  corn 
(IV,  r) ,  and  in  the  depth  of  the  lobule  the  head  and  the  middle  segment  of  the  sperma- 
tozoon (IV,  k)  are  developed  from  a  condensation  of  the  protoplasm.  In  this 
stage  the  spermatoblast  resembles  a  very  large,  irregularly  formed  ciliated  cylin- 
drical cell.  When  development  is  complete  the  head  and  the  middle  segment 
become  separated  from  the  mother-cell  (///,  t} ,  and  the  remainder  of  the  spermato- 
blast, with  its  resulting  goblet-shaped  depressions,  resembles  a  threshed  ear  of 
corn  (///,  /).  Later  it  undergoes  fatty  degeneration.  The  spermatozoon  itself 
often  exhibits  for  a  long  time  an  adherent  mass  of  protoplasm  at  the  junction  of 
the  head  and  the  middle  segment,  representing  a  part  of  the  spermatoblast 
(///,  t).  In  accordance  with  its  development,  the  spermatozoon  may  be  regarded 
as  a  detached,  independently  motile  cilium  of  a  huge  ciliated  epithelial  cell.  Be- 
tween the  spermatoblasts  lie  numerous,  round,  ameboid,  unencapsulated  cells, 
60 


946  THE    OVUM. 

undergoing  division  and  toward  the  termination  of  this  process  still  connected 
with  filaments.  These  are  designated  seminal  cells  (/,  5  and  //,  ///,  IV,  p}. 

Contrary  to  the  description  just  given  the  formation  of  spermatozoa  has 
recently  been  described  as  follows:  The  spermatozoa  originate  from  seminal 
cells,  spermatogonia  or  primitive  seminal  cells.  These  multiply  by  indirect 
division,  move  toward  the  center  of  the  seminal  tubule,  increase  in  size  and  are 
known  as  spermatocytes  or  seminal  mother-cells.  Each  one  now  further  sub- 
divides into  four  cells — the  spermatids  or  seminal  cells,  which  move  further 
toward  the  lumen.  Each  of  these  develops  into  a  seminal  filament  or  spermato- 
coma,  the  nucleus  of  the  cell  forming  the  head,  a  small  portion  of  the  cell-pro- 
toplasm the  cilium  of  the  spermatozoon,  while  the  axial  fiber  of  the  latter  develops 
from  the  central  body  of  the  cell.  For  the  complete  development  of  the  sper- 
matozoa, it  is  now  necessary  that  the  spermatids  (seminal  cells)  unite  with  the  free 
extremity  of  Sertoli's  "supporting  cells"  through  a  form  of  copulation;  and  here 
mature  as  upon  a  nourishing  stem  and  finally  become  detached.  The  united 
formations  are  the  spermatoblasts  of  Ebner. 

In  most  animals,  the  spermatozoa  are  capillary  in  form,  with  larger  or  smaller 
heads.  The  latter  are  elliptical  or  pear-shaped  (mammals)  or  cylindrical 
(birds,  amphibia,  fish)  or  spiral  (singing  birds,  sharks,  viviparidas)  or  simply 
capillary  (insects  and  other  animals)  (Fig.  354).  Nonmotile  seminal  cells  differ- 
ing entirely  from  the  capillary  form  are  found  in  myriapods  and  oysters. 

Considerable  interest  has  been  aroused  by  the  subcutaneous  injection  of 
orchitic  extract  recently  made  by  Brown-Sequard.  This  greatly  increases  the 
ability  to  indulge  in  muscular  exercise ;  coincidently  with  the  diminution  in  fatigue 
there  is  a  diminution  in  the  subjective  sense  of  fatigue.  There  is  greater  endur- 
ance and  recuperation  has  an  increased  influence. 

The  significance  of  the  secretion  of  the  accessory  sexual  glands  (prostate, 
seminal  vesicles,  Cowper's  gland)  has  not  been  fully  made  clear.  That  these  play 
some  part  in  the  act  of  procreation  is  evident  from  the  fact  that  after  their  extir- 
pation the  impregnating  power  of  the  semen  often  ceases.  In  rats  castrated 
before  puberty,  the  accessory  sexual  glands  do  not  develop.  Hammar  found 
secretion  also  in  the  epididymis  of  dogs.  Castration  or  division  of  the  seminal 
tubules  causes  atrophy  of  the  prostate.  The  secretory  nerves  of  the  prostate 
are  the  ^ypogastric.  The  seminal  vesicles  preserve  their  function  in  sexually 
mature  individuals  even  after  castration. 

THE  OVUM. 

The  human  ovum  (from  0.18  to  0.2  mm.  in  diameter)  is  a  globular, 
cell-like  structure,  presenting  a  thick,  firm,  elastic  capsule,  with  delicate 
radiating  striations  (oolemma  or  zona  pellucida),  protoplasmic,  granular 
contractile  contents  (yolk,  vitellus),  including  a  clear  vesicular  nucleus 
from  40  to  50  /j.  in  diameter  and  possessing  a  nuclear  framework  (ger- 
minal vesicle)  and  a  nucleolus  from  5  to  7  [j.  in  diameter  endowed 
with  ameboid  movement  (germinal  spot).  The  chemical  composition 
of  the  ovum  is  described  on  p.  423. 

The  zona  pellucida  (0.02  thick)  (Figs.  356,  357),  to  whose  surface  cells  of 
the  cumulus  oophorus  often  adhere,  may  be  regarded  as  a  cuticular  membrane 
developed  secondarily  from  the  follicle.  Internally  to  it  in  many  mammals  and 
directly  upon  the  yolk  lies  a  delicate  membrane,  which  is  probably  the  original 
cell-membrane  of  the  ovum.  Between  the  zona  pellucida  and  the  yolk  lies  a 
small  perivitelline  space  (Fig.  356).  The  finely  radiate  striations  of  the  zona 
pellucida  are  due  to  the  presence  of  numerous  pore-canals,  through  which  the 
adjacent  cells  of  the  granulosa  send  processes  for  purposes  of  nutrition. 

In  the  ova  of  many  animals— holothurians,  many  fish,  for  example  stickle- 
backs, mussels,  etc. — a  special  micropyle  is  observed.  In  addition,  some  ova 
possess  a  number  of  pore-canals  collected  together  at  a  special  area  of  the  ovular 
membrane  (many  insects,  for  example  the  flea),  and  these  serve  partly  as  a 
means  of  ingress  to  the  spermatozoa  and  partly  for  the  respiratory  interchange 
of  gases. 

The  yolk  has  a  peripheral  clear  layer,  which  encloses  a  finely  granular  layer 
and  the  latter  finally  a  central  mass  containing  numerous  granules — yolk-granules 
or  van  Beneden's  deutoplasm  (Fig.  356). 


THE    OVUM.  947 

The  development  of  the  ovum  takes  place  in  the  following  manner:  The  surface 
of  the  ovary  is  covered  with  cylindrical  epithelium,  the  so-called  germinal  epi- 
thelium, between  which  here  and  there  lie  round  primordial  ova  (Fig.  358,  /,  a  a). 
In  places  the  epithelial  layer  dips  down  to  form  tubular  depressions  in  the  surface  of 
the^ovary  (//)  .  These  tubules,  which,  according  to  Waldeyer,  are  derived  from  the 
germinal  layer  of  the  ovary,  become  deeper  and  deeper,  and  within  them  are 
observed  isolated,  large  globular  cells,  with  nuclei  and  nucleoli,  and  also  a  larger 
number  of  smaller  parietal  cells.  These  tubes  are  the  ovarian  or  ovular  tubes; 
the  larger  round  cells  are  the  ova  (primitive  ova)  ,  the  smaller,  the  epithelial  cells 
of  the  tubes  (/).  At  the  bottom  of  the  tubes  the  ovular  cells,  which  may  undergo 
mitotic  division,  predominate.  Later  on  the  orifices  of  the  tubes  close  and  the 


Corona  ,  r^  Zona 


, 


:.)       Deutoplasra 


Proto- 
plasm 


\ 
I  \ 

\ 

X 

Germinal  vesicle 
with  ameboid 
germinal  spot 
Perivitelline  space 

FlG.  356. — A  Fresh  Ovum  from  the  Ovary  of  a  Woman  Thirty  Years  Old.  The  side  of  the  vitellus  where  the  ger- 
minal vesicle  is  situated  is  directed  toward  the  observer,  who  thus  looks  directly  upon  the  germinal  vesicle, 
which  lies  upon  the  deutoplasm. 

tubes  are  constricted  off  by  the  growth  of  the  ovarian  stroma  into  isolated  rounded 
compartments  (7,  c).  Each  constricted  compartment,  which  contains  usually 
one,  occasionally  two  ova  (IV,  o  o),  becomes  a  Graarian  follicle.  The  follicles 
become  distended  with  fluid;  their  parietal  cells  become  the  epithelium  of  the 
follicle  or  the  cells  of  the  granulosa,  which  at  particular  points  surround  the 
ova  (IV).  Such  areas,  designated  cumuli  oophori,  are  spindle-shaped  or 
cylindrical  and  consist  of  several  layers ;  they  produce  the  zona  pellucida.  Accord- 
ing to  some  observers  the  yolk  also  is  in  part  secreted  by  these  cells  into  the  ovule, 
and  a  number  of  the  cells  are  believed  to  penetrate  into  the  ovum.  The  follicles, 
at  first  only  0.03  mm.  in  diameter,  attain  complete  development  only  at  the  time 


948 


THE    OVUM. 


of  puberty.  The  maturing  follicles  (IV)  at  first  sink  more  deeply  into  the  stroma 
of  the  ovary,  become  distended  by  taking  up  water  (liquor  folliculi),  acquire 
a  vascular,  independent  well-differentiated  capsule  (theca  folliculi),  and  their 
epithelium  (IV ,  g)  (membrana  granulosa)  increases  through  mitosis  in  a  similar 
manner,  to  form  a  layer  of  several  rows  of  small  cells.  In  the  last  stages  of  ripen- 
ing the  follicle  leaves  the  depths  of  the  stroma,  again  to  reach  the  surface:  it  now 
attains  a  diameter  of  from  i  to  1.5  mm.  and  is  ready  to  rupture.  Only  a 
small  number  of  Graafian  follicles  attain  normal  final  development;  the  majority 
previously  undergo  atrophy.  In  some  animals  (rabbits)  the  occurrence  of  furrow- 
ing has  been  observed  as  a  noteworthy  phenomenon. 

The  medullary  substance,  which  extends  from  the  hilus  into  the  interior 
of  the  ovary,  consists  of  vascular,  fibrous  connective  and  elastic  tissue,  with 
bundles  of  unstriated  muscle-fibers;  in  contradistinction  to  the  cortical  sub- 
stance, which  contains  principally  cellular  connective  tissue,  with  the  epithelial 
constituents  in  various  stages  of  development.  The  ovary  possesses  numerous 
nonmedullated  nerves  (connected  with  sympathetic  ganglia) ,  of  which  the  majority 
terminate  in  the  walls  of  the  vessels  (also  the  capillaries),  and  others  between  the 
folliclesjand  upon  their  surface. 


Germinal  spots. 


Accessory  nucleoli,    .. 
(also  /.) 


Cells  of  discus  proligerus  (oophorus). 


Yolk. 


Hit Zona  pellucida. 


FIG.  357-— Mature  Rabbit  Ovum  (after  Waldeyer). 

m  According  to  Paladino  the  ovary  of  woman  is  in  a  state  of  continuous  involu- 
tion and  true  new-formation  through  invagination  of  the  germinal  epithelium. 
According  to  Waldeyer  the  mammalian  ovum  is  not  a  simple  cell,  but  a  more 
complex  structure.  The  original  ovular  cell,  he  believes,  is  formed  only  from 
the  germinal  vesicle  and  germinal  spot,  and  the  surrounding  clear  unencap- 
sulated  portion  of  the  yolk  (Fig.  358,  ///).  The  remaining  portion  of  the  yolk 
is  derived  from  transformed  granulosa-cells,  which  also  constitute  the  zona  pel- 
lucida. 

In  animals  the  following  peculiarities  may  be  observed  in  the  formation  of 
OV?-m-j  st  ovular  cells  are  known  as  primitive  ova  or  ovogonia. 

divide  several  times  by  mitosis   at  first  into  small,  then  into  larger  ova- 
>tner  cells  or  ovocytes.     These  mature  and  after  undergoing  division  by  mitosis 
I  or  twice  give  rise  to  the  polar  bodies  and  thus  form  the  true  fully  devel- 
oped ovules. 

Holoblastic  and  Meroblastic  Ova.— The  ova  of  batrachians  and  cyclostomata 

are  formed  according  to  the  same  type  as  those  of  mammals.     They  are  designated 

holoblastic  ova,  because  their  contents  are  entirely  transformed  into  the  forma- 

that  serve  for  the  development  of  the  embryo.      In  contrast  with  these, 

birds   monotremata  among  mammals,  reptiles,  and  the  remaining  fish  have  so- 

ca  led  meroblastic  ova.      These  contain,   in   addition  to  the    (white)    formative 

yolk,  which  corresponds  to  the  yolk  of  holoblastic  ova,  and  yields  the  embryonal 

cells,  also  the  so-called  nutritive  yolk  (yellow  in  birds),  which  serves  as  a  source 

the  embryo  during  the  period  of  development.     This  nutritive 


THE    OVUM. 


949 


material  penetrates  into  the  originally  small  and  simple  ovular  cell  and  causes  it 
to  swell  considerably.  The  embryology  of  the  bird's  egg  has  shown  that  only 
the  small,  round,  white  protoplasmic  germinal  layer  at  the  center  of  the  surface 
of  the  yolk  (cock's  treadle,  cicatricula),  from  2.5  to  3.5  mm.  wide  and  from  0.28 
to  0.37  mm.  thick,  corresponds  to  the  contents  of  the  mammalian  ovum  and  is 
therefore  the  formative  yolk.  It  contains  the  germinal  vesicle  and  the  germinal 
spot  (Fig.  359).  From  this,  which  contains  also  the  characteristic  white  yolk- 
elements  (Fig.  360,  a)  processes  extend  into  the  yellow  yolk  (Fig.  359).  In 
addition,  a  flask-shaped  mass  of  white  yolk  extends  into  the  center  of  the  yellow 
yolk  (Purkinje's  latebra) ;  the  yolk  is  surrounded  by  an  extremely  thin  mem- 
brane (white  yolk-membrane  or  "the  cortical  protoplasm)  (Fig.  359  and  Fig.  360) 
The  yellow  yolk  (nutritive  yolk)  consists  of  soft,  yellow  non-nucleated  cellular 
structures  from  23  «  to  100  ,«  in  diameter,  and  somewhat  polyhedral  in  shape  from 


IL 


W 


FIG.  358. — I.  Ovarian  Tube  (from  a  Newborn  Child)  in  Process  of  Follicle-formation:  a  a,  Ova  in  the  midst  of 
the  epithelial  cells  of  the  surface  of  the  ovary;  b,  ovarian  tube  with  ova  and  epithelial  cells;  c,  a  constricted-pff 
small  follicle,  with  ovum.  //,  Open  ovarian  tube  of  a  bitch  six  months  old.  ///,  Isolated  human  primordial 
ovum.  IV,  Older  follicle  with  two  ova  (o  6)  and  the  cells  of  the  granulosa  (g)  (dog).  V,  Portion  of  the  sur- 
face of  a  mature  rabbit's  ovum;  z,  zona  pellucida;  d,  yolk;  e,  adherent  cells  of  the  granulosa  (after  Waldeyer). 
VI,  Expulsion  of  the  first  polar  body.  VII,  Expulsion  of  two  polar  bodies  (after  Fol). 

mutual  pressure  (Fig.  360,  6).  These  result  from  proliferating  hyperplasia  of  the 
granulosa-cells  of  the  Graafian  follicle,  which  finally  give  rise  also  to  the  granulo- 
fibrous  two-layered  yolk-membrane  (Fig.  359).  The  entire  yolk  of  the  bird's  egg 
has  been  considered  equivalent  to  the  mammalian  ovum,  together  with  its  cor- 
pus luteum. 

When  the  yolk-globule  in  the  bird's  ovary  is  fully  developed,  the  capsule  of 
the  Graafian  follicle  is  ruptured  and  the  yolk-globule  passes  in  a  rotatory  fashion 
through  the  oviduct,  the  folds  of  whose  mucous  membrane,  like  the  riflings  of  a 
gun-barrel,  always  cause  the  rotation  to  take  place  in  a  definite  manner.  Numer- 
ous glands  in  the  oviduct  secrete  the  albumin  in  which  the  yolk  is  enveloped  in 
layers,  the  chalazae  being  formed  at  either  pole.  As  the  tenacious  layers  of  albu- 
min tend  to  unroll  again,  the  albuminous  layer  is  rotated  about  the  yolk  in  the 
bird's  egg,  and  if  freshly  laid  eggs  are  permitted  to  float  in  concentrated  solu- 
tion of  sodium  chlprid,  all  will  rotate  in  the  same  direction. 

The  albumin  in  the  eggs  of  nesting  birds  is  vitreous  and  translucent  when 


THE    OVUM. 


95° 

boiled,  but  it  is  transformed  in  the  process  of  hatching  into  a  mass  like  the  albumin 
in  the  eggs  of  nonnesting  birds  (hen).  On  the  other  hand,  the  albumin  of  hen's  eggs 
coagulates  on  addition  of  dilute  sodium  hydroxid  into  a  vitreous  transparent  mass. 


Germinal  vesicle  and  spot. 


Blastoderm 


Its  processes. 


L          Marginal 
protoplasm. 


FIG.   359. — Diagrammatic  Representation  of  a   Mesoblastic  Ovum 
(after  Waldeyer). 


FIG.  360. — a  White,  b 
yellow  yolk-globules. 


Ch.l. 


i.s.iri. 
a.c.h. 


The  fibers  of  the  membrana  testacea  are  secreted,  spontaneously  coagulated 
keratin-like  filaments,  wound  spirally  about  the  albumin,  upon  which  a 
porous  cement  (testa)  consisting  of  a  mixture  of  albumin  and  lime  is  deposited 
in  the  lower  portion  of  the  oviduct.  A  structureless,  porous,  mucinous,  occasion- 
ally fatty  cuticula  repre- 
sents the  outermost 
shell-layer  in  some  birds. 
The  limeshell  of  the 
bird's  egg  is  utilized  in 
part  for  the  formation 
of  the  bones  of  the  chick. 
The  coloring-matters  of 
the  surface  of  the  egg, 
which  are  often  present 
in  several  superposed 
layers,  appear  to  be 
derivatives  of  hemoglo- 
bin (hematoporphyrin) 
and  biliverdin.  Between 
the  albumin  and  the 
shell-membrane  there  is 
detached  epithelium  of 
the  oviduct  (Fig.  361). 

The  white  yolk  (hen) 
contains  albumin,  nu- 
clein ,  lecithin ,  potassium , 
glycogen  (?);  the  yolk- 
membrane  keratin.  The 
yellow  yolk  contains  a 
nuclein  containing  iron, 
a  vitellin  resembling 
globulin,  lecithin,  cho- 
lesterin,  fat,  coloring- 
matters  ( iron  -  lutein ) , 
containing  neuridin,  glu- 
cose, mineral  matters, 
cerebrin  (?),  amyloid  granules  (?),  sodium,  potassium,  calcium,  magnesium,  iron, 
phosphoric  acid,  silicic  acid.  The  white  of  egg  contains  crystallizable  ovalbumin 
(a  mixture  of  several  albumins),  together  with  globulin,  a  body  resembling  mucin, 
sugar  and  keratin.  The  ash  contains  more  chlorin  and  alkalies,  but  less  calcium, 
phosphoric  acid  and  iron  than  the  yolk. 


s.m. 


xch.l. 


x. 


FIG.  361. — Diagrammatic  Longitudinal  Section  of  a  Hen's  Egg:  b.l., 
germinal  layer  (cicatricula) ;  w.y.,  latebra,  filled  with  white  yolk;  y.y., 
y.y.,  a  number  of  layers  of  yellow  yolk,  surrounding  the  latebra  concen- 
trically; x,  yolk-membrane;  v.t.,  white  yolk-cortex  (cortical  proto- 
plasm); w,  mass  of  surrounding  albumin  in  layers;  ch.l.,  chalazar, 
a.c.h.,  air-chamber  at  the  blunt  pole  of  the  egg;  i.s.m.  internal  and 
s.m.  external  lamella  of  the  shell-membrane  (membrana  testacea);  s, 
lime-shell  (testa). 


PUBERTY.       MENSTRUATION.  951 


PUBERTY. 

The  time  at  which  man  begins  to  be  sexually  mature  is  designated  the 
age  of  puberty.  In  females  this  occurs  between  the  thirteenth  and  the 
fifteenth  year,  in  males  between  the  fourteenth  and  the  sixteenth  year. 
In  hot  climates  girls  are  often  sexually  mature  as  early  as  the  eighth 
year.  Between  the  forty-fifth  and  the  fiftieth  year,  with  the  cessation  of 
menstruation,  the  reproductive  period  terminates  in  the  female  (climac- 
teric, involution);  while  in  the  male  the  production  of  spermatozoa  is 
observed  even  to  most  advanced  age.  From  the  time  of  puberty  sexual 
desire  is  awakened  and  the  matured  germinal  material  is  expelled.  All 
of  the  internal  and  external  sexual  organs,  together  with  their  accessory 
structures,  undergo  increase  in  size  and  become  more  vascular;  the  pelvis 
of  the  female  acquires  a  characteristic  shape.  The  evolution  of  the 
breasts  is  described  on  p.  418.  The  pubic  and  axillary  hairs,  in  the  male 
the  beard,  make  their  appearance  in  conjunction  with  increased  sebace- 
ous secretion. 

The  period  of  puberty  is  attended  with  alterations  in  many  other  organs: 
the  larynx  of  the  boy  increases  in  size  considerably  in  a  sagittal  direction,  and  the 
vocal  bands  become  longer  and  thicker,  so  that  the  voice  becomes  at  least  one  octave 
deeper  (and  therefore  "breaks").  In  the  female  the  larynx  becomes  longer 
in  its  entirety,  and  the  range  of  the  voice  is  also  increased.  The  vital  capacity  in- 
creases considerably  in  correspondence  with  the  enlargement  of  the  thorax.  The  en- 
tire figure  and  face  acquire  the  contour  characteristic  of  the  sex,  and  the  mental 
tendencies  also  receive  a  characteristic  stamp  at  puberty.  The  vegetative  develop- 
ment with  relation  to  the  individual  is  ended  and  the  stream  of  growth  in  organic 
strength  now  passes  in  the  direction  of  new  production  or  procreation. 

MENSTRUATION. 

At  regular  intervals  of  from  27 J  to  28  days  (solar  month)  there 
occurs  in  the  sexually  mature  woman  rupture  of  one  or  several  mature 
Graafian  follicles,  with  the  coincident  appearance  of  a  bloody  discharge 
from  the  external  genitalia.  This  phenomenon  is  designated  men- 
struation (menses,  catamenia,  courses,  periods,  monthly  purification). 
Most  women  menstruate  during  the  first  quarter  of  the  moon, 
only  a  few  at  the  time  of  the  new  or  full  moon.  In  mammals 
the  analogous  process  is  termed  heat;  especially  in  carnivora, 
horses,  and  cows  there  is  a  bloody  discharge  from  the  genitalia,  and 
the  apes  of  the  old  world  have  a  well  marked  menstrual  bleeding. 

The  onset  of  menstruation  is  usually  preceded  by  signs  indicative  of  increased 
flow  of  blood  to  the  internal  genitalia,  such  as  drawing  pains  in  the  sacral  regions 
and  the  loins,  as  well  as  in  the  region  of  the  uterus  and  the  ovaries,  which  are 
sensitive  to  pressure,  fatigue  in  the  legs,  flushes,  alternate  heat  and  cold,  and 
even  slight  elevation  of  temperature  in  the  external  integument.  In  addition 
there  may  be  sluggishness  of  gastric  digestion,  abnormalities  in  the  evacuation 
of  feces  and  of  urine  and  secretion  of  sweat.  It  is  noteworthy  that  during  men- 
struation the  decomposition  of  the  nitrogenous  elements  of  the  body  in  the  meta- 
bolic process  is  diminished. 

The  menstrual  discharge  is  at  first  mucoid,  then  bloody,  and  it  lasts  three  or 
four  days  (rarely  from  one  day  to  two  weeks) .  The  blood  has  the  characteristics 
of  venous  blood  and,  if  admixed  witbTa  copious  alkaline  genital  secretion,  it  ex- 
hibits a  lessened  tendency  to  coagulation,  which  may,  however,  take  place  in 
clumps  if  the  bleeding  be  active.  The  amount  of  blood  discharged  approximates 
between  100  and  200  grams.  After  cessation  of  the  bleeding  itself  there  is  a 
moderate  discharge  of  mucus.  Subsequently  sexual  desire  is  generally  increased. 


952 


MENSTRUATION. 


The  essential  characteristic  internal  phenomena  of  menstruation 
concern:  (i)  The  alterations  in  the  uterine  mucosa  and  (2)  the  rupture 
of  the  ovarian  follicle. 

The  uterine  mucosa  is  the  actual  source  of  the  hemorrhage.  The 
ciliated  epithelium  of  the  reddened,  greatly  swollen,  spongy  and  soft 
endometrium,  from  3  to  6  mm.  thick,  is  exfoliated.  The  openings  of 
the  numerous  convoluted  uterine  glands  are  distinct,  but  their  cells 
are  in  a  state  of  fatty  degeneration,  as  is  also  the  interglandular  tissue 
of  the  cells  and  the  blood-vessels.  This  fatty  degeneration  and  the 
desquamation  of  the  degenerated  tissue  after  disintegration  take  place 
only  in  the  superficial  layers  of  the  mucosa,  whose  lacerated  vessels 
give  rise  to  the  hemorrhage.  The  deeper  layers  of  the  mucosa  remain 
intact  and  from  them  reconstruction  of  the  entire  mucosa  takes  place  at 
the  close  of  menstruation. 

^--  Ampulla  of  the  tube. 
^__--  Fallopian  tube. 


Isthmus  of  the  tube. 


Infundibulum  of  the  tube 


Fimbriated 
extremity  of 
the  tube. 


Fimbria  ovarica. 


Uterus. 


Infundibulo-pelvic  ligament.          ; 

T    ,.,.,.  ,.  •'  Ovarian  ligament. 

Infundibulo-ovanan  ligament. 

Ovary.     Broad  ligament. 

FIG.  362.— The  Ovary  and  the  Fallopian  Tube  (after  Henle). 

*  Blood-vessel  following  the  margin  of  the  ovary.     Eo.  Epoophoron  exposed  by  removal  of  a  portion  of  the 

broad  ligament. 

The  second  important  internal  process,  ovulation,  takes  place  in 
the  ovary.  The  latter  receives  a  greatly  increased  supply  of  blood,  and 
the  most  mature  follicle  becomes  more  fully  distended,  projects  above 
the  surface,  and  finally  ruptures  its  wall  and  the  ovarian  capsule,  with 
hemorrhage  from  the  laceration.  At  the  same  time  the  fimbriated  ex- 
tremity of  the  tube,  in  a  state  of  erection  from  the  engorgement  of  the 
vessels,  lies  in  close  apposition  to  the  ovary  in  such  a  manner  that  the 
ovum,  carried  out  with  the  liquor  of  the  follicle  and  the  surrounding 
granulosa-cells,  passes  along  the  ovarian  fimbriae  and  falls  into  the  tube. 
The  ciliated  cells  of  the  tube  and  the  fimbriae,  moving  toward  the  uterus, 
cause  a  movement  of  the  fluid  moistening  the  ovary  that  carries  the 
ovum  into  the  funnel  of  the  tube.  Ducalliez  and  Kiiss  were  able  by 
tense  injection  of  the  vessels  to  bring  about  artificial  erection  and  ap- 
plication of  the  abdominal  orifice  of  the  tube  to  the  ovary.  Rouget 
calls  attention  to  the  unstriated  muscle-fibers  of  the  broad  ligament, 
which  it  is  thought  may  by  constriction  cause  the  necessary  injection  of 
the  tubal  vessels. 


MENSTRUATION. 


953 


m 


FIG.  363. — Sagittal  Section  through  the  Normal  Endometrium,  m,  to- 
gether with  a  Portion  of  the  Contiguous  Muscular  Layer,  m\. 


With  regard  to  the  connection  between  ovulation  and  therdischarge  of  blocd 
from  the  endometrium,  there  are  at  the  present  time  two  views.     Pfiuger[  con- 
siders the  bloody  exfoliation  of  the  superficial  layer  of  the  endometrium  as  a 
preparatory     freshening 
of    the    tissues    (in    the 
surgical     sense)      occur- 
ring   physiologically,   as 
a  result   of   which  it   is 
rendered  capable  of  unit- 
ing   firmly  by   adhesion 
(as  in  case  of  thrombosis 
or  cicatrization)  with  the 
ovum  that  finds  its  way 
into  the  uterus,  so  that 
the     ovum     is      further 
nourished  from  the  new 
lining  membrane  of  the 
uterus  like  a   developed 
or  adherent  part.     This 
view  is  entirely  at  vari- 
ance  with    another,  ac- 
cording to  which    there 
develop  within  the  uter- 
us marked  engorgement, 
sponginess,  and  swelling 
of    the    mucosa,    under 
normal  conditions,  even 
before    the    discharge    of    the 
ovum  from  the  follicle,  in  con- 
sequence   of     a     sympathetic 
formative    process.     The    en- 
dometrium  thus    prepared    is 
designated    the  menstrual  de- 
cidual  membrane.     From  this 
point  of  view  it  is  capable,  as 
a  suitable  place  of  incubation, 
of    receiving    an    impregnated 
ovum.     If,  however,  the  ovule 
has  not  been  impregnated  and 
if,  therefore,  it  is  lost  after  its 
passage   through    the    genital 
canal,  destruction  of  the  uter- 
ine mucosa  takes  place  with 
hemorrhage,    as    already    de- 
scribed.     Accordingly,     the 
hemorrhage  from   the  uterine 
mucosa  would    be    a    sign    of 

the  nonoccurrence  of  pregnancy.      The  mucosa  undergoes    destruction  because 
it  could  not  be  utilized  for  the   time   being,   and  the  menstrual    hemorrhage  is, 

therefore,  an  external 
sign  that  the  discharged 

Ovarian  stroma.  ovum  has  not  been  im- 

pregnated.  Accordingly, 

External  tunic  of  follicle.  pregnancy,    that   is    the 

development  of  the  fetus 
in  the  uterus,  must  be 
reckoned  not  from  the 
last  menstruation  that 
occurred,  but  from  the 
first  menstruation  that 
was  absent. 

With  the  rupture  of 
the  follicle,  the  cumulus 

oophorus   first   is   detached   from  the   wall   of  the   latter,    the    most    superficial 
portion    of    the    follicle,    designated    the     stigma,    becomes     thin,     its     vessels 


FIG.   364. — Horizontal   Section  of  the  Normal  Endome- 
trium (after  Orthmann). 


Vessel  between  the   external  tunic  of  the 
follicle  and  the  tunica  propria. 


...  Folded  and  hypertrophied  tunica  propria. 


FIG.  365. — Fresh  Corpus  luteum  (after  Balbiani). 


954 


MENSTRUATION. 


are  obliterated  at  this  point  and  the  tissue  undergoes  atrophy,  so  that  with 
increasing  pressure  rupture  must  take  place  here. 

After  menstruation,  the  epithelium  of  the  uterine  mucosa  is  regenerated 
by  indirect  division,  particularly  from  the  sixteenth  to  the  eighteenth  day  after 
the  beginning  of  menstruation;  the  premenstrual  swelling  of  the  mucosa  begins 
again  between  the  eighteenth  and  the  nineteenth  day. 

In  individual  cases  ovulation  and  the  formation  of  the  menstrual  decidua 
may  take  place  independently;  so  that  menstruation  may  occur  without  ovulation 

(more  frequent)  or  ovulation  without  menstrua- 
tion (seldom).  Menstrual  bleeding  occurs  only 
in  the  presence  of  ovarian  tissue  and  a 
sufficient  development  of  the  uterine  mucosa. 
Although  many  facts  tend  to  support  this  new 
conception,  there  still  remains  the  difficulty  that 
in  animals  that  have  several  placental  sites  (for 
example  the  cow),  bleeding  takes  place  from 
these  situations  at  the  time  of  heat. 

Formation  of  the  Corpus  Luteum. — The 
follicle  whose  contents  have  been  discharged 
collapses.  In  its  interior  there  remains  the  lining 
of  granulosa-cells  and  a  small  amount  of  blood, 
which  quickly  coagulates.  The  small  wound  of 

rupture  undergoes  cicatrization  after  the  serum  has  been  absorbed.  The  wall  of 
the  follicle,  which  has  become  vascular,  now  swells  as  a  result  of  mitotic  division 
of  the  cells  of  the  inner  thecal  wall  and  forces  inward  villous  granulations  of  young 
connective  tissue  (Fig.  367),  rich  in  capillaries  and  cells.  Leukocytes  wander 
into  the  cavity.  Lutein-cells  are  formed  anew  through  proliferation  of  the  in- 
ternal connective  tissue  layer  of  the  wall  of  the  follicle  (Fig.  366).  The  corpus 
luteum  is  not  an  epithelial,  but  a  connective  tissue  structure.  Internal  to  the 
lutein-cells  a  layer  of  connective  tissue  develops  later  on.  The  lutein-cells  subse- 
quently undergo  degeneration  and  there  remains  a  cicatricially  contracted  "cor- 
pus albicans."  The  capsule  becomes  gradually  more  and  more  fused  with  the 
ovarian  stroma. 


FIG.  366. — Lutein-cells  from  the  Corpus 
luteum  of  the  Cow  (after  His). 


Stroma    of    the    ovary  with 
vascular  spaces. 


—   Corpus  luteum  with    fibrous 
center. 


Lymph-vessels. 


FIG.  367.— Corpus  luteum  of  the  Cow,  enlarged  one  and  one-half  times  (after  His). 


Should  pregnancy  not  occur  after  the  menstruation,  absorption  of  the  fat 
formed  takes  place,  with  the  formation  of  a  crystalline  body  formerly  supposed 
to  be  hematoidin,  but  shown  to  be  lutein  or  lipochrome,  and  of  other  pigment- 
derivatives,  while  the  yellow  body  undergoes  uniform  contraction  within  four 
weeks,  down  to  a  small  remnant.  Such  yellow  bodies,  when  pregnancy  does 
not  subsequently  take  place,  are  designated  spurious  corpora  lutea.  If,  however, 
pregnancy  results,  the  size  of  the  body,  in  accordance  with  the  greatly  increased 
formative  processes,  is  quite  considerable  (especially  in  the  third  or  fourth  month). 


ERECTION.  955 

The  wall  is  thicker  and  the  color  is  deeper,  so  that  the  body  at  the  time  of  labor 
still  measures  from  6  to  10  mm.  in  diameter  and  its  remains  may  be  recognizable 
even  after  the  lapse  of  years.  The  yellow  body  after  pregnancy  is  designated 
the  true  corpus  luteum  (Fig.  367). 

ERECTION. 

The  knowledge  of  the  distribution  of  the  blood  in  the  penis  is  due  to  the  in- 
vestigations of  C.  Langer.  The  albuginea  of  the  cavernous  bodies  consists  of 
tendinous  connective  tissue,  closely  reticulated  elastic  tissue  and  unstriated 
muscle-fibers,  which  form  a  firm  fibrous  envelop,  from  which  innumerable  trabec- 
ulas  of  similar  structure  pass  inward,  so  that  the  cavernous  bodies  acquire  the  con- 
figuration of  a  sponge.  The  anastomosing  spaces  thus  produced  form  a  labyrinth 
of  venous  sinuses,  which  are  lined  by  endothelium.  The  largest  of  these  spaces 
are  situated  in  the  lower,  outer  portion  of  the  cavernous  body;  in  the  upper 
portion  the  spaces  diminish  in  number  and  size.  The  smaller  arteries  of  the 
cavernous  bodies  arise  from  a  branch  of  the  arteria  profunda  of  the  penis  running 
along  the  septum  and  they  reach  the  trabeculae  in  a  tortuous  course.  Some  of 
the  small  arterial  branches  in  the  cortical  areas  pass  directly  over  into  the  larger 
venous  sinuses;  but  similar  direct  transition  from  arteries  to  venous  spaces  takes 
place  also  in  the  interior  of  the  cavernous  bodies.  A  capillary  network  occurs 
also  in  the  cortex  and  in  the  interior  of  the  cavernous  bodies /opening  into  the 
venous  spaces.  The  helicine  arteries  of  the  penis  described  by  Johannes  Miiller 
are  only  more  or  less  incompletely  injected  arterial  loops  bent  upon  themselves, 
whose  occurrence  is  due  to  the  cord-like  course  of  the  trabeculae.  From  the  in- 
terior of  the  cavernous  bodies,  the  venas  profundse  of  the  penis  arise  by  means 
of  fine  branches.  In  addition  venous  branches  pass  from  the  cavernous  spaces 
to  the  dorsum  of  the  penis,  uniting  to  form  the  dorsal  vein  of  the  penis.  As 
these  branches  pass  through  the  meshes  of  the  vascular  network  in  the  cortex 
of  the  cavernous  bodies,  it  is  obvious  that  constriction  of  the  meshes  resulting 
from  congestion  of  the  network  must  cause  compression  of  the  efferent  branches. 

The  spongy  body  of  the  urethra  consists  for  the  greater  part  of  an  outer  layer 
of  anastomosing  veins  lying  close  together,  surrounding  the  longitudinal  vessels 
of  the  urethra. 

In  the  dog  all  of  the  arteries  of  the  penis  pass  toward  the  surface,  where  they 
divide  in  tuft-like  fashion.  The  veins  arise  from  the  capillary  loops  of  the  papillae 
and  they  convey  their  blood  into  the  cavernous  bodies.  Onlv  a  small  amount  of 
blood  reaches  the  cavernous  spaces  through  internal  capillaries  and  veins;  and 
arterial  blood  never  flows  directly  into  them. 

The  mechanism  of  erection  consists  in  a  marked  distention  of  the 
blood-vessels  of  the  penis,  with  fourfold  or  fivefold  increase  in  volume, 
elevation  of  temperature,  increase  of  blood-pressure  within  its  vessels 
to  one-sixth  of  the  carotid  pressure  and  initial  pulsatory  movement, 
increased  consistency  and  erection,  with  a  direction  of  the  organ 
in  conformity  with  the  curvature  of  the  vagina.  The  preliminary 
process  consists  in  a  marked  increase  in  the  arterial  supply  of  blood, 
the  arteries  becoming  dilated  and  pulsate  strongly.  This  process  is 
controlled  by  the  erector  nerves,  which  arise  principally  from  the  second 
(less  commonly  from  the  third)  sacral  nerve  (in  the  dog)  and  possess 
ganglion-cells  in  their  course.  These  nerves,  belonging  to  the  vaso- 
dilators, may  be  in  part  stimulated  reflexly  by  irritation  of  the  sensory 
nerves  of  the  penis,  the  transference  of  the  irritation  taking  place  in  the 
erection-center  in  the  spinal  cord.  Thus,  also,  sensory  irritation  induced 
by  voluntary  movements  of  the  genitalia,  may  excite  this  reflex  through 
the  ischiocavernosus  and  bulbocavernosus  and  the  cremaster  muscles, 
even  the  conception  of  sensory  irritation  of  the  penis  may  be  attended 
with  the  same  results. 

Some  vasodilators  pass  (in  the  dog)  also  through  the  lumbar  sympathetic 
and  the  internal  pudendal  nerve.  The  last-named  nerve  usually  contains  vaso- 
constrictor fibers  for  the  penis,  although  the  erector  nerves  contain  some. 


956 


ERECTION. 


i  -_ 


The  erection -center  in  the  spinal  cord  is,  however,  naturally  subordi- 
nate to  the  dominating  vasodilator  center  in  the  medulla  oblongata, 
from  which  connecting  fibers  pass  downward  through  the  cord  to  the 
erection-center.  Therefore,  stimulation  of  the  spinal  cord  above 
causes  erection,  as,  for  example,  by  mechanical  irritation,  asphyxiation, 
or  the  use  ot  muscarin  (pathologically  also  in  cases  of  spinal  irritation). 
Finally,  the  psychical  activity  of  the  brain  has  a  distinct  influence  upon 
the  genital  vasodilators.  In  the  same  way  as  the  psychical  emotions 
of  anger  or  shame  cause  dilatation  of  the  vessels  of  the  head  by  stimu- 
lation of  the  dilators,  the  direction  of  the  attention  to  the  sexual  sphere 
has  an  effect  upon  the  erector  nerves.  This  influence  of  the  brain  has 

been  explicable  since  the  de- 
pendence of  the  local  lumen  of 
the  vessels  upon  the  cerebral 
cortex  has  been  known.  From 
the  cerebral  cortex  the  fibers 
whose  irritation  Eckhard  ob- 
served to  cause  erection  prob- 
ably pass  through  the  cerebral 
peduncles  and  the  pons. 

If,  thus,  the  impulse  to  erec- 
tion is  given  by  the  arterial 
fluxion,  the  complete  develop- 
ment of  the  process  may  take 
place  through  the  activity  of  the 
following  transversely  striated 
muscles : 

i .  The  ischiocavernosus 
muscle  (Fig.  108)  arises  from 
the  ischium,  and  surrounds  the 
root  of  the  penis  by  its  tend- 
inous union  like  a  sling.  In 
its  contraction  it  compresses 
the  root  of  the  penis  from 
above  and  the  sides,  so  that  the 
escape  of  the  venous  blood  is 
prevented.  It  has  no  effect  upon 
the  dorsal  vein  of  the  penis,  as 
this  vessel  is  protected  in  the 
dorsal  groove  of  the  penis  from 
the  pressure  of  the  tendon. 
2.  The  deep  transverse  perineal 
muscle  is  penetrated  by  the  deep 

veins  of  the  penis  coming  from  the  cavernous  bodies  and  later  uniting  with 
the  common  pudenal  vein  and  the  plexus  of  Santorini  in  such  a  manner 
that  its  contraction  must  compress  them  between  the  highly  contracted 
horizontal  fibers  (Fig.  368,  6).  3.  Finally  the  bulbocavernosus  muscle 
also  aids  in  stiffening  the  corpus  spongiosum,  by  compressing  the  bulb  of 
the  urethra  (Fig.  368,  5  and  Fig.  108).  All  of  these  muscles  can  in  part 
be  moved  voluntarily,  and  as  a  result  the  erection  becomes  more 
marked.  Under  ordinary  conditions,  however,  their  contraction  follows 
reflex  excitation  from  the  sensory  nerves  of  the  penis. 


FIG.  368. — Anterior  Pelvic  Wall  with  the  Urogenital 
Diaphragm,  viewed  from  in  front  (externally),  after 
Henle.  The  corpus  cavernosum  of  the  urethra,  4, 
with  the  urethra,  3,  is  divided  beneath  the  point  of 
exit  from  the  pelvis,  i,  pubic  symphysis;  2,  dorsal 
vein  of  the  penis;  5,  portion  of  the  bulbocavernosus 
muscle,  arising  fsom  the  perineal  septum;  t,  deep 
transverse  perineal  muscle,  together  with  its  fascia,  f ; 
6,  deep  vein  of  the  penis;  7,  bulbocavernosus  artery 
and  vein. 


EJACULATION.       RECEPTION    OF    THE    SEMINAL    FLUID.  957 

The  stagnation  of  blood  in  the  penis  is  not  complete;  otherwise,  long-con- 
tinued erection  (priapism,  satyriasis)  would  under  pathological  conditions  give 
rise  to  gangrene. 

Blood-stasis  in  the  penis  is  favored  by  the  fact  that  the  veins  of  the  penis 
originate  in  the  cavernous  bodies,  by  whose  hardening  the  veins  must  be  com- 
pressed. Furthermore,  there  are  on  the  walls  of  the  large  veins  of  the  plexus 
of  Santorini  trabeculae  of  unstriated  muscle,  which  in  contracting  act  as  columns 
penetrating  into  the  lumen  of  the  veins  and  in  part  hinder  the  flow  of  blood. 

The  dependence  of  erection,  as  a  complex  motor  mechanism,  upon  the  nervous 
system  was  demonstrated  by  the  experiments  of  Hausmann,  who  observed  that 
erection  failed  to  appear  after  section  of  the  nerves  of  the  penis  in  stallions. 
The  erection  that  occurs  in  women  is  less  complete  and  extends  to  the  cav- 
ern otis  bodies  of  the  clitoris  and  the  bulb  of  the  vestibule.  During  erec- 
tion the  communication  between  the  urethra  and  the  bladder  is  closed  partly  by 
swelling  of  the  caput  gallinaginis,  a  portion  of  the  spongy  body  of  the  urethra, 
and  partly  through  the  action  of  the  urethral  sphincter,  which  is  connected  with 
the  deep  transverse  perineal  muscle. 

EJACULATION.     RECEPTION  OF  THE  SEMINAL  FLUID. 

In  the  expulsion  of  the  seminal  fluid  two  distinct  factors  are  to  be 
distinguished,  namely:  (i)  The  passage  of  the  seminal  fluid  from  the 
testicle  to  the  seminal  vesicles,  and  (2)  the  act  of  ejaculation  itself. 
The  first  takes  place  continuously  in  consequence  of  the  advance  of 
newly  formed  seminal  fluid  through  the  activity  of  the  ciliated  epithe- 
lium (from  the  epididymis  to  the  beginning  of  the  vas  deferens)  and  as 
a  result  of  the  gradual  peristalsis  of  the  vasa  deferentia,  which  are 
provided  with  a  well-developed  muscular  layer. 

For  the  initiation  of  ejaculation,  however,  a  strong  peristalsis  of 
the  vasa  deferentia  and  of  the  muscular  walls  of  the  seminal  vessels  is 
necessary.  This  is  brought  about  through  reflex  excitation  of  the 
ejaculatory  center  in  the  spinal  cord.  As  soon  as  seminal  fluid  enters 
the  urethra  by  this  means,  rhythmic  contraction  of  the  bulbocavernosus 
muscle  takes  place  as  a  result  of  distention  of  the  urethra  acting  as  a 
mechanical  irritant,  and  the  seminal  fluid  is  vigorously  expelled  from  the 
urethra.  Both  seminal  vesicles  and  both  vasa  deferentia  do  not  always 
discharge  their  contents  into  the  urethra  at  the  same  time.  With 
moderate  stimulation  only  one  of  these  may  empty  itself  at  a  time. 
Coincidently  with  the  contraction  of  the  bulbocavernosus,  the  ischiocav- 
ernosus  and  the  trans  versus  perinei  profundus  also  contract,  but  these 
have  no  influence  upon  ejaculation  itself. 

Also  in  the  female  there  occurs  under  normal  conditions,  at  the  height  of 
sexual  excitement,  a  reflex  motor  process  corresponding  to  ejaculation  in  the  male. 
This  consists  of  movements  analogous  to  those  observed  in  the  male.  There 
occurs,  first,  a  peristaltic  movement  of  the  tubes  and  the  uterus  from  its  cornua 
to  the  vaginal  portion,  induced  by  reflex  irritation  of  t*he  genital  nerves.  Dembo 
observed  in  animals  general  uterine  contractions  after  irritation  of  the  anterior  up- 
per wall  of  the  vagina.  As  a  result  of  the  movement  of  the  tubes  and  the  uterus 
(which  corresponds  to  the  peristalsis  of  the  vasa  deferentia  in  the  male) ,  a  certain 
amount  of  mucoid  fluid  normally  moistening  the  uterine  wall  is  expressed  into  the 
vagina.  This  is  followed  by  rhythmic  contraction  of  the  sphincter  cunni  (analo- 
gous to  the  bulbocavernosus) ,  the  insignificant  ischiocavernosi  and  the  deep  trans- 
versus  perinei  being  at  the  same  time  active.  As  a  result  of  the  vigorous  contrac- 
tion of  the  muscular  fibers  of  the  uterus  and  its  muscular  round  ligaments,  the  organ 
becomes  erect  and  descends  toward  the  vagina,  its  cavity  becoming  more  and 
more  reduced  in  size,  while  its  mucus  contents  are  expressed.  If  the  uterus 
later  on,  after  the  excitation  has  ceased,  gradually  returns  to  its  relaxed  state  of 
rest,  it  aspirates  into  its  cavity  the  seminal  fluid  deposited  at  its  orifice  (con- 
ception) . 


IMPREGNATION    OF    THE    OVUM. 

Such  aspiration  of  the  seminal  fluid  by  the  uterus  irritated  to  maximum 
degree  is  by  no  means  necessary  to  fecundation.  The  spermatozoa  are  capable 
by  their  own  movement  of  entering  the  uterus  from  the  vaginal  portion  through 
the  clear  mucus  that  normally  occupies  the  cervical  canal.  '  Indeed,  observations 
as  to  impregnation  without  entrance  of  the  penis,  in  consequence  of  pathological 
obstructions,  such  as  partial  atresia  of  the  vulva  or  vagina,  show  that  spermatozoa 
may  traverse  the  entire  vagina  into  the  uterus. 

IMPREGNATION  OF  THE   OVUM. 

The  ovum  is  fecundated  by  the  penetration  of  one  spermatozoon. 

Since  the  time  of  Swammerdam  (died  1685)  it  has  been  known  that  for  fecunda- 
tion to  take  place  contact  of  the  ovum  with  the  seminal  fluid  is  necessary  and 
indeed  with  the  spermatozoa,  which  according  to  Hartsoecker  penetrate  into  the 
ovum.  .  Barry  saw  spermatozoa  enter  the  interior  of  the  rabbit's  ovum.  This 
takes  place  with  considerable  rapidity  by  a  boring-movement  through  the  capsule 
of  the  ovum.  The  invasion  takes  place  eventually  through  pores  that  are  present 
or  through  the  micropyle. 

In  the  mouse  and  some  other  mammals  the  ovary  is  surrounded  by  a  space 
filled  with  fluid  (periovarial  space) ,  to  which  both  the  ovum  and  the  spermato- 
zoon gain  access;  both  are  conveyed  by  aspirating  movements  of  the  tube  into  the 
uterus. 

The  viscid  surface  of  the  ovum  affords  a  means  for  the  attachment  of  the 
spermatozoon.  In  the  case  of  meroblastic  ova  the  spermatozoon  penetrates  in 
the  situation  of  the  nucleus;  in  that  of  holoblastic  ova  at  the  animal  pole,  when 
this  is  present.  At  the  spot  where  the  head  of  the  spermatozoon  meets  the  yolk, 
the  latter  throws  out  toward  it  a  humplike  elevation.  As  soon  as  a  spermatozoon 
has  penetrated  into  the  yolk,  the  entrance  of  other  spermatozoa  seems  to  be  op- 
posed by  the  appearance  of  a  firm  membrane — the  yolk-membrane— upon  its 
surface,  which,  acting  as  a  protecting  wall,  prevents  the  penetration  of  other 
spermatozoa.  Nevertheless  in  the  case  of  meroblastic  ova  (selachians,  reptiles, 
insects  and  others)  the  penetration  of  several  spermatozoa  takes  place  normally 
for  the  purpose  of  fecundation — polyspermism. 

The  place  where  fecundation  (impregnation)  takes  place  is  either 
the  ovary  (as  indicated  by  the  occurrence  of  abdominal  pregnancy)  or 
the  tube,  whose  numerous  mucous  folds  constitute  a  suitable  place  of 
lodgment  for  the  spermatozoa.  That  fecundation  may  take  place  also 
in  the  tube  is  shown  by  the  occurrence  of  tubal  gestation.  Spermatozoa 
must,  accordingly,  pass  from  the  uterus  through  the  tube  to  the  ovary 
and  they  do  this  probably  by  their  own  movement.  Whether  the  per- 
istaltic movements  of  the  uterus  and  the  tube  assist  in  this  transpor- 
tation is  uncertain.  The  ciliary  movement  of  the  tubal  epithelium 
can,  however,  have  nothing  to  do  with  the  phenomenon,  as  the  movement 
is  directed  outward.  If  the  ovum  enters  the  uterus  unimpregnated, 
it  does  not  undergo  fecundation  here,  as  it  perishes.  It  is  believed 
that  the  extruded  ovum  reaches  the  uterus  within  two  or  three  weeks 
(in  dogs  from  eight  to  fourteen  days). 

Double  impregnation  (twins)  occurs  once  in  87  times  (in  tropical 
regions  more  commonly);  triplets  once  in  7600  times;  quadruplets 
once  in  330,000  times;  sextuplets  are  extremely  rare;  septuplets  (?) 
were  born  by  Anna  Breyers  of  Hamlin  in  1600.  The  average  number 
of  conceptions  in  women  is  4^.  The  largest  number  of  children  observed 
is  from  32  to  38. 

By  superfecundation  is  understood  the  occurrence  of  the  impregnation  of 
two  ova  discharged  at  the  same  menstrual  period,  as  a  result  of  different  copula- 
tions. For  example,  a  mare  may  throw  a  foal  and  a  mule,  after  having  been  covered 
first  by  a  stallion  and  then  by  an  ass.  Thus,  also,  a  woman  has  been  observed  to 
give  birth  to  a  negro  and  a  white  twin.  If,  however,  the  second  fecundation  occurs 


IMPREGNATION    OF    THE    OVUM. 


959 


FIG.  369. — Ovum  of  Scorpaena 
scrofa.  The  germinal  vesi- 
cle has  extruded  a  polar  body 
and  has  withdrawn  to  the 
center  of  the  ovum  as  the  nu- 
cleus; it  is  being  approached 
by  the  male  pronucleus. 


at  a  later  time  during  pregnancy,  as  for  example,  at  the  second  or  the  third  month 
(as  in  a  case  cited  in  the  Talmud) ,  then  the  rare  phenomenon  of  superfetation  occurs. 
This,  however,  is  possible  only  in  the  presence  of  a  double  uterus  and  the  persistence 
of  menstruation  until  the  time  of  the  second  impregnation.  Hippocrates  explained 
superfetation  as  due  to  independent  pregnancies  in  the  horns  of  the  uterus,  a 
condition  that  according  to  Aristotle  occurs  with  especial  frequency  in  hares. 
Superfetation  cannot  occur  in  the  normal  uterus,  as  a  plug  of  mucus  occludes  the 
cervical  canal  during  pregnancy,  as  Herophilus 
knew,  and  in  addition  from  the  fact  that  menstrua- 
tion usually  ceases. 

Hybrids. — Impregnation  is  possible  also  between 
related  species  (horse,  ass,  zebra;  dog,  jackal,  wolf; 
goat,  ibex;  goat,  sheep;  varieties  of  the  llama; 
camel,  dromedary;  tiger,  lion;  varieties  of  pheasants; 
varieties  of  finch;  goose,  swan;  carp,  crucian;  varieties 
of  the  butterfly).  Most  of  the  hybrids  thus  produced 
are  sterile,  chiefly  because  of  a  deficiency  of  developed 
spermatozoa  in  the  male.  The  female  hybrid,  how- 
ever, may  be  impregnated  by  males  of  the  species  of 
either  of  her  parents;  for  example  the  mule.  The 
progeny,  however,  tends  to  revert  in  type  to  the 
species  of  the  parents.  Only  a  few  hybrids  are  capable 
of  procreation  among  themselves,  as  hybrids  in  dogs. 
In  different  species  of  frogs,  the  cause  of  the  frequent 
failure  of  hybridization  is  to  be  found  in  mechanical 
obstructions  to  the  penetration  of  the  spermatozoa 
into  the  ovum.  Only  such  spermatozoa  as  are  more 
slender  and  more  vigorous  in  movement  than  those  of 

the  other  species  are  capable  of  impregnating  ova  of  the  latter.  Therefore, 
the  possibility  of  hybridization  between  two  species  is  almost  always  one-sided. 
In  some  amphibia  hybrid  fertilization  is  possible,  but  development  does  not  take 
place  beyond  the  first  stages.  This  appears  to  be  due  to  the  circumstance  that 
only  a  portion  of  a  spermatozoon  that  has  incompletely  entered  the  ovum  be- 
comes active.  According  to  O.  and  R.  Hertwig,  hybridization  can  be  more 
readily  effected  in  echinodermata  the  more  virile  the  spermatozoa  and  the 
feebler  the  ova. 

In  breeding  among  close  blood-relationships  (rats)  increase  of  sterile  pairings, 
diminution  in  the  number  of  offspring,  greater  mortality  among  the  young  and 

marked  inability  on  the  part  of  the 
mother  to  nourish  them  occur.  Certain 
bodily  defects  and  weaknesses  appear  to 
be  increased. 

Exceptionally  the  ovum  from  the 
ruptured  follicle  of  one  ovary  may  enter 
the  tube  of  the  opposite  side,  as  indicated 
by  the  cases  of  tubal  pregnancy  and  of 
pregnancy  within  a  rudimentary  uterine 
horn  abnormally  present,  in  which  the 
true  corpus  luteum  has  been  found  in  the 
ovary  of  the  opposite  side  (external  trans- 
migration). In  accordance  with  this 
observation  is  the  fact  that  fine  granules 
suspended  in  water  (India  ink,  etc.), 
and  injected  into  the  peritoneal  cavity, 
penetrate  into  both  tubes,  as  a  result  of 
the  action  of  the  cilia,  and  reach  the  uterus. 
In  animals  ova  may  also  wander  through 

the  double  uterine  mouth:  out  of  the  one  and  through  the  other  into  the 
opposite  uterine  horn  (internal  transmigration). 

In  the  maturing  ovum  the  first  characteristic  change  affects  the  ger- 
minal vesicle,  which  divides  by  mitosis.  At  the  same  time  it  moves  to- 
ward the  surface  of  the  ovum,  and  loses  its  capsule;  its  chromatin-fibrils 
begin  to  form  convolutions  and  become  converted  into  a  longitudinal 
structure  known  as  the  nuclear  spindle.  At  both  poles  of  the  spindle,  the 
granular  elements  of  the  protoplasmic  yolk  become  collected  each  into  a 


FIG.  370. — Ovum  of  a  Starfish  (asteracan- 
thion)  with  two  Extruded  Polar  Bodies: 
male  and  female  pronuclei  in  apposition. 


960 


MATURATION    OF    THE    OVUM. 


radiate  form  (diaster).  When  this  has  taken  place,  the  peripheral  pole 
of  the  nucleus  of  the  ovum  thus  altered  appears  above  the  surface  of 
the  ovum,  becomes  constricted  off  and  expelled  from  the  ovum  like 
a  waste  product  in  the  form  of  a  small  body  (Fig.  358,  VI  and  VII). 
The  formation  of  a  second  polar  body  takes  place  again  by  mitosis  in 
the  same  way  during  the  penetration  of  the  spermatozoon.  Both  of 
the  bodies  thus  eliminated,  which  are  of  no  further  use  in  the  growth 
and  development  of  the  ovum,  are  designated  directing  bodies  or  polar 
cells.  (Figs.  369  and  370.)  The  remaining  portion  of  the  germinal 
vesicle  lying  near  the  center  remains  within  the  yolk,  wanders  back 
toward  the  center  of  the  ovum,  increases  in  size,  and  thus  forms  the  egg- 
nucleus  or  female  pronucleus,  which  has  no  centrosome. 

The  spermatozoon  that  has  entered  the  ovum  moves  toward  the  female 
pronucleus,  its  head  becoming  surrounded  by  a  radiating  crown;  then 


Nucleus  and 
radially  arranged  ^£ 
protoplasm.        &*-• 


First  division. 


,      Segmentation  spheres.  Morula. 

FIG.  371.— Four  Stages  of  Division  of  an  Impregnated  Ovum  of  Echinus  saxatilis. 


its  cilmm  is  dissolved  and  its  head,  alone  remaining,  forms  a  chromatic 
mass  and  swells  into  a  second  new  nucleus,  the  sperm-nucleus  or  the 
male  pronucleus.  From  the  connecting  segment  a  centrosome  (sur- 
rounded by  rays)  develops  and  this  soon  becomes  directed  toward  the 
Qterior  of  the  ovum.  The  centrosome  of  the  male  pronucleus  also 
livides.  I  he  male  and  female  pronuclei  now  unite  to  form  the  new 
nucleus  of  the  impregnated  ovum,  with  which  both  of  the  sperma- 
spneres  resulting  from  the  division  are  in  contact;  and  the  yolk 
assumes  a  radiating  appearance  (Figs.  370  and  371). 

The  entrance  of  several  spermatozoa  into  the  ovum  (polyspermism)  takes 
place  normally  in  large  ova  rich  in  yolk.  From  these  accessory  sperm-nuclei 
develop  all  of  which  probably  disappear  later.  O.  Hertwig  and  Fol  made  the 
remarkable  observation  (m  echinoderms)  that  several  embryos  form  from  one 
ovum,  when  several  spermatozoa  enter  the  ovum  abnormally.  The  male  pro- 
nuclei  resulting  from  the  individual  spermatosomes  then  each  unite  with  a  frag- 
ment of  the  disintegrated  female  pronucleus. 


MATURATION    OF    THE    OVUM.  961 


CLEAVAGE,  MORULA,  BLASTULA,  GASTRULA,  FORMATION    OF 
THE    GERMINAL    LAYERS.        FIRST   RUDIMENTS   OF    THE 

EMBRYO. 

In  the  fecundated  ovum  the  yolk-mass  contracts  more  closely 
about  [;the  newly  [formed  nucleus,  becoming  somewhat  separated 
from  the  yolk-membrane,  and  there  now  follows  division  first  of  the 
nucleus  and  then  of  the  yolk  into  two  nucleated  globules  or  blast omeres. 
This  process,  designated  total  cleavage,  is  repeated  in  accordance  with 
the  method  of  cell-division  in  the-  two  globules  formed,  so  that  first 
4,  then  8,  16,  32,  etc.,  globules  result.  The  division  ceases  only 
after  the  entire  yolk  has  been  subdivided  into  numerous  small 
globules,  the  nucleated  cleavage-spheres,  or  the  unencapsulated  pro- 
toplasmic primitive  cells  (from  20  to  25  /JL  in  diameter).  The  yolk 
now  consists  of  a  collection  of  primitive  cells  and  is  designated  the 
morula  or  the  mulberry  mass. 

The  division  of  the  nucleus  of  the  ovum  takes  place  by  mitosis  after  the 
previous  formation  of  a  spindle-form.  The  centrosomes  of  this  first  cleavage- 
spindle  are  derived  from  the  centrosome  of  the  spermatozoon.  According  to 
the  observations  of  van  Beneden  the  constituents  of  both  the  male  and  the  female 
pronucleus  pass  over  into  the  cleavage-spheres,  so  that  all  cells  of  the  body  are 
formed  from  a  combination  of  the  male  and  female  procreative  elements.  This 
fact  explains  the  process  of  inheritance  from  the  paternal  and  the  maternal  or- 
ganism. Deficiency  of  oxygen  gives  rise  in  the  ova  of  some  fish  to  an  involution  in 
the  process  of  cleavage.  The  globules  become  dissolved  and  coalesce.  A  renewal 
of  the  supply  of  oxygen  stimulates  the  process  of  cleavage  anew. 

The  uniform  mode  of  cleavage  described,  such  as  occurs  in  mammals  and 
amphioxus,  is  designated  equal  or  adequal.  A  second  variety  of  cleavage  is  the 
total  unequal,  in  which,  for  example  in  the  frog's  egg,  one-half  of  the  yolk, 
designated  the  animal  pole,  which  often  is  pigmented,  yields  much  smaller  cleav- 
age-cells than  the  other  or  vegetative  pole.  The  embryo  forms  in  the  animal 
pole.  When,  finally,  the  yolk-mass  has  become  so  large  that  cleavage  remains 
confined  to  the  animal  pole,  then  partial  cleavage  (described  later)  occurs. 

Numerous  attempts  have  recently  been  made  to  trace  the  development  from 
a  single  isolated  blastomere.  Some  investigators  found  that  at  first  only  a  right 
or  a  left  half  of  an  individual  (echinodermata)  is  formed  from  one  blastomere, 
but  that  this  in  the  further  course  is  capable  through  post-generation  to  develop 
into  an  entire  being.  Other  observers,  on  the  other  hand,  from  the  outset  ob- 
tained from  a  single  blastomere  (for  example  from  an  ascidian  ovum)  an  entire 
individual  (even  to  the  sixteenth  division),  but  of  smaller  size.  Under  special 
experimental  conditions,  finally,  it  was  possible  to  produce  double  malformation, 
from  partially  isolated,  but  partially  connected  blastomeres. 

Under  normal  conditions  the  first  line  of  cleavage  (frogs)  passes,  according  to 
Roux,  in  the  same  direction  as  the  central  nervous  system.  The  second  fissure 
intersects  the  first  at  right  angles  and  divides  the  ovum  into  two  unequal  parts, 
of  which  the  larger  serves  to  form  the  cephalic  portion  of  the  embryo. 

Meanwhile  the  ovum  has  increased  in  size  through  the  absorption 
of  fluid.  All  of  the  cells  are  polyhedral  in  shape  from  mutual  pressure, 
and  form  a  cellular  vesicle,  the  germinal  vesicle,  which  is  applied  through- 
out its  periphery  to  the  zona  pellucida. 

The  human  ovum  has  reached  this  stage  of  development  during  the  first 
week;  that  of  rabbits  in  4  days,  of  guinea-pigs  in  3^,  of  cats  in  7,  of  dogs  in  n, 
of  foxes  in  14,  of  ruminants  and  pachydermata  in  from  10  to  12,  of  deer  in  60 
days.  In  some  animals  (for  example  rabbits)  the  zona  pellucida  is  further  sur- 
rounded by  a  layer  of  albumin.  A  small  collection  of  blastomeres  do  not  partici- 
pate in  the  formation.  They  are  apparently  not  utilized,  and  apply  themselves 
at  one  point  on  the  interior  of  the  blastula,  and  here,  later,  the  embryo  develops. 
6x 


962 


MATURATION    OF    THE    OVUM. 


The  germinal  vesicle,  which  as  a  typical  stage  in  the  development 
of  numerous  animal  species  is  also  designated  the  blastula,  thus  consists 
of  a  vesicle  with  walls  made  up  of  a  single  layer  of  cells,  as  represented 
diagrammatically  in  Fig.  372,  i,  in  sagittal  section  (from  amphioxus). 
The  subsequent  important  formative  process  consists  in  the  develop- 
ment from  the  blastula  of  a  hollow  structure,  whose  walls  consist  of  a 
double  layer  of  cells.  This  process  of  transformation  can  be  best 
followed  in  the  ovum  of  the  lancet-fish  (amphioxus).  Here  the  blastula 
is  invaginated  at  one  point  into  the  interior  of  the  vesicle  (Fig.  372,  2), 
and  progressively  until  the  invaginated  layer  of  cells  comes  in  contact 
with  the  opposite  layer  (3).  At  the  same  time  the  invagination-open- 
ing  becomes  smaller  and  smaller.  The  stage  in  development  thus 
attained  is  designated  gastrula.  The  external  layer  of  cells  is  the 
ectoblast  (or  epiblast),  the  internal  layer  the  entoblast  (or  hypoblast). 
The  opening  is  designated  the  blastopore  (or  primitive  mouth),  and 
the  central  space  the  primitive  gut  (archenteron).  In  vertebrates 
the  primitive  mouth  closes  fully  in  the  course  of  further  development. 


FIG  372.— 1-4,  Formation  of  the  hypoblast  by  imagination  of  the  blastula,  and  the  resulting  gastrula  from  amphi 
oxus  (lancet-fish) ;    -    — '-  — J    f   '-•••—   '  .     .  ..     . 

blastc 


from 


(lancet-fish);  5,  early  and,  6,  later  development  of  the  hypoblast  by  invaeination  in  petromyzon;  «, 
>pore  (primitive  mouth);  e,  epiblast;  ft,  hypoblast  in  vertical  section;  7,  the  ovum  at  this  stage  viewed 
the  side;  «,  primitive  mouth;  r,  spinal  furrow  (after  Kupffer) 


Wholly  identical  gastrula-larvag  are  found  in  some  radiates  and  worms  that 
move  about  independently  in  water  and  nourish  themselves  like  the  celenterates 
through  the  primitive  mouth. 

The  formation  of  the  hypoblast  (h)  by  invagination  in  the  situation 
of  the  primitive  mouth  is  exhibited  distinctly  in  a  similar  manner  by 
the  species  of  fish,  the  lampreys  (petromyzon).  In  Fig.  372,5  and  6  illus- 
trate these  processes  of  formation  in  diagrammatic  section,  after  Kupffer. 
It  will  be  observed  that  invagination  takes  place  from  the  primitive 
mouth  (u)  and  thus  the  epiblast  (e)  and  the  hypoblast  (h)  are  formed 
in  layers  one  upon  the  other,  the  primitive  intestinal  cavity  being 
situated  beneath  the  hypoblast.  These  formations  develop  in  much 
the  same  manner  also  in  batrachia. 

It  appears  justifiable  to  interpret  the  analogous  early  developmental 
processes  in  mammals  in  a  similar  manner.  According  to  van  Bene- 
den  the  ovule  after  segmentation  is  completed  likewise  exhibits  two 
layers  of  cells,  the  epiblast  (Fig.  373,  /,  e)t  which  lies  next  the  zona 


MATURATION    OF    THE    OVUM. 


pellucida  (Z),  and  the  hypoblast  (h).  The  primitive  mouth  (u)  here 
also  leads  to  the  central  cavity  of  the  ovum.  When  the  rabbit's  ovum 
has  reached  a  diameter  of  2  mm.  there  appears  at  one  point  the 
oval  embryonal  spot  or  embryonal  shield  (germinative  or  embryonal 
area).  The  cells  of  the  ectoderm  multiply  so  as  to  form  several  layers 
in  the  region  of  the  shield.  Careful  examination  leads  to  the  detection 
further  at  the  border  of  the  latter  of  a  small  longitudinal  area  (//,  u), 
from  which  the  duplication  of  the  cell-layer  of  the  blastula  takes  place, 
and  which,  therefore,  must  be  looked  upon  as  the  blastopore.  From 
the  blastopore  the  lower  layer  of  cells  (hypoblast)  extends  in  the  region 
of  the  embryonal  spot,  although  its  growth  continues  uninterruptedly, 
until  finally  the  entire  blastula  consists  of  two  layers.  The  site  of  the 
primitive  mouth  (//,  u)  becomes  the  so-called  primitive  streak  (///,  pr), 
which  at  first  appears  as  an  oval  elevation,  and  later  as  a  longitudinal 
furrow. 

The  primitive  streak  (like  the  primitive  mouth  in  general  in  vertebrates) 
is  a  temporary  structure.  It  is,  however,  still  present  when  the  medullary  groove 
is  formed  in  the  epiblast  (IV,  rf)  in  front  of  it;  then  it  gradually  atrophies.  This 
subject  will  later  on  be  discussed  at  greater  length.  The  primitive  streak  presents 
a  nodular  swelling  (Hensen's  nodule)  anteriorly,  and  posteriorly  a  terminal  en- 
largement. The  furrow  of  the  primitive  streak  is  also  designated  the  primitive 
groove,  its  borders  the  primitive  folds. 


FIG.  373-— /,  Ovum  of  the  rabbit,  after  van  Beneden;  Z,  zona  pellucida;  e,  epiblast;  h,  hypoblast;  u  primitive 
mouth.  //,  Ovum  of  the  rabbit  with  the  (clear)  rudimentary  embryo;  at  u  the  earliest  formation  of  the 
primitive  streak  (or  primitive  mouth)  can  be  recognized.  ///,  Ebr,  Rudimentary  embryo  from  a  somewhat 
older  rabbit-ovum;  pr,  the  primitive  streak,  with  groove.  IV,  Still  further  developed  embryo  (seventh  day); 
the  rudimentary  embryo  (Ebr)  exhibits  above  the  primitive  streak  the  first  indication  of  the  spinal  furrow 
(after  Kolliker). 


The  embryonal  area  later  on  loses  its  pear-shaped  form  and  be- 
comes dumbbell-shaped.  The  portions  of  the  germinal  vesicle  adjacent 
to  the  rudimentary  embryo  become  more  transparent,  so  that  the  latter 
is  surrounded  by  an  area  pellucida,  about  which  the  dark  embryonal 
spot,  or  opaque  area,  is  situated.  The  zona  pellucida  now  acquires 
a  villous  appearance,  becomes  covered  with  a  gelatinous  layer  and  is 
designated  the  primitive  chorion  or  prochorion. 

In  the  dog  the  zona  becomes  covered  in  the  uterus  with  a  coating  of  mucoid 
secretion.  Bonnet  was  able  to  demonstrate  that  this  tenacious  secretion  pene- 
trates into  the  lumina  of  the  glandular  ducts  and  thus  forms  gelatinous  filaments, 
which  formerly  were  erroneously  looked  upon  as  villi  springing  from  the  zona. 
They  serve  as  a  means  of  attachment  and  of  nourishment  for  the  ovum. 

Later  on  a  new  layer  of  cells  extends  from  the  primitive  streak 
between  the  epiblast  and  the  hypoblast,  namely  the  mesoblast  (Fig. 
376,  I),  which  soon  advances  over  the  region  of  the  embryonal  spot  and 
continues  to  grow  into  the  germinal  vesicle.  Blood-vessels  form,  further, 
within  the  mesoblast,  and  their  area  of  distribution  upon  the  germinal 


964 


MATURATION    OF    THE    OVUM. 


vesicle  is  known  as  the  vascular  area.  The  discovery  of  an  analogous 
formation  in  the  meroblastic  ovum,  as,  for  example,  that  of  birds, 
has  been  attended  with  no  little  difficulty.  In  such  ova  only  partial 
cleavage  takes  place,  that  is  only  the  white  yolk  in  the  region  of  the 
cock's  treadle  undergoes  division  into  many  blastomeres  in  the  process 
of  segmentation  as  a  result  of  processes  in  other  respects  analogous  to 
those  in  the  ova  of  mammals.  The  cells  thus  resulting  form  on  the 
surface  of  the  yolk  the  germinal  membrane;  and  they  later  on  become 
arranged  into  two  superposed,  thin,  circular  layers  or  germinal  plates. 
The  upper  layer  (ectoblast)  is  the  larger  and  contains  smaller,  paler 
cells.  The  lower  layer  (hypoblast),  which  at  first  is  not  arranged  con- 
tinuously, is  smaller,  and  its  cells  are  larger  and  darkly  granular. 

Observation  of  germinal  plates  during  the  first  hours  of  hatching 
permits  the  recognition  of  conditions  indicative  of  a  formative  process 
in  the  development  of  the  hypoblast  analogous  to  that  occurring  in 


FIG. 


E  ^ 

374-— A,  Germinal  plate  of  hen's  egg  in  the  first  hours  of  incubation  (after  Roller);  df,  dark  germinal  area; 

«/,  clear  germinal  area;   £*,  rudimentary  embryo;   u,  point  from  which  the  hypoblast  is  formed  by  invagina- 

tion,  or  the  blastopore  (primitive  mouth)  becomes  sickle-shaped  below  (<r).     B,  Somewhat  older  preparation; 

*"i  P"*" 

Duva 

C, 


:horda  dorsalis. 

holoblastic  ova.     A  formation  corresponding  to  the  primitive  mouth 
has  been  encountered  also  on  the  germinal  plate  of  the  bird  (Fig.  374, 
A,  u)      This  at  first  is  short  and  is  expanded  in  its  lower  area  into 
the  shape  of  a  sickle.     This  blastopore,   gradually   becoming  longer, 
levelops  into  the  primitive  streak  (B,  C,  pr),  which  undoubtedly  is 
comparable  with  that  of  mammals.     That  in  the  ova  of  birds  the  hypo- 
blast  must  likewise  be  considered  to  have  resulted  from  invagination 
the  blastopore  is  rendered  probable  by  the  study  of  a  longitudinal 
ction  of  the  two  germinal  plates  at  this  first  period.     Fig.   374  E 
represents  such  a  sagittal  section  of  the  germinal  plate  from  a  nightin- 
ihe  lower  germinal  plate  (h)  appears  to  be  pushed  out 
trom  the  blastopore  (u)  under  the  ectoblast.     Both  plates  rest  upon 
the  cavity  of  the  archenteron  (c)  filled  with  fluid 


MATURATION    OF    THE    OVUM. 


965 


Between  the  ectoblast  and  the  hypoblast  there  now  develops,  from 
the  primitive  streak,  as  a  product  of  the  cellular  hyperplasia  of  the 
ectoblast,  the  mesoblast,  which,  growing  peripherally,  insinuates  itself 
between  the  two  former.  The  three  germinal  layers  (in  birds)  in  their 
growth  arrange  themselves  according  to  size  in  such  a  manner  that  the 
uppermost  is  the  largest,  the  middle  the  next  in  size,  and  the  under- 
most the  smallest.  All  three  grow  at  the  periphery.  As  the  middle 


Transition  from  close 
to  loose  skein. 


Polar  radiation  (achromatic  substance) 


Convexity    of 
loops. 


Polar  field. 

Longitudinal    di 
vision  of  chro- 
matic  substance 


Loose  skein. 


Segmented  skein  with 
24  loops. 


Polar  radiation. 


Polar  radiation. 


Longitudinal  splitting 
of  loops. 


Polar  radiation. 
Terminal  stage  of  mother-star. 


Loops  arranged  in 
equatorial  plates. 


Polar  radiation. 


Aster. 


Polar  body. 


Connecting  threads. 


Loops. 


New  nucleus. 


Loops 


MeUikinrsis. 


Polar  body. 


Loops. 


New  nucleus. 


Completed  division. 
FIG.  375. — Stages  of  Nuclear  Division  (after  Rabl). 


layer  develops  into  vessels,  its  border  is  always  easily  recognizable 
from  the  sinus — the  future  terminal  vein.  The  border  of  the  upper 
layer  encloses  the  yellowish-white,  wavy  vitelline  area;  the  border  of  the 
middle  layer,  the  vascular  area ;  the  embryo  lies  in  a  portion  of  the 
pellucid  area  that  is  dumbbell-shaped  and  clear  as  glass.  As  all  three 
plates,  finally,  surround  the  entire  yolk,  their  borders  come  in  contact 
with  the  pole  of  the  yolk  lying  opposite  to  the  embryo. 


966  FORMATIONS    FROM    THE    EPIBLAST. 

Thus,  there  are  developed  in  all  vertebrates  three  germinal  layers. 
From  the  ectoblast  there  results  the  central  nervous  system,  the  epider- 
mal formations,  and  also  the  epithelium  of  the  organs  of  special  sense. 
From  the  hypoblast  is  formed  the  epithelium  of  the  intestinal  tract, 
including  the  cells  of  the  glands  that  result  through  evagination  from 
the  intestinal  tube.  All  of  the  other  tissues  of  the  body,  with  the  excep- 
tion of  the  parts  forming  the  vascular  system  and  the  connective- 
tissue  substances,  develop  from  the  mesoblast. 

The  cells  of  the  ectoblast,  but  particularly  those  of  the  hypoblast,  take  up 
during  development,  in  the  bird,  the  constituents  of  the  yolk  through  direct  active 
incorporation,  and  in  this  process  the  ameboid  movement  of  the  cells  plays  a  role. 
The  parts  taken  UJD  are  transformed  (digested)  within  the  cells,  and  employed 
in  the  process  of  building  up. 

The  division  of  the  cells  of  the  growing  tissues  takes  place  in  the  following  manner: 
i.  By  direct  cell-division,  in  which  first  the  nucleus  and  then  the  cell-body  breaks 
up  into  two  halves,  for  example  in  the  division  of  the  embryonal  erythrocytes 
(page  41);  2,  by  indirect  cell-division  (mitotic  division),  in  which  the  following 
processes  are  observed  in  the  cell:  (a)  The  nucleus  becomes  enlarged  and  its 
chromatin-network  increases  and  takes  on  a  definite  grouping.  There  form 
loops,  which  at  one  pole  of  the  nucleus  (polar  field)  exhibit  especially  bendings, 
and  at  the  other  (opposite  polar  field)  the  extremities  of  the  limbs  of  the  loops. 
This  is  the  stage  of  the  close  skein  or  the  spireme.  (6)  The  close  skein  is  trans- 
formed into  the  looser,  the  threads  becoming  separated.  In  this  process  part  of 
the  loops  turn  toward  one  pole,  and  part  to  the  other  (segmented  skein,  c). 
(c)  All  the  loops  move  with  their  bendings  toward  the  center;  and  there  is  thus 
formed  the  star  (first  mother-star,  d).  (d)  Meanwhile,  there  is  formed  the  achro- 
matic nuclear  spindle,  which  bears  at  each  extremity  a  polar  body,  from  which  the 
nuclear  protoplasm  passes  in  a  radiate  manner — polar  rays  (d,  e,  /) .  (e}  The  loops 
divide  lengthwise;  each  half  moves  away  from  its  fellow  (e,  /).  (/)  The  loops 
undergo  a  rearrangement — metakinesis  (e,  /),  and  form  two  equatorial  plates. 
(g)  After  atrophy  of  the  connecting  threads,  the  protoplasm  of  the  nucleus,  and 
later  also  that  of  the  cells,  undergoes  division,  and  the  network  of  both  nuclear 
halves  (dispireme,  g)  appears  as  in  the  original  form  of  the  undivided  nucleus  (a) . 

The  cell  consists  of  body,  nucleus,  and  nucleolus.  The  cell-body  forms  a  mov- 
able protoplasm,  which  appears  as  a  threadwork,  or  network,  or  honey-combwork 
in  the  midst  of  which,  in  a  softer  substance,  lie  small  granules.  The  nucleus 
possesses  a  capsule,  and  consists  of  a  nuclear  ground-substance,  in  which  (color- 
able) chromatin  and  achromatin  lie  as  enclosures.  The  nucleolus  is  a  dense 
mass  of  chromatin ;  Occasionally,  accessory  nucleoli  are  present  (Flemming's 
reticular  nodes).  Finally,  the  cell-body  contains  also  the  centrosome,  surrounded 
by  an  area,  the  actual  center  of  motion  of  the  cell,  which  also  breaks  up  in  the 
process  of  cell- division.  All  cells  are  derived  from  parent-cells;  Omnis  cellula 
ex  cellula  (Virchow).  From  cells  at  first  apparently  similar  the  elements 
of  the  different  organs  and  tissues  develop  through  transformation.  If,  therefore, 
all  tissues  are  referable  morphologically  to  a  single  form  of  primitive  cell,  it 
follows  that  the  physiological  activity  of  the  different  organs  and  tissues  must 
be  referred  to  a  single  primitive  form  of  function,  to  an  "identity  of  physiological 
activity, ' '  present  from  the  beginning.  The  proof  of  the  development  of  the  special 
activity  of  the  tissues  from  this  as  yet  un differentiated  primitive  form  of  vital 
manifestation  will,  with  certainty,  at  a  later  period  constitute  an  important  chapter 
of  the  subject  of  physiological  development. 

FORMATIONS  FROM  THE  EPIBLAST. 

Upon  the  ectoblast  there  is  formed,  in  mammals,  as  in  birds,  in  front 
of  the  primitive  streak,  and  at  a  later  period,  a  longitudinal  furrow 
(Flg- .373,  IV,  and  Fig.  374,  D),  whose  margins,  curved  anteriorly,  pass 
over  into  each  other ;  while  posteriorly  they  pass  side  by  side,  though  in 
a  somewhat  divergent  manner.  This  is  the  medullary  or  spinal  groove. 
Later  on  the  adjacent  margins,  the  medullary  or  spinal  folds  approach 
each  other  at  their  free  edges,  and  finally  join  in  the  median  line,  to 


FORMATIONS    FROM    THE    EPIBLAST. 


967 


FIG.  376. — I,  The  three  germinal  layers  of  the  ovum  of  mammals:  Z,  Zona  pellucida;  E,  epiblast;  m,  mesoblast, 
e,  hypoblast.  II,  Cross-section  of  chick  (with  six.  primitive  vertebra?)  on  the  first  day:  M,  spinal  furrow,  h, 
epidermis;  U,  primitive  vertebra;  c,  chorda  dorsalis;  S,  the  lateral  plates  divided  into  two  lamellae;  e,  hypo- 
blast.  Ill,  Cross-section  of  chick  on  the  second  day,  in  the  region  behind  the  heart:  M,  medullary  canal; 
h,  epidermis;  u,  primitive  vertebra;  c,  chorda;  w,  Wolffian  duct;  K,  ccelom;  x,  cutaneous  plate;  y,  splanch- 
nopleura;  A,  amniotic  fold;  a,  aorta;  e,  hypoblast.  IV,  Diagrammatic  representation  of  the  first  embryonal 
rudiment  in  longitudinal  section.  V,  Diagrammatic  representation  of  the  beginning  of  the  process  of  con- 
striction: r,  headfold;  D,  cavity  of  the  foregut;  S,  caudal  fold;  d,  hind-gut  cavity  in  an  early  stage  of  forma- 
tion. VI,  I  >kiKrammatic  longitudinal  section  of  the  embryo  after  constriction:  A  o,  omphalomesaraic  artery; 
V  o,  omphalomesaraic  vein;  a,  rudimentary  allantois;  A,  amniotic  fold.  VII,  Diagrammatic  longitudinal 
section  through  a  human  ovum:  Z,  zona  pellucida;  S,  serous  capsule;  r,  union  of  amniotic  folds;  A,  amniotic 
cavity;  a,  allantois;  N,  umbilical  vesicle;  m,  mesoblast;  h,  heart;  U,  primitive  gut.  VIII,  Diagrammatic 
longitudinal  section  through  the  pregnant  uterus  at  the  time  of  the  formation  of  the  placenta:  U.  muscular 
wall  of  the  uterus;  p,  mucous  membrane  of  the  same  or  true  decidua;  b,  maternal  placenta  or  serotine  decidua; 
r,  reflex  decidua;  ch,  chorion;  A,  amnion;  n,  umbilical  cord;  a,  allantois  with  urachus;  N,  umbilical  vesicle 
with  D,  the  omphalomesaraic  duct;  t,  t,  tubal  openings;  G,  cervical  canal.  IX,  Human  embryo  at  the  time 
of  the  visceral  arches  (diagrammatic) :  A,  amnion;  V,  forebrain;  M,  midbrain;  H,  hind  brain;  N,  afterbrain; 
U,  primitive  vertebra;  a,  eye;  p,  nasal  depression;  S,  Frontal  process;  y,  internal  nasal  process;  n,  external 
nasal  process;  r,  superior  maxillary  process  of  the  first  visceral  arch;  i,  2,  3,  4,  the  four  visceral  arches  with 
the  intervening  clefts;  o,  auditory  vesicle;  h,  heart  with,  e,  the  primitive  aorta,  which  divides  into  the  five 
aortic  arches;  f,  descending  aorta;  om,  omphalomesaraic  artery;  b,  the  same  artery  upon  the  umbilical  vesicle, 
B;  c,  omphalomesaraic  vein;  L,  liver  with  the  venae  advehentes  and  revehentes;  D,  gut;  i,  inferior  cava; 
T,  coccyx;  all,  allantois  with,  z,  an  umbilical  artery,  and,  x,  an  umbilical  vein. 


968  FORMATIONS    FROM    THE    EPIBLAST. 

form  a  linear  union.  A  tube  is  thus  formed  from  the  furrow,  the  medul- 
lary canal  (Fig.  376,  II,  III).  The  cells  lying  next  the  lumen  of  the 
canal  become  the  ciliated  cylindrical  epithelium  of  the  central  canal  of 
the  spinal  cord;  the  remaining  cells  produce  the  ganglia  of  the  central 
nervous  system  and  their  processes.  At  the  cephalic  portion,  the 
medullary  canal  widens  out  into  the  following  dilatations,  of  progres- 
sively diminishing  size:  the  forebrain,  prosencephalon  (rudiment  of  the 
cerebrum;  the  midbrain,  mesencephalon  (quadrigeminate  bodies);  the 
hindbrain,  metencephalon  (cerebellum) ;  and  the  afterbrain,  myelen- 
cephalon  (oblongata)  (Fig.  376.  IV and  V;  Fig.  374,  F\  Fig.  377),  which 
gradually  passes  over  into  the  spinal  cord.  Below  the  hindbrain, 
in  the  vicinity  of  the  afterbrain,  the  spinal  furrow  does  not  close,  and 
there  remains  here  an  open  passage-way  to  the  contiguous  lower  portion 


onH^  W  h!  7  of  the  Brain  of  a  Human  Embryo  (after  His).  V,  Primary  forebrain  vesicle,  v',  sec- 
ondary forebrain  or  hemisphere  vesicle;  Z,  mterbrain  vesicle;  M,  midbrain  vesicle;  H,  hindbrain  vesicle; 
crkm-afflexurelanterio?)  *  W™  medullary  canal;  Nk,  nuchal  flexure;  Bk,  pontal  flexure;  Sk, 

of  the  fourth  ventricle  (calamus  scriptorius).  At  the  caudal  extremity 
there  appears  also  a  dilatation  of  the  medullary  canal,  the  lumbar  en- 
largement. In  birds  the  spinal  furrow  remains  permanently  open  in 
this  situation,  and  forms  the  rhomboid  sinus. 

While  the  medullary  canal  develops  in  this  way,  the  primitive 
streak  gradually  atrophies,  and  finally  disappears  entirely  (Fig.  374,  F). 
The  medullary  canal  does  not  continue  in  a  straight  course,  but  it  bends 
in  several  places ;  namely  at  the  junction  of  the  spinal  cord  and  oblon- 
gata (nuchal  flexure) ;  at  the  juncture  of  the  afterbrain  and  the  hind- 
brain  (pontal  flexure) ;  finally  almost  at  a  right  angle  between  the  mid- 
brain  and  the  forebrain  (parietal  flexure).  At  first  all  of  the  brain- 
vesicles  are  without  sulci  or  gyri.  From  the  forebrain  vesicle  there 
grows  on  each  side  a  pedunculated  hollow  vesicle  (Fig.  376,  VI,  IX) 
the  primary  optic  vesicle.  The  entire  remaining  portion  of  the  epiblast 


FORMATIONS    FROM    THE    HYPOBLAST    AND    THE    MESOBLAST.          969 

furnishes  the  epidermal  layer  of  the  body,  and  is  known  as  the  horny 
layer.  The  stratum  corneum  can  be  differentiated  early  from  the  Mal- 
pighian  network:  from  the  first  arise  hairs,  nails,  feathers,  etc. 

FORMATIONS  FROM  THE  HYPOBLAST  AND  THE  MESOBLAST. 

From  the  hypoblast  there  forms  from  above  a  cordlike  arrangement 
of  cells,  which  is  placed  lengthwise  under  the  spinal  furrow — the  chorda 
dorsalis  (Fig.  376,  II,  III,  e).  In  man  it  is  relatively  thin.  It  forms  the 
foundation  of  the  spinal  column,  around  which  the  substance  of  the 
vertebras  subsequently  becomes  so  arranged  that  it  pierces  them  like 
a  thread  through  a  string  of  pearls.  After  its  formation,  the  chorda  is 
soon  surrounded  by  a  double  sheathlike  covering.  Further  formations 
from  the  hypoblast  do  not  occur  at  this  time;  it  lies  as  a  thin  layer  of 
single  cells  directly  on  the  splanchnopleure. 

While,  formerly,  the  chorda  dorsalis  was  in  general  believed  to  originate  from 
the  mesoblast,  most  observers  at  present,  incline  to  the  view  that  its  develop- 
ment takes  place  from  the  hypoblast.  The  chorda  begins  to  form  at  the  anterior 
nodular  swelling  of  the  primitive  streak,  and  grows  toward  the  head.  At  first 
it  represents  a  tube  (Kupffer's  canal,  chordal  canal)  which  opens  posteriorly  in 
the  primitive  groove,  later  breaking  into  the  yolk-cavity.  The  chorda  occurs  in 
ascidia  as  well  as  in  all  vertebrates,  although  during  their  development  it  soon 
undergoes  retrogressive  changes. 

On  both  sides  of  the  chorda,  the  cells  of  the  mesoblast  group  them- 
selves into  cubical  structures,  always  arranged  in  pairs  one  after  the 
other:  primitive  vertebra  (primitive  segments  or  somites,  Fig.  376,  II, 
u;  III,  u;  and  Fig.  374,  F,  MS).  The  first  pair  of  these  represent  the 
atlas.  At  a  later  period  a  cellular  cortical  and  a  nuclear  region  can  be 
distinguished  in  each  primitive  vertebra.  The  body  of  the  primitive 
vertebra  is  used  only  in  part  for  the  formation  of  the  later  vertebra. 

The  portion  of  the  mesoblast  that  lies  peripherally  from  the  primitive 
vertebras,  the  lateral  plates  (Fig.  376,  II,  S),  produces  through  the 
dehiscence  of  its  cell-layers  two  lame  lias,  which,  however,  remain  united 
opposite  the  primitive  vertebras  through  the  middle  plates.  The  space 
thus  resulting  within  the  lateral  plates  is  designated  the  pleuroperitoneal 
cavity  or  the  coslom  (III,  K).  The  upper  lamella  of  the  divided  lateral 
plate  is  closely  applied  to  the  ectoblast  and  is  known  as  the  musculo- 
cutaneous  plate,  somatopleure  (Fig.  376,  III,  x) ;  the  inner  layer  unites 
with  the  hypoblast,  and  is  designated  the  gut-fiber  plate  or  splanchno- 
pleure (III,  y).  On  the  opposed  surfaces  of  these  two  plates  there  de- 
velops the  flat  epithelium  of  the  large  pleuroperitoneal  cavity.  On  the 
surface  of  the  middle  plate  turned  toward  the  ccelom  there  remain 
cylindrical  cells,  the  germinal  epithelium  of  Waldeyer,  from  which  the 
oviducts  and  the  ova  are  developed. 

From  the  somatopleure,  according  to  Remak,  originate  the  skin  and  the 
musculature  of  the  trunk,  as  well  as  the  vessels;  according  to  His,  only  the 
musculature  of  the  trunk.  According  to  both  observers  the  smooth  muscle  of 
the  digestive  tract  is  derived  from  the  splanchnopleure. 

Especial  emphasis  should  be  placed  on  the  views  of  His,  who  believes  that 
the  vessels,  together  with  the  blood  and  connective-tissue  structures,  do  not 
arise  autochthonously  from  the  mesoblast,  but  that  certain  cells  wander  from 
the  margins  of  the  germinal  layers,  between  the  epiblast  and  the  hypoblast,  to 
form  the  structures  named.  They  are  not  formed  through  the  process  of  cleavage, 
but  are  derived  from  the  elements  of  the  white  yolk  lying  external  to  the  situ- 
ation of  the  embryo,  and  they  are  thought  originally  to  have  wandered  into  the 


970  HEAD-FOLD    AND    CAUDAL    FOLD. 

ovum  as  derivatives  of  the  epithelium  of  the  Graafian  follicle.  His  designates 
these  formations  parablastic,  in  contradistinction  to  the  archiblastic,  which  belong 
to  the  three  germinal  layers  of  the  embryonal  rudiment.  Waldeyer  also  believes 
in  the  parablastic  formation  of  blood,  vascular  end othelium,  and  connective  tissue, 
although  he  considers  the  material  from  which  the  latter  are  derived  as  cohesive, 
and  as  living  protoplasm  of  the  same  significance  as  the  elements  of  the  germ. 
The  doctrine  of  archiblast  and  parablast  has  recently  experienced  many  modi- 
fications. 

The  development  of  the  middle  germinal  layer  and  the  formation  of  the  organs 
derived  from  it  constitute  one  of  the  most  difficult  problems  for  investigation. 
The  work  of  recent  investigators,  particularly^  that  of  the  brothers  Hertwig,  has 
shown  that  in  the  lower  vertebrates  (amphioxus,  triton),  the  chorda  dorsalis 
and  both  walls  of  the  ccelom-cavity  result  from  evaginations  of  the  hypoblast,  as 


/  II  III 

FIG.  378.— Scheme  of  the  Formation  of  the  Chorda  and  the  Coelom  through  Evagination  of  the  Hypoblast  after  the 

Theory  of  the  Brothers  Hertwig. 

Fig.  378  illustrates  in  a  diagrammatic  way.  In  I  is  the  beginning  of  the  central 
evagination  (for  the  chorda) ;  the  two  lateral  evaginations  (for  the  walls  of  the 
ccelom)  are  still  in  free  communication  with  the  hypoblast ;  in  //  the  points  of  the 
evagination  are  narrowed ;  and  in  ///  the  chorda  (which  now  lies  below  the  medul- 
lary canal  likewise  constricted  off)  is  fully  detached  and  appears  in  cross-section  as  a 
round  body.  In  the  same  way  the  walls  of  the  coelom-cavity  have  become  de- 
tached, and  they  exhibit  their  two  plates,  the  somatopleure  and  the  splanchno- 
pleure,  and  between  the  two  the  large  body-cavity  has  expanded.  The  intestinal 
tube  and  the  body-cavity  have  thus  each  obtained  an  independent  wall.  Accord- 
ing to  many  new  investigations  both  ectoderm  and  entoderm  participate  in  the 
formation  of  the  mesoderm,  which,  in  its  turn,  is  capable  of  producing  the  most 
varied  tissues,  with  the  exception  of  the  nerves. 

FOLDING  OFF  OF  THE  EMBRYO.     FORMATION  OF  THE  HEART 
AND  THE  FIRST  CIRCULATION. 

Up  to  this  time  the  embryo  with  its  three  germinal  layers  has  occu- 
pied the  level  of  the  layers  themselves.  Now  (Fig.  376,  V)  the  cephalic 
portion  raises  itself  above  this  level  and,  becoming  free,  it  grows  more 
and  more  forward.  There  is  thus  formed  in  front  of  and  under  the  head 
an  mvagination  of  the  germinal  layers  known  as  the  head-fold  (V,  r). 
The  prominent  cephalic  portion  is  hollow  within  and  an  entrance  may  be 
gained  from  the  interior  of  the  germinal  vesicle  into  the  cephalic  cavity. 
The  latter  is  designated  the  fore-gut  cavity  (V,  D),  and  the  entrance  to 
the  anterior  intestinal  portal.  The  formation  of  the  fore-gut  through 
the  elevation  of  the  head  from  the  level  of  the  germinal  layers  occurs  in 
the  chick  as  early  as  the  second  day  (in  dogs  on  the  twenty-second  day). 
In  an  entirely  similar  manner,  although  somewhat  later  (in  the  chick 
the  third  day,  in  dogs  on  the  twenty -fourth  day),  the  analogous 
tormation  of  the  caudal  portion  takes  place,  and  in  consequence  of  which 


THE    EMBRYONIC    HEART.  971 

also  this  projects  free,  with  the  formation  of  the  tail-fold  (S)  and  the 
hind-gut  (d),  to  which  the  posterior  intestinal  portal  leads.  The  em- 
bryonal body  thus  communicates  with  the  germinal  vesicle  by  means 
of  a  pedicle  that  is  as  first  wide  open.  This  pedicle  is  known  as  the 
omphalomesenteric  or  vitellointestinal  duct.  The  saccular  vesicle 
attached  to  it  is  designated  in  mammals  the  umbilical  vesicle  (VII,  N), 
while  the  analogous  much  larger  sac  in  birds,  which  contains  nourishment 
from  the  yellow  yolk,  is  known  as  the  yolk-sac.  Toward  the  end  of  the 
third  month  of  pregnancy  the  entodermal  lining  of  the  human  umbilical 
vesicle  develops  genuine  liverlike  glandular  tissue.  The  omphalomes- 
enteric duct  becomes  in  its  further  course  narrower  and  finally  is  oblit- 
erated in  the  chick  on  the  fifth  day.  Where  the  duct  is  inserted  into  the 
abdominal  wall  there  results  the  abdominal  umbilicus ;  where  it  is  inserted 
into  the  primitive  gut  there  results  the  intestinal  navel. 

On  the  ventral  surface  of  the  fore-gut  and  the  hind-gut  there  are  points  where 
the  mesoderm  is  wanting,  and  where,  therefore,  the  epiblast  and  the  entoblast 
come  in  contact.  These  are  known  as  the  pharyngeal  and  the  cloacal  membrane. 
The  openings  for  the  formation  of  the  oral  and  the  anal  orifices  are  later  found 
in  these  situations. 

Even  before  this  process  of  constriction  takes  place  the  primitive 
heart  develops  from  that  portion  of  the  splanchnopleure  that  is  in  con- 
tact below  with  the  fore -gut,  in  the  chick  at  the  conclusion  of  the  first  day 
as  a  rhythmically  moving  point  (<m'/7«y  -^wnu^i^  of  Aristotle,  punctum 
saliens);  in  mammals  however,  much  later.  The  heart  (Fig.  376,  VI) 
develops  as  a  cellular,  hollow,  bladderlike  bud  of  the  splanchnopleure 
(originally  as  a  paired  structure).  Its  cavity  soon  dilates  and  it  grows 
into  the  ccelom  suspended  from  a  mesentery -like  duplicature  (mesocar- 
dium) :  that  part  of  the  ccelom  situated  in  the  vicinity  of  the  heart  is  now 
designated  the  cardiac  fossa  (fovea  cardiaca).  The  heart  acquires  a 
longitudinal  tubular  form,  with  its  aortic  portion  directed  anteriorly 
and  its  venous  portion  directed  posteriorly.  It  then  undergoes  a  mod- 
erate S-shaped  curvature  (Fig.  384,  i).  From  the  middle  of  the  second 
day  the  heart  in  the  chick  beats  regularly,  about  40  times  per  minute. 
At  the  anterior  (aortic)  extremity  of  the  heart,  the  aorta  originates  from 
the  bulbus  aortae;  it  bends  forward,  and,  dividing  into  two  arches 
(primitive  aortas),  it  curves  beneath  the  brain-vesicles  and  descends 
posteriorly  in  front  of  the  primitive  vertebrae.  Both  primitive  aortas 
originally  terminate  blind  at  the  caudal  extremity  of  the  embryo. 
Opposite  the  omphalomesenteric  duct  each  primitive  aorta  in  chicks 
gives  off  one,  in  mammals  several  (in  the  dog  4  or  5)  omphalomesenteric 
arteries  (Fig.  376,  VI,  Ao)  which  divide  within  the  mesoblast  upon  the 
yolk-sac,  or  the  umbilical  vesicle,  into  a  rich  network  of  vessels.  These 
unite  and,  passing  backward  (in  birds  arising  from  the  terminal  sinus 
of  the  subsequent  terminal  vein  of  the  area  vasculosa),  form  omphalomes- 
enteric veins  (Vo),  which  ascend  on  the  duct  and  empty  into  the  two 
venous  trunks  of  the  heart  by  means  of  two  branches. 

Thus  the  first  or  primitive  circulation  is  completed.  Its  pur- 
pose is  to  convey  nutritive  material  for  growth  and  oxygen  to  the 
embryo.  The  latter,  in  birds,  passes  through  the  porous  shell  of  the 
egg  from  the  air ;  the  first  is  supplied  by  the  yolk-sac  until  the  end  of 
the  incubation.  In  mammals  both  are  supplied  to  the  ovum  from  the 
vessels  of  the  uterine  mucosa.  In  birds,  on  account  of  the  consumption 


972  FURTHER  DEVELOPMENT  OF  THE  BODY. 

of  the  contents  of  the  yolk-sac  the  vascular  area  becomes  steadily 
diminished.  Finally,  toward  the  end  of  the  period  of  hatching,  the 
yolk-sac,  which  has  become  smaller,  slips  into  the  abdominal  cavity. 
Upon  the  umbilical  vesicle  of  mammals  the  circulation  usually  disappears 
at  an  early  date  and  the  vesicle  becomes  transformed  into  a  tiny  ap- 
pendage, while  the  second  circulation  develops  to  supplant  the  omphalo- 
mesenteric  circulation.  The  first  vessels  in  birds  are  formed  outside 
the  embryonal  body  in  the  area  vasculosa  as  early  as  the  last  quarter 
of  the  first  day,  even  before  the  heart  can  be  seen.  The  vessels  develop 
from  vasoformative  cells  of  the  blood-islands,  which  at  first  appear 
isolated  and  then  become  confluent,  and  whose  origin,  whether  from 
mesoblast  or  entoblast,  has  not  yet  been  determined.  At  first  solid, 
they  later  become  hollowed  out.  In  mammals  (sheep)  the  first  vessels 
also  appear  outside  the  embryo ;  the  first  blood-corpuscles  are  formed  in 
the  region  of  the  vascular  area  as  a  product  of  the  endothelium 

Within    the    area    vasculosa    of   the    chick,  there    develops    a   closer-meshed 
lymphatic  canal-system,  which  communicates  with  the  amniotic  cavity. 

FURTHER  DEVELOPMENT  OF  THE  BODY. 

The  formative  processes  still  wanting  and  necessary  for  the  typical 
development  of  the  body  are  as  follows: 

1.  The   ccelom   gradually   increases  in  extent,   and  in  consequence 
the    differentiation    between   the  body-wall    and    the  intestinal  canal 
becomes  the  more  distinct.     The  latter  moves  away  from  the  primi- 
tive vertebrae,  the  middle  plate  becoming  elongated'  to  form  the  be- 
ginning  mesentery.     The   body-wall,  which,    at    first,  still  consists  of 
the  epidermis  and  the  external  lamella  of  the  lateral  plate  (cutaneous 
plate),  undergoes  thickening,  the  primitive  muscle  growing  from  the 
muscle-plate,  and  the  primitive  bone,  together  with  the  spinal  nerves, 
from  the  primitive  vertebrae  beneath  the  epidermis  into  the  body -wall. 

2.  From  the  primitive  vertebrae  there  is  detached  a  portion  situated 
dorsally,   which  is   designated  the   muscle-plate.     The   remaining  por- 
tion  of  the  primitive  vertebra  (true  primitive  vertebra)   now  unites 
with  its  fellow  of  the  opposite  side,  both  growing  completely  around 
the  chorda  (membrana  reuniens  inferior;  in  dogs  on  the  third,  in  rabbits 
on  the  tenth  day),  and  also  enclosing  the  medullary  canal  (membrana 
reuniens   superior;    in   chicks   on   the   fourth   day).     Thus,   there   has 
taken  place  in  front  of  the  medullary  canal  a  union  of  the  primitive 
vertebral  masses  that  enclose  the  chorda  and  therefore  form  the  basis 
of    all    of    the    vertebral    bodies,    while    the    membrana    reuniens    su- 
perior, interposed   between  muscle-plates,   and  epidermis    on  the   one 
side    and    the    medullary    canal    on    the    other    side,    represents    the 
rudiment  of  the  entire  system  of  vertebral  arches,   together  with  the 
intervertebral  ligaments  between  them.     The  spinal  column  is  in  this 
membranous  stage  an  exact  reproduction  of  the  spinal  column  of  the 
cyclostomes  (lamprey).     From  the  membrana  reuniens  superior  there 
are  formed,  besides,  the  membranes  of  the  spinal  cord  and  the  spinal 
ganglia  and  nerves. 

TT   A~n  rare  cases  ^e  formation  of  the  membrana  reuniens  superior  does  not  occur. 

Under    such    circumstances    the    medullary    canal    is    covered    posteriorly    by 

the  horny  layer  (epidermis)  alone,  either  throughout  its  entire  extent,  or  only  in 

mted  areas       1  his  defect  in  development  is  known  as  spina  bifida  (at  the  head, 

cephalus) .     Failure  in  the  development  of  the  membrana  reuniens  inferior 


FURTHER  DEVELOPMENT  OF  THE  BODY.  973 

is  exceedingly  rare.     This  arrest  of  development  gives  rise  to  permanent  separa- 
tion of  the  bodies  of  the  vertebras  into  two  lateral  halves. 

The  cutaneous  plates  finally  grow  also  toward  the  middle  line  of 
the  back  and  insinuate  themselves  between  the  muscle-plates  and  the 
epidermis;  in  this  manner  the  dorsal  skin  is  formed.  In  the  mem- 
branous spinal  column  the  individual  cartilaginous  vertebras  are  formed 
successively  (in  man  between  the  sixth  and  seventh  weeks),  but  these 
do  not  at  first  possess  closed  vertebral  arches;  the  latter  close  in  man 
during  the  fourth  month.  Each  cartilaginous  vertebra,  however,  does 
not  develop  from  a  pair  of  primitive  vertebrae  (thus,  the  sixth  cer- 
vical does  not  develop  from  the  sixth  pair  of  primitive  vertebras); 
but  a  new  articulation  of  the  spinal  column  takes  place,  and 
in  such  a  manner  that  the  lower  half  of  the  preceding  and  the  upper 
half  of  the  following  primitive  vertebra  unite  to  form  the  definitive 
vertebra.  In  the  process  of  chondrification  of  the  vertebral  bodies 
the  chorda  suffers  a  reduction,  remaining  larger,  however,  in  the  inter- 
vertebral  discs.  The  body  of  the  first  vertebra  unites  with  that  of  the 
second  to  form  its  odontoid  process;  in  addition,  it  forms  the  anterior 
arch  of  the  atlas  and  the  transverse  ligament.  The  chorda  can  be  fol- 
lowed upward  through  the  ligamentum  suspensorium  dentis  to  the 
posterior  portion  of  the  sphenoid  bone. 

The  histogenetic  formation  of  cartilage  from  the  indifferent  formative  cells 
takes  place  through  multiplication  and  enlargement  of  the  cells  that  finally  become 
clear  nucleated  vesicles.  The  cement-substance  probably  originates  from  the 
union  of  the  cells  at  the  periphery  and  their  outer  portion  (parietal  substance) 
giving  off  the  intercellular  substance.  Whether  the  latter  possesses  fine  canals 
that  connect  the  interstices  of  the  cartilage  is  asserted  by  some  and  denied  by 
others.  According  to  the  statements  of  some  investigators,  the  ground-substance 
after  special  treatment  appears  to  be  made  up  of  fine  fibrils. 

3.  In  the  cervical  portion,  on  each  side,  there  develop  four  cleft- 
like  openings:  the  visceral  clefts  or  branchial  openings.  Above  the  clefts 
are  recesses  in  the  lateral  wall,  the  visceral  arches  (in  the  chick  formed 
at  the  end  of  the  third  day).  The  clefts  result  from  rupture  of  the 
fore-gut  from  within  (although,  perhaps,  this  does  not  always  take 
place  in  the  chick,  in  mammals,  and  in  man),  and  they  are  surrounded  by 
endoblastic  cells.  Upon  the  visceral  arches,  above  and  below  each 
cleft,  there  pass  on  each  side  the  aortic  arches,  of  which  there  may  be 
as  many  as  five  (Fig.  376,  IX).  These  formations  are  permanent  only 
in  fish.  In  man,  all  of  the  clefts  are  obliterated  except  the  uppermost, 
which  forms  the  auditory  canal,  the  tympanum,  and  the  Eustachian 
tube.  The  four  visceral  arches  are  for  the  greater  part  later  transformed 
into  other  formations. 

In  the  middle  line  beneath  the  forebrain  is  a  thin  point  where 
(in  the  region  of  the  pharyngeal  membrane)  an  invagination  with  an 
embankmentlike  or  craterlike  border  first  takes  place,  followed  by  rup- 
ture, and  forming  the  primitive  oral  orifice  (which  still  comprises  the 
mouth  and  the  nose  together).  Later,  a  depression  at  the  caudal  ex- 
tremity (in  the  situation  of  the  cloacal  membrane)  ruptures  into  the 
hind-gut,  forming  the  anus.  Should  this  fail  to  take  place,  atresia  ani 
results.  The  lungs,  the  liver,  the  pancreas,  the  cecum  (in  birds),  and 
the  allantois  (to  be  described  later)  develop  from  the  entoblast  and  the 
adjacent  splanchnopleure  as  diverticula  from  the  primary  intestinal 
tube.  The  extremities  appear  as  short  stumps  upon  the  trunk  at  first 
devoid  of  members. 


974  FORMATION    OF    THE    AMNION    AND    THE    ALLANTOIS. 

FORMATION  OF  THE  AMNION  AND  THE  ALLANTOIS. 

During  the  process  of  folding-off  of  the  embryo  there  results, 
first  (at  the  end  of  the  second  day  in  the  chick)  in  front  of  the  head,  a 
foldlike  elevation,  consisting  of  epiblast  and  the  outer  layer  of  meso- 
blast.  This  is  reflected  like  a  cowl  to  form  the  head-fold  for  the  cephalic 
portion  of  the  embryo  (Fig.  376,  VI,  A).  Later  and  more  slowly  there 
develops  the  caudal  fold  from  behind,  and,  finally,  also  between  these 
two  the  lateral  folds  are  formed  (Fig.  376,  III,  A).  As  all  of  these 
folds  tend  toward  the  back  of  the  embryo  they  finally  grow  together 
and  form  the  amniotic  sac  (in  the  chick  on  the  third  day).  There 
is  thus  formed  about  the  embryo  a  cavity  that  becomes  filled  with 
amniotic  fluid.  Also  in  mammals  the  amnion  develops  early  and 
in  the  same  way  as  in  birds  (Fig.  376,  VII,  A).  From  the  middle  of 
pregnancy  the  amnion  lies  in  immediate  contact  with  the  chorion, 
with  which  it  is  united  by  a  layer  of  gelatinous  tissue  (tunica  media). 

Both  the  amnion  and  the  allantois  develop  only  in  mammals,  birds,  and  rep- 
tiles, which  therefore  are  designated  also  amniota,  while  the  lower  vertebrates, 
the  anamnia,  are  without  these  structures.  The  amniotic  liquor  is  a  clear,  serous 
alkaline  fluid,  having  a  specific  gravity  of  from  1002  to  1028.  It  contains,  in 
addition  to  epithelium,  lanugo-hairs  and  from  £  to  2  per  cent,  of  fixed  solids. 
The  latter  comprise  albumin  (from  TV  to  $  per  cent.),  mucus,  globulin,  a  body  resem- 
bling vitellin,  some  grape-sugar  (cow),  allantoin,  urea,  ammonium  carbonate  (prob- 
ably transformed  from  urea) ,  sometimes  lactic  acid  and  kreatinin,  calcium  sulphate 
and  phosphates,  and  sodium  chlorid.  The  total  amount  of  fluid  at  the  middle  of 
pregnancy  is_  from  i  to  1.5  kilos;  at  the  end  of  pregnancy  0.5  kilo. 

The  amniotic  liquor  is  of  fetal  origin,  as  its  presence  in  birds  indicates,  and  it  may 
be  a  transudate  from  the  ovular  membranes.  In  mammals  the  urine  of  the  fetus 
probably  contributes  to  the  accumulation  of  the  fluid  in  the  second  half  of  preg- 
nancy. In  cattle ,  in  which  the  allantoic  and  the  amniotic  fluids  remain  permanently 
separate,  the  first  may  be  regarded  as  fetal  urine,  the  latter  as  transudate.  In 
the  presence  of  the  pathological  condition  of  hydramnios,  also  the  vessels  of  the 
uterine  mucosa  may  secrete  serum,  especially  when  there  is  stasis  in  the  distri- 
bution of  the  umbilical  vein  in  the  placenta.  The  amniotic  fluid  protects  the  fetus 
and  the  vessels  of  the  fetal  membranes  from  external  injuries;  it  affords  free 
movement  to  the  limbs,  and  thus  prevents  them  from  forming  adhesions ;  finally, 
it  is  important  during  the  act  of  parturition  for  the  dilatation  of  the  mouth  of 
the  uterus.  The  amnion  is  contractile  (in  the  chick  from  the  seventh  day  on), 
from  the  presence  of  smooth  muscle-fibers  that  develop  in  the  cutaneous  plate 
(mesodermal  portion).  Nerves  have  not  been  found. 

From  the  anterior  extremity  of  the  hind-gut  there  grows  a  vesicular 
sac,  which  appears  at  first  as  a  small  double  tubercle  and  then  becoming 
hollow  (Fig.  376,  VII,  a);  it  projects  into  the  ccelom-cavity.  This  is 
the  allantois  or  urinary  sac  (in  the  chick  before  the  fifth  day;  in  man 
during  the  second  week).  As  a  true  evagination  from  the  hind-gut, 
the  allantois  has  two  layers:  one  from  the  entoblast,  and  the  other  from 
the  splanchnopleure.  From  each  side  there  passes  upon  the  sac  the 
allantoic  or  umbilical  artery,  arising  from  the  hypogastric  artery,  and 
ramifying  upon  the  surface  of  the  sac.  The  allantois  grows  (like  a 
steadily  filling  urinary  bladder)  in  front  of  the  hind-gut  in  the  abdominal 
cavity  toward  the  umbilicus,  and  finally  out  of  this  (at  the  side  of  the 
omphalpmesenteric  duct),  together  with  its  vessels  (VII,  a),  and  it  ex- 
hibits different  relations  in  birds  and  in  mammals. 

In  birds,  the  allantois,  after  passing  out  at  the  umbilicus,  undergoes  excessive 

rth,  in  a  short  time  lining  the  entire  inside  of  the  shell  as  a  vascular  sac.      Its 

arteries,  at  first  branches  of  the  primitive  aorta,  appear  with  the  development 


HUMAN    FETAL    MEMBRANES.       PLACENTA.      FETAL    CIRCULATION.    975 

of  the  posterior  extremities,  as  branches  of  the  hypogastric  artery.  From  the 
rich  capillary  network  of  the  allantois  there  originate  two  allantoic  or  umbilical 
veins.  These  enter  the  navel  and  pass,  at  first  in  association  with  the  omphalomes- 
enteric  veins,  into  the  venous  portion  of  the  heart.  In  birds  this  allantoic  circu- 
lation (or  second  circulation)  subserves  the  purpose  of  respiration,  as  its  vessels 
maintain  an  interchange  of  gases  through  the  porous  egg-shell.  This  circulation 
gradually  assumes  the  respiratory  function  of  the  yolk-circulation;  this  is  neces- 
sary, because  the  yolk-sac,  steadily  decreasing  in  size,  no  longer  presents  a  suffi- 
ciently large  respiratory  surface.  Toward  the  end  of  the  period  of  hatching  the 
bird  can  breathe  and  cry  within  the  shell,  a  sign  that  the  respiratory  function  of 
the  allantois  is  taken  up,  at  least  in  part,  by  the  lungs.  The  allantois  is  further- 
more the  excretory  organ  for  the  urinary  constituents.  Especially  in  mammals 
the  excretory  ducts  of  the  primitive  kidneys,  the  Wolffian  or  Oken  ducts,  empty 
into  the  cavity  of  the  allantois  (in  birds  and  snakes,  which  possess  a  cloaca,  they 
empty  into  the  posterior  wall  of  the  cloaca).  The  primitive  kidney,  consisting 
of  many  glomeruli,  discharges  its  secretion  through  the  Wolffian  duct  into  the 
allantois  (in  birds  into  the  cloaca) ;  and  the  secretion  passes  by  way  of  the  allan- 
tois through  the  navel  into  the  peripheral  portion  of  the  urinary  sac.  Remak 
found  in  the  allantoic  contents,  ammonium  and  sodium  urates,  urea,  allantoin, 
grape-sugar,  and  salts.  From  the  eighth  day  on,  the  allantois  of  the  chick  is 
contractile  from  the  presence  of  fibrillar  cells  that  are  derived  from  the  splanch- 
nopleure.  Lymphatic  vessels  accompany  the  arterial  branches. 

In  mammals  and  in  man,  the  relation  of  the  allantois  is  somewhat 
different.  From  the  first  part,  the  urinary  bladder  is  formed;  from  the 
vertex  of  this  the  urachus,  at  first  still  open,  passes  as  a  tube  out  through 
the  navel  (Fig.  376,  VIII,  a). 

The  blind  sac  of  the  allantois,  which  is  situated  outside  the  abdomen, 
is  in  some  animals  filled  with  a  fluid  resembling  urine.  In  man,  how- 
ever, this  sac  atrophies  in  the  course  of  the  second  month.  The  vessels 
alone  remain  and  these  apparently  lie  in  the  splanchnopleural  portion 
of  the  allantois.  In  some  animals  the  allantoic  sac  continues  to  grow, 
without  undergoing  atrophy,  and  then  conveys  from  the  bladder  through 
the  urachus  an  alkaline,  cloudy  fluid  that  contains  some  albumin,  sugar, 
urea,  and  allantoin.  The  relations  of  the  allantoic  vessels  will  be 
described  in  connection  with  the  fetal  membranes. 

HUMAN  FETAL  MEMBRANES.    PLACENTA.    FETAL  CIRCULATION. 

When  the  fecundated  ovum  gains  entrance  into  the  uterus,  it  be- 
comes surrounded  by  a  particular  membrane,  which  William  Hunter 
described  as  the  deciduous  membrane,  because  it  is  expelled  in  the  act 
of  parturition.  A  distinction  is  made  with  regard  to  the  basilar  or  true 
decidua  (Fig.  376,  VIII,  p),  which  is  nothing  else  than  the  thickened,  hy- 
peremic,  spongy  endometrium,  loosely  attached  to  the  uterine  wall.  From 
this  there  develops  an  especial  formation  around  the  ovum,  which 
receives  the  latter  as  in  the  pocket  of  a  swallow's  nest;  this  thinner 
membrane  is  known  as  the  capsular  decidua  or  decidua  reflexa  (VIII,  r). 
Between  the  second  and  the  third  month  there  is  still  a  space  in  the 
uterus  outside  of  the  decidua  reflexa,  but  in  the  fourth  month  the  entire 
cavity  is  occupied  by  the  ovum  and  the  decidua.  At  one  point  the 
ovum  is  thus  applied  directly  to  the  endometrium  (basal  or  true  de- 
cidua}; but  in  its  greatest  extent,  however,  it  is  in  contact  with  the 
decidua  reflexa.  The  first  layer  forms  later  the  placenta. 

The  decidual  swelling  and  softening  of  the  endometrium  begins  in  the  mucosa 
of  the  tubes  of  the  cervical  canal ;  in  the  third  month  the  membrane  is  from  4  to  7 
mm.  thick,  in  the  fourth  month  only  from  i  to  3  mm.,  and  it  is  devoid  of  epithelium, 
rich  in  blood- vessels,  and  has  lymph-spaces  around  the  glands  and  vessels;  its  spongy 


976      HUMAN   FETAL  MEMBRANES.      PLACENTA.      FETAL  CIRCULATION. 

tissue  contains  large  round  cells  (decidual  cells),  which  in  the  depth  are  often 
transformed  into  fibrillar  and  spindle-shaped  cells;  in  addition,  leukocytes  are 
present.  The  uterine  glands,  which,  at  the  beginning  of  pregnancy,  are  enor- 
mously developed,  undergo  a  transformation  between  the  third  and  the  fourth 
month  to  large,  noncellular  dilated  tubes.  In  the  last  months  these  become 
indistinct  and  their  epithelium  (which,  according  to  Friedlander,  Lott,  and  Hen- 
nig  was  originally  ciliated),  disappears  progressively  toward  the  depth. 

The  capsular  decidua,  much  thinner  than  the  true  decidua,  is  devoid  of  epi- 
thelium and  also  of  vessels  and  glands  from  the  middle  of  pregnancy.  Toward 
the  end  of  pregnancy  both  deciduas  unite  completely  with  each  other. 

The  basilar  decidua  and  likewise  the  uterine  placenta  consist  of  a  compact 
layer  (pars  caduca) ,  which  is  detached  during  labor,  and  of  a  deeper  spongy  layer, 
in  which  the  process  of  detachment  takes  place  and  of  which  a  portion  remains 
upon  the  surface  of  the  muscularis  (pars  fixa) .  From  the  latter  the  regeneration 
of  the  new  mucosa  after  labor  takes  place.  Also  the  tubes  exhibit  during  preg- 
nancy hyperplasia  of  the  mucosa  and  of  the  muscularis. 

The  ovum  reaches  the  endometrium  as  a  vesicle  without  villi.  The 
mucosa  has  become  softened  and  hyperemic,  and  the  ovum  sinks  into 
its  tissue,  quickly  to  become  completely  encapsulated.  In  the  basal 
decidua  there  form  lacunar  maternal  blood-passages,  which  undergo 
progressive  enlargement  With  the  formation  of  the  amnion,  there 
occurs,  after  its  closure,  the  production  from  the  epiblast  of  a  special 
entirely  closed  vesicle,  which  passes  over  the  embryo,  the  amnion  and 
the  umbilical  vesicle,  and  thus  lies  next  to  the  primitive  chorion ;  this 
is  the  serous  capsule  (Fig.  376,  VII,  S),  which  applies  itself  closely  to 
the  chorion.  The  allantois,  rich  in  vessels,  passes  out  of  the  navel,  and 
lies  directly  upon  the  ovular  membrane;  its  vesicle  atrophies  about 
the  second  month  in  man,  but  its  vascular  layer  grows  rapidly  and 
lines  the  entire  interior  of  the  ovular  cavity,  where  it  can  be  found  on 
the  eighteenth  day.  From  the  fourth  week  the  vessels,  together  with 
a  connective-tissue  framework,  form  many  intricately  branching  villi  t 
while  the  original  ovular  membrane  (prochorion  or  primitive  chorion) 
disappears  (in  dogs  it  is  absorbed  and  serves  for  nourishment).  There 
is  thus  reached  a  stage  of  general  vascularization  of  the  chorion;  the 
derivative  of  the  zona  pellucida  is  now  replaced  as  the  ovular  mem- 
brane by  the  villous  vascular  layer  of  the  allantois,  which  is  covered 
by  the  cells  of  the  serous  capsule  (derived  from  the  epiblast).  The 
chorionic  villi  grow  downward  in  the  direction  toward  the  decidual 
vascular  spaces.  The  villi  are  separated  from  the  vascular  space  by 
two  layers  of  specialized  cells:  the  chorionic  epithelium,  or  the  layer 
of  Langhans  (derived  from  the  fetal  ectoderm),  and  a  second  layer 
designated  syncytium,  whose  cells  with  large  nuclei  and  indefinite 
outline  are,  according  to  most  recent  investigators,  derived  from  trans- 
formed uterine  epithelium.  In  the  protoplasm  of  the  latter  vacuoles 
appear  and  the  cilia  atrophy  when  the  existing  spaces  are  filled  with 
blood.  The  ovum  adheres  to  the  syncytium  after  the  disappearance 
of  the  zona  pellucida.  The  stage  of  general  vascularization  continues, 
however,  until  the  third  month;  at  that  time  the  vegetation  of  the 
vascular  villi  ceases  upon  the  entire  ovular  membrane  that  is  in  relation 
with  the  decidua  reflexa.  On  the  other  hand,  those  villi  of  the  chorion 
that  are  in  direct  contact  with  the  decidua  vera  become  larger  and  more 
branched.  There  thus  results  the  distinction  between  the  chorion 
laeve  and  the  chorion  frondosum. 

The  chorion  laeve,  which  has  a  connective-tissue   stroma  and  is  covered  by  a 
epithelium,  possesses  besides  at  great  intervals  diminutive  villi 


HUMAN  FETAL  MEMBRANES.      PLACENTA.      FETAL    CIRCULATION.      977 

that  pass  to  the  decidua  reflexa.     Between  the  chorion  and  the  amnion  there  is  a 
gelatinous  layer  (membrana  intermedia)  of  immature  connective  tissue. 

The  large  villi  of  the  chorion  frondosum  (Fig.  379)  penetrate  more 
deeply  into  the  uterine  mucosa  and  first  of  all  into  the  ducts  of  the  glands, 
like  roots  into  loose  soil.  According  to  Selenka  this  penetration  takes 
place  from  the  first  week.  From  the  syncytial  covering  of  the  villi 
there  arise  in  especially  large  number  between  the  second  and  the  third 
month  cell-buds,  which  are  probably  related  to  the  nourishment  of 
the  embryo.  In  the  further  penetration  of  the  villi  through  the  ducts 
of  the  glands  they  make  their  way  through  the  walls  of  the  large  contigu- 
ous blood-vessels,  which  in  structure  are  similar  to  the  capillaries,  so 
that  the  villi,  bathed  in  the  maternal  blood  (uterine  vessels),  float  in 
these  enormous  decidual  capillaries — the  so-called  intervillous  spaces 
(Fig.  376,  VIII,  b).  The  villi  within  the  blood-spaces  are  covered  by 
the  epithelium  of  the  latter. 

Some  villi  that  have  no  epithelium  unite  by  means  of  bulbous  ex- 
tremities with  the  tissue  of  the  uterine  placenta  and  thus  form  adherent 
villi ;   a  means  of  firm  union.     In 
this  way  the  'placenta   is    formed; 

Q    HictinrH-irvn    ic   rnarlp   "hpl-wppn    thp  btrorna  and  Lateral  buds    Epithelium  of 

^LWCt  capillaries  of  Of  the  villi.          the  villi. 

fetal  placenta,  which  includes  the 
entire  mass  of  villi,  and  the  uter- 
ine or  maternal  placenta,  the  por- 
tion of  the  endometrium  in 
relation  with  the  ovum,  which 
is  especially  rich  in  vessels  at 
this  point.  The  two  parts  are 
not  separable  even  at  the  time  of 
birth.  Venous  maternal  vessels 
of  considerable  size  course  around 
the  border  of  the  placenta,  con- 
stituting the  marginal  sinus.  The  Vascular  tnmi 
placenta  is  the  nutritive  and  res- 

•  £    ,  1         £    ,  1   •    1  FlO.  370- — Isolated  Portion  of  Villi  from  a  Human 

piratory  organ  of  the  fetus,  which  Placenta, 

obtains    the     necessary     material 
through  endosmosis  from  the  ma- 
ternal blood-spaces  through  the  coverings  and  vessel-walls  of  the  villi,  in 
which  the  fetal  blood  circulates. 

Between  the  placental  villi  there  is  a  clear  fluid  that  contains  numerous  small, 
albuminoid  globules  and  is  designated  uterine  milk  (abundant  in  the  cow) ;  it  is 
believed  to  originate  from  degeneration  of  decidual  cells.  It  is  thought,  together 
with  the  blood,  to  take  part  in  the  process  of  nutrition. 

The  investigations  of  Walter  have  shown  that  when  pregnant  animals  are 
poisoned  with  strychnin,  morphin,  veratrin,  curare,  and  ergotin,  these  substances 
cannot  be  demonstrated  in  the  fetus.  Certain  other  chemical  substances,  for 
example  phosphorus,  potassium  chlorate,  potassium  bromid,  potassium  iodid, 
arsenic,  mercury,  alcohol,  phenol,  morphin,  and  methylene-blue  do,  however, 
pass  over  to  the  fetus.  Some  substances  pass  also  from  the  fetus  to  the  maternal 
body.  An  examination  of  the  placenta  shows  that  its  villi  are  grouped  in  in- 
dividual sections  of  considerable  size,  between  which  are  furrow-like  indentations. 
These  individual  complexes  may  be  compared  with  the  cotyledons  of  lower 
animals. 

The  position  of  the  placenta  is.  as  a  rule,  upon  the  anterior  or  posterior  uterine 
wall,  less  commonly  at  the  fundus  uteri,  or  laterally  in  front  of  or  beneath 
a  tubal  opening  (lateral  placenta)  or  in  front  of  the  internal  orifice  of  the  uterus 
62 


978      HUMAN  FETAL  MEMBRANES.      PLACENTA.      FETAL    CIRCULATION. 

(placenta  prasvia).  The  last  position  is  a  dangerous  one,  because  rupture  of  the 
vessels  at  birth  may  cause  death  of  the  mother  from  hemorrhage.  Implantation 
of  the  ovum  in  the  cervical  canal  is  extremely  rare. 

The  umbilical  cord  may  be  inserted  either  into  the  center  of  the  placental 
disc  (central  insertion)  or  more  toward  the  border  (marginal  insertion) ;  or  the 
cord  may  be  attached  to  the  chorion  laeve,  so  that  the  vessels  must  pass  to  the 
placenta  through  the  thin  chorion  laeve  (velamentous  insertion).  Rarely  there 
is  an  accessory  placenta  separated  from  the  placenta  proper  (placenta  suc- 
centuriata).  Kolliker  designates  as  marginate  placenta  one  that  has  villi  only  at 
its  center.  If  the  placenta  consists  of  two  halves  it  is  known  as  duplex  or  bipartite 
(constant  in  the  apes  of  the  old  world). 

The  umbilical  cord  (mature,  from  48  to  60  cm.  long  and  from  n 
to  1 8  mm.  thick)  is  covered  by  the  amniotic  sheath.  The  vessels  make 
about  40  spiral  turns  (beginning  after  the  middle  of  the  second  month) 
passing  from  the  embryo  from  left  to  right  toward  the  placenta:  they 
consist  of  two  arteries  with  a  well-developed  muscular  coat  and  one 


FIG.  380.— Section  through  the  Uterus  and  the  Attached  Placenta  at  the  Thirtieth  Week  (after  Ecker):  a,  root  and 
insertion  of  the  umbilical  cord;  b,  amniotic  covering  of  the  umbilical  cord;  c,  chorion;  d,  d,  fetal  portion  of 
the  placenta;  e,  e,  uterine  wall;  /,  /,  villous  radiation  forming  the  framework  of  the  fetal  placenta;  g,  g,  de- 
cidua;  *,  h,  processes  of  the  decidua  penetrating  into  the  fetal  placenta;  i,  L  branches  of  the  uterine  artery 
tp,  an  artery  entering  the  placenta:  k,  k,  k,  k,  uterine  veins. 

(left)  umbilical  vein.  Both  arteries  anastomose  in  the  placenta.  In 
addition,  the  cord  contains  the  continuation  of  the  urachus,  the  ento- 
dermal  portion  of  the  allantois  (Fig.  376,  VIII,  a),  which,  persisting 
until  the  second  month,  is  often  atrophied  later.  The  omphalomesen- 
tenc  duct  can  still  be  dissected  at  the  time  of  birth  near  the  umbilical 
vesicle  as  a  filamentous  pedicle  (VIII,  D)  of  the  umbilical  vesicle  (N)  that 
persists  and  as  a  rule  is  situated  beyond  the  placental  border.  The  ves- 
icle contains  in  its  interior  small  villi,  squamous  epithelium,  and  the 
obliterated  vessels  of  the  first  circulation.  Persistent,  though  diminu- 
tive omphalomesenteric  vessels  are  rare.  Wharton's  jelly,  a  gelatinous 


HUMAN  FETAL  MEMBRANES.      PLACENTA.      FETAL  CIRCULATION.      979 

connective  tissue,  surrounds  all  of  these  parts;  it  contains  connective- 
tissue  fibrils,  connective-tissue  corpuscles  and  lymphoid  cells,  even 
elastic  fibers.  The  gelatinous  substance  contains  mucin.  Numerous 
lymph-channels,  lined  with  endothelium,  traverse  the  jelly;  lymph- 
vessels  and  blood-vessels  are  absent.  Nerves  are  found  from  3  to  8  or 
ii  cm.  from  the  navel. 

The  jelly  contains  two  forms  of  mucin,  like  that  of  the  tendons,  also  globulin 
(myosin?)  and  albumin. 

The  fetal  circulation  that  exists  after  the  development  of  the  allan- 
tois  pursues  the  following  course:  the  blood  of  the  fetus  passes  by  way 
of  the  two  umbilical  arteries  (from  the  hypogastric)  through  the  um- 
bilical cord  to  the  placenta,  where  the  arteries  break  up  into  the  capil- 
laries of  the  placental  villi.  Returning  from  these  the  blood  collects 
in  the  umbilical  vein  (its  color  is  scarcely  a  little  brighter  as  compared 
with  that  of  the  venous  blood  in  the  umbilical  arteries).  The  um- 
bilical vein  (Fig.  387,  3,  u^  turns  upward  from  the  navel  and,  passing 
under  the  border  of  the  liver,  it  anastomoses  with  the  portal  vein  (a) 
and  continues  as  the  ductus  venosus  of  Arantius  to  the  inferior  vena 
cava,  which  then  conveys  the  blood  to  the  right  auricle.  From  here 
the  Eustachian  valve  and  the  tubercle  of  Lower  (Fig.  384,  6,  tL)  deflect 
most  of  the  blood  through  the  foramen  ovale  into  the  left  auricle,  from 
which,  on  account  of  the  presence  of  the  valve  of  the  foramen  ovale,  it 
cannot  flow  back  into  the  right  auricle.  From  the  left  auricle  the  blood 
passes  through  the  left  ventricle,  the  aorta  and  the  hypogastric  artery 
back  into  the  umbilical  arteries.  The  blood  of  the  superior  vena  cava  in  the 
fetus,  by  reason  of  its  peculiar  entrance,  passes  from  the  right  auricle 
into  the  right  ventricle  (Fig.  384,  6,  Cs).  From  here  it  enters  the 
pulmonary  artery  (Fig.  384,  7,  p),  which  conveys  it  into  the  aorta 
through  its  prolongation,  the  ductus  arteriosus  Botalli  (J5),  which 
empties  into  the  aortic  arch.  Only  a  little  blood  passes  by  way  of  the 
small  branches  of  the  pulmonary  artery  (1,2)  through  the  lungs.  The 
course  of  the  blood  makes  it  clear  that  the  head  and  the  upper  extremities 
are  supplied  with  purer  blood  than  is  the  remainder  of  the  trunk,  which 
also  receives  an  admixture  of  the  blood  from  the  superior  vena  cava. 
After  birth  the  umbilical  arteries  are  obliterated,  and  become  the 
lateral  ligaments  of  the  bladder;  their  lower  portion,  however,  persists 
as  the  superior  arteries  of  the  bladder.  The  umbilical  vein  also  is 
obliterated  and  becomes  the  round  ligament;  and  likewise  the  ductus 
venosus  of  Arantius.  Finally  the  oval  foramen  closes,  and  the  ductus  arter- 
iosus Botalli  becomes  obliterated  to  form  the  ligamentum  arteriosum. 

The  relation  of  the  fetal  membranes  in  multiple  pregnancies  is  as  follows: 
(i)  In  the  presence  of  twins  there  are  two  entirely  separate  ova,  with  two  placentas 
and  two  reflex  deciduas.  (2)  Two  entirely  separate  ova  have  but  one  reflex 
decidua,  the  placentas  becoming  adherent,  while  their  vessels  are  separate.  The 
chorion  is  double,  but  not  separable  into  two  lamellae  at  its  surface  of  contact. 
(3)  When  there  are  one  reflex  decidua,  one  chorion,  one  placenta,  two  umbilical 
cords,  and  two  amnia,  the  vessels  anastomose  in  the  placenta,  and,  therefore, 
the  central  stump  of  the  umbilical  cord  of  the  first  born  of  twins  should  always 
be  tied.  Under  such  circumstances  there  has  been  either  one  ovum,  with  a  double 
yolk,  or  two  germinal  vesicles  in  one  yolk;  or  it  must  be  assumed  that  two  sepa- 
rate ova  have  subsequently  united,  with  absorption  of  the  contiguous  parts  of 
the  chorion.  (4)  When  the  conditions  just  described  are  present,  except  that 
there  is  but  one  amnion,  they  are  due  to  the  formation  of  two  embryos  in  the 
same  germinal  area  of  the  same  germinal  vesicle. 


980  CHRONOLOGY  OF   HUMAN  DEVELOPMENT. 

Brief  mention  should  be  made  here  of  the  formation  of  the  fetal  membranes 
in  animals,  which  has  been  followed  since  the  time  of  Home,  Blainville,  H. 
Milne-Edwards,  Owen,  and  others,  in  the  classification  of  mammals. 

1.  The  oldest  mammals  have  no  placenta  or  allantoic  vessels  at  all:    these 
are  the  mammalia  implacentalia,  namely  marsupials   and  monotremata    (duck- 
bills and  echidna).     In  addition  to  a  serous  capsule  and  an  amnion  devoid  of 
villi,  these  animals  have  only  a  large  yolk-sac  which  contains  vessels,  but  which 
never  undergoes   placental   formation.     The   allantois   remains   rudimentary    (in 
the  kangaroo- bear  it  becomes  larger,  and  together  with  the  yolk-sac,  serves  as  a 
respiratory  organ).      (In  the  oviparous  monotremata  the  ovum  develops  outside 
the  maternal  body.) 

2.  The    second    group    includes    the    mammalia    placentalia.     Among    these: 
(a)    the  mammalia  nondeciduata    possess   only  chorionic  villi    (supplied    by  the 
allantoic  vessels),  which  project  into   depressions  in   the   uterine   mucosa,   from 
which  they  retract  during  parturition   (placenta  diffusa,  for  example  pachyder- 
mata,    cetacea,   solidungula,   camelida).      The  umbilical    vesicle,   which,    at    the 
earliest  period,  contains   vessels,  subsequently  undergoes   a   marked  involution, 
in  the  different  groups  of  animals,  into  manifold  modifications.     In  the  ruminants 
the  large  villi  are  arranged  in  groups,  and  they  grow  into  the  greatly  hypertro- 
phied  rolls   of  mucosa    (cotyledons)    corresponding  to   the  uterine  glands,  from 
which  they  retract  at  birth.     The  ovum  is  for  a  long  time  spindle-shaped.      (6) 
The  mammalia  deciduata  form  such  an  intimate  union  between  the  chorionic  villi 
and  the  endometrium  that  the  corresponding  portion  of  the  latter  must  be  thrown 
off  at  birth.     Here,  the  placenta  is  either  girdle-shaped   (placenta  zonaria),  as 
in  carnivora,  pinnipedia,  elephant,  hyrax;  or  it  is  disc-shaped  (placenta  discoidea), 
for  example,  in  apes,  insectivora,  rodents,  alipeds,  and  edentates. 

The  same  placental  formation  as  occurs  in  man  is  found  in  the  anthropoid 
apes,  but  in  none  of  the  others. 

Certain  variations  occur  in  different  animals  in  detail  with  reference  to  the 
formation  of  the  fetal  membranes.  In  rabbits  the  umbilical  vesicle  also  is  greatly 
expanded,  and  the  large  omphalomesenteric  vessels  participate  in  the  formation 
of  the  placenta  through  the  development  of  a  yolk-sac  placenta.  Also  in  guinea- 
pigs  (which,  remarkably,  have  the  three  germinal  layers  in  a  reverse  order,  the 
epiblast  within,  so  that  in  the  folding-off  of  the  embryo,  the  latter  sinks  into 
the  interior  of  the  umbilical  vesicle)  the  omphalomesenteric  vessels  play  a  prom- 
inent part  in  the  formation  of  the  placenta.  In  some  carnivora  (cats),  the  um- 
bilical vesicle  is  provided  with  vessels  until  the  time  of  birth.  It  is  to  be  noted, 
finally,  that,  in  the  uterus  of  the  smooth  shark  (mustela  laevis)  a  yolk-sac  placenta 
is  formed. 

CHRONOLOGY     OF     HUMAN     DEVELOPMENT.       FETAL     MOVE- 
MENTS. 

Development  in  the  First  Month. — The  youngest  ovum  is  described  by  Hub. 
Peters.  It  had  a  diameter  of  i. 6X0. 8X0. 9  mm.,  and  consisted  of  a  vesicle  about 
three  days  old.  The  small  villi  had  already  a  covering  of  two  layers  of  cells. 
It  is  the  only  observed  ovum  aroundwhich  the  capsular  deciduahad  not  yet  closed. 
At  the  point  of  attachment  of  the  ovum  to  the  uterine  mucosa,  there  were  large 
blood-lacunas,  in  which  the  ovum  appeared  embedded. 

Ova  of  from  six  to  eight  days  have  been  described  by  Merttens  and  Siegen- 
beck  van  Heukelom.  They  possess  small  short  villi  covered  by  a  double  layer 
of  cells;  an  outer  layer  of  large  cells  (syncytium),  derived  from  the  uterine  epi- 
thelium, and  a  subjacent  layer,  formed  from  the  ectoderm— cellular  layer  of  Lang- 
hans.  An  ovum  seven  or  eight  days  old  was  3.7  X  4  mm.  in  size;  the  villi  already 
.mail  ramifications.  From  the  twelfth  to  the  thirteenth  day:  (5.5  mm.  and 
3.3  mm.  in  diameter)  there  exists  a  simple  germinal  vesicle,  which,  at  one  point, 
contains  the  germinal  area  consisting  of  two  layers  of  cells.  Ova  from  the 
nrteenth  to  the  sixteenth  day  have  a  diameter  of  from  5  to  6  mm.,  with  simple 
cylindrical  villi,  or  are  provided  with  bulbous  processes  from  the  base  to  the  apex. 
I  he  youngest  ovum  of  Allen  Thomson  he  estimated  to  be  about  fifteen  days  old. 
t  was  13.2  mm.  long,  oval,  and  provided  with  villi;  the  germinal  vesicle  was 
2.2  mm.  (abnormally  small),  the  rudimentary  embryo  2.2  mm.  with  a  spinal  furrow 
and  spinal  ridges,  projecting  beyond  the  vesicle  at  each  extremity;  the  rudimen- 
,ary  heart  was  present  (and  the  amnion?).  A  somewhat  older  ovum  studied  bv 
the  same  investigator  was  6.6  mm.  long,  with  short,  thin  villi,  and  a  large  germinal 


CHRONOLOGY  OF  HUMAN  DEVELOPMENT.  981 

vesicle,  from  which  the  embryo  (2.2  mm.),  with  a  closed  medullary  canal,  had 
begun  to  be  constricted  off. 

There  now  follows  the  stage  in  which  the  formation  of  the  allantois  appears. 
It  is  at  present  a  much-disputed  point  whether  in  man  a  free  allantoic  vesicle, 
growing  from  the  navel,  exists  or  not.  The  youngest  embryo  that  bears  upon 
this  point  has  been  examined  by  v.  Preuschen  and  the  author.  In  the  fresh  state, 
this  measured  3.78  mm.  in  length;  it  was  divided  into  sections  and  thoroughly 
studied.  The  brain-vesicles  were  indicated;  the  organs  of  special  sense  were 
wanting;  the  ganglia  in  the  cephalic  region  were  visible.  The  visceral  arches  were 
visible  as  thickenings  in  cross-section,  but  not  yet  isolated;  the  visceral  clefts, 
the  mouth,  and  the  anus  were  absent.  The  sella  turcica  was  in  process  of  forma- 
tion. Heart,  lungs  and  liver  were  in  their  earliest  form.  The  umbilical  vesicle 
(torn)  was  apparently  still  provided  with  a  wide  opening.  The  allantois  was 
distinct  as  a  free  vessel  outside  of  the  abdomen;  its  lamella  from  the  mesoderm 
was  yet  without  vessels.  The  extremities  were  entirely  absent.  The  chorda 
dorsalis  was  indicated,  and  on  either  side  the  primitive  vertebral  masses. 
A  free  projecting  allantoic  vesicle  has  also  been  described  in  embryos  by  W. 
Krause  and  Bruch,  but  these  were  older. 

An  ovum  of  from  the  fifteenth  to  the  eighteenth  day  has  been  described  by 
Coste;  it  was  13.2  mm.  long;  the  villi  were  small,  and  slightly  branched ;  the  embryo 
was  4.4  mm.  long,  of  curved  form,  with  a  moderately  thickened  cephalic  portion. 
Amnion,  umbilical  vesicle  (with  a  large  omphalomesenteric  duct),  and  allantois 
were  fully  developed,  the  last  already  adherent  to  the  serous  covering.  The 
S-shaped  heart,  lying  in  the  cardiac  cavity,  exhibits  a  cavity  and  the  bulb  of  the 
aorta,  but  no  ventricles  or  auricles.  The  visceral  arches  and  clefts  are  indicated, 
but  the  latter  are  not  yet  broken  through.  Upon  the  umbilical  vesicle  the  first 
circulation  of  the  two  omphalomesenteric  arteries  is  developed;  the  fol ding- 
off  is  only  moderately  advanced;  the  duct  is  still  widely  open;  two  primitive 
aortas  pass  in  front  of  the  primitive  vertebrae.  The  allantois,  adherent  to  the 
fetal  membranes,  possesses  its  vessels.  The  two  omphalomesenteric  veins, 
united  with  the  two  umbilical  veins,  empty  into  the  lowermost,  venous  portion 
of  the  heart.  The  mouth  is  in  process  of  formation.  The  extremities  and  organs 
of  special  sense  are  wanting;  the  Wolffian  bodies  are  probably  present.  Similar 
descriptions  have  recently  been  made  by  His,  although  the  length  of  the  embryo 
was  somewhat  less. 

There  now  follows  a  stage  wherein  all  of  the  visceral  arches  are  indicated, 
and  the  clefts  are  broken  through.  The  midbrain  forms  the  highest  point  of  the 
brain;  the  two  auricles  appear  in  the  heart.  The  communication  with  the  um- 
bilical vesicle  is  still  pretty  free.  The  embryo  is  from  2.6  mm.  to  3.3  or  4  mm.  long. 
The  head  undergoes  a  deflection  to  the  side.  At  a  still  later  period  there  appear 
on  the  brain  the  parietal  and  the  nuchal  curvature;  the  hemispheres  appear  more 
distinct;  the  entrance  to  the  umbilical  vesicle  becomes  constricted,  the  rudiment- 
ary liver  is  discernible;  and  the  extremities  are  still  absent.  In  addition  to  the 
embryo  of  His  one  of  the  twentieth  day  described  by  Johannes  Miiller  belongs 
here.  The  ovum  was  between  15.2  by  17.6  mm.  in  size;  the  embryo  from  5  to 
6  mm.  long;  the  umbilical  cord  1.3  mm.  thick.  The  umbilical  vesicle  was  in 
free  communication  with  the  bowel.  The  amnion  surrounded  the  embryo  and 
formed  a  sheath  for  the  umbilical  cord.  The  visceral  arches  and  clefts  were 
present;  and  behind  them  the  projecting  heart-tube;  the  extremities  were  want- 
ing. 

Third  week  (R.  Wagner):  The  ovum  measured  13  mm.,  the  embryo  from  4  to 
4.5  mm.,  the  umbilical  vesicle  2.2  mm. ;  the  bowel  was  almost  entirely  closed.  Three 
visceral  clefts,  the  Wolffian  bodies,  the  first  rudiments  of  the  extremities,  three  brain- 
vesicles,  and  the  auditory  vesicles  were  present.  A  similar  embryo  described  by 
Hensen  should  be  included  here.  Twenty-first  day  (Coste):  The  nasal  pits,  the 
buccal  orifice,  the  eyes,  the  auditory  vesicles,  four  visceral  arches  and  the  mouth 
(toward  which  the  frontal  and  the  superior  maxillary  process  grow)  were  especially 
marked;  the  heart  with  two  ventricles  and  two  auncles  and  the  vessels  of  the 
umbilical  vesicle  were  present. 

End  of  the  First  Month. — The  embryos  of  from  twenty-five  to  twenty-eight 
days  are  characterized  by  the  distinct  pedunculation  of  the  umbilical  vesicle 
ancl  by  the  definite  appearance  of  the  extremities.  The  length  of  the  ovum  is 
17.6  mm.;  of  the  embryo  from  8  to  n  mm.,  of  umbilical  cord  4.5  mm.  with  its 
vessels. 

Second  Month. — Embryos  of  from  twenty-eight  to  thirty-five  days  begin  to 


982  CHRONOLOGY  OF  HUMAN  DEVELOPMENT. 

extend  in  greater  degree;  the  visceral  clefts  are  closed  with  the  exception  of  the 
first;  the  allantois  has  but  three  vessels,  as  the  right  umbilical  vein  is  obliterated. 
In  the  fifth  week  the  trunk  is  from  0.85  to  1.28  cm.  long;  the  olfactory  pits  are 
connected  with  the  angles  of  the  mouth  by  furrows,  which  close  in  the  sixth  week 
and  form  canals.  In  embryos  from  thirty-five  to  forty- two  days  old  the  trunk 
has  a  length  of  between  i.i  and  1.3  cm.;  the  buccal  and  nasal  openings  are  sepa- 
rate; the  face  is  smooth;  the  extremities  have  three  divisions;  on  the  feet  the 
toes  are  not  so  well  developed  as  the  fingers.  The  auricle  of  the  ear  forms 
first  a  low  projection  in  the  seventh  week.  The  Wolfnan  body  is  consider- 
ably reduced.  The  length  of  the  trunk  at  between  the  seventh  and  the  eighth 
week  is  from  1.6  to  2.1  cm. 

End  of  the  Second  Month. — The  ovum  is  6£  cm.,  the  villi  1.3  mm.  long;  the 
circulation  in  the  umbilical  vesicle  is  obliterated;  the  embryo  is  26  mm.  long  and 
weighs  up  to  4  gm. ;  the  eyelids  and  the  nose  are  present.  The  umbilical  cord  is 
8  cm.  long;  the  abdominal  cavity  closed;  ossification  has  begun  in  the  lower  jaw, 
the  clavicles,  the  ribs,  the  vertebrae;  sex  is  undeterminable;  the  kidneys  are 
indicated. 

Third  Month. — The  ovum  is  as  large  as  a  goose-egg;  the  formation  of  the 
placenta  has  begun;  the  embryo  (trunk-length  between  2.1  and  6.8,  total  length 
from  6  to  1 1  cm. ;  weight  1 1  gm.)  is  from  now  on  known  as  the  fetus.  The  auricles 
of  the  ear  are  developed;  the  umbilical  cord  is  7  cm.  long;  the  external  sexual 
differentiation  has  begun;  the  navel  is  in  the  lower  fourth  of  the  linea  alba. 

Fourth  Month. — The  length  of  the  fetal  trunk  is  between  6.9  and  9  cm. ;  the  total 
length  from  10  to  17  cm.;  the  weight  57  gm.;  the  sex  is  distinct;  hair  and  nails 
have  begun  to  form;  the  placenta  weighs  80  gm.;  the  umbilical  cord  is  19  cm. 
long;  the  navel  is  in  the  lower  third  of  the  linea  alba;  jerking  movements  of  the 
extremities  occur;  the  bowels  contain  meconium;  vessels  are  visible  through 
the  translucent  skin;  the  eyelids  are  closed. 

Fifth  Month. — The  length  of  the  fetal  trunk  is  from  9.7  to  14.7,  the  total  length 
from  1 8  to  28  cm. ;  the  weight  is  up  to  284  gm.  The  hair  of  the  head  and  lanugo- 
hairs  are  distinct;  the  skin  is  still  somewhat  light  pink  and  thin,  covered  with 
vernix  caseosa,  and  not  perfectly  transparent.  The  weight  of  the  placenta  is  178 
gm. ;  the  umbilical  cord  is  31  cm.  long. 

Sixth  Month. — The  length  of  the  fetal  trunk  is  from  15  to  18.7,  the  total  length 
from  26  to  37  cm.;  the  weight  is  634  gm.  The  face  acquires  more  fat  and  has  a 
less  aged  appearance ;  the  lanugo  is  thick  and  fluffy ;  the  amount  of  vernix  is 
increased;  the  testicles  are  in  the  abdomen;  the  pupillary  membrane  and  the 
eye-lashes  are  present;  meconium  is  present  down  to  the  large  intestine. 

Seventh  Month. — The  length  of  the  fetal  trunk  is  from  18  to  22.8,  the  entire 
length  from  35  to  38  cm. ;  the  weight  is  1218  gm. ;  the  large  intestine  has  the  same 
length  as  the  body  (at  an  earlier  date  it  is  shorter,  at  a  later  date  longer) ;  the 
descent  of  the  testicles  has  begun,  one  testicle  finding  its  way  into  the  inguinal 
canal;  the  eyes  are  open;  the  pupillary  membrane  often  has  disappeared  at  its 
center  in  the  twenty-eighth  week;  in  addition  to  the  primitive  fissures,  other 
fissures  begin  to  form.  The  fetus  is  viable.  At  the  beginning  of  this  month 
there  is  a  center  in  the  os  calcis. 

Eighth  Month. — The  length  of  the  fetal  trunk  is  from  24  to  27.5,  the  total 
length  from  41  to  42  cm.;  the  weight  is  1569  gm.;  the  hair  of  the  head  is  thick, 
13  cm.  long;  the  nails  have  narrow  margins;  the  navel  is  below  the  middle  of 
the  linea  alba;  one  testicle  is  in  the  scrotum. 

Ninth  Month. — The  length  of  the  fetal  trunk  is  from  27  to  30,  the  total  length 
from  42  to  65  cm. ;  the  weight  is  197 1  gm. ;  the  fetus  at  this  age  is  not  distinguish- 
able from  the  mature  fetus. 

Tenth  Month. — The  length  of  the  trunk  is  from  30  to  37,  the  total  length  from 
45  to  67  cm.;  the  weight  is  2334  gm. 

The  Mature  Fetus.— The  length  of  the  body  is  51  cm.;    the  weight  3  kilos 

(irom  2.5  to  5  kilos);   lanugo-hair  is  still  present  only  on  the  shoulders;    the  skin 

is  white;    the  cartilages  of  the  nose  and  the  ears  are  hard  to  the  touch.     The 

nails  project  beyond  the  finger-tips.     The  navel  is  somewhat  below  the  middle  of 

the  linea  alba.     The  center  of  ossification  in  the  lower  epiphysis  of  the  femur, 

v£n4  t0t    -L. mm'  m  transverse  diameter  (it  begins  at  the  commencement  or  the 

ie  of  the  ninth  month,  and  is  from  2  to  5  mm.  wide  at  the  end  of  the  ninth 

nonth),  is  a  characteristic  of  the  mature  fetus.     There  is  often  a  center  of  ossi- 

ncation  in  the  upper  epiphysis  of  the  tibia  at  the  end  of  the  tenth  month. 

onclusion,  the  duration  of  development  in  the  following  animals  will  be 


FETAL    MOVEMENTS.       DEVELOPMENT    OF    THE    OSSEOUS    SYSTEM.       983 

given:  Colibri,  twelve  days;  hen,  duck,  twenty-one  days;  goose,  twenty-nine 
days;  stork,  forty-two  days;  cassowary,  sixty-five  days;  mouse,  three  weeks; 
rabbit,  hare,  four  weeks;  rat,  five  weeks;  hedgehog,  seven  weeks;  cat,  marten, 
eight  weeks;  dog,  fox,  polecat,  nine  weeks;  badger,  wolf,  ten  weeks;  lion,  fourteen 
weeks;  pig,  seventeen  weeks;  sheep,  twenty-one  weeks;  goat,  twenty-two  weeks; 
roe,  twenty-four  weeks;  bear,  small  apes,  thirty  weeks;  deer,  from  thirty-six 
to  forty  weeks;  man,  forty  weeks;  horse,  camel,  thirteen  months;  rhinoceros, 
eighteen  months;  elephant,  twenty-one  months.  Limitation  of  the  supply  of 
oxygen  to  the  incubating  egg  of  birds  is  followed  by  dwarf -formation. 

Various  intrauterine  movements  of  the  fetus  are  discernible  through  the 
abdominal  wall  of  the  mother:  extension-movements  of  the  trunk,  movements  ot 
the  extremities,  and  in  the  later  period  of  pregnancy  (and  during  labor)  a  regular 
rhythmical  movement  of  the  respiratory  muscles,  recurring  at  intervals  and 
usually  continuing  for  some  time.  In  addition  the  fetus  makes  sucking  and 
swallowing  movements. 

DEVELOPMENT  OF  THE  OSSEOUS  SYSTEM. 

Spinal  Column. — The  ossification  of  the  vertebrae  begins  between  the  eighth 
and  the  ninth  week,  a  center  appearing  first  in  each  half- arch,  then  a  center, 
probably  consisting  of  two  lying  close  together,  in  the  body  behind  the  chorda.  In 
the  fifth  month  the  bony  tissue  has  reached  the  surfaces,  the  chorda  in  the  body 
is  displaced.  The  three  pieces  unite  in  the  first  year.  The  atlas  has  a  center  in 
the  anterior  arch  and  two  in  the  posterior  arch;  union  occurs  in  the  third  year. 
A  center  appears  in  the  epistropheus  (axis)  during  the  first  year.  The  three 
points  of  the  sacral  vertebrae  unite  between  the  second  and  the  sixth  year;  and 
all  the  vertebrae  (sacral)  join  together  between  the  eighteenth  and  the  twenty- 
fifth  year.  The  four  coccygeal  vertebrae  receive  each  a  center  of  ossification 
between  the  first  and  the  tenth  year.  The  vertebrae  produce  further  in  later  life  one 
or  two  centers  in  each  spinous  process,  one  or  two  in  each  transverse  process,  one 
in  the  mammillary  process  of  the  lumbar  vertebrae,  and  one  center  in  some  of 
the  articular  processes  between  the  eighth  and  the  fifteenth  year.  Each  surface 
of  a  vertebra  develops  further  an  epiphysis-like,  thin  plate  of  bone,  which  may 
still  be  visible  at  the  age  of  twenty  years.  Groups  of  chorda-cells  persist  in  the 
adult  in  the  intervertebral  discs.  So  long  as  the  coccygeal  vertebrae,  the  odontoid 
process  of  the  axis  and  the  base  of  the  skull  are  cartilaginous,  they  contain  remains 
of  chorda.  The  coccygeal  vertebrae  form  the  tail,  as  the  continuation  of  which 
an  invertebrate  caudal  filament  is  prolonged.  The  coccyx  consists  originally 
in  man  of  a  free  projecting  tail,  vertebral  tail  (Fig.  376,  IX,  T),  which  later  becomes 
covered  and  enclosed  by  the  growth  of  the  soft  parts  over  it.  Rarely,  a  free,  pro- 
jecting tail  persists;  if  the  caudal  filament  alone  remains  free,  there  is  formed  the 
so-called  soft  tail. 

The  number  of  rudimentary  vertebrae  is  at  first  small,  then  larger  than  even 
in  adults ;  and,  finally,  again  smaller.  Eventually  the  embryo  has  2 5  true  vertebrae, 
the  ilium  fusing  with  the  twenty-sixth.  Later,  the  ilium  moves  so  far  forward 
that  the  twenty-fifth  vertebra  becomes  the  first  sacral.  The  persistence  of  25 
true  vertebrae  is  to  be  regarded  as  a  developmental  defect. 

The  ribs  bud  out  from  the  primitive  vertebrae;  their  first  rudiments  reside 
in  each  vertebra.  The  thoracic  ribs  become  catilaginous  in  the  second  month 
and  grow  forward  into  the  chest- wall,  the  upper  seven  being  joined  together  by 
a  median  strip  of  cartilage.  The  latter  represents  the  rudimentary  half  of  the 
sternum;  by  the  union  of  the  rudiments  of  the  two  sides  in  the  median  line  the 
sternum  is  formed.  The  developmental  defect  of  fissure  of  the  sternum  occurs 
in  some  howling  apes  in  which  the  manubrium  is  permanently  divided.  The 
lower,  false  ribs  normally  exhibit,  to  a  certain  extent,  a  fissure  of  the  sternum; 
openings  in  the  sternum  as  the  remains  of  a  fissure  are  frequent. 

In  the  sixth  month  a  center  of  ossification  appears  in  the  manubrium;  then 
from  4  to  13,  in  pairs,  in  the  gladiolus,  and  one  in  the  ensiform  process.  Each 
rib  acquires  a  center  of  ossification  in  the  body  in  the  second  month;  between 
the  eighth  and  the  fourteenth  year  one  each  in  the  tubercle  and  the  head  of  the 
bone;  fusion  takes  place  between  the  fourteenth  and  the  twenty-fifth  year.  The 
rudimentary  ribs  in  front  of  the  transverse  processes  in  the  neck  become  the 
anterior  portions  of  these  processes.  Rarely  isolated,  short,  true  cervical  ribs 
persist  in  conjunction  with  the  sixth  and  seventh  cervical  vertebrae  (in  birds  the 
cervical  ribs  are  better  developed).  In  the  lumbar  region  the  cartilaginous 


984  DEVELOPMENT  OF  THE  OSSEOUS  SYSTEM. 

rudiments  of  the  ribs  become  later  the  processus  costarii  (transversi  of  earlier 
writers).  Occasionally  a  thirteenth  rib  is  formed.  The  accessory  process  of 
the  lumbar  vertebne  is  the  true  transverse  process,  as  is  easily  demonstrable  in 
the  skeleton  of  the  ape.  The  sacral  vertebras  have  likewise  3  or  4  rudimentary 
ribs  which  after  the  sixth  year  unite  with  the  superficies  auricularis.  The  rib- 
piece  has  not  yet  been  found  on  the  coccygeal  vertebrae. 

The  cranium,  the  closed  extremity  of  the  vertebral  canal,  contains  the  chorda 
in  the  axial  part  of  its  base  up  to  the  anterior  sphenoid  body.  It  is  at  first  entirely 
membranous  (membranous  primordial  cranium) ;  then  the  basal  portions  become 
cartilaginous  in  the  second  month,  being  held  together  as  if  cast  from  a  mold:  the 
occipital  bone,  with  the  exception  of  the  upper  half,  the  anterior  and  posterior 
sphenoids  with  the  wings,  the  petrous  and  mastoid  portions  of  the  temporal 
bone,  the  ethmoid  with  the  nasal  septum,  and  the  imperfectly  developed  external 
cartilaginous  portion  of  the  nose.  The  other  portions  of  the  cranium  remain 
membranous.  Accordingly,  a  membranous  and  a  cartilaginous  primoidal  cranium 
have  been  distinguished.  In  animals  (pigs)  the  entire  occipital  and  a  portion 
of  the  parietal  region  may  become  cartilaginous. 

Ossification  of  the  individual  bones  of  the  skull  is  completed  as  follows: 

I.  The  occipital  bone  receives  in  the  third  month  a  center  of  ossification  in 
the  basilar  portion,  one  each  in  the  condyloid  portion  and  in  the  fossa  for  the 
cerebellum.     In  addition  two  centers    occur  in  the  membranous    fossae  for  the 
cerebrum.     The  four  centers  of  the  bone  unite  during  intrauterine  life,  although 
a  cleft  can  be  seen  on  each  side  from  the  border  between  the  upper  and  the  lower 
portion  of  the  squamous  portion.     Between  the  first  and  the  second  year  all  the 
other  points  unite.     Rarely  the  upper  half  of  the  squamous  portion  persists,  as 
the  analogue  of  the  interparietal  bone,  which  is  constant  in  many  animals;   this  is 
an  independent  semilunar-shaped  bone  (of  which  the  author  possessed  a  beautiful 
example);    occasionally  one-half  of  this  portion.     It  should  be  pointed  out  as 
particularly  important    (also  with  reference  to  the   development   of  the  brain) 
that  in  man  the  upper  portion  of  the  occipital  bone  enlarges  in  the  process  of 
development,  while  in  apes,   on  the  contrary,  it   diminishes  in  size.     In  some 
skulls  the  upper  and  lower  halves  of  the  occipital  bone  exhibit  differences  in 
development.     According  to  Albrecht,  the  anterior  part  of  the  basilar  portion 
forms  a  special  piece  of  bone,  the  basioticum. 

II.  The  postsphenoid  has  the  following  centers  of  ossification  from  the  third 
month  on:    two  in  the  sella  turcica;   two  in  the  carotid  groove,  and  two  in  both 
great  wings,  which  form  also  the  external  plate  of  the  pterygoid  process  (while 
the  previously  formed  noncartilaginous  internal  plate  is  derived  from  the  superior 
maxillary  process  of  the  first  visceral  arch).     In  the  second  half  of  fetal  life,  these 
centers  unite  to  from  the  great  wings.     The  dorsum  sellae  and  the  clivus  remain 
cartilaginous  up  to  the  spheno-occipital  synchondrosis,  which  ossifies  from  the 
thirteenth  year  on. 

III.  The  pre sphenoid  has  from  the  eighth  month  two  centers  in  the  small 
wings;   then  two  in  the  body.     In  the  sixth  month  these  unite,  although  cartilage 
is  still  found  within  them,  remains  of  which  persist  until  the  thirteenth  year. 

IV.  The  ethmoid  contains  at  the  fifth  month  a  center  in  the  labyrinth,  together 
with  the  os  planum,  the  spongy  bones  and  the  cribriform  plate;    then  in  the  first 
year  there  is  a  center  in  the  perpendicular  plate  and  the  crista  galli.     Fusion  takes 
place  between  the  fifth  and  sixth  years. 

V.  Among  the  bones  developed  from  membrane  are  the  inner  lamina  of  the 
pterygoid  process  (one  center) ;   the  upper  half  of  the  occipital  bone  (two  centers) ; 
the  parietal  bone  (one  center  in  the  parietal  eminence) ;   the  frontal  bone  (a  double 
center  in  the  frontal  eminence) ;   in  addition  three  small  centers  in  the  nasal  spine, 
the  trochelear  spine,  and  the  zygomatic  process;    the  nasal  bone   (one  center); 
the  squamous  portion  of  the  temporal  bone  (one  center) ;   the  tympanic  ring  (one 
center) ;   the  lacrimal  bone,  the  vomer  and  the  intermaxillary  bones.     All  of  these 
bones  are  designated  covering  or  protecting  bones;    they  are  formed  in  a  special 
membranous   deposit,   which  is   applied  externally  to  the   primordial   cranium. 
O.  Hertwig  considers  them  as  due  to  ossification  of  skin  and  mucous  membrane. 

Croethe  appreciated  that  the  cranium  of  mammals  was  "derived  from  ver- 
tebral bones.  The  three  first  vertebrae  are  admitted:  the  occipital  bone, 
the  postsphenoid,  and  the  presphenoid."  The  arch  of  the  middle  cranial 
vertebra  is  closed  by  the  great  wings  and  the  parietal  bones;  the  anterior  by  the 
frontal  bones.  The  condition  is,  however,  much  more  complicated.  Gegenbaur 
and  btohr,  after  careful  investigation  as  to  the  distance  the  chorda  extends  an- 


DEVELOPMENT  OF  THE  OSSEOUS  SYSTEM.  985 

teriorly,  the  number  of  cranial  nerves  that  correspond  to  spinal  nerves,  and  the 
number  of  visceral  arches,  concluded  that  there  are  at  least  nine  cranial  vertebrae 
through  which  the  chorda  passes.  To  this  vertebral  portion  of  the  head  is  sub- 
joined a  pre vertebral  or  an  evertebral  portion,  comprising  the  ethmoid  and  anterior 
orbital  region.  Froriep  showed  that  the  hypoglossal  nerve  represents  the  fusion 
of  several  spinal  nerves.  In  mammals  the  cranium  up  to  the  vagus  results 
from  the  fusion  of  four  rudimentary  vertebrae,  while  the  anterior  portion  of 
the  skull,  through  the  cranial  nerves,  situated  further  forward,  permits  the  recog- 
nition of  a  systematic  arrangement  of  the  vertebrae. 

The  development  of  the  bones  of  the  face  is  intimately  related  to  the  trans- 
formation of  the  visceral  arches  and  clefts.  Toward  the  large  buccal  opening 
there  projects  from  each  side  the  medial  extremity  of  the  first  visceral  arch,  \vith 
two  processes:  the  superior  maxillary  process  (Fig.  382,  ^,3),  which  grows  more 
toward  the  side  of  the  buccal  opening:  and  the  inferior  maxillary  process  (u), 
which  extends  along  the  lower  border  of  the  mouth.  From  above  downward 
there  now  grows  the  frontal  process  (/)  as  a  prolongation  of  the  base  of  the  skull, 
a  thick  process,  provided  at  its  lower  outer  angle  with  a  spine  (i,  the  internal 
nasal  process).  The  frontal  process  and  the  superior  maxillary  process  (3)  unite 
in  such  a  manner  that  the  former  (/)  insinuates  itself  between  the  latter  on  each 
side.  At  the  same  time  a  small  external  nasal  process  (2),  a  continuation  of  the 
lateral  portion  of  the  cranium,  situated  above  the  superior  maxillary  process,  unites 
with  the  latter.  Between  the  superior  maxillary  process  and  the  external  nasal 
process  there  is  a  cleft  leading  to  the  eye  (a),  which  grows  together  to  form  the 
lacrimal  duct  (B,  O).  The  buccal  opening  is  thus  separated  from  the  nasal  open- 
ing above  it.  The  division,  however,  extends  also  in  the  depth  of  the  mouth; 
the  superior  maxillary  process  produces  the  hard  palate,  the  frontal  process  the 
intermaxillary  bone  (Fig.  382,  B,  Z),  which  occurs  also  in  man,  and  later  unites 
with  the  upper  jaw.  In  many  animals  the  inter- 
maxillary bone  persists  as  a  separate  bone  (os 
incisivum) ,  and  bears  the  incisor  teeth.  The  hard 
palate  is  closed  in  the  ninth  week;  and  upon  it 
the  nasal  septum,  which  is  derived  from  the  fron- 
tal process,  is  supported  at  right  angles.  From 
the  inferior  maxillary  process  there  develops  the 
lower  jaw  (B,  U),  At  the  margins  of  the  buccal 
cavity  the  lips  and  alveolar  border  are  formed. 
The  tongue  (z)  develops  behind  the  junction  of  the 
second  and  third  pairs  of  visceral  arches,  according 
to  Born  from  an  intercalated  piece  between  the 
inferior  maxillary  processes;  its  root  from  the 
second  visceral  arch. 

These  formations  may  suffer  interruption.  FIG.  381.— Left-sided  Hare-lip. 

1.  Hare-lip     (oronasal     fissure,     Fig.    382,   Q 
results     from     nonunion     of     the     internal     nasal 

process  on  the  one  hand  and  of  the  superior  maxillary  and  external  nasal 
processes  on  the  other  hand.  The  cleft  runs  into  the  nasal  orifice.  As  a 
rule,  it  passes  between  the  incisor  teeth,  although  rarely  also  in  front  of  the  canine 
tooth.  In  the  presence  of  maxillary  fissure  there  are  often  supernumerary  incisor 
teeth.  The  intermaxillary  bone  has  two  centers  of  ossification,  one  in  the  internal 
nasal  process,  the  other  in  the  region  of  the  superior  maxillary  process.  From 
the  external  nasal  process,  which  does  not  extend  all  the  way  down,  no  especial 
bone  results.  The  nose  and  the  mouth  may  be  united  either  only  through 
the  soft  parts  (hare-lip,  Fig.  381),  or  entirely,  also  through  the  hard  palate  (wolf's 
throat) ;  both  malformations  may  be  unilateral  or  -bilateral.  The  formation 
of  cleft  palate  may  be  due  to  the  circumstance  either  that  the  superior  maxillary 
and  the  frontal  process  wholly  or  in  part  remain  too  short,  so  that  they  do  not 
come  in  contact;  or  the  frontal  process  grows  too  far  forward  like  a  snout,  and  often 
also  is  diminished  in  size;  so  that  the  superior  maxillary  process  cannot  reach  it. 

2.  A  failure  of  union  between  the  internal  and  external  nasal  process  on  the 
one  side  and  the  superior  maxillary  process  of  the  other  side  results  in  the  oblique 
facial  cleft  (oro-orbital  cleft,  Fig.  382,  D) ;    the  nasal  orifice  is  not  slit. 

3.  The  oral  cleft   (macro  stomia}   is  an  abnormally  large  lateral  cleft  between 
the  superior  and  inferior  maxillary  processes,  which  may  extend  as  far  as  the  ear 
(Fig.  382,  B,  ni). 

4.  The  occurrence  of  a  fistula  of  the  lower  lip  is  extremely  rare;  it  is  regarded 


gS6  DEVELOPMENT    OF    THE    OSSEOUS    SYSTEM. 

as  the  remains  of  a  fetal  cleft  between  the  middle  and  lateral  portions  of  the 
forming  lower  lip. 

From  the  posterior  portion  of  the  first  visceral  arch  there  develop  the  incus, 
the  malleus  (which  undergo  ossification  in  the  fourth  month),  and  the  long 
cartilaginous  process  of  Meckel,  which  arises  from  the  malleus  behind  the  tym- 
panic ring,  and  passes  forward,  and  which  extends  on  the  inner  side  of  the  lower  jaw 
almost  to  its  median  union.  This  process  begins  to  atrophy  at  the  sixth  month. 
Nevertheless,  its  posterior  portion  forms  the  internal  lateral  ligament  of  the 
temporomaxillary  joint.  Close  to  it,  at  its  origin  from  the  malleus,  the  processus 
Folli  is  formed.  A  portion  of  its  median  extremity  in  ossifying  unites  with  the 
inferior  maxilla.  The  lower  jaw  originates  in  membrane  as  a  protecting  bone  upon 
the  first  visceral  arch;  the  angle  and  the  condyle  develop  from  a  cartilaginous 
deposit.  The  symphysis  of  the  lower  jaws  unites  in  the  first  year.  From  the 
superior  maxillary  process  there  develops  in  addition  to  the  upper  jaw  also  the 
internal  plate  of  the  pterygoid  process,  as  well  as  the  palatine  process  of  the  up- 
per jaw  and  the  palatine  bone  at  the  end  of  the  second  month;  and,  finally,  the 
zygomatic  bone. 

The  second  visceral  arch,  originating  from  the  temporal  bone,  and  running 
parallel  with  the  first  visceral  arch,  forms  successively  the  stapes  (according  to 
Salensky,  however,  this  originates  from  a  cartilaginous  mass  connected  with 
the  first  arch),  the  pyramidal  eminence  with  the  stapedius  muscle,  the  styloid 
process;  the  (previously  cartilaginous)  stylohyoid  ligament,  the  lesser  cornu  of 


22L  A 


FIG.  382.— Formation  of  the  Face  and  Developmental  Defects  of  the  face:  A,  First  fetal  rudiment;  /,  //,  III,  IV, 
the  four  visceral  arches',  /,  the  frontal  process;  i,  internal  and,  2,  external  nasal  process;  3,  superior  maxillary 
process;  «,  inferior  maxillary  process;  b,  c,  first  and  second  visceral  clefts;  a,  eye;  z,  tongue,  B,  Normal 
union  of  the  embryonal  parts;  Z,  intermaxillary  bone;  Nl,  nasal  orifice;  O,  lacrimal  canal  ;  U,  lower  jaw: 
m,  abnormal  enlargement  of  the  oral  cleft,  macrostomia.  C,  Arrested  development  of  the  oronasal  cleft  (hare- 
lip or  wolf's  throat).  D,  Arrested  development  causing  oblique  facial  cleft,  Q. 

the  hyoid  bone   (Landois   saw  the  styloid  process  transformed  into  bone  down 
to  the  lesser  cornu  on  both  sides),  and  finally  the  glossopalatine  arch. 

From  the  third  visceral  arch  there  develop  the  greater  cornu  and  the  body  of 
the  hyoid  bone  and  finally  the  pharyngopalatine  arch. 

The  fourth  visceral  arch  contains  the  rudimentary  thyroid  cartilage. 
The  branchial  or  visceral  arches  may  in  general  be  regarded  as  the  analogues 
of  the  ribs. 

Of  the  visceral  clefts  only  the  first  remains— as  the  auditory  canal,  which 
is  transformed  into  the  tympanic  cavity  and  the  Eustachian  tube;   all  of  the  others 
.se.     It  one  or  another  remains  open  (arrest  of  development,  occasionally  heredi- 
tary in  certain  families)  there  then  results  the  congenital  complete  cervical  fistula 
(mostly  arising  from  the  second  cleft  alone).     The  passages  may  persist  with 
sr  an  inner  or  an  outer  opening  only;   there  then  result  blind  passages  or  diver- 
:ula,   which  are   designated  incomplete  cervical  fistula.     Also  branchiogenous 
imors  and  cysts  take  their  origin  from  the  visceral  formations.     Partial  duplica- 
e  lower  jaw,  which  is  exceedingly  rare,  is  to  be  attributed  to  an  increase 
in  the  number  of  visceral  arches. 

The  thymus  and  thyroid  glands  are  formed  as  paired  diverticula  or  thicken- 
ings of  the  epithelium  covering  the  visceral  arches.     The  thyroid  gland  results 
(in  swine)   from  a  middle  and  two  lateral  rudiments,  which  subsequently  fuse, 
epithelium  of  the  last  two  pharyngeal  clefts  does  not  atrophy  (swine) ;    it 


DEVELOPMENT    OF    THE    OSSEOUS    SYSTEM.  987 

proliferates,  drives  the  cylindrical  processes  inward  and  develops  into  two  epi- 
thelial vesicles  (the  paired  rudiment  of  the  thyroid  gland).  These  vesicles  have 
a  central  cleft,  which  at  first  still  communicates  with  the  pharynx.  The  paired 
rudiment  of  the  thyroid  gives  off  from  the  original  cavity  buds  that  are  at  first 
solid,  but  subsequently  become  hollow;  later  the  paired  rudiments  fuse.  Ac- 
cording to  His,  the  thyroid  (man,  fourth  week)  in  the  region  of  the  second  pair  of 
visceral  arches  lies  in  front  of  the  tongue  as  an  epithelial  vesicle.  Of  the  epi- 
thelial portion  of  the  thymus  gland  (which,  according  to  Born  and  Fischeles, 
originates  from  the  third  visceral  cleft)  there  persist  only  the  so-called  concentric 
bodies.  His  describes  in  man  (fourth  week)  epithelial  diverticula  from  the  sides 
of  the  fourth  and  fifth  aortic  arches  as  the  rudimentary  thymus.  The  carotid 
gland  also  is  of  epithelial  origin,  a  variety  of  the  thyroid. 

The  Extremities. — The  course  and  the  origin  of  the  nerves  of  the  brachial 
plexus  indicate  that  the  upper  extremity  has  had  a  position  more  toward  the 
cranium  on  the  vertebral  column  (last  cervical  and  first  dorsal  vertebrae) .  The 
rudiment  of  the  lower  extremity  corresponds  to  the  region  between  the  last  lumbar 
and  the  third  or  fourth  sacral  vertebra. 

The  clavicle,  preformed  not  in  connective  tissue,  but  in  cartilage,  like  the 
furcula  of  birds,  exhibits  marked  growth,  so  that  in  the  second  month  it  is  four  times 
as  large  as  the  thigh.  It  ossifies,  the  first  of  all  of  the  bones,  in  the  seventh  week. 
At  the  time  of  puberty  a  sternal  epiphysis  is  added.  Episternal  formations  must 
be  referred  to  the  clavicle.  Ruge  regards  cartilaginous  pieces  between  the  clavicle 
and  the  sternum  as  the  analogues  of  the  episternum  of  animals.  The  clavicle  is 
wanting  in  many  mammals  (hoofed  animals,  beasts  of  prey) ;  in  alipeds  it  is  ex- 
ceedingly large,  in  rabbits  half  membranous.  The  furcula  of  birds  represents  the 
united  clavicles. 

The  scapula  when  first  indicated  is  united  with  the  clavicle;  at  the  end  of 
the  second  month  it  exhibits  a  central  nucleus,  which  soon  enlarges.  Of  the 
accessory  centers  of  ossification,  that  in  the  coracoid  process  is  of  interest  morpho- 
logically; the  latter  forms  at  the  same  time  the  uppermost  portion  of  the  articular 
surface.  In  birds  this  rudiment  grows  as  the  coracoid  bone  up  to  the  sternum, 
while  in  man  only  a  membranous  band  passes  from  the  apex  of  the  coracoid 
process  to  the  sternum.  The  long  basal  separate  strip  of  bone  corresponds  to 
the  suprascapular  bone  of  some  animals.  Other  centers  of  ossification  are  as 
follows :  One  in  the  lower  angle ;  two  or  three  in  the  acromion ;  one  in  the  articular 
surface;  an  inconstant  one  in  the  spine.  Complete  consolidation  occurs  at  the 
time  of  puberty. 

The  humerus  undergoes  ossification  between  the  eighth  and  the  ninth  week 
in  the  diaphysis.  Other  centers  of  ossification  are  as  follows:  One  in  the  upper 
epiphysis  and  one  in  the  eminentia  capitata  (first  year) ;  one  in  the  greater  tuber- 
osity,  and  one  in  the  lesser  tuberosity  (second  year) ;  two  in  the  condyles  (between 
the  fifth  and  the  tenth  year);  one  in  the  trochlea  (twelfth  year).  The  diaphysis 
unites  with  the  epiphysis  between  the  sixteenth  and  the  twentieth  year. 

The  radius  ossifies  in  the  third  month  in  the  diaphysis.  In  addition,  a  center 
occurs  in  the  lower  epiphysis  (fifth  year) ;  one  in  the  upper  epiphysis  (sixth  year) ; 
the  centers  in  the  tuberosity  and  in  the  styloid  process  are  inconstant.  Union 
occurs  at  the  time  of  puberty. 

The  ulna  ossifies  in  its  middle  portion  in  the  third  month.  In  addition  there 
is  a  center  in  the  lower  extremity  (sixth  year)  and  two  in  the  olecranon  (between 
the  eleventh  and  fourteenth  years);  a  center  in  the  coronoid  process  and  one 
in  the  styloid  process  are  inconstant.  Consolidation  of  the  bone  takes  place  at 
puberty.  In  the  flying  dog,  pteropus,  the  olecranon  persists  as  a  special  bone, 
cubital  patella. 

The  carpal  bones  in  vertebrates  are  arranged  in  two  rows.  The  first  row 
contains  three  bones  side  by  side,  the  radial,  the  intermediate,  and  the  ulnar. 
These  are  represented  in  man  by  the  scaphoid,  the  semilunar,  and  the  cuneiform 
(the  pisiform  is  only  a  sesamoid  bone  in  the  tendon  of  the  flexor  carpi  ulnaris) . 
The  second  row  contains  actually  (for  example,  in  the  salamanders)  as  many 
bones  as  there  are  digits;  in  man  the  common  rudiment  of  the  fourth  and  fifth 
fingers  corresponds  to  the  unciform  bone. 

Morphologically  it  is  noteworthy  that  between  both  rows  there  is  at  first 
formed  a  central  bone  (corresponding  to  the  central  carpal  bone  of  reptiles,  am- 
phibia, and  some  mammals) ,  but  this  atrophies  in  the  third  month  or  fuses  with 
the  scaphoid.  Only  in  rare  instances  does  it  persist.  It  persists  constantly 


DEVELOPMENT  OF  THE  OSSEOUS  SYSTEM. 


in  the  orang.  All  of  the  carpal  bones  are  still  cartilaginous  at  birth.  They  ossify 
as  follows:  Os  magnum  unciform  (first  year),  cuneiform  (third  year),  trapezium, 
semilunar  (fifth  year),  scaphoid  (sixth  year),  trapezoid  (seventh  year),  pisiform 
(twelfth  year). 

The  metacarpal  bones  exhibit  a  center  in  the  diaphysis  at  the  end  of  the  third 
month;  the  same  is  true  of  the  phalanges.  All  of  the  phalanges  and  the  first 
bone  of  the  thumb  have  cartilaginous  epiphyses  at  the  proximal  extremity;  the 
remaining  metacarpal  bones  at  the  distal  extremity.  Accordingly,  the  first 
bone  of  the  thumb  is  to  be  regarded  as  a  phalanx.  The  epiphyses  of  the  meta- 
carpal bones  ossify  in  the  second  year;  those  of  the  phalanges  in  the  third  year; 
union  takes  place  at  the  time  of  puberty.  The  assertion  of  Schenk  is  noteworthy, 
that  in  the  first  formation  a  greater  number  of  fingers  (up  to  nine)  are  indicated, 
which  later  diminish  to  five.  Accordingly,  polydactyly  may  be  regarded  as  a 
malformation  due  to  arrest  of  development.  Moreover,  rudimentary  indications 
of  a  sixth  finger  (radial  aspect)  and  of  a  sixth  toe  (tibial  aspect)  are  present  in 
many  mammals,  for  example  in  moles,  v.  Bardeleben  designates  them  respect- 
ively prepollex  and  prehallux,  They  are  rare  in  man  as  an  animal  analogue. 

The  innominate  bone,  in  the  cartilaginous  stage,  consists  of  two  parts,  the 
pubis  and  the  ischium.  Ossification  begins  at  three  centers:  One  in  the  ilium 

(between  the  third  and  fourth 
months),  one  in  the  descending 
ramus  of  the  ischium  (between 
the  fourth  and  fifth  months), 
one  in  the  horizontal  ramus  of 
the  pubis  (between  the  fifth  and 
seventh  months).  Between  the 
sixth  and  the  fourteenth  year 
three  centers  appear  where  the 
bodies  of  the  three  bones  unite 
to  form  the  acetabulum ;  another 
in  the  superficies  auricularis  and 
one  in  the  symphysis.  Further 
accessory  centers  are  as  follows: 
One  each  in  the  anterior  inferior 
spine,  the  crest  of  the  ilium,  the 
tuberosity  and  spine  of  the 
ischium,  the  spine  of  the  pubis, 
the  iliopectineal  eminence  and 
the  floor  of  the  acetabulum.  The 
descending  ramus  of  the  pubis 
and  the  ascending  ramus  of  the 
ischium  are  the  first  to  unite  be- 
tween the  seventh  and  eighth 
years.  The  Y-shaped  suture  in 
the  acetabulum  persists  until 
puberty.  A  special  center  in  the 
margin  of  the  acetabulum  appears 
as  the  os  acetabuli  (twelfth  year) , 
which  fuses  with  the  adjacent 
bones  in  the  eighteenth  year. 

The  femur  acquires   its  mid- 

le  center  of  ossification  at  the  end  of  the  second  month.     At  birth  there  is  a 
:nter  n   the  lower  epiphysis,  and  somewhat  later  one  in  the  head. 

I  here  are  in  addition:    One  in  the  greater  trochanter  (between  the  third  and 

;h  years)   one  in  the  lesser  trochanter  (between  the  thirteenth  and  fourteenth 

•s),  two  in  the  condyles  (between  the  fourth  and  eighth  years).     Union  of  all 

occurs  at  about  the  time  of  puberty.     The  patella  is  a  sesamoid  bone  in  the  tendon 

ol  the  quadriceps  femoris.     In  some  marsupials  it  unites  with  the  fibula  as  the 

olecranon.     The  patella  is  cartilaginous  in  the  second  month;    it  ossifies 

between  the  first  and  third  years. 

and  S6  fi!^la  underg°  ossification  in  their  diaphyses  at  the  beginning 
?he  Up?er  ^Vsis  first  contains  a  center  (between  the 
nf  ^  *henuthe  ^wer.     Accessory  centers  are  present  in  the  tuber- 

osity of  the  tibia  and  m  the  malleoli.     Consolidation  of  all  takes  place  at  puberty. 
;  tarsal  bones  are  formed  in  a  manner  analogous  to  those  of  the  carpus: 


FIG.  383. — Ossification  of  the  Innominate. 


DEVELOPMENT    OF    THE    OSSEOUS    SYSTEM.  989 

.In  the  first  row  the  astragalus  corresponds  to  the  tibia,  the  calcaneum  to  the  fibula. 
As  a  third  bone  of  the  first  row  there  is  particularly  worthy  of  note  a  small  piece 
of  bone  adherent  to  the  astragalus  at  the  insertion  of  the  posterior  fibular  liga- 
ment of  the  tarsus.  This  corresponds  to  the  semilunar  bone  of  the  carpus, 
is  indicated  in  the  second  month  as  an  independent  cartilage,  and  appears  in 
urodela  and  marsupials  as  a  typical  intermediate  tarsal  bone,  although  it  does  not 
undergo  development  in  man. 

In  the  second  row  (as  in  the  carpus)  the  rudiments  of  the  fourth  and  fifth 
bones  are  united  as  the  cuboid.  The  tarsal  bones  ossify  in  the  following  order: 
Calcaneum  (beginning  of  the  seventh  month) :  astragalus  (beginning  of  the  eighth 
month) ;  cuboid  (end  of  the  tenth  month) ;  scaphoid  or  central  (between  the 
first  and  fifth  years) ;  first  and  second  cuneiform  (third  year) ;  third  cuneiform 
(fourth  year) .  In  the  heel  of  the  calcaneum  an  accessory  center  develops  between 
the  fifth  and  the  tenth  year,  and  unites  after  puberty. 

The  metatarsal  bones  are  formed  in  the  same  way  as  the  metacarpal  bones, 
but  later. 

After  numerous  measurements  of  the  diaphyses  of  long  bones  in  embryos 
and  fetuses,  the  writer  has  been  able  to  establish  the  following  general  principles: 
i.  Up  to  the  ninth  or  tenth  week  the  ossified  middle  portions  of  the  long  bones  in 
the  upper  part  of  the  body  are  the  largest,  and  in  the  following  order:  Inferior  max- 
illa, clavicle,  humerus,  radius,  ulna,  femur,  tibia,  fibula.  2.  From  the  sixth  month 
they  range  in  size  as  they  do  in  the  adult.  3.  The  diaphyses  of  the  tubular  bones 
of  the  upper  extremity  are  at  all  periods  of  fetal  life  relatively  larger  than  those 
of  the  lower  extremity.  4.  In  the  first  half  of  fetal  life,  the  diaphyseal  bones 
grow  in  the  same  length  of  time  much  more  than  they  do  later;  even  twice  as 
much  and  more.  Of  the  epiphyses,  ossification  takes  place  earliest  in  those  that 
have  the  greatest  relation  in  weight  as  compared  with  their  diaphyses. 

In  the  formation  of  bone  from  cartilage,  the  cartilage-cells  multiply  in  the 
dilating  spaces  in  which  they  are  contained.  The  latter  unite  to  form  large 
cavities,  upon  whose  walls  the  new  bone-mass  is  deposited  in  layers.  Whether, 
under  such  circumstances,  the  descendants  of  the  cartilage-cells,  greatly  increased 
in  number  by  division,  become  transformed  into  bone-cells,  or  whether  the  cells 
utilized  for  this  purpose  grow,  together  with  the  blood-vessels,  into  the  ossifying 
cartilage  (while  the  cartilage-cells  degenerate)  is  still  an  open  question. 

Dried  bone  consists  one-third  of  organic  matrix  (bone-cartilage,  by  boiling 
reduced  to  gelatin),  further  of  neutral  calcitftn  phosphate  (57  per  cent.),  calcium 
carbonate  (7  per  cent.),  magnesium  phosphate  (from  i  to  2  per  cent.),  calcium 
fluorid  (i  per  cent.)  and  a  trace  of  chlorin.  Fresh  bone  contains  about  23  per 
cent,  of  water;  the  marrow,  fluid  bone-fat,  albumin,  hypoxanthin,  cholesterin, 
and  extractives.  Red  marrow  contains  more  iron  in  conformity  with  the  hemo- 
globin present. 

The  bones  (for  example,  the  tubular  bones)  grow  in  thickness  by  deposition 
from  the  periosteum,  the  cells  of  the  latter  being  transformed  as  osteoblasts 
into  bone-corpuscles. 

In  part  the  peripheral  regions  (parietal  layer)  of  the  osteoblasts,  resembling 
epithelium  lying  close  together,  are  transformed  into  the  hardened  matrix  of  the 
bone,  the  cells  becoming  star-shaped  bone-corpuscles.  In  part,  however,  isolated 
star-shaped  periosteal  cells  also  are  transformed  into  bone-cells,  a  hardening 
blastema  being  poured  out  between  them  and  taking  up  the  fibers  of  the  perios- 
teum as  Sharpey's  fibers  into  the  substance  of  the  bone.  Coincident  with  the 
growth  of  the  bone  at  its  periphery,  the  medullary  cavity  becomes  larger  through 
absorption.  Rings  placed  around  the  shaft  of  long  bones  in  young  animals  subse- 
quently come  to  be  within  the  medullary  cavity. 

The  growth  of  the  bones  in  length  takes  place  in  such  a  manner  that  the  strip 
of  epiphyseal  cartilage  adjacent  to  the  diaphysis  undergoes  constant  ossification, 
while  new  cartilage  is  being  constantly  produced  at  the  peripheral  extremity. 
When  the  growth  of  the  bone  is  completed,  the  epiphyseal  cartilage  finally  ossifies 
as  a  whole.  Whether  in  addition  to  this  growth  of  the  bone  through  apposition, 
there  is  growth  also  through  intussusception  or  interstitial  expansion,  investiga- 
tion (whether  two  pegs  driven  into  the  shaft  of  a  growing  bone  become  further 
removed  or  not)  has  not  yet  determined  conclusively. 

The  form  into  which  the  bones  develop  depends  also  upon  external  influences. 
They  develop  the  more  rapidly  the  greater  the  activity  of  the  muscles  attached 
to  them.  In  overcoming  pressure  normally  applied  to  a  bone  it  yields  in  the 
direction  of  least  resistance,  and  becomes  thicker  in  this  direction.  The  bone 


990  DEVELOPMENT    OF    THE    VASCULAR    SYSTEM. 

grows  more  slowly,  further,  upon  the  side  of  the  greater  external  pressure;  and  it 
bends  in  the  presence  of  one-sided  pressure. 

DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 

Heart The  simple  pouchlike  rudimentary  heart  acquires  the  shape  of  the 

letter  S  (Fie  384  i)  and  soon  exhibits  a  differentiation  into  the  upper  aortic 
portion  (a)  with  the  bulb  (6),  the  middle  ventricular  portion  and  the  lower 
venous  portion  (v} .  The  ventricular  portion  now  bends  upon  itself  in  the  shape  of 
the  stomach  (2)  the  venous  portion  in  consequence  taking  a  higher  position  (A) 
and  later  on  one  somewhat  back  of  the  arterial  portion.  From  the  venous  por- 
tion'there  grows  to  right  and  to  left  a  blind  sac,  the  forerunner  of  the  large 
auricle  (7  o  o  )  The  bend  of  the  heart  body  corresponding  to  the  greater  curva- 
ture (2,  V)  is  divided  externally  by.  a  shallow  groove  into  two  large  parts  (3). 


a 


a 


FIG.  384. — Development  of  the  Heart  (in  Part  Diagrammatic):  i,  First  indication  of  the  heart;  a,  aortic  portion 
with  the  bulb  (&);  v,  venous  portion.  2,  Stomach-shaped  flexure  of  the  heart;  a,  aortic  portion,  with  the 
bulb  (6);  V,  ventricle;  A,  auricular  portion.  3,  Development  of  the  auricular  appendages  o,  o\  and  the  ex- 
ternal groove  on  the  ventricle.  4,  Beginning  division  of  the  aorta  (p)  into  two  longitudinal  tubes  (a).  5,  View 
from  behind  through  the  freely  opened  auricle  (v,  v)  into  the  left  (Z,)  and  the  right  (K)  ventricle,  between  which 
the  septum  projects,  and  in  which  respectively  the  two  large  arterial  vessels  (a)  aorta  and  (*j)  pulmonary 
artery  empty.  6,  Relations  of  the  entrance  of  the  superior  (Cs}  and  inferior  (Cf)  cavae  in  the  auricles  (diagram- 
matic view  from  above);  x,  direction  of  the  blood-stream  from  the  superior  cava  into  the  right  ventricle; 
y,  that  of  the  blood-stream  from  the  inferior  cava  into  the  left  ventricle;  tL  tubercle  of  Lower.  7,  Heart 
of  the  mature  fetus;  R,  right,  L,  left  ventricle;  a,  aorta  with  the  innominate  artery  (cc);  carotid  (c)  and  left 
subclavian  (5)  artery;  B,  duct  of  Botal;  p,  pulmonary  artery  with  the  still  diminutive  pulmonary  branches 
i  and  2. 

The  large  truncus  venosus  (4,  v),  which  becomes  embedded  in  the  middle  of  the 
posterior  wall  of  the  auricular  portion,  is  formed  by  the  union  of  the  superior 
and  inferior  cavae.  Later,  this  common  trunk  is  drawn  into  the  wall  of  the 
enlarging  auricle,  and  in  this  way  there  result  the  separate  openings  for  the 
two  cavae.  In  man  the  development  of  a  special  cavity  in  which  the  heart  lies 
occurs  early;  a  portion  of  the  rudimentary  diaphragm  bounds  this  cavity. 

Between  the  fourth  and  the  fifth  week  the  division  of  the  heart  into  a  right 
and  a  left  begins.  In  correspondence  with  the  perpendicular  groove  in  the  ven- 
tricle there  first  grows  vertically  upward  into  the  ventricle  a  septum  (5)  that 
divides  the  ventricular  portion  into  a  right  and  a  left  half  ($,R,L).  Between  the 
ventricular  portion  and  the  auricular  portion  the  heart  undergoes  constriction, 
forming  the  auricular  canal.  This  contains  a  communication  between  the  auricle  and 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM 


99I 


both  ventricles,  lying  between  an  anterior  and  a  posterior  lip  of  projecting  endothe- 
lium,  from,  which  the  auriculo ventricular  valves  are  formed.  The  ventricular  sep- 
tum grows  upward  toward  the  auricular  canal  and  fuses  at  this  point  with  two  endo- 
thelial  proliferations  (endothelial  cushions),  which  in  the  lumen  of  the  auricular 
canal  traverse  the  mouth  of  the  canal  from  before  and  behind.  In  the  eighth 
week  the  ventricular  septum  is  fully  developed.  A  free  communication  thus 
exists  between  the  large  undivided  auricle  and  the  corresponding  ventricle  (5) 
by  way  of  a  right  and  a  left  auriculo-ventricular  orifice.  There  then  grow  into 
the  large  truncus  arteriosus  (4,  p)  two  wing-like  septa  (4,  p  a),  which  finally 
meet  in  union  and  divide  the  tube  into  two  tubes  (5 ,  a  p).  The  latter  lie  parallel 
to  one  another  like  the  barrels  of  a  double-barreled  gun  (aorta  and  pulmonary 
artery).  The  septum  between  the  two  assumes  a  downward  direction  in  such  a  way 
as  to  meet  the  interventricular  septum  (5).  In  this  way  the  right  ventricle 
communicates  with  the  pulmonary  artery  and  the  left  with  the  aorta.  The  divi- 
sion of  the  truncus  arteriosus,  however,  takes  place  only  in  its  first  part.  Further 
on,  it  is  not  complete,  that  is  the  pulmonary  artery  and  the  aorta  unite  above 
to  form  a  common  trunk — the  ductus  arteriosus  Botalli  (7,  B).  In  the  auricle 
thera  gro-vs  from  before  and  bahind  a  portion  of  a  septum  that  ends  within  the 
cavity  in  a  concave  border.  The  superior  cava  (6,  Cs)  enters  to  the  right  of  this 
fold,  so  that  its  blood  would  have  a  tendency  to  pass  into  the  right  ventricle  (in 
the  direction  of  the  arrow  6,  x).  The  inferior  cava  (6,  Ci) ,  on  the  contrary,  opens 
directly  opposite  the  margin  of  the  fold.  There  is  thus  formed  to  the  left  of  its 


t. 


FIG.  385.— Development  from  the  Aortic  Arches:  i,  The  rudimentary  ist,  2d,  and  3d  aortic  arches.  2,  Five 
aortic  arches:  fa,  common  aortic  trunk;  a  d,  descending  aorta.  3,  Atrophy  of  the  two  uppermost  arches 
on  each  side;  S,  subclavian  artery;  v,  vertebral  artery;  ax,  axillary  artery.  4,  Transition  to  the  definitive 
stage  of  formation;  P,  pulmonary  artery;  A,  aorta;  dB,  ductus  Botalli;  S,  right  subclavian  artery,  joined 
with  the  right  common  carotid,  which  divides  into  the  internal  (Ci)  and  the  external  (Ce)  carotid;  ax-,  axillary 
artery;  v,  vertebral  artery.  (Diagrammatic.) 

entrance,  opposite  the  auricular  fold,  the  valve  of  the  oval  foramen,  which  permits 
the  blood  to  flow  only  to  the  left  in  the  direction  of  the  arrow  y.  To  the  right 
of  the  mouth  of  the  cava,  opposite  the  fold,  there  is  formed  the  Eustachian  valve, 
w.iich  together  with  the  tubercle  of  Lower  (tL)  guides  the  stream  of  the  inferior 
cava  to  the  left  into  the  left  auricle.  After  birth  the  opening  is  closed  by  the 
valve  of  the  oval  foramen.  In  addition,  the  ductus  Botalli  is  obliterated  (by 
increase  of  the  pressure  in  the  aorta,  which  closes  the  lumen  of  the  mouth),  so 
that  the  blood  of  the  pulmonary  artery  is  now  forced  to  pass  through  the  distend- 
ing pulmonary  branches. 

The  persistence  of  the  oval  foramen  is  a  developmental  defect  that  causes 
severe  circulatory  disturbances.  Kergeradek  discovered  the  fetal  heart-sounds. 
Many  anomalous  peculiarities  in  the  development  of  the  heart,  which  have  been 
studied  especially  by  Born  and  Rose,  cannot  be  described  here. 

Arteries. — With  the  development  of  the  visceral  arches  and  clefts,  the  num- 
ber of  aortic  arches  on  each  side  becomes  increased  from  one  up  to  five  (Fig.  385), 
and  these  pass  above  and  below  each  visceral  cleft,  but  subsequently  unite  to  form 
a  common  trunk  (2,  ad).  The  vessels  persist  only  in  gill-breathers,  Fig.  74.  In 
man,  the  two  uppermost  aortic  arches  on  each  side  (3)  atrophy  first.  In  the  division 
of  the  truncus  arteriosus  into  the  pulmonary  artery  and  the  aorta  (4,  PA)  the  lower- 
most arch  on  each  side,  together  with  its  origin,  becomes  the  pulmonary  artery 
(4)  and  therefore  arises  from  the  right  heart.  Of  these,  the  left  lowermost  arch 
forms  the  ductus  -Botalli  (dB),  and  at  its  origin  the  pulmonary  branches  of  the 
pulmonary  artery  arise.  Of  the  arches  joined  to  the  aorta,  the  left  middle  one 


992 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


I. 


(into  which  the  ductus  Botalli  empties)  becomes  the  permanent  aorta,  the  right, 
the  right  subclavian  (5) .  The  uppermost  arch  on  each  side  becomes  the  origin 
of  the  carotids  (Ci,  Ce} .  According  to  Zimmermann  there  occur  in  man  and  in  rab- 
bits the  rudiments  of  a  hitherto  unknown  transitory  arch  between  the  lowermost 
and  the  next  higher  aortic  arch  on  each  side. 

The  arteries  of  the  first  and  the  second  circulation  have  already  been  con- 
sidered. With  the  disappearance  of  the  omphalomesenteric  circulation,  there 
is  but  one  omphalomesenteric  artery  present,  and  this  soon  gives  off  a  branch 
to  the  intestine.  Later,  the  umbilical  artery  atrophies,  so  that  the  trunk  of  the 
intestinal  artery  (the  superior  mesenteric  artery,  the  largest  of  all  arteries)  is 
originally  an  omphalomesenteric  artery. 

The  Veins  of  the  Body. — The  veins  that  first  develop  in  the  body  of  the  embryo 
itself  are  the  two  cardinal  veins:  on  each  side  an  anterior  (Fig.  386,  I,  cs)  and 
a  posterior  (ci} ,  which,  passing  toward  the  heart,  unite  on  each  side  to  form  a 
large  trunk,  the  duct  of  Cuvier  (D  C}.  The  latter  joins  the  venous  portion  of 
the  heart.  The  anterior  cardinal  veins  give  off  the  subclavian  veins  (b  b)  and  the 
common  jugular  veins,  which  divide  into  the  internal  (Ji)  and  external  (le) 

jugular  veins.  In  addition, 
there  is  a  transverse  anas- 
tomosing branch  passing  ob- 
liquely from  the  left  (where 
it  divides)  toward  the  right, 
and  emptying  into  its  trunk 
at  a  somewhat  lower  level. 
In  the  definitive  development 
(II)  this  anastomosing  branch 
(A s)  becomes  large  (forming 
the  left  innominate  vein)  ; 
besides  the  subclavian  veins 
(b  b)  increase  in  size  with  the 
growth  of  the  extremities;  and, 
finally,  the  caliber  of  the  two 
jugular  veins  is  reciprocally 
altered,  so  that  the  rudi- 
mentary internal  jugular  vein 
becomes  large  (Ji},  while  the 
external  jugular  vein  becomes 
smaller  (le) ;  in  many  animals, 
for  example  dogs  and  rab- 
bits, the  embryonal  propor- 
tions persist.  The  portion 
of  the  left  superior  cardinal 
vein  from  the  point  of  anas- 
tomosis down  to  the  left  duct 
FIG.  386.— -I,  Rudimentary  veins  of  the  body  of  the  embryo.  II,  _r  p-,,:  —  attwr^W  T^~ 

Transformation  of  the  same  rudimentary  into  the  definitive  Ot   |-uvier  atrophies.      1  he  pOS- 

veins.    (Diagrammatic.)  tenor    cardinal    veins     divide 

in  the  pelvis  into  the  hypo- 
gastric  (I,  h)  and  the  exter- 
nal iliac  (/  /).  The  inferior  cava  is  at  first  small  (I,  V  c);  it  divides  at 
the  pelvic  inlet,  and  passes  over  on  each  side  to  the  point  of  division  of 
the  cardinal  veins.  In  addition,  there  exists  a  transverse  ascending  anas- 
tomosing branch  between  the  right  and  left  cardinal  veins.  For  the  establish- 
ment of  the  definitive  condition,  the  inferior  cava  dilates  (II,  Ci),  and  with  it, 
downward,  the  hypogastric  and  external  iliac  on  each  side.  The  right  cardinal 
vein  is  replaced  by  the  small  vena  azygos  (A  z) ,  and  on  the  left  side  up  to  the  trans- 
verse anastomosing  branch  in  an  analogous  manner  the  vena  hemiazygos  (Hz) . 
Un  the  other  hand,  the  upper  portion  above  the  anastomosing  branch  up  the  left 
duct  of  Cuvier  atrophies.  The  site  of  entrance  of  the  vena  magna  cordis  is  the 
remains  of  the  left  duct  of  Cuvier.  Finally,  the  combined  venous  trunk  is  so 
withdrawn  into  the  wall  of  the  auricle  (V)  that  the  two  cavse  acquire  independent 
All  vertebrates  possess  the  same  rudimentary  venous  system  in  the 
embryonal  state;  it  persists,  however,  only  in  fishes  (Fig.  74  /) 

Veins  of  the  First  and  the  Second  Circulation,  and  the  Development  of  the 
Portal  System.— Originally  the  two  omphalomesenteric  veins  (om,  om,)  empty  into 
the  truncus  venosus  of  the  first  pouch-shaped  rudimentary  heart  (Fig.  387,  i,  #). 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


993 


The  right  of  these,  however,  soon  atrophies.  As  soon  as  the  allantois  is  formed, 
both  allantoic  or  umbilical  veins  unite  to  form  the  truncus  venosus  (i,  u  u^. 
At  first  the  omphalomesenteric  veins  are  larger  than  the  umbilical  veins:  later, 
the  conditions  are  reversed,  and  also  the  right  umbilical  vein  atrophies.  As  soon 
as  the  veins  of  the  trunk  itself  are  formed,  the  inferior  cava  also  empties  into 
the  truncus  venosus  (2 ,  C  i).  Gradually  the  umbilical  vein  becomes  the  chief 
path  (2 ,  ttt) ,  to  which  the  small  omphalomesenteric  vein  (2 ,  omj  sends  but  little 
blood. 

The  umbilical  and  omphalomesenteric  veins  pass  in  part  directly  beneath 
the  liver  to  the  heart;  in  part,  however,  they  send  also  branches,  carrying  arterial 
blood,  into  the  liver,  which  grows  around  the  vessels  from  above — the  venae 
advehentes  (2  and  3 ,  a) .  The  blood  from  the  latter  passes  back  through  other 


Of/I 


om, 


1. 


u       u 


FIG 


387. — Development  of  the  Veins  of  the  First  and  the  Second  Circulation,  and  of  the  Portal  System:  H,  heart; 
R,  right,  L  left  side  of  the  body,  om,  right  omphalomesenteric  vein,  om\,  left  omphalomesenteric  vein;  «, 
right  umbilical  vein;  Wj,  left  umbilical  vein;  Ci,  inferior  vena  cava;  a,  venae  advehentes;  r,  vena?  reve- 
hentes;  D,  intestine;  m,  mesenteric  vein;  4 /,  splenic  vein;  2 /,  liver.  (Diagrammatic.) 


veins  (venae  revehentes,  2  and  3,  r),  which  again  unite  with  the  main  trunk  of 
the  umbilical  veins  at  the  blunt  border  of  the  liver.  In  the  liver,  the  umbilical 
vein  (3,  Uj)  anastomoses  with  the  omphalomesenteric  vein  (3,  owj. 

.With  the  development  of  the  bowel  (3,  D  )  the  mesenteric  vein  (wi)  empties 
into  the  omphalomesenteric;  as  does  also  the  splenic  vein  (4,  /)  with  the  develop- 
ment of  the  spleen.  When,  later,  the  omphalomesenteric  vein  atrophies  (4,  om^), 
the  mesenteric  vein  is  the  sole  trunk  of  these  previously  united  vessels.  It  is, 
therefore,  the  vein  that  unites  with  the  umbilical  vein  in  the  liver,  and  it  thus 
represents  the  trunk  of  the  portal  vein.  When,  finally,  at  birth  the  umbilical 
vein  atrophies  (4,  %) ,  the  mesenteric  vein  alone  remains  as  the  portal  vein.  This 
must,  however,  send  all  its  blood  through  the  liver,  as  the  ductus  venosus  of 
Arantius  (4,  Da)  becomes  obliterated.  In  this  way  the  portal  circulation  is  com- 
pleted. 


DEVELOPMENT  OF  THE  ALIMENTARY  CANAL. 

The  primitive  intestine  is  originally  a  straight  tube,  passing  from  the  cranial 
to  the  caudal  extremity.  The  omphalomesenteric  duct  is  inserted  at  a  point 
that  corresponds  later  to  the  lower  part  of  the  ileum.  Here  the  tube  in  the  fourth 
week  makes  a  slight  bend  toward  the  navel  (Fig.  388,  /).  It  has  already  been 
pointed  out  that  the  duct  later  is  obliterated  (intestinal  navel)  and  is  finally 
detached  as  a  thread  from  the  intestinal  tube;  it  is  still  discernible  in  the  third 
month.  In  rare  cases  a  short  blind  tube  joined  to  the  bowel  persists  as  a  vestige 
of  the  incompletely  obliterated  duct.  This  is  the  so-called  true  intestinal  diver- 
ticulum:  occasionally  a  cord  (the  obliterated  omphalomesenteric  vessels)  passes 
from  it  to  the  navel;  in  rare  cases  the  duct  may  remain  open  through  the  navel 
even  after  birth,  so  that  a  congenital  fistula  of  the  ileum  results;  or  finally  the 
diverticulum  may  be  the  seat  of  cyst-formation.  In  human  embryos  four  weeks 
old,  His  was  able  to  differentiate  the  mouth,  the  pharynx,  the  esophagus,  the 
stomach,  the  duodenum,  the  mesenteric  intestine,  the  end-gut  and  the  cloaca. 

63 


994 


DEVELOPMENT    OF    THE    ALIMENTARY    CANAL. 


At  a  later  period  the  bowel  forms^the  first  loop  (Fig.  388,  //),  being  rotated  on 
itself  at  the  situation  of  the  intestinal  umbilicus,  so  that  the  lower  portion  of  the 
bowel  lying  next  to  the  knee-shaped  flexure  is  turned  upward,  and  the  upper 
portion  is  turned  downward.  From  the  lower  limb  of  this  loop  there  grow  the 


FIG.  388.— Development  of  the  Intestine:  v, 
Stomach;  o,  insertion  of  the  omphalomes- 
enteric  duct;  t,  small  intestine;  c,  colon; 
r,  rectum.  (Diagrammatic.) 


FIG.  389. — Development  of  the  Lungs:  A, 
Evagination  of  the  lungs  as  double  sacs; 
k,  mesoblastic  layer;  /,  entoblastic  layer; 
m,  stomach;  s,  esophagus.  B,  Further 
ramification  of  the  lungs:  /,  trachea;  b,  e, 
bronchi;  /,  budding  glandular  vesicles. 


m 


coils  of  small  intestine,  constantly  increasing  in  length  (///,  t) .  From  the  upper 
limb,  which  increases  in  length,  the  large  intestine  is  formed  in  such  a  manner 
that  first  the  descending  colon,  then  by  elongation  the  transverse  colon,  and 
finally  also  the  ascending  colon  results. 

The  intestinal  canal  gives  rise  through  evagination  to  various  glands.     This 
process  is  participated  in  by  the  cells  of  the  hypoblast,  which  become  the  secretory 

cells  of  the  glands,  as 
well  as  the  splanchno- 
pleure,  which  supplies 
the  'limiting  membrane 
of  the  glands.  These 
diverticula  are  in  order : 
(i)  The  salivary  glands, 
which  at  first  are  solid, 
but  soon  develop  from 
the  oral  cavity  as  intri- 
cately ramifying  glandu- 
lar bodies.  (2)  The  lungs, 
which  develop  as  two 
separate  hollow  vesicles 
(Fig.  389,  A,  /),  which 
subsequently  take  their 
origin  from  a  common 
tubular  evagination  of 
the  esophagus.  The  up- 
per portion  of  the  united 
tracheal  tube  becomes 
the  larynx.  The  epi- 
glottis and  the  thyroid 
cartilage  are  derived 


from    the     rudimentary 
tongue.   The  two  vesicles 
grow    according    to    the 
type     of     a     branching, 
tubular  gland,  with  hol- 
low buds  (B,f).     In  the 
earliest     stages     of     de- 
velopment there  exists  no  particular  difference  between  the  epithelium  of   the 
bronchi  and  that  of  the  primitive   air-vesicles.      The  spleen  and  the  suprarenal 
bodies,  however,  do  not  develop  in  this  manner.      The  first  is  formed  as  a  fold  of 


FIG.  390.— Development  of  the  Great  Omentum.  /  and  //:  kg, 
hepatogastric  ligament;  m,  greater  and  n  lesser  curvature  of  the 
stomach;  5  posterior  and  i  anterior  layer  of  the  omentum;  me, 
mesocolon;  c,  colon.  ///  (in  addition  to  the  letters  in  /  and  II): 
L,  liver;  /,  small  intestine;  b,  mesentery;  p,  pancreas;  d,  duodenum ; 
r,  rectum;  N,  great  omentum.  (Diagrammatic.) 


DEVELOPMENT  OF  THE  URINARY  AND  SEXUAL  ORGANS.      995 

the  mesogastrium  in  the  second  month;  the  latter  are  at  first  larger  than  the  kid- 
neys. (3)  The  pancreas  develops  in  the  same  way  as  the  salivary  glands,  and 
originally  in  two  rudimentary  parts,  a  dorsal  and  a  ventral.  It  is,  however, 
not  yet  indicated  in  the  fourth  week.  (4)  The  liver  appears  early,  beginning  as 
an  evagination  by  means  of  two  hollow,  primitive  ducts,  which  break  up  to  form 
the  biliary  passages.  At  their  periphery  they  exhibit  solid  cellular  masses,  the 
liver-cells,  which  thus  also  are  derived  from  the  hypoblast.  As  early  as  the  second 
month  the  liver  is  large;  it  secretes  as  early  as  the  third  month.  According 
to  Kupffer  a  single  large  gland,  which  in  lower  animals  extends  throughout  the 
length  of  the  mid-bowel,  corresponds  to  the  liver,  spleen  and  pancreas.  From 
this  the  three  organs  are  subsequently  differentiated.  (5)  In  birds  two 
small  sacs  are  formed  from  the  hind-gut.  (6)  The  fetal  respiratory  organ,  the 
allantois,  has  already  been  considered  (p.  974).  The  inner  surface  of  the  ccelom, 
the  surface  of  the  bowel  and  of  the  mesentery  become  covered  with  a  serous  mem- 
brane, the  peritoneum.  This  encloses  the  bowel,  which  for  a  time  remains  simple, 
in  a  duplicature  or  fold.  On  the  stomach,  which,  at  first,  occupies  a  vertical 
position  as  a  spindle-shaped  dilatation  of  the  digestive  tract,  this  fold  is  known 
as  the  mesogastrium.  Subsequently  the  stomach  comes  to  lie  upon  its  side,  and 
in  such  a  way  that  the  left  aspect  becomes  the  anterior,  the  right  the  posterior. 
In  this  way,  the  insertion  of  the  mesogastrium,  which  at  first  was  directed  pos- 
teriorly, toward  the  vertebral  column,  becomes  directed  toward  the  left.  The 
line  of  insertion  is  formed  by  the  region  of  the  greater  curvature,  which  subse- 
quently becomes  more  markedly  curved.  From  the  greater  curvature,  the  meso- 
gastrium is  prolonged  as  a  pouch-shaped  appendage  (Fig.  390,7  and  //,  5  *) ,  the  omen- 
tal  bursa,  so  far  downward  as  to  extend  over  the  transverse  colon  and  the  coils  of 
small  intestine  ///,  TV).  As  the  mesogastrium  consisted  originally  of  two  layers, 
the  duplicature  formed  from  it,  the  omental  bursa,  must  consist  of  four  layers. 
In  the  fourth  month  the  posterior  surface  of  the  omental  bursa  becomes  adherent 
to  the  surface  of  the  transverse  colon. 

DEVELOPMENT  OF  THE  URINARY  AND  SEXUAL  ORGANS. 

Urinary  Organs. — The  urine-forming  gland  originates  developmentally  from 
three  organs,  wnich  succeed  one  another  in  function:  (i)  The  rudimentary  kid- 
ney (pronephros) .  (2)  The  primitive  kidney  (mesonephros) .  (3)  Definitive 
kidney  (metanephros) . 

1.  The  rudimentary  kidney  is  in  the  amniota  (and  salachians)   only  a  rudi- 
mentary embryonal  organ;    in  the  remaining  vertebrates,  it  still  exhibits  some 
functional  activity  in  the  embryonal  or  larval  period;    it  is  here  the  provisional 
embryonal   kidney   (as   the    Wolffian    body    is    for   the  amniota).     In  bony  fish 
canals  can  be  differentiated  that   begin  anteriorly  within  the  abdominal  cavity 
by  means  of  funnel-shaped  openings  and  unite  to  form  a  common  excretory  duct 
that  empties  into  the  cloaca.     In  front  of  the  funnels  lies  the  glomerulus,  whose 
secretion  is  carried  outward  in  the  canals. 

2.  In  the  amniota  the  primitive  kidney  (mesonephros)  is  the  fetal  uriniferous 
organ.     From  this  there  arises  as  the  first  formation,  in  the  chick  on  the  second 
day,  in  rabbits  on  the  ninth  day,  the  duct  of  the  primitive  kidney  or  Wolffian 
duct  (Fig.  392,  /,  W),  which  is  formed  from  cells  of  the  ectoderm  and  at  first  is 
solid,  to  the  side  of  and  somewhat  behind  the  primitive  vertebrae  and  extending 
from  the  fifth  to  the  last  primitive  vertebras.     Seated  within  this  duct,  there  arise 
in  the  mesoblast  from  the  level  of  the  liver  downward  a  series  of  tubules,  wrhich 
in  the  chick  are  believed  at  first  to  open  free  at  their  other  extremities  into  the 
peritoneal  cavity,  and  which  become  transformed  into  structures  similar  to  the 
glomerulus  of  the  kidney  by  the  ingrowth  of  vascular   convolutions  into   their 
extremities.     The  tubules  elongate,  become  twisted  into  convolutions,  and  increase 
by  the  addition  of  newly  formed  communicating  accessory  tubes.     The   caudal 
extremity  of  the  Wolffian  duct  is  at  first  closed;  its  lower  extremity,  which  lies 
in  a  fold  projecting  into  the  abdominal  cavity  (plica  urogenitalis),  opens  (in  the 
rabbit  on  the  eleventh    day)  into    the    urogenital    sinus.     In   the    anamnia  the 
primitive  kidney  is  the  permanent  uriniferous  gland. 

3.  Just  above  the  outlet  of  the  Wolffian  duct  the  definitive  kidney   (meta- 
nephros) arises  in  an  upward  direction  as  the  renal  duct.     The  elongated  duct 
divides  at  its  upper  extremity  like  a  shrub.     These  accessory  branches    finally 
form  convolutions.     Each  canal  at  its  extremity  assumes  the  form  of  a  pedun- 
culated  hollow  rubber-ball,  with  a  cup-shaped  depression,  into  which  the  vascular 


996 


DEVELOPMENT    OF    THE    URINARY    AND    SEXUAL    ORGANS. 


convolution  formed  independently  penetrates,  and  here  it  becomes  closely 
surrounded.  The  duct  of  the  kidney  later  empties  separately  into  the  urogenital 
sinus,  and  becomes  the  ureter.  The  point  where  the  branching  begins  becomes 
the  site  of  the  pelvis  of  the  kidney;  the  branches  themselves  become  the  urinary 
tubules.  Toldt  found  as  early  as  the  second  month  complete  Malpighian  bodies 
in  the  human  kidney;  in  the  fourth  month  Henle's  loops.  The  urinary  blad- 
der arises  in  its  first  indication  as  early  as  the  fourth  week,  becoming  more 
distinct  in  the  second  month  from  the  first  portion  of  the  allantois  (Fig.  392, 
4,  a).  The  upper  portion  passes  over  into  the  middle  ligament  of  the  bladder 
as  the  obliterated  urachus,  which  often  remains  permeable  for  a  short  distance 
beyond  the  bladder;  although  even  in  adults  there  often  persist,  in  the  lower 
third  of  the  urachus,  unobliterated  portions,  which  may  give  rise  to  cyst-forma- 
tion. 

According  to  Keibel,  the  development  of  the  bladder  takes  place  in  such  a 
manner  that   the  common  cloacal  space  is   divided  by  two  lateral  folds  into  an 

anterior       (the      rudimentary 
urinary  bladder)    and  a  poste- 

V  rior    space     (rectum).        Con- 

genital communications  be- 
tween the  bladder  and  the 
rectum  are  thus  easily  ex- 
plained as  developmental  de- 
fects. Congenital  fissure  of 
the  abdominal  wall  and  the 
bladder  results  from  persistent 
patulousness  of  the  blastopore. 
Internal  Organs  of  Gener- 
ation.— In  front,  and  internally 
to,  the  Wolffian  bodies  there 
develops  in  the  mesoblast  the 
longitudinal,  projecting  sexual 
gland  (Fig.  392,  I,  D),  which 
originally  is  the  same  in  both 
sexes  (hermaphroditic  stage) . 
In  addition ,  there  forms  parallel 
to  the  Wolffian  duct  (W)  a 
canal,  which  empties  down- 
ward likewise  into  the  urogen- 
ital sinus,  the  duct  of  Miiller 
or  the  sexual  duct  (M).  The 
sexual  gland  appears  first  as  a 
longitudinal  protuberance,  and 
is  covered  with  the  high  epi- 
thelium of  the  mesoblast,  the 
germinal  epithelium  of  Wal- 
deyer.  The  duct  of  Miiller 
(which  is  not  yet  present  at 
the  fourth  week)  appears  at 
first  as  a  linear  furrow  in  the 
germinal  epithelium,  which 
then  becomes  deeper  and  con- 
stricts itself  off  to  a  cord  that 
is  at  first  solid,  but  later  be- 
comes hollow.  The  upper  out- 
let of  the  duct  opens  free  into 
In  +^~  ~,^.'^-.:-  :;•'"  --— — — o  ^  both  ducts  fuse  for  a  sbiort  dis- 


E 


r 


FIG. 


39I-— Transverse  Section  through  the  Primitive  Kidney  the 
Rudimentary  Duct  of  Miiller,  and  the  Sexual  Gland  in  a  Chick 
at  the  Fourth  Day  (after  Waldeyer);  enlarged  160  times:  m, 
mesentery,  L,  abdominal  wall;  a',  the  region  of  the  germinal 
epithelium  from  which  the  anterior  extremity  of  the  duct  of 
Muller  (z)  has  invaginated  itself;  a.  thickened  layer  of  the 
germinal  epithelium,  in  which  the  primary  germ-cells  (G  and 
lie;  h,  mesenchyma,  from  which  the  stroma  of  the  sexual 
gland  is  formed;  WK,  primitive  kidney;  y,  duct  of  the  primi- 


the  oviduct  (//, 

.  -_ „  ^-^^^i^ij.j.xuj.^0  vjj.  uuuii,  me  uterus  (£/)• 

^  male  sex  the  germinal  epithelium  is  lower  (although  at  first  it  still 

^SB^ttgESME***** 


DEVELOPMENT  OF  THE  URINARY  AND  SEXUAL  ORGANS. 


997 


and  the  Wolffian  duct  in  man  becomes  the  vas  deferens  (///,  V) ,  together  with 
the  seminal  vesicle.  According  to  Sernoff,  Bornhaupt,  Egli  and  Biegelow,  autoch- 
thonous strands  of  cells  develop  within  the  sexual  gland  of  man  and  these  are 
transformed  into  the  seminal  ducts,  and  later  communicate  with  the  Wolffian 
ducts. 

The  Mullerian  ducts  (the  true  excretory  ducts  of  the  sexual  glands)  undergo 
atrophy  in  man,  with  the  exception  of  the  lowermost  portion,  which  becomes 
the  masculine  utricle  or  the  prostatic  vesicle  (///,  u);  this  is  the  analogue  of  the 
uterus.  In  carnivora  and  ruminants  the  Miillerian  ducts  attain  a  greater  size, 
to  form  a  rudimentary  vagina  and  a  uterus  bicornis;  in  rare  cases  a  true,  small 
uterus  has  also  been  found  in  man.  The  upper  tubules  of  the  Wolffian  body 
unite  in  the  third  month  with  the  sexual  gland,  and  become  the  coni  vasculosi 
of  the  epididymis,  which  is  furnished  with  ciliated  epithelium  (£) ;  the  remaining 
portion  of  the  primitive  kidney  undergoes  atrophy.  A  number  of  detached 
tubules  become  the  vasa  aberrantia  (a)  of  the  testicle.  The  pedunuculated 
hydatid  of  Morgagni  (ti)  at  the  head  of  the  epididymis  is,  according  to  v.  Luschka, 
Becker,  and  M.  Roth,  a  constricted-off  vesicle  of  the  epididymis,  occasionally 
containing  semen  and  lined  by  ciliated  epithelium;  according  to  Waldeyer  it  is 
the  homologue  of  the  infundibuliform  portion  of  the  oviduct,  while  according  to 
Toldt  it  is  derived  from  the  abdominal  extremity  of  the  duct  of  Muller.  The 


FIG.  392. — Development  of  the  Internal  Organs  of  Generation.  /,  Undifferentiated  stage:  D,  sexual  gland 
lying  upon  the  tubules  of  the  Wolffian  body;  W,  Wolffian  duct;  M,  duct  of  Muller;  S,  urogenital  sinus.  77, 
Transformation  into  the  Female  type:  F,  fimbria  with  the  hydatid  (&1);  T,  oviduct;  U,  uterus;  5,  urogenital 
sinus;  O,  ovary;  P,  parovarium.  777,  Transformation  into  the  male  type:  H,  testicle;  E,  epididymis,  with 
the  hydatid  (h);  a,  vas  aberrans;  V,  vas  deferens;  S,  urogenital  sinus;  u,  utriculus  masculinus;  4  d,  end-gut; 
a,  allantois;  «,  urachus;  K,  cloaca;  5  M,  rectum;  m,  perineum;  b,  rudimentary  bladder;  S,  urogenital  sinus. 
(Diagrammatic.) 


organ  of  Giraldes  (convoluted  tubules  with  ciliated  epithelium)  at  the  upper 
extremity  of  the  testicle  is  probably  also  a  vestige  of  the  Wolffian  body.  The 
Wolffian  duct  itself  becomes  the  vas  deferens  (V),  together  with  the  seminal 
vesicle  (as  an  outgrowth).  The  two  Wolffian  and  the  two  Mullerian  ducts  lie 
close  together  at  the  pelvic  inlet  in  a  cord  (genital  cord).  Later,  when  the  Mul- 
lerian ducts  have  undergone  atrophy,  the  seminal  ducts  formed  from  the  Wolffian 
ducts  become  more  widely  separated. 

In  the  female  sex,  the  tubules  of  the  primitive  kidney,  with  the  exception 
of  a  vestige  within  ciliated  tubes  (parovarium  or  Rosenmuller's  organ)  and  a  portion 
in  the  broad  ligament  resembling  the  organ  of  Giraldes,  undergo  atrophy  (II,  P); 
as  do  also  the  Wolffian  ducts;  although  they  are  still  visible  in  fetuses  of  five 
months,  but  downward  only  as  far  as  the  region  of  the  vaginal  vault;  below 
this  and  toward  the  urethral  orifice  they  disappear  completely.  Diminutive 
vestiges  of  the  ducts  are  often  found  anteriorly  and  laterally  embedded  in  the 
uterine  and  vaginal  muscularis,  chiefly  on  the  right.  They  persist  permanently 
in  ruminants,  the  horse,  the  pig,  the  cat,  the  fox,  as  Gartner's  ducts;  in  man 
they  may  give  rise  to  pathological  cyst-formation.  The  Mullerian  ducts  become 


998 


DEVELOPMENT    OF    THE    URINARY    AND    SEXUAL    ORGANS. 


fringes  at  their  upper  opening  to  form  the  fimbrise  (F) ,  upon  which  often  a  hydatid 
isjsituated  (k1).  According  to  Thiersch  and  Leuckart  the  two  Wolffian  and  the 
two  Mullerian  ducts  lie  together  below  in  the  genital  strand.  The  two  Mullerian 
ducts  now  unite  at  their  lower  extremities  (end  of  the  second  month)  and  form 
in  their  combined  lumen  the  vagina  and  the  uterus  ([/)>  while  the  upper,  free 
portion  of  each  becomes  the  oviduct  (T).  It  is  thus  clear  that  the  condition  of 
double  uterus  and  vagina  is  due  to  a  developmental  defect,  resulting  from  a  failure 
in  union.  The  vagina  is  originally  closed  by  epithelium;  arrest  of  development 
may  result  in  atresia  of  the  vagina.  The  Mullerian  ducts  empty  originally  into 
the  lowermost  posterior  portion  of  the  urinary  bladder,  below  the  ureters — uro- 
genital  sinus  (5) ;  later  this  portion  of  the  bladder  becomes  elongated  posteriorly 
in  such  a  manner  that  the  vagina  (the  united  Mullerian  ducts)  and  the  urethra 
are  united  only  at  a  point  deep  down  in  the  vestibule  of  the  vagina. 
.  'J  The  vagina  and  the  uterus  are  first  distinctly  separated  from  each  other  in 
the  fourth  month;  between  the  fifth  and  sixth  months  the  uterus  becomes  charac- 
teristically differentiated.  The  hymen  is  formed  in  the  fifth  month. 

The  testicle  lies  originally  in  the  inguinal  region  of  the  abdomen  (Fig.  393, 
V,  f) ,  supported  by  a  fold  of  peritoneum  (mesorchium,  m).  From  the  hilus  of  the 
testicle  there  passes  through  the  inguinal  canal  to  the  base  of  the  scrotum  (accord- 
ing to  C.  Weil,  only  to  the  root  of  the  penis)  a  cord,  the  gubernaculum  of  Hunter. 
At£the  same  time  there  is  formed  independently  from  the  peritoneum,  a  sheath- 


3. 

FIG.  393 —Development  of  the  External  Genitalia.  /  and  //:  Genital  eminence;  r,  genital  groove;  s,  coccyx; 
w,  cutaneous  elevations.  IV:  P,  penis;  R,  raphe  of  the  penis;  S,  scrotum.  ///:  c,  clitoris;  /,  labia  minora; 
L,  labia  majora;  o,  anus.  V  and  VI:  Descent  of  the  testicle;  t,  testicle;  m,  mesorchium;  pv,  vaginal  process 
of  the  peritoneum;  M,  abdominal  wall;  S,  scrotum.  (Diagrammatic.) 

like  process  extending  down  to  the  base  of  the  scrotum  (pv) .  Arrested  develop- 
ment or  atrophy  of  the  gubernaculum  of  Hunter  causes  the  testicle  to  be  drawn 
down  through  the  inguinal  canal  into  the  scrotum.  In  its  passage  the  testicle 
takes  with  it  from  the  superficial  or  transverse  abdominal  fascia  the  tunica  vagin- 
ahs  commums  as  a  covering;  and  with  it  the  muscular  fibers  carried  down 

rom  the  ascending  and  transverse  oblique  form  the  cremaster  muscle.  The 
peritoneal  covering  of  the  testicle  becomes  the  double  sac  of  the  tunica  vaginalis 
propria;  the  vaginal  process  of  the  peritoneum  is  obliterated  as  a  rule,  and  leaves 

rregular  vestiges  as  the  vaginal  ligament.  If  this  vaginal  process,  communicating 
with  the  peritoneal  cavity,  remains  patulous,  a  passage  is  afforded  for  the  develop- 
ment ot  a  congenital  external  inguinal  hernia. 

The  ovaries  also  pass  somewhat  downward.     A  strand  similar  to  the  guber- 
naculum of  Hunter,  passing  through  the  inguinal  canal,  later  becomes  the  muscular 
I  ligament  of  the  uterus.     Also  in  women  the  peritoneum  sends  a  vaginal 
process  through  the  inguinal  canal    (canal  of  Nuck).     Rarely  even   the  ovaries 

Ascend  into  the  labia  majora,  while,  conversely,  a  retention  of  the  testicles  in 
the  abdominal  cavity  (cryptorchism)  must  be  looked  upon  as  an  arrest  of  develop- 
ment. 

The  external  genitalia  are  at  first  not  to  be  differentiated  in  the  two  sexes 

393-  /I.     In  the  fourth  week  there  is  a  single  orifice  at  the  caudal  extremity, 

constituting  at  the  same  time  the  anus  and  the  opening  of  the  urachus,  thus  a 

•aca  (Fig.  392,  4,  A).     In  the  sixth  week  an  elevation  appears  in  front  of  the 

rig-  393.  /,  »),  the  genital  eminence,  then  laterally  from  the  opening 


DEVELOPMENT    OF    THE    URINARY    AND    SEXUAL    ORGANS.  999 

on  either  side  a  large  cutaneous  elevation  (//,  w) .  At  the  end  of  the  third  month 
there  passes  on  the  under  surface  of  the  genital  eminence  to  the  cloaca  a  groove, 
on  whose  two  sides  distinct  folds  appear  (//,  r).  In  the  middle  of  the  third  month 
the  cloacal  orifice  becomes  divided,  prolongations  from  above  and  from  each 
side  insinuating  themselves  as  the  perineum  (ra)  between  the  urachus,  which  has 
now  become  the  bladder  (Fig.  392,  5,  6),  and  the  rectum  (M). 

In  the  male  (IV)  the  genital  eminence  now  becomes  large,  and  its  groove  closes 
from  the  orifice  of  the  bladder  (the  urachal  orifice  of  the  former  cloaca)  to  the 
apex  of  the  eminence  in  the  tenth  week.  The  entrance  to  the  bladder  is  thus 
displaced  to  the  apex  of  the  genital  eminence.  Should  this  closure  fail  to  take 
place,  either  wholly  or  in  part,  there  occurs  the  arrest  of  development  known  as 
hypospadias.  In  the  fourth  month  the  glans  is  formed,  in  the  sixth  month  the 
prepuce;  both  are  at  first  adherent.  The  cutaneous  folds  that  unite  in  the  raphe 
form  the  scrotum. 

In  the  female  (///)  the  undifferentiated  condition  of  the  original  rudimentary 
sexual  organs  remains,  to  a  certain  degree,  permanent;  the  small  genital  eminence 
becomes  the  clitoris,  the  genital  folds  the  nymphae;  the  cutaneous  folds  remain 
separate  as  the  labia  majora.  The  urogenital  sinus  remains  short,  as  it  was, 
and  it  becomes  the  vestibule  of  the  vagina;  while  in  the  male,  through  closure 
of  the  genital  groove,  a  long  additional  canal  is  formed. 

Hermaprodism. — In  rare  cases  the  external  genitalia  persist  in  their  original 
undifferentiated  rudimentary  stage  (somewhat  as  is  shown  in  Fig.  393,  //),  con- 
stituting an  arrest  of  development.  Under  such  circumstances  an  external 
determination  of  sex  is  impossible  (pseudohermaphrodism) .  In  isolated  cases 
there  occurs  the  development  on  one  side  of  male,  and  on  the  other  side  of  female 
internal  organs  of  generation;  the  external  genitalia  are  then  not  typically  de- 
veloped. Such  cases  are  designated  true  lateral  hermaphrodism.  The  condition 
is  not  rare  in  swine,  goats  and  beeves,  but  it  has  probably  never  been  established 
in  man  beyond  all  doubt. 

The  cause  of  sexual  development  in  one  or  the  other  direction  has  not,  as  yet, 
been  determined  with  certainty.  From  statistical  data  (80,000  cases)  the  influence 
of  the  age  of  the  parents  has  been  established.  If  the  husband  is  younger  than 
the  wife,  boys  and  girls  will  be  produced  in  equal  number.  If  both  parents  are 
of  the  same  age,  there  will  1029  boys  and  1000  girls;  if  the  husband  is  older,  as  many 
as  1057  boys  to  1000  girls.  The  general  application  of  this  law  is  contested  by 
some.  Nutrition,  further,  appears  to  have  some  influence.  Fetuses  with  ad- 
herent placentas  that  communicate  through  the  fetal  vessels  are  always  of  the 
same  sex.  Acardiac  twins  that  receive  blood  that  has  already  nourished  the 
normal  twin  are  always  of  the  same  sex  as  the  well-developed  twin.  These 
facts  find  explanation  in  the  remarkable  observations  upon  armadillos.  In 
these  mammals,  the  numerous  young  of  the  same  brood,  all  of  which  develop 
normally  within  the  same  chorion,  are  always  of  the  same  sex.  In  insects  the 
nutrition  plays  an  important  role,  the  best-nourished  brood  forming  females  in 
preponderant  degree.  In  man,  impaired  nutrition  of  the  mother  leads  to  the 
expectation  of  male  children.  It  has,  further,  been  maintained  that  more  male 
progeny  result  when  greater  demands  are  made  upon  the  father,  also  when  im- 
pregnation of  the  wife  occurs  late,  and  finally  when  the  father  is  very  young 
or  very  old  (when  the  father  has  reached  middle  age,  more  girls  are  born).  Ac- 
cording to  Diising,  in  general  the  impregnation  of  a  young  ovum  with  an  old 
spermatozoid,  when  the  mother  is  well  nourished,  more  frequently  results  in  female 
progeny,  and  conversely  the  impregnation  of  an  old  ovum  with  a  young  sper- 
matozoid, especially  when  the  nutrition  of  the  mother  is  somewhat  impaired,  more 
frequently  results  in  male  children.  Thury  believed  that  animals  (cows)  that 
are  covered  shortly  after  heat  more  frequently  bear  female  offspring.  Fiirst 
believes  the  opposite  is  the  rule  for  man.  Fiquet  maintained  that  female  calves 
can  be  produced  if  the  cow  is  poorly  nourished  while  the  bull  is  well  nourished 
for  weeks  before  intercourse.  Other  investigators  have  come  to  the  conclusion  that 
the  sex  is  unalterably  established  already  at  the  time  of  conception.  Also  Pfliiger's 
investigations  have  shown  that  all  external  influences  (in  frogs)  during  develop- 
ment are  without  effect  upon  the  development  of  the  sex,  that  the  latter,  there- 
fore, is  definitely  established  before  impregnation.  Hermaphrodites  are  common 
among  tadpoles,  later  becoming  males  or  females. 


1000  DEVELOPMENT    OF    THE    CENTRAL    NERVOUS    SYSTEM. 


DEVELOPMENT  OF  THE  CENTRAL  NERVOUS  SYSTEM. 

Upon  each  side  of  the  fore-brain  vesicle,  prosencephalon,  which  is  covered 
externally  by  epiblast  and  internally  by  ependyma,  there  grows  a  large  pe- 
dunculated  hollow  vesicle,  the  rudimentary  cerebral  hemisphere,  telencephalon 
(the  forerunner  of  the  rhinencephalon,  pallium  and  corpus  striatum).  The 
relatively  narrow  opening  in  the  pedicle  is  the  rudimentary  foramen  of  Monro.  The 
small  middle  portion  behind  the  two  hemispheres  is  the  interbrain,  diencephalon 
(the  forerunner  of  the  thalamus,  together  with  the  metathalamus  and  the  epithal- 
amus).  The  interior  of  this  contains  the  third  ventricle,  which  about  the  second 
month  becomes  elongated  toward  the  base  in  the  shape  of  a  funnel  as  the  tuber 
cinereum,  with  the  infundibulum.  The  thalami,  developing  on  each  side  from 
the  floor  of  the  interbrain,  reduce  the  foramen  of  Monro  to  a  semilunar  cleft. 

In  the  second  month  the  corpora  albicantia  also  develop  at  the  base,  in  the 
third  month  the  chiasm;  the  commissures  are  formed  within  the  third  ventricle, 
in  the  third  month.  The  hypophysis,  belonging  to  the  mid-brain,  is  a  diverticulum 
of  the  pharyngeal  mucosa  through  the  base  of  the  cranium  toward  the  hollow 
infundibulum,  which  grows  to  meet  it,  and  which  subsequently  become  constricted 
off.  There  is  thus  an  effort  at  union  between  the  cavity  of  the  fore-gut  and  the 
medullary  canal.  It  should,  further,  be  mentioned  here  that  in  the  amphioxus, 
the  goose,  some  parrots  and  the  lizard,  the  medullary  canal  originally  communicates 
with  the  rudimentary  hind-gut  by  means  of  a  passage-way  (myeloenteric  canal)  . 
The  choroid  plexus,  which  grows  into  the  cavity  of  the  hemispheres  by  way  of 
the  foramen  of  Monro,  is  a  vascular  hyperplasia  of  the  ependyma.  In  the  fourth 
month  the  conarium  develops,  and  at  this  time  the  quadrigeminal  bodies  are 
already  covered  by  the  hemispheres.  Within  the  cavity  of  the  hemisphere 
there  develops  in  the  second  month  the  striate  body,  in  the  fourth  month  the 
cornu  Ammonis.  In  the  third  month  there  develops  the  fossa  of  Sylvius,  at  the 
bottom  of  which  the  insula  is  formed  as  a  part  of  the  original  trunk  of  the  fore- 
brain  and  over  which,  at  the  end  of  fetal  life,  the  operculum  projects.  From 
the  seventh  month  the  remaining  convolutions  of  the  brain  are  formed.  Medul- 
lated  fibers  are  already  present  in  the  cortex  of  the  newborn  in  the  central  con- 
volutions, as  well  as  the  paracentral  lobule.  Finally,  in  the  third  month  such 
fibers  appear  in  some  regions  of  the  frontal  and  parieto-temporal  lobes. 

The  mid-brain  vesicle,  mesencephalon  (rudiment  of  the  quadrigeminal  bodies 
and  cerebral  peduncles)  becomes  gradually  covered  by  the  growth  backward  of 
the  hemispheres;  its  cavity  becomes  reduced  to  the  aqueduct  of  Sylvius.  The 
surface  of  the  vesicle  becomes  divided  into  four  parts,  the  quadrigeminal  bodies; 
a  longitudinal  groove  appearing  in  the  third  month,  and  a  transverse  groove  in 
the  seventh  month.  The  cerebral  peduncles  are  formed  on  the  floor  as  thicken- 
ings. 

From  the  hind-brain,  metencephalon  (rudiment  of  the  pons  and  cerebellum), 
there  develop  separately  the  hemispheres  of  the  cerebellum,  which,  growing  back- 
ward, unite  in  the  middle  line.  In  the  sixth  month  the  hemispheres  are  more  fully 
developed,  and  the  vermiform  process  is  formed.  The  cerebellum  covers  the  sub- 
jacent unclosed  portion  of  the  medullary  tube  down  to  the  calamus.  The  open- 
ing of  the  medullary  tube  at  the  calamus  further  the  tendency  of  the  third 
ventricle  to  communicate  with  the  pharynx,  facilitates  an  understanding  of  the 
structure  of  articulates,  in  which  the  mouth  traverses  the  central  nervous  system, 
and  the  latter  passes  down  on  the  ventral  aspect.  The  pons  is  formed  on  the  floor 
of  the  hind-brain  in  the  third  month. 

The  spindle-shaped  after-brain,  myelencephalon  ,  grows  narrower  in  its  course 
downward  and  becomes  the  oblongata,  the  upper  portion  of  which  exhibits  the 
open  medullary  cavity. 

From  the  medullary  canal,  downward   from  the  after-brain,  the  spinal  cord 

levelops,  the  gray  substance  nearest  the  cavity;   later,  this  becomes  surrounded 

by  the  newly  formed  white  matter.     The  ganglion-cells  (amphibia)  increase  by 

division.     At  first  the  spinal  cord  extends  to  the  coccyx.     As  in  adults  the  extremity 

the  spinal  cord  extends  only  to  the  first  or  second  lumbar  vertebra,  the  spinal 

•rd  does  not  keep  pace  in  growth  with  the  spinal  column;    and  in  consequence 

the  lower  spinal  nerves  must  undergo  increase  in  length.     The  extent  to  which 

disparity  in  the  growth  of  the  spinal  column  and  the  spinal  cord  respectively 

that,  tor  instance,  the  former  grows  too  rapidly,  or  the  latter  too  slowly,  may 

produce  sensory  derangement  or  paralysis  in  the  lower  extremities  in  children 


DEVELOPMENT    OF    THE    CENTRAL    NERVOUS    SYSTEM.  IOOI 

should  be  kept  in  mind.  The  tactile  nerves  of  the  fetus  are  capable  of  executing 
reflex  movement,  for  example  on  pressure  upon  the  palpable  fetal  parts.  The 
first  indications  of  the  muscles  appear  upon  the  back  in  the  second  month;  in 
the  fourth  month,  they  become  reddish.  The  first  appreciable  fetal  movements 
occur  about  the  middle  of  pregnancy;  these  are  reflex,  as  they  are  observed  also 
in  acephalous  fetuses.  It  is  noteworthy  that,  in  the  early  periods  of  develop- 
ment, the  central  nervous  system  has  no  functional  influence  upon  the  vital 
processes,  having  no  sensory,  or  motor,  or  trophic  (morphogenetic)  function,  as 
has  been  demonstrated  by  the  extirpation-experiments  of  Alf.  Schapee. 

The  spinal  ganglia  develop  from  a  special  band,  situate^  on  each  side  of  the 
medullary  canal,  and  forming  the  direct  connection  between  this  and  the  epi- 
dermis. The  spinal  ganglia  are  the  nuclei  of  origin  of  the  sensory  nerves, 
whence  a  communication  with  the  spinal  cord  is  established  and  the  peripheral 
nerve-trunks  grow  in  a  centrifugal  direction.  The  nerves  of  special  sense  also 


FIG.  394. — Development  of  the  Eye:  /,  Invagination  of  the  lenticular  sac  (£)  into  the  primary  optic  vesicle  (P); 
e,  epiderm;  m,  mesoblast;  II,  the  invaginated  primary  optic  vesicle  viewed  from  below;  «,  optic  nerve;  a  the 
outer,  i  the  inner  layer  of  the  invaginated  vesicle;  L,  lens;  ///,  the  same  formation  in  longitudinal  section; 
IV,  further  development:  e,  cornea!  epithelium;  c,  cornea;  m,  capsulopupillary  membrane;  L,  lens;  a, 
central  artery  of  the  retina;  5,  sclera;  ch,  choroid;  p,  pigment-epithelium  of  the  retina;  r,  retina;  V,  per- 
sistent vestige  of  the  pupillary  membrane.  (Diagrammatic.) 

grow  from  the  periphery  into  the  central  organ.  The  motor  nerve-roots  grow 
from  the  rudimentary  ganglia  in  the  central  organ  (neuroblasts)  into  the  periphery. 
At  first  the  nerves  are  non-medullated.  Human  embryos  four  weeks  old  possess 
spinal  ganglia,  anterior  roots  and  in  part  the  trunks  of  the  spinal  nerves, 
whereas  the  posterior  roots  are  absent.  The  ganglia  of  the  fifth,  seventh,  eighth, 
ninth,  and  tenth  cranial  nerves,  and  in  part  their  origins,  are  present;  on  the 
other  hand,  His  failed  to  find  the  first,  second,  third,  and  twelfth  cranial  nerves, 
as  well  as  the  sympathetics.  Fetuses  with  absence  of  the  spinal  cord  show  that 
the  posterior  roots  present  and  the  sensory  nerves  originate  from  the  spinal 
ganglia.  In  the  new-born  the  cranial  motor  nerves  and  the  auditory  are  already 
provided  with  medullary  sheaths;  the  others  are  not.  Their  envelopment  pro- 
gresses peripherally.  In  the  peripheral  spinal  nerves  the  formation  of  the  medul- 
lary sheath  does  not  take  place  before  the  second  and  third  years. 

The  sympathetic  ganglia  of  the  viscera  make  their  way  from  the  sympa- 
thetic cord  into  the  organs. 

DEVELOPMENT  OF  THE  ORGANS  OF  SPECIAL  SENSE. 

Eye. — The  primary  optic  vesicle  grows  out  to  the  external  covering  of  the 
head  (epiblast)  and  then  becomes  invaginated  into  itself  from  before  backward 
(as  has  been  seen  to  take  place  in  human  embryos  four  weeks  old),  so  that  the 
pedunculated  vesicle  has  acquired  the  shape  of  an  egg-cup  (Fig.  394,  /).  The 
interior  of  this  cup,  the  subsequent  cavity  of  the  eye,  is  now  called  the  secondary 
optic  vesicle.  The  portion  of  the  original  vesicle  that  has  undergone  invagina'- 
tion,  namely  the  anterior  convex  portion,  now  made  concave,  becomes  the  retina 
(IV ',  r) ;  the  posterior  portion  of  the  vesicle  becomes  the  pigmented  choroidal 
(retinal)  epithelium  (IV,  p).  The  pedicle  is  the  subsequent  optic  nerve.  The 
invagination  of  the  primary  optic  vesicle  takes  place,  however,  not  exactly  accord- 
ing to  this  simple  plan;  but  there  is  formed  below  on  the  egg-cup-shaped  structure 


IOO2  DEVELOPMENT    OF    THE    ORGANS    OF    SPECIAL    SENSE. 

a  cleft,  which  permits  certain  portions  of  the  mesoblast  to  enter  the  ocular  cavity. 
This  cleft,  which  extends  from  the  pedicle  of  the  optic  vesicle  to  the  border  of 
the  invaginated  cup  (//),  is  known  as  the  coloboma.  It  is  delimited  anteriorly 
as  an  unpigmented  cleft.  At  the  pedicle  of  the  optic  vesicle  it  continues  as  a 
furrow  to  the  base  of  the  cerebral  vesicle;  and  in  this  furrow  lies  the  central  artery 
of  the  retina.  The  margins  of  the  coloboma  subsequently  unite  completely; 
if,  however,  in  rare  cases,  this  union  fails  to  take  place,  a  strip  will  be  wanting 
in  the  retina  and  in  the  choroidal  pigment.  There  then  results  a  congenital  mal- 
formation, or  arrest  of  development,  or  coloboma  of  the  choroid  and  retina.  In 
birds,  the  embryonal  coloboma-cleft  does  not  close  at  all,  but  through  it  a  vascular 
process  of  the  mesoderm  penetrates  into  the  interior  of  the  eye;  this  is 
the  subsequent  pecten.  A  similar  condition  occurs  in  fish,  in  which  the  espe- 
cially large  invaginated  process,  consisting  of  portions  of  mesoblast  and  epiblast, 
persists  as  the  falciform  process. 

Why  does  the  primary,  pedunculated  optic  vesicle  become  invaginated  into 
itself  in  the  form  of  an  egg-cup?  Because  a  sac,  derived  from  the  ectoderm,  in 
the  fourth  week  still  pedunculated,  becomes  lodged  in  the  primary  optic  vesicle 
(/,  L).  From  this  the  crystalline  lens  is  formed,  whose  epithelial  origin  (from 
epiblast)  is  indicated  even  in  later  life  by  its  peculiarities  of  growth.  The  capsule 
of  the  lens  is  a  cuticular  formation  of  the  ectodermal  cells.  The  portion  of  the 
ectoderm  that  covers  the  optic  vesicle  in  front  of  the  lens  subsequently  becomes 
the  laminated  anterior  corneal  epithelium.  The  cornea  exists  as  early  as  the 
sixth  week.  The  pigmentary  layer  of  the  invaginated  optic  vesicle  passes  from 
the  margin  of  the  egg-cup  over  the  ciliary  body  and  over  the  posterior  surface 
of  the  subsequently  formed  iris.  It  is  clear  that  a  persistent  coloboma  must 
thus  give  rise  to  the  formation  of  an  unpigmented  strip  in  the  iris,  or  even  a  cleft, 
the  coloboma  of  the  iris.  The  substance  of  the  choroid,  the  sclera,  and  the  cornea 
is  formed  from  the  mesoblast  surrounding  the  rudimentary  eye  (m) .  The  capsule 
of  the  lens  is  at  first  wholly  surrounded  by  a  vascular  membrane,  the  capsulo- 
pupillary  membrane.  Subsequently,  the  lens  moves  further  backward  into  the 
ocular  cavity,  but  the  anterior  portion  of  the  capsulopupillary  membrane  remains 
in  the  anterior  portion  of  the  eye,  and  toward  it  the  margin  of  the  iris  grows 
(seventh  week) ,  so  that  the  pupil  is  closed  by  this  portion  of  the  vascular  capsule 
(pupillary  membrane).  The  vessels  of  the  iris  are  continuous  with  those 
of  the  pupillary  membrane;  those  of  the  posterior  capsule  of  the  lens  are  given 
off  by  the  hyloid  artery,  a  continuation  of  the  central  artery  of  the  retina;  the 
veins  empty  into  those  of  the  iris  and  the  choroid.  The  vitreous  body  is  first 
represented  as  early  as  the  fourth  week  by  a  large  collection  of  cells  between  the 
lens  and  the  retina.  In  the  seventh  month  the  pupillary  membrane  disappears. 
It  may,  however,  persist  throughout  life  as  an  arrest  of  development  (V). 

The  Organ  of  Smell. — On  the  inferior,  lateral  border  of  the  fore-brain,  the 
epiblast  forms  a  small  pit  lined  with  thickened  epithelium,  which  becomes  de- 
pressed toward  the  brain,  but  always  remains  a  pit — the  olfactory  depression.  The 
olfactory  nerves  arise  in  the  epithelium  of  the  pit,  and  growing  centripetally 
unite  with  the  olfactory  lobe.  The  nasal  cavity  appears  at  first  as  a  blind  sac; 
the  choanae  develop  only  as  secondary  formations. 

The  Organ  of  Hearing. — On  either  side  of  the  after-brain  an  invaginated  pit 
develops  from  the  epiblast,  and  becomes  depressed  toward  the  brain  from  without— 
the  labyrinthine  depression.  This  subsequently  becomes  entirely  closed  off  from 
the  ectoderm  (as  in  the  case  of  the  lens) ,  and  is  known  as  the  vesicle  of  the  labyrinth. 
It  obviously  represents  the  vestibular  vesicle,  from  which,  in  the  second  month, 
the  semicircular  canals  and  the  cochlea  are  formed  by  budding.  In  the  same  way, 
the  union  of  the  brain  with  the  labyrinth  takes  place  subsequently  through  the 
intermediation  of  the  auditory  nerve.  The  first  visceral  cleft  becomes  an  ir- 
regularly shaped,  relatively  small  passage;  in  the  sixth  week  the  auditory  bones 
are  present.  Externally,  the  auricle  develops  in  the  seventh  week;  at  the  bottom 
of  the  auditory  canal  the  tympanic  membrane  is  formed;  the  innermost  portion 
becomes  the  Eustachian  tube. 

The  Organ  of  Taste.— The  gustatory  papillae  develop  in  the  last  period  of 
uterine  life;  the  taste-buds  appear  only  a  few  days  before  birth. 

PARTURITION. 

With  the  growth  of  the  ovum  the  uterus  becomes  more  distended 
and  its  walls  richer  in  muscle-fibers  and  in  vessels.  In  the  last  period, 


PARTURITION.  1003 

the  neck  of  the  uterus  also  becomes  obliterated,  and  after  ten  periods  of 
ovulation,  therefore  about  the  two  hundred  and  eightieth  day  of  preg- 
nancy, labor-pains  set  in  for  the  expulsion  of  the  contents.  The  pains  are 
separated  by  intervals  of  freedom;  each  pain,  further,  begins  gradually, 
then  reaches  its  height,  and  diminishes  slowly.  With  each  pain  the 
temperature  of  the  uterus  increases.  The  activity  of  the  fetal  heart  is, 
further,  somewhat  slowed  and  enfeebled  with  each  pain,  as  a  result  of 
irritation  of  the  vagus  in  the  oblongata  of  the  fetus. 

The  uterine  contraction  passes  in  a  peristaltic  manner  from  the  tubes  to  the  os 
in  from  twenty  to  thirty  seconds.  The  curve  traced  by  this  movement  has  usually 
a  much  more  steep  ascending  than  descending  limb;  rarely  the  reverse;  occasion- 
ally, both  limbs  are  alike.  The  curve  of  contraction  increases  slowly,  persists  on 
the  average  about  eight  seconds  at  its  height,  and  then  falls  in  from  five  to  twenty- 
five  seconds.  The  frequency  of  the  pains  increases  to  the  conclusion  of  labor. 
The  pains  are  shortest  in  the  first  half  of  the  period  of  dilatation,  while  the  ele- 
vation of  the  curve  is  lowest,  and  the  intervals  are  long;  in  the  second  half  the 
pains  become  longer  and  stronger  with  the  dilatation  of  the  os;  and  combined 
pains  appear  (like  superposed  contractions).  In  the  first  half  of  the  period  of 
expulsion  the  curves  are  higher,  in  the  second  half  more  frequent  and  higher, 
but  of  shorter  duration  and  with  shorter  intervals. 

The  pressure  within  the  uterine  cavity  during  a  maximal  contraction  increases 
from  i£  to  6  fold  in  the  course  of  labor  in  consequence  of  the  progressive  expul- 
sion. The  increase  in  pressure  depends  upon  the  increased  thickness  of  the  uterine 
walls,  somewhat  also  upon  their  increased  curvature.  Both  factors  would  of 
themselves  tend  to  increase  the  degree  of  pressure,  were  it  not  that  the  strength  of 
the  muscular  fibers  is  considerably  reduced  by  the  shortening  that  occurs  in  the 
process  of  evacuation  of  the  uterus. 

Polaillon  estimates  the  pressure  that  the  uterus  exerts  upon  the  ovum  with 
each  pain  at  154  kilos;  and  that  the  uterus  with  each  pain  performs  work  equal 
to  8820  kilogram-meters.  The  intra-uterine  pressure  is  greatest  up  to  the  rupture 
of  the  membranes,  after  which  it  diminishes,  to  regain  its  maximum  toward  the 
end  of  labor  (on  making  bearing-down  efforts  it  may  reach  400  mm.  of  mercury). 

After  expulsion  of  the  fetus  the  placenta  remains  behind  for  a  time,  and  about  it, 
with  further  pains,  the  uterus  contracts  tightly.  In  consequence  a  not  inconsider- 
able amount  of  placental  blood  flows  to  the  child.  Therefore,  it  may  be  advis- 
able not  to  tie  the  umbilical  cord  immediately  after  the  birth  of  the  child.  After 
some  time  placenta,  fetal  membranes,  and  decidua  are  expelled  as  the  after-birth. 

With  respect  to  the  dependence  of  the  movements  of  the  uterus  upon  the 
nervous  system,  the  following  is  known:  (i)  Irritation  of  the  hypogastric  plexus 
causes  contraction  of  the  uterus.  The  fibers  arise  from  the  spinal  cord  (the  last 
dorsal  and  the  3d  and  4th  lumbar  vertebrae),  enter  the  abdominal  sympathetic, 
and  pass  from  here  into  the  plexus  named.  (2)  Also  irritation  of  the  nervi 
erigentes,  arising  from  the  sacral  plexus,  has  a  motor  effect.  (3)  Irritation  of 
the  lumbar  and  sacral  portions  of  the  spinal  cord  causes  strong  movements. 
A  center  for  the  act  of  parturition  is  situated  in  the  spinal  cord.  (4)  The  uterus 
probably  possesses,  like  the  intestine,  parenchymatous  centers  of  its  own,  which 
can  be  stimulated  to  movement  by  suspension  of  respiration  and  anemia  (through 
compression  of  the  aorta  or  rapid  hemorrhage).  Reduction  in  the  bodily  tem- 
perature diminishes,  while  increase  augments  the  contractions,  which  cease  in 
the  presence  of  high  fever.  The  experiments  made  by  Rein  on  pregnant  bitches, 
in  which  he  divided  all  of  the  nerves  passing  to  the  uterus,  have  yielded  the  re- 
markable result  that,  in  the  uterus  freed  from  all  connection  with  the  cerebro- 
spinal  centers,  all  of  the  principal  phenomena  are  possible  that  are  connected 
with  impregnation,  pregnancy,  and  parturition.  The  uterus  must,  therefore, 
possess  its  own  automatic  ganglia,  under  whose  control  the  processes  named 
take  place.  According  to  Dembo,  a  center  is  situated  in  the  upper  portion  of 
the  anterior  vaginal  wall  (rabbits).  According  to  Jastreboff  the  vagina  of  the 
rabbit  undergoes  independent  rhythmical  contractions.  Sclerotic  acid  excites 
the  movements  energetically,  as  does  likewise  anemia.  (5)  v.  Basch  and  Hoffmann 
observed  reflex  contractions  after  irritation  of  the  sciatic;  Schlesinger  after  cen- 
tral irritation  of  the  brachial  plexus;  Scanzoni  after  irritation  of  the  nipples  in 
man.  (6)  The  uterus  contains  for  its  vessels  both  vasoconstrictors  (by  way  of 
the  hypogastric  plexus),  derived  from  the  splanchnic,  and  vasodilators  (by  way 


1004  COMPARATIVE.       HISTORICAL. 

of  the  nervi  erigentes).  The  vasomotor  nerves  may  be  excited  reflexly;  also 
through  irritation  of  the  sciatic.  The  internal  os  is  especially  rich  in  nerves. 

After  birth  the  entire  uterus  is  deprived  of  its  mucosa  (decidua) ;  its  inner 
surface,  therefore,  is  like  a  wound- surf  ace,  upon  which  a  new  membrane  is  formed, 
with  a  secretion  at  first  resembling  an  infusion  of  meat,  later  containing  a  larger 
number  of  cells,  and  finally  becoming  mucoid  (lochia).  The  thick  muscular  layer 
of  the  uterus  undergoes  gradual  reduction  through  partial  fatty  degeneration 
of  its  fibers.  Within  the  lumen  of  the  large  vessels  an  obliterating  connective- 
tissue  hyperplasia  begins  from  the  intima,  and  in  the  course  of  several  months 
diminishes  the  lumen  of  the  vessels  or  occludes  them.  The  unstriated  muscle- 
fibers  of  the  media  undergo  fatty  degeneration.  The  relatively  large  blood- 
spaces  at  the  placental  site  are  plugged  by  thrombi,  and  the  latter  are  invaded 
by  connective-tissue  from  the  walls  of  the  vessel. 

After  birth  secretion  of  milk  sets  in,  with  a  peculiar  effect  upon  the  vas- 
cular nervous  system  (milk-fever?),  an  increased  amount  of  blood  being  sent  to 
the  mammary  glands  on  the  second  or  third  day.  The  institution  of  the  first 
respiratory  movements  in  the  new-born  is  discussed  on  p.  755. 

COMPARATIVE.     HISTORICAL. 

Embryology  must  not  omit  to  take  into  consideration  the  general  develop- 
ment of  the  entire  animal  kingdom.  The  question  "How  have  the  innumerable 
animal  forms  at  present  living  originated?"  has  in  part  been  answered  by  the 
statement  that  all  species  have  been  created  as  such  from  the  beginning,  "every 
form  is  an  embodied  idea  of  creation";  all  species,  further,  remain  as  such  without 
alteration;  the  "constancy  of  species  prevails."  In  opposition  to  this  view, 
held  by  Linnaeus,  Cuvier,  Agassiz,  and  others,  Jean  Lamarck  in  1809  developed 
the  doctrine  of  ''the  unity  of  the  animal  kingdom,"  embodying  the  old  idea  of 
Empedocles,  namely  that  all  species  have  developed  by  variation  from  a  few  funda- 
mental species,  that  originally  only  a  few  fundamental  species  of  lower  formation 
existed,  from  which  the  new,  numerous  specie^  have  evolved — a  view  supported 
also  by  Geoffroy  St.  Hilaire  and  Goethe.  After  a  long  interval  this  thought  was  de- 
veloped in  a  particularly  fruitful  way  by  Charles  Darwin  (1859) .  He  supported  his 
''monistic  conception"  of  the  animal  kingdom  by  a  description  of  the  manner  in 
which  gradual  evolution  of  species  can  be  explained.  Among  the  creatures  of  the 
earth  there  takes  place,  for  the  preservation  of  life,  a  struggle  of  all  against  all,  and 
from  this  "struggle  for  existence"  only  those  will  go  forth  victorious  that  are  char- 
acterized by  particularly  striking  qualities.  Such  qualities:  strength,  speed,  size, 
color,  fruitfulness,  are,  however,  hereditary,  and  thus  it  is  evident  that,  in  this 
manner,  to  a  certain  degree  through  natural  selection,  an  uninterrupted  process 
of  improvement  and  thereby  a  gradual  variation  in  species  takes  place.  In 
addition,  the  creatures  are  capable,  within  certain  limits,  of  adapting  themselves 
to  their  surroundings  and  the  prevailing  necessities  of  external  influences.  In 
this  way,  certain  organs  may  undergo  a  useful  transformation,  while  inactive 
parts  can  gradually  undergo  involution  to  rudimentary  organs.  The  gradual 
alteration  of  animal  forms  thus  resulting  through  "natural  selection"  finds  its 
prototype  in  "artificial  selection"  among  animals  and  plants.  It  is  known,  for 
instance,  that  breeders  of  animals  are  able,  in  a  relatively  short  time,  to  produce 
variations  in  form  that  are  much  more  considerable  than  those  between  two  well- 
characterized  species  of  animals.  Thus,  the  skull  of  a  mastiff  and  that  of  an 
Italian  grayhound  exhibit  a  much  greater  difference  than  that  of  a  fox  as  com- 
pared with  that  of  a  similar  species  of  dog.  As  in  the  case  of  artificial  selection, 
however,  there  is  observed  a  sudden  reversion  to  an  ancestral  type,  so  also  in  the 
development  of  natural  species  atavism  may  occur.  Obviously  the  ease  of  varia- 
tion is  increased  by  the  widespread  distribution  of  a  given  species  in  different 
climates,  as  in  this  way  different  influences  become  operative.  Thus,  the  migra- 
tion of  organisms  may  gradually  contribute  to  variations  in  species  (M.  Wagner's 
law  ot  migration).  Inheritance  of  mutilations  does  not  occur. 

Without  entering  upon  the  .details  in  the  development  of  the  different  varieties 
ot  animals,  the  biogenetic  fundamental  law  may  be  briefly  discussed.  According 
to  this  "the  history  of  the  individual  (ontogeny)  is  a  brief  repetition  of  the  history 
ot  the  family  (phylogeny) . "  Applied  especially  to  man,  this  law  implies  that  the 
separate  stages  in  the  development  of  the  human  embryo,  for  example  its  exist- 
ence as  a  unicellular  ovum,  as  a  collection  of  cells  after  cleavage  has  been  completed, 
as  a  cellular  vesicle  (germinal  vesicle),  as  a  two-layered  vesicle,  as  a  being  without 


COMPARATIVE.       HISTORICAL.  1005 

a  coelom,  etc.,  indicate  an  equal  number  of  animal  varieties,  from  which  the  human 
race,  in  the  course  of  inconceivable  time,  has  gradually  evolved.  The  separate 
steps  through  which  the  human  race  has  passed  in  the  process  of  transformation 
have  been  briefly  repeated  in  its  embryonal  development.  This  exposition  has, 
naturally,  not  escaped  criticism.  In  any  event,  the  comparison  of  human  de- 
velopment with  relation  to  the  individual  organs  with  the  corresponding  fully 
developed  organs  of  the  vertebrates  is  important.  Thus  also  mammals  possess 
in  the  development  of  their  organs,  originally,  the  simple  heart,  the  visceral 
clefts,  the  undeveloped  rudimentary  brain,  the  cartilaginous  chorda  dorsalis, 
various  arrangements  of  the  vascular  system,  etc.,  that  are  peculiar  to  the  lowest 
forms  of  vertebrates  throughout  life.  In  the  higher  classes,  these  incomplete 
rudimentary  structures  gradually  approach  perfection.  The  morphological 
differences  between  man  and  the  gorilla  or  the  chimpanzee  are  slighter  than  those 
between  the  anthropoids  mentioned  and  other  apes.  The  fossil  Pithecanthropus 
erectus  was  at  first  regarded  as  an  extinct  link  between  anthropoids  and  man, 
but  recently  more  correctly  as  a  powerful  long-armed  ape  (hylobates,  gibbon) ; 
the  Palasopithecus  sivalensis  may  occupy  an  analogous  position,  with  its  cranial 
cavity  two-thirds  the  size  of  the  human  cranial  cavity  and  occupying  an  inter- 
mediate position  between  the  cranial  cavity  of  the  anthropoids  and  the  lower 
races  of  man.  In  detail,  however,  there  are  still  many  difficulties  in  the  way  of 
establishing  the  Darwinian  theory  and  the  fundamental  biogenetic  law. 

Historical. — Although  the  discoveries  in  embryology,  more  than  those  in  any 
other  branch  of  biological  science,  belong  especially  to'modern  times,  it  is,  never- 
theless, interesting  to  consider  the  views  of  the  ancients  upon  different  points. 
Pythagoras  (550  B.  C.)  rejected  the  theory  of  spontaneous  generation:  All 
life  results  from  seed.  According  to  Alkmaeon  (580  B.  C.)  both  sexes  furnish 
the  fecundating  material;  the  sex  of  the  offspring  corresponds  to  the  sex  supply- 
ing the  most  seed.  In  development  the  head  is  formed  first.  Anaxagoras  (500 
B.  C.)  believed  that  boys  came  from  the  right  and  girls  from  the  left  sexual  gland. 
Empedocles  (473  B.C.)  recognized  the  nutrition  of  the  embryo  through  the  um- 
bilicus; he  was  the  first  to  designate  the  chorion  and  the  amnion,  and  the  segmen- 
tation of  an  embryo  as  complete  on  the  thirty-sixth  day.  He  taught  that  the 
first  animals  of  creation  were  the  most  incomplete.  Hippocrates  considered 
the  seventieth  day  the  earliest  time  for  movement  and  the  two  hundred  and 
tenth  day  as  term.  He  taught,  with  Democritus,  that  the  sexual  material 
came  together  from  all  parts  of  the  body  (Darwin's  pangenesis),  thus  accounting 
for  the  resemblance  of  the  offspring.  He  observed  incubating  eggs  from  day  to 
clay,  and  saw  in  them  the  allantois  emerge  from  the  umbilicus,  and  the  chick 
escape  on  the  twentieth  day.  He  taught  that  seven-month  children  are  viable, 
explained  the  possibility  of  superfetation  from  the  horns  of  the  uterus  and  de- 
scribed the  lithopedion.  According  to  Plato  (430  B.  C.)  the  spinal  cord  is  formed 
first,  as  the  appendix  of  which,  the  brain  appears  anteriorly.  The  writings  of 
Aristotle  (born  384  B.  C.)  are  rich  in  observations  of  which  many  have  already 
been  cited  in  the  text.  He  taught  that  the  embryo  received  its  blood-supply 
through  the  vessels  of  the  umbilical  cord,  and  that  the  placenta  absorbs  blood 
from  the  vascular  uterus,  as  a  tree  absorbs  moisture  through  its  roots.  He  differen- 
tiated the  polycotyledonaryand  the  diffuse  placenta;  he  attributed  the  former  to  ani- 
mals that  do  not  have  complete  rows  of  teeth  in  both  jaws.  In  the  incubated 
bird's  egg  he  recognized  the  vessels  of  the  yolk-sac,  which  convey  nourishment 
from  the  latter  to  the  embryo,  and  the  vessels  of  the  allantois.  The  statement  is 
correct  also  that  the  chick  rests  with  its  head  on  the  right  leg,  and  that  the  yolk- 
sac  finally  enters  the  body.  In  the  birth  of  mammals  when  the  head  alone  is 
born  it  does  not  breathe.  The  formation  of  double  monsters  is  ascribed  to  the 
junction  of  two  germs  or  two  embryos  lying  in  close  proximity.  In  the  process 
of  conception,  the  female  supplies  the  material,  the  male  the  principle  that  is 
responsible  for  form  and  movement.  With  regard  to  reproduction  in  the  lower 
animals,  reference  may  be  made  to  the  generative  arm  of  the  cephalopods,  the 
yolk-sac  of  the  cuttle-fish,  the  yolk-sac  placenta  of  the  smooth  shark,  the  con- 
jugation of  snakes  and  the  absence  of  the  amnion  and  the  allantois  in  fish  and 
amphibia.  Diocles  (a  contemporary  of  Theophrastus,  born  371  B.  C.)  appears 
to  have  seen  the  ovum  as  early  as  the  second  week  as  a  cutaneous  vesicle,  marked 
by  bloody  points  (villi  ?) ;  he  describes  also  the  cotyledons  of  the  uterus.  Erasist- 
ratus  (304  B.  C.)  taught  the  development  of  the  embryo  by  a  neoplastic  process 
in  the  ovum  (epigenesis) ;  he  considered  scar- formation  in  the  uterus  as  a  cause  for 
sterility.  His  contemporary  Herophilus  found  that  the  pregnant  uterus  is  closed. 


I0o6  COMPARATIVE.       HISTORICAL. 

He  noted  the  glandular  character  of  the  prostate  and  named  the  seminal  vesicles 
and  the  epididymis.  Aretasus  (81  A.  D.)  recognized  the  decidua;  Galen  (131-203 
A.  D.)  the  oval  foramen  and  the  passage  of  the  blood  in  the  fetus  through  it  and 
through  the  ductus  arteriosus.  He  was  familiar  with  the  physiological  relations 
between  the  vessels  of  the  breasts  and  the  uterus,  and  he  knew  that  the  uterus  con- 
tracted upon  pressure.  The  Talmud  contains  the  statement  that  an  animal  with  an 
extirpated  uterus  can  live;  that  the  pubic  bones  separate  during  labor,  and  an 
account  of  a  successful  Cesarean  section,  with  a  living  mother  and  child,  performed 
at  the  request  of  Cleopatra.  Sylvius  (1555)  described  the  valve  of  the  oval 
foramen,  Vesalius  (1546)  the  follicles  of  the  ovary,  Eustachius  (died  1570)  the 
ductus  arteriosus  (Botalli)  and  the  branches  of  the  umbilical  vein  to  the  liver. 
Arantius  examined  the  duct  named  after  him,  and  stated  that  the  umbilical 
arteries  do  not  anastomose  with  the  maternal  vessels  in  the  placenta.  Libavins 
(1597)  makes  the  statement  that  a  child  had  cried  aloud  in  the  uterus.  Riolan 
(1618)  recognized  the  corpus  Highmori.  Pavius  (1657)  examined  the  position 
of  the  testicles  in  the  inguinal  region  of  the  fetus.  Harvey  (1633)  laid  down  the 
fundamental  principle:  Omne  vivum  ex  ovo.  Fabricius  ab  Aquapendente  (1600) 
described  the  embryological  development  of  birds.  Regner  de  Graaf  (1668) 
described  the  ovarian  follicle  named  after  him;  he  found  the  ovum  of  mammals 
in  the  oviduct.  He  produced  erection  in  the  cadaver  through  tense  injection 
of  the  cavernous  body.  Mayon  (1679)  observed  in  the  placenta  the  respiratory 
activity  of  the  lung.  Schwammerdam  (died  1685)  discovered  metamorphosis; 
he  developed  the  butterfly  from  the  caterpillar  before  the  Grand  Duke  of  Tuscany. 
He  described  the  cleavage  of  the  frog's  egg.  Malpighi  (died  1694)  described  the 
embryology  of  the  chick,  with  illustrations.  The  first  half  of  the  eighteenth 
century  was  given  up  to  a  discussion  as  to  whether  the  ovum  or  the  semen 
was  the  more  important  in  development  (ovists  and  animalculists) ;  further, 
whether  the  progeny  was  newly  formed  in  the  ovum  (epigenesis) ,  or  whether  it 
merely  evolved  and  grew,  thus  lodged  in  the  ovum  as  a  being  already  formed 
(evolution) .  The  ancients  attributed  the  fructifying  power  to  the  odor  of  semen 
(aura  seminalis) .  The  question  of  spontaneous  generation  has  been  studied 
exhaustively  particularly  since  the  time  of  Needham  (1745),  and  it  has,  until 
recent  times,  been  made  the  subject  of  numerous  investigations,  until  it  was 
finally  overthrown  chiefly  through  the  efforts  of  Pasteur  and  of  Robt.  Koch 
and  his  pupils. 

A  new  epoch  began  with  Caspar  Fried.  Wolff  (1759),  who  first  taught  the 
formation  of  the  embryo  from  germinal  layers,  and  who,  besides,  first  described 
the  tissues  as  composed  of  minute  "globules"  (cells) — an  idea  that  was  first  thor- 
oughly investigated  by  Schleiden  (1838)  with  respect  to  plants,  and  by  Schwann 
(1839)  with  respect  to  animals.  Wolff  published,  as  a  model  of  investigation 
in  special  embryology,  a  monograph  upon  the  development  of  the  gut.  Will. 
Hunter  described  (1775)  the  fetal  membranes  and  the  pregnant  uterus,  Sommering 
(1799)  the  development  of  the  external  bodily  form  of  man,  Oken  and  Kieser 
that  of  the  intestine.  The  intermaxillary  bone  in  man  was  viewed  by  Goethe 
(1786)  in  its  correct  significance;  he  also  suggested  the  correct  morphological 
conception  of  the  development  of  cleft  palate.  Even  prior  to  1791  Goethe  recog- 
nized the  construction  of  the  cranium  from  vertebra.  Tiedemann  (1816)  de- 
scribed the  development  of  the  brain,  Meckel  that  of  monstrosities.  The  work 
of  Pander  (1817),  Carl  Ernst  v.  Baer  (1828-1834),  Rathke,  Th.  Bischoff,  Robert 
Remak  and  many  other  living  investigators,  laid  the  foundation  for  studies  of 
the  development  of  individual  organs  from  the  three  germinal  layers.  Theodore 
Schwann  first  (1839)  traced  the  development  of  all  of  the  tissues  from  the  prim- 
ordial germinal  cells  to  the  stage  of  complete  evolution. 


INDEX. 


Abasia  596. 

Abdominal  pregnancy  958. 

Abdominal  pressure  205,   286. 

Abdominal  respiration  210. 

Abducens  nerve  693. 

Abiogenesis  938. 

Abomasum  344. 

Absence,  80 1. 

Absolute    muscular    energy    570,    596. 

Absorption,  from  the  stomach  348, 
from  the  intestine  354,  of  effusions 
373>  °f  gases  75,  of  proteid  356,  of 
salts  354,  of  soaps  356,  through  the 
skin  539. 

Absorption,  nerve  control  of  359. 

Absorption  spectra  55. 

Acataphasia  797. 

Accessory  nerve  712. 

Accessory  sexual  glands  946. 

Accommodation  of  the  eye  83 1 ,  mechan- 
ism 832,  phenomena  833,  for  distant 
vision  835,  in  animals  835,  measure  of 

837- 

Accommodation  phosphene  846. 
Accommodation-spot  846. 
Accord  900. 
Acetone  315,  359,  489. 
Achromatopsia  86 1. 

Acid-albuminates  in  the  stomach   297. 
Acid  rigor  554. 
Acoustic  nerve  699. 
Acoustic  normal  formula  699. 
Acoustic  tetanus  646. 
Acromegaly  693. 
Acrylic  acids  462. 
Action  current  652,  659. 
Active  insufficiency  586. 
Actual  energy  20. 
Acuity  of  smell  915. 
Acuity  of  hearing  901. 
Adaptation   1004. 
Adaptation  of  the  ear  892. 

eye  855. 

iris  843. 

Addison's  disease   197. 
Adenin  467. 
Adequate  stimuli  813. 
Adipocere  445. 
Adrenals   197. 
Aerobes  330. 
After-birth   1003. 
After-contraction  573. 
After-images  862. 
After-relaxation  573. 


After-sensations  814. 

After-taste  918. 

After-tension  573. 

After- vibrations  of  the  tympanum  890. 

Ageusis  919. 

Agglutinin  74. 

Agonal  respiration  211. 

Agrammatism  797. 

Agraphia  797,  800. 

Air- tube  599. 

Albumins  457. 

Albuminimeter  496. 

Albuminous  glands  259. 

Albuminoids  460. 

Albuminuria  494,  physiological  494. 

Albumose  in  the  stomach  297,  in  the 

urine  496. 

Alcoholic  drinks  429. 
Alcohols  464. 
Alexia  799. 
Alexin  47,   74. 
I   Algesia  737. 
Alkaloids  428.  - 
Alkapton  489. 
Allantoin  485. 
Allantois  974,  975. 
Allochiria  934. 
Allorrhythmia  145. 
Alternating  hemiplegia  747. 
Alternation  of  after-images  864. 
Alternation  of  generations  941. 
Amaurosis  680. 
Amble  597. 
Amblyopia  680. 
Ambulacral  organs  599. 
Ameboid  movements  of  leucocytes  46. 
Amido-acids  467. 
Amids  467. 
Amitnia  797. 
Amins  467. 

Ammonia  derivatives  467. 
Ammoniemia  516. 
Amnesia,  senile  797. 
Amnesic  aphasia  797. 
Amnion,  formation  of  974. 
Amniota  974. 
Amniotic  fluid  974. 
Amreba  46,  939. 
Ampere  640. 
Ampere's  rule  641. 
Amphiarthrosis  583. 
Amphoric  breathing  222. 
Ampullas  898. 
Amusia  797. 


1007 


ioo8 


INDEX. 


Amygdalin  374. 

Amyloid  459. 

Amyloid  degeneration  589. 

Amylolytic  action  of  saliva  264. 

Anabiosis  938. 

Anaerobes  330. 

Anacrotism  148. 

Anacrotic  pulse  curves  137. 

Anacusis  700. 

Anal  closure  284. 

Analgia  936. 

Anamnia  974. 

Anarthria  796. 

Anemia  87. 

Anemic  convulsions  773. 

Anesthesia  737. 

Anesthetics   935,   action   on   the   pupil 

Anelectrotonus  660. 

Aneurysm  156,   183. 

Angina  pectoris  771. 

Angiograph  136. 

Angioneurosis  770. 

Angioparalytic  areas  770. 

Anhepatogenous  icterus  322. 

Anidrosis  538. 

Animalculists  1006. 

Animals  and  plants  25. 

Ankylosis  588. 

Anosmia  679. 

Anospinal  center  734. 

Antagonists  587. 

Antagonistic  movements  732. 

Anterior  roots  717. 

Anthracometer  226. 

Ant i- albumin  297. 

Anti-peptone  297,  304. 

Antiperistalsis  283,  of  the  stomach  340. 

Antitoxin  74. 

Anus,  formation  of  973. 

Anxietas  tibiarum  937. 

Aorta,  time  of  filling  104. 

Aortic  pressure-curve   107. 

Aperistalsis  286. 

Aphasia  796. 

Aphthongia  618. 

Aphonia  617. 

Apnea  752. 

Apparent  size  830. 

Appetite  294. 

Apselaphesia  934. 

Aqueduct  of  the  cochlea  898. 

Aqueduct  of  the  vestibule  897. 

Aqueous  humor  822. 

Arch  of  the  foot  591. 

Archiblast  970. 

Area,  opaca  963,  pellucida  963,  vascu- 

losa  964. 
Arginin  305. 
Aristotle's  lantern  345. 
Aromatic  bodies  468. 
Arrector  pili  muscles  529. 
Arrhythmia  cordis   145. 
Arterial  blood  82. 
Arterial  murmurs   183. 
Arterial  spasm  770. 


Arteries,    structure    129,    development 

991. 

Arterin  52. 
Arteriogram  137. 
Arthrodia  583. 
Artificial  respiration  756. 
Artificial  selection   1004. 
Aspartic  acid  305. 
Asphyctic  pauses  in  respiration  211. 
Asphyxia  753. 
Association  fibers  742. 
Astasia  596,  642,  808. 
Asteatosis  cutis  539. 
Asthenia  808. 

Asthma  204,  bronchial  711,  nervous  711. 
Astigmatism  841. 
Atavism  1004. 
Ataxic  aphasia  797. 
Atelectasis  224,  757. 
Atmospheric     pressure,    _  influence     of, 
251,   diminished   252,  increased   253, 
supporting  the  jaw  2 7 1 . 
Atmospheric  dust  245. 
Atoms   19. 
Atony  809. 
Atresia  ani  973. 
Auditory  after-sensations  911. 

bristles  913. 

hairs  898. 

hallucinations  700,  800. 

ligaments    and   muscles    890. 

organ  885,  development  1002. 

ossicles  890. 
Aura  799. 

Aura  seminalis  1006. 
Auricle  887. 

Auscultation  of  the  pulse  184. 
Auto-intoxication    from    the    intestine 

343- 

Automatic  centers  in  the  heart   115. 
Automatic  regulation  of  the  heart  83. 
Autophony  895. 
Available  energy  of  diets  438. 
Axial  currents  651. 
Axis  cylinder  621. 


Bacilli  330. 

Bacillus  acidi  lactici  331. 
butyricus  331. 
Fitzianus  332. 
liquefaciens  ilei  333. 
pyocyaneus  539. 
subtilis  332. 

Bacteria  329,  in  the  feces  338. 
Bacterium  aceti  331. 

Bischleri  331. 
graveolens  539. 
ilei  331. 

lactis  aerogenes  331. 
lymphagogum  375. 
Bactericidal  power  of  blood  74. 
Balloon  ascensions  239. 
Baresthesiometer  928. 
Basedow's  disease   196,   770. 
Basement  membrane  899. 


INDEX. 


Bass-deafness  902. 

Bdellotomy  345. 

Beat  of  the  heart  96,  100,  pathological 
107. 

Beats  909. 

Beer  430. 

Bee-colonies  942. 

Bell's  law  714. 

Bile  315,  analysis  319,  action  324,  fate 
326,  pigments  317,  325,  resorption 
322,  326,  secretion  319,  341,  abnormal 
secretion  341,  vomited  325. 

Bile-acids  315. 

Bile-ducts  309,  310. 

Bile-duct,  obstruction  of  322. 

Bile-mucin  315,  325. 

Biliary  colic  342. 

Biliary  fistula  319. 

Bilicyanin  317. 

Bilifuscin  317. 

Bilirubin  63,  317. 

Bilirubin-lime  341. 

Biot's  respiration  212. 

Biogenetic  fundamental  law  1004. 

Bladder  518,  519,  development  975, 
996. 

Bladder  center  522,   735. 

Blastomere  961. 

Blastopore  962. 

Blastula  961. 

Bleeder's  disease  68. 

Blinding  of  the  eye  855. 

Blind-spot  850. 

Blood,  color  29,  odor  30,  taste  30, 
specific  gravity  30,  freezing-point  31, 
corpuscles  31,  isotonia  37,  laking  39, 
stroma  39,  development  41,  destruc- 
tion 43,  white  corpuscles  45,  plates  48, 
elementary  granules  49,  abnormal 
changes  50,  parasites  51,  coloring 
matter  51,  plasma  65,  fibrin  65, 
clot  65,  crusta  phlogistica  66,  de- 
fibrinated  blood  66,  fibrin  66,  86, 
coagulation  67,  bleeder's  disease  68, 
action  of  peptone  and  of  ferments 

68,  fibrinogen  69,  fibrin  ferment  69, 
coagulation  experiments  69,  thrombin 

69,  constituents     72,     proteids     73, 
fibrino-plastin    73,    salts    74,    serum 
pigments  74,  bactericidal  substances 
7-4.   gases   74,   qualitative  estimation 
of  gases  76,  quantitative  77,  arterial 
and  venous  82,  amount  83,  abnormal- 
ities 84,  hemorrhage    86,    circulation 

00 

55. 

Blood  channels   132. 

Blood    circulation    88,   in   the   smallest 

vessels   178. 

Blood  corpuscles  in  the  retina  845. 
Blood  crystals  52. 
Blood  distribution  188. 
Blood  gases  74,   78,  extraction   77. 
Blood  in  active  organs  iSS. 
Blood  parasites  51. 
Blood  plasma  65. 
Blood  plates  48,   70. 
64 


Blood-pressure  in  the  arteries  166,  in 
the  capillaries  168,  in  the  veins  169, 
in  the  pulmonary  artery  169. 

Blood-pressure  measurements  162. 

Blood-pressure  variations  170. 

Blood  sweating  539. 

Blood-vessels,  development  42,  971, 
sensory  nerves  771. 

Blood  volume  83. 

Bojanus'  organ  524. 

Bone,  development  from  cartilage  989. 

Bone  deformities  588. 

Bone,  growth  of  989. 

Bony  processes  581. 

Bradyphasia  797. 

Brain  extirpation  775. 

Brain  functions  in  animals  776. 

Brain  pressure  810. 

Brain  pressure  and  respiration  755. 

Brain  schema  742. 

Bread  427. 

Brenner's  normal  formula  699. 

Bromidrosis  539. 

Bromogenic  bacteria  330. 

Bronchi  201. 

Bronchial  breathing  221,  222. 

Bronchial  fremitus  222. 

Bronchial  tree  206. 

Bronchial  vessels  203. 

Bronchophony  223. 

Bronzed  skin   197. 

Brunner's  glands  326. 

Brush-fringe  of  Tornier,  293 

Buccal  fluid  263. 

Buccal  glands  256. 

Buccal  organisms  264. 

Budding  939. 

Bulbar  paralysis  750. 

Butalanin  305. 


Cachexia  strumipriva  196. 

Calories,  adult  production  390. 

Calorimeter  379. 

Calorimetry  379,  389. 

Calory  22. 

Campanula  Halleri  883. 

Canalis  reuniens  897. 

Canal  of  Schlemm  817. 

Capacity  of  the  ventricles  176. 

Capillaries,    structure    130,   movements 

132. 

Capillary  circulation   128. 
Capillary  electrometer  649. 
Capillary  pressure   168. 
Capillary  pulse  160. 
Capillary  tubes  128. 
Caput  obstipum  712. 
Carbohemoglobin  Si. 
Carbohydrates  464. 
Carbohydrate  absorption  355. 
Carbohydrate  diet  443. 
Carbon-monoxid  in  the  blood  58 
Carbpn-monoxid  poisoning  59. 
Cardia,  movnm-ms   280. 
Cardiac  branches  of    the  vagus  710. 


IOIO 


INDEX. 


Cardiac  dulness  220. 

ganglia  114. 

impulse   100,  abnormal   107. 

murmurs   113. 

nerves  114. 

orifices,  stenosis  of  99. 

plexus  114. 

poisons   120. 

stimuli  1 1 8. 
Cardiac  valves  92,  97,  98,  incompetence 

100. 

Cardinal  points  of  the  eye  829. 
Cardinal  veins  992. 
Cardio-accelerator  nerves  761. 
Cardio-augmentor    center    760,    nerves 

761. 

Cardiogram  100. 
Cardie-inhibitory    center    758,    nerves 

758. 

Cardiopneumatic  movement   121. 
Carnivorous  plants  346. 
Carotid  glands   197,   development  987. 
Castoreum  540. 
Catacrotic  pulse  137. 
Cataphoric  effect  644. 
Cavernous  spaces  131. 
Cell   division   966,   direct   and  indirect 

966. 

Cement  273. 
Center    of    gravity    of    the    body    589, 

determination  591. 

Center  of  rotation  of  the  eye  866,  868. 
Centrifugal  nerves  677. 
Centripetal  ataxia  716. 
Centripetal  nerves  678. 
Centripetal  venous  pulse   187. 
Centrosome  966. 
Cereals  426. 
Cerebellum  807. 
Cerebellar  tracts  808. 
Cerebral  ataxia  794. 

chorea  794. 

epilepsy  783,  795. 

membranes  809. 

monoplegia  794. 

monospasm  795. 

motor  tracts  744. 

movements  810. 

murmur  184. 

nerves  678. 

paralysis  of  childhood  794. 

peduncles  804. 

pressure  810. 

vessels  744. 
Cerebrin  627. 
Cerebrpspinal  fluid  367. 
Ceruminous  glands  531. 
Cervical  fistula  986. 
Charcot's  crystals  251. 
Check-ligaments  581. 
Cheese-spirilli  332. 
Chemical  affinity  23. 
Chemotaxis  45,  46. 
Chest-register  609. 
Cheyne-Stokes  respiration  211. 
Chiasma  679. 


I    Chief-cells  289,   293. 
!    Chitin-shields  541. 
!    Chlorocruorin  41. 
|    Chlorosis  50. 

Chocolate  428. 

Cholalic  acid  316,  325. 

Cholemia  322. 

Cholesterin  318,  325,  464,  627. 

Cholesterin  stones  341. 

Choletelin  74,  318. 

Choluria  500. 

Chondroclasts  46. 

Chorda  dorsalis  969. 

Chorda  saliva  260. 

Chorda  tympani  694. 

Chordae  tendineas  98. 

Chorion     laeve     976,     frondosum     977, 
primitivum  963. 

Chorionic  villi  976. 

Choroid  817. 

Choroidal  vessels  818. 

Chromatic  aberration  840. 

Chromatophores  541. 

Chromidrosis  539. 

Chromogenic  bacteria  330. 

Chromopsia  680. 

Chronology     of     human     development 
980. 

Chyle  366,  propulsion  371. 

Chyme  297. 

Cicatrix  454. 

Ciliary  bodies  816. 

Ciliospinal  region  842,-  center  734. 

Circulation  of  the  blood  88,   125,   158, 
in  the  smallest  vessels  178. 

Circulation  schema  160. 

Circulation-time   177. 

Clarke's  column  724. 

Cleavage  961. 

Cleavage-spheres  961. 

Cloaca  998. 

Closing  contraction  632. 

Closing  tetanus  633. 

Closure  of  the  glottis  278. 

Clotting  398. 

Coagulation  65,  67. 

Coccygeal  glands  197,   540. 

Cochlea  898. 

Cochlear  duct  897. 

Coelom  969. 

Cos  minis  941. 

Coffee  428. 

Cog-wheel  respiration  222. 

Coin-sound  221. 

Cold,  .influence    upon    the    body    408, 
employment  of  411. 

Cold-blooded  animals  381. 

Cold-bloodedness,  artificial  409. 

Collapse,  temperature  of  392. 

Collaterals  625,  725. 

Collateral  circulation,  establishment  of 

Colloids  353. 
Coloboma   1002. 
Color-blindness  860. 
Colored  hearing,  911. 


INDEX. 


IOII 


Colored  reflections  865. 
shadows  865. 
vision  799. 

Color  center  798. 
chart  858. 
mixing  857. 

perception,  peripheral  853,   86 1. 
"       theories  859. 

Colorimetric  hemoglobin  estimation  53. 

Colors  856. 

Colostrum  417,  421. 

Columella  912. 

Column  cells  724. 

Coma,  diabetic  315. 

Comedo  539. 

Commissure,  anterior  802,  posterior 
806. 

Commissural  fibres  742,  cells  724. 

Common  sensation  934. 

Complemental  air  206. 

Complementary  colors  857. 

Composite  marginal  cells  258. 

Compressed  air  253. 

Compression  reaction  667. 

Conception  958. 

Concord  908. 

Concrescence  940. 

Conduction  in  animal  tissues  639. 

Conduction  through  the  bones  of  the 
skull  885. 

Conduction  resistance  639. 

Congenital  hernia  998. 

Conglobate  follicles  363. 

Conjugation  940. 

Conservation  of  energy  23. 

Consonants  615. 

Constancy  of  energy,  23. 

Constancy  of  species   1004. 

Constant  batteries  643. 

Constipation  342. 

Contact  spectacles  841. 

Contractility  of  the  vessels  132. 

Contraction,  laws  of  663. 

Contraction-curve  560,  isotonic  560,  of 
the  loaded  muscle  562,  in  fatigue  562, 
white  and  red  muscles  563,  action  of 
poisons  563  pathological  565,  sum- 
mated  565,  isometric  568. 

Contraction  of  the  visual  field  851. 

Contraction  rate  of  muscle  568. 

Contraction  remainder  564. 

Contraction  without  metals  651. 

Contracture  564. 

Contrast  864. 

Contrast-colors  857. 

Convulsions,  path  of  the  impulses  740. 

Cooling  of  the  body  409. 

Coprosterin  325. 

Corium  525. 

Cornea  815. 

Corneal  pressure-folds  844. 

Coronary  vessels  93. 

Corpora  quadrigemina  805. 

Corpulence  445. 

Corpus  albicans  954. 

Corpus  callosum  802. 


Corpus  luteum  955. 

Corpus  striatum  802. 

Cortical  blindness  786,  799. 

Cortical  centers,  motor  780,  792,  stimu- 
lation 780,  794,  positions  781,  792; 
sensory  785,  798,  visceral  790,  ther- 
mic 788,  797. 

Cortical  color  center  798. 
"         deafness  787,   799. 
heat  center  797. 
iris  reflex  843. 

Cortico-motor  paths  792. 

Corti's  membrane  899. 

Corti's  organ  898,  899. 

Costal  respiration  210. 

Coughing  225. 

Coughing-center  749. 

Cracked-pot  sound  221. 

Cranial  nerves  678. 

Cranioscopy  775. 

Cranio-tympanic  conduction  885. 

Cranium,  development  of  984. 

Crescents  of  Gianuzzi  258. 

Crista  acustica  898. 

Croaking  experiment  730. 

Crop  344. 

Crop-milk  344. 

Crying  225. 

Crypts  of  Lieberkuhn  326. 

Crystalline  compound  882. 

Crystalline  rod  882. 

Crystallized  bile  316. 

Crystalloids  353. 

Crystal-sphere  882. 

Cupping-boot  253. 

Curare  556. 

Current  of  action  652,  659. 

Currents  of  the  skin  651. 

Cutaneous  absorption  539. 
pigment  535. 
respiration  241. 

Cylindrical  lenses  841. 

Cyrtometer  217. 

Cysterna  lymphatica  375. 

Cysticula  912. 

Cystin  503. 

Cysticerci  941. 

Cytoglobin  71. 


Damping   of  the   tympanic   membrane 

889. 

Darwinian  theory  1004. 
Deafness  805. 

Decidua  975,  menstrualis  953. 
Deciduous  membrane  975. 
Decubitus,  acute  791. 
Decussations  in  the  cord  747. 
Deep-hearing  individuals  901. 
Defecation  center  734. 
Deficiency  664. 
Deficiency  phenomena  789. 
Defibrination  66. 

Degeneration  of  divided  nerves  716. 
reaction    of    669,    673. 
Deglutition  277. 


IOI2 


INDEX. 


Deglutition,  disorders  of  339. 
Deglutition,  nerves  of  278. 
Deglutition  sounds  278. 
Deglutitional  breathing  755. 
Deiter's  cells  899. 
Delirium  cordis   145. 
Dendrites  625. 
Dentin  272. 
Dental  sac  274. 
Dental  calculi  262. 
Dentinal  fibrils  272,  tubules  272. 
Depressor  nerves  707,  764. 
Descent  of  the  ovaries  998,  of  the  tes- 
ticles 998. 
Dextrin  264. 
Diabetes  mellitus  313. 
Diabetes,  poisons  causing  314. 
Diabetic  coma  315. 
Diapedesis   180. 
Diaphragm  213. 
Diarrhea  283,  342. 
Diarticular  muscles  586. 
Diastatic  action  of  saliva  264. 
Diaster  960. 
Dicrotic  pulse   142. 
Diencephalon   1000. 
Differential  rheotome  654. 
Differential  tones  910. 
Diffusion  351. 

Digestibility  of  various  foods  300. 
Digestion  of  living  tissues  301. 
Digestive  ferments  of  plants  345. 
Dionea  346. 
Diopter  838. 
Diphthongia  618. 
Diphthongs  613. 
Diplacusis  902. 
Direct  vision  852. 
Discordant  sensation  909. 
Disharmony  909. 
Dissociation  of  gases  240. 
Distance,  judgment  of  878. 
Distribution  of  the  blood  188. 
Division  938. 
Division  of  labor  940. 
Diverticula  from  the  intestine  994. 
Dorsal  vessel   199. 
Double    arterial    sound    in    anacrotism 

184. 

Double  conduction  in  nerves  669. 
Double  hearing  908. 
Double  images  872. 
Double  murmur  184. 
Double  uterus  and  vagina  998. 
Dreams  778. 
Dribbling  of  urine  524. 
Dromograph   173. 
Drosera  378. 
Ductus  Botalli  991. 

cochlearis  897,  898. 

Cuvieri  992. 

endolymphaticus  897. 
Duplicate  heart-sound   112. 
Dust  infiltration  of  the  lungs  245. 
Dust  in  respired  air  245. 
Dwarf-formation  983. 


Dynamids   19. 
Dynamometer  572. 
Dysarthria  618. 
Dyschromatopsia  860. 
Dyperistalsis  287. 
Dyphagia   196. 
Dyspnea  211,   752,   753. 


Ear-muscles  890. 

Ear-wax  534. 

v.  Ebner's  glands  256. 

Echinococcus  941. 

Echoes  911. 

Eclampsia  784,  in  uremia  784  and  in 

autointoxications  784. 
Ectoblast  962. 
Edema  374. 
Edentata  276. 
Eel  serum  68. 
Egg,  development  of  946. 
Egg-membranes  in  multiple  pregnancies 

979- 

Egg-membranes  in  animals  980. 
Egg  nucleus  960. 
Eggs  423- 
Egophony  223. 
Ejaculation  957. 
Ejaculation  center  735. 
Elasticity  of  active  muscle  574. 
Elasticity  of  muscle  573. 
Elasticity  of  the  blood  vessels   132. 
Elastic  elevations   141. 
Elastic  traction  of  the  lungs   in,  223. 
Eleidin  granules   527. 
Electrical  odor  916. 

sensations  665. 

taste  sensations  918. 

units  640. 

vertigo  809. 

Electric  charge  of  the  body  674. 
fish  675. 

variations  as  stimuli  632. 
Electro-cardiogram  652. 
Electrolysis  643. 
Electromotors  638. 
Electromuscular  sensibility  937. 
Electrotherapeutics  669. 
Electrotonic  currents  655. 
Electrotonus  660. 
Elementary  granules  49. 
Embracing  experiment   730. 
Embryocardia   112. 
Embryonal  spot  963. 
Embryonal  shield  963. 
Emetics  282. 

Emotional  activities  804. 
Emphysema  204. 
Emulsin  374. 
Emulsification  of  fats  306. 
Enamel  272. 
End-bulbs  921. 

Endocardiographic  experiments   106. 
Endocardium  92. 
Endolymph  897. 
Endolymphatic  duct  897. 


INDEX. 


1013 


Endosmosis  351. 

Endosmotic  equivalent  352. 

Enemata  283,  359. 

Energy,  unity  of  25. 

Entoblast  962. 

Entoptic  shadows  844. 

Entoptic  pulse  phenomena  156. 

Entotic  phenomena  911. 

Enuresis  524. 

Eosinophile  leucocytes  47. 

Epiblast  962. 

Epidermis  527,   532. 

Epididymis  997. 

Epigastric  pulsations   157. 

Epigenesis   1006. 

Epiglottis  604. 

Epilepsy,  cerebral  80 1,  Jacksonian  783, 
795,  medullary  773. 

Epileptic  condition  774. 

Epileptic  insanity  80 1. 

Epileptogenous  zone   774. 

Epileptoid  hallucinations  80 1. 

Episternum  987. 

Epithelio-muscular  cells  599. 

Equilibration,  disturbances  of  805. 

Equilibrium  912. 

Equivocal  generation  938. 

Erection  955. 

Erection-center  735,  956. 

Ergo  graph  580. 

Erythroblasts  41. 

Erythrocytes  31,  discovery  31,  volume 
3 1 ,    weight    3 1 ,    specific    gravity    3  2 , 
number  32,  enumeration  32,  physical 
properties    34,    destruction    34,    43,    . 
structure    34,    vital    phenomena    34,    ! 
color  35,  contraction  35,  changes  in 
form    35,    changes    in    position    35, 
rouleaux    35,    influence    of   heat    36,    j 
erythrocytotripsy     36,     erythrocyto-   ; 
lysis  36,  preservation  36,  preservative   ! 
fluids  36,  permeability  37,  isotony  37,   i 
hyperisotony  38,   hypisotony  38,  os- 
motic tension  38,  solution  36,  38,  44, 
laking  38,  stroma  39,  dissolving  agents 
39,    gas    content    40,    resistance    to   '• 
solution   40,   in   various   animals   40, 
development    41,     division    41,    nu- 
cleated  41,   conditions   of  origin   42, 
disintegration   43,   sign   of  degenera- 
tion 44,  abnormalities  50,  dwarf  and 
giant  erythrocytes   50,  pigments   50, 
parasites    51,    chemical    constituents 
51,  proteids  63,  diastatic  ferment  63, 
stroma-fibrin      63,     other     chemical 
constituents  64,  quantitative  analysis   | 
65,   relation   to   fibrin   formation    71,    ; 
gases  78,  polycythemia  85. 

Erythromelalgia  770. 

Erythrophobia  798. 

Erythropia  791;. 

Esbach's  albumin  imcter  496. 

Esophageal  plexus  709. 

Esophageal  stricture  339. 

Esophagus  279. 

Esthesiometer  924. 


Esthesodic  tracts  736. 

Estimation  of  size  877. 

Ether  18. 

Euperistalsis  287. 

Eupnea  752. 

Eustachian  tube  894,   opening  of  894, 

sounds   895,   catheterization   896. 
Evaginations    from   the   intestine    994. 
Evolution   1004. 
Excitomotor  nerves  677. 
Exophthalmic  goiter  196,   770. 
Exophthalmos  866. 
Expiratory  muscles  212. 
Expired  air  231. 

Exponent    of   refraction    825,    830. 
External  ear  887. 

External    genitalia,    development    998 
External  transmigration  959. 
Extirpation  of  brain  tissue  775. 
Extra-current  apparatus  645. 
Extremities,  development  973. 

development  of  the  bones 

of  the  987. 

Eye,  development   1001. 
Eye,  illumination  of  847. 
Eye  movements  866. 
Eye   muscles    868,    center   for    795. 
Eye,  structure  815. 
Eye-ground  849. 
Eye-lids  879. 

Eye-lids,  center  for  closure  748. 
Eye-lids,  glands  of  531. 


Facial  bones,  development  of  985. 

"        nerve  694. 

"       paralysis  697. 

"       respiratory  movements  216. 
Falciform  process  883. 
Falsetto  voice  609. 
Far-point  836. 
Far-sighted  eye  837. 
Fat  absorption  356. 
Fat,  chemistry  462. 
Fat  deposition  443. 
Fat  diet  443. 
Fat  digestion  306. 
Fat  emboli  86. 
Fat  formation  444. 
Fat,  origin  in  the  body  444. 
Fat-splitting  ferment   of  the   pancreas 

306. 

Fatigue  579. 
Fatigue  of  the  ear  911. 
Fatigue  of  the  eye  855. 
Fatigue  of  muscle  579. 
Fatigue  of  the  organs  of  taste  918. 
Fatigue    of    the    olfactory    organ    915. 
Fatty-acids,  absorption  357. 
Fatty-acids    in    intestinal    putrefaction 

332- 

Fatty  degeneration  of  muscle  636. 
Fecal  odor  336. 
Feces  335,  constituents  337. 
Fellic  acid  316. 
Fermentation  429. 


ioi4 


INDEX. 


Fermentation  test  for  sugar  268. 

Ferments,  fate  in  the  intestine  328. 

Ferments  in  plants  345. 

Ferratin  313. 

Fetal  circulation  979. 

Fetal  membranes  979,  980. 

Fetus,  movements  of  982,  983. 

Fever  404. 

Fever  temperature  392. 

Fibrillary  contraction  95,  114,  119,  559. 

Fibrin  65,  86. 

Fibrin  factors  70. 

Fibrin  ferment  69. 

Fibrinogen  68,  70. 

Fibrin  oplastic  substance  73. 

Fick's  spring  kymograph   163. 

Filling  of  the  aorta  104. 

Filtration  354. 

First  circulation  971. 

Fistula  of  the  lower  lip  985. 

Fixation  852. 

Fixation  of  the  vertebrae  590. 

Fluorescence  of  the  eye  media  831,  856. 

Flying  597. 

Foliate  papillae  919. 

Fontana's  striation  628. 

Food,  necessary  quantity  433. 

Foods  25. 

Foot,  arch  of  the  591. 

Foot  deformities  588. 

Forced  movements  806. 

Forces  19. 

Fore-brain  968,  1000. 

Fore-gut  cavity  970. 

Formation  of  images  by  lenses  824. 

Formic  acid  463,   535. 

Fovea  centralis  853. 

Freezing  408. 

Friction  murmurs   113,  222. 

Frog-current  651. 

Frontal  cortical  injuries  774. 

Fruits,  428. 

Fun  die  glands  289. 

Funic  souffle   184. 


Galloping  597. 

Gall-stones  341. 

Gall-stone  colic  342. 

Galton's  whistle  901. 

Galvanic  conductivity  of  the  skin  540. 

Galvanic  currents  and  circuits   639. 

Galvanic  polarization  643. 

Galvanic  stimulation  of  olfactory  organ 

916. 

Galvanotonus  1 1 6 ,   119. 
Ganglion-cells,  changes  in  activity  628. 
histology  625. 
of  the  retina  819. 
sensory  626. 
sympathetic  626. 
Ganglion,  ciliary  684. 

geniculate  694. 
jugular  ^704. 

of  the  lingual  nerve  703. 
of  the  optic  nerve  819. 


Ganglion  otic  689. 

petrosal  703. 
sphenopalatine  687. 
spiral  699. 
submaxillary  691. 
vestibular  699. 
Gargling  225. 
Gartner's  ducts  997. 
Gas-pump  77. 
Gas-sphygmoscope   137. 
Gastnc  catarrh  340. 
crypts  289. 
disorders  340. 
fistula  295. 
glands  289. 
musculature  280. 
nerves  281. 
neuroses  282. 
plexus  709. 
Gastric  digestion,  disorders  of  340. 

in  fever  and  anemia 

341; 

of     different    tissues 
300. 

Grastnc-juice  292,  constituents  292, 
secretion  293,  vagus  action  295, 
action  of  alcohol  295,  in  the  newborn 
295,  comparative  295,  collection 
295,  artificial  296,  excessive  secretion 

„  340. 

Gastrograph  280. 

Gastroxynsis  340. 

Gastrula  962. 

Gelatin  diet  442. 

Genital  eminence  998. 

Genital  strand  998. 

Germinal  area  963. 

Germinal  centers  45. 

epithelium  996. 
gland  996. 
membrane  964. 
vesicle  961. 

Germs  in  the  atmosphere  246. 

Gianuzzi's  crescents  258. 

Ginglymus  582. 

Giraldes'  organ  997. 

Gland-currents  651. 

Glaucoma  687. 

Globin  60,  63. 

Globulicidal  action  of  blood  74. 

Globulins  458. 

Glossopharyngeal  nerve  703. 

Glossoplegia  713. 

Glottis  in  respiration  216. 

Glottis,  paralysis  of  706. 

Glucosides  462. 

Glutamic  acid  305. 

Glycin  316. 

Glycocholic  acid  316. 

Glycogen  311,  qualitative  and  quan- 
titative estimation  311,  origin  311, 
transformation  into  sugar  312,  chem- 
istry 466. 

Glycogenic  degeneration  315. 

Glycosuria  501. 

Goose-flesh  529. 


INDEX. 


IOI5 


Grandry-Merkel  corpuscles  922. 
Gravitation   19. 

Grinding  movement  in  mastication  271. 
Grinding  stomach  344. 
Grouped  heart  beats   117. 
Growth  in  size  and  weight  455. 
Gubernaculum  of  Hunter  998. 
Gustatory  organ  916. 

"        development  1002. 
Gustatory  region  916. 
Gymnastics  587. 


Haidinger's  polarization  brushes  847. 

Hair  529,  development  530,  graying 
530,  growth  531,  movements  529, 
structure  529. 

Hair-cells  898. 

Hales'  tube   162. 

Halisteresis  588. 

Hallucinations  814,  voluntary  847. 

Harderian  gland  883. 

Hare-lip  985. 

Harmony  908. 

Harrison's  groove  211. 

Hawking  225. 

Hay  em's  fluid  36. 

Head-fold  970. 

Head-register  609. 

Heart  89,  histology  89,  structure  of  the 
auricle  89,  structure  of  the  ventricle 
90,  pericardium  91,  endocardium  92, 
valves  92,  coronary  vessels  93, 
automatic  regulation  93,  nbrillary 
contractions  95,  failure  96,  move- 
ments 96,  systole  96,  diastole  96, 
valve-play  97,  103,  negative  pressure 
97,  99,  residual  blood  98,  chordae 
tendineae  98,  pause  99,  tone  99, 
functional  disturbances  99,  hypertro- 
phy 99,  stenosis  99,  valvular  in- 
sufficiency 100,  apex-beat  100,  car- 
diogram 100,  time  relations  of  the 
beat  104,  endocardiograms  106,  ab- 
normal heart  bea.ts  107,  spurious 
contraction  108,  abnormal  cardio- 
grams 108,  hemi-systole  no,  heart 
sounds  1 10,  abnormal  sounds  112, 
and  murmurs  113,  duration  of  the 
movement  113,  undulating  move- 
ments 114,  ii£,  119,  nerves  114, 
ganglia  114,  minimal  and  maximal 
stimulation  115,  section  and  ligation 
experiments  116,  isolated  apex  117, 
grouped  beats  117,  stair-case  beats 
117,  automaticity  118,  stimuli  118, 
poisons  1 20. 

Heart  as  the  cause  of  blood  pressure 


Heart,   comparative    198,   development 

971,  990. 
Heart-failure  96. 
Heart  sounds   no. 
Heat  22. 

Heat  accumulation  403. 
balance  399. 


Heat  center  394. 

conduction  by  tissues  390. 

dissipation  396. 

dyspnea  753. 

employment  of  407. 

effect  on  the  eye  844,  86 1. 

feeling  of  933. 

production     394,     regulation     of 
394,  variations  in  400. 

production  in  muscle  576. 

production  in  single  organs  385. 

rigor  554. 

source  of  379. 

units  22,  401. 

values  of  foods  378. 
Height  of  lift  574. 
Height  of  velocity  125. 
Helicotrema  897. 
Heliotropism  883. 
Hemamoeba  51. 
Hematin  60. 
Hematin-chlorid  61. 
Hematodynamometer  162. 
Hematoidin  63,  317. 
Hematoidrosis  539. 
Hematoporhyrin  61,  62. 
Hematosiderin  44. 
Hematuria  497. 
Hemautography  139. 
Hemeralopia  680. 
Hemialbumin  297. 
Hemicrania  770. 
Hemimetabola  941. 
Hemin  61. 
Hemiopia  798. 
Hemipeptone  297,  304,  305. 
Hemiplegia,  cerebral  792. 
Hemisystole   1 1  o . 
Hemochromatosis  44. 
Hemochromogen  61. 
Hemocyanin  41. 
Hemodromometer  171. 
Hemofuscin  44. 
Hemoglobin  51. 

crystals  58. 
gas  content  55,  58. 
reduced  56. 
spectroscopic  examination 

54- 

Hemoglobinuria  498. 
Hemometer  53. 
Hemophilia  68. 
Hemorrhage,  death  by,  87. 
Hemotachometer  173. 
Hepatogenic  icterus  323. 
Hermaphrodism  940,  999. 
Heterologous  stimuli  813. 
Hibernation  212,  410. 
High-hearing  individuals  901. 
Hind-brain  968,    1000. 
Hind-gut  971. 
Hinge-joints  582. 
Hippuric  acid  334,  484. 
Hippus  682. 
Histon  63. 
Hoarseness  618. 


ioi6 


INDEX. 


Hollow  muscles  583. 

Holoblastic  ova  948,  958. 

Holometabola  941. 

Homoiothermous  animals  381. 

Homologous  stimuli  813. 

Horopter  872. 

Horse-power  572. 

Huerthle's  manometer  164. 

Humidity  of  the  atmosphere  230. 

Hunger-icterus  322. 

Hunger,  metabolism  in  439. 

Hybrids  959. 

Hydatid  of  Morgagni  997. 

Hydremia  84. 

Hydrobilirubin  74,  318,  325. 

Hydrocephalus  774. 

Hydrochloric  acid  in  the  stomach  292, 

293- 

Hydrocyanic  acid  374. 
Hydrocyanic  acid  hemoglobin  60. 
Hydrodiascope  841. 
Hydrops  375. 
Hydrotics  536. 
Hygrometer  230. 
Hypacusis  700. 
Hypalgia  936. 
Hyperacusis  700. 
Hyperalgia  700,   737,  935. 
Hypercholia  322. 
Hyperesthesia  738,  optic  680. 
Hypergeusis  919. 
Hyperglobula  85. 
Hyperidrosis  538,  unilateral  538. 
Hyperisotonic  solutions  38. 
Hyperkinesis  738. 
Hypernutrition  445. 
Hyperostosis  588. 
Hyperpselaphesia  933. 
Hypisotonic  solutions  38. 
Hypnotism  778,  of  animals  780. 
Hypoblast  962. 
Hypogeusis  919. 
Hypoglobula  87. 

Hypophysis  197,  development  1000. 
Hypopselaphesia  934. 
Hyposmia  679. 
Hypospadia  999. 


Icterus,  hepatogenic  323. 

Icterus  neonatorum  323. 

Identical  retinal  points  871. 

Ideomuscular  contraction  559. 

Ileo-caecal  valve  283. 

Illusions  814. 

Images,  formation  by  lenses  824. 

Impregnation  958. 

Inanition  439. 

Inaudible  tones  901,  903. 

In-breeding  959. 

Inclination  currents  650. 

Incontinence  524. 

Indefinite  respiratory  sounds  222, 

Index  of  refraction  825. 

Indian  corn  428. 

Indican  333,  487. 


Indirect  vision  853. 
Indol  305,  333. 
Induction  645. 
Infectious   diseases    of 

tract  245. 
Inflammation 


the   respiratory 


181. 

Inguinal  glands  540. 
Inheritance  of  mutilations  1004. 
Inhibition  of  reflexes  731,  733,  740. 
Inhibitory  nerves  678. 
Inhibitory  nerves  of  the  heart  758. 
Inhibitory    nerves    of    the    respiratory 

apparatus  711. 
Inhibitory  polar  action  666. 
Initial  contraction   567. 
Initial  vowels  614. 
Innervation  of  the  eye-muscles  870. 
Inorganic     constituents     of    the     body 

456- 

Insalivation  271. 
Inspiratory  muscles  212. 
Intelligence,  seat  of  80  1. 
Intelligence  in  animals  776. 
Intercalary  ducts  258. 
Intercentral  nerves  678. 
Inter-epithelial  nerve  endings  922. 
Interference  of  sound  waves  908. 
Interglobular  spaces  272. 
Interlabyrinthine  pressure  899. 
Intermittent  ophthalmia  686. 
Internal  genital    organs,     development 

996. 

polarization  644. 
respiration  241. 
secretion   193. 
Intervillous  spaces  977. 
Intestinal  absorption  348. 

bacteria  329. 

contents  /reaction  335. 

digestion  in  fever  342. 

exhaustion  287. 

fermentation  329. 

gases  329. 

juice  326,  327,  328. 

navel  971,  993. 

paralysis  288. 

paresis  287. 

putrefaction  329. 

rest  286. 

villi  in  absorption  348. 
Intestine,  length  of  326. 

nerves  of  286,  328,  720. 

stimulation  of  286. 
Intra-ocular  pressure  843. 
Intra-  vascular  hemorrhage  767. 
Inunction  539. 
Inversion  of  intervals  901. 
Inversion  of  the  retinal  image  83  1  . 
Invertin  328,   332. 
Involution  of  the  uterus   1004. 
lodothyrin   197. 

Iris  817,  cortical  reflex  843,   functions 
841,    movements    842,    muscles    842, 
nerves  842. 
Irradiation  864. 

of  pain  935. 


INDEX. 


IOiy 


Irregular  astigmatism  841. 
Irrespirable  gases  245. 
Irritability  of  different  nerve  fibers  633. 
of  nerves  at  different  points 

637. 

Ischemia  933. 
Ischuria  523. 

Isodynamic  food  values  378. 
Isometric  muscular  activity  568. 
Isotonic  muscular  activity  568. 


Jacksonian  epilepsy  783,  795. 
acobson's  organ  916. 
aw,  articulation  of  270. 
aw  movements  270. 
ecorin  313. 
oints  581. 
umping  596. 


Key-electrode  648. 

Kidneys,  development  995,  nerves  514, 

structure  469,  vessels  469. 
Kinematograph  593,  863. 
Kinesodic  tracts  736. 
Kinetic  energy  20. 
Kinetoscope  863. 
Kjeldahl's  method  478. 
Krause's  end  bulbs  921. 
Kymographion   162. 


Lab-formation  300. 

Lab-ferment  in  the  stomach  300,  in  the 

small  intestine  328. 
Lab-stomach  344. 
Labor  pains   1003. 

Labyrinth    885,    896,   pressure   in    899. 
Lactic-acid  fermentation  in  the  stomach 

300. 

Lactic  acid  in  the  intestine  331. 
Lactic  acid  in  the  stomach  292,  294. 
Lagena  912. 

Laryngeal  cartilages  600. 
ligaments  600. 
muscles  600. 
nerves  705. 

Laryngeal  stenosis  sound  222. 
Laryngoscope  606. 
Laryngo-stroboscope  606. 
Larynx  600,  closure  in  deglutition  278. 
Latebra  949. 
Latent  stimulation  561. 
Lateral  line  912. 
Lateral  plates  969. 
Laughing  225. 
Left-handedness  795. 
Legumes  427. 
Lenses  820. 
Lenticular  nucleus  802. 
Leptothrix  264. 
Leucin  305,  333,   503. 
Leukemia  51. 
Leukocytes  45,  demonstration  45,  forms 

45.    structure    45,    development    45, 


division  45,  multiplication  45,  leu- 
kocytosis  45,  51,  number  46,  move- 
ments 46,  chemotaxis  46,  migration 
46,  phagocytosis  46,  solution  47, 
leukocytolysis  47,  staining  prop- 
erties 47,  granules  47,  classifica- 
tion 47,  oxyphile,  neutrophile,  baso- 
phile  granules  47,  48,  nuclein  and 
glycogen  content  48,  leukemia  47, 
51,  abnormalities  51  chemical  con- 
stituents 64,  destruction  70. 

Leukocytosis  45,  48,   51. 

Levator  ani  286. 

Levator-cushion  895. 

Liberating  forces  555. 

Lieberkiihri's  glands  326. 

Light  24,  action  on  the  iris  844,  on 
respiration  236. 

Light  cells  88 1. 

Line  of  fixation  867. 

Lingual  glands  256. 

Lipemia  86. 

Lipochrome  74. 

Liver,  chemical  constituents  311,  con- 
nective tissue  310,  development  995, 
lobules,  cells  308,  lymphatics  310, 
nerves  310,  structure  308,  sugar 
forming  ferment  312,  vessels  308. 

Local  sign  927. 

Lochia  1004. 

Locomotion  in  animals  596. 

Lowe's  ring  845. 

Ludwig's  kymograph   162. 

Lungs,  after  section  of  the  vagi  708, 
development  994,  edema  of  224, 
plexus  of  707,  structure  201,  tonus 
204,  vessels  203. 

Luster  876. 

Lustrous  eyes  of  animals  850. 

Lutein  74,  cells  954. 

Lymph  366,  lymph  cells  366,  lymph- 
plasma  366,  lymph  clot  366,  lymph 
serum  366,  collection  367,  chemistry 
367,  amount  368,  secretion  368, 
source  369,  propulsion  371,  influence 
of  nerves  on  formation  372,  lymph- 
hearts  372,  stasis  374. 

Lymphagogs  369. 

Lymph  capillaries  362. 

cells  366,  370,  origin,  division 

370,  destruction  371. 
"         channels  of  the  eye  821. 
"         channels,  origin  362. 
follicles  363. 
glands  363,  372. 

Lymphocytes  45. 

Lymphomotor  nerves  769. 

Lymph  spaces  360,  362. 

system,  function  360. 
"         vessels  362,  371. 

Lysatinin  305. 

Lysin  305. 


Macrocytes  50. 
Maerostomia  987. 


ioi8 


INDEX. 


Macula  lutea  845. 
Magneto-induction  646. 
Magneto-induction  apparatus  647. 
Malarial  parasites  51. 
Malpighian  vessels  345. 
Maniacal  motor  activity  794. 
Manyplies  344. 
Marginal  bodies  912. 
Mariotte's  experiment  850. 
Massage  588. 
Mastication  center  749. 
Mastication,  comparative  343. 
Masticatory  muscles,  spasm  of  339. 
Masticatory  stomach  344. 
Matter  18. 

Maximal  heart  stimulation  115. 
Meat  423. 

analysis  424. 
broth  425. 
decomposition  426. 
diet  443. 
extract  425. 
preparation  of  425. 
Meckel's  process  986. 
Medulla    oblongata    748,    centers    748, 
pathological    750,    relation    to    loco- 
motion  750. 
Medullary  groove  966. 

tube  968. 

Medusae,  development  939. 
Megaloblasts  50. 
Melanemia  50. 
Membrana  basilaris  899. 
decidua  975. 
pupillaris  1002. 
reticularis  899. 
reuniens  972. 
tectoria  898. 

versicolor   of   Fielding  850. 
Membrane  of  Corti  899. 
Meniere's  disease  701. 
Menstruation  50,  951. 
Mental  development  in  animals  776. 
Meroblastic  ova  948. 
Mesencephalon  968,   1000. 
Mesoblast  965. 
Metabolic  equilibrium  430. 
Metabolism  as  an  index  of  life  28. 
experiments  431. 
in  the  tissues  448. 
laws  of  443. 

.    limits  433- 
Metagenesis  941. 

Metallic  tinkling  respiratory  sound  220. 

Metalloscopy  936. 

Metamorphosing  respiratory  sounds  222. 

Metamorphosis  940. 

Metencephalon  968,   1000. 

Methemoglobin  57. 

Methylmercaptan  336. 

Microbes  in  the  feces  338. 

Microcephalus  774. 

Micrococci  329. 

hematodes  539. 

of  the  epidermis  539. 

ureas  493. 


Microcytes  50. 

Micropyle  946,  958. 

Micturition  520. 

Mid-brain    775,    776,    805,    968,    1000. 

Middle  plates  969. 

Migration,  law  of  1004. 

Migration  of  leukocytes  46,   180. 

Military  standing  position  591. 

Milk  417,  419,  421. 

changes  in  420. 

coagulating  ferment  of  the  pan- 
creas 307. 

coagulating  ferment  of  the  stom- 
ach 300. 

constituents  419. 

digestion  300,  305. 

evacuation  419. 

glands  417,  418. 

preparations  422. 

secretion  417. 

tests  421. 
Minimal  diet  437. 
Mixed  colors  857. 
Mogiphonia  617. 
Molecules  18. 
Monistic  conception   1004. 
Monocular  polyopia  841. 
Monotonia  617. 
Moore's  test  267. 
Morula  961. 
Motion  of  animals  596. 
Motor  nerves  677. 
Mouches  volantes  844. 
Mountain  sickness  253. 
Mouth  fluids  263. 
Mouth  glands  256. 
Mouth  organisms  265. 
Movements  of  expression  618. 
Movements  of  intestinal  contents  282. 
Mucin  of  bile  322,  325. 
Mucolacrimal  spectrum  844. 
Mucous  cells  258. 
Miillerian  duct  997. 
Mutter's  experiment   151. 
Multiple   pregnancies   958,    fetal   mem- 
branes in,  979. 
Multiplicator  641. 
Murexid  test  482. 
Muscae  volitantes  844. 
Muscle,  consistency   547,  refraction    of 
light    548,    chemistry    548,    proteids 

548,  acids  549,  gases  549,  metabolism 

549,  production    of   work    551,    569, 
irritability    555,    stimuli    556,    death 

557,  change     of    form    in     activity 

558,  shortening    558,    volume    558, 
microscopy  in  contraction  559,  curve 
of    contraction    560,    elasticity    572. 

Muscle  currents  648,  theories  657. 

Muscle,  fatty  degeneration  of  636. 

Muscle-fibers,  structure  542,  elements 
542,  relation  to  tendons  544,  nerve 
endings  544,  sensory  nerves  545, 
red  and  pale  545,  563,  structure  545, 
degeneration  546,  smooth  muscle 
546,  cell-bridges  547,  nerves  547. 


INDEX. 


1019 


Muscle,  heat  production  in  576. 
murmur  578. 
stimuli  556. 
stomach  344. 

Muscles,  arrangement  in  the  body  583. 
Muscles,  diarticular  586. 
Muscular  energy,  source  of  549. 
Muscular  fatigue  579. 
Muscularis  mucosae  291. 
Muscular  insufficiency  586. 

degeneration  588. 

atrophy  589. 

hypertrophy  589. 

paresthesias  937. 

sense  936. 

tone  736. 

Musculo-cutaneous  plates  969. 
Musculo-cutaneous  tube  541. 
Mydriasis  682. 
Mydriatics  843. 
Myelemia  51. 
Myelin  622. 

Myelin  forms  in  the  sputum  249. 
Myenteric  plexus  286. 
Myograph  561. 
Myoryctes  Weismanii  548. 
Myosin  549. 
Myosinogen   549. 
Myosis  682. 
Myotics  843. 


Narcotics  935. 
Nasal  pulse  156. 
Nasal  vowels  614. 
Natural  selection   1004. 
Near-point  835. 
Negative  variation  652. 
Nerve,  abducens  693. 

accelerator  761. 

accessory  712. 

acoustic  699. 

depressor  707,   764. 

facial  694. 

glossopharyngeal  703. 

oculomotor  680. 

olfactory  678. 

optic  679. 

phrenic  214. 

splanchnic  288. 

trigeminal  683. 

trochlear  682. 

vagus  704. 
Nerve-cells,  changes  in  activity  628. 
histology  625. 
sensory  626. 
sympathetic  626. 
Nerve  centers   (general)    723. 
Nerve,  chemistry  626. 

currents  '6  50. 

degeneration  633,  death  637. 

fatigue  635. 

fibers   (histology)   621. 

impulse,  rate  of  667. 

irritability  629,  635. 

metabolism  628. 


Nerve,  regeneration  636. 

rigidity  628. 

stimuli  629. 

stretching  630. 

suturing  636. 
Nerves,  functions  of  677. 

pilomotor  529. 
Nervi  engentes  955. 
Nettle-cells  541. 
Neuralgia  936. 
Neurite  625. 
Neuroblasts   1001. 
Neuron  621. 

Nitric-oxid-hemoglobin  60. 
Nitrogen  deficit  431. 
Nodal  points  of  the  eye  829. 
Noeud  vital  750. 
Noise  899. 
Normal  eye  835. 
Normal  position  591. 
Normoblasts  50. 

Nourishment,   quantity  in  health  433 
Nuchal  flexure  968. 
Nuclear  spindle  959. 
Nucleins  459. 
Nutritive  enemata  359. 
Nutritive  subcutaneous  injections  373. 
Nutritive  yolk  949. 
Nyctalopia  680. 
Nystagmus  807,  809. 


Oblique  facial  cleft  985. 
Oblique  illumination  of  the  eye  850. 
Ocular  movements  866. 
Ocular  muscles  868. 
Oculomotor  nerve  680. 
Odontoblasts  273. 
Ohm  640. 
Ohm's  law  639. 
Olfactometer  915. 
Olfactory  cells  914. 
hairs  914. 
hallucinations  679. 
nerve  678. 

organ  913,  development  1002. 
region  913. 
Oligemia  86. 
Oligocythemia  87. 
Omentum,  development  995. 
Oncograph  189. 
Onomatopoesis  619. 
Ontogeny  1004. 
Opening  contraction  632. 
Ophthalmia,    intermittent    586,    neuro- 

paralytic  686. 
Ophthalmometer  830. 
Ophthalmoscope  847,  849. 
Optic  axes  852. 

defects  839. 

nerve  679. 

nerve  entrance  846. 

nerve,     mechanical     stimulation 

of  846. 

perception  field  798. 
thalamus  803. 


I02O 


INDEX. 


Optic  vesicle  968,   1001. 
Optogram  855. 
Optometer  837. 
Oral  pulse  156. 
Organ  of  Corti  898. 
Oro-orbital  cleft  985. 
Orthoscope  850. 
Osmidrosis  539. 
Osmotic  tension  38. 
Ossicles  of  the  middle  ear  890. 
Osteoclasts  46. 
Osteomalacia  588. 
Otoliths  898,  912. 
Overtones  903. 
Ovists  1006. 
Ovulation  951. 
Oxalic  acid  483. 
Oxyhemoglobin  51,   55,  60,  78. 
Oxyphile  leukocytes  47. 
Ozone  79,  in  the  blood  79. 


Pacchionian   granulations  809. 
Pacini's  fluid  36. 
Pacinian  bodies  921. 
Pain  934. 

Pain  anomalies  934,  935. 
Pain  conduction  739. 
Painful  anesthesia  935. 
Pain,  minimum  of  935. 
Pain  points  924. 
Palaeopithecus  1005. 
Pancreas  302. 

activity  of  307. 

amylolytic  activity  304. 

development  995. 

extirpation  308. 

fistula  303. 

lipolytic  activity  306. 

nerves  307. 

preparation  of  ferments  306. 

proteolytic  activity  304. 

resting  303,  307. 

structure  302. 
Pancreas  of  Aselli  375. 
Pancreatic  diabetes  308. 

juice    303,    action    of    304. 
Pansphygmograph   135. 
Pantomime  speech  797. 
Parablast  970. 

Paradoxical  auditory  reaction  700. 
contraction  657. 
light  reaction  844. 
localization     of     sensation 

934- 

Paraglobulin  73. 
Paralgia  936. 
Paralytic  intestinal  secretion  328. 

saliva  261. 

Paramyoclonus  multiplex  794. 
Paraphasia  797. 
Parasites  in  the  blood  5 1 . 
Parenchymatous  injection  373. 
Paridrosis  538. 
Parietal  cells  290,   293. 
Parietal  eye  883. 


Parietal  flexure  968. 

Parotid  259. 

Parotid  saliva  262. 

Parovarium  997. 

Parthenogenesis  942. 

Parturition   1002. 

Parturition  center  735. 

Passavant's  cushion  277. 

Passive  muscular  insufficiency  586. 

Partial  paralysis  of  touch  934. 

Pathogenic  microbes  330. 

Pecten  883. 

Pectoral  fremitus  223,  609. 

Peduncles  804. 

Pendular    movement    in    walking    594. 

Pepsin  292,  293,  296,  297,  299. 

Pepsinogen  293. 

Peptic  cells  289,   293. 

Peptone  297,   298,   299. 

absorption  356. 

reversion  356. 
"         tests  for  298. 
Peptonization  299,  300. 
Percussion  218,  220. 
Pericardial  fluid  367. 
Pericardium  91. 
Perilymph  897. 
Perimetry  853. 
Perineum  999. 
Periodic-regulatory  vascular  movement 

765. 

Periodic  respiration  212. 
Peristalsis  277,  282,   286. 
Peristalsis,  gastric,  disorders  of  340. 
Peri  vascular  lymph-spaces  362. 
Pernicious  anemia  50. 
Perspiration  534. 
Pettenkofer's  test  316. 
Phagocytes  46. 
Phanakistoscope  863. 
Pharyngeal  plexus  705. 
Phenol  305,  334,  488. 
Phenyl-hydrazin  test  267. 
Phlebin  52. 
Phlebogram  185. 
Phonation  center  749. 
Phonation,  disorders  of  617. 
Phonautograph  907. 
Phonograph  906. 
Phonometry  221. 
Phosphenes  845,  846. 
Phosphorescent  organisms  254. 
Photohemotachometer  174. 
Photopsia  680. 
Phrenic  nerve  214. 
Phrenograph  208. 
Phrenology  775. 
Phylogeny   1004. 
Physiology,     definition     17,     aim     and 

relations   17,  protists  18,  28. 
Physiological  rheoscope  651. 
Pial  vessels  810. 
Piercing  tones  890. 
Pigments  462. 

of  the  blood  74. 
of  the  urine  485. 


IXUEX. 


IO2I 


Pigments  of  the  skin   535. 

Pilomotor  muscles  529. 

Pilomotor  nerves  529. 

Pithecanthropus   1005. 

Placenta  975. 

Placental  murmur  184. 

Placenta!  villi  977. 

Plane  of  fixation  867. 

Plant  digestion  345. 

Plant  ferments  345. 

Plant -lice,  development  942. 

Plants  and  animals  25. 

Plasma  65. 

Plasma-fibrin  72. 

Plasmolysis  37. 

Plessimeter  218. 

Plethysmograph    in    measuring    blood 

pressure   165. 
Plethysmography  189. 
Pluricordoiial  cells  725. 
Pneumatic  cabinet   151,   253. 
Pneumatograph  208. 
Pneumatography  208. 
Pneumometry  205,   223. 
Pneumoplethysmograph  209. 
Pneumothorax  204. 
Poikilocytes-  50. 
Poikilothermous  animals  381. 
Point    of    intersection    for    visual    rays 

830. 
Poiseuille's  hematodynamometer  162. 

space   178. 
Polar   action    of   the   constant   current 

665. 

Polar  bodies  948,  960. 
Polarization,  galvanic  643. 
Polarization  test  for  sugars  268. 
Polyarthrodial  muscles  586. 
Polycythemia  85. 
Polyemia  84. 
Polyopia,  monocular  841. 
Polyspermism  958,  960. 
Pons  804. 

Pontal  flexure  968. 
Pore  canals  946,  958. 
Portal  system,  development  of  992. 
Portio  intermedia  of  Wrisberg  694. 
Posterior  roots  717. 
Potatoes  428. 
Potential  energy   20. 
Power-sense  9,^). 
Premortal  respiratory  pause  211. 
Pressor  fibers  in  the  cord  740. 
Pressor  nerves  764. 
Pressure  balance  928. 

phosphenes  845. 

points  924,  927. 

pulse  138,   189. 

sense  927. 

stream   183. 
Primary  albumoscs  297. 

colors  858. 

position  of  the  eyes. 
Primitive  aortas  971. 
cells  961. 
kidneys  995. 


Primitive  mouth  962,  973. 

segments  969. 

speech  619. 

streak  963. 

vertebrae  969. 
Principle  of  least  perceptible  differences 

928. 

Prochorion  963. 
Projection  system  of  the  brain  742,  743, 

744- 

Pronucleus  959. 
Propepsin  293. 
Propeptone  297. 
Prosencephalon  968,   1000. 
Prostatic  vesicle  997. 
Protagon  627. 
Protalbumose  627. 
Proteid  absorption  356. 

diet  442. 
Proteids  457. 

animal  458. 
vegetable  459. 
Proteinuria  494. 
Psalterium  344. 
Pseudo-antagonists  587. 
Pseudo-hermaphrodism  999. 
Pseudomotor  action  559,  695. 
Pseudoscope  876. 
Psychic  brain  functions  774. 
Psycho-acoustic  center  787,  799. 
Psycho-algic  center  800. 
Psycho-esthetic  center  800. 
Psycho-geusic  center  788,  900. 
Psycho-inhibitory  centers  785,  790. 
Psycho-motor    centers    781,    792,  inhi- 
bition of  them  794. 
Psycho-optic  center  786,  798. 
Psycho-osmic  center  788,  800. 
Psycho-sensory  centers  785,   798. 
Psychrometer  230. 
Ptyalin  263,  demonstration  265. 
Ptyalinogen  265. 
Ptosis  682. 
Puberty  951. 
Pulsatory    acceleration    of    the    blood 

stream   159. 

phenomena 'in  various  struc- 
tures 156. 

pressure  variations  167. 
vibration  of  the  body   157. 
Pulse,  alternating  145. 

bigeminate  145. 

caprizans   143. 

contracted   146. 

deficient   145. 

dicrotic   145. 

different   140. 

feeble    145. 

filiform   146. 

frequent   143. 

full  and  empty   145. 

hard  and  soft   145. 

infrequent  146. 

insensible  146. 

intereurrent    145. 

intermittent   145. 


1022 


INDEX. 


Pulse,  large   146. 

monocrotic   143. 
paradoxical  152. 
quick  143. 
serrate  146. 
slow  143. 
small  146. 
strong  145. 
tremulous  146. 
unequal  146. 
vermicular  146. 
vibrant   146. 
Pulse    curve    of    axillary    and    radial 
arteries  146,  of  carotid  146,  of  dorsalis 
pedis  and  tibial  147,  of  femoral  147. 
Pulse    curves    138,     139,    affected    by 
respiration    149,    by    Valsalva's    ex- 
periment   151,   by  Joh.   M  tiller's  ex- 
periment   151,    by  breathing  into   a 
spirometer  151,  pneumatic  chamber 
151,  by  pressure   152. 
Pulse,  entoptic  846. 
Pulse  in  aortic  insufficiency  148. 
Pulse  measurements  137. 
Pulse,  technique   of  examination    133- 

138. 
Pulse    wave,    influences    affecting    153, 

•length  153,  155,  velocity  153. 
Pulmonary  catheter  239. 

circulation  170. 
disturbances  '  following  va- 
gus section  708. 
edema  224. 
inelasticity  225. 
plexus  707. 
vessels  203. 
Pupillary  center  in  medulla   734. 
Pupillary  membrane   1002. 
Pupillo-dilator  center  749,  842. 
Purgatives  289. 
Purkinje's  phenomenon  856. 
Purkinje's  figure  845. 
Purkinje-Sanson  images  833. 
Purring  tremor  113. 
Pyknocardia  143. 
Pyknopnea  757. 
Pyloric  glands  289. 
Pyloric  incompetency  340. 
Pylorus,  movements  of  280. 
Pyramidal  tracts  726,  744,  784. 


Quadrigeminate  bodies  805. 


Rachitis  588. 

Rales  222. 

Rapidity  of  conduction  in  nerves  667. 

Rarefied  air  252,  influence  on  corpuscles 

252. 

Recoil  103. 
Recoil  elevation   139. 
Recurrent  pulse   149. 

sensibility  716. 
Reduced  eye  829. 


Reflexes  728,  kinds  728,  733,  reflex- arc 
728,  elicitation  729,  diffusion  729, 
739,  crossed  729,  laws  governing  730, 
reflex-time  730,  protective  730,  spinal 
731,  cortical  731,  complex  731,  in- 
hibition 731,  740,  theories  732, 
pathological  733. 

Reflex  immobility  of  the  pupil  844. 
nerves  678. 
spasm  740. 

time  730,  of  the  iris  843. 
tone,  muscular  736. 
Refractive  index  825,  830. 
Refractive    indices    of    the    eye    media 

830. 

Refractive  power  of  the  eye  835. 
Regeneration  of  lost  parts  451. 

of  tissues  451. 
Regular  astigmatism  841. 
Reinforcing  tube  599. 
Renal  nerves  514,  Vessels  469. 
Rennet-ferment  in  the  intestine  328. 
ferment  in  the  stomach  300. 
formation  300. 
stomach  344. 
Reserve  air  206. 
Residual  air  205. 
Residual  blood  98. 
Resistance  to  the  circulation  127,  128. 
Resonators  903. 
Resorption-icteru  s  322. 
Resorption  of  bile  322,  326. 
Respiration  apparatus  227. 

automatic  regulation  755. 
types  of  210. 

Respiratory    center    750,    subordinate 

centers  751,  stimulation  752,  factors 

influencing  754,  vagus  influence  754, 

self-regulation  755,  pathological  757. 

Respiratory  curves  209. 

interchange  of  gases  232. 
movements,    pathological 

2  IO. 

pressure  223. 
spasm  757. 

tracts  in  the  cord  740. 
variations    in   blood  pres- 
sure  1 66. 
volumes  205. 
Respired  air  231. 
Rete  mirabile  89. 
Retention  of  urine  520,  522,  523. 
Reticular  membrane  899. 
Reticulum  343. 
Retina,  function  850. 
structure  819. 
Retinal  fatigue  855. 
image  829. 
purple  855. 
rivalry  876. 

stimulation  by  light  854. 
stimulation,        duration       and 

strength  854. 
stimulation,  electrical  846. 
stimulation,  mechanical  846. 
Retino-motor  fibers  855. 


INDEX. 


1023 


Retino-motor  phenomena  855. 

Retractor  muscle  of  the  lens  883.  " 

Reversion   1004. 

Rheocord  640. 

Rheostat  641. 

Rhinoscopy  608. 

Rhonchi  222. 

Ribs,  development  983. 

Rickets  588. 

Right-handedness  795. 

Rigor  552. 

Ringing  in  the  ears  911. 

Ritter's  opening  tetanus  666. 

Ritter-Valli  law  637,  664. 

Roaring  in  the  ears  911. 

Rods  and  cones  851,  853. 

Rumen  343. 

Running  592. 


Saccharomyces  of  the  epidermis  539-. 

of  the  urine  493. 
Saccule  897. 
Saddle  joint  582. 
Saliva,  abnormalities  264. 
action  264. 

decreased  amount  339. 
secretion  of  339. 
Salivary  calculi  262,  339. 
ducts  258. 

glands,  257,  development  994. 
secretion  339. 

center  262. 
nerves  259,  260. 
poisons  262. 
reflex  262. 
Salts,  absorption  of  354. 
Saponih'cation  306. 
Sarcinse  341. 
Sarcoplasm  544. 
Scales  of  snakes  540. 
Schemer's  experiment  835. 
Schizomycetes  329. 
Schlemm,  canal  of  817. 
Schreger's  lines  272. 
Sclera  817. 
Scolex  941. 
Sebaceous  glands  531. 
Seborrhea  539. 
Secondary  contraction  653. 

external  resistance  644. 
positions  of  the  eyes  867 . 
sensations  911. 
tetanus  653. 

Secretion  of  bile  319,  341. 
Secretory  ducts  258. 
Secretory  ducts  of   the   gastric   glands 

289. 

Secretory  nerves  677. 
Self-digestion  of  the  stomach  301. 
Self  regulation  of  respiration  755. 

of  the  heart  93. 
Semicircular  canals  700,  898. 
Semilunar  valves  93,  99. 
Seminal  fluid  942,  reaction  942. 
Sensations  of  speech  movement  796. 


Sense  centers  742,  786,   798. 
Sensomobility  716. 
Sensory  circles  926. 

conduction  in  the  cord  745. 

cortical  centers  785,  798. 

impressions  922. 

nerves  678,  development  1001. 

sphere  788,  800. 
Septic  fever  71. 
Serous  capsule  976. 
cavities  363. 
effusions  374. 
glands  256. 
Serum  65. 
Serum-albumin  73. 
Serum-casein  73. 
Serum-globulin  73. 
Serum  and  saline  transfusion  191. 
Setschenow's  center  731. 
Sex-differentiation,  cause  999. 
Sexual  gland  996. 
Short-sighted  eye  836. 
Sighing  225. 
Single  vision  871. 
Sinuses  of  the  dura  mater  131. 
Sinus,  terminal  965. 

urogenital  996. 
Siren  900. 
Sitting  592. 

positions  592. 
Skatol  88,  305,  334. 
Skin,  conductivity  of  540. 
currents  651. 

suppression  of  the  activity  of  533. 
Skoliosis  588. 

Skull,  development  of  984. 
Sleeping  and  waking  778. 
Sliding  induction  apparatus  646. 
Smegma  preputii  534. 
Smooth  muscle  572,  575. 
Sneezing  225. 

center  748. 
Sniffing  225. 
Snoring  225. 
Snorting  225. 

Soap-formation  in  digestion  306. 
Soaps,  absorption  of  356. 

"        reversion  of  357. 
Sobbing  225. 

Solitary  lymph  follicles  363. 
Somites  969. 
Sound-pantomime  618. 
Sound-picture  theory  908. 
Sound-waves  886. 
Space  sense  924. 
Spanicardia  143. 
Spanipnea  757. 
Spasm  center  773. 
Spasmodic    movements    740,    paths    of 

conduction  for  740. 
Spasm  of  the  glottis  711. 
Specific  energy  677,  813. 
Specific  energy  of  the  rods  and  cones 

853. 

Spectacles  839. 
Speech  611. 


1024 


INDEX. 


Speech  center  795. 

comparative  618. 
"        motor  tract  796. 

Spermatogenesis  945,  946. 

Spermatozoa  944. 

Spermin  943. 

Sperm  nucleus  960. 

Spherical  aberration  840. 

Sphincter  ani  284. 

Sphincters  584. 

Sphygmogram  137. 

Sphygmograph   135,   137. 

Sphygmomanometer  164. 

Sphygmometer  134. 

Sphygmoscope,  gas  137. 

Spices  430. 

Spinal  centers  734. 

Spinal  cord,  structure  723,  white  matter 
723,  columns  723,  gray  matter  724, 
collaterals  725,  secondary  degenera- 
tion 725,  anterior  columns  726, 
pyramidal  tracts  726,  anterior  ground 
bundle  726,  tract  of  Goll  726,  of 
Burdach  726,  of  Gowers  726,  lateral 
ground  bundles  726,  cerebellar  tracts 
726,  746,  development  of  the  tracts 
726,  centers  734,  irritability  736, 
conducting  paths  738,  pathological 
741,  destruction  741. 

Spinal  cord,  development   1000. 

Spinal  ganglia  713,  development  1001. 

Spinal  groove  966. 

Spinal  nerves  713. 

Spiral  joint  582. 

Spiral  valve  344. 

Spirilli  329. 

Spirochaeta3  329. 

Spirometry  206. 

Splanchnic  nerve  288. 

Splanchnopleure  969. 

Spleen   193. 

Spleen  center  735. 

Spontaneous  generation  938. 

Spores  330. 

Sprouting  939. 

Sputum,  pathological  250. 

Stammering  618. 

Standing  589,  596. 

comfortable  position  591. 

Stannius'  experiment   116. 

Stapedius  muscle  893. 

Starch  264. 

Starvation  439. 

Stasis  1 80. 

Static  sense-organs  700. 

Statoliths  912. 

Stenotic  murmurs  183. 

Stereoscope  876. 

Stereoscopic  vision  873. 

Stethograph  208. 

Stomach,  abnormal  movements  340. 
catarrh  of  340. 
disorders  340. 
examination  280. 
extirpation  301. 
gases  301. 


Stomach  movements  280. 
musculature  280. 
nerves  281. 
transillummation  280. 
Stomata  362,  363. 
Strabismus  682,  807. 
Strangury  524. 
Striate  body  802. 
Stroboscope  597,  863. 
Stroma-fibrin  49,  63,   72. 
Stroma-proteids  63. 
Stromuhr  (rheometer)  172. 
Struggle  for  existence   1004. 
Subcutaneous  injections  373. 
Subjective  hearing  911. 

optic  phenomena  844. 
sensations  814. 
taste  919. 

Sublingual  gland  258. 
saliva  263. 

Submaxillary  gland  258. 
saliva  263. 

Successive  contrast  865. 
Succus  entericus  326. 
Succussion  sound  222. 
Sucking  270. 
Sucking  center  749. 
Suffocation  753. 
Sugars  465. 

Sugar  splitting  ferment  307. 
Sugar  tests  267,   268. 
Sulphur  methemoglobin  61. 
Summated  contractions  565. 
Summation  of  heart  stimuli  115. 
Summation  tones  910. 
Sun  as  the  source  of  life  27. 
Superfecundation  958. 
Superfetation  959. 
Suppression  of  double  images  873. 
Suprarenals  197. 
Sutures  583. 
Sweat  534,   536. 
center  735. 
glands  531. 
nerves  536. 

Sweating  in  animals  534. 
Swimming  597. 

Sympathetic  718,  structure,  ganglia 
and  chains  718,  visceral  v  branches 
718,  poisoning  with  nicotin  719,  inde- 
pendent functions  719,  dependent 
functions  719,  cerebral  and  cer- 
vical division  719,  thoracic  and  ab- 
dominal division  719,  development 

I  00  I. 

Sympathetic  nerves,  pathological  720. 

ophthalmia  680. 

saliva  260. 

supply  of  the  eye  685. 
Symphysis  583. 
Synchondrosis  583. 
Syncytium  976. 
Syndesmosis  583. 
Synergists  587.  • 
Synovial  membrane  581. 
Syntonin  in  the  stomach  295. 


INDEX. 


IO25 


Tabes  dorsalis  739. 
Tactile  area  927. 
bulbs  920. 
conduction   738. 
corpuscles  920. 
discs  922. 
reflex  739. 
sensations   738,    739. 
Taenia,  development  941. 
Tail-fold  971. 
Talking-machine  620. 
Tapetum  850. 
Tape-worm  941. 
Taste-buds  917. 

fibers  in  the  chorda  916. 
organ  of  916. 
region  916. 
Taurin  31 6,  325. 
Taurocholic  acid  316. 
Tea  428. 

Tears,  apparatus  879. 
nerves  684,  697. 
secretion  697,  88 1. 
Teeth  chemistry  273. 

development  273. 
growth  275. 
shedding  275. 
Telencephalon   1000. 
Telestereoscope  876,  878. 
Telodendrites  621,  625. 
Temperature  and  the  vascular  nerves 

766. 

accommodation  to  402. 
artificial  elevation  of  406. 
artificially  lowered  408. 
daily  variations  392. 
influences  affecting  403. 
lowest  394. 

of  different  animals  381. 
of  inflamed  parts  411. 
of  single  organs  385. 
of  various  tissues  385. 
points  930. 
postmortem  rise  407. 
regulation  394. 
sense  930. 

substances  affect  ing  406. 
Tendinous  cords  98. 
Tendon  nerves  547. 

reflexes  733. 
Tension    20. 

series  638. 
of  vessel  walls  141 
Tensors  of  fasciae   587. 
Tensor  tympani  muscle  s<>2. 
Terminal  nodules  921. 
Tertiary   positions   of  the   eye   867. 
Testicle,  development  996. 

structure  945. 
Tetanometer  630. 
Tetanus    565. 

in  animals  566. 
in  the  newborn  567. 
voluntary   in    man    5^6. 
Tetany   196. 
Thalamus   803. 

65 


Thaumatrope  863. 
Therapeutic  electricity  669. 
Thermic  center  788. 
Thermo-electric  elements  384. 
needles  384. 
temperature    measure- 
ments 382. 
Thermometer  382. 

maximal     and    minimal 

382. 

metastatic,  outflow  382. 
Thermometry  382. 
Thermopalpation  385. 
Thigh-glands  540. 
Thoracometry  217. 
Threshold  value  814. 

of  stimuli  632. 
Thrombin  69. 

Thymus  195,  development  986. 
Thyroid  196,  development  986. 
i   Ticklish  points  924. 
Timbre  903. 

Time  sense  of  the  ear  902. 
Tinnitus  700. 
!   Tissue  fibrinogen  7 1 . 
Tissue  respiration  241. 
Tone  900. 

color  900,  903. 
height  900. 
intensity  902. 
musical  899. 
quality  903. 
Tones,  analysis  of  903. 
Tone  variations  of  the  heart  99,  167. 
I  Tongue,   glands  256. 

movements  276. 
musculature  276. 
paralysis  276. 
spasm  of  713. 
Tonsils  257. 
Tooth-pulp  273. 
Topography     of    the     cortex     791,     in 

relation  to  the  skull  80 1 . 
Torticollis  712. 
Touch,  anomalies  933. 

partial  paralysis  of  934. 
Toxicogenic  bacteria  330. 
Trachea  201. 

Transference  of  sensibility  936. 
Transfusion,  190. 

depletory  191. 
indications   191. 
methods   191. 
of     heterogeneous      blood 

192. 

Transitional  corpuscle  forms  70. 
Transition    resistance   643. 
Transmigration  of  the  ovum  959. 
Transplanting  454. 
Traube-Hering  curves  167. 
Trichina,   development    041. 
Trichomonads  in  the  intestine  343. 
Trie-rot  ism    146. 
Trigeminal   nerves  683. 
Trochlear  nerve  682. 
Trommer's   test    267. 


IO26 


INDEX. 


Trophic  center  635. 

Trophic  libers  of  the  fifth  685. 

"        nerves  677. 
Trotting  597. 
Trypsin  304. 

formation  305. 
Tryptone  304. 
Tube-casts  505. 
Tumultus  sermonis  797. 
Twins,  triplets  958. 
Two- joint  muscles  586. 
Tympanic  cavity  895. 
Tympanitic  note  220. 
Tympanum  888,  890. 

pulse  of  156. 
Tyrosin  305,  334,  503. 

Umbilical  cord  978. 

murmur  184. 
vesicle  971. 
Union  of  tissues  455. 
Unipolar  induction  646. 
Unity  of  energy  25.     . 
Unity  of  the  animal  kingdom   1004. 
Unpolarizable  electrodes  643 . 
Unstriated  muscle  546. 
Urachus  975. 
Urates  481. 
Urea  475. 

compounds  478. 
demonstration  477. 
estimation  478. 
formation  475. 
Uremia  516. 

Ureters  517,  development  996. 
Urethra  519. 
Urethra!  sphincter  520. 
Uric  acid  479. 

dyscrasia  516. 
Urinary  bladder  518,  519. 

development  975,  996. 
concretions  507. 
organs,  development  995. 
sediments  503,   506. 
tube  casts  505. 
Urine,  bacteria  in  504. 
dribbling  of  524. 
fermentation  493,  504. 
formation  513. 
inorganic  constituents  490. 
physical  properties  472. 
retention  520,   522,   523.  ; 
secretion  509.    r 


Vagus  nerve  704. 

Valves  of  the  heart  92,  97,  98,   100. 

of  the  veins   131. 
Valvular  sounds  in  the  veins  185. 
Varices   169. 

Varnishing  the  skin  411,  533. 
Vasa  vasorum   132,  203. 
Vascular  tension   141. 
Vasodilator     center     771,     subordinate 
spinal  772,  cortical  788. 


!   Vasodilator  fibers  771,  course  772. 
Vasomotor  angina  pectoris  771. 
Vasomotor     center     762,     subordinate 

spinal     735,      768,     peripheral     768, 

cortical  769,   789. 
Vasomotor    fibers    762,    course    in    the 

cord    740,    course    763,  influence    on 

bodily  temperature  767,  local  effects 

766,  influence  on  the  heart's  action 

767,  pathological  768. 

!   Vaso-formative  cells  42. 
Vater's  corpuscles  920. 
Vegetable  foods  426. 

proteids  459. 

Veins  of  the  first  and  second  circula- 
tion 992. 

' '       structure  131. 
valves  of  131. 
Velocity  curve  174. 

of  the  blood  stream  171,  175. 
of  the  nerve  impulse  667. 
pulse   173. 

Vena  terminalis  965. 
Venesection   166,  393. 
Venomotor  nerves  769. 
Venous  blood  82. 

plexuses  809. 
pressure   169. 

pulse  185,  in  the  retina  186. 
sounds  185. 
Ventilation  246. 
Ventricular  capacity  1 6 1 ,  176. 
Verbal  deafness  799. 
Vernix  caseosa  534. 
Vertebrae,  development  972. 
Vertebral  column,  development  983. 

deformities  588. 

Vertebral  derivation  of  the  skull  984. 
Vertigo  701,  807,  809. 
Vesical  sphincter  519. 
j   Vesicospinal  center  735. 
Vesicular  murmur  221. 
Vessels,,  davejopment  of  42. 

,»  qjjftiQptic  shadows  of  844. 

sensory  nerves  of  771. 
I   Vibrio  329. 

Viscera,  cortical  center  790. 
Visceral  arches  973,  development  986. 

clefts  973,  development  986. 
;   Visual  angle  830. 

axis  852,  866. 
'estimation  of  size  and  distance 

.     ;     .     .    .  §77* 

field  831.' 

hallucinations  799,   847. 
J. ,  ,.'.'  .     purple  855. 

Villi  of  the  small  intestine  348 

of  the  placenta  977. 
Vital' capacity  206. 

energy  28. 
Vitreous  body  821. 
•   Vocal  bands  600. 
cavity  905. 
fremitus  223. 
register  609. 
j   Voice,  basis  of  610. 


INDEX. 


IO27 


Voice,  in  animals  618. 

pitch  609. 

range  610. 

timbre  613. 
Volt  640. 

Voltaic  induction  645. 
Volta's  alternative  666. 
Volume  pulse   189. 
Voluntary  hallucinations  847. 
Voluntary  inhibition  of  the  heart  761. 
Voluntary  movement,  path  of  the  im- 
pulses 738. 
Vomiting,  center  282,   749. 

movements  of  281. 
Vowel  analysis  905. 

apparatus  905. 

curves  906. 

flame  curves  907. 

formation  905. 
Vowels  611. 


Wagner's  law  of  migration  1004. 
Walking  592,   596. 
Wandering  of  leukocytes  46,  180. 
Warm  blooded  animals  381. 
Water  413. 

examination  414. 
Water- rigor  554. 
Water- vascular  system  199. 
Watt  640 
Wave  of  contraction  in  the  heart   114, 

116,  118. 
Wave  movements  of  the  blood  128,  133. 


Weber-Fechner  law  814. 

Wheel  movements  of  the  eye  868. 

Whispering  6 1 1 . 

W^ine  430 

Wolffian  bodies  995. 

Wolffian  duct  995,  997. 

Wolf's  throat  985. 

Word-blindness  799. 

Word-deafness  799. 

WTork  19. 

in  bicycling  595. 

in  walking  595 

of  the  heart  178. 

of  the  muscles  569 

relation  to  heat  production  400. 

unit  of  19,  23. 


Xanthin  bases   in  pancreatic  digestion 

305-. 
bases  in  urine  483. 


Yawning  226. 

Yeast-cells  in  the  intestine  331 

Yeasts  429. 

Yellow  body  954. 

Yellow  spot,  recognition  of  845. 

Yellow  vision  323. 

Yolk-sac  971. 


Zooglea  330. 

Zymogenic  microbes  330. 


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